Single light machine binocular display waveguide and AR display device

Abstract

The application relates to a single-projector binocular display waveguide and an AR display device. The binocular display waveguide comprises a waveguide substrate, a polarization beam splitting structure, a light-transmitting optical medium and a coupling-in grating. Display light emitted by a projection light machine is separated into two display lights with different polarization states after being affected by the polarization beam splitting structure and propagates in different directions. The two display lights are reflected and turned back by the light-transmitting optical medium, respectively incident to corresponding coupling-in gratings and coupled into the waveguide substrate to propagate, so that mutually independent binocular display light paths are formed under the condition of a single projector. By avoiding the effective action area of the polarization beam splitting structure in the light path design, the light path crosstalk is reduced and the light energy utilization efficiency is improved, the light path interference and imaging stability problems in the single-projector binocular display are solved, and the use experience of the AR display device is improved.

Description

Technical Field

[0001] This invention belongs to the field of augmented reality display technology, specifically relating to a single-optical-mechanical binocular display waveguide and AR display device. Background Technology

[0002] Augmented Reality (AR) is a display technology that overlays virtual information onto the real world perceived by users through computer systems. It enhances the display of the real world by merging computer-generated images, symbols, or prompts with real-world scenes.

[0003] In AR near-eye display devices, diffractive waveguide display solutions have become one of the mainstream technologies due to their advantages such as small size, high transmittance, and ease of integration with eyeglasses. This type of solution typically involves setting an insertion grating, a pupil-expanding grating, and an exit grating on a transparent medium (such as glass or a high-refractive-index substrate). Display light emitted from the projection optical engine is coupled into the waveguide via the insertion grating, propagates within the waveguide through total internal reflection, and expands the pupil within the pupil-expanding region. Finally, the exit grating guides the display light to the human eye to form an image.

[0004] Existing AR diffractive waveguide systems for binocular display typically employ separate projection engines and waveguide structures for each eye. While this approach is technically mature, it results in a larger overall system size, higher hardware costs, increased power consumption, and stringent requirements for imaging consistency and assembly precision in both eyes. This hinders the development of lightweight and highly integrated AR devices.

[0005] To reduce system complexity and the number of projection optical engines, existing technologies have proposed solutions for achieving binocular display under a single projection optical engine, mainly including the following two technical routes.

[0006] The first type of solution is a beam-splitting display based on polarization beam-splitters. This type of solution typically incorporates a polarization beam-splitter prism (PBS) or other polarization beam-splitter components in the optomechanical system to separate the display light output from the projection optical engine into light with different polarization states. These are then guided to the waveguide structures corresponding to the left and right eyes, respectively, thus achieving binocular display under single-optical-engine conditions. However, this type of solution relies on large polarization beam-splitters and relatively complex optomechanical optical path structures, resulting in a large overall system footprint and high requirements for optical alignment and assembly precision. This hinders further miniaturization and high integration of waveguide display systems.

[0007] The second type of scheme is a beam splitting display scheme based on a waveguide-internal polarization-selective diffraction structure. For example, existing patents disclose a technique that uses multiple polarization volume gratings (PVGs) stacked on the same waveguide substrate to selectively diffract display light of different polarization states, thereby distributing the display light to the exit pupil regions of the left and right eyes. This type of scheme typically requires the precise stacking of multiple volume grating structures with different grating vector directions and polarization response characteristics on the waveguide substrate. However, the above-mentioned single-optical-mechanical binocular display scheme based on the stacking of multiple polarization volume gratings still has certain limitations in practical fabrication and application. On the one hand, the multi-layer PVG structure has high requirements for grating parameter matching, interlayer alignment accuracy, and exposure process stability, resulting in complex fabrication processes and limited yield. On the other hand, the stacking of multiple gratings easily introduces additional scattering loss and polarization crosstalk, leading to reduced system light energy utilization and difficulty in ensuring brightness uniformity and imaging consistency. In addition, under the condition of limited waveguide thickness and space, the multi-layer grating structure may also constrain the field of view design and optical path layout, which is not conducive to the overall optimization of the system.

