Abstract:
A system for inspecting intraocular lenses which utilizes a light source and an electronic camera for obtaining images of the lens under test. A series of masks is utilized during the obtaining of the images and includes a bright field mask which allows the transmission of light through the lens, a dark field mask which blocks a portion of the light which would normally pass through the lens and a transition mask which is constituted by fine stripes. A signal processor analyzes the images obtained utilizing the masks and provides an indication of predetermined defects in the lens.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention in general relates to inspection systems and more particularly to a system which automatically inspects objects such as lenses to determine various defects. 
     2. Description of Related Art 
     In the field of optics manufacture a need exists for determining the presence, as well as severity, of defects in optical components such as lenses for eyeglasses, contact lenses and intraocular lenses (IOL), by way of example. 
     Widely used current inspection techniques include the individual examination of each component by a human operator using a microscope or other magnifying device for defect and quality control. Although defects may be determined using this process, it is tedious and subject to human error. In addition, various defects may not be discernible to the human eye. 
     To improve the examination process, some manufacturers utilize machine vision technology whereby the examination procedure is done automatically using digital video cameras for image capture and image processing for defect determination. This process is a significant improvement over the human operator method but is still not capable of properly or sufficiently enhancing the entire range of defect types and products. 
     The present invention not only can identify a greater range of defects in an optical component than previous techniques but is able to accommodate a greater variety of different product types. 
     SUMMARY OF THE INVENTION 
     Apparatus is provided for determining defects in an optically transmissive object having a lens portion, an intraocular lens being an example. At least one camera is provided, along with a light source for directing light at the camera. An object inspection location is disposed between the light source and camera for receiving an object to be tested. At least two, and preferably three masks are used during the inspection of the object. One of the masks is a bright field mask which allows light to be transmitted through the object, another of the masks is a dark field mask which blocks light which would normally pass through the object and the third is a transition mask which is constituted by a fine pattern of alternating light transmitting and light blocking regions. Images of the object under test are obtained with the masks alternatively in place and a signal processor process the images to obtain indications of predetermined defects. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram broadly illustrating the principle of operation of the present invention. 
     FIG. 2 is a plan view of one type of IOL. 
     FIG. 3 is a plan view of another type of IOL. 
     FIG. 3A is a side view of the IOL of FIG.  3 . 
     FIG. 4 illustrates apparatus for lens inspection in accordance with one embodiment of the present invention. 
     FIGS. 5A and 5B serve to illustrate the production of diffused light. 
     FIGS. 6A and 6B are types of bright field masks that may be used herein. 
     FIG. 7 is a type of dark field mask that may be used herein. 
     FIGS. 8A and 8B are ray diagrams showing the effect of using a bright field mask for detecting defects. 
     FIGS. 9A and 9B are ray diagrams showing the effect of using a dark field mask for detecting defects. 
     FIG. 10 illustrates another embodiment of the present invention, which additionally uses a transition mask for inspection. 
     FIG. 11 is one type of transition mask which may be used herein. 
     FIG. 12 serves to illustrate the patterns obtained using the transition mask of FIG.  11 . 
     FIG. 13 shows the variation in amplitude as a function of distance for the arrangement of FIG.  12 . 
     FIGS. 14 and 14A are ray diagrams illustrating the operation of a transition mask. 
     FIGS. 15 and 15A illustrate the examination of a lens inside and outside of a carrier, respectively. 
     FIG. 16 is a block diagram of another embodiment of the present invention. 
     FIG. 17 is a view of a test which may be performed on one type of lens under test. 
     FIG. 17A illustrates the lens of FIG. 17 as it is held for viewing. 
     FIG. 18 illustrates apparatus in accordance with the embodiment shown in FIG.  16 . 
     FIG. 19 illustrates a mask array of FIG. 18 in more detail. 
     FIG. 20 is a flow chart illustrating the operation of the apparatus of FIGS. 16 and 18. 
     FIGS. 21A to  23 D are displays of various IOLs showing different types of defects. 
     FIG. 24 is a display of an IOL as depicted in FIG.  17 A. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the drawings, which are not necessarily to scale, like or corresponding parts are denoted by like or corresponding reference numerals. 
     FIG. 1 illustrates an automatic inspection system  10  for examining and determining defects in an optically transmissive component having a lens portion. The optical component is brought to an inspection position  12  by means of a component carrier  14  located between a light array  16  and a camera array  18 . As utilized herein the term “array” can mean one or more items. 
