| 摘要 |
PURPOSE:To detect defocusing without finding out a peak point of a contrast signal every fixed period and adding any specific mechanism by collectively judging a change in a video signal within an image pickup field and the contrast signal obtained by differentiating a video signal to detect defocusing. CONSTITUTION:A video signal VD outputted from a CCTV camera 2 is applied to high frequency differentiators 3A, 3B and peak holding circuits 4A, 4B to extract high and low frequency contrast signals VH, VL. The video signal VD is also applied to an integrator 5, where the integrated values A-C of the video signal V in plural areas SA, SB, SC and the exposure value IA of the integrated values A-C at least for one horizontal line are respectively extracted to detect a change on an object in the visual field of the CCTV camera 2. The contrast signals VH, VL are divided by an integrated value IA to normalize the value IA. In the same object, the generation of defocusing is not decided even if the quantity of light is changed. |
