Wide dynamic air-to-ground CMOS imaging performance test method and device

Abstract

The invention discloses a wide dynamic air-to-ground CMOS imaging performance test method and device, and the method comprises the steps: building a corresponding optical axis adjustment environment, a CMOS wide dynamic index test environment, and a resolution test environment, and testing the OECF, resolution, color, shadow, and distortion of an imaging module; three influence factors including a dynamic range DR, a signal-to-noise ratio SNR and visual noise VN are detected through an OECF test, Siemens star and bevel edge indexes are detected through a resolution test, and a color distance delta E, brightness delta L, chromaticity delta C, hue delta H and visual noise VN are detected through a color test. Brightness shadow Shading, a color shadow average value CIE [delta] Eab, the maximum difference [delta] VN of visual noise and an optical center are detected through shadow testing, lens geometric distortion LGD, chromatic aberration CA and longitudinal chromatic aberration LCA are detected through distortion testing, CMOS sensor imaging performance analysis is carried out through OECF, resolution, color, shadow and distortion testing, and imaging module performance indexes can be obtained more accurately.

Description

Technical Field

[0001] The present invention relates to the field of visible light imaging testing, and in particular to a method and device for testing imaging performance of a wide dynamic range visible light camera. Background Art

[0002] At present, with the widespread application of drones and other aircraft in various industries, air-to-ground visual imaging has become one of the core functions of drones, and its imaging quality is the basis for drones to perform intelligent functions such as target recognition and tracking. The air-to-ground visual imaging process may encounter mist, clouds and poor lighting conditions. The dynamic range of the imaging environment is wide, and the target imaging will be over-exposed, under-exposed and color-unbalanced. In addition, affected by aerodynamic forces, air-to-ground imaging is accompanied by severe jitter, which causes a large amount of random noise in the collected images. Therefore, during the image acquisition process, the air-to-ground visual sensor must use automatic exposure, automatic white balance, automatic gain, defogging, bad pixel correction and other processes to make the CMOS sensor better adapt to the wide dynamic imaging environment.

[0003] The quality of the processed image depends on the image clarity under different illuminations. The clarity here refers to high-quality images with good resolution, accurate color, wide dynamic range, and small imaging distortion. Among them, the wide dynamic range enables the normal capture of targets at different time periods during the day, accurate color can discover more target image information, good resolution is to discover more texture details of the target, and small imaging distortion is to ensure that the target image is not deformed or distorted, so as to better serve target identification and tracking. Therefore, for the evaluation of imaging clarity of wide dynamic air-to-ground sensors, an objective test evaluation method is proposed, and the test environment equipment setting is completed. Summary of the invention

[0004] The invention provides a wide dynamic range air-to-ground CMOS imaging performance testing method and device, which can at least solve one of the technical problems in the background technology.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A wide dynamic range air-to-ground CMOS imaging performance test method, comprising the following steps:

[0007] S100, build three imaging performance test environments: optical axis calibration environment for camera imaging modules, CMOS wide dynamic index test environment, and resolution test environment;

[0008] S200, OECF test on imaging module based on CMOS wide dynamic index test environment;

[0009] S300, performing a resolution test on the imaging module based on a resolution test environment;

[0010] S400, color test of imaging module based on CMOS wide dynamic index test environment;

[0011] S500, shadow test of imaging module based on CMOS wide dynamic index test environment;

[0012] S600, distortion test of imaging module based on CMOS wide dynamic index test environment;

[0013] Furthermore, the imaging performance test environment in step S100 of the present invention includes an optical axis adjustment environment, a CMOS wide dynamic index test environment, and a resolution test environment;

[0014] The optical axis calibration environment is to calibrate the optical axis of the camera's CMOS target surface and the lens through a parallel light tube, so that the two optical axes coincide and are parallel to the mechanical axis, ensure that the camera is correctly installed, and adjust the camera focal length to meet the imaging effect required by the test scene;

[0015] The CMOS wide dynamic index test environment includes TE42 test chart, camera module, fill light, mobile rail, image acquisition card and computer;

[0016] The TE42 test chart is a card for testing various indicators of CMOS, including OECF, resolution, color, shadow, and distortion;

[0017] The camera module is a CMOS platform under test;

[0018] The fill light is a device for adjusting different color temperatures, which is used to adjust the ambient color temperature and correct the image color;

[0019] The movable guide rail is used to control the distance between the camera and the image card, and is used to adjust the imaging acquisition range so that the TE42 image card fills the camera target surface;

[0020] The image acquisition card and the computer are image acquisition and image quality analysis stations, which are used for camera imaging quality analysis.

