Multi-electrode circular position-sensitive device (PSD) and its a

摘要

Abstract: Semiconductor position sensitive devices (PSD) enable to measure the position of a light spot using simple construction. A circular PSD, which has a circular photosensitive region, can be used for angular measurement. This paper presents a new type of circular PSD called Multi Electrode Circular PSD (ME-CPSD) and demonstrates its application for angular measurement. This device, constructed on Si substrate, has a photosensitive region, a resistor line and 16 output electrodes. The photosensitive region has the shape of a ring which is formed by a radial arrangement of long and narrow photodiodes. The outer end of the photodiodes are connected to the continuous resistor line. Photoexcited carriers which are generated in the photodiode by the incident light flow to the resistor line and are extracted by the multioutput electrode which divides the resistor into 16 equal parts. To measure the position of the light spot, a pair of electrodes is selected by switches connected to every electrode and the position of the light spot is calculated from the output current of the selected electrodes. Compared to conventional circular PSDs, the reliability of the angular measurement is improved, because the ME-CPSD does not have an undetectable region caused by the unavoidable discontinuity in the structure of conventional circular PSDs. This device can change its measuring range by selecting the pair of electrodes, making it not only capable of measuring any absolute angular position, but allows also a more precise angular measurement by selecting narrower electrode intervals. This device has the capability to realize a high precision noncontact angular measurement system with simple construction.!4