Diffractive optical element and manufacturing method for the same

• US 9,612,372 B2
• Filed: 02/18/2014
• Issued: 04/04/2017
• Est. Priority Date: 02/21/2011
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Iwata, Kenichi
• Primary Examiner(s): Sugarman, Scott J
• Assistant Examiner(s): BROOME, SHARRIEF I
• Application Number:
  US14/182,443
• Publication Number:
  US 20140160567A1
• Time in Patent Office: 1,141 Days
• Field of Search: 359571, 359572, 359900, 359566, 216 24
• CPC Class Codes: C23C 14/042 using masks
• CPC Class Codes: C23C 14/20 on organic substrates
• CPC Class Codes: C23C 14/225 Oblique incidence of vaporised material on substrate
• CPC Class Codes: C23C 14/24 Vacuum evaporation
• CPC Class Codes: C23C 14/5853 Oxidation
• CPC Class Codes: G02B 3/08 with discontinuous faces, e.g. Fresnel lens diffractive Fresnel lenses G02B5/1876
• CPC Class Codes: G02B 5/18 Diffraction gratings holographic optical elements G02B5/32, G03H; integrally combined with optical fibres G02B6/02057; for coupling light guides G02B6/34; integrally combined with optical integrated light guides G02B6/12; grating systems G02B27/44
• CPC Class Codes: G02B 5/1814 structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings G02B5/189 takes precedence
• CPC Class Codes: G02B 5/1842 Gratings for image generation G02B5/1847 takes precedence
• CPC Class Codes: G02B 5/1876 Diffractive Fresnel lenses; Zone plates; Kinoforms G02B5/1842, G02B5/1847 take precedence; optical systems having diffractive correction means G02B27/0037; Fresnel lenses operating by refraction G02B3/08
• CPC Class Codes: G02B 5/1895 such optical elements having dioptric power
• CPC Class Codes: G02B 5/22 Absorbing filters G02B5/201 - G02B5/208 take precedence

Abstract

An Al film is formed so that film forming particles are incident at normal incidence to grating wall surfaces of a diffraction grating having multiple grating portions and are incident at oblique incidence to optical effective surfaces. After that, oxidation treatment is performed from a direction to be incident at normal incidence to the optical effective surface so that the Al layer on the optical effective surface is changed to Al₂O₃ layer. Hence, in the diffraction grating having the multiple grating portions, the Al₂O₃ layer is formed on the optical effective surface for transmitting light, and the Al layer is formed on the grating wall surfaces as a light shielding layer. Thus, flare of the diffractive optical element can be suppressed.

Claims

1. An optical element comprising:

a diffraction grating for diffracting incident light, the diffraction grating having a continuous surface including optical effective surfaces and wall surfaces that are disposed alternately and are directly connected with each other,

wherein an aluminum oxide layer is formed on the optical effective surfaces of the diffraction grating so that incident light can pass through the optical effective surfaces,

wherein an aluminum metal layer is formed on the wall surfaces of the diffraction grating so that incident light cannot pass through the wall surfaces,

wherein the aluminum metal layer has a film thickness of 50 nm or more and 1 μ

m or less, and

wherein the aluminum oxide layer has a film thickness of 5 nm or more and 30 nm or less.

2. The optical element according to claim 1, wherein the optical element has a lens function for converging light transmitted through the optical element.

3. The optical element according to claim 1, wherein the aluminum metal layer is not formed on the optical effective surfaces.

4. A diffractive optical element comprising a diffraction grating made of a resin or glass, the diffraction grating including multiple grating portions arranged in a concentric manner, each grating portion comprising a grating wall surface and a grating slope directly connected with each other,

wherein an aluminum oxide layer covers and contacts with the grating slope, and

wherein an aluminum metal layer covers and contacts with the grating wall surface,

wherein the aluminum metal layer has a film thickness of 50 nm or more and 1 μ

m or less, and

wherein the aluminum oxide layer has a film thickness of 5 nm or more and 30 nm or less.

5. The diffractive optical element according to claim 4, wherein light incident on the diffraction grating passes through the aluminum oxide layer and the grating slope, and

wherein light incident on the diffraction grating is reflected by the aluminum metal layer and does not pass through the grating wall surface.

6. The diffractive optical element according to claim 4, wherein the diffraction grating is provided on a base substrate.

7. The diffractive optical element according to claim 4, wherein the aluminum metal layer has a film density of 2.0 g/cm³ or more and 2.7 g/cm³ or less, and

wherein the aluminum oxide layer has a film density of 0.4 g/cm³ or more and 1.0 g/cm³ or less.

8. The diffractive optical element according to claim 4, wherein the grating slope is not covered with an aluminum metal layer.