Method and apparatus for analyzing maximum vertical field of view of monolithic two-dimensional pupil expanding geometric waveguide

Abstract

The application belongs to the technical field of waveguide and relates to a method and device for analyzing the maximum vertical field of view of a monolithic two-dimensional pupil expanding geometric waveguide. The method comprises the following steps: obtaining performance indicators of the monolithic two-dimensional pupil expanding geometric waveguide and constructing an optical waveguide structure; analyzing the vertical field of view according to the optical waveguide structure, so that the eye movement range condition meets the performance indicators, and a first limiting condition that needs to be met by the vertical field of view angle is obtained; analyzing the vertical field of view according to the optical waveguide structure, so that the total reflection condition meets the imaging condition, and a second limiting condition that needs to be met by the vertical field of view angle is obtained; analyzing the vertical field of view according to the optical waveguide structure, so that the stray light suppression condition meets the imaging quality requirement, and a third limiting condition that needs to be met by the vertical field of view angle is obtained; and obtaining the maximum vertical field of view angle according to the first limiting condition, the second limiting condition and the third limiting condition. The display performance of the waveguide can be fully exerted by using the application.

Description

Technical Field

[0001] This application relates to the field of waveguide technology, and in particular to a method and apparatus for analyzing the maximum vertical field of view of a monolithic two-dimensional pupil-expanding geometric waveguide. Background Technology

[0002] Augmented Reality (AR) technology overlays computer-generated virtual images onto real-world scenes in real time, enabling intuitive and efficient information display. Therefore, since its initial introduction in 1968, AR technology has attracted widespread attention and is hailed by many organizations as the next generation of intelligent reality technology after smartphones and computers. In recent years, AR technology has developed rapidly and has been widely applied in various fields such as medical devices, education, and entertainment. Near-eye displays (NEDs) are key hardware for achieving virtual-reality fusion in AR technology. NEDs can magnify, project, and display virtual images in front of the human eye without obstructing the real-world view, achieving the fusion of virtual images with real-world scenes. To achieve better display effects, NED technology is developing towards thinner and lighter designs, larger field of view (FOV), wider eye-box, and higher display quality. In recent years, many companies have released their products, such as Microsoft's HoloLens, Lumus, Magic Leap, Waveoptics, and LingxiAR. Related research has proposed many methods for realizing NEDs, such as prisms, freeform surfaces, Birdbath, retinal projection, optical waveguides, and metalens displays. However, there is currently no completely satisfactory solution that can simultaneously achieve a large exit pupil diameter (EPD), thinness, and a large field of view.

[0003] Traditional optical display solutions, represented by freeform surfaces and prisms, can achieve large FOVs, but they typically have a thickness exceeding 10 mm. Cheng Dewen et al. proposed two compact, lightweight, and stray light-suppressing freeform prism near-eye display methods, achieving FOVs of 38° and 50° with excellent image quality; however, the prism thicknesses reached approximately 9.5 mm and 12 mm, respectively. Retinal projection displays can achieve large FOVs and overcome convergence conflict, but require the wearer to precisely align their pupil with the convergence point of the Maxwell observation method, making them intolerant of relative eye movement and resulting in a very small range of eye movement. The metasurface display method proposed by Zhaoyi Li et al. can achieve large FOV displays using thin metasurfaces; however, the chromatic aberration problem and the millimeter-level limitations in metalens manufacturing restrict its development.

[0004] Waveguides are a technological solution that can simultaneously achieve a large field of view (FOV) and a compact, lightweight design. Light propagates within a waveguide via total internal reflection (TIR), thus guiding light entering the waveguide in a specific direction. Based on the principles of input and output couplers, optical waveguides can be divided into geometric waveguides and diffractive waveguides. Diffractive waveguides are mainly divided into surface relief grating waveguides (SRG) and volume holographic grating waveguides (VHG). Diffractive waveguides utilize the diffraction effect of light to control the beam; however, due to the limitations of the diffraction principle, diffractive waveguides exhibit significant color distortion and severe light leakage. Geometric waveguides, on the other hand, operate on the principles of geometric optics: when a beam of light propagates within a geometric waveguide and encounters a partial mirror array (PRMA), the beam is broadened into multiple beams that exit in the same direction, achieving an expanded exit pupil and allowing the outgoing light to cover a larger area. Due to its pupil-expanding principle and relatively mature manufacturing technology, geometric waveguides have no dispersion problems and can achieve excellent imaging quality, making them one of the most promising solutions for consumer-grade AR glasses.

[0005] Most existing research on geometric waveguides focuses on one-dimensional geometric waveguides. One-dimensional waveguides can only achieve exit pupil expansion in one direction, and only in this direction can the field of view and exit pupil be expanded. In the other direction, a large field of view and exit pupil can only be achieved through a projection system; therefore, the projection system needs to be very large, resulting in poor image quality, and the geometric waveguide structure needs to be designed to be very wide. The design and fabrication of one-dimensional geometric waveguides are simpler than those of two-dimensional waveguides, but they offer a smaller field of view, exit pupil distance, and eye movement range.

[0006] In 2005, Yaakov Amitai first proposed the two-dimensional pupil-expanding geometric waveguide. In 2018, Gu Luo et al. proposed a design method for a two-dimensional pupil-expanding geometric waveguide head-up display with stray light suppression. Their design used two vertically arranged one-dimensional waveguides to achieve pupil expansion in both directions, and optimized stray light and illumination uniformity. However, the separate vertical and horizontal pupil design requires a long exit pupil distance for the waveguide's projection path, limiting the field of view. Furthermore, the separate pupil two-dimensional geometric waveguide has a complex structure and significant thickness. In 2020, Lumus Ltd. proposed a near-eye display system using a single-layer two-dimensional pupil-expanding geometric waveguide, integrating the horizontal and vertical pupil expansion regions into a single waveguide sheet. In 2022, Cheng Dewen et al. designed a large field-of-view, single-layer, two-dimensional pupil-expanding geometric waveguide and completed the manufacturing and testing of a prototype, achieving a field of view of 45.2°H × 34.6°V, an eye movement range of 12.0 mm × 10.0 mm, and an exit pupil distance of 18.0 mm. These studies demonstrate that monolithic two-dimensional waveguide near-eye display devices possess advantages such as a large field of view, a thin shape, and a large exit pupil range, enabling high-quality image display.

