Simulation analysis method for coupling-in grating efficiency and diffraction optical waveguide

Abstract

The invention provides a simulation analysis method for coupling-in grating efficiency and a diffraction optical waveguide. The simulation analysis method comprises the following steps: dividing a view field of an optical machine into m * n direction angle areas; light beams in each direction angle area are simulated to be incident to the coupling grating; the coupling efficiency corresponding to each direction angle area is calculated through simulation; determining the total coupling efficiency of the coupling grating according to the coupling efficiency corresponding to all the direction angle areas; wherein m and n are integers greater than 1. According to the simulation analysis method provided by the invention, the efficiency calculation of diffracting the incident light power of an optical machine, which is diverged by an AR diffraction optical waveguide to a certain field angle (FOV), into the optical waveguide through a coupled grating in a simulation end is designed and optimized, so that the simulation process of the overall lighting effect of the diffraction optical waveguide is improved; and the light effect data difference between a theoretical design end and a finished product production end is effectively shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diffractive optical waveguide, and particularly relates to a simulation analysis method for coupling grating efficiency and a diffractive optical waveguide. BACKGROUND

[0002] In an augmented reality (AR) diffractive optical waveguide, the ratio of the light power diffracted by a coupling grating to the total light power of the optical-mechanical system is the coupling efficiency. Currently, there is no relevant national standard for AR diffractive optical waveguides, and there is no general process and standard for optical index judgment and detection at the design end, production end and finished product end. Therefore, there is no unified and effective model specification and calculation method for the coupling efficiency, which is not conducive to the design and preparation of the diffractive optical waveguide.

[0003] In the existing coupling efficiency calculation method, the coupling efficiency is calculated according to the following formula:

[0004] ;

[0005] wherein, η is the coupling efficiency, η1 is the first-order diffraction efficiency of the light-mechanical system light rays incident to the coupling grating, η0 is the zero-order diffraction efficiency of the coupling grating, and p is an integer greater than or equal to 1. In the existing coupling efficiency calculation method, it is assumed that all light rays emitted by the light-mechanical system are parallel incident to the coupling grating. This idealized assumption will make the simulated coupling efficiency generally higher than the actual value. SUMMARY

[0006] The embodiment of the present application provides a simulation analysis method for coupling grating efficiency and a diffractive optical waveguide. The simulation analysis method designs and optimizes the efficiency calculation of the light-mechanical system incident light power diffracted by the coupling grating into the optical waveguide in the simulation end for the AR diffractive optical waveguide to diverge a certain field of view (FOV), which helps to perfect the simulation process of the overall light efficiency of the diffractive optical waveguide and effectively shorten the light efficiency data difference between the theoretical design end and the production finished product end.

[0007] According to an aspect of the present application, a simulation analysis method for coupling grating efficiency is provided, comprising:

[0008] dividing the field of view of the light-mechanical system into m*n direction angle regions;

[0009] simulating the light beam incident to the coupling grating in each direction angle region;

[0010] calculating the coupling efficiency corresponding to each direction angle region by simulation;

[0011] determining the total coupling efficiency of the coupling grating according to the coupling efficiencies corresponding to all direction angle regions;

[0012] wherein, m and n are both integers greater than 1.

[0013] Optionally, the field of view of the optical engine includes a horizontal field of view and a vertical field of view, dividing the field of view of the optical engine into m×n angular regions, including:

[0014] The horizontal field of view is divided into n sampling points, and the vertical field of view is divided into m sampling points;

[0015] The direction angles of m×n sampling points are used as the direction angles of the corresponding direction angle regions.

[0016] Optionally, the angle value of the horizontal field of view is H, and the angle value of the vertical field of view is V;

[0017] The horizontal field of view angle value of the k-th sampling point among the n sampling points of the horizontal field of view is determined according to the following formula:

[0018] , where k is a positive integer not greater than n;

[0019] The vertical field of view angle value of the j-th sampling point among the m sampling points in the vertical field of view is determined according to the following formula:

[0020] , where j is a positive integer not greater than m.

[0021] Optionally, simulating the incident light beam onto the coupling grating in each of the said directional angle regions includes:

[0022] The transmission process of the parallel beam incident on the coupling grating is simulated by treating the beam in each of the aforementioned directional angle regions as a parallel beam.

[0023] The direction of the parallel beam corresponds to the direction angle of the direction angle region.

[0024] Optionally, the projected area of ​​the optomechanical exit pupil on the coupling grating is greater than or equal to the area of ​​the coupling grating, and the coupling efficiency corresponding to each directional angle region is calculated through simulation, including:

[0025] The first-order diffraction efficiency η corresponding to the i-th azimuth region is calculated through simulation. 1i Zero-order diffraction efficiency η 0i And the total internal reflection angle θ within the diffracted waveguide after diffraction i ;

[0026] Based on the total internal reflection angle θ i Determine the step distance f for a single total internal reflection corresponding to the i-th orientation angle region. i ;

[0027] With the step distance f i Based on this, the coupled grating is divided into multiple sub-regions;

[0028] The coupling-in efficiency η corresponding to the i-th direction angle region is calculated according to the following formula i :

[0029] ;

[0030] Wherein, the i-th direction angle region corresponds to q sub-regions, S 1i , S 2i , …, S qi are the areas of the q sub-regions, and S 总1 represents the total area of the coupling-in grating.

