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Polarization beam splitter and projection display apparatus

  • US 5,453,859 A
  • Filed: 06/01/1994
  • Issued: 09/26/1995
  • Est. Priority Date: 06/03/1993
  • Status: Expired due to Term
First Claim
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1. A polarization beam splitter comprising a first prism, a second prism, and a dielectric multilayer film which is sandwiched between said first and second prisms,said dielectric multilayer film comprising:

  • first alternating layers of a high refractive index layer having a refractive index higher than refractive indices of said first and second prism and an intermediate refractive index layer having a refractive index lower than the refractive index of said high refractive index layer; and

    second alternating layers of said high refractive index layer and a low refractive index layer having a refractive index lower than the refractive index of said intermediate refractive index layer, a reference incident angle θ

    0 of light which is incident on said dielectric multilayer film through said first or second prism being within a range indicated in the following expression;

    
    
    space="preserve" listing-type="equation">θ

    .sub.1 <

    θ

    .sub.0 <

    θ

    .sub.2 where ##EQU4## wherein nH indicates the refractive index of said high refractive index layer, nM indicates the refractive index of said intermediate refractive index layer, nL indicates the refractive index of said low refractive index layer, and n0 indicates the refractive indices of said first and second prisms.

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