Patent Publication Number: US-6983547-B2

Title: Goniometer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is based from U.S. Provisional Application Ser. No. 60/276,999 filed on Mar. 19, 2001 and entitled “AUTOMATED APPARATUS FOR TESTING OPTICAL FILTERS”. This application is related to an application entitled AUTOMATED APPARATUS FOR TESTING OPTICAL FILTERS, having U.S Pat. App. Ser. No. 10/102,200, filed Mar. 19, 2002, an application entitled METHOD AND APPARATUS FOR CALIBRATING A VISION SYSTEM TO A PARTS HANDLING DEVICE, having U.S. Pat. App. Ser. No. 10/102,515, filed on Mar. 19, 2002, and an application entitled FLEXURE, having U.S. Pat. App. Ser. No. 10/102,170, filed on Mar. 19, 2002 (now abandoned). 

   TECHNICAL FIELD OF THE INVENTION 
   The present invention, in general, is directed to a goniometer, preferably for use in an automated apparatus for testing and sorting optical filters. 
   BACKGROUND OF THE INVENTION 
   Commercially-available optical filters are used for various purposes. For example, in U.S. Pat. No. 6,141,469 to Kashyap, there is disclosed a multiple band pass optical filter that may be used in a wavelength division multiplexed (“WDM”) communication system to filter individual WDM channels. U.S. Pat. No. 6,169,828 B1 to Cao, also relating to an optical filter, discloses a dense wavelength division multiplexer (“DWDM”) for use in a fiber optic network. Various optical filters are well known to those skilled in the art. 
   Current methods of manufacturing such optical filters involve manually moving trays of optical filters, from the manufacturing station to a filter-testing station, and then manually testing each filter one at a time. An operator must manually pick a filter from the transfer tray, place it in a testing jig, align the filter in the jig either manually or automatically, test it with a laser and detector system, remove it from the jig, and place it back into the transfer tray. This process is unsatisfactory because it is very slow and prone to human error. Typical throughput is only 20-100 filters per hour. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   Accordingly, a principal object of the invention is to automate the testing, characterization and sorting of optical filters, resulting in lower labor costs than presently possible, at increased production and product-quality levels. 
   These and other objects of the present invention will become readily apparent to those skilled in the art after reviewing the following summary. 
   One aspect or feature of the present invention may be summarized as a goniometer preferably for use with an apparatus for translating optical filters. The optical filter-translating apparatus comprises a gantry system supported on a base or floor. The gantry system includes a structure translatable in the X and Y directions relative to the base. The optical filter-translating apparatus further comprises a support mounted on the structure as well as a translatable platform disposed adjacent the structure. The support is translatable in the Z direction relative to the base. The optical filter-translating apparatus further comprises a flexure mounted on the platform, a probe assembly mounted on the support, and a light-directing element. The flexure is adapted to retain one of the optical filters. Translation of the platform causes the platform-mounted flexure to be translated from a first X, Y and Z position relative to the base to a second X, Y and Z position relative to the base. The probe assembly is adapted to pick up one of the optical filters from a third X, Y and Z position relative to the base and translate the picked-up optical filter to the first position for retention of the picked-up filter by the flexure. The light-directing element is supported by the goniometer and disposed adjacent the second position, is optically connected to a laser light source, and is adapted to direct coherent light at an angle that is normal to the flexure-retained optical filter which has been translated by the platform to the second position for testing the optical filter. For the optical filter-translating apparatus, a preferred light-directing element is a collimator. 
   Another aspect or feature of the present invention may be summarized as a goniometer comprising a base, a compound member supported by the base, and a light-directing element. The light-directing element (again, preferably a collimator) is operably mounted on the compound member, is optically connected to a coherent light source (e.g. a laser), and is disposed toward an optical filter. The goniometer further comprises a first actuator and a second actuator. The first actuator is disposed along a first axis and is operably coupled to the base for translating the light-directing element along a first arcuate path disposed in a first plane. The second actuator is disposed along a second axis and is operably coupled to the compound member for translating the light-directing element along a second arcuate path that is disposed in a second plane. The first plane is orthogonal to the second plane. The first and second axes are preferably coplanar. In operation, the coherent-light source, thus mounted on the base, and in cooperation with the actuators, is adapted to direct coherent light at an angle that is normal to the optical filter that is being tested. 
   In the above-mentioned goniometer, the base preferably includes a pair of spaced-apart so-called “tip-axis” base plates and a channeled guide member disposed therebetween. The compound member preferably comprises a pair of spaced-apart so-called “tilt-axis” side plates as well as a tilt-axis mount disposed therebetween. The goniometer also preferably includes a first gear set operably coupled between the first actuator and the base, and a second gear set operably coupled between the second actuator and the compound member. The light-directing element is preferably a collimator, and the first and second actuators are preferably DC motors. 
   When a plurality of goniometers are involved, the apparatus for testing optical filters preferably further includes a coherent-light splitter which is optically connected between the coherent light source and each associated one of the corresponding plurality of light-directing elements, for splitting the coherent light from the coherent light source and passing the split coherent light to each of the plural light-directing elements. Each light-directing element is adapted to direct coherent light at an angle that is normal to its associated optical filter. The apparatus for testing optical filters preferably also includes a corresponding plurality of reflected-light circulators. Each reflected-light circulator is operably connected between the coherent-light splitter and a corresponding one of the plural light-directing elements, and each reflected-light circulator is adapted to receive reflected light from its associated optical filter that is being tested. The apparatus for testing optical filters further preferably includes a corresponding plurality of sensor modules. In this regard, each sensor module is operably connected to an associated one of the plural reflected-light circulators for characterizing each associated one of the tested optical filters in response to the reflected light that is received by the associated reflected-light circulator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A clear understanding of the various advantages and features of the present invention, as well as the construction and operation of conventional components and mechanisms associated with the present invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the following drawings which accompany and form a part of this patent specification. 
       FIG. 1  is a system overview, in perspective, of the automated apparatus for testing optical filters of the present invention; 
       FIG. 2  is a plan view of the system overview shown in  FIG. 1 ; 
       FIG. 2A  is a cross sectional view of a gel pack tray as it is disposed in a vacuum mount wherein the sectional view is taken at Section  2 — 2  in  FIG. 2 ; 
       FIG. 3 , a partially fragmented view in perspective, depicts a portion of the optical filter-testing apparatus, on an enlarged scale relative to  FIGS. 1 and 2 ; 
       FIG. 4  is an exploded perspective view of the components of an element of the optical filter-testing apparatus shown in  FIG. 3  on an enlarged scale relative thereto; 
       FIGS. 5A and 5B  are sequenced, sectional views depicting relative movement of the components of the element shown in  FIG. 4  on an enlarged scale relative thereto taken along the central longitudinal axis (“Z” in  FIG. 3 ) at Section  5 — 5 ; 
       FIG. 6  is a perspective view of a lift pin assembly feature of the invention; 
       FIG. 6A  is an auxiliary partially-fragmented side elevational view, showing the relationship of certain elements or components not otherwise viewable from  FIG. 6 ; 
       FIG. 7  is a partially-fragmented side elevational view depicting portions of the automated filter-testing apparatus shown in  FIG. 1  on an enlarged scale relative thereto; 
       FIGS. 8A and 8B  are sequenced and partially-fragmented side elevational views, depicting operation of the filter lift pin assembly of  FIG. 6 ; 
       FIGS. 8C and 8D  are partially-fragmented side elevation views of the probe tip, the lift pin, the tape and a filter illustrating how the filter is partially released from the tape as it is raised by the lift pin; 
       FIGS. 9A and 9B  are sequenced and partially-fragmented perspective views, depicting an aspect or feature of the present invention which is also shown in  FIG. 3 , and on an enlarged scale relative thereto; 
       FIGS. 10A and 10B  are sequenced, partially-fragmented plan views, depicting a detail of the invention shown in  FIGS. 9A and 9B , on an enlarged scale relative thereto; 
       FIG. 11  is a perspective view of an element or component of the invention and which is shown in  FIGS. 9A and 9B , on an enlarged scale relative thereto; 
       FIG. 12  is a plan view, generally depicting certain elements or components of the invention that are also generally shown in  FIGS. 3 and 7 ; 
       FIG. 13  is a partially-fragmented perspective view, depicting yet other elements or components of the invention shown in  FIG. 3 , on an enlarged scale relative thereto; 
       FIG. 14  is a partially-fragmented perspective view depicting yet another aspect or feature of the present invention which appears in the background in  FIG. 3 ; 
       FIG. 15  is a partially-fragmented perspective view of a preferred embodiment of the aspect or feature shown in  FIG. 14 , on an enlarged scale relative thereto; 
       FIG. 16  is a partially-fragmented side elevational view, taken generally along the plane  16 — 16  in  FIG. 15 ; 
       FIG. 17  is a partially-fragmented side elevational view, taken generally along the plane  17 — 17  in  FIG. 15 ; 
       FIG. 17A  is an auxiliary view, in exploded perspective, taken from the backside of FIG.  17  and depicting some features or aspects not otherwise seen in  FIG. 17 ; 
       FIG. 18  is a perspective view of a translation assembly shown in  FIG. 14 , on an enlarged scale relative thereto; 
       FIG. 19  is a schematic illustrating a laser beam-splitting feature of the optics design of the present invention; 
       FIG. 20  is a schematic based on  FIG. 19 ; 
       FIGS. 21A ,  21 B an  21 C together provide a flow chart of a preferred method for testing optical filters; 
       FIG. 22  is a cross sectional view of a filter nest and flexure; 
       FIG. 23  is a perspective view of an aperture mask; 
       FIG. 24  is a top view of the rotating table illustrating the stop block that limits the rotation of the table and the switches that provide an indication of its position; 
       FIG. 25  is a side view of the rotating table of  FIG. 24  showing the stop block and features of the limit switches and their actuating flags; and 
       FIG. 26  is a perspective view of the flexure actuator and the vacuum post. 
   

   Throughout the drawings, like reference numerals refer to like parts. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring initially to  FIGS. 1 and 2 , which depict a system overview of the automated apparatus for testing optical filters, there is shown an “X” gantry system  100 ,  100 A and  100 B; a “Y” gantry system  102 ,  102 A and  102 B; and a “Z” translator system  104 , all of which systems are commercially-available devices, wherein the various components and/or elements of which systems are generally translatable in the “X,” “Y” and/or “Z” directions relative to a base or floor  103 . In particular, included with the “X” direction gantry system is an elongated “X” gantry support beam  100 B that provides support for a generally U-shaped “X” gantry transverse-motion platform  100 A on which an “X” gantry stage  100  is longitudinally disposed and slideably mounted. 
   Also shown is a conventional “X” axis cable protector  101 A disposed generally above the “X” gantry system  100 ,  100 A and  100 B as well as a conventional “Y” axis cable protector  101 B for the “Y” gantry system  102 ,  102 A and  102 B. Included with the “Y” gantry system  102 ,  102 A and  102 B is a pair of spaced-apart elongated “Y” gantry system support beams  102 B (one of which is shown in the background) which are disposed on the floor or platform  103 . The illustrated background floor-support beam  102 B has fixedly mounted thereon one of a spaced-apart pair of elongated gantry rails  102 A on which the “Y” gantry platform  102  is longitudinally disposed and slideably mounted. In reference to the “Y” gantry system, the foreground floor-support arrangement (not visible in  FIG. 1  because of foreground structure) is similarly arranged. Preferably, the “X” gantry transverse-motion support beam  100 B and spaced-apart “Y” gantry longitudinal rails  102 A are mutually perpendicularly disposed. 
   In general, the “X” and “Y” gantry systems (FIG.  1 ), which are characterized as servo-controlled, are each provided with conventional high-speed closed-loop feedback systems adapted to translate the various elements and/or components of the apparatus for testing optical filters (of the present invention) along the “X” axis, the “Y” axis, the “Z” axis and to rotate those filters about the “theta” axis, as disclosed herein. 
   In operation, the “X” gantry system  100 ,  100 A and  100 B translates the “Z” translator system  104  along the “X” axis, while the “Y” gantry system  102 ,  102 A and  102 B translates the “Z” translator system  104  along the “Y” axis, enabling the operative portion of the “Z” translator system  104  to access the plurality of optical filters that are disposed on a UV-releasable adhesive tape  108  stretched on a hoop or frame  111 , as shown in  FIGS. 8A and 8B  on optical filter-input or filter-receiving platform or table  110  and, after testing such optical filters, to transfer the tested optical filters to an assortment of tested-and-sorted optical filter classification trays  112  (shown as a four-by-four array of trays in  FIGS. 1 and 2 ) which are located at a filter-output or filter-dispatch platform or table  114 . The UV-releasable tape  108  may be purchased from Fitel Technologies (formerly Furukawa Electric Co.), as tape number UC-120M-120 (a non-expandable tape) or UC-353EP-110 (an expandable tape). Both tapes are low-tack UV-release tapes that are typically used in wafer-dicing applications. 