     Light from the light array  16 , as indicated by arrow  20 , passes through a mask array  22  prior to illuminating the component under test. The mask array  22 , as will be described, is comprised of at least two masks and the arrangement projects light through the component, the image of which is captured by the camera array. 
     Signal processor  24  is operable to take captured images and perform various diagnostic routines to determine the presence of a multitude of possible defects using images obtained with the different masks. These images may, if desired, be displayed on a high resolution display  26 . Under a preferred mode of operation, the light array  16  is a strobe arrangement and the signal processor  24  is operable to initiate a strobing action by means of a signal on line  28 . 
     A personal computer  30  may be included and allows for operator interaction with the signal processor  24  to enter data such as component lot number, lens power, and to obtain information on defects, product runs, and summaries, by way of example. 
     Although the invention is applicable to various types of optically transmissive components, it will be described by way of example with respect to those having a lens portion, and more particularly to IOLs. 
     An IOL is a surgical implant used to replace the lens within an eye, where the lens has been removed, for example, as a result of cataract surgery, disease, or physical damage. FIG. 2 illustrates, in plan view, one type of IOL  40 . 
     IOL  40  is a one-piece IOL which includes a bi-convex lens defining an optic zone  42 , surrounded by an annular zone  43 , and a flat flange, or non-optic portion, defining a haptic zone  44 . Anchor holes  46  secure the IOL  40  to the interior of the eye. 
     FIG. 3 illustrates a three-piece type of IOL  47  which has an optic zone  48  and which includes loops  49  and  50  for surgical connection to the eye. Each loop  49  and  50  is secured to the optic zone  48  by means of respective loop anchors  51  and  52 . The side view of IOL  47  in FIG. 3A illustrates the bi-convex nature of the lens, which is symmetrical about a mid plane M. 
     During the manufacturing process the IOLs may be subject to a variety of defects. The following list defines various typical defects, although the terminology may vary from one manufacturer to another. 
     Scratches: scratches appear as long, narrow surface abrasions usually specified by observed or apparent width, in micrometers (i.e. 80 scratch=80 μm) 
     Digs: digs are crater-like surface defects with a length/width ratio of approximately 1. This type of defect can occur anywhere on the surface of the IOL and is typically specified in 1/100 of a mm (i.e. 50 dig=0.5 mm). 
     Pits: pits are surface defects with a length/width ratio of approximately 1. The defect is characterized by a lack of IOL material and occurs inward into the IOL surface. Surface contour changes associated with the defect are typically gradual and smooth. 
     Voids: voids are defined in areas generally near the edge of an IOL, where a portion of the IOL is missing. Voids form during the IOL molding process when material does not completely fill the mold. 
     Tears: tears appear as small rips along the edge of the IOLs. They occur mainly in one-piece lenses (FIG.  2 ). Tears can occur at any location along the edge of the lens between the optic edge and the flange, or around the small anchor holes located near the edge of each flange. 
     Bubbles: bubbles are internal voids that can occur anywhere in the one-piece IOL and only in the optic zone of the three-piece IOL (FIG.  3 ). Bubbles are the result of air pockets present in the IOL material when injected into the mold during manufacture. 
     Dark inclusions: dark inclusions are defined as dark foreign particles suspended in an IOL. Dark inclusions can occur anywhere in the one-piece IOL and only in the optic zone of the three-piece IOL. 
     Light inclusions: light inclusions are defined as light foreign particles suspended in an IOL. Light inclusions can occur anywhere in the one-piece IOL and only in the optic zone of the three-piece IOL. 
     Loop damage: loop damage is classified as any kind of damage or malformation of a loop (three-piece IOLs only). The most prevalent type of loop damage include smashed anchors, smashed loops, missing loops and tweezer damage. 
     Edge flash: edge flash appears as flakes of IOL material attached to the edge of an IOL or as a thin coating covering the surface of loops. Edge flash is the result of excess IOL material flowing out of the mold during manufacture. 
     Substance: substance defects are defined as small particles adhering to the surface of an IOL that cannot be removed by cleaning. A substance many times appears as fine mist that causes the IOL to have an unusual tint. 
     Uncured: uncured material primarily occurs near the edge of the optic zone in one-piece IOLs. Uncured material appears as a jelly-like substance on the perimeter of an IOL. This defect develops during the lens curing process due to incorrect heating times or non-uniform heating. 
