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Chapter 7K Agilent 10721A Two-Axis Differential Interferometer

1. fiber optic remote receivers or Agilent 10780C receivers Receiver Alignment Self aligning when mounted to interferometer MEASUREMENT AND REFERENCE PLANE MIRROR RECOMMENDATIONS Reflectance 98 at 633 nm normal incidence Flatness Depending on accuracy requirements of the application mirror flatness may range from 4 to 4 20 0 16 to 0 03 umeters 6 to 1 2 pinches Optical Surface Quality 60 40 per Mil 0 13830 NOTE Flatness deviations will appear as measurement errors when the mirror is translated across the beam Mirror mount should be kinematic so as not to bend mirror If accuracy requirements demand it mirror flatness might be calibrated scanned and stored in the system controller to be used as a correction factor 7K 19 Chapter 7K Agilent 10721A Two Axis Differential Interferometer Specifications and Characteristics 63 5 mm i lt 2 500 gt Recommended Minimum 35 56 mm R1 400 1 a gt i y WIVA 1 As BEAM nee oven 2 BENDER A ETT my Mirrors E ae ERES z A md 35 56 mm f R1 400 gt 43 18 mm Minimum 1 70 9 12 mm lt 0 359 lt gt 19 86 mm 0 782 57 15 mm lt 7 16 mm 7 16 mm 0 282 0 282 fe RE BZ eae a Ref TN Four be ams t o reference mirror 19 05 mm 0 750 J Meas Y Four be ams t o measurement mirror 31 75 mm 1 250 Y gt 12 70 mm 0 500 a LS Ou
2. interferometer use a 33 beam splitter to send one third of the laser power to the Agilent 10719A interferometer which has one receiver and two thirds of the laser power to the Agilent 10721A interferometer which has two receivers Configuration and beam locations The Agilent 10721A interferometer is designed to be used in a straight through configuration only Its input face and measurement face are parallel to each other on opposite sides of the housing The locations of the reference and measurement beams with inputs and outputs identified are shown in Figure 7K 4 Beam diameter The Agilent 10721A interferometer is similar to other plane mirror interferometers except that its reference paths are redirected to be parallel to their related measurement paths outside the interferometer Thus each reference path also requires a plane mirror for its reflector Receiver considerations The Agilent 10721A interferometer requires the 3 mm diameter beam available from an Agilent 5517C 003 Laser Head The smaller diameter beam enables the beam positions on the stage mirror to be closer to the lithographic image plane reducing Abb offset errors User s Manual 7K 7 Chapter 7K Agilent 10721A Two Axis Differential Interferometer Special Considerations BEAM LOCATION FOR AGILENT 10721A Sensor Heads for Remote Receivers Input Beam to Interferometer Top Four Beams are Reference Bea
3. resolution extension Angular pitch or roll 0 7 urad 0 14 arc sec using X32 electronics 0 1 prad 0 02 arc sec using X256 electronics Range Linear 10m 33 ft Angular yaw at distance 150 mm at distance 300 mm 0 88 mrad 3 arc min 0 44 mrad 1 5 arc min Linear and angular resolutions are dependent on the electronics used Optical resolution is dependent only on the interferometer and can be used to determine linear and angular resolutions when the electronic resolution extension is known The linear and angular specifications in this section are for interferometer use with the X32 resolution extension electronics 10885A 10895A or X256 resolution extension electronics 10897B 10898A Linear range here is the sum of the ranges for all axes Angular range is the maximum measurement mirror angle due to all components i e yaw and pitch or yaw and roll between the measurement mirror and the interferometer for a 6 axis system Range will be reduced when the reference mirror is misaligned User s Manual Parallelism Input to output beams lt 0 1 mrad 20 arc sec Optical Efficiency output beam input beam Average 27 Worst Case 18 INSTALLATION RECOMMENDATIONS Installation and alignment Kinematic installation requires a referenced surface Inter axis Alignment All internal optics are reference to mounting surface and have fixed alignment Receivers Agilent 10780F
