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US 2011/0235180 A1Published application
Diffractive optical element and optical device
AssigneePanasonic Corporation
InventorsKazuhiro MINAMI, Kazuhiro Yamada
Life of this patent
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Abstract
A diffractive optical element includes a first optical member having a first diffraction grating with a sawtooth cross section; and a second optical member which has a second diffraction grating having a sawtooth cross section and which has a refractive index different from that of the first optical member. In the diffractive optical element, the first and second optical members are stacked so that the first and second diffraction gratings closely contact each other. Arithmetical mean roughness of a diffraction surface of the first diffraction grating is set so as to fall within a predetermined range.
Claims4
A diffractive optical element, comprising:
- a first optical member including a first diffraction grating having a sawtooth cross section;
- and
- a second optical member which includes a second diffraction grating having an inverted shape of the first diffraction grating and which has a refractive index different from that of the first optical member,
- wherein the first and second optical members are stacked in a state in which the first and second diffraction gratings closely contact each other, and
- a diffraction surface of the first diffraction grating satisfies the following expression (1):
- 4
- ×
- Ra_s
- ≤
- Ra_a
- ≤
- Ra_s
- ·
-
- Δ
-
-
- n
- d
-
- _s
-
-
- Δ
-
-
- n
- d
-
- (
- 1
- )
- where “Ra_a” represents arithmetical mean roughness (μm) of the diffraction surface,
- “Δnd” represents a refractive index difference between the first and second optical members,
- “Ra_s” represents arithmetical mean roughness (μm) of a surface causing the largest scattering among light entering surfaces other than the diffraction surface in the diffractive optical element, and
- “Δnd—s” represents a refractive index difference between mediums sandwiching the surface at which the scattering is largest.
33 more elements
A diffractive optical element, comprising:
- a first optical member including a first diffraction grating having a sawtooth cross section;
- and
- a second optical member which includes a second diffraction grating having an inverted shape of the first diffraction grating and which has a refractive index different from that of the first optical member,
- wherein the first and second optical members are stacked in a state in which the first and second diffraction gratings closely contact each other,
- the first diffraction grating is formed by a mold,
- an inverted structure of tool marks of the mold is formed in a diffraction surface of the first diffraction grating,
- the inverted structure is raised so as to have a segmental section, and
- the diffraction surface of the first diffraction grating satisfies the following expression (2):
- 4
- ×
- Ra_s
- ≤
- R
-
- {
- 1
- -
- 1
- -
- (
- P
- 2
-
- R
- )
- 2
- }
- ≤
- Ra_s
- ·
-
- Δ
-
-
- n
- d
-
- _s
-
-
- Δ
-
-
- n
- d
-
- (
- 2
- )
- where “R” represents a curvature radius (μm) of the cross section of the inverted structure,
- “P” represents a pitch (μm) of the inverted structure,
- “Δnd” represents a refractive index difference between the first and second optical members,
- “Ra_s” represents arithmetical mean roughness (μm) of a surface causing the largest scattering among light entering surfaces other than the diffraction surface in the diffractive optical element, and
- “Δnd—s” represents a refractive index difference between mediums sandwiching the surface at which the scattering is largest.
51 more elements
A diffractive optical element, comprising:
- a first optical member including a first diffraction grating having a sawtooth cross section;
- and
- a second optical member which includes a second diffraction grating having an inverted shape of the first diffraction grating and which has a refractive index different from that of the first optical member,
- wherein the first and second optical members are stacked in a state in which the first and second diffraction gratings closely contact each other, and
- a diffraction surface of the first diffraction grating satisfies the following expression (3):
- λ
- 50
- ≤
- Ra_a
- ≤
- Ra_s
- ·
-
- Δ
-
-
- n
- d
-
- _s
-
-
- Δ
-
-
- n
- d
-
- (
- 3
- )
- where “λ” represents the shortest wavelength (μm) in a wavelength band to be used,
- “Ra_a” represents arithmetical mean roughness (μm) of the diffraction surface,
- “Δnd” represents a refractive index difference between the first and second optical members,
- “Ra_s” represents arithmetical mean roughness (μm) of a surface causing the largest scattering among light entering surfaces other than the diffraction surface in the diffractive optical element, and
- “Δnd—s” represents a refractive index difference between mediums sandwiching the surface at which the scattering is largest.
33 more elements
Dependencies are inferred from the claim text.