AUTO-FOCUSING APPARATUS

An auto-focusing apparatus includes a CCD for imaging an optical image formed by a photographing optical system, a motor for changing the position of the CCD along the direction of the optical axis, a BPF for extracting a predetermined frequency component from an image signal read from the CCD, a detector for outputting a focus signal corresponding to a focusing degree by performing square detection of an output signal from the BPF, and a microprocessor for calculating an intermediate parameter dFZP on the basis of the frequency band of the BPF and the F-number of the photographing optical system, determining a sampling interval .DELTA.x on the basis of a characteristic value COPT of the detector and the intermediate parameter d.sub.FZP, controlling the motor and the CCD in accordance with the sampling interval, sampling a plurality of focus signals, and detecting an in-focus point by interpolating the focus signals.