CN115509006A

CN115509006A - Optical device and electronic device

Info

Publication number: CN115509006A
Application number: CN202110699966.9A
Authority: CN
Inventors: 丁武文; 鲁云开; 李民康
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-06-23
Filing date: 2021-06-23
Publication date: 2022-12-23
Also published as: WO2022267610A1

Abstract

The application relates to the technical field of augmented reality and discloses optical equipment and electronic equipment. The optical device comprises at least one waveguide substrate, and a coupling-in unit, a first relay unit, a second relay unit and a coupling-out unit which are arranged on the waveguide substrate; the first relay unit and the second relay unit define a relay area, so that the traveling path direction of a part of the light rays coupled in by the coupling-in unit is limited to be subjected to total reflection type propagation between the first relay unit and the second relay unit after the light rays enter the waveguide substrate, and the other part of the light rays can be changed in direction at the second relay unit and subjected to total reflection traveling path towards the coupling-out unit; when the light traveling towards the total reflection path of the coupling-out unit encounters the coupling-out unit, a part of the light will continue to travel along the total reflection path in the original direction, and the other part of the light will be coupled out of the human eye. Therefore, when the image edge field angle is increased, the exit pupil expansion of the light in the two-dimensional direction can be realized without increasing the area of the relay grating.

Description

Optical device and electronic device

Technical Field

The present application relates to the field of augmented reality technologies, and in particular, to an optical device and an electronic device.

Background

Augmented Reality (AR) technology has been widely used in various fields such as military, business, industry, fire fighting and entertainment applications as a technology for skillfully fusing virtual information with the real world. The AR technology mainly uses a microdisplay as an image source, and projects an image into a human eye through an optical element for imaging. Among them, the optical element generally employs an optical waveguide structure.

For example, the AR technology may be applied to head-mounted AR glasses, which include a micro-display and a lens, wherein the lens generally adopts an optical waveguide structure; the virtual image emitted by the micro-display can be projected into human eyes for imaging through the lens made of the optical waveguide structure, and the optical waveguide structure is a transparent structure, so that an observer can observe a real mirror image around and the virtual image transmitted by the micro-display at the same time.

At present, an optical waveguide structure adopted in AR glasses generally expands pupils in one direction, namely, a larger image range is seen in one direction, and the AR glasses are difficult to be suitable for people with different pupil distances, different face shapes and different bridge heights.

Disclosure of Invention

The embodiment of the application provides an optical device and an electronic device. The optical device provided by the embodiment of the application can realize the exit pupil expansion in the two-dimensional direction, so that a user can see a larger image range in the two-dimensional direction, and the optical device can be suitable for people with different pupil distances, different face shapes and different nose bridge heights.

In addition, the optical device provided by the embodiment of the application can realize the exit pupil expansion in the x direction without increasing the area of the traditional relay grating when the included angle between the image edge fields of view is increased, and can effectively reduce the area of the waveguide substrate under the condition of a larger field angle, thereby reducing the area of the whole optical device; and the requirement of the existing electronic equipment on a large field angle can be met.

In a first aspect, an embodiment of the present application provides an optical device, including at least one waveguide substrate, and a coupling-in unit, a first relay unit, a second relay unit, and a coupling-out unit disposed on the waveguide substrate;

the incoupling unit is configured to incouple light into the waveguide substrate;

the first relay unit and the second relay unit define a relay area, the relay area extends in a first direction, the first relay unit and the second relay unit are arranged in a second direction, the relay area is provided with a first side and a second side which are opposite to each other in the second direction, and an included angle between the extending direction of the first side and the extending direction of the second side is smaller than a first angle;

the coupling-out unit is configured to couple out light rays in the waveguide substrate from the waveguide substrate, and the coupling-out unit is aligned with the relay region in the second direction.

For example, the first direction may be an x-axis direction mentioned in the following embodiments, and the second direction may be a y-axis direction mentioned in the following embodiments.

It can be understood that the optical device provided by the embodiment of the present application includes a first relay unit and a second relay unit, and the first relay unit and the second relay unit define a relay area, so that the traveling direction of a part of the light rays coupled in by the coupling-in unit after entering the waveguide substrate is limited to perform total reflection type propagation between the first relay unit and the second relay unit, and another part of the light rays can be redirected at the second relay unit close to the coupling-out unit to perform total reflection type traveling towards the coupling-out unit, thereby realizing the exit pupil expansion of the x axis.

For example, the optical device may be a diffractive optical waveguide in the following, the coupling-in unit may be a coupling-in grating in the following, the coupling-out unit may be a coupling-out grating in the following, the first relay unit may be a first relay grating in the following, the second relay unit may be a second relay grating in the following, and the relay area may be defined by grating lines near the first relay grating and the second relay grating in the following, is an area between the first relay grating and the second relay grating, and does not include the first relay grating and the second relay grating. The relay region may also be defined by the grating lines at which the first relay grating and the second relay grating are farthest from each other, and includes not only the region between the first relay grating and the second relay grating, but also the first relay grating and the second relay grating.

In addition, in the embodiment of the application, the exit pupil expansion in the x direction is realized in a mode that light rays are propagated in a total reflection manner between the first relay unit and the second relay unit; the exit pupil expansion in the x direction can be realized without increasing the area of the traditional relay grating when the included angle between the image edge fields of view is increased, the area of the waveguide substrate can be effectively reduced under the condition of a larger field angle, and the area of the whole optical equipment is further reduced; and the requirement of the existing electronic equipment on a large field angle can be met.

In addition, when the light rays with the total reflection path facing the coupling-out unit meet the coupling-out unit, a part of the light rays can continue to be totally reflected along the original direction, and the other part of the light rays is coupled out of human eyes, so that the exit pupil expansion in the y direction is repeatedly realized. Therefore, the optical device provided by the embodiment of the application can realize the exit pupil expansion in two-dimensional directions. Adopt this optical device to make can the user see bigger image range in two-dimensional direction, and can be applicable to the crowd of different interpupillary distances, different face types and different bridge of the nose height.

In one possible implementation of the first aspect, the first angle is between 0 ° and 5 °.

In a possible implementation of the first aspect, the first edge and the second edge are parallel in an extension direction. In the embodiment of the present application, the extending direction of the first edge and the extending direction of the second edge may be arranged in parallel, or may have a small error, for example, an included angle between the extending direction of the first edge and the extending direction of the second edge may be between 0 ° and 5 °. For example, the first edge may be a grating line of a first relay grating, hereinafter, which is most adjacent to the second relay grating, and the second edge may be a grating line of a second relay grating, hereinafter, which is most adjacent to the first relay grating.

In one possible implementation of the first aspect, the second relay unit is configured such that the light propagating through total reflection in the waveguide substrate is propagated through total reflection at least part of the outgoing light toward the first relay unit after being incident on the second relay unit, and at least part of the outgoing light is propagated through total reflection toward the coupling-out unit;

the first relay unit is configured such that a light ray propagating through total reflection in the waveguide substrate is incident on the first relay unit and then exits therefrom for total reflection propagation toward the second relay unit.

For example, taking the first relay unit as a first relay grating and the second relay unit as a second relay grating as an example, the second relay unit may be configured such that, after a light totally reflected and propagated in the waveguide substrate enters the second relay unit, at least part of outgoing light propagates toward the first relay unit by total reflection as shown by an arrow B2 in fig. 18 (a), and at least part of outgoing light propagates toward the outcoupling unit by total reflection as shown by an arrow B3 in fig. 18 (a);

the first relay unit is configured such that the light totally reflected and propagated in the waveguide substrate exits the light after being incident on the first relay unit, and totally reflected and propagated toward the second relay unit as indicated by an arrow B4 in fig. 18.

In a possible implementation of the first aspect, the first relay unit and the second relay unit are gratings; and a first edge of the relay area is a raster line of the first relay unit closest to the second relay unit, and a second edge is a raster line of the second relay unit closest to the first relay unit. That is, the relay area is defined by the adjacent grating lines of the first relay unit and the second relay unit, is an area between the first relay unit and the second relay unit, and does not include the first relay unit and the second relay unit. For example, the blank regions may be blank regions of the first relay grating and the second relay grating shown in fig. 17 later.

In a possible implementation of the first aspect, the first relay unit and the second relay unit are rasters, and a first edge of the relay area is a raster line of the first relay unit farthest from the second relay unit, and a second edge is a raster line of the second relay unit farthest from the first relay unit. That is, the relay area is defined by the grating lines at which the first relay unit and the second relay unit are most distant from each other, and includes not only the area between the first relay unit and the second relay unit but also the first relay unit and the second relay unit. For example, fig. 17 later illustrates an area defined by the grating lines of the first relay grating farthest from the second relay grating and the grating lines of the second relay grating farthest from the first relay grating.

In one possible implementation of the first aspect, the first relay unit and the second relay unit each include a plurality of grating grids, and the grating grids of the first relay unit and the second relay unit are at the first angle with each other.

In one possible implementation of the first aspect, the first relay unit and the second relay unit each include a plurality of grating lines, and the grating lines of the first relay unit and the grating lines of the second relay unit are parallel to each other.

That is, the first relay unit and the second relay unit may both be gratings, the first relay unit may include a plurality of parallel grating lines, and the second relay unit may include a plurality of parallel grating lines. The grating grid line of the first relay unit and the grating grid line of the second relay unit may have an included angle of 0 to 5 degrees. In some embodiments, the grating lines of the first relay unit and the grating lines of the second relay unit may be arranged parallel to each other. It will be appreciated that, as previously mentioned, the parallelism herein may be somewhat erroneous, i.e. not perfectly parallel, but at a small angle, e.g. between 0 and 5.

Specifically, for example, if the first relay unit and the second relay unit are surface relief gratings, the grid lines may refer to the scores of the surface relief gratings, and the grid lines may be parallel to the scores of the surface relief gratings; if the first relay unit and the second relay unit are volume holographic gratings, the grid lines may refer to stripes of the volume holographic gratings, and the grid lines may be parallel to each other and may refer to the stripe extending directions of the volume holographic gratings.

Furthermore, it is practicable that the grating line direction of the grating is a direction perpendicular to the grating vector direction of the grating, and therefore, the grating lines of the first relay unit and the second relay unit are parallel to coincide with or are parallel to the grating vector direction, which may also refer to a surface relief.

In one possible implementation of the first aspect, the first relay unit and the second relay unit are bar gratings parallel to each other.

In a possible implementation of the first aspect, the first relay unit and the second relay unit have the same grating period.

It can be understood that the period and the grating vector direction of the first relay unit are consistent with those of the second relay unit, so that the k-space region of the light coupled out by the coupling-out unit can be completely overlapped with the k-space region of the incident light emitted by the micro display device, and the image distortion can be effectively prevented.

In one possible implementation of the first aspect, the diffraction efficiency of the first relay unit is uniformly distributed, and the diffraction efficiency of the second relay unit gradually decreases from a side away from the coupling-out unit to a side close to the coupling-out unit.

It is understood that setting the diffraction efficiency of the second relay unit to be gradually lower from the side away from the outcoupling unit to the side close to the outcoupling unit makes it possible to cause the light propagating by total reflection in the waveguide substrate to propagate by total reflection at least part of the outgoing light toward the first relay unit and at least part of the outgoing light toward the outcoupling unit after being incident on the second relay unit.

