Photodetector having an integrated function for elimination of the effects of stray light

摘要

A photodetector for measuring the position of an incident light beam on an active surface area of the detector includes an inactive area and a concentric stray light absorbing area, both of which outwardly surround the light-absorbing active area. All light incident on the stray light- absorbing area and the inactive area will generate a photoelectric current which is conducted to an earth ground via an electrode in the stray-light area. An electrical signal from the active area representing a position of the measured light in the active area will be unaffected by any stray light incident on the detector externally of the active area.