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1. 6 AND BACKGROUND iiss 7 Ledra DRE LIDAR GOVOU eon tU M DE EUR M E Cu ME S MESA 7 8 ad cur cfc 8 Bell TOTAL Aa Vereor 8 22 THE PRINCIPER OF CALIBRATION DEL EE 9 2 TAB VIP iae Md 10 23 2 General ACS CIID ON _ ___ _ 11 220 Ihe strutture of q LabVIEW DEOOVOU ________6_6_____ 11 __ ___ ___ _ _ _ _ ___ 6_6_ 12 ZO THEORY 12 Taser ODCHOUON eh __ _6_____ 12 2d aa ngs Eee 13 GENERAL DESCRIPTION edo Ld Rye ue RUE 14 EE DARE SY STEM ieiunia rent Co a piden Serio babeat vi dedii 14 14 32 CALIBRATION UNI HN NR TT t 15 DIOSA a 15 AS SYSTEM DESIGN 16 ZI INTRODUCTION 22 16 d telas cm at 16 AN grs cc 16 d
2. dis 32 Oo REMI Towel id m 32 6 25 2 2 C urrentealibratdotib Sui aes ea ad 32 6 3 2 2 Configuration ofthe calibration Unit eus cie 32 6 37 duEdIt pealedate Or eE dd Maso 34 C alibrauneg the aset echoes e unde p 34 M DR 35 63 3 2 Adding ca librauomjipetlod 35 Adding changing 35 6 25 4 Interacting with the OPOSIQSOF SY SCM oki ote dae vta E 36 63 4 3 Changing wavelength on the Taser Pe li Qu 36 7 EVALUATION e eee nS 1 I s eT NT 97 PIS UN tcs 37 wb on 38 L 36 Ad 39 Jet DISCUSSION ane 40 DEVI NUES deem 40 S IMPROVEMENTS IN THE FUTURE 41
3. 16 ADS FOO CIS 16 BHECALIBEATION UN 17 TOR NR RT T IR 17 45421 E COIS dele LORS aite LEE 17 54 2 o ccs tts LE ae AR C Em 18 DIGITIZER TRIGGERS DELA Y 18 4 6 DETECTOR ELECTRONICS d kat p eve ule e etu Led at 19 A OAD TOTAL 19 2 0 2 Trimming the Para mel ers ise ree 19 c MM EI M NM MP LI 20 AS NEU TRAE DENSITY FILTERS 9 X 20 A9 STEPPER MOTOR NR e 21 4 IO STEPPER MOTOR ELECTRONICS oa ou raid bn 21 4 L1 POSITION DETECTOR PLECTRONICS 21 LR EU RU TERN 2l SN RS deua BEBE T NT NT CER 2l d I4 OVS TEN COMPU LER uten ____ _ ___ 21 Iq LAT PC i gt T 22 22 3 Department of Atomic Physics Lund Institute of Technology T
4. 5 T 11 Department of Atomic Physics Lund Institute of Technology 10 aysu pun 591544 2 jo 3uounzedo q 09 TRIGGER DELRY CRL UNIT COMMON GROUND 12 COMMON GROUND TRIGGER EXTRA DELAY CONTROL 5 COMMON GROUND TRIGGER DELRY DIGITIZER COMMON GROUND 9 8 7 6 5 4 3 2 1 DURL DELRY CONNECTOR 10k 1 2005 EXTRA DELAY DELAY ADJUST 8 25us Shoat Titius DURL DELRY DELAY ADJUST 8 Sms E SHEET a 198311 19211814 21 4 193811 AIZHISIG xipuoddy 1 03 sos nd 198811 SIU Appendix 13 The MOPO 730 laser system Appendix 13 The MOPO 730 laser system Pump beam parameters Nd YAG 355 nm 3 harmonic gt 70 Gaussian fit 50 prads 0 5 mrads 0 001 cm at 355 nm 20 Hz 5 6 ns Pump energy by oscillator Master Oscillator Power Oscilator 200 mJ max 450 mJ Pump energy in total Minimum 200 mJ Maximum 450 mJ Tuning Characteristic 40 to 690 nm Idler tuning range typical 30 to 1800 nm Other Output Characteristics Horizontal gt 97 Beam diameter typical R gt 70 Gaussian fit Table 16 MPO
5. A ts oror OY WT Motor 2 ERDDySIS 22 2 Motor 1 R CL ER Motor 1 B ene ae Opto Coupler Opto couper Une Opto Coupler2 sign Ue tec tor UND PLE 1 1 71 1 n a a Detector Supply 3V Opto Coupler 51 Opto Gaup er 3 51 Motor 4 Motor Motor 2 D Mator 1 Motor 1 Opto Coupler 1 5 Opto Coupler 2 5Y Detector 5 Motor 3 Mator 3 B Motor 3 C Motor 3 D lt lt 2 gt LINN NOILUS8I 182 0 00009 lt 2 lt 2 Ac Shield GNU Detectar 1 Signal Cv 0pto Coupler Signal Hot tor 1 5 1 Dir Notor 2 Step Motor 2 Dir tia 9 5 Motor 3 Dir pto Coupleri Signal Detectar 2 51 Calib Unit Trigger Opto nal ot Motor 4 Step Opto lt 2 lt 2 gt Opto Coupler GND ES COMMUNICATION BETVEEN SYSTEM BLOCKS _____ CONTROL UNIT MAE iM 12 SHEET 0193545 IY 5542014 xIpusddy 194845 5852014 uooAjoq c xipuoddy 2 Jo pun 521644
6. Signalname Pin Pin Signalname ACH 5 6 ACH 7 8 __ __ ___ _ 1 9 1 101 AHI or the AT MIO 16 I O Sei Table14 Pin assignments connector 7 48 Appendix 1 The wiring of the system Signalname 2 4 2 39005 Lo 56 or the PC TIO 10 9 gt 5 45 45 45 B Go Go PRO TRO RO Table 15 Pin assignments connector 7 Department of Atomic Physics Lund Institute of Technology 49 Appendix 2 Cabling between system blocks 50 u 32018 431845 SNI O yout ANNO LINN M3AUd Ere 183 d 437111910 3 LINN 33413233 ddindH0O2 2 YILNdWOD H31S45 gt gt LINN ONIA ES 52 gt E LINN 43581 5 31041003 p 5 2 4 of J 2 lt D 5 E 5 2 lt 5 13 189 W4LSAS MS 2 Jo Jo 3uouredo q Shield Opta Coupler4 signa Opto VOUP eraa une otor 4 A Motor 4 B ara n MN __ _ ______________ _ ____ __ _
7. Department of Atomic Physics Lund Institute of Technology transition Thus there is no energy storage capability This transition has to follow the energy conversion law 0 Where o is the input frequency is the signal wave and is the idler wave In terms of wavelength the equation is 1 1 As 1 In theory an infinite number of signal and idler wavelengths can exist to satisfy the energy conversion law Fixing the pump wavelength and rotating the crystal derives the tuning of the OPO The change of the angle will cause the signal and idler output to vary In figure 17 the tuning region is illustrated By placing the crystal in an appropriate resonant cavity Pump Signal 355nm 400 710 Input pulse 2000 nm Wavelength Figure 17 Signal out from an OPO system 10 oscillation at the signal and or idler wavelength can be obtained The output of an OPO is very similar to that of a laser The signal and the idler beam is have strong coherence are highly monochromatic and have spectrum consisting modes 11 The theory of OPO has been known for 25 years but commercial systems have not been available until recent years The problem has been the lack of suitable non linear materials The crystals must fulfil the following conditions e Phase matching conditions for the pump idler and signal laser beams over the entire tuning region e High damage threshold to sustain t
8. It has been found that the detector electronics is badly mounted It is difficult to adjust and measure on the circuit boards An easy way to avoid this problem would be to mount the electronics on the inside of the hatch Placing the electronics there would also make it easy to mount electronics for coming detectors 8 6 The neutral density filter More filters are needed to adjust the laser input over a wider range It has been found that 10 filters are not enough One other improvement would be the ability to adjust the two laser beams individually This would make the unit more sensitive 8 7 The program Today configuration components for the unit are spread out over the entire system It would be better if all the configuration data were fond at one single place This would help to adjust the calibration program in the future It should be possible to change the default wavelength and the calibration method for the wavelength directly from the Cell Selection VI This would make the handling easier when operating the calibration unit Now the operator has to enter the configuration window to change the default wavelength the one that will be used for calibration To change the calibration method the configuration window for the cell must be entered It would be good to develop an interface in which it could be possible to define a calibration program This would be if the LIDAR system should make measurements involving several
9. PD 1 Signal E Table 9 The pin usage of the connector J12 to the control unit 5 Control unit The control unit communicates with all other components in the calibration system the power unit the calibration unit and the system computer The back plane with all the connectors is shown in figure 54 and a description 15 found in table 10 PORC 9 J19 18 11 J20 0 Jo 0024 VO J12 OT SYSTEM Ua V MO 6VO J13 mi PC TIO 10 J14 2 LASER J3 Connector Description Ground ___ 2 Lo e System 2 Department of Atomic Physics Lund Institute of Technology Angle sensor J18 Calibration detector 2 Input Calibration detector 1 input J20 To power unit calibration cable Table 10 Description of the connectors on the back plane of the control unit To the system computer connection boards are used to connect to flat cables The pins of the connector on the back plane are connected to the system computer through these connection boards Between the control unit and the calibration unit are two BNC cables These cables are used to receive signals from the detectors These cables are connected to the MIO 16DL board see table 13 A pin description of the cable to the to the power unit 1s shown in table 11 A description of the DIO 24 I O connection board is shown in table 12 The wiring of the
10. ode tb estne _ __ 41 5 2 LHBDETEG TORS dope oto dran do edo dae Oto du UD 4 SPON THE BEAM SPLITTER eA 4 8 4 THE BEAM ALIGNING OF THE CALIBRATION SYSTEM 4 SO LHE DETECTOR ELECTRONICS Sorata 4 8 6 LAE DENSITY PIE LER uoo an d VID aA d Eu Rea 4 S THE PROGRAM oorok iori kunt 4 DACKNOWEEDGEMNENTS 42 10 el 43 ILGEOSSARY AND ACRONYMIS 44 4 Department of Atomic Physics Lund Institute of Technology Table of contents APPENDIX THE WIRING OF THE SY STEM 45 ya tcu 45 LVS TENE OVET cT 45 ZU CONN LOI I NP M 45 XCQUDFOon Uil Mi MI M EU MM ERE MI i EE 45 aE A A CM MD M E 46 BEER Ap 47 CDU 46 APPENDIX 2 CABLING BETWEEN SYSTEM BLOCKS ccscsssssssscccccccnssceecsssseseesesccsesseeeeeesssecscsssessscusessseseseeseens 50 APPENDIX 3 COMMUNICATION BETWEEN BLOCKS IN THE CALIBRATION SYSTEM 51 APPENDIX ACC ALIBRA TION ONIT WIRING menit p eee epu ARA dae ene 32 AP
11. 16 265 44 540 70 Table 4 connectors used for the calibration system Department of Atomic Physics Lund Institute of Technology 3 Calibration unit The connectors in the calibration unit are shown in figure 52 and are described in table 5 Connector Description Table 5 Description of the connectors on the calibration unit The cables from the connectors are connected to three connection boards This is done to make it easy too remove the different components in the unit For detailed description see table 6 and appendix 4 Calibration unit wiring Connector connection Description MS3112E 18 board 32P Motor 1 A Motor 1 B Motor 1 C Motor 1 D Motor 2 A Motor 2 B Motor 2 Motor 2 D Motor 3 Motor 3 B Motor 3 C Motor 3 D Motor 4 A Motor 4 B Motor 4 C Motor 4 D PD 1 GRD PD 1 Signal PD 1 5V 10 11 12 13 14 15 16 17 18 19 20 NA 45 Appendix 1 The wiring of the system P 22 2 HEN D 26 5 28 e 35 Deteor MEN NE MN MN OMA 7 p o oou Table6 The wiring between the connector and the connection boards in the calibration unit 4 Power unit The connectors in the power unit are shown in figure 53 and described in table 7The connectors used by the calibration
12. Sub virtual instrument When making a program you have to divide the code into smaller parts This is done to get a better overview of the program It is also done to recycle code that has once been written or to use code that someone else has written in order not to invent the wheel again In LabVIEW this is achieved by using Sub VIs A Sub VI is actually a VI but it is called from another VI i e the caller VI has the Sub VI in its block diagram I O communication to external instruments is done through Sub VIs In LabVIEW you can find hundreds of VIs for data acquisition data control and data analyses For more information about the VIs that can be found in LabVIEW please see the LabVIEW documentation 7 A powerful feature of the program is that each VI can be run by it self or be called from another VI and be used as a Sub VI This means that each VI can be changed tested and debugged by itself before put into a larger program 11 2 Theory 2 3 3 Data flow programming In LabVIEW each node VI or object starts operating only when data is available at all of its inputs When the node finishes executing it produces data for all of its outputs This data driven method of execution is called data flow Data flow programming releases the developer from the linear architecture of text based languages The execution order between different objects is determined by the data flow between the objects This makes it possible
13. e That End Of Scan is between 200 and 4800nm e That Step in larger then If not the value is set to 1 e That Diff Abs in larger then If not the value is set to 1 Cell that Occ Pos Location Spiece lIb Input Info Cluster o Peak Data In Peak Data The data to be checked Cluster Output Parameter Description nfo Cluster Type I TRUE if the data is OK otherwise FALSE Out Cluster Department of Atomic Physics Lund Institute of Technology CloseFile Description Closes an open file Location Lofileop llb Input Parameter Description T The type of file that is to Selector be closed Cluster Boolean If TRUE the VI ignores if Activi the change activity 15 set InfoCluster Cluster Configuration Of The Unit Description This VI is used to configure the calibration unit It is also from this VI the calibration data can be set Location Program llb Input Parameter Description Parameter File Types Info out CalibCluter File Types in File Types Cluster Info Cluster Output out CalibCluter __ File Types File Types Cluster Info Cluster 02022 ContinueExecErrorCheck Description This VI checks if the program shall continue to execute or not Location Execcon
14. 0 050 0 200 7 0 42 2 00 0 050 0 200 0 72 3 20 0 080 0 320 8 0 66 2 17 0 079 0 317 0 87 4 00 0 100 0 400 9 0 80 3 95 0 099 0 395 0 95 4 65 0 116 0 465 10 0 90 4 60 0 115 0 460 1 01 5 05 0 126 0 505 11 0 96 4 95 0 124 0 495 1 17 6 35 0 159 0 635 12 107 5 90 0 148 0 590 1 53 10 10 0 253 1 010 13 1 12 6 35 0 159 0 635 1 82 12 70 0 318 1 270 14 14 9 33 0 234 0 935 2 16 14 90 0 373 1 490 I 1 51 10 10 0 253 1 010 227 16 10 0 403 1 610 16 1 69 11 80 0 295 1 180 2 54 18 70 0 468 1 870 17 1 78 12 65 0 316 1 265 2 70 20 00 0 500 2 000 18 2 11 14 85 0 371 1 485 3 28 27 10 0 678 2 710 19 2 28 15 90 0 398 1 590 3 44 29 00 0 725 2 900 20 2 61 18 75 0 469 1 875 3 50 29 70 0 743 2 970 21 2 76 20 10 0 503 2 010 3 67 31 75 0 794 3 175 22 3 56 29 70 0 743 2 970 3 88 34 00 0 850 3 400 23 3 83 31 70 0 793 3 170 4 12 36 40 0 910 3 640 24 4 38 37 35 0 934 3 795 4 17 37 35 0 934 3 735 25 4 48 40 00 1 000 4 000 4 24 40 00 1 000 4 000 Table 25 Table of the derived detector characteristics Department of Atomic Physics Lund Institute of Technology Appendix 18 Experiment to determine the performance of the detectors Discussion The first two experiments show that the two detectors seem to be linear between 1 and 3 V These two experiments also reveal that laser was unstable i e had fluctuating energy Even taking the average of a large number of pulses does not help to get good test results It is also found that the electronics is saturated at 3 2V This is belo
15. 1992 New operating systems 1990 Microsoft Windows OpenWindows X Windows U S Patent Introduction on other platforms February 1990 U S Patent January 1990 LabVIEW 2 1990 LabVIEW 2 Four years of customer feedback Mature product Compiler to match industry needs 1986 LabVIEW 1 Introduced innovative approach to programming Macintosh only possible platform October 1986 LabVIEW 1 April 1983 LabVIEW Concept 1983 LabVIEW 1 Search for instrumentation software solution Virtual instrument concept Figure 8 The LabVIEW development milestones 6 Sub VI Front Panel Icon Connector c M Opcrotc Controls Windows Text Help AAA Butterworth Filter Fita Fry penes rinks Wer tope her cut tec fh 100 mi zoni int J Signal before filter mfi 22 sum the sine and bandlimited noise 1000 0 Cut Off Filter Order 1 Eb Data Flow Wire Front Panel Terminal Figure 9 The different components in a LabVIEW program Department of Atomic Physics Lund Institute of Technology 10 2 Theory 2 3 2 General description LabVIEW is a graphical programming system for data acquisition and control data analysis and presentation The whole idea of the lang
16. Calib Splitter Pos Test Mode Figure 44 The three clusters and the elements that is defined for the calibration program 30 6 Programmer s guide 6 3 Calibration program This section describes concepts of the program i e where different data can be found and the logic behind The main components of the program are described with a flow chart For detailed information of the program please see the code 6 3 1 Basic concepts The basic concepts of the calibration unit and program are as follows Revolver for 7 cells Neutral density filter wheel with 10 positions e Detector wheel with 2 positions The unit is prepared for adding a variable beam splitter component indexing in the program starts with zero This means that the first position of the neutral density filters cell positions detector Beginning and end point of the program sequence Prosess Action process or action performed by the program Manual operation Manual operation that can be performed by the user typical example can be when the user presses a key Display Message or screen that 15 displayed Predefined process Process containing several actions example 15 another main VI Decision Typically an if statement Case sequence Figure 45 The components used in the flow chart Department of Atomic Physics Lund Institute of Technology positions and so on is 0 The program
17. Data For Cell Department of Atomic Physics Lund Institute of Technology 6 3 2 5 Calibrating the laser This VI is the entry point to the calibration section of the calibration program The VI is called from the main application and has no direct interaction with the configuration part of the calibration program But when the VI is called the calibration parameters in the Info cluster must be set It is in this VI all the different calibration methods are called see figure 50 To move the OPO laser to a specific wavelength the program uses components developed by Fredrik Nordin 20 The calibration program calls these VIs with the wavelength the laser shall move to The name of the VI is Calibrate The Laser Input parameter Info cluster The calibration parameters must be set in the cluster when called Output parameters 1 OK out Tells if the calibration was successful or not Display Error message Data OK Copy Peak data to screen Remove the peak data Add the new data 34 6 Programmer s guide 2 Offset in nm The offset found on the wavelength scale for the laser The VI then performs the steps found in the experiment to determine the performance of detectors see Appendix 18 These steps are 1 Let the filter wheel start with as high optical density as possible i e as dark as possible 2 Let the laser go to the minimum absorption around the region were the calibration s
18. Department of Atomic Physics Lund Institute of Technology 1 1 53 1 HW WW 99 2 NY LH M NN RR gt gt 77 Appendix 19 VI and cluster description sie aS WSU LO DU AIM mer MR Tr ES Which Button is T DNO The clusters CIND Sel ClO nz I D M CAG Oster LOS Cluster Pile Cluster ot Peak ee n e Iuster ob spitter Data ema File Type bee edlen obs EP add liio QM LE Department of Atomic Physics Lund Institute of Technology 13 13 13 14 14 14 15 15 15 15 15 16 16 16 Appendix 19 VI and cluster description Calibrate The Laser Description This VI is the entry point to the calibration part of the program When calling the VI the calibration parameters have to be set in the Info cluster The VI Checks the calibration data Move the motors to the starting position Finds appropriate neutral density filter Select
19. Description Adds a new position to the array of detectors in the Calib cluster Location Array Functions llb Input Calib Cluster Info in Info Cluster Output Calib Cluster Info Cluster The position of the last Detector Pos detector in the array New Splitter Data Description Adds a new position to the array of splitters in the Calib cluster Location Array Functions llb Input Cluster Info in Info Cluster Department of Atomic Physics Lund Institute of Technology Output Parameter Calib out Info out Last Splitter Pos Description Calib Cluster Info Cluster Integer The position of the last splitter in the array OpenFile Description Opens a file for input Location Input Parameter Description File Type Integer The type of file that 15 to Selector be open Cluster Info Cluster S Output Description Parameter File Types File Types Cluster Info out Info Cluster ReadFile Description Reads from file The data that 1s read is stored in the Types cluster Location Lofileop llb Input Selector be read ical d NN Cluster If TRUE the VI ignores if the change activity 15 set Boolean TRUE if end of file is reached End Of File File Types File Types Cluster Reset UNIT Description Th
20. Figure 3 a small segment of an absorption spectrum of a molecule The wavelengths ON and OFF the peaks are displayed Laser beam Distance R Figure 4 The mobile LIDAR system measuring the outlet from two factories 2 Theory The back scattered light from both laser beams is recorded over time This time resolution will give the distance in the measurement See figure 5 For the laser light that is not absorbed on its way through the air the back scattered intensity will show a simple l R dependence R is the distance The light that is absorbed will have the same 1 R2 dependency where the molecule is not present In the plume where the molecule is present the light will be absorbed and the back scattered intensity will decrease The presence of an absorbing gas is best illustrated if the two curves are divided by each other as illustrated in the figure 6 If this curve is differentiated the distance and concentration of gas is found see figure 7 Mathematically the ratio is found from DIAL equation 5 P R AR Prog R AR exp 2 6 Acn 0 9 Where is the concentration o A is the absorption cross section at If the measurement 15 carried out in several directions in a plane and the wind velocity is determined the total outlet from the factories can be calculated 2 2 The principle of calibration The principle of calibration is simple A cell 15 filled with a g