[0008] Therefore, in single-optical binocular AR diffractive waveguide display systems, there is still an urgent need for a display scheme with a simpler structure, higher efficiency in utilizing polarization states, more user-friendly fabrication process, and the ability to achieve stable beam splitting and symmetrical optical path guidance within a limited waveguide space, in order to solve the aforementioned problems in the existing technology. Summary of the Invention

[0009] To address the problems of existing AR diffractive waveguide display systems, such as difficulty in achieving independent binocular display under single-optical-mechanical conditions, complex system structure, and limited light energy utilization, this invention provides a single-optical-mechanical binocular display waveguide and AR display device.

[0010] By separating the polarization state and controlling the propagation direction of the incident display light, the same display light source can be guided to the corresponding binocular display optical path without increasing the number of optical engines. This achieves effective separation and multiplexing of the display light for the left and right eyes, thereby simplifying the optical system structure, reducing size and cost, and improving the integration and engineering applicability of the single-optical-engine AR waveguide display system while ensuring display brightness and imaging consistency.

[0011] The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a single-optical-mechanical binocular display waveguide, comprising: a waveguide substrate, a polarization beam splitter disposed on the waveguide substrate, a light-transmitting optical medium disposed on the waveguide substrate away from the incident side of the display light, and a first coupling grating, a second coupling grating, a first pupil dilator grating, a second pupil dilator grating, a first coupling grating, and a second coupling grating disposed on the waveguide substrate, thereby forming two symmetrically distributed coupling regions, two pupil dilator regions, and two coupling out regions on the waveguide substrate; wherein the polarization beam splitter, the light-transmitting optical medium, and the coupling grating are disposed in the central region of the waveguide substrate.

[0012] Specifically, the polarization beam splitter is used to separate the polarization state and control the propagation direction of the incident light; the transparent optical medium, with a reflective coating, is used to reflect and refract the separated display light; the coupling grating is used to couple the light into the waveguide substrate; the polarization beam splitter coupling structure, composed of the polarization beam splitter, the transparent optical medium, and the coupling grating, is used to achieve selective separation of the polarization state of the display light, reflection and refracting, and dual-channel directional coupling; the pupil grating is used to first expand and deflect the light to the coupling region; and the coupling grating is used to secondly expand and couple the light out of the waveguide substrate. In this process, by matching the effective working area size of the polarization beam splitter, the thickness and refractive index of the light-transmitting optical medium, and the position and effective size of the coupling area, the first and second display lights, after being reflected and refracted, avoid the effective working area of ​​the polarization beam splitter when returning to the waveguide substrate, and are respectively incident on the first and second coupling areas, thereby coupling into the waveguide substrate to form independent binocular propagation optical paths.

[0013] The polarization beam splitter is located at the center of the waveguide substrate and is configured to separate the polarization state of the display light incident on the waveguide substrate, so that the display light is separated into a first display light and a second display light with different polarization states. At the same time, the propagation direction of the first display light and the second display light is controlled so that the first display light and the second display light propagate in different directions respectively.

[0014] After being processed by the polarization beam splitter, the first and second display lights are further incident on a transparent optical medium located beneath the waveguide substrate. Reflection occurs under the action of a reflective coating on the surface of the transparent optical medium, causing the first and second display lights to propagate back along paths different from their incident directions. The reflected first and second display lights then enter two symmetrically distributed coupling regions on the waveguide substrate, and propagate through these coupling regions into the interior of the waveguide substrate.

[0015] Optionally, the polarization beam splitter is configured to have a predetermined effective size, the lateral dimension of which is not less than the spot size of the incident display light at that position, so as to ensure that the incident display light can fully act on the polarization beam splitter.

[0016] Optionally, the effective working area size of the polarization beam splitter and the thickness of the light-transmitting optical medium are set such that the incident positions of the reflected first and second display lights on the waveguide substrate avoid the effective working area of ​​the polarization beam splitter, thereby preventing the reflected light from re-entering the polarization beam splitter. The effective working area refers to the actual working region on the polarization beam splitter that can selectively separate the polarization state of the incident display light; its size is typically matched to the spot size of the incident light at that location.

[0017] Optionally, the polarization beam splitter introduces transverse wave vector components with opposite directions into the display light of different polarization states, thereby achieving angular separation.

