Grating waveguide device and waveguide system based on PVG technology

Abstract

The invention discloses a grating waveguide device and waveguide system based on a polarization volume grating technology, and belongs to the technical field of augmented reality display. The device comprises a waveguide substrate and a grating structure, the grating structure adopts a liquid crystal material to form a periodic refractive index modulated PVG through a light-induced orientation and self-assembly process, the polarization state of a light beam can be selectively regulated and controlled, and the rainbow pattern phenomenon caused by ambient light diffraction is inhibited. The efficient diffraction and total internal reflection transmission of the multi-wavelength light beam are realized by optimizing the grating period, the Bragg inclination angle and the waveguide matrix parameters and combining Zemax simulation to optimize the light beam propagation path. The waveguide system can be matched with AR glasses, a head-mounted display and other devices, the intensity of the rainbow lines is remarkably reduced under the complex ambient light condition, and high-definition and distortion-free visual experience is provided.

Description

Technical Field

[0001] The present invention relates to optical display technology, and in particular to a grating waveguide device and system based on polarization volume grating (PVG), which is used in augmented reality (AR) devices to suppress the rainbow pattern phenomenon caused by diffraction of ambient light and improve image display quality. Background Art

[0002] Augmented reality is a technology that integrates virtual information with the real world and is widely used in the fields of medicine, education, and games. In AR devices, grating waveguide technology is an important way to display images, using tiny gratings to guide images to the user's eyes. However, in actual applications, grating waveguide devices in AR glasses and other wearable devices often face rainbow patterns caused by ambient light.

[0003] Rainbow patterns are caused by ambient light (such as sunlight, indoor lighting, etc.) diffracting through the grating structure and entering the eye, causing image distortion and interference. Current technologies mainly rely on optimizing the period and direction of the grating and directional control of the light source to reduce this interference, but these methods often cannot completely eliminate the rainbow pattern phenomenon and have a significant impact on image quality.

[0004] In order to effectively solve this problem, the present invention adopts polarization volume grating technology. PVG can optimize the modulation of the polarization state and volume effect of light, and by precisely controlling the propagation path of light, avoid the interference of ambient light, eliminate the rainbow pattern phenomenon, and significantly improve the display quality of the image. Summary of the invention

[0005] The present invention proposes a grating waveguide device and waveguide system based on polarization volume grating technology, aiming to solve the rainbow pattern problem caused by ambient light interference in augmented reality display devices. The present invention effectively suppresses ambient light interference and improves display quality and optical performance through innovative PVG structure design combined with the multiple total internal reflection characteristics of the waveguide system.

[0006] PVG technology is based on the optical anisotropy of liquid crystal materials. By adjusting the grating period, Bragg tilt angle and polarization selectivity, it can achieve efficient diffraction of incident light in a specific polarization state while avoiding unnecessary interference in the optical path. Combined with a waveguide device made of high refractive index materials, a two-dimensional pupil expansion design is adopted to achieve multiple total internal reflection propagation, thereby enhancing the efficiency and stability of beam transmission.

[0007] The specific technical solution is: A grating waveguide device based on PVG technology, comprising: Waveguide substrate: Made of high refractive index material, with a refractive index ranging from 1.6 to 2.0, supporting total internal reflection transmission of light beams; Grating structure: It is set on the waveguide substrate and uses polarization volume grating (PVG) technology to modulate the polarization state of the incident light beam; The PVG is a periodic refractive index modulation structure formed by liquid crystal material through photo-induced orientation and self-assembly process; The grating period is 800 nanometers to 1 micron, the Bragg tilt angle is 40° to 65°, and it is suitable for full-color display in red, green, and blue bands; The grating structure guides the light beam into the waveguide matrix through the coupling-in grating, and outputs the light beam through the coupling-out grating after multiple total reflections, thereby suppressing the rainbow pattern phenomenon caused by ambient light.

[0008] Preferably, the liquid crystal material forms a stable periodic grating structure through a photocuring process.

