Techniques for motion detection are presented. An image sensor for motion detection includes a plurality of analog comparators and a two-dimensional pixel array including a plurality of rows of pixels and a plurality of columns of pixels. Each pixel is configured to convert an optical signal on the pixel into an analog signal. The two-dimensional pixel array is organized into a plurality of groups of pixels each associated with a combined group signal determined based on the analog signals from pixels in the group of pixels. Each analog comparator includes two inputs and is used to compare combined group signals generated by two groups of pixels of the plurality of groups of pixels during a same time period to generate a 1-bit inter-pixel digital signal, where each of the two groups of pixels is coupled to a corresponding input of the two inputs of the each analog comparator.