4. to be closer to the upper edge of the X Y stage measurement mirror thereby reducing Abb errors The Agilent 10721A interferometer s basic optical resolution is the same as that of the Agilent 10719A and Agilent 10706B interferometers The Agilent 10721A interferometer s basic angular resolution is 2 56 arc seconds which can be extended electronically by 32X to give 0 08 arc second resolution Applications Differential measurements A differential measurement is one in which both the reference beam and the measurement beam travel to external mirrors outside the interferometer housing This allows measurement of the relative positions of the two external mirrors either or both of which may move 7K 2 User s Manual Chapter 7K Agilent 10721A Two Axis Differential Interferometer Description FRONT VIEW REAR VIEW Agilent 10721A Two Axis Differential Interferometer Figure 7K 1 Agilent 10721A Two Axis Differential Interferometer One useful example of a differential measurement application is in lithography where the motion of an X Y stage is measured relative to its related optical column An example of a laser measurement system for this application including both Agilent 10721A and Agilent 10719A interferometers is presented in the Agilent 10719A subchapter Subchapter 7J of this manual Angular measurements Because the Agilent 10721A interferometer combines the capabilities of two discrete linear interferome
5. 10721A interferometer occurs when the measurement is 19 05 mm 0 750 inch farther from the interferometer housing than the reference mirror is Deadpath compensation for the Agilent 10721A interferometer can be performed in one of two ways e move the measurement mirror to the zero deadpath position before each system reset or e usea deadpath compensation number in software If you use this method be aware that the compensation number can be either positive or negative depending on the relative position of the mirrors at reset 7K 18 User s Manual Chapter 7K Agilent 10721A Two Axis Differential Interferometer Specifications and Characteristics Specifications and Characteristics Agilent 10721A Two Axis Differential Interferometer Specifications USE Multiple axis applications such as precise positioning of a multiaxis stage where the stage must be linearly and angularly positioned with respect to an external object such as a column or inspection tool The interferometer can be made vacuum compatible SPECIFICATIONS Operating Temperature 17 to 23 C Weight 300 grams 11 ounces Dimensions see Figure 7K 5 on the next page Materials Used Housing Aluminum Optics Optical grade glass Adhesives Vaccum grade Axis Linear and yaw Available Beam Size 3 mm Thermal Drift Coefficient Average 150 nm 5 9 pin C Resolution Optical 2 4 Linear 5 nm using 32 x resolution extension 0 62 nm using 256 x
6. 10721A interferometer an alignment aid Agilent Part Number 10706 60202 is provided with it Alignment procedure The objectives of the alignment procedure are 1 to position the measurement point accurately on the measurement mirror 2 to minimize cosine error 3 tomaximize signal strength at the receiver and 4 toensure a symmetrical range of rotation about the zero angle point To accomplish these goals 1 the measurement mirror must be aligned perpendicular to its axis of linear motion and 2 thereference mirror be aligned parallel to the measurement mirror before the following steps For a system having more than one measurement axis choose a practical sequence in which to align the axes before beginning the interferometer alignment Be aware that the laser head and certain beam directing optics may be adjusted for the first axis but then will not be permitted to move while aligning subsequent axes In fact the convenience of independent adjustments may suggest the use of additional beam directing optics in certain cases Begin by installing the laser head and the optics in their desired locations and roughly aligning the laser beam so it is centered on the input aperture of each interferometer Do not install the receivers yet If the interferometers are mounted on adjustable mounts instead of fixed platforms which predetermine their locations position them to within the translational and rotational to
7. 7K Agilent 10721A Two Axis Differential nterferometer Chapter 7K Agilent 10721A Two Axis Differential Interferometer Description Description General The Agilent 10721A Two Axis Differential nterferometer see Figure 7K 1 is a plane mirror type of interferometer similar to the Agilent 10719A One Axis Differential Interferometer described in subchapter 7 except that it provides an additional measurement axis The Agilent 10721A Two Axis Differential Interferometer is intended for making differential linear and angular measurements simultaneously between two separate plane mirrors The Agilent 10721A interferometer makes two simultaneous adjacent parallel linear measurements spaced 12 7 mm 0 500 inch apart The parallelism between the two measurements is guaranteed by the internal optics and eliminates the parallelism adjustment required when separate linear interferometers are used for measuring angle An Agilent 10721A interferometer angle measurement is implemented in software via electronic subtraction The concept of electronic subtraction and a method to calibrate the angle measurement with high accuracy are described in Chapter 4 System Installation and Alignment of this manual The Agilent 10721A interferometer is designed to use a 3 mm diameter laser beam available from an Agilent 5517C 003 Laser Head This beam is smaller than the standard 6 mm beam and allows the measurement plane center of the beam
