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EP-4741888-A1 - GRATING STRUCTURE, LIGHT GUIDE DEVICE, OPTICAL MODULE AND HEAD-MOUNTED DISPLAY DEVICE

EP4741888A1EP 4741888 A1EP4741888 A1EP 4741888A1EP-4741888-A1

Abstract

Some embodiments of the present disclosure provide a grating structure, a light guide device, an optical module and a head-mounted display device; the grating structure includes: a substrate and a grating layer, the grating layer being provided on one side of the substrate, and including a plurality of grating units arranged sequentially at intervals; by regulating a refractive index of a gap between two adjacent grating units, the grating layer is capable of having a target diffraction efficiency; wherein a difference between the refractive index of the gap and that of the grating units is a target value A, and 0 < A ≤ 2. The grating structure design scheme provided by the embodiments of the present disclosure can regulate the diffraction efficiency without changing the shape of the surface relief grating. (FIG. 1)

Inventors

  • CHENG, XIN

Assignees

  • Goertek Optical Technology (Shanghai) Co., Ltd.

Dates

Publication Date
20260513
Application Date
20240703

Claims (14)

  1. A grating structure, characterized by comprising: a substrate (100); and, a grating layer provided on one side of the substrate (100), and comprising a plurality of grating units (101) arranged sequentially at intervals; by regulating a refractive index of a gap between two adjacent grating units (101), the grating layer is capable of having a target diffraction efficiency; wherein a difference between the refractive index of the gap and that of the grating units (101) is a target value A, and 0 < A ≤ 2.
  2. The grating structure according to claim 1, characterized in that a type of the grating structure comprises a surface relief grating.
  3. The grating structure according to claim 1 or 2, characterized in that the grating layer comprises a rectangular grating layer, a blazed grating layer, or a slanted grating layer.
  4. The grating structure according to claim 3, characterized in that at least one material is filled in the gap by means of coating and/or depositing to regulate the refractive index of the gap.
  5. The grating structure according to claim 4, characterized in that a first material (103) is filled in the gap, and has a first refractive index to regulate the refractive index of the gap, so that a difference between the regulated refractive index of the gap and the refractive index of the grating units (101) forms the target value A.
  6. The grating structure according to claim 5, characterized in that the first material (103) is filled to be flush with the grating units (101), or overflows from the gap and covers the grating units (101), so that the gap has the first refractive index.
  7. The grating structure according to claim 4, characterized in that a first material (103) and a second material (104) are filled in the gap, the first material (103) has a first refractive index and the second material (104) has a second refractive index for regulating the refractive index of the gap to be a mean value of the first refractive index and the second refractive index, and a difference between the regulated refractive indexes of the gap and the refractive index of the grating units (101) satisfies the target value A.
  8. The grating structure according to claim 7, characterized in that the first material (103) is filled in the gap, and the second material (104) covers the first material (103); wherein the second material (104) is flush with the grating units (101) or overflows from the gap and covers the grating units (101).
  9. The grating structure according to claim 7, characterized in that the first material (103) is deposited along an outer contour of the grating layer, and the second material (104) fills the gap and covers the first material (103); wherein the second material (104) is flush with the grating units (101) or overflows from the gap and covers the grating units (101).
  10. The grating structure according to claim 3, characterized in that a metal layer (105) covers along an outer contour of the grating layer, and comprises at least one of aluminum and silver.
  11. The grating structure according to claim 10, characterized in that an antioxidant layer (106) covers a side of the metal layer (105) facing away from the grating layer; wherein the antioxidant layer comprises silicon dioxide or titanium dioxide.
  12. A light guide device, characterized by comprising a base (3) and at least a first grating area (1) and a second grating area (2) provided on the base (3); the first grating area (1) is used for coupling light into the base (3) and causing the light to propagate to the second grating area (2) by total internal reflection, and the second grating area (2) is used for coupling out the light; the first grating area (1) comprises the grating structure according to any one of claims 1 to 11 and/or the second grating area (2) comprises the grating structure according to any one of claims 1 to 9.
  13. An optical module, characterized by comprising: the light guide device according to claim 12; and an optical engine configured for projecting light onto the light guide device.
