Method and system for optimizing discontinuity of exit pupil based on optical waveguide system

Abstract

The invention discloses an exit pupil discontinuity optimization method and system based on an optical waveguide system, and the method comprises the steps: extracting a light propagation path and an exit pupil coordinate through building an optical waveguide one-dimensional and two-dimensional pupil expansion exit pupil mapping model; constructing quantitative evaluation indexes of the jump width, the Eyebox connectivity rate and the blind area; by optimizing the waveguide thickness, the entrance pupil width or area and the grating diffraction angle, the jump deviation is minimized; furthermore, staggered arrangement, inclined expansion or cross design is adopted in the two-dimensional pupil expansion structure, and exit pupil energy connectivity and uniformity are improved. And finally, through non-sequence ray tracing and least square error optimization, continuous and uniform exit pupil distribution of the Eyebox region is realized. The method is suitable for various optical waveguide design structures, has high flexibility and expansibility, and can remarkably improve exit pupil quality and visual experience of augmented reality and mixed reality display systems.

Description

Technical Field

[0001] The present invention relates to an exit pupil discontinuity optimization method and system based on an optical waveguide system, belonging to the technical field of near-eye display optical systems. Background Art

[0002] Waveguide display systems have become a mainstream display solution for augmented reality (AR) head-mounted displays due to their advantages such as lightweight, wide field of view, and high transmittance. A typical waveguide structure consists of an input coupling grating, a pupil expansion grating (used to expand the eyebox horizontally or two-dimensionally), and an output grating. Image coupling and output are achieved through volume holography or surface grating structures.

[0003] In practical applications, to expand the exit pupil area, pupil expansion gratings typically use one- or two-dimensional array structures to achieve a multi-eyebox arrangement. However, regardless of the one- or two-dimensional pupil expansion design, current systems generally suffer from the following technical difficulties: the spatial arrangement of the exit pupils exhibits periodic jumps, resulting in visual blind spots or discontinuous bright spots; uneven reflection paths and mismatched grating parameters lead to uneven distribution of light energy, affecting visual consistency; and, in particular, in two-dimensional pupil expansion structures, the horizontal and vertical reflection coupling points are misaligned, resulting in jump boundaries and blind spots.

[0004] Currently, there is a lack of accurate modeling and quantitative evaluation mechanism for the above-mentioned exit pupil discontinuity. Structural design and parameter adjustment rely on manual experience, making it difficult to achieve systematic optical performance optimization.

[0005] Although existing simulation software (such as Zemax and LightTools) can be used for optical waveguide structure modeling, they still have the following shortcomings in optimizing exit pupil continuity, regulating energy consistency, and reversely calculating parameters of specific pupil expansion structures:

[0006] 1. There is a lack of dedicated optimization indicators and evaluation models for exit pupil discontinuity.

[0007] 2. Support for specific grating structures such as PVG (Polarization Volume Grating) is limited, and parameter tuning requires many iterations and is inefficient.

[0008] 3. Existing technologies usually adopt a forward propagation design process and lack a general optimization algorithm that can be used for structural inverse design.

[0009] Therefore, it is urgent to propose an exit pupil discontinuity modeling and optimization algorithm that can be applied to different pupil expansion structures, which can not only quantitatively evaluate the exit pupil characteristics of the optical waveguide system, but also reversely optimize the key structural parameters, thereby improving the overall performance of the near-eye optical waveguide display system in terms of visual continuity, exit pupil uniformity and design controllability. Summary of the Invention

[0010] Objective: To overcome the problems of uneven exit pupil distribution, severe bright spot jumps, and non-connected light exit areas that are common in one-dimensional and two-dimensional pupil expansion waveguide structures in the prior art, the present invention provides an exit pupil discontinuity optimization method and system based on an optical waveguide system. Based on structural modeling, this method integrates light propagation path analysis and exit pupil energy space mapping. By constructing an exit pupil mapping model suitable for different pupil expansion structures (such as one-dimensional, L-type, butterfly type, and cross type), key features such as exit pupil position, jump width, and blind area distribution in the system are quantitatively evaluated and structural parameters are extracted.

[0011] Technical solution: To solve the above technical problems, the technical solution adopted by the present invention is:

[0012] In a first aspect, a method for optimizing exit pupil discontinuity based on an optical waveguide system specifically includes:

[0013] Step 1: Based on the optical waveguide system, establish an optical waveguide exit pupil mapping model.

[0014] Step 2: Based on the optical waveguide exit pupil mapping model, calculate the reflection propagation path of the light inside the waveguide, and extract the exit pupil coordinates based on the intersection position of the light in the reflection propagation path and the waveguide plane.