8. Mirror B X2 z Af 2 4 Plate al A A AAA A MM 214 Plate err irror COMPOSITE fA and fB a 2 AXD Z Agilent 10721A Two Axis Differential Interferometer Y a gt fa X2 A gt fa X1 fB0 1 24f R seiver y lt fa and fB From _ HT gt p X TITE a mn gt SS L aser ME a gt es omy Beam Divider Focal o m m a a dene gt a AME A moa wy y Aan AN sage fg X2 IL LJ fg X1 2 4 Plate LEGEND lt fA ee mu gt fB X fa and fg f r Rounded corners are used to help you trace paths Figure 7K 3 Agilent 10721A Two Axis Differential Interferometer laser beam path 7K 6 User s Manual Chapter 7K Agilent 10721A Two Axis Differential Interferometer Special Considerations Special Considerations Laser beam power consideration When you are working with an application that has more than one measurement axis make sure that you provide enough laser beam power tothe Agilent 10721A soit can drive both receivers connected to it The method for calculating this is described under the Beam Path Loss Computation section in Chapter 3 System Design Considerations of this manual In addition you should try to balance the available net power after all losses have been computed so all receivers in the application will receive nearly equal power F or example in an application using both an Agilent 10719A interferometer and an Agilent 10721A
9. ake relative measurements between a measurement plane mirror and a reference plane mirror Since mirror size requirements depend on the application both plane mirrors must be supplied by the user Recommended optical specifications for these reflectors can be found in the Specifications and Characteristics section at the end of this subchapter You must also provide the mounting system for the mirrors An important consideration in designing the mountings is to provide the means to ensure that the two mirrors are aligned substantially parallel to each other during system reset even though they are not in general coplanar Initial parallelism at reset is important for keeping the permitted measurement mirror angle range symmetrical about the initial zero angle position F or example a parallelism error of 10 seconds during reset will effectively reduce the angle rangein one direction by 10 seconds and increase it in the other direction by the same amount 7K 10 User s Manual Chapter 7K Agilent 10721A Two Axis Differential Interferometer Mounting The general solution is to provide a way to adjust at least one and possibly both mirrors As explained below the alignment procedure requires that the reference and measurement mirrors both be made initially perpendicular to the input laser beam Thus with three items to adjust two mirrors and one input beam at least two of them should be adjustable The input beam itself usu
10. ally allows the first adjustment therefore one of the two mirrors must provide the second In atypical lithography application the reference mirror will usually be stationary that is mounted to the optical column so it is often the convenient choice for attaching to an adjustable mount Whether mounted with adjustment capability or not the mirrors must be held rigidly and stably once they are installed Choose your mounting method should with care to avoid introducing mounting stresses which deform the mirrors surface flatness Adhesives can be used successfully but beware of any stress which may be introduced during curing Your mounting method should also minimize thermal expansion effects which could displace the mirrors and give false displacement or rotation measurements Many methods exist for mounting optics with low stress and high thermal stability F or additional information a useful introductory article is The Optic As A Free Body Photonics Spectra Aug 1985 pp 49 59 Also textbooks on opto mechanical design can provide more information Mounting Vibration isolation Agilent 10721A interferometers are inherently less susceptible to vibration effects than some other interferometers The stability of these interferometers is due to the fact that both their reference beams and their measurement beams travel to external mirrors Any motion of the interferometer itself that is common to both beams will n