[0007] However, existing two-dimensional waveguide design methods struggle to fully realize the display performance of waveguides. Traditional designs employ a reverse design approach, deriving the required waveguide shape from the specifications. While this method can quickly design waveguides that meet specifications, it often allows for superior performance with the same structure through techniques such as prism angle offsetting. Furthermore, after completing the design using traditional methods, compromises must be made between wearing comfort and size performance, inevitably leading to waveguide sizes that are unsuitable for user comfort. Summary of the Invention

[0008] Therefore, it is necessary to provide a method and apparatus for analyzing the maximum vertical field of view of a monolithic two-dimensional expanded pupil geometric waveguide, which can fully utilize the display performance of the waveguide, in order to address the above-mentioned technical problems.

[0009] The maximum vertical field of view analysis method for monolithic two-dimensional pupil-expanding geometric waveguides includes: The performance parameters of a monolithic two-dimensional pupil-expanding geometric waveguide were obtained, and the optical waveguide structure was constructed. Based on the optical waveguide structure, the vertical field of view is analyzed to ensure that the eye movement range condition meets the performance index, thereby obtaining the first constraint condition that the vertical field of view angle needs to satisfy. Based on the optical waveguide structure, the vertical field of view is analyzed to ensure that the total internal reflection condition satisfies the imaging condition, thereby obtaining the second constraint condition that the vertical field of view angle needs to satisfy. Based on the optical waveguide structure, the vertical field of view is analyzed to ensure that the stray light suppression condition meets the imaging quality requirements, thus obtaining the third constraint condition that the vertical field of view angle needs to satisfy. The maximum vertical field of view is obtained based on the first constraint, the second constraint, and the third constraint.

[0010] In one embodiment, based on the optical waveguide structure, the vertical field of view is analyzed to ensure that the eye movement range condition meets the performance index, thereby obtaining a first constraint condition that the vertical field of view angle needs to satisfy, including: Based on the optical waveguide structure, the vertical field of view is analyzed, the distance between some of the mirrors in the vertical pupil expansion region and the eye movement range in the vertical direction are calculated, and the eye movement range condition is made to meet the performance index, so as to obtain the first constraint condition that the vertical field of view angle needs to meet.

[0011] The above-mentioned method and apparatus for analyzing the maximum vertical field of view of a monolithic two-dimensional pupil-expanding geometric waveguide proposes a design method for a monolithic two-dimensional pupil-expanding geometric waveguide with low stray light, large field of view, and large exit pupil distance based on the maximum field of view angle analysis of two-dimensional waveguides. Attached Figure Description

[0012] Figure 1 This is an application scenario diagram of the maximum vertical field of view analysis method for a monolithic two-dimensional pupil-expanding geometric waveguide in one embodiment; Figure 2 This is a flowchart illustrating the maximum vertical field of view analysis method for a monolithic two-dimensional pupil-expanding geometric waveguide in one embodiment; Figure 3 This is a schematic diagram of a two-dimensional pupil-expanding geometric waveguide in one embodiment; Figure 4 This is a top view schematic diagram of a two-dimensional pupil-expanding geometric waveguide in one embodiment; Figure 5 This is a side view schematic diagram of a two-dimensional pupil-expanding geometric waveguide in one embodiment; Figure 6 This is a diagram of light propagation within a waveguide in one embodiment; Figure 7 This is a schematic diagram of the stray light generation process in one embodiment; Figure 8 This is a schematic diagram of stray light emission in one embodiment; Figure 9 This is a graph showing the maximum vertical field of view in one embodiment; Figure 10This is a schematic diagram of the propagation of edge field-of-view rays inside the waveguide in one embodiment, wherein (a) is a top view of the propagation trajectories of four field-of-view rays at different angles inside the waveguide, (b) is a schematic diagram of the propagation trajectory of one edge field-of-view ray, (c) is a schematic diagram of the angular relationship of four edge field-of-view rays at different angles on the surface of the waveguide coupling prism, and (d) is a schematic diagram of the coverage area of ​​four edge field-of-view rays at different angles in the eye-tracking range plane. Figure 11 For any one of the fields of view in one embodiment, The diagram illustrates the incident and exit of light rays, where (a) represents any field of view. A schematic diagram of light rays incident on and coupled into the prism, (b) showing any field of view. A schematic diagram of light rays exiting the waveguide; Figure 12 This is a schematic diagram of the exit pupil matching process in one embodiment; Figure 13 This is a schematic diagram of the process of exit pupil matching to obtain the maximum field of view in one embodiment, wherein (a) is FOV=20°H×20°V, (b) is FOV=40°H×20°V, (c) is FOV=45°H×20°V, (d) is FOV=50°H×20°V, (e) is FOV=30°H×30°V, (f) is FOV=30°H×40°V, (g) is FOV=30°H×50°V, and (h) is FOV=45°H×45°V; Figure 14 In one embodiment, a projection system including a sphere is provided, wherein (a) is the designed projection optical path, (b) is the dot plot of the projection system, (c) is the grid distortion of the projection system, and (d) is the MTF curve of the projection system. Figure 15 This is a diagram showing the maximum field of view exit pupil matching result of the waveguide in one embodiment; Figure 16 is a simulation diagram of the near-eye display system integrated in one embodiment in the Lighttools simulation software; Figure 17 The following is a simulation result diagram of the exit pupil range of four edge fields of view in an embodiment, wherein (a) is the exit pupil simulation result of edge field of view 1, (b) is the exit pupil simulation result of edge field of view 2, (c) is the exit pupil simulation result of edge field of view 3, and (d) is the exit pupil simulation result of edge field of view 4. Figure 18 This is a schematic diagram simulating human eye observation and testing of stray light in a waveguide in one embodiment; Figure 19 This is a block diagram of the maximum vertical field-of-view analysis device for a monolithic two-dimensional pupil-expanding geometric waveguide in one embodiment.

