A solid state imager converts analog pixel values to digital form on an
arrayed per-column basis. An N-bit counter supplies an N-bit DAC to
produce an analog ramp output with a level that varies corresponding to
the contents of the counter. A ripple counter or equivalent is associated
with each respective column. A clock supplies clock signals to the
counter elements. A comparator in each column gates the counter element
when the analog ramp equals the pixel value for that column. The contents
of the counters are transferred sequentially to a video output bus to
produce the digital video signal. Additional black-level readout counter
elements can create and store a digital value that corresponds to a dark
or black video level. A subtraction element subtracts the black level
value from the pixel value to reduce fixed pattern noise. An additional
array of buffer counter/latches can be employed. The 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 clock
pulses for the DAC counter and for the ripple counters can be at the same
or different rates.