Method and system for measuring field angle of near-to-eye display module

Abstract

The invention provides a method and a system for measuring a field angle of a near-to-eye display module. The measurement method comprises the following steps: calibrating the measurement system; according to the target images under the various azimuth angles, establishing a relation table between the field angles of the checkerboard under the various azimuth angles and the pixel positions of the chip of the test camera; a near-to-eye display module to be measured is placed on the lightening tool jig; collecting an image of the near-to-eye display module when the near-to-eye display module displays the 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 a pixel position corresponding to a peak value in the gray gradient curve graph as an edge pixel position of the near-to-eye display module; and determining the field angle of the near-to-eye display module according to the edge pixel position and the relation table. The problems that in the prior art, measurement of the field angle of the near-to-eye display module is inaccurate in measurement result and complex in operation are solved.

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 a field of view angle of a near-eye display module. Background Art

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

[0003] First, this method does not fully consider the brightness non-uniformity of the near-eye display module under different fields of view. The grayscale value of the center area of ​​most near-eye display modules is higher, while the grayscale value of the edge area gradually decreases. Therefore, using only 50% of the grayscale value as the edge definition standard will lead to generally smaller measurement results and cannot accurately reflect the true FOV of the module, thus affecting the design and quality evaluation of the product.

[0004] Secondly, this method requires that the exit pupil position of the near-eye display module be precisely matched with 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 complicated and requires not only precise adjustment, but also in actual operation, it is difficult to achieve an ideal matching state due to factors such as adjustment errors, imperfections of the near-eye display module itself, and instability of the measurement environment. Inaccurate matching will further lead to deviations in the measurement results, reducing the reliability and accuracy of the measurement.

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

[0006] The main purpose of the present invention is to provide a method and 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 a near-eye display module in the prior art.

[0007] To achieve the above-mentioned purpose, 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, comprising the following steps: calibrating a measurement system composed of an adjustment platform, a lighting fixture, a test camera and an anthropomorphic eye lens, including: calibrating the measurement system using a light source having a checkerboard target to obtain target images at multiple azimuths; establishing a relationship table between the field of view angle of the checkerboard at multiple azimuths and the pixel position of a chip of the test camera according to the target images at multiple azimuths; placing a near-eye display module to be measured on the lighting fixture to calibrate 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 according to the grayscale curve graph; determining a pixel position corresponding to a peak value in the grayscale gradient curve graph according to the grayscale gradient curve graph as an edge pixel position of the near-eye display module; determining the field of view angle of the near-eye display module according to the edge pixel position and the relationship table.

[0008] Furthermore, the step of calibrating the measurement system also includes a flat field correction step before calibrating the measurement system using a light source with a checkerboard target: placing a standard light source on the entrance pupil side of an anthropomorphic eye lens, and making the entrance pupil position of the anthropomorphic eye lens fall into the light outlet of the standard light source; adjusting the focal length of the anthropomorphic eye lens so that the focal length of the anthropomorphic eye lens is the same as the virtual image distance of the near-eye display module to be measured; adjusting the test camera so that the test camera captures 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 a target grayscale value of a portion of a central area of ​​an image captured by the test camera is within a range of greater than or equal to 175 and less than or equal to 185.

[0010] Further, a flat field correction matrix is ​​established based on the multiple images, including: determining the grayscale mean corresponding to the same pixel position of the chip of the test camera based on the multiple images ; According to the gray mean , determine the grayscale mean value T of the area of ​​preset size at the center of the image X , establish the flat field correction matrix M,

[0011]

[0012] Wherein, T(i,j) is the grayscale value at the pixel position (i,j) in the valid area of ​​the corresponding image, i≥1, j≥1.

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

[0014] Furthermore, 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 human eye lens, the checkerboard target being arranged in an array of multiple checkerboards; making the center point of the chip of the test camera coincide with the intersection of the checkerboard target; rotating the test camera and the human eye lens clockwise or counterclockwise three times on the HV plane, each time by 90°, and photographing the light source with the checkerboard target by the test camera when not rotated and after each rotation, so as to obtain target images at four azimuth angles.