[0013] Figure label: 1. Microdisplay chip; 2. Projection system; 31. Waveguide coupling prism; 32. Waveguide horizontal pupil expansion region; 321. Partial reflector of the waveguide horizontal pupil expansion region; 33. Waveguide vertical pupil expansion region; 331. Partial reflector of the waveguide vertical pupil expansion region; 4. Eye movement range; 5. Human eye; 6. Waveguide ray; 61. Central field ray; 62. Positive field ray; 63. Negative field ray; 64. Stray light. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments.

[0015] The method described in this application can be used as follows: Figure 1 The application environment is shown. Terminal 102 communicates with server 104 via a network. Terminal 102 includes various computers, smartphones, tablets, and portable wearable devices, etc. Server 104 can be a server corresponding to various portal websites or work system backends, etc.

[0016] This application provides a method for analyzing the maximum vertical field of view of a monolithic two-dimensional pupil-expanding geometric waveguide, such as... Figure 2 As shown, in one embodiment, the method is applied to Figure 1 Taking the terminal in the example, it includes: Step 202: Obtain the performance indicators of the monolithic two-dimensional pupil-expanding geometric waveguide and construct the optical waveguide structure.

[0017] Specifically, the optical waveguide structure includes: a coupling prism and a waveguide sheet; the waveguide sheet includes: a horizontal pupil expansion region and a vertical pupil expansion region, both of which are achieved by partial mirror arrays (PRMA) facing different directions; the coupling prism is connected to the waveguide sheet (specifically, it can be a glued connection) to couple the incident light from the projection optics device into the horizontal and vertical pupil expansion regions of the waveguide sheet, thereby achieving horizontal and vertical pupil expansion.

[0018] The projection optics device includes: spaced-apart microdisplay chips and collimating optical path.

[0019] The optical waveguide structure and projection optics constitute a two-dimensional pupil-expanding geometrical waveguide near-eye display system.

[0020] like Figure 3As shown, light emitted from the microdisplay is amplified and collimated by the projection optics system and coupled into the waveguide by the coupling prism of the geometric waveguide. Once inside the waveguide, the light propagates through the upper and lower surfaces due to total internal reflection (TIR) ​​conditions. Inside the waveguide, the light first reaches the horizontal pupil expansion region. When it encounters the semi-transparent and semi-reflective membrane array arranged in the x-direction of the horizontal plane, the light splits into reflected and transmitted rays, widening in the x-direction, thus completing the exit pupil expansion in the x-direction. Simultaneously, the reflected rays from the horizontal pupil expansion region are redirected and propagate into the vertical pupil expansion region. Similarly, the light passing through the semi-transparent and semi-reflective membrane array in the vertical pupil expansion region completes the exit pupil expansion in the y-direction, is reflected out of the waveguide, propagates parallel to the eye-box, and finally enters the eye for imaging.

[0021] like Figure 4 As shown, the light emitted from the center pixel of the microdisplay chip exits perpendicularly to the projection light path, and is called the center field ray. Figure 4 (represented by solid lines), while the light rays emitted from the edge pixels of the microdisplay chip form the largest angle with the central field of view rays, which are called edge field of view rays ( Figure 4 (Represented by dashed lines). In the initial structure, such as... Figure 5 As shown, the coupling prism is parallel to the side of the waveguide, so the central field of view rays propagate along the X-axis, while the peripheral rays are symmetrical along the X-axis. Through exit pupil expansion in both directions, the exit pupil range of the near-eye display system is expanded from the initial small and inconvenient exit pupil size of the projection system to a larger, farther range suitable for human eye observation. This is called the eye-box. Users can observe the displayed image by looking within the eye-box of the near-eye display system.

[0022] Step 204: Based on the optical waveguide structure, analyze the vertical field of view to ensure that the eye movement range condition meets the performance index, and obtain the first constraint condition that the vertical field of view angle needs to meet.

[0023] Specifically: Waveguide sheets are made of materials with a refractive index of 100%. Made of materials with a higher refractive index, a larger field of view can generally be achieved. The length of the waveguide is... The widths (along the Y direction) of the horizontal and vertical pupil dilation regions are respectively and The thickness of the waveguide is The waveguide should be small and thin, like an eyeglass. The tilt angles between the transflective and reflective membrane arrays (PRMA) in the horizontal and vertical pupil expansion regions and the bottom edge of the waveguide are respectively... and These two angles determine the direction of the incident light, affect the size of the field of view, and are related to the amount of stray light from the waveguide; therefore, they require in-depth analysis. The width of the coupling prism is... The distance parameters typically depend on the exit pupil size of the projection optics and affect the system size and illumination uniformity. The distance parameters for some of the mirrors in the horizontal pupil expansion region are: , where i is the total number of prisms in the horizontal pupillary region, which determines the continuity and uniformity of illumination within the eye movement range.

[0024] Based on the optical waveguide structure, the vertical field of view is analyzed, and the distances between some of the mirrors in the vertical pupil expansion region are calculated to satisfy the following: (1) In the formula, The distance between the partial reflecting mirrors in the vertical pupil expansion area, the larger one This ensures better transmission observation results. The thickness of the waveguide sheet, The tilt angle between the semi-transparent and semi-reflective membrane array in the vertical pupil expansion region and the bottom edge of the waveguide sheet; The vertical display field of view of the system is expressed as:

[0025] The size of the eye movement range is expressed as:

[0026] Vertical eye movement range satisfies: (2) In the formula, This represents the vertical dimension of the eye movement range. This refers to the number of mirrors in the vertical pupil expansion area. The distance from the exit pupil. To display half of the field of view in the vertical direction in the air, satisfying And the angle of the central field of view ray in the counterclockwise direction is defined as positive; According to equations (1) and (2), when the thickness of the waveguide... When increased, the exit pupil range in the Y direction The vertical field of view will also increase accordingly; and when the vertical field of view... or exit pupil distance When increasing, This will decrease. Therefore, the key parameters of the waveguide are interdependent, requiring trade-offs during the design process. Typically, the eye-tracking range... It is selected and determined during the design phase; therefore, when designing the system, the vertical field of view... It is essential to meet the requirements of eye movement range.

