A grating waveguide device and waveguide system based on PVG technology

Abstract

The present invention discloses a grating waveguide device and a waveguide system based on the polarization volume grating technology, belonging to the technical field of augmented reality display. The device includes a waveguide substrate and a grating structure. The grating structure uses a liquid crystal material to form a PVG with periodic refractive index modulation through photo-induced alignment and self-assembly processes, which can selectively control the polarization state of the light beam and suppress the rainbow pattern phenomenon caused by ambient light diffraction. By optimizing the grating period, Bragg tilt angle, and waveguide substrate parameters, and combining Zemax simulation to optimize the light beam propagation path, efficient diffraction and total internal reflection transmission of multi-wavelength light beams are achieved. The waveguide system of the present invention can be adapted to devices such as AR glasses and head-mounted displays, significantly reducing the rainbow pattern intensity under complex ambient light conditions and providing a high-definition and distortion-free visual experience.

Description

Technical Field

[0001] The present invention relates to optical display technology, and in particular to a grating waveguide device and system based on a polarization volume grating (PVG) for suppressing the rainbow pattern phenomenon caused by environmental light diffraction in an augmented reality (AR) device and improving image display quality. Background Art

[0002] Augmented reality technology is a technology that integrates virtual information with the real world and is widely used in fields such as medical treatment, education, and gaming. In AR devices, the grating waveguide technology is an important way to display images, using tiny gratings to guide the images to the user's eyes. However, in practical applications, the grating waveguide devices in AR glasses and other wearable devices often face the rainbow pattern phenomenon caused by environmental light.

[0003] Rainbow patterns are caused by environmental light (such as sunlight, indoor lighting, etc.) diffracting through the grating structure and entering the eyes, resulting in image display distortion and interference. Current technologies mainly rely on optimizing the grating period, direction, 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 greater impact on image quality.

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

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

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

[0007] The specific technical solution is as follows:

[0008] A grating waveguide device based on the PVG technology, comprising:

[0009] A waveguide substrate: made of a high refractive index material with a refractive index range of 1.6 to 2.0, supporting the total internal reflection transmission of light beams;

[0010] Grating structure: It is arranged on the waveguide substrate and uses the polarization volume grating (PVG) technology to modulate the polarization state of the incident light beam;

[0011] The PVG is formed by a liquid crystal material through a photo-induced alignment and self-assembly process to form a periodic refractive index modulation structure;

[0012] The grating period is from 800 nanometers to 1 micrometer, and the Bragg angle is from 40° to 65°, which is suitable for full-color display in the red, green, and blue wavelength bands;

[0013] The grating structure guides the light beam into the waveguide substrate through the coupling-in grating, and after multiple total reflections, it is output by the coupling-out grating, suppressing the rainbow pattern phenomenon caused by ambient light.

[0014] Preferably, the liquid crystal material forms a stable periodic grating structure through a photocuring process.

[0015] Preferably, the thickness of the waveguide substrate is 1 millimeter, the width is 20 millimeters, and the length is 100 millimeters.

[0016] Preferably, the diffraction efficiency of the PVG in the visible light band exceeds 80%.

[0017] A waveguide display system includes the grating waveguide device described above. The system optimizes the grating parameters (period, grating line direction, Bragg angle) and waveguide geometric dimensions (thickness 1mm, width 20mm, length 100mm) through Zemax simulation, realizing efficient light beam transmission (energy loss < 5%) and rainbow pattern suppression (intensity reduction by more than 70%).

[0018] Preferably, the Zemax simulation optimization includes ray tracing analysis to verify the light beam propagation path and the rainbow pattern suppression effect.

[0019] Preferably, the system is adapted to AR glasses and maintains rainbow pattern-free display under complex ambient light conditions.

[0020] Preferably, a preparation method of a grating waveguide device based on the polarization volume grating (PVG) technology includes the following steps:

[0021] Coat a photo-induced alignment layer on the surface of the substrate, and form a periodic alignment pattern through ultraviolet exposure (wavelength 365 nm, exposure time 30 - 60 seconds). The ultraviolet exposure uses a photoinitiator IRGACURE 651 to ensure the self-assembly of the liquid crystal material to form a stable alignment structure in the subsequent steps.