21. Fredrik Nordin Development of a fast wavelength tuning system for OPO based lidar measurements Lund Reports on Atomic Physics LRAP 243 Lund Institute of Technology Lund April 1999 Quanta Ray manual for the MOPO 730 system page 9 Hamamatsu product cataloug Web address http www hamamatsu com or http www hpk co jp hp2e main html Sune Svanberg Atomic and Molecular Spectroscopy page 128 Springer Verlag 1992 LEROY P RIGAUD and E HICKS Visible absorption cross section of NO2 at 298K and 235K by B Annales Geophysicae 1997 5A 4 247 250 D J Brassington Sulfur dioxide absorption cross section measurements from 290 nm to 317 nm Appl Optics 20 3744 3779 1981 N Takeuchi H Shimizu and M Okuda Detectivity estimation of the DAS LIDAR for NO2 Appl Optics 17 2734 2738 1978 43 Department of Atomic Physics Lund Institute of Technology 11 Glossary and acronyms 11 Glossary and acronyms A D ADC BBO DAC DIAL GPIB I O IEEE LIDAR OD OPO PC PMT SubVI TTL VI VME VOC Analogue Digital A D converter Beta Barium Borate D A converter Differential Absorption LIDAR General Purpose Interface Bus Input Output Institute of Electrical and Electronics Engineers Light Detection And Ranging Optical Density Optical Parametric Oscillator Personal Computer Photo Multiplier Tube A VI that is found in another VIs block diagram Transistor Transistor Logic Virtual Instruments Ve
22. Physics Lund Institute of Technology The mechanism to hold the signal until the computer can read it is constructed by using the fact that there is a large difference in energy between the laser pulse and the background The signal from the detector is almost zero when there is no laser intensity The integrator will accumulate the signal from the time when the trigger is received until the value can be read by the computer but since there is no output after the laser pulse the circuit will hold the signal even though it is integrated To reset the integrator a short circuit is put over the integrating capacitor This short circuit is kept until the low flank of the trigger signal is received see figure 24 The detector pulse is then integrated until the capacitor is short circuit again see figure 28 Short circuit pulse Trigger In integrating capacitor Figure 28 Short circuit part When the low flank is received in the trigger in the Short circuit is released and the capacitor can integrate the signal The integration time 0 7 RC 4 6 2 Trimming the parameters Trimming the circuit parameters is done on the integrator circuit If one part is badly adjusted other parts can not correct this error The dynamics in the system must be as big as possible at the same time as no part should be saturated To be able to determine the values of the resistors and capacitors an experiment was conducted on the detecto
23. can be configured with data for many cells For every cell that is defined there shall exist a real cell For each cell many different calibration wavelengths can be defined For each of the wavelength a specific calibration method can be selected No detector shall be placed at position zero In other words the first real detector is found at position 1 This is done to protect the detectors The program will always set the detectors at position 0 blocked except when collecting data during a calibration The filter wheel will always move towards a darker filter except when trying to find the optimal filter during calibration The program starts with the darkest filter Detector 1 is the measuring detector i e the detector that collects the signal from the laser beam that passes through the calibration cell Detector 2 is the reference detector The current positions of the detector wheel the revolver wheel the filter wheel and the beam splitter are always stored in the Info cluster One cell at a time can be selected for calibration The data needed to calibrate is stored in the Info cluster All data configured in the program is stored in a configuration file This file includes information about which cells that are present in the unit Main LIDAR Calibrate The f program Laser Current Calibration Settings Configuration of the calibration unit Edit Peak Data Figure 46 Main sequence of the c
24. from the ref detector Get Names For Cells In Revolver Description Returns the names for the cells that are present in the revolver Location Array Functions llIb Input Calib Cluster Infoin Cluster Output Calib Cluster Cell Array of The names of the cells that Names strings are present in the revolver nfoout InfoCluster Get Splitter For Peak Description Returns the position for a beam splitter that can be used for measuring Location Array Functions llb Input Calib Cluster Info Cluster Wavelength DBL The wavelength for which the splitter have to operate for Output Parameter Cluster Calib out Info Cluster Info out Splitter The name of the Splitter Integer The position of the Splitter Name Splitter Pos Appendix 19 VI and cluster description Goto with comma Description Moves the OPO laser to a specified wavelength Location Sp mopo llb Input laser shall be moved to The GPIB address for the Address laser The wavelength the laser moved to Wavelength DBL Init Calibration Unit Description This VI initialises the calibration program The parameters that are set by the VI are 1 The file path and name of the configuration file The path is set to Calib Data File Path in the File Types cluster 2 The parameters of the detector These parame
25. large range using doubling and mixing systems The ranges the system can be used within are specific for each OPO system The OPO system that is used in Lund can be tuned between 220 690nm 730 1800nm and 2800 4800nm see figure 13 Operation of the optical parametric oscillator OPO is different from the traditional laser system Traditional laser systems derive their gain from stimulated emission generated by atomic transitions The OPO derives its gain from a non linear frequency conversion process Tuning Curve for Lund OPO System Frequency Doubled OPO Signal Idler OPO Signal pu OPO Idler quu Energy OPO Idler Mixed with 1064 nm eSI 1000 2000 3000 Figure 13 Tuning curve for Lund OPO system 8 4000 nm 2 4 1 Traditional laser operation In a traditional laser gain 15 derived from energy that 15 stored in excites of an atomic or molecular transition The principle is shown in figure 14 excitation state 1 3 Soy excitation state 2 Ground state Figure 14 The principle of laser Electrons are excited pumped from the ground state to an upper state excitation state 1 This can be achieved with flash bulbs or with electrical discharge 1 From the upper state the electron will recombine to a lower energy level When doing this the electron can recombine either to excitation state 2 or to the ground state 2 The 12 2 Theory transition between excitation stat
26. possible to change the data for a cell see figure 37 data needed for the calibration is configured in the display The data that is used for calibration depends on the calibration mode used The data for a highlighted calibration peak is displayed in the left field Calibration Data box In this box the calibration values for a specific region are changed and edited Calibration Peak selection box Displays all the calibration peaks for the cell Add Data button When this button is pressed the data that has been entered in the Calibration Data box is checked If the data is correct within thresholds it is added to the cell Change Data button When pressed the data in the edit field is checked If the data is correct the data for the highlighted peak is changed Name 2 um Calibration Data 44810000 fom E 44750000 fam 444850000 E Wavelength On Wavelength om Start OF _ OF Scan T Interval 005000 fom step EB Dit Absorption _ 0 00000 Calibration Made AddData 444770000 fom HD Copy button When pressed the data for the highlighted peak is copied to the edit field Default button Changes the default peak to the highlighted The default peak 15 displayed with two stars in front of the data Delete Data button Deletes the peak that is highlighted in Calibration Peak selecti
27. sends out a trigger pulse see figure 24 This pulse is transmitted to the control unit where a new pulse is generated by the digitizer trigger delay see appendix 12 This new trigger pulse is then used to synchronise the electronics 15 10 Trigger pulse from the laser To the controle unit ms 1 2 3 4 Trigger pulse from the controle unit To the controle detector electronics Laser pulse Signal from the detector Signal from the detector electronics us 35 Figure 24 The trigger pulses 18 4 System design 4 6 Detector electronics The detector electronics will amplify the signal from the detectors integrate the signal and hold the value until the computer reads it this has to be done in synchronisation with the laser Details about the detector electronic are found in appendix 11 4 6 1 Basic design In the lorry the voltage is 12V This voltage is transformed on the circuit board to 5V that is used as input by the components see appendix 11 The pulse from the detector has to be amplified A preamplifier does this see figure 25 The signal from the preamplifier is then integrated with a standard integrator see figure 26 After the integrator the signal is again amplified by a follower see figure 27 R2 AA Amplification R1 R2 R2 Figure 25 Preamplifier Output 1 RC fu dt Figure 26 Integrator R R2 Output R1 R2 Figure 27 Follower Department of Atomic
28. substances The calibration part of the program can be developed further Today only a simple calibration is done with the program Analyses of what outputs the calibration system could produce should be done From these results further development could be done 4 9 Acknowledgements 9 Acknowledgements I would like to thank my supervisor Dr Hans Edner for all the support and help in this work Petter Weibring and Mats Andersson for their extensive help and support throughout many hard and long moments in the LIDAR bus as well as in the lab Professor Sune Svanberg whose enthusiastic lectures caught my interest for this inspiring subject Camilla Hilld n and Martin Kurdve for their help and encouragement during the writing of this report Bertil Hermansson and Ake Bergqvist for the electronic design and the computer support G ran Werner for his work when manufacturing the calibration unit Department of Atomic Physics Lund Institute of Technology 42 10 References 10 References 12 13 14 15 16 17 18 19 20 2l 22 23 24 255 26 Mats Andersson and Petter Weibring A User Friendly LIDAR System Based on LabVIEW Lund Reports on Atomic Physics LRAP 201 Lund Institute of Technology September 1996 sune Svanberg Atomic and Molecular Spectroscopy page 322 329 Springer Verlag 1992 Mie scattering page 60 61 Raman scattering page 58 59 fluorescence page 47 Figure modi
29. system are J12 used for communication to the control unit and J13 used to connect to the calibration unit Unit J13 Motas J11 Figure 53 The back plane of the power unit The connectors used by the calibration system are J12 and J13 H j Grud 2 B Power ig 1 9 1 J9 l Department of Atomic Physics Lund Institute of Technology To control unit calibration cable Table 7 Description of the connector on the back plane of the power unit A detailed description of what the pins are connected to on the connectors is shown in table 8 and table 9 The wiring in the power unit is described in appendix 5 Power unit wiring The stepper motor driver modules are placed in this unit The wiring from these modules are shown in appendix 6 and appendix 7 Connector Description MS3112E 16 26P Shielded GRD N isiga MooB 7 17 71 Motor B T Signal Signal po pu f Table8 The pin usage of the connector J13 to the calibration unit trj e as E 2 C 46 Appendix 1 The wiring of the system Connector Description MS3112E 18 32S A Shielded GRD PD 4 Signal 7 PC TIO 10 DIO 24 I O MIO 16 I O
30. the experiment is adjusted to fit the table value it is found that the OPO system has an error of about 0 225nm see diagram 6 This value is of the same magnitude as the result from the wavemeter However this does not give the precession of the calibration system It only displays the fact that the calibration system can be used to find the error In the curve from experiment one value seems to be completely wrong value at 448 15nm This indicates that further studies and experiments have to be made on the program 7 5 Summary From these experiments it has been fond that The calibration system can find the NO structure even when the laser fluctuates with about 9090 It is possible to find the NO structure when making a fast scan The OPO system can have a wavelength error with up to Inm A fast scan is necessary when making a rough calibration to be able to find out where to start the fine adjustment It 15 possible to find the error in the wavelength scale of the OPO system Further studies have to be done how to record the data Further studies have to be performed on calibration methods One possible calibration method could be to make a fast scan to find a flank of the NO structure like in experiment 1 Then to make a more accurate measurement around a defined structure Another method could be to record entire structure and then make a convolution with the known table value Comparison between table value a
31. the intensity fluctuated This gave poor results Using one of the detectors as a reference solves the problem with the laser When the beam enters the unit it is divided into two beams One passes a neutral density filter in slide box A before hitting the detector The other beam is used to find out which pulses have the same energy A special LabVIEW program is written for this purpose The program performs in the following way 1 The maximum dispersion on the reference value is entered 2 The average value of the laser beam on the reference detector is measured This value is then used as reference value 3 When a measure button is pressed an average of 10 laser pulses is measured Only pulses for which the reference detector is in the range of the reference value the dispersion are counted 4 The result is displayed and new measurement can be carried out It is found that the detector electronics has output offset To eliminate the effect of offset it is measured and subtracted from the output values 68 Department of Atomic Physics Lund Institute of Technology Appendix 18 Experiment to determine the performance of the detectors Result Experiment 1 Description In this experiment the energy of the laser pulses are changed by neutral density filters in slide box B see figure 61 The outputs are measured for different transmittance of the filters Wavelength 500nm Optical density Transmittance Detector 1 Detector 2 De
32. the threshold The VI also compensates for the offset on the detectors Location Detektor llb Input Parameter DBL The offset on the cell detector De Cell Offset The number of values that shall be measured detector detector have to be within Output The mean value from the cell detector The mean value of the divided signals L Info 1n Number Of Points Ref Offset Threshold 96 Info Cluster 00 2 TRUE if the collection of data was successful otherwise FALSE detector Get Detector Signal With Threshold and compensated Description Returns the mean values for the measured signal from the detectors As input this VI must have a reference value The VI will only records the signals for which the value from the reference detector is within the threshold The VI also compensates for the offset on the detectors and compensates for the detector characteristics Location Detektor llb Input Parameter Typ Description Cell Offset DBL The offset on the cell detector InfoClster __ Tvpe Number Of The number of values that Points shall be measured detector Threshold DBL Threshold for which the ref detector have to be within Department of Atomic Physics Lund Institute of Technology Output cell detector The mean value of the divided signals BL Description Info Cluster Ref D The mean value
33. to 1100nm Other alternatives could be the S3590 05 or 3590 06 from Hamamatsu 15 These detectors are fast and big enough 9x9mm If the S3590 06 is chosen it could be used between 190nm to 1100nm One problem with this detector is that it does not have any protection window This would make it sensitive to humidity and human touch To get around this problem a quarts window with good quality could be mounted in front of the detector One detector that would work is the 2 Watt Broadband Power Energy Meter from Melles Griot 16 This detector can measure from 200nm to 20um i e more than enough It works with frequencies up to 60Hz The problem with this detector is that it can not be connected directly to the computer It comes with a control unit Another problem is that it needs rather high pulse energy High pulse energies can cause stimulated emission in the gas cell that disturbs the measurement The detector from the old calibration unit 15 the 51337 1010BQ from HAMAMATSU for detailed data see appendix 17 This detector is too slow to measure the actual pulse When looking at the output from the detector in an oscilloscope it is found that the length of the pulse is some but it is know that the laser pulse is some ns long But since it is the absorption and not the actual energy in the pulses that 15 of interest it is possible to use this detector In an experiment that was performed it was shown that the two detectors are
34. to create multiple data paths and simultaneous operation This is a totally different programming method compared to the sequential structure of a text based language This is also a more realistic and logical programming method when creating programs for a lab environment Even in a data flow program some tasks have to be executed in a sequential order This is achieved by having one or several data flows that tie the sequence together see figure 12 While loop Case Data Flow Wire SubVI Figure 12 example of data flow programming The sequence is determined by the two flows starting with Calib in and info in In the example the program starts with two parameters Calib in and Info in The data flow from these two parameters controls the main sequence The while loop and the VI OK cancel Box can execute independently of each other but the case can not start until the while loop as well as the VI have finished their tasks Department of Atomic Physics Lund Institute of Technology 2 4 Laser theory In the LIDAR system a tuneable laser is required to perform the measurements Historically pumped dye lasers have been used for the tuning The problem with them is that many different dyes are required This since one dye only has a limited tuning range Another disadvantage is that several dyes are toxic In the modern LIDAR system an OPO system is used as laser source The advantage is that it can tune over a
35. will occur OV on OUT and 5 on inverse OUT Department of Atomic Physics Lund Institute of Technology The wheels in the unit are added with a peg or a hole that will block or let the light pass when the start position 1s found 4 12 Power unit The power unit consists of several components to control and power the different parts of the LIDAR system see figure 30 It is connected to the control unit as well as to the calibration unit For additional information about the components in the unit see 1 For the calibration system the unit has been fitted with Stepper motor board motor 5 to 8 to steer the motors in the calibration unit e Connector to the control unit for cables related to the calibration system e Connector to the calibration unit Additional power supply to the stepper motors 4 13 Control unit From the control unit the different components of the LIDAR system are controlled In this unit there are connection boards for wiring to the AT MIO 16 and the PC TIO 10 in the system computer See figure 31 For additional information about the components in the unit see 1 For the calibration system the unit had to be added with e Connector to the power unit for the cables related to the calibration system BNC connectors from the detectors in the calibration unit 4 14 System computer A PC is used to run the calibration system This computer is equipped with several PC cards to be able to s