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

[0016] Furthermore, the near-eye display module to be measured is placed on a lighting fixture, and the position of the near-eye display module is calibrated, including: placing the near-eye display module to be measured on the lighting fixture, and installing the lighting fixture on an adjustment table so that the humanoid eye lens is located on the side of the test camera facing the near-eye display module; turning on the lighting fixture, lighting the near-eye display module, and forming a cross image 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; and 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] Furthermore, in the process of capturing an image of the near-eye display module when displaying an all-white image through a test camera and generating a grayscale curve graph, the brightness value of the all-white image of the near-eye display module is set 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.

[0018] Furthermore, before the step of determining the grayscale gradient curve graph according to the grayscale curve graph, the method further includes: performing mean filtering on the grayscale curve graph to obtain a grayscale curve graph after mean filtering.

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

[0020] Furthermore, in the process of determining the pixel position corresponding to the peak in the grayscale gradient curve graph according to the grayscale gradient curve graph, there are two peaks in the same grayscale 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 relationship table, it includes determining the field of view angle corresponding to the edge pixel position in the relationship table to obtain the field of view angle of the near-eye display module.

[0021] According to another aspect of the present invention, a system for measuring the field of view angle of a near-eye display module is provided, comprising an adjustment platform, a lighting fixture, a test camera and an anthropomorphic eye lens, wherein the lighting fixture is arranged on the adjustment platform, the test camera is connected to the anthropomorphic eye lens, and the anthropomorphic eye lens is located on a side of the test camera facing the lighting fixture, and the lighting fixture and the anthropomorphic eye lens are spaced apart.

[0022] By applying the technical solution of the present invention, a method for measuring the field of view angle of a near-eye display module includes the following steps: calibrating a measurement system composed of an adjustment table, a lighting fixture, a test camera and an anthropomorphic eye lens, including: calibrating the measurement system using a light source with a checkerboard target to obtain target images at multiple azimuths; establishing a relationship table between the field of view angle of the checkerboard at multiple azimuths and the pixel position of a chip of a test camera according to the target images at multiple azimuths; placing a near-eye display module to be measured on the lighting fixture to calibrate the position of the near-eye display module; collecting an image of the near-eye display module when displaying a full white image through a test camera, and generating a grayscale curve graph; determining a grayscale gradient curve graph according to the grayscale curve graph; determining a pixel position corresponding to a peak value in the grayscale gradient curve graph according to the grayscale gradient curve graph as an edge pixel position of the near-eye display module; determining the field of view angle of the near-eye display module according to the edge pixel position and the relationship table.

[0023] The present application calibrates the measurement system by using a light source with a checkerboard target, thereby obtaining target images at various azimuths, and then establishes a relationship table between the field of view angle of the checkerboard at various azimuths and the pixel position of the chip of the test camera according to the target images at various azimuths, so that the relationship between the pixel position and the field of view angle can be more accurately mapped, so that the pixel position of the edge field of view of the near-eye display module can be directly converted to the angle space based on the calibrated relationship table, so as to accurately obtain the field of view angle of the near-eye display module. The edge field of view of the near-eye display module is determined by using the pixel position corresponding to the peak value in the grayscale gradient curve diagram. Compared with the method of defining the edge of the field of view by using the edge grayscale as 50% of the center grayscale in the prior art, it is more accurate and has higher measurement accuracy, effectively reducing the influence of the brightness non-uniformity of the near-eye display module itself under 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, the method is simple to operate, which is conducive to improving the measurement efficiency, and the structure of the measurement system is relatively simple, which effectively reduces the measurement cost. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0025] Figure 1 A schematic flow chart showing a method for measuring the field of view angle of a near-eye display module according to an optional embodiment of the present invention;

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

[0027] Figure 3 A schematic diagram showing a method for measuring the field angle of a near-eye display module of the present invention during a flat field correction process;

[0028] Figure 4 A schematic diagram showing the calibration process of the method for measuring the field angle of a near-eye display module of the present invention;

[0029] Figure 5 The measurement method of the present invention is shown in which a test camera is used to collect an image of a near-eye display module when the near-eye display module displays a full white image;

[0030] Figure 6 Shows Figure 5 Grayscale curve of the image in the V direction;

[0031] Figure 7 Shows Figure 5 Grayscale curve of the image in the H direction;

[0032] Figure 8 Shows Figure 6 The corresponding gray gradient curve graph;

[0033] Fig. 9 Shows Figure 7 The corresponding grayscale gradient curve.

[0034] The above drawings include the following reference numerals:

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

[0036] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0038] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

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

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

[0041] The measurement system composed of the adjustment platform 3, the lighting fixture 2, the test camera 5 and the human eye lens 4 is calibrated, including: using a light source 7 with a checkerboard target to calibrate the measurement system to obtain target images under various azimuth angles.

