US-12619079-B2 - Diffraction optical waveguide, design method thereof and near-eye display device

US12619079B2US 12619079 B2US12619079 B2US 12619079B2US-12619079-B2

Abstract

The disclosure provides a diffraction optical waveguide, a design method thereof and a near-eye display device. The diffraction optical waveguide includes: a waveguide substrate; a coupling-in grating configured to couple image light into the waveguide substrate through diffraction; and a coupling-out grating configured to couple at least a part of diffracted light propagating thereinto out of the waveguide substrate through diffraction, wherein the waveguide substrate includes M layers of waveguide media, a catadioptric interface is formed between adjacent waveguide media, the diffracted light passes through the M layers of waveguide media in sequence and is split by the catadioptric interface, beams after light splitting propagate towards a coupling-out zone along different transmission paths in the M layers of waveguide media, each layer of waveguide medium has a different refractive index, a refractive index of an i th layer of waveguide medium being n i , an air refractive index being n 0 , and |n i −n i−1 |≥0.05.

Inventors

Xingming ZHAO
Zhentao Fan
Kehan Tian

Assignees

JIAXING UPHOTON OPTOELECTRONICS TECHNOLOGY CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20230906
Priority Date: 20221019

Claims (18)

1 . A diffraction optical waveguide, comprising: a waveguide substrate comprising a coupling-in zone and a coupling-out zone, the coupling-in zone spaced apart from the coupling-out zone by a preset distance; a coupling-in grating disposed in the coupling-in zone of the waveguide substrate and configured to couple image light into the waveguide substrate through diffraction; and a coupling-out grating disposed in the coupling-out zone of the waveguide substrate and configured to couple at least a part of the diffracted light propagating thereinto out of the waveguide substrate through diffraction, wherein the waveguide substrate comprises 4 layers of waveguide media, a catadioptric interface is formed between adjacent waveguide media, the diffracted light coupled-in from the coupling-in zone passes through the 4 layers of waveguide media in sequence and is split by the catadioptric interface, beams after light splitting propagate towards the coupling-out zone along different transmission paths in the 4 layers of waveguide media, and each layer of waveguide medium has a different refractive index, wherein a refractive index of an i th layer of waveguide medium is n i , an air refractive index is n 0 , and |n i −n i |≥0.05, such that the diffracted light coupled out of the waveguide substrate has a preset energy distribution, wherein refractive indexes of the 4 layers of waveguide media satisfy: n 1 −n 2 >0.05, n 3 −n 2 >0.05, n 3 −n 4 >0.05, and wherein the image light is diffracted by the coupling-in grating, and a propagation direction of the diffracted light in a first layer of waveguide medium satisfies the following formulae: n 1 ⁢ sin ⁢ θ 1 ⁢ sin ⁢ φ 1 = n 0 ⁢ sin ⁢ θ 0 ⁢ sin ⁢ φ 0 ⁢ n 1 ⁢ sin ⁢ θ 1 ⁢ cos ⁢ φ 1 - n 0 ⁢ sin ⁢ θ 0 ⁢ cos ⁢ φ 0 = λ d where λ is a wavelength of the image light, d is a period of the coupling-in grating, θ 0 is an incident angle when the image light is incident to the coupling-in grating, φ 0 is an azimuthal angle when the image light is incident to the coupling-in grating, θ 1 is a diffraction angle of +1-order diffracted light in the first layer of waveguide medium, and φ 1 is an azimuthal angle of the +1-order diffracted light in the first layer of waveguide medium.
2 . The diffraction optical waveguide according to claim 1 , wherein the i th layer of waveguide medium has a thickness of h i , h i ≤1 mm.
3 . The diffraction optical waveguide according to claim 2 , wherein |h i −h i−1 |≥0.05 mm.
4 . The diffraction optical waveguide according to claim 1 , wherein the coupling-in zone and the coupling-out zone are located at a surface of the waveguide substrate.
5 . The diffraction optical waveguide according to claim 4 , wherein the diffracted light is reflected and/or refracted by the catadioptric layer, and a light propagation direction satisfies: n i sin θ i =n 0 sin θ i−1 ( i≥ 2) when the diffracted light propagates in the i th layer of waveguide medium, a gap L i between adjacent reflection positions satisfies the following formula: L i =2 h i tan θ i where h i is a thickness of the i th layer of waveguide medium, and θ i is an angle of the +1-order diffracted light in the i th layer of waveguide medium.
6 . The diffraction optical waveguide according to claim 1 , wherein the coupling-in grating is a circular grating, and has a coupling-in diameter of m, m≤5 mm.
7 . The diffraction optical waveguide according to claim 1 , wherein the coupling-out grating comprises a plurality of partition gratings, and adjustment is made to one or more of the following: a number of partition gratings, structural depths of the partition gratings, structural types of the partition gratings, and the refractive index and thickness of the i th layer of waveguide medium, so as to improve coupling-out efficiency and/or uniformity of the diffraction optical waveguide.
8 . The diffraction optical waveguide according to claim 1 , wherein the coupling-in grating and the coupling-out grating are surface relief gratings or volume hologram gratings.
