Abstract:
A fast frame-rate imaging device is produced by a attaching a fiberoptic block to an otherwise ordinary and inexpensive CCD. A part of the fiberoptic block is occluded so as to darken a majority of the active imaging photocells. The CCD imaging device is operated at near its maximum horizontal and vertical clock rates, but multiple image frames are defined within the one previous active photocell array field. The added dark areas in the optical field protect the recent frames still in transit within the active array area from being double exposed and thus corrupted. The serial output of the thus-modified CCD imaging device is reinterpreted to include more frames than originally at a multiple equal to the original array dimension divided by the new array dimension (m·n/m′·n′). Such a modified CCD array uses only one-fourth of the original active area, and is operable at a multiple of the original frame rate.

Description:
FIELD OF THE INVENTION 
     The present invention relates to electronic imaging devices, and more particularly to semiconductor processing methods for producing varieties of otherwise ordinary and inexpensive CCD array devices that can operate faster than one hundred frames-per-second. 
     DESCRIPTION OF THE PRIOR ART 
     U.S. Pat. No. 6,255,134 B1, issued Jul. 3, 2001, to one of the present inventors, Toshikazu Hori, describes a modification to an otherwise standard CCD imaging device that can improve its performance. Such comprises modifying the optical mask of an otherwise ordinary and inexpensive CCD integrated circuit to darken a majority of the active imaging photocells. The CCD integrated circuit is operated at near its maximum horizontal and vertical clock rates, but multiple image frames are defined within the one previous active photocell array field. The added dark areas in the optical mask protect the recent frames still in transit within the active array area from being double exposed and thus corrupted. The serial output of the thus-modified CCD device is reinterpreted to include more frames than originally at a multiple equal to the original array dimension divided by the new array dimension (m·n/m′·n′). So a modified CCD array that used only one-fourth of the original active area could be operated at four times the original frame rate. Such Patent is incorporated herein by reference. 
     A certain minimum production quantity is necessary to justify changing or adding a new mask to a commodity CCD device. When the needed volumes of pieces are too low to interest a semiconductor producer, something else is needed to accomplish the same ends as described in the above Patent. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a CCD imaging device that can operate at frame rates over one hundred frames-per-second. 
     It is another object of the present invention to provide a CCD imaging device that is inexpensive to manufacture. 
     It is a further object of the present invention to provide a method for modifying an inexpensive CCD imaging device that can be done economically in low production volumes. 
     Briefly, a CCD imaging device embodiment of the present invention comprises attaching a fiberoptic block to an otherwise ordinary and inexpensive CCD integrated circuit. A part of the fiberoptic block is occluded so as to darken a majority of the active imaging photocells. The CCD integrated circuit is operated at near its maximum horizontal and vertical clock rates, but multiple image frames are defined within the one previous active photocell array field. The added dark areas in the optical field protect the recent frames still in transit within the active array area from being double exposed and thus corrupted. The serial output of the thus-modified CCD device is reinterpreted to include more frames than originally at a multiple equal to the original array dimension divided by the new array dimension (m·n/m′·n′). Such a modified CCD array uses only one-fourth of the original active area, and is operable at a multiple of the original frame rate. 
     An advantage of the present invention is that a CCD imaging device is provided that can operate at frame rates over one hundred frames-per-second and is inexpensive to manufacture. 
     Another advantage of the present invention is that a CCD imaging device with a very fast frame rate is obtainable by attaching a fiberoptic block aperature to an otherwise ordinary and commodity type CCD imaging device. 
     These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the drawing figure. 
    
