Diffraction optical waveguide and augmented reality display device
By using polarization selection in the diffraction optical waveguide, the combination of coupling grating, quarter-wave plate and polarizer, the problem of light leakage of the diffraction optical waveguide is solved, and the protection of user privacy is achieved.
Patent Information
- Application Number
- CN202421663004.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-15
- Publication Date
- 2025-04-25
- Estimated Expiration
- 2034-07-15
AI Technical Summary
There is light leakage problem with diffraction optical waveguides, resulting in the leakage of user's privacy.
A diffraction optical waveguide is designed, using a combination of polarization selection coupling grating, quarter-wave plate and polarizer. Through polarization selection coupling grating, the image light is converted into a circularly biased state, and a quarter-wave plate and polarizer are set on the optical path to ensure that the leakage light is blocked.
It effectively avoids light leakage, protects user privacy, and ensures the security of displayed content.
Smart Images
Figure CN222800903U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of augmented reality, and in particular to a diffraction optical waveguide and an augmented reality display device. Background Art
[0002] Waveguide display technology is one of the most challenging and complex problems in the field of augmented reality. Diffraction waveguide is a commonly used waveguide in waveguide display technology. Since the diffraction grating has multiple diffraction orders and the energy is dispersed, the improvement of energy utilization efficiency is the focus of grating design. The polarization holographic grating can efficiently diffract the incident light to a specific diffraction order, thereby achieving high diffraction efficiency for a specific wavelength range and light from a specific field of view.
[0003] But even so, the diffraction light waveguide still has the problem of light leakage, which causes the content displayed by the diffraction light waveguide to be seen by other people outside, causing the user's privacy to be leaked. Utility Model Content
[0004] In order to solve the above problems, the present application provides a diffraction optical waveguide and an augmented reality display device capable of avoiding light leakage.
[0005] A diffraction optical waveguide comprises: a waveguide substrate, a polarization selective outcoupling grating is arranged on the surface of the waveguide substrate, and the image light after the action of the polarization selective outcoupling grating is in a circularly deflected state; wherein the surface of the waveguide substrate on the side away from the human eye further comprises: a quarter wave plate and a polarizer sequentially attached along a direction away from the human eye; or, the side of the waveguide substrate away from the human eye further comprises a protective sheet, and the surface of the protective sheet further comprises: a quarter wave plate and a polarizer sequentially attached along a direction away from the human eye; or, the side of the waveguide substrate away from the human eye further comprises a protective sheet, and the surface of the waveguide substrate away from the human eye further comprises a quarter wave plate, and the surface of the protective sheet further comprises a polarizer; wherein the angle between the polarization direction of the polarizer and the fast axis direction of the quarter wave plate is 45° or -45°.
[0006] In practice, the polarization selective outcoupling grating includes a single birefringent material layer or a multi-layer stacked birefringent material layer; the birefringent material layer includes a helical structure formed by birefringent material molecules of the birefringent material.
[0007] Practically, the rotation direction of the birefringent material molecules is right-handed, the leakage light is in a right-handed circularly polarized state, and the angle between the polarization direction of the polarizer and the fast axis direction of the quarter wave plate is -45°; or, the rotation direction of the birefringent material molecules is left-handed, the leakage light is in a left-handed circularly polarized state, and the angle between the polarization direction of the polarizer and the fast axis direction of the quarter wave plate is 45°.
[0008] Practically, the refractive index of the birefringent material layer is in the range of 1.5-2.5, and the refractive index difference of the birefringent material layer is in the range of 0.05-1.
[0009] Practically, the birefringent material layer has a thickness ranging from 50 nm to 5 μm.
[0010] Practically, the tilt angle of the periodically tilted refractive index plane in the birefringent material layer is in the range of 5°-85°.