9 . The diffraction optical waveguide according to claim 1 , wherein the 4 layers of waveguide media are integrally formed by means of bonding.
10 . A design method of a diffraction optical waveguide as defined in claim 1 , comprising: setting one or more of the following in the diffraction optical waveguide: a number 4 of layers of waveguide media, a refractive index n i of an i th layer of waveguide medium, a thickness h i of the i th layer of waveguide medium, a number of partition gratings in the coupling-out grating, structural depths of the partition gratings and structural types of the partition gratings; obtaining, through simulation, coupling-out efficiency and uniformity of the diffraction optical waveguide.
11 . A near-eye display device, comprising: an optical machine configured to output image light; and a diffraction optical waveguide, comprising: a waveguide substrate comprising a coupling-in zone and a coupling-out zone, the coupling-in zone spaced apart from the coupling-out zone by a preset distance; a coupling-in grating disposed in the coupling-in zone of the waveguide substrate and configured to couple the image light into the waveguide substrate through diffraction; and a coupling-out grating disposed in the coupling-out zone of the waveguide substrate and configured to couple at least a part of the diffracted light propagating thereinto out of the waveguide substrate through diffraction, wherein the waveguide substrate comprises 4 layers of waveguide media, a catadioptric interface is formed between adjacent waveguide media, the diffracted light coupled-in from the coupling-in zone passes through the 4 layers of waveguide media in sequence and is split by the catadioptric interface, beams after light splitting propagate towards the coupling-out zone along different transmission paths in the 4 layers of waveguide media, and each layer of waveguide medium has a different refractive index, wherein a refractive index of an i th layer of waveguide medium is n i , an air refractive index is no, and |n i −n i−1 |≥0.05, such that the diffracted light coupled out of the waveguide substrate has a preset energy distribution, wherein refractive indexes of the 4 layers of waveguide media satisfy: n 1 −n 2 >0.05, n 3 −n 2 >0.05, n 3 −n 4 >0.05, and wherein the image light is diffracted by the coupling-in grating, and a propagation direction of the diffracted light in a first layer of waveguide medium satisfies the following formulae: n 1 ⁢ sin ⁢ θ 1 ⁢ sin ⁢ φ 1 = n 0 ⁢ sin ⁢ θ 0 ⁢ sin ⁢ φ 0 ⁢ n 1 ⁢ sin ⁢ θ 1 ⁢ cos ⁢ φ 1 - n 0 ⁢ sin ⁢ θ 0 ⁢ cos ⁢ φ 0 = λ d where λ is a wavelength of the image light, d is a period of the coupling-in grating, θ 0 is an incident angle when the image light is incident to the coupling-in grating, φ 0 is an azimuthal angle when the image light is incident to the coupling-in grating, θ 1 is a diffraction angle of +1-order diffracted light in the first layer of waveguide medium, and φ 1 is an azimuthal angle of the +1-order diffracted light in the first layer of waveguide medium, and wherein the image light output by the optical machine enters the diffraction optical waveguide via the coupling-in grating, is split into a plurality of beams in the diffraction optical waveguide and coupled out via the coupling-out grating along the different transmission paths.
12 . The near-eye display device according to claim 11 , wherein the near-eye display device is an Augmented Reality display device or a Virtual Reality display device.
13 . The near-eye display device according to claim 11 , wherein the i th layer of waveguide medium has a thickness of h i , h i ≤1 mm, and wherein |h i −h i−11 |≥0.05 mm.
14 . The near-eye display device according to claim 11 , wherein the coupling-in zone and the coupling-out zone are located at a surface of the waveguide substrate, and wherein the diffracted light is reflected and/or refracted by the catadioptric layer, and a light propagation direction satisfies: n i sin θ i =n 0 sin θ i−1 ( i≥ 2) when the diffracted light propagates in the i th layer of waveguide medium, a gap L i between adjacent reflection positions satisfies the following formula: L i =2 h i tan θ i where h i is a thickness of the i th layer of waveguide medium, and θ i is an angle of the +1-order diffracted light in the i th layer of waveguide medium.
15 . The near-eye display device according to claim 11 , wherein the coupling-in grating is a circular grating, and has a coupling-in diameter of m, m≤5 mm.
16 . The near-eye display device according to claim 11 , wherein the coupling-out grating comprises a plurality of partition gratings, and adjustment is made to one or more of the following: a number of partition gratings, structural depths of the partition gratings, structural types of the partition gratings, and the refractive index and thickness of the i th layer of waveguide medium, so as to improve coupling-out efficiency and/or uniformity of the diffraction optical waveguide.
17 . The near-eye display device according to claim 11 , wherein the coupling-in grating and the coupling-out grating are surface relief gratings or volume hologram gratings.
18 . The near-eye display device according to claim 11 , wherein the 4 layers of waveguide media are integrally formed by means of bonding.

