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Diffractive optical element, and optical system and optical apparatus provided with the same

  • US 20030231396A1
  • Filed: 06/02/2003
  • Published: 12/18/2003
  • Est. Priority Date: 06/17/2002
  • Status: Active Grant
First Claim
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1. A diffractive optical element comprising:

  • a plurality of diffraction gratings made of materials with different Abbe numbers ν

    d, wherein the plurality of diffraction gratings are layered with each other, leaving a certain interval therebetween;

    wherein a partial dispersion ratio θ

    g, F with respect to a g-line and a F-line of the material constituting at least one of the plurality of diffraction gratings satisfies the following condition;

    θ

    g, F<

    (−

    {fraction (1/600)})ν

    d+0.55 where θ

    g, F=(ng

    n
    F)/(nF

    n
    c) ν

    d=(nd

    1)/(nF

    n
    c) and ng, nF, nd and nc are the refractive indices at the g-line, the F-line, a d-line and a C-line, respectively.

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