     Flow marks: flow marks appear as uneven seams or unusual surface contours in the optic or haptic zone. Flow marks typically form as long, thin defects that follow a smoothly winding direction, or path. Flow marks occur during the molding process when the IOL material cures before flowing is completed. 
     Rough edges: rough edge defects are classified as edges that remain rough after an IOL has been de-flashed. In terms of appearance, no distinction can be made between the IOLs containing flash and rough edge defects. The cause of the defect is what distinguishes rough edge from flash. 
     Warp: warped IOL surfaces become wrinkled, especially in the flange area. 
     Anchor defects: anchor defects are an assortment of defects relating to the position and manner in which the loop anchors are imbedded into the IOL material. Anchors may be too far inward in the IOL, not far enough, they may break the surface of the IOL material, they may not have intimate surface contact or there may be tears in the IOL material near the anchor. 
     FIG. 4 illustrates one embodiment of the invention wherein IOLs to be examined are placed in see-through cavities  60  in a component carrier  62  relatively moveable in the direction of arrow  63 . Carrier  62  is indexed such that each IOL is brought under a first camera  66  and then a second camera  67  of a two-camera array. If desired, and as indicated by arrow  68 , the carrier  62  may be moved laterally for inspection of components in additional cavities  60 ′, shown dotted. 
     A light array is constituted by two separate light sources  70  and  71  which are in line with the optical axes of respective cameras  66  and  67  and which direct light through respective masks  74  and  75  of a mask array. The light sources  70 ,  71  and masks  74 ,  75  are such that light is projected through an IOL, the image of which is captured by the cameras  66  and  67  and passed on for image analysis by the signal processor  78  which then provides a resulting image for presentation on high resolution display  80 . A host computer  82  is provided for operator interaction as previously described. 
     After the IOLs have been indexed out of the inspection position of camera  67 , the signal processor  78  will have determined whether an IOL is satisfactory for shipping, is rejected or requires reworking. In order to separate the IOLs into these, or other categories, the signal processor  78  may command an XYZ positioner  84  to direct a vacuum pick-up device  85 , having a thin pick-up tube  86 , to obtain an IOL in a cavity  60 , and  60 ′ if provided, and place the examined IOL in a respective compartment of a disposition tray  88 . 
     As previously stated, light is projected through the IOLs under test. Although conventional light from a light source may be used, in a preferred embodiment of the invention a light source arrangement is incorporated which provides diffused light for the IOL examination. FIGS. 5A and 5B serve to illustrate this concept. In FIG. 5A, a light source  90  projects light through a clear plate  92 . A single ray of light, as represented by arrow  94  passes through the clear plate  92  and emerges as a single ray  94 ′. 
     In FIG. 5B however a similar light source  96  projects light through a diffuser plate  98  and a single ray of light, as represented by arrow  100  emerges from the diffuser plate as a plurality of rays  100 ′ emerging in different directions and with different intensities, depending upon the type of diffuser plate utilized. The diffuser plate may be placed over the light source, or, as utilized herein, may be integral with the masks that are used. 
     One type of mask which is utilized in the present invention is a bright field mask such as mask  102  illustrated in FIG.  6 A. The mask  102  is constituted by a diffuser plate  104  with a light blocking portion  106  and a central light transmitting portion  108 . The diameter of the central portion  108  is such that the image of the IOL optic zone region will have a bright background. As an alternative, and as shown in FIG. 6B, and as used in FIG. 4 (item  74 ), the bright field mask  110  may be constituted by a diffuser plate alone (or a conventional light source alone if diffused light is not used). 
     FIG. 7 illustrates a typical dark field mask  112 , such as used in FIG. 4 (item  75 ), having a central light blocking portion  114 , surrounded by a light transmitting portion  116 . The diameter of the central portion  114  is such that, in the absence of defects, the IOL being imaged will be completely blocked from light passing through the mask in a direction parallel to the optic axis of the camera. This mask  112  is the opposite of the mask  103  illustrated in FIG.  6 A. 
     The principle of operation of the bright field mask is illustrated in FIGS. 8A and 8B. In FIG. 8A a three-piece IOL  120 , having no defects, is positioned at the object plane of camera  122 . Located between the IOL  120  and a light source (not shown) is a bright field mask such as mask  110  illustrated in FIG.  6 B. Two rays of diffused light  124  and  125  are illustrated as emanating from respective points A and B on mask  110 . These particular light rays exit IOL  120  at point X as rays  124 ′ and  125 ′ and strike a camera lens system represented by numeral  128 . The refracted rays  124 ″ and  125 ″ are focused to a point on a CCD array  130 , for example, located at the image plane of the camera  122 . 
