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12 May 2006 New high-dynamic-range camera architecture
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The need for high (wide) dynamic range cameras in the Security and Defense sectors is self-evident. Still the development of a cost-effective and viable system proves to be an elusive goal. To this end we take a new approach which meets a number of requirements, most notably a high "fill" factor for the associated APS (active pixel sensor) array and a minimal technology development curve. The approach can be used with any sensor array technology supporting, on a granular level, random pixel access. To achieve high dynamic range one of the presented camera systems classifies image pixels according to their probable brightness levels. Then it scans the pixels according to their probable brightness, with the pixels most likely to be the brightest being scanned first and the pixels most likely to be the darkest, last. Periodically the system re-adjusts the scanning strategy based on collected data or operator inputs. The overall exposure time is dictated by the sensitivity of the selected array and by the content and frame rate of the image. The local exposure time is determined by the predicted pixel brightness levels. The prediction method we use in this paper is simple duplication; i.e. the brightness of the vast majority of pixels is assumed to change little from frame to frame. This allows us to dedicate resources only to the few pixels undergoing large output excursions. Such approach was found to require only minimal modifications to standard APS array architectures and less "off-sensor" resources than CAMs (Content Addressable Memory) or other DSP intensive methods.
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Andrei Cernasov "New high-dynamic-range camera architecture", Proc. SPIE 6246, Visual Information Processing XV, 624608 (12 May 2006);

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