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Abstract

An automatic focusing device by which the intensity distribution of an image of an object to be photographed is detected by a detecting section having an accumulation mode image sensor with a charge accumulation time in dependence upon the brightness of the object and develop a video signal corresponding to the intensity distribution. A signal processing circuit processes the video signal to determine whether the optical system of the photographing apparatus with which the focusing device is associated is focused or out of focus and when an out-of-focus condition is detected a drive direction signal is developed and applied to a drive to move the lens in a proper direction toward a focusing position. The drive direction signal is applied to the drive for only a predetermined time at each detection that the optical system is out of focus when the brightness of the object is low and when the brightness of the object is high the drive direction signal is applied without interruption until detection that the optical system is in focus irrespective of the charge accumulation time of the image sensor varying in response to the brightness of the object being photographed.

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First Claim