Patent ID: 6900950

Claim:
An image-forming optical system, comprising a first prism, a second prism and an aperture stop interposed between the first prism and the second prism, wherein: said first prism comprises: a first-first transmitting surface through which a light beam transmits, a first-second reflecting surface for reflecting a light beam, and a first-third transmitting surface through which a light beam transmits, wherein said first-first transmitting surface, said first-second reflecting surface and said first-third transmitting surface are arranged in this order in an optical path between entrance of a light beam from said first prism and emergence of said light beam from said first prism, said second prism comprises: a second-first transmitting surface through which a light beam transmits, a second-second reflecting surface for reflecting a light beam, a second-third reflecting surface for reflecting a light beam, and a second-fourth transmitting surface through which a light beam transmits, wherein: said second-first transmitting surface, said second-second reflecting surface, said second-third reflecting surface and said second-fourth transmitting surface are arranged in this order in an optical path between entrance of a light beam in said second prism and emergence of said light beam from said second prism, said second-first transmitting surface is opposed to said second-second reflecting surface, said second-third reflecting surface is opposed to said second-fourth transmitting surface, said first-second reflecting surface, said second-second reflecting surface and said second-third reflecting surface have each a rotationally asymmetric surface shape for giving power to a light beam, said first prism has an equal sign of power in two orthogonal directions, said second prism has an equal sign of power in two orthogonal directions, and the image-forming optical system does not form an intermediate image.