Abstract:
A system and method for aligning optical fibers that takes into account variations due to temperature changes and other nonrandom systemic effects. The system includes an alignment tool having a plurality of internal reflection surfaces and located below a vision plane of the first one of the pair of optical fibers, and an optical detector to receive an indirect image of a bottom surface of the first optical fiber through the alignment tool, such an offset between the first optical fiber and the optical detector is determined based on the indirect image received by the optical detector. The method comprises the steps of providing a cornercube offset tool having a plurality of total internal reflection surfaces below a vision plane of the first optical fiber, and receiving an indirect image of the first optical fiber through the cornercube offset tool.

Description:
[0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 09/912,024 filed on Jul. 24, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates generally to the use of machine vision systems for semiconductor chip bonding/ attaching devices. More specifically, the present invention relates to the use of a corner cube retro-reflector as an offset alignment tool that acquires indirect images of optical fibers optic during the alignment process when the same lie outside the view of the imaging system. From such images, coordinate information on position can be obtained and any positional offset from reference position of the fiber optic alignment tool due to deviations caused by thermal change or other nonrandom systemic errors can be taken into account for correct alignment and placement of optical fibers with respect to other optical fibers or fiber optic detectors/ devices/ elements.  
         BACKGROUND OF THE INVENTION  
         [0003]    The fabrication of electronic assemblies, such as integrated circuit chips and fiber optic cables, requires alignment inspection of the device at various phases of the fabrication process. Such alignment inspection procedures utilize vision systems or image processing systems (systems that capture images, digitize them and use a computer to perform image analysis) to align devices and guide the fabrication machine for correct placement and/or alignment of components.  
           [0004]    In conventional systems, post attach inspection is used to determine if changes in fabrication machine position are necessary to effect proper placement and/or alignment. As such, these conventional systems can only compensate for misalignment after such improper alignment is made, thereby negatively effecting yield and throughput. These conventional systems have additional drawbacks in that they are unable to easily compensate for variations in the system due to thermal changes, for example, requiring periodic checking of completed devices further impacting device yield and negatively impacting manufacturing time.  
           [0005]    In conventional systems the vision system (shown in FIG. 11) consists of two image devices, a first image device  1104  placed below the optical plane  1112  and views objects upward and a second image device  1102  placed above the optical plane and views objects downward. These conventional systems have drawbacks, in that in addition to requiring more than one image device, they are unable to easily compensate for variations in the system due to thermal changes, for example.  
         SUMMARY OF THE INVENTION  
         [0006]    In view of the shortcomings of the prior art, it is an object of the present invention to provide a system and method for aligning optical fibers using a vision system that takes into account variations due to temperature changes and other nonrandom systemic effects.  
           [0007]    The present invention is a vision system for use in aligning optical fibers. The system comprises an alignment tool having a plurality of internal reflection surfaces, the alignment tool located below a vision plane of the first optical fiber; and an optical detector to receive an indirect image of a bottom surface of the first optical fiber through the alignment tool.  
           [0008]    According to another aspect of the invention, the vertex of the alignment tool is located at a position about midway between the optical axis of the optical detector and the optical axis of the first optical fiber.  
           [0009]    According to a further aspect of the invention, the alignment tool comprises a cornercube offset tool.  
           [0010]    According to still another aspect of the invention, the focal plane of the vision system is positioned at or above the alignment tool.  
           [0011]    According to yet another aspect of the present invention, the system includes a lens positioned between the alignment tool and i) the optical detector and ii) the first optical fiber.  
           [0012]    According to still another aspect of the present invention, the system includes a first lens positioned between the optical detector and the alignment tool and a second lens positioned between the first optical fiber and the alignment tool.  
           [0013]    According to a further aspect of the present invention, the first lens and the second lens are located at or below the image plane.  
           [0014]    According to yet a further aspect of the present invention, the reflecting surfaces are three mutually perpendicular faces.  
