Screening method for diffractive optical waveguide

Abstract

The application provides a screening method of a diffractive optical waveguide, comprising: extracting a plurality of appearance features based on a prepared diffractive optical waveguide, the appearance features comprising appearance contrast features and appearance overall features, the appearance contrast features being contrasts between grating regions and non-grating regions on the diffractive optical waveguide; obtaining appearance feature parameters of the diffractive optical waveguide according to weight coefficients of each appearance feature; determining a screening result of the diffractive optical waveguide based on the appearance feature parameters and in combination with an ambient light field model, an observer geometric model and a human eye visual perception model; wherein the ambient light field model is used to reflect ambient light field distribution in a use scene of the diffractive optical waveguide, the observer geometric model is used to reflect a joint probability distribution of external observer behavior characteristics, and the human eye visual perception model is used to reflect human eye visual response characteristics. The scheme provided by the application can effectively realize accurate screening of the diffractive optical waveguide.

Description

Technical Field

[0001] This application relates to the field of augmented reality display technology, and in particular to a screening method for diffractive waveguides. Background Technology

[0002] Augmented reality is a technology that blends the real world with virtual information. Augmented reality display systems typically include micro-projectors and optical displays. The micro-projectors provide virtual display content for the augmented reality display system, which is then projected onto the viewer's eyes through the optical displays. The optical displays are usually transparent optical components, so that users can also see the real world through the optical displays at the same time.

[0003] Diffractive waveguides are a common method for implementing optical displays. While diffraction gratings on diffractive waveguides achieve highly efficient coupling of display light, they are also prone to producing rainbow artifacts, reflections, stray light, and high-order diffraction color reflections under ambient light, leading to abnormal appearances and affecting user acceptance. Furthermore, current technologies cannot accurately reflect users' perceptions of the appearance of diffractive waveguides in real-world social scenarios, thus hindering precise selection and failing to provide reliable technical support for mass production and shipment. Summary of the Invention

[0004] This application provides a screening method for diffractive waveguides, which comprehensively considers multiple appearance features of diffractive waveguides and achieves accurate and objective quantification of subjective appearance features. In addition, it combines real scene modeling, observer geometric modeling and human visual perception modeling, which can effectively achieve accurate screening and production shipment of diffractive waveguides.

[0005] A screening method for diffractive optical waveguides, comprising:

[0006] Multiple appearance features are extracted based on the fabricated diffractive waveguide. These appearance features include comparative appearance features and overall appearance features. The comparative appearance features are the comparison between the grating region and the non-grating region on the diffractive waveguide.

[0007] The appearance feature parameters of the diffractive waveguide are obtained based on the weighting coefficients of each of the aforementioned appearance features.

[0008] Based on the appearance feature parameters, and in combination with the ambient light field model, the observer geometry model, and the human visual perception model, the screening results of the diffractive waveguide are determined; wherein, the ambient light field model is used to reflect the distribution of the ambient light field in the application scenario of the diffractive waveguide, the observer geometry model is used to reflect the joint probability distribution of the behavioral characteristics of the external observer, and the human visual perception model is used to reflect the visual response characteristics of the human eye.

[0009] In practice, the appearance contrast features include at least one of transmittance contrast features, reflectance contrast features, and color difference features, and the overall appearance features include at least one of color change gradient features and stray light features.

[0010] In practice, the stray light characteristic is the ratio of stray light brightness to background brightness, and the stray light brightness includes a diffraction brightness component, a scattering brightness component, and a reflection brightness component.

[0011] In practice, the ambient light field model is constructed based on the light field distribution of various light sources in the target scene and their corresponding influence coefficients.

[0012] Implementably, the ambient light field model is represented as follows:

[0013]

[0014] in, The solid angle of incidence of ambient light, including the angle of incidence pitch. and incident azimuth , The wavelength of the ambient light incident on the diffractive waveguide; Let be the influence coefficient of the k-th type of light source, k=1…Ns, where Ns is the number of types of light sources, and Ns takes a positive integer value. Let be the angular spatial radiation distribution function of the k-th type of light source;

[0015]

[0016] in, Let be the spectral radiance of the k-th type of light source. Let be the pitch angle of the k-th type of light source. Let be the pitch divergence angle of the k-th type of light source; Let be the azimuth angle of the k-th type of light source. Let be the azimuth divergence angle of the k-th type of light source.

[0017] Implementably, the observer geometric model is represented as follows:

[0018]

[0019]

[0020] in, To observe solid angles, including observing pitch angles. Observe the azimuth angle D represents the observation distance, and h represents the height difference between the observer and the wearer. To average the observed pitch angle, To observe the pitch divergence angle, To average the observed azimuth angle, To observe the azimuth divergence angle, The average observation distance, To observe distance dispersion, The average height difference The dispersion of height difference.