   Alternatively, optical filters can be supported in gel packs or vacuum release trays that are disposed on filter receiving table  110 . These trays are supported in specially configured vacuum mounts  700  located on table  110 . 
   Referring to  FIG. 2A , vacuum release trays  702  are placed in vacuum mounts  700  on an O-ring seal  704 . The O-ring seals against both the bottom of the tray and the mount itself to form a vacuum chamber  703  defined by the bottom surface of the tray, the O-ring and the mount. Two grooves  706  extend from the O-ring inwardly to a vacuum port  708 . The vacuum port  708  extends through the table  110  to a vacuum fitting  710  disposed on the bottom surface of table  110 . A vacuum is selectively applied to the vacuum fitting to suck air out of the chamber  703 . This reduction in pressure in the chamber  703  both holds the tray  702  in mount  700  and weakens the grip trays  702  have on filters  196 . 
   As background information, the optical filter array or tray, before being placed by hand or machine as desired onto the filter-receiving table  110 , were formed at a prior station (not shown) where a glass substrate with an optical coating (also not shown) was divided into individual optical filters  196 . 
   Referring next to  FIG. 3 , the “Z” translator system  104  includes a theta-axis stage  116  mounted on a “Z” axis stage  118  via bracket  126 . Theta stage  116  is a motor having an output shaft  168  that is rotatable to predetermined angular positions under computer control. This stage is termed the “theta-axis” stage since it rotates the probe to an angle theta about an axis that is disposed parallel to the “Z” direction or axis (i.e. vertically) and passes through the center of stage  116 . The theta axis therefore translates with the theta stage and (in the preferred embodiment) extends through the longitudinal centerline of the probe assembly. The theta stage may be characterized as a servo-controlled axis. 
   The tray-handling end effector cylinder  119  is connected to bracket  126  via bracket  125  to enable the tray-handling end effector  120  which is coupled to the end of the moveable rod of cylinder  119  to extend and retract along (preferably in non-rotative relationship relative to) a first vertical axis Z 1 —Z 1  relative to the optical filters at the input platform  110  and/or the output platform  114 . The “Z” translator system  104  further includes a standard machine vision camera  121  (FIG.  3 ), to enable accessing the optical filters at the filter-input platform  110  and, after testing such optical filters, to enable transferring the tested filters to the filter-output platform  114 . The camera is also coupled to “Z” axis stage  118 . 
   The tray-handling effector  120  includes tines or fingers  122  operably mounted on the effector  120  for grasping and retrieving the optical filter-carrying trays  112  at the output platform  114  and for transferring such trays, after filter testing, to a front row depot. This depot, identified in  FIGS. 1 and 2  as row  150  is used for storing empty trays, completed trays of tests and lids for trays that can be accessed both to replenish depleted tests, replace depleted input test trays and to remove completed test tray and replace them with empty trays. The effector  120  is configured to drive fingers  122  apart or together to selectively grasp or release the individual trays under computer control. 
   The “Z” translator system  104  further includes a filter-capture end effector  124 , also generally referred to within this patent specification either as the vacuum probe assembly or as “the head”  124 , which is mounted on the rotatable output shaft  168  of theta stage  116  which is mounted on Z translator system  104 , which, in turn, is operably affixed to the moveable “X” gantry stage  100  (FIG.  1 ), to enable the vacuum probe assembly or head  124  to move up and down along (and rotate about) a second vertical axis Z 2 —Z 2  (FIG.  3 ). Vertical axis Z 2 —Z 2  is parallel to the “Z” axis. 
   Referring to  FIG. 4 , the vacuum probe assembly or head  124  includes a generally cylindrical and elongated sleeve  128 , which defines a blind hole  130  ( FIG. 5A ) into which an elongated vacuum probe  152  is disposed. This probe is slidably received in through blind hole  130  in which it is supported. 
   The vacuum probe assembly or head  124  further includes a generally cylindrical collar clamp  142  also defining a through bore  144 . The cylindrical collar clamp  142 , in turn, defines a radially-disposed through-slot  146 . The illustrated clamp  142  further includes a transversely offset threaded fastener  148 , for enabling the cylindrical sleeve  128  and the cylindrical collar clamp  142  to be removably affixed together in a conventional manner. The cylindrical sleeve  128  also defines a cylindrical neck portion  150 , of reduced outer diameter relative to the outer diameter of the cylindrical sleeve  128 , for enabling the cylindrical neck portion  150  of sleeve  128  to be snuggly engageable within, and readily removable from, the through bore  144  of the cylindrical collar clamp  142  in a conventional manner. 
   Shaft  168  (FIG.  5 A), to which neck portion  150  is attached by clamp  142 , defines an axially disposed internal fluid passageway  170  (shown in phantom line in FIGS.  5 A and  5 B). 
   The vacuum probe assembly or head  124  also includes a generally cylindrical alignment clamp  174 , which defines a radially disposed slot  176  and a central through bore  178 . The inner diameter of the alignment clamp through bore is so matched relative to the outer diameter of the lower cylindrical band  172  of vacuum probe  152  as to enable the cylindrical band  172  to be snugly disposable into the alignment clamp through bore  178 . The illustrated alignment clamp  174  further includes a conventional threaded fastener  180  located adjacent to the through bore  178  and disposed transverse to the radial slot  176  for releasably affixing alignment clamp  174  onto the cylindrical band  172  of the generally cylindrical and elongated vacuum probe  152  in a conventional manner. 
   The alignment clamp further defines an axially disposed, stepped bore  182  ( FIG. 5A ) spaced from the through bore  178 , into which stepped bore  182  a matched stepped threaded fastener  184  (which functions as a spacer) is disposed. An end portion  186  of spacer  184  is threaded, and cylindrical outer sleeve  128  defines a threaded bore ( FIGS. 5A and 5B ) having threads that mate with the end portion  186  of fastener  184 . 
   The cylindrical outer sleeve  128  further defines a transversely disposed and threaded side bore  190  of substantially identical inner diameter as a similar transversely disposed and threaded side bore  188 . These two bores are configured to receive threaded vacuum fittings, and are fluidly coupled together with a length of flexible tubing  189 . The inner end of bore  190  is in fluid communication with passageway  170  since both open into a chamber  191  defined at the upper end of sleeve  128  located between the sleeve and the lower end of shaft  168 . 
   Side bore  188  of probe  152  is in fluid communication with an axially oriented intermediate fluid passageway  166 . Probe  152  also includes a threaded plug  162  disposed in the upper portion of bore  154  ( FIGS. 5A and 5B ) and providing a fluid tight seal thereat. Probe  152  defines an axially aligned orifice  164 , which is in fluid communication with bore  154  via an intermediate fluid passageway  166 . 
   Flexible tubing  189  is configured to permit probe  152  to slide up and down within sleeve  128 . 
   When a vacuum is drawn by conventional means to impose vacuum at inner passageway  170 , this vacuum is communicated to bore  190 , through the length of flexible tubing and through bore  188 . The vacuum is then communicated through intermediate fluid passageway  166  and thence to orifice  164 . 
   In operation, downwardly disposed member  168  is axially advanced toward an optical filter  196  (shown in phantom line in FIGS.  5 A and  5 B), for enabling the orifice  164  of the vacuum probe  152  to contact the optical filter  196 . 
   Sufficient vacuum is imposed at fluid passageway  170  to enable the optical filter  196  to be held by the orifice  164 , after the optical filter  196 . When the orifice  164  initially makes contact with the optical filter  196 , vacuum probe  152  moves axially upward relative to sleeve  128 , sliding upward within sleeve  128  into blind hole  130 . 
   By permitting probe  152  to “collapse” the length of the probe assembly on initial contact with the filter, the risk of damage to the filter is substantially reduced by providing a soft landing for advancing vacuum probe  152 . A soft landing is insured but only until alignment clamp  174  abuttingly engages the cylindrical outer sleeve  128 . This abutting relationship is shown in FIG.  5 B. For this reason, the system is configured to stop the downward advance of the “Z” stage (to which probe assembly or head  124  is mounted) before clamp  174  abuts sleeve  128 . In an alternative embodiment, individual filters can be selected from any of the gel trays  702  that are held in vacuum tray mounts  700  ( FIGS. 1 ,  2  and  2 A). 
   Referring back to  FIGS. 1 and 2 , the “X” gantry system  100 ,  100 A and  100 B translates the head  124  along the “X” axis while the “Y” gantry system  102 ,  102 A and  102 B translates the head  124  along the “Y” axis, to enable the head  124  to be moved to any point in the X-Y plane, so that the head  124  can access optical filters on the filter-input platform  110  and, after testing and sorting the optical filters, thereafter transfer tested-and-sorted optical filters wherever desired onto output platform  114 . 
   Reference is next invited to  FIGS. 6 ,  6 A,  7 ,  8 A and  8 B, to discuss a “pick and place” procedure as well as a filter lift pin assembly  200  (FIG.  6 ), both of which are additional features of the present invention. The filter lift pin assembly  200  (not visible in  FIG. 1 ) is located generally beneath the optical filter input platform  110  shown in FIG.  1 . The optical filter lift pin assembly  200  includes a base  202 , a guide bracket  204  mounted on the base  202 , and a pneumatic cylinder  206  spaced in distal relation to the bracket  204 . 
   The pneumatic cylinder  206 , also mounted on the base  202  via a chambered alignment block  208 , is operably connected via a piston rod  210  to a wedge  212 . The guide bracket  204  includes an upper surface  214 , which defines an aperture through which a filter lift pin  216  and a pin guide bushing  218  are disposed. Pin  216 , disposed through the through bore of pin guide bushing  218 , is urged downwardly into sliding engagement with the wedge  212  by a helical spring  217  which is captively retained by the pin  216 , as is shown in FIG.  6 A. An upper surface of wedge  212 , on which lift pin  216  rests, is inclined relative to precision linear slide  219  fixed to the base  202 . 
   The pneumatic cylinder  206  operates in a conventional manner to extend and retract the piston rod  210  along the axis X 1 —X 1  (which is parallel to the “X” axis). Such reciprocal action, in turn, causes the lift pin  216  to extend upward or retract downward relative to the base  202  and the bracket upper surface  214 . The axis of pin extension and retraction is parallel to the “Z” axis. 
   Wedge  212  is supported on and fixed to the upper translating portion  225  of linear slide  219  by conventional threaded fasteners  221 . The lower fixed portion  227  of linear slide  219  is fixed to base  202  by fasteners  223 . See FIG.  6 A. 
   Linear slide  219  is preferably a conventional precision slide that uses recirculating ball bearings between the upper translating portion  225  and the lower fixed portion  227  of slide  219 . By using slide  219 , reduced friction translation of wedge  212  is provided when moving from a pin  216  down position to a pin  216  up position and vice versa. 
   To achieve precision movement of the wedge  212  in this regard, the lift pin assembly  200  further includes a wedge-extension flow-control device  220 , which is operably coupled to pneumatic cylinder  206  via a chambered right-angled pneumatic fitting  240 , as well as a wedge-retraction flow-control device  222 , which is mounted directly on the pneumatic cylinder  206 . 
   A spool-shaped coupling  224  is threaded onto the free end of rod  210  to mechanically couple the free end of the rod to wedge  212 . The spool is locked onto rod  210  by a jam nut  229  that is also threaded onto the free end of rod  210  and is tightened against spool  224  to hold it in place. The spool, in turn, is disposed in a downwardly-facing slot  231  formed in a downwardly-facing surface of wedge  212 . A small cylindrical gap is provided between the spool and the wedge to permit slight misalignment between the cylinder and the wedge. This gap permits a slight lateral and vertical misalignment of the wedge and cylinder to exist without causing the rod to bind in the cylinder. 
   Control devices  220  and  222  are each connected to the pneumatic cylinder  206  (as described above) and separately via conventional fittings  244  and  245  and via conduits  226  and  227  to a flow-control fluid source (not shown) in a conventional manner. 
   As is shown in the foreground in  FIG. 6 , the filter lift pin assembly  200  further includes an optical lift pin extension sensor  228  mounted on the base  202  and disposed transverse to the piston rod  210 . Not visible in  FIG. 6  but located behind the guide bracket  204  is a second extension/retraction sensor that is similarly disposed transverse to the piston rod  210 . As is shown in the foreground in  FIG. 6 , the wedge  212  defines a lateral finger  230 , and the foreground-mounted lift pin extension sensor  228  includes an end portion  232  defining a U-shaped slot through which the lateral finger  230  is passed for sensing extension or retraction of the pin  216  relative to the base  202 . The wedge  212  further includes a similar lateral finger (not visible in  FIG. 6 , as it is hidden behind the guide bracket  204 ); and the background-mounted lift pin extension sensor (not visible in  FIG. 6 ) similarly includes an end portion (not visible in  FIG. 6 ) defining a U-shaped slot through which the background lateral finger is similarly passed for sensing extension or retraction of the pin  216  relative to the base  202 . To provide adjustment of the guide bracket  204  as well as the extension sensors  228  along the upper surface of the base  202 , the guide bracket  204  and extension sensor  228  (as is shown for the foreground sensor) are respectively provided with conventional threaded fasteners  234  and  235 . 