[0009] Preferably, the waveguide matrix has a thickness of 1 mm, a width of 20 mm, and a length of 100 mm.

[0010] Preferably, the diffraction efficiency of the PVG in the visible light band exceeds 80%.

[0011] A waveguide display system comprises the grating waveguide device, wherein the system optimizes grating parameters (period, grating line direction, Bragg tilt angle) and waveguide geometric dimensions (thickness 1 mm, width 20 mm, length 100 mm) through Zemax simulation to achieve efficient light beam transmission (energy loss < 5%) and rainbow pattern suppression (intensity reduction of more than 70%).

[0012] Preferably, the Zemax simulation optimization includes ray tracing analysis to verify the light beam propagation path and rainbow pattern suppression effect.

[0013] Preferably, the system is adapted to AR glasses to maintain a rainbow-free display under complex ambient light conditions.

[0014] Preferably, a method for preparing a grating waveguide device based on polarization volume grating (PVG) technology comprises the following steps: A photoinduced alignment layer is coated on the substrate surface, and a periodic alignment pattern is formed by ultraviolet exposure (wavelength 365 nm, exposure time 30-60 seconds). The ultraviolet exposure uses a photoinitiator IRGACURE 651 to ensure that the liquid crystal material self-assembles to form a stable alignment structure in the subsequent steps.

[0015] The spin-coated liquid crystal material includes an acrylic monomer and a chiral dopant (such as R5011 / S5011), and generates a PVG structure through a self-assembly effect, ensuring that the liquid crystal molecules are spontaneously arranged along the periodic pattern direction of the photoinduced alignment layer to form a periodic structure with high refractive index modulation.

[0016] The curing process is carried out in a nitrogen atmosphere to avoid the influence of oxygen, ensure the stability of the PVG structure, and enhance its optical properties.

[0017] Combined with a high refractive index waveguide substrate (such as glass or polymer), the grating structure is combined with the waveguide substrate to form a complete grating waveguide device. The refractive index of the waveguide substrate is usually controlled between 1.6 and 2.0 to optimize the transmission performance of the optical waveguide.

[0018] Preferably, the photocuring treatment uses ultraviolet light irradiation, and the curing time is 30-60 seconds to ensure the stability of the grating characteristics to improve the diffraction efficiency and energy retention rate of the waveguide system.

[0019] Through the above steps, the prepared grating waveguide device has high diffraction efficiency (>80%) and total internal reflection transmission characteristics (energy retention rate>95%). This system is preferably adapted to AR glasses, and can effectively suppress the rainbow pattern phenomenon under complex ambient light conditions, providing a high-definition, distortion-free visual experience.

[0020] The present invention optimizes the optical system through Zemax simulation technology, covering multi-dimensional simulation of grating design, waveguide parameters and beam propagation path, ensuring excellent performance under different wavelengths and incident conditions. The present invention is suitable for AR glasses, head-mounted displays and other devices, especially showing significant advantages under complex ambient light conditions. The specific steps are as follows: Step 1: Grating waveguide substrate design: a. Material: High refractive index optical glass or polymer matrix with a refractive index range of 1.6 to 2.0, supporting multiple total internal reflection conditions to ensure that the light beam has minimal loss when propagating inside the waveguide;

[0021] b. Size optimization: The thickness of the waveguide substrate is set to 1 mm, the width is 20 mm, and the length is 100 mm to achieve efficient beam transmission while meeting the compact design requirements.

[0022] Step 2: PVG structure design: a. Bragg period: ranging from 800 nanometers to 1 micron, adaptable to infrared and visible light band conditions; b. Bragg tilt: ranging from 40° to 65°, achieving efficient diffraction of multi-wavelength beams through angle optimization while suppressing ambient light interference; c. Grating vector design: designed as a closed loop to reduce scattered light and optimize the beam propagation path, thereby improving transmission efficiency; d. Polarization selectivity: By utilizing the photo-induced orientation and self-assembly process of liquid crystal materials, a periodic refractive index modulation structure with optical anisotropy is formed to achieve selective diffraction of polarized light and significantly reduce the rainbow pattern phenomenon.

