Abstract
A semiconductor image position sensitive device (PSD) is widely used in various measuring systems because of its simplisity of instrumentation and high speed sensing capablity of the position of a light spot as its gravity center. In order to increase the image position sensing precision, the dividing resistance should be manufactured in high accuracy. However, it is very difficult to manufacture uniformly distributed dividing resistance layer in the conventional type PSD. In order to overcome the above difficulty, a concentrated dividing resistor type PSD, in which dividing resistor is constructed separately from the photo-sensitive elements as a concentrated resistor and separately formed photo-sensitive elements are connected to it. A dividing resistor can be manufactured stably and correctly by this scheme. A comb structured PSD is proposed and trialy manufactured as a realization of the new scheme. On the contrary, the comb structure may bring the deviation in detecting characteristics which are caused by its periodic structure. Because of this reason, the interval of teeth is one of the important factors in designing the comb structured PSD. In this study, image position sensing characteristics of the comb structured PSDs which had been manufactured in trial are measured in connection with the size of the light spot. Then the influence of the light spot size to the image position sensing characteristics have been analized. Considering the above experimental results, several methods to decreasing the deviation of image position sensing characteristics caused by the comb teeth structure have been investigated and proposed.
