Method and Measurement System for Measuring Field of View Angle of Near-Eye Display Module

Abstract

The present invention provides a method and a measurement system for measuring the field of view angle of a near-eye display module. The measurement method includes: calibrating the measurement system; establishing a relationship table between the field of view angle of the checkerboard at various azimuth angles and the pixel positions of the chip of the test camera according to the target images at various azimuth angles; placing the near-eye display module to be measured on the lighting tooling fixture; collecting an image of the near-eye display module when it displays a full-white image through the test camera and generating a gray-scale curve graph; determining a gray-scale gradient curve graph according to the gray-scale curve graph; determining the pixel position corresponding to the peak value in the gray-scale gradient curve graph as the edge pixel position of the near-eye display module; and determining the field of view angle of the near-eye display module according to the edge pixel position and the relationship table. The present invention solves the problems of inaccurate measurement results and complex operation in the measurement of the field of view angle of the near-eye display module in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of optical testing equipment, and in particular, to a method and a system for measuring the field of view angle of a near-eye display module. Background Art

[0002] In the field of near-eye display technology, as a key component, the performance of a near-eye display module directly affects the user experience. The field of view (FOV) of a near-eye display module is one of the important parameters for measuring its performance, which determines the range within which a user can see virtual images or information. The conventional method for measuring the FOV of a near-eye display module usually relies on measuring the gray value of the edge field of the module. When this value reaches 50% of the gray value of the central field, it is used as the basis for defining the position of the edge field. Although this method is widely used in optical testing, it has significant limitations and deficiencies.

[0003] Firstly, this method does not fully consider the brightness non-uniformity of the near-eye display module under different fields of view. The gray value of the central region of most near-eye display modules is relatively high, while the gray value of the edge region gradually decreases. Therefore, using only 50% of the gray value as the edge definition standard will result in generally smaller measurement results, which cannot accurately reflect the true FOV of the module, thus affecting the product design and quality assessment.

[0004] Secondly, this method requires the exact matching of the exit pupil position of the near-eye display module and the entrance pupil position of the measurement system to ensure that the entire field of view is fully captured. However, this matching process is very complex, requiring not only precise adjustment, but also in actual operation, due to factors such as adjustment errors, imperfections of the near-eye display module itself, and instability of the measurement environment, it is very difficult to achieve an ideal matching state. Imprecise matching will further lead to measurement result deviations, reducing the reliability and accuracy of the measurement.

[0005] That is to say, there are problems of inaccurate measurement results and complex operation in the measurement of the field of view angle of the near-eye display module in the prior art. Summary of the Invention

[0006] The main objective of the present invention is to provide a method and a system for measuring the field of view angle of a near-eye display module, so as to solve the problems of inaccurate measurement results and complex operation in the measurement of the field of view angle of the near-eye display module in the prior art.

[0007] To achieve the above object, according to one aspect of the present invention, there is provided a method for measuring the field of view angle of a near-eye display module, including the following steps: calibrating a measurement system composed of an adjustment stage, a lighting tooling fixture, a test camera, and a humanoid eye lens, including: calibrating the measurement system with a light source having a checkerboard target to obtain target images at multiple azimuth angles; establishing a relationship table between the field of view angles of the checkerboard at multiple azimuth angles and the pixel positions of the chip of the test camera based on the target images at multiple azimuth angles; placing the near-eye display module to be measured on the lighting tooling fixture and calibrating the position of the near-eye display module; collecting an image of the near-eye display module when displaying a full white image through the test camera and generating a grayscale curve graph; determining a grayscale gradient curve graph based on the grayscale curve graph; determining the pixel position corresponding to the peak value in the grayscale gradient curve graph as the edge pixel position of the near-eye display module; and determining the field of view angle of the near-eye display module based on the edge pixel position and the relationship table.

[0008] Further, in the step of calibrating the measurement system, there is also a flat-field correction step before calibrating the measurement system with a light source having a checkerboard target: placing a standard light source on the pupil side of the humanoid eye lens and making the pupil position of the humanoid eye lens fall within the light exit of the standard light source; adjusting the focal length of the humanoid eye lens to make the focal length of the humanoid eye lens the same as the virtual image distance of the near-eye display module to be measured; adjusting the test camera to enable the test camera to collect multiple images; and establishing a flat-field correction matrix based on the multiple images.

[0009] Further, adjusting the test camera includes: adjusting the exposure time of the test camera so that the target gray value in a partial central area of the image captured by the test camera is within the range of greater than or equal to 175 and less than or equal to 185.

[0010] Further, establishing a flat-field correction matrix based on multiple images includes: determining the average gray value corresponding to the same pixel position of the chip of the test camera based on the multiple images ; determining the average gray value T of a region with a preset size at the center of the image based on the average gray value and establishing a flat-field correction matrix M, X where T(i,j) is the gray value at the pixel position (i,j) within the valid region of the corresponding image, i≥1, j≥1.

[0011]

[0012]

[0013] Further, before placing the standard light source at the pupil position of the humanoid eye lens, it includes: adjusting the brightness of the standard light source to 50% - 80% of the maximum brightness.

[0014] Further, a light source with a checkerboard target is used to calibrate the measurement system to obtain target images at multiple azimuth angles, including: placing the light source with the checkerboard target on the entrance pupil side of the humanoid eye lens, where the checkerboard target is formed by arranging multiple checkerboards in an array; making the center point of the chip of the test camera coincide with the intersection point of the checkerboard target; rotating the test camera and the humanoid eye lens three times clockwise or counterclockwise on the HV plane, each time rotating 90°. When not rotated and after each rotation, the light source with the checkerboard target is photographed by the test camera to obtain target images at four azimuth angles.