    
     IN THE DRAWINGS 
     FIG. 1 is a functional block diagram of a fast frame-rate CCD imaging device embodiment of the present invention that has been implemented by modifying a Kodak KAI1001; 
     FIG. 2 is an exploded assembly diagram that shows on the left the prior art device that uses most of the active photocells, on the right is shown a modified assembly and product of the present invention where a fiberoptic block with occluded portion is used that darkens most of the otherwise available active photocells; 
     FIG. 3 is a diagram that represents the prior art fiberoptic block with occluded portion normally included in conventional devices like the Kodak KAI1001, and shows that the top two rows and the bottom twelve rows of active photocells are blocked, as are the first three columns and the last forty columns; 
     FIG. 4 is a diagram that represents a fiberoptic block with occluded portion of the present invention that would replace the one of FIGS. 2 and 3 in devices like the Kodak KAI1001, and shows that the top two rows and the bottom two hundred rows of active photocells are blocked, as are the first three columns and the last three hundred columns; and 
     FIG. 5 is a functional block diagram that represents an application of a fast frame-rate CCD imaging device system embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A fast frame-rate CCD imaging device embodiment of the present invention is illustrated in FIG.  1  and is referred to herein by the general reference numeral  100 . The system  100  includes an integrated circuit (IC)  102  on which is fabricated a plurality of vertical shift registers  104 - 107  connected to feed a horizontal shift register  108 . In a typical CCD device like the Kodak KAI0372, there will be 811 vertical shift registers that are 508 pixels tall that build an array that is about 410K pixels. The effective pixel array of a Kodak KAI0372 is 768(H) by 494(V) for an array of about 380K pixels. An output unit  110  amplifies the serial output of the horizontal shift register  108  to produce a video output (Vout) on a package pin “11”. 
     A pair of fiberoptic apertures  112  and  114  are limited to an exposure of less than half of these 768(H) by 494(V) pixels in a Kodak KAI0372. Such has been modified in this example according to the present invention by attaching a fiberoptic block with an occluded portion. 
     As a consequence, a group of active photo-sensitive photocells  116 - 121  have been dived by fiberoptic aperture  112  into still-exposed photocells  116 - 118  and newly occluded photocells  119 - 121 . Similarly, a group of active photo-sensitive photocells  122 - 127  have been divided by fiberoptic aperture  114  into still-exposed photocells  122 - 124  and newly occluded photocells  125 - 127 . A group of remaining photocells  128 - 139  are all permanently darkened by the occlusions in the attached fiberoptic block. 
     FIG. 1 is simplified to show only an array four wide (4H) by six high (6V) for a total active matrix area of twenty-four pixels. Actual device embodiments of the present invention will have arrays much larger than the simple one represented in FIG.  1 . Fiberoptic apertures  112  and  114  only allow two columns of pixels, three pixels high, to receive an image. So a new frame is defined herein to have a matrix area of six pixels, or one fourth the size of an array that would be possible if all photocells  116 - 139  are exposed. 
     The advantage is, this six pixel array can be exposed at four times the rate the larger twenty-four pixel can, given the same vertical and horizontal transfer clocking rates. 
     In operation, photocells  119 - 121  act as temporary storage for photocells  116 - 118 . Similarly, photocells  125 - 127  act as temporary storage for photocells  122 - 124 . Photocells  128 - 139  provide zero values that are clocked into horizontal register  108 . Such zero values are overwritten by values provided by photocells  116 - 118  and  122 - 124  in subsequent frames. 
     In the following tables, the two vertical shift registers  104  and  105  that are connected in FIG. 1 to the unblocked photocells  116 - 118  and  122 - 124  are each represented as two columns six pixels high. The bottom row of twenty-four pixels represents the horizontal shift register  108 . Each time the device  100  is clocked, the vertical shift registers move their photocell-captured information down one stage and the horizontal shift register moves such left one stage. The photocell-captured information that drops out the bottom of each vertical shift register is deposited into the cell immediately below in the horizontal shift register. The output of device  100  is taken from the left-most cell of the bottom row of twenty-four pixels. 
     Table I shows the starting condition where frame- 1 , consisting of a 2×3 array, is captured. 
     
       
         
               
             
           
               
                 TABLE I 
               
               
                   
               
               
                 Frame-1 is captured 
               
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
         
       
     
     Table II shows the situation three clocks later where the frame- 1  2×3 image has been shifted down into the cells darkened by the modified fiberoptic block with occluded portion of the present invention. This permits an electronic shutter to capture frame- 2  in the 2×3 array represented by photocells  116 - 118  and  122 - 124 . 
     
       
         
               
             
           
               
                 TABLE II 
               
               
                   
               
               
                 Frame 1 is Shifted, Frame-2 is Captured 
               
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
         
       
     
     Table III shows the situation another three clocks later where the frame- 1  2×3 image has been shifted down into the horizontal shift register and shifted left. The frame- 2  2×3 image now resides in the cells darkened by the modified fiberoptic block with occluded portion of the present invention. The electronic shutter can then capture frame- 3  in the 2×3 array represented by photocells  116 - 118  and  122 - 124 . 
     
       
         
               
             
           
               
                 TABLE III 
               
               
                   
               
               
                 Frames-1, 2 are Shifted, Frame-3 is Captured 
               
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
         
       
     
     Table IV shows the situation another three clocks later where the frame- 1  2×3 image has been shifted left another three cells and frame- 2  has been shifted down from the vertical shift registers and then left in the horizontal shift register. The frame- 3  2×3 image now resides in the cells darkened by the modified fiberoptic block with occluded portion of the present invention. The electronic shutter can then capture frame- 4  in the 2×3 array represented by photocells  116 - 118  and  122 - 124 . 
     
       
         
               
             
           
               
                 TABLE IV 
               
               
                   
               
               
                 Frames 1-3 are Shifted, Frame-4 is Captured 
               
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
         
       
     
     Table V shows the situation three more clocks later where the frame  1  and  2  images have been shifted left another three cells and frame- 3  has been shifted down from the vertical shift registers and then left in the horizontal shift register. The frame- 4  2×3 image now resides in the cells darkened by the modified fiberoptic block with occluded portion of the present invention. The electronic shutter can then capture frame- 5  in the 2×3 array represented by photocells  116 - 118  and  122 - 124 . 
     
