Abstract
An image sensor chip and a sensing method thereof are provided. The image sensor chip includes a pixel array. The pixel array includes a plurality of pixel units, and each of the pixel units includes a light sensing circuit, a reset switch and an output circuit. The reset switch is coupled to a first terminal of the light sensing circuit. The reset switch resets the light sensing circuit during reset period. The output circuit is coupled to the first terminal of the light sensing circuit. The output circuit of the pixel unit outputs difference information corresponding to the difference between the first sensing result of the light sensing circuit in a first frame period and the second sensing result of the light sensing circuit in a second frame period after the first frame period to a corresponding one of a plurality of readout lines of the pixel array.