Patent Publication Number: US-6989895-B2

Title: Automated fiber optic inspection system

Description:
This application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 60/365,442, filed Mar. 18, 2002, of Mike Buzzetti, for AUTOMATED FIBER OPTIC INSPECTION SYSTEM, which U.S. Provisional Patent Application is hereby fully incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to automated inspection systems and methods, and more particularly to automated inspection systems and methods for fiber optic connectors. 
   Analyzing fiber optic connector end faces for defects is required to effectively weed out those connectors that may not deliver acceptable performance to those who use them. With the abundant quantity of fiber optic connectors being manufactured, there exists a need for a system and method for quickly inspecting a number of connector ends and determining those that are defective. 
   Traditionally, a camera or a microscope individually magnifies and focuses on each connector end. An individual then either manually, or by use of a computer program, picks out particular defects. The time it takes to center the image, focus, inspect the image and then manually center a new connector end, and focus and inspect the image makes the inspection process very tedious and time consuming, especially when inspecting large numbers of connector ends. 
   Therefore, a need exists to be able to automatically inspect a number of connector ends with little human intervention. 
   The present invention advantageously addresses the above and other needs. 
   SUMMARY OF THE INVENTION 
   The present invention advantageously addresses the needs above as well as other needs by providing an automated fiber optic inspection system and method for fiber optic connectors. 
   In one embodiment, the invention can be characterized as a method for vision inspection of optical connectors that comprises placing a plurality of optical connectors into a corresponding plurality of positions in a fixture, retrieving a motion profile for said fixture from a motion profile database, centering an image of one of the plurality of optical connectors by moving a camera relative to the fixture using the motion profile, and focusing the camera on the one of the plurality of optical connectors. Then, the one of the plurality of optical connectors is inspected using the camera. The next steps include centering an image for another of the plurality of optical connectors by moving the camera relative to the fixture using the motion profile, focusing the camera on the other of the plurality of optical connectors, and inspecting the other of the plurality of optical connectors. 
   In another embodiment, the invention can be characterized as a system for vision inspection of optical connectors comprising a motion control system comprising a motion controller for moving a camera relative to a fixture in at least two dimensions, the fixture comprising a plurality of positions for holding a plurality of optical connectors. An image interface is coupled to the processor for receiving an image of one of the plurality of optical connectors from said camera. An inspection software subsystem is coupled to the processor for inspecting the one of the plurality of optical connectors. A motion control software subsystem is coupled to the processor for generating motion control signals, wherein the control signals are received by the motion control system. The motion control system moves the camera relative to the one of the plurality of optical connectors in response to the control signals. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
       FIG. 1  is a high level block diagram of an automated fiber optic inspection system according to the present invention; 
       FIG. 2  is a lower level block diagram of the automated fiber optic inspection system of  FIG. 1 ; 
       FIG. 3  is a top perspective view of a partially constructed inspection station of the automated fiber optic inspection system of  FIG. 2 ; 
       FIG. 4  is a top perspective view of the partially constructed inspection station of  FIG. 3  rotated clockwise 90°; 
       FIG. 5  is a top perspective view of the complete construction of the inspection station of  FIG. 4  rotated clockwise 90°; 
       FIG. 6  is a top planar view of a sample fiber optic connector fixture for inspection by the inspection station of  FIG. 5 ; 
       FIG. 7  is a process flow chart for the automated fiber optic inspection system of FIG.  1  and  FIG. 2 ; and 
       FIG. 8  is a screen shot of the graphical user interface and graphical display of test results of the automated fiber optic inspection system of FIG.  1  and FIG.  7 . 
   

   Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the presently contemplated best mode of practicing the invention is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims. 
   Referring first to  FIG. 1 , shown is a high level block diagram of an automated fiber optic inspection system according to one embodiment of the present invention. 
   Shown is an inspection station  105  including a camera  110 , camera movement hardware  115 , and a motion controller  120 . Also shown is a computer  125  having a test results database  130 , an inspection software  135 , and a motion routine software  140 . Lastly, a display  145  and user input device  150  are shown. 