[0022] Spin-coat a liquid crystal material, which includes acrylic monomers and a chiral dopant (such as R5011 / S5011). Generate a PVG structure through the self-assembly effect to ensure that the liquid crystal molecules are spontaneously arranged along the direction of the periodic pattern of the photo-alignment layer, forming a periodic structure with a high refractive index modulation.

[0023] Perform a photo-curing process to stabilize the grating characteristics. The curing process is carried out in a nitrogen protection environment to avoid the influence of oxygen, ensure the stability of the PVG structure, and enhance its optical characteristics.

[0024] Combine with a high refractive index waveguide substrate (such as glass or polymer) to integrate the grating structure 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.

[0025] Preferably, the photo-curing process uses ultraviolet light irradiation, and the curing time is 30 - 60 seconds to ensure the stability of the grating characteristics, so as to improve the diffraction efficiency and energy retention rate of the waveguide system.

[0026] Through the above steps, the prepared grating waveguide device has a 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 and distortion-free visual experience.

[0027] The present invention optimizes the optical system through Zemax simulation technology, covering multi-dimensional simulations of grating design, waveguide parameters, and beam propagation paths, ensuring excellent performance under different wavelengths and incident conditions. The present invention is applicable to devices such as AR glasses and head-mounted displays, and shows significant advantages especially under complex ambient light conditions. The specific steps are as follows:

[0028] Step 1, Grating waveguide substrate design:

[0029] a. Material: Use a high refractive index optical glass or polymer substrate with a refractive index range of 1.6 to 2.0, which supports multiple total internal reflection conditions to minimize the loss of the beam when propagating inside the waveguide;

[0030] b. Size optimization: Set the thickness of the waveguide substrate to 1 mm, the width to 20 mm, and the length to 100 mm to achieve efficient beam transmission while meeting the requirements of a compact design.

[0031] Step 2, PVG structure design:

[0032] a. Bragg period: Ranging from 800 nm to 1 µm, which can adapt to the conditions of the infrared and visible light bands;

[0033] b. Bragg tilt angle: ranging from 40° to 65°, achieving efficient diffraction of multi-wavelength light beams through angle optimization while suppressing ambient light interference;

[0034] c. Grating vector design: designed in the form of a closed loop, reducing scattered light and optimizing the light beam propagation path to improve transmission efficiency;

[0035] d. Polarization selectivity: using the photo-induced orientation and self-assembly process of liquid crystal materials to form a periodically refractive index modulation structure with optical anisotropy, realizing selective diffraction of polarized light and significantly reducing the rainbow pattern phenomenon.

[0036] Step Three, Design of Input and Output Gratings

[0037] a. Input grating: After the incident light enters the waveguide substrate through the input grating, the polarization state and propagation path are regulated by the PVG structure to ensure that the light beam undergoes multiple total internal reflections inside the waveguide;

[0038] b. Output grating: The light beam is output through the output grating to form a high-quality imaging light beam while avoiding unnecessary light energy loss.

[0039] Step Four, Design of Detector Unit:

[0040] a. Capture the light beam output from the waveguide exit and measure its energy distribution;

[0041] b. Analyze the imaging quality to verify the suppression effect on rainbow patterns and the overall performance of the system.

[0042] Step Five, Fabrication Process:

[0043] (1) Grating Fabrication Process

[0044] a. Photo-induced orientation: Generate an orientation layer on the substrate surface and use the self-assembly of liquid crystal materials to form a grating structure with periodically refractive index modulation;

[0045] b. Laser exposure: Adopt laser exposure technology to precisely control the Bragg period to adapt to the target wavelength band;

[0046] c. Photo-curing treatment: Improve the stability and anti-interference ability of the grating structure through the photo-curing process.

[0047] Step Six, Simulation and Optimization:

[0048] (1) Grating Design Optimization

[0049] a. Bragg tilt angle optimization: Through Zemax simulation, adjust the Bragg tilt angle to 45° to achieve efficient diffraction of the light beam;

[0050] b. Grating period optimization: Fine-tune the grating period to 800 nm to adapt to a specific wavelength range and further improve the diffraction efficiency.

[0051] (2)Waveguide parameter optimization

[0052] a. Adjust the combination of waveguide thickness and refractive index to ensure that the energy retention rate of the light beam under multiple total internal reflection conditions is higher than 95%;

[0053] b. Optimize the waveguide geometry to balance the light beam transmission efficiency and the device compactness.