[0021] Furthermore, the OECF test method for the imaging module based on the CMOS wide dynamic index test environment in S200 of the present invention is as follows:

[0022] S210, build a test environment based on the dynamic range DR, signal-to-noise ratio SNR, and visual noise VN indicator measurement model;

[0023] S220, place the chart card in the card slot of the LG3 light box, turn on the light box, set the light box to the NORM working mode, and the light source illumination unit is lux;

[0024] S230, fix the camera on the mobile bracket, adjust the relative position of the camera and the image card, make the optical axis perpendicular to the image card, and make the image of the image card located at the center of the field of view and occupy about 1 / 2 to 2 / 3 of the camera field of view;

[0025] S240, placing the shading plate between the chart and the camera, so that the camera field of view just passes through the light hole in the middle of the shading plate, to prevent other stray light from affecting the test results;

[0026] S250, observe the chart image, with the bright area on the top, and adjust the polarization angle in the middle of the chart to change the center brightness. The top is the darkest, and 90 degrees is the brightest. By changing the center brightness, the exposure can be normal.

[0027] S260, collecting a card image, and detecting the background value of the card in real time according to the set illumination value, and checking the test result;

[0028] S270, adjust the illumination value of the light box, repeat Step 4 to Step 5, and obtain multiple groups of test results.

[0029] Furthermore, the dynamic range DR indicator measurement model of the present invention is:

[0030]

[0031] Among them, Lsat and Lmin are the set brightness value and the minimum brightness value.

[0032] Furthermore, the signal-to-noise ratio (SNR) indicator measurement model of the present invention is:

[0033]

[0034] L SNR =0.13×R ref (4)

[0035] R ref =S -1 (I)| I＝245 (5)

[0036] Among them, σ is the standard deviation of noise, gain is the increment, L SNR For the reference exposure R at a brightness value of 13% ref The time signal under measurement noise ratio, R ref is the reference exposure, which is the logarithmic value of the exposure brightness corresponding to a pixel value of 245 on the focal plane.

[0037] Furthermore, the visual noise VN index measurement model of the present invention is:

[0038] Set the observation conditions to 100% observation on the monitor, observation distance 0.5m, monitor resolution 96ppi, and calculate VN according to the following formula:

[0039] VN=1.000ΔL*+0.8520Δu*+0.3230Δv* (6)

[0040] Among them, △L* is the brightness of the object, and △u* and △v* are the chromaticity of the object.

[0041] Furthermore, the method for performing a resolution test on the imaging module based on the resolution test environment in S300 of the present invention includes:

[0042] S310, build a resolution test environment;

[0043] S320, conduct Siemens Star / MTF test;

[0044] S330, performing a bevel edge / SFR test to obtain a sharpness level of the camera;

[0045] The resolution test includes Siemens star / MTF, slant edge / SFR, and TE42 chart test;

[0046] The Siemens Star / MTF test uses a full Siemens star in the center of the chart and half Siemens stars in the four corners. A Siemens star is divided into multiple parts, with a total of 8 parts in the center and 3 parts in the corners.

[0047] The bevel edges used in the bevel edge / SFR test are mainly used to detect the sharpness of the camera. The TE42 chart has four bevel edges, with two different contrasts for horizontal and vertical. By using a sharpening algorithm to process image signals with different contrasts, the contrast of the bevel edges can be detected, and the sharpening can be adjusted based on this information.

[0048] Furthermore, the method for performing distortion testing on the imaging module based on the CMOS wide dynamic index testing environment in step S600 of the present invention includes:

[0049] S610, adjust the position of the guide rail and the focal length of the lens so that the camera faces the image card and ensures that the camera does not tilt in any direction;

[0050] S620, coordinate with the illuminance meter to adjust the light source in real time, and fill in the light evenly for the chart, to ensure that the illumination and intensity of the four corners and the center of the chart are not much different, and the difference between the center and the four corners cannot exceed 10%, so that the image is clear and discernible;

[0051] S630, fix the camera on the moving guide rail, turn on the power supply and the display (set the cross reference), adjust the relative position and posture of the camera and the chart card, make the center of the chart card image coincide with the center reference of the display, and make the image frame meet the chart card test requirements;

[0052] S640, collect the image of the chart card and check the test results;

[0053] S650, adjust the light source to different illuminations, repeat the measurement, and obtain multiple groups of test results.

