Patent ID: 8772695
Filing Date: 2014-07-08
Classification: H04N

Abstract:
1. An image sensor, comprising: a plurality of pixels arranged in rows and columns to form a pixel array, each pixel column comprising at least two column bitlines, such that an output of each pixel is connected to one of the column bitlines of the column of which it is comprised; a readout input circuit comprising a plurality of first inputs and a second input, each of said first inputs and said second input being connected via a capacitance to a single comparator input node; and a readout comparator circuit connected to said single comparator input node, wherein the readout input circuit is operable such that each of said first inputs receives, in parallel, an analog signal, said analog signals being acquired from the signal output of one or more of said pixels via the column bitline to which the pixel is connected, said analog signals varying during a pixel readout period and having a first level during a first calibration period and a second level during a second read period; said readout input circuit being further operable such that said analog signals at said first inputs and a reference signal from a time varying reference circuit on said second input are constantly read onto their respective capacitances during both the first calibration period and the second read period; and wherein said readout comparator circuit is operable to compare an average of the signals on each of said plurality of first inputs to said reference signal.