Method of monitoring focusing condition using rate of change signal at a border in a semiconductor image position sensitive device

摘要

Disclosed is a method of monitoring the state of focusing of an image on a semiconductor image position sensitive device of the type having a photosensitive layer, a resistance layer provided on the photosensitive layer and output terminals provided on the resistance layer. In this method, a bright spot image is moved across a border between a light- insensitive or non-sensitive zone and a light-sensitive zone. The rate of change in the level of an output signal obtained when the bright spot image is moved across the border is then detected. The degree of focusing of the bright spot image is then derived from the state of change in the level of the output signal.