Optical equipment and electronic equipment

Abstract

This application relates to the field of augmented reality technology and discloses an optical device and an electronic device. The optical device includes at least one waveguide substrate, and coupling-in unit, a first relay unit, a second relay unit, and a coupling-out unit disposed on the waveguide substrate. The first and second relay units define a relay region, enabling light coupled into the waveguide substrate to have a portion of its path direction restricted to total internal reflection between the first and second relay units after entering the waveguide substrate, while another portion of the light can be redirected at the second relay unit to undergo total internal reflection towards the coupling-out unit. When the light rays undergoing total internal reflection towards the coupling-out unit encounter the coupling-out unit, a portion of the light continues its original path of total internal reflection, while the other portion is coupled out of the eye. Thus, it is possible to achieve two-dimensional exit pupil expansion without increasing the area of ​​the relay grating when increasing the field of view angle at the image edge.

Description

Technical Field

[0001] This application relates to the field of augmented reality technology, and in particular to an optical device and an electronic device. Background Technology

[0002] Augmented Reality (AR) technology, which cleverly integrates virtual information with the real world, has been widely applied in various fields such as military, commerce, industry, fire protection, and entertainment. AR technology primarily uses microdisplays as image sources, projecting images into the human eye through optical elements. These optical elements typically employ waveguide structures.

[0003] For example, AR technology can be applied to head-mounted AR glasses, which include a microdisplay and lenses. The lenses generally use an optical waveguide structure. The virtual images emitted by the microdisplay can be projected into the human eye through the lenses made of the optical waveguide structure. The optical waveguide structure is transparent, which allows the observer to simultaneously observe the real images of the surroundings and the virtual images transmitted by the microdisplay.

[0004] Currently, the waveguide structure used in AR glasses generally expands the pupil in one direction, meaning that a larger image range can be seen in one direction. This makes it difficult to adapt to people with different interpupillary distances, different face shapes, and different nose bridge heights. Summary of the Invention

[0005] This application provides an optical device and an electronic device. The optical device provided in this application can achieve exit pupil expansion in a two-dimensional direction, enabling users to see a larger image range in a two-dimensional direction, and is suitable for people with different interpupillary distances, different face shapes, and different nose bridge heights.

[0006] In addition, the optical device provided in this application embodiment enables the expansion of the exit pupil in the x-direction without increasing the area of ​​the traditional relay grating when increasing the angle between the edge and field of view of the image. It can effectively reduce the area of ​​the waveguide substrate under a large field of view, thereby reducing the area of ​​the entire optical device; and can meet the requirements of existing electronic devices for a large field of view.

[0007] In a first aspect, embodiments of this application provide 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;

[0008] The coupling unit is configured to couple light into the waveguide substrate;

[0009] The first relay unit and the second relay unit define a relay area that extends in a first direction. The first relay unit and the second relay unit are arranged in a second direction. The relay area has a first side and a second side opposite to each other in the second direction. The angle between the extension direction of the first side and the extension direction of the second side is less than a first angle.

[0010] The coupling unit is configured to couple light from the waveguide substrate out of the waveguide substrate, and the coupling unit and the relay region are arranged in the second direction.

[0011] For example, the first direction mentioned above can be the x-axis direction mentioned in the following embodiments, and the second direction can be the y-axis direction mentioned in the following embodiments.

[0012] It is understood that the optical device provided in this application includes a first relay unit and a second relay unit, and the first relay unit and the second relay unit define a relay region, which enables a portion of the light coupled into the coupling unit to be restricted to propagate by total internal reflection between the first relay unit and the second relay unit after entering the waveguide substrate, while the other portion of the light can be changed in direction at the second relay unit near the coupling unit and propagate by total internal reflection towards the coupling unit, thereby achieving x-axis exit pupil expansion.

[0013] For example, the optical device can be a diffractive waveguide (described later), the coupling unit can be a coupling grating (described later), the coupling unit can be a coupling grating (described later), the first relay unit can be a first relay grating (described later), the second relay unit can be a second relay grating (described later), and the relay region can be defined by the closest grating lines of the first and second relay gratings (described later), which is the area between the first and second relay gratings, excluding the first and second relay gratings. Alternatively, the relay region can be defined by the grating lines of the first and second relay gratings that are furthest apart, including not only the area between the first and second relay gratings but also the first and second relay gratings.

[0014] Furthermore, in this embodiment, the exit pupil expansion in the x-direction is achieved by total internal reflection propagation of light between the first and second relay units, instead of achieving x-direction exit pupil expansion by linear propagation within the relay units. This allows for x-direction exit pupil expansion without increasing the area of ​​the traditional relay grating when increasing the angle between the image edge fields of view. It can effectively reduce the area of ​​the waveguide substrate under a large field of view, thereby reducing the area of ​​the entire optical device. It can also meet the requirements of existing electronic devices for a large field of view.

[0015] Furthermore, when light rays traveling towards the coupling unit undergo total internal reflection, some rays continue their total internal reflection along the original direction upon encountering the coupling unit, while the other portion is coupled out of the eye. This process is repeated to achieve exit pupil expansion in the y-direction. Therefore, the optical device provided in this application embodiment can also achieve exit pupil expansion in a two-dimensional direction. Using this optical device allows users to see a larger image range in a two-dimensional direction and is suitable for people with different interpupillary distances, different face shapes, and different nose bridge heights.

[0016] In one possible implementation of the first aspect described above, the first angle is between 0° and 5°.

[0017] In one possible implementation of the first aspect described above, the first side and the second side are parallel in their extension directions. In this embodiment, the extension directions of the first side and the second side can be parallel, or they can have a small error. For example, the angle between the extension directions of the first side and the second side can be between 0° and 5°. For example, the first side can be the grating line of the first relay grating that is closest to the second relay grating (described later), and the second side can be the grating line of the second relay grating that is closest to the first relay grating (described later).

[0018] In one possible implementation of the first aspect above, the second relay unit is configured such that light rays propagating by total internal reflection in the waveguide substrate, after being incident on the second relay unit, at least a portion of the outgoing light rays propagate by total internal reflection toward the first relay unit, and at least a portion of the outgoing light rays propagate by total internal reflection toward the coupling unit.

[0019] The first relay unit is configured such that light rays propagating by total internal reflection in the waveguide substrate, after being incident on the first relay unit, propagate by total internal reflection towards the second relay unit.

[0020] For example, taking a first relay unit as a first relay grating and a second relay unit as a second relay grating, the second relay unit can be configured such that light rays propagating through total internal reflection in the waveguide substrate, after incident on the second relay unit, at least partially exit as... Figure 18 As indicated by arrow B2 in (a), the light propagates towards the first relay unit via total internal reflection, with at least a portion of the emitted light rays as shown in the image. Figure 18 As indicated by arrow B3 in (a), it propagates via total internal reflection toward the coupling unit;

[0021] The first relay unit is configured such that light rays propagating through total internal reflection in the waveguide substrate, after incident on the first relay unit, exit as follows: Figure 18 As indicated by arrow B4, propagation is carried out via total internal reflection towards the second relay unit.

[0022] In one possible implementation of the first aspect described above, the first relay unit and the second relay unit are gratings; and the first side of the relay region is the grating line of the first relay unit closest to the second relay unit, and the second side is the grating line of the second relay unit closest to the first relay unit. That is, the relay region is defined by the grating lines closest to the first and second relay units, and is the region between the first and second relay units, excluding both the first and second relay units. For example, it can be... (The text abruptly ends here.) Figure 17 The blank areas of the first and second relay gratings shown in the diagram.

[0023] In one possible implementation of the first aspect described above, the first relay unit and the second relay unit are gratings, and the first side of the relay region is the grating line of the first relay unit furthest from the second relay unit, and the second side is the grating line of the second relay unit furthest from the first relay unit. That is, the relay region is defined by the grating line furthest from the first relay unit and the second relay unit, and includes not only the area between the first and second relay units, but also the area between the first and second relay units. For example, as described below... Figure 17 The region defined by the grating line of the first relay grating furthest from the second relay grating and the grating line of the second relay grating furthest from the first relay grating.

[0024] In one possible implementation of the first aspect described above, both the first relay unit and the second relay unit include multiple grating lines, and the grating lines of the first relay unit and the second relay unit are at the first angle to each other.

[0025] In one possible implementation of the first aspect described above, both the first relay unit and the second relay unit include multiple grating lines, and the grating lines of the first relay unit and the second relay unit are parallel to each other.

[0026] That is, both the first relay unit and the second relay unit can be gratings. The first relay unit can include multiple parallel grating lines, and the second relay unit can also include multiple parallel grating lines. The grating lines of the first relay unit can have an angle of 0° to 5° with the grating lines of the second relay unit. In some embodiments, the grating lines of the first relay unit and the grating lines of the second relay unit can be set to be parallel to each other. It is understood that, as mentioned above, the parallelism here can have a certain error, that is, it is not completely parallel, but at a certain small angle, for example, the angle between the two is between 0° and 5°.

[0027] Specifically, for example, if the first relay unit and the second relay unit are surface relief gratings, then the grating lines can refer to the engravings of the surface relief grating, and parallel grating lines can refer to the parallel directions of the engravings of the surface relief grating; if the first relay unit and the second relay unit are volume holographic gratings, then the grating lines can refer to the stripes of the volume holographic grating, and parallel grating lines can refer to the parallel directions of the stripes of the volume holographic grating.

[0028] Furthermore, it is feasible that the grating line direction is perpendicular to the grating vector direction of the grating. Therefore, the parallelism of the grating lines of the first relay unit and the second relay unit can also refer to the grating vector direction of the surface relief, which is consistent with or parallel to the direction of the grating vector.

[0029] In one possible implementation of the first aspect described above, the first relay unit and the second relay unit are parallel bar gratings.

[0030] In one possible implementation of the first aspect described above, the grating period of the first relay unit is the same as that of the second relay unit.

[0031] It is understandable that setting the period and grating vector direction of the first relay unit to be consistent with the period and grating vector direction of the second relay unit can make the k-space region of the light coupled out by the coupling unit completely coincide with the k-space region of the incident light emitted by the micro-display device, thereby effectively preventing the generation of image distortion.

[0032] In one possible implementation of the first aspect described above, the diffraction efficiency of the first relay unit is uniformly distributed, and the diffraction efficiency of the second relay unit gradually decreases from the side away from the coupling unit to the side closer to the coupling unit.

[0033] It is understood that setting the diffraction efficiency of the second relay unit to gradually decrease from the side away from the coupling unit to the side closer to the coupling unit can make light propagating by total internal reflection in the waveguide substrate propagate by total internal reflection towards the first relay unit after incident on the second relay unit, and at least some of the light propagating by total internal reflection towards the coupling unit.

[0034] Meanwhile, by setting the diffraction efficiency of the first relay unit to be uniformly distributed, the light rays propagating by total internal reflection in the waveguide substrate can change the direction of total internal reflection propagation after being incident on the first relay unit, and propagate by total internal reflection towards the second relay unit.

[0035] In one possible implementation of the first aspect described above, the first relay unit is a surface-embossed grating, and the grating height of the first relay unit is evenly distributed.

[0036] It is understandable that setting the grating height of the first relay unit to be evenly distributed can make the diffraction efficiency of the first relay unit evenly distributed.

