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Multiple prism image forming optical system

  • US 6,185,046 B1
  • Filed: 06/11/1999
  • Issued: 02/06/2001
  • Est. Priority Date: 07/24/1998
  • Status: Expired due to Term
First Claim
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1. An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising:

  • a first prism and a second prism, each of said first prism and second prism being formed from a medium having a refractive index (n) larger than 1 (n>

    1), said second prism being placed at a position on an image side of said first prism in an optical path exiting said first prism and leading to a plane where said object image is formed, wherein no intermediate image is formed, said first prism having, in order from an object side thereof;

    a first surface through which a light beam enters said first prism;

    a second surface that reflects said light beam in said first prism;

    a third surface that reflects said light beam reflected by said second surface in said first prism; and

    a fourth surface through which said light beam exits from said first prism;

    wherein at least one of said second surface and said third surface of said first prism has a curved surface configuration providing a refractive power acting on said light beam, said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration;

    said second prism having, in order from an object side thereof;

    a first surface through which said light beam enters said second prism;

    a second surface that reflects said light beam in said second prism;

    a third surface that reflects said light beam reflected by said second surface in said second prism; and

    a fourth surface through which said light beam exits from said second prism;

    wherein at least one of said second surface and third surface of said second prism has a curved surface configuration providing a refractive power acting on said light beam, said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration; and

    wherein any optical element that gives a refracting power contributing to an image-forming action of said light beam is placed other than between said second prism and an image formed by said image-forming optical system.

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