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DOEK-Kit - Department of Physics and Physical Oceanography

1. Such transmission function can be sinusoidal as in the case of a grating obtained by holographic recording of a two wave interference The transmission function may in this example take any value within a certain range In contrast the values of the transmission function obtained when addressing a LCD are limited to 256 values due to the transmission of the signal as a VGA grayscale value The most simple example is of course a signal that consists of only two different transmission values binary elements For a binary linear phase only grating the structure can be described by the transition points x at which the grating changes its transmission value from T exp 1D to T2 exp iM2 or vice versa The diffraction orders obtained from such gratings are given by Ara sin Ad 2 Y Depor mx y g8 m nm k 1 for all diffraction orders with m 0 where AD denotes the phase difference between the two transmission values For simple examples the diffraction pattern can be easily analysed with this formula Fourier transformation with a lens The diffraction image has to be changed with a lens from an infinite to a finite dimensional distance The transmission of the field through the lens results in a position depending phase shift and can be described by multiplication with the following lens transmission function i 124 y Tiens e A The description of the diffraction occurs because of the finite distance in the
2. SONY LCXO16AL Grey level image playback 26 6 mm x 20 0 mm 1 3 832 x 624 32 um max 60 Hz typically 200 1 82 mm x 82 mm x 23 mm 0 15 kg 100 240 V DC 50 60 Hz max 150 mA 15 V AC 5 ca 250 mA Users Manual DK LCMH 800A 21 4 3 Connectors mig pea 1 2 3 Figure 6 Connectors of the DK LCMH S00A The device provides three female connectors As depicted in Figure 6 these connectors are 1 the serial port connector for configuration of the device 2 the power supply connector 3 the VGA video input connector 4 3 1 1 Serial Port Configuration of serial port connector 1 Pin 1 5V AC Pin5 RXD Pin 2 5V AC Pin6 CTS Pin 3 TXD Pin7 GND Pin 4 RTR Pin8 GND Connection parameters Transfer rate 4800 19200 Bit s Data bits 8 Parity No Stop bits 1 Data flow control Hardware handshake RTR CTS 22 User s Manual DK LCMH 800A 4 3 1 2 4 3 1 3 4 4 Power Supply The direct current DC connector 2 is used for power supply of the device The power pack cable 15 V has to be plugged to this connector The positive terminal is the inner connector pin Video Input The video input 3 must be connected to the graphics board of a personal computer using the VGA adapter cable delivered with the SLM The computer is used as the source of image and video data The connector configuration is specified as follows Pin Function Red colour si
3. The expanded and collimated laser beam illuminates the display homogenously The linear polarisation of the laser has to be adjusted in that way that the addressed image will be displayed with optimal contrast and brightness Use a Fourier lens with a long focal length for projection A focused and enlarged projection without other lenses can be created Define the focal plane of the lens with the help of an adjustment paper The Fourier image in that plane can be filtered spatially The filtering has to be progressed only in the central diffraction order blind out other orders A digital camera can be mounted on a tripod to take pictures from the screen m e Polarised Laser U Module SLM L Filter L2 Screen Figure 26 Set up for Spatial frequency filtering Suggested tasks 1 Why don t you need polarisers before and behind the display Test the influence of an analyser behind the display 2 Use a grating with a well known diffraction image in the Fourier plane Exercise the following spatial filtering a block the zero diffraction order b keep the zero diffraction order c keep only higher diffraction orders e g higher than 3rd order Tutorial Experimental Part 81 8 4 5 8 5 8 5 1 8 5 2 8 5 3 3 Use two crossed gratings as image chess board pattern Carry out a spatial filtering and see if the horizontal lines disappear on the projection screen 4 Design a simple image with a drawing
4. 6 4 Full Screen window functions This full screen image will display a task bar immediately after its appearance This taskbar will disappear but emerge again when the position of the mouse pointer of the PC is moved towards the right edge of the window Indicator for currently active toolbar button Slider and value indicator for parameter Zoom of basic tile image Toolbar button explanation appears Figure 19 Toolbar of the full screen window The functions accessibly by the taskbar buttons offer the possibility to manipulate the basic tile image by superposition of signals that represent optical elements lens prisms by zooming and translating the image and by changing its grayscale values Application Software Manual 45 The taskbar will have the following buttons Zoom In Button Pushing this button will perform a fast zoom in operation on the image that is the basic tile of the displayed image composition Note that the zoom does not change superimposed optical functions it will only be applied to the basic tile a Zoom Out Button Pushing this button will perform a fast zoom out operation on the image that is the basic tile of the displayed image composition Note that the zoom does not change superimposed optical functions it will only be applied to the basic tile Save Button Pushing this button will open a dialog in which a file name can be s
5. Fresnel approximation Here 4z is the distance behind the lens were the Fourier transform of the light is observed ey 0 0 y y ikz 00 e ik e A e E x y Az E x y O e f e dx dy PADS A x y 0 J y Tutorial Theoretical Part 69 7 3 8 The exponents of the exponential function are quite similar By using 4z f Shift of the observation point to the focal plane of the lens both can be simplified e 472 ik Tr ed y E x yn Lat MIES ye dedy E ea 12 inf Df Af In the focus plane of a lens a field distribution is obtained which is similar to the Fourier transformation of the lens multiplied with a phase factor The corresponding intensity distribution is proportional to the intensity distribution obtained from Fourier transformation of the incident field which describes its far field diffraction pattern Spatial frequency filtering For an object placed in front of a lens having a distance d to it the light propagation in front of the lens can be simulated using the Fresnel approximation of the Kirchhoff diffraction integral The result shows that the light in the focal plane is only changed by a phase factor dependent on d and for the special case d f the field in the focus plane is equivalent to the Fourier transformation of the field in the object plane apart from a factor which does not depend on x and y The calculation yields as i x l 2f es a E x y f Ta X E ee v T
6. Rectangular Aperture binary Use this function to create a rectangular aperture The size of the aperture can be defined by specifying the aperture width and aperture height With the sliders on the taskbar one can change the gray levels of the background and of the aperture 50 Application Software Manual 6 6 6 6 6 7 6 6 8 6 6 9 6 6 10 Circular Aperture binary Use this function to create a circular aperture The radius of the aperture can be defined by specifying a numbers of pixels With the sliders on the taskbar one can change the graylevels of the background and of the aperture Binary Fresnel Zone Lens binary Use this function to create a Binary Fresnel Zone Lens graylevel image representation In the dialogue field the lens function can be characterized by the radius of the smallest ring which is defined by a number of pixels Fresnel Zone Lens multilevel Use this function to create a 256 level Fresnel Zone Lens graylevel image representation In the dialogue field the lens function can be characterized by the radius of the smallest ring which is defined by a number of pixels It can be specified whether the image representing the lens should be positive or negative Binary Axicon binary Use this function to create a Binary Axicon graylevel image representation In the dialogue field the lens function can be characterized by the radius of the smallest ring which is defined by a number of
7. software can be started from the Microsoft Windows Start menu as shown in the next section Start of DK LCMH 800A Control Program You can start the SLM control program by selecting Programs gt LC2002 Control Program in the Microsoft Windows Start menu as shown in Figure 8 Figure 8 Starting the LC2002 control program After starting the program the user dialog LC2002 as shown in Figure 9 appears At the same time the program tries to identify automatically the Users Manual DK LCMH 800A 25 SLM display that should be connected to the RS 232 port COM1 or COM2 If the identification succeeds the coloured Connected sign appears in the lower right corner of the dialog window In the title of the dialog window the version of the LC2002 s firmware and its individual series number are displayed LC2002C Firmware Version 1 07 SN 10162 Figure 9 User dialog of the control program after start up If no SLM device is found to be connected to the RS 232 interface the error message in Figure 10 will be displayed LC2002 EXE Error Figure 10 Error message if no DK LCMH 800A device has been recognised 26 User s Manual DK LCMH 800A In this case confirm the message to make the program change into the demonstration mode In this mode no commands are directed to RS 232 port Then check if all cables are properly connected to their corresponding ports It is also possible to select
8. 02 38 40 51 56 Asia Newport Opto Electronics Technologies HE EET ARE 2535 37 32 C Hk 200131 253 Aidu Road Bld 3 Flr 3 Sec C Shanghai 200131 China Telephone 86 21 5046 2300 Fax 86 21 5046 2323 Newport Corporation Calling Procedure If there are any defects in material or workmanship or a failure to meet specifications promptly notify Newport s Returns Department by calling 1 800 222 6440 or by visiting our website at www newport com returns within the warranty period to obtain a Return Material Authorization Number RMA Return the product to Newport Corporation freight prepaid clearly marked with the RMA and we will either repair or replace it at our discretion Newport is not responsible for damage occurring in transit and is not obligated to accept products returned without an RMA E mail rma service O newport com When calling Newport Corporation please provide the customer care representative with the following information e Your Contact Information e Serial number or original order number e Description of problem i e hardware or software To help our Technical Support Representatives diagnose your problem please note the following conditions Is the system used for manufacturing or research and development What was the state of the system right before the problem Have you seen this problem before If so how often Can the system continue to operate with this
9. 3 10 4 6 3 11 4 6 4 4 6 4 1 Example GGW 254 lt CR gt OK Contrast Parameter Command name min max CON 0 255 Example CON 196 lt CR gt OK Brightness Command name min Parameter max BRT 0 255 Example BRT 183 lt CR gt OK Other Commands Echo switching on off The command ECHO OFF lt CR gt suppresses the mandatory response with OK on each correctly decoded command or error code messages The command ECHO ON lt CR gt can be used to switch the echo on again 38 User s Manual DK LCMH 800A 4 7 Error Messages The meaning of error messages is given in the following list ERR 1 Overflow of the symbol RS 232 receiving buffer handshake does not work internal or external error ERR 2 Unexpected symbol in Command command neither letter incorrect digit nor underscore ERR 3 Unknown command Command incorrect ERR 4 Parameter of preceding Parameter command not allowed incorrect ERR 5 Unknown parameter Parameter incorrect ERR 6 Unexpected symbol in Parameter parameter neither letter incorrect digit nor underscore ERR 7 Digit was expected but a different symbol received ERR 8 Command did not end correctly instead of end symbol another symbol was received ERR 9 Command parameter missing ERR Internal error EEPWR LC2002 defective 10 ERR Internal
10. Lens Show Binary Axicon Show Axicon Show Concentric Ring Segments Show Single Slit Show Double Slit Show Binary Linear Grating Show Binary 1 to 5 Linear Beamsplitter Grating Show Binary 1 to 2x2 Separable Array Beamsplitter Grating Show Binary 1 to 5x5 Separable Array Beamsplitter Grating Show Binary 1 to 5x5 Non separable Array Beamsplitter Grating Show Sinusoidal Grating Show Blazed Grating Figure 20 Menu entries for optical functions Application Software Manual 49 6 6 1 6 6 2 6 6 3 6 6 4 6 6 5 Blank Screen binary With this function you can create a homogeneous gray level screen If the mouse pointer is moved to the right edge of the window a taskbar for changing the addressed gray level occurs Horizontally Divided Screen binary With this function you will create a horizontally divided screen constitng of two homogeneous graylevel partial screens If the mouse pointer is moved to the right right edge of the window a taskbar for changing the addressed gray levels occurs Random Bitmap multilevel With this function you will create a random pixel distribution using 256 grayscale values This function can be used to realize the optical function of a random phase plate Random Binary Bitmap binary With this function you will create a random pixel distribution using only two grayscale values This function can be used to realize the optical function of a random binary phase plate
