A low-illumination calibration device and test method for spatial point targets

Abstract

The present invention discloses a low-illuminance calibration device and a test method for spatial point targets, which solves the problem of how to improve the photometric detection ability of spatial optoelectronic devices for spatial low-illuminance point targets; it belongs to the field of optoelectronic detection; it includes: removing background noise data, selecting a star point target board and a light attenuation sheet to simulate the actual measurement state of spatial low-illuminance point targets; using the annular region method to estimate the gray value of the point target, and fitting the calibration coefficient with the true calibration beam illuminance value to obtain a point target calibration model; adjusting the illuminance of the light source and replacing the star point target board, and inversely calculating the theoretical calibration beam illuminance value through the point target calibration model to obtain a stable calibration coefficient and optimize the point target calibration model, obtaining the photometric measurement deviation of point targets with different photometric magnitudes and imaging sizes, and verifying the low-illuminance calibration test accuracy of spatial point targets; the present invention reduces measurement errors and obtains high-precision calibration coefficients and reliable photometric quantitative measurement capabilities.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic detection, and relates to a low-illumination calibration device and a test method for space point targets. Background Technique

[0002] To deeply understand and master the state and changes of space targets, it is particularly important to carry out space target detection and recognition. The effective information that can be extracted from space targets mainly includes characteristic parameters such as target size, shape, orbital parameters, attitude changes, luminosity, spectrum, and scattering characteristics. Traditional space target detection and recognition mostly use ground-based optical telescopes, radars and other equipment. The ground-based observation method is technically mature and low-cost, but it is easily restricted by factors such as weather and geographical location. The space-based observation method has the advantages of a large observation range, all-weather operation, and no need for global station deployment, and has been widely and deeply studied at home and abroad. The space environment of space-based observation is mostly a low-temperature, black space background and dense bright spot targets. Through reasonable planning, the optical characteristic information of the concerned targets can be effectively extracted.

[0003] Limited by the space orbit, in actual space-based observation, space targets such as satellites mostly appear as points. Moreover, due to factors such as long distance, attitude changes, and solar phase angle, the luminosity information of the targets is weak and non-constant. To realize the model identification, cataloging, and attitude change detection of space targets, it is required to carry an optoelectronic device with high sensitivity and quantitative test ability, especially an optoelectronic device with quantitative test ability under low-illumination conditions.

[0004] To ensure the quantitative detection ability of optoelectronic devices, it is first necessary to carry out ground radiation calibration tests. The mainstream ground extended surface element radiation calibration method focuses on the global response ability and uniformity of optoelectronic devices, and is generally mainly applicable to remote sensing quantitative applications in large-scale scenes. However, in space-based observation, the vast majority of scenes are space targets observed at a distance of hundreds of kilometers. At the same time, compared with radiation calibration based on brightness, radiation calibration based on illuminance does not require precise measurement of the divergence solid angle of the collimator, the process is simple, and less error is introduced. Therefore, carrying out space point target simulation, low-illumination calibration and detection ability test is of great significance for improving the application ability of space-based optoelectronic devices. Summary of the Invention

[0005] To solve the technical problem of how to improve the photometric detection ability of optoelectronic devices for low-illuminance point targets in space, the present invention proposes a low-illuminance calibration device and test method for space point targets. By simulating the imaging of space point targets, using the irradiance of the light source system as the test object, and the method of fixed-ratio attenuation spectroscopy, it can perform low-illuminance calibration tests on the optoelectronic device to be tested. At the same time, by establishing the relationship between the target magnitude and the gray value DN of the point target through an optimized point target calibration model, it can reduce measurement error factors, and finally obtain high-precision calibration coefficients and reliable photometric quantitative measurement capabilities. The present invention can be applied to fields such as star sensor design, space target detection, and magnitude measurement.

[0006] The object of the present invention is specifically realized through the following technical solutions:

[0007] The present invention discloses a low-illuminance calibration test method for space point targets, including:

[0008] Step 1: Adjust the optical axis of the collimator to be parallel to that of the optoelectronic device to be tested placed in the darkroom, and confirm that the outgoing light of the collimator covers the entire aperture of the optoelectronic device to be tested; place a beam splitter on the parallel optical axis of the collimator and the optoelectronic device to be tested, and use the beam splitter to divide the outgoing light of the collimator into a calibration beam and a test beam; place an optical attenuator on the calibration beam optical path between the optoelectronic device to be tested and the beam splitter to obtain the relationship function between the test beam illuminance value and the light source system brightness value, and the relationship function between the test beam illuminance value and the calibration beam illuminance value;

[0009] Step 2: Set the initial state of calibration data acquisition according to the dynamic range of the optoelectronic device to be tested, collect and store the output signal of the optoelectronic device to be tested when there is no radiation input from the light source system as the background noise data;

