Video camera with autofocus function and method of controlling the same

Abstract

A video camera has a memory for storing the position of an image lens in relation to the position of a variator lens, that is, zoom tracing curves in respect of individual subject distances, a motor for moving the image lens while vibrating it slightly during zooming operation, a variation component extractor circuit for extracting the amplitude and phase of a slight variation component of focusing voltage generated by moving the image lens while vibrating it slightly, and a controller for controlling drive means on the basis of the stored zoom tracing curves and an extracted slight variation component. During zooming operation, the controller first controls the motor in compliance with a position of the variator lens pursuant to a zoom tracing curve stored in the memory in association with a position assumed by the image lens immediately before start of the zooming operation. The controller also operates to correct a drive amount of the image lens on the basis of amplitude of an extracted slight variation component and when the amplitude of the slight variation component falls below a predetermined value, the controller controls the motor pursuant to a newly determined zoom tracing curve.