  14. A head-mounted display device, characterized by comprising: a front frame assembly comprising at least one lens mounting portion; a wearing assembly detachably connected to the front frame assembly; and, the optical module according to claim 13; wherein the light guide device is provided in the lens mounting portion, and the optical engine is provided on the front frame assembly and located on a side close to the wearing assembly.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority to Chinese patent application No. 202310828956.X filed with the CNIPA on July 6, 2023 and entitled "GRATING STRUCTURE, LIGHT GUIDE DEVICE, OPTICAL MODULE AND HEAD-MOUNTED DISPLAY DEVICE", which is hereby incorporated by reference in its entirety. TECHNICAL FIELD The embodiments of the present application relate to the field of optical technology, and particularly to a grating structure, a light guide device, an optical module and a head-mounted display device. BACKGROUND Among various diffractive optical devices, diffraction optical waveguide is currently one of the mainstream technical solutions for implementing augmented reality. It utilizes the diffraction effect of micro/nano-structured gratings to couple light in and out, and transmits light by means of total internal reflection within transparent substrate. In existing technologies, diffraction efficiency is regulated basically by changing the shape of the gratings in the grating-based diffraction optical schemes, which results in insufficient flexibility in controlling the diffraction efficiency of the gratings. SUMMARY An objective of the present disclosure is to provide new technical solutions for a grating structure, a light guide device, an optical module and a head-mounted display device. In a first aspect, an embodiment of the present disclosure provides a grating structure. The grating structure comprises: a substrate; and,a grating layer provided on one side of the substrate, and comprising a plurality of grating units arranged sequentially at intervals;by regulating a refractive index of a gap between two adjacent grating units, the grating layer is capable of having a target diffraction efficiency; wherein a difference between the refractive index of the gap and that of the grating units is a target value A, and 0 < A ≤ 2. Optionally, a type of the grating structure comprises a surface relief grating. Optionally, the grating layer comprises a rectangular grating layer, a blazed grating layer, or a slanted grating layer. Optionally, at least one material is filled in the gap by means of coating and/or depositing to regulate the refractive index of the gap. Optionally, a first material is filled in the gap, and has a first refractive index to regulate the refractive index of the gap, so that a difference between the regulated refractive index of the gap and the refractive index of the grating units forms the target value A. Optionally, the first material is filled to be flush with the grating units, or overflows from the gap and covers the grating units, so that the gap has the first refractive index. Optionally, a first material and a second material are filled in the gap, the first material has a first refractive index and the second material has a second refractive index for regulating the refractive index of the gap to be a mean value of the first refractive index and the second refractive index, and a difference between the regulated refractive indexes of the gap and the refractive index of the grating units satisfies the target value A. Optionally, the first material is filled in the gap, and the second material covers the first material; wherein the second material is flush with the grating units or overflows from the gap and covers the grating units. Optionally, the first material is deposited along an outer contour of the grating layer, and the second material fills the gap and covers the first material; wherein the second material is flush with the grating units or overflows from the gap and covers the grating units. Optionally, a metal layer covers along an outer contour of the grating layer, and comprises at least one of aluminum and silver. Optionally, an antioxidant layer covers a side of the metal layer facing away from the grating layer; wherein the antioxidant layer comprises silicon dioxide or titanium dioxide. In a second aspect, an embodiment of the present disclosure provides a light guide device. The light guide device comprises a base and at least a first grating area and a second grating area provided on the base; the first grating area comprises the grating structure according to any one of the first aspect and/or the second grating area comprises the grating structure according to a part of the first aspect. In a third aspect, an embodiment of the present disclosure provides an optical module. The optical module comprises: the light guide device according to the second aspect; andan optical engine configured for projecting light onto the light guide device. In a fourth aspect, an embodiment of the present disclosure provides a head-mounted display device. The head-mounted display device comprises: a front frame assembly comprising at least one lens mounting portion;a wearing assembly detachably connected to the front frame assembly; and,the optical module according to the third aspect; wherein the light guide device is provided in the len