With the advance of processing ability of processors, more autonomy is expected for various kinds of robots. To enhance the autonomy of robots, various sensors are employed on robots. Especially, we can derive various information such as speed, distance, object, material from vision sensor. However, to extract these information from vision sensor and realize realtime image processing, vision sensor should be more intelligent and have pre-processing ability on itself. We employed a silicon retina sensor as vision sensor and add higher level functions using FPGA. In this paper, we explain velocity estimation of mobile robot by using optical flow obtained from silicon retina.