US-12625314-B2 - Curved waveguide-based augmented reality device, method for operation of said device, augmented reality glasses based on said device

US12625314B2US 12625314 B2US12625314 B2US 12625314B2US-12625314-B2

Abstract

A curved waveguide-based augmented reality device is provided. The device includes a projector, and a curved waveguide. The waveguide has a shape of a concentric cylindrical meniscus and includes an in-coupling diffractive optical element and an out-coupling diffractive optical element, a grating period of a diffraction grating of the in-coupling diffractive optical element at each point of the in-coupling diffractive optical element is such that rays from one point of an initial image are input into the curved waveguide in each point of the in-coupling diffractive optical element at the same angle relative to a normal to a surface of the curved waveguide at a point of ray incidence, and at least at one point on each of the diffractive optical elements a diffraction grating period of the in-coupling diffractive optical element is equal to a diffraction grating period of the out-coupling diffractive optical element.

Inventors

Gavril Nikolaevich VOSTRIKOV
Nikolay Viktorovich Muravyev
Aleksandr Evgenyevich Angervaks
Roman Aleksandrovich Okun
Anastasia Sergeevna PEREVOZNIKOVA

Assignees

SAMSUNG ELECTRONICS CO., LTD.

Dates

Publication Date: 20260512
Application Date: 20230824
Priority Date: 20221219

Claims (15)

