CN218567743U

CN218567743U - Optical device and near-to-eye display apparatus

Info

Publication number: CN218567743U
Application number: CN202222570175.9U
Authority: CN
Inventors: 鲁云开; 闫冠屹
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-09-26
Filing date: 2022-09-26
Publication date: 2023-03-03
Anticipated expiration: 2032-09-26

Abstract

The application relates to the field of optics and discloses an optical device and near-to-eye display equipment. The optical device comprises an optical waveguide, a light incoupling device, a light outcoupling device and a diffraction device. The optical waveguide comprises a first part, a second part and a third part which are sequentially connected along a first direction, and the optical coupling-in device and the optical coupling-out device are respectively arranged on the first part and the third part; the top surfaces of the first part, the second part and the third part are sequentially connected to form a first surface of the optical waveguide, and the first surface is a plane; the bottom surfaces of the first part, the second part and the third part are sequentially connected to form a second surface of the optical waveguide; the bottom surfaces of the first and third portions are parallel to the first surface, the bottom surface of the second portion is inclined with respect to the first surface such that the first portion has a thickness greater than the third portion, and the diffraction device is disposed on the bottom surface of the second portion. The application provides an optical device can avoid light to take place the secondary diffraction, ensures the exit pupil continuity. In addition, the weight can be effectively reduced.

Description

Optical device and near-to-eye display apparatus

Technical Field

The present application relates to the field of optics, and in particular, to an optical device and a near-eye display apparatus.

Background

With the development of display technology, near-eye display devices using Augmented Reality (AR) technology are widely used. The AR technology mainly uses an optical machine as an image source, and projects an image into a human eye through an optical element for imaging. Among them, the optical element generally employs an optical waveguide structure.

In the optical waveguide structure, incident light is coupled into the optical waveguide through the optical coupler-in device and is propagated in the optical waveguide in a total reflection mode, and light propagated to the optical coupler-out device is coupled out of the optical waveguide. In order to ensure that human eyes can observe images within a certain range and the images do not flicker or jump when the human eyes continuously move within the certain range, the exit pupil needs to be expanded and the continuity of the exit pupil is ensured. Meanwhile, the light is ensured not to be secondarily diffracted at the position of the light-coupled device so as to avoid energy waste, and the two conditions are contradictory.

It is therefore desirable to provide an optical waveguide structure that simultaneously meets the requirements of avoiding energy waste and ensuring a continuous exit pupil.

SUMMERY OF THE UTILITY MODEL

Embodiments of the present application provide an optical device and a near-eye display apparatus, which are described below in various aspects, embodiments and advantageous effects of which are mutually referenced.

In a first aspect, the present application provides an optical device comprising: optical waveguides, optical incoupling devices, optical outcoupling devices and diffraction devices. The optical waveguide comprises a first part, a second part and a third part which are sequentially connected along a first direction, and the optical coupling-in device and the optical coupling-out device are respectively arranged on the first part and the third part; the top surfaces of the first part, the second part and the third part are sequentially connected to form a first surface of the optical waveguide, and the first surface is a plane; the bottom surfaces of the first portion, the second portion and the third portion are connected in sequence to form a second surface of the optical waveguide; the bottom surface of the first portion and the bottom surface of the third portion are parallel to the first surface, the bottom surface of the second portion is inclined with respect to the first surface such that the thickness of the first portion is greater than the thickness of the third portion, and the diffraction device is disposed on the bottom surface of the second portion.

The optical device provided by the embodiment of the application can avoid secondary diffraction of light rays and ensure the continuity of the exit pupil. In addition, the weight can be effectively reduced, and the user experience is further improved.

In some of these embodiments, the light incoupling means may be provided on a top surface of the first portion of the light guide and the light outcoupling means on a top surface of the third portion of the light guide.

In some of these embodiments, the light incoupling means is provided on a bottom surface of the first portion of the light guide and/or the light outcoupling means is provided on a bottom surface of the third portion of the light guide.

In the optical device, the light is coupled into the first part of the optical waveguide through the optical incoupling device, and the thickness of the first part is larger, so that secondary diffraction of the light at the optical incoupling device is avoided. The light ray in the first part is transmitted to the third part through the second part. The light rays propagating to the third part are coupled out of the third part of the optical waveguide through the light out-coupling device arranged on the third part, and the thickness of the third part is small, so that the continuity of the extended exit pupil can be ensured. In addition, the optical device has a more compact structure, the thickness of the optical waveguide is smaller, and the weight is effectively reduced.

In some embodiments, the diffraction device diffracts a first light ray incident from the first portion to the bottom surface of the second portion to the third portion at a first angle, wherein a difference between the first angle and a second angle is smaller than a first threshold, the second angle being an angle of a reflected light ray when the first light ray is incident to the bottom surface of the first portion.

According to the embodiment of the application, the first light is diffracted by the diffraction device after being incident to the bottom surface of the second part, so as to generate the diffracted light. The diffracted light has substantially the same angle as the reflected light produced when the first light is directed to the bottom surface of the first portion (the difference between the two is less than the first threshold), thereby allowing the optical device to form a sharp image.

In some embodiments, the diffractive device comprises a plurality of holographic gratings having different fringe inclinations to diffract a plurality of different angles of the first light into the third portion.

The plurality of holographic gratings are formed by respectively exposing a plurality of holographic materials, and are superposed in a sequential lamination manner, so that the diffraction device is formed.

In some embodiments, the diffractive device is a volume holographic grating. Wherein the volume holographic grating is formed by multiple exposures of the same holographic material.

In some embodiments, the first light ray includes an angle of 30 ° to 75 ° with respect to the normal to the bottom surface of the first portion. For example, the first light ray forms an angle of 30 ° with the normal of the bottom surface of the first portion. For another example, the first light ray forms an angle of 40 ° with the normal of the bottom surface of the first portion. It is understood that the angle between the first light ray and the normal of the bottom surface of the first portion may be an angle between the first light ray and a Z-axis direction mentioned in the following embodiments.

In some embodiments, the first threshold is 0 ° to 1 °. For example, the first threshold may be 0.1 °. For another example, the first threshold may also be 0.3 °.

In some embodiments, the bottom surface of the second portion is inclined at an angle of 5.5 ° to 20 ° relative to the first surface. For example, the bottom surface of the second portion is inclined at an angle of 6 ° to the first surface. For another example, the bottom surface of the second portion is inclined at an angle of 7 ° with respect to said first surface. It is to be understood that the bottom surface of the second portion may be inclined with respect to the first surface at an angle to the X-axis direction mentioned in the following embodiments.

In some embodiments, wherein the ratio of the length of the light out-coupling device to the thickness of the third portion is from 2 to 10, the length of the light out-coupling device being the dimension of the light out-coupling device in the first direction. E.g., 2,4, etc.

In some embodiments, the bottom surface of the second portion is planar.

In some embodiments, the light incoupling and outcoupling devices are diffraction gratings; alternatively, the light incoupling and outcoupling devices are super-surface devices.

