| 摘要 |
PURPOSE:To focus a video camera quickly and accurately by sampling a video signal, which is outputted from the video camera and constitutes one picture, along a distance measuring line preliminarily determined on the picture while moving a focus lens and discriminating the in-focus state to stop the focus lens when the gradient of a luminance signal of the sampled video signal exceeds a prescribed value. CONSTITUTION:The video signal stored in a memory 7 is used to check the gradient of variance of the luminance level by a CPU5, and it is discriminated whether this gradient is sharper than the prescribed value or not, and the in- focus state is discriminated to stop an auto-focus driving motor 9 if the gradient is sharper; but otherwise, it is discriminated whether the gradient is getting sharper or not. As the result, approaching the focus position is discriminated to rotate the motor 9 continuously if the gradient is getting sharper in comparison with the preceding frame, but otherwise, going away from the focus position is discriminating to reverse the motor 9. |
