Method for testing linearity of astronomical imaging detector after irradiation

Abstract

The invention relates to a method for testing linearity of an astronomical imaging detector after irradiation. A device involved in the method is composed of an electrostatic test platform, an integrating sphere light source, a three-dimensional sample adjusting table, a sample test board, an astronomical imaging detector sample, a direct-current power supply and a computer. The method comprises the following steps: carrying out an astronomical imaging detector proton irradiation damage test, extracting gray values of single pixels of collected background images and light field images with different exposure times, calculating a gray average value of the light field images without the background, finding out a full well signal value, and taking the exposure time as a horizontal axis to obtain a full well signal value; the method comprises the following steps of: taking the exposure time and the light field gray average as a vertical axis, taking the partial light field image gray average as a vertical axis, carrying out least square fitting on linearity data, extracting the linear region slope and intercept of a fitting curve, carrying out linearity calculation on each group of exposure time and the light field gray average, and then solving the average value of all groups of linearity data, namely the linearity of the astronomical imaging detector. The method is suitable for various astronomical imaging detectors and has the advantages of being convenient to test, small in error, high in speed, high in practicability and the like.

Description

Technical Field

[0001] The invention relates to the fields of astronomical imaging detection and radiation image parameter testing, and in particular to a method for testing the linearity of an astronomical imaging detector after irradiation. Background Art

[0002] Linearity reflects the changing relationship between the input signal and the output signal, that is, whether the pixel output signal and the exposure time are in a linear relationship within the dynamic range of the device. Usually, the linearity is poor when the signal is weak and close to the full well signal. This is because when the signal is weak, the device noise has a large impact and the signal-to-noise ratio is low, causing a certain degree of discreteness; when close to the full well, the depletion region under the photosensitive unit becomes narrower, causing the quantum efficiency to decrease and the sensitivity to decrease. The linearity of the device affects the accuracy of the capture and conversion process of the optical signal. If the linearity of the device deviates or is unstable, it will cause distortion or loss of the optical signal, thereby affecting the clarity and accuracy of the image obtained by the astronomical imaging detector, which is not conducive to the analysis of the astronomical data in the image. Therefore, the linearity of the device has a great impact on the results of astronomical imaging detection. However, when the space astronomical telescope is working in orbit, the space cumulative radiation effect will cause the linearity of the guide imaging device (astronomical imaging detector) to degrade, which will in turn affect the pointing accuracy of the fine guide. If the fine guide generates incorrect boresight attitude information, it will have a great impact on the safe and reliable operation of the space astronomical telescope.

[0003] At present, the linearity test for astronomical imaging detectors is mainly based on the EMVA1288 test standard. For astronomical imaging detectors, the test requirements are higher. The EMVA1288 standard test steps are more and do not take into account the impact of background noise and voltage bias on linearity testing. After irradiation, the increase in background noise will affect the linearity of astronomical imaging detectors, resulting in an increase in linearity parameter test errors, and cannot provide basic data for the reliability assessment of space astronomical telescopes.

[0004] Therefore, this paper proposes a test method for the linearity of astronomical imaging detectors after irradiation. In the dark field test, the test steps are reduced and only the dark field background grayscale image is collected for testing, thereby shortening the test time. In the light field test, the background is eliminated to reduce the influence of background noise and voltage bias on linearity, and the linearity parameters of the astronomical imaging detector after irradiation are extracted, and 20%μ Sat ≤μ y.optical ≤80%μ Sat The grayscale mean μ of the light field image in the interval ideal, reducing the impact of weak signals and near-full-well signal data on linearity testing, improving the test accuracy of the linearity of astronomical imaging detectors after irradiation, shortening the test time, and providing a basic data testing method for the reliability assessment of space astronomical telescopes. Summary of the invention

[0005] The purpose of the present invention is to solve the limitations of existing linearity testing methods and provide a method for testing the linearity of an astronomical imaging detector after irradiation. The method involves a device consisting of an electrostatic test platform, an integrating sphere light source, a three-dimensional sample adjustment table, a sample test board, an astronomical imaging detector sample, a DC power supply and a computer. By carrying out a proton irradiation damage test on an astronomical imaging detector, the grayscale values ​​of individual pixels of the collected background image and light field image are extracted. Based on the dark field background data under zero exposure time, with the purpose of shortening the test time and improving the accuracy of the test linearity, the collected light field images under different exposure times are analyzed pixel by pixel to obtain data that can characterize the linearity, and the grayscale mean μ of the light field image with the background removed is calculated. y.optical , then in μ y.optic Find the full-well signal value μ Sat And calculate 20%μ Sat ≤μ y.optical ≤80%μ Sat The grayscale mean μ of the light field image in the interval ideal . With exposure time as the horizontal axis, μ ideal The linearity data is fitted by the least square method, and the slope k and intercept b of the linear region of the fitting curve are extracted. For each group of exposure time t and light field grayscale mean μ y.optical Linearity calculation is performed, and then the mean value MeanLinearity of all groups of Linearity data is obtained, which is the linearity of the astronomical imaging detector, thereby shortening the test time and improving the test accuracy of the linearity of the astronomical imaging detector after irradiation.