Meanwhile, the diffraction efficiency of the first relay unit is set to be equally distributed, so that the light totally reflected and propagated in the waveguide substrate changes the direction of the totally reflected and propagated after being incident on the first relay unit, and totally reflected and propagated towards the second relay unit.

In one possible implementation of the first aspect, the first relay unit is a surface relief grating, and the grating heights of the first relay units are equally distributed.

It is understood that the grating height equal distribution of the first relay unit may be set such that the diffraction efficiency of the first relay unit is equally distributed.

In one possible implementation of the first aspect, the second relay unit is a surface relief grating, and the grating height of the second relay unit gradually decreases from a side away from the coupling-out unit to a side close to the coupling-out unit.

It is understood that the grating height of the second relay unit is gradually decreased from the side away from the coupling-out unit to the side close to the coupling-out unit, so that the diffraction efficiency of the second relay unit is gradually decreased from the side away from the coupling-out unit to the side close to the coupling-out unit.

In one possible implementation of the first aspect, the first relay unit is a volume holographic grating, and the refractive index modulation degrees of the first relay unit are equally distributed.

It is understood that the refractive index modulation degree equal distribution of the first relay unit may be set such that the diffraction efficiency of the first relay unit is equally distributed.

In one possible implementation of the first aspect, the second relay unit is a volume hologram grating, and a grating refractive index modulation degree of the second relay unit gradually decreases from a side away from the coupling-out unit to a side close to the coupling-out unit.

It is understood that the degree of modulation of the grating refractive index of the second relay unit is set to gradually decrease from the side away from the outcoupling unit to the side close to the outcoupling unit, so that the diffraction efficiency of the second relay unit gradually decreases from the side away from the outcoupling unit to the side close to the outcoupling unit.

In a possible implementation of the first aspect, the waveguide substrate further includes at least one third relay unit disposed on the waveguide substrate, the third relay unit is disposed between the first relay unit and the second relay unit, the third relay unit divides the relay area into a plurality of relay areas, and an included angle between two long sides of the relay areas in the extending direction is smaller than the first angle.

That is, in the embodiment of the present application, there may be a plurality of relay units, and the third relay unit may divide the relay area defined by the first relay unit and the second relay unit into a plurality of relay sub-areas. For example, after a third relay unit is added between the first relay unit and the second relay unit, the relay area is divided into two relay sub-areas. For example, in the following, the first relay unit may be a first relay grating in the following, the second relay unit may be a second relay grating in the following, and the third relay unit may be a third relay grating mentioned in the following, and one third relay grating is added to divide the relay area into two relay sub-areas.

In one possible implementation of the first aspect, the third relay unit is configured to: after the light rays which are subjected to total reflection propagation in the waveguide substrate enter the third relay unit, at least part of emergent light rays are subjected to total reflection propagation towards the first relay unit, and at least part of emergent light rays are subjected to total reflection propagation towards the second relay unit.

For example, in the following description, taking as an example that the first relay unit may be a first relay grating, the second relay unit may be a second relay grating, and the third relay unit may be a third relay grating, the third relay unit may be configured such that the light totally reflected and propagated in the waveguide substrate, after entering the third relay unit, at least part of the outgoing light, as shown by the arrow B4 direction in fig. 26, is totally reflected and propagated toward the first relay unit, and at least part of the outgoing light, as shown by the arrow B5 direction in fig. 26, is totally reflected and propagated toward the second relay unit.

In a possible implementation of the first aspect, the first relay unit, the second relay unit, and the third relay unit are gratings.

For example, the first relay unit may be a first relay grating described later, the second relay unit may be a second relay grating described later, and the third relay unit may be a third relay grating described later.

In one possible implementation of the first aspect, the first relay unit, the second relay unit, and the third relay unit each include a plurality of gate lines parallel to each other.

In one possible implementation of the first aspect, the third relay unit is a stripe grating.

In one possible implementation of the first aspect, the diffraction efficiency of the third relay unit gradually decreases from a side close to the first relay unit to a side close to the second relay unit.

It is understood that the diffraction efficiency of the third relay unit is gradually decreased from the side close to the first relay unit to the side close to the second relay unit, so that after the light propagating through total reflection in the waveguide substrate is incident on the third relay unit, at least part of the emergent light propagates through total reflection toward the first relay unit, and at least part of the emergent light propagates through total reflection toward the second relay unit.

In one possible implementation of the first aspect, the third relay unit is a surface relief grating, and a grating height of the third relay unit gradually decreases from a side close to the first relay unit to a side close to the second relay unit.

It is understood that the grating height of the third relay unit is gradually reduced from the side close to the first relay unit to the side close to the second relay unit, so that the diffraction efficiency of the third relay unit is gradually reduced from the side close to the first relay unit to the side close to the second relay unit.

In one possible implementation of the first aspect, the third relay unit is a volume hologram grating, and a grating refractive index modulation degree of the third relay unit gradually decreases from a side close to the first relay unit to a side close to the second relay unit.

It is understood that the degree of grating refractive index modulation at which the third relay unit is provided gradually decreases from the side close to the first relay unit to the side close to the second relay unit, so that the diffraction efficiency of the third relay unit gradually decreases from the side close to the first relay unit to the side close to the second relay unit.

In one possible implementation of the first aspect, the coupling-in unit is located in the relay area.

It is understood that the incoupling unit may be located between the first relay unit and the second relay unit, or may be located at other positions such that the light emitted by the incoupling unit is guided by the incoupling unit to propagate in the direction of the second relay unit.

In one possible implementation of the first aspect, the coupling-in unit and the coupling-out unit are gratings, and the periods and the grating vector directions of the coupling-in unit and the coupling-out unit are the same.

It is to be understood that the incoupling unit may be an incoupling grating in the following, and the outcoupling unit may be an outcoupling grating in the following. In the embodiment of the application, the periods and the grating vector directions of the coupling-in unit and the coupling-out unit are the same, so that the k space area of the light coupled out by the coupling-out unit and the k space area of the incident light emitted by the micro display device are completely overlapped, and the image distortion is effectively prevented.

In one possible implementation of the first aspect, the coupling-in unit is a surface relief grating or a volume holographic grating; and is provided with

The coupling-out unit is a surface relief grating or a volume holographic grating.

In one possible implementation of the first aspect, the coupling-in unit, the first relay unit, the second relay unit, and the coupling-out unit are located on at least one bottom surface of the waveguide substrate.

It is to be understood that the coupling-in unit, the first relay unit, the second relay unit, and the coupling-out unit may be located on the same bottom surface of the waveguide substrate, and may be located on opposite bottom surfaces, for example, the coupling-in unit, the first relay unit, the second relay unit are located on an upper bottom surface, and the coupling-out unit may be located on a lower bottom surface.

In a possible implementation of the first aspect, the waveguide substrate further includes two holographic material layers, and the two holographic material layers are sandwiched between the two waveguide substrates;

the coupling-in unit, the first relay unit, the second relay unit, and the coupling-out unit are located on at least one bottom surface of the holographic material layer.

It is understood that the coupling-in unit, the first relay unit, the second relay unit, and the coupling-out unit may be a coupling-in grating, a first relay grating, a second relay grating, and a coupling-out grating formed by exposing the holographic material layer.

In a second aspect, embodiments of the present application provide an electronic device, which includes a micro-display device and the above optical device, and the micro-display device is configured to project light to a coupling-in unit of the optical device.

It will be appreciated that the optical device may be a diffractive optical waveguide as referred to in the embodiments hereinafter.

In one possible implementation of the second aspect, the electronic device is augmented reality glasses.

It is understood that some or all of the lenses of the augmented reality glasses may be the optical device, and the micro reality device may be disposed on the lens frame of the augmented reality glasses.

In one possible implementation of the second aspect described above, the electronic device is an in-vehicle head-up display.

Drawings

FIG. 1 illustrates a schematic diagram of a transmissive diffraction grating, according to some embodiments of the present application;

FIG. 2 illustrates a spectroscopic diagram of a diffraction grating, according to some embodiments of the present application;

3 (a) - (c) illustrate schematic diagrams of diffraction gratings of different shapes, according to some embodiments of the present application;

FIG. 4 illustrates a schematic diagram of the principle of total reflection, according to some embodiments of the present application;

FIG. 5 illustrates a schematic structural diagram of a planar optical waveguide, according to some embodiments of the present application;

FIG. 6 illustrates an optical path diagram of the planar optical waveguide of FIG. 5, according to some embodiments of the present application;

FIG. 7 illustrates a schematic diagram of a diffractive light waveguide for AR glasses, according to some embodiments of the present application;

FIG. 8 (a) shows a schematic representation of the direction of light propagating in a diffractive light waveguide 100, according to some embodiments of the present application;

FIGS. 8 (b) and (c) illustrate specific optical path diagrams of light propagating in a waveguide substrate, according to some embodiments of the present application;

FIG. 9 illustrates a schematic structural view of AR eyewear employing diffractive optical waveguides as lenses, in accordance with some embodiments of the present application;

FIG. 10 illustrates a schematic diagram of a virtual image coupled into a human eye through a left lens or a right lens of AR glasses according to some embodiments of the present application;

FIG. 11 illustrates a schematic of a structure for a diffractive light waveguide, according to some embodiments of the present application.

12 (a) and (b) respectively show guiding schematics of light rays in a diffractive optical waveguide at different angles of field, according to some embodiments of the present application;

13 (a) and (b) illustrate diffraction patterns of light at a relay grating and an outcoupling grating, respectively, according to some embodiments of the present application;

FIG. 14 illustrates a schematic diagram of an AR eyeglass design that employs diffractive optical waveguides as lenses, according to some embodiments of the present application;

FIG. 15 illustrates a schematic view of an angle of view, according to some embodiments of the present application;

16 (a) and (b) are schematic diagrams illustrating, according to some embodiments of the present application, the propagation of images of a smaller edge field angle A1 and a larger edge field angle A2, respectively, in the diffractive light waveguide structure shown in FIG. 11;

figure 17 illustrates a schematic diagram of a diffractive optical waveguide including two relay gratings, according to some embodiments of the present application.

18 (a) and (b) are schematic diagrams illustrating, respectively, different angular orientations of light propagating in a waveguide substrate according to embodiments of the present application;

FIG. 19 (a) illustrates a diffraction pattern of light rays at a first relay grating and a second relay grating, according to some embodiments of the present application;

FIG. 19 (b) illustrates a diffraction pattern of light at an outcoupling grating, according to some embodiments of the present application;

FIGS. 20 (a) and (b) show directional contrast diagrams of images propagating in the diffractive optical waveguide of FIG. 17 for smaller edge field angle A1 and larger edge field angle A2, respectively, according to some embodiments of the present application.

FIG. 21 illustrates a schematic diagram of a second relay grating, according to some embodiments of the present application;

FIG. 22 illustrates a schematic diagram of the location of an incoupling grating, according to some embodiments of the present application;

FIG. 23 illustrates a schematic diagram of the location of an incoupling grating, according to some embodiments of the present application;

FIG. 24 illustrates a schematic structural view of AR eyewear employing the diffractive optical waveguide of FIG. 17 as a lens, according to some embodiments of the present application;

FIG. 25 illustrates a schematic structural view of a diffractive light waveguide, according to some embodiments of the present application;

FIG. 26 illustrates a schematic of the direction of light rays in a diffractive light waveguide of three relay gratings, according to some embodiments of the present application;

FIG. 27 illustrates a schematic diagram of a diffractive light waveguide, according to some embodiments of the present application;

FIG. 28 illustrates a schematic diagram of a diffractive light waveguide, according to some embodiments of the present application;

FIG. 29 illustrates a k-space path schematic of the diffractive light waveguide illustrated in FIG. 17, according to some embodiments of the present application.