[0054] On the other hand, the present invention further discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the above method.

[0055] It can be known from the above technical scheme that a wide dynamic air-to-ground CMOS imaging performance test method and device of the present invention is tested and verified by decomposing the imaging performance of the CMOS sensor into five indicators of OECF, resolution, color, shadow, and distortion. The three influencing factors of dynamic range DR, signal-to-noise ratio SNR, and visual noise VN are detected by OECF test, the Siemens star and hypotenuse indicators are detected by resolution test, the color distance ΔE, brightness ΔL, chromaticity ΔC, hue ΔH and visual noise VN are detected by color test, the brightness shadow Shading, the color shadow average CIEΔEab, the maximum difference ΔVN and the optical center of the visual noise are detected by shadow test, the lens geometric distortion LGD, chromatic aberration CA, and longitudinal chromatic aberration LCA are detected by distortion test, and the imaging performance analysis of the CMOS sensor is achieved through the test results of OECF, resolution, color, shadow, and distortion. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a wide dynamic COMS imaging index system;

[0057] Figure 2 This is a schematic diagram of the imaging module performance test process of the present invention;

[0058] Figure 3 A schematic diagram of the optical axis adjustment environment of the present invention;

[0059] Figure 4 It is the CMOS wide dynamic index test environment of the present invention;

[0060] Figure 5 A schematic diagram of a test card and a test environment of the present invention;

[0061] Figure 6 It is a schematic diagram of the dynamic range curve of the present invention;

[0062] Figure 7 It is a test chart and a test effect schematic diagram of the present invention;

[0063] Figure 8 The dynamic range analysis result of the camera of the present invention;

[0064] Fig. 9 Siemens Star used for testing the present invention;

[0065] Fig.10 A bevel edge used for measuring the present invention;

[0066] Fig.11 A schematic diagram of color block recognition according to the present invention;

[0067] Fig.12 The numerical results and visual comparison of the color test of the present invention;

[0068] Fig.13 Comparison results between the images taken by cameras with different color temperatures and the standard 24 color chart;

[0069] Fig.14 It is the shadow and identification diagram of TE42 chart;

[0070] Fig.15 This is a distortion chart and identification diagram;

[0071] Fig.16 This is the distortion quadrant division diagram;

[0072] Fig.17 Schematic diagram of lens collective distortion;

[0073] Fig.18 It is a schematic diagram of the color correction result of the present invention;

[0074] Fig.19 It is a schematic diagram of the Siemens star resolution test results of the present invention;

[0075] Fig. 20 It is a schematic diagram of the dead leaves graph test results of the present invention;

[0076] Fig.21 It is a schematic diagram of brightness test results of the present invention. DETAILED DESCRIPTION

[0077] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0078] Combined with the requirements of wide dynamic range air-to-ground CMOS sensors for imaging clarity, the present invention decomposes the clarity index into tests of OECF, resolution, color, shadow, and distortion. By testing and verifying the OECF, resolution, color, shadow, and distortion of CMOS sensor imaging, various indicators that affect camera imaging are obtained to verify and evaluate the imaging effect. Figure 1 As shown:

[0079] Among them, OECF includes three indicators: dynamic range DR, signal-to-noise ratio SNR, and visual noise VN. The larger the DR value, the wider the dynamic range; the larger the SNR, the less noise the camera has; the smaller the VN value, the less noise;

[0080] The resolution is evaluated by Siemens star and slant edge test indicators. The closer the modulation transfer function MTF and visual modulation transfer function vMTF are to 1, the better, and the smaller the edge width Edge-Width is, the better;

[0081] Color is measured by color distance ΔE, brightness ΔL, chromaticity ΔC, hue ΔH and visual noise VN. The smaller the average color distance ΔE value, the better the result and the more standard the color. The other indicators are similar;

[0082] Shadow is measured by brightness shading, color shading average CIEΔEab, maximum difference of visual noise ΔVN and optical center. The smaller the measurement value, the better.