   In operation, the piston rod  210 , spaced above and parallel to base  202 , is caused to move relative to the base  202 , for causing the optical filter lift pin  216  to extend toward or retract from platform or table  110  and tape  108  in frame  111 , as shown in FIG.  7 . More particularly, as the lift pin  216  contacts the underside of adhesive tape  108 , the tape  108  as well as the optical filters  196  adhesively held thereon are urged slightly upwardly, toward the machine vision camera  121  and the head  124 , as shown in  FIGS. 8A and 8B , to help break the adhesive bond between the filter  196  and the tape  108 . 
   As shown in  FIG. 8C , each filter is in substantial complete contact with adhesive tape  108  when the tape is relaxed.  FIG. 8D , however, illustrates how the tape-to-filter relationship changes when lift pin  216  deflects tape  108  upwards. As tape  108  is forced upward by pin  216 , it causes the contact area between the tape and the filter to be reduced. The tape is deformed over the radiused tip  233  of pin  216 , causing it to form a curved surface. The formation of this curved surface causes the portions of the tape that were previously adhered to the filter (as shown in  FIG. 8C , to pull away from the filter. As a result, the area of the filter that is adhesively attached to the tape is significantly reduced and the filter, when grasped and pulled away from the tape by probe  152  will release from the tape more gently and with reduced force. 
   Note that the degree of deflection provided by lift pin  216  in FIG.  8 D and the degree that the tape is curved due to pin  216  has been deliberately exaggerated to make the reduced contact area between tape  108  and filter  196  more apparent. 
   The machine vision camera  121 , fixedly mounted to the “Z” axis stage  118  and to the “X” gantry stage  100 , is in parallel relation to head  124 ; and the “Z” axis stage  118  is laterally translatable along “X” gantry support beam  100 B, as shown in FIG.  7 . As described above in regard to  FIG. 1 , the “Y” gantry platform  102  is also movable along “Y” gantry beams to provide motion of the “Z” axis stage  118  in a direction that is orthogonal to the “X” direction motion provided by the “X” gantry stage. Thus, the system is configured to move the “Z” axis stage  118  in both the “X” and the “Y” direction under computer control. The head  124  picks up optical filters  196  ( FIGS. 8A-D ) and places them in proper position in individual nests  236  of a rotary processing table  238  ( FIGS. 3 and 7 ) to be tested individually. In general, the head  124  first picks up optical filters  196  individually from the input tape frame  111  (or the vacuum release trays  702 ) and then, after the filters have been optically tested, places the tested optical filters  196  individually into filter classification trays  112 , as shown in  FIGS. 1 ,  2 ,  3  and  13 . 
   The base  202  of the filter lift pin assembly  200  is fixedly mounted on a separate “X” direction translation device  242  and a “Y” direction translation device  243  ( FIG. 7 ) for moving the filter lift pin assembly  200  across the base  103  relative to the input table  110  and the input tape frame  111 . The two devices  242  and  243  permit the filter lift pin assembly to be moved in both the “X” and the “Y” direction and thereby positioned under any filter  196  on adhesive tape  108 . These two devices operate under computer control to permit lift pin  216  to be located under and to lift any of filters  196  under computer control. Translation devices  242  and  243  are preferably linear electrical motors configured to be operated under computer control. 
   The machine vision camera  121  ( FIGS. 3 and 7 ) has a collimated field of view for viewing and locating the optical filters  196  to be picked up. The camera  121  and head  124  are spaced in parallel relation. Head  124  is moved by the “X” and “Y” gantry systems in response to information provided by the machine vision camera  121 , so that the head  124  is located directly above one optical filter  196  to be picked up. 
   After being vertically aligned above such optical filter  196 , the “Z” axis stage  118  ( FIG. 7 ) is then actuated causing head  124  and vacuum probe  152  ( FIGS. 8A and 8B ) to extend downwardly to contact such optical filter  196 . Downward movement of the head  124  is generally completed before the outer sleeve  128  of head  124  contacts the alignment clamp  174  (which is shown in  FIG. 5B ) to avoid damaging the optical filters  196 . In addition, the “Z” stage is also provided with sufficient extra travel such that it does not reach the end of its travel before vacuum probe  152  contacts filter  196 , but has a comfortable margin of extra motion available. This margin will, of course, be determined on a case-by-case basis depending upon the particular geometry of the machine. 
   Once the probe  152  and filter  196  make contact, a vacuum is applied to orifice  164  and hence to filter  196 . Optical filter lift pin  216  is then raised upwardly until it is in the position shown in FIG.  8 C. At this point, the filter is captive between pin  216  and probe  152 . 
   Pin  216  continues moving upward causing the adhesive tape to deflect upwardly and bend around the radiused tip of lift pin  216 , thereby reducing the area of adhesion between filter  196  and the adhesive tape as described above. 
   At the same time lift pin is deflecting the tape upwardly, it is also moving the desired filter  196  upwardly and is collapsing vacuum probe  152  into sleeve  128  as shown in FIG.  8 D. 
   Next, the head  124  is retracted upwardly by operation of the “Z” axis stage  118 , causing the head  124  to be lifted above the table  110  and frame  111 . As probe  152  is lifted, it pulls filter  196  away from the remaining portion of adhesive tape holding filter  196  to the adhesive tape by way of the vacuum applied to the top of filter  196 . Once free of the surface with the filter attached to the end of the probe the “X” and “Y” gantry systems translate head  124  and hence filter  196  in both the “X” and the “Y” directions above processing table  238 , as shown in FIG.  7 . In general, this “pick and place” procedure is repeated until each of the four forward most nests  236  of processing table  238  is provided with an optical filter  196  for testing. 
   To insure that the probe is accurately positioned with respect to the filter, a calibration routine is performed in which errors or misalignments of the probe with respect to the camera  121  are determined. 
   As described above, the position of the filter is determined based upon the position of the camera (indicated by the drive signals applied to the “X” and “Y” stages when the filter is in the camera&#39;s field of view) and by the offset of the filter within the camera image. 
   The absolute position of the filter is determined by summing these two values. 
   As described above, once the position of the filter is determined, the probe must be moved to a precise position above the filter in order to contact and pick up the filter. 
   In order to position the probe accurately above the filter, the distance between the probe tip and the camera must also be known, for the “X” and “Y” stages must be moved this distance in order to locate the probe above the filter. 
   The camera-to-probe distance, however, can be known only approximately based solely upon the dimensions (and their associated dimensional errors) of the parts located between the probe tip and the camera. 
   The dimensional errors refers to errors in manufacturing and assembling the probe tip, the probe sleeve in which the tip is inserted, the “theta” stage motor that supports and rotates the probe, the rotating shaft in the theta stage, the theta stage motor mounts and the location of the theta stage mounting holes with respect to the camera mounting holes, among others. 
   Errors in any of these dimensions are additive and provide a relatively large circle of positional uncertainty of the probe with respect to the camera. 
   To eliminate this error, one might manufacture or purchase extremely accurate components and provide extremely precise adjustment features. This, however, would be prohibitively expensive. An alternative approach, and the one employed by the present invention, is to first determine the location of a feature (a corner of the touch-off block) using the camera and then again determine the location of the corner of the touch-off block, but this time by making electrical contact, using the probe, with each of the two edges that intersect at the corner that was located by the camera. Since both locations use the same frame of reference (the X, Y gantry), the offset between the camera and probe can be calculated by simply subtracting the corresponding X and Y values. 
   The first step is to pre-position the camera over the corner of the touch-off block so that the corner is in the field of the view. This is done one time when the machine is first set up and the coordinates are saved. After going to the pre-position, the computer finds the corner and records the x and y coordinates of the corner relative to the center of the camera. 
   Next, the probe is pre-positioned near the touch-off block in x, y and z for performing the “touch-off” in the “y” direction. This is done one time when the machine is first set up and the coordinates are saved. The same procedure is repeated for “touchoff” in the “x” direction. The “touch-off” procedure. The probe is (1) rotated using the “theta” stage to a first predetermined angle, (2) moved until it contacts first surface  5000  of touch-off block  5002  as indicated by a contact sensor connected to the computer and (3) a record of its position is made by the computer. 
   In the preferred embodiment, the sensor is a single digital signal line with a pull-up that is coupled to the computer. The digital signal line is coupled to the touch-off block, which is electrically isolate from the structure to which it is mounted. As a result, as long as the probe, which is grounded, is not contacting the touch-off block, the signal on the signal line will be pulled up to a logical “1”. The moment the probe contacts the touch-off block, the pull-up will be grounded and the signal on the signal line will be a logic “0”. The touch-off block is made of a conductive metal. Therefore, whenever the probe touches the touch-off block, the signal on the signal line goes from a logical “1” to a logical “0”. 
   The computer signals the “X” stage to move the probe in the “X” direction very slowly (approximately 0.01 in/sec) until the sensor signal goes to logical “0”. Once the signal goes to a logical “0”, the position of the probe (as a function of the position of the “X” stage) is recorded. 
   The probe is then backed away from the block in the “X” direction, rotated to a second predetermined angle (preferably 90 degrees from the first predetermined angle) and the incremental moving, touching and recording steps are repeated. 
   The probe is again backed away from the block in the “X” direction again, rotated to a third predetermined angle (preferably 180 degrees from the first predetermined angle) and the touching and recording steps are repeated again. 
   If the probe were perfectly symmetric and centered about the rotational axis of the theta stage, each of these three positions would be the same. As a practical matter, however, there will be a small but significant off-center rotation of the probe when the theta stage (to which it is attached) rotates. 
   As a result, the true position of the probe with respect to the surface it touches, and hence the true position of the probe with respect to the camera will vary depending upon the rotational position of the theta stage. 
   For convenience in calculating the offset, the offset can be broken down into two components: (1) a combination of a fixed offset distance from the camera to the center of rotation of the theta axis, plus (2) an additional offset due to the misaligned and off-center coupling of the probe to the rotating shaft of the theta stage. 
   For this reason, the computer calculates these two offsets (one fixed and invariant, the other a function of the rotational position of the probe) and saves them for later use when positioning the probe in a specific rotational position near a filter. 
   These two offsets (fixed and rotational) are used (1) to position the probe over a gel pack or tape frame when the probe picks up a filter, (2) to position the probe with attached filter over a flexure before placing it in the flexure, (3) to position the probe over a flexure before picking up the filter, and (4) to position the probe over the appropriate sorting tray before depositing a tested filter in one of the sorting trays. 
   It should be clear that the calibration process described above only provides the probe offset from the camera to the probe in a single direction: the direction perpendicular to the surface of the touch off block that it contacts. Since the contact was made with surface  5000  of the touch-off block and since this surface is perpendicular to the “X” direction of travel, this calibration method will only provide a true measure of the camera-to-probe distance in the “X” direction using the “X” stage. 
   The probe is also moved in the “Y” direction using the “Y” stage and therefore the same calibration process is used to determine a fixed and rotational offset in the “Y” direction by touching the probe three more times as described above, but this time against surface  5004  which is perpendicular to the “Y” direction of travel. 
   At the end of this process, the system has determined a fixed, (i.e. rotationally independent) “X” and “Y” offset of the probe with respect to the camera and has also determined a rotational “X” and “Y” offset that is a function of the rotational position of the probe provided by the theta stage. Whenever the probe is rotated to particular angle, either for picking up a part or for placing a part, the proper “X” and “Y” positions of the “X” and “Y” stages are calculated to take the rotational offset into account. 
   In an alternative embodiment, a table (or tables) of pairs of “X” and “Y” offsets versus probe rotational positions may be calculated after calibration and used during all subsequent pick and place probe operations. In this manner, one can eliminate the repetitive calculation of “X” and “Y” offsets based on new rotational positions that would otherwise be required every time the probe is rotated. 
   Calibrating for the Post Height: 
   Just as the system need to know the “X” and “Y” offsets of the probe with respect to the camera, it similarly needs to know the location of post  512  (SEE  FIG. 9A ) with respect to the probe the “Z” direction. A separate calibration process is performed to determine this distance. 
   As described above, when probe approaches each of the flexures to either pick or place a filter, it moves downward until the filter is mechanically held between the post and the probe tip with a slight compression of the probe tip within its sleeve. Once in this position, the filter is securely held on its top and bottom planar surfaces by the probe and the post. The flexures can be moved or vacuum turned on or off without the risk that the filter will be accidentally ejected from the machine. 
