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Diffractive optical element and manufacturing method for the same

  • US 9,366,791 B2
  • Filed: 02/10/2012
  • Issued: 06/14/2016
  • Est. Priority Date: 02/21/2011
  • Status: Active Grant
First Claim
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1. A manufacturing method for a diffractive optical element, the manufacturing method comprising:

  • forming multiple grating portions including grating optical effective surfaces for transmitting the incident light and grating wall surfaces for shielding the incident light continuously on a base substrate;

    forming an Al layer on the grating wall surfaces and the grating optical effective surfaces such that the density and film thickness of the Al layer formed on the grating wall surfaces are different from those of the Al layer formed on the grating optical effective surfaces; and

    performing oxidation treatment of the Al layer under a condition that an oxidation speed is faster in the Al layer formed on the grating optical effective surfaces than in the Al layer formed on the grating wall surfaces, thereby converting the Al layer formed on the grating optical effective surfaces into an Al2O3 layer,wherein the oxidation treatment is performed to form an Al layer on the grating wall surfaces to have a film density of 2.0 g/cm3 or more and 2.7 g/cm3 or less, and a film thickness of 50 nm or more and 1 μ

    m or less, and to obtain the Al2O2 layer formed on the grating optical effective surfaces having a film density of 0.4 g/cm3 or more, and 1.0 g/cm3 or less, and a film thickness of 5 nm or more and 30 nm or less.

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