[0031] Optionally, the projection area of the light-mechanism exit pupil on the coupling-in grating is less than the area of the coupling-in grating, and the coupling-in efficiency corresponding to each direction angle region is calculated by simulation, comprising:

[0032] The first-order diffraction efficiency η 1i , zero-order efficiency η 0i and the total internal reflection angle θ i after diffraction in the diffractive optical waveguide corresponding to the i-th direction angle region are calculated by simulation.

[0033] The step distance f i of single total internal reflection corresponding to the i-th direction angle region is determined according to the total internal reflection angle θ i ;

[0034] The projection of the light-mechanism exit pupil on the coupling-in grating is divided into multiple sub-regions according to the direction angle direction of the i-th direction angle region with the step distance f i as the reference;

[0035] The coupling-in efficiency η corresponding to the i-th direction angle region is calculated according to the following formula i :

[0036] ;

[0037] Wherein, the i-th direction angle region corresponds to q sub-regions, S 1i , S 2i , …, S qi are the areas of the q sub-regions, and S 总2 represents the projection area of the light-mechanism exit pupil on the coupling-in grating.

[0038] Optionally, the total coupling-in efficiency is determined according to the following formula:

[0039] ;

[0040] Wherein, η 总total in-coupling efficiency of the in-coupling grating, η i the in-coupling efficiency of the i-th direction angle region, i is a positive integer less than or equal to m*n.

[0041] Optionally, the in-coupling grating is arranged on the diffractive optical waveguide, and after the total in-coupling efficiency of the in-coupling grating is determined according to the in-coupling efficiencies corresponding to all the direction angle regions, the method further comprises:

[0042] The structure parameters of the diffractive optical waveguide are modified, and the structure parameters corresponding to the maximum total in-coupling efficiency are determined through simulation and iterative calculation.

[0043] Optionally, the diffractive optical waveguide further comprises an out-coupling grating, and after the structure parameters corresponding to the maximum total in-coupling efficiency are determined, the method further comprises:

[0044] Simulation of the out-coupling grating is performed to determine the overall structure of the diffractive optical waveguide.

[0045] According to another aspect of the present application, a diffractive optical waveguide is provided, comprising an in-coupling grating, and the in-coupling efficiency of the in-coupling grating is calculated by using the simulation analysis method described above.

[0046] The simulation analysis method for the in-coupling grating efficiency provided by the embodiments of the present application considers the actual size of the optical machine, discretizes the continuous field of view in space by grid division, divides the field of view of the optical machine into m*n direction angle regions, and each direction angle region has a parallel light beam with a specific angle; then the transmission process of the light beam in each direction angle region to the in-coupling grating is simulated; the in-coupling efficiency corresponding to each direction angle region is calculated through simulation, and a complete data set describing the in-coupling efficiency is formed; the total in-coupling efficiency of the in-coupling grating is determined according to the in-coupling efficiencies corresponding to all the direction angle regions, thereby perfecting the simulation process of the overall optical efficiency of the diffractive optical waveguide and effectively shortening the optical efficiency data difference between the theoretical design end and the production end.

[0047] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent through the following description. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0049] Figure 1A flowchart of a simulation analysis method of the coupling-in grating efficiency provided by the embodiment of the present application is shown in the figure.

[0050] Figure 2 A schematic diagram of the field of view of the optical machine being divided into 9 direction angle regions in the embodiment of the present application is shown in the figure.

[0051] Figure 3 A structural schematic diagram of the parallel light beam being incident to the coupling-in grating of the diffractive optical waveguide provided by the embodiment of the present application is shown in the figure.

[0052] Figure 4 A schematic diagram of an interval division in the embodiment of the present application is shown in the figure.

[0053] Figure 5 A schematic diagram of a direction angle region division in the embodiment of the present application is shown in the figure.

[0054] Figure 6 A schematic diagram of the projection of each direction angle region to the coupling-in grating provided by the embodiment of the present application is shown in the figure.

[0055] Figure 7 A schematic diagram of the region division provided by the embodiment of the present application is shown in the figure.

[0056] Figure 8 A schematic diagram of the region area calculation method provided by the embodiment of the present application is shown in the figure.

[0057] Figure 9 A flowchart of another simulation analysis method of the coupling-in grating efficiency provided by the embodiment of the present application is shown in the figure.

[0058] Figure 10 A flowchart of still another simulation analysis method of the coupling-in grating efficiency provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0059] In order to make the personnel in the technical field better understand the present application scheme, the technical scheme in the embodiment of the present application will be described clearly and completely in the following by combining the figures in the embodiment of the present application. Obviously, the described embodiment is only a part of the embodiment of the present application, but not all the embodiments. Based on the embodiment in the present application, all the other embodiments obtained by the personnel in the field without making creative labor should belong to the protection range of the present application.