[0011] In practice, the quarter-wave plate is a first quarter-wave plate, the polarizer is a first polarizer, and the arrangement positions of the first quarter-wave plate and the first polarizer correspond to the polarization-selective outcoupling grating; a polarization-selective turning grating is also arranged on the surface of the waveguide substrate, and the polarization-selective turning grating is used to diffract light whose polarization rotation direction matches the rotation direction of the polarization-selective turning grating, wherein the surface of the waveguide substrate away from the human eye further includes: a second quarter-wave plate and a second polarizer sequentially attached in a direction away from the human eye; or, the side of the waveguide substrate away from the human eye further includes a protective sheet, and the surface of the protective sheet further includes: a second quarter-wave plate and a second polarizer sequentially attached in a direction away from the human eye. The second quarter wave plate and the second polarizer are sequentially attached in the direction of the human eye; or, the side of the waveguide substrate facing away from the human eye also includes a protective plate, the surface of the waveguide substrate facing away from the human eye also includes a second quarter wave plate, and the surface of the protective plate also includes a second polarizer; wherein the angle between the polarization direction of the second polarizer and the fast axis direction of the second quarter wave plate is 45° or -45°, so that the polarization rotation direction of the external light after passing through the second polarizer and the second quarter wave plate in sequence is mismatched with the rotation direction of the polarization selection turning grating, and the setting positions of the second quarter wave plate and the second polarizer correspond to the polarization selection turning grating.
[0012] In practice, the polarization selective turning grating includes a single birefringent material layer or a multi-layer stacked birefringent material layer; the birefringent material layer includes a helical structure formed by birefringent material molecules of the birefringent material.
[0013] In practice, the rotation direction of the birefringent material molecules is right-handed, the angle between the polarization direction of the second polarizer and the fast axis direction of the second quarter wave plate is 45°, and the external light is in a left-handed circular deflection state after passing through the second polarizer and the second quarter wave plate in sequence; or, the rotation direction of the birefringent material molecules is left-handed, the angle between the polarization direction of the second polarizer and the fast axis direction of the second quarter wave plate is -45°, and the external light is in a right-handed circular deflection state after passing through the second polarizer and the second quarter wave plate in sequence.
[0014] An augmented reality display device comprises a micro display and any of the diffractive optical waveguides described above.
[0015] The present application provides a diffraction optical waveguide and an augmented reality display device, wherein a polarization-selective coupling grating is selected as a coupling element, and the image light after the action of the polarization-selective coupling grating is in a circularly deflected state, and the leakage light is also in a circularly deflected state. In this way, a quarter-wave plate and a polarizer are sequentially arranged on the optical path away from the direction of the human eye, that is, the optical path where the leakage light leaks to the external environment, and the alignment relationship between the quarter-wave plate and the polarizer is designed, so that the leakage light in the circularly deflected state can be converted into linear polarized light whose polarization direction is inconsistent with or even perpendicular to the polarization direction of the polarizer after passing through the quarter-wave plate, and then absorbed or returned after being blocked by the polarizer, thereby avoiding light leakage and thus avoiding the leakage of user privacy.
[0016] Furthermore, in an embodiment including a turning element, the turning element uses a polarization-selective turning grating, which is used to diffract light whose polarization rotation direction matches its rotation direction, and basically does not diffract light whose polarization rotation direction does not match its rotation direction. A polarizer and a quarter-wave plate are arranged at a position on the optical path of the external light corresponding to the polarization rotation turning grating, and the alignment relationship between the quarter-wave plate and the polarizer is designed, so that the external light, after passing through the quarter-wave plate, will be converted into circularly polarized light whose polarization rotation direction is opposite to the liquid crystal rotation direction of the polarization-selective turning grating. When the circularly polarized light is incident on the polarization-selective turning grating, it will basically not be diffracted by the polarization-selective turning grating, thereby avoiding the generation of a rainbow. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0018] Figure 1 A schematic diagram of light diffraction of a polarization-selective volume holographic grating provided in an embodiment of the present application;
[0019] Figure 2 A schematic diagram of the structure of a diffractive optical waveguide provided in an embodiment of the present application;
[0020] Figure 3 A schematic diagram of the structure of another diffractive optical waveguide provided in an embodiment of the present application;
[0021] Figure 4 A schematic diagram of the structure of another diffractive optical waveguide provided in an embodiment of the present application;
[0022] Figure ID:
[0023] 100: Polarization selective volume holographic grating;
[0024] 101: Microdisplay;
[0025] 102: Image light;
[0026] 103: coupling element;
[0027] 104: polarization selective outcoupling grating;
[0028] 105: waveguide substrate;
[0029] 106: outcoupling light;
[0030] 107: Leaking light;
[0031] 108: first quarter wave plate;
[0032] 109: a first polarizer;
[0033] 110: protective sheet;
[0034] 111: external light;
[0035] 112: Polarization selective turning grating;
[0036] 113: second quarter wave plate;
[0037] 114: A second polarizing plate. DETAILED DESCRIPTION
[0038] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0039] The technical solution of the present application is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.
