Diffractive optical waveguide system, projection optical machine

Abstract

This application provides a diffractive waveguide system and a projection optical engine. The system includes a substrate and, on the substrate, a coupling grating, a first pupil grating, a second pupil grating, a deflection grating, and an output grating. The coupling grating is used to diffract and couple incoming light to obtain diffracted light. The deflection grating receives first diffracted light rays emitted from a first diffraction direction and outputs them from its output end. The first pupil grating receives the first diffracted light rays propagating along a target diffraction direction, performs a first pupil expansion process on these rays to obtain first pupil-expanded light rays, and outputs them from its output end. The output grating receives the first pupil-expanded light rays output from the first pupil grating and guides them out. This system is used to improve the uniformity of the field of view.

Description

Technical Field

[0001] This application relates to the field of diffractive waveguide technology, and in particular to a diffractive waveguide system and a projection optical engine. Background Technology

[0002] Emerging technologies such as Augmented Reality (AR), Virtual Reality (VR), Mixed Reality (MR), and in-vehicle Augmented Reality Head-Up Displays (AR-HUD) are developing rapidly, providing users with immersive experiences while continuously expanding the boundaries of applications. Among these fields, diffractive waveguide technology, due to its thin and light characteristics, relatively simple manufacturing process, and low mass production cost, is considered one of the key technological paths driving innovation in near-eye display devices. This technology efficiently utilizes light, providing a wide field of view and high-definition image quality while maintaining a compact device.

[0003] To address the issue of insufficient field-of-view uniformity in diffractive waveguide systems, a widely adopted solution is to implement software correction at the projection engine level. This involves preprocessing the original image source to adjust the brightness distribution in advance, compensating for non-uniformity caused by the waveguide hardware itself. This method attempts to correct any brightness differences that might affect the visual experience before the end user sees the image, ensuring overall image consistency and clarity.

[0004] However, while software correction can improve field uniformity to some extent, this method requires reducing the overall average brightness of the projector to achieve the desired effect. This may result in a dim display and significant differences in brightness at different locations, thus failing to solve the problem of insufficient field uniformity. Summary of the Invention

[0005] This application provides a diffractive waveguide system and a projection optical engine to solve the problem of insufficient field uniformity.

[0006] In a first aspect, embodiments of this application provide a diffractive optical waveguide system, the system including a substrate, and coupling gratings, a first pupil grating, a second pupil grating, a transition grating, and a coupling grating disposed on the substrate, wherein...

[0007] A coupling grating is used to diffract and couple external light rays to obtain diffracted light rays after diffraction deflection.

[0008] The deflection grating is disposed on one side of the coupling grating relative to the second pupil grating. It is used to receive the first diffracted light emitted from the first diffraction direction in the diffracted light. After adjusting the diffraction direction of the first diffracted light from the first diffraction direction to the target diffraction direction, it is output from the output end of the deflection grating.

[0009] The first pupil-expanding grating is used to receive the first diffracted light rays transmitted along the target diffraction direction, perform a first pupil-expanding process on the first diffracted light rays transmitted along the target diffraction direction to obtain the first pupil-expanded light rays, and output the first pupil-expanded light rays from the output end of the first pupil-expanding grating.

[0010] The coupling grating is used to receive the first pupil light output from the first pupil grating and to export the first pupil light.

[0011] In one possible implementation, a second pupil-expanding grating is disposed on the other side of the coupling grating and is used to receive the second diffracted light rays emitted from the second diffracting direction in the diffracted light rays, perform a second pupil-expanding process on the second diffracted light rays to obtain second pupil-expanded light rays, and output the second pupil-expanded light rays from the output end of the second pupil-expanding grating. The first diffracting direction and the second diffracting direction are different.

[0012] The coupling grating is also used to receive the second pupil light and to export the second pupil light.

[0013] In one possible implementation, the coupling grating is located between the first pupil grating and the second pupil grating.

[0014] In one possible implementation, the second pupil grating is a one-dimensional grating.

[0015] In one possible implementation, the period of the folding grating is less than the period of the first pupil grating and the second pupil grating.

[0016] In one possible implementation, the angle between the vertical direction and the horizontal direction of the grating lines coupled into the grating is -45 to 45 degrees.