[0015] Further, according to the target images at multiple azimuth angles, a relationship table is established between the field of view angles of the checkerboards at multiple azimuth angles and the pixel positions of the chip of the test camera, including: according to the target images at multiple azimuth angles, calculating the field of view angle FOV of the checkerboards of the checkerboard target corresponding to different pixel positions of the chip of the test camera at different azimuth angles, ; where h is the length or width of the checkerboard, and d is the vertical distance from the checkerboard target to the humanoid eye lens; establishing a relationship table between the field of view angles of the checkerboards of the checkerboard target at multiple azimuth angles and the pixel positions of the chip of the test camera.

[0016] Further, placing the near-eye display module to be measured on the lighting fixture and calibrating the position of the near-eye display module, including: placing the near-eye display module to be measured on the lighting fixture and installing the lighting fixture on the adjustment table, with the humanoid eye lens on the side of the test camera facing the near-eye display module; turning on the lighting fixture to light up the near-eye display module, so that a cross image is formed on the display screen of the near-eye display module; adjusting the adjustment table until the cross image coincides with the center point of the chip of the test camera; continuing to adjust the adjustment table so that the exit pupil position of the near-eye display module coincides with the entrance pupil position of the humanoid eye lens.

[0017] Further, during the process of collecting the image of the near-eye display module when displaying a full-white image through the test camera and generating a gray-scale curve graph, setting the brightness value of the full-white image of the near-eye display module to be greater than or equal to 500 cd / m² and less than or equal to 600 cd / m²; and / or, the gray-scale curve graph includes a gray-scale curve graph in the H direction and a gray-scale curve graph in the V direction.

[0018] Further, before the step of determining the gray-scale gradient curve graph according to the gray-scale curve graph, it further includes: performing mean filtering processing on the gray-scale curve graph to obtain the gray-scale curve graph after mean filtering processing.

[0019] Further, determining the gray-scale gradient curve graph according to the gray-scale curve graph, including: performing a first-order derivative processing on the gray-scale curve graph to generate a gray-scale gradient curve graph corresponding to the gray-scale curve graph.

[0020] Further, in the process of determining the pixel position corresponding to the peak in the gray-scale gradient curve graph according to the gray-scale gradient curve graph, there are two peaks in the same gray-scale gradient curve graph; and / or, in the process of determining the field of view angle of the near-eye display module according to the edge pixel position and the relation table, it includes determining the corresponding field of view angle in the relation table according to the edge pixel position to obtain the field of view angle of the near-eye display module.

[0021] According to another aspect of the present invention, there is provided a measurement system for the field of view angle of a near-eye display module, including an adjustment table, a lighting tooling fixture, a test camera, and a humanoid eye lens. The lighting tooling fixture is arranged on the adjustment table. The test camera is connected to the humanoid eye lens, and the humanoid eye lens is located on the side of the test camera facing the lighting tooling fixture. The lighting tooling fixture and the humanoid eye lens are arranged at intervals.

[0022] Applying the technical solution of the present invention, the method for measuring the field of view angle of a near-eye display module includes the following steps: calibrating the measurement system composed of an adjustment table, a lighting tooling fixture, a test camera, and a humanoid eye lens, including: calibrating the measurement system with a light source having a checkerboard target to obtain target images at various azimuth angles; establishing a relation table between the field of view angles of the checkerboard at various azimuth angles and the pixel positions of the chip of the test camera according to the target images at various azimuth angles; placing the near-eye display module to be measured on the lighting tooling fixture and calibrating the position of the near-eye display module; collecting an image of the near-eye display module when it displays a full-white image through the test camera and generating a gray-scale curve graph; determining a gray-scale gradient curve graph according to the gray-scale curve graph; determining the pixel position corresponding to the peak in the gray-scale gradient curve graph as the edge pixel position of the near-eye display module; and determining the field of view angle of the near-eye display module according to the edge pixel position and the relation table.

[0023] This application calibrates the measurement system by using a light source with a checkerboard target, thereby obtaining target images at multiple azimuth angles. Then, based on the target images at multiple azimuth angles, a relationship table between the field of view angles of the checkerboard at multiple azimuth angles and the pixel positions of the chip of the test camera is established. Thus, the relationship between pixel positions and field of view angles can be mapped more accurately. As a result, the pixel positions in the edge field of view of the near-eye display module can be directly converted to the angular space based on the calibrated relationship table, thereby accurately obtaining the field of view angle of the near-eye display module. By using the pixel positions corresponding to the peaks in the gray gradient curve graph, the edge field of view of the near-eye display module is determined. Compared with the prior art method of defining the field of view edge by using the edge gray level being 50% of the central gray level, it is more accurate, has higher measurement accuracy, effectively reduces the influence of the brightness non-uniformity of the near-eye display module itself at different fields of view on the measurement accuracy, and can more accurately obtain the field of view angle of the near-eye display module. Moreover, this method is simple to operate, is beneficial to improving the measurement efficiency, the structure of the measurement system is relatively simple, and the measurement cost is effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0025] Figure 1 The flowchart of the method for measuring the field of view angle of the near-eye display module according to an alternative embodiment of the present invention is shown;

[0026] Figure 2 The schematic structural diagram of the measurement system for the field of view angle of the near-eye display module according to an alternative embodiment of the present invention is shown;

[0027] Figure 3 The schematic diagram of the method for measuring the field of view angle of the near-eye display module of the present invention during the flat-field correction process is shown;

[0028] Figure 4 The schematic diagram of the method for measuring the field of view angle of the near-eye display module of the present invention during the calibration process is shown;

[0029] Figure 5 The image of the near-eye display module when displaying a full-white image collected by the test camera according to the measurement method of the present invention is shown;

[0030] Figure 6 Shows Figure 5 The gray curve graph of the image in the V direction;

[0031] Figure 7 Shows Figure 5 The gray curve graph of the image in the H direction;

[0032] Figure 8 shows Figure 6 the corresponding grayscale gradient curve graph;

[0033] Figure 9 shows Figure 7 the corresponding grayscale gradient curve graph.

