Antireflection structure and optical device including the same
View Patent ↗A diffusing plate is formed so as to have a surface having a larger surface roughness than a predetermined wavelength and having an aperiodic roughness shape. A plurality of fine concave/convex portions are formed on the surface so as to be regularly arranged within a cycle equal to and smaller than a predetermined wavelength.
1. An antireflection structure for suppressing reflection of light having a wavelength equal to or larger than a predetermined wavelength, the antireflection structure comprising:
a rough surface having a larger surface roughness than the predetermined wavelength and having an aperiodic roughness shape,
wherein a plurality of fine concave/convex portions are further formed on the rough surface so as to be regularly arranged within a smaller cycle than the predetermined wavelength, and
wherein the rough surface is formed so that a distribution width of cycles standardized with a center cycle of the roughness shape is equal to or larger than 0.4 times as large as the center cycle.
2. The antireflection structure of claim 1 , wherein the rough surface is formed so that a distribution width of cycles standardized with a center cycle of the roughness shape is equal to or larger than ⅔ times as large as the center cycle.
3. The antireflection structure of claim 1 , wherein a height distribution in a normal direction of a reference plane of the rough surface of the light absorbing antireflection structure presents a peak for a roughness shape of the rough surface having a larger width than a width of a peak for the fine concave/convex portions in the spectrum in a spatial frequency domain.
4. The antireflection structure of claim 1 , wherein the antireflection structure transmits the light of which reflection is suppressed.
5. The antireflection structure of claim 1 , wherein the fine concave/convex portions are approximately conical/pyramidal concaves and convexes, or filiform concaves and convexes.
6. The antireflection structure of claim 1 , wherein a surface roughness of the rough surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is larger than the predetermined wavelength.
7. The antireflection structure of claim 1 , wherein a surface roughness of the rough surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is smaller than 100 μm.
8. The antireflection structure of claim 1 , wherein a surface roughness of the rough surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is smaller than 50 μm.
9. The antireflection structure of claim 1 , wherein a surface roughness of the rough surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is smaller than 30 μm.
10. The antireflection structure of claim 1 , wherein respective heights of the plurality of fine concave/convex portions from the rough surface in a normal direction of a reference plane of the rough surface are approximately the same.
11. The antireflection structure of claim 1 , wherein the rough surface is substantially formed of a plane in which an angle between a normal vector of a tangent plane of a roughness shape and a normal vector of a reference plane of the rough surface is 90 degrees or less.
12. The antireflection structure of claim 1 , wherein each of the plurality of fine concave/convex portions is a conical/pyramidal concave or convex and respective center axes of the plurality of fine concave/convex portions are parallel to each other, each of the center axes connecting a center of a base and a top point of each of the concave/convex portions.
13. The antireflection structure of claim 1 , wherein each of the plurality of fine concave/convex portions has a height equal to or larger than 0.4 times as large as a wavelength of light of which reflection is suppressed.
14. An optical device comprising the antireflection structure of claim 1 .
15. An antireflection structure for suppressing reflection of light having a wavelength equal to or larger than a predetermined wavelength, the antireflection structure comprising:
a rough surface having a larger surface roughness than the predetermined wavelength and having an aperiodic roughness shape,
wherein a plurality of fine concave/convex portions are further formed on the rough surface so as to be regularly arranged within a smaller cycle than the predetermined wavelength,
wherein a surface roughness of the rough surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is smaller than 100 μm, and
wherein the rough surface is formed so that a distribution width of cycles standardized with a center cycle of the roughness shape is equal to or larger than ⅔ times as large as the center cycle.