[0017] In one possible implementation, the incident surface of the folding grating is disposed on one side of the coupling grating along the first diffraction direction, the exit surface of the folding grating is disposed opposite to the incident surface of the first pupil dilator grating, and the exit surface of the folding grating and the incident surface of the first pupil dilator grating are disposed close to each other.

[0018] In one possible implementation, the first pupil grating and the transition grating are one-dimensional gratings;

[0019] The input grating and output grating are either one-dimensional or two-dimensional gratings.

[0020] In one possible implementation, the coupling grating, the first pupil grating, the turning grating, and the coupling grating are distributed on the first bottom surface or the second bottom surface of the substrate;

[0021] or,

[0022] The coupling grating, the first pupil grating, the turning grating, and the coupling grating are distributed on the first bottom surface and the second bottom surface.

[0023] Secondly, embodiments of this application provide a projection optical engine, including a diffractive waveguide system.

[0024] Secondly, embodiments of this application provide a microcrack identification device, comprising:

[0025] The diffractive waveguide system and projection optical engine provided in this application include a substrate and a coupling grating, a first pupil grating, a second pupil grating, a deflection grating, and an output grating disposed on the substrate. The coupling grating is used to diffract and couple externally input light to obtain diffracted light after diffraction deflection. The deflection grating, disposed on one side of the coupling grating, is used to receive the first diffracted light emitted from the first diffraction direction, and outputs it from the output end of the deflection grating after adjusting the diffraction direction of the first diffracted light from the first diffraction direction to the target diffraction direction. The first pupil grating is used to receive... The first diffracted ray propagating along the target diffraction direction is received, and the first diffracted ray propagating along the target diffraction direction is subjected to a first pupil expansion process to obtain a first pupil expanded ray. The first pupil expanded ray is output from the output end of the first pupil expanded grating. The coupling grating is used to receive the first pupil expanded ray output from the first pupil expanded grating and to guide the first pupil expanded ray. By setting a turning grating, the light diffracted outside the coupling grating can be input into the coupling grating. Thus, based on the light directly diffracted to the coupling grating, the coupling efficiency of the coupling grating is improved, resulting in better image brightness and improved field uniformity. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0027] Figure 1a is a schematic diagram of the existing diffractive waveguide system provided in this application.

[0028] Figure 1b is a schematic diagram of the existing diffraction waveguide system provided in this application. Figure 2 ;

[0029] Figure 1c Schematic diagram of the existing diffractive waveguide system provided in this application Figure 3 ;

[0030] Figure 2 A schematic diagram of a diffractive optical waveguide system provided in this application;

[0031] Figure 3 A schematic diagram of the structure of a grating in a diffractive waveguide system provided in this application;

[0032] Figure 3a K-domain distribution diagram of the first pupil grating channel provided in this application;

[0033] Figure 3b The K-domain distribution diagram of the second pupil grating channel provided in this application;

[0034] Figure 3c A ray transmission tracing diagram of the first diffraction channel provided in this application;

[0035] Figure 3d Ray transmission tracing diagram of the second diffraction channel provided in this application;

[0036] Figure 3e The light rays from the first and second diffraction channels provided in this application are simultaneously traced.

[0037] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0038] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0039] First, let me explain the terms used in this application:

[0040] A grating is an optical element consisting of a series of equally spaced parallel lines, grooves, or alternating transparent and opaque stripes, used to precisely disperse and diffract light. When light passes through or is reflected from a grating, it is decomposed into multiple diffraction orders, each corresponding to a different diffraction angle, depending on the wavelength of the light and the periodic structure of the grating. Gratings are widely used in fields such as spectral analysis, laser systems, display technology, and communications because they can efficiently separate light of different wavelengths or control the direction of a light beam.

[0041] Grating type refers to the classification of diffraction gratings based on their structure and functional characteristics, mainly divided into one-dimensional gratings and two-dimensional gratings. A one-dimensional grating is a grating where the scribe lines or grooves are periodically arranged in only one direction. It is mainly used to control the diffraction behavior of light in a specific direction and is suitable for applications requiring unidirectional beam control, such as spectral analysis or simple beam steering. A two-dimensional grating, on the other hand, has the characteristic of periodic structures in two mutually perpendicular directions, enabling it to simultaneously affect the diffraction of light in two dimensions. It is suitable for more complex optical systems, such as multi-directional beam control, image processing, or holographic displays. These two types of gratings each have their unique advantages and application scenarios; the choice of which type to use depends on the performance requirements and design goals of the specific optical system.