Description of reference numerals:

100-diffractive optical waveguides; 101-coupling in a grating; 102-a relay grating; 1021-a first relay grating; 1022-a second relay grating; 1023-a third relay grating; 103-out-coupling grating; 104-a waveguide substrate; 105-a microdisplay device; 106-a light source; 107-waveguide top layer; 108-a layer of holographic material;

200-AR glasses; 201-left temple; 202-right temple; 203-lens frame 203, 204-left lens; 205-right lens;

300-diffraction grating; 301-a slit; 302-scoring; 303-a glass substrate; 304-dielectric film.

Detailed Description

The following description of the embodiments of the present application is provided by way of specific examples, and other advantages and effects of the present application will be readily apparent to those skilled in the art from the disclosure herein.

To facilitate understanding of the technical solutions of the present application, some technical terms, optical elements, and related principles referred to in the present application will now be described.

Diffraction of light: the light encounters an opaque or transparent obstruction or aperture (slit) in the propagation path, bypasses the obstruction, and deviates from straight line propagation, and is called diffraction of the light.

(II) grating: the diffraction grating is an optical device comprising a large number of parallel slits having the same width and the same pitch, and can change the propagation direction of light applied to the diffraction grating by diffraction of the diffraction grating. Wherein the diffraction grating may include a grating that diffracts using transmitted light, referred to as a transmissive diffraction grating; a grating that diffracts light reflected between two notches is also called a reflective diffraction grating.

For example, fig. 1 shows a schematic diagram of a transmissive diffraction grating 300. As shown in fig. 1, the diffraction grating 300 may be formed by a plurality of slits 301 and scores 302 etched on glass, wherein the slits 301 are light-transmitting portions and the scores 302 are light-non-transmitting portions. The optical characteristics of the diffraction grating 300 are related to the period of the diffraction grating, which is the sum of the widths of the single slit 301 and the single notch 302, e.g. if the width of the slit 301 is a and the width of the notch 302 is b, then the period d of the diffraction grating 300 is the sum of the width a of the slit 301 and the width b of the notch 302, i.e. d = a + b; here, the smaller the grating period, the larger the number of slits 301 per unit length, and the narrower the width of a single slit 301.

It is also possible to implement the diffraction grating 300 by exposing the inside of the material to form a holographic grating by a holographic technique, i.e. by holography, exposing the interference fringes generated by laser on a dry plate, developing and fixing to form the holographic grating.

The diffraction grating 300 has a light splitting characteristic, and for example, a diffraction light waveguide used in the AR glasses of the present application uses the light splitting characteristic to guide a light propagation direction, which will be described in detail below.

Specifically, as shown in fig. 2, when an incident light i is incident on the diffraction grating 300 with a grating height h and a period d, it is divided into several diffraction orders (diffraction orders) by the diffraction grating 300, and each diffraction order continues to propagate along different directions, including reflective diffraction, such as 0-order reflective diffraction R0, first-order reflective diffraction R1, negative first-order reflective diffraction R-1, and transmissive diffraction, such as 0-order transmissive diffraction T0, first-order transmissive diffraction T1, negative first-order transmissive diffraction T-1.

In order to allow m-order diffraction of the light ray that enters the diffraction grating 300, the diffraction grating needs to satisfy the following formula (1):

wherein d is the period of the diffraction grating, m is the diffraction order, m is an integer, and can be, for example, 0,1, -1,2, -2, etc.; n is the refractive index of glass 3; theta _m And

respectively the polar angle and the azimuth angle of the diffracted light corresponding to the m-order; λ is the wavelength of the incident light i, θ and

respectively the polar angle and the azimuth angle of the incident ray i; theta.theta. _Gin Is the angle of the notch 302 of the diffraction grating. :

the above formula (1) shows that when the wavelength λ of the incident ray i, the polar angle θ and the azimuth angle of the incident ray i

At a certain time, the angle theta of the notch 302 of the diffraction grating is regulated and controlled _Gin The period d of the diffraction grating can diffract the diffraction light at the order of the diffraction order, the polar angle theta _m And azimuth angle

And (6) adjusting.

For example, in a diffractive optical waveguide used for AR glasses, the angle θ of the notch 302 of each diffraction grating on the surface of the waveguide substrate can be controlled _Gin Period d of diffraction grating, diffraction order m of diffracted light, and polar angle θ _m And azimuth angle

The adjustment is made so that the light totally reflected and propagated in the waveguide substrate of the diffractive optical waveguide can propagate in a desired direction after being incident on the diffraction grating on the surface of the waveguide substrate.

The shape of the diffraction grating can be designed into various shapes according to actual requirements, for example, fig. 3 (a) - (c) show schematic diagrams of diffraction gratings with different shapes, wherein, as shown in fig. 3 (a), the diffraction grating can be a uniform vertical grating, as shown in fig. 3 (b), the diffraction grating can also be an inclined grating, as shown in fig. 3 (c), and the diffraction grating can also be a grating with uneven height.

Total reflection of light

Total reflection of light, also known as total internal reflection of light, means that when a light ray enters a medium with a lower refractive index from a medium with a higher refractive index, if the incident angle is larger than a certain critical angle C (the light ray is far from the normal), the refracted light ray will disappear, and all the incident light ray will be reflected without entering the medium with a lower refractive index.

For example, as shown in FIG. 4, when an incident light ray i travels from a medium P1 having a refractive index n1 to a medium having a refractive index n ₂ If n is the medium P2 ₁ Greater than n ₂ And the incident angle C1 of the light ray is greater than the critical angle C, the incident light ray i will be reflected without entering the low refractive index n ₂ Medium P2.

The condition that the critical angle C needs to satisfy, that is, the total reflection formula of light, is as follows:

sinC＝n ₂ /n ₁ (2)

as shown in fig. 4, when the refractive index is n ₂ When the medium P2 is air, n is ₂ =1, the critical angle C needs to satisfy the condition: sinC =1/n ₁ 。

(IV) optical waveguide:

an optical waveguide refers to an optical element that guides a light wave to propagate in itself using the principle of total reflection. A common optical waveguide can be a guiding structure composed of an optically transparent medium (such as quartz glass with a large refractive index) for transmitting electromagnetic waves at optical frequencies. Optical waveguides can be classified into planar structures and strip structures.

For example, fig. 5 shows a structural diagram of a planar optical waveguide 10, and fig. 6 shows an optical path diagram of the planar optical waveguide 10.

As shown in fig. 5, the planar structured optical waveguide 10 may include a glass substrate 303 and a dielectric film 304 positioned over the glass substrate 303. Wherein the refractive index of the dielectric film 304 is assumed to be n ₁ The refractive index of the glass substrate 303 is n2, and the critical angle of total reflection of light generated on the interface between the dielectric film 304 and the glass substrate 303 is θ ₁ The critical angle of the total reflection of the light on the interface between the dielectric film 304 and the air is θ ₂ 。

The incident light i is incident on the interface between the dielectric film 304 and the glass substrate 303 by refraction from the air, and can be reflected totally at a refractive index n so that the light incident on the interface between the dielectric film 304 and the glass substrate 303 can be reflected totally ₁ The total reflection propagation between the upper and lower surfaces of the dielectric film is required to make the refractive index n of the dielectric film 304 be equal ₁ Refractive index n of glass substrate 303 ₂ And refractive index n of air ₃ The satisfied relationship is: n is a radical of an alkyl radical ₁ ＞n ₂ ＞n ₃ 。

The incident angle theta of the incident light i and the critical angle theta of the light generated by the total reflection on the interface between the dielectric film 304 and the glass substrate 303 are required ₁ And critical angle theta of total reflection of light on the interface between the dielectric film 304 and air ₂ The satisfied relationship is: theta > theta ₁ ＞θ ₂ 。

Wherein, theta ₁ And theta ₂ The calculation method of (c) is as follows:

θ ₁ ＝arcsin(n ₂ /n ₁ )；

θ ₂ ＝arcsin(n ₃ /n ₁ )。

specifically, as shown in fig. 6, an optical path diagram of the light propagating through the optical waveguide is that an incident light i is incident on the interface between the dielectric film 304 and the glass substrate 303 through refraction from the air, and is totally reflected at the interface between the dielectric film 304 and the glass substrate 303, and when the light is totally reflected at the interface between the dielectric film 304 and the air, the light is continuously totally reflected at the interface between the dielectric film 304 and the glass substrate 303. Thus, the light propagates through the dielectric film 304 by total reflection between the upper and lower surfaces thereof.

It can be seen that the optical waveguide may be a medium layer with a relatively large refractive index, so that the light can be propagated by total reflection inside the optical waveguide. In order to introduce light emitted from a microdisplay in the AR glasses 200 into a predetermined position of the lenses of the AR glasses 200 and to guide the light out to the eyes at the predetermined position of the lenses, the diffraction grating is generally provided on the surface of the optical waveguide 100. For example, fig. 7 shows a schematic of the structure of a diffractive light waveguide 100 for AR glasses 200.

As shown in fig. 7, the diffractive light waveguide 100 includes a waveguide substrate 104, an incoupling grating 101 for coupling light into the waveguide substrate, and an outcoupling grating 103 for coupling light out of the waveguide substrate. The waveguide substrate 104 may be formed of the planar structure optical waveguide shown in fig. 6 and may be made of a high refractive index glass material, for example, having a refractive index in the range of 1.5 to 2.2.

Fig. 8 (a) shows a schematic diagram of the guidance of light propagating in the diffractive light waveguide 100.

It can be understood that, in the embodiments of the present application, the schematic guidance diagram of the light is different from the optical path diagram, and is not an actual propagation path of the light, but an entire traveling direction of the light during the total reflection of the light is illustrated. For example, for the total reflection optical path diagram shown in fig. 6, the actual optical path of the light in the dielectric film 304 is represented by the light with arrows, and the whole traveling direction of the total reflection light can be considered as the traveling along the negative half axis of the x-axis.

The light traveling direction of the diffractive light waveguide 100 will be described with continued reference to fig. 8 (a). As shown in fig. 8 (a), light i1 emitted from the light source 106 enters the incoupling grating 101, is coupled into the waveguide substrate 104 by diffraction of the incoupling grating 101, and is propagated by total reflection between the upper and lower surfaces of the waveguide substrate 104. The arrow B1 in fig. 8 (a) shows the entire advancing path of the light totally reflected in the waveguide substrate 104, i.e., advancing in the direction of the negative half axis of the x-axis. After the total reflection light rays advancing in the waveguide substrate 104 along the direction of the negative half axis of the x axis encounter the light coupling grating 103, a part of the light rays are coupled out of the waveguide substrate 104, and the traveling direction of the coupled-out light rays is shown by an arrow B2 in fig. 8, i.e. the direction of the positive half axis of the z axis.