1 . An augmented reality display device comprising a projector forming an initial image; and a curved waveguide having a shape of a concentric cylindrical meniscus and comprising an in-coupling diffractive optical element and an out-coupling diffractive optical element, wherein a grating period of the in-coupling diffractive optical element at each point of the in-coupling diffractive optical element is such that rays emanating from one point of the initial image undergo diffraction at the in-coupling diffractive optical element at a same angle relative to a normal to a surface of the curved waveguide at a point of incidence, and wherein, when a point radiation source corresponding to the one point of the initial image is located at a finite distance Z LGT from a concave surface of the curved waveguide, the grating period of the in-coupling diffractive optical element in the cross-section under consideration is defined by an expression: T YOZ OUT ( L out ) = λ … ⁢ sin ⁢ ( L out / R ⁢ 1 ) + λ / T 0 , where Lin is a linear coordinate along a concave surface of the curved waveguide with an origin in the center of the in-coupling diffractive optical element, R1 is a curvature radius of the concave surface of the curved waveguide, λ is an incident radiation wavelength corresponding to the initial image, and T o is a diffraction grating period of the in-coupling diffractive optical element in the point where ray with a wavelength λ falling on the in-coupling diffractive optical element along the normal to the surface of the curved waveguide undergoes diffraction into a −1st diffraction order by the in-coupling diffractive optical element.
2 . The device of claim 1 , wherein the curved waveguide is configured to propagate rays of the initial image from the in-coupling diffractive optical element to the out-coupling diffractive optical element based on total internal reflection from surfaces of the curved waveguide, wherein, when propagating the rays of the initial image, angles of incidence on and of reflection from a concave surface of the curved waveguide inside the curved waveguide are equal to each other and constant, and angles of incidence on and of reflection from a convex surface of the curved waveguide inside the curved waveguide are equal to each other and constant.
3 . The device of claim 1 , wherein the out-coupling diffractive optical element is configured to form a virtual image on a user retina by converting the rays passed through the curved waveguide and falling on the out-coupling diffractive optical element into parallel beams of rays.
4 . The device of claim 1 , wherein at least at one point on each of diffractive optical elements, a diffraction grating period of the in-coupling diffractive optical element is equal to a diffraction grating period of the out-coupling diffractive optical element.
5 . The device of claim 4 , wherein the diffraction grating period of the in-coupling diffractive optical element is equal to the diffraction grating period of the out-coupling diffractive optical element in a center of the in-coupling diffractive optical element and in the center of the diffraction grating of the out-coupling diffractive optical element.
6 . The device of claim 5 , wherein the center of the initial image lies on the normal to a waveguide surface in the center of the in-coupling diffractive optical element, and the center of an image formed by the out-coupling diffractive optical element lies on the normal to the waveguide surface in the center of the out-coupling diffractive optical element.
7 . The device of claim 5 , wherein, when the projector forms an image at infinity, for each point of the in-coupling diffractive optical element with coordinates x in and L in its period is defined by an expression: T IN ( x i ⁢ n , L i ⁢ n ) = λ sin ⁢ ( L i ⁢ n R ⁢ 1 ) + λ T 0 , xin is a linear coordinate of the point on the waveguide surface on which the ray falls along an OinXin axis in a coordinate system OinXinYinZin, wherein a center Oin of a coordinate system is disposed at the center of the in-coupling diffractive optical element, a Zin axis is directed along the normal to the surface of the curved waveguide, a Yin axis is directed tangentially to the surface of the curved waveguide in a point Oin along a length of the curved waveguide and perpendicularly to the Zin axis, an Xin axis is directed along a generatrix of a cylindrical surface of the curved waveguide in the point Oin across a width of the curved waveguide and perpendicularly to the Zin axis; Lin is a linear coordinate along the concave surface of the curved waveguide with an origin in the center Oin of the in-coupling diffractive optical element, R1 is a curvature radius of the concave surface of the curved waveguide, λ is an incident radiation wavelength corresponding to the initial image, T0 is a diffraction grating period of the in-coupling diffractive optical element in the point where ray with a wavelength λ falling on the in-coupling diffractive optical element along the normal to the surface of the curved waveguide undergoes diffraction into a −1st diffraction order by the in-coupling diffractive optical element, and wherein grating grooves of the in-coupling diffractive optical element are parallel to a common axis of the cylindrical surface of the curved waveguide.
8 . The device of claim 1 , wherein, when the out-coupling diffractive optical element forms an image at infinity, a variation of a period of the out-coupling diffractive optical element is equal to: T YOZ OUT ( L out ) = λ - sin ⁢ ( L out / R ⁢ 1 ) + λ / T 0 , Lout is a linear coordinate along the concave surface of the curved waveguide in a cross-section YoutOoutZout with an origin in a center Oout of the out-coupling diffractive optical element, where the period of the out-coupling diffractive optical element is equal to T0, a Zout axis is directed along the normal to the surface of the curved waveguide, a Yout axis is directed tangentially to the surface of the curved waveguide in a point Oout along a length of the curved waveguide and perpendicularly to the Zout axis, an Xout axis is directed tangentially to the surface of the curved waveguide in the point Oout across a width of the curved waveguide and perpendicularly to the Zout axis, R1 is a curvature radius of the concave surface of the curved waveguide, λ is an incident radiation wavelength corresponding to the initial image, and wherein grating grooves of the out-coupling diffractive optical element are parallel to a common axis of the cylindrical surface of the curved waveguide.
9 . The device of claim 1 , further comprising: two flat waveguides disposed between the projector and the in-coupling diffractive optical element, wherein each of the flat waveguides has a constant-period diffraction grating of the flat waveguide, and wherein grooves of the diffraction grating of each flat waveguide are perpendicular to an axis of the cylindrical surface of the curved waveguide.