   An electrical potential is applied to the post, which is a conductive metal. This potential may be always applied, or it may be selectively applied via a computer-switched electrical connection coupled to the post. 
   The post is first positioned by the linear motor  510  to the right (as viewed in  FIG. 1 ) of rotary processing plate  238 . The post is raised into position adjacent the bottom of a flexure, in the same position it would be in when supporting a filter at a flexure. 
   The probe (which is coupled to the sensor circuit as described above) is moved into position over the post at the flexure. 
   The probe is lowered by the computer which moves the “Z” stage downward very slowly (approximately 0.01 in/sec). The computer continuously checks the sensor signal line to see whether the probe has contacted the post. 
   This process of lowering and checking continues until the probe touches the post. Once the probe touches the post, the signal line will go from logic “1” to logic “0” as electricity is communicated from the probe, through the post to electrical ground. 
   When the probe contacts the post, the system records the position of the probe (as a function of the “Z” stage position). 
   Once the “Z” height of the post is recorded, it is used to determine the proper downward (“Z” direction) stopping point of the probe, based on the thickness of the filter, when the probe is lowered into contact with the filter. 
   For a filter having a nominal thickness “Q”, the probe is lowered to the calibrated height (“Z” direction) of the post plus the thickness of the filter, minus a small amount of desired probe compression in the probe sleeve. These calculations are performed by the computer when it brings the probe downward in contact with the filter at each flexure location. 
   Calibrating the probe for Lift Pin Height: 
   In a similar fashion to the post height calibration, the lift pin height may also be calibrated. 
   A small fixture could be placed, temporarily, over the lift pin  216 . This fixture would be connected to the touch-off circuit and electrically insulated from the pin. The fixture would have a “touch-off” surface coplanar with end of the lift pin  216 . A touch-off procedure similar to that used for determining the post height can also be used for determining the height of the lift pin in its raised position. The lift pin height can be used to calculate the proper lowered position of the probe over the tape frame when picking a filter off the frame. 
   Reference is next directed to  FIGS. 9A ,  9 B,  10 A,  10 B,  11 ,  12 ,  13 , and  22  to discuss an “automated material handling system,” which is yet another aspect or feature of the present invention. As mentioned above, the head  124  picks up selected optical filters  196  individually from the input tape frame  111  ( FIGS. 8A and 8B ) and the “X” and “Y” gantry systems are employed to move the “Z” axis stage  118 , that has been spaced above a selected nest  236  of the rotary processing table  238  (FIG.  7 ), so as to place an optical filter  196  into each nest  236  for further optical filter processing. For this purpose, each nest  236  of the rotary processing table  238  is provided with an individual flexure  250  ( FIGS. 3 ,  11  and  12 ) for holding a single optical filter  196 . 
   The flexure  250  is generally elongated (FIG.  11 ), defining circular apertures  252  for fixedly mounting individual flexures  250  to the rotary table  238 . The flexure  250  also defines generally elongated and opposed apertures  254 . The flexure  250  further defines a longitudinal slit  256  that is generally disposed between the elongated apertures  254 . In particular, the elongated apertures  254  are defined both by external sidewalls  258  as well as by inner sidewalls  260  of the flexure  250 . The inner sidewalls  260 , which form a portion of the elongated apertures  254 , straddle and define the slit  256 . The external sidewalls  258  as well as the inner sidewalls  260  are sufficiently dimensioned, in a direction transverse to the slit  256 , and the material of flexure  250  sufficiently elastically flexible or “springy” such that spaced-apart jaws  262 , also defined by the flexure  250 , repeatedly return to their original spacing, after being spread-apart by a small distance, as described below. 
   The flexure is preferably a monolithic device manufactured out of a single piece of metal such as steel, using electro-discharge machining (EDM) operations. Each of the inner and outer sidewalls is preferably of substantially the same length and are substantially parallel thereby defining (together with the mounting portion  253  and the jaws  262 ) two parallel four bar linkages. 
   Unlike common four bar linkages, in which there is a separate mechanical coupling at each of the junctions, the inner and outer sidewalls elastically deform forming a slight “S” shape as each arm is moved away from gap  256 . 
   Each arm includes an inner and an outer sidewall that are of substantially the same length and are substantially parallel. With this arrangement, when the arms are deflected apart, they move apart with limited rotation each moving along a short curvilinear path. 
   By constraining the motion of the free ends of the arms to curvilinear translation, the lateral forces applied to open the arms is substantially the same as the lateral force applied by the arms against the filter to hold the filter in place. 
   The thickness of the sidewalls (as measured in the “T” direction) is preferably smaller than the height of the sidewalls (as measured in the “H” direction). To insure equal deflection of both arms when a force is applied, the length of the sidewalls and their cross-sectional areas are preferably the same and are constant over substantially their entire length. In a typical flexure, the height of the sidewalls will be between 0.05 and 0.15 inches. The thickness of the sidewalls will be 0.015 to 0.04 inches. The thickness to height ratio is preferably between 2 and 5. As this ratio increases, the arms become more stiff and resistant to deflections in the “H” direction, as compared to deflection in the “T” direction. 
   The height to length ratio of the sidewalls of the flexures is a strong indicator of the flexure arms&#39; resistance to bending in the “H” direction. If the arms were susceptible to bending either upward or downward more than a tiny amount, the filters will not consistently be held in a flat orientation—the position in which they need to be held for testing. Only a slight bending upward of one arm with respect to the other, on the order of an angle of 0.1 degrees or so, will cause the filter to be twisted between the two arms (i.e. rotated about the “L” axis) by perhaps 5-20 degrees. This large twisting would require significant (and slow) movement of the goniometers to find and move to their proper perpendicular position with respect to the bottom surface of the (twisted) filter before testing can begin. For this reason, and given the specific requirements of this application, the length to height ratio of the arms of the flexure is preferably at least 5 and no greater than 50. More preferably, it is at least 8 and no greater than 40. Even more preferably, it is at least 15 and no greater than 30. 
   The thickness to length ratio of the sidewalls of the flexures is a strong indicator of the sidewall&#39;s flexibility and ability of the arms to accommodate a wide variety of filter widths. As the length-to-thickness ratio of the sidewalls decreases, the arms become more resistant to deflection in the “T” direction. The force required to spread the arms a specific distance apart increases. For a flexure adapted to hold optical filters (as the present flexures are), too great a force can crush the filter, yet too small a force will permit the filter to fall out of the flexure. For this reason, the force to spread the arms of the flexure must be carefully tailored if the machine is to accommodate a wide variety of filters having different widths without crushing them. A preferred ratio length (“L” direction) to thickness (“T” direction) ratio for the sidewalls of the flexure is therefore preferably between 25 and 300. More preferably it is between 40 and 200. Even more preferably it is between 55 and 140. 
   In  FIG. 22 , a typical flexure  250  is shown in its relationship to table  238  and the particular filter nest  236  to which it is oriented. Threaded fasteners  2202  extend through the apertures  252  in the flexure and hold the flexure to table  238 . The arms of the flexure extend from the table toward and underneath nest  236  in close proximity thereto. Several ball bearings  2206  are located in a linear bearing race  2208  that is formed in the bottom of the filter nest to insure that the free ends of the arms are located at a precise distance away from the bottom of the nest. As shown in phantom lines in  FIG. 10A , the bearing race  2208  extends substantially perpendicular to the longitudinal extent of arms and substantially parallel to the direction the arms travel when they are deflected outwardly to receive the filter  196 . 
   Each arm is supported on two ball bearings  2206  that are spaced apart in the bearing race  2208  by ball guide  2210 . These balls rest against flat bearing surface  2212  located on the back of each arm. When the arms are deflected outward, spreading them to receive the filter, the ball bearings roll in the race as well as across bearing surface  2212  to keep the arms at a constant angular relationship with respect to each other and to keep them in the same plane. The flexure and the table are preferably dimensioned such that the flexure, when attached to the table, preloads the flexure arms against the ball bearings. In this manner, the flexures make good contact with the ball bearings, and the preload further reduces the likelihood that they will be lifted up away from the bearings when the arms are spread apart to receive the filter. 
   Reference is next directed to  FIGS. 3 ,  9 A,  9 B,  12  and  26  to discuss an actuator assembly  264  for the flexure  250  discussed above. The flexure actuator assembly  264  is fixedly mounted on pneumatically actuated linear stage  266 . This stage is moved in a linear direction by a pneumatic cylinder integral to stage  266  (not shown). Stage  266 , in turn, is mounted on flexure actuator cylinder base  500 . Base  500 , in turn, is adjustably fixed to plate  502 . Plate  502  is coupled to the output side of linear motor  510 , which in turn is fixed to base  103 . 
   Linear motor  510  is configured to translate plate  502  in the “X” direction. The components mounted on plate  502  are similarly translated in the “X” direction whenever linear motor  510  moves. Translating stage  266  moves flexure actuator assembly  264  in the “Y” direction (i.e. toward and away from a flexure) when air under pressure is applied to translating stage  266 . 
   The flexure actuator  264  includes a pair of spaced-apart rollers  274  rotatably mounted on an upper portion  276  ( FIGS. 10A and 10B ) of L-shaped member  269 . By design, the rollers  274  move in a plane coinciding with a forward planar portion  280  ( FIG. 10B ) of flexure  250  that defines the jaws  262 . Also, the spacing of the rollers  274  is such that the rollers  274  cause the jaws  262  of flexure  250  to spread apart slightly, which in turn laterally opens the flexure&#39;s longitudinal slit  256  slightly, after the rollers  274  are first aligned with the jaws  262  ( FIG. 10A ) and thereafter brought into engagement with the jaws  262  ( FIG. 10B ) by operation of pneumatic cylinder  270 , as shown in FIG.  9 B. Also by design, the L-shaped member  269  is so spaced in the “Z” direction relative to the nest  236  of processing table  238  as to achieve such an effect. 
   For grasping a single optical filter  196 , the forward portion  280  of the flexure  250  defines a gap  282  (FIG.  10 A). The gap  282  is bounded on one side by two adjacent fingers  283  and  284  that extend inwardly into gap  282  from one jaw  262  of the flexure and on the other side by another finger  286  that extends inwardly into gap  282  from the other jaw  262  of the flexure. The gap  282  is dimensioned relative to a single optical filter  196  to permit such optical filter  196  (when disposed in the plane of the forward portion  280  of flexure  250 ) to fit snugly into the gap  282 , after the jaws  262  have been spread slightly (as shown in FIG.  10 B), and thereafter to be held in place in the gap  282  by fingers  283  and  284  and the finger  286  after the flexure actuator assembly  264  is retracted from the flexure  250 . By providing these three points of contact, the filter is gripped consistently at three points on the centerline of the filter: two points on one side of the (typically rectangular) filter and one point on the opposing side of the filter. This three-point contact assures accurate positioning and location of the filter and tolerates slight variations in straightness of the opposing sides it contacts. 
   In addition to supporting and positioning flexure actuator assembly  264 , linear motor  510  also supports and positions a vacuum post  512 . This post is positioned underneath gap  282  before filter  196  is inserted into gap  282 . The post is positioned underneath filter  250  and adheres to filter  196  using a vacuum applied to a hole that extends through the post  512  to a vacuum port  513 . A vacuum is selectively applied to port  513  under computer control to provide or remove a vacuum at the top of post  512 . Without this post, the flexure arms might knock the filter off the bottom of vacuum probe  152  as they move in to contact and support filter  196 . 
   Post  512  is configured to be raised and lowered slightly during the positioning process. It is lowered under computer control whenever linear motor  510  moves in the “X” direction from flexure to flexure in order to clear the lower surfaces of the flexures and of the rotary processing table  238  to which they are attached. Since post  512  is positioned so closely to the bottom of the flexures whenever a filter is inserted into a flexure, it is necessary in this embodiment to provide some up-and-down motion of post  512  while motor  510  moves to prevent the post from damaging the table or the other flexures. 
   The post is fixed to post support  514 . Post support  514 , in turn is fixed to post mount  516  with a conventional screw fastener and two dowel pins. Post mount  516 , in turn, is fixed to insulator block  518  by conventional screw fasteners and dowel pins. Insulator block  518 , in turn is fixed to the output side of a precision linear stage  520 . Linear stage or actuator  520  generally includes an integral pneumatic actuator (not shown) that is operated by a supply of compressed air selectively applied to hose fittings  522 . The two hose fittings permit the output side of actuator  520  to be moved up or down (i.e. in the “Z” direction) with respect to the input side of actuator  520  by selectively applying air under pressure by computer control to one or the other of fittings  522 . 
   The fixed side of actuator  520  is fixed to post base  526 , which in turn is fixed to plate  502 . As explained above, plate  502  is fixed to move in the “X” direction with linear motor  510 . Thus, both the flexure actuator and post  512  translate together with linear motor  510 . Flexure actuator  264  can be moved in and out (toward or away) from the flexure  250  in the “Y” direction and post  512  can be moved up or down (toward or away) from gap  282  of the flexure in the “Z” direction. 