[0083] The distortion is evaluated by lens geometric distortion LGD, chromatic aberration CA, and longitudinal chromatic aberration LCA. The closer LGD is to 0, the smaller the distortion. Less than 0 is barrel distortion, and greater than 0 is pincushion distortion. The average chromatic aberration of the GR / GB channel is closer to 0, the better.

[0084] like Figure 2 As shown, a wide dynamic range air-to-ground CMOS imaging performance test method proposed by the present invention comprises the following steps:

[0085] S100, build three imaging performance test environments: optical axis calibration environment for camera imaging modules, CMOS wide dynamic index test environment, and resolution test environment;

[0086] S200, OECF test on imaging module based on CMOS wide dynamic index test environment;

[0087] S300, performing a resolution test on the imaging module based on a resolution test environment;

[0088] S400, color test of imaging module based on CMOS wide dynamic index test environment;

[0089] S500, shadow test of imaging module based on CMOS wide dynamic index test environment;

[0090] S600, distortion test of imaging module based on CMOS wide dynamic index test environment;

[0091] The following is a detailed description of each step:

[0092] S100, build an imaging performance test environment for various cameras;

[0093] The imaging performance test environments of various cameras include the optical axis adjustment environment, CMOS wide dynamic index test environment, and resolution test environment;

[0094] like Figure 3 As shown, the optical axis adjustment environment is specifically as follows: the optical axis of the camera's CMOS target surface and the lens is adjusted through a parallel light tube;

[0095] Make the two optical axes coincide and be parallel to the mechanical axis, ensure the camera is correctly installed, adjust the camera focal length, meet the imaging effect required by the test scene, and ignore the system error. During the adjustment process, ensure that the crosshairs in the monitor coincide with the center of the "BMW image" in the graphic field of view, and the image is subjectively clear.

[0096] Secondly, the various indicators of the wide dynamic CMOS camera are tested using transmissive charts and reflective charts.

[0097] like Figure 4 , Figure 5 As shown in the figure, the CMOS wide dynamic index test environment includes TE42 test chart, camera module, fill light, mobile rail, image acquisition card and computer;

[0098] TE42 test chart is a card for testing various indicators of CMOS, including OECF, resolution, color, shadow, distortion, etc.

[0099] The camera module is the CMOS platform under test;

[0100] The fill light is a device for adjusting different color temperatures, which is used to adjust the ambient color temperature and correct the image color;

[0101] The movable guide rail is used to control the distance between the camera and the image card, and to adjust the imaging acquisition range so that the TE42 image card fills the camera target surface;

[0102] The image acquisition card and computer are image acquisition and image quality analysis platforms, which are used for camera imaging quality analysis.

[0103] S200, OECF test on imaging module based on CMOS wide dynamic index test environment;

[0104] The optoelectronic conversion function (OECF) describes the characteristics of digital cameras in converting brightness into numerical values. It can verify and evaluate the wide dynamic performance of CMOS imaging. The calculation models of its various indicators are as follows:

[0105] (1) Dynamic range (DR)

[0106] Dynamic range (DR) describes the maximum scene contrast that a camera can restore. The brightest point that a camera can reach is the maximum output value. According to ISO15739, the SNR value of the darkest point is 1. The dynamic range is defined on the basis of SNR 1. The dynamic range is the contrast between the brightest point and the darkest point.

[0107] like Figure 6 As shown, the dotted line is the signal-to-noise ratio (SNR) curve, the solid line is the RGB curve, and the two vertical lines are the dynamic range curves. The left vertical line is obtained by the logarithmic value of the brightness when the signal-to-noise ratio is 1, and the right vertical line is obtained by the logarithmic value of the brightness at the intersection of the RGB curve fitting. The dynamic range value of the camera is obtained according to the two red lines.

[0108] The dynamic range calculation formula has the following relationship:

[0109]

[0110] Among them, Lsat and Lmin are the set brightness value and the minimum brightness value.