[0042] Pupil dilation refers to the process by which a pupil dilation grating expands the light passing through it, thereby increasing the beam diameter or exit pupil area. Specifically, when light passes through the pupil dilation grating, the grating's microstructure decomposes and redirects the incident light, causing it to diffuse in a specific direction, forming a larger and more uniformly distributed light spot.

[0043] The period of a grating refers to the distance between two adjacent grating lines (or grooves), and is one of the most fundamental parameters in a grating structure. The grating period determines how the grating interacts with incident light, directly affecting diffraction efficiency, diffraction angle, and the separable wavelength range. Shorter periods are suitable for handling shorter wavelengths of light (such as blue light), while longer periods are better suited for handling longer wavelengths of light (such as red light). The choice of grating period is crucial for optimizing optical performance in specific applications, such as spectral analysis, laser modulation, display technology, and communication systems, ensuring that light is dispersed and modulated in the desired manner.

[0044] Figure 1a A schematic diagram of the existing diffractive waveguide system provided in this application is shown below. Figure 1a As shown, an existing diffractive waveguide system includes a waveguide substrate 110, a coupling grating 120, and an output grating 130. Rays a, b, and c with different field of view angles, after diffraction by the coupling grating 120, enter the waveguide substrate 110 at different angles and are transmitted via total internal reflection towards the output grating 130. However, due to the inherent diffraction characteristics of the coupling grating 120, the diffraction efficiency varies for rays with different field of view angles, resulting in a problem with field uniformity.

[0045] Figure 1b Schematic diagram of the existing diffractive waveguide system provided in this application Figure 2 , Figure 1c Schematic diagram of the existing diffractive waveguide system provided in this application Figure 3 ,like Figure 1bAs shown, an existing diffractive waveguide system includes: a waveguide substrate 110, a coupling grating 120, and a coupling grating 130. A ray b at any field of view, after passing through the coupling grating 120, will generate three main diffraction orders: a +1st order diffracted ray (diffracting towards the coupling grating 130), a 0th order diffracted ray, and a -1st order diffracted ray (diffracting away from the coupling grating 130). Currently, in existing diffractive waveguide systems, typically only the +1st order diffracted ray is coupled into the waveguide; the energy carried by other orders, such as the 0th and -1st orders, is wasted. Since the +1st order only carries a small portion of the light energy from all diffraction orders, higher coupling efficiency cannot be achieved, resulting in limited overall brightness of the diffractive waveguide. Furthermore, this single-channel coupling architecture inherently suffers from field-of-view inhomogeneity, i.e., ... Figure 1c As shown, the coupled image corresponding to the right field of view is darker, while the coupled image corresponding to the left field of view is brighter, resulting in an overall image that is bright on one side and dark on the other. This is especially true for full-color waveguides, where the shorter wavelength of blue light leads to a smaller diffraction angle for the +1st order, making the field-of-view inhomogeneity problem even more pronounced.

[0046] Therefore, existing diffractive waveguide systems suffer from low coupling efficiency due to using only +1st order diffracted rays for coupling, which limits the overall brightness of the system. More seriously, this single-channel coupling method also leads to natural field-of-view inhomogeneity, making the aforementioned field-of-view inhomogeneity problem more pronounced and severely affecting the user's visual experience and image quality.

[0047] To address the aforementioned technical challenges, this application provides a diffractive waveguide system and a projection optical engine. This system also couples -1st order diffracted light into the image. Thus, compared to the conventional single-channel coupling architecture, it has two different transmission channels, resulting in higher transmission efficiency and improved uniformity across the entire field of view.