   As mentioned, the head  124  is used to precisely place a single optical filter  196  into the gap  282  of each flexure  250 , as illustrated by FIG.  9 A. In general, the flexure actuator assembly  264  is moved relative to the rotary processing table  238  ( FIG. 12 ) by linear actuator  510  to line up the rollers  274  of the flexure actuator assembly  264  with another flexure  250  that is not yet provided with an optical filter  196  (as depicted in FIG.  10 A). 
   In an initial position, both the actuator assembly  264  and the post  512  are moved away from table  238  and flexures  250 . In this position, both the actuator assembly  264  and the post  512  will not mechanically interfere with table  238  and flexures  250 . 
   Linear motor  510  is then energized to move both of assembly  164  and post  512  in the “X” direction until they are positioned adjacent to a particular flexure  250 . 
   At this point, the actuator assembly is moved forward in the “Y” direction to engage and spread the flexure arms. Post  512  is moved upward (in the “Z” direction) until post  512  is positioned just below gap  282 . The order in which these two steps occur is not critical. 
   The “X” and “Y” gantries are energized to move head  124  until probe  152  (holding filter  196  by vacuum) is located directly above gap  282 . Once in position, the “Z” stage is energized to move probe  152  downward toward gap  282 . As the “Z” stage is lowered, filter  196  will engage post  512  and stop moving. Probe  152  will collapse slightly as described above regarding the operation and construction of head  124 . The “Z” stage is then stopped with the filter held firmly between post  512  and probe  152 . Vacuum is applied to post  512 . The vacuum applied to probe  152  is released and head  124  is lifted up and away from the filter. 
   Once the filter is held in place between the two flexure arms, the flexure actuator assembly is withdrawn away from the flexure causing the flexure arms to move together and grip the edges of the filter with the three fingers extending from opposing sides of the arms. 
   The vacuum applied to post  512  is released and post  512  is lowered away from the filter. 
   At this stage, a new filter has been inserted into an empty flexure and both the post  512  and flexure actuator assembly  264  have been withdrawn away from flexure  250  and table  238 . Linear motor  510  can then be energized to move the flexure actuator assembly and the post to another flexure in order to insert another filter at the new flexure. 
   The above-described procedure is repeated until all four flexures  250  (each in a respective nest  236 ) located on one side of the processing table  238  are provided with an optical filter  196  that is to be tested. 
   Once the filters  196  have been tested (a process to be described below) they are similarly removed from the flexures in the following manner. First, the linear motor  510  moves the flexure actuator assembly until it is adjacent to the flexure to be unloaded. At substantially the same time, probe  152  is moved downward using the “Z” stage until it contacts and holds the filter in that flexure by application of a vacuum to the probe tip. Once the probe has gripped the filter, the flexure actuator assembly is advanced until it spreads the flexure arms apart. Once spread, the filter is supported by the probe alone, which is then raised by its associated “Z” stage 
   Attention is next directed to  FIGS. 7 ,  12 ,  23 , and  24  for discussing one particular aspect or feature of the present invention, referred to as a “compactness” feature. In this regard, the rotary processing table  238  is one of several elements or components of a rotatable assembly  288  which shall now be described. Rotatable assembly  288  includes a rotary stage frame  600  that is fixed to base  103  and supports rotatable shaft  602  on bearings  604 . A rotary adapter  606  is fixed to the bottom of frame  600 . Adapter  606  is also fixed to rotary actuator  608 . An actuator shaft  610  extends from actuator  608  and is rotated by pneumatic actuators  612  and  614 . The linear motion provided by these pneumatic cylinders is converted to rotary position by an internal gear arrangement (not shown). A preferred rotary actuator is model number RLS-I-32×180°-NB-U4 manufactured by PHD. This actuator rotates a nominal 180 degrees both in a clockwise and in a counter-clockwise direction. Air is supplied to actuator  608  by pneumatic tubing  616  coupled to the pneumatic ports of the actuator. One skilled in the art understands that the rotary processing table  238  may be made to rotate through its 180° span of motion under the control of a servomotor (not shown), rather than via pneumatic control. 
   A flexible coupling  618  is attached to both the rotary actuator shaft  610  and to rotary shaft  602  to permit slight misalignment of the two rotatable shafts. Shaft  602  extends upward through frame  600  and terminates in a mounting flange  622 . This flange is fixed to table  238  using standard threaded fasteners. 
   When air under pressure is supplied to one port of actuator  608 , it rotates clockwise approximately 180 degrees. Since the actuator is rotationally coupled to table  238 , table  238  also rotates clockwise about 180 degrees. 
   When air under pressure is applied to the other port of actuator  608 , the actuator rotates counter-clockwise approximately 180 degrees. Since the actuator is rotationally coupled to table  238 , table  238  also rotates counter-clockwise about 180 degrees. 
   The actuator assembly needs to rotationally position the table to within a few thousandths of an inch to insure that the filters are accurately positioned with respect to the goniometers in the goniometer station. Since the actuator selected for use cannot rotate to that degree of accuracy, additional components have been incorporated into the actuator assembly to provide this precise positioning. 
   Frame  600  includes a cylindrical portion  624  in which the bearings  604  and shaft  602  are mounted. In addition, it includes a stop block  626  fixed to cylindrical portion  624  by conventional threaded fasteners. Stop block  626  does not rotate with table  238  and shaft  602 , but is fixed with respect to base  103 . 
   Adjustable rotation stops  628  and  630  are threadedly engaged with stop block  626 . These stops serve to limit the rotation of table  238  by engaging mating surfaces on stop block  640  that is fixed to the bottom of table  238 . When stop  628  abuts stop block  640 , table  238  stops rotating in one direction. When stop  630  abuts stop block  640 , table  238  stops rotating in the other direction. 
   Rotatable assembly  288  also includes a first sensor  636  that generates a signal when stop  628  abuts stop block  640  and a second sensor  638  that generates a signal whenever stop  630  abuts block  640 . Sensors  636  and  638  are actuated whenever sensor flags  632  and  634  interrupt a light beam passing between the opposing arms of the sensors. 
   Sensor flags  632  and  634  are fixed to stop block  640 , which in turn is fixed to the underside of table  238 .  FIG. 25  is a partial cross-sectional view of block  640  showing the configuration of flag  634  and its relationship with sensor  638 . Flag  632  is arranged identically in block  640  but extends in the opposite direction to engage sensor  636 . 
   Each of flags  632  and  634  fit into corresponding and adjacent slots  642  formed in the bottom of stop block  640 . Each of flags  632  and  634  has elongated slots  646  through which flag mounting fasteners  650  extend. The ends of fasteners  650  are threaded into stop block  640  such that they bind with flags  632  and  634 , and fix them to stop block  640 . By loosening the fasteners, flags  632  and  634  can be slid back and forth inside their corresponding slots  642 . 
   Each of flags  632  and  634  has a threaded adjusting screw  652  that permits the accurate and incremental positioning of each stop with respect to stop block  640 . The threaded ends of fasteners  652  abut stop block  640 . 
   The position of either of the stops is adjusted by rotating its fastener  652  once fasteners  650  holding that flag to block  640  are loosened. As fastener  652  is rotated, it moves its flag in its slot  642 . Once the flag is in its the proper position, its fasteners  650  are tightened to lock it in that position. 
   In this manner, the position of the sensor flags can be adjusted, and therefore the signal sent by the sensors to the computer indicating that the table is in the proper rotational position can also be adjusted. By providing these sensors and their associated flags, their signals are provided to the computer which thereby knows when the table (1) is in a first rotational position in which a first set of four flexures is disposed for loading and unloading and a second set is disposed for testing, or (2) is in a second rotational position in which the first set of flexures is disposed for testing and the second set is disposed for loading and unloading, and (3) is in a range of third rotational positions between the first two rotational positions in which no testing, loading or unloading should be done. 
   Attention is next directed to  FIGS. 14-18 , to discuss the goniometer station  300  mentioned above. Preferably, two-axis goniometers are used; and a particularly preferred goniometer measures less than two inches (five centimeters) wide, less than seven inches (about eighteen centimeters) long, and less than four inches (ten centimeters) high. For compactness purposes, goniometers taking up less volume would be even more preferred. The illustrated goniometers can be placed on two-inch (five-centimeter) centers with no interference, within the total travel envelope of each axis, between adjacent goniometers. The lower axis provides ±6° of travel, while the upper axis provides ±5°. The resolution of the upper axis is approximately 0.0007° while that of the lower axis is approximately 0.0005°. Actual accuracy for both axes is about ±0.0035°. Both axes are controlled by a commercially-available closed-loop servo system using brushless DC (direct current) servomotors and linear encoders. For each axis, commercially-available solid-state optical limit switches are employed to signal the end of travel/home positions. 
   As will become apparent, the total number and spacing of adjacent nests  236  on process table  238  is, in general, determined by the total number and volume occupied by the goniometers incorporated into the apparatus of the invention. As was mentioned above, after all four filter nests  236  are individually provided with a single optical filter  196 , the process stage  238  is rotated a full 180° ( FIGS. 3 and 12 ) for optical filter-testing purposes, to cause each such nest  236  to be precisely positioned between a goniometer  302  and an associated optical detector  304 , as is illustrated in FIG.  14 . 
   Referring to  FIGS. 15-17 , each goniometer  302  includes a pair of spaced-apart apertured base plates  306  between which a channeled guide member  308  is both sandwiched and fixedly mounted in a conventional manner. In particular, conventional threaded fasteners  310  ( FIG. 15 ) are used to releasably fix the base plates  306  and the guide member  308  together. The guide member  308  defines a generally elongated channel  312  as well as a generally-cylindrical longitudinally disposed through bore  314  communicating with the channel  312 , as is shown in  FIGS. 16 and 17 . A conventional elongated worm-gear shaft  316  is rotatably mounted via conventional spherical bearings  318 A and  318 B ( FIG. 16 ) in the generally cylindrical through bore  314  in a conventional manner. 
   In particular, the outer bearing  318 B, rotatably carrying one end portion of the worm-gear shaft  316 , is removably retained within the generally-cylindrical through bore  314  via a conventional spanner nut  320  ( FIG. 16 ) which is removably threadedly joined to the channeled guide member  308  via intermeshing threads (not shown) in a conventional manner. The inner bearing  318 A, rotatably carrying the opposite end portion of the worm gear shaft  316 , is removably urged via an end portion of the worm-gear shaft  316  (as is illustrated) into abutting engagement with an annular shoulder that is defined by the channeled guide member  308 , which annular shoulder is concentric with the generally-cylindrical bore  314 , as is shown in FIG.  16 . The outer end of the worm gear shaft  316  (at bearing  318 B) is non-rotatably (yet removably) fixed to a flexible coupling  322  that is driven by a commercially available lower axis DC motor  324 . The lower-axis DC motor  324 , which is provided power via a conduit  326 , is mounted on the channeled guide member  308  via an axially channeled motor mount  328 . In particular, the lower axis DC motor  324  is releasably mounted on the motor mount  328  in a conventional manner using threaded fasteners  330  (FIGS.  15  and  16 ). The motor mount  328  is removably affixed to the channeled guide member  308  via threaded fasteners (not shown) in a similarly conventional manner. The lower-axis DC motor  324  includes a rotatable motor shaft  332  ( FIG. 16 ) on which the flexible coupling  322  is non-rotatably (yet removably) mounted. In this regard, the axially disposed channeling of the motor mount  328  is so dimensioned relative to the external surfaces of the flexible coupling  322  such that the flexible coupling  322  is able to rotate relative to the motor mount  328  with no interference between the flexible coupling  322  and the motor mount  328 . 
   A “tip” feature of the illustrated goniometer  302  shall now be discussed. A worm gear-driven platform  334 , having a lower end portion disposed into the elongated channel  312  of the guide member  308 , defines a threaded bottom portion that intermeshes with the worm-gear threads on shaft  316 , as shown in  FIG. 16. A  grooved guide member  336  (FIG.  17 A), spaced above the channeled guide member  308  (FIGS.  16  and  17 ), is mounted on top of the driven platform  334  (FIG.  16 ). 
   Spaced-apart lower portions of the grooved guide member  336  define an arcuate groove  344 , one of which is shown in  FIG. 17A ; and inwardly-disposed upper surface portions of apertured base plates  306  respectively define grooves  346  of complementary arcuate curvature into which conventional spherical bearings  348  ( FIGS. 17 and 17A ) are disposed. Spaced-apart optical limit switches  350 , operably connected to the lower-axis DC motor  324 , are fixedly mounted in an upper surface of the channeled guide member  308  (FIGS.  15 - 17 ); and an optical limit-switch flag  352  ( FIG. 17 ) which is fixedly carried by the grooved guide member  336 , and which is adapted for engagement with one of the limit switches  350  in a conventional manner, is operably disposed therebetween. 