[0060] It should be noted that the terms used in the embodiments of the present application are merely for the purpose of describing specific embodiments and are not intended to limit the present application. It should be noted that the "upper", "lower", "left", "right", and the like described in the embodiments of the present application are described with the angle shown in the drawings, and should not be understood as a limitation on the embodiments of the present application. In addition, in the context, it should also be understood that when referring to one element being formed "on" or "under" another element, it can be directly formed "on" or "under" another element, or indirectly formed "on" or "under" another element through an intermediate element. The terms "first", "second", and the like are only for the purpose of description and do not represent any order, quantity or importance, but are only used to distinguish different components. It should be understood that the terms used in this way can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0061] In the simulation of the diffraction optical waveguide, after the grating topography and parameters of the diffraction optical waveguide are determined, the diffraction order and diffraction efficiency are calculated according to FMM (full name Fourier Modal Method) and RCWA (full name Rigorous Coupled-Wave Analysis), and the data is expressed in percentage form, that is, the energy ratio of the diffraction order light to the incident light.

[0062] To calculate the overall coupling-in efficiency, the projection area and projection angle of the illuminating light of the optical machine in the incident coupling-in grating need to be calculated. In this area, the diffraction efficiency of the light incident on the grating at a certain angle is η1. Part of the area is totally reflected once in the coupling-in grating area and in the diffraction optical waveguide, and the coupling-in efficiency of this area is:

[0063] ;

[0064] Part of the area reaches the outside of the coupling-in grating area after 1 diffraction and multiple total reflections, so the diffraction efficiency of this area should be equal to the first-order diffraction efficiency multiplied by p-1 zero-order diffraction efficiency, and the coupling-in efficiency is:

[0065] .

[0066] In the existing coupling-in efficiency calculation method, two assumptions are usually made: 1. The default optical machine size is the same as the coupling-in grating size; 2. It is assumed that all the light rays of all the exit angles of the optical machine can uniformly cover the entire coupling-in grating. The idealized assumptions based thereon make the simulated coupling-in efficiency generally higher than the actual value.

[0067] Based on this, the embodiment of the present application provides a simulation analysis method for coupling-in efficiency, which optimizes the simulation process of the coupling-in grating in detail. In the new optimized process, the actual size of the optical machine is projected onto the coupling-in grating area according to different angles. The simulation calculation is strictly limited within the projection area of the optical machine at each angle, so as to more truly reflect the incidence of the light rays. The optimized simulation model is more consistent with the actual propagation mode of the optical machine, and the fitting degree of the simulation data and the actual measurement results is significantly improved. The simulation analysis method for coupling-in grating efficiency provided by the embodiment of the present application is specifically introduced below.

[0068] Figure 1 The flowchart of the simulation analysis method for coupling-in grating efficiency provided by the embodiment of the present application is shown in Figure 1 The simulation analysis method comprises the following steps.

[0069] S110, dividing the field of view of the optical machine into m*n direction angle regions.

[0070] Wherein, m and n are both integers greater than 1, which can be selected according to the actual situation in specific implementation. In the embodiment, the continuous field of view (FOV) of the optical machine is discretely grid divided in space, for example, divided into 3*3 or 3*5 direction angle regions. Each direction angle region corresponds to a parallel light with a specific angle. The projection region on the coupling-in grating is consistent with the actual light emitting area of the optical machine, which ensures the physical authenticity of the simulation. Figure 2 The schematic diagram of dividing the field of view of the optical machine into 9 direction angle regions in the embodiment of the present application is shown in Figure 2 The FOV is divided into 3*3 direction angle regions.

[0071] After dividing the FOV into multiple direction angle regions, the polarization state of the light rays can also be considered in the subsequent simulation process, and the efficiencies of p-polarized light and s-polarized light are calculated respectively, because the responses of the grating to different polarized light are usually different. The first-order diffraction efficiency of the light rays when they are incident to the coupling-in grating for the first time and enter the diffractive optical waveguide is calculated; at the same time, the zero-order diffraction (i.e. reflection) efficiency of the grating when the light rays occur total internal reflection in the diffractive optical waveguide is calculated. For a field of view divided into 3*3 (9 direction angle regions), 2 polarizations*2 diffraction orders=4 efficiency data need to be calculated for each direction. Therefore, each group of coupling-in grating models will correspond to generate 4*9=36 diffraction efficiency data, forming a complete data set describing the performance thereof.

[0072] S120, simulate the light beam in each direction angle region incident to the coupling-in grating.

[0073] Optionally, the simulating the light beam in each direction angle region incident to the coupling-in grating comprises:

[0074] The simulating the parallel light beam incident to the coupling-in grating comprises:

[0075] The direction of the parallel light beam corresponds to the direction angle of the direction angle region.

