Patent US 6,067,115

A video camera apparatus in which a signal of a certain frequency is extracted from an image pickup signal from an image pickup element such as CCD by a band-pass filter, a difference between the maximum and minimum values of the frequency of the image pickup signal is detected by a detecting circuit, the extraction value extracted by a band-pass filter is divided by the detection value detected by the detecting circuit by a normalizing circuit, thereby normalizing a focus estimation value, and a focus adjusting lens is moved by a lens driving motor on the basis of the normalized focus estimation value, thereby executing an automatic focus adjustment.