Imaging device

An imaging device, comprising:

• an imaging element configured to receive subject light;
• an optical member configured to guide the subject light traveling through a first opening in a housing to the imaging element;
• a light shield between the first opening and the optical member, the light shield being at a first position to restrict the subject light from entering the imaging element or at a second position to allow the subject light to enter the imaging element;
• a drive configured to move the light shield in a first direction intersecting with an optical axis of the optical member to cause the light shield to be at the first position or at the second position;
• an auxiliary opening outside a viewing range of the optical member to allow the subject light to travel through;
• and
• a controller configured to control driving of the drive to move the light shield at the first position to the second position based on a change in an output from the imaging element receiving diffused light traveling through the auxiliary opening and reflected from inside the housing when the light shield is at the first position.