[0021] In practice, the human visual perception model is represented as follows:

[0022]

[0023] in, The spectral luminous efficiency function for photopic vision. To contrast the sensitivity function, To observe the angle sensitivity function;

[0024]

[0025]

[0026] in, Spatial frequency; The angular attenuation index ranges from 2 to 4.

[0027] In practice, the sample holder is adjusted to a simulated wearing angle and the prepared diffractive waveguide is fixed on the sample holder. Multiple light source components used to simulate the target environment light field are turned on in sequence. The spectrum of the diffractive waveguide under test is tested at a preset observation position using a detection component to extract multiple appearance features of the diffractive waveguide.

[0028] In practice, the plurality of light source components can be configured as a plurality of independent light sources, or as a single ring light source that is equivalent to a plurality of light sources by adjusting the pitch angle; the detection components include a luminance and colorimeter and a scattering meter, and different detection components are used when extracting different appearance features.

[0029] In practice, determining the selection result of the diffracted waveguide based on the appearance feature parameters, combined with the ambient light field model, the observer geometry model, and the human visual perception model, includes:

[0030] By combining the appearance feature parameters of the diffractive waveguide with the ambient light field model, the observer geometric model, and the human visual perception model, a comprehensive evaluation model is obtained.

[0031] According to the pre-set data filtering range, if the evaluation result obtained based on the comprehensive evaluation model falls within the first interval, the appearance quality of the diffractive waveguide is determined to have passed the screening; if the evaluation result obtained based on the comprehensive evaluation model exceeds the first interval but falls within the second interval, the appearance quality of the diffractive waveguide is determined to have failed the screening.

[0032] The screening method for diffractive waveguides provided in this application comprehensively extracts and analyzes multiple appearance features of diffractive waveguides from two dimensions: local microstructure and global macromorphology. This provides accurate and objective quantitative characterization of appearance indicators that were previously dependent on subjective judgment. Furthermore, it integrates real-world application scenario modeling, observer geometry modeling, and human visual perception modeling to comprehensively recreate the actual usage environment and human visual characteristics. This method can efficiently screen diffractive waveguide products, providing reliable technical support for mass production and batch shipment. In particular, by transforming subjective diffractive waveguide screening into objective and quantifiable data characterization, the screening results obtained in this application can directly serve the closed loop of diagnosis and optimization between front-end waveguide design and back-end manufacturing processes, which is conducive to continuously improving the manufacturing quality of diffractive waveguides. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A schematic diagram illustrating the steps of a screening method for a diffractive optical waveguide provided in this application;

[0035] Figure 2 A test environment diagram for a diffractive optical waveguide provided in this application;

[0036] Figure reference numerals: 1000, diffractive waveguide; 2000, detector assembly; 3000, light source assembly. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0038] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0039] refer to Figure 1 This application provides a method for screening diffractive optical waveguides, specifically including the following steps:

[0040] S1. Extract multiple appearance features based on the prepared diffractive waveguide. The appearance features include appearance contrast features and overall appearance features. The appearance contrast features are the contrast between the grating region and the non-grating region on the diffractive waveguide.

[0041] S2. Based on the weighting coefficients of each appearance feature, obtain the appearance feature parameters of the diffractive waveguide;

[0042] S3. Based on appearance feature parameters, and combined with the ambient light field model, the observer geometry model, and the human visual perception model, the screening results of the diffractive waveguide are determined. Among them, the ambient light field model is used to reflect the distribution of the ambient light field in the application scenario of the diffractive waveguide, the observer geometry model is used to reflect the joint probability distribution of the external observer's behavioral characteristics, and the human visual perception model is used to reflect the human visual response characteristics.

[0043] In this application, multiple appearance features are extracted from the fabricated diffractive waveguide to comprehensively evaluate its manufacturing process quality and optical performance potential. These appearance features are specifically subdivided into contrasting appearance features and overall appearance features, which characterize the diffractive waveguide from two dimensions: local microstructure and global macroscopic morphology, respectively. Contrasting appearance features primarily focus on the differences between the grating and non-grating regions of the diffractive waveguide. This contrast is not only reflected in the visual contrast between light and dark areas but also, more profoundly, in the grating structure's ability to control light. Overall appearance features, on the other hand, emphasize the overall consistency of the diffractive waveguide. This includes an overall evaluation of the entire diffractive waveguide area.