[0037] In one possible implementation of the first aspect described above, the second relay unit is a surface-embossed grating, and the grating height of the second relay unit gradually decreases from the side away from the coupling unit to the side closer to the coupling unit.

[0038] It is understandable that setting the grating height of the second relay unit to gradually decrease from the side away from the coupling unit to the side closer to the coupling unit can make the diffraction efficiency of the second relay unit gradually decrease from the side away from the coupling unit to the side closer to the coupling unit.

[0039] In one possible implementation of the first aspect described above, the first relay unit is a volume holographic grating, and the refractive index modulation of the first relay unit is evenly distributed.

[0040] It is understandable that setting the refractive index modulation of the first relay unit to be evenly distributed can make the diffraction efficiency of the first relay unit evenly distributed.

[0041] In one possible implementation of the first aspect described above, the second relay unit is a volume holographic grating, and the grating refractive index modulation of the second relay unit gradually decreases from the side away from the coupling unit to the side closer to the coupling unit.

[0042] It is understandable that setting the grating refractive index modulation of the second relay unit to gradually decrease from the side away from the coupling unit to the side closer to the coupling unit can make the diffraction efficiency of the second relay unit gradually decrease from the side away from the coupling unit to the side closer to the coupling unit.

[0043] In one possible implementation of the first aspect described above, at least one third relay unit is further disposed on the waveguide substrate, the third relay unit being located between the first relay unit and the second relay unit, and the third relay unit dividing the relay region into a plurality of relay sub-regions, wherein the angle between the two long sides of the relay sub-regions in the extending direction is less than the first angle.

[0044] In this embodiment, there can be multiple relay units, and the third relay unit can divide the relay area defined by the first and second relay units into multiple relay sub-regions. For example, by adding a third relay unit between the first and second relay units, the relay area is divided into two relay sub-regions. For example, in the following text, the first relay unit can be the first relay grating mentioned later, the second relay unit can be the second relay grating mentioned later, and the third relay unit can be the third relay grating mentioned later, adding a third relay grating to divide the relay area into two relay sub-regions.

[0045] In one possible implementation of the first aspect described above, the third relay unit is configured such that after light propagating through total internal reflection in the waveguide substrate is incident on the third relay unit, at least a portion of the outgoing light propagates through total internal reflection toward the first relay unit, and at least a portion of the outgoing light propagates through total internal reflection toward the second relay unit.

[0046] For example, as described below, if the first relay unit can be a first relay grating, the second relay unit can be a second relay grating, and the third relay unit can be a third relay grating, then the third relay unit can be configured such that light rays propagating through total internal reflection in the waveguide substrate, after being incident on the third relay unit, at least partially exit as... Figure 26 As indicated by arrow B4, the light propagates towards the first relay unit via total internal reflection, with at least a portion of the emitted light rays as follows: Figure 26 As indicated by arrow B5, propagation is carried out via total internal reflection towards the second relay unit.

[0047] In one possible implementation of the first aspect described above, the first relay unit, the second relay unit, and the third relay unit are gratings.

[0048] For example, the first relay unit can be the first relay grating mentioned later, the second relay unit can be the second relay grating mentioned later, and the third relay unit can be the third relay grating mentioned later.

[0049] In one possible implementation of the first aspect described above, the first relay unit, the second relay unit, and the third relay unit each include multiple parallel gate lines.

[0050] In one possible implementation of the first aspect described above, the third relay unit is a strip grating.

[0051] In one possible implementation of the first aspect described above, the diffraction efficiency of the third relay unit gradually decreases from the side closer to the first relay unit to the side closer to the second relay unit.

[0052] It is understandable that setting the diffraction efficiency of the third relay unit to gradually decrease from the side closer to the first relay unit to the side closer to the second relay unit can ensure that after the light propagating by total internal reflection in the waveguide substrate is incident on the third relay unit, at least a portion of the outgoing light propagates by total internal reflection towards the first relay unit, and at least a portion of the outgoing light propagates by total internal reflection towards the second relay unit.

[0053] In one possible implementation of the first aspect described above, the third relay unit is a surface-embossed grating, and the grating height of the third relay unit gradually decreases from the side closer to the first relay unit to the side closer to the second relay unit.

[0054] It is understandable that setting the grating height of the third relay unit to gradually decrease from the side closer to the first relay unit to the side closer to the second relay unit can make the diffraction efficiency of the third relay unit gradually decrease from the side closer to the first relay unit to the side closer to the second relay unit.

[0055] In one possible implementation of the first aspect described above, the third relay unit is a volume holographic grating, and the grating refractive index modulation of the third relay unit gradually decreases from the side closer to the first relay unit to the side closer to the second relay unit.

[0056] It is understandable that setting the grating refractive index modulation of the third relay unit to gradually decrease from the side closer to the first relay unit to the side closer to the second relay unit can make the diffraction efficiency of the third relay unit gradually decrease from the side closer to the first relay unit to the side closer to the second relay unit.

[0057] In one possible implementation of the first aspect described above, the coupling unit is located in the relay region.

[0058] It is understood that the coupling unit can be located between the first relay unit and the second relay unit, or it can be located at other positions that allow light rays to be guided by the coupling unit to propagate in the direction of the second relay unit after hitting the coupling unit.

[0059] In one possible implementation of the first aspect described above, the coupling-in unit and the coupling-out unit are gratings, and the period and grating vector direction of the coupling-in unit and the coupling-out unit are the same.

[0060] It is understood that the coupling unit can be the coupling grating described later, and the coupling out unit can be the coupling out grating described later. In this embodiment, the coupling unit and the coupling out unit are set to have the same period and grating vector direction, which can make the k-space region of the light emitted by the coupling out unit completely coincide with the k-space region of the incident light emitted by the micro-display device, thereby effectively preventing the generation of image distortion.

[0061] In one possible implementation of the first aspect described above, the coupling unit is a surface relief grating or a volume holographic grating; and

[0062] The coupling unit is a surface relief grating or a volume holographic grating.

[0063] In one possible implementation of the first aspect described above, 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.

[0064] It is understood that the coupling unit, the first relay unit, the second relay unit, and the coupling unit can be located on the same bottom surface of the waveguide substrate, or on two opposite bottom surfaces. For example, the coupling unit, the first relay unit, and the second relay unit are located on the upper bottom surface, and the coupling unit is located on the lower bottom surface.

[0065] In one possible implementation of the first aspect described above, a holographic material layer is further included, and the number of waveguide substrates is two, with the holographic material layer sandwiched between the two waveguide substrates.

[0066] The coupling unit, the first relay unit, the second relay unit, and the coupling unit are located on at least one bottom surface of the holographic material layer.

[0067] It can be understood that the coupling unit, the first relay unit, the second relay unit, and the coupling unit can be a coupling grating, a first relay grating, a second relay grating, and a coupling grating formed by exposing the holographic material layer.

[0068] Secondly, embodiments of this application provide an electronic device, including a micro-display device and the aforementioned optical device, wherein the micro-display device is used to project light onto the coupling unit of the optical device.

[0069] It is understood that the optical device can be the diffractive waveguide mentioned in the embodiments below.

[0070] In one possible implementation of the second aspect described above, the electronic device is augmented reality glasses.

[0071] It is understood that some or all of the lenses of augmented reality glasses can use the aforementioned optical devices, and the miniature reality device can be set on the lens frame of the augmented reality glasses.

[0072] In one possible implementation of the second aspect above, the electronic device is a vehicle-mounted head-up display. Attached Figure Description

[0073] Figure 1 According to some embodiments of this application, a schematic diagram of a transmission diffraction grating is shown.

[0074] Figure 2 According to some embodiments of this application, a schematic diagram of beam splitting of a diffraction grating is shown;

[0075] Figure 3 (a)-(c) Schematic diagrams of diffraction gratings of different shapes are shown according to some embodiments of this application;

[0076] Figure 4 According to some embodiments of this application, a schematic diagram of the principle of total internal reflection is shown;

[0077] Figure 5 According to some embodiments of this application, a schematic diagram of a planar optical waveguide structure is shown;

[0078] Figure 6 According to some embodiments of this application, it is shown that Figure 5 Optical path diagram of a mid-plane optical waveguide;

[0079] Figure 7 According to some embodiments of this application, a schematic diagram of a diffractive waveguide structure for AR glasses is shown;

[0080] Figure 8 (a) According to some embodiments of this application, a schematic diagram of the guidance of light propagation in a diffractive waveguide 100 is shown;

[0081] Figure 8 (b) and (c) illustrate specific optical path diagrams of light propagation in a waveguide substrate according to some embodiments of this application;

[0082] Figure 9 According to some embodiments of this application, a schematic diagram of the structure of AR glasses using diffractive waveguides as lenses is shown;

[0083] Figure 10 According to some embodiments of this application, a schematic diagram of the principle of a virtual image being coupled into the human eye through the left or right lens of AR glasses is shown.

[0084] Figure 11 According to some embodiments of this application, a schematic diagram of a diffractive optical waveguide structure is shown.

[0085] Figure 12(a) and (b) respectively illustrate schematic diagrams of light guiding in a diffractive waveguide at different field of view angles according to some embodiments of this application;

[0086] Figure 13 (a) and (b) show diffraction patterns of light at the relay grating and the coupling grating, respectively, according to some embodiments of this application;

[0087] Figure 14 According to some embodiments of this application, a schematic diagram of the structure of AR glasses using diffractive waveguides as lenses is shown;

[0088] Figure 15 A schematic diagram of a field of view is shown according to some embodiments of this application;

[0089] Figure 16 (a) and (b) show images with smaller edge field of view angle A1 and larger edge field of view angle A2, respectively, according to some embodiments of this application. Figure 11 A schematic diagram showing the guiding direction of propagation in the diffractive waveguide structure shown in the figure;

[0090] Figure 17 According to some embodiments of this application, a schematic diagram of a diffractive optical waveguide including two relay gratings is shown.

[0091] Figure 18 (a) and (b) illustrate schematic diagrams of different angles of light propagation in a waveguide substrate according to some embodiments of the present application;

[0092] Figure 19 (a) According to some embodiments of this application, a diffraction pattern of light at a first relay grating and a second relay grating is shown;

[0093] Figure 19 (b) According to some embodiments of this application, a diffraction pattern of light at the coupling grating is shown;

[0094] Figure 20 (a) and (b) show images with smaller edge field of view angle A1 and larger edge field of view angle A2, respectively, according to some embodiments of this application. Figure 17 The diagram shows a comparison of the guiding direction of light propagating in a diffractive waveguide.

[0095] Figure 21 A schematic diagram of a second relay grating is shown according to some embodiments of this application;

[0096] Figure 22 According to some embodiments of this application, a schematic diagram of the position of a coupling grating is shown;

[0097] Figure 23 According to some embodiments of this application, a schematic diagram of the position of a coupling grating is shown;

[0098] Figure 24 According to some embodiments of this application, a method of using Figure 17 The diagram shows the structure of AR glasses with a diffractive waveguide as a lens.

