| 摘要 |
PROBLEM TO BE SOLVED: To provide an image monitoring system that issues warning when a monitoring camera is covered. SOLUTION: An analog/digital converter section 2 converts a video signal from a camera 1 into a digital signal, an image processing section 3 applies gamma correction and image quality correction to the digital signal, a digital/analog converter section 4 converts the processed digital signal into an analog signal, and a monitor 5 displays the signal. An auxiliary illumination 6 comprising a plurality of LEDs arranged longitudinally to both left and right sides of the camera turns on/turns off, a luminance calculation section 7 calculates the luminance in the middle of an image from the image processing section, a cover discrimination section 9 discriminates that the camera is covered when the lightness is of a prescribed level or below at both lighting/light off of the auxiliary illumination and a warning section 10 raises a warning. The cover discrimination section 9 discriminates no cover on the camera when the lightness is bright at daytime, at lighting, and at lighting off or bright at night at lighting and dark at lighting off. When the cover discrimination section 9 discriminates no cover, the luminance is again calculated when a prescribed time elapses depending on count of a clock section 11 to discriminate the presence/absence of cover. Or the luminance is calculated for each prescribed time independently of the presence/absence of cover to discriminate the presence/absence of cover.
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