11. No Meaning Internal symbol 0 Most significant byte PLL factor 1 Least significant byte PLL factor 2 HPOS image position horizontal 3 VPOS image position vertical 4 Internal configuration HDN 5 SHP pixel synchronicity of image playback 6 Internal configuration HCKP 7 Internal configuration HSTP 8 Internal configuration CLPP 9 Internal configuration SHD 10 Internal configuration SH 11 Internal configuration MBK 12 MODE image format switching 13 DIR e g scanning direction 14 GCW entry point gamma corrector white 15 GCB entry point gamma corrector black 16 GGW enhancement gamma corrector white 17 GGB enhancement gamma corrector black User s Manual DK LCMH 800A 18 BRT brightness medium transparency 19 CON contrast 20 Internal configuration BLIM 21 Internal configuration WLIM 22 Internal configuration SBRT 23 Internal configuration SID 24 Internal configuration VCOM 25 Internal configuration CENT 26 ID number Most significant byte 27 ID number Least significant byte 4 6 3 1 Image width Parameter min max PLLP 848 2045 Command name Example PLLP 1054 lt CR gt OK The parameter influences the pixel synchronicity of the image playback For the image format SVGA 800 x 600 image pixels usually 1054 is the correct value 4 6 3 2 Horizontal image position Command name i Pa
12. OO 80 SAA A O angeeearteies 80 8 4 5 Keywords for preparatiON ooococonocccnnncccnonncnnoncnnnnnccnnnnccnnn 81 8 5 Mach Zehnder Interferometer with controllable phase shift 81 A CU VE ca se ccassencttet a a a ee 81 8 5 2 Required elements O oe 81 sem Pio A e Ree een ROC re 81 S J SUBBESEd tas Katia eel eias aes 82 8 5 5 Keywords for preparation eeeeseesseceseeeeeeeneeesaeeees 82 9 Maintenance and Service 83 9 T SODAS SOLVICE il gaitas 83 9 2 Service POr dad 84 Preface IX List of Figures Figure 1 General Warning or Caution Symbol cssccsscsssssssseseeeees 10 Figure 2 Electrical Shock Symbol e ssesooeseesossooesosssesooesosssossoossosssssoossosso 10 Figure 3 CSA mark with C and US Indicators moommsmmoo 10 Figure 4 O DY E i sumi iaa ao coeda d 11 Figure 5 Locations of warnings on the LaseP sccscscccccscsccsseeseees 13 Figure 6 Connectors of the DK LCMH 800A sesoossessoesoossessossosesesssssooe 21 Figure 7 Connecting the DK LCMH 800A for usage essessoesosssessosso 23 Figure 8 Starting the LC2002 control program ccscessscscscsesssseeeees 24 Figure 9 User dialog of the control program after start up ooooomoooooo 25 Figure 10 Error message if no DK LCMH 800A device has been TECOS dci e is 25 Figure 11 Selection of COM port iiscsccesicasecassscsszeontssacsbinccsetscnperasiveaezenseods 26 Figure 12 Gamma Correction controls
13. V and V are complex numbers which tell about the relative amplitudes and phases of the two basic linear polarizations It is convenient to normalize this vector V so that IVI 1 and the field strength i a amplitude is expressed in a separate variable A linear polarization is given by vectors of the form COS V sin a which tells that the polarization components in x and y direction do not have a mutual phase delay Arbitrary states of polarization are referred to as elliptic polarization and are given by vectors y cosa exp il 2 sina exp il 2 where T denotes the phase delay between the polarization components The expression of polarization states can be used to analyse the propagation of light in anisotropic media like solid state matter crystals or liquid crystals 58 Tutorial Theoretical Part 7 2 3 Propagation in anisotroptic media Materials which on the atomic level can be decribed as a regular arrangement of particles in a well defined lattice are referred to as crystals If the material 1s not isotropic this highly ordered state of matter nevertheless leads to the existance of optical axes in the material Liquid crystals can be described by the same model due to the translational order of the molecules Light propagation parallel to an optical axis is characterized by two indices of refraction n and n which are usually different and are valid for two different states of polarization Thi
14. controls are O Contrast Control This control can be used to modify the image contrast tt Brightness Control This control can be used to modify the image brightness YO Image Width Control This control can be used to modify the image width Many technical applications require a very exact control of the image width For this purpose a test image with a fine stripe pattern is used If the image width is not adjusted exactly a Moir pattern results from the stripe pattern and the pixel structure of the LCD matrix This Moir pattern can be seen in the projected test image and vanishes when the image width is correctly adjusted Horizontal Image Position Control This control can be used to modify the horizontal image position Vertical Image Position Control This control can be used to modify the vertical image position e Image Sharpness Control This control can be used to modify the image sharpness Many technical applications require a very exact control of the image width For this purpose a test image with a fine vertical stripe pattern and a bright dark transition is recommended to be used If the image sharpness is not exactly adjusted shadow effects ghosts can appear However if the adjustment is corrected the stripe pattern is rich in contrast and sharpness and no ghost patterns appear 28 User s Manual DK LCMH 800A 4 5 5 Controls in the Field Gamma Correction The Gamma Correction f
15. entering a value The gamma curve is linear if the entered value is 0 and can be changed to concave and convex nonlinear curves by entering positive and negative values respectively yr Invert displayed bitmap Button This toggle button will invert the grayscale value of the displayed full screen image This includes any superimposed lens and or prism functions This inversion can be reversed simply by clicking the button again which will cause the button to be no longer toggled Translate in X direction Button Pushing this button will move the shown image with respect to the X direction This function can be used to align the displayed functions with respect to the incident beam Note that the translation does change the basic tile and any superimposed optical functions if present simultaneously In order to switch to a translation in Y direction click on the button again Translate in Y direction Button Pushing this button will move the shown image with respect to the X direction This function can be used to align the displayed functions with respect to the incident beam Note that the translation does change the basic tile and any superimposed optical functions if present simultaneously In order to switch back to a translation in X direction click on the button again Calculating a diffractive optical element DOE To compute a DOE the signal image size needs to be smaller than 200x200 p
16. error EEPRD LC2002 defective 11 ERR Internal error DACWR LC2002 defective 12 ERR Internal error EPTWR LC2002 defective 13 ERR Internal error RESTORE LC2002 defective 14 User s Manual DK LCMH 800A 39 4 8 Assembly Drawing In order to assemble the SLM device on one side four drill holes M2 are provided Caution The assembly screws must not go deeper than 8mm into the box Figure 16 presents the SLM assembly drawing The dimension values are given in mm M2 82 0 82 0 Figure 16 DK LCMH 8004 assembly drawing 40 Laser Module 5 Laser Module 5 1 Technical data Wavelength 532 nm Operating voltage 5 V DC Power input lt 250 mA Aperture 15 20 mm Output power 1 mW Beam diameter focus adjustable Operating temperature 15 C 30 C Laser class Class 2 laser with FDA registration 5mm Thread Adjustment Range 20 mm Thread 62 mm max 144 mm Figure 17 Geometrical size of the provided laser module Laser Module 41 The provided laser is a class 2 laser module Class 2 laser products can emit 1 mW of accessible laser emission A class 2 laser can cause eye damage if a person deliberately forces himself to stare into the beam despite the strong natural reflex to avert his gaze Do not look into the laser beam or on any reflections Some basic guidelines for Laser Safety Never look into the beam of any
17. image with a grayscale signal that resembles the optical phase function of a prism in Y direction This means that all diffraction angles created by the signal on the LC Display are changed when such function is superimposed The strength of the optical prism function can be changed by adjusting the value given on the task bar by moving the slider or by directly entering a value In order to switch back to a prism superposition in X direction click on the button again 1 Adjust Graylevel 1 Button This button will only be accessible if the basic tile image is binary i e consists of only two different graylevel values Pushing this button will than permit a change of one of the two grayscale values by moving the slider or by directly entering a value Adjust Graylevel 2 Button This button will only be accessible if the basic tile image is binary i e consists of only two different graylevel values Pushing this button will than permit a change of the second of the two grayscale values by moving the slider or by directly entering a value Adjust Gamma curve Button This button will be accessible if either the basic tile image is binary and a lens and or prism functions are superimposed or if the basic tile image is not binary Application Software Manual 47 6 5 Pushing this button will than permit a simultaneous change of all grayscale values by moving the slider or by directly
18. in contrast to the contiguous diffraction pattern produced by nonperiodic objects The discreteness of the spectrum of spatial frequencies contained in a periodic object leads to maxima in the far field diffraction which are observed at well defined diffraction angles and referred to as diffraction orders For simplicity of the discussion only objects with a periodicity in one spatial dimension will be treated here If the grating period i e the distance after which the diffraction object repeats its structure is denoted by the symbol g the diffraction angles m can be obtained from the grating equation g sin 0 sin 8 ma where the incidence angle is denoted as 9 and from the simpler form gsing M which is valid for waves incident perpendicular to the grating As a result the Fourier transformation integral is simplified to a Fourier series with coefficients Am describing the field amplitudes of the diffracted waves given by g A 1 exp 215 dx 8 0 68 Tutorial Theoretical Part 7 3 7 In this formula the diffracting object is described by a spatially resolved complex valued transmission function t x which summarizes changes of amplitude and phase of the transmitted wave as a function of the position The given integral does not take the second spatial coordinate into account so that it is only valid for objects with a constant transmission function with respect to the y direction linear gratings
19. in digital clocks digital thermometers pocket calculators and video and data projectors Due to the low cost robustness compactness and the advantage of electrical addressing with low power consumption LCD s are superior to other technologies They feature an even wider spectrum of applications than the mentioned and open further fascinating possibilities in the frame of photonics as a key technology of the 21st century Main component of the kit is a spatial light modulator based on a translucent LCD Five experiments see section 8 with questions show the diversity of topics that can be experimentally investigated Hence the experiments are qualified for introductory courses and advanced laboratory in scientific classes depending on the chosen questions Introduction to liquid crystal physics Liquid crystals LCs are a phase of matter where the molecule order is between the crystalline solid state and the liquid state The LCs differ from ordinary liquids due to long range orders of their basic particles i e molecules which are typical for crystals As a result they usually show anisotropy of certain properties including dielectric and optical anisotropies At the same time they show typical flow behavior of liquids and do not have stable positioning of single molecules There are different types of liquid crystals among which are nematic and smectic liquid crystals Nematic liquid crystals show a characteristic linear alignment
20. in the recording material A requirement for recording such a hologram is the ability for interference referred to as coherence of object and reference wave field If the hologram is illuminated with a reference wave it behaves like a diffraction grating and a wave field proportional to the object wave appears in one particular diffraction order Thus optical waves are created that permit the three dimensional observation of the recorded object It is possible to compute the diffraction patterns created by object and reference waves leading to the name Computer generated Hologram for objects that create the same spatial wave modulation by means of a microstructure of a swichable light modulator For such computation the intensity and phase must be calculated and accordingly added for every object and hologram point Such computation is very demanding and therefore CGHs which reproduce three dimensional objects will not be the subject of the experiments in this kit keywords off axis on axis set up thin and thick holograms coherence CGH 64 Tutorial Theoretical Part 7 3 3 Kirchhoff diffraction integral A plane wave En kz ot E E e propagates in z direction and is incident onto an object at z 0 Here denotes the frequency of the light and 27 k A is the wavenumber which is inversely proportional to the wavelength of the light A This object is assumed to be thin so that it can be described by a complex transmis
