Black level calibration method for imager with hysteresis...

Television – Camera – system and detail – Combined image signal generator and general image signal...

Reexamination Certificate

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Details

C348S615000, C348S226100, C250S208100

Reexamination Certificate

active

07084911

ABSTRACT:
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.

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“Color CMOS Inage Sensor SXGA 18 FPS”,National Semiconductor Corporation, LM9648, May 2002, pp. 1-2.

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