   The inspection station  105  has a motion controller  120  that is in communication, e.g., electrical communication, with the camera movement hardware  115 . The motion controller  120  is also in communication, e.g., electrical communication, with the computer  125  and ultimately in logical communication with the motion routine software  140  on the computer  125 . The camera  110  is in communication, e.g., electrical communication, with the computer  125  and ultimately is in logical communication with the inspection software  135 . The inspection software  135  is in logical communication with the motion routine software  140 , test results database  130  and the display  145 , which is coupled to the computer  125 . Finally, the motion routine software  140  is in logical communication with the motion controller  120  and the user input device  150 , which is coupled to the computer  125 . 
   A user initiates a fiber optic connector test through the user input device, e.g., a keyboard and/or a mouse. The motion routine software  140  on the computer  125  controls the motion controller  120 , which in turn controls the movement of the camera movement hardware  115 . The camera movement hardware  115  physically moves the camera  110  to a specified location below a specified fiber optic connector, according to a motion profile that is retrieved from the database and used by the motion routine software  140 , and images from the camera  110  are communicated directly to the inspection software  135 . The inspection software  135 , such as the inspection software available from COGNEX software company is in communication with the motion routine software  140  in order to coordinate the correct movement of the camera  110  once inspection of a particular fiber optic connector is complete. The inspection software  135  uses data from the images from the camera  110  to inspect fiber optic connectors. Once all the connectors are inspected, the test results are stored in the test results database and output on the display  145 . 
   Referring next to  FIG. 2 , shown is a lower level block diagram of the automated fiber optic inspection system of FIG.  1 . 
   In addition to that already shown in  FIG. 1 , shown are X, Y and Z axis drivers  200 ,  205 ,  210  and motors  215 ,  220 ,  225  which collectively make up the camera movement hardware  115  of FIG.  1 . Also shown are a com port  230 , a frame grabber  235 , an inspection process  240  and focus data module  245  within the inspection software  135 . X-Y-Z motion control  250  and motion database  255  are shown within the motion routine software  140 . A computer bus  260  is shown in the computer  125  as well. 
   The motion controller  120  is in electrical communication with the X, Y, and Z axis drivers  200 ,  205 ,  210 , which are in turn in electrical communication with the X, Y and Z axis motors  215 ,  220 ,  225 . The motion controller  120  is also in electrical communication with the com port  230  in the computer  125  and the camera  110  is in electrical communication with the frame grabber  235  in the computer  125 . The frame grabber  235  and com port  230  are electrically connected to the computer bus  260  and via the computer bus  260  are in communication with the focus data module  245  and the X-Y-Z motion control  250  within the inspection software  135  and motion control software  250 , respectively. The inspection process  240  and focus data module  245  are logically connected to and are in duplex communication with the X-Y-Z motion control  250  within the motion routine software  140 . The motion database  255  is also logically connected to and in communication with the X-Y-Z motion control  250 . 
   The motion controller  120  controls each of the X, Y, and Z axis drivers  200 ,  205 ,  210 , which in turn control their corresponding X, Y and Z axis motors  215 ,  220 ,  225 . This allows full three dimensional movement of the camera  110 . Movement in the Z axis is required for focusing, while movement in the X axis and Y axis allow movement of the camera to different connectors. 
   The com port  230  communicates control signals to the motion controller from the computer according to the X-Y-Z motion control  125  commands. The motion database  255  contains a motion routine for all the connectors to be inspected in a particular fixture and the X-Y-Z motion control uses the appropriate motion routine to determine which movement signals to send to the motion controller  120  for a particular connector within a fixture. 
   Advantageously, the fixture may be the same fixture used in other processing steps in the manufacture or processing of the connectors. Specifically, the fixture may be the same fixture used with a polishing machine used to polish the fiber surfaces within the fiber optic connector. As a result, a significant amount of manual handling is avoided because the connectors do not need to be removed from the fixture after polishing of the connectors prior to inspection of the connectors. 
   The present embodiment preferably accommodates a plurality of different fixture types from polishing machines from a plurality of different manufacturers. 
   Once a particular connector is inspected by way of the inspection process  240 , this is communicated to the X-Y-Z motion control  250  to initiate the correct movement of the camera for further inspections, if any. The frame grabber  235  communicates image data from the camera  110  to the computer  125  which image date gets delivered internally into the focus data module  245 . Focus data such as contrast values are computed in the focus data module and are communicated to the X-Y-Z motion control  250  for focusing purposes. 