[0040] The present application provides a diffraction optical waveguide, comprising: a waveguide substrate, a polarization selective outcoupling grating is arranged on the surface of the waveguide substrate, and the image light after the action of the polarization selective outcoupling grating is in a circularly deflected state; wherein, the surface of the waveguide substrate on the side away from the human eye further comprises: a quarter wave plate and a polarizer sequentially attached along a direction away from the human eye; or, the waveguide substrate on the side away from the human eye further comprises a protective sheet, and the surface of the protective sheet further comprises: a quarter wave plate and a polarizer sequentially attached along a direction away from the human eye; or, the waveguide substrate on the side away from the human eye further comprises a protective sheet, and the surface of the waveguide substrate on the side away from the human eye further comprises a quarter wave plate, and the surface of the protective sheet further comprises a polarizer; wherein, the angle between the polarization direction of the polarizer and the fast axis direction of the quarter wave plate is 45° or -45°.
[0041] The polarization selective outcoupling grating may specifically be a polarization selective volume holographic grating (PVG). The polarization selective volume holographic grating has angle selectivity and polarization selectivity, and can have extremely high diffraction efficiency for light of a specific polarization state within a certain angle range.
[0042] In practice, the polarization selective outcoupling grating comprises a single birefringent material layer or a multi-layer stacked birefringent material layer; the birefringent material layer comprises a helical structure formed by birefringent material molecules of the birefringent material, wherein the birefringent material may be a liquid crystal material, and the birefringent material molecules are liquid crystal material molecules.
[0043] Practically, the coupling element (ie, polarization selective coupling grating) provided by the present application can be a right-handed polarization selective volume holographic grating or a left-handed polarization selective volume holographic grating. The image light after the polarization selective coupling grating acts is in a circularly polarized state.
[0044] refer to Figure 1 , Figure 1Schematic diagram of light diffraction of a polarization-selective volume holographic grating provided in an embodiment of the present application; the polarization-selective volume holographic grating 100 shown in the figure is a reflective grating, and light is incident on the polarization-selective volume holographic grating at an angle θ and diffracted, generating at least diffracted light of reflection order 0 (R0), reflection order 1 (R1) and transmission order 0 (T0). When the incident light is unpolarized light or linearly polarized light, the polarization rotation direction of the reflected diffraction order is opposite to that of the polarization-selective volume holographic grating, and the polarization rotation direction of the transmitted diffraction order is consistent with that of the polarization-selective volume holographic grating; when the incident light is circularly polarized light, since the polarization-selective volume holographic grating has polarization selectivity, the polarization-selective volume holographic grating basically has diffraction efficiency only for circularly polarized light with the same polarization rotation direction as the polarization-selective volume holographic grating, and basically has no diffraction efficiency for circularly polarized light with the opposite polarization rotation direction as the polarization-selective volume holographic grating. Taking the polarization selective volume holographic grating as a right-handed polarization selective volume holographic grating as an example, when unpolarized light or linearly polarized light is incident on the right-handed polarization selective volume holographic grating, diffraction occurs, and the reflected diffraction order is basically left-handed circularly polarized light, and the transmitted diffraction order is basically right-handed circularly polarized light; when right-handed circularly polarized light is incident on the right-handed polarization selective volume holographic grating, diffraction occurs, and the reflected diffraction order and the transmitted diffraction order are both right-handed circularly polarized light, and when left-handed circularly polarized light is incident on the right-handed polarization selective volume holographic grating, basically no diffraction occurs. It can be seen that the image light after the polarization selective outcoupling grating is in a circularly deflected state.
