Image sensor with single-slope scheme using 2-step structure and multiple differential ramping up/down signal, processing the same, and image processing device having the image sensor

Method of operating an image sensor for generating a plurality of ramping up / down signal (a) step and the pixel signal and the up / down signal a first ramp of the plurality of ramping up / down signal output from during the reset period of pixels and a comparison step (b) to. The method in one or more of the sampling time for the image period, the pixel signals of the first ramp-up / down, and (c) comparing the signal, wherein step (c) on the basis of the result of the step of the plurality of ramping up / a down signal in the step of outputting a second ramp up / down signal of the further included.