Abstract:
A method of manufacturing an image sensor from two defective image sensor arrays having identical structural design, each having substantially the same field of view and aligned to view substantially the same scene. The method includes providing a first defective image sensor array, having known defective pixels, providing a second defective image sensor array, having known defective pixels, and fusing the first image sensor array and the second image sensor array into a single output image array.

Description:
RELATED APPLICATION 
       [0001]    The present application claims the benefit of U.S. provisional application 61/167,226 filed on Apr. 7, 2009, the disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to imaging systems, and more particularly, the present invention relates to a method of manufacturing an imaging system from two or more image sensors having defective pixels. 
       BACKGROUND OF THE INVENTION AND PRIOR ART 
       [0003]    In the production of image sensors, often, one or more pixels of the produced image sensor are defective. The image sensor arrays are scanned and all detected defective pixels are sorted out, mapped and marked. In some types of image sensors such a defective image sensor is rejected. In other types of image sensors such a defective image sensor is computed from the adjacently surrounding pixels, for example, from the 4 or 8 adjacently surrounding pixels. 
         [0004]    For Example, the yield of infra red (IR) image sensors is very low—about 0.1-5%, due to defective pixels. Therefore, there is a need for and it would be advantageous to have a method to substantially raise the production yield of image sensors, such as infra red image sensors. 
       SUMMARY OF THE INVENTION 
       [0005]    According to teachings of the present invention, there is provided a method of manufacturing an image sensor from two defective image sensor arrays having identical structural design, each having substantially the same field of view (FOV) and aligned to view substantially the same scene. The method includes providing a first defective image sensor array, having known defective pixels, providing a second defective image sensor array, having known defective pixels, and fusing the first image sensor array and the second image sensor array into a single output image array. 
         [0006]    For each of the defective pixels of the first image sensor array the respective pixel from the second image sensor array is selected to be an output pixel of the output image array. For each of the defective pixels of the second image sensor array the respective pixel from the first image sensor array is selected to be an output pixel of the output image array. For each valid pixel in the first image sensor array, having a respective valid pixel in the second image sensor array, either of the respective valid pixels is selected to be an output pixel of the output image array. 
         [0007]    Preferably, the first defective image sensor array and the second defective image sensor array have no overlapping defective pixels. 
         [0008]    In variations of the present invention, if the first defective image sensor array and the second defective image sensor array have overlapping defective pixels, then for each of the overlapping defective pixels, setting the value of a corresponding final output pixel in the output image array to be the average of the K immediately adjacent neighboring pixels of the overlapping defective pixel, in the output image array. In some variations of the present invention, K=4. In other variations of the present invention, K=8. 
         [0009]    According to further teachings of the present invention, there is provided a computerized image acquisition system. The system includes a first image sensor array having defective pixels, a second image sensor array having defective pixels, and an image fusion module. The first image sensor array and the second image sensor array have substantially the same FOV and are aligned to view substantially the same scene. For each of the defective pixels of the first image sensor array, the image fusion module selects the respective pixel from the second image sensor array to be an output pixel of an output image array. For each of the defective pixels of the second image sensor array, the image fusion module selects the respective pixel from the first image sensor array to be an output pixel of the output image array. For each valid pixel in the first image sensor array having a respective valid pixel in the second image sensor array, the image fusion module selects either of the respective valid pixels to be an output pixel of the output image array. 
         [0010]    Preferably, the first defective image sensor array and the second defective image sensor array have no overlapping defective pixels. 
         [0011]    In variations of the present invention, if the first defective image sensor array and the second defective image sensor array have overlapping defective pixels, then for each of the overlapping defective pixels, the image fusion module sets the value of a corresponding final output pixel in the output image array to be the average of the K immediately adjacent neighboring pixels of the overlapping defective pixel, in the output image array. In some variations of the present invention, K=4. In other variations of the present invention, K=8. 
         [0012]    In variations of the present invention, if the first defective image sensor array and the second defective image sensor array have overlapping defective pixels that have partial light energy sensitivity, a weighted average of the partially defective pixels is computed. The weights are directly proportional to the partial light energy sensitivity of each of the partially defective pixels. The computed weighted average is then assigned to the corresponding output pixel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The present invention will become fully understood from the detailed description given herein below and the accompanying drawings, which are given by way of illustration and example only and thus not limitative of the present invention, and wherein: 
           [0014]      FIG. 1  is a block diagram illustration of a camera system, according to embodiments of the present invention, built from two defective image sensors; 
           [0015]      FIG. 2  is a block diagram illustration of a camera system, according to variations of the present invention; 
           [0016]      FIG. 3  illustrates examples of a defective pixel having immediately adjacent valid pixels; and 
           [0017]      FIG. 4  illustrates examples beam splitter configuration for camera systems according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided, so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0019]    Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The methods and examples provided herein are only illustrative and not intended to be limiting. 
         [0020]    By way of introduction, a principal intention of the present invention includes providing a method for producing an imaging system having two or more defective image sensors, yielding a single logical valid image sensor. 
         [0021]    Reference is made to  FIG. 1 , which is a block diagram illustration of exemplary imaging system  100 , according to embodiments of the present invention. Imaging system  100  includes two defective image acquisition devices  110   a  and  110   b,  each of which includes respective an image sensor array,  130   a  and  130   b,  and an image fusion module  140  wherein the methodology of image fusion module  140  yields a single output image frame  150 . Both image acquisition devices  110  have substantially the same FOV and pointing substantially to the same distal object  20 . Image fusion module  140  selects valid pixels from either image sensors  130   a  and  130   b  to yield a single output image frame  150 . 
         [0022]    It should be noted that the manufacturing method of the present invention, substantially increases the image sensors production, for example, the yield of IR image sensors may increase to over 90%. 
         [0023]    Preferably, image sensor arrays  130   a  and  130   b  are selected such that there are no respective pairs of pixels, where both pixels are defective. 
         [0024]    The methodology of image fusion module  140  may be embodied in various methods. In a first embodiment, the methodology of image fusion module  140  includes the following steps:
       a) selecting image sensor  130   a  as the primary image sensor and image sensor  130   b  as the secondary image sensor; and   b) for each pair of respective pixels, performs the following steps:
           i. if the pixel of the primary image sensor is valid, setting the value of the corresponding output pixel in image frame  150  to be the value of the pixel of the primary image sensor; else   ii. setting the value of the corresponding output pixel in image frame  150  to be the value of the pixel of the secondary image sensor.   
               