10 . A method of operating an augmented reality device, the method comprising: forming, by a projector, an initial image; and inputting, by an in-coupling diffractive optical element, rays of the initial image into a curved waveguide, wherein rays emanating from one point of the initial image undergo diffraction at the in-coupling diffractive optical element at a same angle relative to a normal to a surface of the curved waveguide at a point of incidence, wherein the rays inputted into the curved waveguide propagate within the curved waveguide based on total internal reflection from surfaces of the curved waveguide; and transforming, based on an out-coupling diffractive optical element, the rays passed through the curved waveguide into parallel beams of rays to form a virtual image on a user retina, wherein, when a point radiation source corresponding to the one point of the initial image is located at a finite distance Z LGT from a concave surface of the curved waveguide, the grating period of the in-coupling diffractive optical element in the cross-section under consideration is defined by an expression: T TOZ IN ( L i ⁢ n ) = λ sin ⁡ ( tan - 1 ( R ⁢ 1 · sin ⁡ ( L i ⁢ n / R ⁢ 1 ) Z LGT - R ⁢ 1 · cos ⁡ ( L i ⁢ n / R ⁢ 1 ) + R ⁢ 1 ) + L i ⁢ n R ⁢ 1 ) + λ T 0 . where Lin is a linear coordinate along a concave surface of the curved waveguide with an origin in the center of the in-coupling diffractive optical element, R1 is a curvature radius of the concave surface of the curved waveguide, λ is an incident radiation wavelength corresponding to the initial image, and T o is a diffraction grating period of the in-coupling diffractive optical element in the point where ray with a wavelength λ falling on the in-coupling diffractive optical element along the normal to the surface of the curved waveguide undergoes diffraction into a −1st diffraction order by the in-coupling diffractive optical element.
11 . The method of claim 10 , wherein the augmented reality device includes augmented reality glasses comprising an element for left eye and an element for right eye, and wherein each of the elements for left and right eye is an augmented reality display device.
12 . The method of claim 11 , wherein a distance between centers of an out-coupling diffractive optical elements corresponds to a user interpupillary distance.
13 . The method of claim 11 , wherein the normal to a waveguide surface in a center of the out-coupling diffractive optical element for right eye is parallel to the normal to the waveguide surface in the center of the out-coupling diffractive optical element for left eye.
14 . The method of claim 11 , wherein at least at one point on each of diffractive optical elements, a diffraction grating period of the in-coupling diffractive optical element is equal to a diffraction grating period of the out-coupling diffractive optical element.
15 . The method of claim 14 , wherein the diffraction grating period of the in-coupling diffractive optical element is equal to the diffraction grating period of the out-coupling diffractive optical element in the center of the in-coupling diffractive optical element and in the center of the diffraction grating of the out-coupling diffractive optical element, and wherein the center of the initial image lies on the normal to the waveguide surface in the center of the in-coupling diffractive optical element, and the center of an image formed by the out-coupling diffractive optical element lies on the normal to the waveguide surface in the center of the out-coupling diffractive optical element.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S) This application is a continuation application, claiming priority under § 365(c), of an International application No. PCT/KR2023/010613, filed on Jul. 21, 2023, which is based on and claims the benefit of a Russian patent application number 2022133304, filed on Dec. 19, 2022, in the Russian Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. TECHNICAL FIELD The disclosure relates to augmented reality devices. More particularly, the disclosure relates to augmented reality glasses. BACKGROUND OF INVENTION Wearable augmented reality glasses (AR) are a personal device that a user can use as a source of video information (image) projected directly into the user eye in the form of a virtual image that complements a user surrounding real world. For mass-market consumer, it is necessary to develop devices of augmented reality glasses with a wide field of view (FOV) is angular characteristic showing in what range of angles it is possible to observe virtual images that complement the user surrounding real world), a low-weight and low-cost, compactness and high resolution. Such wearable devices can replace any source of video information for the user, such as (televisions) TVs, smartphones, etc. The following requirements are imposed on systems of augmented reality glasses: a wide field of view to enable overlapping a virtual image on a large area of space that the human eye sees;good image quality, i.e., high resolution, high contrast, etc.;low weight;compactness;low cost. An optical device that combines a virtual image with the user surrounding real world is an optical combiner. As a combiner, planar (flat) waveguides are currently most widely used, on the surface of which diffractive optical elements (DOEs) for inputting, conversing and outputting optical radiation are located. A planar waveguide is a transparent plate made of an optical material with two plane-parallel surfaces. A beam of parallel rays can propagate without distortions to any distance within such a waveguide. Augmented reality devices with such combiners have low weight, small size, low cost, can provide a wide field of view, and have high transmissivity, that is, high transmission of a real image. However, in such devices, the edges where image projectors are located are disposed far from temporal part of the user head, so such glasses occupy a large space during use. In addition, such combiners form a virtual image not only from the side where the user eye is located, but also from the opposite side from the user. This may lead to that an external observer, at a certain location, will be able in the same manner as the user to partially or completely see the virtual image formed for the user, which may be undesirable. Curved waveguides located on the user head such that they go around the oval of the user head can be used as an optical combiner, wherein the glasses with such a combiner will be more compact and convenient, they will have smaller dimensions, a device with such a combiner will be more ergonomic and aesthetic. However, the use of a curved waveguide as a combiner is associated with significant difficulties in converting and transmitting optical radiation therethrough. For example, let is consider the case of falling a parallel beam of rays on a curved waveguide. Let this beam be input into the waveguide using a constant-period in-coupling diffraction grating. The beam of parallel rays falling (incident) on the waveguide will turn into a non-parallel beam inside the waveguide, the rays of which will propagate at different angles within the waveguide. This effect should be taken into account and compensated for when designing augmented reality glasses with a curved combiner. A document U.S. Ser. No. 10/983,346B2 (publication date is 20.04.2021) is known from prior art. This document discloses a curved waveguide-based display device, wherein a portion of the waveguide for inputting radiation is flat and a portion of the waveguide for outputting radiation is curved. On the curved portion of the waveguide, an out-coupling diffractive optical element (DOE) with a variable period is disposed, wherein all the radiation entering the waveguide from a projector is output based on the out-coupling DOE at one angle, that is, all the rays that are output from the waveguide are parallel each other, so that an image has no distortions. The disadvantage of the known device is the low quality of the image formed by such a combiner due to that a parallel beam of rays propagating without distortions within the flat portion of the waveguide, having passed into the curved portion of the waveguide, will be inevitably distorted when propagating along the curved portion of the waveguide because the angle of incidence of various rays from the parallel beam on the curved surface of the waveguide will be different due to curvature of this surface. A document “Field o