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

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

[0044] The image of the near-eye display module 1 when displaying a full white image is captured by the test camera 5 , and a grayscale curve graph is generated.

[0045] According to the grayscale curve graph, a grayscale gradient curve graph is determined.

[0046] According to the grayscale gradient curve diagram, the pixel position corresponding to the peak value in the grayscale gradient curve diagram is determined as the edge pixel position of the near-eye display module 1 .

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

[0048] The present application calibrates the measurement system by using a light source 7 with a checkerboard target, thereby obtaining target images at various azimuths, and then establishes a relationship table between the field of view angle of the checkerboard 711 at various azimuths and the pixel position of the chip of the test camera 5, so that the relationship between the pixel position and the field of view angle can be more accurately mapped, so that the pixel position of the edge field of view of the near-eye display module 1 can be directly converted to the angle space based on the calibrated relationship table, so as to accurately obtain the field of view angle of the near-eye display module 1. The edge field of view of the near-eye display module 1 is determined by using the pixel position corresponding to the peak value in the grayscale gradient curve diagram. Compared with the method of defining the edge of the field of view by using the edge grayscale as 50% of the center grayscale in the prior art, it is more accurate and has higher measurement accuracy, effectively reducing the influence of the brightness non-uniformity of the near-eye display module 1 itself under different fields of view on the measurement accuracy, and can more accurately obtain the field of view angle of the near-eye display module 1. Moreover, the method is simple to operate, which is conducive to improving the measurement efficiency, and the structure of the measurement system is relatively simple, which effectively reduces the measurement cost.

[0049] Specifically, in the above-mentioned step of calibrating the measurement system, a flat field correction step is also included before the measurement system is calibrated using the light source 7 with a checkerboard target. The step of calibrating the measurement system specifically includes a flat field correction step and a step of calibrating the measurement system. The flat field correction step is before calibrating the measurement system. That is to say, this method first performs a flat field correction on the measurement system and then calibrates the measurement system, thereby completing the calibration of the measurement system.

[0050] like Figure 3As shown, the flat field correction step includes: placing the standard light source 6 on the entrance pupil side of the human-eye lens 4, and making the entrance pupil position 41 of the human-eye lens 4 fall into the light outlet 61 of the standard light source 6. Then, adjusting the focal length of the human-eye lens 4 so that the focal length of the human-eye lens 4 is the same as the virtual image distance of the near-eye display module 1 to be measured. Then, adjusting 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 the flat field correction matrix is ​​the calibration file for the flat field correction.

[0051] By setting the focal length of the anthropomorphic eye lens 4 to be the same as the virtual image distance of the near-eye display module 1 to be measured during the flat field correction process, it can be ensured that the anthropomorphic 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 when the image is in focus will the image be clear and the edges will be sharp, which is conducive to subsequent image analysis and data acquisition. Focal length matching also helps to reduce image distortion caused by the near-eye display module 1, especially edge distortion and pincushion or barrel distortion. Distortion interferes with the accurate measurement of the grayscale value of the image, thereby affecting the accuracy of FOV measurement. When the focal length is well matched, distortion can be minimized, thereby improving the accuracy of measurement. When the focal length of the anthropomorphic eye lens 4 is consistent with the virtual image distance of the near-eye display module 1, the imaging is clearest, which is convenient for subsequent measurement work and ensures the accuracy of measurement.

