FOCUS STATE DETECTOR

摘要

A focus state detector has light receiving transducers (6A, 6B) formed so that the light levels received on the respective light receiving surfaces (5A, 5B) differ depending on the distance from an object that is to be viewed or photographed. In conventional focus state detectors for detecting whether an optical image of an object is in a correct focusing state with the image clearly formed at a predetermined image forming surface, if the object to be photographed is dark, or if a dark-ground optical system is used, the detector output of the or each light receiving transducer element will generally be so small that focus state detection is virtually impossible, or at best the precision of the focus state detection will be relatively low. To overcome this problem means project a light onto an object (9) through a small aperture (4) to provide a spot illumination for focus state detection, and the light receiving transducer means (6A, 6B) are so formed that the light levels reaching the respective light receiving surfaces (5A, 5B) differ depending on distance from the object (9).