Automatic focus detecting device

摘要

An automatic focus detecting device comprising an image sensor for electrically converting distributions of two images of an object which are formed by two restricted light beams passed through different areas in a zooming lens system into time sequence video signals which in turn are extracted at predetermined extraction intervals and directed to a correlator for deciding the degree of agreement between the two images. The video signal extraction is effected in two operation modes; one is for a high accuracy focus detection and the other for a rough accuracy focus detection. In the former operation mode, a time sequence video signal of a narrow image is extracted at short intervals and on the other hand, in the latter operation mode, a time sequence video signal of a wide image is extracted at long intervals. The automatic focus detecting device is set up to the rough accuracy focus detection mode in the early stage of operation and changed to the high accuracy focus detection mode when a rough focus detection is attained.