[0099] Figure 25 According to some embodiments of this application, a schematic diagram of the structure of a diffractive optical waveguide is shown;

[0100] Figure 26 According to some embodiments of this application, a schematic diagram of the guidance of light in a diffractive waveguide with three relay gratings is shown;

[0101] Figure 27 A schematic diagram of a diffractive optical waveguide is shown according to some embodiments of this application;

[0102] Figure 28 A schematic diagram of a diffractive optical waveguide is shown according to some embodiments of this application;

[0103] Figure 29 According to some embodiments of this application, it is shown that Figure 17 The diagram shows the k-space path of the diffractive waveguide.

[0104] Explanation of reference numerals in the attached figures:

[0105] 100-Diffractive waveguide; 101-Coupled grating; 102-Relay grating; 1021-First relay grating; 1022-Second relay grating; 1023-Third relay grating; 103-Coupled grating; 104-Waveguide substrate; 105-Micro display device; 106-Light source; 107-Waveguide top layer; 108-Holographic material layer;

[0106] 200 - AR glasses; 201 - Left temple; 202 - Right temple; 203 - Lens frame; 203, 204 - Left lens; 205 - Right lens;

[0107] 300 - Diffraction grating; 301 - Slit; 302 - Marking; 303 - Glass substrate; 304 - Dielectric film. Detailed Implementation

[0108] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification.

[0109] To facilitate understanding of the technical solution of this application, some technical terms, optical components and related principles involved in this application will be introduced below.

[0110] (I) Diffraction of light: When light encounters an opaque or transparent obstacle or a small hole (narrow slit) in its propagation path, it deviates from the straight-line propagation and goes around the obstacle. This phenomenon is called diffraction of light.

[0111] (ii) A grating: An optical device consisting of a large number of parallel slits of equal width and spacing, also known as a diffraction grating, which can change the propagation direction of light rays incident on it through diffraction. Among them, diffraction gratings can include gratings that utilize transmitted light diffraction, called transmission diffraction gratings; and gratings that utilize reflected light between two slits for diffraction, called reflection diffraction gratings.

[0112] For example, Figure 1 A schematic diagram of a transmission diffraction grating 300 is shown. Figure 1 As shown, the diffraction grating 300 can be formed by etching multiple slits 301 and grooves 302 on the glass, where slits 301 are the light-transmitting parts and grooves 302 are the opaque parts. The optical properties of the diffraction grating 300 are related to its period, which is the sum of the widths of a single slit 301 and a single groove 302. For example, if the width of the slit 301 is a and the width of the groove 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 groove 302, i.e., d = a + b. The smaller the grating period, the more slits 301 there are per unit length, and the narrower the width of a single slit 301.

[0113] It is feasible that the diffraction grating 300 can also be formed by holographic technology by exposing the material inside the holographic grating, that is, by holographic photography, the interference fringes generated by the laser are exposed on a dry plate, and then formed by development and fixing.

[0114] The diffraction grating 300 has spectral splitting characteristics. For example, the diffraction waveguide used in the AR glasses of this application utilizes this spectral splitting characteristic to guide the direction of light propagation, which will be described in detail below.

[0115] Specifically, such as Figure 2 As shown, when the incident ray i is incident on the diffraction grating 300 with a grating height of h and a period of d, it will be divided into several diffraction orders by the diffraction grating 300. Each diffraction order continues to propagate in different directions, including reflection diffraction, such as 0th order reflection diffraction R0, first order reflection diffraction R1, negative first order reflection diffraction R-1, etc., and transmission diffraction, such as 0th order transmission diffraction T0, first order transmission diffraction T1, negative first order transmission diffraction T-1, etc.

[0116] In order for the incident ray i to undergo m-th order diffraction through the diffraction grating 300, the parameters of the diffraction grating must satisfy the following formula (1):

[0117]

[0118] Where d is the period of the diffraction grating, m is the diffraction order (where m is an integer, such as 0, 1, -1, 2, -2, etc.), n is the refractive index of glass 3, and θ m and θ and θ represent the polar angle and azimuth angle of the diffracted light corresponding to the m-th order, respectively; λ is the wavelength of the incident ray i, and θ and θ are the polar angle and azimuth angle of the diffracted light. θ represents the polar angle and azimuth angle of the incident ray i, respectively; Gin The angle of the 302mm notch in the diffraction grating.

[0119] Equation (1) above shows that when the wavelength λ of the incident ray i, the polar angle θ of the incident ray i, and the azimuth angle are... At a certain time, by adjusting the angle θ of the 302 notch of the diffraction grating... Gin The period d of the diffraction grating can be used to determine the diffraction order of the diffracted light, and the polar angle θ. m and azimuth Adjustments will be made.

[0120] For example, in the diffractive waveguide used in AR glasses, the angle θ of the notches 302 of each diffraction grating on the surface of the waveguide substrate can be adjusted. Gin The period d of the diffraction grating, the diffraction order m of the diffracted light, and the polar angle θ m and azimuth Adjustments are made so that light rays propagating by total internal reflection in the waveguide substrate of the diffractive waveguide can propagate in the desired direction after being incident on the diffraction grating on the surface of the waveguide substrate.

[0121] The shape of a diffraction grating can be designed in various ways to meet specific needs, for example, Figure 3 (a)-(c) show schematic diagrams of diffraction gratings of different shapes, such as Figure 3 As shown in (a), the diffraction grating can be a uniform vertical grating, such as... Figure 3 As shown in (b), the diffraction grating can also be tilted, such as... Figure 3 As shown in (c), the diffraction grating can also be a grating with uneven height.

[0122] (III) Total Internal Reflection

[0123] Total internal reflection, also known as total internal reflection, refers to the phenomenon where, when light travels from a medium with a higher refractive index to a medium with a lower refractive index, if the angle of incidence is greater than a certain critical angle C (where the light ray is away from the normal), the refracted ray will disappear, and all incident rays will be reflected and will not enter the medium with the lower refractive index.

[0124] For example, such as Figure 4 As shown, when incident ray i travels from medium P1 with refractive index n1 to medium P2 with refractive index n2, if n1 is greater than n2 and the incident angle C1 is greater than the critical angle C, then incident ray i will be reflected and will not enter medium P2 with low refractive index n2.

[0125] The critical angle C must satisfy the condition, i.e., the formula for total internal reflection, which is:

[0126] sinC=n2 / n1 (2)

[0127] like Figure 4 As shown, when the medium P2 with refractive index n2 is air, since n2 = 1, the critical angle C must satisfy the condition: sinC = 1 / n1.

[0128] (iv) Optical waveguide:

[0129] An optical waveguide is an optical element that uses the principle of total internal reflection to guide light waves to propagate within itself. Common optical waveguides are guiding structures for transmitting optical frequency electromagnetic waves, made of optically transparent media (such as quartz glass with a high refractive index). Optical waveguides can be specifically divided into planar structures and strip structures.

[0130] For example, Figure 5 A structural diagram of a planar optical waveguide 10 is shown, while Figure 6 The optical path diagram of the planar optical waveguide 10 is shown.

[0131] like Figure 5 As shown, the planar optical waveguide 10 may include a glass substrate 303 and a dielectric film 304 located above the glass substrate 303. It is assumed that the refractive index of the dielectric film 304 is n1, the refractive index of the glass substrate 303 is n2, the critical angle for total internal reflection at the interface between the dielectric film 304 and the glass substrate 303 is θ1, and the critical angle for total internal reflection at the interface between the dielectric film 304 and air is θ2.

[0132] An incident ray i is refracted from air and enters the interface between the dielectric film 304 and the glass substrate 303. In order for the ray that hits the interface between the dielectric film 304 and the glass substrate 303 to undergo total internal reflection and to propagate between the upper and lower surfaces of the dielectric film with a refractive index of n1, the refractive index n1 of the dielectric film 304, the refractive index n2 of the glass substrate 303, and the refractive index n3 of air must satisfy the following relationship: n1 > n2 > n3.

[0133] The following relationship must be satisfied for the incident angle θ of incident ray i, the critical angle θ1 for total internal reflection at the interface between dielectric film 304 and glass substrate 303, and the critical angle θ2 for total internal reflection at the interface between dielectric film 304 and air: θ > θ1 > θ2.

[0134] The calculation methods for θ1 and θ2 are as follows:

[0135] θ1 = arcsin(n2 / n1);

[0136] θ2 = arcsin(n3 / n1).

[0137] Specifically, the optical path diagram of light propagating in an optical waveguide is as follows: Figure 6 As shown, incident ray i enters the interface between the dielectric film 304 and the glass substrate 303 from the air through refraction. Total internal reflection occurs at the interface between the dielectric film 304 and the glass substrate 303. When the ray is totally internally reflected to the interface between the dielectric film 304 and the air, it will continue to be totally internally reflected to the interface between the dielectric film 304 and the glass substrate 303. In this way, the ray propagates between the upper and lower surfaces of the dielectric film 304 through total internal reflection.

[0138] As can be seen, an optical waveguide can essentially be a dielectric layer with a high refractive index, enabling light to propagate through total internal reflection. Currently, the lenses of commonly used AR glasses 200 are diffractive optical waveguides 100. That is, in order to guide the light emitted from the microdisplay in the AR glasses 200 to a designated position on the lens and then guide it to the eye, a diffraction grating is typically placed on the surface of the optical waveguide. For example, Figure 7 A schematic diagram of a diffractive waveguide 100 for AR glasses 200 is shown.

[0139] like Figure 7 As shown, the diffractive waveguide 100 includes a waveguide substrate 104, a coupling grating 101 for coupling light into the waveguide substrate, and a coupling grating 103 for coupling light out of the waveguide substrate. The waveguide substrate 104 can be made of the aforementioned... Figure 6 The planar structure optical waveguide shown can be made of high refractive index glass, for example, with a refractive index range of 1.5-2.2.

[0140] Figure 8 (a) shows a schematic diagram of the guidance of light propagation in the diffractive waveguide 100.

[0141] It is understood that in the various embodiments of this application, the light guiding diagram differs from the light path diagram; it is not the actual propagation path of the light, but rather a schematic representation of the entire path direction of the light during total internal reflection. For example, for Figure 6 The total internal reflection light path diagram shown is represented by the light rays with arrows in the dielectric film 304, and the entire direction of the total internal reflection light ray can be considered as traveling along the negative half-axis of the x-axis.

[0142] The following is a reference. Figure 8 (a) Describe the ray trajectory direction of the diffractive waveguide 100. For example... Figure 8 As shown in (a), the light ray i1 emitted by the light source 106 is incident on the coupling grating 101, and is coupled into the waveguide substrate 104 through the diffraction of the coupling grating 101, and propagates between the upper and lower surfaces of the waveguide substrate 104 by total internal reflection. Figure 8 Arrow B1 in (a) shows the entire path of the light ray undergoing total internal reflection in the waveguide substrate 104, i.e., traveling along the negative x-axis. After encountering the coupling grating 103, a portion of the totally internalized light ray traveling along the negative x-axis in the waveguide substrate 104 is coupled out of the waveguide substrate 104, and the direction of travel of the coupled light ray is as follows... Figure 8 As shown by arrow B2, this is the direction of the positive z-axis.