[0027] According to equation (2), to ensure that the eye movement range condition meets the performance index, the first constraint condition that the vertical field of view needs to satisfy is obtained: (3) Step 206: Based on the optical waveguide structure, analyze the vertical field of view to ensure that the total internal reflection condition meets the imaging condition, and obtain the second constraint condition that the vertical field of view angle needs to satisfy.

[0028] Specifically: Based on the optical waveguide structure, the vertical field of view is analyzed, such as... Figure 6 As shown, when the vertical field of view in the air is... When light rays at an angle are coupled into an optical waveguide, they are refracted at the waveguide surface. According to the law of refraction, the angle of refraction of the light ray inside the waveguide sheet can be calculated: (4) In the formula, The angle between the incident ray in the vertical direction and the central field of view within the waveguide. The angle of the field of view in the vertical direction in the air. The refractive index of the waveguide sheet; When light propagates inside a waveguide, the light rays not reflected by the partial mirrors must satisfy the condition of total internal reflection to propagate normally. Based on geometric relationships, the field of view in the vertical direction... ( The angle of incidence for a ray of light at an angle of 0 to undergo total internal reflection within a waveguide is 0. ,in( When light propagates inside a waveguide, it satisfies the condition for total internal reflection, meaning the angle of incidence is greater than the critical angle for total internal reflection. (5) In the formula, This is the critical angle at which light undergoes total internal reflection within the waveguide; when Pick When the angle of incidence reaches its minimum value, it is... It should be greater than the critical angle for total internal reflection. Therefore, based on the total internal reflection condition, to satisfy the imaging condition, we obtain the second constraint that the vertical field of view must satisfy: (6) Step 208: Based on the optical waveguide structure, analyze the vertical field of view to ensure that the stray light suppression condition meets the imaging quality requirements, and obtain the third constraint condition that the vertical field of view angle needs to satisfy.

[0029] Specifically: Wang et al. proposed that stray light in one-dimensional geometric waveguides can be divided into three types: stray light caused by the coupling structure, and stray light caused by abnormal reflections from the front and rear surfaces of partial mirrors. In this design, stray light generated in the vertical pupil expansion region of the two-dimensional waveguide may fall into two of these three categories: stray light caused by unnecessary reflections of light rays incident at large angles on the front and rear surfaces of partial mirrors. After being generated, stray light propagates within the waveguide via total internal reflection. When the stray light encounters the next partial mirror, it is either reflected and coupled out by the partial mirror, becoming observable stray light that affects image quality; or it is reflected after large-angle incidence and transforms back into normal light. When analyzing waveguide stray light, only the stray light that is successfully coupled out needs to be considered.

[0030] Based on the optical waveguide structure, the vertical field of view is analyzed, and through geometric analysis, such as... Figure 7 As shown, the stray light emission angle is inversely proportional to the half-field angle. Calculate the stray light emission angle: (7) In the formula, This is the angle of incidence when stray light refracts and exits the waveguide sheet. The positive sign indicates that the stray light propagates in the direction of normal light propagation within the waveguide. This represents the angle between the incident ray in the vertical direction and the central field of view within the waveguide, ranging from... When light rays are in the central field of view, the angle is positive if they are counterclockwise and negative if they are clockwise. According to equation (7), the waveguide structure can be specially designed through calculation to guide stray light outside the eye movement range, directly preventing the human eye from observing stray light inside the eye movement range. Take the maximum value At that time, the angle of departure of stray light Reaching the minimum value At this point, the emitted stray light is closest to the eye movement range. It's important to note that, under normal circumstances, stray light only appears at the second partial mirror. For example... Figure 8 As shown, when stray light just reaches the boundary of the eye movement range, the angle between the stray light and the eye movement range is called the critical angle. This means that, when stray light reaches the boundary of the eye movement range, the critical angle satisfies: (8) In the formula, This represents the vertical offset distance of the eye movement range, with the positive Y-axis as the positive value. No offset indicates that the center of the eye movement range is directly opposite the center of the vertical waveguide region. The minimum exit angle of the emitted stray light... Greater than the critical value of the exit angle At this point, all stray light generated by the vertical waveguide is coupled out of the eye-tracking range, thus completing the suppression of stray light; To ensure that stray light suppression meets imaging quality requirements, the third constraint that the vertical field of view must satisfy is obtained: (9) Step 210: Obtain the maximum vertical field of view based on the first constraint, the second constraint, and the third constraint.

[0031] Specifically: Using the partial reflection angle of the vertical pupil expansion region as the abscissa, the field of view of the incident light in the air as the ordinate, and the first, second, and third constraints, as well as the field of view of the incident light in the air being greater than zero, as boundary conditions, the safe zone is obtained, and the point where the maximum value of the ordinate in the safe zone is located is the maximum vertical field of view angle.

[0032] More specifically: Based on the above derivation, the maximum vertical field of view is calculated under the conditions of eye movement range, total internal reflection, and stray light suppression. For example... Figure 9 As shown, the horizontal axis represents the partial mirror tilt angle perpendicular to the pupil expansion region. The vertical axis represents the field of view of the incident light ray in the air. The line segments in the figure represent the three constraints and the field of view mentioned above, respectively. With a limit greater than 0, the safe zone in the diagram represents the selectable stray light-free imaging region, and the uppermost point of the safe zone is the maximum field of view of the vertical pupil expansion region. For example: when the refractive index of the waveguide material is greater than 0... eye movement range Exit pupil distance ,thickness The number of partial reflectors Eye movement range offset As shown in the figure, it can be concluded that when When the vertical field of view is, the maximum field of view is ,Right now That is, the maximum vertical field of view can reach 60° under this structure. .

[0033] In this embodiment, the three most critical performance parameters of the near-eye display system are: field of view, eye movement range, and exit pupil distance. The design of the projection optical path determines the size of the field of view; while the waveguide design determines the size of the eye movement range and exit pupil distance. Generally, the eye movement range and exit pupil distance are determined first in the design process of the near-eye display system: if the designed waveguide has a large eye movement range, the user can still clearly observe the displayed image when there is a slight displacement relative to the near-eye display device. Therefore, the size of the eye movement range is usually set to 8-14mm; the exit pupil distance of the near-eye display system is generally designed to be 16-20mm, so that the user can use the near-eye display device as if wearing glasses. In order to fully realize excellent display performance, after the eye movement range and exit pupil distance have been determined, analyzing and finding the maximum value of the waveguide's field of view becomes the most critical step in the waveguide design process. In the Y direction, the maximum value of the vertical field of view is limited by the eye movement range condition, the total internal reflection condition, and the stray light suppression condition.