[0015] Step 3: Construct a quantitative evaluation index of exit pupil discontinuity based on the exit pupil coordinates.

[0016] Step 4: Construct a discontinuity optimization algorithm based on the quantitative evaluation index of exit pupil discontinuity, solve the discontinuity optimization algorithm, and obtain the structural parameters of the optimized optical waveguide system.

[0017] As a preferred solution, the optical waveguide system includes a one-dimensional optical waveguide system and a two-dimensional optical waveguide system.

[0018] As a preferred solution, the light waveguide out-pupil mapping model includes: an L-shaped expanded pupil light waveguide out-pupil mapping model, a cross-pupil expanded pupil light waveguide out-pupil mapping model, and a butterfly-shaped expanded pupil light waveguide out-pupil mapping model.

[0019] As a preferred solution, the quantitative evaluation index of exit pupil discontinuity includes: exit pupil illumination continuity , angular illumination continuity and the standard deviation of the exit pupil jump width .

[0020] As a preferred solution, the expression of the discontinuity optimization algorithm is as follows:

[0021]

[0022] Among them, in the one-dimensional pupil expansion structure, the following constraints must be met:

[0023]

[0024] In the two-dimensional pupil expansion structure, the following constraints must be met:

[0025] The horizontal and vertical step sizes must satisfy the following constraints:

[0026]

[0027] The jump matrix satisfies:

[0028]

[0029] in, , , are the first, second and third weight coefficients respectively. d is the waveguide thickness. is the grating diffraction angle. Indicates the horizontal width of the exit pupil jump, Indicates the vertical width of the exit pupil jump, represents the horizontal reflection step size, represents the vertical reflection step size, represents the horizontal diffraction angle, represents the vertical diffraction angle, represents the error value of the jump error matrix at the outcoupling grating (i, j) coordinate, Indicates the horizontal width of the exit pupil jump at the horizontal coordinate i, Indicates the vertical width of the exit pupil jump at the horizontal coordinate j, Indicates the number of horizontal grating arrangements, Indicates the number of vertical grating arrangements, represents the grating Bragg horizontal period, represents the grating Bragg vertical period.

[0030] As a preferred solution, the step 4 specifically includes:

[0031] The waveguide thickness, entrance pupil size and grating parameters are jointly optimized through non-sequential ray tracing and least squares error iterative optimization method until the uniformity index of the discontinuity optimization algorithm converges to the optimal one. The optimized waveguide thickness, entrance pupil size and grating parameters of different optical waveguides such as one-dimensional and two-dimensional are obtained.

[0032] As a preferred solution, the pupil mapping model expression of the L-shaped pupil expansion light waveguide is as follows:

[0033]

[0034] Among them, kx With k y Represent the spatial frequency components of light in the horizontal and vertical directions respectively, is the magnitude of the wave vector in vacuum, K x With K y Represent the incident coupling grating G in The spatial frequency components of the outgoing coupling grating G out The spatial frequency component, n g is the effective refractive index of the L-shaped pupil expansion waveguide material, θ max Indicates the maximum total reflection angle supported by the L-shaped pupil expansion waveguide.

[0035] The cross-pupil expansion light waveguide pupil mapping model expression is as follows:

[0036]

[0037] Among them, G ip is the grating vector of the incident grating, deflected along the y direction; G op1 and G op2 are the grating vector of the first exit grating and the grating vector of the second exit grating, which deflect the light in different directions respectively; θ0, θ1, θ2 are the diffraction angles of the first grating angle, the second grating angle, and the third grating angle respectively. is the effective refractive index of the cross-pupil waveguide material. It is expressed as the spatial frequency of the output grating along the x-axis, Expressed as the magnitude of the wave vector in free space, are the horizontal and vertical unit vectors defined in the waveguide system respectively.

[0038] The butterfly-type pupil expansion light waveguide pupil mapping model expression is as follows:

[0039]

[0040] Among them, G in1 , G in2 represent the grating vectors of the grating coupling paths incident from the left and right sides respectively; is the effective refractive index of the butterfly-shaped pupil expansion waveguide material; is the magnitude of the wave vector in vacuum; 、 、 are the unit vectors in the horizontal, vertical and thickness directions in the waveguide space respectively; G f1 , G f2 They are the vectors of the center turning grating, which guide the light from the left and right splicing to the center symmetrical convergence, G out1 , G out2are the outgoing grating vectors corresponding to the left and right outgoing rays, and their directions eventually coincide; is the deflection angle between the initial incident light and the normal.