21. light source and LCD matrix We strongly recommend you to consult Newport in this case Keep water away If water or some other liquid is spilled into the SEM device serious damage can occur Please consult Newport services in such a case Avoid touching the LCD User s Manual DK LCMH 800A 19 4 1 7 Avoid touching the LCD because this might cause damage to it or reduce its optical quality Cleaning the LCD Wipe the LCD very carefully with a soft dry and clean cloth or with compressed air If you are not sure if and how to clean the LCD consult Newport services Electrical Connections Connect the SLM only to other components if the power supplies of all components are switched off For power supply of the SLM use only the power pack plug which is delivered with the SLM Housing Do not open and touch the SLM device as this is dangerous and may seriously damage it Do not attempt to disassemble the SLM There are no user serviceable or adjustable parts inside NOTE If the stated cautions are disregarded the warranty claim expires 20 User s Manual DK LCMH 800A 4 2 Technical Data Display Type Colours Active Area Number of image pixels Pixel Pitch Image frame rate Contrast ratio Device Dimensions L x W x D Weight Operating voltage of power pack plug Power input of power pack plug Operating voltage of LC2002 Positive terminal at inner pin Power input of LC2002
22. of the molecules they have an orientational order but a random distribution of the molecule centers Smectic liquid crystals additionally form layers and these layers have a different linear orientation directions Therefore smectic liquid crystals have an orientational and a translational order For usage in LCD s liquid crystals are arranged in spatially separated cells with carefully chosen dimensions The optical properties of such cell can be manipulated by application of an external electric field which changes the orientation of the molecules in a reversible way Due to the long range order of the molecules and the overall regular orientation a single LCD element features voltage dependent birefringent properties Tutorial Theoretical Part 55 7 2 1 The LC cells have boundaries which are needed to firstly separate the cell and secondly to accommodate the wires needed for adressing each cell with an independent voltage value Because the cells are arranged in a regular two dimensional array the cell boundaries act as a two dimensional grating and produce a corresponding diffraction effect Twisted nematic LC cell The following discussion will focus on LCD based on twisted nematic liquid crystals In the cells of such LCDs the bottom and the top cover have alignment structures for the molecules which are typically perpendicular to each other As a result of the long range order of the LC the molecules form a helix struc
23. pixels Axicon multilevel Use this function to create a 256 level Axicon graylevel image representation In the dialogue field the axicon function can be characterized by the radius of the smallest ring which is defined by a number of pixels It can be specified whether the image representing the lens should be positive or negative Application Software Manual 51 6 6 11 6 6 12 6 6 13 6 6 14 Concentric ring segments binary Use this function to create binary images consisting of concentric ring segments In the dialogue field the image function can be characterized by the radius of the smallest ring which is defined by a number of pixels and the desired number of segments which can be varied from two to 20 even numbers only Single Slit and Double Slit binary To create a single slit choose the point Show Single Slit from the menu point Elementary Optical Functions The slit width can be defined by the number of pixels in the dialog window To create a double slit choose the point Show Double Slit from the menu point Elementary Optical Functions Moreover the slit distance can also be defined This refers to the gap between both slits Linear Gratings and Crossed Linear gratings binary Choose from the menu Elementary Optical Functions the item Show Binary Linear Grating to create a grating The grating period can be defined by the number of pixel By selecting the boxes the grating dir
24. program black white lines and filled plain Address this image onto the display and make sure that a clear projection is on the screen 5 Carry out a high and low pass filtering in the focal plane of the Fourier lens Record the filtered images with a digital camera Keywords for preparation Liquid crystal functionality of a LC display phase and amplitude modulation two dimensional Fourier transformation spatial filtering 4f set up high low pass filtering resolution Mach Zehnder Interferometer with controllable phase shift Objective The modulator should be used as a phase shifting element in an interferometer set up Define the phase shift as a function of the addressed voltage important parameter of a modulator Required elements Modulator laser with beam expander LDR photo resistor or Si photo diode with pin diaphragm two beam splitter mirror or cube two in two axis adjustable surface mirrors Set up The expanded slightly collimated laser beam illuminates a large part of the display homogeneously A homogenous full screen pattern is addressed onto the display The semiconductor laser with beam expander 82 Tutorial Experimental Part optics included in the kit should rotated until the light is horizontally polarised along the axis of the elliptical beam profile Place a beam splitter in front of and behind the modulator Assemble a Mach Zehnder interferometer using the
25. the Projects in Diffractive Optics Education Kit Work performed by persons not authorized by Newport Corporation will void the warranty Obtaining Service The components of the Projects in Diffractive Optics Education Kit contain no user serviceable parts To obtain information regarding factory service contact Newport Corporation or your Newport representative Please have the following information available 2 Instrument model number on the device 3 Instrument serial number 4 Description of the problem If the instrument is to be returned to Newport Corporation you will be given a Return Number which you should reference in your shipping documents Please fill out a copy of the service form located on the following page and have the information ready when contacting Newport Corporation Return the completed service form with the instrument 84 Maintenance and Service 9 2 Service Form GYD Newport Corporation U S A Office 800 222 6440 FAX 949 253 1479 Newport Name Return Authorization Please obtain RA prior to return of item Company Please obtain RA prior to return of item Address Date Country Phone Number P O Number FAX Number ltem s Being Returned Model Serial Description Reason for return of goods please list any specific problems Newport Corporation Worldwide Headquarters 1791 Deere Avenue Irvine CA 92606 In U S 8
26. the COM port from the user dialog This is shown in Figure 11 where the COM2 port is selected from the menu Options gt Select Port gt C0OM2 The currently used COM port is marked by a tick LC2002C Firmware Version 1 07 SN 10162 Options Adjustments Info Select Port Check Connection o o O L 2 l Ps 1 pa 1 0 11 1 u i 1 Toa zi T 1 toa o a a Sa 2 a Le nm Le COM 1 opened Connected g Figure 11 Selection of COM port If the selected port is still free then the status message COM 2 opened is displayed in the status bar in the bottom left of the dialog In case the selected COM port does not exist or is not free the message in the status bar states COM 2 already in use or not available Now if the selected COM port is free select from the menu Options gt Check Connection to establish the connection to the SLM If the SLM is correctly connected as described in section 4 4 1t is automatically identified and its configuration data are transmitted to the control program The user dialog displays the mostly used parameter controls in the field Contrast Brightness Geometry Users Manual DK LCMH 800A 27 4 5 4 Controls Contrast Brightness Geometry The field Contrast Brightness Geometry is obtained by selection of Adjustments Video from the menu and pushing the F2 button The
27. this situation the Jones matrix can be approximated as N cosp sinBj 1 0 Win 1c R B sinB cos a hi which means that for a strong voltage applied to the LC cell the light polarization is not changed The analysis of the intermediate cases in which the molecules are no more aligned in the helix structure but not yet parallel to the field can be done with the matrix Wryx 1c without one of the two approximations given above With such analysis the voltage dependent optical properties can be obtained As a result incident light with linear polarization leaves the cell with an elliptic state of polarization 62 Tutorial Theoretical Part 7 3 7 3 1 However the voltages applied to the LC cell are not directly accessible in the SLM device contained in this kit The voltages applied to the cells can be controlled via a costumized electronic drive board This drive board receives information on what voltage should be applied to the cell as graylevel values of the signal created by the VGA output of a graphics adapter of a common PC The voltages that are applied to the cells of the LC display are in a range that permits an almost continuous transition between the helix state which rotates the incident polarization to the isotropic state in which the polarization remains unchanged It is obvious that by inserting an analyser behind the display the LC display one can achieve an amplitude modulation of a transmit
28. wavelengths can be analysed The possible contrast is depending on the wavelength Diffractive optical elements DOE Objective Creation of diffractive optical elements with the spatial light modulator observation of diffraction patterns in the far field symmetry considerations for diffraction patterns superposition of different diffractive optical elements Required elements Modulator laser with beam expander can be used as a collimator and also to replace the Fourier lens by creating a slightly convergent beam to get a focal plane Fourier lens f 300 400 mm optional two lenses for example 100 and 50 mm for the enlargement of the diffractive structure in a telescope arrangement optional projection screen digital camera optional one polarizer Set up The expanded parallel laser beam illuminates the display homogenously A lens with large focal length should be placed closely behind the display Define the focal plane of the lens with the help of an adjustment paper The Tutorial Experimental Part 77 8 3 4 light pattern which is observed in this plane corresponds to the far field of light propagation Higher diffraction orders can be eliminated with the iris diaphragm A digital camera can be mounted on a tripod to take pictures from the screen Polarised Laser U Module SLM Ana Fourier Lens Screen LDR Figure 25 Set up for Diffractive optical elements experiment Suggested ta
29. x LE ax rend C Program Files LC2002 y Look in LC2002 E Files of type ini Cancel Connected __ Figure 15 Factory Defaults Setting Remarks All adjustments effect the display immediately but need at least 10 seconds to be permanent RS 232 Commands Command structure The SLM control program uses RS 232 commands to perform its tasks on the LCD In principle these commands can be also send by another control device This makes it possible to integrate the SLM in prototype systems where the control unit may be a different device than a PC In the following we describe the RS 232 commands that are used to control the SLM The RS 232 commands are strings of ASCII symbols that have to end with an end symbol An end symbol is used to separate a command from its subsequent one and trigger the LC2002 to decode and execute the command Specified end symbols are Carriage Return 0Dh Line Feed OAh and semicolon 3Bh 32 User s Manual DK LCMH 800A For the commands there is no distinction between capital and small letters Generally blanks are not allowed in a command unless they are directly in front of an end symbol The SLM device has an echo function that confirms each correctly decoded command After successful decoding the string OK is sent by the SLM to its RS 232 interface In case of a false command or an unsuccessful execution the SLM send an error code e g ERR 3 The l
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31. ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE NEWPORT CORPORATION SHALL NOT BE LIABLE FOR ANY INDIRECT SPECIAL OR CONSEQUENTIAL DAMAGES RESULTING FROM THE PURCHASE OR USE OF ITS PRODUCTS First printing 2006 2006 by Newport Corporation Irvine CA All rights reserved No part of this manual may be reproduced or copied without the prior written approval of Newport Corporation This manual has been provided for information only and product specifications are subject to change without notice Any change will be reflected in future printings Newport Corporation 1791 Deere Avenue Irvine CA 92606 USA Model Number DOEK KIT TEXT Preface Il Confidentiality amp Proprietary Rights Reservation of Title The Newport programs and all materials furnished or produced in connection with them Related Materials contain trade secrets of Newport and are for use only in the manner expressly permitted Newport claims and reserves all rights and benefits afforded under law in the Programs provided by Newport Corporation Newport shall retain full ownership of Intellectual Property Rights in and to all development process align or assembly technologies developed and other derivative work that may be developed by Newport Customer shall not challenge or cause any third party to challenge the rights of Newport Preservation of Secrecy and Confidentiality and Restrictions to Access Customer shall protec