[0006] The present invention discloses a method for testing the linearity of an astronomical imaging detector after irradiation. The method involves a device consisting of an electrostatic test platform, an integrating sphere light source, a three-dimensional sample adjustment platform, a sample test board, an astronomical imaging detector sample, a direct current power supply and a computer. An integrating sphere light source (2) and a three-dimensional sample adjustment platform (3) are respectively arranged on the electrostatic test platform (1), a sample test board (4) is fixed on the three-dimensional sample adjustment platform (3), an astronomical imaging detector sample (5) is placed on the sample test board (4), the sample test board (4) is connected to a direct current power supply (6), and the electrostatic test platform (1) is connected to a computer (7). The specific operation is performed according to the following steps:

[0007] a. According to the actual on-orbit working environment of the astronomical imaging detector and its typical proton irradiation dose, the actual irradiation parameters are determined, and proton irradiation tests of the astronomical imaging detector under different cumulative injection doses are carried out;

[0008] b. Fixing the irradiated astronomical imaging detector sample (5) on the sample test board (4), and then connecting the sample test board (4) to the DC power supply (6) and the computer (7) respectively, and starting the dark field test. During the dark field test, the integrating sphere light source (2) and other lighting sources in the test room need to be turned off, and the astronomical imaging detector sample (5) is covered with a light-proof black box cover;

[0009] c. adjusting the exposure time of the astronomical imaging detector sample (5) on the sample test plate (4) through a computer (7), selecting a zero exposure time, and collecting 20 frames of grayscale images, and saving the collected zero exposure time images;

[0010] d. Put the 20 frames of grayscale images at the dark field zero exposure time point in step c into a three-dimensional matrix, and then extract the grayscale value of each pixel one by one based on the pixel positioning, and calculate the grayscale mean value of each pixel corresponding to the position of the 20 frames of images according to the pixel position, that is, μ y.biasdark [m][n], a grayscale image containing the grayscale mean of each pixel at the corresponding position is obtained and used as the background;

[0011] The grayscale mean μ of each pixel at the corresponding position of the background 20 frames of images y.biasdark [m][n] is calculated according to formula (1):

[0012]

[0013] y d.1 [m][n]、y d.2 [m][n], ..., y d.20 [m][n], where m and n represent the pixel position of a certain gray value 1≤m≤M,1≤n≤N,m,n,M,N are the total number of pixel rows and columns, which are all positive integers, y d.q [m][n] represents the grayscale value of the pixel (m, n), the subscripts dark and d represent the dark field, the subscripts q = 1, 2, ..., 20 represent the sequence of 20 frames of images, the subscript bias represents the background, μ y.biasdark [m][n] represents the grayscale mean of the pixel (m,n) at the position of the background 20 frames;

[0014] e. Take out the black box, turn on the integrating sphere light source, select a fixed irradiance, and start the light field test. Use the computer (7) to adjust the exposure time of the astronomical imaging detector sample (5) on the sample test board (4). Start from zero exposure time, and limit the pixel potential well to be exactly full well. The maximum grayscale mean value of the image output by the detector with the exposure time is the full well signal value. Select 20 exposure time points at equal intervals, start collecting images from the zero exposure time of the detector, collect 20 frames of grayscale images at each exposure time point, and save the collected images according to the exposure time;

[0015] f. Select the first exposure time point, put the collected 20 frames of grayscale images into a three-dimensional matrix, extract the grayscale value of each pixel based on pixel positioning, and then calculate the corresponding position y of each pixel in the 20 frames of images according to the pixel position. o.q [m][n] minus μ y.biasdark The grayscale mean of [m][n] is used to obtain μ corresponding to each exposure time. y.optical [m][n], obtain the light field grayscale image of the grayscale mean of each pixel corresponding to a frame without the background, and calculate the grayscale mean of all pixel positions in this frame, that is, μ y.optical , which is taken as the grayscale mean value under this light field exposure time;

[0016] The corresponding position y of each pixel in the 20 frames of light field images o.q [m][n] minus μ y.biasdark The grayscale mean μ of [m][n] y.optical [m][n] and the grayscale mean μ of all pixel positions in the background-removed frame y.optical Calculate according to formula (2) and formula (3):

[0017]

[0018]