In a second aspect, the present application provides a near-eye display device comprising an optical engine and the optical apparatus of any one of the embodiments of the first aspect of the present application, wherein light of the optical engine can be coupled into the optical waveguide through a light incoupling device of the optical apparatus.

Drawings

FIG. 1 shows a schematic diagram of a structure of an optical waveguide 110;

FIG. 2 (a) shows a perspective view of a diffractive light waveguide 100;

fig. 2 (b) shows an optical path diagram of a diffractive light waveguide 100;

FIG. 3 illustrates a schematic structural view of AR glasses 200 in some embodiments of the present application;

FIG. 4 shows a schematic diagram of light coupling into the human eye through the left lens 221 or the right lens 222 of the AR glasses 200;

figure 5 (a) shows a schematic diagram of exit pupil discontinuity;

figure 5 (b) shows a schematic diagram of exit pupil progression;

FIG. 6 (a) shows a schematic diagram in which secondary diffraction occurs;

FIG. 6 (b) shows a schematic diagram without secondary diffraction;

FIG. 7 is a schematic diagram of a diffractive optical waveguide 100a in some embodiments;

FIG. 8 is a schematic diagram showing the structure of another diffractive optical waveguide 100b in some embodiments;

fig. 9 is a schematic structural diagram of a diffractive light waveguide 100 according to an embodiment of the present application;

FIG. 10 shows a schematic diagram of the structure of an optical waveguide 110 in the diffractive optical waveguide 100;

FIG. 11 shows a light ray L ₁ For example, the propagation of light in the diffractive light waveguide 100 is shown;

fig. 12 shows a schematic diagram of the total reflection of the first ray La at the first portion 111 according to fig. 11;

FIG. 13 shows a schematic of the structure of a holographic grating;

fig. 14 shows a schematic diagram of the diffraction of a first ray La at the holographic grating 150 corresponding to fig. 11;

FIGS. 15 (a) to 15 (c) show diffraction diagrams of holographic gratings of different periods and fringe inclinations;

FIG. 16 exemplarily shows an exposure method of a holographic grating;

fig. 17 (a) to 17 (c) show optical path diagrams of the first light ray La at different angles within the diffractive light waveguide 100;

fig. 18 (a) shows an exposure schematic diagram of the hologram grating 150a diffracting the first light La 1;

fig. 18 (b) shows an exposure schematic diagram of the hologram grating 150b diffracting the first light La 2;

fig. 18 (c) shows an exposure schematic diagram of the hologram grating 150c diffracting the first light La 3;

FIG. 19 shows a volume holographic grating 160 having a plurality of different grating periods;

FIG. 20 illustrates light L in some embodiments ₁ A schematic view of the negative direction propagation along the X-axis in the diffractive light waveguide 100;

fig. 21 shows a schematic dimensional view of the bottom surface 117 of the second part 112 according to fig. 10;

FIG. 22 (a) is a schematic diagram showing the dimension parameters of the first light ray La and the diffractive light waveguide 100 according to some embodiments of the present application, wherein the third angle θ ₃ At 5.5 °;

FIG. 22 (b) is a schematic diagram showing the dimension parameters of the first light ray La and the diffracted light waveguide 100 according to some embodiments of the present application, wherein the third angle θ ₃ Is 20 degrees;

23 (a) -23 (d) show structural schematics of different shapes of surface relief gratings in some embodiments of the present application;

FIG. 24 illustrates a schematic structural view of a super-surface device in some embodiments of the present application;

FIG. 25 shows a light ray L ₂ For example, the propagation of light in the diffractive light waveguide 100 is shown。

Description of reference numerals: 100-diffractive light waveguide; 100 a-diffractive optical waveguide; 100 b-a diffractive optical waveguide; 110-an optical waveguide; 111-a first part; 112-a second portion; 113-a third part; 114-the top surface of the optical waveguide; 115-the bottom surface of the optical waveguide; 116-a first portion bottom surface; 117-second portion bottom surface; 118-a third portion bottom surface; 120-optical incoupling devices; 130-optical out-coupling devices; 130 a-an optical out-coupling device; 130 b-an optical out-coupling device; 140-a diffractive device; 150-volume holographic grating; 151-holographic material; 152-stripes; 152 a-bright stripes; 152 b-dark stripes; 160-volume holographic grating; 170-a light splitting film; s. the ₁ -a light incoupling region; s ₂ -a light outcoupling region; 200-AR glasses; 210-a frame; 211-left temple; 212-right temple; 213-a lens frame; 220-a lens; 221-left lens; 222-a right lens; 230-an optical machine; 300-exit pupil.

Detailed Description

While the description of the present application will be presented in conjunction with certain embodiments, this is not intended to limit the features of this application to that embodiment. Rather, the embodiments are described as applications in order to cover other alternatives or modifications that may extend from the claims of the present application. In the following description, numerous specific details are included to provide a thorough understanding of the present application. The present application may be practiced without these particulars. Moreover, some of the specific details have been omitted from the description in order to avoid obscuring, or obscuring, the focus of the present application. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

In the embodiments of the present application, the terms "first", "second", "third", and "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, features defined as "first", "second", "third", "fourth" may explicitly or implicitly include one or more of the features.

In the description of the embodiments of the present application, it should be noted that the terms "mounted" and "connected" are to be interpreted broadly, unless explicitly stated or limited otherwise, and for example, "connected" may or may not be detachably connected; may be directly connected or indirectly connected through an intermediate. The directional terms used in the embodiments of the present application, such as "upper", "lower", "left", "right", "inner", "outer", and the like, are merely directions referring to the drawings, and thus, are used for better and clearer illustration and understanding of the embodiments of the present application, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the embodiments of the present application. "plurality" means at least two.

Reference throughout this specification to "one embodiment" or "some embodiments," or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the present application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," or the like, in various places throughout this specification are not necessarily all referring to the same embodiment, but rather mean "one or more but not all embodiments" unless specifically stated otherwise. The terms "comprising," "including," "having," and variations thereof mean "including, but not limited to," unless expressly specified otherwise.

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

(1) An optical waveguide:

the optical waveguide refers to an optical element that guides a light wave to propagate by total reflection in itself by using the principle of total reflection. A common optical waveguide can be a guided structure made of an optically transparent medium (e.g., quartz glass) that transmits electromagnetic waves at optical frequencies. The optical waveguide may be specifically classified into a planar structure and a strip structure.

Fig. 1 shows a schematic diagram of a structure of an optical waveguide 110. Referring to fig. 1, one side of the optical waveguide 110 is a medium m ₁ The other side is a medium m ₂ . The refractive index of the optical waveguide 110 is n ₀ Medium m of ₁ Has a refractive index of n _m1 Medium m of ₂ Has a refractive index of n _m2 Wherein n is ₀ ＞n _m1 And n is ₀ ＞n _m2 . Medium m ₁ And medium m ₂ May be a material having a relatively small refractive index. For example, as shown in FIG. 1, medium m ₁ And medium m ₂ All are air. As another example, medium m ₁ And medium m ₂ One of which is air and the other of which is a film covering the surface of the optical waveguide 110. As another example, medium m ₁ And medium m ₂ May be a film covering the surface of the optical waveguide 110.