       
         
               
             
           
               
                 TABLE V 
               
               
                   
               
               
                 Frames 1-4 are Shifted, Frame-5 is Captured 
               
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
         
       
     
     Table VI shows the situation three more clocks later where the frame  1 - 3  images have been shifted left another three cells and frame- 4  has been shifted down from the vertical shift registers and then left in the horizontal shift register. The frame- 5  2×3 image now resides in the cells darkened by the modified fiberoptic block with occluded portion of the present invention. The electronic shutter can then capture frame- 6  in the 2×3 array represented by photocells  116 - 118  and  122 - 124 . The very first output from the device will occur on the next clock cycle from the left-most cell of the horizontal shift register. It should be clear from the contents of the horizontal shift register represented in Table VI that some sorting will be required to undo the mixture of frames  1 - 4  that has occurred. In an unmodified CCD device, the horizontal shift register at this point would contain only one frame of information, not four frames. So this is how the embodiments of the present invention are able to multiply the frame rate of an otherwise ordinary CCD device, albeit at reduced resolution. 
     
       
         
               
             
           
               
                 TABLE VI 
               
               
                   
               
               
                 Frames 1-5 are Shifted, Frame-6 is Captured 
               
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
         
       
     
     FIG. 2 illustrates a prior art commodity CCD imaging device  200  that is converted by a method embodiment of the present invention into a modified CCD imaging device  204  having improved speed. Both, for example, use a dual inline pin (DIP) ceramic package  206 . In the prior art device  200 , a semiconductor chip  208  ordinarily includes an optical mask  210  with a large aperture that creates an active imaging area  212 . 
     As part of the modification embraced by the present invention, a fiberoptic block  214  is bonded directly to the semiconductor chip  208  and optical mask  210 . An optical epoxy is preferably used for such attachment. A clear area coherent-light conduit  216  is surrounded by an occluded space  218 . The occluded space  218  typically provides five decades of light attenuation and may be constructed of black glass. 
     Such clear area conduit  216  typically comprises many parallel fiberoptic light pipes with a pitch finer than the pixel spacing pitch of the imaging photocells in the active imaging area  220  of semiconductor chip  208 . For example, a pitch of four microns is a practical size that would be used in many applications. 
     Material mechanical matching and differences in the thermal coefficients of expansion should be considered. The occluded space  218  may comprise darkened glass, or a sawed off and re-attached fiberoptic block with its parallel fiberoptic light pipes turned orthogonal to the clear area conduit  216  direction of light travel. The advantage of that would be a perfect mechanical match between the transmissive and non-transmissive parts of the fiberoptic block  214 . 
     The attachment of the fiberoptic block  214  to the semiconductor chip  208  and optical mask  210  is such that minimal light leakage occurs between pixels at an interface at an active imaging area  220 . The fiberoptic block  214  may also be stepped around its perimeter shoulders to allow secondary attachment to the device package  206 . The occluded space  218  creates an imaging area  220  that uses a minority of the CCD photocells arrayed within the chip  208 . A frame-rate multiplication during use is made possible by clocking the photocell image information from the unblocked CCD imaging photocells in area  220  into the permanently darkened CCD imaging photocells when a next image frame exposure occurs. 
     FIG. 3 represents an optical mask  300  that is normally included in conventional devices like the Kodak KAI0372. A large aperture  302  allows all but the top two rows, the bottom twelve rows, the first three columns, and the last forty columns of active photocells to receive light. 
     FIG. 4 is a diagram that represents a fiberoptic block with occluded portion of the present invention that would attach to a CCD device like the Kodak KAI0372. An aperture  402  allows all but the top two rows, the bottom two hundred rows, the first three columns, and the last three hundred columns of active photocells to receive optical images. 
     FIG. 5 represents an application of a fast frame-rate CCD imaging device system embodiment of the present invention, and is referred to herein by the general reference numeral  500 . A fast frame-rate CCD imaging device  502  is connected to a horizontal rate timing clock  504  and a vertical rate timing clock  506 . A vertical sync signal  508  and a horizontal sync signal  510  are both derived from a system oscillator  512 . An output signal  513  contains a serially scrambled mixture of more than one image frame. A buffer  514  amplifies the signal for a sample and hold unit  516 . An analog-to-digital converter (ADC)  518  produces a binary digital word equivalent of the analog image signals captured by the CCD  502 . A sorter  520  writes a digital memory array with the digitized image signals as they are received. It then sorts them into corresponding frames for an organized frame-by-frame output signal  522 . Sorter  520  is described here as a digital device, but an analog sorter based on CCD memory technology could alternatively be substituted in front of the ADC  518 . 
     Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that the disclosure is not to be interpreted as limiting. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alterations and modifications as fall within the true spirit and scope of the invention.