[0076] Specifically, the simulating the light beam in each direction angle region incident to the coupling-in grating and the transmission process in the diffractive optical waveguide can be simulated by an optical simulation software one by one. Figure 3 The structure diagram of the parallel light beam incident to the coupling-in grating of the diffractive optical waveguide is provided in the embodiment of the present application, referring to Figure 3 The right light ray 1 irradiates on the right region of the coupling-in grating 10, and after entering the diffractive optical waveguide by one order of diffraction, the first total reflection point falls outside the region where the coupling-in grating 10 is located, so that only one diffraction occurs. The left light ray 2 irradiating on the left region enters the diffractive waveguide, and the first total reflection point still falls on the coupling-in grating 10, so that the second (zero order diffraction) or even more interactions occur before reaching outside the region where the coupling-in grating 10 is located. Figure 3 The footstep in the step S110 is defined as the lateral propagation distance between the adjacent two times of hitting the upper surface of the waveguide flat plate by the diffractive light. It is a fixed value determined by the waveguide thickness and the incident angle. Based on the physical scale of the footstep, the coupling-in grating can be divided into a plurality of continuous intervals with the width equal to the footstep along the axis in the direction of the propagation direction of the diffractive light. The number of times of the interaction of the light rays in each interval with the coupling-in grating is fixed, so that the complex continuous interaction can be discretized into clear stages for calculation.

[0077] S130, calculating the coupling-in efficiency corresponding to each direction angle region by simulation.

[0078] Based on the foregoing method, a calculation model can be established, and the interval division is performed based on the footstep, Figure 4 The diagram of the interval division in the embodiment of the present application is provided, referring to Figure 4 It is necessary to determine the number of times of diffraction of the light rays in each interval before reaching the turning / coupling-out grating in the coupling-in grating region (for example, S1: one first order diffraction; S2: one first order diffraction + one zero order diffraction; …… S5: one first order diffraction + four zero order diffractions), the corresponding efficiency data of each interval is calculated, and the total light intensity finally coupled into the waveguide for propagation from the interval is calculated by linear superposition.

[0079] In implementation, the light beam transmission process in each direction angle area can be analyzed based on RCWA, and the calculation process of RCWA is as follows:

[0080] 1) The solved grating is layered, the electromagnetic field of each layer is Fourier expanded, the electromagnetic field expressions of the incident layer and the exit layer of the grating are written as follows:

[0081] ;

[0082] ;

[0083] is the electric field of the incident layer, is the electric field of the incident light, is the electric field of the exit layer, and is the electric field amplitude of the reflected i-th diffraction order, and is the electric field amplitude of the transmitted i-th diffraction order, and is the wave vector of the reflected i-th diffraction order, and is the wave vector of the transmitted i-th diffraction order, and h is the grating height.

[0084] The Fourier series expansion of the electric field and the magnetic field of the grating layer is:

[0085] ;

[0086] ;

[0087] and is the Fourier expansion coefficient function of the field wave vector of the electric field and the magnetic field of the grating area, is the vacuum dielectric constant, is the magnetic permeability.

[0088] 2) The dielectric constant of the grating layer is Fourier series expanded, and the coupled wave equation is derived by using Maxwell equation:

[0089] ;

[0090] ;

[0091] ;

[0092] ;

[0093] is the Fourier expansion series of the dielectric constant, is the Fourier expansion coefficient of permittivity, is the Fourier expansion series of permeability, is the Fourier expansion coefficient of permeability, is the period of grating in x direction, is the period of grating in y direction, is the vector direction of grating in x direction, is the vector direction of grating in y direction, a is the diffraction order of grating in x direction, b is the diffraction order of grating in y direction.

[0094] Coupled-wave equation:

[0095] ;

[0096] ;

[0097] ;

[0098] ;

[0099] ;

[0100] ;

[0101] , , are the components of scattering matrix in x, y, z respectively, , are the unit vectors of wave in x and y.

[0102] 3) Using the boundary conditions of electromagnetic field at the interface of different layers, the amplitude coefficient, propagation constant and other physical parameters of each layer eigenmode are solved, and finally the corresponding diffraction efficiency is calculated using these parameters, as follows:

[0103] ;

[0104] ;

[0105] ;

[0106] ;

[0107] R is the diffraction efficiency of reflection diffraction, T is the diffraction efficiency of transmission diffraction, , , are the electric field amplitudes of reflected diffraction wave in x, y, z directions respectively, , , These represent the electric field amplitudes of the transmitted diffracted wave in the x, y, and z directions, respectively. The wavenumber unit vector for the reflection segment. The magnetic permeability of the incident layer, denoted as ρ, where ρ is the permeability of the transmission layer.

[0108] S140. Determine the total coupling efficiency of the coupling grating based on the coupling efficiency corresponding to all directional angular regions.

[0109] The coupling efficiency at a given direction angle is obtained by linearly superimposing the total outgoing light intensity across all intervals in a given direction. This result is then averaged between p-polarized and s-polarized beams to obtain the efficiency of the unpolarized light in that direction. Finally, the average efficiency of the unpolarized light at all sampled direction angles is calculated to obtain the final average coupling efficiency of the coupling grating design.

[0110] The simulation analysis method for coupling efficiency provided in this invention designs and optimizes the efficiency calculation of the optical-mechanical incident light power that diverges at a certain field of view (FOV) in the AR diffracting waveguide in the simulation end, which is diffracted into the waveguide by the coupling grating. This helps to improve the simulation process of the overall optical effect of the diffracting waveguide and effectively shortens the difference in optical effect data between the theoretical design end and the production end.

