Optical structure and authentication body
There is provided an optical structure having a quantization phase difference structure on one surface of a quantization phase difference structure layer, wherein in the quantization phase difference structure, a plurality of quantization projecting portions in a constant size and a plurality of quantization recessed portions in a constant size are aligned, wherein a multiple diffraction region has the quantization phase difference structure where ribbed projecting portions, in which the quantization projecting portions are aligned in one direction, are arranged adjacent to and alternately with groove-like recessed portions, in which the quantization recessed portions are aligned parallel to the ribbed projecting portions, and wherein the multiple diffraction region is a quantization phase difference structure configured to reproduce a plurality of reproduction points discrete in one direction and arranged regularly.
1. An optical structure comprising:
a quantization phase difference structure in which,
a plurality of quantization projecting portions in a constant size and a plurality of quantization recessed portions in a constant size are aligned, on one surface of a quantization phase difference structure layer, and
a multiple diffraction region is arranged, the multiple diffraction region having the quantization phase difference structure where ribbed projecting portions, in which the plurality of quantization projecting portions are aligned in one direction, are arranged adjacent to and alternately with grooved recessed portions, in which the quantization recessed portions are aligned parallel to the ribbed projecting portions,
the quantization phase difference structure to reproduce a plurality of reproduction points discrete in one direction and arranged regularly.
2. The optical structure according to claim 1 , wherein surface roughness of a bottom surface of the quantization recessed portions of the quantization phase difference structure is different from surface roughness of a top surface of the quantization recessed portions of the quantization phase difference structure.
3. The optical structure according to claim 1 , wherein the multiple diffraction region includes a plurality of multiple diffraction regions arranged regularly in the quantization phase difference structure.
4. The optical structure according to claim 3 , wherein a multiple diffraction region, from among the plurality of multiple diffraction regions, has a direction of a spatial frequency component determined in accordance with a direction toward which an inclined surface of a projecting structure in the multiple diffraction region faces.
5. The optical structure according to claim 4 , wherein the plurality of reproduction points are reproduced from the spatial frequency component, and wherein a shortest distance R from the plurality of reproduction points to a plane where the reproduction points are provided satisfies a relationship of R>D 2 /λ, where D is an entire length of the multiple diffraction region and A is a wavelength of light in the multiple diffraction region.
6. The optical structure according to claim 5 , wherein an incident light vector perpendicular to the plane is {right arrow over (I)}=(0,0,−1), and a normal vector relative to an inclined surface of a polygon in a phantom 3D shape constructed on the plane is {right arrow over (n)}, an angle between −{right arrow over (I)} and the normal vector {right arrow over (n)} is θ1, an angle between an alignment direction {right arrow over (a)} of the plurality of reproduction points, and the normal vector {right arrow over (n)} is θ2, and if θ1=θ2=θ, the plurality of reproduction points are distributed in accordance with the alignment direction {right arrow over (a)}={right arrow over (I)}+2 cos(θ)·{right arrow over (n)}.
7. The optical structure according to claim 6 , wherein light intensity distribution of the plurality of reproduction points is obtained such that, among the plurality of reproduction points, a reproduction point existing in a direction in which incident light is reflected on the inclined surface of the polygon in a specular manner has a highest light intensity, and a reproduction point shifted further from the direction in which the incident light is reflected in a specular manner has a lower light intensity.
8. The optical structure according to claim 6 , wherein the plurality of reproduction points are arranged at an irregular interval in a space.
9. The optical structure according to claim 3 , wherein the multiple diffraction region is of a cell type.
10. The optical structure according to claim 3 , wherein a depth of the quantization phase difference structure is different for each of the multiple diffraction regions.
11. The optical structure according to claim 3 , the optical structure comprising a reflection layer on a surface of the quantization phase difference structure.
12. An authentication body comprising the optical structure according to claim 1 .