[0054] (3)Analysis of the light beam propagation path

[0055] Adopt high-precision ray tracing technology to analyze the propagation path of the light beam inside the waveguide and verify the environmental light suppression effect and the light beam transmission efficiency.

[0056] Furthermore, the system has the following application scenarios:

[0057] (1)Augmented reality display device

[0058] Adapt to complex ambient light conditions, significantly reduce the rainbow pattern phenomenon, improve the display stability, and are applicable to AR glasses and head-mounted display devices;

[0059] (2)Medical imaging device

[0060] Provide high-precision imaging and are applicable to medical display and diagnostic applications under complex light source conditions;

[0061] (3)Industrial navigation and display

[0062] Adapt to a variety of complex working conditions, provide stable visual output, and are used for industrial navigation and precise positioning.

[0063] Step six, performance verification:

[0064] (1)Rainbow pattern suppression

[0065] Through optimizing the grating design, the system can significantly suppress the rainbow pattern phenomenon. The zemax simulation results show that the reduction of the rainbow pattern phenomenon is more than 70%;

[0066] (2)Diffraction efficiency

[0067] The simulation results show that the diffraction efficiency of the PVG structure in a multi-wavelength range exceeds 90%, and the energy loss of the light beam inside the waveguide is controlled within 5%.

[0068] The present invention has the following beneficial effects compared with the prior art:

[0069] The present invention discloses a grating waveguide device and its waveguide system based on polarization volume grating (PVG) technology, aiming to effectively suppress the rainbow pattern phenomenon caused by environmental 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 the projection beam from the imaging device and precisely modulate the polarization state of the beam through PVG technology, so that the beam forms a modulated beam after passing through the grating structure. The modulated beam propagates in the waveguide substrate by total internal reflection, thus ensuring the efficient transmission of the optical path.

[0070] The grating vector of this device forms a single closed loop in space through the optimized design of the grating period, grating line direction, and grating line density, ensuring the stability and consistency of the beam propagation path and effectively suppressing the interference of environmental light diffraction on the imaging quality. Different from traditional grating waveguide devices, the PVG technology in the present invention can significantly reduce the rainbow pattern phenomenon caused by environmental light, prevent diffracted light from entering the user's field of view, and thus maintain stable image quality under various lighting conditions. The grating waveguide device is applicable to augmented reality display systems, which can not only provide a distortion-free and aberration-free visual effect but also maintain a good display effect under complex environmental light conditions, greatly enhancing the user's visual immersion experience.

[0071] Utilizing the polarization selection characteristics of the PVG grating, the system can significantly reduce the interference of environmental light, improve the stability and clarity of the display effect, especially outstanding in complex environments. By optimizing the waveguide structure and grating parameters, the system can achieve miniaturized design, making it more suitable for the application of portable AR / VR devices, 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 various scenarios, and ensure stable operation under various environmental conditions. Moreover, the design of the PVG grating enables the diffraction efficiency of the system to exceed 90%, thus ensuring the efficient transmission of the beam and improving the overall optical performance. This technology is not only applicable to fields such as augmented reality display, medical imaging, and industrial navigation but also can be extended to other complex optical applications, with strong applicability and market potential. Brief Description of the Drawings

[0072] Figure 1 : Schematic diagram of the basic structure of the PVG grating waveguide system;

[0073] Figure 2 : Schematic diagram of the working principle of polarization volume grating technology; the horizontal period p in the figure x (also known as the surface period) refers to the spacing of the periodic stripes of the grating in the direction parallel to the reference direction (usually the x-axis or the edge of the device); it usually affects the horizontal diffraction direction, that is, the horizontal component of the exit angle;

[0074] Bragg period p B : It refers to the periodic component projected along the direction of the incident light propagation (or the direction of the k vector) perpendicular to the direction of the diffraction fringes; p B Determines whether the Bragg condition can be satisfied, that is, the position where strong coupling (maximum energy transfer) can be achieved;

[0075] Grating tilt angle Is the angle between the fringe direction and the reference axis (such as the device edge or the incident plane), in degrees (°); when the grating fringes are not arranged completely parallel to the x-axis (i.e., tilted arrangement), this angle needs to be introduced to decompose the period;

[0076] Figure 3 : Schematic diagram of the formation principle of the rainbow pattern when the existing grating waveguide is used as the lens of the AR glasses;

[0077] Figure 4 : Flowchart in Zemax provided in the implementation of the present invention;