32. Determine the focal plane with the help of an adjustment paper The image which is created in this plane far field diffraction pattern should be projected precisely It may be enlarged with the help of further lenses Higher diffraction orders can be eliminated with the iris diaphragm Turn the linearly polarized laser until an optimal diffraction pattern can be seen A digital camera can be mounted on a tripod to take pictures from the screen A LDR photo resistor on a carrier can measure the diffraction pattern as well The whole set up can reach a length of 2 to 2 5m Hence a folded set up with the help of mirrors is recommended Polarised Laser l a Module SLM Ana Fourier Lens Screen LDR Figure 24 Set up for investigation of dynamic diffractive structures Suggested tasks 1 Preparative tasks on the computer Create bitmap structures of a diffraction structure in a desktop resolution of 800x600 pixel with the software 3 gratings with different grating period lines grooves in black and white geometrical identical Ronchi grating stripes use the grating functions of the software an inverted grating a 90 rotated grating three different basic slits choose low slit width three double slit arrangements 3 circular apertures and the corresponding inverse structures Tutorial Experimental Part 75 10 11 12 1 cross grating and the inverse structure 1 grating in 5 versions in whic
33. General Information Introduction Main component of the Projects in Diffractive Optics Educational Kit is the spatial light modulator SLM DK LCMH 800A The device is a general purpose and easy to use device for displaying images by use of a monochrome transparent liquid crystal display LCD It simplifies the application of LCD s in experimental set ups e g for prototype development or in research labs The small size of the device and its comfortable control interface are major characteristics for enabling an easy usage Key Features The SLM can be used e g for purposes in technical optics image projection machine vision diffractive optics pattern recognition optical information processing sensing etc The device is designed to be plugged to the graphics board of a personal computer with a resolution up to SVGA format 1 e 800 x 600 pixels The device converts colour signals into corresponding grey level signals Functionality The SLM can be plugged to a personal computer using the serial RS 232 port After installing the SLM driver software the image parameters of the LCD can be easily controlled by the computer The driver software always saves the current setting of the image parameters Hence whenever the system is started this latest setting will be automatically loaded General Information 15 2 3 Offering Description Comparison Five experiments with several possible questions show the wide area
34. L2 Screen LDR Figure 23 Set up for Projection and display characterisation Suggested tasks 1 Measure the polarisation characteristics of the light source Lamp with condenser rotary analyser objective lens photo resistor 2 Create linearly polarised light lamp with condenser polariser and measure the angle distribution of the intensity with the 2 polariser analyser Present the results in polar coordinates Which mathematical function describes the results Make sure to verify the linearity of the detector 3 Arrange the projection set up with illuminating and imaging beam path A classical photo slide is helpful and will be replaced later on by the polariser LC Display analyser As objective lens try a normal lens with different iris diaphragm apertures and the 72 Tutorial Experimental Part 10 achromatic lens Discuss the influence of the aperture regarding to the depth of focus brightness influence of lens aberrations as well as the way to avoid aberrations Set up the projection arrangement with the LC display and optimise the contrast Therefore a picture has to be addressed to the monitor and the LC display The picture should be imaged onto the projection screen Rotate the polarisers which are perpendicular to each other in adequate angle steps ca 10 and measure the changing contrast quantitatively What do you observe if one or both polarisers are removed What do you ob
35. Newport DOEK Education Kit SLM Operating Instructions Tutorial DOEK Application Software Laboratory Tutorial GYD Newport II Preface Warranty Newport Corporation warrants that this product will be free from defects in material and workmanship and will comply with Newport s published specifications at the time of sale for a period of one year from date of shipment If found to be defective during the warranty period the product will either be repaired or replaced at Newport s option To exercise this warranty write or call your local Newport office or representative or contact Newport headquarters in Irvine California You will be given prompt assistance and return instructions Send the product freight prepaid to the indicated service facility Repairs will be made and the instrument returned freight prepaid Repaired products are warranted for the remainder of the original warranty period or 90 days whichever first occurs Limitation of Warranty The above warranties do not apply to products which have been repaired or modified without Newport s written approval or products subjected to unusual physical thermal or electrical stress improper installation misuse abuse accident or negligence in use storage transportation or handling This warranty also does not apply to fuses batteries or damage from battery leakage THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING
36. OE R a eer eaae 19 AD Technical Dita OR 20 ADs A an aaa e accor E N aiai 21 4 4 Connecting the DK LCMH 800A for Usage sesers 22 4 5 DK LCMH 800A Control Softwale cooconoccnnnnnnocononncncncnnancnnnonos 23 4 5 1 System Requirements criadas 23 45 2 Installation a ida 24 4 5 3 Start of DK LCMH 800A Control Program 24 4 5 4 Controls Contrast Brightness Geometty oooococ 21 4 5 5 Controls in the Field Gamma Correction 06 28 4 5 6 Controls in Field Screen Format oseese 29 4 5 1 Factory DES SS 30 40 RS 232 CORA a 31 4 6 1 Command Suc 31 4 6 2 Request Commands Requests ooooconnccnnoccnocononnnanncnnnoss 32 4 6 3 Configuration Commands Configs oconoconocccnncnnannnnnnns 33 4 6 4 Other Commands 2405s et GaN ee Raise cee 37 T Error Messar est did 38 4 8 Assembly Dra witht ccoo cai aia 39 5 Laser Module 40 Duk Techimical date rs ales 40 6 Application Software Manual 42 El Is dd ide cae ane 42 6 2 Statuine the SOW ALS sisi autos ibid di bon 42 6 3 Openitie an Mate Ai i 42 6 4 Full Screen window fUNCHONS oooonocononcnonnnononcnoncnoncnannconn ccoo anno 44 6 5 Calculating a diffractive optical element DOE 0 47 6 6 Creating elementary optical fUNCtONS ooononnnnnnononcnoccnnacnnnnncnnos 48 G62 Blank SCreent segs tesa cet a a 49 6 6 2 Horizontally Divided Screen oo ee eee eeseeeeeeeeeeeenees 49 6 6 3 Random BEN 49 6 6 4 Random Binary Bi
37. adjustable surface mirrors in what the display is situated in one arm Cut a small area as big or a bit smaller than one fringe from the beam in front of the detector in that way that changes can be realised in the interference pattern The set up has to be stabilized for outside vibrations and requires high demands regarding the experimental know how It is advisable to use high quality optomechanical elements BS N Polarised Laser SLM Ana NX Module Figure 27 Set up for Mach Zehnder Interferometer experiment Detector BS 8 5 4 Suggested tasks 1 Adjust the set up in such a way that an interference pattern can be seen Adjust the pin diaphragm to the centre of the interference stripes 2 Increase the applied voltage step by step and measure the intensity with the detector Repeat the procedure for different wavelength 4 Present the results in a diagram Define the phase shift for all wavelengths as a function of the addressed voltage 8 5 5 Keywords for preparation Liquid crystal functionality of a LC display coherence interference mathematical description of light propagation plane wave phase speed group speed optical path Michelson Mach Zehnder interferometer interferometry interferometric methods in the spectroscopy Maintenance and Service 83 9 9 1 Maintenance and Service CAUTION There are no user serviceable parts inside any components of
38. amma corrected User s Manual DK LCMH 800A 29 4 5 6 Black Level Gain This control specifies the intense of the correction effect on dark image pixels 1 e the increase of the intense beyond the correction entry point White Level Control This control operates on the gamma correction of brighter image pixels The control shifts the given correction entry point onto a certain grey level With respect to this point all brighter image pixels and corresponding image locations are gamma corrected White Level Gain This control specifies the intense of the correction effect on bright image pixels 1 e the increase of the intense beyond the correction entry point After first start up of the control program all gamma correction controls are set to zero 1 e they have not effect In order to use the gamma correction in a sensible manner suitable test images and optical instruments for measuring the LCD s transmission properties are required Controls in Field Screen Format The screen format controls shown in Figure 13 can be used to modify the image resolution an orientation They can accessed by the menu option Adjustments gt Screen Format LC2002C Firmware Version 1 07 SN 10162 Options Adjustments Info Mirror Image _ r Screen Format gt Right E SVGA 800x600 dots v COM 1 opened Connected Figure 13 Image orientation and image format 30 U
39. arning or Caution Symbol The Exclamation Symbol in the figure above appears in Warning and Caution tables throughout this document This symbol designates an area where personal injury or damage to the equipment is possible Electric Shock Figure 2 Electrical Shock Symbol The Electrical Shock Symbol in the figure above appears throughout this manual This symbol indicates a hazard arising from dangerous voltage Any mishandling could result in irreparable damage to the equipment and personal injury or death CSA Mark with C and US Indicators E Figure 3 CSA mark with C and US Indicators Safety Precautions 11 1 2 The presence of the CSA mark with C and US indicates that it has been designed tested and certified as complying with all applicable U S and Canadian safety standards European Union CE Mark CE Figure 4 CE Mark The presence of the CE Mark on Newport Corporation equipment means that it has been designed tested and certified as complying with all applicable European Union CE regulations and recommendations Warnings and Cautions The following are definitions of the Warnings Cautions and Notes that are used throughout this manual to call your attention to important information regarding your safety the safety and preservation of your equipment or an important tip WARNING Situation has the potential to cause bodily harm or death CAUTION Situation has t
40. ctive structures Objective Implementation of the modulator to create different primary diffractive structures which base on phase modulation of light Descriptive comparison of direct changes of the diffractive pattern by changing the projected diffractive structure Comparison of the diffraction behaviour of complement structures Babinet s theorem Measurement of the progression of diffraction intensity and definition of diffraction efficiency of selected structures Superposition of simple diffraction pattern as a base for diffractive optical elements Required elements Modulator laser with beam expander can be used as a collimator and also to replace the fourier lens by creating a slightly convergent beam to get a focal plane fourier lens optional one or two lenses for example 100 or 50 80 or 100 50 mm to magnify the diffractive structure iris diaphragm to eliminate the higher diffraction orders which appear due to the pixel structure of the display two polarisers projection screen digital camera or LDR 74 Tutorial Experimental Part 8 2 3 8 2 4 photo resistor with aperture plate 1mm or Si photo diode on a relocatable carriage for documentation and measurement of the diffraction structures Set up The expanded and collimated laser beam if no Fourier lens for focusing is used the laser module should be set slightly convergent to get a focus illuminates the display in a homogenous manner
41. e and eventually ceases to happen at all so that the light leaves the cell with unchanged linear polarization It is straightforward to combine such switchable element with a polarizer referred to as analyzer to obtain a light valve for incident polarized light For unpolarized light sources it is only necessary to place a second polarizer in front of the LC cell to obtain the same functionality To gain a more detailed insight it is necessary to review the polarization of light fields 9 Y S i oe6989000 Lee H A B H C Figure22 LC cells with different applied voltages V 0 with untilted molecules V gt V with tilted partially aligned molecules Vea Vi with aligned molecules in the central region of the cell Tutorial Theoretical Part 57 7 2 2 Polarization of light The polarization of light is defined by orientation of its field amplitude vector While unpolarized light consists of contributions of all the different possible directions of the field amplitude vectors polarized light can be characterized by either a single field component linear polarization or by a superposition of field components in two directions The state of polarization of a light field propagating into the z direction can be expressed by a Jones vector representation e V Y where
