Abstract:
An optical module inspection circuit on an optical platform includes an optical module carrier for precisely aligning optical devices with optical interfaces of inspection equipment located at fixed positions in the optical module inspection circuit. The module-includes an apparatus for conveyance along a top surface of the optical platform. The module may be conveyed automatically to predetermined positions on the optical platform to automate alignment and positioning of optical devices with respect to optical inspection stations in the optical test circuit.

Description:
This is a divisional of U.S. patent application Ser. No. 09/144,434, filed Sep. 1, 1998. 

   BACKGROUND OF THE INVENTION 
   1) Field of the Invention 
   This invention pertains to the field of optical device testing and in particular to an apparatus and method for facilitating inspection of the surfaces of optical devices on an a optical module. 
   2) Background of the Related Art 
   Optical devices combined with electronics are increasingly being used in communication and information systems. It is important to inspect the surfaces of the optical devices after final assembly onto on optical module to insure that the module will perform as expected. 
   Inspection of the optical device surfaces is typically performed at one or more optical inspection stations in an optical test circuit on an optical bench or platform. An inspection station may typically include a microscope or an electronic imaging device or camera for inspecting the optical device(s). Each optical device surface is manually aligned with an optical device interface at one or more inspection stations and then inspected. A connector may be provided between an optical device interface of the inspection station and an optical device to be inspected. 
   Unfortunately, manual alignment is labor-intensive and somewhat difficult. A microscope or optical camera is typically heavy, rigid and fixed with little or no alignment flexibility. Likewise, the optical module is often heavy and rigid. Also, the degree of precision required for optical alignment precludes the use of flexible connectors between the microscope and the optical device. 
   Often during the alignment process, one or more optical device surfaces inadvertently strike against the platform or inspection apparatus, damaging the optical surface. This can necessitate costly repairs or even cause the module to be wasted. For example an optical module can cost $50,000 or more, and it is not uncommon for repairs caused by damage to an optical device during inspection to amount to $10,000. 
   Accordingly, it would be advantageous to provide an apparatus and method for easily bringing optical device surfaces reliably into alignment with inspection stations. It would also be advantageous to provide an apparatus and method which provides an extra degree of freedom of movement when aligning an optical inspection station with an optical device on an optical module. It would further be advantageous to provide an automated apparatus and method which reduces the amount of labor involved in the process. Other and further objects and advantages will appear hereinafter. 
   SUMMARY OF THE INVENTION 
   The present invention comprises an apparatus and method for facilitating inspection of the surfaces of optical devices on an optical module. 
   In one aspect of the invention, an optical module carrier is provided which includes means for conveying an optical module to one or more optical inspection stations in an optical test circuit. The carrier aligns optical devices on the module with each corresponding optical device interface for the optical inspection stations. 
   In another aspect of the invention, an optical module inspection circuit automates the alignment and positioning of optical devices with respect to optical inspection stations. Each inspection station is located at a predetermined position on an optical platform. An optical module is automatically conveyed to position an optical device to be inspected at the corresponding optical inspection station on the optical platform. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a first embodiment of an optical module inspection circuit. 
       FIG. 2  shows an embodiment of an optical module carrier. 
       FIG. 3A  shows a first embodiment of a tray for an optical module carrier. 
       FIG. 3B  shows a second embodiment of a tray for an optical module carrier. 
       FIG. 4  shows an optical module mounted on an optical module carrier in an optical module inspection circuit. 
       FIG. 5  shows a second embodiment of an optical module inspection circuit. 
       FIG. 6  shows a third embodiment of an optical module inspection circuit. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a preferred embodiment of an optical module inspection circuit  100 . The optical module inspection circuit  100  includes an optical platform  110  upon which are arranged one or more optical inspection stations  120  at fixed positions. Each optical inspection station  120  may be mounted in a fixed position on the optical platform  110 . 
   In a preferred embodiment, the optical module platform  110  has a low-friction or virtually frictionless top surface. The optical module platform  110  top surface may be coated with a silicone based coating or TEFLON™. Also, the top-surface may be made more frictionless by providing an air cushion. 
   Each optical inspection station  120  includes an optical inspection apparatus  130  having an optical interface  140  located a fixed distance above the top of the optical platform  110 . The optical inspection apparatus  130  may be, for example, a microscope or an electronic imaging device or camera. An inspector may use the optical inspection apparatus to inspect an edge or planar surface of an optical device. 