     All light emitted from the mask  110  between points A and B that strike IOL  120  and emerge from point X will be intercepted by the camera lens system  128  and will be imaged. The same is true of all light rays between points A and B which emerge from the surface of the IOL. 
     FIG. 8B illustrates the same arrangement as FIG. 8A except that the IOL  120 ′ has a defect at point X. In addition, a third ray of light  131  from point C on mask  110  is illustrated. The complex contour found at the defect point X causes light that originally would be intercepted by the camera lens system  128 , for example rays  124 ′ and  131 ′, to be reflected and/or refracted in directions that are no longer intercepted and imaged. Although some rays, such as  125 ″ may still be imaged, the net effect is that less light (and in some cases no light) is imaged and point X in the final image appears dark, as will all other points of the IOL where defects exist. 
     This bright field process is particularly useful for detecting edge defects such as flash, tears and voids and interior surface defects such as dark inclusions, digs and scratches. 
     The principle of operation of the dark field mask is illustrated in FIGS. 9A and 9B. In FIG. 9A the three-piece IOL  120 , having no defects, is positioned at the object plane of the same camera  122 . Located between the IOL  120  and a light source (not shown) is a dark field mask such as the mask  112  illustrated in FIG.  7 . By way of example, for a  22  Diopter IOL  120  with a camera  122  having a 60 mm focal length lens with a field of view of 15 mm by 15 mm, and the mid plane of the IOL located 30 mm above the mask  112 , the central light blocking portion  114  of the mask  112  may have a diameter of 30 mm. 
     Two rays of diffused light  132  and  133  are illustrated as emanating from respective points A and B on either side of the central light blocking portion  114  of mask  112 . These particular light rays exit IOL  120  at point X as rays  132 ′ and  133 ′ which are not intercepted by the lens system  128  of camera  122  and are therefore not imaged such that point X will appear dark at the CCD  130 . 
     FIG. 9B illustrates the same arrangement as FIG. 9A except that the IOL  120 ′ has a defect at point X. Light emitted from outside of the light blocking portion  114  of the mask  112  which originally would not be intercepted by the lens system of camera  122  now strikes the defect point X and is reflected and/or refracted in a direction that is now intercepted by the camera lens system  128  and is imaged as a bright spot, as will all other points of the IOL where defects exist. 
     This dark field process is particularly useful for enhancing edge defects such as flash, uncured material, tears and large voids. Interior surface defects are enhanced such as dark inclusions, light inclusions, digs, scratches, bubbles, uncured material, warp, tears, and various loop damage. 
     There is a class of IOL defects that show up very poorly or not at all when using either the bright field or dark field technique. The class of defects include flow defects, warp defects, pit defects and some anchor placement defects. These defects are characterized by very subtle changes in the contour of the IOL. In a preferred embodiment of the invention therefore a third mask is utilized to provide for a more extensive examination procedure. By way of example, a third inspection position is provided to the arrangement of FIG.  4 . This is illustrated in FIG. 10 wherein a third camera  140  has been added for imaging IOLs through which diffused light is transmitted by the combination of third light source  142  and a third mask, transition mask  144 . 
     A transition mask as used herein is composed of alternate bands of light transmitting and light blocking portions. In one embodiment these alternating bands take the form of stripes as illustrated by transition mask  150  in FIG.  11 . Dark stripe portions  151  and clear stripe portions are positioned upon a diffuser plate  153 . 
     The nature of the transition mask is such that the diffused light from the clear portions between the dark stripes interact in a constructive and destructive manner at different distances from the mask. With reference to FIG. 12, the combination of light source  156  and transition mask  150  will produce a cyclical pattern going from stripes to a uniform pattern, as a function of distance. This is shown for two different distances D1 and D2. At D1 the pattern is comprised of distinct stripes, while at distance D2 the pattern is essentially uniform. A camera  158  positioned along the optical axis X can be focused to an object plane where the pattern of constructive and destructive light rays will show up, at the camera image plane (where the CCD array is located) as a striped pattern, as an essentially uniform pattern or somewhere in-between, depending on the position of the camera along the optical axis. For this to occur the light striking the CCD array of the camera  158  should be monochromatic light such as may be provided by a monochromatic light source or an appropriate filter positioned on the optical axis. 