           [0015]    According to yet another aspect of the present invention, the angle between each of the internal reflective surfaces and the top surface of the cornercube offset tool is about 45°.  
           [0016]    According to still another aspect of the invention, the optical detector is a CCD camera.  
           [0017]    According to yet another aspect of the invention, the optical detector is a CMOS imager.  
           [0018]    According to yet a further aspect of the invention, the optical detector is a position sensitive detector.  
           [0019]    According to an exemplary method of the present invention, a cornercube offset tool is positioned below a vision plane of the first optical fiber; a lens is positioned between i) the first optical fiber and the cornercube offset tool and ii) between the optical imager and the cornercube offset tool; and the first optical fiber is viewed indirectly through the cornercube offset tool and the lens.  
           [0020]    These and other aspects of the invention are set forth below with reference to the drawings and the description of exemplary embodiments of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The invention is best understood from the following detailed description when read in connection with the accompanying drawing. It is emphasized that, according to common practice, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawing are the following Figures:  
         [0022]    [0022]FIG. 1 is a perspective view of an exemplary embodiment of the present invention;  
         [0023]    [0023]FIG. 2A is a side view of image ray traces according to a first exemplary embodiment of the present invention;  
         [0024]    [0024]FIG. 2B is a side view of image ray traces according to a second exemplary embodiment of the present invention;  
         [0025]    [0025]FIG. 3 is a perspective view of image ray traces according to an exemplary embodiment of the present invention;  
         [0026]    [0026]FIGS. 4A and 4B are perspective and side views, respectively, of an exemplary embodiment of the present invention;  
         [0027]    [0027]FIG. 5 illustrates the telecentricity of an exemplary embodiment of the present invention;  
         [0028]    [0028]FIG. 6 is a detailed view of an exemplary retroreflective cornercube offset tool according to the present invention;  
         [0029]    FIGS.  7 A- 7 C illustrate the effect of tilt about the vertex of the cornercube tool of the exemplary vision system;  
         [0030]    FIGS.  8 A- 8 C illustrate the effect of tilt about the X and Y axis of the exemplary vision system;  
         [0031]    [0031]FIG. 9 is a side view of image ray traces according to a third exemplary embodiment of the present invention;  
         [0032]    FIGS.  10 A- 10 E are various views of a fourth exemplary embodiment of the present invention;  
         [0033]    [0033]FIG. 11 is a vision system according to the prior art;  
         [0034]    [0034]FIG. 12 is an illustration of a fifth exemplary embodiment of the present invention; and  
         [0035]    FIGS.  13 A- 13 D are various views of a sixth exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0036]    The entire disclosure of U.S. patent application Ser. No. 09/912,024 filed on Jul. 24, 2001 is expressly incorporated by reference herein  
         [0037]    Referring to FIG. 1 a perspective view of an exemplary embodiment of the present invention is shown. The system is included in wire bonding machine  100 , and employs a cornercube  106 , having a plurality of internal reflection surfaces (best shown in FIG. 6), located at or below image plane  112  of bonding tool  104 .  
         [0038]    In an exemplary embodiment, cornercube offset alignment tool  109  (comprising cornercube  106  and lens elements  108 ,  110 ), has a total of three internal reflection surfaces,  218 ,  220 , and  221  (best shown in FIG. 6 and described below). In another exemplary embodiment, cornercube  106  may have a plurality of total internal reflective surfaces. In one exemplary embodiment, cornercube  106  is formed from fused silica, sapphire, diamond, calcium fluoride or other optical glass. Note, optical quality glass, such as BK7 made by Schott Glass Technologies of Duryea, Pa., may also be used. Note also that materials for cornercube  106  can be selected for maximum transmission with respect to the desired operating wavelength.  
