Device for detecting the movement of a surface of an object

摘要

A light emitting diode (7) directs light through a prism (8) and an aperture (3) to a field (4) of the surface of a tracker ball (1). Reflected light is focussed by a lens (10) on to an optoelectronic sensor (13). The light emitting diode, prism and optical system are all supported by the printed circuit card (6) such that their mutual positions are precise and stable. The prism and lens are mounted on a common frame (12) which clips to the printed circuit card