[0111] Based on the above embodiments, optionally, the field of view of the optical engine includes a horizontal field of view and a vertical field of view, dividing the field of view of the optical engine into m×n directional angular regions, including:

[0112] The horizontal field of view is divided into n sampling points, and the vertical field of view is divided into m sampling points;

[0113] The direction angles of m×n sampling points are used as the direction angles of the corresponding direction angle regions.

[0114] In this context, the field of view of the optical engine is equal to the horizontal field of view multiplied by the vertical field of view. The field of view of the optical engine is a uniformly divergent light field propagating along the central optical axis. After the field of view is divided into m×n directional angular regions, each directional angular region is no longer a divergent light field, but rather a parallel light field propagating along the directional angle of that point. Therefore, dividing the field of view of the optical engine into m×n directional angular regions can be understood as taking n sampling points on a horizontal line in the horizontal field of view and m sampling points on a vertical line in the vertical field of view, thus dividing the field of view of the optical engine into m×n parallel light fields, each with a corresponding directional angle.

[0115] Optionally, the horizontal field of view angle is H, and the vertical field of view angle is V;

[0116] The horizontal field of view angle value of the k-th sampling point out of n sampling points is determined according to the following formula:

[0117] wherein k is a positive integer not greater than n;

[0118] The vertical field of view angle value of the jth sample point in the vertical field of view m sample points is determined according to the following formula:

[0119] wherein j is a positive integer not greater than m.

[0120] For example, the field of view of the light engine is divided into 15 (3x5) direction angle regions, Figure 5 is a schematic diagram of one direction angle region division in the embodiment of the application, for reference Figure 5 , the FOV of 4:3 (or any aspect ratio) is divided into 15 direction angle regions (or any m*n regions), and the direction angle of each direction angle region corresponds to a group of spherical coordinates (θ, φ), the light field propagating under the same direction angle is parallel light, the diffraction order and diffraction efficiency of the in-coupling grating corresponding to the parallel light are calculated through simulation, and the zero-order diffraction efficiency η0 and the first-order diffraction efficiency η1 are obtained. Among them, Figure 5 The corresponding direction angles are θ1, θ2, θ3, … θ 15 The field of view angle corresponding to each direction angle region is determined according to the foregoing formula, Figure 5 The left and upper sides in the mark show the angular interval in the horizontal direction and the angular interval in the vertical direction in the direction angle region.

[0121] The direction angle of each direction angle region is different, and the total reflection angle (θ in ) of the light ray under each direction angle after first-order diffraction in the diffractive optical waveguide is different. Therefore, the horizontal direction footstep of single total reflection corresponding to each direction angle is inconsistent. The data of 15 footsteps is calculated by using the total reflection angle θ in and the waveguide thickness d:

[0122] .

[0123] In an embodiment, optionally, the projection area of the light engine exit pupil on the in-coupling grating is greater than or equal to the area of the in-coupling grating, and the in-coupling efficiency corresponding to each direction angle region is calculated through simulation, including:

[0124] The first-order diffraction efficiency η 1i , the zero-order diffraction efficiency η 0i and the total internal reflection angle θ i of the diffractive optical waveguide after diffraction corresponding to the ith direction angle region are calculated through simulation;

[0125] It can be understood that the direction angle of each direction angle region is different, and for each direction angle region, the corresponding first-order diffraction efficiency, zero-order diffraction efficiency and total internal reflection angle can be calculated, η 1i , that is, η1of the i-th direction angle region (the same as the foregoing definition), η 0i , that is, η0of the i-th direction angle region, θ i , that is, θ of the i-th direction angle region in .

[0126] According to the total internal reflection angle θ i , the step distance f of single total internal reflection corresponding to the i-th direction angle region is determined i .

[0127] f i , that is, the footstep of the i-th direction angle region, according to the foregoing footstep calculation formula, the step distance of single total internal reflection corresponding to each direction angle region can be calculated.

[0128] With the step distance f i as the benchmark, the coupling-in grating is divided into a plurality of sub-regions.

[0129] For example, taking the foregoing 15 direction angle regions of the embodiment as an example, it is assumed that the light field of the 15 spherical coordinate propagation can uniformly irradiate the entire coupling-in grating, and therefore the azimuth angle of the total reflection light after grating diffraction can be ignored. For the light field of any propagation direction, the grating K direction is horizontally to the right.

[0130] Commonly, the coupling-in grating is a circular grating with a diameter of 2 mm to 6 mm. The i-th azimuth angle corresponds to the i-th footstep, and according to the length of the footstep (that is, the horizontal step distance of single total reflection), the coupling-in grating region is divided into S 1i : the light field area reaching outside the coupling-in grating region after 1st first-order diffraction + 1st total reflection; S 2i : the light field area reaching outside the grating region after 1st first-order diffraction + 2nd total reflection (1st zero-order diffraction); …… qi : the light field area reaching outside the coupling-in grating region after 1st first-order diffraction + qth total reflection (q-1th zero-order diffraction). Each group of footsteps corresponds to different S 1i ……S qi , and the total area of the coupling-in grating is S 总1 . Each group of spherical coordinates corresponds to a group of diffraction efficiencies η 0i and η 1i .

