Inside each optical mouse is a powerful camera. The camera is capable of taking about 1500 pictures per second. Below the mouse is a red LED light . From this the light falls on the surface and is reflected back to the CMOS sensor . This sensor sends each image to a digital signal processor for analysis. The digital signal processor analyzes each image, distinguishes between its pre- and post-image, and the signal is transmitted to the computer accordingly, and we see the mouse cursor move on the computer screen as the output.