[0018] The expression for the grating equation is: ; in, The refractive index of the incident medium; The refractive index of the waveguide substrate is denoted by . The incident angle is the incident angle onto the polarization beam splitter. The emission angles of the first and second display lights on the waveguide side; To display the wavelength of light; Equivalent grating period.

[0019] During the propagation of the first and second display lights from the waveguide substrate to the light-transmitting optical medium and their return after reflection, the propagation directions at the interfaces of the different media satisfy the law of refraction.

[0020] In one embodiment of the present invention, the propagation directions of the first display light and the second display light may satisfy the following refraction relationship: The expression for Snell's Law is: ; in, The refractive index of the waveguide substrate; The refractive index of a light-transmitting optical medium; The propagation angle within the waveguide; It is the propagation angle within the transparent optical medium.

[0021] Optionally, to determine the incident position of the reflected display light on the waveguide substrate, its lateral displacement can be calculated based on the propagation path of the display light in the transparent optical medium and the waveguide substrate. The calculation expression is as follows: ; in, The thickness of the light-transmitting optical medium; The thickness of the waveguide substrate.

[0022] The above formula is only used to illustrate one way of displaying the relationship of light propagation, and the present invention is not limited to using this specific calculation form.

[0023] Therefore, based on the size of the polarization beam splitter, the thickness and refractive index of the light-transmitting optical medium, the lateral displacement of the first and second display lights reflected back on the waveguide substrate can be determined, thereby designing the position of the coupling region to ensure that the reflected display light can be accurately incident on the coupling region and coupled into the waveguide substrate for propagation.

[0024] Starting from the location of the polarization beam splitter, the first display light coupled into the waveguide substrate propagates sequentially through the first pupil expansion region, undergoing pupil expansion and deflection, and finally reaches the first coupling region. The second display light coupled into the waveguide substrate propagates sequentially through the second pupil expansion region, undergoing pupil expansion and deflection, and finally reaches the second coupling region. The first and second pupil expansion regions are symmetrically arranged with respect to the polarization beam splitter, and the first and second coupling regions correspond to the exit pupil positions of the left and right eyes in binocular display, respectively.

[0025] The present invention also provides an AR display device, including a projection optical engine and the aforementioned single-optical-engine binocular display waveguide.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: The single-optical-engine binocular display waveguide of the present invention, by setting a polarization beam splitting structure at the center of the waveguide substrate, and combining it with the reflective and transparent optical medium below and the coupling gratings on both sides, enables the display light output from the same projection light source to complete polarization state separation and propagation direction control, thereby realizing binocular display under single-optical-engine conditions without the need to configure multiple projection optical engines, effectively reducing the system size and weight, and lowering the overall cost.

[0027] This invention, through the coordinated design of parameters such as the size of the polarization beam splitter structure, the thickness and refractive index of the light-transmitting optical medium, and the structural parameters and relative positions of the coupling grating, ensures that the separated first and second display lights are accurately incident on their respective coupling regions after reflection and refraction. This avoids the reflected light from being incident on the polarization beam splitter structure again, which helps to improve system stability and reduce stray light interference.

[0028] This invention designs the propagation angle and lateral displacement of the separated light beam based on the grating equation and the law of refraction, so that the separated display light forms two independent and symmetrical propagation light paths in the waveguide substrate, ensuring the imaging consistency of the left and right eye display light paths, which is beneficial to improving the brightness uniformity and imaging consistency of binocular display.

[0029] This invention sets up symmetrically distributed pupil expansion and coupling regions within the waveguide substrate, enabling the display light to undergo multi-stage pupil expansion and deflection propagation within the waveguide. This achieves a larger exit pupil range and good eye box coverage while maintaining high light energy utilization, thus improving the visual comfort of near-eye displays.

[0030] This invention features a compact structure and a clear optical path. The polarization beam splitting structure can be implemented in various forms such as PB phase grating and Bragg transmission grating, exhibiting good process compatibility and engineering feasibility. It is suitable for various AR diffraction waveguide display systems.