36. with an OPO system the MOPO 730 from Quanta ray For details see appendix 13 Optical component that reflects the laser beam Laser beam Mirror Beamsplitter Filter Mirror Figure 21 Principal sketch on the calibration unit Department of Atomic Physics Lund Institute of Technology 15 4 System design 4 System design 4 1 Introduction This section describes the components electronics and the communication in the calibration system It also describes how and why the parts have been designed or selected 4 2 General To be able to choose components and design the electronics one has to understand the purpose of the measurement what will be measured and what problems arise when measuring 4 2 1 Purpose The purpose of the laser calibration system 15 to find the deviation in frequency wavelength between the laser s setting value and its real value This is achieved by comparing the spectrum of a known and well defined vapour in a gas cell with the results from a measurement Le measuring an absorption spectrum in a region where the physical data is known for the vapour When designing and selecting components for the calibration system it is important to know what should be achieved At a first glance it may seem like it is the energy of every pulse that is important to measure But in this case the absorption is relevant Knowing the exact energy of every pulse may give more information bu
37. 0 9 0 126 0 968 0 965 0 93 0 117 0 906 1 0 100 0 806 0 795 1 1 0 079 0 655 123 0 050 0 416 0 455 1 4 0 040 0 341 0 032 0 251 0 235 Table 23 Table of the detector characteristics of detector 1 Nr 3 Output V 4 477 4 362 3 888 3 598 2 799 2 620 characteristics detector 1 4 5 w gt ip ub Output V N eo N EN N o e A 0 6 Transmittance Diagram 10 77e detector characteristics of detector 1 Department of Atomic Physics Lund Institute of Technology 1 2 Nr3 Obtained T2 Appendix 18 Experiment to determine the performance of the detectors Detector characteristics detector 2 Description To record the characteristics of detector 1 the energy in the pulses is adjusted until the output has a value of 4 2V This is done with neutral density filters in slide box B see figure 61 The energy in the laser pulses is changed by neutral density filters in slide box A Detector 1 is used as reference Recording Nr 1 Nr 2 Nr 3 Nr 4 Optical Transmittance Output Output Output Output density V V V V 0 1 4 237 4 216 4 1812 4 09 0 03 0 933254 4 197 4 161 4 1112 3 97 0 1 0 794328 3 947 3 67 3 7712 3 56 0 13 0 74131 3 547 3 502 3 2912 3 35 0 3 0 501187 3 187 2 754 2 4812 2 54 0 33 0 467735 2 747 2 484 2 3412 2 36 0 4 0 398107 2 387 2 274 2 0912 2 16 0 43 0 37153
38. 1 274 0 6 0 251 0 910 1 745 1 670 1 080 0 630 1 144 1 081 0 8 0 158 0 625 1 195 1 155 0 752 0 462 0 880 0 833 0 9 0 126 0 525 0 965 0 925 0 620 0 385 0 815 0 705 1 0 100 0 425 0 820 0 798 0 501 0 343 0 653 0 603 Lo 0 032 0 191 0 350 0 360 0 228 0 154 0 190 0 199 Table 22 Result from experiment 3 Experiment 3 1 W 500 R 3 4 Nr2 W 500 R 5 7 3 W 448 R 5 7 4 W 448 R 3 4 c 5 W 448 3 4 6 W 448 R 10 7 W 448 R 10 Output V 1 0 0 2 0 4 0 6 0 8 1 1 2 Trancmittance Diagram 9 Resutl from experiment 3 7 Department of Atomic Physics Lund Institute of Technology Appendix 18 Experiment to determine the performance of the detectors Detector characteristics of detector 1 Description To record the characteristics of detector 1 the energy of the pulses is adjusted until the output reaches a value of 4 4V This is done with filters in slide box B see figure 61 The energy in the laser pulses is changed by neutral density filters in slide box A Detector 2 is used as reference Recording Nr1 Nr 2 Optical Transmittance Output Output density V V 0 1 000 4 484 4 478 0 03 0 933 4 396 0 1 0 794 3 826 3 945 0 13 0 74 3 576 0 3 0 501 2 766 2 765 0 33 0 468 2 614 0 4 0 398 2 316 2 285 0 43 0 372 2 146 0 5 0 316 1 806 1 790 0 53 0 295 1 696 0 6 0 251 1 506 1 505 0 63 0 234 1 426 0 8 0 158 1 146 1 145 0 83 0 148 1 071
39. 4 3uounedo q Shield GND nto Coupler amp signa pto Coupler3 signa atar Hotor B Motor 2 f Motor 2 8 R B Motor 2 notar 1 Motor 1 Qpta Coupler GND to Coupleri signa Misi na etector GND Jetector Supply Qpto Coupler 4 5V pto Coupler 3 51 Motor 4 4 0 2 0 Motor 1 Motor 1 0 Opto Coupler 1 51 pto Coupler 2 51 delector Supply 3Y Motor 3 Motor 3 B Motor 3 Mator 3 D Defectori Signal Out C Defector2 Signal o Trigger Puls in 17232 se cS NN il 3 HE Aia mma a ea onnection Board 3 _ 4 00009 N XS C A02uzZr xcrommoom INSTITUTE TECHNOLOGY 3 PHYSICS 4 PST son P2M8 18 12 SHEET 1 p xipuoddy Iun uo 1 SUTITA ZUM PUN p xipueddy So ouuoo Jo oinjsu 015404 21 jo 1uounedoqq S Shield GND Opto Couplert signa Opto 4 A Motor 4 Motor 2 f Motor 2 Motor 2 Motor 1 Mator 1 Opta Coupler GND Opto Coupleri signa to Coupnler2 signa Ue C 23 3292 tector Detector Supply 5V pto Coupler 4 5Y Qpto Coupler 3 51 Mator 4 C 4 Opto Coupler 1 5Y Op
40. 5 2 242 2 184 1 9712 1 97 0 5 0 316228 1 742 1 82 1 6612 0 53 0 295121 1 717 1 5712 0 6 0 251189 1 557 1 53 1 4412 0 63 0 234423 1 437 0 8 0 158489 1 167 1 17 0 83 0 147911 1 137 0 9 0 125893 0 992 1 032 0 93 0 11749 0 947 1 0 1 0 877 0 88 0 79 1 1 0 079433 0 717 1 3 0 050119 0 487 0 54 1 4 0 039811 0 372 1 5 0 031623 0 277 0 31 0 267 1 6 0 025119 0 207 1 8 0 015849 0 132 0 24 1 9 0 012589 0 102 Table 24 Table of the detector characteristics of detector 2 Characteristics detector 2 2 IL REL 5 M DR UM ILE 229 2 BF Output V 0 0 2 0 4 0 6 0 8 1 1 2 Transmittance Diagram 11 77e detector characteristics of detector 2 73 Department of Atomic Physics Lund Institute of Technology Appendix 18 Experiment to determine the performance of the detectors Obtained detector characteristics Description The obtained values received from the recording of characteristics for detector 1 and 2 The Curves for these values are shown in the diagram 10 and diagram 11 above Characteristics of detector 1 Characteristics of detector 2 Nr Output X value Transmittance Converted Output X value Transmittance Converted V l 0 00 0 00 0 000 0 000 0 00 0 00 0 000 0 000 2 0 10 0 53 0 013 0 053 0 14 0 62 0 016 0 062 3 0 14 0 70 0 018 0 070 0 23 1 00 0 025 0 100 4 0 20 1 00 0 025 0 100 0 28 1 20 0 030 0 120 5 0 24 1 18 0 030 0 118 0 39 1 60 0 040 0 160 6 0 34 1 60 0 040 0 160 0 50 2 00
41. 5 recorded Output from detector V N gt N 4 RE TORT eee 447 3 447 5 447 7 Diagram 4 Data from experiment 2 Experiment 2 447 9 Wevelength nm For each measuring point the mean value of 5 laser pulses was recorded Number of measuring points 256 Scan region 447 300 nm to 448 320 nm The result from the experiment is found in diagram 4 and diagram 5 Cell output Ref output _ Cell Ref E Comparison between table value and measured absorption Adjusted data 447 3 447 5 447 7 447 9 448 1 Wavelength nm Cell Ref Adjusted Table value 448 3 448 5 448 7 Diagram 5 Comparison between the table value and the measured absorption for NO The scale for the two has been adjusted to be able to see the structure easier The table value is adjusted to air wavelength Department of Atomic Physics Lund Institute of Technology 39 7 Evaluation 7 4 Discussion Looking at the result from the first experiment it can be seen that it is possible to se the rough outline of the NO2 structure see diagram 3 This even though the laser energy is fluctuating with about 90 It is also possible to see that the wavelength scale of the OPO system has an error with about 0 2nm In the second experiment it is clearly seen that the unit can record the NO structure If the wavelength scale from
42. Development and construction of an automatic calibration unit for a differential absorption LIDAR system Diploma Paper by Fabian Lund Reports on Atomic Physics LRAP 264 Lund October 2000 Abstract Abstract This diploma work is part of a larger project in the development of the LIDAR system at the Department of Physics at Lund Institute of Technology The LIDAR equipment which is used for environmental measurements operates like an optical radar Pulsed laser light is sent through the atmosphere and back scattered light carries information about the elements in the air The purpose of this part of the project is to automatize and improve the wavelength calibration for the laser This will lead to more accurate results in LIDAR measurements Today the calibration system has been constructed and the program and unit have been integrated to the main LIDAR system The system is fully implemented Department of Atomic Physics Lund Institute of Technology Table of contents Table of contents ABSERACT imm IU LA e CEU E 2 COIN TEN PTT 3 INTRODUCTION ova eee Ens 6 NDS mL 6 RA ESI TON 6 ie SOL 6 LA FE PROGRESS OF
43. File Types out File Types in If true the VI is allowed to overwrite older file File Types Cluster Info Cluster Info out Delete Cell Description Deletes a cell form the array in the Calib cluster Location Array Functions llb Input Calib Cluster Cell Pos Integer The position of the cell in the Calib cluster Info Cluster Output I Pe oe cee Calib Cluster Delete Peak From Cell Description Deletes the data for one peak for a cell Location Array Functions lIb Input Type Description Calib Cluster The position of the cell in the Calib cluster Infoin_ InfoCluster_ The position of the peak in the peak array for the cell Output Calib Cluster Info Cluster Appendix 19 VI and cluster description Dialogue Box With OK Description Displays a message Location Popupp llb Input Infoin InfoCluster Output Info Cluster Dialogue Box With OK and Cancel Description Displays a message Location Popupp llb put InfoClster Message to display Info Cluster OK out Boolean TRUE if the OK is pressed otherwise FALSE Edit Peak Data For Cell Description This VI is used to configure the calibration parameters for a cell Location Spiece llb Input Calib Cluster Cell Pos In Integer The position in the Calib Array cluster of the cell for which the p
44. I is called from Cell Selection see section 6 3 2 2 the cell data that are changed or added is stored in the When called the front panel of the VI is displayed This Cluster This is done instantly when the change is screen will be open until the OK button is pressed or until made The screen is also updated when changes are made an error occurs In this way the screen and the Calib cluster are always mirrors of each other Because of this relation the index of the highlighted field is used directly when operations Initialisation of the VI Printing of data to screen Wait for user input Printing of data to screen Error message cell in the revolver cell in the revolver Error message Display message to hange the cell Change pressed Rotate the Revolver Rotate the Revolver Is cell in place Printing of data to screen Edit Peak Data VI ancel Pressed Display message to emove the cell Remove pressed Edit box for new name New Cell pressed Change cell data pressed Display Error message to screen Printing of data to screen Printing of data Delete Cell to screen pressed 4 Reset the UNIT pressed Warming message celi in th revolver Change the default peak Meka Peak Defult pressed Reset UNIT pressed Position in the revolver has changed Printing of data to
45. NoErrorCheck The difference between these is that the first one also checks if there are any errors in the Info cluster For further information see appendix 19 The first thing done when a VI is called is to check if every thing is OK This is done as in figure 38 In For and While loops the ContinueExecNoError Check 15 used see figure 39 6 2 2 2 Input screens The performance of the input screen is achieved as seen in figure 40 First the VI checks if it shall execute or not Then the VI is initialised After this two loops are started The lower loop is responsible for collecting the user input i e which buttons are pressed on the front panel The upper is responsible for performing the tasks related to the button pushed An occurrence object achieves the synchronisation of the loops The upper loop enters the default case where it waits for occurrence from the lower loop Every 200ms the lower loop checks if any button is pressed If a button has been pressed the variable execution frame 15 set to the case number that shall be executed by the upper loop and the occurrence is generated After this the lower loop waits for the occurrence from the upper loop The upper loop performs its tasks and when ready it returns to the default case Here it generates the occurrence so the Cont EXEC Error Figure 38 Before executing the code the status is with ContinueExecErrorCheck EXEC Err Figure 39 for every
46. P 730 Laser Specification 21 Beam shape typical ound 20 Department of Atomic Physics Lund Institute of Technology 61 Appendix 14 Stepper motor Appendix 14 Stepper motor Two phase stepper motor of hybrid type The motor can be driven in unipolar or bipolar mode 18 The specified torque is in unipolar mode 5090 of the windings are used When the motor is configured in bipolar mode the current must be reduced with a factor 0 6 to 0 7 or else the motor will be overheated The stepper motor uses the Bipolar stepper motor drive module shown in appendix 15 Technical data No of phases 2 No of windings 4 Torque 550 mNm No of steps revolution 200 Stepper angle 1 8 Axis diameter 6 35 mm Currency phase 1 2 Resistance phase 50 Inductance phase 8 5 mH Temperature range 10 to 50 C RED BLACK OA WHITE READ B OB WHITE GREEN Figure 55 Stepper motor KP56LM2 502 from ELFA 16 62 Department of Atomic Physics Lund Institute of Technology Appendix 15 Bipolar stepper motor drive module Appendix 15 Bipolar stepper motor drive module The GS D200S driver module can drive a bipolar stepper motor with constant current through a chopper output The module can drive the motor either with half or full step The output current is set in the factory to 2 A but this can be modified between 0 5 to 2 5 A The module also has short circuit protected outputs For more detailed infor
47. PENDIX S POWER UNIT WIRING S entente 53 APPENDIX O STEPPER MOTOR BOARDS vl ot teinte quite adi se 54 APPENDIX 7 STEPPER MOTOR BOARD sten Daun Vased ubt tai fedele npo eet rosa dele 35 APPENDIX S CONTROL UNIT WIRINGTMIOsTODD iecit EH CH TECH RS Po 56 APPENDDCO CONTROL UNIT WIRING DIO 24 Pola tape Det ui da b eve und Poids 57 APPENDIX 10 POSITION DETECTOR ELECTRONICS 58 APPENDIX LL DETECTOR ELECTRONICS 59 APPENDIX 12 DIGITIZER TRIGGER DELAY De eas 60 APPENDIX 13 THE MOPO 730 LASER 220202 evo ae veo te ebore 61 APPENDIX STEPPER MOTOR mat ee edet n Loco 62 APPENDIX 15 BIPOLAR STEPPER MOTOR DRIVE MODULE 1 1 6 esses 63 APPENDIX 16 PICTURES FROM THE LIDAR BUS 0 0 22 000 11 e iren esses nne einen nen 65 APPENDIX 17 DETECTOR THAT IS USED IN THE CALIBRATION UNIT ntn nnne enne 67 APPENDIX 18 EXPERIMENT TO DETERMINE THE PERFORMANCE OF THE DETECTORS 68 P RII NERONE T 66 TENET TIN ONL 68 WO 69 TORONTO etat c D
48. ab Figure 60 Working with the calibration unit Department of Atomic Physics Lund Institute of Technology 66 Appendix 17 Detector that is used in the calibration unit Appendix 17 Detector that is used in the calibration unit The detector used in the calibration unit is the silicon photocell S1337 1010BQ from Hamamatsu Below follows the information about the detector 22 15 Photosensitive Package Characteristics at 25 Surface mm Size Effective Spectral Response Typical Radiant Sensitivity A W mm Area Range mm nm Wavelength Wavelength 254nm W Hz emeHz 2 W nm 633nm 930nm 101x102 98 15x16 5 Table 18 The characteristics of the detector 1337 1010BQ Characteristics at 25 Absolute Maximum Rating Short Circuir Current Dark Temperature Shunt Resistance Junction Rise Reverse Temperature Range Time tr Voltage 2856K 100 Current Dependence Capacitance at of Va 710mV Cj at V4 0V A A C C 65 80 50 115 002 01 110 3 5 10 560 20 80 Table 19 The characteristics of the detector 1337 1010BQ NEP Noice Current 2 Radiant Sensitivity at Peak A W T D Effective Sensitiv Area cm NEP Rg 10 mV Dark Current at V 10mV t isthe time required to transition from 10 to 90 of the normal height l
49. able of contents SUSERAMANUAE aaa HH nude denne uam NU se 23 3 INTRODUCTION Tp 23 DL CONFIGURATION PART NE 23 2 2 23 22a hange m ealan On UnU mm 24 IAN CENONE CAN 26 0 PROGRAMMER S GUIDE sunra bunian E R 27 TRODUG ON EE E O NE 27 Or BASIC CONG US _64 24 QUA MIT OI TTE EET 27 OZ A Das CSI OU 25 6 22 LS topping the S 27 622 2 nb MEI EM 27 02 23 Synchronisation Th the progra oss cob eet t etes i UE 28 o2 24386 Info e steed abaci feb Eisen udis UR o 28 2 2 5 Te Rus ML Eo C 29 p 2 2 60 THE dato C RR cnm 29 6 22 Ehe elata SIC enm br 29 Data P 29 6 2 2 9 Paramelersdan tlie POOR ama cel cs 30 CALIBRATION PROGRAM Re 31 Os MEL qued M 3l 0 2 FloWwehartscol malt COMPONCIIS cc
50. alibration program Calibration Method 0 Calibration Method 1 Calibration Method 2 31 6 Programmer s guide 6 3 2 Flow charts of main components This section describes the main program The flow chart objects that are used are mainly standard objects The objects used are displayed in figure 45 6 3 2 1 Main flow chart The main components of the program are displayed in figure 46 The figure shows the two parts of the calibration program the configuration part and the calibration part The main LIDAR program shall during normal operation call the configuration part The calibration part is also called from the main application This can be done whenever it is necessary Since this part is a separate component other interfaces can be constructed to use it 6 3 2 2 Current calibration settings This VI is the entry point to the configuration section of the calibration program The VIs front panel is the user interface for selecting which cell shall be used when calibrating the laser See picture 47 The name of the VI is Cell Selection This VI shall be called with a regular interval from the main program No all the initialise Yes Initialisation of the V Change EN pressed urrent cel s change Set parameters Clusters Print of data to screen The first time the VI is called a parameter shall be set so the program know
51. and data of the calibration program That is the current position of the revolver position of the detector etc It also carries the data used by the calibration part to make the calibration The different parameters are explained in 6 2 2 7 The data structure Department of Atomic Physics Lund Institute of Technology d cont ExEc gt 3 Wo Err Current Detector Posl 00000 W avelen eor D 00000 os ES bark OF Scan sue Current FilterPosp 00000 _ End OF Sean Rev Pos a E Detector T E h Ew Abd Calib Splitter 0 be TestModel 220 Figure 41 The parameters used by the calibration program in the Info cluster 28 6 Programmer s guide 6 2 2 5 The File Types cluster This cluster contains the data needed when making file transactions See figure 42 This cluster is only passed on to VIs that need to save or retrieve data from the calibration file More information about saving the calibration data is found in section 6 2 2 8 Data storage Parameters used by the calibration program Calib Data File Path The file path to the calibration data file The path includes the file name Cell The data format that 15 saved to the file The information is in the same format as for the Calib cluster see 6 2 2 7 The data structure Cell Refnum A position reference used by La
52. andle graphics The Macintosh computer platform was the only one where LabVIEW could perform properly During the 1990 s the PC computers began to be powerful enough and when Microsoft launched Windows 3 1 it was possible to run LabVIEW on a PC The development of LabVIEW is seen in figure 8 Top Level Front Panel m File Edit Operate Controls Windows Text Help a enl 22 25 9 igne Frequency 1000 Cut Off Frequency 50 00 50 H 0 00 Signal after filte Filter Order Controls Sub VI Extract sinewave lowpass Icon uniform noise sequence filtering the noisy signal Front Panel Control Top Level Block Diagram Operate Functions Windows Text Help e AB Generates an artay containing a sinusoidal pattern Another big problem was the speed of the program In 1986 when a new version of LabVIEW 1 was launched the speed of the program was equivalent to BASIC But some applications could be up to 20 times slower Today these problems are overcome The execution speed of the program 15 determined by the C compiler alone LabVIEW Product History 1996 1996 LabVIEW 4 LabVIEW for Win95 Designed For You 1994 Customizable Interface LabVIEW for HP UX Add On Toolkits 1994 LabVIEW 3 x LabVIEW for HP UX Add On Toolkits September 1992 LabVIEW for Windows LabVIEW for Sun
53. as with a known absorption spectrum From this vapour you take up an absorption spectrum The measured spectrum is compared to the known spectrum for the gas By comparing the two it is easy to determine the wavelength inaccuracy of the laser The normal case is to try to find one absorption maximum for the gas An example would be to scan over the peak at in figure 3 When the max value is found the wavelength displayed by the laser is compared to the known table value Even if the principle is simple it is hard to accomplish There are lots of obstacles to overcome The laser energy is fluctuating the detector characteristics are not linear and so on The biggest problem 15 that it has to be done automatically by a program and not by a person A person knows what is needed to find in the spectra to be able to calibrate he knows when to ignore values that are out of bound and so on The program has to be made robust so it always is able to calibrate Since every absorption spectra is unique a variety of calibration algorithms are possible The one developed in this project is described in the programming documentation The principle of the calibration unit The principle of the unit 15 shown in figure 21 A laser beam is directed into the unit The beam is split into two One of the beams passes through the known gas cell Department of Atomic Physics Lund Institute of Technology beam and the other is directed straight to a d
