A fine-line-spot-position (FLSP) sensitive photodetector

A new fine-line-spot-position (FLSP) sensitive photodetector is described in which the signal is the ratio of the short-circuit photocurrents induced in a pair of adjacent Schottky-barrier or shallow p-n junction diodes, fabricated on the same semiconductor chip. The analysis of the new structure is given, and its theoretical feasibility is demonstrated. Because a finely focused light beam is used in this new detector, the light-spot position can be measured with very high accuracy, without requiring a beam with uniform intensity over its entire cross section. Furthermore, because the signal is the ratio of two currents, it is not affected by possible temperature and light-intensity fluctuations.