[0052] The flat field correction step is used to ensure that the brightness uniformity of the measurement system is consistent in each field of view, thereby eliminating the influence of the uneven brightness of the measurement system itself in each field of view on the test results of the field of view angle. The principle of this step is to eliminate the influence of the uneven brightness of the test system itself in different fields of view on the measurement results through the uniform radiation characteristics of the standard light source 6, thereby ensuring the accuracy of the measurement results. The implementation effect is 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 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 step of adjusting the test camera 5, the following steps are included: adjusting the exposure time of the test camera 5 so that the target grayscale value of a part of the central area of ​​the image captured by the test camera 5 is within a range of greater than or equal to 175 and less than or equal to 185. Specifically, the part of the central area can be the 30% area of ​​the image captured by the test camera 5 located in the center, and the area can be selected according to the actual situation. Such a setting is conducive to improving the consistency of measurement. By controlling the grayscale value within a specific range, it can be ensured that the brightness of the image is relatively stable during each measurement, thereby improving the comparability and consistency between different measurements. The grayscale value of the central area is kept within a relatively high and stable range, which helps to improve the signal-to-noise ratio of the image. At high grayscale values, the signal in the image is stronger and the noise is relatively reduced, which makes subsequent processing, such as edge detection and grayscale analysis, more accurate. When the grayscale value is within a preset and relatively ideal range, the image processing algorithm can be simplified, the need for complex adjustments to the image can be reduced, the processing speed can be accelerated, and the overall measurement efficiency can be improved. Under the condition of stable and high grayscale values, the measurement system responds more linearly to the image, which helps to reduce the measurement error caused by the nonlinear response of the system. The control of grayscale value makes the contrast and resolution of the image in the best state, which is crucial for detecting image edges and calculating the field of view (FOV), and can improve the measurement accuracy.

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

[0055] Specifically, the above-mentioned flat field correction matrix is ​​established based on multiple images, including determining the grayscale mean corresponding to the same pixel position of the chip of the test camera 5 based on the multiple images. .

[0056] .

[0057] Wherein, n is the number of images captured by the test camera 5, that is, the number of multiple images; The gray value of the first image corresponding to the same pixel position of the chip of the test camera 5, The same pixel position of the chip of test camera 5 corresponds to the grayscale value of the second image, and so on, until the same pixel position of the chip of test camera 5 corresponds to the grayscale value of the nth image. That is to say, this step requires the acquisition of the n images at the same pixel position. Take the mean . Get the grayscale mean of each pixel position Then, the grayscale mean T of the area of ​​preset size located at the center of the image is calculated. X , that is, the grayscale mean of all pixels in an area of ​​preset size located in the center of the image Divide by the number of pixels in the area to get the grayscale mean T X .

[0058] Then, according to the gray mean , determine the grayscale mean value T of the area of ​​preset size at the center of the image X is the ideal value, and then the flat field correction matrix M is established, and T X Divide by the grayscale value T(i,j) at the pixel position (i,j) in the effective area of ​​the entire image collected, and you can get the flat field correction matrix M. M refers to the flat field correction matrix, which means that if you want to make the grayscale values ​​of other fields consistent with the grayscale values ​​at the center, you need to multiply it by this coefficient. M is to convert the center grayscale mean T X The ratio of the grayscale value of the pixel to that of other pixels in the field of view.

[0059]

[0060] Wherein, T(i, j) is the grayscale 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 grayscale mean value T of the area of ​​the preset size at the center of the image is determined. X The preset size in can be 30 30 pixels.

[0061] Specifically, before placing the standard light source 6 at the entrance pupil position 41 of the human eye lens 4, the brightness of the standard light source 6 is adjusted to 50% to 80% of the maximum brightness. By adjusting the brightness of the standard light source 6 within this range, it is helpful to ensure the stability of the brightness of the standard light source 6, and ensure that the brightness change of the standard light source 6 does not exceed 0.5%, thereby ensuring a better calibration result.

[0062] like Figure 4 As shown, the above-mentioned light source 7 with a checkerboard target is used to calibrate the measurement system to obtain target images at various azimuth angles, specifically including:

[0063] A light source 7 with a checkerboard target is placed on the entrance pupil side of the human eye lens 4, and the checkerboard target 71 is formed by a plurality of checkerboards 711 arranged in a rectangular array. The light source is specifically a uniform surface light source. Each checkerboard 711 is specifically a small rectangular square, and the plurality of checkerboards 711 include a plurality of black checkerboards 711 and a plurality of white checkerboards 711. In the H direction, the plurality of black checkerboards 711 and the plurality of white checkerboards 711 are arranged alternately, and in the V direction, the plurality of black checkerboards 711 and the plurality of white checkerboards 711 are arranged alternately. The H direction is perpendicular to the V direction. In other words, the plurality of checkerboards 711 are arranged in a rectangular array in a plurality of rows and columns to form a checkerboard target 71 arranged in a grid shape, and the plurality of checkerboards 711 in the same row and the same column are arranged alternately in black and white.