54. ata for the new cell will be displayed Change button This button is used when the configuration in the calibration unit is to be changed When pressed the Change in calibration unit front panel will be displayed oe Cun rre nt E Change poo Wavelength or on n Wavelength off Calibration mode Detector T Beam spliter m A Figure 32 Front panel of the Current calibration setting Current Cell m NO2 Wavelength on Wavelength off Calibration mode D etector Beam splitter Ch ange Figure 33 Front panel when changing the cell 23 5 User manual 5 2 2 Change in calibration unit This module makes it possible to change the cells in the calibration unit se figure 34 Calibration Cell selection box Displays all the calibration cells that are defined in the system Cell in Revolver selection box Displays all the cells that are present in the calibration unit Calibration Peak selection box Displays all calibration peaks for the cell that is highlighted in the Cell in Revolver selection box Change Data button This button is used if the calibration data for a defined cell 15 to be changed To change the data the cell has to be highlighted in the Calibration Cell selection box When the button is pressed the program will open the front panel for the Change Calibration Data New Data button This but
55. auredo LS NE ONE our A ne otor 1 Step Hotor 1 Dir Motor 2 Step Motor 2 Dir Motor 3 Step Motor 3 Dir Qpto Coupleri Signa Motor 4 Step pto Coupler d igna Datector 1 Signal H Detector 2 Signal FLAT CABLE CONNECTOR 58 10 18 14 SHEET 1 Sura pun 6 xipuoddy FC OIQ yun o guo 6 Appendix 10 Position detector electronics Appendix 10 Position detector electronics gt e pe e gt Bedifisstiu detur 2888 18 12 5V OUT OUT GND m o o 58 Department of Atomic Physics Lund Institute of Technology Appendix 11 Detector electronics Appendix 11 Detector electronics gt e ce X Ls 4 12 SHEET 1 OF 1 oF PHYSICS eMe lector Electronics Led T gt pese in ALY am 138 440 ajs gt Lir 213 rr in in an i 3 I E po in l ALY gt gt T 5 T nij 3 9 k a D gt AL 5
56. bVIEW when reading and writing to the file 6 2 2 6 The Calib cluster It contains all the data that 15 necessary to configure the calibration unit i e the data for every cell of vapour the calibration peaks for the cell the detector and splitter settings See figure 43 File ie Types in DM Calib Data File Path a info File Path e a Cel Measurement Info Maas rement Intnl Measurement 5 Fie Path Raw Data Fie Path It is important to see the cells detectors and beam splitters as physical objects Each cell that is defined in the system shall have a physical cell For this cell many different calibration regions peaks can be defined The different parameters are explained in 6 2 2 7 The data structure 6 2 2 7 The data structure The structure of the data in the program is shown in figure 44 In this figure the dependency between the clusters is shown For detailed information about the different elements in the clusters see appendix 19 VI and Cluster description 6 2 2 8 Data storage Three things are important when designing data storage 1 The configuration should not be lost when the program is terminated 2 Dynamic data shall be easy to change 3 All dynamic data are retrieved at a restart When looking at these three criteria it is found that the dynamic data are the cell data with all the peaks the calibration data together with which cells are present in th
57. bration shall be made 3 Select lower optical density with the filter wheel until one of the detectors has an output larger than 1V Use this detector to find the maximum energy in the pulse 4 Select the filter with the lowest optical density but for which the output on the detector is below 4 1V Now there is as much dynamics as possible in the system Check that the other detector is within the acceptable region 0 5V to 4 1V Record the offset from the two detectors 7 When doing the scan compensate for the offset and then use the conversion tables for the detectors 73 Department of Atomic Physics Lund Institute of Technology Appendix 18 Experiment to determine the performance of the detectors The set up for neutral density filters in the filter wheel the table show the values for the magnitude of two powers of ten E 100 1 0000 31 i cu d NENNEN NENNEN gt XN NES 1 MEAM NER NINE adsom es o Table 26 The set up for the neutral density filters Department of Atomic Physics Lund Institute of Technology 76 Appendix 19 VI and cluster description Appendix 19 VI and cluster description The VI s ea aai Um sop Maeva nee d ORAE RED Check If Array Pos OCcupted u us cose ete eee Check IT RI Cela idee ips Check If Rev
58. c Physics Lund Institute of Technology Appendix 7 Stepper motor board Appendix 7 Stepper motor board gt e Li CS 83 23 88 o wu 55 Department of Atomic Physics Lund Institute of Technology K So ougoo Jo pun sorsAuq oruojy Jo 1usuniedo q 95 LONE La 1 s e 7 9 53112 16 265 Shield GND otar 1 Step 1 Dir Motor 2 Step Motar 2 Dir Hotar 3 Step Motar 3 Dir Opto Cauplerl Signat 0pto Caupler3 Signal 4 Motor END Motor 4 Step Hot i pto Caup an Mr pto Coupler GND C D E F G H J K L M N P R S 1 U V X Y Z a b BNC Detector 1 Signal p gt BNC Detector 2 Signal 9 COMMON GROUND ORE BLK E 2 DACS 0 DAC 0 0 161 0 CONNECTOR BOARD FLAT CABLE CONNECTOR 58 POL 0 0 13 UT UT mnc REC di FLRT CRBLE JUIUN 0101 80101 10102 58 1 INSTITUTE OF TECHNOLOGY PHYSICS LUND 18 12 SHEET 1 1991 yun 0210 8 xrpuoddy IG9T OIIA pun 8 Jo ojnjnsug pun 21 Jo ju
59. control unit is shown in appendix 8 and appendix 9 47 Appendix 1 The wiring of the system Connector connection MS3112E 18 board 32P eee MEN eee aCe MM 2 __ Motor 1 Step ___ ____ _8 Motor 2 Step __ 9 2 MEMINI M ERE B5 NM __ 4 _ ______ Table 11 The pin usage of the connector J20 to the power unit J12 ae MOSS 7 BO 31 Optolsignal M AO 47 Step motor 5 BONNER DM Table 12 Connectors used by the calibration system on the DIO 24 I O connector board Department of Atomic Physics Lund Institute of Technology Mio 16DL To device Connector J14 ACHA Detector 1 Cell BNC J19 ACHS 13 Detector 2 Ref BNC 718 Table 13 Connector used by the calibration system on the MIO 16DL connector board 6 System computer The system computer is used to control and acquire data from the calibration system To perform this the computer is equipped with two PC cards the AT MIO 16 and the PC TIO 10 from National Instruments 7 These cards are connected with a flat cable to the control unit The pin description of these cards are found in table 14 and table 15
60. e 2 and the ground state is a so called forbidden transition An electron in excitation state 2 will therefore remain in this state If a photon passes with the same energy as between state 2 and the ground state the photon will make the electron recombine to the ground state 3 This will result in two coherent photons with the same energy wavelength i e light has been amplified 9 A dye has an energy level band structure instead of distinct energy levels see figure 15 Due to this band structure the laser light is tuneable Electrons are pumped from the ground state to the upper energy band From this higher level the electrons can recombine to any level in the lower band This gives a broad fluorescent signal By using a wavelength dispersive element the laser light can be to any wavelength within this fluorescent band 2 4 2 The OPO theory The gain on an OPO system is derived from the non Figure 15 Principe of dye laser linear interaction between an intense optical wave and a crystal having a large non linear polarisation In principle this means that an incoming photon from the pump laser is transformed into two photons in the crystal see figure 16 The difference between this process and the laser process is that it does not require a real atomic or molecular 5 Variable 0 410 690 nm signal 730 2000nm idler NNN 355 nm BBO Op Pump Beam Figure 16 Principal operation of the OPO 10
61. e been defined this calibration will be done For more info ne see Cluster of Peak Data Pos in The position the cell has in the revolver If Revolver the cell is not present in the revolver the value is 1 This value is saved to file through the File Types cluster When the system is started this parameter makes it possible to find how the unit was configured when it was last in action Cluster of Detector Data Description This cluster contains the data needed for the detector Location Controls lIb Parameters The name of the detector OFF the detector stops to work This is the wavelength in nm for which ON the detector starts to work Cluster of File Types Description This 1s the cluster used when saving and retrieving data from file This cluster contains information for all the elements that are saved fin the LIDAR system In this description only the parameters used by the calibration program are explained For additional information see 1 Location Controls llb Parameters File Path The path includes the file name Cell The format of the data that 1s saved to the file The information has the same format as for the Peak Data For more info see Cluster of Peak Data when reading and writing to the file Cluster of Peak Data Description This cluster contains all the parameters for one peak This is also the data that is used when calibrating Location Controls llb Parameters Calib Th
62. e calibration program is explained For additional information see 1 Location Controls llb Parameters Calib Cell The revolver position of the cell for which Rev Pos the calibration shall be done The calibration data that is to be used for this cell is the default data for the peak This data is stored in the Peak Data The position of the detector that shall be used when calibrating using the cell selected in Calib Cell Rev Pos When selecting a cell the default data for this cell determines which detector shall be used The position of the beam splitter that shall be used when calibrating using the cell selected in Calib Cell Rev Pos When selecting a cell the default data for this cell determines which beam splitter shall be used Detector Pos the calibration unit Filter Pos wheel currently has in the calibration unit Pos the calibration unit Splitter Pos has in the calibration unit error have occurred Peak Data This is the data that is used when calibrating This data is the same as the default data for the cell that is selected in Calib Cell Rev Pos The data 15 stored in Peak Data format For more info see Cluster of Peak Data This parameter is used to indicate that the Calib Detector Pos Calib Splitter Pos program is run in test mode If it 1s set then the program can run on a stand alone PC i e with out being connected to the calibrati
63. e revolver When restarting the program these data need to be retrieved The of a cell in the revolver is stored in the F Pat 2 T D AABAAAP 15 i HH d flot atti n NC EE HE eu Deco emere mh ces i Measurement 00700 Figure 42 The parameters used the calibration unit the File Types cluster Department of Atomic Physics Lund Institute of Technology 29 6 Programmer s guide Cell cluster in the array of Cells in the Calib cluster see figure 44 This Cell cluster is saved to disk The data for the detectors and beam splitters are static data i e the data does not change often For this reason the data are not stored on disk but are instead hard coded in the initialising section of the program 6 2 2 9 Parameters in the program To be able to run the program some parameters have to be defined For detailed information on the parameters that can be set see appendix 19 VI and Cluster description The configuration of the parameters has to be done for e Initialising of the unit Configured in VI Init Calibration Unit Checking calibration data Configured in VI Check Peak Data e Finding motor position 0 Configured in VI Find Motor Pos 0 e Moving a motor Configured in VI Rotate Selected Motor To e Changin
64. e transmittance of the neutral density filters in the filter wheel was found The wheel should be able to reduce the intensity over an as large region as possible At the same time the number of filters can not be too many The values shown in the summary give a resolution of about 0 8V electronics have some offset that has to be compensated for Measuring the offset before a measurement can do this The characteristics of the detectors were then recorded This was done to be able to use the entire span from 4 1V to 0 5V During this recording the laser became worse This made the recordings on the second detector bad Even so a conversion table was made for this detector This table will make the measurements better but not perfect It is important to remember that the calibration unit will not measure the exact absorption it will only find an absorption peak This implicates that the conversion table will make the measurements better From these recordings it was also decided that detector 2 would be the reference detector When using the results from the experiment the procedure for calibration could be determined see summary Summary Detector 2 is to be used as reference detector From this experiment the following was determined when making a calibration 1 Let the filter wheel start with as high optical density as possible i e as dark as possible 2 Let laser go to the minimum absorption around the region were the cali
65. e type of calibration method that shall Selector be used for the peak The parameters for the peak can be used differently depending on which calibration method that 15 used Diff Abs The differential absorption cross section for the peak End Of Scan This is the wavelength in nm where the scan shall stop when calibrating 15 Appendix 19 VI and cluster description Scan scan shall start when calibrating The step in nm that shall be used when calibrating If the value 15 not set is should be 1 OFF peak has its absorption minimum ON peak has its absorption maximum Cluster of Splitter Data Description This cluster contains the data needed for the beam splitter Location Controls lIb Parameters The name of the beam splitter OFF the beam splitter stops to work ON the beam splitter starts to work File Type Selector Description This selector is used to inform what type of file that shall be used In the calibration program the type is Cell Data 1 Location Controls llb Parameters Sorting Type of file Selector 0 Info 1 Cell Data 2 Meas Data 3 Raw Data 4 Eval Data 5 Department of Atomic Physics Lund Institute of Technology InfoCluster Description This cluster is the main cluster for the LIDAR system This cluster contains information for the entire system but only the parameters used by th
66. eaks shall be configured Output Calib CalibCluster nfoou Cluster Find Motor Pos 0 Description Finds the starting position for a motor Description In this VI the following parameters are set 1 Maximum numbers of steps per revolution This 15 the maximum number of steps the unit will take for finding the position 0 2 Line for the direction This is the input line to the A T MIO 16D card for the direction of the motor 3 The direction This is the direction the motor shall have when trying to find the position 0 Department of Atomic Physics Lund Institute of Technology 4 Line for the motor movement This is the line to the AT MIO 16D card for moving the motor 5 Line for the location detector This is the line to the AT MIO 16D card for the position detector 6 Trigger flank The appearance of the signal from the position detector when position 0 is found The signal is either Hi or Low The trigger flank can also be configured on the position detector circuit 7 Direction for fine adjusts The directions the motor shall have to fine adjust the position 8 Number of steps for fine adjustment The parameters are found in table 27 The device number and the digital channel for AT MIO 16D card must also be set The values for these parameters are 1 Device number for the AT MIO 16D card 1 2 Digital cha
67. el for the AT MIO 16D card must also be set The values for these parameters are 1 Device number for the AT MIO 16D card 1 2 Digital channel for motors 2 Location Revolver llb Input 1 Revolver motor 6 2 Filter motor 7 Info Cluster 0 24 New Pos Integer The position the motor shall move to Choice Integer 0 Detector motor 5 3 Beam splitter motor 8 Output Department of Atomic Physics Lund Institute of Technology Info Cluster Save All Cell Data Description Saves all the data for the cells Location FileOp llb Input Calib Cluster File Typesin FileTypesCluster Info in Info Cluster Output Cluster ___ File Types out File Types Cluster Info Cluster Save Detector Data Description Saves data from a measurement Location Detektor llb Input Parameter Description Detector detector divided values Cluster Input The wavelengths the Wavelength data has been recorded for to the file detector Output Info Cluster O Select Demp Automatically 2 Description This VI selects the neutral density filters automatically Path The following data are set in the VI 1 No points first The number of points that shall be used when finding the first output This shall be low so the beam can be blocked fast if the intensity from t
68. ell gt 72 MUT ARTE T EE 75 APPENDIX 19 VI AND CLUSTER 1 1 1 71 5 Department of Atomic Physics Lund Institute of Technology 1 Introduction 1 Introduction 1 1 Purpose The purpose of this diploma work is to replace and improve the calibration unit for the laser in a LIDAR system This work is a part of a larger work to improve and automate the LIDAR system at the Department of Atomic Physics at Lund Institute of Technology Previously the laser was calibrated by hand after which measurements were performed During the measure ments the laser can drift for instance due to temperature changes There where no way to know whether the laser drifted during the measurements or not The new calibration system will make it possible to check the calibration whenever desired The department has also replaced the old laser system with a new OPO system This new system sets new requirements on the calibration system The unit must perform in a wider wavelength span For this reason automatic change between optical components in the unit is necessary Another improvement is the possibility to place up to seven cells in the unit This will make it possible to measure on more than one substance during a LIDAR experiment The work will r
69. end and acquire data form the LIDAR system The PC cards used to communicate with the calibration system are the PC MIO 16 and the PC TIO 10 from National Instruments 7 21 4 System design 4 141 AT MIO 161 O PC Card The MIO 16I O PC card consists of 12 bits ADC with 16 analogue inputs two 12 bits DAC s with voltage output and eight lines of TTL compatible digital I O interface This card is used to acquire the analogue signals from the calibration system 1 the signal from the detectors The PC card is connected to the control unit with a flat cable The cable is connected to a 50 pins connector board For details of the wiring see appendix 1 The Wiring of the system Fine 10V 0250 Polarity QW MO 16 I O Rear Panel 6 J19 J18 J11 J10 n SYSTEM 4 J2 LASER J3 110 24 J12 MO 16 J13 Cu PC TIO 10 J14 Figure 30 Overview of the control nit Department of Atomic Physics Lund Institute of Technology 4 14 2 PC TIO 10 PC Card The PC TIO 10 PC card is a timing and digital I O interface It consists of sixteen TTL compatible digital lines ten counters and has two edge sensitive interrupt inputs with programmable edge selection This card is used for the TTL input and out to the calibration system The PC card is connected to a 50 pin connector board in the control unit For d
70. er the cell Appendix 19 VI and cluster description Get Detector For Peak Description Returns the position for a detector that can be used for measuring Location Array Functions lIb Input Description Calib Cluster Info in Info Cluster Wavelength DBL The wavelength for which the detector have to operate for Output Description Calib Cluster Detector String The name of the detector Name Detector Pos Integer The position of the detector Info Cluster Get Detector Signal Description Returns mean values of the measured signal from the detectors Location Detektor lIb Input Description Info Cluster Number Of Integer The number of values that Points shall be measured Output cell detector The mean value of the divided signals BL nfoout InfoCluster The mean value from the ref detector Get Detector Signal No Outliers Description Returns mean values of the measured signal from the detectors The VI removes points that differ too much from the mean value Location Detektor llb Input Description Info Cluster Number Of Integer The number of values that Points shall be measured Description The mean value from the cell detector Department of Atomic Physics Lund Institute of Technology Info Cluster The mean value from the