   In operation, activation of the lower axis DC motor  324  powers and causes rotation of the worm-gear shaft  316  which, in turn, causes movement of the worm gear-driven platform  334  to the left or right, as shown in FIG.  16 . While such motion of the worm gear-driven platform  334  is linear relative to the channeled guide member  308 , the resultant relative motion between the grooved guide member  336  and the channeled guide member  308  is arcuate, because movement of the grooved guide member  336  is tied to the worm gear-driven platform  334  via the dowel pin  342  ( FIG. 17 ) and is guided by the arcuate grooves  344  and  346  ( FIG. 17A ) and ball bearings  348  therein. 
   A “tilt” feature of the illustrated goniometer  302  shall now be discussed. An underside surface of the grooved guide member  336  defines a generally rectangular channel  354  ( FIG. 17A ) into which the driven platform  334  is disposed (FIG.  17 ); and an intermediate portion of the grooved guide member  336  defines a generally cylindrical through bore  356  ( FIG. 17A ) into which a spur-gear shaft  358  ( FIGS. 16 and 17 ) is longitudinally disposed. The spur-gear shaft  358  is rotatably mounted in spaced-apart bearings  359  ( FIG. 16 ) longitudinally mounted within the cylindrical through bore  356  of the grooved guide member  336 . 
   An upper axis DC motor  360 , provided electrical power in a conventional manner via a conduit  362 , is removably operably connected in a conventional manner to a gearbox  364  having an output shaft  366  operably connected to spur-gear shaft  358  via a flexible coupling  368 . A hollow motor mount  370  (FIG.  16 ), within which flexible coupling  368  is freely rotatable, is removably affixed to grooved guide member  336  via threaded fasteners (not shown), and has gearbox  364  removably mounted thereon ( FIG. 16 ) in a conventional manner via threaded fasteners  372 . 
   An upper surface of grooved guide member  336  defines an elongated slot  374  (FIG.  17 A); and a spur gear-driven platform  376  (FIGS.  16  and  17 ), longitudinally disposed in the slot  374  ( FIG. 17 ) has a lower portion which defines threads that intermesh with the threads of the spur-gear shaft  358 . Mounted on the spur gear-driven platform  376  is a grooved tilt-axis mount  378  (FIGS.  16  and  17 ). 
   Spaced-apart tilt-axis side plates  386  have the tilt-axis mount  378  removably affixed therebetween ( FIGS. 15 and 16 ) via conventional threaded fasteners  388 . Spaced-apart upper portions of the grooved guide member  336  define an arcuate groove  390 , one of which is shown in  FIG. 17A ; and inwardly-disposed lower surface portions of the tilt-axis side plates  386  respectively define grooves  392  of complementary arcuate curvature into which conventional spherical bearings  394  ( FIGS. 17 and 17A ) are disposed. Spaced-apart optical limit switches  396 , operably connected to the upper-axis DC motor  360 , are fixedly mounted in an upper surface of the grooved guide member  336  (FIG.  16 ); and a pair of limit-switch flags  398  which are fixedly carried by the grooved tilt-axis mount  378 , and which are adapted for engagement with corresponding ones of the limit switches  396  are operably disposed therebetween. 
   In operation, activation of the upper-axis DC motor  360  powers and causes rotation of spur-gear shaft  358  which, in turn, causes movement of the spur gear-driven platform  376 , generally to the left or right ( FIG. 17 ) along an arcuate path that is defined by the interaction between balls  394  as they roll in grooves  390  and  392 . These balls and grooves together constrain the tilt-axis to rotate about an axis located at the top of the goniometer. 
   In particular, balls  394  and grooves  390  and  392  in which they roll have been configured to rotate the tilt_axis portion of the goniometer (including collimator  500 ) about an axis that is in the plane of the lower surface of a filter loaded into the flexure immediately above the goniometer. As a result, when motor  360  rotates, the tilt-axis pivots about an axis that is parallel to the “Y” vector that defines the “Y” direction. 
   Whenever the lower motor  324  is engaged, it rotates the worm gear shaft, which engages platform  334 . As in the example of motor  360 , above, this causes the platform  334  and all the components mounted on it, including guide member  336 , motor  360  and collimator  500  mounted on member  336  to similarly rotate. In the case of motor  324 , however, this rotation is constrained by balls  348  that travel in grooves  346  and  344 . Since this ball and groove arrangement is orthogonal to the ball  394  and groove  392  arrangement located on the upper portion of the goniometer, the motion caused by motor  324  is orthogonal to that of motor  360 . 
   As in the case of motor  360 , above, balls  348  and grooves  344  and  346  in which they roll are configured to rotate the platform  334 , the grooved guide member  336  and all components mounted on it (including collimator  500 ) about an axis that is in the plane of the lower surface of a filter loaded into the flexure immediately above the goniometer. As a result, when motor  324  rotates, these components pivot about an axis that is parallel to the “X” vector that defines the “X” direction. This vector is orthogonal to the “Y” vector. 
   Summarizing, when motors  360  and  324  rotate to drive the goniometer, the upper portions of the goniometer pivots about two orthogonal pivotal axes that are in the plane of the lower surface of a filter mounted in the flexure immediately above that goniometer. 
   In this manner, the goniometer can be tilted to provide a specific angular orientation of the collimator with respect to a planar surface of the filter, while at the same time keeping the collimator pointed at the surface of the filter. As we will discuss below, each goniometer is provided with translating “X” and “Y” stages that move the goniometer in the “X”-“Y” plane while not changing the angular orientation of the goniometer with respect to a surface of its corresponding filter. 
   In this manner, the light beam transmitted by the collimator through the filter can be separately and independently adjusted both (1) angularly (i.e. without changing the point of incidence of the light on the surface of the filter), and (2) translationally across the surface of the filter (without changing the angular orientation of the incident light beam with respect to the filter). 
   It will therefore be appreciated by those skilled in the art, because the plural goniometers  302  are operably disposed upwardly toward associated optical detectors  304  (FIG.  14 ), that the two-axis “tilt” and “tip” features, which are thus provided by the lower-axis and upper-axis DC motors  324  and  360  (FIG.  15 ), will enable the operative end of each goniometer  302  to “track” along an arcuate path in the “X” plane as well as along an arcuate path in the “Y” plane, simultaneously, where the center of each such arcuate path is spaced above the goniometer  302 , which is a result of the grooves  344  and  346  in the guide member  336  and the spaced-apart lower side plates  306  as well as the grooves  390  and  392  in the guide member  336  and the spaced-apart upper side plates  386 , as shown in FIG.  17 A. 
   A scale mount  400  ( FIGS. 15 and 16 ) is fixed to the tilt-axis side plates  386  via threaded fasteners  402  for mounting an optional optical scale (not shown). An upper axis (tilt) encoder  404  ( FIGS. 15 and 16 ) for optically detecting the optical scale in order to determine the degree of tilt of the upper stage, is fixedly-mounted in a conventional manner to an upper encoder bracket  406  ( FIG. 16 ) which, in turn, is mounted in a conventional manner on the grooved guide member  336 . An encoder cable  408  (FIG.  15 ), is operably connected to the upper axis (tilt) encoder  404 . A lower axis (tip) encoder  410  (FIG.  17 ), disposed between the lower axis base plates  306 , is for detecting the degree of tip. 
   Referring to  FIG. 18 , each goniometer  302  ( FIG. 14 ) is mounted on a separate X-Y translation stage  412 , which allows each goniometer  302  to translate in both the “X” and “Y” directions in a plane that is horizontal to the base  103 . 
   Each goniometer  302  includes an associated collimator  500  ( FIGS. 14-17 ) having a base  502  ( FIG. 15 ) that is fixed to the tilt-axis mount  378  via conventional fasteners  504 . For each goniometer  302 , the associated collimator  500  is disposed generally upwardly, toward a corresponding nest  236  on the rotary processing table  238 , as is shown in FIG.  14 . Also, for each goniometer  302  there is an optical detector  304  which is optically facing its associated goniometer  302  and spaced sufficiently vertically above its associated collimator  500  as to permit the processing table  238  to rotate therebetween (in the manner described above), to present a single optical filter  196 , which is held in a single associated nest  236  of the processing table  238  by the forward portion  280  of the associated flexure  250  (FIG.  10 B), for optical filter testing. The associated optical detectors  304 , disposed above the rotary processing table  238  and optically facing each respective one of the filter nests  236 , are affixed with fasteners  505  in a conventional manner to a transverse frame  506  ( FIG. 14 ) supported by the base  103 . 
   For each goniometer  302 , the associated lower-axis DC motor  324  as well as the associated upper-axis DC motor  360  are together operated to cause the goniometer  302  to “tilt” and/or “tip” (as described above) so that the associated collimator  500  may be directed precisely at the single corresponding optical filter  196  that is to be tested. 
   In general, laser light from a conventional tunable laser source coupled to each collimator  500  is directed toward the lower surface of a filter  196 . This laser light is reflected off the lower surface of filter  196  if the wavelength of the light is a non-accepted wavelength. If the light is at an accepted wavelength, it is transmitted through the filter and impinges upon associated optical detector  304 . Detector  304  converts that incident light energy into an electrical signal, which is fed to the system. 
   Light at wavelengths that are not accepted (i.e. reflected) by filter  196  is reflected by the optical filter  196  and passes back through the collimator  500  into light circulator  616  and into power module  604   [PC1] . 
   More particularly, in a first test step, goniometer tip and tilt are adjusted until the energy of the reflected light at a wavelength outside the accepted (i.e. transmitted) wavelengths of the filter is a maximum as measured by the power module  604 . 
   Inherently, light energy reflected back into the collimator  500  is at a maximum when the laser beam is oriented precisely 90° relative to the surface of each optical filter  196  (i.e., precisely “normal” to the lower surface of the filter). In this regard, for each goniometer  302 , the associated lower-axis and upper-axis DC motors  324  and  360  are operated to cause the light from the associated collimator  500  to be precisely normal to the surface of a single optical filter  196  that is to be tested. This requires that the goniometer  302  be able to adjust its tip and tilt by very small increments of preferably 0.007° or less. 
   To do this, a computer moves motor  324  in a sequence of steps, reading the intensity of the reflected light signal. After the desired alignment maximizing reflected light energy is achieved, the wavelength of light directed onto each of the filters  196  is varied in small increments within a range of wavelengths dependent on the type of filters being tested, since each filter  196  must transmit a preselected wavelength range of light as dictated by its performance specification. Filters that do not transmit the correct wavelength are rejected or classified according to their transmission characteristics. 
   Reference is next directed to  FIG. 19  wherein a mainframe  600  includes a conventional tunable laser  602 , a power sensor module  604  and an interface module  606 , all of which are commercially available. The laser  602  is a conventional tunable laser optically coupled via a conventional fiber-optic cable  608  in a known manner to a commercially-available one-to-four (1:4) beam splitter  610 , which optically splits the laser beam from fiber-optic cable  608  into four output beams, each of which is carried by a separate conventional fiber-optic cable  612  to an optical filter-testing station  614 . Each such optical filter-testing station  614  includes a commercially-available reflected-light circulator  616 , and one each of the collimators  500 , optical filters  196  and optical detectors  304 , as described above. An electrical connector  618  electrically connects in a conventional manner the optical detector  304  to the interface module  606  and an optical connector  620  optically connects via a conventional fiber optic cable the power sensor module  604  to each reflected-light circulator  616 . 
   In operation, laser light from the laser source  602  in the mainframe  600  is passed via the fiber-optic cable  608  through the laser-beam splitter  610 , which optically splits such laser light into plural (preferably four) laser-based light beams. Each such split light beam is passed via the fiber-optic cable  612  to an associated reflected-light circulator  616 . From the reflected-light circulator  616 , the laser beam is passed through the associated collimator  500  and is incident upon an associated optical filter  196  as above described. Reflected light from the optical filter  196  that passes back through the associated collimator  500  is received by the associated reflected-light circulator  616  and is thereafter passed via the optical connector  620  to the power sensor module  604  where its intensity is measured. The position of the collimator  500  is adjusted using motors  324  and  360  to tip and tilt the goniometer until maximum intensity of the reflected light is achieved. After alignment, the transmitted light received by the associated optical detector  304  is passed from the optical detector  304  via the electrical connector  618  to the interface module  606 . The wavelength of the tunable laser scans a range of 1 to 30 nanometers in small increments, preferably ranging in incremental size between 1 and 10 picometers, both above and below the specified wavelength of the optical filter under test to measure its transmission characteristics. 