[0045] Generally, a diffraction optical waveguide is used to guide the image light emitted by a micro display to the human eye. Specifically, the diffraction optical waveguide includes a waveguide substrate, on which at least a coupling-in element and a coupling-out element are arranged. The coupling-in element couples the image light emitted by the micro display into the waveguide substrate, and after the image light is totally reflected in the waveguide substrate and transmitted to the coupling-out element, the coupling-out element couples the image light out of the waveguide substrate and into the human eye.
[0046] However, since grating diffraction has transmission orders and reflection orders in opposite directions at the same time, if no additional processing is done, the diffraction orders in one direction will be coupled out of the waveguide base and enter the human eye, and the diffraction orders in the other opposite direction will inevitably be coupled out of the waveguide base and leak away from the human eye into the real world outside.
[0047] In practice, a quarter wave plate is used to change the polarization state of light. The polarizer is used to pass light along the polarization direction of the polarizer, and block and absorb or reflect light that is inconsistent with the polarization direction of the polarizer. The quarter wave plate is located between the polarizer and the polarization-selective outcoupling grating, and can be used to convert image light in a circularly polarized state into image light in a linearly polarized state. In this way, based on the polarization selectivity of the above-mentioned polarization-selective volume holographic grating, the quarter wave plate and the polarizer are cleverly used to eliminate light leakage.
[0048] Specifically, the rotation direction of the birefringent material molecules is right-handed, the leaked light is in a right-handed circular deflection state, and the angle between the polarization direction of the polarizer and the fast axis direction of the quarter wave plate is -45°; or, the rotation direction of the birefringent material molecules is left-handed, the leaked light is in a left-handed circular deflection state, and the angle between the polarization direction of the polarizer and the fast axis direction of the quarter wave plate is 45°. Wherein, taking the fast axis direction of the quarter wave plate as the reference direction, the counterclockwise rotation angle is positive, and the clockwise rotation angle is negative.
[0049] In this way, a quarter-wave plate and a polarizer are arranged in sequence on the optical path of the leaked light to the external environment, and the alignment relationship between the quarter-wave plate and the polarizer is designed. The leaked light can be converted into linear polarized light with a polarization direction inconsistent with or even perpendicular to the polarization direction of the polarizer after passing through the quarter-wave plate, and then absorbed or returned after being blocked by the polarizer, which can reduce or even avoid light leakage, thereby preventing user privacy leakage.
[0050] Further practicably, the quarter wave plate and the polarizer may be realized as a film layer structure attached to the surface of the waveguide substrate or the surface of the protective film.
[0051] Specifically, when the polarization-selective outcoupling grating is arranged on the surface of the waveguide substrate close to the human eye, the quarter-wave plate and the polarizer may both be attached to the surface of the waveguide substrate away from the human eye, and the quarter-wave plate and the polarizer are attached in sequence along the direction away from the human eye; or, the quarter-wave plate is attached to the surface of the waveguide substrate away from the human eye, and the polarizer is attached to the surface of any side of the protective sheet; or, the quarter-wave plate and the polarizer may both be attached to the surface of the protective sheet, wherein the quarter-wave plate and the polarizer may be attached to the same surface of the protective sheet, or may be attached to different surfaces respectively, and the order of attachment is the quarter-wave plate and the polarizer in sequence along the direction away from the human eye. When the polarization-selective outcoupling grating is arranged on the surface of the waveguide substrate away from the human eye, the quarter-wave plate and the polarizer are both attached to the surface of the protective sheet, wherein the quarter-wave plate and the polarizer may be attached to the same surface of the protective sheet, or may be attached to different surfaces respectively, and the order of attachment is the quarter-wave plate and the polarizer in sequence along the direction away from the human eye.