[0111] (2) Signal-to-noise ratio (SNR)

[0112] The signal-to-noise ratio describes the relationship between the signal and the noise and is defined as the ratio of the signal value to the standard deviation of the signal value. The noise is displayed as the standard deviation. The standard deviation is defined as the root mean square of the absolute value of the sum of the standard deviations within the signal range. The larger the SNR, the lower the camera noise. The signal-to-noise ratio is determined by the following formula:

[0113]

[0114] L SNR =0.13×R ref (4)

[0115] R ref =S -1 (I)| I＝245 (5)

[0116] Among them, σ is the standard deviation of noise, gain is the increment, L SNR For the reference exposure R at a brightness value of 13% ref The time signal under measurement noise ratio, R ref is the reference exposure, which is the logarithmic value of the exposure brightness corresponding to a pixel value of 245 on the focal plane.

[0117] (3) Visual Noise (VN)

[0118] Compared to the signal-to-noise ratio, different observers have different perceptions of visual noise, and the CIE-Luv color space has better visual perception characteristics than the CIE-Lab color space. To this end, the RGB image is converted to the XYZ color space, and the color receptors are analyzed based on the results of the human eye and the processing of color signals. The visual noise value VN is the weighted sum of the standard deviations of the △L*, △u*, and △v* channels in the CIE-Luv color space.

[0119] In the visual noise calculation, the default observation conditions are 100% observation on the display, observation distance 0.5m, and display resolution 96ppi. VN is calculated according to the following formula:

[0120] VN=1.000ΔL*+0.8520Δu*+0.3230Δv* (6)

[0121] Among them, △L* is the brightness of the object, and △u* and △v* are the chromaticity of the object.

[0122] The OECF test method steps are as follows:

[0123] S210. Build a test environment based on the dynamic range (DR), signal-to-noise ratio (SNR), and visual noise (VN) indicator measurement model;

[0124] S220, place the chart card in the card slot of the LG3 light box, turn on the light box, set the light box to the NORM working mode, and the light source illumination unit is lux;

[0125] S230, fix the camera on the mobile bracket, adjust the relative position of the camera and the image card, make the optical axis perpendicular to the image card, and make the image of the image card located at the center of the field of view and occupy about 1 / 2 to 2 / 3 of the camera field of view;

[0126] S240, placing the shading plate between the chart and the camera, so that the camera field of view just passes through the light hole in the middle of the shading plate, to prevent other stray light from affecting the test results;

[0127] S250, observe the chart image, with the bright area on the top, and adjust the polarization angle in the middle of the chart to change the center brightness. The top is the darkest, and 90 degrees is the brightest. By changing the center brightness, the exposure can be normal.

[0128] S260, collecting a card image, and detecting the background value of the card in real time according to the set illumination value, and checking the test result;

[0129] S270, adjust the illumination value of the light box, repeat Step 4 to Step 5, and obtain multiple groups of test results.

[0130] Test results such as Figure 7 As shown, Figure 7 (a) shows the LG3 chart display effect under a certain illumination value of the light box. Figure 7 (b) is the image effect captured by CMOS under the current illumination value. The calculation result (S260) can be obtained by analyzing the richness of dark details and bright details under the current illumination conditions. By repeating S270, the dynamic range of CMSO can be obtained by comprehensive analysis of multiple results. The captured image data results are imported into the image analysis software. The analysis results are shown in Figure 7 shown.

[0131] in, Figure 8 The two red vertical lines in the figure show the dynamic range. The larger the range, the wider the dynamic range. The dynamic range of the missile-borne camera in the automatic exposure mode can be determined by formula (1): 94.40. The dynamic range of CMOS is wider, and more layered details can be displayed in the image. In addition, from the R / G / B curve with brightness in the figure, it can be seen that the R / G / B curves are basically overlapped, and the white balance correction capability of the camera imaging system is good.

[0132] S300, performing a resolution test on the imaging module based on a resolution test environment;

[0133] S310, build a resolution test environment;

[0134] Resolution tests include Siemens star / MTF, slant edge / SFR. The TE42 chart can cover all of the above test indicators. Its test environment continues to use the COMS wide dynamic index test environment.

[0135] S320, Siemens Star / MTF test

[0136] During the test, a full Siemens star in the center of the chart and four half Siemens stars at the corners are used. A Siemens star is divided into multiple parts, with 8 parts in the center and 3 parts in the corners. Fig. 9 The average value of each part of each star contains information about the image sharpness and resolution at different positions and directions, which is used to check the optical center of the camera, to analyze optical errors such as astigmatism, to verify image processing in a specific direction or at a specific frequency, and to determine the limiting resolution.