[0034] Among them, the above-mentioned drawings include the following reference numerals:

[0035] 1. Near-eye display module; 11. Exit pupil position; 2. Lighting fixture jig; 3. Adjusting table; 4. Humanoid eye lens; 41. Entrance pupil position; 5. Test camera; 6. Standard light source; 61. Light output port; 7. Light source with checkerboard target; 71. Checkerboard target; 711. Checkerboard. Specific embodiments

[0036] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0037] It should be pointed out that unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0038] In the present invention, unless otherwise stated, the orientation words such as "upper, lower, top, bottom" are usually in the direction shown in the drawings, or in the vertical, perpendicular or gravitational direction of the component itself; similarly, for the convenience of understanding and description, "inner, outer" refer to the inner and outer of the contour of each component itself, but the above orientation words do not limit the present invention.

[0039] In order to solve the problems of inaccurate measurement results and complex operation in the measurement of the field of view angle of the near-eye display module in the prior art, the present invention provides a method and a measurement system for measuring the field of view angle of the near-eye display module.

[0040] As Figures 1 to 9 shown, the method for measuring the field of view angle of the near-eye display module 1 includes the following steps:

[0041] Calibrate the measurement system composed of the adjusting table 3, the lighting fixture jig 2, the test camera 5 and the humanoid eye lens 4, including: calibrate the measurement system with the light source 7 having a checkerboard target to obtain the target images at various azimuth angles. [[ID=4"]]

[0042] According to the target images at various azimuth angles, establish a relationship table between the field of view angles of the checkerboard 711 at various azimuth angles and the pixel positions of the chip of the test camera 5.

[0043] Place the near-eye display module 1 to be measured on the lighting fixture 2 and calibrate the position of the near-eye display module 1.

[0044] Collect an image of the near-eye display module 1 when it displays a full-white image through the test camera 5 and generate a grayscale curve graph.

[0045] Determine the grayscale gradient curve graph according to the grayscale curve graph.

[0046] Determine the pixel position corresponding to the peak in the grayscale gradient curve graph according to the grayscale gradient curve graph, and use it as the edge pixel position of the near-eye display module 1.

[0047] Determine the field of view angle of the near-eye display module 1 according to the edge pixel position and the relationship table.

[0048] In this application, the measurement system is calibrated by using a light source 7 with a checkerboard target, so as to obtain target images at multiple azimuth angles. Then, according to the target images at multiple azimuth angles, a relationship table between the field of view angle of the checkerboard 711 at multiple azimuth angles and the pixel position of the chip of the test camera 5 is established. Thus, the relationship between the pixel position and the field of view angle can be mapped more accurately. Therefore, the pixel position of the edge field of view of the near-eye display module 1 can be directly converted to the angular space based on the calibrated relationship table, and the field of view angle of the near-eye display module 1 can be accurately obtained. By using the pixel position corresponding to the peak in the grayscale gradient curve graph to determine the edge field of view of the near-eye display module 1, compared with the prior art method of defining the field of view edge by using the edge grayscale as 50% of the central grayscale, it is more accurate, the measurement accuracy is higher, and the influence of the brightness non-uniformity of the near-eye display module 1 itself in different fields of view on the measurement accuracy is effectively reduced, and the field of view angle of the near-eye display module 1 can be obtained more accurately. Moreover, this method is simple to operate, which is beneficial to improving the measurement efficiency. The structure of the measurement system is relatively simple, effectively reducing the measurement cost.

[0049] Specifically, in the above steps of calibrating the measurement system, it further includes a flat-field correction step before calibrating the measurement system by using a light source 7 with a checkerboard target. The steps of calibrating the measurement system specifically include a flat-field correction step and a step of calibrating the measurement system. The flat-field correction step is before the step of calibrating the measurement system. That is to say, this method first performs flat-field correction on the measurement system and then calibrates the measurement system, so as to complete the calibration of the measurement system.

[0050] Such as Figure 3As shown in the figure, the flat-field correction step includes: placing the standard light source 6 on the entrance pupil side of the humanoid eye lens 4, and making the entrance pupil position 41 of the humanoid eye lens 4 fall within the light exit 61 of the standard light source 6. Then, adjust the focal length of the humanoid eye lens 4 so that the focal length of the humanoid eye lens 4 is the same as the virtual image distance of the near-eye display module 1 to be measured. Then, adjust the test camera 5 so that the test camera 5 captures multiple images. A flat-field correction matrix is established based on the multiple images, and this flat-field correction matrix is the calibration file for flat-field correction.

[0051] During the flat-field correction process, by setting the focal length of the humanoid eye lens 4 to be the same as the virtual image distance of the near-eye display module 1 to be measured, it can be ensured that the humanoid eye lens 4 can accurately focus on the virtual image generated by the near-eye display module 1. This is crucial for obtaining clear and accurate images because only at the focal point will the image be clear and the edges be sharp, which is beneficial for subsequent image analysis and data acquisition. The focal length matching also helps to reduce the image distortion caused by the near-eye display module 1, especially edge distortion and pincushion or barrel distortion. Distortion will interfere with the accurate measurement of the image gray value, thereby affecting the accuracy of FOV measurement. When the focal length is well-matched, the distortion can be minimized, thus improving the measurement accuracy. When the focal length of the humanoid eye lens 4 is consistent with the virtual image distance of the near-eye display module 1, the imaging is the clearest, facilitating subsequent measurement work and ensuring the accuracy of the measurement.

