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Prism optical system

  • US 5,991,103 A
  • Filed: 09/12/1997
  • Issued: 11/23/1999
  • Est. Priority Date: 10/21/1994
  • Status: Expired due to Term
First Claim
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1. A prism optical system comprising, in order from an image surface side along an optical path:

  • a first transparent surface;

    a concave first reflecting surface;

    a second reflecting surface; and

    a second transparent surface;

    said first transparent surface, said first reflecting surface, said second reflecting surface, and said second transparent surface are disposed so that the four surfaces form surrounding surfaces of a single prism that face each other across said medium;

    a space between said first transparent surface, which is disposed at said image surface side, and said second transparent surface, which is disposed at a pupil side of said prism optical system, being filled with a medium having a refractive index not less than 1.3;

    the concavity of said first reflecting surface facing said medium;

    said first reflecting surface and said second reflecting surface being tilted with respect to a chief ray, said chief ray being a light ray which emanates from a center of an image surface of said prism optical system, which is reflected by said first reflecting surface and said second reflecting surface, and which is perpendicularly incident on a pupil position of said prism optical system;

    said first reflecting surface and said second reflecting surface are tilted relative to each other so as to diverge toward at least one of said image surface of said prism optical system and said pupil position in a plane in which an optical axis of said prism optical system bends;

    said first reflecting surface and said second reflecting surface are disposed so that a light ray emanating from said image surface of said prism optical system approximately intersects a light ray emanating from said second transparent surface and enters said pupil position; and

    an angle θ

    between said chief ray and a line normal to at least one of said first reflecting surface and said second reflecting surface satisfies the following condition;

    
    
    space="preserve" listing-type="equation">12.5°

    <

    θ

    <

    32.5°

    .

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