Adaptive exposure control system
First Claim
1. Optical scanning apparatus employing adaptive scanner exposure control, comprising:
- an image sensor array of photosensitive pixel elements;
means for exposing said pixel elements during sequential exposure intervals of selectable duration for capturing sequential images of the portion of said surface within the field of view of said array;
means for reading out from said imaging array after each exposure interval thereof resulting digital data values for said pixel elements and providing sequential frames of binary-valued image data wherein one possible value for each pixel indicates a white pixel and the other possible value indicates a black pixel;
means responsive to a scanner "initiate" signal for adaptively determining an exposure interval duration for said surface, said means comprising a means for measuring the reflectivity of a background portion of said surface, comprising;
means for providing an initial exposure interval duration;
means for capturing an image of a background portion of said surface with said imaging array employing said initial exposure interval duration;
means for determining the number of black pixels in said resulting image;
means for repetitively adjusting said exposure interval duration, capturing an image of said background portion and determining the number of black pixels in said resulting image; and
means responsive to said black pixel number determinations for setting said exposure time to an exposure value which provides a substantially zero black pixel count in said image of said background portion.
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Accused Products
Abstract
An adaptive image acquisition system employing a hand-held optical scanner or camera is disclosed. The system includes an adaptive camera exposure control system to adjust the camera exposure time to the media'"'"'s reflectivity characteristics. The system assembles a "film-strip" of images from compressed video data, wherein redundant image data appearing in successive image frames has been removed. The system employs a correlation process between successive frames to identify the redundant frame information and determine the camera velocity. By adapting the correlation process to the velocity of the camera, the effects of variations in the velocity may be substantially eliminated.
56 Citations
10 Claims
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1. Optical scanning apparatus employing adaptive scanner exposure control, comprising:
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an image sensor array of photosensitive pixel elements; means for exposing said pixel elements during sequential exposure intervals of selectable duration for capturing sequential images of the portion of said surface within the field of view of said array; means for reading out from said imaging array after each exposure interval thereof resulting digital data values for said pixel elements and providing sequential frames of binary-valued image data wherein one possible value for each pixel indicates a white pixel and the other possible value indicates a black pixel; means responsive to a scanner "initiate" signal for adaptively determining an exposure interval duration for said surface, said means comprising a means for measuring the reflectivity of a background portion of said surface, comprising; means for providing an initial exposure interval duration; means for capturing an image of a background portion of said surface with said imaging array employing said initial exposure interval duration; means for determining the number of black pixels in said resulting image; means for repetitively adjusting said exposure interval duration, capturing an image of said background portion and determining the number of black pixels in said resulting image; and means responsive to said black pixel number determinations for setting said exposure time to an exposure value which provides a substantially zero black pixel count in said image of said background portion. - View Dependent Claims (2)
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3. An adaptive image acquisition system for acquiring digital data representative of images of a media surface being scanned, comprising:
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an optical camera, comprising an image sensor having a plurality of light sensitive pixel elements and means for illuminating said media surface with illumination light during successive exposure intervals so as to expose said pixels by illumination light reflected from said media surface; means for reading the status of each light sensitive pixel after each illumination interval and assigning a binary-leveled value in dependence on the status of said pixel element, the binary-leveled values comprising said digital data representation of the image acquired during said illumination interval; and exposure control means for adaptively controlling the duration of said exposure intervals in dependence on the reflectivity of a background portion of said media surface, said exposure control means comprising means for acquiring a plurality of exposure measurement images of a background portion of said media surface with different exposure interval durations, and means for determining the number of black pixels in said respective images and processing said black pixel numbers to determine said exposure interval duration which yields a minimal number of black pixels for said background portion of said surface. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10)
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Specification