11. erances within the application do not permit the use of a pre determined non adjustable platform Coarse adjustments may be provided in a variety of ways such as using slotted holes for the mounting screws F or fine adjustments micro positioning stages are available from a variety of vendors When using adjustable mounts a key consideration is to ensure that the adjustment capability does not introduce creep or instability into the mounting system In some applications a combined approach may be best For example perhaps a platform having an accurate fixed height can be used in conjunction with an adjustment for yaw and side to side motion Whatever approach is used the interferometer should always be held rigidly and stably once installed User s Manual 7K 13 Chapter 7K Agilent 10721A Two Axis Differential Interferometer Installation Installation Pre installation checklist In addition to reading chapters 2 through 4 and Chapter 15 Accuracy and Repeatability complete the following items before installing a laser positioning system into any application g Complete Beam Path Loss Calculation see Calculation of signal loss in Chapter 3 System Design Considerations of this manual o Supply plane mirror reflectors See Chapter 15 Accuracy and Repeatability or Specifications and Characteristics section at the end of this subchapter for mirror specifications g Determine the direction se
12. h of the six degrees of freedom three translational three rotational The recommended positional tolerances for mounting the interferometers are given below Consider an ideal case in which the input laser beam is perfectly aligned to its desired axis 1 Thereis no recommended tolerance for locating the Agilent 10721A interferometer along the X axis since this has no influence on the measurement 2 Therecommended tolerances for locating the interferometer along the Y axis and Z axis are 0 15 mm 0 006 inch Positional errors here will displace the effective measurement points on the mirrors by an equal amount Also mislocation can offset the beam centering in the input and output apertures 3 The recommended tolerances for pitch roll and yaw of the interferometers are 15 arc minutes relative to the input beam Here again mislocation chiefly affects beam centering though gross errors in roll that is over 1 degree can start to induce non linearity error due to polarization misalignment The primary reason for these tolerances is to control the measurement points on the mirrors and to ensure that the laser beams will reach the receivers properly aligned with no clipping or signal loss Small positional errors do not impair the measurement accuracy provided they are fixed and do not change during the measurement 7K 12 User s Manual Chapter 7K Agilent 10721A Two Axis Differential Interferometer Mounting With these p
13. lerances described in the previous Mounting section This determines locations of the measurement points on the mirrors User s Manual 7K 15 NOTE NOTE Chapter 7K Agilent 10721A Two Axis Differential Interferometer Alignment With the interferometers and mirrors properly positioned finish the alignment by adjusting the input laser beam s angle and position for each interferometer individually a Adjust the angle of the input beam first using the autoreflection technique 1 Start by selecting the small aperture on the front turret of the laser head 2 Insert the alignment aid Agilent Part Number 10706 60202 into the measurement beam between the interferometer and the measurement mirror This may be held in position temporarily by affixing a piece of tape to its yellow label This will cause the beam reflecting off the mirror to reflect back out through the input aperture toward the laser head 3 Angularly adjust the input beam using the beam directing optics or the laser head or both until the reflected beam re enters the small aperture of the laser head Careful accurate autoreflection at this step is essential to minimizing cosine errors assuming the mirror is perpendicular tothe linear axis of travel b Adjust the centering of the input beam on the input aperture second by visual alignment 1 Start by switching back to the large aperture on the turret of the laser head because the small aperture is only r
14. ms Bottom Four Beams are Measurement Beams 31 75 FRONT VIEW REAR VIEW Figure 7K 4 Agilent 10721A Two Axis Differential Interferometer Reference and Measurement beams The Agilent 10721A interferometer is designed primarily for use with the Agilent 10780F Remote Receiver however any other Agilent receiver may be used One receiver is required for each Agilent 10721A output to be used The advantage of using the remote receiver is that the fiber optic sensor head can be directly attached to the interferometer eliminating the need for separate mounting brackets When laying out an application be sure to allow enough clearance for the fiber optic cable without bending it tighter than its minimum bend radius of 35 mm 1 4 inches Also avoid any kinking where the fiber connects to the sensor head Kinking or excessive bending of this cable can cause signal attenuation 7K 8 User s Manual Chapter 7K Agilent 10721A Two Axis Differential Interferometer Special Considerations Mounting pins on the interferometer eliminate the need for any user alignment of the sensor head With the Agilent 10721A interferometer the receiver s sensor head can be oriented only one way at each interferometer output aperture as determined by the location of the threaded mounting hole Use 4 40x1 inch screws to fasten the sensor heads to the interferometer Spacing to beam directing optic The recommended minimum spacing between the interfer
