Imaging device and imaging method thereof

The invention relates to an imaging device which comprises a pixel array. The pixel array includes a plurality of pixels which are arrayed into lines and rows, and a plurality of column circuits, wherein each column circuit corresponds to one row of pixels in the pixel array. Each column circuit comprises a comparator and a radix-minus-one complement counter, wherein the comparator compares signals from pixels of a corresponding row with ramp signals, and the radix-minus-one complement counter counts and conducts radix-minus-one complement calculation on output signals of the comparator.