[0041] As a preferred solution, the exit pupil illumination continuity , angular illumination continuity and the standard deviation of the exit pupil jump width The expression is as follows:

[0042]

[0043]

[0044] in, 、 are the maximum and minimum exit pupil energies in the same field of view, 、 are the maximum and minimum energies at the same exit pupil position under different field angles. d is the waveguide thickness, is the incident angle of the i-th ray, Λ x is the output grating arrangement period.

[0045] In a second aspect, an optical waveguide system is provided, wherein the structural parameters of the optical waveguide system are obtained by the exit pupil discontinuity optimization method based on the optical waveguide system in the first aspect.

[0046] As a preferred solution, the structural parameters of the optical waveguide system include: waveguide thickness, entrance pupil width or entrance pupil area, and horizontal and vertical diffraction angles.

[0047] Beneficial Effects: The present invention provides a method and system for optimizing exit pupil discontinuity based on an optical waveguide system, belonging to the field of near-eye display technology. This invention establishes one-dimensional and two-dimensional pupil expansion exit pupil mapping models for optical waveguides to extract light propagation paths and exit pupil coordinates. It also constructs quantitative evaluation indicators for transition width, eyebox connectivity, and blind spot area. It minimizes transition deviation by optimizing waveguide thickness, entrance pupil width or area, and grating diffraction angle. Furthermore, staggered, tilted, or cross designs are employed within the two-dimensional pupil expansion structure to improve exit pupil energy connectivity and uniformity. Finally, through non-sequential ray tracing and least-squares error optimization, a continuous and uniform exit pupil distribution in the eyebox region is achieved. The method of the present invention is applicable to a variety of optical waveguide design structures (such as L-type, cross-type, butterfly-type, etc.), possesses strong flexibility and scalability, and can significantly improve the exit pupil quality and visual experience of augmented reality and mixed reality display systems. The optimization results can be widely applied in commercial near-eye display devices, promoting the further development of optical waveguide display technology and possessing broad market application prospects. Compared to existing technologies, the present invention has the following advantages:

[0048] 1. The present invention has a wide range of applications. By flexibly applying the method of the present invention, the problem of uneven exit pupils in different pupil expansion structures can be effectively solved, and it has high versatility.

[0049] 2. Based on the exit pupil mapping function and optical path analysis, this paper systematically constructs a jump model and discontinuity evaluation index system. Through quantitative evaluation, it can not only accurately quantify the exit pupil discontinuity, but also provide a reliable optimization basis for subsequent design.

[0050] 3. By introducing a directionally controlled exit grating structure and an interference compensation mechanism, this invention achieves a transition from a discrete transition to a connected distribution in the exit pupil array, significantly improving brightness uniformity in the exit pupil region. Furthermore, this invention effectively suppresses image streaks, dark bands, and energy discontinuities, enhancing the optical quality of the display system. Within the eye movement tolerance range, this invention maintains visual continuity of the image, significantly improving the user experience of augmented reality waveguide systems.

[0051] 4. The present invention can provide stable and consistent display effects under different viewing angles and high-angle applications, ensuring that users have better visual effects and immersive feeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Flowchart of the exit pupil discontinuity optimization method.

[0053] Figure 2 Schematic diagram of total reflection in the waveguide.

[0054] Figure 3 Schematic diagram of one-dimensional light propagation.

[0055] Figure 4 is the one-dimensional exit pupil energy distribution diagram, where Figure 4 (a) is the one-dimensional exit pupil energy distribution diagram before optimization. Figure 4 (b) is the optimized one-dimensional exit pupil energy distribution diagram.

[0056] Figure 5 is a schematic diagram of a two-dimensional grating structure, where Figure 5 (a) is a schematic diagram of the L-shaped structure. Figure 5 (b) is a schematic diagram of the butterfly structure. Figure 5 (c) is a schematic diagram of the cross-shaped structure.

[0057] Figure 6 is a schematic diagram of two-dimensional light propagation, where Figure 6 (a) is a schematic diagram of two-dimensional light propagation in an L-shaped structure. Figure 6 (b) is a schematic diagram of two-dimensional light propagation in a butterfly-shaped structure. Figure 6(c) is a schematic diagram of two-dimensional light propagation in a cross-shaped structure.

[0058] Figure 7 is the L-shaped exit pupil energy distribution diagram, where Figure 7 (a) is the L-shaped exit pupil energy distribution diagram before optimization. Figure 7 Middle (b) L-shaped exit pupil energy distribution diagram after optimization.