As shown in fig. 8 (b), the light i1 emitted from the light source 106 is incident on the incoupling grating 101, and then the original propagation direction is changed by diffraction of the incoupling grating 101, and the light is emitted to the bottom of the waveguide substrate 104. Based on the aforementioned total reflection principle, since the incident angle of the light beam incident to the bottom of the waveguide substrate 104 is larger than the critical angle of total reflection at the interface between the waveguide substrate 104 and the air, and the refractive index of the waveguide substrate 104 is larger than that of the air, the light beam i1 coupled into the waveguide substrate 104 through the incoupling grating 101 can propagate between the upper and lower surfaces of the waveguide substrate 104 by total reflection.

In the process of total reflection propagation of the light i1 in the waveguide substrate 104, as shown in fig. 8 (c), when the light i1 encounters the position D1 of the coupling-out grating 103 on the surface of the waveguide substrate 104 in the total reflection process, a part of the light i2 is released by diffraction of the grating, i.e., is coupled out of the waveguide substrate 104, and the remaining part of the light i3 continues to be total reflection propagated in the waveguide substrate 104. In the subsequent propagation process, when the light i3 propagating through total reflection enters the position D2 on the outcoupling grating 103 on the surface of the waveguide substrate 104, the above-mentioned phenomenon is repeated, that is, a part of the light i4 continues to be outcoupled from the waveguide substrate 104 through grating diffraction, and the remaining part of the light i5 continues to propagate through total reflection in the waveguide substrate 104 until all the light propagating through total reflection in the waveguide substrate 104 is outcoupled from the waveguide substrate 104.

As can be seen from the above description, in the diffractive light waveguide 100 shown in fig. 6 to 8, during the total reflection propagation of the light in the waveguide substrate 104, each time the same light encounters a certain position of the outcoupling grating 103 on the surface of the waveguide substrate 104, a part of the light is released from the waveguide substrate 104 by diffraction, and the other part of the light continues to propagate by total reflection in the waveguide, and the above phenomenon is repeated at different positions of the outcoupling grating 103, so that the light incident from the light source 106 is duplicated in the positive half-axis direction of the x-axis, and thus the light outcoupled by the outcoupling grating 103 is also amplified in the negative half-axis direction of the x-axis. This phenomenon may be referred to as exit pupil expansion, and for the diffractive light waveguide 100 shown in fig. 6 to 8, when it is used as a lens of AR glasses, a virtual image emitted by a microdisplay of the AR glasses may be subjected to exit pupil expansion in the negative semi-axis direction of the x-axis, i.e., a virtual one-dimensional expanding pupil is realized, which will be described in detail below.

It will be appreciated that in conventional optical imaging systems, the image typically has only one "exit" called exit pupil. For example, assuming that a 4mm diameter beam enters the waveguide "entrance pupil," since the waveguide is responsible for transmission only and does not enlarge or reduce the image, etc., then the "exit pupil" is also a 4mm beam, in which case the center of the pupil of the human eye sees the image with a range of motion of only 4mm. The exit pupil can be copied in multiple horizontal directions by arranging the diffraction grating on the surface, and each exit pupil outputs the same image, so that the moving range of the image seen by the pupil center of human eyes is enlarged, and the image can be seen even if the eyes move in a large range, which is called exit pupil expansion.

(V) AR glasses using diffractive light waveguide

Fig. 9 shows a schematic configuration of AR eyeglasses 200 using the diffractive light waveguide 100 as a lens.

As shown in fig. 9, the AR glasses 200 may include a frame part and a lens part, wherein the frame part may include a left temple 201, a right temple 202 and a lens frame 203, and the lens part may include a left lens 204 and a right lens 205, wherein the left lens 204 and the right lens 205 may employ a diffractive light waveguide structure, specifically, the left lens 204 and the right lens 205 may each employ a waveguide substrate of the diffractive light waveguide 100 in whole or in part, for example, a schematic diagram of employing the diffractive light waveguide 100 shown in fig. 8 as a lens is shown in fig. 9. The AR glasses 200 further include a micro-display device 105 for projecting a virtual image, and the virtual image is projected onto the left lens 204 and the right lens 205 formed by the diffractive optical waveguide 100 by the micro-display device 105, and is further introduced into human eyes by the left lens 204 and the right lens 205.

In some embodiments, the micro-display device 105 may be disposed in the middle of the lens frame for projecting light to the incoupling gratings 101 in the left lens 204 and the right lens 205. In addition, in other embodiments, two micro display devices may be provided, for example, on the left temple 201 or the right temple 202, respectively, or may be provided on an extended area of the left temple 201 or the right temple 202 toward the front of the human eye.

In some embodiments, the micro display device 105 may include a micro display 1051 (shown in FIG. 10) and a collimating lens 1052 (shown in FIG. 10). The microdisplay 1051 is used to provide a virtual image, and can be a self-luminous active device, such as an led panel, a liquid crystal display panel that needs an external light source for illumination, a digital micromirror array based on mems technology, a laser beam scanner, or the like. The collimating lens 1052 may be used to convert the light of each virtual image point into a parallel light beam for projection into the incoupling grating 101.

Fig. 10 shows a schematic diagram of the principle of coupling a virtual image into the human eye through the left lens 204 or the right lens 205 of the AR glasses 200.

As shown in fig. 10, a point light emitted by the microdisplay 1051 is transformed into a parallel light beam by the collimating lens 1052 and is projected into the incoupling grating 101, after the incoupling grating 101 couples the light beam into the waveguide substrate 104, the light beam propagates in the waveguide substrate 104 by total reflection, during the propagation by total reflection, each time it encounters the outcoupling grating 103 on the surface of the waveguide substrate 104, a part of the light will continue to be released by diffraction and enter the eye, and the remaining part of the light will continue to propagate in the waveguide until it hits the outcoupling grating 103 on the surface of the waveguide next time, so as to realize the exit pupil expansion in the x direction.

However, as described above, with the diffractive light guide 100 used for the lens in the AR glasses 200 shown in fig. 9, the exit pupil expansion of the image can be performed only in one direction, and for example, the virtual image provided by the microdisplay 1051 is enlarged only in the lateral direction (x-axis direction in fig. 9) or the vertical direction (y-axis direction in fig. 9) when being led out through the outcoupling grating 103, so that there is a problem that the led-out image is difficult to be applied to people with different interpupillary distances, different face shapes, and different heights of the nose bridge.

To solve the problem of single exit pupil expansion direction, fig. 11 shows a schematic structural diagram of a diffractive light waveguide 100. In the diffractive light waveguide 100 shown in fig. 11, the relay grating is added between the optical paths of the in-coupling grating and the out-coupling grating to realize the exit pupil expansion in the horizontal and vertical directions, so that a user can observe a larger image view range, and the diffractive light waveguide can be better suitable for people with different interpupillary distances, different face shapes and different heights of nose bridges.

Specifically, the diffractive light waveguide 100 shown in fig. 11 may include a waveguide substrate 104, an incoupling grating 101, a relay grating 102, and an outcoupling grating 103. The in-coupling grating 101, the relay grating 102 and the out-coupling grating 103 shown in fig. 11 are all located on the upper surface of the waveguide substrate 104, and are all in a diffraction grating structure.

It is understood that in other embodiments of the present application, the incoupling grating 101, the relay grating 102 and the outcoupling grating 103 may be all located on the lower surface of the waveguide substrate 104 or three of them may be distributed on the upper and lower surfaces of the waveguide substrate 104, and are not limited to the positions shown in fig. 11. In addition, although the coupling-in grating 101 shown in fig. 11 is circular, the relay grating 102 is trapezoidal, and the coupling-out grating 103 is rectangular, the shape shown in fig. 11 is merely exemplary, and the three shapes may be set to any shape according to the actual optical design requirement or the shape requirement of the AR lens.

In order to realize the exit pupil expansion in the horizontal and vertical directions, as shown in fig. 11, the grating notch direction of the relay grating 102 may form a set angle with the grating notch direction of the coupled-in grating 101, so that when the light coupled in from the coupled-in grating 101 encounters the relay grating 102 in the propagation process, a part of the light is changed in direction and propagates toward the coupled-out grating 103, that is, a part of the light continues to be totally reflected and propagated in the waveguide substrate 104 by using the negative half axis of the y-axis as the guiding direction, and the rest of the light continues to propagate along the original direction, that is, the light is totally reflected and propagated by using the positive half axis of the x-axis as the guiding direction. For example, in the diffractive optical waveguide 100 shown in fig. 11, the notch direction of the relay grating 102 and the grating notch direction of the coupling grating 101 are set at an angle of 45 degrees to achieve the above-described function. Specifically, fig. 12 (a) and (b) show schematic views of guiding light rays in the diffractive light waveguide 100 at different viewing angles, respectively.

As shown in fig. 12 (a), light i1 emitted from the micro-display device 105 is coupled into the waveguide substrate 104 by diffraction of the coupling-in grating 101 after being incident on the coupling-in grating 101, and is totally reflected and propagated in the waveguide substrate 104 along the positive half axis of the x-axis. After the light i1 coupled in through the coupling-in grating 101 encounters the relay grating 102, the light is divided into two parts due to the light splitting characteristic of the relay grating, and the two parts are respectively reflected and propagated towards different diffraction angles. Specifically, a part of the light continues to be totally reflected in the waveguide substrate 104 in the x-axis positive semiaxis direction, as indicated by an arrow B1 in the figure; another part is totally reflected in the waveguide substrate 104 in the direction of the negative half axis of the y-axis, as indicated by the arrow B2 in the figure. The light beams that go forward after encountering the relay grating 102 and are totally reflected in the direction of the y-axis negative half axis are guided into the coupling-out grating 103, and are coupled out of the waveguide substrate 104 by the coupling-out grating 103, and the traveling direction of the coupled-out light beams is shown by an arrow B3 in the figure, i.e., the direction of the z-axis positive half axis.

Specifically, fig. 13 (a) and (b) show diffraction optical path diagrams of light at the relay grating 102 and the outcoupling grating 103, respectively.

It will be appreciated that in the embodiments of the present application, for a two-dimensional light path diagram, light rays incident from a plane are represented by a circle with an "x" symbol added.

As shown in fig. 13 (a), when a light ray i1 totally reflected and propagated along the positive x-axis half axis in the waveguide substrate 104 after being coupled in by the incoupling grating 101 enters the position H1 of the relay grating 102, the light ray is divided into two parts and propagates toward different diffraction angles. Specifically, a part of the light i3 continues to enter the other surface of the waveguide substrate 104 to propagate through total reflection along the positive half axis of the x-axis, and another part of the light i2 enters the waveguide substrate 104 along the inward direction perpendicular to the image and propagates through total reflection along the negative half axis of the y-axis toward the outcoupling grating 103. It is understood that when the light ray i3 is incident on other positions of the relay grating 102, such as the H2 position, the above process is repeated to separate out the light rays i4 and i5 which are totally reflected and propagated along the positive half axis and the negative half axis of the x-axis respectively. In this manner, the relay grating 102 makes the total reflection propagation of the light i1 along the x-axis positive half axis expand the light in the x-axis positive half axis, i.e. the virtual image emitted by the micro-display device 105 is expanded by the exit pupil in the x-axis positive half axis direction.