71. esult in e Improved and automatic wavelength calibration of the laser e Improved calibration unit to contain seven cells e Improved calibration unit to function from 250 to 3500 nm e Improved uncertainty calibration in the measurement e Improved detector system for more reliable calibration evaluations e Improved user interface To achieve this it is needed to Design a new calibration unit e Design the electronics for the detectors e Design the electronics for the stepper motors Chose components allowing the unit to work in the desired wavelength span Purchase the components for the calibration unit Program the automatic calibration of the laser e Program the uncertainty calculations in measure ments e Program the user interface Integrate the system in the total LIDAR system In summary design construct and implement the new calibration unit Department of Atomic Physics Lund Institute of Technology 1 2 Limitations Some time into the project it became clear that it would take too long time to make the system work in the whole wavelength span For this reason the unit is only equipped to make measurements up to 1100nm In other words only one detector and beam splitter is installed Additional beam splitters and detectors have to be mounted to make the unit to work up to 4800nm Furthermore no experiments have been done to calculate the errors in the measurements This has been left out for fu
72. etails of the wiring see appendix 1 The Wiring of the system Figure 31 Overview of the power unit 22 5 User manual 5 User manual 5 1 Introduction This manual describes the calibration program from a user perspective The calibration program consists of two parts configuration and calibration The calibration part is called from other programs in the LIDAR system The actual calibration is done automatically even though the calibration properties are retrieved from the configuration part The only user interactions in the calibration part are dialogue boxes displayed when errors or problems in the calibration are detected For this reason only the configuration part is described in this manual For a description of the calibration part and for technical details please refer to the 6 Programmer s Guide 5 2 Configuration part In the configuration part of the program the calibration unit is set up the cells with vapour are defined and the calibration method is defined The settings from this part are used when the actual calibration is performed The configuration of the unit is done from three main windows Current calibration settings Used to show the current settings of the calibration unit From this module the data to the calibration part is passed on From this panel it is possible to display the Change in calibration unit front panel Change in calibration unit This front panel is used to c
73. etector reference beam The measured energy of the pulses is corrected for the detector characteristics Then the measured energy of the cell beam is divided by the energy of the reference beam This gives a value proportional to the absorption of the gas Backscattered from pulse Aoff Backscattered from pulse Xon Backscattered Intensity Distance R Figure 5 The measured back scattered intensity 4 Ratio Intensity Intensity Distance R Figure 6 The quotient between Ap and Aoff 4 Gas Concentration Distance R Figure 7 The differentiated ratio from the curve in figure 6 From this curve you can read out the distance and the concentration of the gas that was measured 4 2 Theory 2 3 LabVIEW software LabVIEW is a modern graphical programming system for data acquisition and control data analysis and presentation The idea of such a programming tool came up when Jeff Kodosky began to think of a new way of programming He focused on what the program user wanted to see on the screen The idea was that the screen should look like an actual instrument When he started to work for National Instruments USA the idea was put to practice In April 1983 LabVIEW was born In the beginning there were considerable problems with the performance of the program this due to the graphic technology of the language The computers of that time did not have enough process power or memory to h
74. evel output value The light source is a GaAsP LED 655nm and the load resistance is 1 67 Department of Atomic Physics Lund Institute of Technology Appendix 18 Experiment to determine the performance of the detectors Appendix 18 Experiment to determine the performance of the detectors Abstract The purpose of the experiment is to find out the characteristics of the detector and the detector circuit The aim is to correctly adjust the detector circuit i e to correctly select gains This is done to find out the procedure needed at calibration Experiment The idea of the experiment is to measure the output for different energies at a fixed wavelength The experimental set up in figure 61 is used To determine if the detectors are wavelength dependent A 500nm as well as A 448nm are used To be able to find the dependency of the gain in the electronics the laser intensity is varied during the experiment Slide box B Optical bench with neutral density filter Bl Slide box with neutral density filter Mirror Detectors Figure 61 Test set up for the experiment Two different set ups are used In the first one the energy in the pulses is changed with neutral density filters in slide box B see figure 61 This 15 done to determine if the two detectors are linear 1 to see if the relation between detector 1 and detector 2 15 constant Due to problems with the OPO system the laser pulses were poor and
75. fied from Sune Svanberg Atomic and Molecular Spectroscopy page 325 Springer Verlag 1992 Figure modified from Sune Svanberg Atomic and Molecular Spectroscopy page 326 Springer Verlag 1992 Sune Svanberg Atomic and Molecular Spectroscopy page 326 Springer Verlag 1992 Figure from National Instruments Web address http www national com or www natinst com LabVIEW documentation from National Instruments Web address http www national com or www natinst com Figure from Petter Weibring at the department of Atomic Physics Lund institute of Technology Sune Svanberg Atomic and Molecular Spectroscopy page 212 Springer Verlag 1992 Figure modified from manual for the MOPO 730 system from Quanta ray Steven E Harris Tunable Optical Parametric Oscillators Proceedings of the IEEE Volume 57 No 12 December 1969 Picture form LIDAR measurements in Almad n in Spain Figure modified from Lund Reports on Atomic Physics LRAP 201 Lund September 1996 1 Advanced Photonix Inc Web address http www advancedphotonix com Hamamatsu Web address http www hamamatsu com or http www hpk co jp hp2e main html Melles Griot Web address http www mellesgriot com Figure from Advanced Photonix Inc Web address http www advancedphotonix com ELFA Stepper motor KP56LM2 502 Web address http www elfa se ELFA Stepper motor module GS D200S from SGS THOMSON MICROELECTRONICS ELFA article number 54 503 33 Web address http www elfa se
76. g cell in the revolver Configuration in VI Change In Revolver e Finding neutral density filter 5252892898 77 eie Spits c s Figure 43 The Calib cluster Department of Atomic Physics Lund Institute of Technology Configured in VI Select Demp Automaticaly 2 e Calibrating Calibration Method 0 Calibration Method 1 Calibration Method 2 Configured in VIs e Indexing of the motors The addressing of motors in the program is done by an index This index 1s NOT the same as the motor number in the calibration unit The difference has evolved since there are more motors in the LIDAR system The numbering of the motors in the program is found in table 3 below 0 5 Thedetector motor The revolver motor The filter motor Table3 The numbering of the motors in the The beam splitter motor This program motor is not implemented in the calibration unit Last Cell Last Detector Last Splitter Splitters Array Name Wavelength ON Wavelength OFF Detectors Array Name Wavelength ON Wavelength OFF Cells Array Name Pos in Revolver Defult data Last Data Peaks For Cell Array Wavelength ON Wavelength OFF Start Of Scan End Of Scan Step Diff Abs Calib Selector Calib cluster File Types cluste Info cluster Current Rev Pos Current Detector Pos Current Splitter Pos Current Filter Pos Calib Cell Rev Pos Calib Detector Pos
77. gitiser The digitizer is responsible for capturing the signal from the PMT during a LIDAR measurement It is controlled through the GPIB board in the system computer 11 Power Unit This unit powers and controls stepper motors choppers and other equipment in the bus 1 For information on the interaction with the Calibration Unit see section 4 12 Nd YAG Laser Detectors Dye Laser Calibration L Unit Gas Cell 3 2 Calibration unit The calibration unit illustrated in figure 21 performs the wavelength calibration A diffuse reflex from the laser is transmitted into the unit where it is divided into two parallel beams One passes through a reference cell with the gas that is to be measured and then to a detector cell detector The other passes directly to a second detector reference detector The output signals from the detectors are sent to the system computer via the Control Unit in the system cabinet Looking at the quotient between the pulses you can determine if the laser has drifted during a measurement and it is possible to calculate the errors in the measurement interactions between the calibration program and the unit are done through the Control Unit All components in the unit are powered from the Power Unit For details see appendix 1 3 3 Laser system When the project started the laser system used in the LIDAR system was a tuneable dye laser pumped with a Nd YAG laser This system was replaced
78. gitizer and is read out to a computer system The computer system is mounted in the system cabinet One of the computers is used for controlling the planar mirror the laser wavelength etc It also performs signal averaging and necessary processing of the LIDAR signals 3 2 System cabinet The system cabinet 15 the heart of the LIDAR bus In this rack processing control and power units are installed see figure 20 For detailed information se 1 The Rack contains of e Security Unit This unit controls the output from the laser If a security switch is activated then the unit will stop the laser pulses 1 Security Unit Controle Unit System Computer Evaluation Computer Digitizer Power Unit Figure 20 The system cabinet 14 Department of Atomic Physics Lund Institute of Technology 3 General description Control Unit This unit handles the Input and Output between the system computer and the units in the bus See section 4 13 System Computer This is the main computer in the system from which the applications are run This computer has plug in boards that are the interfaces towards the Control Unit These boards are AT MIO 16 PC TIO 10 GPIB and network board 1 For detailed information on the interaction with the calibration program see section 4 14 e Evaluation Computer This computer is used for processing and presenting data from a LIDAR measurement 1 e Di
79. hall be made 3 Select lower optical density filters with the filter wheel until one of the detectors have an output larger than the minimum output limit from the detectors Use this detector to find the maximum energy in the pulse 4 Select the filter with the lowest optical density but for which the output is below the maximum output from the detector Now there is as much dynamics as possible in the system 5 Check that the second detector is within the operational region between upper and lower output limit 6 Record the offset from the two detectors 7 Perform the scan Additional steps the procedure performs are 8 Check the output from the detectors once more This is to determine that none of them have passed the output limits Move the filter wheel to the OFF position 10 Move the detector to OFF position Finding neutral density filter To find the correct neutral density filter the VI Select Demp automatically is used The calibration methods The recording of offset and the performing of the scan is done by the calibration method used Each calibration method can have different ways to find the offset of the laser They can also include additional user interfaces For example showing the output from the detectors in a graph and saving recorded data to file Further additional configuration parameters can be set For detailed information please see the code The outputs from all calibration methods mus
80. he high energy in the pump pulses needed e Low absorption over the entire tuning region significant degradation over time e Possible to manufacture in large enough sizes to reasonable cost One of the best suited crystals forfeiting these criteria is the BBO crystal 13 3 General description 3 General description 3 1 The LIDAR system The LIDAR system is mounted in a Volvo F610 see figure 18 and figure 19 This makes the system easy to place wherever the discharge may be Figure 18 The mobile LIDAR system Mounted in a Volvo F610 12 Transmitting amp receiving Air Conditioner System Figure 19 Principal drawing on the LIDAR bus 13 A laser is used to produce pulses that are transmitted into the atmosphere via a planar mirror in the telescope The same mirror is used for directing back scattered light down into a fixed telescope In the focal plane of the telescope there is a polished metal mirror with a small hole which defines the field of view of the telescope In order to suppress background light it is essential that the telescope only observe regions where laser photons can be back scattered A photo multiplier tube detects the light passing through the aperture the other light 15 directed into a TV camera that produces a picture of the target area except for the laser beam region which is seen as a black spot The detected LIDAR signal is transferred to a transient di
81. he laser beam is to high 2 No points The number of points that shall be used to find the average output from the detectors Maximum output from the detector 1 Is set to 4 0V Maximum output from detector 2 Is set to 4 0V Minimum output from detector 1 Is set to 1 0V Minimum output from detector 2 Is set to 1 0V MN lc 12 Appendix 19 VI and cluster description 7 The index number of the last neutral density filter Is set to 9 this equals 10 filter positions Location Dempfilt lIb Input InfoCluster sd Output Parameter Description Info Cluster Info out OK out TRUE if the VI was able to find a filter Set Cell Data Description The VI sets the parameters for a cell according to the save parameter Location Array Functions llb Input kai HN MEE Cluster The position the cell has in the Calib cluster peak data E ee Info in Info Cluster Last Data Integer The position of the last peak data for the cell String The name of the cell Pos In Integer The position the cell has in Revolver the revolver Save Integer Determines what dada shall be set 1 Name 2 Pos in Revolver 4 Default Data 8 Last data If Save 9 then the Name and Last data 15 set Output Parameter Calib Cluster Info Cluster e Description Department of Atomic Physics Lund Institute of Technology Set Detector Data Description The VI
82. ions To be able to cover the whole range a number of beam splitters need to be installed A normal beam splitter from manufacturers has its operation region within a couple of hundred nanometers The problem 15 to get a reasonable number of beam splitters The problem can be solved with the pellice beam splitter nr 03 BPL 001 04 from Melles Griot 16 This beam splitter has 40 40 splitting between 400 to 1060nm Above this region normal quartz can operate and below the original beam splitter works fine In other words three beam splitters would cover the whole region The problem with this beam splitter is that it is sensitive It may not be touched and only be cleaned with a gentle Department of Atomic Physics Lund Institute of Technology flow of clean air If this was to be used then it had to be enclosed A decision was taken that it would take too long to make a changeable beam splitter device Therefore only the original beam splitter was installed 4 8 Neutral density filters The filter wheel is used to adjust the intensity of the laser light The problem is that the laser produces light that is much to strong for the unit Even a reflection from the laser beam has to high intensity The unit must therefore be able to reduce the intensity of the light several powers of ten During the experiment described in appendix 18 the optical density of each different filter was found The filter wheel has 10 positions This a
83. is VI resets the UNIT i e remove all cells from the revolver The VI will NOT remove any data that has been entered It will only remove the references to the positions in the revolver If someone wants to remove all data the file with the data has to be removed and the program restarted Location Array Functions lIb Input Info out 11 Appendix 19 VI and cluster description CalibCluster Infoin InfoCluster oo Output Description Calibout CalibCluster oo Info Cluster Rotate Selected Motor To Description Moves a selected motor to a new position The parameters that have to be configured are 1 Upper position limit Used to check that the position the motor shall move to The position the motor shall be moved to shall be below this value 2 Lower position limit Used to check the position the motor shall move to The position the motor shall be moved to shall be equal to or greater than this value Number of steps between two positions Number of positions for the motor Direction of movement Line for direction This is the input line to the AT MIO 16D card for the direction for the motor 7 Line for movement This is the line to the AT MIO 16D card for moving the motor The parameters are found in table 28 Ne a Table 28 The configuration parameters needed when moving a motor The device number and the digital chann
84. is rather difficult to align the calibration system The active area on the two detectors and the holes that the beam travels through are small This together with the fact that the laser beam is normally received from a reflection from any optical component which causes the direction and distance to vary sincerely leads to unnecessary time to align the system To improve this the following could be done 1 Two diode lasers could be mounted on the detector wheel The beams from these lasers can be used to align the system from the opposite direction The beams could be used to set up pinholes that would then be used for the aligning 2 Mount two static pinholes These pinholes shall be fixed once and for all once the system has been aligned 3 Widen the hole that is used to pass through the optical table Widening this hole would make the alignment easier 4 optical fibre to direct the laser beam into the unit This would make it extremely easy to get the beam into the unit A problem would be that different fibres are needed for different wavelength intervals Department of Atomic Physics Lund Institute of Technology 8 5 The detector electronics During testing of the calibration unit it has been found that the electronics drift This causes problem when measuring with the unit The detector electronics should be changed to include a real sample and hold circuit The design of today 15 only an integrator circuit
85. linear towards absorption 17 4 System design 4 4 2 The chosen detector The old detectors were chosen since they fourfold the necessary conditions To be able to understand why this slow working detector Works one has to understand how a photodiode works Basic photodiode theory photodiode is a solid state device that converts light into electric current It normally consists of doped silicon that forms a so called p n junction see figure 23 SiO thermally grown AR Coatin 9 Xx y Front Contact A Depletion Region p n Junction Edge n Type Silicon n Back Diffusion Back Figure 23 Basic configuration of a photodiode 17 joue The n type region is created when impurities i e other atoms with extra electrons are defused into the silicon These atoms are called donors since they give away their extra electron The p type silicon 15 created in the same way but the silicon is doped with acceptors or holes These atoms accept electrons When the two regions are in contact the electrons in the n doped region and the holes in the p doped region feel a lower potential on the opposite side of the edge This potential difference makes the electrons and holes flow across the p n junction This charge movement establishes an electric field that works against the movement After some time equilibrium is established and a depletio
