2. Technique description
Fig. 1a illustrates the standard operation of an optical
mouse for opaque object sensing. A light emitting diode
(LED) illuminates the surface at an angle. A lens is used
to image the surface of the mouse pad onto a CMOS sensor
located in the camera chip. The off-axis illumination by the
LED helps to put the tiny textures on the surface in sharp
contrast. The CMOS sensor typically comprises 18 by 18
pixels (324 pixels in total). The mouse works by comparing
the images of the surface that are refreshed approximately