To acquire an image with high image quality of a prescribed region by prescribing a direction of a region wherein a change takes place when the change is caused in an imaging region.

The supervisory system includes: a mirror unit; an imaging section for imaging an image reflected by the mirror unit; a mirror rotation control section for rotating the mirror unit so that the mirror unit may reflect images in a plurality of different regions continuously in a direction of the imaging section; an exposure time control section that synchronizes an exposure period by the imaging section with a rotation period of the mirror unit, exposes the images in the different regions continuously reflected by the mirror unit and allows the imaging section to image the images; a difference calculation section that calculates a difference between the images in the same region imaged by the imaging section for every rotation of the mirror unit; and a state change detection section that detects a change in the state around the mirror unit on the basis of the difference calculated by the difference calculation section.

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