         [0039]    Optical imaging unit  102 , such as a CCD imager, CMOS imager or a camera, for example, is mounted above image plane  112  in order to receive an indirect image of bonding tool  104  through cornercube offset alignment tool  109 . In another exemplary embodiment, a position sensitive detector (PSD), such as that manufactured by Ionwerks Inc., of Houston, Tex., may also be used as optical imaging unit  102 . In such an embodiment, when the hole in bonding tool  104  is illuminated, such as by using an optical fiber for example, the PSD can be utilized to record the position of the spot of light exiting bonding tool  104 . It is also contemplated that the PSD may be quad cell or bi-cell detector, as desired.  
         [0040]    In the exemplary embodiment, the focal point of the vision system (coincident with imaginary plane  211  shown in FIG. 2A) is located above bottom surface  223  (shown in FIG. 2A) of cornercube  106 . In addition, the exemplary embodiment includes two preferably identical lens elements  108 ,  110  located at or below image plane  112 . Another embodiment, shown in FIG. 2B, includes a single lens element  205  located below image plane  112  and in line with optical axes  114 ,  116 . Hereinafter, the combination of cornercube offset tool  106 , and lens elements  108 ,  110  (or lens element  205 ) will be referred to as assembly  109 .  
         [0041]    Image plane  112  of cornercube  106 , including lens elements  108 ,  110 , is positioned at the object plane of optical imaging unit  102 . In other words, the object plane of cornercube  106  and lens elements  108 ,  110  are aligned to bonding tool  104  which also lies in image plane  112 . In the exemplary embodiment, lens elements  108 ,  110  (or  205 ) preferably have a unitary magnification factor. First lens element  108  is positioned in a first optical axis  114  between bonding tool  104  and cornercube  106 . Second lens element  110  is substantially in the same plane as that of first lens element  108  and is positioned in a second optical axis  116  between optical imaging unit  102  and cornercube  106 . In one exemplary embodiment, first and second optical axes  114  and  116  are substantially parallel to one another, and are spaced apart from on another based on specific design considerations of bonding machine  100 . In one exemplary embodiment the distance  118  between first optical axis  114  and second optical axis  116  is about 0.400 in. (10.160 mm.) although distance  118  may be as small as about 0.100 in. (2.54 mm) depending on design considerations related to the bonding machine.  
         [0042]    [0042]FIG. 2A is a detailed side view of image ray traces and illustrates the general imaging concept of an exemplary embodiment of the present invention. In FIG. 2A, exemplary ray traces  210 ,  214  are separated for clarity to illustrate the relative immunity of the resultant image due to positional changes. The same distance also separates the image points because lens elements  108 ,  110  serve as unitary magnification relays. FIG. 2A also demonstrates how changes in the bonding tool  104  position are compensated for. For example, once conventional methods have been used to accurately measure the distance between imaging unit  102  and bonding tool  104  (shown in FIG. 1), the present invention is able to compensate for changes in the bonding tool  104  offset position  222  due to changes in the system. The location of bonding tool  104  can be accurately measured because cornercube offset tool  106  images bonding tool  104  onto image plane  112  of the optical system.  
         [0043]    The reference position of bonding tool  104  is shown as a reflected ray which travels from first position  202  along first optical axis  114  (shown in FIG. 1), as direct image ray bundle  210  from first position  202  through first lens element  108 . Direct image ray bundle  210  continues along first optical axis  114  where it then passes through top surface  226  of cornercube  106  onto first internal reflection surface  218 . Direct image ray bundle  210  is then reflected onto second internal reflection surface  220 , which in turn directs it onto third internal reflective surface  221  (best shown in FIG. 3). Next, direct image ray bundle  210  travels back through top surface  226  of cornercube  106  as reflected image ray bundle  212  along the second optical axis  116  (shown in FIG. 1) and through second lens element  110  to image plane  112 . It is reflected image ray bundle  212  that is detected by imaging unit  102  as image  204 .  