Light i from the medium m ₂ After being refracted into the optical waveguide 110, the light beam i propagating to the bottom surface of the optical waveguide 110 is not refracted into the medium m so that the light beam i incident to the bottom surface of the optical waveguide 110 can be totally reflected ₁ Angle of incidence θ of light ray i on the bottom surface _r Greater than critical angle C ₁ . Wherein the critical angle C ₁ ＝arcsin(n _m1 /n ₀ )。

The light i is totally reflected at the bottom surface of the optical waveguide 110 at an incident angle θ ₂ Incident on the top surface of the optical waveguide 110. Similarly, the light i incident on the top surface of the optical waveguide 110 is totally reflected, rather than refracted into the medium m ₂ Angle of incidence θ of light ray i on the top surface _m Greater than critical angle C ₂ . Wherein the critical angle C ₂ ＝arcsin(n _m2 /n ₀ )。

Thus, the light i is repeatedly propagated by total reflection in the optical waveguide 110.

(2) Diffractive light waveguide:

a diffractive optical waveguide is an optical device in which a grating is provided on an optical waveguide. The grating, which may also be referred to as a diffraction grating, has a parallel slit structure, which can change the propagation direction of light. By arranging the diffraction grating on the optical waveguide, external light can be coupled into the optical waveguide at a designated position of the optical waveguide and coupled out at the designated position.

Fig. 2 (a) shows a perspective view of a diffractive light waveguide 100. Fig. 2 (b) shows an optical path diagram of one diffractive light waveguide 100. For convenience of description, the present application first defines an X-axis direction (as a first direction), a Y-axis direction, and a Z-axis direction with reference to fig. 2 (a) and 2 (b). The X-axis direction is a traveling direction of light in the diffractive light waveguide 100, the Z-axis direction is a thickness direction of the diffractive light waveguide 100 (may also be referred to as a height direction of the diffractive light waveguide 100), and the Y-axis direction is perpendicular to the X-direction and the Z-direction. In the present application, the thickness dimension of each member is the dimension of the member in the Z-axis direction.

As shown in fig. 2 (a), the diffractive light waveguide 100 includes an optical waveguide 110, and a light incoupling device 120 and a light outcoupling device 130 disposed on a surface of the optical waveguide 110. The light incoupling device 120 is configured to couple light into the optical waveguide 110, the light outcoupling device 130 is configured to couple light out of the optical waveguide 110, and the light incoupling device 120 and the light outcoupling device 130 may be surface relief gratings, holographic gratings, or super-surface devices.

As shown in fig. 2 (b), after the light i is incident into the light incoupling device 120, the light i is emitted to the bottom surface of the light waveguide 110 through the light incoupling device 120, and is repeatedly propagated by total reflection between the top surface 114 (or "first surface") and the bottom surface 115 (or "second surface") of the light waveguide 110 in a guiding direction of the positive X-axis direction. The top surface 114 and the bottom surface 115 of the optical waveguide are two surfaces that are opposite to each other in the thickness direction (i.e., the Z-axis direction) of the optical waveguide.

When the ray i reaches P ₁ In position, the light ray i is divided into light rays i ₁₁ And a light ray i ₁₂ Light ray i ₁₁ Is coupled out of the optical waveguide 110 by the light outcoupling device 130, the light i ₁₂ Continue to propagate by total reflection in the optical waveguide 110, the light i ₁₂ Is transmitted by total reflection and enters P ₂ While in position, the above phenomenon is repeated again, i.e. light i ₁₂ Is divided into light rays i ₁₃ And a light ray i ₁₄ Light ray i ₁₃ Is coupled out of the optical waveguide 110 by the light outcoupling device 130, light i ₁₄ The total reflection propagation in the optical waveguide 110 is continued, and the above-mentioned phenomenon is repeated until all the light propagating in the optical waveguide 110 is coupled out of the optical waveguide 110. Incident lightLine i corresponds to a plurality of outgoing rays (e.g., outgoing ray i) ₁₁ 、i ₁₃ 、i ₁₅ ) The plurality of outgoing light rays are emitted from different positions of the light out-coupling device 130, and thus the light rays coupled out by the light out-coupling device 130 are amplified in the X-axis direction, which is called "exit pupil expansion".

It will be appreciated that in conventional optical imaging systems, the image typically has only one "exit" known as the "exit pupil". For example, since the light with a diameter of 2 mm is incident into the light guide and the light guide only takes charge of transmission and does not enlarge or reduce the image, the exit pupil is also the light with a diameter of 2 mm, in which case, the moving range of the image can be seen in the center of the pupil of the human eye is only 2 mm. As shown in fig. 2 (b), the exit pupil can be duplicated in multiple numbers in the X-axis direction by providing the diffraction grating on the optical waveguide 110, and each exit pupil can output the same image, thereby increasing the moving range of the image that can be seen by the pupil center of the human eye, so that the human eye can see the image even when moving in a wide range, which is called "exit pupil expansion".

For ease of understanding, the total reflection step is described first, and as shown in fig. 2 (b), each time the light ray i encounters the top surface 114 of the optical waveguide 110, total reflection occurs at a position on the top surface 114 of the optical waveguide 110, and the distance between any two adjacent positions is referred to as the total reflection step. For example, P ₁ Position and P ₂ The distance between the positions is the total reflection step f of the light ray i in the diffractive light waveguide 100. The length of the total reflection step length f is positively correlated with the thickness D of the optical waveguide 110, that is, the larger the thickness D of the optical waveguide 110 is, the longer the total reflection step length f is; conversely, the smaller the thickness D of the optical waveguide 110, the shorter the total reflection step f.

The following will continue to describe the optical device and the near-eye display apparatus provided by the present application.

The near-eye Display device may be Augmented Reality (AR) glasses, virtual Reality (VR) glasses, mixed Reality (MR) glasses, AR/VR/MR masks, helmets, head Up Displays (HUDs), and the like, which is not limited in this application. For convenience of description, AR glasses will be hereinafter exemplified as the near-eye display device.

Fig. 3 shows a schematic structural view of AR glasses 200 in some embodiments of the present application. As shown in fig. 3, the AR glasses 200 include a frame 210, and a lens 220 and an opto-mechanical 230 secured to the frame 210. Wherein frame 210 includes left temple 211, right temple 212, and lens frame 213. The lens 220 includes a left lens 221 and a right lens 222, and the left lens 221 and the right lens 222 are fixed in the lens frame 213. The optical engine 230 is used for projecting the virtual image into the lens 210, and guiding the virtual image to human eyes through the lens 210. The optical machine 230 may be a micro-display for projecting image light to the lens. In this application, the optical device 230 may be any one of a Liquid Crystal On Silicon (LCOS) Display, a Micro Light Emitting Diode (Micro led) Display, a Digital Light Processing (DLP) Display, a Laser Beam Scanning (LBS) Display, and the like, as long as it can emit image Light.