[0023] Step 3: In-coupling and out-coupling grating design a. In-coupling grating: After the incident light enters the waveguide matrix through the in-coupling grating, the PVG structure regulates the polarization state and propagation path to ensure that the light beam propagates through multiple total reflections inside the waveguide; b. Outcoupling grating: The light beam is output through the outcoupling grating to form a high-quality imaging beam while avoiding unnecessary light energy loss.

[0024] Step 4: Detector unit design: a. Capture the beam output from the waveguide outlet and measure its energy distribution; b. Analyze the imaging quality to verify the rainbow suppression effect and the overall system performance.

[0025] Step 5, preparation process: (1) Grating preparation process a. Photoinduced alignment: an alignment layer is generated on the substrate surface, and a grating structure with periodic refractive index modulation is formed by self-assembly of liquid crystal materials; b. Laser exposure: Laser exposure technology is used to precisely control the Bragg period to adapt to the target band; c. Photocuring treatment: The photocuring process is used to improve the stability and anti-interference ability of the grating structure.

[0026] Step 6: Simulation optimization: (1) Grating design optimization a. Bragg tilt angle optimization: Through Zemax simulation, the Bragg tilt angle is adjusted to 45° to achieve efficient diffraction of the light beam; b. Grating period optimization: Fine-tune the grating period to 800 nanometers to adapt to a specific wavelength range and further improve the diffraction efficiency.

[0027] (2) Waveguide parameter optimization a. Adjust the waveguide thickness and refractive index combination to ensure that the energy retention rate of the light beam is higher than 95% under multiple total internal reflection conditions; b. Optimize waveguide geometry to balance beam delivery efficiency and device compactness.

[0028] (3) Analysis of beam propagation path High-precision ray tracing technology is used to analyze the propagation path of the light beam inside the waveguide to verify the ambient light suppression effect and beam transmission efficiency.

[0029] Furthermore, the system has the following application scenarios: (1) Augmented reality display devices Adapt to complex ambient light conditions, significantly reduce rainbow pattern phenomenon, improve display stability, and is suitable for AR glasses and head-mounted display devices; (2) Medical imaging equipment Provides high-precision imaging for medical display and diagnostic applications under complex lighting conditions; (3) Industrial navigation and display It can adapt to various complex working conditions and provide stable visual output for industrial navigation and precise positioning.

[0030] Step 6: Performance Verification: (1) Rainbow suppression By optimizing the grating design, the system can significantly suppress the rainbow phenomenon. Zemax simulation results show that the rainbow phenomenon is reduced by more than 70%; (2) Diffraction efficiency Simulation results show that the diffraction efficiency of the PVG structure exceeds 90% in a multi-wavelength range, and the energy loss of the beam inside the waveguide is controlled within 5%.

[0031] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a grating waveguide device and a waveguide system based on polarization volume grating (PVG) technology, which is intended to effectively suppress the rainbow pattern phenomenon caused by ambient light interference in augmented reality (AR) devices, thereby significantly improving the clarity and stability of image display. The grating waveguide device consists of a waveguide substrate and a grating structure located thereon, the grating structure is used to receive a projected light beam from an imaging device, and accurately modulate the polarization state of the light beam through the PVG technology, so that the light beam forms a modulated light beam after passing through the grating structure. The modulated light beam propagates in a total reflection manner inside the waveguide substrate, thereby ensuring efficient transmission of the optical path.

[0032] The grating vector of this device forms a single closed loop in space by optimizing the design of the grating period, grating line direction and grating line density, ensuring the stability and consistency of the light beam propagation path and effectively suppressing the interference of ambient light diffraction on the imaging quality. Unlike traditional grating waveguide devices, the PVG technology in the present invention can significantly reduce the rainbow pattern phenomenon caused by ambient light and prevent diffracted light from entering the user's field of view, thereby maintaining stable image quality under various lighting conditions. The grating waveguide device is suitable for augmented reality display systems, which can not only provide distortion-free and distortion-free visual effects, but also maintain good display effects under complex ambient light conditions, greatly enhancing the user's visual immersion experience.