[0044] In practice, the appearance contrast features include at least one of transmittance contrast features, reflectance contrast features, and color difference features, and the overall appearance features include at least one of color change gradient features and stray light features.

[0045] Specifically, in terms of appearance contrast features, its core lies in converting the appearance into a quantifiable difference in optical parameters between the grating area and the non-grating area, specifically including at least one of the following features:

[0046] Transmittance contrast characteristic: This characteristic reflects the ability of the diffracting waveguide to balance modulation and transmission. It is quantified by the transmittance difference between the grating region and the non-grating region. The transmittance contrast characteristic is typically the transmittance difference measured at 0 degrees.

[0047] For example, the transmittance contrast feature can be expressed as: ;in, To detect solid angle Transmittance of the lower grating region For detection angle Transmittance in the lower non-grating region. Detection solid angle. Including detecting pitch angle and detection azimuth angle At this time, the solid angle is detected. Just take 0.

[0048] Reflectivity contrast feature: This feature is mainly used to evaluate the diffraction efficiency and surface quality of the grating structure. The grating region, as the area where the projected light signal is applied, should possess specific reflection / diffraction characteristics, while the non-grating region should maintain low reflectivity to reduce glare caused by ambient light reflection. This is quantified by the difference in reflectivity between the grating and non-grating regions. Specifically, the reflectivity contrast feature typically requires the difference in reflectivity between the grating and non-grating regions at multiple viewing angles.

[0049] For example, the reflectance contrast feature can be expressed as: ;in, To detect solid angle The reflectivity of the lower grating region To detect solid angle The reflectivity of the non-grating region. At this point, the detection solid angle range is the same as the observation solid angle range when an external observer observes the diffracted waveguide.

[0050] Chromatic aberration characteristics: Because diffractive waveguides have different diffraction angles for different wavelengths of light, they are prone to producing rainbow patterns or dispersion phenomena. Chromatic aberration characteristics quantify the degree of spectral separation caused by the grating structure by comparing the differences in chromaticity coordinates between the grating and non-grating regions. Typically, chromatic aberration characteristics require the chromatic differences between the grating and non-grating regions at multiple observation angles.

[0051] For example, color difference characteristics can be represented as: ;in, To detect solid angle The color vector of the lower raster region. To detect solid angle The color vector of the non-grating region. At this point, the detection solid angle range is the observation solid angle range when an external observer observes the diffracted waveguide. The transmitted and reflected colors can be calculated from the transmittance and reflectance curves.

[0052] Regarding the overall appearance characteristics, the focus is on evaluating the consistency of the diffracted waveguide over a large field of view, specifically including at least one of the following characteristics:

[0053] Color change gradient feature: This feature is used to characterize the continuity and uniformity of the color distribution on the surface of an optical waveguide in space.

[0054] For example, the color change gradient feature can be represented as:

[0055] At this point, the detection solid angle range is the observation solid angle range when an external observer observes the diffracted waveguide.

[0056] Stray light characteristics: This characteristic primarily detects the distribution of non-imaging rays. Specifically, the stray light characteristic is the ratio of stray light brightness to background brightness, which includes diffraction brightness, scattering brightness, and reflection brightness. In other words, the brightness of non-imaging rays caused by diffraction, scattering, or reflection all fall under the category of stray light brightness.

[0057] For example, stray light characteristics can be represented as:

[0058] in, For stray light brightness, This is the background brightness.

[0059] Furthermore, after extracting multiple appearance features of the diffracting waveguide, this application can obtain the appearance feature parameters of the diffracting waveguide based on the weighting coefficients of each appearance feature. It can be understood that obtaining the appearance feature parameters of the diffracting waveguide based on the weighting coefficients of each appearance feature involves establishing a multi-dimensional weighted evaluation model. This process is not merely a simple numerical accumulation, but rather a grading of the importance of various optical indicators based on different application scenarios, thereby quantifying a comprehensive quality score. For example, in see-through AR devices that pursue high transparency, the weighting coefficients of transmittance contrast features and stray light features are significantly increased to suppress background light interference and ensure a clear field of view; while in display applications that emphasize color reproduction, the weights of color difference features and color change gradient features are correspondingly increased.

[0060] In this application, after determining the weights based on the target application scenario, the measured normalized values ​​of each appearance feature are linearly or nonlinearly weighted and summed with their corresponding weight coefficients to obtain the appearance feature parameters. These parameters, as a standardized comprehensive indicator, can intuitively reflect the overall appearance quality level of the diffractive waveguide, providing a direct decision-making basis for automatic sorting and yield determination on the production line, ensuring that every diffractive waveguide that flows out meets the design expectations in terms of visual experience.