[0131] The division mode can be expressed as:

[0132] A q= The area of ​​intersection between the coupling grating circle shifted left by q footsteps and the coupling grating circle before shifting left. S2=S 总1 -S1-A2; ...;S q =S 总1 -S1-S2-…-S n-1 -A q .

[0133] For example, with Figure 4 For example, A1 = S2 + S3 + S4 + S5, A2 = S3 + S4 + S5, A3 = S4 + S5, A4 = S5, where A is used to calculate the area of ​​S. For S... qi S qi q corresponds to the actual number of diffractions required (including 1st first-order diffraction and q-1st zeroth-order diffraction), and i corresponds to the i-th of the m×n angles divided by the FOV, because the footstep is different for different FOV angles.

[0134] The coupling efficiency η corresponding to the i-th directional angle region is calculated using the following formula. i :

[0135] ;

[0136] Wherein, the i-th orientation angle region corresponds to q sub-regions, S 1i S 2i S qi S represents the area of ​​each of the q subregions. 总1 This represents the total area of ​​the coupled grating.

[0137] Using the above calculations, the total coupling efficiency of the selected waveguide + coupling grating to the current optomechanical system can be obtained.

[0138] In the above calculations, the assumption that "the light fields propagating from 15 spherical coordinates can uniformly illuminate the entire coupling grating" only applies when the size of the optomechanism and the area of ​​the coupling grating are the same or the difference is extremely small. The resulting coupling efficiency is approximately equal to the ratio of the actual incident light intensity to the total light intensity diffracted through the coupling grating. In actual systems, the physical size of the optomechanism is smaller than the coupling grating, and the distance between the optomechanism and the coupling grating is fixed within a certain range (1mm~2.5mm). Therefore, at different directional angles, the area of ​​the illumination region projected by the optomechanism onto the coupling grating is also smaller than the coupling grating itself. This directly leads to a key phenomenon: there is always a "dark area" on the coupling grating that cannot be illuminated. The previous ideal assumption overestimated the efficiency; therefore, a correction was made based on the aforementioned embodiment to ensure the physical realism of the simulation.

[0139] In another embodiment, optionally, the projected area of ​​the optomechanical exit pupil on the coupling grating is smaller than the area of ​​the coupling grating, and the coupling efficiency corresponding to each directional angle region is calculated by simulation, including:

[0140] The first-order diffraction efficiency η corresponding to the i-th orientation angle region was calculated through simulation. 1i Zero-order efficiency η 0i And the total internal reflection angle θ within the diffracted waveguide after diffraction i .

[0141] Based on the total internal reflection angle θ i Determine the step distance f for a single total internal reflection corresponding to the i-th orientation angle region. i .

[0142] η 1i η 0i θ i and f i Similar to the aforementioned embodiments, details will not be repeated here.

[0143] With step distance f i Based on this, the projection of the optomechanical exit pupil onto the coupling grating is divided into multiple sub-regions according to the azimuth direction of the i-th azimuth region. Specifically, dividing the projection of the optomechanical exit pupil onto the coupling grating into multiple sub-regions according to the azimuth direction of the i-th azimuth region means that when dividing the projected area of ​​the optomechanical exit pupil onto the coupling grating in the corresponding azimuth region, the circular region of the coupling grating is moved according to the azimuth direction of the corresponding azimuth region. The azimuth is the angle between the projection of the azimuth angle on the xy-plane and the positive x-axis. This ensures that the coupling efficiency calculated by simulation is closer to the actual measured efficiency.

[0144] For example, in this embodiment, the entire field of view is discretized and divided into 3×3 directional angular regions for analysis. Figure 6 This is a schematic diagram of the projection of various directional angular regions onto the coupling grating provided in an embodiment of the present invention. In each sub-diagram, the red circle represents the region boundary of the coupling grating, and the blue circle represents the actual projection area of ​​the optical engine onto the coupling grating plane at that specific directional angle. Through comparison, it can be found that the projection position of the optical engine systematically shifts with changes in the incident angle. (The diagram is presented with a step distance f.) i Based on this, the blue circle can be divided into multiple sub-regions. When the blue circle is divided into sub-regions at different azimuth angles, the red circle representing the coupling grating moves in different directions according to the step distance. In other words, the arc (black line) inside the blue circle moves in different directions at different azimuth angles when it is formed, thus ensuring that the coupling efficiency can be calculated according to the actual changes in each azimuth angle region.

[0145] The following introduces the area (S qi ) calculation method after different regional division:

[0146] Figure 7 The regional division schematic diagram provided for the embodiment of the application, Figure 8 The regional area calculation method schematic diagram provided for the embodiment of the application, refer to Figure 7 The shadow area is the overlapping part of the large circle (coupling-in grating pattern) and the small circle (light machine projection) obtained by moving in the reverse direction of the stepping direction once, the shadow area S 阴影 and the area of the small circle S 小圆 , the area of S1 can be calculated:

[0147] S1=S 小圆 -S 阴影 ;

[0148] Similarly, the shadow area S 阴影2 after moving the second time is calculated again, the area of S2 can be calculated:

[0149] S2=S 小圆 -S1-S 阴影2 ;

[0150] Regarding the calculation of S 阴影 , the following several geometric area calculation formulas are involved:

[0151] As shown in Figure 8 , S 阴影1 =the area of the circular arc AO2B and the circular arc AO1B.