[0059] Figure 8 is a butterfly-shaped exit pupil energy distribution diagram, where Figure 8 (a) is the butterfly-shaped exit pupil energy distribution diagram before optimization. Figure 8 Middle (b) is the optimized butterfly-shaped exit pupil energy distribution diagram.

[0060] Figure 9 is a cross-exit pupil energy distribution diagram, where Figure 9 (a) is the cross-exit pupil energy distribution diagram before optimization. Figure 9 Middle (b) is the optimized cross-exit pupil energy distribution diagram. DETAILED DESCRIPTION

[0061] The following is a clear and complete description of the technical solutions in the examples of the present invention, in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0062] The present invention will be further described below with reference to specific embodiments.

[0063] Example 1:

[0064] This embodiment introduces a method for optimizing exit pupil discontinuity based on an optical waveguide system, specifically including:

[0065] Step 1: Establish a waveguide exit-pupil mapping model based on different waveguide systems such as one-dimensional and two-dimensional ones.

[0066] Step 2: Based on the optical waveguide exit pupil mapping model, calculate the reflection propagation path of the light inside the waveguide, and extract the exit pupil coordinates based on the intersection position of the light in the reflection propagation path and the waveguide plane.

[0067] Step 3: Construct a quantitative evaluation index of exit pupil discontinuity based on the exit pupil coordinates.

[0068] Step 4: Construct a discontinuity optimization algorithm based on the quantitative evaluation index of exit pupil discontinuity, solve the discontinuity optimization algorithm, and obtain the optimized structural parameters of different optical waveguide systems such as one-dimensional and two-dimensional.

[0069] Furthermore, the light waveguide out-pupil mapping model can be divided into: an L-shaped expanded pupil light waveguide out-pupil mapping model, a cross-pupil expanded pupil light waveguide out-pupil mapping model, and a butterfly-shaped expanded pupil light waveguide out-pupil mapping model according to the diffraction characteristics of the grating.

[0070] The pupil mapping model expression of the L-shaped pupil expansion light waveguide is as follows:

[0071]

[0072] Among them, k x With k y Represent the spatial frequency components of light in the horizontal and vertical directions respectively, is the magnitude of the wave vector in vacuum, represents the wavelength of light, represents pi, K x With K y Represent the incident coupling grating G in The spatial frequency components of the outgoing coupling grating G out The spatial frequency component, n g is the effective refractive index of the L-shaped pupil expansion waveguide material, θ max represents the maximum total internal reflection angle supported by the L-shaped expanded pupil waveguide. This inequality describes the wave vector constraints satisfied by all effective light rays that propagate through total internal reflection in the waveguide and is used to describe the expansion effect of the L-shaped expanded pupil waveguide in the horizontal and vertical directions.

[0073] The cross-pupil expansion light waveguide pupil mapping model expression is as follows:

[0074]

[0075] Among them, G ip is the grating vector of the incident grating, deflected along the y direction; G op1 and G op2 are the grating vector of the first exit grating and the grating vector of the second exit grating, which deflect the light in different directions respectively; θ0, θ1, θ2 are the diffraction angles of the first grating angle, the second grating angle, and the third grating angle respectively. is the effective refractive index of the cross-pupil waveguide material. Expressed as the spatial frequency of the output grating along the x-axis (the number of grating periods per unit length), Expressed as the magnitude of the wave vector in free space, are the horizontal and vertical unit vectors defined in the waveguide system, respectively. The above grating vectors satisfy certain relationships to ensure high efficiency and accurate optical expansion of the system. The specific formula is as follows:

[0076]

[0077] That is, the sum of the main grating vectors in the cross-pupil expansion optical waveguide is zero, thereby ensuring that the light propagates in the waveguide in a controllable manner and achieves efficient emission.

[0078] The butterfly-type pupil expansion light waveguide pupil mapping model expression is as follows:

[0079]

[0080] Among them, G in1 , G in2 represent the grating vectors of the grating coupling paths incident from the left and right sides respectively; is the effective refractive index of the butterfly-shaped pupil expansion waveguide material; is the magnitude of the wave vector in vacuum; 、 、 are the unit vectors in the horizontal, vertical and thickness directions in the waveguide space respectively; G f1 , G f2 They are the vectors of the center turning grating, which guide the light from the left and right splicing to the center symmetrical convergence, G out1 , G out2 are the outgoing grating vectors corresponding to the left and right outgoing rays, and their directions eventually coincide; is the deflection angle between the initial incident light and the normal.