Description

TECHNICAL FIELD The disclosure relates to the technical field of diffraction optics, and, in particular, to a diffraction optical waveguide, a near-eye display device and a design method of a diffraction optical waveguide. BACKGROUND With the development of the semiconductor technology, the way of human-computer interaction is making rapid progress. Augmented Reality (AR) can provide humans with more dimensional information. AR glasses are one of important media in the Augmented Reality field. An optical waveguide is a device capable of binding a light beam inside the same and transmitting an optical signal in a certain direction, which may serve as a front end of AR glasses. The optical waveguide transmits light carrying virtual information to human eyes to form an image on the retina. Furthermore, due to the good light transmittance of the optical waveguide, human eyes can also capture an image of a real environment, and a virtual image is finally integrated with the image of the real-environment to achieve the purpose of Augmented Reality. When light propagates within an optical waveguide, the light is diffracted by a coupling-out grating to be output and is split into beams, which causes fast attenuation of the light energy. Although the diffraction efficiencies of the grating at different positions can be modulated by partition so as to regulate the uniformity of waveguide coupling-out, the modulation for the uniformity of the waveguide coupling-out is limited due to the degree of freedom of the grating per se. The existing waveguides mostly employ partition gratings to modulate the uniformity of the waveguide coupling-out, thereby reducing the grating efficiency of a coupling-out end while improving the uniformity. The contents in the Background are only the technologies known by the inventor, and do not necessarily represent the existing technology in the field. SUMMARY In view of one or more defects in the existing technology, the disclosure provides a diffraction optical waveguide, including: a waveguide substrate including a coupling-in zone and a coupling-out zone, the coupling-in zone spaced apart from the coupling-out zone by a preset distance;a coupling-in grating disposed in the coupling-in zone of the waveguide substrate and configured to couple image light into the waveguide substrate through diffraction; anda coupling-out grating disposed in the coupling-out zone of the waveguide substrate and configured to couple at least a part of diffracted light propagating thereinto out of the waveguide substrate through diffraction,wherein the waveguide substrate includes M layers of waveguide media, where M≥2, the refractive indexes of the M layers of waveguide media are configured with a non-sequential distribution, a catadioptric interface is formed between adjacent waveguide media, the diffracted light coupled-in from the coupling-in zone passes through the M layers of waveguide media in sequence and is split by the catadioptric interface, beams after light splitting propagate towards the coupling-out zone along different transmission paths in the M layers of waveguide media, and each layer of waveguide medium has a different refractive index, wherein a refractive index of an ith layer of waveguide medium is ni, an air refractive index is n0, and |ni−ni−1≥0.05, such that the diffracted light coupled out of the waveguide substrate has a preset energy distribution. According to one aspect of the disclosure, the ith layer of waveguide medium has a thickness of hi, hi≤1 mm. According to one aspect of the disclosure, |hi−hi−1|≥0.05 mm. According to one aspect of the disclosure, the coupling-in zone and the coupling-out zone are located at a surface of the waveguide substrate. According to one aspect of the disclosure, the image light is diffracted by the coupling-in grating, and a propagation direction of the diffracted light in a first layer of waveguide medium satisfies the following formulae: n1⁢ sin⁢ θ1⁢sin⁢φ1=n0⁢ sin⁢ θ0⁢ sin⁢φ0⁢ n1⁢ sin⁢ θ1⁢cos⁢φ1-n0⁢ sin⁢ θ0⁢ cos⁢φ0=λdwhere λ is a wavelength of the image light, d is a period of the coupling-in grating, θ0 is an incident angle when the image light is incident to the coupling-in grating, φ0 is an azimuthal angle when the image light is incident to the coupling-in grating, θ1 is a diffraction angle of +1-order diffracted light in the first layer of waveguide medium, and φ1 is an azimuthal angle of the +1-order diffracted light in the first layer of waveguide medium. According to one aspect of the disclosure, the image light is diffracted by the coupling-in grating, the diffracted light is reflected and/or refracted by the catadioptric layer, and a light propagation direction satisfies: ni sin θi=n0 sin θi−1 (i≥2) when the diffracted light propagates in the ith layer of waveguide medium, a gap Li between adjacent reflection positions satisfies the following formula: Li=2hi tan θi where hi is a thickness of the ith layer of w