The number of the optical engines 230 may be one or more. In some embodiments, as shown in fig. 3, the optical engine 230 is one and disposed in the middle of the lens frame 213, and can project image light to the left lens 221 and the right lens 222 simultaneously. In other embodiments, there are two optical engines 230, each provided on left temple 211 and right temple 212 of frame 210, or on an extended area of left temple 211 or right temple 212, respectively, facing the front of the human eye, said two optical engines 230 being used to project image light to left lens 221 and right lens 222, respectively.

At least one of the left optic 221 and the right optic 222 has an optical waveguide structure (e.g., the diffractive optical waveguide 100 described above). The optical waveguide structure is used for receiving the image light projected by the optical engine 230 and emitting the image light at a designated position of the lens 220, so as to guide the image light into human eyes.

Fig. 4 shows a schematic diagram of light coupling into the human eye through the left lens 221 or the right lens 222 of the AR glasses 200. As shown in fig. 4, point light emitted from the optical engine 230 is converted into parallel light through a collimating lens (not labeled) and projected into the optical incoupling device 120, the optical incoupling device 120 couples the light into the optical waveguide 110, the light is propagated by total reflection in the optical waveguide 110, during the process of total reflection propagation, when the light encounters the optical outcoupling device 130, a part of the light is outcoupled into human eyes through the optical outcoupling device 130, and the remaining other part of the light is continuously propagated by total reflection in the optical waveguide 110, and the above-mentioned phenomenon is repeated until all the light propagated by total reflection in the optical waveguide 110 is outcoupled out of the optical waveguide 110, thereby realizing exit pupil expansion in the X-axis direction. Therefore, when wearing the AR glasses, the user can see the image even when the pupil moves over a wide range.

In the case of realizing exit pupil expansion, the problem of exit pupil discontinuity, that is, the image may be lost or flicker when the human eye moves continuously within a certain range, may occur. Figure 5 (a) shows a schematic diagram of exit pupil discontinuity. As shown in fig. 5 (a), the total reflection step f is too long, and at this time, a gap d exists between the exit pupils 300, and when the human eye moves to the gap d during the observation process, image loss or flicker occurs, and the user experience is poor. Therefore, to ensure the exit pupil is continuous, the total reflection step f needs to be reduced as much as possible. Fig. 5 (b) shows a schematic diagram of exit pupil continuity, as shown in fig. 5 (b), when the total reflection step length f is short, the extended exit pupils 400 overlap each other, no matter where the human eyes observe, the problem of image missing does not occur, and the problem of exit pupil discontinuity is effectively avoided.

However, the shorter total reflection step f causes secondary diffraction of light at the light incoupling device 120, resulting in a loss of energy. Fig. 6 (a) shows a schematic diagram of the occurrence of secondary diffraction. As shown in fig. 6 (a), light is incident into the optical waveguide 110 through the optical coupler 120, after a total reflection is performed on the bottom surface of the optical waveguide 110 for one time, the light is incident into the optical coupler 120 again, and the light incident into the optical coupler 120 may be diffracted for a second time, that is, the light incident into the optical coupler 120 may be split into two parts of light at the optical coupler 120, where a part of light is diffracted out of the optical waveguide 110 through the optical coupler 120, and another part of light continues to be propagated by a total reflection in the optical waveguide 110, thereby causing energy loss waste.

In order to ensure that the energy can be effectively utilized, it is necessary to ensure that no secondary diffraction occurs at the optical coupler 120, that is, all light rays can be totally reflected and propagate forward in the optical waveguide 110 after passing through the optical coupler 120, and the total reflection step length f needs to be long enough. Fig. 6 (b) shows a schematic diagram in which no secondary diffraction occurs. As shown in fig. 6 (b), the light coupled into the optical waveguide 110 via the light incoupling device 120 is totally reflected once and is not incident on the light incoupling device 120 again.

As can be seen from fig. 5 (a) to fig. 6 (b), if the total reflection step length f is too short, the light will be diffracted twice at the optical incoupling device 120, which results in energy waste, and if the continuity of the exit pupil is to be ensured, the total reflection step length f cannot be too long, which are contradictory to each other on the optical path, so that an optical waveguide structure needs to be provided, and the requirements of avoiding energy waste and ensuring continuous exit pupil are met.

For the convenience of the following description, the region for light coupling-in the diffractive light waveguide is first defined as a light coupling-in region S ₁ The region for light out-coupling in the diffractive light waveguide is defined as a light out-coupling region S ₂ . In the light-coupling-out region S ₂ The light is emitted from one surface of the optical waveguide, and the surface is defined as a light-emitting surface.

In some technical schemes, a transmission-type coupling-out grating is arranged on the light-emitting surface of the optical waveguide, and a reflection-type coupling-out grating is arranged on the surface opposite to the light-emitting surface, so that two mutually contradictory conditions of no secondary diffraction and extended exit pupil continuity are met.

FIG. 7 illustrates a schematic diagram of a diffractive optical waveguide 100a in some embodiments. As shown in fig. 7, the diffractive light guide 100a includes an optical waveguide 110, and a light incoupling device 120, a light outcoupling device 130a, and a light outcoupling device 130b provided on the optical waveguide 110.

The light incoupling device 120 is located in the light incoupling region S ₁ And is disposed on a surface of the optical waveguide 100. The transmissive light outcoupling device 130a and the reflective light outcoupling device 130b are both located in the light outcoupling region S ₂ In particular, the light out-coupling device 130a is arranged at the light exit surface of the light guide 110. The light out-coupling means 130b are arranged at the light waveThe other surface of the optical waveguide 110 is opposite to the light emitting surface of the optical waveguide 110.

Based on this, the light is coupled into the optical waveguide 110 through the optical incoupling device 120 and is totally reflected and propagated in the optical waveguide 110, the light propagated to the optical outcoupling device 130b is divided into two parts, one part is diffracted light, the other part is reflected light, is reflected to the optical outcoupling device 130a and is again divided into two parts, one part is diffracted light, the other part is transmitted light, and is reflected to the optical outcoupling device 130b, and the above phenomenon is repeated until all the light totally reflected and propagated in the optical waveguide 110 is coupled out of the optical waveguide 110.

As can be seen from the foregoing, the length of the total reflection step is in positive correlation with the thickness of the optical waveguide 110, and the diffractive optical waveguide 100a adopts the thick optical waveguide 110 to ensure that the light is coupled into the light coupling region S ₁ The total internal reflection step (not indicated) is long enough to avoid secondary diffraction of the light at the light incoupling device 120.