[0052] Through the flat-field correction step, it is ensured that the brightness uniformity of the measurement system is consistent in each field of view, thereby eliminating the influence of the brightness non-uniformity of the measurement system itself in each field of view on the test result of the field of view angle. The principle of this step is to eliminate the influence of the brightness non-uniformity of the test system itself in different fields of view on the measurement result through the uniform radiation characteristic of the standard light source 6, ensuring the accuracy of the measurement result. The implementation effect shows that the calibrated test system can provide a more uniform background brightness, thereby improving the accuracy and stability of image acquisition. Reference Figure 3 As shown in the figure, in a specific embodiment of the present application, the standard light source 6 is an integrating sphere light source. Preferably, the model of the integrating sphere light source is LS-100.

[0053] Specifically, in the above step of adjusting the test camera 5, it includes: adjusting the exposure time of the test camera 5 so that the target gray value of a partial central region of the image captured by the test camera 5 is within the range of greater than or equal to 175 and less than or equal to 185. Specifically, this partial central region can be the region in the center of the image captured by the test camera 5 that accounts for 30% of the center, and this region can be selected according to the actual situation. Such a setting is conducive to improving the consistency of measurement. By controlling the gray value within a specific range, it can ensure that the brightness of the image is relatively stable during each measurement, thereby improving the comparability and consistency between different measurements. Keeping the gray value of the central region within a relatively high and stable range helps to improve the signal-to-noise ratio of the image. At a high gray value, the signal in the image is stronger and the noise is relatively reduced, which makes subsequent processing, such as edge detection and gray analysis, more accurate. When the gray value is within a preset and relatively ideal range, it can simplify the image processing algorithm, reduce the need for complex adjustments to the image, speed up the processing speed, and improve the overall measurement efficiency. Under the condition of a stable and high gray value, the response of the measurement system to the image is more linear, which helps to reduce measurement errors caused by the non-linear response of the system. Controlling the gray value makes the contrast and resolution of the image in the best state, which is crucial for detecting the image edge and calculating the field of view (FOV), and can improve the measurement accuracy.

[0054] It should be noted that the above range of the target gray value being greater than or equal to 175 and less than or equal to 185 is mainly for images with a bit depth of 8 bits.

[0055] Specifically, the above-mentioned establishment of the flat-field correction matrix based on multiple images includes determining the gray mean value corresponding to the same pixel position on the chip of the test camera 5 according to multiple images .

[0056] .

[0057] Among them, n is the number of images collected by the test camera 5, that is, the number of multiple images; is the gray value of the first image corresponding to the same pixel position on the chip of the test camera 5, the gray value of the second image corresponding to the same pixel position on the chip of the test camera 5, and so on, until the gray value of the nth image corresponding to the same pixel position on the chip of the test camera 5 . That is to say, in this step, the gray values of these n images collected at the same pixel position are averaged . The gray mean value of each pixel position is obtained After that, calculate the gray mean value T of the region with a preset size located in the center of the image X , that is, the gray mean value of all pixels within the region with a preset size located in the center of the image Dividing by the number of pixels in this area to obtain the average gray value T X .

[0058] Then, according to the average gray value , determine the average gray value T of the area with a preset size at the center of the image X as the ideal value, and then establish a flat-field correction matrix M. Divide T X by the gray value T(i,j) at the pixel position (i,j) in the effective area of the entire acquired image to obtain the flat-field correction matrix M. M refers to the flat-field correction matrix, that is, if the gray values of other fields of view are to be made consistent with the gray value at the center, this coefficient needs to be multiplied. M is also the ratio of the average gray value T at the center X to the gray values of the pixels in other fields of view.

[0059]

[0060] Among them, T(i,j) is the gray value at the pixel position (i,j) in the effective area of the corresponding image, i≥1, j≥1. In a specific embodiment of the present application, the preset size in determining the average gray value T of the area with a preset size at the center of the image X can specifically be 30 30 pixels.

[0061] Specifically, before placing the standard light source 6 at the entrance pupil position 41 of the humanoid eye lens 4, it includes adjusting the brightness of the standard light source 6 to 50% - ~80% of the maximum brightness. By adjusting the brightness of the standard light source 6 within this range, it is beneficial to ensure the stability of the brightness of the standard light source 6, ensure that the brightness change of the standard light source 6 does not exceed 0.5%, and further ensure better calibration results.

[0062] As Figure 4 shown, the above-mentioned calibration of the measurement system using a light source 7 with a checkerboard target to obtain target images at various azimuth angles specifically includes:

[0063] Place the light source 7 with a checkerboard target on the entrance pupil side of the humanoid eye lens 4. The checkerboard target 71 is formed by arranging multiple checkerboards 711 in a rectangular array. The light source is specifically a uniform surface light source. Each checkerboard 711 is specifically a small rectangular grid. The multiple checkerboards 711 include multiple black checkerboards 711 and multiple white checkerboards 711. In the H direction, the multiple black checkerboards 711 and the multiple white checkerboards 711 are alternately arranged, and in the V direction, the multiple black checkerboards 711 and the multiple white checkerboards 711 are alternately arranged. The H direction is perpendicular to the V direction. That is to say, the multiple checkerboards 711 are arranged in a rectangular array in a multi-row and multi-column manner to form a grid-like checkerboard target 71, and the multiple checkerboards 711 in the same row and the same column are alternately black and white.