[0137] During the test, the limiting resolution is calculated from the MTF data of the specified frequency modulation. The modulation transfer function (MTF) describes the modulation loss of the spatial frequency. It is a response of the imaging system on the spatial frequency, representing that the modulation starts from 0 line pairs and continues to decrease at a given spatial frequency. As the line pair density increases, the difference between the black and white lines of the line pair decreases, and the MTF decreases. The Siemens Star is simulated by radial lines of different frequencies.

[0138] S330, perform bevel edge / SFR test to obtain the sharpness of the camera

[0139] like Fig.10 The following figure shows the bevel edges used in the bevel edge / SFR test. The bevel edges are mainly used to detect the sharpness of the camera. The TE42 chart has four bevel edges, with two different contrasts for horizontal and vertical. The sharpening algorithm is used to process the image signal with different contrasts. The contrast of the bevel edges can be detected and the sharpening can be adjusted based on this information. The test results include two modulation contrast deviations with different contrasts.

[0140] S400, color test of imaging module based on CMOS wide dynamic index test environment;

[0141] like Fig.11 As shown, the color test mainly verifies and evaluates the camera's color reproduction ability. Figure 5 The environment layout and TE42 chart are used for testing. The color blocks in the chart are distributed around the grayscale blocks. Each color block has a default value for test calculation.

[0142] like Fig.12 As shown in the figure, under the influence of light sources in different environments, colors will appear metamerism, causing the human eye to see incorrect colors. This phenomenon can be alleviated by adaptively adjusting the standard. The graphic results can intuitively reflect the camera's ability to truly restore each color block image.

[0143] By adjusting the fill light to obtain the TE42 chart image, changing different color temperature values, and obtaining images under different color temperature conditions, the comparative analysis results between the captured image and the reference image are shown in the figure below. Fig.13 As shown;

[0144] from Fig.13 It can be analyzed that after the camera is white balanced, the color difference between the pictures taken at different color temperatures and the standard color card is small, especially for the "19-24" grayscale color block, the color reproduction ability is better, and the color difference is basically maintained within 10 gray levels.

[0145] S500, shadow test of imaging module based on CMOS wide dynamic index test environment;

[0146] The shadow test is mainly used to verify and evaluate the brightness shadow and color shadow of the camera. It measures 24 ROIs evenly distributed on the image of the TE42 chart to obtain the shadow intensity in the aperture and the color shadow in ΔEab.

[0147] like Fig.14 As shown, the graphical results intuitively reflect the brightness shadow and color shadow. The imaging color and shadow can be tested according to the correction coefficient.

[0148] S600, distortion test of imaging module based on CMOS wide dynamic index test environment;

[0149] like Fig.15 As shown in the figure, the distortion test is mainly used to verify and evaluate the distortion and chromatic aberration of camera imaging. The TE251 chart is used. The chart contains 13 rows × 23 columns of small crosses and 4 mark points. It is used for geometric distortion testing of normal-angle lenses.

[0150] like Fig.16 As shown in the figure, the geometric distortion of the lens is divided into four quadrants based on the center of the image: Quadrant I, Quadrant II, Quadrant III, and Quadrant IV. During the distortion test, the cross is divided into the four quadrants of the image.

[0151]

[0152] Where H is the position of the point without distortion, and H′ is the distance from the point to the center of the image. Fig.15 As shown, the geometric distortion of a grid position is the value between the radial distance H′ of the actual grid position divided by the ideal grid position H and the ideal grid position H. Fig.17 (a) indicates that the image is undistorted when H′ is equal to H; Fig.17 (b) indicates negative image distortion (barrel distortion) when H′ is less than H; Fig.17 (c) indicates that the image is positively distorted (pincushion distortion) when H′ is greater than H.

[0153] S610, adjust the position of the guide rail and the focal length of the lens so that the camera faces the image card and ensures that the camera does not tilt in any direction;

[0154] S620, coordinate with the illuminance meter to adjust the light source in real time, and fill in the light evenly for the chart, to ensure that the illumination and intensity of the four corners and the center of the chart are not much different, and the difference between the center and the four corners cannot exceed 10%, so that the image is clear and discernible;

[0155] S630, fix the camera on the moving guide rail, turn on the power supply and the display (set the cross reference), adjust the relative position and posture of the camera and the chart card, make the center of the chart card image coincide with the center reference of the display, and make the image frame meet the chart card test requirements;

[0156] S640, collect the image of the chart card and check the test results.