86. llows a maximum decrease of intensity down to 4 9 positions are used for filters and one is blocked to protect the unit The result 15 shown in Table 1 Due to economical reasons old filters are used The filter set up used is described in table 2 Rounded OD Blocked Position Transmittance 96 4 00 __ NO 40 m c 100 1 The best choice of filters according to experiment in appendix 16 Optical Densi Blocked Blocked Position RIN TRIN o Table 2 optical density of the filters that are used in the unit 20 4 System design 4 9 Stepper motor The chosen stepper motor is the two phase KPS6LM2 502 from ELFA 18 This motor can operate as a unipolar as well as a bipolar motor The bipolar configuration is chosen see appendix 14 4 10 Stepper motor electronics To power and control the operation of the stepper motor the GS D200S driver from ELFA is used 19 see appendix 15 To be able to configure and use the module it is mounted on a circuit card as shown in appendix 7 The configuration is as follows for pin description see appendix 15 Pin 4 is connected to earth This means that the full step mode is selected Half step mode makes the drive module step the motor with half steps i e the double number of steps is needed for the motor to make one revolution The stepper motor has 200 steps revolution That is enough for the compo
87. loop the status is checked with ContinueExecNoErrorCheck 27 6 Programmer s guide DO 171 Default A Waits here until a button is pressed x 2 Then reads Execution frame and goes s the frame with that number 5 out COMER RED PRECOR EI CA 5 e n 2 ci T 2 MUR RR AAA ts Figure 40 Standard code for input screen lower loop can start again and then it once more waits for the lower loop 6 2 2 3 Synchronisation in the program The execution sequence in the program is achieved by the data flow of three clusters These are The Info cluster e The File Types cluster e The Calib cluster These clusters carry the data within the system The Info and File Types cluster are general clusters containing data of the total LIDAR system while the Calib cluster is used only in the calibration program 6 2 2 4 The Info cluster In the calibration program all the VIs have the Info cluster as input This cluster is the main object for the synchronisation If an error occurs the error number 15 saved in this object See figure 41 This cluster carries all the current settings
88. m The VIs front panel is the user interface for selecting which cell that shall be used when calibrating the laser Location Program lIb Input Parameter Calib in Description Calib Cluster File Types File Types in Cluster Info in Info Cluster Initialise Description set to TRUE it the program shall be initialised Parameter Calib out Calib Cluster out Cluster Info out Info Cluster Change In Revolver Description This VI 15 used when the user wants to add remove or change a cell in the revolver When a cell shall be added or removed in the calibration unit the revolver must be moved to make this easy The configuration of this movement is done in this VI Location Revolver llb Input Parameter Calib in Description Calib Cluster 1 Add cell Integer 2 Remove and add cell Info Cluster 0 2 Integer The position the new cell has in the array in the Calib cluster Choice 0 Remove cell Info in New Cell Pos In Array Old Cell Pos In Array The position the old cell has in the array in the cluster The position in the revolver where the change shall be made Pos In Revolver Department of Atomic Physics Lund Institute of Technology Output Parameter Description Cluster OK out Boolean TRUE if the operation was successful otherwise FALSE Check If Array Pos Occu
89. mation see 19 Technical data Logical voltage 5 Vss Motor voltage 12V to 40V Vz Motor current Max 2 5A Logical signals TTL CMOS compatible Chopper frequency 17kHz can be modified Dimension 85x66x20mm Vss 5V Vs e e O eee g BIPOLAR STEPPING MOTOR OSC SYNC GND1 GND2 Figure 56 GS D200S Modules typical application 19 63 Department of Atomic Physics Lund Institute of Technology Appendix 15 Bipolar stepper motor drive module Function Description Return path for logical signal and 5V suppl wl Chopper oscillator output lt 4 2 Home When low this output indicates that the internal counter is in its initial state ABCD 0101 The motor is moved one step on the rising ed nal Connecting a resistor between this pin and VSS or a capacitor between this pin and GND1 Phase current setting input A resistor connected between this pin and GND1 allows the factory selected phase current value 2A for GS D200S to be changed normal operation D output Several modules can be synchronised by connecting together all Sync pins This pin can be 3 Reset Asynchronous reset input An active low pulse on this input pre set the internal logic to the initial state ABCD 0101 This signal should be ANDed with the outpu
90. n 0 Figure 36 Confirmation dialogue box Department of Atomic Physics Lund Institute of Technology Change button This button is used when a cell shall be added to the unit The cell is highlighted in the Calibration Cell selection box The position where the cell shall be inserted in the unit has to be highlighted in the Cell in Revolver selection box It is possible to change a cell even if the position is occupied It is not possible to have the same cell in two positions in the unit at the same time When the action is performed the program checks if the cell is present in the unit A warning message is displayed if the cell has already been added Then the revolver is positioned so it is possible to add change the cell A dialogue box is displayed in which the action shall be confirmed see figure 36 Default button This button changes the default peak for the cell highlighted in the Cell in Revolver selection box The peak that becomes default is the one that is highlighted in the Calibration Peak selection box Reset UNIT button This button shall be used when the set up in the program does not correspond to the actual configuration in the unit This action will NOT reset the cells and data defined in the system OK button saves all data and exits the panel The program will returns to the Current calibration settings front panel 25 5 User manual 5 2 3 Change calibration data This module makes it
91. n region has been created between the two regions When photons fall on the device they are absorbed and electron hole pairs are created The electron hole pairs drift apart and when the minority carriers reach the junction edge they are swept across by the electric field If the two sides are electrically connected an external current flows through the connection The photodiode behaves as a current source when illuminated If the created minority carriers of that region recombine before reaching the junction field the carriers are lost and no external current flows An external voltage 15 applied to the photo diode to increase the sensibility This will increase the depletion region i e make it more likely for Department of Atomic Physics Lund Institute of Technology the minority carriers to reach the region before they are recombined How the old detector works The old detector does not measure the actual laser pulse The fast pulse injects electrons and holes into the depletion region These charged carriers drift towards the depletion region If the carriers reach the region before they recombine the charge can be measured This process in the detector is much slower than the actual laser pulse but if the number of carriers that is measured is proportional to the energy in the laser pulse there is no problem using these detectors 4 5 Digitizer trigger delay The laser triggers the synchronisation of the system The laser
92. nd back to the detector The principle of LIDAR is illustrated in Figure 1 Detector PMT Figure 1 The principle of lidar Different processes cause the back scattering The main ones are Rayleigh Raman process and Mie scattering 2 One example of LIDAR measurement is shown in figure 2 2 1 1 DIAL a LIDAR technique LIDAR is a common name for measuring methods where light is transmitted and the back scattered light is detected The technique used at the LIDAR group is called DIAL DIfferential Absorption LIDAR Backscattered intensity RY unda 0 100 200 300 Distance d m from laser Figure 2 Particle monitoring with LIDAR technique The Mie scattering process is used to resolve the particle concentration 3 Department of Atomic Physics Lund Institute of Technology In DIAL the differential absorption at close lying wavelengths of molecules is used In practice this means that two laser beams are sent into the atmosphere One with the wavelength of a absorption peak and the other of a close lying minima See figure 3 This method is useful for qualitative as well as for quantitative range resolved measurements of molecules in the air The principles of a DIAL measurement A laser shoots alternately on a known absorption wavelength Aj and on a nearby reference frequency Aoff for the molecule measured see figure 3 and figure 4 Absorption Wavelength
93. nd measured absorption Adjusted data 447 2 447 4 447 6 447 8 448 448 2 Wavelength nm Cell Ref Adjusted Table value 448 4 448 6 448 8 Diagram 6 Measured absorption is matched against the table value for NO2 The table value is adjusted to air wavelength Department of Atomic Physics Lund Institute of Technology 40 8 Improvements in the future 8 Improvements in the future 8 1 Introduction During development of the calibration system some inconveniences and problems with the unit has been found Some of these issues have been considered to fall outside the scope of this work This chapter describes issues that can be improved for the future 8 2 The detectors The detectors used in the system are to slow to record the actual shape of the laser pulses In appendix 18 tests are made to find the characteristics of the detectors The result is that there seems to be a linear response from the detectors Despite this it could be a good thing to investigate if other detectors could improve the calibration system 8 3 The beam splitter The beam splitter used in the system does not operate over the total tuning region of the OPO system The calibration unit can be upgraded with a module that can change the beam splitter The unit and the program are already prepared for this 8 4 The beam aligning of the calibration system One problem that was found during testing of the unit is that it
94. nents in the calibration unit e Pin9 is connected to Pinl GNDI via a 3000 resistor This is done to lower the current to the stepper motor in order to prevent over heating The resistance can be calculated from R I 3 03 1 43xDkQ where I is the current The operation of the motor does not need high hold torque Because of this the lowest currency 0 5A is chosen This gives a resistance of 0 22kQ The resistance is set to R 300Q which gives a current I 0 64A This is below the suggested value when driving the motor in bipolar mode See appendix 14 e Pin 1 4 6 7 9 12 13 14 15 16 17 and 18 are connected to cable connectors Pin2 3 5 8 10 and 11 are not used The four stepper motor boards are mounted in the power unit Here cables are connected from the cable connector on the circuit card to other cable connectors in the unit See appendix 6 This is done for easier handling 4 11 Position detector electronics Finding the exact position of the components is extremely important If the positions are not known it would not be possible to select detector gas cell or neutral density filter i e it would be impossible to use the unit The position detector is used to find the locations of the components The circuit drawing is found in appendix 10 The operation is simple If the light from the diode hits the detector there will be 5V on the OUT and OV on inverse OUT If the detector light is blocked opposite
95. nents that need to be changeable are mounted on wheels or cylinders that are controlled by stepper motors To be able to measure on several gases during one measurement a revolver wheel is constructed In this revolver up to 7 different cells can placed The parts in the calibration unit are constructed in blocks This is done to make it easy to rebuild or change the components The moving parts are mounted with the stepper motor on a plate This plate can easily be removed from the unit for modification or replacement The modular construction also has the advantage that parts not needed for the moment can be developed and manufactured when needed Department of Atomic Physics Lund Institute of Technology Smooth operation of the unit is considered in the design Changing of the cells must be simple This is achieved with clips to which cells can be attached These clips can be mounted with different sizes and at different distances so all kinds of cells can be used 4 4 Detector The detector and its electronics are the most vital parts for the calibration These components determine the different parameters needed in the program maximal intensity minimum intensity and so on Speed size and operation region are taken under consideration when selecting detector 4 4 1 Useable detectors One detector that would serve the purpose is the SD290 11 31 241 from Advanced Photonix Inc 14 This diode detector can measure between 300nm
96. nnel for motors 3 Digital channel for position detectors 3 Table 27 The configuration parameters needed when finding the motor positions Location Revolver llb Input 2 Filter motor 7 Choice Integer 3 Beam splitter motor 8 InfoCluster Output Info Cluster OK out Boolean TRUE if the operation was successful otherwise FALSE 0 Detector motor 5 1 Revolver motor 6 Appendix 19 VI and cluster description Find Offset Method 0 Description Finds the offset of the laser Method 0 Location Calibrate llb Input Description Array of DBL Measured values Info Cluster Input Array of DBL The wavelengths that goes Wavelength with the measured values Output Info Cluster OK out Boolean TRUE if the offset was found otherwise FALSE Get Cell Names Description Returns all the names of the cells Location Array Functions llb Input Parameter Description CalibCluster Info in Info Cluster Output Array with all the cell Names strings names Calibout CalibCluster Infoout j InfoClute Get Peaks From Cell Description The all the peak names for a cell Location Array Functions lIb Input Calib Cluster Cell Pos Integer The cell position array in the Calib cluster Info Cluster Output Parameter Names strings names fo
97. nsert New Peak Data Into Cell Description Inserts a new peak into the peak array for a cell The VI sorts the peak array after the names of the peaks Location Array Functions lIb Input Parameter Description Calib Cluster Type Cell Pos Integer The position of the cell in the Calib cluster Info Cluster Peak Data In Peak Data The peak data that shall be cluster stored Output Calib Cluster Info Cluster Insert Peak Data Into Cell Description Inserts a peak data into an existing position in the peak array Location Array Functions llIb Input Calib Cluster The position of the cell in the Calib cluster nfoin InfoCluster Peak Data In Peak Data The peak data that shall be cluster stored Integer The position of the peak in 10 Appendix 19 VI and cluster description the peak array Output Calibout CalibCluster nfoout InfoCluster New Cell Name Description This VI is used when the user shall enter a new name of a cell Location Spiece lIb Input Caibin CalibCluter O oO o Info in Info Cluster Cd Output Calibout CalibCluster Infoout InfoCluser The position the new cell Pos have in the array in the Calib cluster TRUE if a name has been typed and the OK button is pressed New Detector Data
98. olver Pos IS Uh Check ecd p ates PT Conneurauon Of The zi oclo d ae ConunuebxecbrrorC Deck i den f a Conver ees este orci het bre Convert Deteetor Data cose eee cor debate a Create Cell Data iex ume Paus bau brute n m Delete Peak Brom Cello Dialogue Box With OK v idle M uses eus Dialogue Box With OK and Cancel ec eva e Edit Peak Data For tdi t RES DER iet Firid MOtoP POS Mena Pind Offset dose eme b E on rA en is opto es da ux Get AIL Cell Get ATL Peaks Prom Cello oit oer er Ee whats VR CORE St Ger Cell Data From P Hed uo i itera Ger Cell Pos From Revolver POS Get Default Peak Data For Cell 5 52 Bc Get Detector Por Peake men PAR VOIR RS Get Deteetor EDO Lana Dee et Get Detector Signal de Va EN Detecto
99. ompleted using the old system or be adjusted for the new The decision was to use the new system This had vital impact on the project The whole program had to be rewritten The detector electronics had to be redesigned 1 Introduction 1 5 History and background LIDAR Light Detection And Ranging measurements have been performed since the 1930 s In those early days searching light was used for measurements on aerosols in the stratosphere When lasers where developed they were found to be a superior light source In 1963 the ruby laser came into use for LIDAR measurements and in 1966 it was possible to measure gas concentrations with differential absorption LIDAR DIAL Improvement of the LIDAR technique has continued during the last 30 years along with development of electronics lasers and computers In the end LIDAR technique has become fast and cost efficient The need for efficient monitoring of the atmosphere has dramatically increased since it has become clear that man has a profound impact on the global environment The LIDAR technique has became a very useful tool for performing these environmental measurements 1 5 2 The LIDAR group The Department of Physics has had a LIDAR group for 15 years During this period of time the group has developed the technical know how and the existing system It has also generated a spin off company in this field Department of Atomic Physics Lund Institute of Technology The p
100. on box If the peak is the default one then default setting will change to the peak that is first in the list OK button Exits the panel and returns to Change in calibration unit front panel J Calibration Peak Start md eon 44 n n 448 5 447 000 449 50 Way 447 500 447 500 TEA on 448 100 22 448 200 Loe Delete Data Figure 37 Front panel of New Spiece Data vi In this VI the data for a calibrating cell can be changed Department of Atomic Physics Lund Institute of Technology 26 6 Programmer s guide 6 Programmer s guide 6 1 Introduction This guide describes the concepts of the calibration program It is intended for programmers and persons who want to change or add functionality to the program The guide has three sections The first section 6 2 describes the basic concepts and the main parts of the program The second 6 3 describes the program in further detail and how to add functionality The third section is an overview of the Virtual Instruments VIs and the main data clusters in the program This section is found in appendix 19 VI and Cluster description 6 2 Basic concepts This section describes the basic design pattern of the program It also gives an overview of the calibration program 6 2 1 Introduction The calibration program consists of two parts One part handles the configuration of the unit and sets the current da
101. on unit
102. onfigure the calibration unit i e change the cells in the unit From this panel it is possible to display the change calibration data front panel e Change calibration data This module is used to configure the calibration data for a cell In the calibration system many cells can be configured For each of these cells many calibration regions can be defined i e data used when calibrating with that cell These regions are called Peak or Peak Data For each cell one peak is defined as the default peak The data for this default peak are used by the system when calibrating using the cell This means that if non default peak data shall be used for calibration then this peak has to be changed to the default peak for the cell 5 2 1 Current calibration settings This module displays the current settings calibration unit see figure 32 in the From this screen it is possible to select one cell When a cell is selected the name of the cell along with the default Department of Atomic Physics Lund Institute of Technology peak data for the cell is displayed The selected cell will be the one used if a calibration is started Current cell selection box This box shows the cell that is currently ready for calibration With this control it is possible to change the cell that the calibration shall be performed for see figure 33 If the cell is changed the new cell will be rotated to the calibration position in the unit and the default d
103. pied Description Checks if an array position is occupied Location Spiece llb Input Parameter Array In Description 1 Array of Array to be checked strings Info Cluster The position to be checked nfo in Pos In Arra Output Parameter Info out Occupied InfoCluster Boolean TRUE if the position is occupied otherwise FALSE Check If Cell Is In Revolver Description Checks if a cell exists in the revolver Location Revolver llb Input Parameter Description Calib in Calib Cluster Info Cluster Info in Output Cluster Exist In Boolean revolver otherwise FALSE Revolver Check If Revolver Pos Is Occupied Info Cluster Description Checks if a revolver position is occupied Location Spiece lIb Input Parameter Description Cluster Appendix 19 VI and cluster description Info Cluster Pos Output I ne Cluster The position in calib cluster of the cell that occupies the position nfoout InfoClster TRUE if the cell id in the revolver otherwise FALSE Check Peak Data Description Checks if the calibration data has a relevant value The data checked is e That Wavelength ON is between 220 and 3600nm That Wavelength OFF is between 220 and 3600nm e That Start of Scan is between 220 and 4800nm