[0033] By utilizing the polarization-selective characteristics of the PVG grating, the system can significantly reduce the interference of ambient light and improve the stability and clarity of the display effect, especially in complex environments. By optimizing the waveguide structure and grating parameters, the system can achieve a miniaturized design, making it more suitable for the application of portable AR / VR devices and meeting the dual requirements of modern portable devices for size and performance. The system can support multi-wavelength conditions, adapt to different light source environments, meet the optical application requirements in a variety of scenarios, and ensure stable operation under various environmental conditions. The design of the PVG grating makes the diffraction efficiency of the system exceed 90%, thereby ensuring the efficient transmission of the light beam and improving the overall optical performance. This technology is not only suitable for fields such as augmented reality display, medical imaging, and industrial navigation, but can also be extended to other complex optical applications, with strong applicability and market potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 :Schematic diagram of the basic structure of the PVG grating waveguide system; Figure 2 : Schematic diagram of the working principle of polarization volume grating technology; the lateral period p in the figure x (also called surface period) refers to the spacing of the periodic fringes of the grating in a direction parallel to a reference direction (usually the x-axis or the edge of the device); it usually affects the lateral diffraction direction, that is, the horizontal component of the exit angle; Bragg period p B : refers to the periodic component perpendicular to the diffraction fringe direction and projected along the propagation direction of the incident light (or the k vector direction); p B It determines whether the Bragg conditions can be met, that is, whether strong coupling (maximum energy transfer) can be achieved; Grating tilt angle It is the angle between the stripe direction and the reference axis (such as the device edge or the incident plane), measured in degrees (°); when the grating stripes are not arranged completely parallel to the x-axis (i.e., tilted), this angle needs to be introduced to decompose the period; Figure 3 : Schematic diagram of the formation principle of rainbow pattern phenomenon when the existing grating waveguide is used as an AR glasses lens; Figure 4 : Flowchart of Zemax provided in the implementation of the present invention; Figure 5 :Schematic diagram of the beam propagation path of the grating waveguide device based on PVG technology; Figure 6 :PVG process preparation flow chart; Figure 7: Figures obtained by measuring and analyzing the rainbow phenomenon under the condition of ambient light, where (a) is the rainbow phenomenon caused by ambient light in traditional AR glasses; (b) is the suppression effect of the device of the present invention on the rainbow phenomenon; In the figure, 1-1, in-coupling grating, 1-2, paraxial lens, 1-3, turning grating, 1-4, rectangular light source, 1-5, detection unit, 1-6, out-coupling grating, 3-1, reflected ambient light, 3-2, transmitted rainbow pattern, 3-3, grating lens, 3-4, reflected rainbow pattern, 3-5, transmitted ambient light, 7-1, rainbow pattern phenomenon. DETAILED DESCRIPTION

[0035] The implementation of the present invention is described in detail below in conjunction with the accompanying drawings and a specific embodiment. The present invention aims to solve the rainbow pattern problem caused by ambient light interference in AR display devices through the innovative design of PVG technology, thereby achieving high-quality image display effects.

[0036] Step 1: Analyze the conditions and principles of rainbow pattern generation in AR system: like Figure 3 As shown in the figure, rainbow stripes usually appear in traditional grating waveguides, mainly because the external ambient light is diffracted through the grating and enters the observation field. The generation of rainbow stripes is closely related to the diffraction characteristics of the grating. When ambient light enters the grating structure at different angles and wavelengths, light at specific angles and wavelengths will diffract to form stripes of different colors. The figure shows the distribution of rainbow stripes, which has a significant impact on display quality in traditional waveguide structures.

[0037] Step 2: Set the parameters of the incident light: like Figure 4 As shown, the present invention simulates and optimizes the grating waveguide system by Zemax simulation software. The parameters of the incident light, including the light source type, wavelength range and incident angle, are set in the simulation environment to simulate the light conditions in actual applications. The wavelength of the incident light is set to the visible light range of 550 to 650 nanometers, and the parallel light source mode is selected to ensure uniform propagation of the light beam and stable optical transmission effect.

