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Beam expanding optical element, beam expansion method, image display apparatus, and head-mounted display

  • US 20070188837A1
  • Filed: 02/07/2007
  • Published: 08/16/2007
  • Est. Priority Date: 02/16/2006
  • Status: Abandoned Application
First Claim
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1. A beam expanding optical element, comprising:

  • an optical waveguide member that has two mutually opposite faces that respectively have mutually parallel flat surfaces;

    a first holographic diffractive optical element arranged at one location on the flat surface of the optical waveguide member, the first holographic diffractive optical element diffracting light incident from outside on the optical waveguide member such that the light is then totally reflected inside the optical waveguide member; and

    a second holographic diffractive optical element arranged at another location on the flat surface of the optical waveguide member, the second holographic diffractive optical element diffracting, according to diffraction efficiency thereof, part of the light incident thereon after being guided inside the optical waveguide member such that this part of the light is then emitted to outside substantially parallel to the light incident on the optical waveguide member, the second holographic diffractive optical element simultaneously totally reflecting the rest of the light incident thereon,wherein the first and second holographic diffractive optical elements each have interference fringes with n different pitches (where n is a natural number equal to or greater than two) so as to diffract light of n different wavelengths at substantially equal angles.

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