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Projection optical system and image projection device

  • US 8,905,550 B2
  • Filed: 05/09/2011
  • Issued: 12/09/2014
  • Est. Priority Date: 05/18/2010
  • Status: Active Grant
First Claim
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1. A projection optical system projecting images on a surface to be projected on, the projection optical system comprising:

  • a first optical system including at least one refraction optical system and having positive power as a whole;

    a folding mirror; and

    a second optical system including at least one reflection surface having power and having positive power as a whole;

    wherein the folding mirror folds a light path from the first optical system to the second optical system, in a plane including an optical axis of the first optical system and a normal line of the surface to be projected on,wherein, when a projection distance refers to a distance, which is on a line orthogonal to the surface to be projected on, from the surface to be projected on to a position which is inside an area where light is reflected by the second optical system and which is a farthest from the surface to be projected on and a projection size refers to a size in a horizontal direction of an image projected on the surface to be projected on, a ratio of the projection distance to the projection size is less than or equal to 0.23, andwherein the following conditional expressions (1) through (3) are satisfied
    0.43

    d
    1;





    (1)
    0.43

    d
    2;





    (2)
    and
    0.7

    d
    2/d1

    2.0, 



    (3)further d1 is expressed in the following equation (1)

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