[0157] S650, adjust the light source to different illuminations, repeat the measurement, and obtain multiple groups of test results.

[0158] The TE42 v2 chart is a comprehensive test chart. It contains features such as dead leaves, beveled edges, and 24-color charts. It can be used to conduct a comprehensive analysis of the camera's imaging details. The positional relationship between the missile-borne camera and the comprehensive chart is adjusted using the guide rails. Clear TE42 v2 chart images are taken according to the test requirements. The test results of the camera's performance indicators such as resolution, texture details, and color reproduction capabilities are obtained:

[0159] like Fig.18 The figure shows the camera color correction test, the differences between the color blocks in the captured image and the standard color card. The differences between most of the color blocks are within 5 gray levels, and the white balance correction is well achieved. Fig.19 and 20 In order to test the resolution of the missile-borne camera using Siemens stars and dead leaves images, the modulation transfer function (MTF) is used to measure the camera's ultimate spatial resolution, which is between 1000 and 1200, and can well display the texture details of the scene in the field of view. Fig.21 This is the test result of camera brightness. It can be seen that the brightness distribution of the camera is uneven, which is prone to dark corners and color deviation. The camera brightness can be corrected for consistency later.

[0160] In summary, the present invention decomposes the imaging performance of the CMOS sensor into five indicators, namely, OECF, resolution, color, shadow, and distortion, and performs testing and verification. The three influencing factors, namely, dynamic range DR, signal-to-noise ratio SNR, and visual noise VN, are detected through the OECF test. The Siemens star and hypotenuse indicators are detected through the resolution test. The color distance ΔE, brightness ΔL, chromaticity ΔC, hue ΔH, and visual noise VN are detected through the color test. The brightness shadow Shading, color shadow average CIEΔEab, maximum difference ΔVN of visual noise, and optical center are detected through the shadow test. The lens geometric distortion LGD, chromatic aberration CA, and longitudinal chromatic aberration LCA are detected through the distortion test. The imaging performance of the CMOS sensor is analyzed through the tests of OECF, resolution, color, shadow, and distortion.

[0161] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0162] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0163] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wide dynamic range air-to-ground CMOS imaging performance test method, characterized in that: The following steps are involved: S100, build three imaging performance test environments: optical axis calibration environment for camera imaging modules, CMOS wide dynamic index test environment, and resolution test environment; S200, OECF test on imaging module based on CMOS wide dynamic index test environment; S300, performing a resolution test on the imaging module based on a resolution test environment; S400, color test of imaging module based on CMOS wide dynamic index test environment; S500, shadow test of imaging module based on CMOS wide dynamic index test environment; S600, conduct distortion test on imaging module based on CMOS wide dynamic index test environment.

2. The wide dynamic range air-to-ground CMOS imaging performance test method according to claim 1, characterized in that: The imaging performance test environment in step S100 includes an optical axis adjustment environment, a CMOS wide dynamic index test environment, and a resolution test environment; The optical axis calibration environment is to calibrate the optical axis of the camera's CMOS target surface and the lens through a parallel light tube, so that the two optical axes coincide and are parallel to the mechanical axis, ensure that the camera is correctly installed, and adjust the camera focal length to meet the imaging effect required by the test scene; The CMOS wide dynamic index test environment includes TE42 test chart, camera module, fill light, mobile rail, image acquisition card and computer; The TE42 test chart is a card for testing various indicators of CMOS, including OECF, resolution, color, shadow, and distortion; The camera module is a CMOS platform under test; The fill light is a device for adjusting different color temperatures, which is used to adjust the ambient color temperature and correct the image color; The movable guide rail is used to control the distance between the camera and the image card, and is used to adjust the imaging acquisition range so that the TE42 image card fills the camera target surface; The image acquisition card and the computer are image acquisition and image quality analysis stations, which are used for camera imaging quality analysis.