         [0044]    Consider now that the position of bonding tool  104  is displaced by a distance  222  due to a variation in system temperature, for example. As shown in FIG. 2A, the displaced image of bonding tool  104  is shown as position  206  and imaged along the path of second position ray trace  214 . As shown in FIG. 2A, direct image ray bundle  214  travels along a path similar to that of direct image ray bundle  210  from first position  202 . Second position  206  image travels as a direct image ray bundle  214 , through first lens element  108 . Direct image ray bundle  214  then passes through top surface  226  of cornercube  106  onto first internal reflection surface  218 . Direct image ray bundle  214  is then reflected onto second internal reflection surface  220 , which in turn directs it onto third internal reflection surface  221  (best shown in FIG. 3). Next, direct image ray bundle  214  travels through top surface  226  of cornercube  106  as reflected image ray bundle  216  and through second lens element  110  to image plane  112 . Reflected image ray bundle  216  is viewed as a reflected image by imaging unit  102  as being in second position  208 . Although the above example was described based on positional changes along the X axis, it is equally applicable to changes along the Y axis.  
         [0045]    As illustrated, the original displacement of bonding tool  104 , shown as offset position  222 , is evidenced by the difference  224  in the measured location of bonding tool  104  at second position  208  with respect to reference location  204 . As evidenced by the above illustration, a positional shift in assembly  109  does not affect the reflected image as viewed by imaging unit  102 . In other words, assembly  109  of the present invention may be translated along one or both the X and Y axes such that the image of the bonding tool  104  appears relatively stationary to imaging unit  102 . There will be some minimal degree of error, however, in the measured position of bonding tool  104  due to distortion in the lens system (discussed in detail below).  
         [0046]    Referring again to FIG. 2A, vertex  228  (shown in phantom) of cornercube offset alignment tool  109  is located at a position approximately midway between first optical axis  114  and second optical axis  116 . To facilitate mounting of cornercube  106 , a lower portion  235  of the cornercube may be removed providing bottom surface  223 , which may be substantially parallel to top surface  226 . Removal of lower portion  235  does not affect the reflection of image rays since the image rays emanating from image plane  112  do not impinge upon bottom surface  223 .  
         [0047]    Exemplary cornercube  106  comprises top surface  226 , first reflective surface  218 , bottom surface  223 , second reflective surface  220 , and third reflective surface  221 . If top surface  226  is set such that optical axes  114 ,  116  are normal to top surface  226 , first reflective surface  218  will have a first angle  230  of about 45° relative to top surface  226 , and a second angle  234  of about 135° relative to bottom surface  223 . Likewise, ridgeline  225  (formed by the intersection of second and third reflective surfaces  220  and  221 ) has similar angles  232  and  236  relative to top surface  226  and bottom surface  223 , respectively. In addition, second and third reflective surfaces  220  and  221  are orthogonal to one another along ridgeline  225 . In the exemplary embodiment, bottom surface  223  of cornercube  106  may be used as a mounting surface if desired. It should be noted, however, that it is not necessary to form top surface  226  so that the image and reflected rays are normal thereto. As such, the corner cube will redirect the incident light or transmit image of bonding tool  104  parallel to itself with an offset equal to 118.  
         [0048]    The present invention can be used with light in the visible, UV and IR spectrum, and preferably with light having a wavelength that exhibits total internal reflection based on the material from which cornercube  106  is fabricated. The material selected to fabricate cornercube offset alignment tool  109  is based on the desired wavelength of light which the tool will pass. It is contemplated that cornercube offset alignment tool  109  may be fabricated to handle a predetermined range of light wavelengths between the UV (1 nm) to the near IR (3000 nm). In a preferred embodiment, the range of wavelength of light may be selected from between about i) 1 and 400 nm, ii) 630 and 690 nm, and iii) 750 and 3000 nm. Illumination may also be provided by ambient light or by the use of an artificial light source (not shown). In one exemplary embodiment, typical optical glass, having an index of refraction of 1.5 to 1.7, may be used to fabricate cornercube  106 . Note, the index of refraction is based upon the material chosen for maximum transmission at the desired operating wavelength. In one embodiment, cornercube offset alignment tool  109  has an index of refraction of about 1.517.  