In addition, in the diffractive optical waveguide 100a, the periods of the light out-coupling device 130a and the light out-coupling device 130b are the same, and the directions of the periods are the same, so that the problem of aliasing of images formed by the coupled-out light rays is avoided. Meanwhile, because the periods of the transmissive light outcoupler 130a and the reflective light outcoupler 130b are the same, the incident angle of the light beam coupled from the light incoupling device 120 to the transmissive light outcoupler 130a and the incident angle of the light beam coupled to the reflective light outcoupler 130a are also the same, so the diffraction angles of the transmissive light outcoupler 130a and the reflective light outcoupler 130b are the same, and the purpose of continuously expanding the exit pupil is achieved.

According to the structure of the diffractive light waveguide 100a, it is difficult to find that, due to errors, it is technically difficult to ensure that the periodic directions of the transmissive light outcoupling device 130a and the reflective light outcoupling device 130b are completely consistent, which finally results in a problem of poor imaging quality. In addition, since the thickness of the optical waveguide 110 is thick, the weight of the diffractive optical waveguide 100a is heavy, and the user experience is affected after the diffractive optical waveguide 100a is applied to the AR glasses.

In other technical schemes, a light splitting film is added in the diffraction light waveguide so as to simultaneously meet two conditions of no secondary diffraction and continuity of extended exit pupil of light at the light incoupling device.

FIG. 8 shows a schematic structural view of another diffractive optical waveguide 100b in some embodiments. As shown in fig. 8, the diffractive light waveguide 100b includes a light waveguide 110, a light incoupling device 120, a light outcoupling device 130b, and a light splitting film 140. Wherein the light out-coupling device 130b is a reflective light out-coupling grating. The light incoupling device 120 is located in the light incoupling region S ₁ And is disposed on a surface of the optical waveguide 110. The light out-coupling device 130b and the light splitting film 150 are both located in the light out-coupling area S ₂ In particular, the light outcoupling device 130b is provided on the surface of the optical waveguide 110, and the spectroscopic film 150 is provided inside the optical waveguide 110 and extended along the X-axis direction.

The optical coupler 120 couples light into the optical waveguide 110, and the light propagates through the optical waveguide 110 by total reflection repeatedly, and when the light propagates to the light splitting film 150 at each time, the light is divided into two beams: reflected light and transmitted light. The reflected light is reflected to the light-emitting surface of the optical waveguide 110, a part of the reflected light is emitted from the light-emitting surface, and the remaining part of the reflected light is reflected to the light-splitting film 150 from the light-emitting surface, and is continuously split into two beams of light by the light-splitting film 150, and the two beams of light are circularly reciprocated; the transmitted light passes through the light splitting film 150 to the light out-coupling device 130b, a part of the transmitted light is coupled out from the light emitting surface of the optical waveguide 110, the remaining part of the transmitted light is reflected from the light out-coupling device 130 to the light splitting film 150, and is continuously split into two light beams by the light splitting film 170, and the above-mentioned phenomenon is continuously repeated until the light in the optical waveguide 110 is completely coupled out of the optical waveguide 110.

The diffractive optical waveguide 100b ensures light in the light-coupling region S by using the thick optical waveguide 110 ₁ The total internal reflection step (not indicated) is long enough to avoid secondary diffraction of the light at the light incoupling device 120. Meanwhile, in the light out-coupling region S of the light guide 110 ₂ Two thin optical waveguides 110 are bonded by a light splitting film to reduce the light coupling-out area S ₂ Total internal reflection step (not labeled) to avoid the problem of extended exit pupil discontinuity. But due to the fact thatA light splitting film is added between the two layers of thin optical waveguides 110, and the transmittance of the diffraction optical waveguide 100b is reduced, so that poor imaging quality is caused. In addition, like the diffractive optical waveguide 100a, since the thickness of the optical waveguide 110 is thick, the weight of the diffractive optical waveguide 100b is difficult to be reduced, and the user experience is poor.

In order to solve the above problems, the present application provides a diffractive light waveguide (or "optical device") to avoid the occurrence of secondary diffraction of light, so as to ensure the continuity of the exit pupil, and in addition, the weight can be effectively reduced, thereby further improving the user experience. The following detailed description is made with reference to the accompanying drawings. Fig. 9 shows a schematic structural diagram of a diffractive optical waveguide 100 provided in an embodiment of the present application. As shown in fig. 9, diffractive light guide 100 includes an optical waveguide 110, and an optical incoupling device 120, an optical outcoupling device 130, and a diffractive device 140 provided on optical waveguide 110.

Fig. 10 shows a schematic view of the structure of the optical waveguide 110 in the diffractive optical waveguide 100. As shown in fig. 9 and 10, the optical waveguide 110 includes a first portion 111, a second portion 112, and a third portion 113, and the first portion 111, the second portion 112, and the third portion 113 are sequentially connected in the X direction (as a first direction). The top surface 116a of the first portion 111, the top surface 117a of the second portion 112, and the top surface 118a of the third portion 113 are sequentially connected to form the top surface 114 of the optical waveguide 110, and the top surface 114 is a plane. The bottom surface 116b of the first portion 111, the bottom surface 117b of the second portion 112, and the bottom surface 118b of the third portion 113 are connected in sequence to form the bottom surface 115 of the light guide 110. Wherein the bottom surface 116b of the first portion 111 and the bottom surface 118b of the third portion 113 are parallel to the top surface 114 of the optical waveguide 110, and the bottom surface 117b of the second portion 112 is inclined with respect to the top surface 114 of the optical waveguide 110, such that the thickness D of the first portion 111 ₁ Greater than the thickness D of the third portion 113 ₂ 。

As can be seen from fig. 9 and 10, the light incoupling device 120 is disposed on the first portion 111 of the light guide 110, and the light outcoupling device 130 is disposed on the third portion 130 of the light guide 110, so that external light can be coupled into the light guide 110 through the light incoupling device 120 and coupled out of the light guide 110 through the light outcoupling device 130.

Specifically, the light incoupling device 120 is provided on the top surface 116a of the first portion 111 of the light guide 110 and the light outcoupling device 130 is provided on the top surface 118a of the third portion 113 of the light guide 110. In other embodiments, the light incoupling means 120 may also be provided on the bottom surface 116b of the first portion 111 of the light guide 110 and/or the light outcoupling means 140 may be provided on the bottom surface 118b of the third portion 113 of the light guide 110.

Light diffraction device 140 is disposed on bottom surface 117b of second portion 112 of optical waveguide 110, and light diffraction device 140 diffracts light into third portion 113 when the light is incident from first portion 111 to bottom surface 115 of second portion 112. In this embodiment, bottom surface 117b of second portion 112 is a plane, so as to reduce the difficulty in manufacturing diffraction device 140. In other embodiments, the bottom surface 117b of the second portion 112 may also be curved.