42. e convolution of the transmitted field with a impulse response of the structure Multiplying the quadratic expression in the exponent results in eo ine pox yyy Elx y z f E x y 0 e dxdy Ineo Sy with ikz ik x2 y2 e ES A x z e a 1 Z and which are referred to as spatial frequencies analog to the frequencies of the Fourier transformation above written as of temporal signals The Fresnel diffraction covers the common situation in which the observation plane is at an finite distance behind the object 66 Tutorial Theoretical Part 7 3 5 Fraunhofer approximation The Fraunhofer diffraction is a special case and analytically a simplification of the Fresnel diffraction which is valid for large distances The Fraunhofer approximation applies if 2 2 t X E lt lt Z y is satisfied for x y and x y In this case E x y z A x y DH E x y 0 v v with _ exp ikz A x y Z hz The far field in the Fraunhofer approximation is given by the Fourier transformation of the field directly behind the diffracting object The spatial frequencies of the diffracting structure create waves which propagate with the angles and BrtanB 2 4v Z to the optical axis respectively Thus the far field diffraction pattern of a spatial distribution of phase or amplitude transmission values given by a graylevel bitmap signal of the LCD can be calcula
43. e ssessoesoessessossocssessosssessossoossesss 28 Figure 13 Image orientation and image format sessoesoessessoesocssessossossse 29 Figure 14 Upload Factory Default ooesoossesooesoessessoesoossessossoossessossoossosss 30 Figure 15 Factory Defaults Setting ooooomomsssssssso 31 Figure 16 DK LCMH 800A assembly drawing ooocomooocm 39 Figure 17 Geometrical size of the provided laser module ss0s00e 40 Figure 18 Image window of the application software sccsscssssesseeee 42 Figure 19 Toolbar of the full screen Window scccccscscscssscessseseceees 44 Figure 20 Menu entries for optical functions ooooomss s 48 Figure 21 Polarization guided light transmission scscsccsesccsessees 55 Figure 22 LC cells with different applied voltages ommoomm 56 Figure 23 Set up for Projection and display characterisation 71 Figure 24 Set up for investigation of dynamic diffractive structures 74 Figure 25 Set up for Diffractive optical elements experiment 77 Figure 26 Set up for Spatial frequency filtering ooooooooo 80 Figure 27 Set up for Mach Zehnder Interferometer experiment 82 Safety Precautions 1 1 1 1 1 Safety Precautions Definitions and Symbols The following terms and symbols are used in this documentation where safety related issues occur General Warning or Caution Figure 1 General W
44. ection can be chosen horizontal and or vertical Check both boxes to overlap a horizontal with a vertical grating Linear and Array Beamsplitter Gratings binary Choose from the menu Elementary Optical Functions one of the menu items Show Binary Linear 1 to 5 Linear Beamsplitter Grating Grating period 26 Pixels Show Binary 1 to 2x2 Separable Array Beamsplitter Grating Grating period 18x18 Pixels Show Binary Array 1 to 5x5 Separable Array Beamsplitter Grating Grating period 26x26 Pixels 52 Application Software Manual 6 6 15 6 6 16 6 7 Show Binary Array 1 to 5x5 Non separable Array Beamsplitter Grating Grating period 26x26 Pixels to obtain a full screen window with one of the mentioned diffractive elements The basic tiles of these gratings are fixed and usable as examples for separable and non separable binary DOEs Sinusoidal Grating multilevel Choose from the menu point Elementary Optical Functions Show Sinusoidal Grating to create a sinusoidal grating The size of the grating period can be specified by the number of pixels Blazed Grating multilevel Choose from the menu point Elementary Optical Functions Show Blazed Grating to create a blazed grating The size of the grating period can be specified by the number of pixels The Window Menu The Menu Windows contains the usual options for tiling cascading and closing windows that are opened inside the main windo
45. ed by an optical path of half the wavelength with respect to the other polarization The Jones matrix of a half wave plate is obtained as Pee E HWP 0 i If the incident light is linearly polarized with an angle a of the polarization vector to the ordinary polarization direction its Jones vector can be expressed by means of a rotation matrix R a as V V cosa sina V V Va sina cosa IV The matrix of a waveplate in the xy coordinate system is then given by Wwp R a W R a 60 Tutorial Theoretical Part 7 2 5 For linearly polarized incident light with an angle of a 45 of the polarization with respect to the ordinary polarization the half wave plate with the thickness d as given above will modify the incident light as given by the matrix e 0 i me i This means that light polarized parallel to the x direction which is assumed to have an angle of 45 with respect to the direction of ordinary polarization will have its Jones vector changed from vel elo A which corresponds to a rotation of the polarization direction by an angle of 90 Amplitude and phase modulation by a TN LC cell A twisted nematic LC cell can be described as a succession of a high number of very thin waveplates which change the orientation of their optical axis according to the change of the direction of the molecular axis The total Jones matrix of the cell is then obtained by matrix multiplication of all the matrices of the assu
46. gnal Green colour signal Blue colour signal HSYNC line synchronisation signal VSYNC image synchronisation signal GND red colour signal GND green colour signal GND blue colour signal GND VD ON NHN U RA LU Nel Connecting the DK LCMH 800A for Usage For using the SLM at least one computer with an VGA graphics board is required The computer is required for controlling the SLM and providing images or videos to be displayed on the LCD Instead of the PC a VGA camera can be used as image signal source First the SLM driver software must be correctly installed on the computer Then the computer can be connected to the SEM as shown in Figure 7 Users Manual DK LCMH 800A 23 Attention Plug the serial port and VGA connector first and the power supply connector always at last fe 9 100 230 V 50 60 Hz Figure 7 Connecting the DK LCMH 800A for usage 4 5 DK LCMH 800A Control Software 4 5 1 System Requirements e IBM or compatible PC e Processor 80486 or Pentium e 32 MB main memory or more e VGA graphics board 24 User s Manual DK LCMH 800A 4 5 2 4 5 3 e Free RS 232 port COM1 or COM2 e CD ROM drive e Operating systems Windows 95 98 2000 and XP Installation For installing the control software execute the program SETUP EXE on CD ROM This program requests for all information required for the installation process After the installation has been completed successfully the SEM control
47. h the primary black areas are filled with different grey levels rectangular aperture Record the projected diffraction patterns e g with a digital camera and interpret them Determine the intensity distribution of the obtained diffraction pattern and the diffraction efficiency for the gratings and the slits Ip is the total intensity of the central order which passes the iris diaphragm for a non addressed modulator The intensity distribution measurement can be done with a LDR photo resistor or from digital camera pictures Compare the results with the theoretical expectations Determine the ratio of the grating period relative to the grating with the highest grating period of the diffraction pattern and the bitmap structures Determine the diffraction efficiency of the diffraction structures for all graylevel gratings Diffraction efficiency is defined as the ratio between the intensities of the desired orders e g the 1st and 1st orders and the intensities of the incident light Discuss the results of the inverted structures Discuss the diffraction structures of the circles with respect to possible constructions of a diffractive lens Fresnel zone lens Vary the grating period of a grating with the application software Explain your observations Place a horizontal grating on the left side and a vertical grating on the right side of the monitor Explain the observed diffraction pattern If the beam expander of the lase
48. hat can be opened are JPG BMP PNG PGM The loaded picture will be transformed to a 256 grey scale picture In order to display all 256 gray scales a monitor setting of minimum 16 Mio colours 24bit is required The image window will have the following buttons n Zoom In Button Pushing this button will perform a fast zoom in operation on the image a Zoom Out Button Pushing this button will perform a fast zoom out operation on the image Save Button Pushing this button will open a dialog in which a file name can be specified for saving the image in one of the supported formats PNG or BMP Image ASCII textfile matrix of integer values representing the grayscale values Es Compute DOE Button This button will only appear if the displayed image taking zoom operations into account is no larger than 200x200 pixels Pushing this button will start a computation of a Computer generated hologram CGH phase function for the signal displayed in the image window Please see section 6 5 for more information The result of the computation will be displayed in a full screen window where it can be manipulated as explained in section 6 4 He SERRA onai SEBH Replicate to full screen size Button Pushing this button will open a full screen window in which the shown image is used as a single tile which is replicated until the whole screen is covered 44 Application Software Manual
49. he potential to cause damage to property or equipment NOTE Additional information the user or operator should consider Safety Precautions 1 2 1 1 2 2 General Warnings Observe these general warnings when operating or servicing this equipment Heed all warnings on the unit and in the operating instructions Do not use this equipment in or near water e Route power cords and other cables so they are not likely to be damaged e Disconnect power before cleaning the equipment Please refer to chapter 4 1 5 To avoid explosion do not operate this equipment in an explosive atmosphere Qualified service personnel should perform safety checks after any service General Cautions Observe these cautions when operating or servicing this equipment If this equipment is used in a manner not specified in this manual the protection provided by this equipment may be impaired Follow precautions for static sensitive devices when handling this equipment This product should only be powered as described in the manual e There are no user serviceable parts inside the Product e To prevent damage to the equipment read the instructions in the equipment manual for proper input voltage Adhere to good laser safety practices when using this equipment Safety Precautions 13 1 3 1 3 1 Location of Warnings Laser Figure 5 Locations of warnings on the Laser General Information 2 1 2 2
50. he spatial frequency spectrum can be manipulated in the focus plane Transformation and inverse e g with 4f set up 70 Tutorial Experimental Part 8 1 8 1 1 8 1 2 Tutorial Experimental Part The first part deals with a white light set up in order to demonstrate phenomena like light polarization and basic properties of LC Displays along with the necessary basic geometrical optics In the second part basic experiments relating to diffraction and interference of light will be performed Part number three deals with diffractive optical elements DOE s and computer generated holograms Basic examples of Spatial frequency filtering in the Fourier plane are described in the fourth part Finally a Mach Zehnder Interferometer set up is used in the fifth part With this interferometer the phase shift generated by the liquid crystals can be measured This set up requires additional high quality optical components which are not included in the basic set Projection and display characterisation Objective Implementation of the modulator as a projection device identification of the mode of operation creation of amplitude modulation by rotation of the polarization axis of the light as a function of the applied voltage identification of parameters like pixel size length of molecule axis maximum phase shift illuminating and imaging optical path Required elements Modulator halogen lamp with condenser e g 2 bi convex fie