[0143] The specific optical path diagram of light propagating in waveguide substrate 104 is as follows: Figure 8 As shown in (b), the light ray i1 emitted by the light source 106, after being incident on the coupling grating 101, changes its original propagation direction through diffraction by the coupling grating 101 and is directed toward the bottom of the waveguide substrate 104. Based on the aforementioned principle of total internal reflection, since the incident angle of the light ray directed toward the bottom of the waveguide substrate 104 is greater than the critical angle for total internal reflection at the interface between the waveguide substrate 104 and the air, and the refractive index of the waveguide substrate 104 is greater than the refractive index of air, the light ray i1 coupled into the waveguide substrate 104 through the coupling grating 101 can propagate through total internal reflection between the upper and lower surfaces of the waveguide substrate 104.

[0144] During the total internal reflection propagation of light ray i1 in waveguide substrate 104, such as Figure 8 As shown in (c), when light ray i1 encounters position D1 of the coupling grating 103 on the surface of waveguide substrate 104 during total internal reflection, a portion of light ray i2 is released through grating diffraction, i.e., it is coupled out of waveguide substrate 104, while the remaining portion of light ray i3 continues to propagate through total internal reflection in waveguide substrate 104. During subsequent propagation, when the light ray i3, propagating through total internal reflection, encounters position D2 on the coupling grating 103 on the surface of waveguide substrate 104, the above phenomenon repeats, i.e., a portion of light ray i4 continues to be coupled out of waveguide substrate 104 through grating diffraction, while the remaining portion of light ray i5 continues to propagate through total internal reflection in waveguide substrate 104, until all the light rays propagating through total internal reflection in waveguide substrate 104 are coupled out of waveguide substrate 104.

[0145] Based on the above description, it can be seen that for Figures 6 to 8 The diffractive waveguide 100 shown in the diagram, during the total internal reflection propagation of light within the waveguide substrate 104, each time the same beam of light encounters a certain position on the coupling grating 103 on the surface of the waveguide substrate 104, a portion of the light is released from the waveguide substrate 104 through diffraction, while the other portion continues to propagate through total internal reflection within the waveguide, repeating the above phenomenon at different positions on the coupling grating 103. This effectively replicates the incident light from the light source 106 along the positive x-axis, thus amplifying the light coupled out through the coupling grating 103 along the negative x-axis. This phenomenon can be called exit pupil expansion. Figures 6 to 8 The diffractive waveguide 100 shown can be used as a lens for AR glasses to expand the exit pupil of the virtual image emitted by the microdisplay of the AR glasses in the negative x-axis direction, thus realizing virtual one-dimensional pupil expansion, which will be described in detail below.

[0146] In traditional optical imaging systems, an image typically has only one "exit," called the exit pupil. For example, suppose a beam of light with a diameter of 4 millimeters enters the waveguide's "entry pupil." Since the waveguide only transmits the light and does not magnify or reduce the image, the "exit pupil" also produces a 4-millimeter beam. In this case, the range of image movement visible to the center of the human pupil is only 4 millimeters. By placing a diffraction grating on the surface, multiple copies of the exit pupil can be made horizontally, with each exit pupil outputting the same image. This increases the range of image movement visible to the center of the human pupil, allowing the image to be seen even when the eye moves significantly; this is called exit pupil expansion.

[0147] (v) AR glasses using diffractive waveguides

[0148] Figure 9 A schematic diagram of an AR glasses 200 using a diffractive waveguide 100 as a lens is shown.

[0149] like Figure 9 As shown, the AR glasses 200 may include a frame portion and a lens portion. The frame portion may include a left temple 201, a right temple 202, and a lens frame 203. The lens portion may include a left lens 204 and a right lens 205. The left lens 204 and right lens 205 may employ a diffractive waveguide structure. Specifically, both the left lens 204 and right lens 205 may be wholly or partially made from the waveguide substrate of the diffractive waveguide 100, for example... Figure 9 The text shows the use of... Figure 8The diffractive waveguide 100 shown is a schematic diagram of a lens. In addition, the AR glasses 200 also includes a micro-display device 105 for projecting virtual images. The virtual images are projected into the left lens 204 and right lens 205 made of the diffractive waveguide 100 through the micro-display device 105, and then the virtual images are introduced into the human eye through the left lens 204 and right lens 205.

[0150] In some embodiments, the microdisplay device 105 may be disposed in the middle of the lens frame for projecting light onto the coupling grating 101 in the left lens 204 and the right lens 205. Furthermore, in other embodiments, two microdisplay devices may be provided, for example, respectively disposed on the left temple 201 or the right temple 202, or disposed on the extended area of ​​the left temple 201 or the right temple 202 facing the eye.

[0151] In some embodiments, the microdisplay device 105 may include a microdisplay 1051 (e.g., Figure 10 (as shown) and collimating lens 1052 (as shown) Figure 10 (As shown). The microdisplay 1051, used to provide virtual images, can be a self-emissive active device, such as a light-emitting diode panel, or a liquid crystal display screen requiring external illumination, or a digital micromirror array and laser beam scanner based on microelectromechanical systems (MEMS) technology. The collimating lens 1052 can be used to convert the light rays from each virtual image point into parallel beams that are projected into the coupling grating 101.

[0152] Figure 10 A schematic diagram illustrating the principle of virtual images being coupled into the human eye through the left lens 204 or right lens 205 of AR glasses 200 is shown.

[0153] like Figure 10 As shown, the point light emitted by the microdisplay 1051 is converted into a parallel beam of light after passing through the collimating lens 1052 and projected into the coupling grating 101. After the coupling grating 101 couples the beam of light into the waveguide substrate 104, the light propagates through total internal reflection within the waveguide substrate 104. During the total internal reflection propagation, each time the light encounters the output grating 103 on the surface of the waveguide substrate 104, a portion of the light continues to be released through diffraction and enters the eye, while the remaining portion of the light continues to propagate in the waveguide until it hits the output grating 103 on the surface of the waveguide again, thus achieving the expansion of the exit pupil in the x-direction.

[0154] However, as mentioned earlier, for Figure 9 The diffractive waveguide 100 used in the lenses of the AR glasses 200 shown has an exit pupil expansion that can only extend the image in one direction. For example, a virtual image provided by a microdisplay 1051, when exported through the coupling grating 103, is only extended in the horizontal direction (e.g., ...). Figure 9 (x-axis direction) or vertical (e.g.) Figure 9 The image is magnified along the y-axis, resulting in a problem where the exported image is not applicable to people with different interpupillary distances, face shapes, and nose bridge heights.

[0155] To solve the problem of the single direction of exit pupil expansion mentioned above Figure 11 A schematic diagram of a diffractive optical waveguide 100 is shown. Figure 11 In the diffractive waveguide 100 shown, by adding a relay grating between the optical paths of the input grating and the output grating, the exit pupil is expanded in both the horizontal and vertical directions, enabling users to observe a larger field of view of the image, and making it more suitable for people with different interpupillary distances, different face shapes and different nose bridge heights.

[0156] Specifically, Figure 11 The diffractive waveguide 100 shown may include a waveguide substrate 104, a coupling grating 101, a relay grating 102, and an output grating 103. Figure 11 The coupling grating 101, relay grating 102 and coupling grating 103 shown are all located on the upper surface of the waveguide substrate 104 and are all diffraction grating structures.

[0157] It is understood that in other embodiments of this application, the coupling grating 101, the relay grating 102, and the coupling output grating 103 may all be located on the lower surface of the waveguide substrate 104, or the three may be distributed on the upper and lower surfaces of the waveguide substrate 104 respectively, and are not limited to these embodiments. Figure 11 The location settings are shown. Furthermore, although... Figure 11 The coupling grating 101 shown is circular, the relay grating 102 is trapezoidal, and the coupling output grating 103 is rectangular. However, Figure 11 The shapes shown are merely illustrative and can be set to any shape according to actual optical design requirements or the shape requirements of AR lenses.

[0158] In order to achieve pupil expansion in both horizontal and vertical directions, such as Figure 11 As shown, the grating marking direction of the relay grating 102 can be at a set angle to the grating marking direction of the coupling grating 101. This allows light rays coupled from the coupling grating 101 to have their direction changed when they encounter the relay grating 102, propagating towards the coupling grating 103. Specifically, a portion continues to propagate by total internal reflection in the waveguide substrate 104, guided by the negative y-axis, while the remaining portion continues to propagate along its original direction, guided by the positive x-axis. For example, Figure 11 In the diffractive waveguide 100 shown, the grating direction of the relay grating 102 is set at a 45-degree angle to the grating grating direction of the coupling grating 101 to achieve the above-mentioned function. Specifically, Figure 12(a) and (b) show schematic diagrams of light guiding in the diffractive waveguide 100 from different perspectives.

[0159] like Figure 12 As shown in (a), the light ray i1 emitted by the microdisplay device 105, after incident on the coupling grating 101, is coupled into the waveguide substrate 104 by diffraction through the coupling grating 101, and propagates in the waveguide substrate 104 by total internal reflection along the positive x-axis. When the light ray i1 coupled into the coupling grating 101 encounters the relay grating 102, due to the beam-splitting characteristics of the relay grating, the light ray is split into two parts, which propagate by total internal reflection at different diffraction angles. Specifically, one part continues to propagate in the waveguide substrate 104 by total internal reflection along the positive x-axis direction, as shown by arrow B1 in the figure; the other part propagates in the waveguide substrate 104 by total internal reflection along the negative y-axis direction, as shown by arrow B2 in the figure. Among them, the light rays that are totally internally reflected after encountering the relay grating 102 and proceeding in the direction of the negative half-axis of the y-axis are guided into the coupling grating 103, and the waveguide substrate 104 is coupled out by the coupling grating 103. The direction of travel of the coupled light rays is shown by arrow B3 in the figure, that is, the direction of the positive half-axis of the z-axis.

[0160] Specifically, Figure 13 (a) and (b) show the diffraction patterns of light at relay grating 102 and coupling grating 103, respectively.

[0161] It is understood that in the various embodiments of this application, for a two-dimensional light path diagram, light rays incident from the plane are represented by a circle with an "x" symbol inside.

[0162] like Figure 13 As shown in (a), when the light ray i1, after being coupled into the waveguide substrate 104 by the coupling grating 101, is totally internally reflected along the positive x-axis, it is incident on the relay grating 102 at position H1. The light ray is split into two parts, which propagate towards different diffraction angles. Specifically, one part of the light ray i3 continues to be incident on another surface of the waveguide substrate 104 and undergoes totally internal reflection along the positive x-axis, while the other part of the light ray i2 enters the waveguide substrate 104 in a direction perpendicular to the image and propagates towards the coupling grating 103 along the negative y-axis. It can be understood that when the light ray i3 is incident on other positions of the relay grating 102, such as position H2, the above process will be repeated, resulting in light rays i4 and i5 that are totally internally reflected along the positive x-axis and negative y-axis, respectively. Thus, the relay grating 102 causes the light ray i1 to propagate by total internal reflection along the positive x-axis, which extends the light ray along the positive x-axis. That is, for the virtual image emitted by the micro display device 105, it is extended by the exit pupil in the direction of the positive x-axis.

