CN111679360A

CN111679360A - Large-view-field grating waveguide element and near-to-eye display device

Info

Publication number: CN111679360A
Application number: CN202010573970.6A
Authority: CN
Inventors: 史晓刚; 薛正辉; 王丙杰
Original assignee: Beijing Xloong Technologies Co ltd; Beijing Institute of Technology BIT
Current assignee: Beijing Xloong Technologies Co ltd; Beijing Institute of Technology BIT
Priority date: 2020-06-22
Filing date: 2020-06-22
Publication date: 2020-09-18

Abstract

The invention discloses a large-field grating waveguide element and a near-to-eye display device, which comprises a grating waveguide device, wherein the grating waveguide device consists of an optical substrate and grating regions positioned on the surface of the optical substrate, the grating regions have five groups of functional regions, and comprise two incident grating regions a and b, two turning grating regions a and b and an emergent grating region, the incident grating regions a and b are used for guiding virtual image light beams with a certain field angle and a certain entrance pupil diameter into the grating region waveguide device, the invention leads the light ranges conducted by different incident gratings and turning gratings to be complementary by providing grating waveguide structures of the two incident gratings, the two turning gratings and the emergent gratings and designs the field angles of the incident gratings, the turning gratings and the emergent gratings, and splicing to form a larger field angle.

Description

Large-view-field grating waveguide element and near-to-eye display device

Technical Field

The invention relates to the technical field of waveguide elements, in particular to a large-field grating waveguide element and a near-to-eye display device.

Background

Near-eye display devices have evolved rapidly as virtual reality and augmented reality technologies have become recognized and accepted. The near-to-eye display in the augmented reality technology can superimpose a virtual image onto a real scene, and simultaneously has perspective characteristic, so that the normal observation of the real scene is not influenced. Means for coupling the virtual image into the human eye using conventional optical elements have been employed, including prisms, half-mirrors, free-form waveguides, mirror array waveguides, diffractive waveguides, and the like. The diffraction waveguide display technology is to realize the incidence, turning and emergence of light rays by using a diffraction grating, realize light ray transmission by using a total reflection principle, transmit an image of a micro display to human eyes and further see a virtual image. Because the total reflection principle the same as that of the optical fiber technology is adopted, the diffraction waveguide display component can be made as light, thin and transparent as common spectacle lenses. And because the turning of the light is realized by the diffraction grating on the surface of the lens, the shape of the lens is basically irrelevant to the shape of the bottom plate, the lens is easy to manufacture in batches, and the production cost is low.

In a diffractive waveguide element, light can only be guided and expanded over a range of angles. When the light is parallel to the upper and lower surfaces of the waveguide sheet (at this time, the incident angle of the light on the upper and lower surfaces is 90 degrees), the light cannot be incident to the exit or turning grating on the waveguide surface, so that the expansion and exit of the light beam cannot be realized, and when the incident angle of the light on the upper and lower surfaces of the waveguide sheet is smaller than the critical angle, the total reflection cannot occur, the light can be rapidly transmitted and attenuated, and the conduction cannot be realized. The incident angle of the light is only greater than the critical angle and less than 90 degrees, so that the waveguide can normally work. The critical angle is related to the material of the waveguide plate, such as the critical angle of 42 degrees for BK7 glass material. The critical angle can be reduced by using a high-refractive-index glass, but the refractive index of the current optical glass is at most about 2.0, and the corresponding critical angle is 30 degrees. Due to the limitations of current optical glass materials, the critical angle is difficult to reduce again, and the amplitude is limited if not reduced. Thus, the range of angles over which light is guided within the waveguide is typically less than 60 degrees. This limitation also makes it difficult for the angle of view of the diffractive waveguide to exceed 60 degrees. If other design factors such as ghost image avoidance, light transmission efficiency, etc. are considered, the angle is smaller, and usually is difficult to exceed 55 degrees, the diffraction waveguide is an emerging technology, although the current technology level has reached a higher level, so the current diffraction waveguide has a problem that the field angle is difficult to improve, and therefore, a large-field grating waveguide element and a near-eye display device are provided.

Disclosure of Invention

The invention aims to provide a large-field grating waveguide element and a near-eye display device, which solve the problem that the field angle of a diffraction waveguide in the prior art is difficult to improve.