[0081] The butterfly-shaped pupil expansion waveguide satisfies the complete wave vector transmission path starting from the left and right incident gratings, deflected by the turning grating, and finally directed to the output grating. in1 With G in2 They are strictly symmetrical in direction, representing the incident paths of light rays in different directions in the left and right fields of view respectively; G f1 With G f2 As the control vector of the intermediate turning path, the light direction is uniformly deflected to the central splicing area through the 60° angle symmetry; finally, G out1 With G out2 Pointing to the same outgoing direction, a high degree of light overlap is achieved.

[0082] From a vector perspective, this relationship forms two closed, symmetrical vector triangle systems, satisfying geometric matching of path directions and wave vector conservation. This design approach not only ensures the same optical path length for the two channels, but also guarantees consistent exit angles, a key design prerequisite for maintaining pupil continuity and smooth brightness transitions in the spliced ​​area.

[0083] Furthermore, the quantitative evaluation index of exit pupil discontinuity includes: exit pupil illumination continuity , angular illumination continuity and the standard deviation of the exit pupil jump width .

[0084] The calculation formula is as follows:

[0085]

[0086]

[0087] in, 、 are the maximum and minimum exit pupil energies in the same field of view, 、 are the maximum and minimum energies at the same exit pupil position under different field angles. d is the waveguide thickness, is the incident angle of the i-th ray, Λ x is the output grating arrangement period. The formula describes the quantitative relationship between structural parameters and jump error.

[0088] in, 、 、 、 The calculation formula is as follows:

[0089]

[0090]

[0091]

[0092] in: is the exit pupil position x viewed from direction θ i Angular illumination when .

[0093] Among the quantitative evaluation indicators of exit pupil discontinuity, the standard deviation of the jump width is less than 10% of the exit pupil grid spacing, and the eyebox connectivity rate is greater than 95%.

[0094] Furthermore, the expression of the discontinuity optimization algorithm is as follows:

[0095]

[0096] In the one-dimensional pupil expansion structure, the constraints must be met:

[0097]

[0098] In the two-dimensional pupil expansion structure, the horizontal and vertical step sizes must satisfy the following constraints:

[0099]

[0100] The jump matrix satisfies:

[0101]

[0102] in, , , are weight coefficients, which are used to adjust the proportion of different optimization objectives in the total loss function. (Recommended values: =0.4, =0.3, =0.3). d is the waveguide thickness. The output gratings are arranged with a certain period Λx, is the grating diffraction angle. Based on this formula, the exit pupil jump deviation is minimized to improve the connectivity and uniformity of the exit pupil energy. Indicates the horizontal width of the exit pupil jump, Indicates the vertical width of the exit pupil jump, represents the horizontal reflection step size, represents the vertical reflection step size, represents the horizontal diffraction angle, represents the vertical diffraction angle, It represents the error value of the jump error matrix at a certain out-coupling grating (i, j) coordinate, Indicates the horizontal width of the exit pupil jump at the horizontal coordinate i, Indicates the vertical width of the exit pupil jump at the horizontal coordinate j, Indicates the number of horizontal grating arrangements, Indicates the number of vertical grating arrangements, represents the grating Bragg horizontal period, represents the grating Bragg vertical period.

[0103] Furthermore, the step 4 specifically includes:

[0104] The waveguide thickness, entrance pupil size and grating parameters are jointly optimized through non-sequential ray tracing and least squares error iterative optimization method until the uniformity index of the discontinuity optimization algorithm converges to the optimal one. The optimized waveguide thickness, entrance pupil size and grating parameters of different optical waveguides such as one-dimensional and two-dimensional are obtained.

[0105] This algorithm overcomes the shortcomings of current optical simulation software for optimizing PVG exit pupil discontinuity, including poor accuracy, high iteration counts, and reliance on experience rather than formulas. It also introduces a multi-metric, comprehensive optimization of exit pupil connectivity. Based on non-sequential ray tracing and a least-squares error iterative method, it automatically adjusts waveguide and grating structure parameters until the exit pupil energy distribution is continuous and uniform.

[0106] Example 2:

[0107] This embodiment introduces an optical waveguide system, the structural parameters of which are obtained by the exit pupil discontinuity optimization method based on the optical waveguide system in embodiment 1. The following are examples of the structural parameters of the optical waveguide system:

[0108] In the one-dimensional pupil expansion structure, the waveguide thickness is preferably 1.5 microns to 2.5 microns, the entrance pupil width is preferably 2 mm to 3 mm, and the main diffraction angle is preferably 45 degrees to 60 degrees.