   Referring next to  FIG. 3  shown is a top perspective view of a partially constructed inspection station  105  of the automated fiber optic inspection system of FIG.  2 . 
   Shown is a base  300 , vibration isolators  305 , a mounting plate  310 , a power supply  315 , the motion controller  120 , the X, Y and Z axis motors  215 ,  220 ,  225 , lead screws  335 ,  340 ,  345 , lead nuts  350 ,  355 ,  360  and stages  365 ,  370 ,  375 . Also shown are X axis and Y axis motor mounts  380 ,  385 , an X axis block  386 , an X-Y adaptor plate  388 , the Y axis driver  205 , Z axis mount  389  and X axis limit switches  390 . Lastly, shown are an objective lens  392 , a digital camera  110 , and an optical block  396 . 
   The motion controller  120  and power supply  315  are mounted on the base  300 . Four vibration isolators  305  (one not shown) are also mounted on the base  300  and the mounting plate  310  is attached on top of the vibration isolators  305  with one vibration isolator  305  positioned at each corner of the mounting plate  310 . 
   Attached to the mounting plate  310  is the X axis block  386  with the X axis stage  365  slidably attached to it. Also attached to the mounting plate  310  is the X axis motor mount  380  to which the X axis motor  215  is attached. The X axis lead screw is operably attached to the X axis motor  215  and runs parallel lengthwise with the X axis stage  365 . The X axis lead screw  335  goes through the X axis lead nut  350  which is attached to the X axis stage  365 . Also attached to the mounting plate are the X axis limit switches  390  along side the X axis lead screw, and the Y axis driver. 
   Attached to the X axis stage  365  is the X-Y adapter plate  388  with the Y axis stage  370  slidably attached to it. The Y axis stage  370  runs lengthwise horizontally perpendicular to the X axis stage  365 . Also attached to the X axis stage  365  is the Y axis motor mount  385  to which the Y axis motor  220  is attached. The Y axis lead screw  340  is operably attached to the Y axis motor  220  and runs parallel lengthwise with the Y axis stage  370 . The Y axis lead screw  340  goes through the Y axis lead nut  355  which is attached to the Y axis stage  370 . 
   Attached to the Y axis stage  370  is the Z axis mount  389  with the Z axis stage  375  slidably attached to it. The Y axis stage  370  runs lengthwise vertically perpendicular to the Y axis stage  370 : Also attached to the Y axis stage  370  is the Z axis motor  225 . The Z axis lead screw  345  is operably attached to the Z axis motor  225  and runs parallel lengthwise with the Z axis stage  375 . The Z axis lead screw  345  goes through the Z axis lead nut  360  which is attached to the camera block  396 . The camera block is in turn attached to the Z axis stage  375 . On the side of the camera block is attached a digital camera  110  and an objective lens  392  is attached atop the camera block  396 . 
   By way of operation each motor  215 ,  220 ,  225  turns a lead screw  335 ,  340 ,  345  through a lead nut  350 ,  355   360  that is attached to a slidable stage  365 ,  370 ,  375 . For example, as the Y axis lead screw  340  is screwed through the Y axis lead nut  355  by the turning of the lead screw  340  by the Y axis motor  220 , the Y axis motor  220  pulls the Y axis lead nut  355  axially (along the Y axis) toward or away from the Y axis motor  220  depending on the direction the Y axis motor  220  is turning. This is because the Y axis motor  220  is fixedly attached to the X axis stage  365  (which is only slidable along the X axis) while the Y axis lead screw  355  is attached to the Y axis stage (which is slidable along the Y axis). This, therefore, causes movement of the Y axis stage  370  along the Y axis when the Y axis motor  220  runs. The same principle applies to the X axis and Z axis motors  215 ,  225  as well. Since each stage sits atop the other, movement of a stage below will also move the stage above. The camera and the objective lens are attached to the top stage (or the Z axis stage  375 ) and thus can move in the X, Y or Z direction. The limit switches  390  limit how far the X axis stage can move by changing states, i.e., opening or closing, when movement limits are reached, thereby providing an indication to the motion control software and to the motors to stop movement of the X axis stage (and thereby prevent damage to the stages, fixtures, camera, etc. There are also limit switches for the Y axis and Z axis, but these are not shown in FIG.  3 . Thus, the motors  215 ,  220 ,  225  can move the camera  110  to any location within a 6″×6″ square area with the X-Y plane and along the Z axis for focusing. 