15. ng the input aperture the laser beam is split into two parallel beams 12 7 mm 0 500 inch apart Each of these beams is then split into its separate reference and measurement components Each of the two measurement beam continues straight through the interferometer to its measurement aperture Each reference path includes two 90 degree bends causing that reference beam to be parallel to its related measurement beam but offset from it by 19 05 mm 0 750 inch Toreduce thermal drift errors the measurement and related reference beam paths have the same optical path length in glass This reduces measurement errors due to temperature changes in the interferometer User s Manual 7K 5 Chapter 7K Agilent 10721A Two Axis Differential Interferometer Description 2o a M4 Plate Reference REFERENCE PATH fa Mirror An aX Z Agilent 10721A Two Axis A Differential Interferometer j lt 2 e a wy To _ fa X1 Receiver j f i gt A F A 5 a Z Laser gt y p amp ve To A A Receiver iN Stage Beam Divider fA X2 il y fa X1 at Plats Mirror 2 4 Plate MEASUREMENT PATH fB Reference Mirror Agilent 10721A Two Axis Y Differential Interferometer Y Z A To y fB X1 2AF A Receiver mn mm ee e gt fp X1 fp X1 Z E A D m a a gt el ls rom From pa Y eee gt E E E a r ee Ss e n A gt jo x2 A Receiver d TBX2 EZAr a a a lt u gt A Beam Divider J A Stage pal Y Y Tx
16. nse for each axis based on the orientation of the laser head beam directing optic and interferometer Enter the direction sense for each axis into the measurement system electronics See Chapter 5 Laser Heads Chapter 14 Principles of Operation and Chapter 15 Accuracy and Repeatability in this manual g Supply suitable mounting means for all components of the laser measurement system based on the recommendations given earlier in this subchapter and elsewhere in this manual g Provide for aligning the optics laser head and receiver s on the machine g Besureto allow for transmitted beam offset of beam splitters Agilent 10700A and Agilent 10701A in your design See the offset specifications under the Specifications and Characteristics section at the end of this subchapter Receivers 1 Agilent 10780F E1708A or E1709A receiver s fiber optic sensor heads may be mounted directly to the Agilent 10719A interferometer s output aperture Alignment pins are provided for easy installation and alignment This eliminates the need for any other user supplied mount for the sensor head 2 Maintain a bend radius not less than 35 mm 1 4 inches to prevent signal attenuation in the Agilent 10780F E1708A or E1709A receiver s fiber optic cable 7K 14 User s Manual Chapter 7K Agilent 10721A Two Axis Differential Interferometer Alignment Alignment Alignment aid To help in aligning the Agilent
17. o the measurement path This configuration will result in the fringe counts DECREASING when the measurement mirror moves AWAY from the interferometer User s Manual 7K 9 Chapter 7K Agilent 10721A Two Axis Differential Interferometer Special Considerations The direction sense will change sign for any configuration which rotates either the laser head or the interferometer by 90 degrees The configuration of the beam directing optics between the laser head and the interferometer may effectively rotate the laser beam changing which laser frequency polarization is in which interferometer path and thus the direction sense of the interferometer Deadpath For the Agilent 10721A interferometer zero deadpath the condition in which the measurement beam path length and the reference beam path length are equal does not occur when the reference and measurement mirrors are coplanar Because the reference beam travels 19 05 mm 0 750 inch further through air inside the interferometer than the measurement beam does the zero deadpath condition for the Agilent 10721A interferometer occurs when the measurement mirror is 19 05 mm 0 750 inch farther from the interferometer housing than the reference mirror is The consequences of this are discussed in more detail under the Operation section later in this subchapter Reference and measurement mirror requirements A key feature of the Agilent 10721A interferometer is its ability to m