[0034] The above-mentioned maximum vertical field of view analysis method for monolithic two-dimensional pupil-expanding geometric waveguides proposes a design method for monolithic two-dimensional pupil-expanding geometric waveguides with low stray light, large field of view, and large exit pupil distance based on the maximum field of view angle analysis of two-dimensional waveguides. The structural characteristics of the two-dimensional waveguide are analyzed, and the constraints and calculation methods for the maximum vertical field of view angle in the vertical pupil expansion region are proposed. Simultaneously, the causes and propagation characteristics of stray light are analyzed, and methods for suppressing stray light are proposed. The projection optical path of the two-dimensional geometric waveguide is designed, and system integration is completed. A two-dimensional pupil-expanding geometric waveguide is designed using the maximum field of view angle analysis method, and simulation verification is performed using the optical software Lighttools. It has an eye movement range of 12.0 mm × 12.0 mm, an exit pupil distance of 18.0 mm, a field of view angle of 50.00°H × 29.92°V, and a thickness of 1.7 mm. Simulation results show the feasibility of the proposed maximum field of view angle analysis, and the designed system has good illumination uniformity, achieving excellent performance for human eye observation.

[0035] It should be understood that, although Figure 2 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 2At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0036] In one specific embodiment, the propagation path of the incident light ray in the monolithic two-dimensional pupil-expanding geometric waveguide is calculated and the bias angle of the coupling prism is designed. The exit pupil is matched through numerical simulation so that the exit pupil range covers the eye movement range and the maximum field of view is obtained.

[0037] Figure 10 (a) A top view showing the propagation trajectories of light rays from four different angles within the waveguide. It is worth noting that only the light reflection in the horizontal pupil dilation region is shown in the figure, because only this part of the light is the "effective light" that ultimately covers the eye movement range, while the light in other parts is not observed by the human eye and therefore does not affect the imaging effect, so it is not shown in the figure. Figure 10 (b) illustrates the propagation of light rays from a single field of view (edge ​​field of view 3) within the waveguide, their reflection out of the waveguide, and their final arrival at the eye-tracking plane. The area covered by the light rays within the eye-tracking plane is called the exit pupil region of the field of view. The human eye can observe the light rays of this field of view when it is within this exit pupil region. Within the exit pupil plane of the waveguide, the exit pupil region of each field of view has a different position, shape, and size. The overlapping portion of the exit pupil regions of all fields of view constitutes the effective imaging region, within which the human eye can observe the complete image. The exit pupil matching process involves adjusting the exit pupil regions of all fields of view to ensure that the effective imaging region meets the exit pupil range requirements, such as... Figure 10 As shown in (d).

[0038] Exit pupil matching is a crucial step in the design of two-dimensional geometric waveguides, requiring the design of a suitable waveguide structure based on the propagation path of light. During the design process, the waveguide's field of view, exit pupil distance, and exit pupil area are interdependent; increasing one parameter will decrease the others. Generally, to achieve the maximum field of view of the waveguide, while ensuring that the exit pupil matching meets the requirements for exit pupil distance and eye movement range, minimizing the additional exit pupil area is key.

[0039] To achieve exit pupil matching, the optical propagation path should first be numerically calculated. This represents the horizontal and vertical field of view of the coupled waveguide ray in air, such as... Figure 10 As shown in (c). Consider four edge field rays. The coverage areas on the exit pupil plane are: peripheral fields of view 1, 2, 3, and 4, represented by red, orange, green, and blue, respectively. When the exit pupil range of the rays from the four peripheral fields of view can cover the entire eye movement range on the exit pupil plane, the exit pupil range of the rays from all fields of view can completely cover the eye movement range. At this time, the user can observe the complete display image within the eye movement range. To ensure that the rays from the central field of view exit perpendicularly to the waveguide surface, the tilt angle of the coupling prism is usually designed as follows: The central field of view is perpendicular to the surface of the coupled prism. Figure 10 (c) shows a schematic diagram of the incidence of four peripheral fields of view on the coupling prism, where white rays represent central field of view rays, white dashed lines represent auxiliary lines perpendicular to the surface of the coupling prism, and red line segments represent incident and refracted rays of peripheral field of view 1.

[0040] Calculating the propagation path of the incident ray within a monolithic two-dimensional pupil-expanding geometric waveguide includes: Figure 11 (a) represents any field of view as A schematic diagram of light rays incident on a coupling prism, where the incident angle of the light rays on the surface of the coupling prism satisfies: (10) In the formula, Let be the angle of incidence of the light ray on the surface of the coupling prism. The horizontal field of view of light in the air; After refraction, the angle between the light rays inside the waveguide and the surface of the coupling prism satisfies: (11) In the formula, The angle between the light ray inside the waveguide and the surface of the coupling prism; According to geometric relationships, the field of view angle of the refracted light rays satisfies: (12) In the formula, The vertical field of view of light in the waveguide. The horizontal field of view of light rays in the waveguide; After entering the waveguide for propagation, for ease of calculation, the propagation of light can be described by two parameters: the angle between the projection of the light ray into the XOY plane and the Y-axis. and the angle between the light ray and the XOY plane. These describe the direction of light propagation and the angle between the light ray and the waveguide surface in the top view, respectively. For a waveguide sheet with no bias angle for the coupling prism, i.e., a waveguide where the coupling prism is parallel to the side of the waveguide, the following conditions are met: (13) In the formula, Let be the angle between the projection of light rays within the vertical pupil region onto the bottom plane of the waveguide and the side of the vertical pupil region. Let be the angle between the projection of light rays within the horizontal pupil region onto the bottom plane of the waveguide and the side of the horizontal pupil region. The angle between the ray and the bottom plane of the waveguide. Based on the above formulas, the propagation direction and coverage area of ​​light rays in any field of view after entering the waveguide can be calculated, as well as the propagation direction of light rays in any field of view before exiting the waveguide. Furthermore, the propagation direction of light rays after exiting the waveguide can be further deduced.