     The cyclical nature of the pattern caused by the transition mask  150  may be demonstrated with reference to FIG. 13 wherein curve  164  represents the intensity of light with respect to lateral distance at one point along the optical axis. The positive peaks  165  of curve  164  represent maximum intensity and are indicative of clear stripes, whereas the negative peaks  166  represent minimum intensity and are indicative of dark stripes. The transition from clear to dark stripes is represented by the sloping portion  167  of the curve and it is in this region that defects are most pronounced. 
     At a different position along the optical axis, the intensity of the clear and dark stripes is diminished, as represented by curve  164 ′. Curve  164 ″ shows the intensity at still another location, whereas the horizontal line  168  represents an essentially uniform pattern at some other position. 
     When using the transition mask, and as illustrated in FIG. 14, an IOL  180  is placed at the object plane  182  of the camera  184 , having a lens system  186  and a CCD array  188  at its image plane. The combined IOL and camera lenses form a somewhat out of focus image of the transition mask  150  onto the image plane, and it is this image which is disrupted by defects in the IOL  180 . 
     One form of disruption is the redirection of incident light away from or towards the camera lens, depending on the defect type and location. The pattern of alternating dark and clear stripes can be thought of as small regions that utilize the bright field and dark field principles previously described. The redirection of light is optimized by the alternating clear and dark stripe pattern because all defects are in close proximity to a dark field/bright field boundary. In this regard, the stripe spacing is selected to be small to maximize this effect. By way of example, for a 22 Diopter IOL  180 , in FIG. 14, with a camera  184  having a 60 mm focal length lens with a field of view of 15 mm by 15 mm, a transition mask  150 , located 70 mm behind the IOL, may have a dimension of 40 mm by 40 mm with a stripe spacing of less than 1 mm, for example 0.5 to 0.8 mm. 
     In FIG. 14 rays  190  and  191  emanating from point A, just at the edge of a dark stripe  151 , image at point A′ on the CCD array  188 . Similarly, rays  192  and  193  from point B at the other edge of stripe  151  and rays  194  and  195  from point C image at points B′ and C′, respectively. A defect in the IOL  180  at point X is above a dark stripe  151 , as indicated by dotted line  197 . A ray of light  198  from point C passes through the IOL  180  at point X and is deflected by the defect so as to be imaged as a bright region in the normally dark area  199  between points A′ and B′ on the CCD array  188 . 
     For a given localized area all extraneous light that might degrade defect contrast is minimized since the dark stripes  151  on either side of the clear stripes  152  prevent extraneous light from more distant clear stripes from washing out the defect contrast. The defect may additionally show up in the transition region and may even transcend several stripes. That is, different classes of defects will cause different distortions of the stripe pattern, depending upon the type, location, size and severity of the lens defect. 
     Another mechanism exists that causes subtle surface type defects to distort the image and thus allow for their detection. As the surface contour of the desired lens deviates, the refractive power of the defective area changes. The different refractive power of the defective area, in turn, causes a localized shift of the mask stripe pattern such that there is a clear disturbance in the resulting image. This mechanism essentially is equivalent to an unwanted small lens being superimposed, or inserted, onto an existing lens within the optical system. If this unwanted small lens has an optical axis that differs from the main lens, it will image its target off axis with respect to the main lens and will cause detail to shift in that area of the image. 
     More particularly, FIG. 14A illustrates the principles involved with this detail shift. In FIG. 14A, for clarity, the camera and CCD array are not shown. Rays  200  and  201  emanate from point A on the transition mask  150 , proceed through IOL  202 , having an optical axis OA 1 , and are imaged at point A′ on the IOL&#39;s image plane  203 , (The CCD array would normally be located at this image plane) at which is formed a striped pattern, as indicated by reference numeral  204 . 
     A defect or protrusion  205  forms a small lens having a different optical power than IOL  202  and with an optical axis OA 2 , of different orientation than the optical axis OA 1 , of IOL  202 . Rays  206  and  207  also emanating from point A on the transition mask  150  proceed to point A″ on the image plane  208  of lens  205  and which image plane also has a striped pattern, as indicated by reference numeral  209 . 
     In the regions where the image plane  208  of the lens  205  is in close proximity to the image plane  203  of the IOL  202 , the resulting image will be a combination of the two and will result in detail shifts. 