[0163] similar Figure 8 (c), such as Figure 13As shown in (b), when the light ray i2, which propagates along the negative y-axis towards the coupling grating 103 through total internal reflection, reaches position D1 of the coupling grating 103, a portion of the light ray i21 is released through grating diffraction, i.e., it is coupled out of the waveguide substrate 104, while the remaining portion of the light ray i22 continues to propagate through total internal reflection within the waveguide substrate 104. During subsequent propagation, when the light ray i22 is incident on position D2 of the coupling grating 103 on the surface of the waveguide substrate 104, the above phenomenon is repeated. Thus, the light ray i1 is expanded in the negative y-axis direction; that is, for the virtual image emitted by the micro-display device 105, it is expanded by the exit pupil in the negative y-axis direction.

[0164] As can be seen from the above description, Figures 11 to 13 The diffractive waveguide 100 shown can expand the exit pupil in both the positive x-axis and negative y-axis directions. When applied to AR glasses, it enables users to observe a larger field of view of the image and is better suited for people with different interpupillary distances, different face shapes, and different nose bridge heights.

[0165] Figure 14 A schematic diagram of an AR glasses 200 using the aforementioned diffractive waveguide 100 as a lens is shown. Figure 14 As shown, the left lens 201 and right lens 201 of the AR glasses 200 can both adopt Figure 14 The diffractive waveguide 100 is shown. Wherein, Figure 15 Other structural components of the AR glasses 200 Figure 10 Similar to the case in China, I will not repeat it here.

[0166] However, Figures 11 to 13 While the diffractive waveguide 100 shown can achieve exit pupil expansion in both the positive x-axis and negative y-axis directions, to meet the market demand for further increasing the vertical field of view in AR glasses—that is, to further increase the vertical field of view visible to the human eye—the area of ​​the relay grating 102 in the diffractive waveguide 100 needs to be increased. However, since the area of ​​the diffractive waveguide 100 is limited when used as a lens in AR glasses, the area of ​​the relay grating 102 is also limited. Figures 11 to 13 The diffractive waveguide 100 shown is insufficient to meet the requirements of AR glasses to further increase the vertical field of view.

[0167] To describe this problem in more detail, we first introduce the concept of field of view. Specifically, the field of view angle is generally used to measure the size of the range of vision that the human eye can see. For example, ... Figure 15 As shown, taking an image visible to the observer's eye as an example, the field of view is the angle between the image edge and the line connecting the eye, and can include the horizontal and vertical field of view; for example, in Figure 15In this context, AOB is the horizontal field of view and BOC is the vertical field of view. Pupil replication in the y-direction increases the vertical field of view; pupil replication in the x-direction increases the horizontal field of view.

[0168] Specifically, in conjunction with the aforementioned field of view concept, the AR glasses 200 of this application emits virtual images (such as...) from the micro-display device 105 of the AR glasses 200. Figure 16 (a) and (b) the micro-display device 105 shown in the dashed box) generally includes an upper edge field of view S1 and a lower edge field of view S2 (as shown in the dashed box). Figure 16 (as shown in (a) and (b)), where the upper edge field of view S1 can be defined as the ray of light from one of the light points at the upper edge of the virtual image emitted by the micro-display device 105, and the lower edge field of view S2 can be defined as the ray of light from the lower edge of the virtual image corresponding to the light point at the upper edge; for example, the upper edge field of view S1 can be defined as the ray from the midpoint P1 of the upper edge of the virtual image, and the lower edge field of view S2 can be defined as the ray from 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 called the edge field of view angle. The edge field of view angle of the virtual image can affect the vertical field of view range that the human eye can see, that is, the size of the vertical field of view angle is consistent with the edge field of view angle of the image, specifically: the vertical field of view angle increases as the edge field of view angle increases. Therefore, if the vertical field of view range that the human eye can see, that is, the vertical field of view angle, needs to be increased, the edge field of view angle of the image needs to be increased. If using Figure 11 As shown, when the edge field of view angle of the image is increased, the area of ​​the relay grating 102 needs to be increased to achieve the same size exit pupil. Therefore, this leads to an increase in the area of ​​the entire diffraction waveguide 100. The specific reasons are as follows:

[0169] like Figure 16 As shown in (a) and (b), Figure 16 (a) and (b) show schematic diagrams illustrating the guiding contrast of images propagating in the diffractive waveguide structure shown in 11 at smaller edge field of view angles A1 and A2, respectively. Figure 16 As shown in (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 disperse in the waveguide, and both the upper edge field of view S1 and the lower edge field of view S2 must propagate in the relay grating 102 to achieve exit pupil expansion in the X direction; therefore, as... Figure 16 As shown in (a) and (b), as the angle between the edge fields of view increases from A1 to A2, the dispersion of the upper edge field of view S1 and the lower edge field of view S2 increases. If the light ray is to continue along the x-direction to achieve the same size exit pupil, the area of ​​the relay grating 102 needs to be expanded along the extension direction of the upper edge field of view S1 and the lower edge field of view S2, that is... Figure 16 (b) The longer base of the trapezoidal repeater grating 102 needs to be lengthened, and the two sides also need to be expanded outwards. Therefore, increasing the field of view angle at the image edge leads to an increase in the area of ​​the repeater grating 102, which in turn leads to an increase in the overall waveguide structure. Conversely, if the area of ​​the repeater grating 102 is not increased, the number of times light hits the repeater grating 102 will decrease, resulting in a decrease in the exit pupil size in the x-direction.

[0170] To address this problem, embodiments of this application provide another diffractive waveguide 100, which... Figure 11 In the diffractive waveguide 100 shown, the relay grating 102 is transformed from a single grating into multiple gratings with different refractive indices. Light coupled into the relay grating 101 continues to propagate by total internal reflection within the waveguide substrate 104 after entering it. However, the path direction of a portion of this totally internally reflected light is restricted between the multiple relay gratings, while a portion can be redirected near the relay grating 103, undergoing total internal reflection towards it, and finally being coupled out by the relay grating 103 to the human eye. This allows light to propagate through reciprocating total internal reflection between the multiple relay gratings, achieving exit pupil expansion without requiring an increase in the area of ​​the relay gratings as the vertical field of view increases. Specific embodiments will be described below.

[0171] Figure 17 This is a schematic diagram of a diffractive waveguide 100 including two relay gratings according to an embodiment of this application.

[0172] like Figure 17 As shown, the diffractive waveguide 100 may include a waveguide substrate 104, a coupling grating 101, a first relay grating 1021, a second relay grating 1022, and a coupling grating 103. The first relay grating 1021 and the second relay grating 1022 are arranged in parallel and spaced apart by a first distance. This first distance allows the light diffracted from the coupling grating to propagate back and forth between the first relay grating 1021 and the second relay grating 1022 via total internal reflection, as will be described in detail below. Furthermore, the coupling grating 103 is disposed between the first relay grating 1021 and the second relay grating 1022.

[0173] In this embodiment of the application, the first relay grating 1021 and the second relay grating 1022 can define a relay region. The relay region extends in a first direction, and 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 the angle between the extension direction of the first side and the extension direction of the second side is less than the first angle.

[0174] For example, the first direction mentioned above can be the x-axis direction, and the second direction can be the y-axis direction.

[0175] It can be understood that the relay region can be defined by the adjacent grating lines of the first relay grating 1021 and the second relay grating 1022, and is 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. Specifically, the first side can be the grating line of the first relay grating 1021 that is closest to the second relay grating 1022, and the second side can be the grating line of the second relay grating 1022 that is closest to the first relay grating 1021.

[0176] The relay area can also be defined by the grating line that is furthest apart from the first relay grating 1021 and the second relay grating 1022, including not only the area between the first relay grating 1021 and the second relay grating 1022, but also the area between the first relay grating 1021 and the second relay grating 1022. The first side can be the grating line of the first relay grating 1021 that is furthest apart from the second relay grating 1022, and the second side can be the grating line of the second relay grating 1022 that is furthest apart from the first relay grating 1021.

[0177] It is understood that in the embodiments of this application, the first relay grating 1021 and the second relay grating 1022 are arranged in parallel. The parallel arrangement is allowed to have a certain error. For example, the extension direction of the grating lines or grooves of the first relay grating 1021 and the second relay grating 1022 can have a certain angle, such as 0-5 degrees.

[0178] Understandable, although Figure 17 The coupling grating 101, the first relay grating 1021, the second relay grating 1022, and the coupling grating 103 shown are all located on the same surface of the waveguide substrate 104. However, in other embodiments, the four can all be located on another surface of the waveguide substrate 104 or distributed on different surfaces. For example, the coupling grating 101 and the coupling grating 103 are located on the same surface of the optical waveguide substrate 104, while the first relay grating 1021 and the second relay grating 1022 are located on another surface of the optical waveguide substrate 104. This is not a limitation.

[0179] Furthermore, it is understandable that, although Figure 17 The relay grating shown has only two, namely the first relay grating 1021 and the second relay grating 1022. However, in other embodiments, the relay grating 102 may also include three or more grating regions with different diffraction indices.

[0180] Figure 18 (a) and (b) are schematic diagrams showing the guidance of light at different angles in the waveguide substrate according to embodiments of this application.

[0181] It is understandable that, since light propagates through total internal reflection in the waveguide substrate 104, the guiding effect of the first relay grating 1021, the second relay grating 1022, or the coupling grating 103 located on two different bottom surfaces of the waveguide substrate 104 in the direction of total internal reflection is the same. Therefore, regardless of which bottom surface of the waveguide substrate 104 the coupling grating 101, the first relay grating 1021, the second relay grating 1022, and the coupling grating 103 are located on, the guiding diagram of light propagation in the waveguide substrate 104 can be obtained from... Figure 18 (a) and (b) represent.

[0182] like Figure 18 As shown in (a) and (b), the light ray i1 emitted by the microdisplay device 105, after incident on the coupling grating 101, is coupled to the coupling waveguide substrate 104 of the coupling grating 101 and propagates through total internal reflection in the waveguide substrate 104 toward the second relay grating 1022, as indicated by arrow B1 in the figure. After the light ray i1 coupled to the coupling grating 101 encounters the second relay grating 1022, as mentioned above, the light ray is split into two parts by the beam-splitting characteristics of the diffraction grating, and propagates through total internal reflection toward different diffraction angles. Specifically, a portion of the light propagates through total internal reflection in the waveguide substrate 104 toward the first relay grating 1021, as shown by arrow B2 in the figure; the other portion is guided to the coupling grating 103 in the direction shown by arrow B3 in the figure, and is coupled out of the waveguide substrate 104 by the coupling grating 103. The direction of travel of the coupled light is shown by arrow B5 (positive z-axis direction) in the figure. The light transmitted to the first relay grating 1021 is totally internally reflected and is redirected to the second relay grating 1022 along the guiding direction shown by arrow B4. The above process is repeated in subsequent processes.

[0183] Specifically, Figure 19 (a) shows the diffraction path of light at the first relay grating 1021 and the second relay grating 1022.