[0152] Suppose the center coordinates of the circle O1=(a1, b1) and O2=(m1, n1). Then the distance between the two circle centers is:

[0153] ;

[0154] And the small circle radius r1 and the large circle radius r0 are known, so the half of the central angle of the circular arc can be obtained through the inverse cosine theorem:

[0155] ;

[0156] ;

[0157] Alpha and beta are radian values. The two sector areas can be obtained from the half circle central angle:

[0158] ;

[0159] ;

[0160] It is easy to find that when S 扇形AO1B +S扇形AO2B >S 阴影1 Therefore, it is necessary to calculate the overlapping area of ​​the two sectors, which is... Figure 8 Quadrilateral AO1BO2 in the diagram.

[0161] S AO1BO2 =2×SAO1O2=r1×sin(α)×d=r2×sin(β)×d;

[0162] Therefore S 阴影1 =S 扇形AO1B +S 扇形AO2B -S AO1BO2 .

[0163] The coupling efficiency η corresponding to the i-th directional angle region is calculated using the following formula. i :

[0164] ;

[0165] Wherein, the i-th orientation angle region corresponds to q sub-regions, S 1i S 2i S qi S represents the area of ​​each of the q subregions. 总2 This represents the projected area of ​​the optomechanical exit pupil onto the coupling grating.

[0166] Optionally, the overall coupling efficiency is determined according to the following formula:

[0167] ;

[0168] Where, η 总 η is the total coupling efficiency of the coupling grating. i Let be the coupling efficiency of the i-th directional angular region, where i is a positive integer less than or equal to m×n.

[0169] After calculating the coupling efficiency for each directional angle region, the average of all efficiencies is taken to obtain the average coupling efficiency of the coupling grating design.

[0170] Figure 9 This is a flowchart illustrating another simulation analysis method for coupling grating efficiency provided in an embodiment of the present invention. After determining the total coupling efficiency of the coupling grating, the simulation analysis method provided in this embodiment further optimizes the parameters of the diffractive waveguide to obtain the coupling grating structure with the maximum coupling efficiency. (Refer to...) Figure 9 The simulation analysis method includes:

[0171] S210. Divide the field of view of the optical engine into m×n directional angular regions.

[0172] S220, Simulates the incident light beam onto the coupling grating in each directional angular region.

[0173] S230, calculate the coupling-in efficiency corresponding to each direction angle region through simulation.

[0174] S240, determine the total coupling-in efficiency of the coupling-in grating according to the coupling-in efficiencies corresponding to all direction angle regions.

[0175] S250, correct the structure parameters of the diffractive optical waveguide, and determine the structure parameters corresponding to the maximum total coupling-in efficiency through simulation iterative calculation.

[0176] The structure parameters include at least one of coupling-in grating parameters and / or waveguide parameters, the coupling-in grating parameters include at least one of grating period, grating height, grating duty cycle, grating topography and grating material, and the waveguide parameters include at least one of coating, waveguide material and waveguide thickness. The grating topography can include a sawtooth grating, an inclined grating, a rectangular grating, a blazed grating, a volume holographic grating, etc. After each parameter is corrected, iterative calculation is performed to find the structure parameters and material parameters that are most suitable for the current optical machine and incident mode.

[0177] Figure 10 Another flowchart of the simulation analysis method of the coupling-in grating efficiency provided by the embodiment of the present application is provided, and optionally, the diffractive optical waveguide further includes a coupling-out grating. After the coupling-in grating structure with the maximum coupling-in efficiency is determined, the simulation of the output grating is performed to obtain the overall structure of the diffractive optical waveguide. Figure 10 The simulation analysis method includes:

[0178] S310, divide the field of view of the optical machine into m*n direction angle regions.

[0179] S320, simulate the incident of the light beam in each direction angle region to the coupling-in grating.

[0180] S330, calculate the coupling-in efficiency corresponding to each direction angle region through simulation.

[0181] S340, determine the total coupling-in efficiency of the coupling-in grating according to the coupling-in efficiencies corresponding to all direction angle regions.

[0182] S350, correct the structure parameters of the diffractive optical waveguide, and determine the structure parameters corresponding to the maximum total coupling-in efficiency through simulation iterative calculation.

[0183] S360, perform simulation of the coupling-out grating to determine the overall structure of the diffractive optical waveguide.

[0184] After the coupling-in grating is determined, the simulation of the coupling-out grating in the latter stage is performed to complete the simulation of the overall light efficiency of the diffractive optical waveguide. Finally, the model structure is output to the production end, and further testing of the light efficiency difference between the production product and the actual waveguide is required.

[0185] The embodiment of the present application further provides a diffraction optical waveguide, comprising a coupling-in grating, wherein the coupling-in grating is calculated with the simulation analysis method provided in the above embodiment.

[0186] The simulation analysis method provided in the embodiment of the present application can be used to calculate the real transmission efficiency of light in different directions of a micro optical machine in a diffraction optical waveguide, which helps to improve the simulation process of the overall light efficiency of the diffraction optical waveguide and effectively shorten the difference of light efficiency data between the theoretical design end and the production end.

