Light-absorbing member

1. A light-absorbing member comprising:

a substrate made of a material capable of absorbing light of which reflection is to be prevented, the substrate having the shape of a curve viewed from a macroscopic viewpoint; and

an antireflection structure comprising structural elements arranged on the surface of the curve in an array form at a period smaller than the wavelength of the light, wherein the structural elements have a shape protruding or being recessed from a reference face corresponding to the curve of the substrate, and are arranged so that straight lines connecting from a center portion of each of the structural elements disposed on the reference face to the tips of the respective structural elements are nearly parallel to one another.

2. A light-absorbing member in accordance with claim 1 , wherein the length between the reference face and the tip of each of the respective structural elements in the direction along the straight line corresponds to the period or more.

3. A light-absorbing member comprising:

a substrate made of a material capable of absorbing light of which reflection is to be prevented, the substrate having the shape of a curve viewed from a macroscopic viewpoint; and

an antireflection structure comprising structural elements arranged on the surface of the curve in an array form at a period smaller than the wavelength of the light, wherein:

the structural elements have a shape protruding or being recessed from a reference face corresponding to the curve of the substrate, and are arranged so that the straight lines connecting the reference face to the tips of the respective structural elements are nearly parallel to one another, and

height or depth of each of the structural elements of the antireflection structure varies so that the height or depth increases gradually from a position near a central area in an area in which the antireflection structure is formed to a position near a periphery in the area.

4. A light-absorbing member in accordance with claim 3 , wherein each of the structural elements satisfies a relationship of θ<90 degrees,

where θ represents an angle formed by the normal vector of the side face of the protruding shape or the internal face of the recessed shape with respect to the reference vector in the direction from the reference face to the tip of each structural element.

5. A light-absorbing member in accordance with claim 3 , wherein the antireflection structure is integrally formed as part of the substrate.

6. A light-absorbing member in accordance with claim 3 , wherein the antireflection structure is formed on a sheet member bonded to the substrate.

7. A light-absorbing member in accordance with claim 3 , wherein the length between the reference face and the tip of each of the respective structural elements in the direction along the straight line corresponds to the period or more.

8. A light-absorbing member in accordance with claim 3 , wherein the shape of the curve is a recess.

9. A light-absorbing member in accordance with claim 3 , wherein the amount of a sag of the surface of the curve is 20 μm or more.

10. A light-absorbing member in accordance with claim 3 , wherein the light is selected from the group consisting of ultraviolet light, visible light, near-infrared light and far-infrared light.

11. A light-absorbing member in accordance with claim 3 , wherein each of the structural elements is a protrusion having a nearly conical shape or a recess having a nearly conical shape.

12. A light-absorbing member in accordance with claim 3 , wherein each of the structural elements is a protrusion having a nearly bell shape or a recess having a nearly bell shape.

13. A light-absorbing member in accordance with claim 3 , wherein each of the structural elements is a protrusion having a nearly truncated conical or pyramidal shape or a recess having a nearly truncated conical or pyramidal shape.

14. A light-absorbing member in accordance with claim 3 , wherein each of the structural elements is a protrusion having a nearly columnar shape or a recess having a nearly columnar shape.

15. A light-absorbing member in accordance with claim 3 , wherein in each of the structural elements, the bottom face of the protrusion on the reference face or the upper face of the recess in the reference face has a shape selected from the group consisting of a nearly circular shape, a nearly elliptical shape, a nearly rectangular shape and a nearly polygonal shape.

16. A light-absorbing member in accordance with claim 3 , wherein the substrate includes a dye.

17. A light-absorbing member in accordance with claim 3 , wherein the substrate includes a pigment.

18. A lens barrel comprising three or more light-absorbing members, wherein

the shape of the lens barrel is a cylinder formed from three or more light-absorbing members, and wherein

each of the light-absorbing members comprises

a substrate made of a material capable of absorbing light of which reflection is to be prevented, the substrate having the shape of a curve viewed from a macroscopic viewpoint, and

an antireflection structure comprising structural elements arranged on the surface of the curve in an array form at a period smaller than the wavelength of the light, in which

the structural elements have a shape protruding or being recessed from a reference face corresponding to the curve of the substrate, and are arranged so that the straight lines connecting the reference face to the tips of the respective structural elements are nearly parallel to one another,

the shape of the curve is a recess, and

height or depth of each of the structural elements of the antireflection structure varies so that the height or depth increases gradually from a position near a central area in an area in which the antireflection structure is formed to a position near a periphery in the area.