[0031] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of a single-optical-mechanical binocular display waveguide provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the projection optical engine and binocular waveguide provided in the embodiments of the invention; Figure 3 This is a schematic diagram illustrating the working principle of the polarization beam splitting structure provided in the embodiments of the invention; Figure 4 This is a schematic diagram of the optical path provided by the embodiment of the invention for determining the size of the coupled grating based on the size of the polarization beam splitting structure and the propagation path of the displayed light; Figure 5 This is a schematic diagram of the diffraction efficiency response of the coupled grating under different incident angles provided in the embodiments of the invention; Figure 6 This is a schematic diagram of the light propagation process provided in the embodiments of the invention, in which the display light is separated by a polarization beam splitter, reflected back by a light-transmitting optical medium, and coupled into a coupling grating.

[0033] Figure reference numerals: 1-waveguide substrate; 2-polarization beam splitting structure; 3-transmitting optical medium; 4-coupled grating; 5-pupil grating; 6-coupled grating; 7-projection optical engine. Detailed Implementation

[0034] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of a single-optical-mechanical binocular display waveguide and AR display device according to the present invention is provided in conjunction with the accompanying drawings and specific embodiments.

[0035] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0036] Example 1 like Figure 1 As shown, the present invention provides a single-optical-mechanical binocular display waveguide, comprising: The waveguide substrate 1, the polarization beam splitting structure 2 disposed on the waveguide substrate 1, the light-transmitting optical medium 3 disposed on the side of the waveguide substrate 1 away from the incident side of the display light, the coupling grating 4 disposed on the waveguide substrate 1, and the pupil dilator grating 5 corresponding to the left and right eyes respectively, and the coupling output grating 6 corresponding to the left and right eyes respectively; wherein, the polarization beam splitting structure 2, the light-transmitting optical medium 3 and the coupling grating 4 together constitute the polarization beam splitting coupling structure, which is used to realize the selective separation of polarization state of display light, reflection and folding, and dual-channel directional coupling.

[0037] Specifically, the polarization beam splitter 2 is used to selectively separate the polarization state of the display light incident on the waveguide substrate 1, so that the display light is separated into a first display light and a second display light with different polarization states, and the first display light and the second display light have different propagation directions; the light-transmitting optical medium 3 has a predetermined refractive index and thickness, and a reflection structure is provided on its side away from the waveguide substrate 1, which is used to reflect the first display light and the second display light separated by the polarization beam splitter 2 back to the waveguide substrate 1; the coupling grating 4 includes a first coupling grating and a second coupling grating symmetrically arranged on the waveguide substrate 1, forming a first coupling region and a second coupling region respectively. It couples the display light reflected and refracted by the light-transmitting optical medium 3 into the waveguide substrate 1 to propagate, so as to form two independent propagation optical paths for the left and right eyes, thereby realizing binocular display output under single-optical-mechanical conditions.

[0038] The pupil-expanding grating 5 includes a first pupil-expanding grating and a second pupil-expanding grating symmetrically arranged on the waveguide substrate 1. The first pupil-expanding grating and the second pupil-expanding grating correspondingly form a first pupil-expanding region and a second pupil-expanding region on the waveguide substrate 1. The coupling-out grating 6 includes a first coupling-out grating and a second coupling-out grating symmetrically arranged on the waveguide substrate 1. The first coupling-out grating and the second coupling-out grating correspondingly form a first coupling-out region and a second coupling-out region on the waveguide substrate 1. Thus, the first display light coupled into the waveguide substrate 1 is expanded and coupled out sequentially through the first pupil-expanding region and the first coupling-out region, and the second display light is expanded and coupled out sequentially through the second pupil-expanding region and the second coupling-out region.

[0039] By matching the effective working area size of the polarization beam splitter 2 with the thickness and refractive index of the light-transmitting optical medium 3, the first and second display lights, after being reflected and refracted, avoid the effective working area of ​​the polarization beam splitter 2 when returning to the waveguide substrate 1, and are respectively incident into the first coupling region and the second coupling region, thereby coupling into the waveguide substrate 1 to form independent binocular propagation optical paths.