[0061] For example, appearance feature parameters can be expressed as:

[0062]

[0063] in, Transmittance contrast features The weighting coefficients, Reflectance contrast characteristics The weighting coefficients, Color difference characteristics The weighting coefficients, Color change gradient features The weighting coefficients, Stray light characteristics The weighting coefficients.

[0064] By integrating the above-mentioned multi-dimensional characteristics such as transmittance, reflectance, chromatic difference, color change gradient, and stray light, it is possible to achieve a comprehensive and accurate quantitative characterization of diffractive waveguides from microstructure to macroscopic display effect.

[0065] Furthermore, after obtaining the appearance characteristic parameters of the diffractive waveguide, this application combines the ambient light field model, the observer geometry model, and the human visual perception model to determine the screening results of the diffractive waveguide.

[0066] (I) The ambient light field model is used to reflect the distribution of the ambient light field in the application scenarios of diffractive waveguides. The ambient light field model is a key bridge connecting laboratory test data of diffractive waveguides with actual user experience. It no longer treats diffractive waveguides as isolated optical components, but places them in a dynamically changing real-world lighting environment, and uses mathematical modeling to simulate and predict the optical performance of diffractive waveguides in different application scenarios. The core of the ambient light field model lies in quantifying the ambient light field.

[0067] For example, the ambient light field model is represented as:

[0068]

[0069] in, The solid angle of incidence of ambient light, including the angle of incidence pitch. and incident azimuth , The wavelength of the ambient light incident on the diffractive waveguide; Let be the influence coefficient of the k-th type of light source, k=1…Ns, where Ns is the number of types of light sources, and Ns takes a positive integer value. Let be the angular spatial radiation distribution function of the k-th type of light source;

[0070]

[0071] in, Let be the spectral radiance of the k-th type of light source. Let be the pitch angle of the k-th type of light source. Let be the pitch divergence angle of the k-th type of light source; Let be the azimuth angle of the k-th type of light source. Let be the azimuth divergence angle of the k-th type of light source.

[0072] It is understandable that when constructing an ambient light field model, incorporating the influence coefficients of different light sources is crucial. These coefficients represent the proportion of a particular light source within the ambient light field and are key to ensuring the model accurately reflects the complexity of the physical world. Real-world illumination is never single-dimensional but rather a composite field dynamically superimposed from multiple light sources. Considering practical applications, different types of light sources may coexist within the ambient light field, and the forms of light sources are not singular. For example, this application uses a light field involving four types of light sources, i.e., Ns=4, as an example for illustration.

[0073] The light field of the first type of light source is the solar light field, and the angular spatial radiation distribution function of the solar light field can be expressed as:

[0074]

[0075] in, The elevation angle at the center of the sun, The azimuth of the sun's center. For the solar divergence angle, This refers to the solar spectral radiance. For example, the radiance of sunlight ranges from 10^4 to 10^5 cd / m²; the azimuth angle of the solar center ranges from −180° to 180°, typically... The angle of elevation at the center of the sun ranges from 10° to 80°, typically being... .

[0076] The second type of light source is the flash lamp field, and the angular spatial radiation distribution function of the flash lamp field can be expressed as:

[0077]

[0078] in, The flash tilt angle, This is the azimuth angle of the flash. For the flash pitch divergence angle, This refers to the azimuth divergence angle of the flash. This refers to the spectral radiance of the flash unit. For example, the flash unit's radiance range is 10^3 to 10^5 cd / m²; the flash unit's azimuth angle ranges from −90° to 90°, typically... The flash pitch angle ranges from -20° to 60°, typically... .

[0079] The third type of light source is the indoor light field, and the angular spatial radiation distribution function of the indoor light field can be expressed as:

[0080]

[0081] in, The tilt angle of the indoor light. This refers to the azimuth angle of the indoor lights. For the pitch divergence angle of indoor lights, The azimuth angle of the indoor lights. This refers to the spectral radiance of indoor lamps.

[0082] It should be noted that the light sources for indoor lighting fields can include ceiling lights and electronic display terminals (such as LED advertising screens). These two light sources have different weights, 0.7 and 0.3 respectively. For example, the brightness range of ceiling lights is 300–800 ppm. The incident solid angle range is as follows: incident azimuth: 0°±30°, incident elevation: 70°±15°. The brightness range of the LED advertising screen is 500~5000. The range of incident solid angles is as follows: incident azimuth: 45°±20°, incident elevation: 0°±20°.