[0048] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0049] Figure 2 A schematic diagram of a diffractive optical waveguide system provided in this application is shown below. Figure 2As shown, the diffractive waveguide system includes: a substrate 210, and a coupling grating 220, a first pupil grating 230, a deflection grating 240, and a coupling grating 250 disposed on the substrate 210. The coupling grating 220 is used to diffract and couple externally input light to obtain diffracted light after diffraction deflection. The deflection grating 240, disposed on one side of the coupling grating 220, is used to receive the first diffracted light emitted from the first diffraction direction, and to deflect the first diffracted light in the diffraction direction... After being adjusted from the first diffraction direction to the target diffraction direction, the light is output from the output end of the turning grating 240; the first pupil expanding grating 230 is used to receive the first diffracted light transmitted along the target diffraction direction, perform a first pupil expanding process on the first diffracted light transmitted along the target diffraction direction to obtain the first pupil expanding light, and output the first pupil expanding light from the output end of the first pupil expanding grating 230; the coupling grating 250 is used to receive the first pupil expanding light output from the first pupil expanding grating 230 and export the first pupil expanding light.

[0050] In this context, substrate 210 can refer to the waveguide substrate. In a diffractive waveguide system, the waveguide substrate serves as a transparent optical material layer for light transmission, forming the core of the waveguide. The waveguide substrate is typically made of materials with high optical transparency and low scattering loss, such as specific types of glass or plastic, to ensure efficient light propagation. The primary function of the waveguide substrate is to guide light entering from the coupling grating 220 along a predetermined path via total internal reflection, until the light is extracted by the decoupling grating 250 and projected onto the user's eye. The design and material selection of the waveguide substrate are crucial for ensuring image quality, field of view size, and overall system performance. Furthermore, the thickness and flatness of substrate 210 directly affect the thinness of the waveguide and the uniformity of the visual experience.

[0051] The coupling grating 220 is a key optical element in a diffracting optical waveguide system, used to efficiently guide light from a projection system into the waveguide substrate. It diffracts incident light through precisely arranged microstructures (such as scribe lines or grooves), allowing diffracted rays of a specific order to enter the waveguide at a predetermined angle and propagate within the waveguide via total internal reflection. The design and parameters of the coupling grating 220 (such as period, scribe line angle, and depth) determine the effective coupling efficiency, field of view, and image quality. Its performance is crucial for ensuring the brightness uniformity and overall optical performance of the optical waveguide system.

[0052] In this embodiment, the coupling grating 220 can be a circular or square area on the substrate 210, the grating type of the coupling grating 220 can be a one-dimensional grating, and the angle between the vertical direction and the horizontal direction of the grating lines on the coupling grating 220 is -45 to 45 degrees.

[0053] The perpendicular direction of the grating line can refer to the direction along the normal of the grating line (i.e., perpendicular to the grating line).

[0054] The horizontal direction of the grating line can refer to a reference direction within the plane where the grating is located. In this embodiment, it is a horizontal line perpendicular to the direction of gravity.

[0055] The output grating 250 is another key optical component in the diffractive waveguide system, responsible for efficiently extracting light propagating through total internal reflection within the waveguide substrate and projecting it into the user's eyes. The output grating 250 re-diffracts the propagating light, causing it to exit the waveguide at a specific angle and direction, forming a clearly visible image. The design of the output grating 250 must match that of the input grating 220 to ensure the correct path of light within the waveguide and the final display effect. Its performance directly affects image quality, brightness uniformity, and field of view, and is crucial for achieving high-quality augmented reality (AR) or virtual reality (VR) visual experiences.

[0056] In this embodiment, the coupling grating 250 can be a rectangular area on the substrate 210. The grating type of the coupling grating 250 can be a two-dimensional grating. In some embodiments, the grating unit structure of the coupling grating 250 can also include rectangular, cylindrical, elliptical cylindrical, other polygonal, and other structures.

[0057] The deflection grating 240 is a special optical element in a diffractive waveguide system used to change the propagation direction of light, allowing it to be redirected or folded at a specific angle within the waveguide substrate. Through a carefully designed microstructure, it efficiently diffracts light, enabling light rays that were originally propagating in one direction to continue propagating at a new angle, typically guiding light from the coupling grating 220 to the pupil grating or the output grating 250. This deflection capability is crucial for achieving compact and thin waveguide designs because it allows the optical path to be folded multiple times within a limited space without increasing the overall size of the device. Furthermore, the design parameters of the deflection grating 240 (such as period, scribe angle, and depth) need to be precisely controlled to ensure high diffraction efficiency and minimized light loss, thereby guaranteeing image quality and brightness.

[0058] The first diffracted ray received by the deflection grating 240 from the first diffraction direction can refer to the ray diffracted in the direction away from the position of the coupling grating 250, and the target diffraction direction can refer to the direction that will be diffracted toward the first pupil grating 230.

