US Patent 7196315 Eccentric optical system and optical apparatus using same

An eccentric optical system forming an optical path where an incident light beam is internally reflected three times to fold the optical path, and then emitted from a transmission surface and imaged on an image surface, and an optical path where the incident light beam is internally reflected two times to fold the optical path, and then emitted from a branching surface and imaged on an image surface. At least two surfaces of the optical operating surfaces are rotationally asymmetric surfaces.