Eastman-kodak Company

National Semiconductor Corporation

Andrew Kenneth John McMahon

David Michael Boisvert

Bumha Lee

Joseph D Clark

Michael Joseph Maigret

Robert James LeBoeuf Ii

The present invention provides a method and apparatus for calibrating a black level in an imager to reduce flicker noise. A first and a second range is set. The first range corresponds to a range that is larger than a noise level at a highest PGA gain. The second range corresponds to a range that is smaller than a level which reduces an ADC dynamic range too much due to a large black level. The ranges may be adjusted to changes in an imager in real time. When the black level is within the second range a determination is made as to whether the black level has been calibrated before. When it has, the DAC output is held constant. Otherwise the DAC code is adjusted such that the black level is moved toward the first range. A small step size is used in adjusting the DAC code in order to reduce flicker. Step sizes may be adjusted according to the black level in relation to the ranges. A small step size is used when the black level is within the second range. A large step size is used when the black level is beyond the second range.

Black level calibration method for imager with hysteresis comparison and adaptive step size

A linear pixel-array processing systems uses a combination of digital and analog signal processing techniques to calibrate the gain and offset of each pixel in the analog domain. A plurality of fixed gain and offset values are applied in the analog domain to adjust the gain and offset of each pixel at high speeds (on the order of 25&#x2013;50 MHz). By adjusting the gain and offset in the analog domain, the dynamic range of pixel conversion is improved such that the conversion range is fully utilized (over 90%, on the order of 95%&#x2013;99%). The gain and offset values are determined with an algorithmic calibration routine that corrects for non-ideal effects in the signal path. A single processing channel can be multiplexed to process multiple pixel arrays to provide for a cost effective solution. In higher speed systems, the single processing channel can be extended to multiple processing channels for improved throughput.

Pixel processing system for image scanning applications

The reduced signal-to-noise ratio of colored pixels that results from a lower conversion efficiency is eliminated by utilizing a programmable gain amplifier which individually applies a gain to the output of each colored pixel so that the maximum signal level of each colored pixel is matched to the maximum input range of an A/D converter.

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Sunnyvale, CA, United States of America

Andrew Kenneth John McMahon