         [0049]    [0049]FIG. 3 is a perspective view of image ray traces according to an exemplary embodiment of the present invention translated in a direction perpendicular to the separation of lens elements  108 ,  110 . The same image properties shown in FIG. 2A are also evident in FIG. 3. For example, the reference position of bonding tool  104  is represented by first position  302  and its image  304  is viewed as a first direct image ray  310  which travels along first optical axis  114  through first lens element  108 ; passes through top surface  226  of cornercube  106 ; strikes first reflective surface  218  of cornercube  106 ; travels through cornercube  106  in a path parallel to top surface  226 ; strikes second reflective surface  220 ; strikes third reflective surface  221  before exiting the cornercube  106  through top surface  226  and travels along second optical axis  116  through second lens element  110  onto image plane  112  and viewed by imaging unit  102  at position  304 . Positional displacement of bonding tool  104  is also shown in FIG. 3 and is illustrated by the path of the ray traces  314 ,  316  from second position  306  to second viewed position  308 .  
         [0050]    FIGS.  4 A- 4 B are perspective and side views, respectively, of an exemplary embodiment of the present invention illustrating lens elements  108 ,  110  and cornercube  106 . The two lens elements  108 ,  110  (or  205 ) are preferably doublets located above the cornercube  106  based on their focal distance from image plane  112  and imaginary plane  211 . Doublets are preferred based on their superior optical qualities. As illustrated in FIGS.  4 A- 4 B, an exemplary embodiment of cornercube  106  has three internal reflective surfaces,  218 ,  220  and  221 . As shown in FIG. 4B, the exterior edges of lens elements  108 ,  110  and cornercube  106  are coincident with one another.  
         [0051]    [0051]FIG. 5 illustrates the telecentricity of an exemplary embodiment of the image system of the present invention. As shown in FIG. 5, lens elements  108 ,  110  produce a unitary magnification and are arranged relative to cornercube  106  such that the telecentricity of the machine vision system is maintained. Note that front focal length  502  from lens element  108  to vertex  228  of cornercube  106  is equal to front focal  502  from lens element  110  to vertex  228  of cornercube  106 . Note also, that back focal length  504  from lens element  108  to image plane  112  is equal to back focal length  504  from lens element  110  to image plane  112 .  
         [0052]    [0052]FIG. 6 is a detailed view of an exemplary cornercube  106  of the present invention. Note that internal reflection surface,  218  and ridgeline  225  allow an image of bonding tool  104  to be translated in the X and Y directions. Note also, that the surfaces of cornercube  106  are preferably ground so that a reflected beam is parallel to the incident beam to within 5 arc seconds.  
         [0053]    As shown in FIG. 6, surfaces  220  and  221  are orthogonal to one another along ridgeline  225 . In addition, the angle between ridgeline  225  and surface  218  is about 90°. Furthermore, surface  218  and ridgeline form an angle of 45° relative to top surface  226  and bottom surface  223 . Note also, that surfaces,  218 ,  220 , and  221  meet to form triangular shaped bottom surface  223 , which may be used to facilitate mounting of cornercube  106 .  
         [0054]    FIGS.  7 A- 7 C illustrate the effect of tilt about the orthogonal of cornercube offset alignment tool  109  in an exemplary vision system. FIG. 7A is an overhead view of lens elements  108 ,  110  and cornercube  106 . Exemplary image origins,  702 ,  704 ,  706 , and  708  correspond to the position of image ray traces  210 ,  214  (shown in FIG. 2A). Note that optic axis position  710  corresponds to the position where the image of bonding tool  104  (shown in FIG. 1) would be if cornercube  106  was not tilted along the Z axis.  
         [0055]    FIGS.  7 B- 7 C are graphs of the effect of tilt around the Z axis in terms of tilt in arc minutes vs. error in microns. FIG. 7B shows the effect of tilt around the Z axis versus error and image location along the Y axis. FIG. 7C shows the effect of tilt around the Z axis versus error and image location along the X axis.  