[0019] y optical.1 [m][n]、y optical.2 [m][n], ..., y optical.20 [m][n], where m and n represent the pixel position of a certain gray value 1≤m≤M,1≤n≤N,m,n,M,N are the total number of pixel rows and columns, which are all positive integers, y optical.q [m][n] represents the grayscale value of the pixel (m, n). The subscripts dark and d represent the dark field, optical represents the light field, the subscript q = 1, 2, ..., 20 represents the sequence number of the 20 frames, the subscript bias represents the background, μ y.biasdark [m][n] represents the grayscale mean of the pixel (m,n) at the position of the background 20 frames, μ y.optical[m][n] represents the grayscale mean of the pixel (m,n) position in 20 frames of images under the selected light field exposure time, μ y.optical It represents the grayscale mean of all pixel positions excluding the background under the selected light field exposure time;

[0020] g. Repeat step f to calculate μ for all 20 light field exposure times. y.optical [m][n] and μ y.optical , the grayscale mean μ of the image background removed at each exposure time of the 20 light field exposure time points y.optical Record and find the full well signal value μ that eliminates the image background Sat ;

[0021] μ Sat Indicates the full-well signal value after removing the image background;

[0022] h, in μ y.optical Find 20% μ Sat ≤μ y.optical ≤80%μ Sat The grayscale mean μ of the light field image in the interval ideal , the corresponding exposure time and μ ideal Record the exposure time as the horizontal axis and μ ideal The data is fitted using the least squares method, and the linear slope k and intercept b of the fitting curve are extracted. For each group of exposure time t and light field grayscale mean μ y.optical Perform Linearity calculation, and then find the mean value MeanLinearity of all groups of Linearity data, which is the linearity of the astronomical imaging detector;

[0023] The linearity of a single group Linearity and the linearity of all groups MeanLinearity are calculated according to formula (4) and formula (5):

[0024]

[0025]

[0026] μ ideal Indicates 20%μ Sat ≤μ y.optical ≤80%μ Sat The mean grayscale value of the light field image in the interval, μ y.optical [m][n] represents the grayscale mean of the pixel (m,n) position in 20 frames of images under the selected light field exposure time, μ y.opticalrepresents the grayscale mean of all pixel positions excluding the background under the selected light field exposure time, k and b represent the slope and intercept of the linear region of the least squares fitting curve, i=1, 2, ..., 20 represents the order of 20 light field exposure times, Linearity represents the linearity under the selected light field exposure time, MeanLinearity represents the mean of the linearity under the 20 light field exposure times, that is, the linearity of the astronomical imaging detector.

[0027] The present invention combines the ideas and shortcomings of existing linearity test methods, considers the impact of space cumulative radiation damage on astronomical imaging detectors, makes the linearity test more detailed, and simplifies the linearity test steps. This method can not only improve the accuracy of light field image data analysis, but also effectively shorten the test time and reduce the impact of background noise and voltage bias on linearity parameter testing, reduce the error of linearity testing, and provide a basic data testing method for reliability evaluation of space astronomical telescopes.

[0028] The present invention provides a method for testing the linearity of an astronomical imaging detector after irradiation, which comprises a linearity testing system for the astronomical imaging detector after irradiation, which is composed of an integrating sphere light source, a three-dimensional sample adjustment table, a sample testing board, a power supply, and a computer placed on an electrostatic test platform. The exposure time range of the astronomical imaging detector in the system can be controlled by a computer. The specific steps are as follows:

[0029] a. According to the actual on-orbit working environment of the astronomical imaging detector and its typical proton irradiation dose, the actual irradiation parameters are determined, and proton irradiation tests of the astronomical imaging detector under different cumulative injection doses are carried out;

[0030] b. Fix the irradiated sample (5) on the sample test board (4), and then connect the sample test board (4) to the DC power supply (6) and the computer (7) respectively, and start the dark field test. During the dark field test, the integrating sphere light source (2) and other lighting sources in the test room need to be turned off, and the astronomical imaging detector sample (5) is covered with a light-proof black box cover;

[0031] c. adjusting the exposure time of the astronomical imaging detector sample (5) on the sample test plate (4) through a computer (7), selecting a zero exposure time, and collecting 20 frames of grayscale images, and saving the collected zero exposure time images;

[0032] d. Put the 20 frames of grayscale images at the dark field zero exposure time point in c into a three-dimensional matrix, and then extract the grayscale value of each pixel one by one based on the pixel positioning, and calculate the grayscale mean value of each pixel corresponding to the position of the 20 frames of images according to the pixel position, that is, μ y.biasdark [m][n], so that a frame of grayscale image containing the grayscale mean value of each pixel corresponding to the position can be obtained and used as the background;

[0033] The grayscale mean μ of each pixel at the corresponding position of the background 20 frames of images y.biasdark [m][n] is calculated according to formula (1):

[0034]

