To improve the accuracy of detecting a detection target object by changing decision standards in accordance with a luminance distribution of a screen in an image sensor.

The image sensor is provided with an image picking up part 10 for picking up a monitoring space and generating and outputting an image in luminance resolution in accordance with a contrast distribution and determines whether a specific detection target object exists in the monitoring space on the basis of a feature quantity extracted from the image obtained by picking up the monitoring space in accordance with the luminance distribution of the image picked up by the image picking up part 10.

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