104. r reno Dae etti o e out d su pad oto Ud Get Detector Signal With Threshold suse ceste o e pto amt Get Detector Signal With Threshold 2 eoa ies ttes tty Get Detector Signal With Threshold and compensated Get Names For Cells In 1 Ger Spuer For GOO t veld D das Init CalibrdlopD Insert New Into Attdy Insert New Cell Into Array No 0 02 0 Insert New Peak Data Into Cell eese err rr e Insert Peak Data Into o xoci hex to eheu eate daa ad ING Ee New Detector vd New Dal usse Rua ead Open ile ens RESC OUNI Rotate Selected Motor Save A Data tiles id Save Detector surdi ebd d Select Demp Automatically 2 apa MER Mens
105. r the cell Calib out CalibCluser Info Cluster Info out Department of Atomic Physics Lund Institute of Technology Get Cell Data From File Description Fetches saved cell data from file The VI updates the Calib cluster with the data Location FileOp llb Input CalibClstr File Types in File Types Cluster ___ Info in Info Cluster 207 Description _____ Output Parameter Calib out File Types out Info out Type Description CalibChster Tvpe Info Cluster Get Cell Pos From Revolver Pos Description This VI is used when a position of a cell is known in the revolver Returns the position of the cell in the array in the Calib cluster Location Array Functions lIb Input Parameter CalibCluster Info Cluster Pos revolver Output Calib Cluster Cell Pos Integer Info in Integer Description TRUE if the position if found otherwise FALSE The position in the attay in the Calib cluster Infoout j InfoCluster Get Default Peak Data For Cell Description Returns the default peak data for a cell Location Array Functions llb Input Calib Cluster The position of the cell in the Calib cluster InfoCluster 2 Output Calib out CalibCluster nfoout InfoCluster Peak Data Peak data The default peak data for clust
106. r the configuration part of the program Location Controls llb Parameters Array of all the beam splitters defined in the system For more info see Cluster of Splitter Data Cells Array of all the cells that have been defined in the system For more info see Cluster of Cell Data Detectors Cluster of Detector Data Last Cell The index number of the last Cell that has been defined array Cells If 5 different cells have been defined this number will be 5 174 since the counting defined in the array Splitters For the time being there 15 only one which gives Cluster of Cell Data Description This cluster contains all the data for one cell Location Controls llb Default data The peak for which the calibration shall be done The number 15 the index of the peak in the array Peaks For Cell Last Data The index number of the last peak that has been defined in the array Peaks For The name of the cell Peaks For The array of peaks defined for the cell cell This 15 also the data for which the Department of Atomic Physics Lund Institute of Technology defined in the system For more info see Last Splitter The index number of the last beam splitter number will be 5 1 4 since the counting Array of all the detectors that have been The index number of the last detector Detector defined in the array Detectors Parameters Cell If 5 peaks hav
107. ref detector Get Detector Signal Offset Description Returns the offset for the detectors Location Detektor lIb Input Infoin Cluster Number Of The number of values that Points shall be measured Output Parameter Description Cell Offset DBL The offset for the cell detector nfoout Cluster The offset for the ref detector Get Detector Signal With Threshold Description Returns the mean values for the measured signal from the detectors As input this VI must have a reference value The VI will only record the signals for which the value from the reference detector is within the threshold Location Detektor llb Input Parameter Type Description 0 Info in nfo Cluster Type I Number Of The number of values that Points shall be measured Ref value detector have to be within utput Parameter DBL The mean value from the BL B cell detector Cell Ref The mean value of the divided signals Info out InfoClster Ref DBL The mean value from the ref detector Appendix 19 VI and cluster description Get Detector Signal With Threshold 2 Description Returns the mean values for the measured signal from the detectors This VI finds the mean values for the reference detector and uses this value to check that the reference detector is within the threshold The signals recorded are those within
108. revious system was a Nd Y AG pumped dye laser which covers the wavelength region from the ultra violet to the infra red With this system it 15 possible to measure substances like 502 NO NO Cl and Hg It is not possible to measure volatile hydrocarbons VOC The need to measure VOC 15 great in petrochemical and chemical industry In those industries there can be diffuse discharge of VOC and normally only rough estimations of these can be made That is why the use of remote analysing technique is very interesting in these areas The new laser system that has been installed contains one OPO and two YAG lasers With these lasers a larger wavelength interval can be covered This will make measurements on VOC possible To make reliable measurements it is necessary to calibrate the laser precisely and to know the errors Another improvement done by the LIDAR group is the development of a user friendly and automatic system using LabVIEW 1 2 Theory 2 Theory 2 1 The LIDAR technique LIDAR which is an acronym for Light Detection And Ranging is a measurement technique working a lot like a common radar The main difference is that a LIDAR system uses light pulses instead of microwave pulses Pulsed laser radiation is transmitted into the atmosphere and a photo multiplier tube PMT detects back scattered light The distance to the molecules is determined by measuring the time it takes for the light to travel from the laser a
109. rogram that looks like a real instrument For example if a radio was to be constructed the knob to change frequency can be put on the panel When the knob is turned a linear display can show the current frequency Just like an old radio receiver Department of Atomic Physics Lund Institute of Technology the controls and indicators on the front panel are found in the block diagram as controls and terminals see figure 9 The block diagram The block diagram is the VI s source code In this window the actual programming is done In the block diagram all the components from the front panel are found controls and indicators Here you will also find Sub VIs The programming is done by binding these components together by Data Flow Wires This creation of data flow between the objects 15 called data flow programming Se section 2 3 3 Every object in the block diagram is the graphical representation of the object s code The actual code for each object is written in C This makes the performance of the program fast and efficient The icon connector The icon connector is the calling interface for a VI The icon is displayed in the block diagram of a calling VI The connector shows what input output the VI has See figure 11 Number Of points Cell Offset TOES leer Ref Offset Info in nfo in out Get Detector Signal Offset vi Figure 11 A VI and its icon and the data flow wires that is attached to the VI
110. ront panel it is possible to set the Test Mode parameter in the Info cluster If this is done the application can be run as a stand alone application Location Program llb Input Parameter Type File Types File Types in Cluster Description Info in Info Cluster ee Output Type File Types File Types out Cluster InfoCluster Which Button is Pressed Description This VI is used to find out which button a user has pressed The VI checks a string of Boolean and returns the index where a Boolean is true Location Array Functions llb Input Parameter Description Array of Boolean Input Output Integer C WriteFile Description Writes data to file The data shall be stored in the File Types cluster Location Lofileop llb put In Selector be closed Cluster Ignore Change Boolean If TRUE the VI ignores if quo the change activity 1s set Info in Info Department of Atomic Physics Lund Institute of Technology Output Parameter Description Cluster Info Cluster 14 Appendix 19 VI and cluster description The Clusters Calib Selector Description This 1s a calibration selector The names of the different calibration methods shall be defined in this selector Location Controls lIb Parameter Description Calib Contains all the names of the calibration CalibCluster Description The main cluster fo
111. rs with electronics see appendix 18 This experiment showed problems with offset and badly balanced electronics This is illustrated in figure 29 If the detector electronics are not balanced the output value can increase or decrease over time It takes some time until the computer reads out the value During this time the value can change see figure 29 This will lead to errors in the measurements 19 4 System design t Figure 29 Problem with offset 4 7 Beam splitter The beam splitter divides the light from the laser to the detectors This is done in order to use one detector as reference In this way compensations for the fluctuations in the laser energy can be made The demands on the beam splitter are e A 50 50 distribution but if slightly more of the intensity travels through the gas cell it would be good since the gas will absorb some light Operate in the entire specified wavelength region with the same splitting ration A problem when splitting laser beams is that the laser light is polarised Beam splitters often split the light differently in the p and s plane The pulses that will be used are derived from a reflection from some optical component in the beam path of the OPO system Which component used depends on the experiment the OPO system is used for i e the direction of the polarisation will change between experiments For this reason the beam splitter must have the same division in both direct
112. rsa Module Eurocard or IEEE 1014 Volatile Hydrocarbons Extension for Instrumentation Department of Atomic Physics Lund Institute of Technology 44 Appendix 1 The wiring of the system 12 Appendix Appendix 1 The wiring of the system This section describes all the wiring needed to run the calibration system First the system overview is described and after that each of the main components These are the calibration unit the power unit the control unit and the system computer For further description of the LIDAR system see 1 1 Glossary and acronyms Ground NA Not Applicable PD Positioning Detector 2 System overview The main components of the LIDAR system are The control unit The system computer Evaluation computer Digitizer Power unit Laser unit Wind unit Receiver unit Calibration unit See appendix 2 Cabling between system blocks For the calibration system the components needed to be wired are e The calibration unit The power unit Thecontrol unit e The system computer See appendix 3 communication between blocks in the calibration system 2 1 Connectors The connector used is of the type MIL C 26482 from the manufacturer FCI Souriau see table 4 Product nr ELFA prod nr 18 Placed Calibration unit Cable Cable Power unit Power unit Cable Cabel Control unit 53116 16 265 44 541 95 MS3116F 16 26P 44 541 87 53 112
113. s between different experiments The actual energy 15 dependent on how the pulse was received which reflection used and how it is transmitted to the calibration unit The intensity can vary several powers of ten The laser pulse is extremely short This makes it extremely difficult to read the values directly from the detectors with the computer A D electronics 4 3 The calibration unit All components that are chosen should manage the strain in the lorry Every thing has to be built robust This can be seen in figure 21 and figure 22 In order to get the right amount of energy in the laser pulses is must be possible to reduce the intensity A wheel with neutral density filters at the entry does this Splitting the beam into two beams reduces the problem of a fluctuating laser One beam is used as a reference When the energy of the pulses change it will change with the same factor in both beams By dividing the energy value of the pulse travelling through the vapour by the reference value the fluctuation is annihilated To come around the problem with the large frequency interval a detector wheel 15 constructed On this several detectors can be installed The detector electronics must be constructed to measure the value of the energy and then to hold the signal until the computer program registers it Since everything will be controlled from a computer program the unit also has to be completely automatic For this reason all compo
114. s calibration method Sets detector and beam splitter to off position pe 2 p Location Calibrate lIb Input Info Cluster _ Output Parameter Info out Offset Info Cluster The offset in nm found on the laser Boolean TRUE if the calibration was successful otherwise FALSE Calibration Method 0 With GOTO Description Calibration method number 0 OK Out In this VI the folowing parameters are set 1 No Samples the numbers of samples that shall be recorded for every step in the wavelength scan 2 No Steps the number of steps that shall be taken for the scan 1f the Step parameter is not set for the Peak Data 3 Threshold the thresholds value This value defines the maximum region the laser can fluctuate 4 No Threshold samples The number of samples that shall be used when finding the average laser intensity Location Calibrate lIb Input Info Cluster Output Parameter Info out Offset Info Cluster The offset in nm found on the laser TRUE if the calibration was successful otherwise FALSE Calibration Method 1 With GOTO Description OK Out Department of Atomic Physics Lund Institute of Technology Calibration method number 1 In this VI the following parameters are set 1 No Samples the numbers of samples that shall be recorded for every step in the wavelength scan 2 No Steps the number of steps that shall be taken for the
115. s it shall initialise the calibration unit This parameter can be set every time a recalibration is wanted When calling the VI the program checks if it shall initialise the unit or not When initialising the unit the program will set all motors in the unit to their starting positions Then the saved data is fetched from a configuration file The front panel screen is updated and then the VI returns to the main program If the VI is called without the initialising parameter set it will check if anything has changed from the previous visit The things that can have changed are e change button has been pressed The VI will then call the VI for configuration of the calibration unit see section 6 3 2 3 e Anew cell for calibration might have been selected In both cases the display will be updated and the configuration data will be stored in the Info cluster 6 3 2 3 Configuration of the calibration unit This 1s the user interface for configuring the calibration unit From this screen cells can be added and removed and calibration data can be changed See picture 48 Configuration Of The Unit VI Figure 47 Flow chart for Current Calibration Settings Department of Atomic Physics Lund Institute of Technology 32 6 Programmer s guide When changing in the unit the current positions of the The name of the VI is Configuration Of the Unit This motors are always stored in the Info cluster V
116. s that it operates faster when moving the laser towards shorter wavelength This behaviour appears since the laser can be tuned in two ways If the wavelength shall be moved a short distance 1 2nm a piezo electrical crystal 1s used If the wavelength has to be changed over a larger distance the OPO crystal must be rotated Rotating the crystal takes considerable longer time to perform but the piezo electrical crystal can only change the beam towards lower wavelength In other words the best way of using the OPO laser interface is by scanning the laser from a higher to lower wavelength 36 7 Evaluation 7 Evaluation 7 1 Introduction The performance of the calibration system experiments is performed is studied in two experiments The purpose of the experiment is to find out if it is possible to use the system for calibration purposes The experiments are not performed to validate any calibration method The valuation of the calibration system is performed by hand 7 2 Experiment The test set up that is used for the experiments is shown in figure 51 To validate the system absorption spectra of NO are recorded These spectra are then compared with table values for see diagram 1 The vacuum wavelength in the diagram has to be adjusted to the air wavelength This 15 done according to the following equation AA n 1 A By using a wavelength correction curve it was found that the vacuum wavelength has to be adj
117. scan if the Step parameter is not set for the Peak Data 3 Threshold the thresholds value This value defines the maximum region the laser can fluctuate 4 No Threshold samples The number of samples that shall be used when finding the average laser intensity Location Calibrate lIb Input Info Cluster O Parameter Type Infoout I The offset in nm found on the laser nail TRUE if the calibration was successful otherwise FALSE Calibration Method 2 With GOTO Description Calibration method number 2 Description In this VI the following parameters are set 1 No Samples the numbers of samples that shall be recorded for every step in the wavelength scan 2 No Steps the number of steps that shall be taken for the scan if the Step parameter is not set for the Peak Data 3 Threshold 90 the thresholds value This value defines the maximum region the laser can fluctuate 4 No Threshold samples The number of samples that shall be used when finding the average laser intensity Location Calibrate llb Input Info Cluster O 0000 Info Cluster The offset in nm found on the laser TRUE if the calibration was successful otherwise FALSE Parameter Info out Offset OK Out Appendix 19 VI and cluster description Cell Selection Description This VI is the entry point to the configuration section of the progra
118. screen OK pressed P Save calibration data Figure 48 Flowchart for the configuration of the unit 33 Department of Atomic Physics Lund Institute of Technology 6 Programmer s guide are carried out on the cluster Example If the peak data for an existing cell shall be changed the user will first highlight the cell on the screen and then press the button to change the data Since the screen and cluster are reflected images of each other the program now know that the index of the highlighted field on the screen is the same as the index for that cell in the array cells in the Calib cluster When exiting the Configuration Of the Unit the data of the Calib cluster are stored to the calibration file 6 3 2 4 Edit peak data for cell This 15 the user interface changing the peak data for one cell See picture 49 The name of the VI is Edit Peak Data For Cell The VI is called from Configuration Of the Unit see section 6 3 2 3 The VI is called with an index parameter This index is the position of the cell in the array cells in the cluster All operations will be performed on this cell only Initialisation of the VI Print of data to screen Wait for user input Ba Add Data EN pressed uM Change Data pressed 4 Copy Data pressed Make Default pressed Change the default peak Delete pressed OK pressed Va Figure 49 Flow chart for the VI Edit Peak
119. sets the parameters for a detector according to the save parameter Location Array Functions llb Inp Parameter Description Calib in Detector pos The position the detector has in Calib cluster Wavelength The wavelength where the OFF detector stops to operate Wavelength The wavelength where the ON detector starts to operate Output Calib out CalibCluster __ Infoout InfoCluster Set Splitter Data Description The VI sets the parameters for a beam splitter according to the save parameter Location Array Functions llb Input Info in Name Save The name of the detector Determines what dada shall be set Name 16 Wavelength ON 32 Wavelength OFF Info Cluster Name Wavelength DBL The wavelength where the splitter stops to operate Output The name of the splitter save integer Determines what dada 16 Wavelength ON 32 Wavelength OFF OFF Wavelength DBL The wavelength where the detector starts to operate Calib Cluster 00 shall be set The position the splitter has in the Calib cluster ON 13 Appendix 19 VI and cluster description Test Program Description With this VI the calibration program can run by it self with out interacting with the total LIDAR application It is possible to enter both the configuration and the calibration part of the program From the f