[0083] The fourth type of light source is the light field of vehicle headlights, and the directional distribution of the vehicle headlight field can be represented as:

[0084]

[0085] in, For the headlight tilt angle, This refers to the headlight azimuth angle. The width of the vertical beam of the headlight. The width of the horizontal beam of the headlight. This refers to the spectral radiance of the vehicle headlights. For example, the headlight luminance range is 10^3 to 10^5 cd / m², and the headlight azimuth angle ranges from −60° to 60°, typically... The headlight pitch angle ranges from -10° to 20°, typically... .

[0086] It's understandable that different product types have different primary usage scenarios, i.e., different ambient light fields, resulting in different influence coefficients for these four types of light sources. For example, for sports AR glasses, the influence coefficients for these four types of light sources are: sunlight field 0.5, flashlight field 0.2, indoor lighting field 0.3, and vehicle headlight field 0.1; as another example, for movie-watching AR glasses, the influence coefficients for these four types of light sources are: sunlight field 0.3, flashlight field 0.3, indoor lighting field 0.3, and vehicle headlight field 0.1.

[0087] (II) The observer geometry model is used to reflect the joint probability distribution of external observer behavior characteristics. The observer geometry model complements and improves the ambient light field model. Simply put, the ambient light field model describes where the light comes from, while the observer geometry model defines where a person is looking. This model uses mathematical statistical methods to abstract the eye movements, head posture, and gaze habits of the external observer (i.e., the user or viewer wearing AR glasses) into a set of spatial geometric parameters and constructs a joint probability distribution. The core function of this distribution is to quantify the optical interaction between the observer and the diffracted waveguide.

[0088] For example, the observer geometric model can be represented as:

[0089]

[0090]

[0091] in, To observe solid angles, including observing pitch angles. Observe the azimuth angle D represents the observation distance, and h represents the height difference between the observer and the wearer. To average the observed pitch angle, To observe the pitch divergence angle, To average the observed azimuth angle, To observe the azimuth divergence angle, The average observation distance, To observe distance dispersion, The average height difference The dispersion of height difference.

[0092] (III) The human visual perception model is used to reflect the characteristics of human visual response. The human visual perception model is a bridge connecting objective physical optical indicators and subjective visual experience. From a biological perspective, the human visual perception model accurately describes how the human brain and retina process, filter, and evaluate light signals.

[0093] For example, the human visual perception model can be represented as:

[0094]

[0095] in, The spectral luminous efficiency function for photopic vision. For the contrast sensitivity function: , For spatial frequency, , The characteristic brightness variation period; To observe the angle sensitivity function: , The angular attenuation index ranges from 2 to 4.

[0096] In this application, the appearance characteristic parameters of the diffractive waveguide are combined with the ambient light field model, the observer geometric model, and the human visual perception model to obtain a comprehensive evaluation model, which can be expressed as:

[0097]

[0098] Understandably, to ensure the physical authenticity, data accuracy, and consistency of subjective experience of the test results, the "detection solid angle" will be considered during the optical inspection and appearance feature extraction process of the diffractive waveguide. "and "observing solid angles" If the angle range is set to be consistent (except for transmittance contrast features), then .

[0099] in, This data is used to quantify the visual evaluation of a diffracted waveguide by an observer's eye. Based on the value of this data, the screening result of whether the appearance quality of the diffracted waveguide is qualified can be determined.

[0100] In practice, based on a pre-set data filtering range, if the calculated... If the value falls within the first interval, the appearance quality of the diffractive waveguide is deemed to meet the standard and it is approved for screening; if... The value exceeds this first interval, especially when If the value falls within the second interval, the product is considered non-conforming. The first and second intervals have no overlap and are typically determined through statistical analysis of extensive subjective evaluation experiments and objective measurement data to ensure... The indicators are highly correlated with actual human perception.

[0101] Furthermore, the ambient light field in which a diffractive waveguide operates is not constant in actual use. To better reflect the real-world application scenarios of diffractive waveguides, this application assigns differentiated weighting coefficients to different ambient light fields. The comprehensive evaluation model after adding these weighting coefficients can be expressed as follows:

[0102]

[0103] wherein s is the number of types of ambient light fields, are the weights of different ambient light fields, which may be specifically expressed as:

[0104]

[0105] wherein, is the scene brightness factor, is the scene duration, is the scene occurrence frequency, is the scene criticality. are respectively the importance coefficients of the respective factors.

[0106] In this embodiment, by introducing multiple ambient light fields and their weights for comprehensive evaluation, the optical detection standards are essentially mapped to actual application scenarios. The use of the weighting model can convert the visual sensitivity of the target audience in a specific environment into specific engineering evaluation indicators. This not only overcomes the limitation of testing in a single ideal environment, but also provides quantitative guidance for the design and manufacturing of optical waveguides, thereby ensuring the consistency of optical performance and the visual experience of products in complex real environments.