[0040] For example, the incident positions of the first and second display lights, after reflection and refraction, on the waveguide substrate 1 are located outside the effective operating region of the polarization beam splitter 2. Further, the incident positions of the first and second display lights on the waveguide substrate 1 are determined based on the size of the effective operating region of the polarization beam splitter 2 and the geometric dimensions of the light-transmitting optical medium 3. Furthermore, the propagation directions of the first and second display lights within the waveguide substrate 1 and their lateral displacement on the waveguide substrate 1 are determined based on the refractive index of the waveguide substrate 1, the refractive index of the light-transmitting optical medium 3, and the geometric parameters (such as thickness) of the light-transmitting optical medium 3.

[0041] In this embodiment, the waveguide substrate 1 is a diffractive waveguide substrate with a refractive index of approximately n=1.9 and a thickness of approximately 1 mm. Its outline is roughly the shape of an eyeglass lens, and it includes symmetrically arranged coupling-out regions and pupil-expanding regions. To facilitate miniaturized integration, the polarization beam splitting structure 2 is located near the bridge location region or in the middle region of the waveguide substrate 1, so that the display light from a single projection optical engine can be split and independently coupled to the left and right eyes after entering the waveguide.

[0042] Preferably, the polarization beam splitting structure 2 is a polarization-selective optical structure, which includes any one of a PB phase grating, a Bragg transmission grating, or a cholesteric liquid crystal polarization beam splitting structure.

[0043] Preferably, both the first coupling grating and the second coupling grating are diffraction grating structures, and the diffraction grating structure is any one of a polarizing volume grating, a volume holographic grating, a surface relief grating, a PB phase grating, a Bragg grating, or a composite diffraction grating.

[0044] like Figure 2 As shown, this embodiment also includes a projection optical engine 7, which is disposed opposite to the polarization beam splitter 2 and is capable of emitting a display beam to the polarization beam splitter 2. The display beam in this embodiment is linearly polarized light.

[0045] In one optional embodiment, the dominant wavelength of the display light may be 532nm, but is not limited thereto, and the incident angle range when it is incident on the polarization beam splitting structure 2 is set to -15° to +15° to meet the display requirements within a predetermined field of view.

[0046] like Figure 3As shown, the polarization beam splitter 2 is disposed on the incident side surface of the waveguide substrate 1, such as the upper surface, to perform polarization-state selective diffraction on the linearly polarized incident display light, thereby separating the incident display light into a first display light and a second display light. The first display light and the second display light are different in polarization state and propagate along the first direction and the second direction, respectively, thereby achieving the initial separation of the left and right eye channels.

[0047] Preferably, the polarization beam splitter 2 is used to introduce transverse wave vector components with opposite directions into the display light with different polarization states, so that the separated first and second display light have different propagation directions. The polarization beam splitter 2 can be a Pancharatnam-Berry phase grating (PB phase grating), with the effective working area width set to approximately 2 mm, its thickness to approximately 1.57 μm, and its in-plane period set to approximately 1.258 μm. By setting the period and orientation of the PB phase grating, the diffraction orders corresponding to different polarization components can be made to produce opposite or different deflection directions in space, thereby forming two beams of display light that can be guided to the first coupling grating and the second coupling grating respectively.

[0048] Furthermore, in this embodiment, the material parameters of the polarization beam-splitting structure 2 can be achieved using liquid crystal or equivalent birefringent materials. In a specific embodiment, a common refractive index n can be used. o =1.508 and the most common refractive index n e A birefringent material configuration of 1.678 is used to obtain the desired phase modulation capability and polarization-selective response, but is not limited thereto.

[0049] like Figure 4 As shown, to prevent the displayed light after beam splitting from re-entering the effective working area of ​​the polarization beam splitting structure 2 during the refracting process, thus avoiding crosstalk, efficiency loss, or stray light, this embodiment provides a transparent optical medium 3 below the waveguide substrate 1, and a reflective structure at the bottom of the transparent optical medium 3 to reflect and refract the first and second displayed light back to the waveguide substrate 1. The reflective structure can be a reflective surface, a reflective film, a dielectric mirror, or an equivalent reflective unit; the transparent optical medium 3 can be any of optical glass, transparent resin, polymer optical materials, or other transparent media with a predetermined refractive index. In a specific embodiment, the transparent optical medium 3 can be fluorine-doped glass with a refractive index of approximately n=1.25 and a thickness of approximately 8 mm, the effective lateral size of which meets the propagation and refracting requirements of the beam within a predetermined angle range.