     The distortion of a light ray path by one or more various defects in the haptic zone of the IOL will also be detected by utilizing the principles described with respect to the bright field, dark field and transition masks. By way of example, FIG. 15 illustrates an IOL  210  of the variety shown in FIG. 2, having a central optic zone  211  and a flat haptic zone  212 . The lens portion ( 211 ) of the IOL  210  sits within an aperture  214  of a carrier  216  while the flat portion ( 212 ) rests on a peripheral ledge  218 . With this arrangement, light from a mask  220  is blocked by the ledge  218  and the haptic zone cannot be imaged at the same time as the optic zone. 
     If the haptic zone is to be examined for defects, and as illustrated in FIG. 15A, the IOL  210  may be removed from the carrier  216  by means of a vacuum pick up tube  222  similar to tube  86  of FIG. 10, and the carrier moved away so as to allow imaging of the haptic zone  212 . As will be seen in FIGS. 21C,  21 D,  22 C,  22 D,  23 C, and  23 D, the image will include a section which is completely blocked by the tube  222 , however this section will have been previously imaged. 
     When examining the haptic zone, or any flat object, the camera is placed at a height to view an object plane where the transition pattern is imaged as an essentially uniform pattern at the camera CCD array. The lens is placed at a position slightly above this object plane, as more fully described and claimed in copending application Ser. No. 09/055,536, filed Apr. 6, 1998, and assigned to the same assignee as the present invention. 
     In the embodiment of the invention described in FIG. 10, three inspection stations are utilized for examining the IOLs, with each station including a separate camera, a separate light source and a separate mask. In another embodiment of the invention, and as illustrated in FIG. 16, a single inspection station having a single camera and a single light source may be used for detecting defects in the IOLs. 
     As seen in the block diagram of FIG. 16, inspection station  240  includes a first light source  242  located in line with the optical axis of a camera  244 , as is an IOL carrier  246 . A mask array  248  includes a plurality of different masks and is moveable to selectively position a desired one of the masks into the optical field. In order to remove individual IOLs from the carrier, a vacuum pick-up device  250  is included, as previously described with respect to FIGS. 4 and 10. 
     The carrier  246  and mask array  248  are moveable in two dimensions by means of respective X-Y positioners  252  and  253 , while the vacuum pick-up device  250  is moveable in a horizontal and vertical direction by means of X-Z positioner  254 . 
     A signal processor  260  is operable to provide the necessary drive signals X c Y c , X m Y m , and X p Z p  to the respective positioners  252  to  254 . The signal processor additionally triggers the light source at the proper time by means of a signal on line L 1 , and receives the output from the camera  244 , via a signal on line C 1 , for image analysis and for displaying the image on display  262 . Operator interaction is provided by means of a host computer  264 . 
     For examining a three-piece IOL, as illustrated in FIGS. 3 and 3A, it may be desirable to examine the loops to see if they are bent or otherwise deviate from a mid plane by more than a predetermined amount. With additional reference to FIGS. 17 and 17A, a second camera  266  is provided, along with a second light source  268 . In FIG. 16, a signal on line L 2  from signal processor  260  controls the light source  268  and the output from camera  266  is provided via line C 2 . 
     The IOL  47  of FIG. 3 is positioned such that it is back lit by diffused light from the light source  268  with the camera  266  looking at the side view of the IOL, as in FIG.  17 A. For this test, no mask is required and the IOL is removed from the carrier and held in position by means of the pick-up device  250 . The camera  266  captures an image such as in FIG.  17 A and the signal processor  260  will examine the image and determine if either of the loops  49  or  50  deviate by more than a predetermined angle θ, as measured from a mid plane M. 
     The arrangement of FIG. 16, in one component form embodiment, is illustrated by way of example in FIG.  18 . The inspection station  240  includes a support table  270  (shown with a portion broken away) having a top  271  with a central aperture  272  through which projects the X-Z positioner  254  attached to pick-up device  250 . Camera  244  is vertically moveable on holder  274  secured to the top  271 , while second camera  266  is secured to the undersurface thereof. 
     Upon command of the signal processor  260  (FIG. 16) light source  242  will project a flash of light toward the camera  244  through the aperture  272  for each of the three masks utilized. This light will pass through a particular mask placed in the optical path by positioner  253 , and through an IOL under test. After irradiation with one mask in place, the mask array  248  is indexed to bring subsequent masks into position. If however, a bright field image is obtained first, one has the option of leaving the bright field mask in place while the subsequent dark field and transition mask images are obtained. One embodiment of a mask array is illustrated in more detail in FIG.  19 . 
