Patent ID: 6657668
Filing Date: 2003-12-02
Classification: G02B,H04N

Abstract:
An automatic focusing device for a digital camera, comprising:an optical system including a focusing lens system; an imaging device which receives a light flux from an object to be photographed, the received light flux being passed through the optical system to form an image of the object, and converts the received light flux into an output image signal; analog-to-digital converting means for converting the image signal to output digital image data; automatic exposure (AE) evaluation value outputting means for outputting luminance data according to the digital image data as an AE evaluation value; automatic focusing (AF) area setting means for setting at least an area of an imaging screen of the imaging device as an AF area; AF evaluation value outputting means for integrating high frequency components of luminance data of the digital image data in the AF area and outputting resulting data as an AF evaluation value; AF evaluation value sampling means for enabling the AF evaluation value outputting means to sample AF evaluation values output by the AF evaluation value outputting means while moving the focusing lens system; focusing lens driving means for determining if the device is in focus based upon a result of sampling the AF evaluation values and driving the focusing lens system to a focusing position when the device is not in focus; and AF area enlarging means for setting an enlarged AF area as the AF area based on a comparison of the AF evaluation value output by the AF evaluation value outputting means to a first predetermined value and based on a comparison of the AE evaluation value output by the AE evaluation value outputting means to a second predetermined value.