[0052] For example, see Figure 2 and Figure 3 , the polarization selective outcoupling grating is a right-handed polarization selective volume holographic grating and a reflective grating, Figure 2 It shows that the quarter wave plate and the polarizing plate are respectively attached to different surfaces of the protective plate, and the attaching order is the quarter wave plate and the polarizing plate in the direction away from the human eye; Figure 3It is shown that the quarter wave plate and the polarizer are attached to the same surface of the protective film, and the order of attachment is the quarter wave plate and the polarizer in the direction away from the human eye. It can be seen that after the image light 102 emitted by the micro display 101 is coupled into the waveguide substrate 105 through the coupling element 103 and transmitted to the polarization selective coupling grating 104, it diffracts to produce coupling light 106 and leakage light 107, wherein the leakage light 107 is right-handed circularly polarized light, which becomes linearly polarized light after passing through the first quarter wave plate 108 on the protective film 110. The polarization direction of the linear polarized light is inconsistent with the polarization direction of the second polarizer 109 on the protective film 110 (even perpendicular), and is thus blocked (even completely blocked) by the second polarizer 109, thereby reducing (even avoiding) the leakage light 107 from entering the external environment, thereby avoiding the leakage of user privacy.
[0053] Further, in some embodiments, a turning grating is also provided on the surface of the waveguide substrate, and the turning grating is implemented as a polarization-selective turning grating. However, the turning grating easily diffracts external light (such as sunlight, light, etc.) to produce rainbows, affecting the imaging effect. The present application also cleverly eliminates the rainbow caused by the diffraction of external light by the turning grating through a quarter-wave plate and a polarizer. In order to distinguish from the quarter-wave plate and polarizer used to solve the light leakage problem for the polarization-selective outcoupling grating in the previous embodiment, it is agreed here that the quarter-wave plate and polarizer used to solve the light leakage problem for the polarization-selective outcoupling grating are the first quarter-wave plate and the first polarizer, and the quarter-wave plate and polarizer used to solve the rainbow problem for the polarization-selective turning grating are the second quarter-wave plate and the second polarizer; wherein, the setting position of the first quarter-wave plate and the first polarizer corresponds to the position of the polarization-selective outcoupling grating, and the setting position of the second quarter-wave plate and the second polarizer corresponds to the position of the polarization-selective turning grating. It can be understood that the first quarter wave plate and the second quarter wave plate are both quarter wave plates, which are the same optical element; the first polarizer and the second polarizer are both polarizers, which are the same optical element; the alignment relationship between the quarter wave plate and the polarizer is different from the corresponding relationship between the rotation direction of the polarization selective holographic grating in order to solve different problems (light leakage problem or rainbow problem).
[0054] The polarization selective turning grating may be a polarization selective volume holographic grating (PVG). In practice, the polarization selective turning grating may also include a single birefringent material layer or a multi-layer stacked birefringent material layer; the birefringent material layer includes a helical structure formed by birefringent material molecules of the birefringent material. The birefringent material may be a liquid crystal material, and the birefringent material molecules are liquid crystal material molecules.
[0055] In practice, a polarizer and a quarter wave plate are sequentially arranged on the optical path of the external light, and the polarizer is used to pass the light along the polarization direction of the polarizer and block the light that is inconsistent with the polarization direction of the polarizer. The quarter wave plate is located between the polarizer and the polarization selection turning grating, and can be used to convert the external light in a linearly deflected state into image light in a circularly deflected state. In this way, based on the polarization selectivity of the above-mentioned polarization selection volume holographic grating, the rainbow can be eliminated by cleverly coordinating the alignment relationship between the quarter wave plate and the polarizer.
[0056] Specifically, the rotation direction of the birefringent material molecules is right-handed, the angle between the polarization direction of the second polarizer and the fast axis direction of the second quarter wave plate is -45°, and the external light is in a left-handed circular deflection state after passing through the second polarizer and the second quarter wave plate in sequence; or, the rotation direction of the birefringent material molecules is left-handed, the angle between the polarization direction of the second polarizer and the fast axis direction of the second quarter wave plate is 45°, and the external light is in a right-handed circular deflection state after passing through the second polarizer and the second quarter wave plate in sequence.