[0041] In the vertical pupil expansion region, light is reflected by the vertical mirrors and refracts out of the waveguide, such as... Figure 11 As shown in (b). Starting from the highest point of the light ray (point A), draw a perpendicular line AO ​​to the bottom surface of the waveguide, intersecting the bottom surface at point O. Set point O as the origin of the local coordinate system, with coordinates... Then the coordinates of point A are Line segment AB is perpendicular to the plane of the perpendicular part of the reflector; that is, the normal vector of the perpendicular part of the reflector is... The vector AC represents the light ray that is reflected. This indicates that the vector of the reflected ray is .

[0042] (14) Then the reflection vector for: (15) The angle between the reflected ray and the top surface of the waveguide The angle between the projection of the ray on the top surface and the y-axis of the local coordinate system. for: (16) Typically, waveguide design follows the principle of "center field of view perpendicular to the waveguide surface upon exit," and the waveguide does not possess optical power. In this case, the field of view of the light rays exiting the waveguide is the same as that at incidence. That is, the following relationship exists: (17) Using equations (10)-(16), the incident light rays in any field of view can be calculated. The trajectory of rays coupled out within the waveguide. Numerical simulations of forward ray tracing in two-dimensional geometric waveguides can be performed, calculating the propagation path and effective exit pupil range for each field of view. Through optimization design, numerical simulations of exit pupil matching in the two-dimensional waveguide can be completed. In the two-dimensional waveguide, the specific propagation path of edge rays is as follows: Figure 12As shown in (a), four edge rays propagate to the exit pupil plane, and the exit pupil range can be calculated through numerical simulation. The numerical simulation results are displayed as color-filled parallelograms. Figure 12 (b) in. In Figure 12 As shown in (b), when the coupling prism is parallel to the waveguide side, the incident edge field rays are horizontally symmetrically distributed in the horizontal pupil expansion region, and the effective imaging area of ​​the exit pupil plane cannot completely cover the central square eye movement range. This is because the green and blue fields of view cannot propagate to the farthest end of the waveguide, resulting in a smaller coverage area on the exit pupil plane. Therefore, in Figure 12 In (b), the coupling prism is given a bias angle that rotates clockwise. Let the counterclockwise offset be positive. At this point, both green and blue edge field rays can reach the far end of the waveguide, and the reflected light exit pupil range can also cover the eye movement range. That is, the two-dimensional waveguide pupil matching of this parameter meets the system requirements.

[0043] To ensure that the central field of view rays are perpendicular to the waveguide, an offset angle is designed for the coupling prism. When the coupling prism introduces an offset angle, the tilt angle of the partial reflectors in the horizontal pupil expansion region should satisfy the following: (18) In the formula, The tilt angle of the partial reflecting mirror in the horizontal pupil expansion area. The offset angle of the coupling prism.

[0044] During exit pupil matching, the waveguide dimensions Width of the horizontal pupil dilation area Waveguide thickness Width of the coupling prism The position and angle of the coupling prism, and the angle of the vertical part of the reflector. Many parameters can affect the final result. Furthermore, as the field of view increases, the effective imaging area of ​​the waveguide shrinks dramatically, eventually failing to meet the eye-tracking range requirements. Figure 13 As shown. Figure 13 The basic parameters of the two-dimensional waveguide for exit pupil matching are: refractive index Exit pupil distance eye movement range The width of the coupling prism is Vertical pupil expansion region partial mirror tilt angle Then by Figure 9 It can be seen that the maximum vertical field of view without stray light is . Figure 13 middle Indicates the offset angle of the coupling prism; This indicates the distance offset of the eye movement range in the Y-axis direction. The positive Y-axis is taken as positive. When there is no offset, the eye movement range is located at the center of the vertical pupil dilation area. This indicates the distance offset of the coupling prism in the Y-axis direction. The positive Y-axis is taken as positive. When there is no offset, the coupling prism is located at the center of the horizontal pupil expansion region.

[0045] Depend on Figure 13 It can be seen that increasing the horizontal field of view mainly affects the length of the effective imaging region, while increasing the vertical field of view mainly affects the width of the effective imaging region. Analysis shows that increasing the waveguide length... Angle offsetting of the coupling prism can effectively expand the width of the effective imaging area, while increasing the width of the vertical pupil expansion area can significantly increase the width of the effective imaging area. Therefore, under the premise of meeting the exit pupil distance and eye movement range indicators, in the process of performing exit pupil matching to find the maximum field of view of the waveguide, it is necessary to change the waveguide parameters multiple times and try iteratively to finally find the maximum field of view that the waveguide can achieve.

[0046] In waveguide near-eye display systems, a projection optics system is needed to magnify the image from the microdisplay and project it onto the coupling prism of the waveguide. Since the waveguide lacks optical power, the field of view of the waveguide near-eye display system is the same as the field of view of the projection optical path, provided the maximum field of view of the waveguide is met. Therefore, to maximize the performance of the waveguide display, the field of view of the projection optical path should be close to the maximum field of view achievable by the waveguide.

[0047] Based on the previous analysis of the maximum field of view achievable by the waveguide, we selected the tilt angle of the vertical part of the reflector. The corresponding maximum vertical field of view without stray light is That is, select We use common For microdisplays with high resolution, the horizontal field of view is selected. After exit pupil matching, the configuration parameters of our designed two-dimensional waveguide are listed in Table 1.

[0048] Table 1

[0049] In this study, one Silicon-inorganic light-emitting diode (Si-OLED) microdisplays were selected as the image source, with pixel sizes approximately [missing information]. The display size of Si-OLED microdisplays is The resolution is Based on the waveguide designed during the exit pupil matching process, we designed a projection system including a sphere, such as... Figure 14 As shown in (a), the length of the projection system ( )for The FOV and exit pupil size of the projection system are respectively... ( )and Exit pupil distance is The effective focal length (EFL) and F-number of the projection system are respectively... and . Figure 14 (b) shows a dot plot of the designed projection system. Figure 14 (c) illustrates the grid distortion of the projection system, with the maximum distortion being less than [missing value]. . Figure 14 (d) is the modulation transfer function (MTF) diagram of the system. The MTF of the system remains constant across the entire field of view. When it is higher than 0.5.