[0184] like Figure 19 As shown in (a), when the light ray i1, after being coupled into the waveguide substrate 104 via the coupling grating 101 and propagating through total internal reflection in the direction indicated by arrow B1, is incident on the second relay grating 1022 at position F1, the light ray is split into two parts, which propagate towards different diffraction angles. For example, one part of the light ray i2 is incident on the other surface of the waveguide substrate 104 and propagates through total internal reflection between the upper and lower surfaces of the waveguide substrate 104 in the direction indicated by arrow B2 until it reaches the first relay grating 1021 at position G1; the other part of the light ray i3 is incident on the other surface of the waveguide substrate 104 and propagates through total internal reflection in the direction indicated by arrow B3 (as shown in the image). Figure 18The light ray i2 propagates in the direction shown in (a)-(b) with total internal reflection until it is guided to the coupling grating; the light ray i2 that propagates to position G1 of the first relay grating 1021 is totally internally reflected to the other surface of the waveguide substrate and propagates with total internal reflection between the upper and lower surfaces of the waveguide substrate 104 in the direction shown by arrow B4 until the light ray i2 hits position F2 of the second relay grating 1021. The above process is repeated. For example, the light ray i2 is divided into two parts, one part of the light ray i4 is guided to position G2 towards the first relay grating 1021 for total internal reflection propagation, and the other part of the light ray i5 is guided to position towards the coupling grating 103 for total internal reflection propagation. In this way, the light ray i1 achieves the expansion of the exit pupil in the positive half-axis direction of the x-axis by reciprocating propagation between the first relay grating 1021 and the second relay grating 1022.

[0185] similar Figure 8 (c), such as Figure 19 As shown in (b), when the light ray i3, which propagates along the B3 direction towards the coupling grating 103 through total internal reflection, reaches position D1 of the coupling grating 103, a portion of the light ray i6 is released through grating diffraction, i.e., it is coupled out of the waveguide substrate 104 in the positive z-axis direction, while the remaining portion of the light ray i7 continues to propagate through total internal reflection in the waveguide substrate 104. During subsequent propagation, when the light ray i7 is incident on position D2 of the coupling grating 103 on the surface of the waveguide substrate 104, the above phenomenon is repeated. Thus, the light ray i1 is expanded in the negative y-axis direction, i.e., for the virtual image emitted by the micro-display device 105, it is expanded by the exit pupil in the negative y-axis direction.

[0186] In this embodiment, the exit pupil expansion in the x-direction is achieved by total internal reflection propagation between the first relay grating 1021 and the second relay grating 1022, instead of achieving x-direction exit pupil expansion by linear propagation in the relay grating 102 region. This allows for x-direction exit pupil expansion without increasing the area of ​​the relay grating 102 region when increasing the angle between the field of view at the image edge.

[0187] Specifically, Figure 20 (a) and (b) show schematic diagrams illustrating the guiding contrast of images propagating in the diffractive waveguide 100 at smaller edge field-of-view angles A1 and A2, respectively. Figure 20 As shown in (a) and (b), the changes caused by the increase in the included angle of the edge field of view are as follows:

[0188] After the light rays from the edge field of view are coupled into the coupling grating 101, the guiding direction of the light rays to the second relay grating 1022 changes, that is, the angle between the guiding direction and the positive x-axis increases. Because the light rays propagate back and forth in the relay grating 102 through total internal reflection, the guiding direction of the light rays diffracted by the second relay grating 1022 to the first relay grating 1021 will change accordingly. Therefore, when the angle of the edge field of view increases, the only change is that the guiding direction of the light rays diffracted by the second relay grating 1022 to the first relay grating 1021 changes accordingly. The number of times the light rays hit the first relay grating 1021 does not decrease significantly. Therefore, the number of exit pupils does not decrease significantly, that is, it does not significantly affect the change in the size of the exit pupil.

[0189] In summary, when the included angle of the edge field of view of the diffractive waveguide 100 provided in this application increases, it only causes a change in the guiding direction of the light by the two relay gratings, and the same exit pupil expansion in the x-direction can be achieved without increasing the area of ​​the relay gratings.

[0190] It is understood that, in this embodiment of the application, in order to achieve a coupling efficiency of over 95% for the coupling grating 101, that is, to couple as much light as possible into the second relay grating 1022 at a specific angle, the diffraction efficiency of the coupling grating 101 can be optimized to the highest level by designing the parameters of the coupling grating 101, such as refractive index n, grating shape, thickness, and duty cycle, so that most of the light propagates mainly along this direction after diffraction. Furthermore, in order to reduce the single-stage coupling efficiency, so that the light achieves both expansion in a specific direction and coupling out to the human eye in the coupling grating 103, the coupling efficiency of the coupling grating 103 can be 1%-10%, thereby reducing the single-stage coupling efficiency and achieving exit pupil expansion.

[0191] Furthermore, in this embodiment, in order to ensure that the k-space region of the light rays coupled out of the coupling grating 103 completely coincides with the k-space region of the incident light emitted by the microdisplay device 105, thereby effectively preventing image distortion, it is necessary to set the parameters of each grating. For example, the period and grating vector direction of the coupling grating 103 are set to be consistent with the period and grating vector direction of the coupling grating 101; and the period and grating vector direction of the first relay grating 1021 are set to be consistent with the period and grating vector direction of the second relay grating 1022. Here, the grating vector direction mentioned in this embodiment is the direction perpendicular to the grating's marking direction.

[0192] For example, such as Figure 17As shown, the angle between the scribe direction of the coupling grating 101 and the positive direction of the positive x-axis and the angle between the scribe direction of the coupling grating 103 and the positive direction of the positive x-axis can both be 45°. The scribe directions of the first relay grating 1021 and the second relay grating 1022 can both be parallel to the x-axis.

[0193] In some embodiments, the angle between the etched direction of the coupling grating 101 and the positive direction of the positive x-axis needs to satisfy the condition that light rays hitting the coupling grating 101 can be guided by the coupling grating 101 to propagate in the direction toward the second relay grating 1022. For example, it can be between -70° and 10°.

[0194] In this embodiment of the application, in order to ensure that the light can be controlled to propagate by total internal reflection within the relay area defined by the relay grating, the first relay grating 1021 and the second relay grating 1022 can be configured with different diffraction efficiency distributions.

[0195] Specifically, the diffraction efficiency requirement of the first relay grating 1021 is as follows: the diffraction efficiency distribution of the first relay grating 1021 can be uniformly distributed so that the 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 diffracted light rays exiting the first relay grating 1021 can be controlled to be relatively small when diffracting light incident on the first relay grating 1021 occurs, for example, the diffraction efficiency is set to be less than 0.1%; while the diffracted light rays reflected back to the second relay grating 1022 have a higher diffraction efficiency, for example, it can be set to be greater than 99.5%, thereby effectively ensuring that no energy overflows from the relay grating.

[0196] Specifically, the diffraction efficiency requirement of the second relay grating 1022 is as follows: the second relay grating 1022 can have non-uniform diffraction efficiency, so that some light rays are coupled out of the second relay grating 1022 and enter the coupling grating 103. For example, the diffraction efficiency of the part of the second relay grating 1022 near the coupling grating 103 is lower, and the diffraction efficiency of the part near the first relay grating 1021 is higher, thereby effectively ensuring that some light rays are coupled out of the first relay grating 1021 and enter the 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 emitted to the coupling grating 103 can be 0.5-20%, and the diffraction efficiency of the diffracted light reflected back to the first relay grating 1021 is greater than 80%. This effectively ensures that a small portion of the light is coupled out of the second relay grating 1021 and enters the coupling grating 103, while a larger portion of the light continues to be reflected back to the first relay grating 1021, thereby achieving an expansion of the exit pupil in the x-direction.

[0197] In some embodiments, both the first relay grating 1021 and the second relay grating 1022 can be surface-embossed gratings, and their diffraction efficiency can be modulated by the grating height of the surface-embossed grating. 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 uniformly distributed, such as... Figure 3 As shown in (a).

[0198] For example, by setting the grating height of the second relay grating 1022 to an uneven distribution, the second relay grating 1022 achieves uneven diffraction efficiency. For example, as... Figure 21 As shown, the grating height is set lower on the side closer to the coupling grating 103, resulting in lower diffraction efficiency on that side; while the grating height is set higher on the side closer to the first relay grating 1021, ensuring higher diffraction efficiency on that side. Alternatively, the diffraction efficiency can be modulated using other grating parameters, for example, adjusting the grating's duty cycle distribution to adjust the diffraction efficiency distribution.

[0199] It is understood that in the embodiments of this application, the surface relief grating can be a grating formed on the surface of the optical waveguide using a surface relief process. By designing the relevant parameters of the surface relief grating, such as its height, the diffraction efficiency of the surface relief grating can be adjusted.

[0200] In some other embodiments, both the first relay grating 1021 and the second relay grating 1022 can be volume holographic gratings. The volume holographic grating is formed by directly interfering and forming bright and dark distribution interference fringes inside a volume holographic material with a thickness of micrometers through dual-beam holographic exposure. The diffraction efficiency of the volume holographic grating can be controlled by the refractive index modulation of the volume holographic grating. The lower the refractive index modulation of the grating region, the lower the diffraction efficiency of the corresponding grating region. That is, the refractive index modulation of the grating region is proportional to the diffraction efficiency of the corresponding grating region.

[0201] Therefore, to ensure a uniform diffraction efficiency distribution in the first relay grating 1021, the refractive index modulation of the first relay grating 1021 can be set to be uniformly distributed. To ensure a non-uniform diffraction efficiency in the second relay grating 1022, the refractive index modulation of the second relay grating 1022 can be set to be non-uniformly distributed. Specifically, the refractive index modulation can be gradually reduced from the region far from the coupling grating 103 to the region close to the coupling grating 103.

[0202] The refractive index modulation of the volume holographic grating can be adjusted by the ultraviolet exposure time; for example, the longer the ultraviolet exposure time, the higher the refractive index modulation.

[0203] Furthermore, in other embodiments, one of the grating regions in the first relay grating 1021 and the second relay grating 1022 can be a surface relief grating, and the other grating region can be a volume holographic grating. For example, the first relay grating 1021 can be a surface relief grating, and the second relay grating 1022 can be a volume holographic grating. The specific adjustment of diffraction efficiency can be referred to the method described above.

[0204] Furthermore, it is understood that the placement of the coupling grating 101 in this embodiment is relatively flexible. For example, it can be positioned as follows: Figure 17 As shown, the coupling grating 101 is disposed in the relay region between the first relay grating 1021 and the second relay grating 1022, or as shown in the figure. Figure 22 As shown, it is located between the extended regions of the first relay grating 1021 and the second relay grating 1022, or alternatively, it can be as follows: Figure 23 As shown, the coupling grating 101 is disposed on either side of the first relay grating 1021 or the second relay grating 1022. It should be noted that, in this embodiment, the position of the coupling grating 103 needs to be such that the light incident on the coupling grating 103 can be guided to the second relay grating 1023.

[0205] Figure 24 An example of using Figure 17 The diagram shows the structure of AR glasses 200 with the diffractive waveguide 100 as a lens. Figure 24 As shown, the left lens 201 and right lens 201 of the AR glasses 200 can both adopt Figure 17 The diffractive waveguide 100 is shown. Wherein, Figure 17 Other structural components of the AR glasses 200 Figure 9 Similar to the case in China, I will not repeat it here.

[0206] In Embodiment 2 of this application, the diffractive waveguide 100 may not be limited to the implementation scheme including the two relay gratings mentioned above, but may also include an implementation scheme including three or more relay gratings.

[0207] If the diffractive waveguide 100 may include three or more relay gratings, then the period and grating vector of each relay grating are the same; the light rays can propagate to all but the second relay grating 1022 after diffraction by the coupled grating.