   Referring next to  FIG. 4  shown is a top perspective view of the partially constructed inspection station  105  of  FIG. 3  rotated clockwise 90°. 
   In addition to that already shown in  FIG. 3 , is the X axis driver  200 , Y axis limit switch  405  and the Z axis limit switch  410 . The Z axis driver is integrated with the motion controller  120 . Also more visible is the Z axis stage  375  and the Z axis mount  389 . 
   The X axis driver  200  is attached to the mounting plate  310  next to the Y axis driver  205 . The Y axis limit switch  405  is mounted on the Y axis stage  370  and the Z axis limit switch  410  is mounted on the side of the Z axis stage  375 . 
   The power supply  315  provides power to run the motion controller  120  which controls the drivers  200 ,  205 ,  210  that drive the motors  215 ,  220 ,  225 . The Y and Z axis limit switches  405 ,  410  limit the extent to which the Y and Z stages  370 ,  375  can move. 
   Referring next to FIG.  5  and  FIG. 6 , shown in  FIG. 5  is a top perspective view of the complete construction of the inspection station  105  of  FIG. 4  rotated clockwise 90° and shown in  FIG. 6  is a top planar view of a sample fiber optic connector fixture  600  for inspection by the inspection station  105  of FIG.  5 . 
   In addition to that already shown in  FIG. 4 , shown in  FIG. 5  is a cage, an interface plate  505 , a jig plate  510 , and four locating pins  515 . Also shown is the second Y limit switch  520 . Shown in  FIG. 6  is a sample fiber optic connector fixture  600  with a plurality of fiber optic connectors (1-48)  605  affixed thereto for inspection by the inspection station  105  of FIG.  5 . The fixture  600  has four holes  610 , one at each corner. 
   The cage  500  is made of two arched bars  525 ,  530  connected by lateral beams  535 ,  540  and is attached to the mounting plate  310 . Attached flat to the to top the cage is the interface plate  505 . Attached on top of the interface plate is the jig plate  510 . The jig plate  510  has four locating pins  515  for securing the fixture  600  (shown in  FIG. 6 ) onto the inspection system. The jig plate  510  and the interface plate  505  have a square hole  545  through which the objective lens  392  can see fiber optic connectors within the fixture  600  once it is placed on the jig plate  510 . The fixture  600  may be, and is intended to be, switched out with a variety of different types of fixtures from different manufacturers and placed on the inspection station  105  for inspection. 
   The jig plate  510  and locating pins  515  preferably can be adjusted to accomodate a plurality of fixtures from a plurality of manufactures, such as manufactures of polishing machines. As a result, the present embodiment can be used in conjunction with the same fixtures used with in the polishing machines, and therefore the connectors do not need to be removed from seperate polishing machine fixtures and inserted into inspection system fixtures prior to inspection. 
   Thus, polishing of the connectors are preferably effected using a polishing machine having a fixture. And, the inspection using the inspection system of the present embodiment is preferably carried out (after polishing) using the same fixture. Any number of other pieces of processing equipment can precede the inspection system of the present embodiment in a fiber optic connector manufacturing or processing facility, and such other pieces of processing equipment may, in accordance with the present embodiment, share their fixture with the inspection system of the present embodiment, thereby achieving a similar advantage of not having to remove the connectors from one fixture (used for processing) and reposition the fixtures in another fixture (for inspection). 
   Referring next to  FIG. 7  shown is a process flow chart for the automated fiber optic inspection system of FIG.  1  and FIG.  2 .  FIG. 1 , FIG.  2  and  FIG. 6  will also be referred to in conjunction with FIG.  7 . 
   First, the computer  125  is started  700  and the inspection station  105  is powered up  700 . The user then puts  705  a fixture  600  (shown in  FIG. 6 ) onto the inspection station  105 . The user selects  710  manufacturer, serial number and fixture type for the fixture  600  being used by use of the user input device  150  such as a mouse for instance. The user then pushes a start button  715 . 