Similar to fig. 8 (c), when the light i2 totally reflected and propagated along the negative half axis of the y-axis toward the coupling-out grating 103 reaches the position D1 of the coupling-out grating 103, a part of the light i21 is released by diffraction of the grating, and is coupled out of the waveguide substrate 104, and the remaining part of the light i22 continues to be totally reflected and propagated in the waveguide substrate 104, as shown in fig. 13 (b). The above phenomenon is repeated when the light ray i22 is incident on the surface of the waveguide substrate 104 at the position D2 on the outcoupling grating 103 during the subsequent propagation. In this manner, the light ray i1 is expanded in the negative y-axis direction, i.e., in the negative y-axis direction by the exit pupil for the virtual image emitted by the microdisplay 105.

As can be seen from the above description, the diffractive light waveguide 100 shown in fig. 11 to 13 can realize exit pupil expansion in two directions of the x-axis positive half axis and the y-axis negative half axis, and when the diffractive light waveguide is applied to AR glasses, a user can observe a larger image view range, and the diffractive light waveguide can be better suitable for people with different interpupillary distances, different face shapes and different nose bridge heights.

Fig. 14 shows a schematic configuration diagram of AR eyeglasses 200 using the above diffractive light waveguide 100 as a lens. As shown in fig. 14, the left lens 201 and the right lens 201 of the AR eyeglasses 200 may each employ the diffractive light waveguide 100 shown in fig. 14. The structure of the other parts of the AR glasses 200 in fig. 15 is similar to that in fig. 10, and is not repeated herein.

However, although the diffractive light waveguide 100 shown in fig. 11 to 13 can realize the exit pupil expansion in both directions of the x-axis positive half axis and the y-axis negative half axis, if it is desired to satisfy the market demand of the AR glasses to further increase the vertical field angle, that is, if it is desired to further increase the vertical field range seen by the human eye, it is necessary to increase the area of the relay grating 102 of the diffractive light waveguide 100, whereas the area of the relay grating 102 is limited because the area of the diffractive light waveguide 100 is limited when it is used as a lens of the AR glasses, and it is difficult for the diffractive light waveguide 100 shown in fig. 11 to 13 to satisfy the demand of the AR glasses to further increase the vertical field angle.

To describe this problem in more detail, the concept of the field of view is first introduced. Specifically, the field angle is generally used to measure the size of the field range that can be seen by the human eye. For example, as shown in fig. 15, taking an image that can be seen by eyes of an observer as an example, the field angle is an angle between an edge of the image and a line connecting the eyes, and may include a horizontal field angle and a vertical field angle; for example, in fig. 15, the AOB angle is the horizontal field angle, the BOC angle is the vertical field angle, and pupil replication is performed in the y direction, so that the vertical field angle can be increased; pupil replication in the x-direction can increase the horizontal field of view.

Specifically, in conjunction with the above-mentioned field angle concept, the AR glasses 200 of the present application, the virtual image (as indicated by the dashed box in the micro-display device 105 in fig. 16 (a) and (b)) emitted by the micro-display device 105 of the AR glasses 200 generally includes an upper edge field S1 and a lower edge field S2 (as indicated in fig. 16 (a) and (b)), wherein the upper edge field S1 may be defined as a ray of one of the light spots at the upper edge of the virtual image emitted by the micro-display device 105, and the lower edge field S2 may be defined as a ray of the light spot at the lower edge of the virtual image corresponding to the light spot at the upper edge; for example, the upper edge field of view S1 may be defined as a ray of the midpoint P1 of the upper edge of the virtual image, and the lower edge field of view S2 may be defined as a ray of the midpoint P2 of the lower edge of the virtual image; the angle between the upper edge field of view S2 and the lower edge field of view S1 is referred to as the edge field angle. The edge view field included angle of the virtual image can influence the vertical view field range which can be seen by human eyes, namely, the size of the vertical view field angle is consistent with the edge view field included angle of the image, and the specific relationship is as follows: the vertical field angle increases with increasing edge field angle. Therefore, in order to increase the vertical field of view, i.e., the vertical field angle, which can be seen by human eyes, the edge field angle of the image needs to be increased. If the diffractive light waveguide shown in fig. 11 is used, in the case of increasing the peripheral field angle of the image, the area of the relay grating 102 needs to be increased to realize the exit pupil with the same size, and therefore, the area of the whole diffractive light waveguide 100 is increased, which is specifically caused by the following reasons:

as shown in fig. 16 (a) and (b), fig. 16 (a) and (b) show the directional contrast schematic diagram of the propagation of the images of the smaller and larger marginal angle of field A1 and A2, respectively, in the diffractive light waveguide structure shown in fig. 11. As shown in fig. 16 (a) and (b), the virtual image includes an upper edge field of view S1 and a lower edge field of view S2. The upper edge field of view S1 and the lower edge field of view S2 of the virtual image gradually diverge in the waveguide, and the upper edge field of view S1 and the lower edge field of view S2 must also propagate in the relay grating 102 to achieve exit pupil expansion in the X direction; therefore, as shown in fig. 16 (a) and (b), as the edge field angle increases from A1 to A2, the degree of dispersion of the upper edge field S1 and the lower edge field S2 increases, and if the light rays are to continue to extend in the x direction to realize an exit pupil of the same size, the area of the relay grating 102 needs to be enlarged in the extending direction of the upper edge field S1 and the lower edge field S2, that is, the longer bottom side of the trapezoidal relay grating 102 shown in fig. 16 (b) needs to be lengthened, and both waists need to be enlarged outward. Thus, increasing the image edge field angle results in an increase in the area of the relay grating 102, which in turn results in an increase in the overall waveguide structure. Conversely, if the area of the relay grating 102 is not increased, the number of times the light strikes the relay grating 102 is reduced, resulting in a reduction in the exit pupil size in the x-direction.

To solve this problem, in another diffractive optical waveguide 100 according to the embodiment of the present application, the relay grating 102 in the diffractive optical waveguide 100 shown in fig. 11 is changed from one grating to a plurality of gratings with different refractive indexes, the light coupled in by the incoupling grating 101 still totally reflects in the waveguide substrate 104 after entering the waveguide substrate 104, but the traveling direction of a part of the totally reflected and propagated light is limited among the plurality of relay gratings, and a part of the light can be changed in direction at the relay grating near the outcoupling grating 103, totally reflected toward the outcoupling grating 103, and finally coupled out by the outcoupling grating 103 to the human eye. In this way, the light rays realize exit pupil expansion through reciprocal total reflection propagation among the relay gratings, and the area of the relay gratings does not need to be increased along with the increase of the vertical field angle. The following description will be given with reference to specific examples.

Fig. 17 is a schematic diagram of a diffractive optical waveguide 100 including two relay gratings according to an embodiment of the present application.

As shown in fig. 17, the diffractive optical waveguide 100 may include a waveguide substrate 104, an incoupling grating 101, a first relay grating 1021, a second relay grating 1022, and an outcoupling grating 103. The first relay grating 1021 and the second relay grating 1022 are disposed in parallel and spaced apart by a first distance, which is disposed to guide the light diffracted from the coupling grating to the reciprocal total reflection propagation between the first relay grating 1021 and the second relay grating 1022, as will be described in detail below. Further, the outcoupling grating 103 is provided between the first relay grating 1021 and the second relay grating 1022.

In this embodiment, the first relay grating 1021 and the second relay grating 1022 may define a relay region, the relay region extends in a first direction, the first relay grating 1021 and the second relay grating 1022 are arranged in a second direction, the relay region has a first side and a second side opposite to each other in the second direction, and an included angle between the extending direction of the first side and the extending direction of the second side is smaller than a first angle;

for example, the first direction may be an x-axis direction, and the second direction may be a y-axis direction.

It will be appreciated that the relay area may be defined by the raster lines adjacent to the first relay grating 1021 and the second relay grating 1022, being the area between the first relay grating 1021 and the second relay grating 1022, excluding the first relay grating 1021 and the second relay grating 1022. The first edge may be a grating line of the first relay grating 1021 which is closest to the second relay grating 1022, and the second edge may be a grating line of the second relay grating 1022 which is closest to the first relay grating 1021.

The relay area may also be defined by grating lines of the first relay grating 1021 and the second relay grating 1022 which are farthest apart, including not only the area between the first relay grating 1021 and the second relay grating 1022, but also the first relay grating 1021 and the second relay grating 1022. The first edge may be a grating line of the first relay grating 1021 which is farthest from the second relay grating 1022, and the second edge may be a grating line of the second relay grating 1022 which is farthest from the first relay grating 1021.

It is understood that in the embodiment of the present application, the parallel arrangement of the first relay grating 1021 and the second relay grating 1022 allows a certain error, for example, the extending directions of the grids or the notches of the first relay grating 1021 and the second relay grating 1022 may have a certain included angle, for example, 0 to 5 degrees.

It is to be understood that, although the in-coupling grating 101, the first relay grating 1021, the second relay grating 1022, and the out-coupling grating 103 shown in fig. 17 are all located on the same surface of the waveguide substrate 104, in other embodiments, the four may all be located on another surface of the waveguide substrate 104 or distributed on different surfaces, for example, the in-coupling grating 101 and the out-coupling grating 103 are located on the same surface of the waveguide substrate 104, and the first relay grating 1021 and the second relay grating 1022 are located on another surface of the waveguide substrate 104, which is not limited herein.

Furthermore, it is to be understood that although only two relay gratings, i.e. the first relay grating 1021 and the second relay grating 1022, are shown in fig. 17, in other embodiments, the relay grating 102 may also comprise three or more grating regions with different diffraction rates.

Fig. 18 (a) and (b) are schematic diagrams illustrating different angle orientations of light propagating in the waveguide substrate according to the embodiment of the present application, respectively.

It can be understood that since the light is totally reflected and propagated in the waveguide substrate 104, the guiding function of the total reflection propagation direction of the first relay grating 1021, the second relay grating 1022, or the coupling-out grating 103 on two different bottom surfaces of the waveguide substrate 104 is the same, and therefore, the guiding schematic diagram of the light propagating in the waveguide substrate 104 can be represented by fig. 18 (a) and (b) no matter which bottom surface of the waveguide substrate 104 the coupling-in grating 101, the first relay grating 1021, the second relay grating 1022, and the coupling-out grating 103 are located.

As shown in fig. 18 (a) and (B), the light i1 emitted from the micro-display device 105 is coupled into the coupling waveguide substrate 104 of the optical grating 101 after being incident on the coupling grating 101, and is propagated by total reflection in the waveguide substrate 104 toward the second relay grating 1022, as shown by an arrow B1. After the light i1 coupled in through the coupling-in grating 101 meets the second relay grating 1022, as mentioned above, the light is divided into two parts by the light splitting characteristic of the diffraction grating, and the two parts are respectively reflected and propagated towards different diffraction angles. Specifically, a part thereof is propagated by total reflection in the waveguide substrate 104 toward the first relay grating 1021, as indicated by an arrow B2 in the drawing; the other part is guided to the outcoupling grating 103 toward the direction shown by the arrow B3 in the figure, and is outcoupled from the outcoupling grating 103 to the waveguide substrate 104, the traveling direction of the outcoupled light is shown by the arrow B5 (positive half axis direction of z-axis) in the figure, the light transmitted to the first relay grating 1021 is totally reflected and is redirected to the second relay grating 1022 along the guiding direction shown by the arrow B4, and the above process is repeated in the subsequent process.