[0064] During the test, the side of the human eye lens 4 away from the test camera 5 is required to be set directly opposite to the light source 7 with the checkerboard target, and the checkerboard target 71 is located on the side of the light source facing the human eye lens 4, so that the center point of the chip of the test camera 5 coincides with any intersection of the checkerboard target 71. It should be explained here that the intersection of the checkerboard target 71 is specifically the intersection of two straight lines in the checkerboard target 71 that are perpendicular to each other.

[0065] Then, since the field of view of the humanoid eye lens 4 is large, during the calibration process, the test camera 5 and the humanoid eye lens 4 can be rotated three times clockwise or counterclockwise on the HV plane, each time by 90°. When not rotated and after each rotation, the light source 7 with the checkerboard target is photographed by the test camera 5 to obtain the target image under four azimuth angles. It should be explained here 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 the test camera 5 is connected to the humanoid eye lens 4, so the two rotate synchronously. When not rotated, it is photographed once by the test camera 5, and then once after each rotation by the test camera 5, and a total of four times, so the four azimuth angles are 0°, 90°, 180°, and 270° to cover the full field of view of the measurement system. If the first rotation is performed clockwise, then the subsequent rotations are also clockwise; if the first rotation is performed counterclockwise, then the subsequent rotations are also counterclockwise to ensure coverage of the full field of view.

[0066] It should be noted that the above-mentioned checkerboard target 71 can be composed of multiple small checkerboard targets, specifically five small checkerboard targets, which are sequentially laid on the surface of the light source. In the specific embodiment of the present application, the size of the checkerboard target 71 is 600mm 600mm, the smallest checkerboard 711 in the checkerboard target 71 has a size of 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 chessboard 711 at various azimuths and the pixel positions of the chip of the test camera 5 is established based on the target images at various azimuths, including:

[0068] According to the target images at various azimuth angles, 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 is calculated. The field of view FOV is obtained according to the following trigonometric function formula: ; wherein, h is the length or width of the chessboard 711. Since the chessboard 711 is rectangular, h is specifically the side length of the chessboard 711; d is the vertical distance from the chessboard target 71 to the anthropomorphic eye lens 4; since the anthropomorphic eye lens 4 is distorted, the side length h of at least part of the chessboard 711 in the same target image collected by it is different. Therefore, in this formula, h is a variable, not a fixed value. Therefore, the field of view FOV of the chessboard 711 of the chessboard target 71 corresponding to different pixel positions of different chips is also a variable value, not a fixed value.

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

[0070] Table 1

[0071]

[0072]

[0073]

[0074] Specifically, the above-mentioned placing of 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] The near-eye display module 1 to be measured is placed on the lighting fixture 2, and the lighting fixture 2 is installed on the adjustment platform 3, so that the test camera 5 and the humanoid eye lens 4 remain connected, and the humanoid eye lens 4 is located on the side of the test camera 5 facing the near-eye display module 1. First, the height of the adjustment platform 3 in the z-axis direction is adjusted 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 level.

[0076] Then, turn on the lighting fixture 2, so that the lighting fixture 2 lights 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; 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 the lens groups in the near-eye display module 1 and the human eye lens 4.

[0077] Then, the rotation angle Rx around the x-axis and the rotation angle Ry around the y-axis of the adjustment platform 3 are adjusted 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, so that the optical axis of the near-eye display module 1 coincides with the optical axis of the measurement system.

[0078] Then, refer to Figure 1 , continue to adjust the position of the adjustment platform 3 on the x-axis and the position on the y-axis, 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.

[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 is possible to 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 that of the human eye. This is crucial for accurately evaluating FOV, because the measurement of FOV relies on simulating the visual reception range of the 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 ensures that the light path is consistent with the design, reduces these distortions, and improves measurement accuracy. At the same time, it can ensure that the measurement system can fully 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] like Figures 5 to 7As shown, in 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 constraining 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 captured by the test camera 5 is specifically an image formed on the test camera 5 through the human eye lens 4 when the near-eye display module 1 displays a full white image.

[0082] Figure 5 The image of the near-eye display module 1 when displaying a full white image is captured by the test camera 5 in this step. As can be seen from the figure, 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 when displaying a full white image captured by the test camera 5, 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 They are shown respectively Figure 5 The grayscale curves in the V direction and the H direction are automatically generated by the computer through the images collected by the test camera 5. Therefore, this application will not elaborate on them. Figure 6 and Figure 7 The two coordinate points on the curve in are the locations of the peaks.