   Reference is next directed to  FIG. 20 , which is a schematic showing the path of transmitted and reflected light. In  FIG. 20 , transmitted light from laser  602 , shown as a solid line, passes through the circulator  616  and its associated collimator  500  and through an individual optical filter  196 . Transmitted light from such optical filter  196  is received by the associated optical detector  304 . An electrical signal, represented by the dot-and-dashed line, is passed to the interface module  606  (FIG.  19 ). 
   The optical detector  304  is spaced above its associated optical filter  196  by the distance Z T , which indicates vertical transmitted-light spacing. A reflected wavefront, represented by the dashed line, is reflected by the optical filter  196  (in response to the incident transmitted light passed from collimator  500  to optical filter  196 ) back through the associated collimator  500  and reflected-light circulator  616 . The light circulator  616  passes the reflected light (as shown by the dashed line) back to the power sensor module  604  ( FIG. 19 ) via the optical connector  620 . The filter  196  is spaced above its associated collimator  500  by the distance Z R , which indicates vertical reflected-light spacing. 
   Referring back to  FIG. 17 , a filter aperture mask  2302  is disposed above filter nest  236  in the path of transmitted light to mask off stray light that passes through filter  196  before that stray light arrives at detector  304 . The mask has a small circular opening or aperture  2304  through which the laser light passes to reach detector  304 . 
     FIG. 23  shows the aperture mask in greater detail in perspective view.  FIG. 22  shows the aperture mask in cross section in its position over a filter nest  236  during filter loading and unloading.  FIG. 22  shows the aperture mask in side view, extending across all four filter nests  236  on one side of table  238 . For clarity of illustration, this mask is not shown in the other FIGURES of this application. Nonetheless, all the embodiments of this invention preferably employ this mask to increase the performance of the system by masking off stray environmental light and light scattered from the surface of the filter during testing at the goniometer test stations. 
   As shown in  FIG. 23 , the mask is in the form of an elongate bar  2306  that defines several apertures. Table  238  has two such masks  2302 . One mask  2302  is disposed across four flexures on one side of the table and the other is disposed across four flexures on the opposite side of the table. 
   Each of the four flexure locations along the mask defines a plurality of apertures, including (1) a large aperture  2308  sized to pass the tip of probe  152  when it is lowered to the flexure during insertion or removal of filter  196  from the flexure, (2) a small aperture  2304  that is sized to permit the passage of laser light to detector  304  in the goniometer testing position, and (3) an elongate aperture  2310  sized to permit the passage of the beam of laser light for tests conducted with the goniometer disposed at an acute angle with respect to the bottom surface of the filter. According to another embodiment of the aperture mask  2302 , the mask may define but a single sized/shaped aperture, such as defining only elongated apertures  2310 . This aperture is utilized during all forms of testing. Thus, the aperture mask  2302  does not need to be adjested from test to test, yet still serves its basic function of reducing the transmission of stray light. 
   The bar also includes two couplings  2312 , here shown as two tabs located at and extending outward from either end of bar  2306 . These couplings are configured to be coupled to a mating coupling (not shown) that is fixed to plate  502 , which is driven side-to-side in the “X” direction by linear motor  510 . 
   The mask is fixed to table  238  by two headed fasteners  2314  disposed at each end of the mask. These fasteners are disposed in slots  2316  defined by the mask that are located at either end of bar  2306 . As shown in  FIG. 12 , the two fasteners  2314  are fixed to and extend upward from table  238  at either end of the table. 
   Slots  2316  receive the fasteners and are sized to permit the fasteners to slide in the slots, or rather, since the fasteners are fixed to the table, to permit the aperture mask to slide side-to-side with respect to the table. 
   The slots and fasteners are disposed and configured such that the mask can be shifted by linear motor  510  to any one of three positions, yet will hold the mask in each of these positions when table  238  is rotated 180 degrees from the filter loading position to the filter testing position. 
   A first position of mask  2302  with respect to table  238  is a loading position in which the lower tip portion of probe  152  can pass through all four large apertures  2308  in order to place a filter  196  in each of the flexures during flexure loading and to remove each of the filters during flexure unloading. Thus, once linear motor  510  shifts mask  2302  to the loading position, all four flexures can be sequentially loaded using probe  152  with no necessary intermediate movement of mask  2302  with respect to table  238 . 
   A second position of mask  2302  with respect to table  238  is a testing position in which the laser light beams generated by the four collimators  500  can simultaneously pass through all four small apertures  2304  (the position shown in  FIG. 17 ) and impinge upon the bottom surface of filters  196  at each of the four filter nests. By providing a position of mask  2302  at which all the collimators can reach their filters with their orthogonal laser beams, all the filters can be simultaneously or sequentially tested without having to move mask  2302  between each filter test. 
   A third position of mask  2302  with respect to table  238  is a second testing position in which the laser light beams generated by the four collimators  500  can simultaneously pass through all four elongate apertures  2310  and impinge upon the bottom surface of filters  196  at each of the four filter nests. By providing a position of mask  2302  at which all the collimators can reach their filters, all the filters can be simultaneously or sequentially tested without having to move mask  2302  between each filter test. 
   In operation, the linear motor  510  will move laterally until the aperture mask coupling supported by linear motor  510  can engage its mating coupling  2312  on mask  2302 . Once engaged, linear motor  510  moves in the “X” direction to slide mask  2302  with respect to table  238 . During this process, table  238  does not move, but is held stationary. 
   Once mask  2302  is moved to the proper location, thereby locating large aperture  2308  at each of the flexures, the coupling on linear motor  510  is disengaged from coupling  2312  on mask  2302 . Filter loading and unloading can then begin. 
   Once a new set of filters-to-be-tested are loaded, however, and before the table  238  (and hence the filters  196 ) are rotated to locate the filters at their goniometers for testing, the mask is shifted to locate the elongate or small circular apertures in position above the flexures. Once in this position the table is rotated and testing begins. 
   Alternatively, the mask  2302  may be fixedly mounted so as to be interposed between the optical filter under test and the optical detector  304 . Per such an embodiment, the mask  2302  remains stationary, simplifying the testing system. 
   The mask, while useful, is not necessary to the operation of the other parts of the system. Certainly there are many filters and substrates that may be tested in an automatic fashion without an aperture mask. In addition, each flexure may be provided with an individual mask, although these would require either more time or more actuators to move them. While the mask is operated when the flexures are at their loading stations, a mask actuator could as easily be disposed in the region of the goniometer to move the mask once it is back by the goniometer stations. Alternatively, a fixed or movable mask could be mounted by the goniometer stations that does not rotate with the table. 
   The following discussion summarizes operation of the optical filter testing and sorting apparatus of the present invention. The apparatus, capable of operating continuously, will pause automatically in response to optical filter availability (input) and take-away (output) constraints as well as for maintenance reasons. 
   The general overall flow of the filter testing process includes locating a filter on either the tape from the tape frame  111  (or the gel packs/vacuum release trays  702 ), moving them to and inserting them in the flexures, rotating table  238  until the flexures are located between the collimator and the detector at the four testing stations, testing the filters, rotating the table back to its original position, removing the four filters from the flexures, and inserting them in the output trays  112 . 
   Due to the construction of the machine, there are several of these operations that can be overlapped in time. This overlapping permits the machine to be engaged in several testing operations simultaneously, thus increasing productivity. 
   For example, loading and unloading can take place at the same time the filters are being tested. Table  238  has eight flexure stations, four on each side of the table, with one set of four in a testing position at the goniometers while the other set of four flexures is facing outward to be loaded or unloaded by the “X”, “Y” and “Z” stages. Thus, at the same time the goniometers are performing their tip and tilt adjustments or their scanning of wavelengths, the “X”, “Y” and “Z” stages can remove tested filters from the four flexures facing the “X”, “Y” and “Z” stages (i.e. the set of flexures that are not located at the goniometer test stations) and replace them with four new filters to be tested. 
   As another example of additional overlapping functions, the “X”, “Y” and “Z” stages can also perform various “housekeeping” functions while waiting for the goniometers to perform their testing. For example, assume the four filters that have been tested have already been removed from the flexures, placed in output trays, and have been replaced with four additional to-be-tested filters in the four flexures that are not at the goniometer test station. At this point the “X”, “Y”, and “Z” stages may be operated to move trays of tested parts from one area of table  114  to another area of table  114 . 
   As yet another example, the “X”, “Y”, and “Z” stages can move effector  120  to grasp and move trays of tested filters from the sorting area of table  114  to the depot area (i.e. row  150 ). 
   As another example of these housekeeping functions, the “X”, “Y” and “Z” stages can pick to-be-tested filters off of the tape frame  111  and place them in the vacuum trays  702 . In addition, while testing is occurring at he goniometer stations, effector  120  can pick and place lids that are stacked in depot locations (row  150 ) or are on top of their corresponding output trays  112  or gel pack trays  702 . 
   As another example of the system&#39;s ability to perform multiple operations simultaneously, the system&#39;s four goniometers can be operated substantially simultaneously. For example, as one goniometer is adjusted to a proper tip and tilt angle using motors  324  and  360 , the other goniometers can be likewise simultaneously adjusted. 
   As another example, while one goniometer detector is receiving a transmitted light signal from the laser light source, the other goniometer detectors can likewise simultaneously receive the same signal at their detectors. 
   All of these features are possible due to the arrangement of the system described herein. 
   Referring to the flow chart of  FIG. 21 , at step  2100 , a tape frame  111  or one or more gel pack trays  702  are loaded ( FIG. 7 ) into the machine. 
   At step  2102 , lot information representative of the optical filters  196  to be tested ( FIGS. 8A and 8B ) is preferably either scanned from bar code information associated with the to-be-tested optical filters  196  located on the tape frame  111  or the gel pack trays  702  by a bar code reader (not shown) or is manually entered by the operator into the system&#39;s computer. 
   This lot code information specifies a recipe number that preferably includes (1) the nominal filter-to-filter pitch (both in “X” and in “Y”) of the filters, (2) the nominal dimensions of the filters (the thickness, the width and the height of the filters), (3) the nominal location of one filter (the reference filter) with respect to a reference point on the tray itself, (4) the nominal center wavelength of the passband of the filters, and (5) the nominal passband width of the filters. 
   At step  2104 , machine vision camera  121  ( FIGS. 7 and 8A ) scans the target area for each such optical filter  196 . The system moves camera  1212  using the “X” and “Y” stages until the camera is located over the location of the reference filter. 
   At step  2106 , the system takes a picture of the tray at this reference location using camera  121 . 
   At step  2108 , the system analyzes the image using the previously entered nominal dimensions of the filter to extract edge characteristics indicative of a filter. If the image processing indicates that an entire filter is within the image (step  2110 ), the system continues processing at step  2110 . 
   If the system is unable to identify a filter in the image that matches the nominal dimensions of the filter, the system then moves to another location adjacent to the nominal location and repeats the image capture and image processing performed in steps  2106  and  2108 . 
   In the preferred embodiment, the system is configured to move camera  121  in a predetermined path in the vicinity of the reference filter, moving from one predetermined location to another predetermined location until a complete image of a filter is in the camera&#39;s ( 121 ) field of view. This search path may vary based upon the size of the filter (in particular the width and height of the filter). For larger filters, larger increments of motion are preferably made. For smaller filters, smaller increments of motion may be made. 
   The preferred path along which the camera is moved in successive attempts to get an image of an entire filter is preferably curvilinear such as a spiral path or a circular path. Starting from the nominal location of the first filter, previously stored in the computer, the camera is moved in an outward spiral. Alternatively it may be moved to a sequence of locations that collectively define several substantially concentric circles. 
   The system performs this moving, image gathering and image analyzing process at a succession of locations along the path until a filter is ultimately found, at which point processing continues at step  2110 . 
   In step  2110 , the system calculates the location of the geometric center of the filter based upon the actual location of the edges of the filter extracted from the image. The system also determines the rotational angle of the filter in the “X” and “Y” planes and about the “Z” axis—the “theta” angle of the filter. 
   The “X” and “Y” locations of the center of the filter are determined based upon (1) the “X” and “Y” position of the camera (typically the center of the image shown in the camera) and the “X” and “Y” offset of the filter within the camera image. The combination of the “X” and “Y” camera location and the “X” and “Y” offset of the center of the filter within the camera image itself provides the actual “X” and “Y” location of the filter. 
   In step  2110 , the system also saves data indicative of the actual “X” and “Y” location of the center of this reference filter (the “actual reference location”) for later use when the system returns to the tray to locate and pick up subsequent filters in the tray. 
   In step  2112 , the system moves the “X” and “Y” stages to position vacuum probe  152  directly above the center of the reference filter. As described above, the camera  121  and the probe  152  are both supported on the “X” and “Y” stages, and are fixed with respect to each other in the “X” and “Y” directions. As a result, they have a fixed “X” and “Y” offset from each other. This offset is electronically stored in the computer. and is used to offset the “X” and “Y” stages to position the probe directly over the center of the filter. 