Specifically, fig. 19 (a) shows a diffraction optical path diagram of light at the first relay grating 1021 and the second relay grating 1022.

As shown in fig. 19 (a), when a light i1 totally reflected and propagated in the waveguide substrate 104 in the direction indicated by the arrow B1 after being coupled in by the coupling-in grating 101 enters the F1 position of the second relay grating 1022, the light is divided into two parts, and propagates respectively toward different diffraction angles, for example, a part of the light i2 enters the other surface of the waveguide substrate 104 and totally reflects and propagates between the upper and lower surfaces of the waveguide substrate 104 in the direction indicated by the arrow B2 until propagating to the G1 position of the first relay grating 1021; another part of the light i3 is incident on the other surface of the waveguide substrate 104 and propagates by total reflection in the direction indicated by the arrow B3 (as shown in fig. 18 (a) - (B)) until being guided to the outcoupling grating; the light i2 propagating to the G1 position of the first relay grating 1021 is totally reflected to the other surface of the waveguide substrate, and is totally reflected and propagated between the upper and lower surfaces of the waveguide substrate 104 along the direction indicated by the arrow B4, and the above process is repeated until the light i2 reaches the F2 position of the second relay grating 1021, for example, the light i2 is divided into two parts, wherein one part of the light i4 is guided to the G2 position of the first relay grating 1021 for total reflection propagation, and the other part of the light i5 is guided to the position facing the coupling grating 103 for total reflection propagation. In this way, the light ray i1 realizes the exit pupil expansion in the x-axis positive semiaxis direction in such a manner as to travel back and forth between the first relay grating 1021 and the second relay grating 1022.

Similar to fig. 8 (c), when the light i3 totally reflected toward the coupling-out grating 103 in the direction B3 reaches the position D1 of the coupling-out grating 103, a part of the light i6 is released by diffraction of the grating, i.e. is coupled out of the waveguide substrate 104 toward the positive half-axis direction of the z-axis, and the remaining part of the light i7 continues to be totally reflected in the waveguide substrate 104, as shown in fig. 19 (B). The above phenomenon is repeated when the light ray i7 is incident on the surface of the waveguide substrate 104 at the position D2 on the outcoupling grating 103 in the course of subsequent propagation. In this manner, the light ray i1 is expanded in the y-axis negative semi-axis direction, i.e., in the y-axis negative semi-axis direction by the exit pupil for the virtual image emitted by the micro-display device 105.

In the embodiment of the application, the exit pupil expansion in the x direction is realized by adopting a mode of total reflection propagation between the first relay grating 1021 and the second relay grating 1022; instead of realizing the exit pupil expansion in the x direction in a linear propagation manner in the relay grating 102 region, the exit pupil expansion in the x direction can be realized without increasing the area of the relay grating 102 region when the included angle between the image fringe fields is increased.

Specifically, fig. 20 (a) and (b) show schematic guidance contrast diagrams of the propagation of the images of the smaller edge field angle A1 and the larger edge field angle A2 in the diffractive light waveguide 100, respectively. As shown in fig. 20 (a) and (b), the change caused when the edge field angle is increased from small to large is as follows:

after the light of the peripheral field is coupled in by the coupling grating 101, the guiding direction guided to the second relay grating 1022 changes, i.e. the included angle between the guiding direction and the positive half axis of the x-axis increases, because the light is propagated back and forth in the relay grating 102 in a total reflection manner, the guiding direction of the light diffracted to the first relay grating 1021 by the second relay grating 1022 changes accordingly. Therefore, when the peripheral field angle is increased from small to large, the induced change is only that the guiding direction of the light diffracted to the first relay grating 1021 by the second relay grating 1022 is changed correspondingly, and the number of times that the light strikes the first relay grating 1021 is not reduced significantly, so that the number of times of exit pupils is not reduced significantly, that is, the change of the size of the exit pupils of the light is not affected significantly.

In summary, when the included angle of the peripheral field of view is increased from small to large, the diffractive optical waveguide 100 provided in the embodiment of the present application only causes the change of the guiding directions of the two relay gratings to the light, and can also realize the exit pupil expansion of the same size in the x direction without increasing the area of the relay gratings.

It is understood that, in the embodiment of the present application, in order to enable the coupling-in efficiency of the coupling-in grating 101 to reach more than 95%, that is, to enable the coupling-in grating 101 to couple in as much light as possible to the second relay grating 1022 at a specific angle, the required diffraction efficiency of the coupling-in grating 101 may be optimized to be the highest by designing parameters of the coupling-in grating 101, such as the refractive index n, the grating shape, the thickness, the duty ratio, and the like, so that most of the light propagates mainly in this direction after being diffracted. In addition, in order to reduce the single-pass outcoupling efficiency, so that the light is coupled out to the human eye in the outcoupling grating 103 while expanding in a specific direction, the outcoupling efficiency of the outcoupling grating 103 can be 1% -10%, so as to reduce the single-pass outcoupling efficiency and realize the exit pupil expansion.

In addition, in the embodiment of the present application, in order to make the k-space region of the light coupled out by the light grating 103 completely coincide with the k-space region of the incident light emitted by the micro-display device 105, so as to effectively prevent the generation of image distortion, parameters of each light grating need to be set. For example, the period and the grating vector direction of the coupling-out grating 103 are set to be consistent with the period and the grating vector direction of the coupling-in grating 101; and the period and grating vector direction of the first relay grating 1021 are set to coincide with the period and grating vector direction of the second relay grating 1022. The vector direction of the grating mentioned in the embodiment of the present application is a direction perpendicular to the scoring direction of the grating.

For example, as shown in fig. 17, the angles between the notch direction of the coupling grating 101 and the positive X-axis direction and the angles between the notch direction of the coupling grating 103 and the positive X-axis direction may both be 45 °. The direction of the cuts of the first relay grating 1021 and the direction of the cuts of the second relay grating 1022 may both be parallel to the x-axis.

In some embodiments, the scoring direction of the in-coupling grating 101 is at an angle with the positive x-axis direction, which is required to satisfy the condition that the light incident on the in-coupling grating 101 can be guided by the in-coupling grating 101 to propagate toward the second relay grating 1022, for example, may be between-70 ° and 10 °.

In the embodiment of the present application, in order to ensure that the light can be controlled to propagate in a total reflection manner in the relay region defined by the relay grating, the first relay grating 1021 and the second relay grating 1022 may be provided with different diffraction efficiency distributions.

Specifically, the diffraction efficiency of the first relay grating 1021 is required to be as follows: the diffraction efficiency distribution of the first relay grating 1021 may be uniform distribution so that light incident on the first relay grating 1021 can be totally reflected to the second relay grating 1022. For example, in some embodiments, the diffraction efficiency of the light incident on the first relay grating 1021 when diffracted can be controlled to be small, for example, the diffraction efficiency is set to be less than 0.1%; the diffracted light reflected back to the second relay grating 1022 has a higher diffraction efficiency, which may be set to be greater than 99.5%, for example, thereby effectively ensuring that no energy escapes the relay grating.

Specifically, the diffraction efficiency of the second relay grating 1022 is required as follows: the second relay grating 1022 may have a non-uniform diffraction efficiency such that a portion of the light is coupled out of the second relay grating 1022 and into the out-coupling grating 103. For example, the diffraction efficiency of the portion of the second relay grating 1022 close to the out-coupling grating 103 is low, and the diffraction efficiency of the portion close to the first relay grating 1021 is high, so that it can be effectively ensured that a part of the light is coupled out from the first relay grating 1021 into the out-coupling grating 103. For example, in some embodiments, when the light incident on the second relay grating 1022 is diffracted, the diffraction efficiency of the diffracted light exiting to the coupling-out grating 103 may be 0.5 to 20%, and the diffraction efficiency of the diffracted light reflected back to the first relay grating 1021 is greater than 80%, so that it can be effectively ensured that a small amount of light is coupled out from the second relay grating 1021 and enters the coupling-out grating 103, and a large amount of light is continuously reflected back to the first relay grating 1021, thereby realizing the exit pupil expansion in the x direction.

In some embodiments, the first relay grating 1021 and the second relay grating 1022 may both employ surface relief gratings, and the diffraction efficiency thereof may be modulated by the grating height of the surface relief gratings. For example, by setting the grating height of the first relay grating 1021 to be evenly distributed, the diffraction efficiency of the first relay grating 1021 is made evenly distributed, as shown in fig. 3 (a).

For another example, the second relay grating 1022 has uneven diffraction efficiency by setting the grating heights of the second relay grating 1022 to be unevenly distributed. For example, as shown in fig. 21, the grating height is set lower near the side of the out-coupling grating 103, so that the diffraction efficiency is lower near the side of the out-coupling grating 103; the grating height on the side close to the first relay grating 1021 is higher, so that the diffraction efficiency on the side close to the first relay grating 1021 is higher. It is feasible that the diffraction efficiency can also be modulated by other grating parameters, for example. The duty cycle distribution of the grating may be adjusted to adjust the diffraction efficiency distribution of the grating.

It is understood that, in the embodiment of the present application, the surface relief grating may be a grating formed on the surface of the optical waveguide by using a surface relief process. The diffraction efficiency of the surface relief grating can be tuned by designing the relevant parameters of the surface relief grating, such as height.

In some other embodiments, the first relay grating 1021 and the second relay grating 1022 may both adopt volume holographic gratings, where the volume holographic gratings are formed by directly interfering inside a volume holographic material with a micrometer-scale thickness to form interference fringes with light and shade distribution by means of two-beam holographic exposure; the diffraction efficiency of the volume holographic grating can be regulated and controlled through the refractive index modulation degree of the volume holographic grating, and the lower the refractive index modulation degree of the grating area is, the lower the diffraction efficiency of the corresponding grating area is, namely, the refractive index modulation degree of the grating area is in direct proportion to the diffraction efficiency of the corresponding grating area.

Therefore, in order to uniformly distribute the diffraction efficiency distribution of the first relay grating 1021, the refractive index modulation degree uniform distribution of the first relay grating 1021 may be provided. In order to make the second relay grating 1022 have non-uniform diffraction efficiency, the refractive index modulation degree of the second relay grating 1022 may be distributed non-uniformly, specifically, the refractive index modulation degree may gradually decrease from a region far from the coupling-out grating 103 to a region close to the coupling-out grating 103.

The refractive index modulation degree of the volume hologram grating may be adjusted by the ultraviolet exposure time, for example, the longer the ultraviolet exposure time, the higher the refractive index modulation degree.

Further, in other embodiments, one of the first relay grating 1021 and the second relay grating 1022 may employ a surface relief grating, and the other may employ a volume holographic grating, for example, the first relay grating 1021 may employ a surface relief grating, and the second relay grating 1022 may employ a volume holographic grating. And the adjustment of the specific diffraction efficiency can be made by the method described above.

In addition, it can be understood that, in the embodiment of the present application, the arrangement position of the incoupling grating 101 is flexible. For example, the in-coupling grating 101 may be disposed in a relay region between the first relay grating 1021 and the second relay grating 1022 as shown in fig. 17, may be disposed between extended regions of the first relay grating 1021 and the second relay grating 1022 as shown in fig. 22, or may be disposed on either side of the first relay grating 1021 or the second relay grating 1022 as shown in fig. 23. It should be noted that the position of the incoupling grating 103 in the embodiment of the present application needs to be sufficient to enable the light incident on the incoupling grating 103 to be guided to the second relay grating 1023.