[0059] In this embodiment, the incident surface of the folding grating 240 is disposed on one side of the coupling grating 220 along the first diffraction direction, and the exit surface of the folding grating 240 is disposed opposite to the incident surface of the first pupil diffraction grating 230, with the exit surface of the folding grating 240 and the incident surface of the first pupil diffraction grating 230 being close together. Therefore, the first diffracted light rays along the target diffraction direction can be processed.

[0060] A pupil expander grating is a key optical element in a diffractive waveguide system used to extend the diameter of a light beam. Its function is to increase the width of the light propagation path within the waveguide, thereby effectively expanding the exit pupil (the area from which the eye can receive the image). Through the diffraction effect of the pupil expander grating, the incident light beam is broken down and redirected, allowing the light to be evenly distributed over a larger area. This not only improves the user's visual experience and allows for a greater range of eye movements, but also enhances the brightness uniformity and overall quality of the image. The design of pupil expander gratings typically involves precise control of the grating period and structural parameters to optimize diffraction efficiency and angular distribution, ensuring efficient and uniform beam expansion, which is crucial for achieving high-quality augmented reality (AR) and virtual reality (VR) displays.

[0061] In this embodiment of the application, the first pupil grating 230 can refer to a pupil grating used to perform a first pupil expansion process on the first diffracted light rays transmitted along the target diffraction direction to obtain the first pupil expanded light rays.

[0062] Therefore, the folding grating 240 and the first pupil grating 230 provided in this application embodiment can form a channel to couple the -1st order diffracted light (the first diffracted light) into the image, thereby improving the coupling efficiency and making the brightness of the image light output by the coupling grating 250 higher, and also improving the uniformity of the image field of view.

[0063] In this embodiment of the application, the system further includes a second pupil grating;

[0064] The second pupil expanding grating 260 is disposed on the other side of the coupling grating 220. It is used to receive the second diffracted light rays emitted from the second diffracting direction in the diffracted light rays, perform the second pupil expanding process on the second diffracted light rays to obtain the second pupil expanding light rays, and output the second pupil expanding light rays from the output end of the second pupil expanding grating 260. The first diffracting direction and the second diffracting direction are different.

[0065] The coupling grating 250 is also used to receive the second pupil light and to export the second pupil light.

[0066] The second pupil grating 260 can refer to a grating used to perform a second pupil expansion process on the second diffracted light rays transmitted along the second diffraction direction to obtain second pupil expanded light rays. The second diffracted light rays emitted from the second diffraction direction can refer to the +1st order diffracted light rays diffracted towards the coupling grating 250. By setting the second pupil grating 260, the second pupil expanded light rays can be better diffracted to the coupling grating 250, thereby improving the effect of the coupling grating 250 in extracting image light rays. Simultaneously, combined with the first pupil expanded light rays, the uniformity of the image field of view can be improved.

[0067] In this embodiment, to further and significantly improve the uniformity of the entire field of view, the coupling grating 250 is located between the first pupil grating 230 and the second pupil grating 260. Therefore, during use, the image is coupled in simultaneously using both the first pupil grating 230 and the second pupil grating 260, allowing the first and second pupil rays to be transmitted separately for the left and right halves of the image. Since each pupil grating only needs to optimize half of the field of view, it is equivalent to halving the optimized field of view, thus greatly reducing the optimization pressure for large field of view angles and improving the optimized average light efficiency. Simultaneously, the light from the two pupil gratings is superimposed at the eyebox position, improving the overall light efficiency and significantly improving the field of view uniformity problem of uneven brightness on one side and darkness on the other in the diffraction waveguide system, thus improving the field of view uniformity of the diffraction waveguide. Furthermore, since each pupil grating only transmits half of the field of view angle, the diffraction waveguide system can achieve a larger field of view transmission without requiring expensive materials with higher refractive indices.

[0068] In this embodiment, the period of the folding grating 240 is less than the period of the first pupil grating 230 and the second pupil grating 260.

[0069] In this embodiment, the coupling grating 220, the first pupil grating 230, the turning grating 240 and the coupling grating 250 are distributed on the first bottom surface or the second bottom surface of the substrate 210.

