# US 2025/0093559 A1 · Diffraction grating and mold for forming diffraction grating

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- Number: US 2025/0093559 A1
- Document ID: US20250093559A1
- Status: Published application
- Kind: A1
- Application number: 18/728,361
- Filed: 2023-01-18
- Published: 2025-03-20
- Earliest claimed: 2022-01-20
- Assignees: Dai Nippon Printing Co., Ltd.
- Applicants: Dai Nippon Printing Co., Ltd.
- Inventors: Yukie NAITO
- Web page: https://patentgrep.com/patent/US20250093559A1

## CPC

- G02B 5/1819: {Plural gratings positioned on the same surface, e.g. array of gratings (plural diffractive elements positioned sequentially along the optical path G02B27/4272)}
- G02B 5/1823: {in an overlapping or superposed manner}
- G02B 5/1852: {using mechanical means, e.g. ruling with diamond tool, moulding}
- 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)}
- G02B 5/1866: {Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials (G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A diffraction grating including: an optically transparent substrate; and a diffraction grating structure, with a step-like cross-sectional shape, on a surface of the optically transparent substrate, wherein the diffraction grating structure is formed of a single member, the diffraction grating structure includes a first diffraction grating portion and a second diffraction grating portion with different grating periods and different numbers of steps, a grating period of the second diffraction grating portion is shorter than a grating period of the first diffraction grating portion, a number of steps of the second diffraction grating portion is more than a number of steps of the first diffraction grating portion, and a difference between a grating height of the first diffraction grating portion and a grating height of the second diffraction grating portion is less than a minimum height of one step of the first diffraction grating portion.

## Claims

### Claim 1

A diffraction grating comprising:
an optically transparent substrate; and
a diffraction grating structure, with a step-like cross-sectional shape, on a surface of the optically transparent substrate, wherein
the diffraction grating structure is formed of a single member,
the diffraction grating structure includes a first diffraction grating portion and a second diffraction grating portion with different grating periods and different numbers of steps,
a grating period of the second diffraction grating portion is shorter than a grating period of the first diffraction grating portion,
a number of steps of the second diffraction grating portion is more than a number of steps of the first diffraction grating portion, and
a difference between a grating height of the first diffraction grating portion and a grating height of the second diffraction grating portion is less than a minimum height of one step of the first diffraction grating portion.

### Claim 2 (depends on 1)

The diffraction grating according to claim 1, wherein the difference between the grating height of the first diffraction grating portion and the grating height of the second diffraction grating portion is 15% or less with respect to 100% of the grating height of the first diffraction grating portion.

### Claim 3 (depends on 1)

The diffraction grating according to claim 1, wherein the number of steps of the first diffraction grating portion is 7 or more.

### Claim 4 (depends on 1)

A mold for forming a diffraction grating comprising a pattern structure configured to duplicate the diffraction grating according to claim 1.

### Claim 5

A mold for forming a diffraction grating comprising:
an optically transparent substrate; and
a pattern structure, with a step-like cross-sectional shape, on a surface of the optically transparent substrate, wherein
the pattern structure is formed of a single member,
the pattern structure includes a first pattern portion and a second pattern portion with different pattern periods and different numbers of steps,
a pattern period of the second pattern portion is shorter than a pattern period of the first pattern portion,
a number of steps of the second pattern portion is more than a number of steps of the first pattern portion, and
a difference between a pattern height of the first pattern portion and a pattern height of the second pattern portion is less than a minimum height of one step of the first pattern portion.

### Claim 6 (depends on 5)

The mold for forming a diffraction grating according to claim 5, wherein the difference between the pattern height of the first pattern portion and the pattern height of the second pattern portion is 15% or less with respect to 100% of the pattern height of the first pattern portion.

### Claim 7 (depends on 5)

The mold for forming a diffraction grating according to claim 5, wherein the number of steps of the first pattern portion is 7 or more.

### Claim 8 (depends on 5)

A diffraction grating comprising a diffraction grating structure duplicated by the mold for forming a diffraction grating according to claim 5.