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Image-forming optical system using prism elements

  • US 6,166,858 A
  • Filed: 06/11/1999
  • Issued: 12/26/2000
  • Est. Priority Date: 06/24/1998
  • 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 prism medium, said second prism being placed on an image side of said first prism,wherein an intermediate image is not formed,said first prism having;

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

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

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

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

    wherein at least one of said second surface and said third surface has a curved surface configuration that gives a power to a light beam;

    said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration;

    said second prism having at least one reflecting surface that reflects a light beam in said second prism, said reflecting surface having a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration;

    wherein said first prism satisfies the following condition;

    
    
    space="preserve" listing-type="equation">10°

    <

    θ

    '"'"'<

    90°

    wherein θ

    '"'"' is an angle formed between an axial principal ray entering the first surface of said first prism and an axial principal ray exiting from the fourth surface of said first prism.

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