In order to achieve the purpose, the invention provides the following technical scheme: a grating waveguide element with a large field of view comprises a grating waveguide device, wherein the grating waveguide device consists of an optical substrate and a grating region positioned on the surface of the optical substrate, and the grating region has five groups of functional regions, including two incident grating regions a and b, two turning grating regions a and b and an emergent grating region;

the incident grating areas a and b are used for guiding virtual image light beams with a certain field angle and a certain entrance pupil diameter into the grating area waveguide device; the incident grating area a mainly diffracts the incident light towards the direction of the turning grating area a, and the incident grating area b mainly diffracts the incident light towards the direction of the turning grating area b;

the diffraction light generated by the incident grating areas a and b is transmitted through the turns of the turning grating areas a and b, and then enters the emergent grating area to be utilized.

Preferably, the turning grating region a may expand a part of the diffracted light beams of the entrance gratings a, b, typically + order diffracted light beams, in a vertically upward direction while generating diffracted light beams propagating towards the exit grating region.

Preferably, the turning grating region b may expand another part of the diffracted beams of the entrance grating regions a, b, typically-order diffracted beams, in a vertically downward direction while generating diffracted beams directed towards the exit grating region, which may expand the beams in a horizontal direction while directing light energy out of the grating waveguide device.

Preferably, the field angle covered by the light rays conducted by the incident grating area a and the turning grating area a is F, the field angle covered by the light rays conducted by the grating waveguide device is F, and grating parameters of the waveguide, the incident grating area a, b, the turning grating area a, b and the emergent grating area are respectively set;

if F is positioned on the left side of the normal line of the surface of the grating waveguide device and F is positioned on the right side of the normal line of the surface of the waveguide device, the incident grating area a, the incident grating area b, the turning grating area a, the turning grating area b and the emergent grating area are superposed together to form the field angle of the grating waveguide device:

F＝F1+F2。

preferably, the incident grating regions a, b and the turning grating regions a, b are arranged in a staggered manner, so that no gap exists between the turning grating regions a and the turning grating regions b when the incident grating regions a, b and the turning grating regions a, b are observed along the direction of the x axis.

A near-to-eye display device of a large-field-of-view grating waveguide element comprises a grating waveguide device, a micro display A and a micro display B;

the micro display A emits a light beam to an incident grating area a, the diffracted light beam generated by the incident grating area a is transmitted along the y direction in an incident grating area b and is continuously diffracted to generate diffracted light transmitted towards an exit grating area, and the diffracted light generated by the turning grating area a is transmitted to the exit grating area and then is diffracted out of the waveguide by the exit grating area and is perceived by human eyes;

the micro display B emits a light beam which is projected to the incident grating area B, the diffracted light beam generated by the incident grating area B is transmitted along the-y direction in the turning grating area B and is continuously diffracted to generate diffracted light which is transmitted towards the emergent grating area, and the diffracted light generated by the turning grating area B is transmitted to the emergent grating area and then is diffracted out of the waveguide by the emergent grating area and is perceived by human eyes.

Preferably, the image produced by microdisplay a has less overlap or even no overlap with the image produced by microdisplay B, resulting in a picture that is nearly as many as a single microdisplay image.

Preferably, the micro display A and the micro display B are one or more of MEMS micro display, fiber scanning micro display, micro LED micro display system, DMD micro projection system and LCOS micro projection system.

Preferably, the micro display A is an MEMS micro display, a laser and a collimating optical system are arranged in the micro display A, laser emitted by the laser is collimated by the collimating optical system to generate a collimated laser beam, the collimated laser beam is incident on the MEMS galvanometer, and the laser beam generated by reflection of the MEMS galvanometer is incident on the grating waveguide device.

The invention provides a large-field-of-view grating waveguide element and a near-to-eye display device, which have the following beneficial effects:

(1) the invention provides a grating waveguide structure of two incident gratings, two turning gratings and an emergent grating, and the field angles of the incident gratings, the turning gratings and the emergent gratings are designed, so that the light ray ranges conducted by different incident gratings and turning gratings are complementary, the field angles of different incident gratings and turning gratings are superposed together to form a larger field angle, the field angle of the waveguide is greatly increased, and the problem that the field angle of the existing diffraction waveguide is difficult to increase is solved.

(2) According to the near-eye display device, a mode that a plurality of projection systems are combined with the large-field-of-view waveguide element is adopted, and different projection systems are matched with different incident gratings, so that an image with a larger field angle is spliced, and the problem that the field angle of a traditional waveguide near-eye display device is small is solved.