[0107] The comprehensive evaluation score Vtotal of the diffractive optical waveguide calculated based on the comprehensive evaluation model with added weight coefficients is used to quantitatively evaluate the appearance quality of the diffractive optical waveguide. The magnitude of the Vtotal value is positively correlated with the degree of appearance defects perceptible to the human eye. A smaller value indicates higher appearance consistency between the grating region and the non-grating region of the diffractive optical waveguide, and weaker appearance defects perceptible to human vision.

[0108] Exemplarily, the comprehensive evaluation score Vtotal of the diffractive optical waveguide is calculated based on the comprehensive evaluation model with added weight coefficients. The comprehensive evaluation score Vtotal is compared with a preset first threshold Vth1 and a preset second threshold Vth2, where the first threshold is smaller than the second threshold (Vth1<Vth2). The following hierarchical determination is performed according to the comparison result:

[0109] When Vtotal≤Vth1, the diffractive optical waveguide is determined to be a qualified product;

[0110] When Vth1<Vtotal≤Vth2, the diffractive optical waveguide is determined to be a secondary product;

[0111] When Vtotal>Vth2, the diffractive optical waveguide is determined to be an unqualified product.

[0112] Based on the above embodiments, this application, by extracting multiple appearance features of the diffractive waveguide and combining an ambient light field model, an observer geometry model, and a human visual perception model, can accurately quantify the degree of defect perception under real lighting and typical viewing postures, thereby establishing a highly human-like automated quality inspection standard. Simultaneously, the evaluation results can also guide upstream design optimization, ensuring a high degree of consistency between the physical optical performance of the diffractive waveguide and the subjective visual experience of humans.

[0113] In some embodiments, for ease of engineering implementation, the continuous integral model can be transformed into a discrete model. In this case, the comprehensive evaluation model can be expressed as:

[0114]

[0115] Where i is the light source sampling point (the number of samples ranges from 5 to 20); j is the observation angle sampling point (the number of samples ranges from 10 to 30); and k is the wavelength sampling point (the sampling wavelength ranges from 380 to 780 nm).

[0116] In some embodiments, in order to make the ambient light field model and the observer geometry model engineering feasible, this application also calibrates the model parameters through experimental measurements.

[0117] Specifically, the calibration of the light field model parameters includes conducting actual measurements on various types of light sources using a spectrophotometer. For example, a spectrophotometer (wavelength range 380-780nm) is used as the measuring device. Spatial sampling of the light source is performed according to a preset incident direction, with a sampling interval of 10° for both elevation and azimuth angles. Measurements are repeated 20 times for each sampling direction to reduce random measurement errors. For the k-th type of light source, the spectral radiance is defined as:

[0118]

[0119] Where N is the number of repeated measurements in the same sampling direction, preferably 20. For the first The measurement obtained from the first measurement Light-emitting light sources at wavelength Spectral radiance at that location.

[0120] The divergence angle of the light source is calculated using the full width at half maximum (FWHM) of the measured spectral radiance:

[0121]

[0122]

[0123] in, Let be the pitch divergence angle of the k-th light source. Let be the full width at half maximum (FWHM) of the spectral radiance of the k-th light source in the pitch direction. Let be the azimuth divergence angle of the k-th luminous source. Let be the full width at half maximum (FWHM) of the spectral radiance of the k-th light source in the azimuth direction.

[0124] Specifically, the calibration of the observer's geometric model includes obtaining statistical data through real-world social observation experiments. For example, selecting a group of 30-50 participants and recording the distribution of observation distances and angles in various environments such as shopping malls, outdoors, car headlights, and flashlights, to obtain statistical data. ; ; ; . D=0.5-2.0m, h=-0.45-0.45m.

[0125] In some embodiments, step S1 involves extracting multiple appearance features based on the prepared diffractive waveguide, specifically including: adjusting the sample holder to a simulated wearing angle and fixing the prepared diffractive waveguide on the sample holder; sequentially turning on multiple light source components used to simulate the target environment light field; and using a detection component to test the spectrum of the diffractive waveguide under test at a preset observation position in order to extract multiple appearance features of the diffractive waveguide.

[0126] The multiple light source components used to simulate the target environment's light field are configured as multiple independent light sources, or as a single ring light source that can be equivalent to multiple light sources by adjusting the pitch angle. The detection components include a luminance meter and a scattering meter; the detection components used differ when extracting different appearance features.

