Automatic focusing device wherein loop gain is set responsively to variation of magnification

摘要

An automatic focus adjusting device comprising extracting circuitry for extracting a focus signal from an image sensor corresponding to the degree of focusing of an image sensing signal output from the sensor, a drive device for adjusting focus so as to bring an optical system into a focuses state on the basis of the focus signal and a control unit operative to detect a magnification varying operation of the optical system for controlling a loop gain of a closed loop encompassing the image sensor, the extracting circuitry and the drive device.