     Mask array  248  includes at least one bright field mask  280 , at least one dark field mask  281  and at least one transition mask  282 , all contained within a holder  283 . For examining a variety of different IOLs with differing powers, however, it is preferred that the mask array include a plurality of each mask type as indicated by the additional masks with primed and double primed reference numerals. In addition, each mask of the array may be vertically positionable by means of screw clamps  284  moveable in vertical slots  286 . 
     FIG. 20 illustrates a flow chart  300  of a process for inspecting a lens such as an IOL, with the equipment of FIG.  18 . After the process is started, step  302 , the pallet, that is, the carrier  246  is indexed to present a first IOL for imaging and testing, as indicated by step  303 . At step  304  the mask array  248  is indexed to present a first mask, a dark field mask, in the optical path and a first image is obtained at step  305 . 
     In steps  306  and  307  the mask array is again indexed to present a bright field mask and a second image is obtained. The process is repeated a third time in steps  308  and  309  to obtain a third image, utilizing the transition mask. 
     The three images, now stored in the signal processor  260  are examined for defects at step  310 . In addition, the vacuum pick-up device removes the IOL from the pallet, which itself is removed from the optical path and the IOL replaced for further inspection, as depicted by steps  311  to  313 . Steps  314  to  319  repeat steps  304  to  309 , however without the pallet, to obtain three more images which are processed at step  320 . 
     If the IOL is a three-piece type such as illustrated in FIG. 3 then it must be tested to see if the loops meet certain predetermined standards. This is accomplished in steps  321  to  323 . After this processing, or if the IOL is not a three-piece lens, then step  324  determines if the IOL is satisfactory for use. That is, it has no defects or it has certain allowable defects. If the IOL passes the test, it is placed in a shipping package at step  325 , and then indexed out of the system at step  326 . If there are more IOLs to be tested then the operation moves on to the next IOL, as indicated by steps  327  and  328 . 
     If the IOL did not pass the inspection qualifications at step  324 , then step  329  determines if the IOL can be reworked and if so, it is placed into a separate case or compact at step  330 . When the compact is full, it is swapped with an empty one at step  332  and the lot is removed for reworking. 
     If the IOL cannot be reworked after it is inspected, step  333  determines if it should be rejected. If a rejection is indicated, the IOL is placed in a compact which is removed after filling, as indicated in steps  334  to  336 . 
     If the rejection determination at step  333  is negative, then, in steps  337  and  338 , it is put back into the pallet for adjustment and further testing. When the last IOL has been examined the pallet is reloaded with a new set of IOLs for testing, as indicated at step  339  and the process stops at step  340  whereby the operator can, if necessary, enter new data for the new lot to be tested. 
     The camera used to obtain the various images includes a CCD array which provides the signal processor with a plurality of signals indicative of individual pixel values of the image, as is well known. In the processing of the images at steps  310 ,  320  and  323 , the signal processor may examine and store the individual pixel values. In accordance with a variety of different defect recognition programs, the signal processor will compare each pixel value with its immediate neighbor pixel values to see if certain predetermined criteria are met, to determine type, severity and location of defects. By utilizing at least the bright field and dark field masks the images will be able to show a vast variety of different defects. An even greater number of defects can be accommodated if the transition mask is additionally used, as depicted by steps  308  and  318 . 
     In a variety of pattern recognition programs, the signal processing, whereby each pixel is compared with it neighbors may be reduced by providing the program with a already known information. For example, in the present invention this already known information may include the known size of the aperture which holds the IOL, and the known shape of the particular IOL under test. In this manner only the pixels on the edge of, and within the known shape need be processed. 
     The equipment shown in FIG. 18 has been utilized to examine various IOLs and the following Figs. illustrate various displayed images, showing a variety of defects described herein, such defects being labeled on the respective Figs. 
     FIGS. 21A to  21 D are images obtained using a bright field mask, FIGS. 22A to  22 D show some results using a dark field mask and FIGS. 23A to  23 D are displays using the transition mask. FIG. 24 is included, and although it does not show any defects it is included to show a typical image obtained with the second camera for determining loop angle with respect to a mid plane. 
     Although the present invention has been described with a certain degree of particularity, it is to be understood that various substitutions and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.