   To inspect each optical device mounted on an optical module, the optical device must be aligned with the optical interface  140  of the corresponding optical inspection station  120 . In a preferred embodiment, an optical module is mounted on an optical module carrier  160  which conveys the optical module to each optical inspection station  120  in the optical module inspection circuit  100 . The optical module carrier  160  is designed to place each optical device on the optical module the same distance above the top surface of the optical platform  110  as the optical interface  140  of the corresponding optical inspection station  120 . This insures that the optical device is properly aligned with the optical inspection apparatus to prevent damage to the optical device. 
   A preferred embodiment of an optical module carrier  200  according to one or more aspects of the present invention is shown in  FIG. 2 . 
   In the preferred embodiment of  FIG. 2 , the optical module carrier  200  includes a tray  210  upon which an optical module may be mounted. The tray preferably has a flat top surface, or it may have a raised edge or lip along its outer top surface for helping to align or maintain the optical module in a fixed position with respect to the carrier. 
   In a preferred embodiment, the optical module carrier  200  also includes one or more vertically extending pillars  220  for securing the optical module into a fixed position on the top surface of the tray  210 . The pillars  220  may be clamps which hold an optical module to the tray. Alternatively, the pillars  210  may include one or more slots for sliding an optical module into and thereby securing the optical module on the optical module carrier  200 . 
   Optionally, the optical module and the optical module carrier may each include threaded holes which are aligned with corresponding holes in an optical module when the optical module is properly placed on the top surface of the optical module carrier  200 . In that case, the optical module may be secured to the optical module carrier  200  by means of one or more screws or bolts. 
   In a preferred embodiment, the optical module carrier  200  includes one or more rollers  230  which may be used to transport the optical module carrier  200 . In a preferred embodiment, the rollers may be balls (e.g., ball bearings) which partially extend through holes in the bottom surface of the tray  210 . Alternatively, the rollers may be wheels, cylindrical rollers, or similar devices mounted to the bottom surface of the tray  210 . 
   In a preferred embodiment, the optical module carrier  200  includes loaders which are spring loaded to provide an additional degree of freedom in the vertical direction. By applying pressure in a downward direction, the springs may be compressed and the vertical position of an optical module mounted on the optical module carrier may be precisely adjusted. 
     FIG. 3A  shows a first preferred embodiment of a tray  300  for an optical module carrier. In a preferred embodiment, the tray  300  may consist of a top portion  310  and a bottom cover plate  320  which are attached together. The top portion  310  and the bottom cover plate  320  may snap together, or they may be attached by any convenient means such as by screws, solder joints, welding etc. In a preferred embodiment, the top portion  310  has a plurality of recesses  330  in its bottom surface  340  which may accommodate balls  350 . The recesses  330  also may be coated with Teflon or packed with lubricant to help the balls  350  to roll more freely. Corresponding to each recess  3 . 30 , the bottom cover plate  320  has a hole  360  having a diameter which is slightly smaller than the diameter of the recess  330 . The balls  350  are placed in the recesses  330  of the top portion  310  and the bottom cover plate  320  is then attached. Thus the balls  350  extend through the holes  360  a fixed distance below the bottom surface of the tray  300  such that they freely rotate in the holes  360 . In this way, the optical module carrier may easily convey an optical module upon a top surface of an optical platform to one or more optical inspection stations while placing each optical device at the same distance above the top surface of the optical platform as the optical interface of the corresponding optical inspection station. 
   In some cases, the optical inspection stations each may have an optical interface which is a different distance above the top surface of the optical platform. In that case, the optical devices on an module each may need to be placed at different distances above the top surface of the optical platform to be aligned with the optical interface of the corresponding optical inspection station. 
   In a preferred embodiment, the optical module carrier tray  300  includes a spring  355  for each recess  330  and ball  350 . The spring  355  allows the vertical positioning of the tray  300  to be adjusted slightly for precisely aligning an optical module with an optical device interface of an optical module inspection station. 
     FIG. 3B  shows a second preferred embodiment of a tray  370  for an optical module carrier which may also accommodate the need to place different optical devices at different heights to align them with the optical device interfaces of corresponding inspection apparatuses. The tray  370  is similar to the tray  300  shown in  FIG. 3A  except that it includes a top cover  375  and one or more elevation mechanisms  380 . The elevation mechanism  380  may be used to raise or lower top cover  375  above the rest of the optical module carrier. In this way, an optical module may be raised or lowered so that each optical device on an optical module may be precisely positioned to match the distance above the top surface of the optical platform as the optical interface of the corresponding optical inspection station. Although  FIG. 3B  shows a “scissors-type” elevation mechanism, one skilled in the art would recognize that many other elevation mechanisms could be incorporated into the optical module carrier to raise or lower the optical module. 
