IMAGE SENSOR ADC AND CDS PER COLUMN

摘要

A solid state imager converts analog pixel values to digital. A counter (16) coupled to an N-bit DAC (20) produces an analog ramp corresponding to the contents of the counter. A ripple counter (90, 92) is associated with each respective column. Column comparators (22) gate the counter elements when the analog ramp equals the pixel value. The counter contents feed a video output bus to produce the digital video signal. Additional black-level readout counters elements (26) can create and store a black level values for reduction of fixed pattern noise. Additional buffer counter/latches can be employed. Ripple counters can be configured as counters to capture the digital video level, and then as shift registers to clock out the video levels to an output bus. The clocks for the DAC counter and ripple counters can be at the same or different rates.