Automatic focusing apparatus having a variable focusing speed and particularly suited for use with interlaced scanning

Abstract From the Canadian patent

In an automatic focusing apparatus of a video camera, a first focus evaluating value which steeply changes and a second focus evaluating value which gently changes relative to the position of a lens are detected in, response to a video signal obtained in an image sensing circuit. A switching circuit alternately selects the first and second focus evaluating values every one field to apply the same to in-focus state detecting circuits respectively. The in-focus state detecting circuits together with a focusing motor control circuit, perform an automatic focusing operation by hill-climbing control. In addition a calculating circuit calculates the relative ratio of the first focus evaluating …