[0083] Specifically, before determining the grayscale gradient curve graph according to the grayscale curve graph, the step further includes performing mean filtering on the grayscale curve graph to obtain the grayscale curve graph after mean filtering. 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 results, which is conducive to ensuring the accuracy of the measurement results. Optionally, in the specific operation, the time window of the mean filtering process 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. The time window of 3 is small, which can effectively suppress high-frequency noise while retaining image details, which is crucial to improving the smoothness of the grayscale curve and measurement accuracy. The filtering process can adopt the existing filtering process program or process, and only needs to adjust the time window of the filtering process to 3 pixels. 3 pixels is sufficient. This can better preserve the edge and detail features of the image, which is very beneficial for subsequent edge detection based on grayscale gradients and can more accurately determine the boundaries of the field of view. Compared with a larger time window, 3 The mean filter of the 3-time window has a small amount of calculation, which can improve the speed of image processing while ensuring the processing effect. This is especially important for scenes that require batch processing of a large number of images, and can improve the efficiency of the entire measurement system.

[0085] Specifically, the grayscale gradient curve graph is determined according to the grayscale curve graph, specifically including: performing first-order derivative processing on the grayscale curve graph to generate a grayscale gradient curve graph corresponding to the grayscale curve graph. The first-order derivative uses the gradient operator [-1, 0, 1] to process the one-dimensional grayscale curve, that is, the differential operator of the first-order derivative processing is [-1, 0, 1]. The first-order derivative processing can highlight the grayscale changes in the grayscale curve graph, especially where the grayscale value drops rapidly from the high value in the center area to the low value in the edge area. The appearance of the peak in the grayscale gradient curve graph often corresponds to the beginning or end of the edge in the grayscale curve graph, which provides a basis for accurately identifying the edge of the field of view angle. The first-order derivative processing can enhance the detail contrast in the image, especially in the boundary area of ​​the grayscale change, which helps to more clearly identify and locate the features in the subsequent processing. Through the first-order derivative processing, the influence of the slow change of the background grayscale on the measurement result can be effectively reduced. The first-order derivative focuses on the rapid change of the grayscale value, while the slow change of the background grayscale is weak on the gradient curve, which helps to improve the accuracy of the measurement. In the grayscale gradient curve, the peak at the edge can more accurately reflect the boundary of the field of view angle. Compared with directly using the grayscale curve, this method can more accurately determine the size of the FOV and improve the signal-to-noise ratio and reliability of the measurement results.

[0086] In summary, using the gradient operator [-1, 0, 1] for first-order derivative processing is a common discrete differential method that can calculate local changes in image grayscale values ​​and is very effective for edge detection and feature location. It estimates the derivative of grayscale values ​​by differentiating adjacent pixel values, thereby highlighting edges and details, and is a key step in determining the field of view boundary in image analysis.

[0087] Specifically, refer to Figure 8 and Fig. 9 As shown, in this step, the grayscale curve graph in the V direction is processed by a first-order derivative to generate a grayscale gradient curve graph in the V direction, and the grayscale curve graph in the H direction is processed by a first-order derivative to generate a grayscale gradient curve graph in the H direction.

[0088] refer to Figure 8 and Fig. 9 As shown in, in the process of determining the pixel position corresponding to the peak in the grayscale gradient curve graph according to the grayscale gradient curve graph, there are two peaks in the same grayscale gradient curve graph. Specifically, there are two peaks in the grayscale curve graph in the H direction, and there are two peaks in the grayscale gradient curve graph in the H direction.

[0089] by Figure 8For example, according to Figure 8 By using the two peaks in , the corresponding two pixel positions can be known, and the 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 the two edge pixel positions, a search is performed in the relationship table 1 to determine the field of view angle corresponding to the edge pixel position in the relationship table 1, so as to convert the pixel position into the angle space, so as to 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 are the locations of the peaks.

[0090] by Fig. 9 For example, according to Fig. 9 By using the two peaks in , the corresponding two pixel positions can be known, and the 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 the two edge pixel positions, a search is performed in the relationship table 1 to determine the field of view angle corresponding to the edge pixel position in the relationship table 1, thereby converting the pixel position into the angle space, thereby determining the half field of view angle and the full field of view angle of the near-eye display module 1 in the H direction. Fig. 9 The two coordinate points on the curve in are the locations of the peaks.