[0064] During the test, the side of the humanoid eye lens 4 away from the test camera 5 should be facing the light source 7 with the checkerboard target, and the checkerboard target 71 should be located on the side of the light source facing the humanoid eye lens 4, so that the center point of the chip of the test camera 5 coincides with any intersection point of the checkerboard target 71. Here, it should be explained that the intersection point of the checkerboard target 71 is specifically the intersection point of two mutually perpendicular straight lines in the checkerboard target 71.

[0065] Then, since the field of view angle of the humanoid eye lens 4 is relatively large, during the calibration process, the test camera 5 and the humanoid eye lens 4 can be rotated three times clockwise or counterclockwise in the HV plane, each time rotating 90°. Before rotation and after each rotation, the light source 7 with the checkerboard target is photographed by the test camera 5 to obtain target images at four azimuth angles. Here, it should be explained that the HV plane is the plane where the H direction and the V direction are located. The test camera 5 is located on the exit pupil side of the humanoid eye lens 4 and is connected to the humanoid eye lens 4, so the two rotate synchronously. Before rotation, it is photographed once by the test camera 5, and then once by the test camera 5 after each rotation, for a total of four photographs. Therefore, the four azimuth angles are 0°, 90°, 180°, and 270° to cover the entire field of view of the measurement system. If the first rotation is clockwise, then subsequent rotations are also clockwise; if the first rotation is counterclockwise, then subsequent rotations are also counterclockwise to ensure coverage of the entire field of view.

[0066] It should be noted that the above checkerboard target 71 can be spliced by multiple small checkerboard targets, specifically by five small checkerboard targets, and the five small checkerboard targets are tiled on the surface of the light source in sequence. In a specific embodiment of the present application, the size of the checkerboard target 71 is 600mm 600mm, and the size of the smallest checkerboard 711 in the checkerboard target 71 is 25mm 25 mm, that is, the side length h of the smallest checkerboard 711 in the checkerboard target 71 is 25 mm.

[0067] Specifically, the relationship table between the field of view angles of the checkerboards 711 at various azimuth angles and the pixel positions of the chip of the test camera 5 is established based on the target images at various azimuth angles, including:

[0068] Based on the target images at various azimuth angles, calculate the field of view angles FOV of the checkerboards 711 of the checkerboard target 71 corresponding to different pixel positions of the chip of the test camera 5 at different azimuth angles. The field of view angle FOV is obtained according to the following trigonometric formula. ; where h is the length or width of the checkerboard 711. Since the checkerboard 711 is rectangular, h is specifically the side length of the checkerboard 711; d is the vertical distance from the checkerboard target 71 to the artificial eye lens 4. Since the artificial eye lens 4 has distortion, the side lengths h of at least some of the checkerboards 711 in the same target image collected by it are different. Therefore, in this formula, h is a variable, not a fixed value. Therefore, the field of view angles FOV of the checkerboards 711 of the checkerboard target 71 corresponding to different pixel positions of different chips are also variable values, not fixed values.

[0069] Based on the target images at various azimuth angles collected by the test camera 5, the pixel positions corresponding to each checkerboard 711 can be obtained. One pixel position corresponds to a corner point of a checkerboard 711, which is the intersection point of the above-mentioned checkerboard target 71. Finally, through linear interpolation, the field of view angle values corresponding to each pixel position on the chip can be obtained, so as to establish the relationship table between the field of view angles of the checkerboards 711 of the checkerboard target 71 at various azimuth angles and the pixel positions of the chip of the test camera 5, as shown in Table 1 below.

[0070] Table 1

[0071]

[0072]

[0073]

[0074] Specifically, placing the near-eye display module 1 to be measured on the lighting fixture 2 and calibrating the position of the near-eye display module 1 includes:

[0075] Place the near-eye display module 1 to be measured on the lighting fixture 2, and install the lighting fixture 2 on the adjustment table 3. Keep the test camera 5 and the humanoid eye lens 4 connected, and position the humanoid eye lens 4 on the side of the test camera 5 facing the near-eye display module 1. First, adjust the height of the adjustment table 3 in the z-axis direction based on the standard block of the structural design, so that the entrance pupil position 41 of the humanoid eye lens 4 and the exit pupil position 11 of the near-eye display module 1 are at the same horizontal height.

[0076] Then, turn on the lighting fixture 2, so that the lighting fixture 2 lights up the near-eye display module 1 and forms a cross image on the display screen of the near-eye display module 1; the cross image on the display screen of the near-eye display module 1 is imaged on the chip of the test camera 5 through each lens group in the near-eye display module 1 and the humanoid eye lens 4.

[0077] Then, adjust the rotation angle Rx of the adjustment table 3 around the x-axis and the rotation angle Ry around the y-axis until the cross image coincides with the center point of the chip of the test camera 5. In this way, the calibration of the optical axis of the near-eye display module 1 and the optical axis of the measurement system is completed, making the optical axis of the near-eye display module 1 coincide with the optical axis of the measurement system.

[0078] Then, refer to Figure 1 , and continue to adjust the position of the adjustment table 3 on the x-axis and the position on the y-axis to make the exit pupil position 11 of the near-eye display module 1 coincide with the entrance pupil position 41 of the humanoid eye lens 4.

[0079] By calibrating the position of the near-eye display module 1 in the measurement system to ensure that the exit pupil position 11 of the near-eye display module 1 coincides with the entrance pupil position 41 of the humanoid eye lens 4, it can ensure that the humanoid eye lens 4 and the test camera 5 of the measurement system receive the light emitted by the near-eye display module 1 in a manner similar to the human eye. This is crucial for accurately evaluating the FOV because the measurement of the FOV depends on the visual reception range of the simulated human eye. When the exit pupil position 11 does not match the entrance pupil position 41, additional optical distortions such as image shift, deformation, or chromatic aberration may be introduced. Adjusting the position to ensure that the light path is consistent with the design reduces these distortions and improves the measurement accuracy. At the same time, it can ensure that the measurement system can completely capture the field of view of the near-eye display module 1, avoiding the loss of field-of-view edge information due to position mismatch, thereby affecting the integrity of the FOV measurement.