   The motion routine software  140  employs motion profiles stored in the motion database  255 . Each motion profile is for the particular manufacturer, serial number and/or fixture type (plate) being used. In response to, e.g., the fixture type being used (i.e., in response to the user entering the fixture type), the motion routine software  140  retrieves  720  a specified motion profile from the motion database  255 . The specified motion profile specifies the first individual connector on the fixture to be inspected, the order in which other individual connectors on the fixture are to be inspected, and the movements that the camera must make in order to be in position to inspect each individual connector. (These movements may, for example, be in the nature of coordinates to which the camera must be moved, and may, for example, define a serpentine pattern for movement of the camera from the first individual connector, through all of the other individual connectors, to the last individual connector.) 
   The camera  110  is then automatically moved  725  to the first connector of the plurality of connectors  605  in the fixture  600  in accordance with the motion profile. An image center value of the connector image is then automatically acquired  730  by the inspection software  135  and passed to the motion routine software  140 . The image center value is the location of the center of the image. If the image is not already centered above the lens  735  of the camera (as a result of the camera having been moved in accordance with the motion profile), then the motion routine software  140  re-centers  740  the image using the image center value and the new image center value is acquired  730 . This loop repeats until the image is centered  745 . 
   Next, the inspection software  135  acquires contrast data from the image focusing purposes  750 . The motion routine software  250  uses the contrast data to determine how much to move the camera  110  along the z axis to focus  755  the image. Then the contrast data is obtained to determine a focus score and check whether the score meets a minimum threshold  760 , preferably  90 . If the threshold is not met  765 , the system continues to focus using the contrast data  755  until the minimum threshold is met  770 . Then the inspection software  135  (available from, e.g., COGNEX software company) automatically inspects  775  the connector image looking for defects such as scratches, spots and boundaries (a spot type component in the area between the fiber and ferrule interface). The inspection software  135  finds and catalogs defects and anomalies in the surface of the fiber optic connector and then stores  780  these test results in a database  130 . These results are compared  785  to preset pass/fail parameters entered by the user. The inspection results are then output graphically to a computer display  145  (as shown in FIG.  8 ). If the connector is not  790  the last connector in the fixture  600 , the camera  110  is automatically moved  795  to the next connector by the motion routine software  140  and the process is started over from the step of acquiring the image center value  730 . This sub-process loops  799  until the last connector in the fixture  600  has been reached  796 . The camera  110  is then moved to the home position  797  which finishes  798  the process. 
   Referring next to  FIG. 8 , shown is a screen shot of the graphical user interface and graphical display of test results of the automated fiber optic inspection system of FIG.  1  and FIG.  7 . 
   Shown are the connector image and associated defects  800 , a user input dialog box  805  and tab buttons  810  to view different result formats. The user may see the results in a variety of formats including statistical trends and analysis of defects. 
   More specifically, the motion routine software includes a reporting module for extracting information from the test results database and for displaying or otherwise outputting the information having been extracted. The information includes, e.g., the fixture type, the serial number of the fixture, the position (or location) within the fixture (or plate) of the connector being tested, the manufacturer, the date of the inspection, and the results of the inspection, e.g., the number of scratches, pits, and boundaries, and whether the connector passed or failed inspection. 
   The reporting module includes a reporting wizard, which prompts a user for a date range of interest, a manufacturer, and/or a fixture serial number, and then directs the reporting module to extract information from the database on the basis of the date range of interest, a manufacturer, and/or a fixture serial number. Using the extracted information, the reporting module may, for example, display a line graph of the number of failures per day over the date range of interest. Using such a line graph, the user is able to visually observe any anomalies, or trends (such as an increasing number of failures, either slowly, over time, or suddenly) that may indicate a change in quality of the connectors, or equipment used to process the connectors. 
   Another report that can be generated by the reporting module is a daily report, such as may list all of the inspections for a particular day, including the fixture type, the serial number, the manufacturer and test results. Included in the daily report maybe for example, summary information, including the number or fixtures (or, e.g., connectors) inspected, the number of connectors that passed inspection, the number of connectors that failed inspection, e.g., a pass/fail ratio, and a total number of defects detected. 
   Additional reports may include monthly reports, pass/fail reports for selected days or months. 
   Furthermore, the reporting module is capable of outputting extracted information in the form of a data file, such as a comma delimited file, or an EXCEL spreadsheet file. In this way, the extracted information can be displayed, summarized, graphed and the like using third-party software packages. 
   Also notice in  FIG. 8  that the result of whether the inspection passed or failed is clearly displayed and the test may be started, stopped or paused at the touch of a button. 
   While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.