[0091] Then, the half field angle and the full field angle of the near-eye display module 1 can be obtained. It should be noted here that, since in the above steps, the relationship table between the field angle of the checkerboard 711 and the pixel position of the chip of the test camera 5, i.e., Table 1, has been obtained, after the edge pixel position is obtained, it is only necessary to look up Table 1 to obtain the corresponding field angle.

[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 the all-white screen, the area occupied by the all-white screen in the measurement system is the field of view area of ​​the near-eye display module 1. Therefore, it is only necessary to clarify the edge pixel position of the all-white screen and convert it into an angle, which is the field of view angle of the near-eye display module 1.

[0093] like Figure 1 As shown, the present invention also provides a system for measuring the field of view angle of a near-eye display module 1, comprising an adjustment platform 3, a lighting fixture 2, a test camera 5 and an anthropomorphic eye lens 4, wherein the lighting fixture 2 is arranged on the adjustment platform 3, the test camera 5 is connected to the anthropomorphic eye lens 4, and the anthropomorphic eye lens 4 is located on the side of the test camera 5 facing the lighting fixture 2, and the lighting fixture 2 is spaced apart from the anthropomorphic eye lens 4. The entrance pupil position 41 of the anthropomorphic eye lens 4 coincides with the exit pupil position 11 of the near-eye display module 1 to be detected.

[0094] The measuring system for the viewing angle of the near-eye display module 1 of the present invention has simple components and can be applied to the viewing angle measurement of different types of near-eye display modules 1, and has wide applicability. Moreover, the measuring system of the present invention is simple to operate, which is conducive to improving the measuring efficiency and reducing the measuring cost.

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

[0096] Specifically, the adjustment platform 3 is a six-degree-of-freedom adjustment platform 3, which can realize the adjustment function of six degrees of freedom Rx, Ry, Rz, 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-mentioned measurement system is a measurement system with an aperture in front, which means that the aperture of the humanoid eye lens 4 is located on the side facing the lighting fixture 2, and the position of the aperture is the entrance pupil position 41 of the humanoid eye lens 4. The aperture diameter is 4mm, and the field of view of the humanoid eye 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 humanoid eye lens 4 and the test camera 5 are always connected. The above-mentioned images collected by the test camera 5 are all images collected by the test camera 5 through the humanoid eye lens 4. The test camera 5 and the humanoid eye lens 4 are used in combination and cannot be separated.

[0098] Obviously, the above-described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection 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, it indicates 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 specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring the viewing angle of a near-eye display module, characterized in that: The steps include: Calibration of a measurement system composed of an adjustment platform (3), a lighting fixture (2), a test camera (5), and an anthropomorphic eye lens (4) includes: calibrating the measurement system using a light source (7) having a checkerboard target to obtain target images at various azimuth angles; According to the target images at the multiple azimuth angles, establishing a relationship table between the field of view angles of the chessboard (711) at the multiple azimuth angles and the pixel positions of the chip of the test camera (5); Placing the near-eye display module (1) to be measured on the lighting fixture (2) to calibrate the position of the near-eye display module (1); The test camera (5) is used to capture an image of the near-eye display module (1) when displaying a full white image, and to generate a grayscale curve graph; Determine a grayscale gradient curve diagram according to the grayscale curve diagram; According to the grayscale gradient curve diagram, determining the pixel position corresponding to the peak value in the grayscale gradient curve diagram as the edge pixel position of the near-eye display module (1); The field of view angle of the near-eye display module (1) is determined according to the edge pixel position and the relationship table.

2. The method for measuring the viewing angle of a near-eye display module according to claim 1, characterized in that: The step of calibrating the measuring system further includes a flat field correction step before calibrating the measuring system using the light source (7) having a checkerboard target: Placing a standard light source (6) on the entrance pupil side of the anthropomorphic eye lens (4), and making the entrance pupil position (41) of the anthropomorphic eye lens (4) fall within the light outlet (61) of the standard light source (6); Adjusting the focal length of the anthropomorphic eye lens (4) so ​​that the focal length of the anthropomorphic eye lens (4) is the same as the virtual image distance of the near-eye display module (1) to be measured; Adjusting the test camera (5) so that the test camera (5) captures a plurality of images; A flat-field correction matrix is ​​established based on the multiple images.

3. The method for measuring the viewing angle of a near-eye display module according to claim 2, characterized in that: The step of adjusting the test camera (5) comprises: The exposure time of the test camera (5) is adjusted so that the target grayscale value of a portion of the central area of ​​the image captured by the test camera (5) is within a range of greater than or equal to 175 and less than or equal to 185.

