The signal processing unit 20 includes a pixel index value calculating unit that calculates a pixel index value based on an input signal for each pixel 48, a chunk determining unit that performs consecutiveness determination which determines whether or not a pixel 48, having a pixel index value between an upper boundary value and a lower boundary value is consecutive from the starting pixel, and determines consecutive pixels as a chunk, a chunk index value calculating unit that calculates a chunk index value, a region index value calculating unit that calculates a region index value of a target region, and a light irradiation amount deciding unit that compares the chunk index value with the region index value, and decides the irradiation amount of the light of the light source unit in the target region based on the one by which the irradiation amount of the light is increased.