[0078] Figure 5 : Schematic diagram of the beam propagation path of the grating waveguide device based on the PVG technology;

[0079] Figure 6 : PVG process preparation flowchart;

[0080] Figure 7 : Diagram obtained by measuring and analyzing the rainbow pattern phenomenon under the condition of the presence of ambient light, where (a) is the rainbow pattern phenomenon caused by ambient light in the traditional AR glasses; (b) is the effect diagram of suppressing the rainbow pattern phenomenon by the device of the present invention;

[0081] In the figure, 1-1, input coupling grating, 1-2, paraxial lens, 1-3, turning grating, 1-4, rectangular light source, 1-5, detection unit, 1-6, output 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 implementation method

[0082] The following combines the drawings and a specific embodiment to detail the implementation manner of the present invention. Through the innovative design of the PVG technology, the present invention aims to solve the problem of the rainbow pattern phenomenon caused by ambient light interference in AR display devices, thereby achieving a high-quality image display effect.

[0083] Step 1: Analyze the generation conditions and principles of the rainbow pattern in the AR system:

[0084] Such as Figure 3As shown, the rainbow pattern phenomenon usually appears in traditional grating waveguides, mainly because ambient light diffracts through the grating and enters the observation field of view. The generation of the rainbow pattern is closely related to the diffraction characteristics of the grating. When ambient light enters the grating structure at different angles and wavelengths, light of specific angles and wavelengths will diffract to form stripes of different colors. This figure shows the distribution of the rainbow pattern, and this phenomenon has a significant impact on the display quality in traditional waveguide structures.

[0085] Step 2: Set the parameters of the incident light:

[0086] As Figure 4 shown, the present invention simulates and optimizes the grating waveguide system through 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 incident light wavelength is set in the visible light range of 550 to 650 nanometers, and the parallel light source mode is selected to ensure the uniform propagation of the light beam and a stable optical transmission effect.

[0087] Step 3: Define the parameters of the PVG waveguide system

[0088] As Figure 1 shown, the PVG grating waveguide system includes an input 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 output coupling grating 1-6. The PVG grating structure is the core of the present invention. By adjusting the grating period, Bragg tilt angle, and polarization state, the propagation path of the light beam is optimized, and the rainbow pattern phenomenon caused by ambient light is reduced. As Figure 2 shown, the transverse period p x is set to 800 nanometers to ensure that the incident light can generate efficient polarization-selective diffraction in the PVG structure. The grating tilt angle is set at about 45° to ensure the maximum diffraction efficiency of the light beam in the grating and optimize its polarization characteristics. The Bragg period p B is set to 200 nanometers to meet strong light coupling and achieve the purpose of maximum energy transfer.

[0089] Step 4: Construct the geometric model of the optical waveguide

[0090] As Figure 1 and Figure 5 shown, the waveguide system is designed as a compact structure suitable for use in AR devices and combined with the PVG grating. The waveguide substrate is made of a transparent material with a high refractive index, supporting multiple total internal reflections of the light beam in the waveguide, enabling the light beam to propagate long distances 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.

[0091] Step 5: Perform ray tracing simulation

[0092] Perform high-precision ray tracing simulation on the entire system in Zemax, as Figure 5 shown, to observe the propagation path of the light beam in the PVG grating and waveguide. Analyze the propagation trajectory of the light beam through simulation to verify the propagation effect of the light beam under the modulation of the PVG structure:

[0093] Light beam propagation path: After multiple diffractions and polarization modulations of the light beam by the PVG grating inside the waveguide, it can maintain a stable propagation path and avoid ambient light interference.

[0094] Rainbow pattern suppression effect: The simulation results show that the PVG structure effectively minimizes the rainbow pattern phenomenon caused by ambient light diffraction, ensuring the image display quality.

[0095] Step 6: PVG preparation

[0096] As Figure 6 shown, a photo-alignment layer is formed on the substrate surface by ultraviolet exposure (365 nm, exposure time 30 - 60 seconds, using photoinitiator IRGACURE651). Spin-coat the liquid crystal material (including acrylic monomer and chiral dopant R5011 / S5011) and utilize the self-assembly effect to generate the PVG structure. Subsequently, perform ultraviolet curing (ultraviolet light intensity 15 - 25 mW / cm², curing time 30 - 60 seconds) to stabilize the grating characteristics and ensure the refractive index modulation of the liquid crystal material. Finally, combine the grating 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 and realizes efficient light beam diffraction and total internal reflection transmission under complex ambient light conditions.

