Endoscope system which generates an image of high dynamic range

An endoscope system, comprising:

• an illuminator configured to switch between a first illumination light and a second illumination light for which a ratio of a quantity of light is 1/α, where α denotes a coefficient;
• an objective optical system;
• an image sensor;
• an optical path splitter which is disposed between the objective optical system and the image sensor,
• the optical path splitter including:
• (i) an optical path splitting surface for splitting a light beam from the objective optical system into a light beam reflected and a light beam transmitted,
• (ii) a first reflecting surface having a first reflectance, the first reflecting surface reflecting the light beam that has been reflected at the optical path splitting surface, and
• (iii) a second reflecting surface having a second reflectance differing from the first reflectance, the second reflecting surface reflecting the light beam that has been transmitted through the optical path splitting surface;
• and
• a processor configured to:
• acquire, for each of the first illumination light and the second illumination light, a first image pickup signal formed as an image in a first area of the image sensor by a light beam reflected at the first reflecting surface and a second image pickup signal formed as an image in a second area of the image sensor, which is different from the first area, by a light beam reflected at the second reflecting surface,
• combine the first image pickup signal and the second image pickup signal for the first illumination light and the first image pickup signal and the second image pickup signal for the second illumination light, and
• generate an image of a high dynamic range.