Drawings

FIG. 1 is a top view of an exemplary diffractive waveguide structure of the present invention;

FIG. 2 is a typical configuration of a near-eye display optical system employing a diffractive waveguide according to the present invention;

FIG. 3 is a schematic view of a waveguide structure according to the present invention;

fig. 4 is a schematic diagram illustrating a process in which light of the present invention is incident on the incident grating 312a, and diffracted light generated by the incident grating 312a is transmitted to the turning grating 314a, is transmitted to the exit grating 316 after being diffracted by the turning grating 314a, and is finally diffracted by the exit grating 316 and guided out of the waveguide;

fig. 5 is a schematic diagram of a process that light enters the incident grating 312b, and diffracted light generated by the incident grating 312b is transmitted to the turning grating 314b, is transmitted to the exit grating 316 after being diffracted by the turning grating 314b, and is finally diffracted by the exit grating 316 and is guided out of the waveguide;

FIG. 6 is a schematic view of an arrangement for increasing the field angle of a waveguide device;

FIG. 7 is a schematic diagram of a near-eye display device according to the present invention;

FIG. 8 is a cross-sectional schematic diagram of a beam-steering process produced by microdisplay 400;

FIG. 9 is a cross-sectional schematic view of a beam-steering process produced by microdisplay 500;

fig. 10 is a cross-sectional view of the beam-propagating process of the entire near-eye display device.

In the figure: 100. a diffractive waveguide; 106. a substrate; 108. a first surface; 110. a second surface 110; 112. an incident grating 112; 114. a middle grating; 116. an exit grating 116; 210. a projection assembly;

300. a grating waveguide device; 312a, an incident grating region; 312b, an incident grating region; 314a, a turning grating region; 314b, a turning grating region; 316. a grating region is emitted; 400. a micro display A; 41. collimating the laser beam; 411. a laser; 412. a collimating optical system; 42. a laser beam; 500. and a micro display B.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

Example 1: traditional diffraction waveguide structure and typical structure of near-to-eye display optical system thereof

As shown in fig. 1-2, the diffractive waveguide 100 includes a substrate 106, an incident grating 112, an intermediate grating 114, and an exit grating 116, wherein the incident grating 112 guides the image beam modulated by the projection assembly 210 into the substrate 106, the beam satisfying the total reflection condition is almost transmitted in the substrate 106 without loss, the intermediate grating 114 expands the beam in the y direction and turns the expanded beam toward the exit grating 116, and the exit grating 116 expands the beam in the x direction and guides the light energy out of the substrate 106 to the human eye for sensing.

The substrate 106 may be made of optical glass or optical plastic, the substrate 106 includes a first surface 108 and a second surface 110, the first surface 108 and the second surface 110 are located on two sides of the substrate 106 and are parallel to each other, the substrate 106 is a medium for guiding light beams, the light beams can be guided in the substrate 106 almost without loss by total reflection on the first surface 108 and the second surface 110, the substrate 106 and the diffractive waveguide 100 are transparent, so that human eyes can see an external scene through the diffractive waveguide 100.

The structure of the diffractive waveguide may also consist of only the substrate, the entrance grating and the exit grating, without an intermediate grating. In this configuration, the entrance grating directs the modulated image beam into the substrate and toward the exit grating. The exit grating guides light energy out of the substrate to the human eye while expanding the light beam in one direction (horizontal or vertical).

The substrate 106 has one internal parameter: the critical angle A0, A0 is dependent on the refractive index n of the material of the substrate 106, and is calculated as follows:

when the reflection angle of the light beam is A when the light beam is conducted in the substrate 106, when A is less than or equal to A0, the light energy can be transmitted out of the substrate and lost, and the light beam cannot be conducted in the substrate; the light beam may be transmitted in the substrate 106 only if it is totally reflected at the first surface 108 and the second surface 110 of the substrate 106 when a > a 0. When a is 90 °, the light beam cannot enter the exit grating 116 and cannot be expanded and exit, and thus a ranges from a0 < a < 90 °. Currently, A0 is difficult to be smaller than 30 degrees due to the limitations of optical materials, so 30 ° < A < 90 ° is common. If the grating efficiency factors of the incident grating 112, the intermediate grating 114 and the exit grating 116 are considered, the angle range of a is further reduced.

The above-mentioned limitation of the angle range a also limits the magnitude of the exit angle B, which actually corresponds to the angle of view of the diffractive waveguide. The limitation of the angle range of a makes it difficult to achieve a field angle of 60 degrees, typically 40-50 degrees, for the diffractive waveguide.

The conventional waveguide element has a problem that the total angle of view is covered by the light diffracted by the single incident grating and the turning grating, and as described above, the range of the internal reflection angle a limits the size of the angle of view of the waveguide element, so that the angle of view of the diffractive waveguide is difficult to be increased.

