AUTOFOCUS APPARATUS

An autofocus apparatus sets a portion of an image frame as an AF area. Then, in first image-pickup, acquires first image data for the AF area within the image frame according to a first light flux from an object passing through an aperture of the diaphragm when the diaphragm is not shifted. Further, in second image-pickup, acquires second image data for the AF area within the image frame according to a second light flux from the object passing through the aperture of the diaphragm when the diaphragm is shifted in one vertical direction with respect to the optical axis. A cross correlation between the first image data and the second image data is computed, and a distance up to a focus position of the focal lens as well as a direction thereof is computed according to the cross correlation. Then, the focal lens is driven to the focus position.