Patent ID: 6510006
Filing Date: 2003-01-21
Classification: A61B,G02B

Abstract:
An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising:at least one prism formed from a medium having a refractive index (n) larger than 1.3 (n>1.3); said image-forming optical system having a pupil in said prism and being adapted to lead light rays from an object to an image plane without forming an image in said prism; wherein said prism has at least four optical surfaces that transmit or reflect a light beam; said at least four optical surfaces including a first optical surface, a second optical surface and a third optical surface provided in order from said image plane; at least one of said second optical surface and said third optical surface having a curved surface configuration that gives a power to the light beam; said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration; said first optical surface having a transmitting action by which rays internally reflected from said second optical surface are allowed to exit from said prism; said second optical surface having a reflecting action to reflect rays internally reflected from said third optical surface; and said third optical surface having a reflecting action, wherein rays incident on said third optical surface and the rays reflected from said second optical surface intersect each other.