[0050] In this embodiment, the transverse net light transmission size of the light-transmitting optical medium 3 is set to approximately 21 mm to cover the propagation range of the two reflected display beams. By designing the thickness and refractive index of the light-transmitting optical medium 3, and combining it with the effective working area size of the polarization beam splitter 2, the incident positions of the first and second display beams when returning to the waveguide substrate 1 after reflection can avoid the effective working area of ​​the polarization beam splitter 2, thereby preventing optical path crosstalk caused by the reflected light being diffracted again by the polarization beam splitter 2.

[0051] Please see again Figure 4 This embodiment further discloses a method for determining the size and placement of the coupling grating 4. The method is based on at least the following known parameters: the refractive index of the waveguide substrate n_wg = 1.9 and the waveguide thickness t_wg = 1 mm; the refractive index of the fluorine-doped optical glass n_g = 1.25 and the thickness t_g = 8 mm; the period Λ_PB of the polarization beam splitter 2 is 1.258 μm, the thickness is about 1.57 μm, and the effective working area width W_PB = 2 mm; the incident light is linearly polarized light with an incident angle range of -15° to +15°; and the dominant wavelength can be λ = 532 nm.

[0052] Within a predetermined incident angle range, the incident display light, after being diffracted by the polarization beam splitter 2, forms two separate beams with different transverse wave vector components within the waveguide substrate 1. Taking one of these beams (e.g., the first display light) as an example, its propagation angle within the waveguide can be determined by the diffraction relationship, and further obtained from the refraction relationship at the waveguide-glass interface, its propagation angle within the optical glass. Since this beam propagates within the waveguide layer and the glass layer and is reflected back by the glass layer, it will generate a transverse displacement when it finally returns to the upper surface of the waveguide substrate 1 (or the predetermined coupling plane). There is a corresponding relationship between the transverse displacement and the propagation angle, the waveguide thickness, and the glass thickness.

[0053] To determine the size of the coupling grating 4, this embodiment defines the coverage area of ​​the reflected beam on the coupling plane as the landing point range. Under the condition of scanning from -15° to +15° at the incident angle, the landing point of the center ray of the reflected display light will form a continuous interval. Simultaneously, considering that the effective working area width of the polarization beam splitter 2 is 2mm, the spot width of the reflected beam on the coupling plane can be approximately considered as the superposition of the initial spot width and the lateral widening caused by the angle scan. Therefore, to ensure that the reflected beam can be coupled into the waveguide substrate 1 throughout the entire incident angle range, this embodiment sets the effective size of the first and second coupling gratings to at least cover the landing point range.

[0054] In one specific embodiment, after estimating the landing point range through optical path geometry, the effective width of each coupling grating 4 is determined to be approximately 10.8 mm to cover the landing point distribution of the returned beam within the incident angle range of -15° to +15°. In this specific embodiment, through comprehensive matching design of the thickness and refractive index of the transparent optical medium 3 and the effective working area size of the polarization beam splitter 2, a certain lateral spacing is formed between the returned display light and the effective working area of ​​the polarization beam splitter 2 when returning to the waveguide substrate 1. Under the parameter conditions shown in this embodiment, this lateral spacing can be set to approximately 0.3 mm to prevent the returned light from re-entering the effective working area of ​​the polarization beam splitter 2.

[0055] Therefore, by combining the parameters of the polarization beam splitting structure 2, the waveguide / glass structure parameters, and the incident angle range, the size and placement of the coupling grating 4 can be determined, so that the first and second display lights after reflection are incident on the first and second coupling gratings respectively and coupled into the waveguide substrate 1, ultimately achieving binocular display output in the corresponding areas of the left and right eyes.

[0056] In this embodiment, the first and second coupling gratings can be implemented using a volume polarizer (PVG) to achieve a high-efficiency coupling response to specific polarization states and angles. The structural parameters of the PVG coupling grating may include: an isorefractive surface tilt angle of approximately 22°, a Bragg period of approximately 395 nm, and a thickness of approximately 4 μm. By matching the incident angle range of the reflected display light within the waveguide, the PVG coupling grating can achieve high coupling efficiency within the angular range, thereby improving the overall light efficiency of the single-optical-mechanical binocular display system.