In the above-described diffractive optical waveguide 100, light is coupled into the first portion 111 of the optical waveguide 110 through the light incoupling device 120, and the thickness D of the first portion 111 ₁ Larger, therefore, the total reflection step (e.g. total reflection step f in FIG. 11) of the light coupled into the optical waveguide 110 in the first portion 111 ₁ ) Long enough to avoid secondary diffraction of the light at the light incoupling device 120. The light at the first portion 111 travels through the second portion 112 to the third portion 113. The light propagating to the third portion 113 is coupled out of the third portion 113 of the optical waveguide 110 by the light out-coupling device 130 arranged at the third portion 113, and the thickness D of the third portion 113 ₂ Smaller, thereby causing the total reflection step of the light within the third portion 113 (e.g., total reflection step f in FIG. 11) ₂ ) Sufficiently short to ensure continuity of the extended exit pupil. Meanwhile, compared with the prior art, the structure of the diffractive light waveguide 100 is more compact, and the thickness of the light waveguide 110 is smaller, so that the diffractive light waveguide in the application can effectively reduce the weight and further improve the user experience under the condition of ensuring that the exit pupil is continuous and does not generate secondary diffraction.

FIG. 11 shows a light ray L ₁ For example, the propagation of light in diffractive light waveguide 100 is shown. As shown in fig. 11, the light ray L ₁ Is coupled into the first part 111 by the light incoupling means 120 and propagates with total reflection in the first part 111. Then, the light L ₁ From the first portion 111 into the second portion 112 and to the bottom surface of the second portion 112. In the present embodiment, a light ray incident from the first portion 111 to the bottom surface of the second portion 112 is defined as a first light ray La. After the first light La is incident on the bottom surface 117b of the second portion 112, the diffraction device 140 diffracts it to generate diffracted light Lb. In this embodiment, an angle between the diffracted light Lb and the set reference axis S (e.g., Z axis) is referred to as a first angle θ ₁ . That is, the diffraction device 140 may cause the first light La to be at the first angle θ ₁ Diffracting into the third portion 113.

At a first angle theta ₁ Light L diffracted to the third portion 113 ₁ Propagating in the third portion 113 as a total reflection ₁ When reaching the light out-coupling device 130, a part of the light L ₁₁ The third portion 113 is coupled out by the light outcoupling device 130, and the remaining other portion of the light L ₁₂ Continues to propagate within the third portion 113 of the optical waveguide 110 and repeats the above-described phenomenon, i.e., when the light L is incident ₁₂ Incident on the light outcoupling device 130 is divided into two parts, a part of the light L ₁₃ The light guide 110 is coupled out by the light out-coupling device 130, and the remaining part of the light L ₁₄ The total reflection propagation in the third portion 113 of the light guide 110 continues, and so on, until all the light rays are coupled out of the third portion 113, thereby realizing exit pupil expansion in the X-axis direction.

Fig. 12 shows a schematic diagram of the total reflection of the first ray La at the first portion 111 according to fig. 11. For convenience of description, the second angle θ is defined in conjunction with fig. 12 ₂ As shown in fig. 12, when the first light La is emitted to the bottom surface 116b of the first portion 111, a reflected light Lc is generated, and an included angle between the reflected light Lc and the set reference axis S (e.g., the Z axis) is defined as two angles θ ₂ . Wherein, the first angle θ corresponding to the first light La ₁ To a second angle theta ₂ The difference between them is less than the first threshold. That is, the diffracted light ray Lb corresponding to the first light ray La can propagate to the third portion 113 along the propagation direction of the reflected light ray Lc, so that the diffracted light waveguide 100 avoids the problem of image aliasing.

In some embodiments of the present application, the first threshold value ranges from 0 ° to 1 °, for example, the first threshold value may be 0.2 °, and for example, the first threshold value may also be 0.3 °. In the examples of the present application, the numerical ranges include the end values. For example, a numerical range of 0 ° to 1 ° includes 0 ° and 1 °.

An exemplary arrangement of diffractive device 140 is described below.

In the embodiment of the present application, the diffraction device 140 includes one or more holographic gratings, wherein the holographic gratings are formed by directly interfering light and dark distributed interference fringes inside a holographic material (for example, a micron-sized holographic material) by means of a two-photon holographic exposure. Fig. 13 shows a schematic structural view of a holographic grating. As shown in fig. 13, the holographic grating 150 includes a holographic material 151 and a plurality of stripes 152 uniformly arranged in the holographic material 151, and the stripes 152 include light stripes 152a and dark stripes 152b distributed at intervals. Wherein the sum of the widths of any adjacent set of the light stripe 152a and the dark stripe 152b is the grating period d of the holographic grating, and any stripe 152 is the grating normal l _a The included angle between the two is a stripe dip angle theta _n For example, dark fringe 152b and grating normal l in FIG. 13 _a The included angle between the two is a stripe dip angle theta _n 。

Fig. 14 shows a schematic diagram of diffraction of the first light ray La at the hologram grating 150 corresponding to fig. 11. Referring to fig. 14, the parameters of the first light La and the holographic grating 150 satisfy the following relation:

wherein, theta _d Is the diffraction angle of the first light ray La at the holographic grating 150; theta _in Is the incident angle of the first light ray La at the holographic grating 150; n is ₁ Is the refractive index of the incident medium (i.e., optical waveguide 110); n is ₂ Is the refractive index of the exit medium (also optical waveguide 110); λ is the wavelength of the first light La; d is the grating period of the holographic grating 150.

As can be seen from the combination of FIG. 11, FIG. 14 and the above formula (1), the first step isWavelength λ of light ray La, incident angle θ of first light ray La at holographic grating 150 _in At a certain time, the grating period d of the holographic grating 150 and the diffraction angle θ of the first light La at the holographic grating 150 _d In a negative correlation relationship, the smaller the grating period d of the holographic grating 150, the smaller the diffraction angle θ of the first light La at the holographic grating 150 _d The larger the grating period d of the holographic grating 150, the larger the diffraction angle θ of the first light La at the holographic grating 150 _d The smaller.

As can be seen from fig. 11 and 14 and the above formula (1), the diffraction angle θ of the first light La at the diffraction device 140 can be achieved by adjusting the grating period d of the holographic grating 150 _d So that the first angle theta ₁ And a second angle theta ₂ Is less than a set threshold. In addition, fringe Normal l _b Is an angular bisector of an angle between the first ray La and the diffracted ray Lb.

It can be understood that the grating period d and the fringe inclination angle theta of the holographic grating 150 are adjusted _n The holographic grating 150 may be caused to diffract the first light La at different angles. Fig. 15 (a) to 15 (c) show diffraction diagrams of holographic gratings of different periods and fringe inclinations. The holographic grating 150, grating period d and fringe inclination angle θ shown in FIGS. 15 (a) to 15 (c) _n The larger the grating size, the thicker the fringes 152 of the holographic grating 150, and the relative distance between the fringes 152 and the grating normal l _a Gradually becomes larger, and the incident angle θ of the first light ray La at the holographic grating 150 at the wavelength λ of the first light ray La _in Under the condition of no change, the diffraction angle theta of the first light ray La at the holographic grating _d And will be reduced accordingly.

The grating period d and the fringe tilt angle θ are described below _n Exemplary adjustment methods of (a).