[0127] Specifically, after the light source emission stabilizes, the pitch and azimuth angles of the luminance and colorimeter are adjusted so that the luminance and colorimeter probe corresponds to the simulated human eye observation position, and the transmission spectrum, reflection spectrum, brightness and colorimetric data of the diffracted light waveguide under different light source conditions are collected; at the same time, the intensity data of the scattered light in the optical path is collected through the scattering measurement instrument, and the data collection of all preset scenarios is completed in a loop.

[0128] For example, when measuring transmittance and reflectance, the brightness adjustment range of the light source component is 10 cd / m² to 10000 cd / m², and the spectral response range is 380 nm to 780 nm; the pitch angle adjustment range of the light source component is -90° to 90°, and the azimuth angle adjustment range is 0° to 360°. The specific testing steps include: first, fixing the diffractive waveguide to the sample holder and adjusting the light source component to the target pitch and azimuth angles; second, sequentially turning on the light sources used to simulate the target scene; and then, sequentially acquiring the transmission and reflection spectra of the diffractive waveguide using a luminance-colorimeter. The incident angle for the transmission test is set to 0°, and the incident angle range for the reflection test is 0° to 80°, with an angle step of 5°. In addition, to ensure the accuracy of the test data, multiple sampling points were performed on the plane of the diffractive waveguide at preset intervals of 5 mm. Multiple measurements were performed at each sampling point and the average value was taken. The number of measurements was set to 3.

[0129] For example, when testing stray light characteristics, firstly, under standard illumination conditions, a planar brightness distribution image of the diffracted light waveguide is acquired. Then, the planar brightness distribution image is divided into regions and its brightness is extracted: the region without a grating structure in the image is selected as the background region of interest (ROI_bg), and the average brightness within this region is calculated, denoted as . Simultaneously, the scattering region excluding the main outgoing beam and the zeroth-order diffracted beam is selected as the region of interest (ROI_stray) for stray light, and the average brightness within this region is calculated and denoted as . Ultimately, based on and The stray light characteristics of the diffracted waveguide are calculated.

[0130] Furthermore, this application also provides two sets of comparative test schemes for diffractive waveguides, with the following specific configurations: one set consists of diffractive waveguide samples without coating treatment; the other set consists of diffractive waveguide samples coated with antireflective thin film materials such as silicon dioxide and zirconium oxide. To eliminate the interference of irrelevant variables on the experimental results and ensure the validity and comparability of the experimental data of the two sets of samples, this comparative experiment uses completely identical test conditions, specifically including: a unified ambient light field model, an observer geometric model, and a human visual perception model, while ensuring that the spectral characteristics of the light source, the brightness of the light source, the BSDF scanning parameters, and the appearance performance test conditions are completely consistent.

[0131] Actual measurements show that after depositing the silicon dioxide antireflection coating, all appearance defect parameters of the diffractive waveguide are significantly optimized, with a marked decrease in transmittance difference, reflectance difference, chromatic aberration, and stray light ratio. Specifically, the transmittance difference decreased from 0.07 to 0.03, the reflectance difference decreased from 0.06 to 0.03, the CIE2000 chromatic aberration decreased from 3.2 to 1.5, and the stray light characteristic value decreased from 0.35 to 0.18.

[0132] Furthermore, based on the comprehensive evaluation model with added weighting coefficients, the comprehensive evaluation scores for the two groups of diffractive waveguides were calculated to be 0.61 (uncoated) and 0.32 (coated with silicon dioxide antireflective film), respectively. The quantitative evaluation based on Vtotal confirms that the overall appearance consistency of the diffractive waveguide is significantly improved after coating with silicon dioxide antireflective film. Simultaneously, the above measured results highly match the subjective visual perception patterns of the human eye, verifying that the comprehensive perception evaluation model constructed in this application can accurately and effectively characterize the subjective perception effect of the human eye on the appearance quality of the diffractive waveguide, and possesses good engineering application value.

[0133] The screening method for diffractive waveguides provided in this application comprehensively extracts and analyzes multiple appearance features of diffractive waveguides from two dimensions: local microstructure and global macromorphology. This provides accurate and objective quantitative characterization of appearance indicators that were previously dependent on subjective judgment. Furthermore, it integrates real-world application scenario modeling, observer geometry modeling, and human visual perception modeling to comprehensively recreate the actual usage environment and human visual characteristics. This method can efficiently screen diffractive waveguide products, providing reliable technical support for mass production and batch shipment. In particular, by transforming subjective diffractive waveguide screening into objective and quantifiable data characterization, the screening results obtained in this application can directly serve the closed loop of diagnosis and optimization between front-end waveguide design and back-end manufacturing processes, which is conducive to continuously improving the manufacturing quality of diffractive waveguides.