[0080] As Figures 5 to 7As shown, during the process of collecting the image of the near-eye display module 1 when displaying a full-white image through the test camera 5 and generating a grayscale curve graph, the brightness value of the full-white image of the near-eye display module 1 is set to be greater than or equal to 500 cd / m² and less than or equal to 600 cd / m²; preferably 600 cd / m². By reasonably restricting the brightness value of the full-white image of the near-eye display module 1, it is beneficial to match the needs of the human eye and meet the application requirements of the product.

[0081] It should be noted that the image collected by the test camera 5 is specifically the image formed by the near-eye display module 1 passing through the human-eye simulation lens 4 in the test camera 5 when displaying a full-white image.

[0082] Figure 5 Shows the image of the near-eye display module 1 collected by the test camera 5 when displaying a full-white image in this step. It can be seen from the figure that the horizontal direction is the H direction and the vertical direction is the V direction. According to the image of the near-eye display module 1 collected by the test camera 5 when displaying a full-white image, a grayscale curve graph is generated, and the grayscale curve graph includes a grayscale curve graph in the H direction and a grayscale curve graph in the V direction. Figure 6 and Figure 7 respectively show Figure 5 the grayscale curve graphs in the V direction and the H direction. The generation of the grayscale curve graph from the image collected by the test camera 5 is automatically generated by the computer. Therefore, this application will not elaborate. Figure 6 and Figure 7 The two coordinate points on the curve in [] are the positions where the peaks are located.

[0083] Specifically, before the step of determining the grayscale gradient curve graph according to the grayscale curve graph, it also includes performing mean filtering processing on the grayscale curve graph to obtain the grayscale curve graph after mean filtering processing. Specifically, the grayscale curve graph in the H direction and the grayscale curve graph in the V direction are filtered to reduce the influence of the noise of the measurement system on the test result, which is beneficial to ensuring the accuracy of the measurement result. Optionally, during specific operation, the time window of the value filtering processing can be set to 3 pixels 3 pixels.

[0084] It should be noted that mean filtering is a common image processing method used to smooth images and remove noise. 3 The time window of 3 is small, which can effectively suppress high-frequency noise while retaining the details of the image. This is crucial for improving the smoothness and measurement accuracy of the grayscale curve. The filtering processing can adopt existing filtering processing programs or processes, and only need to adjust the time window of the filtering processing to 3 pixels 3 pixels. This can better retain the edge and detail features of the image, which is very beneficial for subsequent edge detection based on grayscale gradient and can more accurately determine the boundary of the field of view angle. Compared with a larger time window, 3 The mean filtering of the 3-time window has a relatively small computational amount. It can improve the speed of image processing while ensuring the processing effect, which is particularly important for scenarios that require batch processing of a large number of images and can improve the efficiency of the entire measurement system.

[0085] Specifically, determining the gray gradient curve diagram based on the gray curve diagram specifically includes: performing a first-order derivative process on the gray curve diagram to generate a gray gradient curve diagram corresponding to the gray curve diagram. The first-order derivative uses the gradient operator [-1, 0, 1] to process this one-dimensional gray curve, that is, the difference operator for the first-order derivative process is [-1, 0, 1]. The first-order derivative process can highlight the gray changes in the gray curve diagram, especially where the gray value rapidly drops from a high value in the central region to a low value in the edge region. The appearance of peaks in the gray gradient curve diagram often corresponds to the start or end of the edge in the gray curve diagram, which provides a basis for accurately identifying the edge of the field of view angle. The first-order derivative process can enhance the detail contrast in the image, especially in the boundary region of gray changes, which helps to more clearly identify and locate features in subsequent processing. By the first-order derivative process, the influence of the slow change of the background gray level on the measurement result can be effectively reduced. The first-order derivative mainly focuses on the rapid change of the gray value, and the slow change of the background gray level is weakly expressed on the gradient curve, which helps to improve the accuracy of the measurement. In the gray gradient curve diagram, the peaks at the edges can more accurately reflect the boundaries of the field of view angle. Compared with directly using the gray curve, this method can more precisely determine the size of the FOV, improving the signal-to-noise ratio and reliability of the measurement result.

[0086] In summary, using the gradient operator [-1, 0, 1] for the first-order derivative process is a common discrete differential method that can calculate the local change of the image gray value and is very effective for edge detection and feature localization. It estimates the derivative of the gray value by taking the difference of adjacent pixel values, thereby highlighting edges and details, which is a key step in determining the field of view boundary in image analysis.

[0087] Specifically, referring to Figure 8 and Figure 9 as shown, in this step, the gray curve diagram in the V direction generates a gray gradient curve diagram in the V direction after the first-order derivative process, and the gray curve diagram in the H direction generates a gray gradient curve diagram in the H direction after the first-order derivative process.

[0088] Referring to Figure 8 and Figure 9 as shown, in the process of determining the pixel positions corresponding to the peaks in the gray gradient curve diagram based on the gray gradient curve diagram, there are two peaks in the same gray gradient curve diagram. Specifically, there are two peaks in the gray curve diagram in the H direction, and there are two peaks in the gray gradient curve diagram in the H direction.

[0089] Taking Figure 8For example, according to Figure 8 the two peaks in it, the corresponding two pixel positions can be known, and these two pixel positions are used as the two edge pixel positions of the near-eye display module 1 in the V direction. Then, according to these two edge pixel positions, a search is performed in the relationship table 1 to determine the field of view angles corresponding to the edge pixel positions in the relationship table 1, so as to convert the pixel positions into the angular space, and thus determine the half field of view angle and the full field of view angle of the near-eye display module 1 in the V direction. Figure 8 The two coordinate points on the curve in it are the positions where the peaks are located.