[0208] In some embodiments, including multiple relay gratings, the diffraction efficiency requirement of the relay grating furthest from the coupling grating is the same as that of the first relay grating 1021 in the embodiment including two grating regions, so that all light incident on this relay grating can be totally reflected to the other relay gratings. The diffraction efficiency requirement of the remaining relay gratings is the same as that of the second relay grating 1022 in the embodiment including two relay gratings, so that some light incident on the remaining relay gratings can be guided to the first relay grating 1021, and the other part can be guided to the coupling grating 103.

[0209] For example, such as Figure 25 As shown, the structure of the diffractive waveguide 100 is similar to... Figure 17 The two methods are largely the same, with the main difference being that a third relay grating 1023 can 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 all the same; a coupling grating can be provided on the upper part of the third relay grating 1023.

[0210] It is understood that the coupling grating 101 can also be located at other positions that allow light to be guided by the coupling grating 101 to propagate in the direction of the second relay grating 1022. For example, the coupling grating 101 can also be located between the second relay grating 1022 and the third relay grating 1023.

[0211] The first relay grating 1021 has a uniformly distributed diffraction efficiency, which can effectively ensure that there is no energy overflow in the relay region.

[0212] The second relay grating 1022 may have non-uniform grating efficiency. For example, the diffraction efficiency is lower on the side closer to the coupling grating 103 and higher on the side closer to the third relay grating 1023. This effectively ensures that some light rays are coupled from the second relay grating 1022 into the third grating region 1023, and that some light rays are coupled out of the second grating region 1022 into the coupling grating 103.

[0213] The third relay grating 1023 may have non-uniform grating efficiency. For example, the diffraction efficiency is lower on the side closer to the second relay grating 1022 and higher on the side closer to the first relay grating 1021. This effectively ensures that some light rays are coupled into the second grating region 1022 from the third relay grating 1023, and that some light rays are coupled into the first relay grating 1021 from the third grating region 1023.

[0214] In this embodiment of the application, the space between the first relay grating 1021 and the second relay grating 1022 can be a surface relief grating, a volume holographic grating, or the like.

[0215] Figure 26 A schematic diagram of the guidance of light in the diffraction waveguide 100 with three relay gratings is shown.

[0216] like Figure 26 As shown, the coupling grating 101 couples the light ray i1 projected by the microdisplay device 105 into the waveguide substrate 104 and guides the light ray i1 toward the second relay grating 1022, as indicated by arrow B1 in the figure. When the light ray is incident on the second relay grating 1022 in the direction indicated by arrow B2, the light ray is split into two parts, which propagate toward different diffraction angles. Specifically, one part of the light ray undergoes total internal reflection inside the waveguide substrate 104, and the direction of total internal reflection propagation is incident on the third relay grating 1023 in the direction indicated by arrow B2. The other part of the light ray also undergoes total internal reflection inside the waveguide substrate 104, but the direction of total internal reflection propagation is incident on the output grating 103 in the direction indicated by arrow B3.

[0217] The light rays incident on the third relay grating 1023 along the direction indicated by arrow B2 are split into two parts, which propagate towards different diffraction angles. Specifically, one part of the light rays undergoes total internal reflection inside the waveguide substrate 104, and the direction of total internal reflection propagation is indicated by arrow B4, which then enters the first relay grating 1021. The other part of the light rays also undergoes total internal reflection inside the waveguide substrate 104, and the direction of total internal reflection propagation is indicated by arrow B5, which then enters the second relay grating 1022.

[0218] The light rays incident on the first relay grating 1021 in the direction shown by arrow B4 are incident on the third relay grating 1023 in the direction shown by arrow B6, and the light rays incident on the third relay grating 1023 repeat the above process.

[0219] The specific optical path diagram of the light rays in the diffractive waveguide 100 is as follows: Figure 19 Similarly, the propagation occurs via total internal reflection between the upper and lower surfaces of the waveguide substrate 104 in accordance with the guiding direction, which will not be elaborated further here.

[0220] In this embodiment, the relay grating 102 can also be formed by discontinuously distributed refractive index modulation regions generated in the relay region. For example, by irradiating the waveguide substrate 104 with ultraviolet light, discontinuously distributed regions with different refractive index modulation levels are generated in the relay region. Specifically, the refractive index modulation level of each region can be adjusted by adjusting the ultraviolet light exposure time, so that the refractive index modulation level of each region of the relay grating 102 is different.

[0221] In some embodiments, taking a relay region comprising three grating regions as an example, Figure 27Three relay gratings with different refractive index modulations are shown, arranged along the negative y-axis of the diffractive waveguide: a first relay grating 1021, a second relay grating 1022, and a third relay grating 1023. The first relay grating 1021, the second relay grating 1022, and the third relay grating 1023 all have the same period and grating vector. The coupling grating is disposed on the surface of the relay region, for example, on the surface located at the position of the third relay grating 1023.

[0222] in, Figure 27 The diffraction efficiency distribution and light guiding direction of the first relay grating 1021, the second optical relay grating 1022, and the third relay grating 1023 are all related to... Figure 26 Same as above.

[0223] In Embodiment 3 of this application, unlike the structure described above, the diffractive waveguide 100 can also be as follows: Figure 28 As shown, it includes two waveguide layers. For example, the lower waveguide layer can be defined as the waveguide substrate 104, and the upper waveguide layer can be defined as the waveguide top layer 106. That is, the diffractive waveguide 100 can include the waveguide substrate 104 and the waveguide top layer 107. A grating layer can be sandwiched between the waveguide substrate 104 and the waveguide top layer 107. The grating layer can be formed in an arrangement including any of the coupling gratings 101, multiple relay gratings (such as the first relay grating 1021 and the second relay grating 1022) and coupling gratings 103 mentioned in the above embodiments. The grating layer can be formed by setting a holographic material layer 108 between the waveguide substrate 104 and the waveguide top layer 107, and using holographic exposure technology to generate any of the coupling gratings 101, multiple relay gratings (such as the first relay grating 1021 and the second relay grating 1022) and coupling gratings 103 mentioned in the above embodiments on the holographic material layer 108.

[0224] It is understood that any of the coupling gratings 101, multiple relay gratings (such as the first relay grating 1021 and the second relay grating 1022), and coupling gratings 103 mentioned in the above embodiments of the grating layer can also be gratings formed by other means such as surface relief gratings. The corresponding light propagation mode is the same as in the above embodiments, and will not be repeated here.

[0225] In this embodiment, sandwiching a holographic material layer between two waveguide layers ensures uniform thickness of the holographic material layer and increases the stability of light propagation. In some embodiments, the holographic material can also be directly coated on one surface of the waveguide layer, for example, on the upper surface of the waveguide substrate 104 or the lower surface of the waveguide top layer 107, using holographic exposure technology to generate any of the coupling gratings 101, multiple relay gratings (such as the first relay grating 1021 and the second relay grating 1022), and coupling gratings 103 arrangements mentioned in the above embodiments.

[0226] In other embodiments, the diffractive waveguide may also include multiple waveguide substrates 104 and a grating layer on each waveguide substrate 104, with the multiple waveguide substrates 104 stacked and connected in the z-axis direction. This approach allows each waveguide substrate 104 to propagate only one or more monochromatic lights of different wavelengths, which can reduce crosstalk in the system colors and thus improve the color uniformity at the exit pupil position. For example, if the microdisplay device 105 projects three monochromatic lights—red, blue, and green—a grating layer can be added to the upper surface of the waveguide top layer 107 or the lower surface of the waveguide bottom layer 104, based on the aforementioned scheme of setting a grating layer between the waveguide substrate 104 and the waveguide top layer 107. Green light is propagated through the waveguide top layer 107, while red and blue light are propagated through the waveguide substrates 104. As another example, the three diffractive waveguides 100 mentioned in the above embodiments can be stacked and connected in the z-axis direction, with each diffractive waveguide 100 propagating one monochromatic light, ultimately coupled into the human eye.

[0227] It is understood that in the various embodiments of this application, various gratings are disposed on the surface of the optical waveguide substrate to achieve the guiding effect of light. In other embodiments, other optical elements with grating diffraction function can also be used to achieve the above technical solution. In addition, these optical elements may not be disposed on the surface of the optical waveguide substrate, but may be disposed inside the optical waveguide substrate to achieve the guiding effect of light. For example, by changing the microstructure in a certain region of the optical waveguide substrate, the microscopic molecular structure of that region can realize the function of coupling in grating 101, first relay grating 1021, second relay grating 1022, or coupling out grating 103.

[0228] The relay grating 102 provided in the above embodiments of this application may include a technical solution of multiple relay gratings with different refractive indices, which enables light to propagate through multiple relay gratings to achieve the expansion of the exit pupil of the light without increasing the area of ​​the relay grating as the field of view increases, so that the diffraction waveguide 100 can be applied to various devices with a large field of view.

[0229] The following describes a method for setting the dimensions of each grating on the diffractive waveguide 100, based on some embodiments of this application.

[0230] (1) Determination of the dimensions of the coupling grating 101

[0231] In this embodiment, the size of the coupling grating 101 can be square as shown in 27, which is feasible. It can also be set to other shapes, such as circles, according to actual needs.

[0232] The size of the coupling grating 101 must be greater than or equal to the exit pupil size of the microdisplay device 105 used. For example, if the exit pupil size is 4mm in diameter and the shape of the coupling grating 101 is circular, then the size of the coupling grating 101 must be at least 4mm in diameter; if the shape of the coupling grating 101 is square, then the size of the coupling grating 101 must be at least 4*4mm. Implementably, the size of the coupling grating 101 can be adjusted according to the size of the AR glasses, for example, based on the size of typical AR glasses, the size of the coupling grating 101 can be set between 0.5*0.5mm and 10*10mm.

[0233] (2) Determination of the dimensions of the first relay grating and the second relay grating

[0234] The spacing between the first relay grating 1021 and the second relay grating 1022 is greater than or equal to the dimension of the coupling grating 101 in the y-direction. Alternatively, the width of the first relay grating 1021 and the second relay grating 1022 in the y-direction can be adjusted according to the size of the AR glasses, for example, based on the size of typical AR glasses, the width of the first relay grating 1021 and the second relay grating 1022 in the y-direction can be between 0.1 and 10 mm.

[0235] (3) Determination of the size of the coupling grating

[0236] The size of the coupling grating 101 must be greater than or equal to the final exit pupil size of the light in the waveguide substrate 104. For example, if the final exit pupil size is 4*4mm, then the size of the coupling grating 101 can be 5*5mm, etc., to meet the exit pupil requirements of the light.

[0237] In this embodiment of the application, the period of the coupling grating 101 also needs to meet the set conditions, as described below:

[0238] Assuming the FOV of an augmented reality display corresponds to the horizontal and vertical fields of view, respectively, FOV... hor and FOV ver Within this field of view, the light rays of a certain field of view can be represented by (θ). hor ,θ ver Let ) represent it, and have θ hor ∈FOV hor and θ ver ∈FOV ver ;

[0239] For coupled grating 101, the polar angle θ of the diffracted light corresponding to the m-th order is... m For light rays coupled into the waveguide substrate 104 to propagate through total internal reflection within the waveguide substrate 104, certain conditions must be met. These conditions are:

[0240]

[0241] In order for the light rays passing through the coupling grating 101 to satisfy the diffraction at a set angle, such as the m-th order diffraction, as shown in expression (1) above, the period d of the coupling grating 101 needs to satisfy the following set condition:

[0242]

[0243] Where m is the diffraction order, n is the refractive index of the waveguide substrate 104, and θ m and Let θ be the polar angle and azimuth angle of the diffracted light corresponding to the m-th order, λ be the wavelength of the incident light, and θ be the polar angle and azimuth angle of the diffracted light. θ represents the polar angle and azimuth angle of the incident light, respectively. Gin The angle of the grating's markings.

