Invention Grant
US08179455B2 Optical black-level cancellation for optical sensors using open-loop sample calibration amplifier 有权
使用开环采样校准放大器的光学传感器的光学黑电平消除

Optical black-level cancellation for optical sensors using open-loop sample calibration amplifier
Abstract:
A Optical Black Pixel (OBP) cancellation circuit corrects offsets in sensors in a CCD/CMOS image sensor when reading dark pixels such at the periphery. A pixel voltage is switched to a sampling capacitor during two phases of the same pixel pulse. Sampling capacitors and feedback capacitors connect to differential inputs of an amplifier. An accumulating capacitor accumulates voltage differences and generates a common-mode voltage that is fed back to another sampling capacitor that stores an amplifier offset. The sampling capacitor and accumulating capacitor and their associated switches form a discrete-time first-order low-pass filter that filters the pixel voltage during the first phase. In the second phase the amplifier acts as a unity-gain amplifier to output an average of the pixel voltage differences generated during an OBP time when blackened or covered pixels are read from the image sensor.
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