         [0056]    FIGS.  8 A- 8 C illustrate the effect of tilt about the X and Y axis of the exemplary vision system. FIG. 8A is an additional side view of exemplary image ray traces  210 ,  212 ,  214 ,  216 . In FIG. 8A, arrow  804  and dot  802  are used to depict the X and Y axes, respectively.  
         [0057]    FIGS.  8 B- 8 C are graphs of the effect of tilt around the X and Y axes in terms of tilt in arc minutes vs. error in microns. FIG. 8B shows the effect of tilt around the X axis versus error and image location along the Y axis. FIG. 8C shows the effect of tilt around the Y axis versus error and image location along the X axis.  
         [0058]    [0058]FIG. 9 is a detailed side view of image ray traces according to a third exemplary embodiment of the present invention. In FIG. 9, the reference position of bonding tool  104  is shown as a reflected ray which travels from first position  914  (on image plane  112 ) along first optical axis  114  (shown in FIG. 1), as direct image ray bundle  922  from first position  914  through lens element  902 . Note that in this exemplary embodiment, lens element  902  has a relatively planar, upper surface  904  and a convex lower surface  906 . Direct image ray bundle  922  continues along first optical axis  114  where it then passes through upper surface  904  of lens element  902 , and in turn through convex surface  906 . Direct image ray bundle  922  is then reflected onto total reflective surface  908 . In a preferred embodiment, total reflective surface  908  is a mirror. Next, direct image ray bundle  922  travels back through lens element  902  as reflected image ray bundle  920  along second optical axis  116  (shown in FIG. 1) and onto image plane  112 . It is reflected image ray bundle  920  that is detected by imaging unit  102  (shown in FIG. 1) as image  912 . Similarly, positional displacement of bonding tool  104  is also shown in FIG. 9 and is illustrated by the path of direct image ray bundles  918 ,  924  from second position  910  to second viewed position  916 .  
         [0059]    FIGS.  10 A- 10 E illustrate a further embodiment of the present invention. In this exemplary embodiment, a cornercube alignment tool is used to improve the accuracy of alignment of fibers, such as optical fibers  1008  and  1009 . As in the previous exemplary embodiment, the use of a corner cube offset tool allows for the use of a single optical detector instead of the conventional multiple detector systems.  
         [0060]    Referring to FIG. 10A, the exemplary embodiment includes cornercube  1014 , lenses  1016 ,  1018 , dark field illumination systems  1020 ,  1021  (which are well known to those practicing the art) to illuminate the fiber cladding edge  1010 ,  1011  of fiber cores  1012 ,  1013 , respectively (which in turn produces reflections  1024 ,  1025  to outline cladding edges  1010 ,  1011 ), and optical detector  1002 . In this exemplary embodiment, downward facing fiber  1008  is viewed by downward looking optical detector  1002 , such as a camera (i.e., a substrate camera). Downward looking optical detector  1002  detects the emission of light  1022  from fiber core  1012  and is then be able to determine the proper offset  1027  between the optical fiber centerline  1023  and central ray  1029  of downward looking optical detector  1002 . As is further shown in FIG. 10A, downward facing fiber  1008  and optical detector  1002  are offset from one another by predetermined distance  1006 .  
         [0061]    [0061]FIG. 10B is a plan view of the exemplary embodiment illustrated in FIG. 10A illustrating the relative positions of lenses  1016  and  1018 , and cornercube  1014 .  
         [0062]    In FIG. 10C, downward looking optical detector  1002  and downward facing fiber  1008  are then repositioned such that central ray  1029  of downward looking optical detector  1002  is aligned with fiber centerline  1031  of upward facing fiber  1009 . Once again dark field illumination system  1021  is used to illuminate upward facing fiber  1009  for recognition by the vision system to ensure proper alignment with optical detector  1002 .  
