Video camera apparatus and automatic focusing circuit

Claim 1

An automatic focusing circuit including a lens section having a movable focusing lens driven at a controllable speed and photoelectric converting means for photoelectrically converting an amount of light passing through said lens section into an image pickup signal, comprising: first filter means having first frequency characteristics for extracting a first high frequency component from a luminance signal included in said image pickup signal; second filter means having second frequency characteristics steeper than said first frequency characteristics for extracting a second high frequency component from said luminance signal; optical black level detecting means for detecting an optical black level of said image pickup signal; and control means for controlling the speed of moving said focusing lens on the basis of said optical black level and said first and second high frequency component such that said focusing lens is moved at a high speed when said first high frequency component is less than a predetermined threshold which is a function of said optical black level, said focusing lens is moved at a low speed when (i) said first high frequency component is larger than said predetermined threshold and (ii) a ratio of said second high frequency component to said first high frequency component is substantially equal to a predetermined value, and said focusing lens is moved at an intermediate speed when (i) said first high frequency component is larger than said predetermined threshold and (ii) said ratio of said second high frequency component to said first high frequency component is not substantially equal to said predetermined value.