   At substantially the same time that the “X” and “Y” stages move the probe  152  into position in step  2114 , the system also moves the “X” and “Y” stages (on which the lift pin assembly in mounted) to position the lift pin directly underneath the actual center of the filter. While the positioning of probe  152  and the lift pin assembly may be done sequentially, it is preferably that they move simultaneously in order to reduce the overall cycle time of the system. Since one feature of the preferred embodiment of this invention is to locate the pin and the probe on separate “X” and “Y” translatable stages, the present system is capable of simultaneous positioning of both the probe and the pin. 
   Once the center of the probe reaches the center of the filter in question, it is lowered until it just contacts the filter in step  2116 . In the preferred embodiment, the system also applies a vacuum to probe  152  to adhere the filter to the bottom of the probe. 
   In step  2118 , the system raises the lift pin, now in position under the filter, by applying compressed air to cylinder  206  until the filter is lifted a predetermined distance. The system monitors the signal from sensor  228  to determine when the lift pin has been raised to the proper height. As described above, this driving upward of the filter against probe  152  is accompanied by the step of peeling a portion of the tape away from the filter, thus leaving the filter stuck to a small portion of the tape. 
   As a reminder, not every filter to be tested is held on the adhesive tape on tape frame  111 . Some filters to be tested are located in gel packs  702  on vacuum mounts  700 . In the case where filters are held in gel packs, the process is slightly different. When gel packs are used, the lift pin assembly is not used to help release the filters, and thus the steps above related to moving and positioning the lift pin assembly are not performed. Indeed, the entire lift pin process may be eliminated if the adhesive to which the filters are held is of a sufficiently low tackiness that it will release the filters by the vacuum applied to probe  152  alone. New adhesives and packaging methods for filters will no doubt be developed that may permit the elimination of the lift pin assembly. 
   Gel packs are formed of a plastic tray over which a thin flexible matrix is attached. The matrix is formed of a tacky gel material. The filters are stuck to this matrix. Between the matrix and the inside bottom of the tray is an irregular grid. This grid may be in the form of a woven mat. A vacuum is applied to the bottom side of the gel pack, shown in  FIG. 2A , causing the matrix to be pulled downward and into close contact with this irregular grid. This happens because the vacuum pulls air out from between the irregular surface and the planar matrix. The irregular grid does not flatten out, however. The gel matrix assumes an irregular bumpy surface to match the irregular grid. 
   When the matrix is distorted downwardly, portions of the matrix are pulled away from the bottom surface of each of the filters stuck to the top surface of the matrix. The bottom surfaces of the filters generally contact an equal area of adhesive coated matrix before the vacuum is applied. When the vacuum is applied and the matrix deforms downwardly curving and conforming to the grid, at least a portion of the adhesive-coated matrix pulls away from the back of the filters. This pulling away causes all of the filters in the gel pack to be in contact with a smaller area of sticky gel, and thus to be held more weakly to the matrix than they are when no vacuum is applied and the matrix is in its normally flat planar orientation. 
   As a result, when the system applies a vacuum to the gel pack using the arrangement shown in  FIG. 2A , the system provides a reduction in surface contact area that is similar to the reduction in adhesive bond area provided by operation of the lift pin, but without the lift pin assembly apparatus, and merely by the application of a vacuum to the gel pack. 
   All that is required is a tray mount that is configured to receive the gel pack and the application of a vacuum to the underside of a gel pack. This capability is provided by mounts  700  illustrated in cross-section in  FIG. 2A , shown in  FIGS. 1 and 2 , and discussed above. 
   Referring back to the process, in step  2120 , the system lifts probe  152  by commanding the “Z” stage to raise, thereby pulling (by the vacuum applied to probe  152 ) the filter away from the remaining portion of the tape to which the filter is adhered. Alternatively, the probe retracts from the gel pack and similarly pulls the filter away from the gel matrix. 
   If the probe  152  is retrieving filters from a gel pack, the step of applying a vacuum to the gel pack is performed just before step  2118  in order to reduce the surface contact between the filter and the gel pack. This insures that the probe is capable of pulling the filter free from the gel pack in step  2118 . Applying vacuum after step  2106  also assures a higher quality image of the filter when the image of the filter is acquired. 
   Once removed from the tape, the “X” and “Y” stages translate the filter on the end of the probe to the flexures in step  2122 . Each flexure has a predetermined X-Y location stored in the computer, expressed either as an absolute location or as an offset from a predetermined reference location, that is accessed by the system&#39;s computer to provide the X-Y location of each flexure to the system. 
   During the process of translating the filter, the system also commands the “theta” stage to rotate the filter to a proper graspable position. In the preferred embodiment, this position is one that will permit the three protrusions  283 ,  284 ,  286  on the arms of flexure  250  to effectively grasp the filter when the system retracts the flexure actuator assembly and thereby releases the flexure arms  262 . 
   In the preferred embodiment, the system determines the rotational angle of the filter based upon the electronic image received from camera  121 , as described above in step  2106 . This angle indicates the rotational position of the filter in its tray, and with respect to the “X” and “Y” axes of the system. 
   The system retrieves the “theta” or rotational angle of the filter about the “Z” axis. This value was calculated during step  2110  above in which the filter was identified and its center calculated. 
   The system then converts the theta angle into a drive signal that is applied to the theta stage. In response to this signal, the theta stage rotates through an angle that is calculated to align the filter with its intended flexure. Once the proper filter angle has been achieved, the theta stage stops rotating. 
   This rotation can occur at any time between the time the filter has been picked up by probe  152  at step  2120  and the time that the flexure arms are released to grasp that same filter. In the preferred embodiment, this theta rotation is effected as the filter is translated by the “X” and “Y” stages to the desired flexure. 
   Before the filter that the “X” and “Y” stages are moving to a flexure can be inserted into that flexure, table  238  must first be prepared by moving the aperture mask into the proper position. This occurs in step  2124 . 
   To permit loading, the aperture mask must be shifted to located the large apertures just above gap  282  in which the filters are inserted. The system translates the linear motor  510  until its coupling engages coupling  2312  on the aperture mask. Once engaged, linear motor  510  moves in a direction and for a distance that aligns all four of the large apertures underneath each of their corresponding flexures. 
   Since a single manipulation of the aperture mask moves all four large apertures simultaneously into position at their flexures, this step only occurs once during flexure loading. 
   In step  2126 , the flexure actuator assembly and the post assembly are moved into lateral position at the flexure that will receive the filter suspended from probe  152 . Linear motor  510  moves plate  502  until the flexure actuator assembly, is located directly in front of and between the two arms of the flexure. In this position, post  512  is also located directly below the flexure. 
   In step  2128 , the system prepares the flexure to receive the filter. As part of this preparation, the system drives post  512  upward by applying compressed air to stage  520 . Stage  520  moves post  512  upward until the top surface of post  512  is substantially coplanar with the bottom planar surface of flexure  250 . After the post is positioned, in step  2130  the system drives flexure actuator  294  forward by applying compressed air to pneumatic stage  266 . This forward motion of stage  266  separates the flexure arms. 
   The system then inserts filter  196  into the flexure. In step  2132 , the system commands the “Z” stage to lower probe  152  a predetermined amount that will locate filter  196  between the arms of the flexure and place it in contact with the top of post  512 . 
   In the preferred embodiment, the system drives the “Z” stage downward to a position at which probe  152  is slightly compressed in its sleeve, the guaranteeing that the filter will be mechanically held between and in contact with both the post and the probe by their contact with opposing planar sides of the filter. 
   The system then applies a vacuum to post  512  to hold the filter in step  2134 . Once the vacuum has been applied to the post and the system determines (using a vacuum sensor) that the vacuum has been applied, the system removes the vacuum from the probe. The system then determines (based upon a vacuum sensor disposed to sense the probe vacuum) that the vacuum has been removed and drives the “Z” stage (and therefore probe  152 ) upward away from the filter nest to permit completion of flexure loading (in step  2138 ). 
   The system then retracts the flexure actuator assembly in step  2136 , thereby releasing the flexure arms, and permitting the flexure arms to move inwardly and mechanically engage the filter. The system then releases the vacuum applied to post  512 , and drives stage  520  downward to lower post  512  away from the filter. 
   Once a single flexure has been loaded, the system repeats the process of steps  2104 - 2138  three more times as indicated by step  2140  (with the exception of the step of shifting the aperture, which is not repeated at each successive filter placement) until all four apertures are loaded. 
   At the conclusion of this loading process, the system moves aperture mask  2302  in step  2142  using the process described above in conjunction with step  2124 . The system commands linear motor  510  to move the aperture mask to either of its two testing positions, depending upon the particular tests that the system will perform on the filters. 
   Once four untested filters are mounted in their corresponding flexures and the system has completed its optical testing of four filters previously loaded into the machine and located at the test stations, the tested filters are moved away from the test stations and the four just-loaded filters are moved into position at the test stations. This happens in step  2144 . 
   The system then rotates table  238  by applying compressed air to one of the two opposed cylinders  612 . This causes shaft  602 , and hence table  238  to begin rotating. The system applies air to the appropriate cylinder  612  until stop block  640  on the bottom of table  238  abuts one of adjustable stops  628 . 
   At substantially the same time this abutting occurs, one of optical limit switch flags  632  or  634  (depending upon which of the two opposed 180 degree positions the table is being driven to) causes its corresponding sensor  636  or  638  (again, depending upon the position the table is driven to) to generate a signal indicating that the table has rotated 180 degrees. The air pressure the cylinder holds the table in position against adjustable stop  628  or  630  (again, depending upon the rotational position of the table). Note that this process is reversed using the other one of cylinder  612  and the other one of the two limit switches and flags when the table is moved back to its original position after testing. 
   Once the table  238  has been rotated in step  2144 , as indicated by sensor  636  or  638 , the four to-be-tested filters are now at their corresponding goniometer test stations and the system begins optical testing. Note also that, at the same time the table rotated four filters into position for testing, it simultaneously moved the four filters on the opposite side of the table into position for unloading and sorting by probe  152 . 
   At step  2146 , the system optically aligns each goniometer  302  with a corresponding nest  236  ( FIGS. 12 and 14 ) by selectively driving motors  324  and  360 . 
   At step  2148 , the system controls goniometer  302  and performs a signal maximization routine to determine signal as a function of angular position. The system positions each goniometer  302  at the angular position that generated peak intensity (normal incidence). 
   At step  2150 , the system varies the wavelength of the tunable laser and tests for the transmission characteristics of each filter. 
   After filter testing, at step  2152 , the processing table  238  again rotates 180° presenting a new set of optical filters  196  for testing ( FIGS. 12 and 14 ) and returning the tested optical filters  196  to their original position adjacent to linear motor  510  ( FIGS. 3 and 12 ) for further processing. 
   At step  2154 , the system drives the “X” and “Y” gantry systems ( FIGS. 1 and 2 ) to move the head  124  ( FIGS. 5A and 5B ) over the first tested filter to be unloaded. 
   At step  2156  the system drives linear motor  510 , and hence the flexure actuator assembly  294  laterally into a position adjacent a filter nest. 
   At step  2160 , the system drives the “Z” stage downward causing vacuum probe  152  to make contact with that filter, and applies a vacuum to orifice  164 . 
   At step  2162 , the system applies compressed air to translating stage  266  thereby causing flexure actuator assembly  264  to translate and spread jaws  262  and thereby releasing the first tested filter  196  to the vacuum probe  152  ( FIGS. 9A and 9B ) of the head  124 . 
   At step  2164 , the system deposits the tested filter in the appropriate output tray. The system commands the “X” and “Y” stages to move the tested filter to a predetermined empty filter position over the appropriate output tray  112  (based upon the results of the test) and then commands the “Z” stage to lower the filter on the end of probe  152  until it is in position on the tray. Once in position, the system releases the vacuum applied to probe  152  and commands the “Z” stage to translate upward away from that tray. 
   This process of unloading described in steps  2154  through  2164  is repeated four times, once for (and at) each of the four filter nests  236  containing a tested filter. 
   While the loading and unloading process described above indicates that all four tested filters are unloaded from the flexures before four to-be-tested filters are loaded into the flexures, this is not necessary. It is equally satisfactory (and considered to be within the scope of this invention) to interleave the unloading and loading. When the loading and unloading processes are interleaved, each of the four filter nests is sequentially unloaded and loaded in turn. 
   What has been illustrated and described herein is an automated apparatus for testing optical filters. However, as the automated apparatus of the present invention has been illustrated and described with reference to several preferred embodiments, it is to be understood that the full scope of the invention is not to be limited to these embodiments. In particular, and as those skilled in the relevant art can appreciate, functional alternatives will readily become apparent after reviewing this patent specification and enclosed FIGURES. Accordingly, all such functional equivalents, alternatives, and/or modifications are to be considered as forming a part of the present invention insofar as they fall within the spirit and scope of the appended claims.