Exposing the holographic material 151 at a certain exposure angle by different light rays to obtain a light beam having a specific grating period d and a specific fringe inclination angle theta _n The holographic grating 150. Fig. 16 exemplarily shows an exposure method of the holographic grating. As shown in fig. 16, a light ray i is used ₁ And a light ray i ₂ Exposing the holographic material 151 at an exposure angleLight. Exposure angle is ray i ₁ Incident angle θ incident to the holographic material 151 _i1 And a light ray i ₂ Incident angle theta to the holographic material 141 _i2 . Wherein the light ray i ₁ Incident angle theta of the holographic material 151 _i1 The incident angle theta of the first light La on the holographic grating 150 _in Equal, ray i ₂ Incident angle θ incident to the holographic material 151 _i2 Diffraction angle theta with first light ray La at holographic grating 150 _d Are equal.

In general, the diffractive optical waveguide 100 can receive light L at multiple angles ₁ And thus can have a certain field angle range. When the light L is ₁ When the light is incident into the diffractive light waveguide 100 at different angles, a plurality of first light La with different angles is generated. For example, fig. 17 (a) to 17 (c) show optical path diagrams of first light rays La at different angles within the diffractive light waveguide 100. As can be seen from fig. 17 (a) to 17 (c), the light L ₁ The first light La1, the first light La2 and the first light La3 with three different angles are generated when the light enters the diffractive optical waveguide 100 at three different angles.

In order to make the plurality of first light rays La propagate correctly in the diffractive light waveguide 100, in the present embodiment, the diffraction device 140 includes a plurality of holographic gratings 150, and different holographic gratings 150 can diffract the first light rays La at different angles. Illustratively, the incident angle θ of the first light ray La at the holographic grating 150 _in The range of (a) is 35 to 55 degrees. For example, the incident angle θ of the first light La1 at the holographic grating 150 _in Is 36 degrees, and the incidence angle theta of the first light ray La2 at the holographic grating 150 _in Is 38 DEG, and the incidence angle theta of the first light ray La2 at the holographic grating 150 _in Is 40 deg..

Fig. 18 (a) shows an exposure schematic diagram of the hologram grating 150a diffracting the first light La 1. As can be seen from FIGS. 17 (a) and 18 (a), the light ray i is used ₁ And a light ray i ₂ The holographic material 151 is exposed to light, wherein the light i ₁ Is parallel to the direction of the first light ray La1, i.e. the light ray i ₁ Incident angle theta of the holographic material 151 _i1 An incident angle theta of the first light La1 at the holographic grating 150 _in Equal; light ray i ₂ Is parallel to the direction of the diffracted light Lb1 corresponding to the first light La1, i.e. the light i ₁ Incident angle theta of the holographic material 151 _i1 Diffraction angle θ from first light La1 at holographic grating 150 _d Are equal. The hologram grating 150a obtained by the above exposure method can cause the first light La1 incident to the hologram grating 150a to propagate in a correct direction.

Fig. 18 (b) shows an exposure schematic diagram of the hologram grating 150b diffracting the first light La 2. Fig. 18 (c) shows an exposure schematic diagram of the hologram grating 150c diffracting the first light La3. The exposure method of the holographic grating 150b and the holographic grating 150c is the same as that of the holographic grating 150a, and is not described herein.

In the present embodiment, a plurality of holographic gratings 150 are superimposed in a sequentially stacked manner to form the diffraction device 140. For example, the hologram grating 150a, the hologram grating 150b, and the hologram grating 150c obtained by exposure in fig. 18 (a) to 18 (c) are stacked in a sequential manner to form the diffraction device 140, and the diffraction device 140 can enable the first light La1, the first light La2, and the first light La3 in fig. 17 (a) to 17 (c) to correctly propagate in the optical waveguide 110, thereby avoiding the problem of image aliasing in the diffractive optical waveguide 100 and effectively expanding the display range of images.

In other embodiments, diffractive device 140 is a volume holographic grating 160. The volume hologram grating 160 is formed by multiple exposures. That is, the volume holographic grating 160 may be understood as a plurality of holographic gratings 150 integrated in the same holographic material. For example, FIG. 19 shows a volume holographic grating 160 having a plurality of different grating periods and fringe tilt angles. As shown in fig. 19, the holographic material 151 is exposed a plurality of times, thereby obtaining a volume hologram grating 160 having a plurality of different grating periods and fringe inclinations. The specific exposure method is the same as the exposure method of the holographic gratings 150a, 150b, and 150c, and is not repeated herein. The volume hologram grating 160 can diffract the first light La1, the first light La2, and the first light La3 shown in fig. 17 (a) to 17 (c) in a desired direction at the same time, and the diffraction light waveguide 100 having the volume hologram grating 160 is applied to the AR glasses 200, and the angle of field can be significantly increased.

In other embodiments, diffractive device 140 may also be a super-surface device.

The third angle θ provided by the present embodiment is described below with reference to fig. 10 and 20 to 22 (b) ₃ In an exemplary arrangement, wherein the third angle θ ₃ Is the angle of the bottom surface 117b of the second portion 112 with the X-axis direction.

Third angle theta ₃ If the length of the diffraction device 110 is too small, the length of the optical waveguide 110 needs to be increased to make the optical waveguide 110 have the same thickness, which increases the cost and makes the manufacturing of the diffraction device 140 more difficult; third angle theta ₃ If too large, the bottom surface 117b of the second portion 112 will be made too steep, so that light striking the bottom surface 117b will propagate in the negative X-axis direction, resulting in an abnormal operation of the diffractive light waveguide 100.

FIG. 20 illustrates light L in some embodiments ₁ Schematic representation of the negative direction propagation along the X-axis in a diffractive light waveguide 100. As shown in fig. 20, in the diffractive light waveguide 100, the light L incident from the first portion 111 to the bottom surface 117b of the second portion 112 ₁ Does not continue to the third portion 113 but returns to the first portion 111, the light ray L ₁ The light cannot be coupled out from the third portion 113 through the light out-coupling device 130, which may result in the diffractive optical waveguide 100 not operating properly.

Therefore, in this embodiment, the third angle θ is set ₃ The angle is set to 5.5-20 degrees, so that the manufacturing difficulty of the diffraction device 140 is further reduced while the normal work of the diffraction light waveguide 100 is ensured. For example, the third angle θ ₃ Is 6 deg., and a third angle theta ₃ Is 7 deg..

In the following example, referring to fig. 10, assuming that the dimension of the light incoupling device 120 in the X-axis direction is 4mm, the thickness D of the third portion 113 is ₂ 0.5mm, refractive index n of the optical waveguide 110 ₀ Is 2, the first light ray La forms an included angle theta with the Z-axis direction ₄ Is 30-75 degrees.