[0109] In the two-dimensional pupil expansion structure, the waveguide thickness is preferably 1.5 microns to 2.8 microns, the entrance pupil area is preferably 4 square millimeters to 10 square millimeters, the horizontal diffraction angle is preferably 45 degrees to 65 degrees, and the vertical diffraction angle is preferably 30 degrees to 50 degrees.

[0110] When the two-dimensional pupil expansion adopts an L-shaped structure, the waveguide thickness is 1.5 microns to 2.5 microns, the horizontal diffraction angle is 45 degrees to 60 degrees, the vertical diffraction angle is 35 degrees to 50 degrees, and the entrance pupil area is 4 square millimeters to 9 square millimeters.

[0111] When the two-dimensional pupil expansion adopts a butterfly-shaped structure, the waveguide thickness is 1.5 microns to 2.2 microns, the entrance pupil width is 2 mm to 3 mm, the height is 1.5 mm to 2.5 mm, the horizontal diffraction angle is 40 degrees to 55 degrees, and the vertical diffraction angle is 30 degrees to 45 degrees.

[0112] When the two-dimensional pupil expansion adopts a cross-type structure, the waveguide thickness is 1.8 microns to 2.8 microns, the diffraction angles in the horizontal and vertical directions are preferably 50 degrees to 65 degrees, and the entrance pupil area is 4 square millimeters to 10 square millimeters.

[0113] The final pupil expansion waveguide system has an eyebox exit pupil connectivity rate greater than 95%, exit pupil illumination uniformity greater than 90%, and angular illumination uniformity greater than 85% under a wide field of view (FOV>30 degrees).

[0114] Example 3:

[0115] This example demonstrates the simulation of the front-to-back contrast of an optical waveguide system optimized using the method of the present invention. It addresses the issues of pupil jump, energy discontinuity, and blind spot distribution in one- and two-dimensional pupil expansion structures, presenting a comprehensive modeling analysis, quantitative evaluation, parameter optimization, and structural reconstruction. By adjusting the waveguide structural parameters and grating arrangement, a continuous distribution and highly uniform coverage of the exit pupil energy in the eyebox region are achieved, improving the display quality and user experience of near-eye displays.

[0116] Building on this foundation, the present invention further proposes an optimization mechanism with inverse design capabilities. By manipulating key structural parameters (including waveguide thickness, entrance pupil width / area, horizontal and vertical diffraction angles), combined with non-sequential ray tracing and least-squares error algorithms, this mechanism systematically optimizes the spatial connectivity and energy uniformity of the exit pupil array. The resulting structural optimization system is not only highly adaptable to various pupil expansion structural designs, but also significantly improves visual consistency and dynamic display quality during eye movement. This provides more efficient structural design support and engineering implementation for near-eye display devices in augmented and mixed reality applications.

[0117] In a one-dimensional pupil expansion structure, such as Figure 2 As shown in Figure 1, the incident light enters the waveguide at an incident angle θ and propagates back in the horizontal direction. The horizontal step length after each reflection of the light is determined by the following formula:

[0118]

[0119] Where d is the waveguide thickness. The output gratings are arranged with a certain period Λx. Ideally, the light should be coupled out after each reflection. However, due to the mismatch between the step size and the period, the actual arrangement has jump errors, and the deviation can be expressed as:

[0120]

[0121] To this end, the present invention proposes a waveguide thickness d between 1.5 and 2.5 μm, an entrance pupil width x between 2 and 3 mm, and an incident angle θ between 45° and 60°. This range, verified through simulation and modeling, ensures a standard deviation of exit pupil transitions less than 10%, while also balancing process feasibility and system optical performance.

[0122] like Figure 3 As shown in the figure, the one-dimensional jump phenomenon is mainly concentrated in the horizontal direction. If the thickness, entrance pupil width and diffraction angle are properly controlled, the jump accumulation can be effectively reduced and the consistency of the bright spot can be improved. Figure 4 As shown in the figure, there are obvious jumps and energy faults before optimization; after optimization, the horizontal exit pupils are evenly arranged and the energy distribution is continuous.

[0123] In a two-dimensional pupil expansion structure, such as Figure 5 As shown, the light is reflected and propagated alternately in the horizontal and vertical directions, and the horizontal and vertical step sizes are:

[0124]

[0125] The transition matrix is ​​expressed as:

[0126]

[0127] The present invention proposes that for a two-dimensional pupil expansion structure, the waveguide thickness d is preferably in the range of 1.5-2.8 μm, and the entrance pupil area is preferably 4-10 mm 2 The horizontal diffraction angle is preferably 45°-65°, and the vertical diffraction angle is preferably 30°-50°. This parameter configuration can ensure the synchronization of the step size of horizontal and vertical expansion, avoid bidirectional superposition jumps, and increase the continuity of Eyebox coverage.