[0097] Step 7: Measure the rainbow pattern suppression effect

[0098] As Figure 7 shown, the present invention measures and analyzes the rainbow pattern phenomenon under the condition of ambient light. Figure 7 In (a) of [reference], the AR lens prepared by the traditional grating shows obvious rainbow pattern phenomenon under ambient light, while Figure 7 in (b) of [reference] shows the rainbow pattern suppression effect of the PVG waveguide system of the present invention under the same conditions. The PVG grating design of the present invention greatly reduces the interference of ambient light, making the rainbow pattern phenomenon significantly weakened and improving the clarity of the display effect.

[0099] Step 8: System optimization and parameter adjustment

[0100] Based on the simulation results, further optimize the parameters of the grating and waveguide system to achieve the best rainbow pattern suppression effect.

[0101] Fine-tuning of grating period: Fine-tune the period parameters of the PVG grating to meet the requirements under different light sources and environmental conditions, and improve the anti-interference ability of the system.

[0102] Adjustment of grating line direction: By precisely adjusting the direction of the grating lines and the Bragg tilt angle, enhance the polarization control effect of the light beam, and further reduce the diffraction interference of ambient light.

[0103] Simulation optimization: Conduct repeated simulations under different ambient light intensities and incident angles to ensure the stable rainbow pattern suppression effect of the system under complex lighting conditions.

[0104] Step 9: Analysis of data results and effects

[0105] As Figure 7 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, reduces 70% of the rainbow pattern generated by ambient light compared with the prior art, and ensures the clarity and stability of the image. This effect gives the present invention significant advantages in the application of augmented reality display devices.

[0106] The polarization volume grating (PVG) grating waveguide system of the present invention demonstrates a good rainbow pattern suppression effect through Zemax simulation and experimental verification. Those skilled in the art can further optimize the implementation manner without departing from the core idea of the present invention, and these improvements all fall within the protection scope of the present invention.

Claims

1. A grating waveguide device based on PVG technology, characterized in that, Comprising: Waveguide substrate: Made of a high refractive index material with a refractive index range of 1.6 to 2.0, supporting total internal reflection transmission of light beams; Grating structure: Disposed on the waveguide substrate, using the PVG technology to modulate the polarization state of the incident light beam; The PVG is formed by a liquid crystal material through a photo-induced alignment and self-assembly process to form a periodic refractive index modulation structure; The grating period is 800 nanometers to 1 micrometer, and the Bragg tilt angle is 40° to 65°, adapted for full-color display in the red, green, and blue bands; The grating structure guides the light beam into the waveguide substrate through the coupling grating, and after multiple total reflections, it is output by the coupling-out grating, suppressing the rainbow pattern phenomenon caused by ambient light; The liquid crystal material forms a stable periodic grating structure through a photocuring process; The thickness of the waveguide substrate is 1 millimeter, the width is 20 millimeters, and the length is 100 millimeters; The diffraction efficiency of the PVG in the visible light band exceeds 80%.

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

3. The system according to claim 2, wherein The Zemax simulation optimization includes ray tracing analysis to verify the light beam propagation path and rainbow pattern suppression effect.

4. The system according to claim 2, wherein The system is adapted to AR glasses, maintaining rainbow-free display under complex ambient light conditions.

5. A method for preparing a grating waveguide device based on the PVG technology according to claim 1, characterized in that, Comprising the following steps: Coating a photo-induced alignment layer on the surface of the substrate, and forming a periodic alignment pattern through ultraviolet exposure; Spin-coating a liquid crystal material, the liquid crystal material including a reactive liquid crystal monomer and a chiral dopant, and generating a PVG structure using the self-assembly effect; Performing photocuring treatment to stabilize the grating characteristics; Combining with a high refractive index waveguide substrate for encapsulation to form a complete grating waveguide device, the high refractive index waveguide substrate being glass or polymer.

6. The method according to claim 5, wherein The photocuring treatment uses ultraviolet light irradiation, the ultraviolet light source being an LED ultraviolet light source with a wavelength of 365 nm, the curing time being 30 - 60 seconds, a photoinitiator IRGACURE 651 being used during the photocuring process, the liquid crystal material being a reactive liquid crystal monomer including an acrylic double bond, and the chiral dopant being R5011 / S5011.

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