 
         [0029]    In a second embodiment, the methodology of image fusion module  140  includes the following steps:
       a) selecting image sensor  130   b  as the primary image sensor and image sensor  130   a  as the secondary image sensor; and   b) for each pair of respective pixels, performs the following steps:
           i. if the pixel of the primary image sensor is valid, setting the value of the corresponding output pixel in image frame  150  to be the value of the pixel of the primary image sensor; else   ii. setting the value of the corresponding output pixel in image frame  150  to be the value of the pixel of the secondary image sensor.   
               
 
         [0034]    Reference is made to  FIG. 2 , which is a block diagram illustration of exemplary imaging system  200 , according to variations of the present invention. As in system  100 , imaging system  200  includes two defective image acquisition devices  110   a  and  110   b , each of which includes respective an image sensor array,  130   a  and  130   b.  Both image acquisition devices  110  have substantially the same FOV and pointing substantially to the same distal object  20 . Imaging system  200  further includes an image fusion module  140   a  which fusion module selects valid pixels from either image sensors  130   a  and  130   b  to yield a single output image frame  150   a,  an image fusion module  140   b  which fusion module selects valid pixels from either image sensors  130   a  and  130   b  to yield a single output image frame  150   b,  an averaging module  240 , which averaging module averages image frames  150   a  and  150   b  to yield a single output image frame  250 . 
         [0035]    In a third embodiment, the methodology of image fusion modules  140   a,    140   b  and averaging module  240  includes the following steps:
       a) performing the fusion method as in the first embodiment, thereby creating an output image frame  150   a ;   b) performing the fusion method as in the second embodiment, thereby creating an output image frame  150   b;  and   c) averaging each pair of pixels from image frames  150   a  and  150   b  whereby setting the value of a corresponding final output pixel in image frame  250 .       
 
         [0039]    In variations of the present invention, image sensor arrays  130   a  and  130   b  are selected such that there are a limited number of respective pairs of pixels, where both pixels are defective. Reference is also made to  FIG. 3 , which illustrates examples of a defective pixel  134  having immediately adjacent valid pixels  132 . In such cases, at least one of image sensor arrays  130   a  and  130   b  are selected such that the mutual defective pixels  134  have no immediately adjacent defective pixel  134 . For the purpose of a clear description, with no limitation, image sensor arrays  130   a  is taken as the image sensor array that has no immediately adjacent defective pixels  134 . In such variations of the present invention, for each pair of mutual defective pixels  134 , the value of a corresponding final output pixel in image frame  250  is set to be the average of the K immediately adjacent neighboring pixels  132  of the defective pixel  134 , in image sensor arrays  130   a.    FIG. 3  illustrates two examples: in one example K=4 and in the other, K=8. 
         [0040]    In other variations of the present invention, image sensor arrays  130   a  and  130   b  are selected such that there are a limited number of respective pairs of pixels, where both pixels are partially defective. The output pixel is proportionally average from the partially defective pixels. For example, pixel P i a senses 60% of the arriving energy and pixel P i b senses 75% of the arriving energy. In such a case the output pixel P i out is averaged as follow: 
         [0000]        P   i out=( P   i   a* 60+ P   i   b* 75)/130. 
         [0041]    Reference is also made to  FIG. 4 , which illustrates examples beam splitter configuration for camera systems ( 100 ,  200 ) according to the present invention. In such variations, image acquisition devices  110   a  and  110   b  share a single front lens  170  and the incoming light is split by beam splitter  180  into two beams, where a first beam is directed towards image sensor arrays  130   a  and the second beam is directed towards image sensor arrays  130   a.    
         [0042]    The invention being thus described in terms of embodiments and examples, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the claims.