120. t be 1 BOOLEAN telling if the calibration was successful or not 2 The offset in nm Department of Atomic Physics Lund Institute of Technology 6 3 3 Changing the code This section describes what steps that has to be taken when changing in the calibration program Only the most common changes that can be performed are described 6 3 3 2 Adding calibration method When a new calibration method is to be included the following steps shall be performed 1 The name of the calibration method has to be added to the Calib Selector See appendix 19 for more info 2 A new VI for the calibration method has to be created The VI should preferably be named Calibration Method X were X is a number The VI must have two outputs e Boolean that indicates if the calibration went OK e DBL float with the offset from the laser 3 A new case has to be added in the VI Calibrate The Laser In this case the new calibration method shall be called Data OK Check the calibration data Move motors to starting position Move laser to OFF position Select Demp Automatically VI Calibration EN method 0 4 Calibration method 1 Calibration Method 0 Calibration Method 1 Move detector and splitter to blocked position Figure 50 The Calibration part 35 6 Programmer s guide 6 3 3 3 Adding changing calibrating data If more or different data has to be added
121. t it is probably unnecessary to measure Furthermore it is not the actual absorption in exact figures that is relevant It is finding the pattern of the absorption for the vapour 4 2 2 Measuring conditions The laser pulses that are measured contain typically some 10 Joule of energy The length of the pulse is about 3 4ns and the laser repetition frequency is 20Hz 20 pulses per second The wavelength range is between 250nm to 4800nm The energy of the laser pulses fluctuates with about 1090 The pulses are transmitted into the calibration unit from a reflection of the DIAL laser beam 4 2 3 Problems To be able to measure the exact appearance of the pulses a fast detector is needed To be able to hit the detector when aligning the system the active area must be at least 50mm These conditions contradict each other The bigger the detector becomes the slower it gets The frequency range of operation is vast It is a problem to a find detector that is big enough and yet operates fast enough in the whole range A fluctuating laser is a problem If every laser pulse does not have the same energy it is not possible to know if a change in measured energy is due to the laser or to a change of absorption in the vapour EN Filter Wheel Figure 22 Picture of the calibration unit in operation 16 Department of Atomic Physics Lund Institute of Technology 4 System design The intensity of the pulse varie
122. t llb Input Ignore Change Boolean If TRUE then the VI Activity Output Parameter Description eem continue otherwise Info Cluster FALSE Appendix 19 VI and cluster description ContinueExecNoErrorCheck Description This VI checks if the program shall continue to execute or not Location Execcont llb Input Output Parameter Continue Boolean TRUE if the program can continue otherwise FALSE Convert Detector Data Description This VI 1s used to convert measured detector data towards a look up table This is done to minimise the detector characteristics in a measurement Location Detektor lIb Input Parameter Description Integer 0 measuring detector 1 Ref detector Array of DBL The measured values Info in Info Cluster Output Parameter Info Cluster Array of DBL Convert Detector Data2 Description This VI is used to convert one measured value from the detector towards a look up table This is done to minimise effects of the detector characteristics in a measurement Location Detektor llb Input 0 measuring detector Ref detector Measured value Output DBL Department of Atomic Physics Lund Institute of Technology Create Cell Data File Description Creates a file for cell data Location FileOp llb Input File Types Cluster Info Cluster Output Parameter
123. t of a mechanical switch to be used as a system 7 CW CCW Direction control input When high or unconnected clockwise rotation is selected Physical can modify the chopper oscillator timing internally fixed at 17kHz The oscillator input 0 Control Logical input that allows the phase current decay mode selection When high or unconnected the slow decay is selected 5V supply input Maximum voltage must not exceed 7V C output used as the input for an external clock source 4 Half Full Half full step selection input When high or unconnected the half step operation is selected Home indicator direction of motor rotation depends also on winding connection Oscillator must be grounded when the unit is externally synchronised Enable Module enables input When low this input floats the outputs enabling the manual positioning of the motor Must be LOW during power up and down sequence HIGH during GND2 Return path for the power section B A A output Vs Module and motor supply voltage Maximum voltage must not exceed the specified values Table 17 Pin description of the GS D200S 19 Department of Atomic Physics Lund Institute of Technology 64 Appendix 16 Pictures from the LIDAR bus and lab Appendix 16 Pictures from the LIDAR bus and lab Figure 58 Petter working with the OPO system Department of Atomic Physics Lund Institute of Technology 65 Appendix 16 Pictures from the LIDAR bus and l
124. ta that are necessary to calibrate The second part handles the calibration These two parts are separated although the calibration part uses the data set by the configuration part Since the calibration program is one part of the total LIDAR system developed by the LIDAR group there are some basic rules that must be followed 6 2 2 Basic design In this section the basics of the program are explained These things are e Stopping of the program There must be a way to stop the program at any given time Screens for input of data How to control the sequence of execution How data is passed to the different modules The main data clusters in the program storage of data from the calibration program Parameters in the program 6 2 2 1 Stopping the program To be able to stop the program at any time two global Boolean have been implemented These are Change activity and Run If the system has to change activity the Change activity variable is set to TRUE modules in the LIDAR system shall then stop to make the action possible In the same way the Run variable is set to FALSE when the system shall be shut down These two variables are never set in the calibration program but they are checked to determine if the program shall continue execution or not Two VIs implemented to perform the check These ContinueExecErrorCheck and Department of Atomic Physics Lund Institute of Technology ContinueExec
125. tector 1 Detector 2 V 0 1 000 2 2 3 32 1 04 0 03 0 933 3 2 3 2 1 04 0 1 0 794 3 2 3 1 0 13 0 741 3 2 3 0 9 0 3 0 501 2 7 2 2 0 82 0 33 0 468 2 5 221 0 92 0 4 0 398 2 3 1 9 0 78 0 43 0 372 1 65 0 79 0 5 0 316 1 6 1 35 0 82 0 53 0 295 1 55 1 2 0 83 0 6 0 251 1 4 1 15 0 83 0 63 0 234 1 3 1 1 0 83 0 8 0 158 0 9 0 7 0 83 0 83 0 148 0 75 0 61 0 8 0 9 0 126 0 82 0 7 0 8 0 93 0 117 0 7 0 55 0 72 1 0 100 0 8 0 6 0 78 Table 20 Result from experiment 1 Experiment 1 Output V i 1 Detector 1 Detector 2 amp Ratio 1 5 0 5 0 000 0 200 0 400 0 600 0 800 1 000 1 200 Trancmittance Diagram 7 Resutl from experiment 1 69 Department of Atomic Physics Lund Institute of Technology Appendix 18 Experiment to determine the performance of the detectors Experiment 2 Description Wavelength 500nm Optical density Transmittance 0 1 0 03 0 933 0 1 0 794 0 13 0 741 0 3 0 501 0 33 0 468 0 4 0 398 0 43 0 572 0 5 0 316 0 53 0 295 0 6 0 251 0 63 0 234 0 8 0 158 0 83 0 148 0 9 0 126 0 93 0 117 1 0 1 1 03 0 093 1 1 0 079 1 13 0 074 1 3 0 050 1 33 0 047 1 4 0 040 1 43 0 037 Table 21 Result from experiment 2 Diagram 8 Resutl from experiment 2 Department of Atomic Physics Lund Institute of Technology Detector 1 V 222 252 3 2 3 19 2 5 2 4 2 3 2 2 1 7 1 65 1 5 1 45 1 0 9 0 95 0 94 0 9 0 84 0 75 0 7 0 46 0 4 0 4 0 26 Experiment 2 Transmi
126. ters are not stored on disk 3 The parameters of the beam parameters are not saved to file 4 The data for the cells is retrieved from data file and stored in the Calib cluster 5 All motors are moved to the starting position splitter These Location Program llb Input Parameter Description T Calib Cluster File Types Cluster Info Cluster 8 Output Parameter Description Calib Cluster File Types out File Types Cluster Info Cluster Insert New Cell Into Array Description Inserts new cell into the cell array in the cluster The VI sorts the array after the names of the cells Location Array Functions llb Input I Calib Cluster ________ InfoCluster o The name of the new cell Department of Atomic Physics Lund Institute of Technology Calib Cluster Info Cluster Integer The position the new cell has in the array in the Calib cluster Insert New Cell Into Array No Sorting Description Inserts new cell into the cell array in the Calib cluster The VI does not sort the cells This VI shall only be used when the cell data 1s retrieved form file Location Array Functions lIb Input Calibin CalibCluster Data Cellcluster Info in Info Cluster Output out CalibCluster InfoClster O Z O 0 I
127. the system can detect the structure even if the laser fluctuates Experiment 1 Output from detector V 447 447 5 448 448 5 Wevelength nm Diagram 2 Data from experiment 1 For each measuring point the mean value of 5 laser pulses is recorded Number of measuring points 50 scan region 447 000 nm to 449 450 nm The result from the experiment is found in diagram 2 and diagram 3 Cell output a Ref output Cell Ref Comparison between table value and measured absorption Adjusted data 446 5 447 447 5 448 448 5 Wavelength nm Table value Cell Ref Adjusted Diagram 3 Comparison between the table value and the measured absorption for NO The scale for the two has been adjusted to be able to see the structure easier The table value is adjusted to air wavelength Department of Atomic Physics Lund Institute of Technology 38 7 Evaluation 7 3 2 Experiment 2 In this experiment a scan is performed over the NO structure This 15 done to see 1f it is possible to use the system to find and in theory correct the wavelength scale in the OPO system From the first experiment it is found that the laser energy fluctuated with about 90 In order to get more accurate measurements the reference detector is used as a gate If the energy in a laser pulse is outside a window of 25 of a mean value for the reference detector then this value is discarded and a new value 1
128. to Coupler 2 51 Detector Por 5 Motor 3 A 3 B 8 Mator 3 0 1 Shield GND pto sr m otar 1 Step Motor 1 Dir F Notor 2 Step Matar 2 Dir Motor 3 Step Motor 3 Dir pto Coupleri Signa G pto Coupler3 Signa p Notar Hator H Opta Coupler GND A B C D E F G H J K L M N P R S T U V W X Y Z a b d e f g h B D E F G H J K L M N P R S T U V Y 2 b LI s an i LLLBLU 1 LLLBLU ___ BRN ABCD ABCD ABCD STEPPING MOTORS ABCO Motor 1 Motor 2 Motar 3 Motor 4 5 18Y POCHE EST sch 17324 POVER SUPPLY 1 AN POWER SUPPLY 2 SHEET 1 yun xipuoddy SULIIM SULILM IaMOg xIpuaddy Appendix 6 Stepper motor boards Appendix 6 Stepper motor boards UTE OF TECHNOLOGY CS ECTION TO STEPPER MOTORS Ep e sss dd 2883 18 12 SHEET 1 OF 1 3 25 38 Sch STEPPING MOTOR STEPPING MOTOR STEPPING MOTOR BORRD 3 STEPPING MOTOR VAN 4 4 RN ea gt n 0 ze n OOOO us 54 Department of Atomi
129. to make a calibration the following changes have to be made 1 The Cluster of Peak Data has to be updated with the new parameters 2 The VI Edit Peak Data For Cell has to be updated to make the user able to change the parameter 3 The VI Check Peak Data has to be updated to check the reasonableness of the new parameter If the parameter is to be displayed the following have to be made l The VI Get Peaks From Cell have to be changed for the new parameter The front panels of the VIs Configuration Of The Unit and Edit Peak Data For Cell have to be updated with the new parameter 2 The front panel of the VI Cell Selection has to be updated 6 3 4 Interacting with the OPO laser system The interaction with the OPO laser is done through a LabVIEW interface the configuration and interacting needed to control the laser is performed within this interface This means that the calibration program does not know what laser system it is using 20 Department of Atomic Physics Lund Institute of Technology 6 3 4 3 Changing wavelength on the laser When the calibration program wants to change the wavelength form the laser it simply sends the value of the new wavelength to the OPO laser interface The control of the execution will be returned to the calibration program when the new wavelength is adjusted in the laser The only thing that must be taken into consideration when using the OPO laser interface i
130. ton is used when a new calibration cell shall be added to the system When pressed a dialogue box is displayed in which the new name of the cell shall be typed see figure 35 After the name is entered the program will open the front panel for the Change Calibration Data see below Delete button Calibration Cell _ Revolver This button is used if a defined cell shall be erased from the system To delete the cell highlight it in the Calibration Cell selection box and then press the Delete data button A warning message box in which the action has to be confirmed is displayed before the cell is removed Figure 35 Front panel of New Spiece Name vi This VI is used when a new cell shall be added to the system _ Calibration Peak 448 100 4475 448 200 447 500 SUD nu Figure 34 The front panel for Change in calibration unit The configuration of the calibration unit is executed from this VI Department of Atomic Physics Lund Institute of Technology 24 5 User manual Remove button This button is used when a cell shall be removed from the calibration unit The program checks if there is a cell present in the unit If not a warning message is displayed The revolver will then be moved to make it possible to remove the cell A dialogue box is displayed see figure 36 in which the action shall be confirmed Confirm when you have removedthe cell _ at positio
131. ttance Detector 2 V 3 92 3 32 3 2 7 2 05 2 1 8 1 8 1 4 1 38 1 2 1 15 0 83 0 78 0 74 0 73 0 65 0 61 0 55 0 5 0 25 0 25 0 24 0 15 1 1 Detector 1 Detector 2 1 04 1 04 0 9 0 83 0 83 0 78 0 79 0 82 0 82 0 81 0 82 0 83 0 83 0 81 0 8 0 76 0 74 0 71 0 69 0 61 0 6 0 58 0 58 4 Ratio Detector 1 Detector 2 This experiment is performed in the same way as for experiment 1 The only difference is that the detectors have changed place see figure 61 The outputs are measured for different transmittance of the filters in slide box B The average of 1200 pulses is used for every transmittance 70 Appendix 18 Experiment to determine the performance of the detectors Experiment 3 Description In this experiment the energy of the laser pulses are changed by neutral density filters in slide box A see figure 61 The Detector 2 is used as a reference detector Recording Nr 1 Nr 2 Nr 3 Nr 4 Nr 5 Nr 6 Nr 7 A 500 A 500 lt 448 1 448 A 448 A 448 448 R 3 4k R 5 7k R 5 7k R 3 4k R 3 4k R 10k R 10k Optical Transmit Output Output Output Output Output Output Output density tance V V V V V V V 0 1 000 3 915 4 780 4 802 4 474 2 568 3 950 3 510 0 1 0 794 3 075 4 783 4 808 3 599 1 980 3217 2 892 0 3 0 501 2 035 4 095 3 850 2 434 1 343 2 253 2 004 0 4 0 398 1 585 3 265 3 040 1 909 1 045 1 808 1 659 0 5 0 316 1 161 2 270 2 135 1 374 0 771 1 367
132. ture development 1 3 Results The calibration system has been constructed and the program and unit have been integrated to the main LIDAR system The system 15 fully implemented The task that was not completed in this project was a fully implemented tested calibration method However experiments have been performed that clearly indicates that the unit can perform a calibration see section 7 Evaluation But more study and development are needed to achieve a fully automatic calibration mechanism Further developments on the calibration system have started to improve its performance These will make the unit work in the infrared region 1 4 The progress of the project This project has been ongoing since September 1995 During the period up till now many things have happened that have changed the direction of the project When the project started in 1995 the purpose was to develop a calibration unit as well as a program for the existing system that operated with a Nd YAG pumped dye laser The laser was controlled by an external PC which was steered from the calibration system through a serial port The intention of the LIDAR group was to change this laser system to a new OPO system Optical Parametric Oscillator The unit should be prepared for this The unit was constructed as well as the electronics and program In 1998 the OPO lasers were ready to be installed For this project a decision had to be taken Should it be c
133. uage is to generate programs that look and perform like all other instruments that are found in a lab LabVIEW is designed for instrumentation and is equipped with the tools needed for test and measurement applications In LabVIEW you build programs called virtual instruments VIs instead of text based programs From the VIs it is possible to control plug in boards and external equipment via serial communication VXI VME or GPIB Through these interfaces the program can control all the instruments in a lab It 15 easy to change the set up and the presentation of an experiment see figure 10 Computer Networking ENS B GPIB Instrumen ts TN VXI Instruments Plug in Data Acquisiti Boards and Signal Conditioning RS 232 Instruments UUT 55 Figure 10 The different ways LabVIEW controls surrounding equipment 6 2 3 3 The structure of a LabVIEW program The components of a LabVIEW program are the VIs Each VI consists of two different windows a front panel and a block diagram These windows also have an icon connector See figure 9 The front panel The front panel is the user interface in LabVIEW program This is the virtual instrument that the users will se while executing the program On this panel all the control components for user input are found knobs buttons switches Here are also the graphs and indicators used for data presentation found The idea is to construct a p
134. usted with 0 125nm at 450nm 23 Detectors Figure 51 7est set up for the experiments Beamsplitter Cell containing NO To be able to know the error in the wavelength scale of the OPO system and to find out if it 15 possible for the calibration system to find this error a wavemeter is used to find the correct wavelength The wavemeter shows that the wavelength from the OPO system has an offset of about 0 22nm Two experiments are performed In the first experiment a fast scan is made over the absorption structure This is done to verify if the system can find the structure when scanning fast This is necessary when making rough calibration It is also performed to see if the system can operate with a fluctuating laser power The second experiment is done to determine if it is possible to find the error in the wavelength scale of the OPO system Laser beam Mirror Filter NO2 absorption cross section Inst Environmental Physics Univ of Bremen no2 293h dat 9 00E 19 8 00E 19 7 00E 19 6 00E 19 Cross section cm2 5 00E 19 4 00E 19 3 00E 19 445 5 446 446 5 447 447 5 448 448 5 449 449 5 450 450 5 Vacuum wavelength nm Diagram 1 Measured crosssection for in vacum 24 Department of Atomic Physics Lund Institute of Technology 37 7 Evaluation 7 3 Result 7 3 1 Experiment 1 In this experiment a fast scan is performed over the NO structure This is performed to evaluate if
135. w the expected 5 the input voltage SV minus the drop in the semiconductors The problem was found and corrected After this the output could reach 4 5 To solve the problem with the fluctuating laser energy the experiment is changed to the second set up where one of the detectors is used as a reference From experiment 3 the following is found e The detector has two linear regions with a transition area The characteristics is linear in the region 4 1V to 2 0V and from 1 7V to 0 7 Due to this a conversion table is recorded for the two detectors The electronics become saturated above 4 2V e The gain in the electronics has no impact on the characteristics The important thing is to let the signal start at an as high value as possible without saturating the electronics When this was found it was decided that the electronics should have high gain This is also to spare the detector i e not illuminate the detector more than necessary This also implicates that the filter wheel has to be able to suppress the laser beam some magnitudes of ten detector is not wavelength dependent At least not in the region 450nm to 500nm The characteristics are not changed over time The recordings are done during 3 days and the set up was completely changed one time This showed that a characteristic that has been recorded can be used again The active area on the detector is large and it is not important where the beam hits e Th

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