[0035] y d.1 [m][n]、y d.2 [m][n], ..., y d.20 [m][n], where m and n represent the pixel position of a certain gray value (1≤m≤M,1≤n≤N, m,n,M,N are the total number of pixel rows and columns, all of which are positive integers), y d.q [m][n] represents the grayscale value of the pixel (m, n), the subscripts dark and d represent the dark field, the subscripts q = 1, 2, ..., 20 represent the sequence of 20 frames of images, the subscript bias represents the background, μ y.biasdark [m][n] represents the grayscale mean of the pixel (m,n) at the position of the background 20 frames;

[0036] e. Take out the black box, turn on the integrating sphere light source, select a fixed irradiance, and start the light field test. Use the computer (7) to adjust the exposure time of the astronomical imaging detector sample (5) on the sample test board (4). Start from zero exposure time, and limit the pixel potential well to be exactly full well (the maximum grayscale mean of the image output by the detector with exposure time is the full well signal value). Select 20 exposure time points at equal intervals, and start collecting images from the zero exposure time of the detector. Collect 20 frames of grayscale images at each exposure time point, and save the collected images according to the exposure time.

[0037] f. Select the first exposure time point, put the 20 frames of grayscale images collected at this exposure time point into a three-dimensional matrix, extract the grayscale value of each pixel based on pixel positioning, and then calculate the corresponding position y of each pixel in the 20 frames of images according to the pixel position. o.q [m][n] minus μ y.biasdark The grayscale mean of [m][n] is used to obtain μ corresponding to each exposure time. y.optical [m][n], so that we can get a light field grayscale image of the grayscale mean of each pixel corresponding to a frame without the background, and calculate the grayscale mean of all pixel positions in this frame, that is, μ y.optical , which is taken as the grayscale mean value under this light field exposure time;

[0038] The corresponding position y of each pixel in the 20 frames of light field images o.q [m][n] minus μ y.biasdark The grayscale mean μ of [m][n] y.optical [m][n] and the grayscale mean μ of all pixel positions in the background-removed framey.optical Calculate according to formula (2) and formula (3):

[0039]

[0040]

[0041] y optical.1 [m][n]、y optical.2 [m][n], ..., y optical.20 [m][n], where m and n represent the pixel position of a certain gray value 1≤m≤M,1≤n≤N,m,n,M,N are the total number of pixel rows and columns, which are all positive integers, y optical.q [m][n] represents the grayscale value of the pixel (m, n). The subscripts dark and d represent the dark field, optical represents the light field, the subscript q = 1, 2, ..., 20 represents the sequence number of the 20 frames, the subscript bias represents the background, μ y.biasdark [m][n] represents the grayscale mean of the pixel (m,n) at the position of the background 20 frames, μ y.optical [m][n] represents the grayscale mean of the pixel (m,n) position in 20 frames of images under the selected light field exposure time, μ y.optical It represents the grayscale mean of all pixel positions excluding the background under the selected light field exposure time;

[0042] g. Repeat step f to calculate μ for all 20 light field exposure times. y.optical [m][n] and μ y.optical , the grayscale mean μ of the image background removed at each exposure time of the 20 light field exposure time points y.optical Record and find the full well signal value μ that eliminates the image background Sat ;

[0043] μ Sat Indicates the full-well signal value after removing the image background;

[0044] h, in μ y.optical Find 20% μ Sat ≤μ y.optical ≤80%μ Sat The grayscale mean μ of the light field image in the interval ideal , the corresponding exposure time and μ ideal Record the exposure time as the horizontal axis and μ ideal The data is fitted using the least squares method, and the linear slope k and intercept b of the fitting curve are extracted. For each group of exposure time t and light field grayscale mean μ y.opticalPerform Linearity calculation, and then find the mean value MeanLinearity of all groups of Linearity data, which is the linearity of the astronomical imaging detector;

[0045] The linearity of a single group Linearity and the linearity of all groups MeanLinearity are calculated according to formula (4) and formula (5):

[0046]

[0047]

[0048] μ ideal Indicates 20%μ Sat ≤μ y.optical ≤80%μ Sat The mean grayscale value of the light field image in the interval, μ y.optical [m][n] represents the grayscale mean of the pixel (m,n) position in 20 frames of images under the selected light field exposure time, μ y.optical represents the grayscale mean of all pixel positions excluding the background under the selected light field exposure time, k and b represent the slope and intercept of the linear region of the least squares fitting curve, i=1, 2, ..., 20 represents the order of 20 light field exposure times, Linearity represents the linearity under the selected light field exposure time, MeanLinearity represents the mean of the linearity under the 20 light field exposure times, that is, the linearity of the astronomical imaging detector.