[0050] A two-dimensional optical waveguide, projection optical path, and microdisplay chip were integrated to obtain a compact, glasses-like near-eye display system. This demonstrates that the designed two-dimensional waveguide near-eye display system overcomes the drawbacks of traditional near-eye display systems, which are large and bulky. The integrated near-eye display system was simulated in Lighttools simulation software to verify the design method proposed in this paper. Figure 16 As shown. Figure 16 The integrated two-dimensional waveguide near-eye display system was demonstrated. Light is emitted from a rectangular microdisplay, collimated through the projection light path, and then incident and coupled into a prism, entering the interior of the optical waveguide. After pupil dilation, the light exits the waveguide.

[0051] We performed waveguide exit pupil matching to analyze the maximum field of view achievable by the waveguide. Figure 15 The results of the designed two-dimensional waveguide pupil matching are shown. The effective imaging areas of the four marginal fields of view within the exit pupil plane completely cover the eye movement range, at which point the maximum field of view of the waveguide is [value missing]. To verify the full-field exit pupil matching of the designed two-dimensional geometric waveguide, a receiver was added to the exit pupil plane, and four light sources were placed at the four corners of the microdisplay to simulate the edge field of view formed by the light emitted from the pixels after passing through the projection optical path. The exit pupil range of the four edge fields on the exit pupil plane is as follows: Figure 17 As shown, the result is compared with the image obtained by exit pupil matching calculation ( Figure 15 The results are basically the same. In this case, the exit pupil range of three of the four edge field rays just meets the requirements of the eye movement range index, and the waveguide's field of view at this time is the maximum field of view that can meet the performance index, that is, the waveguide's performance is fully utilized.

[0052] Distance from waveguide surface exit pupil At that location, a device with a diameter of [missing information] was placed. An ideal lens is formed, and a receiver is placed at the focal plane of the ideal lens. The focal length of the ideal lens is... Similar to the human eye, it is used to simulate human observation and examine stray light in waveguides. For example... Figure 18 As shown, nine light sources were positioned on the surface of the microdisplay. Light emitted from each light source passed through an ideal lens and formed an image on the receiver. The results are as follows: Figure 18 As shown, each light source point is imaged as a point in the receiving plane, proving that the pixels on the microdisplay in the near-eye display system can be clearly observed by the human eye, that is, the near-eye display system can realize the projection function.

[0053] There is no stray light in the vertical pupil expansion region of the system because the vertical field of view of the system does not exceed the analyzed maximum vertical field of view. However, a small amount of crosstalk stray light still exists in the waveguide, such as... Figure 17 (a), (b) and Figure 18 As shown. The reason for this is that the angle offset of the coupling prism introduced during the design process makes the angle at which light rays enter the vertical pupil region too large. The light rays are reflected by the vertical part of the mirror and return to the horizontal pupil region. The two pupil regions work together to form crosstalk stray light. Crosstalk stray light can be partially suppressed by adding a prism in the horizontal pupil region, such as... Figure 18 As shown, at this point, crosstalk stray light only exists near the edge of the field of view, but it is difficult to completely eliminate it. Avoiding excessively large offset angles of the coupling prism is also a way to suppress crosstalk stray light, but this will limit the waveguide's field of view.

[0054] In this application, a single-layer, large exit pupil range, and maximum field of view two-dimensional expanding pupil geometric waveguide was designed. The basic design principles, analysis, and calculation methods for two-dimensional geometric waveguides are proposed. An analytical method for determining the maximum field of view achievable by a two-dimensional waveguide is presented, and a compact projection system with a waveguide-limited field of view is designed based on the waveguide's field of view limitation. Finally, the waveguide near-eye display system is integrated and verified. Ultimately, the designed single-layer two-dimensional geometric waveguide has a thickness of 1.7 mm, a field of view of 50.00°H × 29.92°V, and an exit pupil size of 12 mm × 12 mm at an exit pupil distance of 18 mm. It also suppresses all vertical expanding pupil stray light and most crosstalk stray light. Simulation results demonstrate the correctness of the maximum field of view exit pupil matching design method and show that the brightness uniformity of the designed waveguide across different fields of view is within an acceptable range. Most stray light is separated from normal light, and only crosstalk stray light near the edge of the field of view can be observed by the simulated human eye. For a waveguide of a given size, the proposed two-dimensional waveguide maximum field of view analysis and design method can fully utilize the waveguide's display performance. Typically, the size and exit pupil of a consumer-grade AR waveguide should meet the user's viewing habits while also possessing excellent optical performance. The design method proposed in this application provides a possible solution for consumer-grade AR devices to simultaneously meet both ergonomic and optical performance requirements.

[0055] This application also provides a maximum vertical field-of-view analysis device for a monolithic two-dimensional pupil-expanding geometric waveguide, such as... Figure 19 As shown, in one embodiment, it includes: an acquisition module 1902, a first calculation module 1904, a second calculation module 1906, a third calculation module 1908, and an output module 1910, wherein: The acquisition module 1902 is used to acquire the performance indicators of a monolithic two-dimensional pupil-expanding geometric waveguide and to construct the optical waveguide structure. The first calculation module 1904 is used to analyze the vertical field of view based on the optical waveguide structure, so that the eye movement range condition meets the performance index, and obtain the first constraint condition that the vertical field of view angle needs to meet. The second calculation module 1906 is used to analyze the vertical field of view based on the optical waveguide structure, so that the total internal reflection condition satisfies the imaging condition, and obtain the second constraint condition that the vertical field of view angle needs to satisfy. The third calculation module 1908 is used to analyze the vertical field of view based on the optical waveguide structure, so that the stray light suppression condition meets the imaging quality requirements, and obtain the third constraint condition that the vertical field of view angle needs to meet. The output module 1910 is used to obtain the maximum vertical field of view based on the first constraint, the second constraint, and the third constraint.