3. The wide dynamic range air-to-ground CMOS imaging performance test method according to claim 1, characterized in that: The OECF test method for the imaging module based on the CMOS wide dynamic index test environment in S200 is as follows: S210, build a test environment based on the dynamic range DR, signal-to-noise ratio SNR, and visual noise VN indicator measurement model; S220, place the chart card in the card slot of the LG3 light box, turn on the light box, set the light box to the NORM working mode, and the light source illumination unit is lux; S230, fix the camera on the mobile bracket, adjust the relative position of the camera and the image card, make the optical axis perpendicular to the image card, and make the image of the image card located at the center of the field of view and occupy about 1 / 2 to 2 / 3 of the camera field of view; S240, placing the shading plate between the chart and the camera, so that the camera field of view just passes through the light hole in the middle of the shading plate, to prevent other stray light from affecting the test results; S250, observe the chart image, with the bright area on the top, and adjust the polarization angle in the middle of the chart to change the center brightness. The top is the darkest, and 90 degrees is the brightest. By changing the center brightness, the exposure can be normal. S260, collecting a card image, and detecting the background value of the card in real time according to the set illumination value, and checking the test result; S270, adjust the illumination value of the light box, repeat Step 4 to Step 5, and obtain multiple groups of test results.

4. The wide dynamic range air-to-ground CMOS imaging performance test method according to claim 3, characterized in that ,The dynamic range DR indicator measurement model is: Among them, Lsat and Lmin are the set brightness value and the minimum brightness value.

5. The wide dynamic range air-to-ground CMOS imaging performance test method according to claim 3, characterized in that: The signal-to-noise ratio (SNR) indicator measurement model is: L SNR =0.13×R ref (4) R ref =S -1 (I)| I＝245 (5) Among them, σ is the standard deviation of noise, gain is the increment, L SNR For the reference exposure R at a brightness value of 13% ref The time signal under measurement noise ratio, R ref is the reference exposure, which is the logarithmic value of the exposure brightness corresponding to a pixel value of 245 on the focal plane.

6. The wide dynamic range air-to-ground CMOS imaging performance test method according to claim 3, characterized in that: The visual noise VN indicator measurement model is: Set the observation conditions to 100% observation on the monitor, observation distance 0.5m, monitor resolution 96ppi, and calculate VN according to the following formula: VN=1.000ΔL*+0.8520Δu*+0.3230Δv* (6) Among them, △L* is the brightness of the object, and △u* and △v* are the chromaticity of the object.

7. The wide dynamic range air-to-ground CMOS imaging performance test method according to claim 1, characterized in that: The method for performing a resolution test on the imaging module based on the resolution test environment in S300 includes: S310, build a resolution test environment; S320, conduct Siemens Star / MTF test; S330, performing a bevel edge / SFR test to obtain a sharpness level of the camera; The resolution test includes Siemens star / MTF, slant edge / SFR, and TE42 chart test; The Siemens Star / MTF test uses a full Siemens star in the center of the chart and half Siemens stars in the four corners. A Siemens star is divided into multiple parts, with a total of 8 parts in the center and 3 parts in the corners. The bevel edges used in the bevel edge / SFR test are mainly used to detect the sharpness of the camera. The TE42 chart has four bevel edges, with two different contrasts for horizontal and vertical. By using a sharpening algorithm to process image signals with different contrasts, the contrast of the bevel edges can be detected, and the sharpening can be adjusted based on this information.

8. The wide dynamic range air-to-ground CMOS imaging performance test method according to claim 1, characterized in that: The method for performing distortion testing on the imaging module based on the CMOS wide dynamic index testing environment in step S600 includes: S610, adjust the position of the guide rail and the focal length of the lens so that the camera faces the image card and ensures that the camera does not tilt in any direction; S620, coordinate with the illuminance meter to adjust the light source in real time, and fill in the light evenly for the chart, to ensure that the illumination and intensity of the four corners and the center of the chart are not much different, and the difference between the center and the four corners cannot exceed 10%, so that the image is clear and discernible; S630, fix the camera on the moving guide rail, turn on the power supply and the display, adjust the relative position and posture of the camera and the chart card, make the center of the chart card image coincide with the center reference of the display, and make the image frame meet the chart card test requirements; S640, collect the image of the chart card and check the test results; S650, adjust the light source to different illuminations, repeat the measurement, and obtain multiple groups of test results.

9. A computer device comprising a memory and a processor, characterized in that: The memory stores a computer program, and when the computer program is executed by the processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 8.

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