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

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Iwata, Kenichi
• Primary Examiner(s): Pham, Thomas K
• Assistant Examiner(s): BROOME, SHARRIEF I
• Application Number:
  US13/370,603
• Publication Number:
  US 20120212821A1
• Time in Patent Office: 1,586 Days
• Field of Search: 359/571, 359/572, 359/900, 359/566, 216/24
• US Class Current: 1/1
• 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. 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.

2. The manufacturing method for a diffractive optical element according to claim 1, wherein the optical element is an optical lens.

3. The manufacturing method for a diffractive optical element according to claim 2, wherein the forming the multiple grating portions comprises forming multiple grating portions including grating optical effective surfaces and grating wall surfaces arranged in a concentric manner continuously on the base substrate, and

wherein the forming an Al layer is performed while the optical element, whose half surface is masked, is rotated.

4. The manufacturing method for a diffractive optical element according to claim 1, wherein the forming the Al layer includes forming the Al layer on the grating wall surfaces to have a higher density and to be thicker than the Al layer formed on the grating optical effective surfaces.

5. The manufacturing method for a diffractive optical element according to claim 1, wherein in the forming the Al layer, Al particles are incident to the grating wall surfaces at an angle from 85°

to 95°

.

6. The manufacturing method for a diffractive optical element according to claim 1, wherein the base substrate comprises optical glass and has a convex surface opposite the surface on which the multiple grating portions are formed.

7. The manufacturing method for a diffractive optical element according to claim 6, wherein the forming the Al layer comprises performing vacuum vapor deposition, and

wherein the performing the oxidation treatment comprises performing oxygen plasma treatment.

8. The manufacturing method for a diffractive optical element according to claim 7, further comprising, before the forming the Al layer, performing oxygen plasma ashing.

12. The manufacturing method for a diffractive optical element according to claim 1, wherein the optical element is an optical lens having a curved surface.

13. The manufacturing method for a diffractive optical element according to claim 12, wherein the forming the Al layer includes forming the Al layer on the grating wall surfaces to have a higher density and to be thicker than the Al layer formed on the grating optical effective surfaces, wherein the forming the Al layer comprises performing vacuum vapor deposition, wherein the performing the oxidation treatment comprises performing oxygen plasma treatment, and wherein the method further comprises, before the forming the Al layer, performing oxygen plasma ashing.

14. The manufacturing method for a diffractive optical element according to claim 13, wherein in the forming the Al layer, Al particles are incident to the grating wall surfaces at an angle from 85°

to 95° and

are obliquely incident to the grating optical effective surfaces.

9. 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; 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 Al2O3 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.

10. The manufacturing method for a diffractive optical element according to claim 9, wherein the forming the Al layer includes forming the Al layer such that the film density of the Al layer formed on the grating wall surfaces are higher than those of the Al layer formed on the grating optical effective surfaces or the film thickness of Al layer formed on the grating wall surfaces are thicker than those of the Al layer formed on the grating optical effective surfaces.

11. The manufacturing method for a diffractive optical element according to claim 9, wherein the forming the Al layer includes forming the Al layer such that the film density of the Al layer formed on the grating wall surfaces are higher than those of the Al layer formed on the grating optical effective surfaces and the film thickness of Al layer formed on the grating wall surfaces are thicker than those of the Al layer formed on the grating optical effective surfaces.