         [0063]    Next, and as shown in FIG. 10D, optical detector  1002  and downward facing fiber  1008  are again repositioned based on the offset  1027  determined during the process discussed above with respect to FIG. 10A. As a result downward facing fiber  1008  and upward facing fiber  1009  are aligned with one another.  
         [0064]    As shown in FIG. 10E, optical fibers  1008  and  1009  are then joined using conventional techniques, such as fusing the fibers together using radiation (not shown), or mechanical means, for example.  
         [0065]    [0065]FIG. 12 illustrates yet a further embodiment of the present invention. In this exemplary embodiment, a cornercube alignment tool is used to align individual fibers (sub-fibers)  1202   a  of a fiber optic splitter  1200  with respective individual optical fibers  1008 , etc. As in the previous exemplary embodiment, the use of a corner cube offset tool allows for the use of a single optical detector instead of the conventional multiple detector systems. As the steps leading up to alignment and coupling of optical fiber  1008  and sub-fiber  1202  are similar to the above exemplary embodiment, they are not repeated here.  
         [0066]    Once the first sub-fiber is aligned with single fiber  1008 , the process is repeated for a further sub-fiber, such as  1202   b , and another single fiber (not shown).  
         [0067]    Of course the exemplary embodiment is not limited to the fiber optic bundle of a fiber optic splitter being below optical detector  1002 . The embodiment also contemplates that the relative positions of fiber optic bundle  1200  and optical fiber  1008  are reversed, such that fiber optic bundle  1200  is positioned above cornercube  1014 .  
         [0068]    FIGS.  13 A- 13 D illustrate a further embodiment of the present invention. In this exemplary embodiment, a cornercube alignment tool is used to improve the accuracy of alignment of an optical fiber  1008  with a circuit element, such as a detector  1302 . In FIG. 13A, exemplary detector  1302  is part of an array  1300 , although the invention is not so limited. It is also contemplated that circuit element  1302  may be a diode, such as a photodiode or an emitter of optical radiation. As in the previous exemplary embodiments, the use of a corner cube offset tool allows for the use of a single optical detector instead of the conventional multiple detector systems.  
         [0069]    Referring to FIG. 13A, the exemplary embodiment includes cornercube  1014 , lenses  1016 ,  1018 , dark field illumination system  1020  (which is well known to those practicing the art) to illuminate the fiber cladding edge  1010  of fiber core  1012  (which in turn produces reflections  1024  to outline cladding edge  1010 ), and optical detector  1002 . In this exemplary embodiment, downward facing fiber  1008  is viewed by downward looking optical detector  1002 , such as a camera (i.e., a substrate camera). Downward looking optical detector  1002  detects the emission of light  1022  from fiber core  1012  and is then be able to determine the proper offset  1027  between the optical fiber centerline  1023  and central ray  1029  of downward looking optical detector  1002 . As is further shown in FIG. 10A, downward facing fiber  1008  and optical detector  1002  are offset from one another by predetermined distance  1006 .  
         [0070]    In FIG. 13B, downward looking optical detector  1002  and downward facing fiber  1008  are then repositioned such that central ray  1029  of downward looking optical detector  1002  is aligned with optical centerline  1304  of detector  1302 . It is understood that optical centerline  1304 , may not necessarily coincide with the physical center of detector  1302 , but rather is dependant on the layout of the particular detector  1302 . In this case the determination of optical centerline  1304  may be accomplished by the location of the center of the active sensing area of the detector.  
         [0071]    Next, and as shown in FIG. 13C, optical detector  1002  and downward facing fiber  1008  are again repositioned based on the offset  1027  determined during the process discussed above with respect to FIG. 13A. As a result downward facing fiber  1008  and detector  1302  are aligned with one another. As shown in FIG. 13D, optical fiber  1008  and detector  1302  are then kept in aligned position using conventional techniques, such as optical epoxies, UV epoxies, for example.  
         [0072]    Although the invention has been described with reference to exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the true spirit and scope of the present invention.