LUMINANCE CONTROL DEVICE, LUMINANCE CONTROL SYSTEM, AND LUMINANCE CONTROL METHOD

A luminance control device () calculates a pupil diameter difference, which is the difference between a pupil diameter (R) measured by a measurement unit () and a pupil diameter (r) estimated by a pupil diameter estimation unit (), and when it is determined, on the basis of the pupil diameter difference, that a dark portion is being focused on, the luminance control device () executes a luminance control method for outputting control information for controlling a control subject so that the luminance is increased in at least one display region in which an image is displayed of the surroundings of a vehicle () imaged by at least one imaging device.