[0070] or,

[0071] The coupling grating 220, the first pupil grating 230, the turning grating 240 and the coupling grating 250 are distributed on the first bottom surface and the second bottom surface.

[0072] The first bottom surface can refer to one bottom surface (upper or lower) on the substrate 210, and the second bottom surface is another bottom surface opposite to the first bottom surface. The coupling grating 220, the first pupil dilator grating 230, the second pupil dilator grating 260, the turning grating 240, and the coupling out grating 250 can all be distributed on the first bottom surface or the second bottom surface; or the first bottom surface or the second bottom surface can be set as needed. For example, the coupling grating 220 and the first pupil dilator grating 230 can be set on the first bottom surface, and the second pupil dilator grating 260, the turning grating 240, and the coupling out grating 250 can be set on the second bottom surface; or the coupling grating 220, the turning grating 240, and the coupling out grating 250 can be set on the first bottom surface, and the first pupil dilator grating 230 and the second pupil dilator grating 260 can be set on the second bottom surface.

[0073] Figure 3 This is a schematic diagram of the structure of a grating in a diffractive waveguide system provided in this application. Figure 3a This application provides a K-domain distribution diagram of the first pupil grating channel. Figure 3b This is a K-domain distribution diagram of the second pupil grating channel provided in this application. Figure 3c The ray transmission tracing diagram of the first diffraction channel provided in this application. Figure 3d The ray transmission tracing diagram of the second diffraction channel provided in this application. Figure 3e The light rays from the first and second diffraction channels provided in this application are simultaneously traced.

[0074] like Figure 3 As shown, the diffractive waveguide system includes: a coupling grating region 310, a first pupil-expanding grating channel 320, a transition grating 330, a second pupil-expanding grating channel 340, and a coupling grating 350. Among them,

[0075] The first pupil expansion grating channel 320 and the turning grating 330 are located on both sides of the coupling grating region 310. Preferably, the first pupil expansion grating channel 320 and the turning grating 330 are collinear with the geometric center of the coupling grating region 310, and the direction of the line connecting the geometric centers has an angle with the horizontal direction.

[0076] The basic working process of the diffraction waveguide system is as follows: The image light signal projected from the optical engine first hits the coupling grating region 310. After diffraction by the coupling grating region 310, two diffraction orders, ±1, are generated, dividing the image information projected from the optical engine into two parts: The +1 order image propagates forward along the first pupil grating channel 320 by total internal reflection, and after diffraction by the first pupil grating channel 320, the +1 order is expanded and transmitted to the coupling grating 350, and the image is extracted from the coupling grating 350 to reach the human eye; In addition, the -1 order diffraction order generated by the coupling grating region 310 propagates towards the direction of the turning grating 330. After diffraction by the turning grating 330, the direction of light propagation is changed, causing it to propagate forward along the direction of the second pupil grating channel 340. After diffraction by the second pupil grating channel 340, the image is expanded and transmitted to the coupling grating 350, and the image is extracted from the coupling grating 350 to reach the human eye.

[0077] In some embodiments, the characteristic parameters of the diffractive waveguide system can be as follows: the coupling grating region 310 is a 4mm circle, using a one-dimensional grating with a grating period of 400nm, and the angle between the perpendicular direction of the grating line and the X-axis is 25°; the first pupil grating channel 320 is a polygonal region, using a one-dimensional grating with a grating period of 428.54nm, and the angle between the perpendicular direction of the grating line and the X-axis is -91.77°; the turning grating 330 is a trapezoidal region, using a one-dimensional grating with a grating period of 202nm, and the angle between the perpendicular direction of the grating line and the X-axis is 0-5.42°; the coupling grating 350 is a rectangular region with a size of 22mm x 18mm, using a two-dimensional grating with a grating period of 423.26nm in the X-direction and 719.6nm in the Y-direction, and the rotation direction of the two-dimensional grating relative to the X-axis is -5.46°. The K-domain distribution of the first pupil grating channel 320 is as follows. Figure 3a As shown, the K-domain distribution of the second pupil grating channel 340 is as follows: Figure 3b As shown.

[0078] Therefore, as Figure 3c As shown, the light from the light engine is diffracted by the coupling grating and then deflected along the angular direction, entering the first pupil grating channel 320. After the diffraction of the first pupil grating, the light beam is expanded into multiple beams, which are then deflected into the coupling grating 350. The coupling grating 350 outputs the multiple beams of light after pupil expansion in the same direction as the coupling, reaching the observer's eye.