[0049] Beneficial effects of the present invention: The present invention provides a method for testing the linearity of an astronomical imaging detector after irradiation. By considering the impact of space cumulative radiation damage on the astronomical imaging detector, the method makes the linearity test more detailed and simplifies the linearity test steps. The method can not only improve the accuracy of the analysis of light field image data, but also effectively shorten the test time and reduce the impact of background noise and voltage bias on linearity parameter testing, thereby reducing the error of linearity testing.

[0050] The method for testing the linearity of an astronomical imaging detector after irradiation described in the present invention can not only accurately test the linearity of the astronomical imaging detector after irradiation, improve the test accuracy of the linearity of the astronomical imaging detection after irradiation, but also solve the problems of the EMVA1288 standard having more steps, longer test time, and not taking the influence of background noise and voltage bias on the linearity test into account, thereby reducing the error of the linearity test. The method of the present invention is applicable to a variety of astronomical imaging detectors, and has the advantages of convenient testing, small error, fast speed, strong practicality, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the test system of the present invention;

[0052] Figure 2 It is a schematic diagram of the process of the present invention;

[0053] Figure 3 It is a background image collected before irradiation of astronomical imaging detectors;

[0054] Figure 4 It is the background image collected after irradiation of the astronomical imaging detector;

[0055] Figure 5 It is the least squares fitting result of the light field image grayscale mean and exposure time in the range of 20%-80% full well signal value after irradiation in the light field test after removing the image background. DETAILED DESCRIPTION

[0056] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0057] Example

[0058] The present invention discloses a method for testing the linearity of an astronomical imaging detector after irradiation. The method involves a device consisting of an electrostatic test platform, an integrating sphere light source, a three-dimensional sample adjustment platform, a sample test board, an astronomical imaging detector sample, a DC power supply and a computer. An integrating sphere light source 2 and a three-dimensional sample adjustment platform 3 are respectively provided on the electrostatic test platform 1, a sample test board 4 is fixed on the three-dimensional sample adjustment platform 3, an astronomical imaging detector sample 5 is placed on the sample test board 4, the sample test board 4 is connected to a DC power supply 6, and the electrostatic test platform 1 is connected to a computer 7. The connection method is shown in the attached Figure 1 , the implementation process is attached Figure 2 , the specific operation is as follows:

[0059] a. Use a CMOS astronomical imaging detector with a pixel specification of 2048*2048 of model GSENSE2020BSI, select the proton irradiation parameters shown in Table 1, and conduct a proton irradiation test;

[0060] Table 1 shows the proton irradiation test parameters.

[0061]

[0062] b. Before the test, first insert the astronomical imaging detector sample 5 into the sample test board 4 (whose model is vesion2.0), then fix the sample 5 with the zero insertion force socket on the sample test board 4, and then connect the sample test board 4 to the DC power supply 6 and the computer 7 respectively. After the connection, set the two channels of the DC power supply to 1 channel +12V and 2 channels +12V and share the two channels. Set the normal working current of the sample test board 4 under 1 channel +12V to 600mA to 700mA, and the current limit is set to 2A at this time; the normal working current of the sample test board 4 under 2 channels +12V is 2A. The current limit is set to 2A at 10mA to 400mA. The timing and configuration parameters of the sample test board 4 are provided by Changchun Changguang Chenxin Optoelectronics Technology Co., Ltd. In this test, the timing of the high dynamic range mode and the default configuration parameters in this mode are used. Before the parameter test, the computer 7 needs to set the number of image acquisition frames in the test software to 20. After the DC power supply 6 and the computer setting 7 are set, the dark field test is started. During the test, the integrating sphere light source 2 needs to be turned off, and other lighting sources in the test room are turned off at the same time, and the astronomical imaging detector sample 5 is covered with a light-proof black box cover.

[0063] c. During the dark field test, the ambient temperature is set to 25°C and the humidity is set to 30% RH. The exposure time of the astronomical imaging detector sample 5 on the sample test plate 4 is adjusted by the computer 7. The zero exposure time is selected, and 20 frames of grayscale images are collected. The collected zero exposure time images are saved;

[0064] d. Put the 20 frames of grayscale images at the dark field zero exposure time point in c into a three-dimensional matrix, and then extract the grayscale value of each pixel one by one based on the pixel positioning, and calculate the grayscale mean value of each pixel corresponding to the position of the 20 frames of images according to the pixel position, that is, μ y.biasdark [m][n], so that a frame of grayscale image containing the grayscale mean value of each pixel corresponding to the position can be obtained and used as the background;

[0065] The grayscale mean μ of each pixel at the corresponding position of the background 20 frames of images y.biasdark [m][n] is calculated according to formula (1):

[0066]