Example 2: the invention provides a waveguide structure schematic diagram

As shown in fig. 3-6, the present invention provides a technical solution: a large-field-of-view grating waveguide element and a near-to-eye display device comprise a grating waveguide device 300, wherein the grating waveguide device 300 is composed of an optical substrate and grating regions positioned on the surface of the optical substrate, and the grating regions have five groups of functional regions, including two

incident grating regions

312a and 312b, two turning

grating regions

314a and 314b and an emergent grating region 316;

the

entrance grating regions

312a, 312b are used for guiding a virtual image light beam with a certain field angle and a certain entrance pupil diameter into the grating region waveguide device 300; the incident grating region 312a diffracts the incident light mainly toward the turning grating region 314a, and the incident grating region 312b diffracts the incident light mainly toward the turning grating region 314 b;

the diffracted light generated by the

incident grating regions

312a and 312b is transmitted through the turns of the

turning grating regions

314a and 314b, and then enters the exit grating region 316 for utilization.

Preferably, the turning grating region 314a may expand a portion of the diffracted beams of the

entrance gratings

312a, 312b, typically +1 st order diffracted beams, in a vertically upward direction while generating diffracted beams that are directed towards the exit grating region 316.

Preferably, the turning grating region 314b may expand another portion of the diffracted beams of the

entrance grating regions

312a, 312b, typically-1 st order diffracted beams, in a vertically downward direction while producing diffracted beams that are directed toward the exit grating region 316, which may expand the beams in a horizontal direction while directing light energy out of the grating waveguide device 300 by the exit grating region 316.

Preferably, the angle of view covered by the light rays transmitted by the incident grating region 312a and the turning grating region 314a is F1, the angle of view covered by the light rays transmitted by the grating waveguide device 300 is F2, and the grating parameters (such as grating period) of the waveguide 32, the

incident grating regions

312a and 312b, the

turning grating regions

314a and 314b, and the exit grating region 316 are respectively set;

if F1 is located at the left side of the normal of the surface of the grating waveguide device 300 (negative y-axis direction), and F2 is located at the right side of the normal of the surface of the waveguide (positive y-axis direction), the incident grating region 312a, the incident grating region 312b, the turning grating region 314a, the turning grating region 314b and the exit grating region 316 are overlapped together to form the field angle of the grating waveguide device 300:

F＝F1+F2。

preferably, the

incident grating regions

312a, 312b and the

turning grating regions

314a, 314b are arranged in a staggered manner, so that when viewed along the x-axis direction, no gap exists between the turning grating region 314a and the turning grating region 314b, thereby avoiding a dark band when light is guided out of the exit grating 316.

Example 3:

as shown in fig. 7-10, the present invention provides a technical solution: a near-to-eye display device of a large-field-of-view grating waveguide element comprises a grating waveguide device 300, a micro display A400 and a micro display B500;

the light beam emitted by the micro-display a400 is projected to the incident grating area 312a, the diffracted light beam generated by the incident grating area 312a is transmitted along the y direction in the incident grating area 312b and is continuously diffracted to generate diffracted light transmitted towards the exit grating area 316, and the diffracted light generated by the turning grating area 314a is transmitted to the exit grating area 316 and is diffracted out of the waveguide by the exit grating area 316 and is perceived by human eyes;

the light beam emitted by the microdisplay B500 is projected to the incident grating region 312B, the diffracted light beam generated by the incident grating region 312B is transmitted in the turning grating region 314B along the-y direction and is continuously diffracted to generate diffracted light which is transmitted towards the exit grating region 316, and the diffracted light generated by the turning grating region 314B is transmitted to the exit grating region 316 and is then diffracted out of the waveguide by the exit grating region 316 and is perceived by human eyes.

Preferably, the image produced by microdisplay a400 has less overlap or even no overlap with the image produced by microdisplay B500, resulting in a picture that is nearly 2 times that of a single microdisplay image.

Preferably, the Micro display a400 and the Micro display B500 are one or more of a MEMS Micro display, a fiber scanning Micro display, a Micro LED Micro display system, a DMD Micro projection system, and an LCOS Micro projection system.