[0057] For example, the effective size of the first coupling region and the second coupling region is determined based on the size of the light spot formed by the reflected first display light and the second display light at corresponding positions.

[0058] like Figure 5 As shown in the figure, this embodiment provides a schematic curve of the diffraction / coupling efficiency response of the coupling grating 4 (e.g., PVG coupling grating) under different incident angle conditions. It can be seen that the coupling grating 4 has a high coupling efficiency within a predetermined angle range, which enables the first display light and the second display light after reflection to be coupled into the waveguide substrate 1 for propagation, thereby forming a stable binocular display output in the left and right eye coupling regions.

[0059] It should be noted that this application is not limited to the specific parameters mentioned above. The polarization beam splitting structure 2 can be replaced with other elements that have polarization-selective beam splitting capabilities; the refractive index, thickness, and lateral dimensions of the light-transmitting optical medium 3 can be adjusted according to actual spatial constraints and optical path requirements; the reflection structure can be any one of metal film reflection, medium mirror, or equivalent reflection structure formed by total internal reflection; the coupling grating 4 can be in the form of a volume holographic grating, surface relief grating, or polarization volume grating, etc., and its period, tilt angle, and thickness can be matched and optimized according to a predetermined wavelength and incident angle range. All equivalent substitutions or modifications made based on the structure and principle of this application shall fall within the protection scope of this application.

[0060] like Figure 6 As shown, to further illustrate the integrity and feasibility of the optical path in the embodiments of this application, this embodiment verifies the actual propagation path of the display light between the polarization beam splitting structure 2, the light-transmitting optical medium 3, and the coupling grating 4 by ray tracing.

[0061] like Figure 6 As shown, the incident angle range of the incident display light is... Under the conditions of 15° to +15°, the first display light and the second display light, which are separated by the polarization beam splitting structure 2, are further refracted into the light-transmitting optical medium 3 located below the waveguide substrate 1 after entering the waveguide substrate 1, and are reflected back at the bottom reflection structure of the light-transmitting optical medium 3.

[0062] Within the light-transmitting optical medium 3, both the first and second display lights propagate at an incident angle greater than their critical angle, ensuring stable reflection and refracting within the medium without overflowing from its sides or bottom. Thus, the light-transmitting optical medium 3 not only reflects the display light but also limits its propagation space.

[0063] Furthermore, since the thickness and refractive index of the light-transmitting optical medium 3, as well as the effective operating area size of the polarization beam splitter 2, are all designed to be matched, the incident positions of the first and second display lights are laterally offset relative to the effective operating area of ​​the polarization beam splitter 2 when they are folded back to the waveguide substrate 1. This lateral offset causes the folded-back beam to avoid the effective operating area of ​​the polarization beam splitter 2, thereby preventing the folded-back light from re-entering the polarization beam splitter 2 and causing repeated diffraction, energy loss, or crosstalk.

[0064] like Figure 6As shown, the reflected display light forms a stable and continuous drop point distribution range on the upper surface of the waveguide substrate 1, and this drop point range completely falls within the effective range of the corresponding coupling grating 4. Therefore, the first display light and the second display light can be effectively coupled into the waveguide substrate 1 by the corresponding coupling grating 4, and propagate along a predetermined direction within the waveguide substrate 1 to the pupil dilation region and the coupling out region corresponding to the left and right eyes.

[0065] Through the above-described structural and parameter design, the embodiments of this application can ensure that the displayed light is always propagated in a controlled manner within the optical structure composed of the waveguide substrate 1 and the light-transmitting optical medium 3 during the polarization beam splitting, folding, and coupling process within a large incident angle scanning range, thereby avoiding light overflow, back interference, or ineffective loss, and thus improving the light efficiency stability and imaging consistency of the single-optical-mechanical binocular display system.

[0066] The present invention also provides an AR display device, including a projection optical engine and the aforementioned single-optical-engine binocular display waveguide.