[0128] like Figure 6 As shown in the figure, if not optimized, obvious blind spots and stripe energy jumps will appear in the two-dimensional pupil expansion structure. The present invention controls the matching relationship between waveguide thickness, entrance pupil area and horizontal / vertical diffraction angles to achieve a uniform transition of the two-dimensional jump mapping and maximize the eyebox connectivity.

[0129] For L-shaped pupil expansion structure, such as Figure 7 As shown in the figure, the conventional design has a mismatch between the horizontal and vertical expansion paths, resulting in excessive brightness at the center and insufficient brightness at the edges. The preferred waveguide thickness of the present invention is 1.5-2.5 μm, and the entrance pupil area is 4-9 mm. 2 The horizontal diffraction angle is 45°-60°, and the vertical diffraction angle is 35°-50°, so that the horizontal and vertical reflection step lengths are similar, the energy transition is uniform, and the exit pupil connectivity rate exceeds 95%.

[0130] like Figure 8 As shown in the figure, in a butterfly-shaped pupil expansion structure, the energy distribution in the corners is traditionally sparse. The present invention optimizes the waveguide thickness to 1.5-2.2 μm, the entrance pupil width to 2-3 mm, the height to 1.5-2.5 mm (area to 3-7.5 mm²), the horizontal diffraction angle to 40°-55°, and the vertical diffraction angle to 30°-45°. By using a slightly center-biased distribution strategy and corner compensation, the overall eyebox energy uniformity is improved to over 90%.

[0131] like Figure 9 As shown in the figure, in the cross-type pupil expansion structure, due to the cross-over and superposition of horizontal and vertical paths, the center jump of the traditional design is serious. 2 , the horizontal and vertical diffraction angles are controlled in the range of 50°-65°, and the inclined cross grating design is introduced to achieve two-way compensation pupil expansion, significantly eliminate exit pupil jump, and improve energy distribution uniformity.

[0132] In order to accurately evaluate the optimization effect, the present invention defines the exit pupil illumination continuity Γ P and angular illumination continuity Γ A , the calculation formula is as follows:

[0133]

[0134] Among them, P max 、P min are the maximum and minimum exit pupil energies in the same field of view, A max 、A min They are the maximum and minimum energies at the same exit pupil position at different field angles.

[0135] During the optimization process, the present invention adopts non-sequential ray tracing simulation and least squares error optimization method, and jointly optimizes multiple indicators based on eyebox connectivity, exit pupil brightness uniformity and angular illumination uniformity until converging to the optimal solution.

[0136] Through the above method, the present invention finally achieves the exit pupil energy connectivity rate Γ under the conditions of wide field of view (FOV>30°) and large eyebox (>10mm×10mm). C >95%, exit pupil illumination continuity Γ P >90%, angular illumination continuity Γ A >85%, effectively improving the image consistency and user experience of augmented reality and mixed reality near-eye optical waveguide display systems.

[0137] The polarization volume grating grating waveguide system of the present invention has demonstrated good exit pupil discontinuity suppression effect through simulation and experimental verification.

[0138] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for optimizing exit pupil discontinuity based on an optical waveguide system, characterized by: Specifically include: Step 1: Based on the optical waveguide system, establish an optical waveguide pupil mapping model; Step 2: Based on the optical waveguide exit pupil mapping model, calculate the reflection propagation path of the light inside the waveguide, and extract the exit pupil coordinates based on the intersection position of the light in the reflection propagation path and the waveguide plane; Step 3: Construct a quantitative evaluation index of exit pupil discontinuity based on the exit pupil coordinates; Step 4: Construct a discontinuity optimization algorithm based on the quantitative evaluation index of exit pupil discontinuity, solve the discontinuity optimization algorithm, and obtain the structural parameters of the optimized optical waveguide system.

2. The method for optimizing exit pupil discontinuity based on an optical waveguide system according to claim 1, characterized in that: The optical waveguide system includes a one-dimensional optical waveguide system and a two-dimensional optical waveguide system.

3. The method for optimizing exit pupil discontinuity based on an optical waveguide system according to claim 1, wherein: The light waveguide out-pupil mapping model includes: an L-shaped expanded pupil light waveguide out-pupil mapping model, a cross-pupil expanded light waveguide out-pupil mapping model, and a butterfly-shaped expanded pupil light waveguide out-pupil mapping model.

4. The method for optimizing exit pupil discontinuity based on an optical waveguide system according to claim 1, wherein: The quantitative evaluation index of exit pupil discontinuity includes: exit pupil illumination continuity , angular illumination continuity and the standard deviation of the exit pupil jump width .

