US Patent 9876946 Imaging device and electronic device

An imaging device with low power consumption is provided. A pixel circuit has a configuration of detecting difference data between data of a reference frame and data of a target frame in a pixel, and a peripheral circuit has a configuration of efficiently converting the difference data by A/D conversion so as to obtain high compressibility. Difference data which is encoded by compression is written into a memory element and read sequentially. At this time, the frequency of a clock signal can be lowered in accordance with the amount of data. The read data is expanded and the expanded data is added to the reference frame to constitute an image.