     FIG. 4  shows an optical module inspection circuit  400  with an optical module carrier  405  on an optical platform  410  having two optical inspection stations  420 . An optical module  460  is mounted on the optical module carrier  405 . The optical module  460  shown here includes a faceplate  462  and several bulkheads  464  which house optical device surfaces to be inspected at the inspection stations  420 . The bulkheads  462  may include an optical connector for interfacing with a microscope or electronic imaging device. 
   The optical module carrier  405  includes two vertical pillars  425  having slots for holding the optical module  460 . The optical module carrier  405  also includes a tray  430  for conveying the optical module  460  along the top surface of the optical platform  410 . As shown here, the vertical pillars  425  are attached to the tray  430  by means of a plate  435 . 
   In a preferred embodiment, the optical module carrier  405  may be fabricated of aluminum or another lightweight metal, plastic, or another appropriate material. 
   As described above, in a preferred embodiment, the tray  430  includes a plurality of rollers such as ball bearings on a bottom surface for smoothly conveying the optical module to an optical inspection station  420 . Also, in a preferred embodiment, the top surface of the optical platform  410  is made to have low friction using, for example, a silicone based coating. 
     FIG. 5  shows a preferred embodiment of an automated optical module inspection circuit  500 . The optical module inspection circuit  500  includes an optical platform  510  upon which are arranged one or more optical inspection stations  520  at fixed positions. Each optical inspection station  520  includes an optical inspection apparatus  530  having an optical interface  540  located a fixed distance above the top of the optical platform  510 . 
   The optical module inspection circuit  500  also includes a movable arm  550  extendable from a base  555  over the surface of the optical platform  510 . In a preferred embodiment, the movable arm  550  is attached to an optical module carrier  560  which conveys an optical module to each optical inspection station  520  in the optical module inspection circuit  500 . The optical module carrier  560  is designed to place each optical device on the optical module the same distance above the top surface of the optical platform  510  as the optical interface  540  of the corresponding optical inspection station  520 . This insures that the optical device is aligned with the optical inspection apparatus to prevent damage to the optical device. 
   Preferably, the movable arm  550  is mechanically controlled by one or more signals from a programmable processor  570  to automatically position the optical module at one or more optical inspection stations  520  on the optical platform  510 . In that case, the processor  570  executes a program which divides the top surface of the optical platform  510  into an X-Y Cartesian coordinate grid. The X-Y coordinates for the optical interface  540  of each optical inspection station  520  are stored in processor memory, and the processor  570  executes a software program to automatically position the movable arm  550  at the X-Y coordinates for each optical interface in order to inspect an optical device on an optical module. 
   Preferably, the processor  570  has one or more data entry devices such as a keyboard  582 , a mouse  584 , a graphics tablet  586  and/or a light pen  588 . The processor  570  also has a display device such as a monitor  590 . 
   Preferably, the processor  570  executes a first training routine for storing in memory the X-Y coordinates for each optical interface  540  of the optical inspection stations  520  along the optical platform  510 . The movable arm  550  is steered to the proper location for each optical inspection station  520  either manually or under computer control. The arm is positioned so that an optical module on the optical module carrier  560  is properly positioned and oriented to align an optical device with the optical interface  540  for the corresponding optical inspection station  520 . Then the corresponding X-Y coordinate of the optical interface  540  is manually or automatically stored into memory by the processor  570 . This process is repeated for each optical inspection station  520  in the optical module inspection circuit  500 . 
   The processor  570  also executes a second inspection routine for controlling the movable arm  550  to automatically position an optical device on an optical module to be inspected at the optical interface  540  of the corresponding optical inspection station  520  on the optical platform  510 . A user may enter an identification number for an inspection station  520  and the processor  570  retrieves the corresponding X-Y coordinates of the optical interface  540  from memory. The processor  570  then supplies control signals to the movable arm  550  to move it to align the optical device to be inspected with the optical interface  540  for the corresponding optical inspection station  520 . This is repeated for each optical device and each inspection station in the optical module inspection circuit  500 . 