18. ometer and its beam directing optic is 63 5 mm 2 50 inches This spacing will provide the minimum clearance for the fiber optic cable when the Agilent 10780F Remote Receiver is used Input and output apertures The Agilent 10721A interferometer has three apertures which are not interchangeable The middle aperture must be used for the input beam The outer two apertures are for the output beams Both output apertures are equipped with mounting pins for the Agilent 10780F fiber optic sensor head therefore either aperture can be used for the output beam Direction sense The Agilent 10721A interferometer direction sense depends fundamentally on which laser frequency is in its measurement path This is affected by on the mounting orientations of both the interferometer and the laser head In most cases the Agilent 10721A interferometer will be oriented upright that is with its top and bottom mounting surfaces horizontal In this orientation the internal polarizing beam splitter will send the vertical polarization into the measurement beam path and the horizontal polarization into the reference beam path As mentioned in Chapter 5 Laser Heads of this manual the Agilent 5517C 003 Laser Head produces f4 its lower frequency with horizontal polarization and f its higher frequency with vertical polarization Thus an Agilent 5517C 003 with its mounting plane horizontal will direct fi into the reference path and fp int
19. ositional accuracy goals in mind there are two recommended approaches to designing the mounting system e Create an accurate fixed mounting platform which predetermines the location of each interferometer using reference surfaces or e Create an adjustable mount with adjustments to dial in the positional accuracy after each interferometer is installed Fixed Mounting Platform f you use the first approach the best design for a mounting platform is to make it kinematic Kinematic means that all 6 degrees of freedom are singly and unambiguously restricted It is best to use a locating plane a locating line anda locating point The locating plane will be the surface to which the top or the bottom of the interferometer is bolted The locating line should be a 2 point contact or rail which aligns the front face of the interferometer The locating point should bea 1 point contact or pad which constrains side to side translations of the interferometer To install the interferometer it should be firmly pressed against its locating plane line and point while the mounting screws are torqued down If the platform is made with the above mentioned accuracy this mounting method can completely eliminate the need to adjust or align the interferometers during installation Then only the laser beam itself will need to be aligned to its proper position Adjustable Mount The adjustable mount approach is recommended when the mechanical tol
20. ot appear as a measurement Of course any vibration between the reference and measurement mirrors will constitute real measurable displacements Interferometer mounting system user supplied Since the mounting system requirements depend on the application the mounting system must be designed and provided by the user The following paragraphs provide some guidelines and recommendations for designing the mounting system User s Manual 7K 11 Chapter 7K Agilent 10721A Two Axis Differential Interferometer Mounting The Agilent 10721A interferometer is designed for easy mounting and alignment It may be mounted in any orientation using the mounting hole patterns on either the top or bottom surfaces of the housing The mounting screw thread is 6 32 A key feature of the Agilent 10721A interferometer is that it is designed as a referenced interferometer In other words the relationships of its internal optical components and laser beam paths to reference surfaces on its housing is specified This opens the possibility of a mounting scheme which eliminates the need for aligning or adjusting the interferometer Designing the mounting system The first step in designing the mounting scheme is to determine the nominal position of each interferometer This is generally dictated by the intended location of the measurement beams on the measurement mirror The mounting system for each interferometer should be designed to restrict eac