[0079] like Figure 3dAs shown, light from the light engine is diffracted by the coupling grating and then deflected in the opposite direction of the angle, entering the deflection grating 330. The deflection grating 330 deflects the light to the second pupil diffraction grating channel 340. After the diffraction of the second pupil diffraction grating, the light beam is expanded into multiple beams, which are then deflected into the output grating 350. The output grating 350 directs the multiple beams after pupil diffraction to the observer's eye in the same direction as the coupling.

[0080] like Figure 3e As shown, the light from the light engine is diffracted by the coupling grating and then deflected in opposite directions to generate two diffraction channels. The light then propagates forward along their respective transmission paths and finally reaches the coupling grating 350, where they converge. The light from the two channels overlaps in space, so after passing through the coupling grating 350, the light from both channels is output in the same coupling direction and finally converges to form an image in the human eye.

[0081] This application also provides a projection optical engine, including the diffractive waveguide system in the embodiments of this application.

[0082] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A diffractive optical waveguide system, characterized in that, The system includes a substrate, and coupling gratings, a first pupil grating, a second pupil grating, a transition grating, and a coupling grating disposed on the substrate, wherein, The coupling grating is used to diffract and couple externally input light to obtain diffracted light after diffraction deflection. The folding grating is disposed on one side of the coupling grating relative to the second pupil grating, and is used to receive the first diffracted light emitted from the first diffraction direction in the diffracted light. After adjusting the diffraction direction of the first diffracted light from the first diffraction direction to the target diffraction direction, it is output from the output end of the folding grating. The first pupil-expanding grating is used to receive the first diffracted light rays transmitted along the target diffraction direction, perform a first pupil-expanding process on the first diffracted light rays transmitted along the target diffraction direction to obtain the first pupil-expanded light rays, and output the first pupil-expanded light rays from the output end of the first pupil-expanding grating; The coupling grating is used to receive the first pupil-expanding light output from the first pupil-expanding grating and to export the first pupil-expanding light.

2. The diffractive waveguide system according to claim 1, characterized in that, The second pupil-expanding grating is disposed on the other side of the coupling grating and is used to receive the second diffracted light emitted from the second diffracting direction in the diffracted light, perform a second pupil-expanding process on the second diffracted light to obtain a second pupil-expanded light, and output the second pupil-expanded light from the output end of the second pupil-expanding grating. The first diffracting direction and the second diffracting direction are different. The coupling grating is also used to receive the second pupil-expanding light and to export the second pupil-expanding light.

3. The diffractive waveguide system according to claim 2, characterized in that, The coupling grating is located between the first pupil grating and the second pupil grating.

4. The diffractive waveguide system according to claim 2, characterized in that, The second pupil grating is a one-dimensional grating.

5. The diffractive waveguide system according to claim 2, characterized in that, The period of the folding grating is less than the periods of the first pupil grating and the second pupil grating.

6. The diffractive waveguide system according to any one of claims 1-5, characterized in that, The angle between the vertical direction and the horizontal direction of the grating line on the coupled grating is -45 to 45 degrees.

7. The diffractive waveguide system according to any one of claims 1-5, characterized in that, The incident surface of the folding grating is disposed on one side of the coupling grating along the first diffraction direction, and the exit surface of the folding grating is disposed opposite to the incident surface of the first pupil dilator grating, with the exit surface of the folding grating and the incident surface of the first pupil dilator grating being close together.

8. The diffractive waveguide system according to any one of claims 1-5, characterized in that, The first pupil grating and the transition grating are one-dimensional gratings; The coupled-in grating and the coupled-out grating are one-dimensional gratings or two-dimensional gratings.

9. The diffractive waveguide system according to any one of claims 1-5, characterized in that, The coupling grating, the first pupil grating, the turning grating, and the coupling grating are distributed on the first bottom surface or the second bottom surface of the substrate; or, The coupling grating, the first pupil grating, the turning grating, and the coupling grating are distributed on the first bottom surface and the second bottom surface.

10. A projection optical engine, characterized in that, The diffractive waveguide system included in any one of claims 1-9.

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