[0187] The above specific embodiments do not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A simulation analysis method for coupling grating efficiency, characterized in that, include: The field of view of the optical engine is divided into m×n directional angular regions; Simulate the incident light beam onto the coupling grating within each of the aforementioned directional angle regions; The coupling efficiency corresponding to each of the aforementioned directional angle regions was calculated through simulation. The total coupling efficiency of the coupling grating is determined based on the coupling efficiency corresponding to all the aforementioned directional angle regions. Where m and n are both integers greater than 1.

2. The simulation analysis method for coupling grating efficiency according to claim 1, characterized in that, The field of view of the optical engine includes a horizontal field of view and a vertical field of view. The field of view of the optical engine is divided into m×n angular regions, including: The horizontal field of view is divided into n sampling points, and the vertical field of view is divided into m sampling points; The direction angles of m×n sampling points are used as the direction angles of the corresponding direction angle regions.

3. The simulation analysis method for coupling grating efficiency according to claim 2, characterized in that, The angle value of the horizontal field of view is H, and the angle value of the vertical field of view is V; The horizontal field of view angle value of the k-th sampling point among the n sampling points of the horizontal field of view is determined according to the following formula: , where k is a positive integer not greater than n; The vertical field of view angle value of the j-th sampling point among the m sampling points in the vertical field of view is determined according to the following formula: , where j is a positive integer not greater than m.

4. The simulation analysis method for coupling grating efficiency according to claim 2, characterized in that, Simulating the incident light beam onto the coupling grating in each of the aforementioned directional angle regions includes: The transmission process of the parallel beam incident on the coupling grating is simulated by treating the beam in each of the aforementioned directional angle regions as a parallel beam. The direction of the parallel beam corresponds to the direction angle of the direction angle region.

5. The simulation analysis method for coupling grating efficiency according to claim 4, characterized in that, The projected area of ​​the optomechanical exit pupil on the coupling grating is greater than or equal to the area of ​​the coupling grating. The coupling efficiency corresponding to each directional angle region is calculated through simulation, including: The first-order diffraction efficiency η corresponding to the i-th azimuth region is calculated through simulation. 1i Zero-order diffraction efficiency η 0i And the total internal reflection angle θ within the diffracted waveguide after diffraction i ; Based on the total internal reflection angle θ i Determine the step distance f for a single total internal reflection corresponding to the i-th orientation angle region. i ; With the step distance f i Based on this, the coupled grating is divided into multiple sub-regions; The coupling efficiency η corresponding to the i-th directional angle region is calculated using the following formula. i : ； Wherein, the i-th orientation angle region corresponds to q sub-regions, S 1i S 2i S qi Let q be the areas of the q subregions. This represents the total area of ​​the coupled grating.

6. The simulation analysis method for coupling grating efficiency according to claim 4, characterized in that, The projected area of ​​the optomechanical exit pupil on the coupling grating is smaller than the area of ​​the coupling grating. The coupling efficiency corresponding to each directional angle region is calculated through simulation, including: The first-order diffraction efficiency η corresponding to the i-th azimuth region is calculated through simulation. 1i Zero-order efficiency η 0i And the total internal reflection angle θ within the diffracted waveguide after diffraction i ; Based on the total internal reflection angle θ i Determine the step distance f for a single total internal reflection corresponding to the i-th orientation angle region. i ; With the step distance f i Based on the directional angle direction of the i-th directional angle region, the projection of the optomechanical exit pupil onto the coupling grating is divided into multiple sub-regions; The coupling efficiency η corresponding to the i-th directional angle region is calculated using the following formula. i : ； Wherein, the i-th orientation angle region corresponds to q sub-regions, S 1i S 2i S qi Let q be the areas of the q subregions. This represents the projected area of ​​the optomechanical exit pupil in the coupled grating.

7. The simulation analysis method for coupling grating efficiency according to claim 5 or 6, characterized in that, The overall coupling efficiency is determined according to the following formula: ； Where, η 总 η is the total coupling efficiency of the coupling grating. i Let be the coupling efficiency of the i-th directional angle region, where i is a positive integer less than or equal to m×n.

8. The simulation analysis method for coupling grating efficiency according to claim 1, characterized in that, The coupling grating is disposed on the diffractive waveguide. After determining the total coupling efficiency of the coupling grating based on the coupling efficiency corresponding to all the directional angle regions, the method further includes: The structural parameters of the diffractive waveguide were modified, and the structural parameters corresponding to the maximum total coupling efficiency were determined through simulation and iterative calculation.

9. The simulation analysis method for coupling grating efficiency according to claim 8, characterized in that, The diffractive waveguide also includes a coupling grating, and after determining the structural parameters corresponding to the maximum total coupling efficiency, it further includes: The coupling grating is simulated to determine the overall structure of the diffractive waveguide.

10. A diffractive optical waveguide, characterized in that, It includes a coupling grating, wherein the coupling efficiency of the coupling grating is calculated using the simulation analysis method described in any one of claims 1 to 9.

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