51. ist and meaning of all error codes is given in section 4 7 The echo function can be switched on and off When the device is switched on the echo function is automatically switched on as well In the following all available commands and their meaning are described The commands are ended with lt CR gt respectively The response of the SLM to each command is written indent Remark The symbol lt CR gt is obtained by pressing the enter button J on the keyboard So do not use the symbols C and R 4 6 2 Request Commands Requests Request commands always result in a response of the SLM They are characterised by a question mark at the end of the command followed by an end symbol 4 6 2 1 Request the device ID number IDN lt CR gt LC2002A 4 6 2 2 Request the firmware version VER lt CR gt 1 07 User s Manual DK LCMH 800A 33 4 6 2 3 4 6 3 Request the configuration CONF lt CR gt 4 1E BE 13 0 0 0 1 0 O 51 CC 77 FF A7 O O A O 089 D 15 F A3C 6 The response values shown here are examples and can vary with respect to the configuration of the device The meaning of the bytes can be obtained from the following table The bytes specify user specific as well as device internal configurations Configuration Commands Configs Configuration commands consist of a command name and a parameter value that is separated from the name by a colon The parameter value must be given as an integer Byte
52. ixel DOE computation for larger pictures is not supported by this software Load the image as described in section 6 3 If the image is not larger than 200x200 pixel the Compute DOE Button will appear with the option to calculate a diffractive optical element DOE for this image Press this button 48 Application Software Manual 6 6 to start the iterative Fourier Transformation Algorithm IFTA Note that the process of computing may take a while depending strongly on the signal picture size When the process is finished two windows will appear They show the DOE phase function in a full screen window and the calculated intensity of the diffraction pattern This calculated intensity should look quite similar to the image in the original window if the DOE calculation algorithm has properly converged Creating elementary optical functions All optical functions from the menu point Elementary Optical Functions appear in a new windows after input of the required parameters Depending on the optical function binary or multilevel the task bar of the full screen window will be slightly different compare section 6 4 Im JNEWPORT Projects in Diffractive Optics 1 0 2 File Elementary Optical Functions Windows Help Show Blank Screen Show Horizontally Divided Screen Show Random Bitmap Show Random Binary Bitmap Show Rectangular Aperture Show Circular Aperture Show Binary Fresnel Zone Lens Show Fresnel Zone
53. l as theoretically Compare the results c Calculate the pixel size of the display from the focal lengths measured for different smallest radii of the zone lenses If experiment 8 1 Projection and display characterisation has already been accomplished compare the obtained pixel sizes Use binary DOEs contained in the elementary optical functions of the application software to evaluate which symmetry the diffraction patterns have Calculate a DOE image for a high contrast asymmetric picture of your choice with the application software Does the diffraction pattern you have obtained follow the symmetry of the diffraction patterns of binary elements If not why can multilevel DOEs produce diffraction patterns with different properties Acquire information of how computer generated holograms of a complex structure are created If you have done the projection experiment figure out how to get separated phase and amplitude modulation with two SLMs Spatial frequency filtering Objective Projection set up spatial filtering in Fourier plane high low pass filter filtering of structures 80 Tutorial Experimental Part 8 4 2 8 4 3 8 4 4 Required elements Modulator laser with beam expander Fourier lens f 300 400 mm Spatial filter diaphragms Iris diaphragm rectangle diaphragm two razor blades negative hole diaphragm middle size pinhead projection screen digital camera polarizer Set up
54. laser Be aware of the hazards posed by your laser Aim the laser well away from others Use an appropriate target A A le E Do not allow the beam to inadvertently reflect from metal or glass surfaces 6 Use protective eyewear Certain preventive measurements have to be done before the usage of the provided laser Inform yourself about applicable regulations with laser products of the class 2 and consider these by application of the laser NEWPORT assumes no liability for any damage caused by the laser 42 Application Software Manual 6 1 6 2 6 3 Application Software Manual Installation Start installer exe and follow the instructions of the installation menu Please accept the license agreement before choosing the required program components Mark all checkboxes to install the complete version Choose the destination folder as well as the start menu folder Click Install to start the installation procedure and click finally Close to finish the installation Starting the software Start the program using the start menu entry Application Software Opening an Image In NEWPORT Projects in Diffractive Optics 1 0 2 File Elementary Optical Functions Windows Help squcord bmp 200 x 200 pixels Zoom 100 Figure 18 Image window of the application software Application Software Manual 43 Choose from the File menu the point Open Image File Possible image formats t
55. ld lens f 130 to 150 mm 2 rotary polarisers objective lens e g simple lens iris diaphragm and or an achromatic lens f 80 to 130 mm with high aperture projection screen colour filter red blue LDR photo resistor and Ohmmeter optional iris diaphragm Tutorial Experimental Part 71 8 1 4 Set up Optical path for illumination adjust the halogen lamp in such a way that it emits parallel or slightly convergent light The parallel light beam should illuminate the display completely Make sure that no scattered light bypasses the display preferably use a rectangular aperture e g e made of black cardboard in front of the display Place and adjust polarisers 1 polariser 2 analyser in front of and behind the display in a way that the polarisation axes are 90 rotated to each other Address a test image onto the display Optical path for imaging Place an objective lens e g simple lens iris diaphragm and or achromatic lens behind the display and adjust it in such a way that a focused and enlarged image appears on the screen For measuring the parameters the photo resistor has to be placed in the focal plane of the lens The total intensity will be measured this way A neutral density filter may be necessary to reduce the intensity In fact a photo resistor measures indirectly proportional but compared to a photo diode the linear characteristic is more than 3 orders of magnitude higher Li Pol SLM Ana
56. med thin waveplates as 3 cosy i a sin x siny Wine R B i ke A Z sinx cos 1 sin x 2 Tutorial Theoretical Part 61 where is f is the total twist angle of the molecules throughout the cell and the quantity y is given by yB 0 2 Even though the assumptions which are necessary for the derivation of the Jones matrix given above require some approximations the resulting theory is sufficient for understanding the main optical properties of the cells If a LC cell satisfies B 1 2 which is the case for thick cells the Jones matrix can be significantly simplified and permits an intuitive interpretation exf i r 0 Win 1c RB T 0 exp i aiz If the incident light is polarized parallel to the x or y axis the polarization axis will be rotated by the twist angle B between the direction of the alignment layers as implied by the intuitive explanation illustrated in Figure 21 If a voltage is applied to the cell the molecules tend to align parallel to the electric field Thereby the anisotropy of the liquid crystal is reduced because the angle between the direction of light propagation and the molecular axes gets smaller until eventually both direction are parallel and the liquid crystal appears to be isotropic see Figure 22 In terms of the analysis done here the difference An n n gets smaller and therefore for sufficiently high voltages one gets 0 For
57. ninnnos 64 7 3 5 Fraunhofer approximation ocoooccnonccononoccnononicnncncn nnncinnnos 66 7 3 6 Diffraction at spatially periodic Objects o oo 67 7 3 7 Fourier transformation with a lens eee eeeeeeeeeeeee 68 7 3 8 Spatial frequency filtering oooooconnnococnnocaconnncnonnncnnnnos 69 8 Tutorial Experimental Part 70 8 1 Projection and display characterisation ooonocononcnonnnnocnnooncnoncnnnos 70 AS 70 9 1 2 Required ele menisco Bhs 70 REN 71 SLA o AS A na E a a 71 8 1 5 Keywords for preparatiON ooooononcccnonccnnonncnnonacnnnnccnnnnncnnn 73 8 2 Generation and analysis of dynamic diffractive structures 73 S2 ds ODEVE ate a cae dees E E O E 73 Vill Preface 8 22 Required elements nnns whee atte 73 Oe 22S P SO CUP sara chads sos cons suas E A Mat ciel eat ge 74 8 24 VOUS CSIC LAS A ES 74 8 2 5 Keywords for preparation cceeccecesececsseeeesseeeeeeeeees 76 9 2 0 Addition an A nGnia ee teases nah eas 76 8 3 Diffractive optical elements DOE eee eeeeeeeseeenteeeteetees 76 A ODJECU VE steht Fok su staan cuits a ain vain AS 76 8 3 2 Required elements ir ee eee aS 76 A AULD dees esata apn uaa aca S a anaes gaat alle S 76 8 3 4 Suggested 185 ksi sc ccaes cece ts gan maciceetiurecontdoeesca ts Be casenme 77 8 4 Spatial frequency filtering oonncccnnnccinoncccnoncccnnnnnononccononcnonnnnnos 79 SA O eee oi A ela ee 79 0452 Required elemen id 80 SA A E
58. of physical phenomena which can be investigated experimentally with the Projects in Diffractive Optics Educational Kit These are e g optical set up of a projector properties of polarized light optical properties of liquid crystals phase and amplitude modulation of light fields diffraction of light at dynamically changing structures diffractive optical elements DOE s and the combination Spatial frequency filtering and interferometry phase shifter Thus the device is suitable for introductory and advanced laboratory classes in physics and engineering study courses User s Manual DK LCMH 800A 3 1 3 2 3 3 Getting Started Unpacking and Handling do not touch the LCD Inspection for Damage WARNING Do not attempt to operate this equipment if there is evidence of shipping damage or you suspect the unit is damaged Damaged equipment may present additional hazards to you Contact Newport technical support for advice before attempting to plug in and operate damaged equipment Parts List e 1 DK LCMH 800A LCD image display device SLM e 1 PS LCMH 1 Power supply 15V 0 8A e 1 232 CBL M M RS 232 adapter cable e 1 VGA CBL LCMH VGA monitor cable e 1 DOEK HLD Mounting ring for laser module e 1 LD 635 20MM Beam expander laser module focus adjustable e 1 PS LD DOEK Power supply 5V 1A e 1 DK LCMH 800A User s Manual e 1 DOEK KIT CD CD ROM with Driver Software Applica
59. pecified for saving the full screen image image in one of the supported formats PNG or BMP Image ASCII textfile matrix of integer values representing the grayscale values The image will be saved as displayed 1 e including effects by superposition of optical functions etc KA Superimpose lens Button This button will superimpose the displayed image with a XY grayscale signal that resembles the optical phase function of a lens This means that the focal plane of the light source incident on the LC Display is changed when such function is superimposed The focussing defocussing strength of the optical lens function can be changed by adjusting the value given on the task bar by moving the slider or by directly entering a value 111 Superimpose prism in X direction Button Pushing this button will superimpose the displayed image with a grayscale signal that resembles the optical phase function of a prism in X direction This means that all diffraction angles created by the signal on the LC Display are changed when such function is superimposed 46 Application Software Manual The strength of the optical prism function can be changed by adjusting the value given on the task bar by moving the slider or by directly entering a value In order to switch to a prism superposition in Y direction click on the button again Superimpose prism in Y direction Button Pushing this button will superimpose the displayed
60. picture in the far field Within certain limits lenses can be replaced by DOE s DOE s can also act as beam splitters and beam shapers or more Tutorial Theoretical Part 63 7 3 2 advanced optical elements like multi focus lenses A problem not yet satisfactorily solved is the elimination of the 0 order as well as the diffused light from other diffraction orders However DOE s exhibit severe chromatic aberrations and due to the fabrication issues they usually will diffract light into the 0 order may this be desired or not Moreover the light efficiency is usually limited Keywords Solution of the diffraction integral Dammann Gitter Computer generated hologram CGH Diffractive optical elements are sometimes referred to as Computer Generated Holograms This term was introduced because it is possible to compute the interference pattern created by an object with a reference wave and to fabricate an optical element from the obtained data without an interferometric recording technique which is used for conventional holograms In such recording technique the diffuse light wave reflected by an object interferes with a reference wave and the appearing interference wave field is recorded in a photosensitive material or detector in the majority of cases a photo film If the object wave is created by a three dimensional object with an irregular shape the interference pattern leads to a structure of a complex diffraction grating