4. The method for measuring the viewing angle of a near-eye display module according to claim 2, characterized in that: The step of establishing a flat field correction matrix according to the plurality of images comprises: Determine the grayscale mean value corresponding to the same pixel position of the chip of the test camera (5) based on the multiple images ; According to the grayscale mean , determine the grayscale mean value T of the area of ​​preset size at the center of the image X , establish the flat field correction matrix M, ； Wherein, T(i, j) is the grayscale value at the pixel position (i, j) in the effective area corresponding to the image, i≥1, j≥1.

5. The method for measuring the viewing angle of a near-eye display module according to claim 2, characterized in that: Before placing the standard light source (6) at the entrance pupil position (41) of the humanoid eye lens (4), the method comprises: The brightness of the standard light source (6) is adjusted to 50% to 80% of the maximum brightness.

6. The method for measuring the viewing angle of a near-eye display module according to claim 1, characterized in that: The light source (7) with a checkerboard target is used to calibrate the measurement system to obtain target images at various azimuth angles, including: Placing a light source (7) having a checkerboard target on the entrance pupil side of the humanoid eye lens (4), wherein the checkerboard target (71) is composed of a plurality of checkerboards (711) arranged in an array; Making the center point of the chip of the test camera (5) coincide with the intersection point of the checkerboard target (71); The test camera (5) and the humanoid eye lens (4) are rotated three times clockwise or counterclockwise on the HV plane, each time by 90°, and the light source (7) with the checkerboard target is photographed by the test camera (5) when not rotated and after each rotation, so as to obtain target images at four azimuth angles.

7. The method for measuring the viewing angle of a near-eye display module according to claim 1, characterized in that: The step of establishing a relationship table between the field of view angles of the chessboard (711) at various azimuth angles and the pixel positions of the chip of the test camera (5) at various azimuth angles based on the target images at various azimuth angles comprises: Calculating the field of view angle 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 according to the target images at the multiple azimuth angles, ; wherein h is the length or width of the chessboard (711), and d is the vertical distance from the chessboard target (71) to the humanoid eye lens (4); A relationship table is established between the field of view angles of the checkerboard (711) of the checkerboard target (71) and the pixel positions of the chip of the test camera (5) at various azimuth angles.

8. The method for measuring the viewing angle of a near-eye display module according to claim 1, characterized in that: 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) comprises: Placing the near-eye display module (1) to be measured on the lighting fixture (2), and installing the lighting fixture (2) on the adjustment platform (3) so that the human-eye lens (4) is located on the side of the test camera (5) facing the near-eye display module (1); Turning 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); Adjusting the adjustment platform (3) until the cross image coincides with the center point of the chip of the test camera (5); The adjustment platform (3) is further adjusted so that the exit pupil position (11) of the near-eye display module (1) coincides with the entrance pupil position (41) of the anthropomorphic eye lens (4).

9. The method for measuring the viewing angle of a near-eye display module according to claim 1, characterized in that: In the process of collecting an 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, Setting 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 viewing angle of a near-eye display module according to claim 1, characterized in that: Before the step of determining the grayscale gradient curve graph according to the grayscale curve graph, the method further comprises: The grayscale curve graph is subjected to mean filtering processing to obtain a grayscale curve graph after mean filtering processing.

11. The method for measuring the viewing angle of a near-eye display module according to any one of claims 1 to 10, characterized in that: Determining a grayscale gradient curve graph according to the grayscale curve graph includes: Performing first-order 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: In the process of determining the pixel position corresponding to the peak value in the grayscale gradient curve graph according to the grayscale gradient curve graph, there are two peak values ​​in the same grayscale gradient curve graph; and / or, The process of determining the field of view angle of the near-eye display module (1) according to the edge pixel position and the relationship table includes determining the field of view angle corresponding to the edge pixel position in the relationship table to obtain the field of view angle of the near-eye display module (1).

13. A system for measuring the viewing angle of a near-eye display module, characterized in that: It includes an adjustment table (3), a lighting fixture (2), a test camera (5) and an anthropomorphic eye lens (4), The lighting fixture (2) is arranged on the adjustment platform (3), the test camera (5) is connected to the humanoid eye lens (4), and the humanoid eye lens (4) is located on a 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 a distance.

Images