5. The method for optimizing exit pupil discontinuity based on an optical waveguide system according to claim 1, wherein: The expression of the discontinuity optimization algorithm is as follows: ； Among them, in the one-dimensional pupil expansion structure, the following constraints must be met: ； In the two-dimensional pupil expansion structure, the following constraints must be met: The horizontal and vertical step sizes must satisfy the following constraints: ； The jump matrix satisfies: ； in, , , are the first, second and third weight coefficients respectively. d is the waveguide thickness. is the grating diffraction angle. Indicates the horizontal width of the exit pupil jump, Indicates the vertical width of the exit pupil jump, represents the horizontal reflection step size, represents the vertical reflection step size, represents the horizontal diffraction angle, represents the vertical diffraction angle, represents the error value of the jump error matrix at the outcoupling grating (i, j) coordinate, Indicates the horizontal width of the exit pupil jump at the horizontal coordinate i, Indicates the vertical width of the exit pupil jump at the horizontal coordinate j, Indicates the number of horizontal grating arrangements, Indicates the number of vertical grating arrangements, represents the grating Bragg horizontal period, represents the grating Bragg vertical period.

6. The method for optimizing exit pupil discontinuity based on an optical waveguide system according to claim 1, characterized in that: The step 4 specifically includes: The waveguide thickness, entrance pupil size and grating parameters are jointly optimized through non-sequential ray tracing and least squares error iterative optimization method until the uniformity index of the discontinuity optimization algorithm converges to the optimal one. The optimized waveguide thickness, entrance pupil size and grating parameters of different optical waveguides such as one-dimensional and two-dimensional are obtained.

7. The method for optimizing exit pupil discontinuity based on an optical waveguide system according to claim 3, wherein: The pupil mapping model expression of the L-shaped pupil expansion light waveguide is as follows: ； Among them, k x With k y Represent the spatial frequency components of light in the horizontal and vertical directions respectively, is the magnitude of the wave vector in vacuum, K x With K y Represent the incident coupling grating G in The spatial frequency components of the outgoing coupling grating G out The spatial frequency component, n g is the effective refractive index of the L-shaped pupil expansion waveguide material, θ max Indicates the maximum total reflection angle supported by the L-shaped pupil expansion waveguide; The cross-pupil expansion light waveguide pupil mapping model expression is as follows: ； Among them, G ip is the grating vector of the incident grating, deflected along the y direction; G op1 and G op2 are the grating vector of the first exit grating and the grating vector of the second exit grating, respectively, which deflect the light in different directions; θ0, θ1, θ2 are the diffraction angles of the first grating angle, the second grating angle, and the third grating angle, respectively; is the effective refractive index of the cross-pupil expansion waveguide material; It is expressed as the spatial frequency of the output grating along the x-axis direction, Expressed as the magnitude of the wave vector in free space, are the horizontal and vertical unit vectors defined in the waveguide system respectively; The butterfly-type pupil expansion light waveguide pupil mapping model expression is as follows: ； Among them, G in1 , G in2 represent the grating vectors of the grating coupling paths incident from the left and right sides respectively; is the effective refractive index of the butterfly-shaped pupil expansion waveguide material; is the magnitude of the wave vector in vacuum; 、 、 are the unit vectors in the horizontal, vertical and thickness directions in the waveguide space respectively; G f1 , G f2 They are the vectors of the center turning grating, which guide the light from the left and right splicing to the center symmetrical convergence, G out1 , G out2 are the outgoing grating vectors corresponding to the left and right outgoing rays, and their directions eventually coincide; is the deflection angle between the initial incident light and the normal.

8. The method for optimizing exit pupil discontinuity based on an optical waveguide system according to claim 4, characterized in that: The exit pupil illumination continuity , angular illumination continuity and the standard deviation of the exit pupil jump width The expression is as follows: ； ； in, 、 are the maximum and minimum exit pupil energies in the same field of view, 、 are the maximum and minimum energies at the same exit pupil position at different field angles; d is the waveguide thickness, is the incident angle of the i-th ray, Λ x is the output grating arrangement period.

9. An optical waveguide system, characterized in that: The structural parameters of the optical waveguide system are obtained by an exit pupil discontinuity optimization method based on an optical waveguide system according to claims 1 to 8.

10. The optical waveguide system according to claim 9, wherein: The structural parameters of the optical waveguide system include: waveguide thickness, entrance pupil width or entrance pupil area, and horizontal and vertical diffraction angles.

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