[0057] In this way, a polarizer and a quarter-wave plate are arranged at a position on the optical path of the external light corresponding to the polarization rotation turning grating. After passing through the quarter-wave plate, the external light will be converted into circularly polarized light whose polarization rotation direction is opposite to the liquid crystal rotation direction of the polarization selection turning grating. When the circularly polarized light is incident on the polarization selection turning grating, it will basically not be diffracted by the polarization selection turning grating, thereby avoiding the generation of rainbow.
[0058] Further practicably, the second quarter wave plate and the second polarizer may also be realized as a film layer structure attached to the surface of the waveguide substrate or the surface of the protective film.
[0059] Specifically, when the polarization-selective coupling grating is arranged on the surface of the waveguide substrate close to the human eye, the second quarter-wave plate and the second polarizer may both be attached to the surface of the waveguide substrate away from the human eye, and the second quarter-wave plate and the second polarizer are sequentially attached along the direction away from the human eye; or, the second quarter-wave plate is attached to the surface of the waveguide substrate away from the human eye, and the second polarizer is attached to any side surface of the protective plate; or, the second quarter-wave plate and the second polarizer may both be attached to the surface of the protective plate, wherein the second quarter-wave plate and the second polarizer may be attached to the same surface of the protective plate, or may be attached to different surfaces respectively, and the attaching order is the quarter-wave plate and the polarizer sequentially along the direction away from the human eye. When the polarization-selective coupling coupling grating is arranged on the surface of the waveguide substrate away from the human eye, the second quarter-wave plate and the second polarizer are both attached to the surface of the protective plate, wherein the second quarter-wave plate and the second polarizer may be attached to the same surface of the protective plate, or may be attached to different surfaces respectively, and the attaching order is the second quarter-wave plate and the second polarizer sequentially along the direction away from the human eye.
[0060] For example, see Figure 4 , the polarization selection turning grating is a right-handed polarization selection volume holographic grating. The figure shows that the quarter wave plate and the polarizer are respectively attached to different surfaces of the protective sheet, and the order of attachment is the quarter wave plate and the polarizer in the direction away from the human eye. It can be seen that when the angle between the polarization direction of the second polarizer 114 and the fast axis direction of the second quarter wave plate 113 is -45°, the external light 111 is unpolarized light, and becomes linearly polarized light after passing through the second polarizer 114 on the protective sheet 110, and then the light after passing through the second quarter wave plate 113 is left-handed circularly polarized light. The polarization selection turning grating 112 basically does not diffract the left-handed circularly polarized light, thereby avoiding the generation of rainbows.
[0061] In practice, the refractive index of the birefringent material layer is in the range of 1.5-2.5, the refractive index difference of the birefringent material layer is in the range of 0.05-1, the thickness of the birefringent material layer is in the range of 50nm-5μm, and the tilt angle of the periodically tilted refractive index plane in the birefringent material layer is in the range of 5°-85°.
[0062] Practically, the coupling element of the diffraction optical waveguide can be realized as a surface relief grating (SRG), a volume holographic grating (VHG), a polarization selective volume holographic grating (PVG), etc.
[0063] The present application also provides an augmented reality display device, which includes a micro display and the diffraction light waveguide in the aforementioned embodiments.
[0064] Among them, the micro display can be digital light processing (DLP), laser beam scanner (LBS), liquid crystal on silicon (LCOS), digital micro-mirror device (DMD), organic light-emitting diode (OLED), micro electro mechanical system (MEMS), etc. The augmented reality display device can be augmented reality (AR) glasses, car head up display (HUD), etc.
[0065] It can be understood that the augmented reality display device has the diffractive optical waveguide in the aforementioned embodiments, and thus also has the advantages of the diffractive optical waveguide in the aforementioned embodiments.
[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present utility model.