[0038] Step 3: Define the parameters of the PVG waveguide system like Figure 1 As shown, the PVG grating waveguide system includes an in-coupling grating 1-1, a paraxial lens 1-2, a turning grating 1-3, a rectangular light source 1-4, a detection unit 1-5 and an out-coupling grating 1-6. The PVG grating structure is the core of the present invention, which optimizes the propagation path of the light beam by adjusting the grating period, Bragg tilt angle and polarization state, and reduces the rainbow pattern phenomenon caused by ambient light. Figure 2 As shown, the horizontal period p xThe grating tilt angle is set to 800 nm to ensure that the incident light can produce efficient polarization-selective diffraction in the PVG structure. It is set at about 45° to ensure that the diffraction efficiency of the light beam in the grating is maximized and its polarization characteristics are optimized. B It is set to 200 nanometers to ensure strong light coupling and achieve maximum energy transfer.

[0039] Step 4: Construct the geometric model of the optical waveguide like Figure 1 and Figure 5 As shown in the figure, the waveguide system is designed to be a compact structure suitable for use in AR devices and is combined with a PVG grating. The waveguide substrate is made of a transparent material with a high refractive index, which supports multiple total reflections of the light beam in the waveguide, allowing the light beam to propagate over a long distance in the waveguide without energy loss. The geometric parameters of the waveguide (such as thickness and width) are optimized to meet the modulation requirements of the PVG grating.

[0040] Step 5: Perform a ray tracing simulation The whole system is simulated with high-precision ray tracing in Zemax, such as Figure 5 As shown, observe the propagation path of the light beam in the PVG grating and waveguide. By simulating and analyzing the propagation trajectory of the light beam, the propagation effect of the light beam under the modulation of the PVG structure is verified: Beam propagation path: After multiple diffraction and polarization modulation by the PVG grating inside the waveguide, the light beam can maintain a stable propagation path and avoid interference from ambient light.

[0041] Rainbow pattern suppression effect: Simulation results show that the PVG structure effectively minimizes the rainbow pattern phenomenon caused by ambient light diffraction, ensuring image display quality.

[0042] Step 6: PVG preparation like Figure 6 As shown, a photo-induced alignment layer is formed on the substrate surface by UV exposure (365 nm, exposure time 30-60 seconds, using photoinitiator IRGACURE651), and liquid crystal materials (including acrylic monomers and chiral dopants R5011 / S5011) are spin-coated to generate PVG structures using the self-assembly effect. Subsequently, UV curing (UV light intensity 15-25 mW / cm², curing time 30-60 seconds) is performed to stabilize the grating characteristics and ensure the refractive index modulation of the liquid crystal material. Finally, the grating is combined with a high refractive index waveguide substrate (such as glass or polymer) to form a complete grating waveguide device, ensuring that the system effectively suppresses the rainbow pattern phenomenon under complex ambient light conditions and achieves efficient beam diffraction and total internal reflection transmission.

[0043] Step 7: Measure the rainbow suppression effect like Figure 7 As shown, the present invention measures and analyzes the rainbow phenomenon under the condition of the presence of ambient light. Figure 7 The AR lens made of traditional gratings shown at 7-1 in (a) produces obvious rainbow pattern under ambient light. Figure 7 (b) shows the suppression effect of the PVG waveguide system of the present invention on rainbow stripes under the same conditions. The PVG grating design of the present invention greatly reduces the interference of ambient light, significantly weakens the rainbow stripe phenomenon, and improves the clarity of the display effect.

[0044] Step 8: System optimization and parameter adjustment Based on the simulation results, the parameters of the grating and waveguide system are further optimized to achieve the best rainbow ripple suppression effect.

[0045] Grating period fine-tuning: Fine-tune the period parameters of the PVG grating to meet the needs of different light sources and environmental conditions and improve the system's anti-interference ability.

