Automatic focusing apparatus for automatically adjusting focus in response to video signal by fuzzy inference

摘要

An automatic focusing apparatus of a video camera automatically matches a focus in response to a video signal obtained from an image sensing circuit. The automatic focusing apparatus detects the level of a high frequency component of the video signal in order to supply a focus evaluating value which takes a maximum value in an in-focus position. A focusing motor controlling circuit performs an automatic focusing operation by a hill-climbing servo system based on the supplied focus evaluating value. A determination is made by employing a fuzzy inference with respect to the initialization of the direction of movement of a lens when the automatic focusing operation starts, the selection of a focusing area from a plurality of areas, and the reactivation of the automatic focusing operation due to a change of an object after once the automatic focusing operation is completed.