[0090] Taking Figure 9 as an example, according to Figure 9 the two peaks in it, the corresponding two pixel positions can be known, and these two pixel positions are used as the two edge pixel positions of the near-eye display module 1 in the H direction. Then, according to these two edge pixel positions, a search is performed in the relationship table 1 to determine the field of view angles corresponding to the edge pixel positions in the relationship table 1, so as to convert the pixel positions into the angular space, and thus determine the half field of view angle and the full field of view angle of the near-eye display module 1 in the H direction. Figure 9 The two coordinate points on the curve in it are the positions where the peaks are located.

[0091] Furthermore, the half field of view angle and the full field of view angle of the near-eye display module 1 can be obtained. It should be noted here that since the relationship table between the field of view angle of the checkerboard 711 and the pixel positions of the chip of the test camera 5, that is, Table 1, has been obtained in the above steps, after obtaining the edge pixel positions, only by looking up Table 1 can the corresponding field of view angles be obtained.

[0092] It should be noted here that since the entrance pupil position of the measurement system matches the exit pupil position of the near-eye display module 1, when the near-eye display module 1 lights up a full white screen, the area occupied by the full white screen in the measurement system is the field of view area of the near-eye display module 1. Therefore, only by clarifying the edge pixel positions of the full white screen and converting them into angles, this angle is the field of view angle of the near-eye display module 1.

[0093] As Figure 1 shown, the present invention also provides a measurement system for the field of view angle of a near-eye display module 1, including an adjustment table 3, a lighting fixture 2, a test camera 5, and a humanoid eye lens 4. The lighting fixture 2 is arranged on the adjustment table 3, the test camera 5 is connected to the humanoid eye lens 4, and the humanoid eye lens 4 is located on the side of the test camera 5 facing the lighting fixture 2, and the lighting fixture 2 and the humanoid eye lens 4 are arranged at intervals. The entrance pupil position 41 of the humanoid eye lens 4 coincides with the exit pupil position 11 of the near-eye display module 1 to be detected.

[0094] The measurement system components of the near-eye display module 1 of the present invention are simple and can be applied to the field of view angle measurement of different types of near-eye display modules 1, having wide applicability. Moreover, when the measurement system of the present invention is used for measurement, the operation is simple, which is beneficial to improving the measurement efficiency and can reduce the measurement cost.

[0095] Specifically, the near-eye display module 1 includes a plurality of optical elements and a display screen. The plurality of optical elements can be a plurality of lenses, and the display screen can specifically be an LCD display screen.

[0096] Specifically, the adjustment stage 3 is specifically a six-degree-of-freedom adjustment stage 3, which can realize the adjustment functions of six degrees of freedom in the Rx, Ry, Rz directions, in the x-axis direction, in the y-axis direction, and in the z-axis direction. Rx is the rotation angle around the x-axis, Ry is the rotation angle around the y-axis, and Rz is the rotation angle around the y-axis.

[0097] It should be noted that the above measurement system is a measurement system with a front-mounted diaphragm. Specifically, that is, the diaphragm of the human-eye simulation lens 4 is located on the side facing the lighting tooling fixture 2. The position where the diaphragm is located is the entrance pupil position 41 of the human-eye simulation lens 4. The diaphragm aperture is 4 mm, and the field of view angle of the human-eye simulation lens 4 is 140°. The test camera 5 is specifically an industrial camera with a large target surface, and the specific model is MV-EM100. The human-eye simulation lens 4 and the test camera 5 are always connected. The images collected by the test camera 5 mentioned above are all the images collected by the test camera 5 through the human-eye simulation lens 4. The test camera 5 and the human-eye simulation lens 4 are used in combination and cannot be disassembled.

[0098] Obviously, the above-described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0099] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0100] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of this application are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here.

[0101] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for measuring the field of view angle of a near-eye display module, characterized in that, Including the following steps: Calibrate the measurement system composed of an adjustment stage (3), a lighting tooling fixture (2), a test camera (5), and a humanoid eye lens (4), including: calibrating the measurement system using a light source (7) with a checkerboard target to obtain target images at multiple azimuth angles; According to the target images at multiple azimuth angles, establish a relationship table between the field of view angles of the checkerboards (711) at multiple azimuth angles and the pixel positions of the chip of the test camera (5); Place the near-eye display module (1) to be measured on the lighting tooling fixture (2) and calibrate the position of the near-eye display module (1); Collect an image of the near-eye display module (1) when it displays a full-white image through the test camera (5) and generate a grayscale curve graph; Determine a grayscale gradient curve graph according to the grayscale curve graph; According to the grayscale gradient curve graph, determine the pixel position corresponding to the peak value in the grayscale gradient curve graph as the edge pixel position of the near-eye display module (1); Determine the field of view angle of the near-eye display module (1) according to the edge pixel position and the relationship table; 2. The method for measuring the field of view angle of the near-eye display module according to claim 1, wherein In the step of calibrating the measurement system, it further includes a flat-field correction step before calibrating the measurement system using the light source (7) with a checkerboard target: Place a standard light source (6) on the entrance pupil side of the humanoid eye lens (4) and make the entrance pupil position (41) of the humanoid eye lens (4) fall within the light exit port (61) of the standard light source (6); Adjust the focal length of the humanoid eye lens (4) so that the focal length of the humanoid eye lens (4) is the same as the virtual image distance of the near-eye display module (1) to be measured; Adjust the test camera (5) so that the test camera (5) collects multiple images; Establish a flat-field correction matrix according to the multiple images; 3. The method for measuring the field of view angle of the near-eye display module according to claim 2, wherein, The adjustment of the test camera (5) includes: Adjust the exposure time of the test camera (5) so that the target gray value in a partial central area of the image captured by the test camera (5) is in the range of greater than or equal to 175 and less than or equal to 185; 4. The method for measuring the field of view angle of the near-eye display module according to claim 2, wherein The establishment of the flat-field correction matrix according to the multiple images includes: Determine the average gray value corresponding to the same pixel position of the chip of the test camera (5) according to the multiple images ; According to the grayscale mean value , determine the grayscale mean value T of the region with a preset size at the center of the image X , and establish a flat-field correction matrix M ； Wherein, T(i,j) is the gray value at the pixel position within the valid region corresponding to the image (i,j) , where i≥1 and j≥1.