[0056] For specific limitations regarding the maximum vertical field-of-view analysis device for monolithic two-dimensional expanded pupil geometric waveguides, please refer to the limitations on the maximum vertical field-of-view analysis method for monolithic two-dimensional expanded pupil geometric waveguides mentioned above. Each module in the aforementioned device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independently of the processor in a computer device, or stored in software in the memory of a computer device, so that the processor can call and execute the corresponding operations of each module.

[0057] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0058] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. For those skilled in the art, various modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method of analyzing the maximum vertical field of view of a monolithic two-dimensional pupil expanding geometric waveguide, the method comprising: include: The performance parameters of a monolithic two-dimensional pupil-expanding geometric waveguide were obtained, and the optical waveguide structure was constructed. Performance indicators include: eye movement range and exit pupil distance; optical waveguide structure, including: coupling prism and waveguide plate; the waveguide plate includes: horizontal pupil dilation region and vertical pupil dilation region; the coupling prism is connected to the waveguide plate to couple the incident light from the projection optical device into the horizontal pupil dilation region and vertical pupil dilation region of the waveguide plate to achieve horizontal pupil dilation and vertical pupil dilation. Based on the optical waveguide structure, the vertical field of view is analyzed, the distance between some of the mirrors in the vertical pupil expansion region and the eye movement range in the vertical direction are calculated, and the eye movement range condition is made to meet the performance index, so as to obtain the first constraint condition that the vertical field of view angle needs to meet. Based on the optical waveguide structure, the vertical field of view is analyzed, the refraction angle of light inside the waveguide sheet and the total internal reflection condition satisfied when light propagates inside the waveguide sheet are calculated, so that the total internal reflection condition satisfies the imaging condition, and the second constraint condition that the vertical field of view angle needs to satisfy is obtained. Based on the optical waveguide structure, the vertical field of view is analyzed, the stray light emission angle and the critical angle when the stray light reaches the boundary of the eye movement range are calculated, so that the stray light suppression condition meets the imaging quality requirements, and the third constraint condition that the vertical field of view angle needs to meet is obtained. Using the partial reflector tilt angle of the vertical pupil expansion region as the abscissa, the field of view of the incident light in the air as the ordinate, and the first constraint, the second constraint, the third constraint, and the field of view of the incident light in the air being greater than zero as boundary conditions, a safe zone is obtained, and the point where the maximum value of the ordinate in the safe zone is located is the maximum vertical field of view angle.

2. The method of claim 1, wherein, Based on the aforementioned waveguide structure, the vertical field of view is analyzed, and the distance between some of the reflecting mirrors in the vertical pupil expansion region and the eye movement range in the vertical direction are calculated. The eye movement range condition is made to satisfy the aforementioned performance index, resulting in the first constraint condition that the vertical field of view angle needs to meet, including: Based on the described optical waveguide structure, an analysis of the vertical field of view reveals that the distances between some of the reflecting mirrors in the vertical pupil expansion region satisfy the following: wherein is the distance between the partial mirrors of the vertical pupil expansion region, is the thickness of the waveguide sheet, is the angle of the partial mirrors of the vertical pupil expansion region with the bottom edge of the waveguide sheet; Vertical eye movement range satisfies: In the formula, is the size of the eye movement range in the vertical direction, is the number of partial mirrors of the vertical pupil expansion region, is the exit pupil distance, is half of the display field of view in the vertical direction in air; The first constraint that must be satisfied to obtain the vertical field of view is: 。 3. The method of claim 2, wherein, Based on the optical waveguide structure, the vertical field of view is analyzed, and the refraction angle of light inside the waveguide and the total internal reflection condition satisfied by the light propagating inside the waveguide are calculated. The total internal reflection condition satisfies the imaging condition, thus obtaining the second constraint condition that the vertical field of view angle needs to satisfy, including: According to the optical waveguide structure, the vertical field of view is analyzed, and the refraction angle of the light in the waveguide sheet is calculated : wherein is the angle of the field of view in the vertical direction in air, is the refractive index of the waveguide sheet; When light propagates inside the waveguide, it satisfies the condition of total internal reflection: wherein is the critical angle at which light will undergo total internal reflection within the waveguide; The second constraint that needs to be satisfied to obtain the vertical field of view is: 。 4. The method of claim 3, wherein, Based on the aforementioned optical waveguide structure, the vertical field of view is analyzed to calculate the stray light emission angle and the critical angle at which the stray light reaches the boundary of the eye movement range. This ensures that the stray light suppression condition meets the imaging quality requirements, resulting in the third constraint condition that the vertical field of view angle must satisfy, including: Based on the described optical waveguide structure, the vertical field of view is analyzed, and the stray light emission angle is calculated: In the formula, is the incident angle of the stray light in the waveguide sheet refracted out of the waveguide sheet. The critical angle for stray light to reach the boundary of the eye movement range satisfies: In the formula, is the offset distance of the eye movement range in the vertical direction; The third constraint that must be satisfied to obtain the vertical field of view is: 。 5. Apparatus for analyzing the maximum vertical field of view of a monolithic two-dimensional pupil expanding geometric waveguide, characterized in that, The method for analyzing the maximum vertical field of view of a monolithic two-dimensional pupil-expanding geometric waveguide as described in any one of claims 1 to 4 includes: The acquisition module is used to acquire the performance indicators of a monolithic two-dimensional pupil-expanding geometric waveguide and to construct the optical waveguide structure. The first calculation module is used to analyze the vertical field of view based on the optical waveguide structure, so that the eye movement range condition meets the performance index, and obtain the first constraint condition that the vertical field of view angle needs to meet. The second calculation module is used to analyze the vertical field of view based on the optical waveguide structure, so that the total internal reflection condition satisfies the imaging condition, and obtain the second constraint condition that the vertical field of view angle needs to satisfy. The third calculation module is used to analyze the vertical field of view based on the optical waveguide structure, so that the stray light suppression condition meets the imaging quality requirements, and obtain the third constraint condition that the vertical field of view angle needs to meet. The output module is used to obtain the maximum vertical field of view based on the first constraint, the second constraint, and the third constraint.

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