[0046] Grating line direction adjustment: By precisely adjusting the direction and Bragg tilt of the grating lines, the polarization control effect of the light beam can be enhanced and the diffraction interference of ambient light can be further reduced.

[0047] Simulation optimization: Repeated simulations are performed under different ambient light intensities and incident angles to ensure that the system has stable rainbow suppression effects under complex lighting conditions.

[0048] Step 9: Data results and effect analysis like Figure 7 As shown, through the polarization modulation characteristics of the PVG grating, the grating waveguide system of the present invention significantly reduces the intensity of the rainbow pattern phenomenon, and reduces the rainbow pattern generated by ambient light by 70% compared with the prior art, ensuring the clarity and stability of the image. This effect makes the application of the present invention in augmented reality display devices have significant advantages.

[0049] The polarization volume grating (PVG) grating waveguide system of the present invention has been verified by Zemax simulation and experiment, showing good rainbow ripple suppression effect. Those skilled in the art can further optimize the implementation method without departing from the core idea of ​​the present invention, and these improvements belong to the protection scope of the present invention.

Claims

1. A grating waveguide device based on PVG technology, characterized in that: include: Waveguide substrate: Made of high refractive index material, with a refractive index ranging from 1.6 to 2.0, supporting total internal reflection transmission of light beams; Grating structure: set on the waveguide substrate, using PVG technology to modulate the polarization state of the incident light beam; The PVG is a periodic refractive index modulation structure formed by liquid crystal material through photo-induced orientation and self-assembly process; The grating period is 800 nanometers to 1 micron, the Bragg tilt angle is 40° to 65°, and it is suitable for full-color display in red, green, and blue bands; The grating structure guides the light beam into the waveguide matrix through the coupling-in grating, and outputs the light beam through the coupling-out grating after multiple total reflections, thereby suppressing the rainbow pattern phenomenon caused by ambient light.

2. The device according to claim 1, characterized in that The liquid crystal material forms a stable periodic grating structure through a photocuring process.

3. The device according to claim 1, characterized in that The waveguide substrate has a thickness of 1 mm, a width of 20 mm, and a length of 100 mm.

4. The device according to claim 1, characterized in that The diffraction efficiency of the PVG in the visible light band exceeds 80%.

5. A waveguide display system, characterized in that: Comprising a grating waveguide device as described in any one of claims 1 to 4, the system optimizes grating parameters and waveguide geometric dimensions through Zemax simulation to achieve a light beam transmission energy loss of less than 5% and a rainbow ripple intensity reduction of more than 70%; the grating parameters include period, grating line direction, and Bragg tilt; the waveguide geometric dimensions include a thickness of 1 mm, a width of 20 mm, and a length of 100 mm.

6. The system according to claim 5, characterized in that The Zemax simulation optimization includes ray tracing analysis to verify the beam propagation path and rainbow pattern suppression effect.

7. The system according to claim 5, characterized in that The system is adapted to AR glasses and maintains a rainbow-free display under complex ambient light conditions.

8. A method for preparing a grating waveguide device based on PVG technology, characterized in that: The following steps are involved: A photoinduced alignment layer is coated on the surface of the substrate, and a periodic alignment pattern is formed by ultraviolet exposure; Spin coating liquid crystal material, wherein the liquid crystal material includes a reactive liquid crystal monomer and a chiral dopant, and utilizes a self-assembly effect to generate a PVG structure; Photocuring treatment to stabilize grating characteristics; The grating waveguide device is packaged with a high refractive index waveguide substrate to form a complete grating waveguide device, wherein the high refractive index waveguide substrate is glass or polymer.

9. The method according to claim 8, characterized in that The photocuring treatment uses ultraviolet light irradiation, the ultraviolet light source is an LED ultraviolet light source with a wavelength of 365 nm, the curing time is 30-60 seconds, the photoinitiator IRGACURE 651 is used in the photocuring process, the liquid crystal material is a reactive liquid crystal monomer including acrylic double bonds, and the chiral dopant is R5011 / S5011.

Images