Patent Document ID: 4638364
Application ID: 06791843
Patent Status: 1

Claim One:
1. An auto focus circuit for a video camera including a focusing motor for focusing, comprising: a high-pass filter circuit to which a luminance signal of a video signal is applied so that a high frequency component higher than a predetermined frequency is extracted from said applied luminance signal, an absolute value calculating circuit connected to said high-pass filter circuit for obtaining an absolute value of the output of said high-pass filter circuit, an A-D converting circuit connected to said absolute value calculating circuit for converting an analog absolute value output signal provided from said absolute value calculating circuit to a digital signal, a calculating circuit connected to said A-D converting circuit for adding the converted digital signal with a predetermined period cycle, a comparing circuit connected to said calculating circuit for comparing the output of calculation in one predetermined period and the output of calculation in the predetermined period coming one predetermined period ahead of said predetermined period, and a focusing motor control circuit connected to said comparing circuit for providing a signal for controlling the rotation of the focusing motor included in said video camera in the clockwise direction or in the counterclockwise direction based on the output of said comparing circuit.