Fig. 24 is a schematic diagram showing a structure of AR eyeglasses 200 using the diffractive light waveguide 100 shown in fig. 17 as a lens. As shown in fig. 24, the left lens 201 and the right lens 201 of the AR eyeglasses 200 may each employ the diffractive light waveguide 100 shown in fig. 17. The structure of the other parts of the AR glasses 200 in fig. 17 is similar to that in fig. 9, and is not repeated herein.

In the second embodiment of the present application, the diffractive optical waveguide 100 may not only be limited to the embodiment including the two relay gratings, but also include three or more relay gratings.

It is practicable that if the diffractive optical waveguide 100 may include three or more relay gratings, the period and the grating vector of each relay grating are the same; the light can propagate through the second relay grating 1022 by diffraction of the in-coupling grating.

In some embodiments, in embodiments comprising multiple relay gratings, the diffraction efficiency requirement of the relay grating furthest from the outcoupling grating is the same as the diffraction efficiency requirement of the first relay grating 1021 in the above-described embodiments comprising two grating regions, so that all light incident on this relay grating can be totally reflected to the other relay gratings. The diffraction efficiency requirements of the remaining relay gratings are the same as the diffraction efficiency distribution requirements of the second relay grating 1022 in the above-described embodiment including two relay gratings, so that light incident on the remaining relay gratings can be partially guided to the first relay grating 1021 and the other part guided to the outcoupling grating 103.

For example, as shown in fig. 25, the structure of the diffractive light waveguide 100 is substantially the same as that shown in fig. 17, and the main differences are: a third relay grating 1023 may be provided between the first relay grating 1021 and the second relay grating 1022. The periods and grating vectors of the first relay grating 1021, the second relay grating 1022 and the third relay grating 1023 are the same; an incoupling grating may be disposed above the third relay grating 1023,

It is understood that the incoupling grating 101 may also be disposed at other positions that enable the light to be guided by the incoupling grating 101 to propagate toward the second relay grating 1022, for example, the incoupling grating 101 may also be disposed between the second relay grating 1022 and the third relay grating 1023.

The diffraction efficiency of the first relay grating 1021 is uniformly distributed, and no energy overflows the relay area.

The second relay grating 1022 may have a non-uniform grating efficiency, e.g., a lower diffraction efficiency on the side near the outcoupling grating 103 and a higher diffraction efficiency on the side near the third relay grating 1023, so as to effectively ensure that some light is coupled into the third grating area 1023 by the second relay grating 1022 and that some light can be outcoupled from the second grating area 1022 into the outcoupling grating 103.

The third relay grating 1023 may have non-uniform grating efficiency, for example, the side near the second relay grating 1022 has lower diffraction efficiency and the side near the first relay grating 1021 has higher diffraction efficiency, so as to effectively ensure that some light is coupled into the second grating region 1022 through the third relay grating 1023 and some light can be coupled into the first relay grating 1021 from the third grating region 1023.

In the embodiment of the present application, a surface relief grating, a volume hologram grating, and the like may be disposed between the first relay grating 1021 and the second relay grating 1022.

Fig. 26 shows a schematic diagram of the guiding of light rays in the diffractive light guide 100 of the three relay gratings.

As shown in fig. 26, the incoupling grating 101 couples the light i1 projected by the micro-display device 105 into the waveguide substrate 104, and guides the light i1 toward the second relay grating 1022, as shown by an arrow B1; when a light ray is incident on the second relay grating 1022 in the direction indicated by the arrow B2, the light ray is divided into two parts, and the two parts propagate toward different diffraction angles, respectively. Specifically, a part of the light is propagated by total reflection inside the waveguide substrate 104, and the direction of the propagation by total reflection is incident on the third relay grating 1023 in the direction indicated by the arrow B2, and the other part is also propagated by total reflection inside the waveguide substrate 104, but the direction of the propagation by total reflection is incident on the outcoupling grating 103 in the direction indicated by the arrow B3.

The light incident on the third relay grating 1023 in the direction indicated by the arrow B2 is divided into two parts and propagates toward different diffraction angles, respectively. Specifically, a part of the light is propagated by total reflection inside the waveguide substrate 104, and the direction of the propagation by total reflection is incident on the first relay grating 1021 in the direction indicated by the arrow B4, and the other part of the light is also propagated by total reflection inside the waveguide substrate 104, and the direction of the propagation by total reflection is incident on the second relay grating 1022 in the direction indicated by the arrow B5.

The light incident on the first relay grating 1021 in the direction indicated by the arrow B4 is incident on the third relay grating 1023 in the direction indicated by the arrow B6, and the light incident on the third relay grating 1023 repeats the above process.

The specific optical path schematic diagram of the light in the diffractive light waveguide 100 is similar to that in fig. 19, and the light is totally reflected and propagated between the upper surface and the lower surface of the waveguide substrate 104 according to the guiding direction, which is not described herein again.

In the embodiment of the present application, the relay grating 102 may also be formed by an intermittently distributed refractive index modulation region generated in the relay region. For example, irradiation of the waveguide substrate 104 by ultraviolet light produces an intermittent distribution of regions of different refractive index modulation in the relay region. Specifically, the refractive index modulation degree of each region may be adjusted by adjusting the time of the ultraviolet light exposure so that the refractive index modulation degree of each region of the relay grating 102 is different.

In some embodiments, taking the example that the relay area includes three grating areas, fig. 27 shows three relay gratings, a first relay grating 1021, a second relay grating 1022, and a third relay grating 1023, with different refractive index modulation degrees, arranged in the negative y-axis direction of the diffractive light waveguide. The periods and grating vectors of the first relay grating 1021, the second relay grating 1022 and the third relay grating 1023 are the same; the incoupling grating is disposed on the surface of the relay area, for example, the surface at the position of the third relay grating 1023.

In fig. 27, the diffraction efficiency distributions and the light guiding directions of the first relay grating 1021, the second light relay grating 1022, and the third relay grating 1023 are the same as those in fig. 26.

In the third embodiment of the present application, unlike the structure described above, the diffractive optical waveguide 100 may include two waveguide layers as shown in fig. 28. For example, the lower waveguide layer may be defined as the waveguide substrate 104 and the upper waveguide layer as the waveguide top layer 106, i.e., the diffractive optical waveguide 100 may include the waveguide substrate 104 and the waveguide top layer 107. A grating layer may be interposed between the waveguide substrate 104 and the waveguide top layer 107, and the grating layer may be formed with an arrangement manner including any of the incoupling gratings 101, the plurality of relay gratings (such as the first relay grating 1021 and the second relay grating 1022), and the outcoupling grating 103 mentioned in the above embodiments, where the grating layer may be an arrangement manner in which the holographic material layer 108 is disposed between the waveguide substrate 104 and the waveguide top layer 107, and the holographic material layer 108 generates any of the incoupling gratings 101, the plurality of relay gratings (such as the first relay grating 1021 and the second relay grating 1022), and the outcoupling grating 103 mentioned in the above embodiments by a holographic exposure technology.

It is understood that any of the in-coupling gratings 101, the plurality of relay gratings (e.g., the first relay grating 1021 and the second relay grating 1022), and the out-coupling grating 103 mentioned in the above embodiments of the grating layer may also be gratings formed by other methods, such as surface relief gratings. The corresponding light propagation manner is the same as that in the above embodiments, and is not described herein again.

In the embodiment of the application, the holographic material layer is clamped by the two waveguide layers, so that the thickness uniformity of the holographic material layer can be ensured, and the light propagation stability is improved. In some embodiments, the holographic material may be directly coated on one surface of the waveguide layer, for example, the upper surface of the waveguide substrate 104 or the lower surface of the waveguide top layer 107, and any of the arrangements of the incoupling grating 101, the plurality of relay gratings (such as the first relay grating 1021 and the second relay grating 1022), and the outcoupling grating 103 mentioned in the above embodiments may be generated on the holographic material by a holographic exposure technique.

In other embodiments, the diffractive optical waveguide may also include a plurality of waveguide substrates 104 and a grating layer on each waveguide substrate 104, and the plurality of waveguide substrates 104 are stacked and connected in the z-axis direction. This approach, which can employ only one or more monochromatic lights of different wavelengths propagating per waveguide substrate 104, can reduce the crosstalk of system colors, and thus can improve the color uniformity ultimately at the exit pupil location. For example, the micro display device 105 projects three monochromatic lights of red light, blue light and green light, and a grating layer may be added on the upper surface of the waveguide top layer 107 or the lower surface of the waveguide bottom layer 104 on the basis of the above-mentioned scheme of arranging the grating layer between the waveguide substrate 104 and the waveguide top layer 107, so that the green light is transmitted through the waveguide top layer 107, and the red light and the blue light are transmitted through the waveguide substrate 104. For another example, three diffractive light waveguides 100 mentioned in the above embodiments may be stacked and connected in the z-axis direction, and each diffractive light waveguide 100 propagates one of the monochromatic lights and is finally coupled into the human eye together.

It is understood that in the embodiments of the present application, the light guiding function is realized by disposing various gratings on the surface of the optical waveguide substrate, and in other embodiments, other optical elements with grating diffraction function may also be adopted to realize the above technical solution. Further, these optical elements may be provided not on the surface of the optical waveguide substrate but inside the optical waveguide substrate to achieve the light guiding function, for example, by changing the microstructure in a certain region of the optical waveguide substrate, the microstructure in the region can achieve the function of the coupling grating 101, the first relay grating 1021, the second relay grating 1022, or the coupling grating 103.

The above-mentioned embodiments of the present application provide a technical solution that the relay grating 102 may include a plurality of relay gratings with different refractive indexes, so that the light can realize exit pupil expansion of the light by reciprocating propagation in the plurality of relay gratings without increasing the area of the relay gratings with an increase of the field angle, so that the diffractive light waveguide 100 can be applied to various devices with large field angles.

The following describes a method for setting the size of each grating on the diffractive optical waveguide 100 according to some embodiments of the present application.

(1) Dimensioning of the incoupling grating 101

In the embodiment of the present application, the size of the incoupling grating 101 may be square as shown in 27, and may be implemented, or may be configured into other shapes according to actual requirements, for example, a circle.

The size of the incoupling grating 101 is equal to or larger than the exit pupil size of the micro-display device 105 used. For example, if the exit pupil size is 4mm in diameter and the coupling-in grating 101 is circular in shape, the size of the coupling-in grating 101 is at least 4mm in diameter; if the incoupling grating 101 has a square shape, the size of the incoupling grating 101 is at least 4 x 4mm. It is practicable that the size of the incoupling grating 101 may be adjusted according to the size of the AR glasses or the like, for example, the size of the incoupling grating 101 may be set to be between 0.5 × 0.5mm and 10 × 10mm according to the size of general AR glasses.