FIG. 21 shows the bottom surface of the second portion 112 obtained according to FIG. 10117b are shown schematically in size. For the convenience of the following description, the dimension of the bottom surface 117b of the second portion 112 along the Z-axis direction is defined as a first dimension l in conjunction with fig. 10 and 18 ₁ The bottom surface 117b of the second portion 112 is disposed at a third angle θ with respect to the X-axis direction ₃ Is defined as a second dimension l ₂ 。

FIG. 22 (a) is a schematic diagram showing the dimension parameters of the first light ray La and the diffractive light waveguide 100 according to some embodiments of the present application, wherein the third angle θ ₃ Is 5.5 degrees. As can be seen from a combination of FIGS. 18 and 22 (a), the third angle θ is ₃ At 5.5 deg. corresponding to the first dimension l ₁ Set to 2.9mm, second dimension l ₂ Is 3cm, and the included angle theta between the first light ray La and the Z-axis direction ₄ Can be 30 degrees, and can avoid light L ₁ The second diffraction occurs at first portion 111 and reduces the practical difficulty of fabricating diffractive device 140.

FIG. 22 (b) is a schematic diagram showing the dimension parameters of the first light ray La and the diffractive light waveguide 100 according to some embodiments of the present application, wherein the third angle θ ₃ Is 20 deg.. As can be seen from a combination of FIGS. 18 and 22 (b), the third angle θ is ₃ At 20 deg. corresponding to the first dimension l ₁ Set to 3.4mm, second dimension l ₂ Is 1cm, and the included angle theta between the first light ray La and the Z-axis direction ₄ May be 70 deg., so that the light L is directed ₁ No second diffraction occurs at first portion 111 and continues through diffractive device 140 to third portion 113.

It is to be understood that the dimensional parameters in fig. 10, 22 (a), and 22 (b) are merely exemplary illustrations. In other embodiments, other dimensional parameters may be set as desired.

With continued reference to fig. 9, for ease of description, the dimension of the light out-coupling device 130 along the X-axis direction is defined as the length dimension l of the light out-coupling device 130 ₃ . The light rays emitted into the light guide 110 are coupled out of the light guide 110 through the light out-coupling device 130, and if the number of coupling-out times of the light rays at the light out-coupling device 130 is too large, the coupled-out light rays are not uniformly distributed, so that the image formed by the light rays is uneven in brightness and darkness, and the imaging quality is poor; if the light is outcoupled at the light outcoupling device 130 for too many timesA small number will result in a small number of expanded exit pupils, which in turn results in a small imaging range.

In the present embodiment, the length dimension l of the light out-coupling device 130 ₃ And the thickness D of the third part ₂ The ratio of (a) to (b) is 2 to 10, for example, 2,4, etc., so as to uniformly distribute the light coupled out of the optical waveguide 110, ensure the effectiveness of expanding the exit pupil, and further improve the imaging effect of the diffractive optical waveguide 100.

In the present embodiment, the light incoupling device 120 and the light outcoupling device 130 are diffraction gratings. In some of these implementations, the light incoupling means 120 and the light outcoupling means 130 may be surface relief gratings. For example, fig. 23 (a) to 23 (d) show structural schematic diagrams of different shapes of surface relief gratings in some embodiments of the present application, wherein, as shown in fig. 23 (a), the light incoupling device 120 and the light outcoupling device 130 may be uniform vertical surface relief gratings. The light incoupling device 120 and the light outcoupling device 130 may also be tilted surface relief gratings, wherein the tilted surface relief gratings may be designed in different structures according to actual requirements, such as a trapezoidal tilted surface relief grating in fig. 23 (b), a parallelogram tilted surface relief grating in fig. 23 (c), and a triangular tilted surface relief grating in fig. 23 (d). In other implementations, the light incoupling device 120 and the light outcoupling device 130 may also be holographic gratings.

In other embodiments of the present application, the light incoupling means 120 and the light outcoupling means 130 may also be other means, for example, super-surface means. Fig. 22 shows a schematic structure diagram of a super-surface device in some embodiments of the present application, and the light incoupling device 120 and the light outcoupling device 130 may be the super-surface device shown in fig. 24.

In other embodiments, the light incident on the first portion 111 of the diffractive light waveguide 100 may also be totally reflected at the top surface of the second portion 112 and propagate to the third portion 113 without being diffracted to the third portion 113 by the diffractive device 140. For example, FIG. 25 shows a light ray L ₂ For example, the propagation of light in the diffractive light waveguide 100 is shown. As shown in fig. 25, in the diffractive light waveguide 100, the light L ₂ By being provided in the first portionThe light incoupling means 120 of the section 111 is coupled into the first section 111 and propagates by total reflection in the first section 111, the second section 112 and the third section 113 in sequence until the third section 113 is outcoupled from the light outcoupling means 130 provided in the third section 113 and an exit pupil expansion in the X-axis direction is achieved.

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

Claims

1. An optical device comprising an optical waveguide, an optical incoupling means, an optical outcoupling means and a diffraction means, wherein:

the optical waveguide comprises a first part, a second part and a third part which are sequentially connected along a first direction, and the light in-coupling device and the light out-coupling device are respectively arranged on the first part and the third part;

the top surfaces of the first portion, the second portion and the third portion are sequentially connected to form a first surface of the optical waveguide, and the first surface is a plane;

the bottom surfaces of the first part, the second part and the third part are sequentially connected to form a second surface of the optical waveguide; a bottom surface of the first portion and a bottom surface of the third portion are parallel to the first surface, and a bottom surface of the second portion is inclined with respect to the first surface such that a thickness of the first portion is greater than a thickness of the third portion;

wherein the diffraction device is disposed on a bottom surface of the second portion.

2. The optical apparatus of claim 1, wherein the diffractive device diffracts a first light ray incident on the bottom surface of the second portion from the first portion to the third portion at a first angle, wherein a difference between the first angle and a second angle is smaller than a first threshold, and the second angle is an angle of a reflected light ray when the first light ray is incident on the bottom surface of the first portion.

3. The optical apparatus of claim 1, wherein the diffractive device comprises a plurality of holographic gratings having different fringe inclinations to diffract a plurality of different angles of the first light rays into the third portion.

4. The optical device of claim 2, wherein the diffractive device is a volume holographic grating.

5. An optical device as recited in claim 2, wherein said first light ray includes an angle of from 30 ° to 75 ° with respect to a normal to said first portion base.

6. The optical device of claim 2, wherein the first threshold is 0 ° to 1 °.

7. The optical device of claim 1, wherein the bottom surface of the second portion is inclined at an angle of 5.5 ° to 20 ° with respect to the first surface.

8. An optical device as claimed in claim 1, wherein the ratio of the length of the light out-coupling means to the thickness of the third portion is in the range of 2 to 10, the length of the light out-coupling means being the dimension of the light out-coupling means in the first direction.

9. The optical device of claim 1, wherein the bottom surface of the second portion is planar.

10. An optical device according to claim 1, wherein the light incoupling means and the light outcoupling means are diffraction gratings; alternatively, the light incoupling device and the light outcoupling device are super-surface devices.

11. A near-eye display device comprising an optical engine and the optical apparatus of claim 1, light of the optical engine being couplable into the light guide through the light incoupling means of the optical apparatus.