   In a variation of the first preferred embodiment of an automated optical module inspection circuit, the movable arm may also move the optical module carrier in the Z dimension above the top surface of the optical platform  510 . This may allow the movable arm to automatically place different optical device on an module at different heights above the top surface of the optical platform to align them with corresponding inspection apparatuses. 
   In that case, during the training routine, the Z coordinate for each optical interface  540  of the optical inspection stations  520  along the optical platform  510  is stored in memory along with the X-Y coordinates. Likewise, during the inspection routine the movable arm  550  automatically positions each optical device on an optical module to be inspected at the proper X, Y and Z coordinates for the optical interface  540  of the corresponding optical inspection station  520  on the optical platform  510 . 
     FIG. 6  shows another preferred embodiment of an automated optical module inspection circuit  600 . The optical module inspection circuit  600  includes an optical platform  610  upon which are arranged one or more optical inspection stations  620  at fixed positions. Each optical inspection station  620  includes an optical inspection apparatus  630  having an optical interface  640  located a fixed distance above the top of the optical platform  610 . 
   The optical module inspection circuit  600  also includes an optical module carrier  660  which conveys an optical module to each optical inspection station  620  in the optical module inspection circuit  600 . The optical module carrier  660  is designed to place each optical device on the optical module the same distance above the top surface of the optical platform  610  as the optical interface  640  of the corresponding optical inspection station  620 . This insures that the optical device is aligned with the optical inspection apparatus to prevent damage to the optical device. 
   Preferably, the optical module carrier  660  is mechanically controlled by one or more signals from a programmable processor  670  to automatically position the optical module at one or more optical inspection stations  620  on the optical platform  610 . Preferably, the optical module carrier  660  includes an electrical motor for turning rolling means  665  which transport the optical module carrier  660 . The rolling means  665  may be wheels, cylindrical rollers, similar devices mounted to the bottom surface of the optical module carrier  660 . 
   Preferably, the top surface of the optical platform  610  is divided into an X-Y Cartesian coordinate grid. The X-Y coordinates for the optical interface  640  of each optical inspection station  620  are stored in processor memory, and the processor  670  executes a software program to automatically position the optical module at the X-Y coordinates for each optical interface in order to inspect an optical device on an optical module. 
   Preferably, the processor  670  has one or more data entry devices such as a keyboard  682 , a mouse  684 , a graphics tablet  686  and/or a light pen  688 . The processor  670  also has a display device such as a monitor  690 . 
   Preferably, the processor  670  executes a first training routine for storing in memory the X-Y coordinates for each optical interface  640  of the optical inspection stations  620  along the optical platform  610 . The optical module carrier  660  is steered to the proper location for each optical inspection station  620  either manually or under computer control. The optical module carrier  660  is positioned so that an optical module mounted thereon is properly positioned and oriented to align an optical device with the optical interface  640  for the corresponding optical inspection station  620 . Then the corresponding X-Y coordinate of the optical interface  640  is manually or automatically stored into memory by the processor  670 . This process is repeated for each optical inspection station  620  in the optical module inspection circuit  600 . 
   The processor  670  also executes a second inspection routine for transporting the optical module carrier  660  to automatically position an optical device on an optical module to be inspected at the optical interface  640  of the corresponding optical inspection station  620  on the optical platform  610 . A user may enter an identification number for an inspection station  620  and the processor  670  retrieves the corresponding X-Y coordinates of the optical interface  640  from memory. The processor  670  then supplies control signals to the optical module carrier  660  to move it to align the optical device to be inspected with the optical interface  640  for the corresponding optical inspection station  620 . This is repeated for each optical device and each inspection station in the optical module inspection circuit  600 . 
   In a variation of the second preferred embodiment of an automated optical module inspection circuit, the optical module carrier may include automatic means for elevation in the Z dimension above the top surface of the optical platform  610 . This may allow the optical module carrier  660 , under control of the processor  670 , to automatically place different optical device on an module at different heights above the top surface of the optical platform to align them with corresponding inspection apparatuses. 
   By the above-described system and process, optical devices may be quickly aligned for inspection without risk of damage. 
   While preferred embodiments are disclosed herein, many variations are possible which remain within the concept and scope of the invention. Such variations would become clear to one of ordinary skill in the art after inspection of the specification, drawings and claims herein. The invention therefore is not to be restricted except within the spirit and scope of the appended claims.