Preferably, the micro display a400 is an MEMS micro display, a laser 411 and a collimating optical system 412 are disposed in the micro display a400, laser emitted by the laser 411 is collimated by the collimating optical system 412 to generate a collimated laser beam 41, the collimated laser beam 41 is incident on the MEMS galvanometer, and a laser beam 42 generated by reflection of the MEMS galvanometer is incident on the grating waveguide device 300.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A large field of view grating waveguide component, comprising a grating waveguide device (300), wherein the grating waveguide device (300) is composed of an optical substrate and a grating region on the surface of the optical substrate, the grating region has five groups of functional regions, including two incident grating regions (312a, 312b), two turning grating regions (314a, 314b) and one exit grating region (316);

the entrance grating regions (312a, 312b) are used for guiding virtual image light beams with certain field angles and certain entrance pupil diameters into the grating region waveguide device (300); the incident grating region (312a) diffracts the incident light mainly towards the direction of the turning grating region (314a), and the incident grating region (312b) diffracts the incident light mainly towards the direction of the turning grating region (314 b);

the diffracted light generated by the incident grating regions (312a, 312b) is transmitted through the turns of the turning grating regions (314a, 314b), and then enters the emergent grating region (316) to be utilized.

2. A large field of view grating waveguide element according to claim 1, wherein: the turning grating region (314a) may expand a portion of the diffracted beams (typically +1 st order diffracted beams) of the entrance grating (312a, 312b) in a vertically upward direction while producing diffracted beams that are directed towards the exit grating region (316).

3. A large field of view grating waveguide element according to claim 1, wherein: the turning grating region (314b) may expand another portion of the diffracted beams (typically-1 order diffracted beams) of the entrance grating regions (312a, 312b) in a vertically downward direction while producing diffracted beams that are directed toward the exit grating region (316), and the exit grating region (316) may expand the beams in a horizontal direction while directing light energy out of the grating waveguide device (300).

4. A large field of view grating waveguide element according to claim 1, wherein: the field angle covered by the light rays conducted by the incident grating region (312a) and the turning grating region (314a) is F1, the field angle covered by the light rays conducted by the grating waveguide device (300) is F2, and grating parameters of the waveguide (32), the incident grating region (312a, 312b), the turning grating region (314a, 314b) and the exit grating region (316) are respectively set;

if F1 is located at the left side of the normal of the surface of the grating waveguide device (300) and F2 is located at the right side of the normal of the surface of the grating waveguide device, the incident grating region (312a), the incident grating region (312b), the turning grating region (314a), the turning grating region (314b) and the exit grating region (316) are superposed together to form the field angle of the grating waveguide device (300):

F＝F1+F2。

5. a large field of view grating waveguide element according to claim 1, wherein: the incident grating regions (312a, 312b) and the turning grating regions (314a, 314b) are arranged in a staggered manner such that, viewed in the x-axis direction, there is no gap between the turning grating region (314a) and the turning grating region (314 b).

6. The near-to-eye display device of a large field of view grating waveguide element of any one of claims 1-5, wherein: the micro-display comprises a grating waveguide device (300), a micro-display A (400) and a micro-display B (500);

the light beam emitted by the micro display A (400) is projected to the incident grating area (312a), the diffracted light beam generated by the incident grating area (312a) is transmitted along the y direction in the incident grating area (312b) and is continuously diffracted to generate diffracted light transmitted towards the emergent grating area (316), and the diffracted light generated by the turning grating area (314a) is transmitted to the emergent grating area (316) and is diffracted out of the waveguide by the emergent grating area (316) and is perceived by human eyes;

the light beam emitted by the micro-display B (500) is projected to the incident grating area (312B), the diffracted light beam generated by the incident grating area (312B) is transmitted along the-y direction in the turning grating area (314B) and is continuously diffracted to generate diffracted light transmitted towards the exit grating area (316), and the diffracted light generated by the turning grating area (314B) is transmitted to the exit grating area (316) and is diffracted out of the waveguide by the exit grating area (316) and is perceived by human eyes.

7. The near-to-eye display device of claim 6, wherein: the image produced by microdisplay a (400) has less overlap or even no overlap with the image produced by microdisplay B (500), resulting in a picture that is nearly 2 times that of a single microdisplay image.

8. The near-to-eye display device of claim 6, wherein: the Micro display A (400) and the Micro display B (500) are one or more of MEMS Micro display, optical fiber scanning Micro display, Micro LED Micro display system, DMD Micro projection system and LCOS Micro projection system.

9. The near-to-eye display device of claim 8, wherein: the micro display A (400) is an MEMS micro display, a laser (411) and a collimating optical system (412) are arranged in the micro display A (400), laser emitted by the laser (411) is collimated by the collimating optical system (412) to generate a collimated laser beam (41), the collimated laser beam (41) is incident on the MEMS galvanometer, and a laser beam (42) generated by reflection of the MEMS galvanometer is incident on the grating waveguide device (300).