Abstract: An auto-focus device or a camera equipped with such a device includes a focus detecting circuit for repeatedly detecting focus, in which an image forming optical system is driven on the basis of the focusing quantity detected by the focus detecting circuit. A speed computing circuit is provided for computing a speed of movement of an image plane corresponding to movement of the object on the basis of past autofocusing operation data. A drive data computing circuit is provided for predictive-computing data relating to a drive position of the image forming optical system, considering the movement of the object, on the basis of the past autofocusing operation data. A speed control circuit is provided for controlling a driving speed of the image forming optical system on the basis of the speed obtained by the speed computing circuit.

Abstract: An automatic focusing device for foreseeing or predicting the position of object after a predetermined time, based on plural past focusing operations on the object, utilizing a function of a higher order, and driving a lens for focusing to the predicted object position. According to the present invention there is provided a correcting circuit for correcting the coefficients of the higher-order function to reduce the influence of the measuring errors contained in the past focusing results, thus constantly enabling appropriate focusing.

Abstract: An focus detecting apparatus has a scanning plate disposed on or near the predetermined imaging plane of an objective lens and reciprocally movable to grating-scan the image of an object, a mask having an aperture adjacent to the scanning plate and movable to a desired position in a plane perpendicular to the optic axis of the objective lens to determine a range for detection, a plurality of light-receiving devices for receiving light fluxes passed through the scanning plate and the mask and outputting a signal regarding the focus adjusted state of the objective lens, and a field lens for relating the light fluxes entering the light-receiving devices to each other so as to pass through different areas of the exit pupil of the objective lens.