AUTOMATIC FOCUSING DEVICE

摘要

PURPOSE:To realize automatic focusing by using a lens position control means so as to move a lens to a position at which a focus voltage is minimized. CONSTITUTION:A high brightness detector 6 compares a high brightness detection voltage with a video signal and outputs a high level when the voltage of the video signal is the high brightness detection voltage or over and outputs a low level when the voltage of the video signal is the high brightness detection voltage or below. A focus voltage VF is obtained by integrating a high brightness part signal B1 and an area B1B represents a focus voltage at out of focus and an area B1J depicts a focus voltage at in-focus. The said focus voltage VF is large at out of focus and minimized at focusing. A lens 1 is controlled to be moved to a position to minimize the focus voltage VF from a high brightness object and to be stopped at the position thereby realizing automatic focusing.