61. problem Or is the system non operational e Can you identify anything that was different before this problem occurred Preface Table of Contents Warranty Technical Support Table of Contents List of Figures 1 Safety Precautions 1 1 Definitions and Symbols oooonnocccnoncccnnocccinoncconanacinnncnnnnos 1 1 1 General Warning or CautiOM oooonooccccconcccnoncnnnnnos LAD Electric Shock ins 1 13 CSA Mark with C and US Indicators 1 1 4 European Union CE Mark 1 2 Warnings and Cautin side 1 2 1 General Warnings cocinar 1 2 2 General Cautions tacto 1 3 Location of Warnings eeeseseseseereeserereerersersresrrrsreseese A ria e es erisa 2 General Information Zal Introducci n usd do lada 22 Functionality illo e a a tees 2 3 Offering Description Comparison cocccooccnoncnnnnnnnnncnonennnos 3 Getting Started 3 1 Unpacking and Handling oonoccnnncnnononononannnonnnonncnoncnnos 3 2 Inspection for Damage ut dsd 3 3 Par s List erensia ai dada 3 4 Electrical Requirements 1 cisesdecessaceeteadsd eetetesnyasiosersdencats 4 User s Manual DK LCMH 800A AT CAOS ii agave 4 1 1 Avoid humidity and dust ooooocccocccncccnocnconncconcnnns 4 1 2 Ke p cata Way da 4 1 3 Keep water away LA VI Preface 4 1 4 Avoid touching the LCD nc Seed eed 18 ALS Cleanange the LED cn caldo iria lios cacon Geeta edd 19 4 1 6 Electrical CONMMECIONS 2 it tit 19 4 lhe HOUSE 7550 cos gszascaseste cose a A R
62. r module is used as a collimator discuss the function of the Fourier lens directly behind the modulator If the beam expander of the laser module is used instead of the Fourier lens discuss why the lens function may be added to the beam before transmitting the display Analyse the diffraction efficiency of phase and amplitude gratings Place crossed polarisers in front and behind the modulator at maximum contrast compare with experiment 8 1 Choose as diffraction structure a symmetric black white Ronchi grating Measure the diffraction pattern with a camera or with the LDR photo resistor aperture plate or a Si photo diode Remove both polarisers measure once more and compare the results Discuss the differences in terms of the various ways of the diffraction pattern development Measure the sinc function of the diffraction structure without iris diaphragm and with non addressed display 76 Tutorial Experimental Part 8 2 5 8 2 6 8 3 8 3 1 8 3 2 8 3 3 Keywords for preparation Liquid crystal functionality of a LC display plane wave coherence diffraction interferometry diffraction on slit double slit grating circle aperture mathematic description in the far field slit function grating function Fraunhofer and Fresnel diffraction Babinet s theorem Fourier transformation resolution Addition If there are more laser with different wavelengths available diffraction pattern of different
63. rameter min max HPOS 0 255 Example HPOS 207 lt CR gt OK User s Manual DK LCMH 800A 35 4 6 3 3 4 6 3 4 4 6 3 5 Vertical image position Parameter Command name i min max VPOS 0 255 Example VPOS 19 lt CR gt OK Pixel phase pixel synchronicity Parameter Command name min max SHP 0 15 Example SHP 1 lt CR gt OK Image format Command name Parameter Meaning 204 SVGA 800x600 CCh MODE 201 PC 98 640x400 C9h 206 VGA 640x480 CEh Example MODE 204 lt CR gt OK Remark When setting the image format using the MODE command the pixel synchronised playback is preserved Image formats that that do not fill up the display are automatically centred and surrounded by a black frame 36 User s Manual DK LCMH 800A 4 6 3 6 Entry point of gamma correction white Command name f Parameter min max GCW 255 Example GCW 1 lt CR gt OK 4 6 3 7 Intense of gamma correction white Command name Paranciet min max GGW 255 Example GGW 1 lt CR gt OK 4 6 3 8 Entry point of gamma correction white Command name z Earaieter min max GCB 255 Example GCB 1 lt CR gt OK 4 6 3 9 Intense of gamma correction black Command name Pararioter min max GGB 255 User s Manual DK LCMH 800A 37 4 6
64. s effect is referred to as birefringence Here the discussion shall be limited to uniaxial crystals in which the polarization states are referred to as ordinary o and extraordinary eo polarization with refractive indices n and no The impact on a transmitting light wave can be expressed by matrices which convert the Jones vector of the incident light see previous section to a new Jones vector The different refractive indices introduce a mutual phase delay between the two partials fields corresponding to the two linear polarizations which are propagating with the velocities c n and c n The transmitted light after a distance d given by the thickness of the material is therefore given by Vo V v IN 3 V eo Vo where d 0 0 exp i a C An optical component with parallel entrance and exit facets made from an uniaxial birefringent material with its optical axis perpendicular to the direction of light propagation is referred to as a waveplate Tutorial Theoretical Part 59 7 2 4 Waveplates The matrix W of a waveplate can be expressed in the form T exf i gt 0 W exp ib r 0 m fiz where the quantities F and q are given by 21 n n d oO E A and 21 1 n n d b 54 o eo de A half wave plate is a particular example of a waveplate with a thickness O A 2 n eL Moo so that the mutual phase delay is given by x This means that the one polarization direction is delay
65. sed by the diffraction and interference of light in contrast to refractive optical components The usage of diffraction and interference requires structures in the dimension of the optical wavelength These structures became available in the context of modern methods of Nano technology Lithographical production technologies and replication processes have made it possible that DOE s can be produced in mass production Thus diffractive optical elements which act as lenses prisms or beam splitters to create images or writings as diffraction patterns are easier to produce and more compact than corresponding conventional elements if they exist at all A well known example are DOE s which can be mounted on laser pointers to create arrows crosses and other patterns Also diffractive optical beam splitters can create beams with the same intensity in a geometrical grid for example to measure objectives and 54 Tutorial Theoretical Part 7 2 telescope mirrors faster and more precisely compared to the possibility with one beam or with mechanical scan devices In the tutorial a liquid crystal modulator will be used as a spatial light modulator to create diffractive optical structures for exploration of dynamical diffraction structures as well as the investigation of the functionality and the physical properties of the device itself Liquid crystal displays LCD s with pixel sizes significantly smaller than 100 um are used nowadays
66. ser s Manual DK LCMH 800A 4 5 7 You can use the buttons on the left hand side to mirror the image on the LCD in both directions This is helpful to make optical experiments more comfortable gt Right Button Pushing this button mirrors the image horizontally Up Button Pushing this button mirrors the image vertically Format Button Pushing this button you can select the image format to be applied Three standard image formats SVGA VGA and PC 98 are offered for selection The image is always displayed in a pixel synchronised manner That means images of formats with less than 800 x 600 pixels are centric positioned and have a surrounding black frame Factory Defaults At every time the driver s configuration memory can be reset to the delivery state To do this select Upload Factory Defaults from the Adjustments menu shown in Figure 14 LC2002C Firmware Version 1 07 SN 10162 Iof xi Options Adjustments Info Video F2 Ce Gamma Control F3 Screen Format gt l Ps fe COM 1 opened Connected Figure 14 Upload Factory Default Users Manual DK LCMH 800A 31 4 6 4 6 1 As shown in Figure 15 a new user dialog appears Just load the pre selected factory ini This will reload the Factory Defaults The c2002 ini is used for manufacturer s settings only and should not utilised by customers LC2002 Control Panel Demo Mod 1501
67. serve with both polarisers at best contrast 1f the polarisation position of the analyser is rotated by 45 90 180 Discuss the results Use a grating with grating period 400 to create an image half white half black This image should be used to measure the contrast with the LDR photo resistor Determine the orientation of the molecule axis of the addressed liquid crystal pixel from the results Determine the pixel size from the geometrical reproduction scale unit and a e g rectangular image what is defined by a specific number of pixels on the monitor display use geometrical optics for calculation The magnification of the lens system should be known Investigate the dependency of pixel voltage and twist on the polarization direction Change the voltage by using different homogeneous full screen gray level images use the supplied software and measure the intensity with the LDR photo resistor in the focus of the objective lens Use a projection set up with the optimal contrast The results should be presented graphically In order to compare the results a linear dependency should be theoretically assumed if necessary consider an offset In this connection the calculated progression of the translucent intensity as a function of the addressed voltage should be presented in the same diagram a detailed calculation has to be given Discuss the differences Figure out a function in which the polarisation angle on a scale from 0
68. sion function 7 x y The transmitted field is E x y 2 0 r x y E x y 2 0 The resulting light propagation can be described by applications of Huygens principle According to this principle a spherical wave is created by each point x y at z 0 of the diffraction structure All spherical waves must be added i e integrated to obtain the field amplitude from a point x y z behind the diffracting object This description contains also waves in negative z direction which are not observed In the Fresnel Kirchhoff diffraction theory a direction factor is therefore introduced which excludes the waves in negative z direction The resultant field is obtained as eik o 3 A a f f E x y 0 e CIEN A cos F dxdy 1 Z 00 00 In general this equation is too complicated to solve diffraction problems but for many relevant situations suitable approximations can be used 7 3 4 Fresnel approximation The spatial dimension of the diffracting object should be small compared to the distance between object and diffraction pattern paraxial approximation In this case cos _ r 1 Tutorial Theoretical Part 65 and the distance can be written as As the amplitude is less sensitive than the phase within the denominator the 2 2 Ef bot 27 22 approximation with r z can be used r z From this we have in 2 y E x y z A x y Z X E x y 0 e Iv v This equation describes th
69. sks 1 3 Address one of the provided DOE images preferably grid or coord onto the screen display and observe the far field diffraction pattern Record this pattern with a camera or make a hand drawing showing the essential features of your observations Determine the minimum distance for a far field observation and give an explanation of this value What do you observe in the near field Advice 1 For the analysis of the phase DOE no polarisers are required Consider the linear polarisation of the laser The display effects and turns the polarisation plane even in a non addressed state Therefore the polarisation axis of the laser should be adjusted by rotating the laser in order to obtain a bright and clear diffraction pattern Advice 2 Display all images in full screen because the edges of windows buttons and task bars have an influence on the light field which may distort the desired far field pattern Open binary images representing linear beamsplitters and array generators Optimize the observable diffraction pattern by adjusting the contrast This can be done by changing the grayscale values using the corresponding sliders Note down at which grayscale values the best diffraction pattern is observed Observe the diffraction patterns in the far field a Of the provided 5x5 binary separable array beam splitter DOE image 78 Tutorial Experimental Part 10 b of the provided 5
70. t the Newport Programs and Related Materials as trade secrets of Newport and shall devote its best efforts to ensure that all its personnel protect the Newport Programs as trade secrets of Newport Corporation Customer shall not at any time disclose Newport s trade secrets to any other person firm organization or employee that does not need consistent with Customer s right of use hereunder to obtain access to the Newport Programs and Related Materials These restrictions shall not apply to information 1 generally known to the public or obtainable from public sources 2 readily apparent from the keyboard operations visual display or output reports of the Programs 3 previously in the possession of Customer or subsequently developed or acquired without reliance on the Newport Programs or 4 approved by Newport for release without restriction Service Information This section contains information regarding factory service for the source The user should not attempt any maintenance or service of the system or optional equipment beyond the procedures outlined in this manual Any problem that cannot be resolved should be referred to Newport Corporation IV Preface Technical Support North America amp Asia Europe Newport Corporation Service Dept Newport MICRO CONTROLE S A 1791 Deere Ave Irvine CA 92606 Zone Industrielle Telephone 949 253 1694 45340 Beaune la Rolande FRANCE Telephone 800 222 6440 x31694 Telephone 33