[0067] y d.1 [m][n]、y d，2 [m][n], ..., y d.20 [m][n], where m and n represent the pixel position of a certain gray value (1≤m≤M, 1≤n≤N, m, n, M, N are the total number of pixel rows and columns, all of which are positive integers), y d.q[m][n] represents the grayscale value of the pixel (m, n), the subscripts dark and d represent the dark field, the subscripts q=1, 2, ..., 20 represent the sequence of 20 frames of images, the subscript bias represents the background, μ y.biasdark [m][n] represents the grayscale mean of the pixel (m, n) at the position of the background 20 frames;

[0068] e. During the light field test, the light source maintains the same ambient temperature and humidity as the dark field, turns on the integrating sphere light source, and selects a fixed irradiance of 0.00908W / m 2 / Sr, take out the black box, the sample test plate 4 needs to be adjusted in the X, Y, and Z directions through the three-dimensional sample adjustment table 3, so that it is 5 cm away from the integrating sphere light source 2, and the sample 5 on the sample test plate 4 is directly opposite to the light outlet of the integrating sphere light source and aligned with the edge of the light outlet, and the exposure time of the astronomical imaging detector sample 5 on the sample test plate 4 is adjusted by the computer 7, the exposure time range is 0 to 106.4080ms, and 20 exposure time points are selected at equal intervals within the exposure time range, as shown in the first column of Table 2, and images are collected starting from the zero exposure time of the detector, and 20 frames of grayscale images are collected at each exposure time point, and the collected images are saved respectively according to the exposure time;

[0069] Table 2 shows the test results of the light field grayscale mean after astronomical imaging detector irradiation and background removal

[0070] Exptime(s) Signal(ADU) 0.00000804 0.058751189 0.00560804 445.5911935 0.01120804 893.476595 0.01680804 1306.356992 0.02240804 1665.083675 0.02800804 1978.113429 0.03360804 2253.352593 0.03920804 2480.631678 0.04480804 2695.597622 0.05040804 2892.084844 0.05600804 3062.611071 0.06160804 3203.605683 0.06720804 3350.646397 0.07280804 3474.797415 0.07840804 3568.125489 0.08400804 3657.819782 0.08960804 3730.186133 0.09520804 3789.608375 0.10080804 3830.617838 0.10640804 3860.034925

[0071] f. Select the first exposure time point, put the 20 frames of grayscale images collected at this exposure time point into a three-dimensional matrix, extract the grayscale value of each pixel based on pixel positioning, and then calculate the corresponding position y of each pixel in the 20 frames of images according to the pixel position. o.q [m][n] minus μ y.biasdark The grayscale mean of [m][n] is used to obtain μ corresponding to each exposure time. y.optical [m][n], so that we can get a light field grayscale image of the grayscale mean of each pixel corresponding to a frame without the background, and calculate the grayscale mean of all pixel positions in this frame, that is, μ y.optical , which is taken as the grayscale mean value under this light field exposure time;

[0072] The corresponding position y of each pixel in the 20 frames of light field images o.q [m][n] minus μ y.biasdark The grayscale mean μ of [m][n] y.optical [m][n] and the grayscale mean μ of all pixel positions in the background-removed frame y.optical Calculate according to formula (2) and formula (3):

[0073]

[0074] y optical.1 [m][n]、y optical.2 [m][n], ..., y optical.20 [m][n], where m and n represent the pixel position of a certain gray value 1≤m≤M,1≤n≤N,m,n,M,N are the total number of pixel rows and columns, which are all positive integers, y optical.q [m][n] represents the grayscale value of the pixel (m, n). The subscripts dark and d represent the dark field, optical represents the light field, the subscript q = 1, 2, ..., 20 represents the sequence number of the 20 frames, the subscript bias represents the background, μ y.biasdark [m][n] represents the grayscale mean of the pixel (m,n) at the position of the background 20 frames, μ y.optical [m][n] represents the grayscale mean of the pixel (m,n) position in 20 frames of images under the selected light field exposure time, μ y.optical It represents the grayscale mean of all pixel positions excluding the background under the selected light field exposure time;

[0075] g. Repeat step f to calculate μ for all 20 light field exposure times. y.optical [m][n] and μ y.optical , the grayscale mean μ of the image background removed at each exposure time of the 20 light field exposure time points y.optical Record and find the full well signal value μ that eliminates the image background Sat ;

[0076] μ Sat It represents the full well signal value after removing the image background. From Table 2, we can know that μ Sat 3860ADU;

[0077] The calculated cumulative injection volume is 3.36×10 10 p / cm 2 The grayscale mean μ of all pixel positions of the light field with different exposure times after removing the background y.optical , the results are shown in the second column of Table 2;