21. oughly aligned to the beam center 2 Place a piece of translucent tape across the input aperture of the interferometer to make the input beam easily visible 3 Translate the beam directing optics or the laser head or both to center the input beam on the aperture Do not disturb the angular alignments already made With care you can center the beam visually to within 40 15 mm 40 006 inch of its ideal position c Go back to steps 3a and 3b and alternately recheck and readjust the input beam angle and centering until both are simultaneously optimized Then remove the tape from the input aperture and remove the alignment aid d Asa further alignment check place a piece of translucent tape across the output aperture s to make the output beam s easily visible Each output beam should now be approximately centered in its aperture without clipping Any clipping observed here indicates a centering problem at the input aperture or an autoreflection problem 7K 16 User s Manual NOTE Chapter 7K Agilent 10721A Two Axis Differential Interferometer Alignment e Clamp down the laser and the beam directing optics without altering their alignment At this point the reference beam has also been automatically aligned assuming the reference mirror is parallel to the measurement mirror If any parallelism error exists then the beam overlap in the output aperture s will be degraded and this may be visible Beam overlap can be checked q
22. ters into a single package it can be used to make angular measurements For angular measurements the Agilent 10721A interferometer makes twolinear measurements Y and Y with built in parallelism spaced 12 7 mm 0 5 inch apart The angular measurement is calculated by taking the arctangent of the difference between these linear measurements divided by their separation THETA arctan Y Y D User s Manual 7K 3 Chapter 7K Agilent 10721A Two Axis Differential Interferometer Description For more information about angular measurements see the Electronic Y aw Calculation Method and Optical Y aw Calculation Method subsections under the Three Axis System Using Discrete Plane Mirror Interferometers X Y YAW section in Chapter 3 System Design Considerations of this manual Measurements possible using the Agilent 10721A interferometer are illustrated in Figure 7K 2 LINEAR ANGULAR MEASUREMENT WITH AGILENT 10721A REAR VIEW Figure 7K 2 Agilent 10721A Two Axis Differential Interferometer measurements Multiaxis configurations Refer to the Multiaxis Configurations subsection in the Agilent 10719A subchapter subchapter 7J of this manual 7K 4 User s Manual Chapter 7K Agilent 10721A Two Axis Differential Interferometer Description Optical schematic Figure 7K 3 shows the optical schematic of the Agilent 10721A Two Axis Differential nterferometer After enteri
23. tput spacing bet ween w3 Aperture 2 lt gt 12 70 mm linear measurements put Aperture METE 0 500 feet ber er i FRONT VIEW REAR VIEW S 31 75 mm 1 250 38 10 mm 1 500 Fiber Optic sensor head mounting pi ns y Four mounting holes 31 75 l ont op and b ottom lt lt mim lt 9 53 mm surfaces 6 32 1 250 0 375 8 0 mm 0 31 deep Figure 7K 5 Agilent 10721A Two Axis Differential Interferometer dimensions Product specifications and descriptions in this document subject to change without notice Copyright C 2002 Agilent Technologies Printed in U S A 07 02 This is a chapter from the manual titled Laser and Optics User s Manual For complete manual order Paper version p n 05517 90045 CD version p n 05517 90063 This chapter is p n 05517 90118 7K 20 User s Manual
24. ualitatively by alternately blocking the reference and measurement beams and observing their respective positions on the tape across the output aperture s Remove tape when done If a beam overlap problem exists recheck the parallelism of the reference mirror relative to the measurement mirror Adjust as needed Attach the fiber optic sensor heads using 4 40 screws Repeat the above steps for all other interferometers in the application being careful to adjust only beam directing optics which do not disturb the alignments already completed User s Manual 7K 17 Chapter 7K Agilent 10721A Two Axis Differential Interferometer Operation Operation Reset considerations If the reflectors you use with the interferometer are not at their zero deadpath positions when you reset the system you should enter a zero deadpath compensation value as described under Deadpath Compensation Considerations below Deadpath compensation considerations Proper use of deadpath compensation is essential to achieving maximum accuracy For the Agilent 10721A interferometer zero deadpath the condition in which the measurement beam path length and the reference beam path length are equal does not occur when the reference and measurement mirrors are coplanar Because the reference beam travels 19 05 mm 0 750 inch further through air inside the interferometer than the measurement beam does the zero deadpath condition for the Agilent

Chapter 7K Agilent 10721A Two-Axis Differential Interferometer

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