5. The method for measuring the field of view angle of the near-eye display module according to claim 2, wherein Before placing the standard light source (6) at the entrance pupil position (41) of the humanoid eye lens (4), it includes: Adjust the brightness of the standard light source (6) to 50% - 80% of the maximum brightness; 6. The method for measuring the field of view angle of the near-eye display module according to claim 1, wherein The calibration of the measurement system using the light source (7) with a checkerboard target to obtain target images at multiple azimuth angles includes: Place the light source (7) with a checkerboard target on the entrance pupil side of the humanoid eye lens (4), and the checkerboard target (71) is formed by arranging a plurality of checkerboards (711) in an array; Make the center point of the chip of the test camera (5) coincide with the intersection point of the checkerboard target (71); Rotate the test camera (5) and the humanoid eye lens (4) three times clockwise or counterclockwise on the HV plane, each time rotating 90°. Before rotation and after each rotation, capture the light source (7) with the checkerboard target through the test camera (5) to obtain target images at four azimuth angles.

7. The method for measuring the field of view angle of the near-eye display module according to claim 1, wherein Based on the target images at the multiple azimuth angles, establish a relationship table between the field of view angles of the checkerboard (711) at the multiple azimuth angles and the pixel positions of the chip of the test camera (5), including: Based on the target images at the multiple azimuth angles, calculate the field of view (FOV) of the checkerboard (711) of the checkerboard target (71) corresponding to different pixel positions of the chip of the test camera (5) at different azimuth angles. ; where h is the length or width of the checkerboard (711), and d is the vertical distance from the checkerboard target (71) to the humanoid eye lens (4). Establish a relationship table between the field of view angles of the checkerboard (711) of the checkerboard target (71) at the multiple azimuth angles and the pixel positions of the chip of the test camera (5).

8. The method for measuring the field of view angle of the near-eye display module according to claim 1, wherein Place the near-eye display module (1) to be measured on the lighting fixture (2), and calibrate the position of the near-eye display module (1), including: Place the near-eye display module (1) to be measured on the lighting fixture (2), and install the lighting fixture (2) on the adjustment table (3), so that the humanoid eye lens (4) is located on the side of the test camera (5) facing the near-eye display module (1); Turn on the lighting fixture (2) to light up the near-eye display module (1) so that a cross image is formed on the display screen of the near-eye display module (1); Adjust the adjustment table (3) until the cross image coincides with the center point of the chip of the test camera (5); Continue to adjust the adjustment table (3) so that the exit pupil position (11) of the near-eye display module (1) coincides with the entrance pupil position (41) of the humanoid eye lens (4).

9. The method for measuring the field of view angle of the near-eye display module according to claim 1, wherein During the process of collecting an image of the near-eye display module (1) when it displays a full white image through the test camera (5) and generating a grayscale curve graph, Set the brightness value of the full white image of the near-eye display module (1) to be greater than or equal to 500 cd / m² and less than or equal to 600 cd / m²; and / or, The grayscale curve graph includes a grayscale curve graph in the H direction and a grayscale curve graph in the V direction.

10. The method for measuring the field of view angle of the near-eye display module according to claim 1, wherein, Before the step of determining the grayscale gradient curve graph based on the grayscale curve graph, it further includes: Perform mean filtering processing on the grayscale curve graph to obtain a grayscale curve graph after mean filtering processing.

11. The method for measuring the field of view angle of the near-eye display module according to any one of claims 1 to 10, characterized in that, Determine the grayscale gradient curve graph based on the grayscale curve graph, including: Perform a first derivative processing on the grayscale curve graph to generate a grayscale gradient curve graph corresponding to the grayscale curve graph.

12. The method for measuring the field of view angle of a near-eye display module according to any one of claims 1 to 10, characterized in that, During the process of determining the pixel positions corresponding to the peaks in the grayscale gradient curve graph based on the grayscale gradient curve graph, there are two peaks in the same grayscale gradient curve graph; and / or, During the process of determining the field of view angle of the near-eye display module (1) based on the edge pixel positions and the relationship table, it includes determining the corresponding field of view angle in the relationship table based on the edge pixel positions to obtain the field of view angle of the near-eye display module (1).

13. A measurement system for the field of view angle of a near-eye display module, characterized in that, The measurement system for the field of view angle of the near-eye display module is used to implement the measurement method for the field of view angle of the near-eye display module according to any one of claims 1-12, and includes an adjustment table (3), a lighting tooling fixture (2), a test camera (5), and a humanoid eye lens (4). The lighting tooling fixture (2) is arranged on the adjustment table (3), the test camera (5) is connected to the humanoid eye lens (4), and the humanoid eye lens (4) is located on the side of the test camera (5) facing the lighting tooling fixture (2), and the lighting tooling fixture (2) is arranged at an interval from the humanoid eye lens (4).

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