Claims
1. A diffractive optical waveguide, characterized in that: include: A waveguide substrate, wherein a polarization selective outcoupling grating is arranged on the surface of the waveguide substrate, and the image light after the action of the polarization selective outcoupling grating is in a circularly polarized state; wherein the surface of the waveguide substrate on the side away from the human eye further includes: a quarter wave plate and a polarizer sequentially attached along a direction away from the human eye; or, the side of the waveguide substrate away from the human eye further includes a protective sheet, and the surface of the protective sheet further includes: a quarter wave plate and a polarizer sequentially attached along a direction away from the human eye; or, the side of the waveguide substrate away from the human eye further includes a protective sheet, and the surface of the waveguide substrate away from the human eye further includes a quarter wave plate, and the surface of the protective sheet further includes a polarizer; wherein the angle between the polarization direction of the polarizer and the fast axis direction of the quarter wave plate is 45° or -45°.
2. The diffractive optical waveguide according to claim 1, characterized in that: The polarization selective outcoupling grating includes a single birefringent material layer or a multi-layer stacked birefringent material layer; the birefringent material layer includes a helical structure formed by birefringent material molecules of the birefringent material.
3. The diffractive optical waveguide according to claim 2, characterized in that: The rotation direction of the birefringent material molecules is right-handed, the leakage light is in a right-handed circularly deflected state, and the angle between the polarization direction of the polarizer and the fast axis direction of the quarter wave plate is -45°; or, the rotation direction of the birefringent material molecules is left-handed, the leakage light is in a left-handed circularly deflected state, and the angle between the polarization direction of the polarizer and the fast axis direction of the quarter wave plate is 45°.
4. The diffractive optical waveguide according to claim 2, characterized in that: The refractive index of the birefringent material layer is in the range of 1.5-2.5, and the refractive index difference of the birefringent material layer is in the range of 0.05-1.
5. The diffractive optical waveguide according to claim 2, characterized in that: The thickness of the birefringent material layer is in the range of 50 nm to 5 μm.
6. The diffractive optical waveguide according to claim 2, characterized in that: The tilt angle of the periodically tilted refractive index plane in the birefringent material layer is in the range of 5°-85°.
7. The diffractive optical waveguide according to claim 1, characterized in that: The quarter wave plate is a first quarter wave plate, the polarizer is a first polarizer, and the first quarter wave plate and the first polarizer are arranged at positions corresponding to the polarization selective outcoupling grating; A polarization selection turning grating is also arranged on the surface of the waveguide substrate, and the polarization selection turning grating is used to diffract light whose polarization rotation direction matches the rotation direction of the polarization selection turning grating, wherein the surface of the waveguide substrate away from the human eye further includes: a second quarter wave plate and a second polarizer sequentially bonded in a direction away from the human eye; or, the waveguide substrate further includes a protective plate on the side away from the human eye, and the surface of the protective plate further includes: a second quarter wave plate and a second polarizer sequentially bonded in a direction away from the human eye; or, the waveguide substrate further includes a protective plate on the side away from the human eye, and the surface of the waveguide substrate further includes a second quarter wave plate, and the surface of the protective plate further includes a second polarizer; wherein the angle between the polarization direction of the second polarizer and the fast axis direction of the second quarter wave plate is 45° or -45°, so that the polarization rotation direction of the external light after passing through the second polarizer and the second quarter wave plate in sequence is mismatched with the rotation direction of the polarization selection turning grating, and the setting positions of the second quarter wave plate and the second polarizer correspond to the polarization selection turning grating.
8. The diffractive optical waveguide according to claim 7, characterized in that: The polarization selective turning grating includes a single birefringent material layer or a multi-layer stacked birefringent material layer; the birefringent material layer includes a helical structure formed by birefringent material molecules of the birefringent material.
9. The diffractive optical waveguide according to claim 8, characterized in that: The rotation direction of the birefringent material molecules is right-handed, the angle between the polarization direction of the second polarizer and the fast axis direction of the second quarter wave plate is 45°, and the external light is in a left-handed circular deflection state after passing through the second polarizer and the second quarter wave plate in sequence; or, the rotation direction of the birefringent material molecules is left-handed, the angle between the polarization direction of the second polarizer and the fast axis direction of the second quarter wave plate is -45°, and the external light is in a right-handed circular deflection state after passing through the second polarizer and the second quarter wave plate in sequence.
10. An augmented reality display device, characterized in that: The invention comprises a micro display and a diffractive optical waveguide as claimed in any one of claims 1 to 9.