[0067] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0068] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A single-optical-mechanical binocular display waveguide, characterized in that, include: Waveguide substrate; A polarization beam splitting structure is disposed on the waveguide substrate to selectively separate the polarization state of display light incident on the waveguide substrate, so that the display light is separated into a first display light and a second display light with different polarization states, and the first display light and the second display light have different propagation directions; A light-transmitting optical medium is disposed on the waveguide substrate away from the incident side of the display light. The light-transmitting optical medium has a predetermined refractive index and thickness, and a reflective structure is disposed on the side of it away from the waveguide substrate to reflect the first display light and the second display light separated by the polarization beam splitting structure back to the waveguide substrate. The coupling grating includes a first coupling grating and a second coupling grating, which are symmetrically arranged on the waveguide substrate and form a first coupling region and a second coupling region, respectively, for coupling the first display light and the second display light, which are reflected and refracted by the light-transmitting optical medium, into the waveguide substrate for propagation. Specifically, by matching the effective working area size of the polarization beam splitter with the thickness and refractive index of the light-transmitting optical medium, the first and second display lights, after being reflected and refracted, avoid the effective working area of ​​the polarization beam splitter when returning to the waveguide substrate, and are respectively incident on the first coupling region and the second coupling region, thereby coupling into the waveguide substrate to form mutually independent binocular propagation optical paths.

2. The single-optical-mechanical binocular display waveguide according to claim 1, characterized in that, The polarization beam splitting structure is a polarization-selective optical structure, which includes any one of the following: PB phase grating, Bragg transmission grating, and cholesteric liquid crystal polarization beam splitting structure.

3. The single-optical-mechanical binocular display waveguide according to claim 1, characterized in that, The incident positions of the first and second display lights, after being reflected and refracted, on the waveguide substrate are located outside the effective operating area of ​​the polarization beam splitting structure.

4. The single-optical-mechanical binocular display waveguide according to claim 3, characterized in that, The incident positions of the first and second display lights, after reflection and refraction, on the waveguide substrate are determined based on the effective area size of the polarization beam splitting structure and the geometric dimensions of the light-transmitting optical medium.

5. The single-optical-mechanical binocular display waveguide according to claim 1, characterized in that, The polarization beam splitter structure is used to introduce transverse wave vector components with opposite directions into display light with different polarization states, so that the separated first and second display light have different propagation directions.

6. The single-optical-mechanical binocular display waveguide according to claim 1, characterized in that, The propagation directions of the first and second display lights within the waveguide substrate and their lateral displacements on the waveguide substrate are determined based on the refractive index of the waveguide substrate, the refractive index of the light-transmitting optical medium, and the geometric parameters of the light-transmitting optical medium.

7. The single-optical-mechanical binocular display waveguide according to claim 1, characterized in that, The effective size of the first coupling region and the second coupling region is determined based on the size of the light spot formed by the reflected first display light and the second display light at corresponding positions.

8. The single-optical-mechanical binocular display waveguide according to claim 1, characterized in that, The waveguide substrate is further provided with a pupil-expanding grating and a coupling grating. The pupil-expanding grating includes a first pupil-expanding grating and a second pupil-expanding grating symmetrically arranged on the waveguide substrate. The coupling grating includes a first coupling grating and a second coupling grating symmetrically arranged on the waveguide substrate. Wherein, the first pupil-expanding grating and the second pupil-expanding grating are respectively formed on the waveguide substrate to form a first pupil-expanding region and a second pupil-expanding region, and the first coupling-out grating and the second coupling-out grating are respectively formed on the waveguide substrate to form a first coupling-out region and a second coupling-out region. The first display light coupled into the waveguide substrate is dilated and coupled out sequentially through the first pupil dilation region and the first coupling out region, and the second display light is dilated and coupled out sequentially through the second pupil dilation region and the second coupling out region.

9. The single-optical-mechanical binocular display waveguide according to claim 1, characterized in that, Both the first and second coupling gratings are diffraction grating structures, and the diffraction grating structure is any one of a polarizing volume grating, a volume holographic grating, a surface relief grating, a PB phase grating, a Bragg grating, or a composite diffraction grating.

10. An AR display device, characterized in that, Includes a projection optical engine and a single-optical-engine binocular display waveguide as described in any one of claims 1 to 9.

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