[0078] h, in μ y.optical Find 20% μ Sat ≤μ y.optical ≤80%μ Sat The grayscale mean μ of the light field image in the interval ideal , the corresponding exposure time and μ ideal Record the exposure time as the horizontal axis and μ ideal The data is fitted using the least squares method, and the linear slope k and intercept b of the fitting curve are extracted. For each group of exposure time t and light field grayscale mean μ y.opticalPerform Linearity calculation, and then find the mean value MeanLinearity of all groups of Linearity data, which is the linearity of the astronomical imaging detector;

[0079] The linearity of a single group Linearity and the linearity of all groups MeanLinearity are calculated according to formula (4) and formula (5):

[0080]

[0081]

[0082] μ ideal Indicates 20%μ Sat ≤μ y.optical ≤80%μ Sat The mean grayscale value of the light field image in the interval, μ y.optical [m][n] represents the grayscale mean of the pixel (m,n) position in 20 frames of images under the selected light field exposure time, μ y.optical represents the grayscale mean of all pixel positions excluding the background under the selected light field exposure time, k and b represent the slope and intercept of the linear region of the least squares fitting curve, i=1, 2, ..., 20 represents the order of 20 light field exposure times, Linearity represents the linearity under the selected light field exposure time, MeanLinearity represents the mean of the linearity under the 20 light field exposure times, that is, the linearity of the astronomical imaging detector;

[0083] With exposure time as the horizontal axis, μ ideal The vertical axis is the curve fitted by the least square method. Figure 5 As shown, μ ideal The data are shown in column 2 of Table 3;

[0084] Table 3 shows the 20% μ of the background after irradiation Sat ≤μ y.optical ≤80%μ Sat The test results of the grayscale mean of the light field image within;

[0085] S-Exptime(s) S-Signal(ADU) 0.01120804 893.476595 0.01680804 1306.356992 0.02240804 1665.083675 0.02800804 1978.113429 0.03360804 2253.352593 0.03920804 2480.631678 0.04480804 2695.597622 0.05040804 2892.084844 0.05600804 3062.611071

[0086] 20%μ Sat ≤μ y.optical ≤80%μ Sat The calculation results of Linearity of each group of exposure time in the interval are shown in the second column of Table 4;

[0087] Table 4 is 20%μ Sat ≤μ y.optical ≤80%μ SatThe test results of Linearity for each exposure time group within the interval

[0088] S-Exptime(s) Linearity 0.01120804 83.5116％ 0.01680804 97.7443％ 0.02240804 96.1352％ 0.02800804 94.2042％ 0.03360804 94.5241％ 0.03920804 96.7689％ 0.04480804 99.0265％ 0.05040804 98.4965％ 0.05600804 95.6214％ MeanLinearity 95.1147％

[0089] From the second column of Table 4, it can be concluded that the MeanLinearity is 95.1147%, that is, the linearity of the astronomical imaging detector is 95.1147%.

[0090] The above is only a specific implementation of the method for testing the linearity of an astronomical imaging detector after irradiation described in the present invention, but the protection scope of the present invention is not limited to this. Any replacement or addition or reduction that can be understood by anyone familiar with the technology within the technical scope disclosed by the present invention should be included in the scope of the present invention.