(2) Sizing of first and second relay gratings

The interval between the first relay grating 1021 and the second relay grating 1022 is greater than or equal to the size value of the in-coupling grating 101 in the y direction. For example, the width of the first relay grating 1021 and the second relay grating 1022 in the y direction may be adjusted according to the size of the AR glasses, and the width of the first relay grating 1021 and the second relay grating 1022 in the y direction may be 0.1 to 10mm according to the size of the general AR glasses.

(3) Dimensioning of coupled-out gratings

The size of the outcoupling grating 101 is equal to or larger than the final exit pupil size of the light in the waveguide substrate 104. For example, if the final exit pupil size is 4 × 4mm, the size of the coupling grating 101 may be 5 × 5mm, etc. to satisfy the exit pupil requirement of the light.

In the embodiment of the present application, the period of coupling in the grating 101 also needs to satisfy the setting condition, as follows:

suppose that the FOV of the augmented reality display corresponds to a horizontal field of view and a vertical field of view which are respectively FOV _hor And FOV _ver Within the field of view, a certain field of view can be used (theta) _hor ,θ _ver ) And is represented by θ _hor ∈FOV _hor And theta _ver ∈FOV _ver ；

For the incident grating 101, the polar angle θ of the diffracted light corresponding to the m-order _m The light coupled into the waveguide substrate 104 needs to be propagated by total reflection in the waveguide substrate 104 under the following conditions:

in order to allow light passing through the incoupling grating 101 to satisfy a set angle of diffraction, for example, m-order diffraction, as shown in the above expression (1), the period d of the incoupling grating 101 needs to satisfy the set condition:

where m is the diffraction order, n is the refractive index of the waveguide substrate 104, θ _m And

is the polar angle and azimuth angle of the diffracted light corresponding to the m-order, λ is the wavelength of the incident light, θ and

respectively polar and azimuthal angles, theta, of incident light _Gin Is the angle of the notch of the diffraction grating.

Wherein, θ and

the calculation process of (2) is as follows:

for example, if the light of a certain field of view is (45 ° ), the polar angle θ and the azimuth angle of the incident light are

All at 45 °, the wavelength of incident light is 650nm, the diffraction order m is 1, the angle of the notch of the diffraction grating is 45 °, and the refractive index of the selected waveguide substrate structure 104 is 2, and the polar angle and the azimuth angle of the diffracted light corresponding to the m order are 45 °, then the period d of the incoupling grating 101 is calculated to be 248nm.

In some embodiments, the period of the incoupling grating may be adjusted according to the diffraction angle requirements for light passing through the incoupling grating 101, for example, the period of the incoupling grating may be in the range of 200nm-500nm.

The following description will take the propagation of light in k-space in the diffractive light waveguide 100 shown in fig. 17 as an example to ensure that the grating vector of the coupled-out grating 103 is the same as that of the coupled-in grating 101, and the grating vectors of the first relay grating 1021 and the second relay grating 1022 are the same, so that the k-space region of the coupled-out light can be completely overlapped with the incident light, and the specific reason for effectively preventing the occurrence of image distortion is described. As follows:

let the incident light correspond to a k-space vector of:

the diffraction of the incident light by the in-coupling grating 101 can be expressed as

Namely that

Wherein,

in order to diffract the light k-vector,

is the vector of k of the incident light,

is a raster k vector, an

For the diffractive light waveguide 100 shown in fig. 17, the k-space path is as shown in fig. 29, and the central area square indicates the k-space area corresponding to the field of view of the incident light. For example, after passing through the coupling-in grating 101, under the multiple reflection action of the first relay grating 1021 and the second relay grating 1022, the k-space region where the diffracted light 100 propagates back and forth is the region indicated by the lower left square and the region indicated by the upper left square in fig. 14, and after the multiple reflection action of the first relay grating 1021 and the second relay grating 1022, the k-space region returns to the region indicated by the lower left square in fig. 29, and then enters the coupling-out grating 103, the coupling-out grating 103 can couple out the light from the waveguide, wherein the k-space region of the coupled-out light completely coincides with the k-space region of the incident light, and thus the occurrence of image distortion can be effectively prevented.

For example, let the K vector coupled into the grating 101 be

Let K vector of out-coupling grating 103 be

Let K vectors of the first relay grating 1021 and the second relay grating 1022 be

Since the K-vectors of the incoupling grating 101 and the outcoupling grating 103 are the same and the K-vectors of the first 1021 and second 1022 relay gratings are the same, the incoupling grating 101 and the outcoupling grating 103 are identical

The above formula can show that the light entering the waveguide passes through the multiple actions of the incoupling grating 101, the first relay grating 1021, the second relay grating 1022 and the outcoupling grating 103 in the waveguide structure, and when the light exits the waveguide structure again, the direction of the light does not change, thereby ensuring that the image does not have distortion.

And because the K-vectors of the incoupling grating 101 and the outcoupling grating 103 are the same, and the K-vectors of the first relay grating 1021 and the second relay grating 1022 are the same, i.e. the

Thus:

where N represents the number of times a light ray makes multiple reciprocal propagations between the first relay grating 1021 and the second relay grating 1022, as can be seen from the above equation, because

So that no matter what the value of N is,

are all equal to 0, so that the light rays repeatedly propagate between the first relay grating 1021 and the area of the second grating for multiple times without introducing extra phase difference, and the direction of the light rays entering the first relay grating 1021 can be ensured to be consistent with the propagation direction of the light rays diffracted from the first grating.

To sum up, according to the technical solution provided by the embodiment of the present application, the periods and the grating vector directions of the coupling-out grating 103 and the coupling-in grating 101 are the same, and the periods and the grating vector directions of the first relay grating 1021 and the second relay grating 1022 of the relay grating 102 are also the same, so that the light entering the waveguide structure passes through the multiple actions of the coupling-in grating 101, the first relay grating 1021, the second relay grating 1022, and the coupling-out grating 103 in the waveguide structure, and when the light exits the waveguide structure again, the direction of the light cannot be changed, thereby ensuring that the image cannot be distorted.

It should be noted that the diffractive optical waveguide 100 provided in the embodiment of the present application may be applied to other fields besides the AR glasses 200, for example, may be applied to a Head Up Display (HUD), and the diffractive optical waveguide 100 provided in the embodiment of the present application projects important driving data or images onto a front windshield, so as to facilitate viewing by a driver and improve driving safety.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims

1. An optical apparatus comprising at least one waveguide substrate, and a coupling-in unit, a first relay unit, a second relay unit, and a coupling-out unit provided on the waveguide substrate;

the coupling-out unit is configured to couple out light in the waveguide substrate out of the waveguide substrate, the coupling-out unit being aligned with the relay region in the second direction.

2. The optical apparatus of claim 1 wherein said first angle is between 0 ° and 5 °.

3. The optical device of claim 1, wherein the first edge and the second edge are parallel in a direction of extension.

4. The optical device according to claim 1, wherein the second relay unit is configured such that the light propagating by total reflection in the waveguide substrate propagates by total reflection at least a part of the outgoing light toward the first relay unit after being incident on the second relay unit, and propagates by total reflection at least a part of the outgoing light toward the outcoupling unit;

5. The optical device of claim 1, wherein the first and second relay units are gratings; and is

The first edge of the relay area is the grid line of the first relay unit closest to the second relay unit, and the second edge is the grid line of the second relay unit closest to the first relay unit;

or,

the first edge of the relay area is the grating of the first relay unit which is farthest away from the second relay unit, and the second edge is the grating of the second relay unit which is farthest away from the first relay unit.

6. The optical device of claim 5, wherein the first and second relay units each include a plurality of grating gridlines, and wherein the grating gridlines of the first and second relay units are at the first angle with respect to each other.

7. The optical device of claim 6, wherein the first and second relay units each comprise a plurality of grating gridlines, and wherein the grating gridlines of the first and second relay units are parallel to each other.

8. The optical device of claim 5, wherein the first and second relay units are mutually parallel bar gratings.

9. The optical device of claim 5, wherein the grating periods of the first relay unit and the second relay unit are the same.

10. The optical device according to claim 5, wherein the diffraction efficiency of the first relay unit is equally distributed, and the diffraction efficiency of the second relay unit is gradually decreased from a side away from the coupling-out unit to a side close to the coupling-out unit.

11. The optical device of claim 10, wherein the first relay unit is a surface relief grating and the grating heights of the first relay unit are equally distributed.

12. The optical apparatus according to claim 10, wherein the second relay unit is a surface relief grating, and a grating height of the second relay unit is gradually reduced from a side away from the outcoupling unit to a side close to the outcoupling unit.

13. The optical apparatus according to claim 10, wherein the first relay unit is a volume hologram grating, and a refractive index modulation degree of the first relay unit is equally distributed.

14. The optical apparatus according to claim 10, wherein the second relay unit is a volume hologram grating, and a grating refractive index modulation degree of the second relay unit gradually decreases from a side away from the coupling-out unit to a side close to the coupling-out unit.

15. The optical device of claim 1, further comprising at least one third relay unit disposed on the waveguide substrate, the third relay unit being disposed between the first relay unit and the second relay unit, and

the third relay unit divides the relay area into a plurality of relay areas, and an included angle between two long sides of each relay area in the extension direction is smaller than the first angle.

16. The optical device of claim 15,

the third relay unit is configured to: after the light rays which are subjected to total reflection propagation in the waveguide substrate enter the third relay unit, at least part of emergent light rays are subjected to total reflection propagation towards the first relay unit, and at least part of emergent light rays are subjected to total reflection propagation towards the second relay unit.

17. The optical device of claim 15, wherein the first relay unit, second relay unit, and third relay unit are gratings.

18. The optical apparatus of claim 17, wherein the first relay unit, the second relay unit, and the third relay unit each comprise a plurality of grating lines parallel to each other.

19. The optical device of claim 15, wherein the third relay unit is a stripe grating.

20. The optical apparatus according to claim 17, wherein the diffraction efficiency of the third relay unit gradually decreases from a side close to the first relay unit to a side close to the second relay unit.

21. The optical apparatus according to claim 20, wherein the third relay unit is a surface relief grating, and a grating height of the third relay unit is gradually reduced from a side close to the first relay unit to a side close to the second relay unit.

22. The optical apparatus according to claim 20, wherein the third relay unit is a volume hologram grating, and a grating refractive index modulation degree of the third relay unit gradually decreases from a side close to the first relay unit to a side close to the second relay unit.

23. The optical device of claim 1, wherein the incoupling unit is located in the relay area.

24. The optical device according to claim 1, wherein the incoupling unit and the outcoupling unit are gratings, and the periods and grating vector directions of the incoupling unit and the outcoupling unit are the same.

25. The optical device of claim 1, wherein the incoupling unit is a surface relief grating or a volume holographic grating; and is provided with

26. The optical device of claim 1, wherein the incoupling unit, the first relay unit, the second relay unit, and the outcoupling unit are located on at least one bottom surface of the waveguide substrate.

27. The optical device of claim 1, further comprising a layer of holographic material, and wherein the number of waveguide substrates is two, the layer of holographic material being sandwiched between the two waveguide substrates;

28. An electronic apparatus, characterized in that it comprises a micro-display device and an optical apparatus of any one of claims 1 to 27, and the micro-display device is used to project light to a coupling-in unit of the optical apparatus.

29. The electronic device of claim 28, wherein the electronic device is augmented reality glasses.

30. The electronic device of claim 28, wherein the electronic device is an in-vehicle heads-up display.