| 摘要 |
PROBLEM TO BE SOLVED: To judge the abnormality of a detection state by detecting the shield and the dirt of a whole sensor and a sensor part. SOLUTION: A detector 11 detecting the existence of an invader into a monitor area and outputting a detection signal, an image sensor 12 which image-picks up the monitor area and takes in the image of the invader, a light emitting part 13 emitting light to the monitor area at the time of picking up the image, a storage part 14 storing the reference value of brightness, which judges the brightness of the image that the image sensor 12 takes in, a timer 15 clocking first prescribed time which is previously set and a control part 16 emitting the light emitting part 13 at every first prescribed time, taking in the image from the image sensor 12 and judging it to be abnormal when pixels depending on the brightness of the image which is taken in exist much more than the brightness reference value of the storage part 14, are installed.
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