[0134] The specific embodiments described above do not constitute a limitation on the scope of protection of this 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 modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for screening diffractive optical waveguides, characterized in that, include: Multiple appearance features are extracted based on the fabricated diffractive waveguide. These appearance features include comparative appearance features and overall appearance features. The comparative appearance features are the comparison between the grating region and the non-grating region on the diffractive waveguide. The appearance feature parameters of the diffractive waveguide are obtained based on the weighting coefficients of each of the aforementioned appearance features. Based on the appearance feature parameters, and combined with the ambient light field model, the observer geometry model, and the human visual perception model, the screening results of the diffractive waveguide are determined; wherein, the ambient light field model is used to reflect the distribution of the ambient light field in the application scenario of the diffractive waveguide, the observer geometry model is used to reflect the joint probability distribution of the behavioral characteristics of the external observer, and the human visual perception model is used to reflect the visual response characteristics of the human eye. The appearance contrast features include at least one of transmittance contrast features, reflectance contrast features, and color difference features, and the overall appearance features include at least one of color change gradient features and stray light features.

2. The screening method for diffractive waveguides according to claim 1, characterized in that, The stray light characteristic is the ratio of stray light brightness to background brightness, and the stray light brightness includes diffraction brightness, scattering brightness, and reflection brightness.

3. The screening method for diffractive waveguides according to claim 1, characterized in that, The ambient light field model is constructed based on the light field distribution of various light sources in the target scene and their corresponding influence coefficients.

4. The screening method for diffractive waveguides according to claim 3, characterized in that, The ambient light field model is represented as follows: in, The solid angle of incidence of ambient light, including the angle of incidence pitch. and incident azimuth angle , The wavelength of the ambient light incident on the diffractive waveguide; Let be the influence coefficient of the k-th type of light source, k=1…Ns, where Ns is the number of types of light sources, and Ns takes a positive integer value. Let be the angular spatial radiation distribution function of the k-th type of light source; in, Let be the spectral radiance of the k-th type of light source. Let be the pitch angle of the k-th type of light source. Let be the pitch divergence angle of the k-th type of light source; Let be the azimuth angle of the k-th type of light source. Let be the azimuth divergence angle of the k-th type of light source.

5. The screening method for diffractive waveguides according to claim 1, characterized in that, The observer geometric model is represented as follows: in, To observe solid angles, including observing pitch angles. Observe the azimuth angle D represents the observation distance, and h represents the height difference between the observer and the wearer. To average the observed pitch angle, To observe the pitch divergence angle, To average the observed azimuth angle, To observe the azimuth divergence angle, The average observation distance, To observe the distance dispersion, The average height difference The dispersion of height difference.

6. The screening method for diffractive waveguides according to claim 1, characterized in that, The human visual perception model is represented as follows: in, The spectral luminous efficiency function for photopic vision. To contrast the sensitivity function, To observe the angle sensitivity function; in, Spatial frequency; The angular attenuation index ranges from 2 to 4.

7. The screening method for diffractive waveguides according to claim 1, characterized in that, The extraction of multiple appearance features based on the fabricated diffractive waveguide includes: Adjust the sample holder to the simulated wearing angle and fix the prepared diffractive waveguide on the sample holder. Then, turn on multiple light source components to simulate the target environment light field in sequence. Use the detection component to test the spectrum of the diffractive waveguide at a preset observation position to extract multiple appearance features of the diffractive waveguide.

8. The screening method for diffractive waveguides according to claim 7, characterized in that, The multiple light source components are configured as multiple independent light sources, or as a single ring light source that can be equivalent to multiple light sources by adjusting the pitch angle; the detection components include a luminance meter and a scattering meter, and different detection components are used when extracting different appearance features.

9. The screening method for diffractive waveguides according to claim 1, characterized in that, The process of determining the selection results of the diffractive waveguide based on the appearance feature parameters, combined with the ambient light field model, the observer geometry model, and the human visual perception model, includes: By combining the appearance feature parameters of the diffractive waveguide with the ambient light field model, the observer geometric model, and the human visual perception model, a comprehensive evaluation model is obtained. According to the pre-set data filtering range, if the evaluation result obtained based on the comprehensive evaluation model falls within the first interval, the appearance quality of the diffractive waveguide is determined to have passed the screening; if the evaluation result obtained based on the comprehensive evaluation model exceeds the first interval but falls within the second interval, the appearance quality of the diffractive waveguide is determined to have failed the screening.

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