Claims

1. A method for testing the linearity of an astronomical imaging detector after irradiation, characterized in that: The method involves a device comprising an electrostatic test platform, an integrating sphere light source, a three-dimensional sample adjustment platform, a sample test board, an astronomical imaging detector sample, a direct current power supply and a computer. An integrating sphere light source (2) and a three-dimensional sample adjustment platform (3) are respectively arranged on the electrostatic test platform (1), a sample test board (4) is fixed on the three-dimensional sample adjustment platform (3), an astronomical imaging detector sample (5) is placed on the sample test board (4), the sample test board (4) is connected to a direct current power supply (6), and the electrostatic test platform (1) is connected to a computer (7). The specific operation is performed according to the following steps: a. According to the actual on-orbit working environment of the astronomical imaging detector and its typical proton irradiation dose, the actual irradiation parameters are determined, and proton irradiation tests of the astronomical imaging detector under different cumulative injection doses are carried out; b. Fixing the irradiated astronomical imaging detector sample (5) on the sample test board (4), and then connecting the sample test board (4) to the DC power supply (6) and the computer (7) respectively, and starting the dark field test. During the dark field test, the integrating sphere light source (2) and other lighting sources in the test room need to be turned off, and the astronomical imaging detector sample (5) is covered with a light-proof black box cover; c. adjusting the exposure time of the astronomical imaging detector sample (5) on the sample test plate (4) through a computer (7), selecting a zero exposure time, and collecting 20 frames of grayscale images, and saving the collected zero exposure time images; d. Put the 20 frames of grayscale images at the dark field zero exposure time point in step c into a three-dimensional matrix, and then extract the grayscale value of each pixel one by one based on the pixel positioning, and calculate the grayscale mean value of each pixel corresponding to the position of the 20 frames of images according to the pixel position, that is, μ y.biasdark [m][n], a grayscale image containing the grayscale mean of each pixel at the corresponding position is obtained and used as the background; The grayscale mean μ of each pixel at the corresponding position of the background 20 frames of images y.biasdark [m][n] is calculated according to formula (1): y d.1 [m][n]、y d.2 [m][n], ..., y d.20 [m][n], where m and n represent the pixel position of a certain gray value 1≤m≤M,1≤n≤N,m,n,M,N are the total number of pixel rows and columns, which are all positive integers, y d.q [m][n] represents the grayscale value of the pixel (m, n), the subscripts dark and d represent the dark field, the subscripts q = 1, 2, ..., 20 represent the sequence of 20 frames of images, the subscript bias represents the background, μ y.biasdark [m][n] represents the grayscale mean of the pixel (m,n) at the position of the background 20 frames; e. Take out the black box, turn on the integrating sphere light source, select a fixed irradiance, and start the light field test. Use the computer (7) to adjust the exposure time of the astronomical imaging detector sample (5) on the sample test board (4). Start from zero exposure time, and limit the pixel potential well to be exactly full well. The maximum grayscale mean value of the image output by the detector with the exposure time is the full well signal value. Select 20 exposure time points at equal intervals, start collecting images from the zero exposure time of the detector, collect 20 frames of grayscale images at each exposure time point, and save the collected images according to the exposure time; f. Select the first exposure time point, put the collected 20 frames of grayscale images into a three-dimensional matrix, extract the grayscale value of each pixel based on pixel positioning, and then calculate the corresponding position y of each pixel in the 20 frames of images according to the pixel position. o.q [m][n] minus μ y.biasdark The grayscale mean of [m][n] is used to obtain μ corresponding to each exposure time. y.optical [m][n], obtain the light field grayscale image of each pixel corresponding to a frame without background, and calculate the grayscale mean of all pixel positions in this frame, that is, μ y.optical , and use it as the grayscale mean value under this light field exposure time; The corresponding position y of each pixel in the 20 frames of light field images o.q [m][n] minus μ y.biasdark The grayscale mean μ of [m][n] y.optical [m][n] and the grayscale mean μ of all pixel positions in the background-removed frame y.optical Calculate according to formula (2) and formula (3): y optical.1 [m][n]、y optical.2 [m][n], ..., y optical.20 [m][n], where m and n represent the pixel position of a certain gray value 1≤m≤M,1≤n≤N,m,n,M,N are the total number of pixel rows and columns, which are all positive integers, y optical.q [m][n] represents the grayscale value of the pixel (m,n). The subscripts dark and d represent the dark field, optical represents the light field, and q =1, 2, ..., 20 represents the sequence number of 20 frames of images, the subscript bias represents the background, μ y.biasdark [m][n] represents the grayscale mean of the pixel (m,n) at the position of the background 20 frames, μ y.optical [m][n] represents the grayscale mean of the pixel (m,n) position in 20 frames of images under the selected light field exposure time, μ y.optical It represents the grayscale mean of all pixel positions excluding the background under the selected light field exposure time; g. Repeat step f to calculate μ for all 20 light field exposure times. y.optical [m][n] and μ y.optical , the grayscale mean μ of the image background removed at each exposure time of the 20 light field exposure time points y.optical Record and find the full well signal value μ that eliminates the image background Sat ; μ Sat Indicates the full-well signal value after removing the image background; h, in μ y.optical Find 20% μ Sat ≤μ y.optical ≤80%μ Sat The grayscale mean μ of the light field image in the interval ideal , the corresponding exposure time and μ ideal Record the exposure time as the horizontal axis and μ ideal The data is fitted using the least squares method, and the linear slope k and intercept b of the fitting curve are extracted. For each group of exposure time t and light field grayscale mean μ y.optical Perform Linearity calculation, and then find the mean value MeanLinearity of all groups of Linearity data, which is the linearity of the astronomical imaging detector; The linearity of a single group Linearity and the linearity of all groups MeanLinearity are calculated according to formula (4) and formula (5): μ ideal Indicates 20%μ Sat ≤μ y.optical ≤80%μ Sat The mean grayscale value of the light field image in the interval, μ y.optical [m][n] represents the grayscale mean of the pixel (m,n) position in 20 frames of images under the selected light field exposure time, μ y.optical represents the grayscale mean of all pixel positions excluding the background under the selected light field exposure time, k and b represent the slope and intercept of the linear region of the least squares fitting curve, i=1, 2, ..., 20 represents the order of 20 light field exposure times, Linearity represents the linearity under the selected light field exposure time, MeanLinearity represents the mean of the linearity under the 20 light field exposure times, that is, the linearity of the astronomical imaging detector.

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