71. ted with a Fourier transformation With the help of a lens the far field of the light propagation can be obtained in the focal plane of the lens see section 7 3 7 This means that in optics propagation of the light field realizes a Fourier transformation in a natural way simply by propagation The Fourier transformation of a two dimensional object can be observed directly in terms of the spatial frequencies which can be associated with diffraction orders These spatial frequencies can be manipulated and filtered The Fourier filtering is a passive parallel image processing performed at the speed of light see section 7 3 8 Tutorial Theoretical Part 67 7 3 6 A rather well known application of the Fourier Transformation FT written in formulas as is its use to compute the frequency spectrum of a time dependent signal In Fourier optics the signal is dependent on a spatial coordinate rather than on a time coordinate Moreover the spatial optical field is two dimensional rather than one dimensional In other words in optics the corresponding variables are the positions x y and the so called spatial frequencies v v which are linked by the two dimensional FT and its inverse transformation Flv v X G I v v fo y exp 2i v x v y dxdy Diffraction at spatially periodic objects Spatially periodic objects which are often referred to as gratings have a far field diffraction pattern that is discrete
72. the laser beam transmitting the LCD Discuss the light pattern observed in the far field Compute a image representing a DOE using an asymmetric image as desired far field light pattern use e g the file newportlogo In a full screen window created from the computed DOE image invert the DOE using the provided toolbar button Explain your observations What happens to the phase function created by the LCD when the grayscale image is inverted Superimpose a DOE with a lens with the application software Create different superpositions using different lens strengths and determine the plane of the best observation of the diffraction pattern as a function of the lens strength Explain the result Create a bitmap consisting of several black and white circles This should be addressed with the following shapes onto the display Tutorial Experimental Part 79 8 4 8 4 1 11 12 13 14 a concentric full circles b positive and negative concentric half circles c positive and negative concentric quarter circles Evaluate the diffraction patterns in the far field Note down your observations Use the function of the software to create a binary Fresnel zone plate The radius of the smallest ring can be defined to change the focal length a Try and check the lens effect with different radii of the smallest ring b Determine the focal length of different binary Fresnel zone lenses experimentally as wel
73. ting polarized light wave By examination of the Jones matrices Wry1c one can also deduce that the phase of the light passing the analyser is changed dependent on the voltage dependent parameter I If the SLM is illuminated by a a coherent light sources e g a laser various diffraction effects that are based on this phase modulation can be observed For the experiments it is important to note that the incident polarization for obtaining a comparatively strong phase modulation with only weak amplitude modulation is not parallel or perpendicular to the alignment layers For the experiments dealing with diffraction effects that can be done with the SLM it is sufficient to understand that mutual voltage dependent phase shifts between the waves passing through individual LC cells can be obtained This means that diffractive optical elements can be realized with the help of LCD s In the same way optical elements like Fresnel lenses gratings and beam splitters are switchable by means of electronics Introduction to scalar diffraction theory In the following some keywords will be discussed which are important especially for the experiments described in sections 8 2 and 8 3 Diffractive optical element DOE For a designated diffraction pattern a diffraction structure can be calculated as a solution of the inverse diffraction problem and manufactured with a suitable method The result is a DOE which reconstructs by illumination the desired
74. tion Software DOE sample structures Users Manual DK LCMH 800A 17 3 4 e 1 MRL 12M 12 Micro Optical Rail e 5 MCF Flat Carrier e 4 VPH 2 2 Post Holder e 4 SP 2 2 Post e 2 LHI IR 1 Lens Holder e 2 LMI R Lens Mount e 1 12454 Polarizer Disk If you are missing any hardware or have questions about the hardware you have received please contact Newport Corporation Electrical Requirements Before attempting to power up the unit for the first time the following precautions must be followed WARNING To avoid electric shock connect the instrument to properly earth grounded 3 prong receptacles only Failure to observe this precaution can result in severe injury User s Manual DK LCMH 800A 4 1 4 1 1 User s Manual DK LCMH 800A Cautions The DK LCMH 800A SLM is an electro optical device of high quality and value In order to operate and maintain the SLM in a proper manner be sure to read this manual carefully Avoid humidity and dust Do not use the SLM outside buildings and in humid or dusty places Keep heat away Keep the SLM away from extreme heat as it may cause damage When using the SLM its display case and power pack become warm Take care for sufficient ventilation and keep the devices away from heat such as heating radiators strong sun light etc If you plan to apply the SLM with powerful light sources heat protection filters must be introduced between
75. tmap ooooocooccccnoccncnoccnonancnononanonanacinnnos 49 6 6 5 Rectangular ApertUtE it 49 6 6 6 Circular APO A oes ceca a a RIRS 50 Preface VII 6 6 7 Binary Fresnel Zone Lens iia 50 00 38 Fresnel Zone Lens ent ar ie Beaded EENES 50 0 69 Binary AKRICO aeo r EEA EE ET Ei 50 06 10 ARICON TE AG ai eae 50 6 6 11 Concentric ring segments esa ii 51 6 6 12 Single Slit and Double St uuiaiiaiciniians 51 6 6 13 Linear Gratings and Crossed Linear gratings 51 6 6 14 Linear and Array Beamsplitter Gratings 0 0 00 eee 51 6 6 15 Sinusoidal Grating ti cgettedatisie ta eaten 52 66 16 Bl zed Grating muii adi 52 67 Th Window Medi BA ee ae 52 7 Tutorial Theoretical Part 53 7 1 Preliminary remarks reinicias 53 7 2 Introduction to liquid crystal physics oooonnncccnnoccccnonccinnnnnnnnos 54 7 2 1 Twisted nematic LC cell ici niiatnn lis ini 55 722 Polarization of HEL tias iria 57 7 2 3 Propagation in anisotroptic Media eee eeeeeeeeeee 58 FL WANE PALES a a 59 7 2 5 Amplitude and phase modulation by a TN LC cell 60 7 3 Introduction to scalar diffraction theory ooonnccccnoncccnoncccnananinns 62 7 3 1 Diffractive optical element DOE oconccnnncnnonononnnannninnnos 62 7 3 2 Computer generated hologram CGH ococonncccnoccnacncnnnos 63 7 3 3 Kirchhoff diffraction integral oooonccnnnncocnnncccnncnccnonccinnnos 64 7 3 4 Fresnel approximation cooooccnnnnccnoncccnnonccnnnnnnnnnncnonnna
76. to 90 can be varied This is possible by an appropriate choice of a polynomial an appropriate order level must be chosen Repeat the experiment from point 7 using colour filters for red and blue light For the case of maximum polarisation change the ellipticity of the transmitted light originally linear should be estimated by measuring the Stokes parameter Set up as used in point 7 measure the intensities at analyser positions 0 45 90 45 Tutorial Experimental Part 73 8 2 8 2 1 8 2 2 11 Discuss and summarize the function of an LC display as a polarisation modifier Does it have influence on the amplitude or phase of light How can you get an amplitude modulation of light 12 If experiment 4 Mach Zehnder interferometer has already been accomplished please try to figure out how a separate phase and amplitude modulation with two modulators can be realised Keywords for preparation Polarization of light possibility to create polarized light optical elements for changing the polarization state contrast stokes parameter birefringence connection between polarisation state and angular momentum of photons mathematical description of a plane wave liquid crystal functionality of an LC display pixel size fill factor functionality of a photo resistor and characteristic line geometrical optic Kohler illumination field lens lens aberration aperture Generation and analysis of dynamic diffra
77. ture which means that the angle of the molecular axis changes along the optical path of light propagating through the LC cell The helix structure of twisted nematic crystals can be used to change the polarization status of incident light When the polarization of the light is parallel to the molecules of the cell at the entrance facet the polarization follows the twist of the molecule axis Therefore the light leaves the LC cell with a polarization that is perpendicular to the incident polarization surface aligned molecules light polarization light propagation twisted nematic LC cell Figure 21 Polarization guided light transmission In order to realize a dynamic optical element a voltage is applied to the LC cell This voltage causes changes of the molecular orientation as is illustrated in Figure 22 for three voltages Va Vg Vc Additionally to the twist caused by the alignment layers present already at V4 0 the molecules experience a voltage dependent tilt if the voltage is higher than a certain threshold Vg gt Vinr With increasing voltage Vea Vinr only some molecules close to the cell surface are still influenced by the alignment layers but the majority of molecules in the center of the cell will get aligned parallel to the electic field direction 56 Tutorial Theoretical Part If the helix arrangement of the LC cell is disturbed by the external voltage the guidance of the light gets less effectiv
78. unction of the SLM is supposed to be used in advanced experiments as it requires experiences to be used in an effective manner The Gamma Correction controls shown in Figure 12 can be accessed by the menu option Adjustments gt Gamma Control or by pushing the F3 key These controls influence the linearity of the transmission of image brightness signals Within certain limits the Gamma Correction can be used to equalise non linearities in the LCD s transformation of electrical signals into optical transparency signals LC2002C Firmware Version 1 07 SN 10162 Oy x Options Adjustments Info Gamma Correction Transfer Function White Level i l i Control Gain EE o o fo COM 1 opened Connected 9 Figure 12 Gamma Correction controls There are four different controls the resulting effect of which is depicted by the image of the transfer function in the centre Depending on which control is selected the image of the transfer function changes respectively The grey scale is used to visualise which video signals corresponding to grey levels and image location are influenced by a control Black Level Control This control operates on the gamma correction of darker image pixels The control shifts the given correction entry point onto a certain grey level With respect to this point all darker image pixels and corresponding image locations are g
79. w When fullscreen windows are open outside the main window they can be closed via a separate menu point Close all windows outside the main window Of course the menu item Close all windows inside the main window does not affect full screen windows outside and vice versa Tutorial Theoretical Part 53 7 1 Tutorial Theoretical Part Five experiments have been chosen which demonstrate the wide range of physical phenomena which can be investigated experimentally with this educational kit These are e g the optical set up of a projector properties of polarized light optical properties of liquid crystals the modulation of phase amplitude and polarization of light fields the diffraction of light at dynamically changing structures Diffractive Optical Elements DOE s Spatial frequency filtering and interferometry phase shifter Thus the device is suitable for introductory and advanced laboratory classes in physics and engineering study courses Preliminary remarks The diffraction of light at dynamically adjustable optical elements as represented by the LC cells of a spatial light modulator can be described by the transmission through the LC material which is characterized by its electrooptical properties and the following pattern formation due to propagation for the diffracted wave Diffractive optical elements DOE s are applied more and more in modern optical instruments The optical function is cau
80. x5 binary non separable array beam splitter DOE image Note down and explain your observations especially concerning the symmetry properties of the diffracted light pattern Observe the diffraction patterns in the far field a of the provided 2x2 binary array beam splitter DOE image b of a checkerboard bitmap with a grating period of 18 pixels i e 9 pixels line and 9 pixels groove c of checkerboard bitmaps with the same grating period but uneven duty cycles e g 12 pixels line and 6 pixels groove 13 pixels line and 5 pixels groove Why are certain diffraction orders missing for some of the DOEs Hint the images are separable i e the transmission function 7 x y of the LCD can be written as a product 7 x y 7 x m y The diffraction pattern in each direction x and y can be understood from the Fourier series expansion of the diffraction pattern as a function to the transition function see section 7 3 6 Change the scale of an image representing a DOE To do this magnify or shrink the image using the zoom buttons of the application software Discuss the results Cover the image representing the DOE on the screen or just on the display to half or 34 size with a blacked out area Observe each time the light pattern in the far field Compare them regarding the contrast and speckles and discuss the results Place two different images representing DOEs on the screen next to each other so that both of them are illuminated by

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