[0244] Where, θ and The calculation process is as follows:

[0245]

[0246]

[0247] For example, if the light rays in a certain field of view are (45°, 45°), that is, the polar angle θ and azimuth angle of the incident light. With all angles set at 45°, the incident light wavelength at 650 nm, the diffraction order m = 1, the grating notch angle at 45°, and the refractive index of the selected waveguide substrate structure 104 being 2, and the polar angle and azimuth angle of the diffracted light corresponding to the m order being both 45°, the period d of the coupled grating 101 is calculated to be 248 nm.

[0248] In some embodiments, the period of the coupling grating can be adjusted according to the required diffraction angle of the light passing through the coupling grating 101. For example, the period of the coupling grating can be in the range of 200nm-500nm.

[0249] Below, we will consider light in k-space... Figure 17 Taking the propagation of the diffractive waveguide 100 as an example, this illustrates the specific reasons why ensuring the grating vector of the output grating 103 is the same as that of the input grating 101, and that the grating vectors of the first relay grating 1021 and the second relay grating 1022 are the same, allows the k-space region of the output light to completely coincide with the incident light, effectively preventing image distortion. The details are as follows:

[0250] Assume the k-space vector corresponding to the incident light is:

[0251]

[0252] The diffraction of the incident light by the coupling grating 101 can then be expressed as:

[0253]

[0254] Right now

[0255]

[0256] in, The k-vector of the diffracted light. Let k be the incident light vector. Let k be the grating vector, and

[0257]

[0258]

[0259]

[0260] for Figure 17 The diffractive waveguide 100 shown has the following k-space path: Figure 29 As shown, the central square represents the k-space region corresponding to the field of view of the incident light. For example, after passing through the coupling grating 101, under the multiple reflections of the first relay grating 1021 and the second relay grating 1022, the k-space region that propagates back and forth within the diffracted light 100 is... Figure 14 The regions represented by the lower left square and the upper left square, after multiple reflections by the first relay grating 1021 and the second relay grating 1022, return to the k-space region. Figure 29 The area represented by the square in the lower left corner is then incident on the coupling grating 103. The coupling grating 103 can couple the light out of the waveguide. The k-space region of the coupled light completely coincides with the k-space region of the incident light, which can effectively prevent the generation of image distortion.

[0261] For example, let the K vector of the coupled grating 101 be...

[0262]

[0263] Let the K vector of the coupling grating 103 be...

[0264]

[0265] Let the K vectors of the first relay grating 1021 and the second relay grating 1022 be respectively

[0266]

[0267]

[0268] Because the K-vectors of the input grating 101 and the output grating 103 are the same, and the K-vectors of the first relay grating 1021 and the second relay grating 1022 are the same, therefore

[0269]

[0270] The above formula shows that when light rays entering the waveguide exit the waveguide structure again after passing through the coupling grating 101, the first relay grating 1021, the second relay grating 1022, and the coupling grating 103 in the waveguide structure, the direction of the light rays will not change, thus ensuring that there is no image distortion.

[0271] Furthermore, because the K-vectors of the input grating 101 and the output grating 103 are the same, and the K-vectors of the first relay grating 1021 and the second relay grating 1022 are the same, that is...

[0272]

[0273]

[0274] therefore:

[0275]

[0276] Where N represents the number of times the light travels back and forth between the first relay grating 1021 and the second relay grating 1022. As can be seen from the above formula, because... Therefore, regardless of the value of N, Since both are equal to 0, the light will not introduce an additional phase difference when it propagates back and forth between the first relay grating 1021 and the second grating region multiple times. This ensures that the direction of the light when it enters the first relay grating 1021 is consistent with the direction of propagation diffracted from the first grating.

[0277] In summary, the technical solution provided in this application, in which the period and grating vector direction of the output grating 103 are consistent with those of the input grating 101, and the periods and grating vector directions of the first relay grating 1021 and the second relay grating 1022 of the relay grating 102 are also consistent, enables the light entering the waveguide structure to pass through the input grating 101, the first relay grating 1021, the second relay grating 1022 and the output grating 103 in the waveguide structure multiple times, and when it exits the waveguide structure again, the direction of the light will not change, thereby ensuring that the image will not be distorted.

[0278] It should be noted that the diffractive waveguide 100 provided in this application embodiment can be applied not only to the AR glasses 200 mentioned above, but also to other fields, such as to vehicle head-up displays (HUDs). The diffractive waveguide 100 provided in this application embodiment can project important driving data or images onto the windshield, making it convenient for the driver to view and improving driving safety.

[0279] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. An optical device, characterized in that, It includes 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 coupling unit is configured to couple light into the waveguide substrate; The first relay unit and the second relay unit define a relay area that extends in a first direction. The first relay unit and the second relay unit are arranged in a second direction. The relay area has a first side and a second side opposite to each other in the second direction. The angle between the extension direction of the first side and the extension direction of the second side is less than a first angle. The coupling unit is configured to couple light from the waveguide substrate out of the waveguide substrate, and the coupling unit and the relay region are arranged in the second direction; The first relay unit and the second relay unit are gratings, and the coupling unit is located in the relay region; In the absence of a third relay unit, the second relay unit is configured such that after light propagating through total internal reflection in the waveguide substrate is incident on the second relay unit, a first portion of the outgoing light propagates through total internal reflection toward the first relay unit based on a first diffraction angle, and the remaining outgoing light propagates through total internal reflection toward the coupling unit based on a second diffraction angle. In the case where the optical device includes the third relay unit, and the third relay unit is located between the first relay unit and the second relay unit, and the third relay unit divides the relay area into two relay sub-regions: The second relay unit is configured such that after light propagating through total internal reflection in the waveguide substrate is incident on the second relay unit, a second portion of the outgoing light propagates through total internal reflection towards the third relay unit based on a third diffraction angle, and the outgoing light other than the second portion propagates through total internal reflection towards the coupling unit based on a fourth diffraction angle. The third relay unit is configured such that after the second portion of the emitted light rays is incident on the third relay unit, the third portion of the emitted light rays propagates towards the first relay unit by total internal reflection based on a fifth diffraction angle, and the emitted light rays other than the third portion propagate towards the second relay unit by total internal reflection based on a sixth diffraction angle.

2. The optical device according to claim 1, characterized in that, The first angle is 0 o ~5 o .

3. The optical device according to claim 1, characterized in that, The first side and the second side are parallel in the direction of extension.

4. The optical device according to claim 1, characterized in that, In the absence of the third relay unit in the optical device, the first relay unit is configured such that light rays propagating by total internal reflection in the waveguide substrate, after being incident on the first relay unit, propagate by total internal reflection toward the second relay unit.

5. The optical device according to claim 1, characterized in that, The first side of the relay region is the gate line of the first relay unit that is closest to the second relay unit, and the second side is the gate line of the second relay unit that is closest to the first relay unit. or, The first side of the relay region is the gate line of the first relay unit that is furthest from the second relay unit, and the second side is the gate line of the second relay unit that is furthest from the first relay unit.

6. The optical device according to claim 5, characterized in that, Both the first relay unit and the second relay unit include multiple grating lines, and the grating lines of the first relay unit and the second relay unit are at the first angle to each other.

7. The optical device according to claim 6, characterized in that, Both the first relay unit and the second relay unit include multiple grating lines, and the grating lines of the first relay unit and the second relay unit are parallel to each other.

8. The optical device according to claim 5, characterized in that, The first relay unit and the second relay unit are parallel bar gratings.

9. The optical device according to claim 5, characterized in that, The first relay unit and the second relay unit have the same grating period.

10. The optical device according to claim 5, characterized in that, The diffraction efficiency of the first relay unit is evenly distributed, and the diffraction efficiency of the second relay unit gradually decreases from the side away from the coupling unit to the side closer to the coupling unit.

11. The optical device according to claim 10, characterized in that, The first relay unit is a surface-embossed grating, and the grating height of the first relay unit is evenly distributed.

12. The optical device according to claim 10, characterized in that, The second relay unit is a surface-embossed grating, and the grating height of the second relay unit gradually decreases from the side away from the coupling unit to the side closer to the coupling unit.

13. The optical device according to claim 10, characterized in that, The first relay unit is a volume holographic grating, and the refractive index modulation of the first relay unit is evenly distributed.

14. The optical device according to claim 10, characterized in that, The second relay unit is a volume holographic grating, and the grating refractive index modulation of the second relay unit gradually decreases from the side away from the coupling unit to the side closer to the coupling unit.

15. The optical device according to claim 1, characterized in that, The angle between the two long sides of the relay sub-region in the extending direction is smaller than the first angle.

16. The optical device according to claim 15, characterized in that, The third relay unit is a grating.

17. The optical device according to claim 16, characterized in that, The first relay unit, the second relay unit, and the third relay unit each include multiple parallel grid lines.

18. The optical device according to claim 15, characterized in that, The third relay unit is a strip grating.

19. The optical device according to claim 18, characterized in that, The diffraction efficiency of the third relay unit gradually decreases from the side closer to the first relay unit to the side closer to the second relay unit.

20. The optical device according to claim 19, characterized in that, The third relay unit is a surface-embossed grating, and the grating height of the third relay unit gradually decreases from the side closer to the first relay unit to the side closer to the second relay unit.

21. The optical device according to claim 20, characterized in that, The third relay unit is a volume holographic grating, and the grating refractive index modulation of the third relay unit gradually decreases from the side closer to the first relay unit to the side closer to the second relay unit.

22. The optical device according to claim 1, characterized in that, The coupling-in unit and the coupling-out unit are gratings, and the period and grating vector direction of the coupling-in unit and the coupling-out unit are the same.

23. The optical device according to claim 1, characterized in that, The coupling unit is a surface-embossed grating or a volume holographic grating; and The coupling unit is a surface relief grating or a volume holographic grating.

24. The optical device according to claim 1, characterized in that, The coupling unit, the first relay unit, the second relay unit, and the coupling unit are located on at least one bottom surface of the waveguide substrate.

25. The optical device according to claim 1, characterized in that, It also includes a holographic material layer, and the number of waveguide substrates is two, with the holographic material layer sandwiched between the two waveguide substrates; The coupling unit, the first relay unit, the second relay unit, and the coupling unit are located on at least one bottom surface of the holographic material layer.

26. An electronic device, characterized in that, It includes a microdisplay device and an optical device according to any one of claims 1 to 25, wherein the microdisplay device is used to project light onto the coupling unit of the optical device.

27. The electronic device according to claim 26, characterized in that, The electronic device is augmented reality glasses.

28. The electronic device according to claim 26, characterized in that, The electronic device is a vehicle-mounted head-up display.

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