[0010] Step 3: After removing the background noise data, select a star point target plate corresponding to the clear aperture, place it between the beam splitter and the collimator to simulate a space point target, select an optical attenuator to simulate a space weak point target, and make the imaging size of the detector in the optoelectronic device to be tested less than 80 pixels; place a micro-illuminometer on the test beam optical path, and the micro-illuminometer records the real test beam illuminance value, and obtain the real calibration beam illuminance value based on the relationship function between the test beam illuminance value and the calibration beam illuminance value;

[0011] Use a two-dimensional Gaussian distribution template to determine the center of the point target, and combine the center of the point target to estimate the gray value of the point target by the annular region method; use multiple groups of gray values of the point target and the real calibration beam illuminance value to fit the calibration coefficient of the optoelectronic device to be tested to obtain a point target calibration model;

[0012] Step 4: Adjust the exposure time and reduce the brightness value of the light source system until the detector no longer responds, obtain the extreme brightness value of the light source system, and acquire and record the output image of the optoelectronic device under test, the true illumination value of the test light beam recorded by the micro-illuminometer, the true illumination value of the calibration light beam, and the illumination value of the light beam emitted by the collimator;

[0013] Step 5: Adjust the brightness value of the light source system within the range of the extreme brightness value of the light source system, so that the true illumination value of the calibration light beam varies within a preset range, and convert it into the true magnitude of the calibration light beam through the conversion equation; at the same time, obtain multiple groups of point target gray values, and inversely calculate multiple groups of theoretical illumination values of the calibration light beam from the multiple groups of point target gray values through the point target calibration model, and convert them into the theoretical magnitude of the calibration light beam through the conversion equation; calculate the difference between the theoretical magnitude of the calibration light beam and the true magnitude of the calibration light beam to obtain the photometric measurement deviation of point targets with different photometric magnitudes;

[0014] Step 6: Swap the light passing aperture of the star point target board, change the imaging size on the image plane, and repeat Step 5 until the average value of the photometric measurement deviations of point targets with different photometric magnitudes is less than the threshold, obtain the stable calibration coefficient, optimize the point target calibration model through the stable calibration coefficient, and calculate the difference between the theoretical magnitude of the calibration light beam and the true magnitude of the calibration light beam under the optimized point target calibration model to obtain the photometric measurement deviations of point targets with different photometric magnitudes and different imaging sizes;

[0015] Step 7: Verify the low-illumination calibration test accuracy of spatial point targets through the photometric measurement deviations of point targets with different photometric magnitudes and different imaging sizes.

[0016] In Step 1, the relationship function between the illumination value of the test light beam and the brightness value of the light source system is:

[0017]

[0018] where E coll is the true illumination value of the test light beam, d0 is the light passing aperture of the star point target board, f is the focal length of the optoelectronic device under test, L0 is the brightness value of the light source system, and τ coll is the transmittance of the collimator;

[0019] The relationship function between the illumination value of the test light beam and the illumination value of the calibration light beam is:

[0020] E cal = E coll ·δ·β;

[0021] In the formula, E cal is the true illumination value of the calibration light beam, E coll is the true illumination value of the test light beam, δ is the attenuation coefficient of the optical attenuator, and β is the splitting ratio of the beam splitter.

[0022] In step two, the output signal V of the optoelectronic device under test when there is no radiation input from the light source system is collected and stored as follows:

[0023] V = Φ·R V ;

[0024] Φ = E e0 ·A0;

[0025] where Φ is the luminous flux incident on the optoelectronic device under test, R V is the responsivity of the optoelectronic device under test, A0 is the entrance pupil area of the optoelectronic device under test, and E e0 is the entrance pupil illuminance of the optoelectronic device under test, that is, the true calibration beam illuminance value.

[0026] In step three, the calculation method for determining the center of the point target using a two-dimensional Gaussian distribution template is as follows:

[0027]

[0028] where G(x, y) is the gray-scale distribution of the point target, that is, the gray-scale value of any pixel point, B is the background gray-scale value, H is the difference between the gray-scale peak value of the point target area and the background gray-scale value, (x, y) is any point in the point target area of the image, (x0, y0) is the center of the point target, and R is the pixel radius of the point target area.

[0029] In step three, the method for estimating the gray-scale value of the point target using the annular region method based on the center of the point target is as follows:

[0030] Based on the center of the point target, a circular initial area of the point target is set as r = 3 pixels;

[0031] The circular initial area of the point target is evenly divided into four regions in the horizontal and vertical directions, and the gray-scale standard deviation and average value of each region are calculated respectively;

[0032] r is expanded with a step size of 1 pixel each time and the gray-scale standard deviation and average value of the four expanded regions are continuously solved until the gray-scale standard deviation reaches the peak value. At this time, the corresponding r range is the point target area;

[0033] The average background gray-scale value in the region outside the point target area is removed, which is the gray-scale value of the point target.

[0034] In step three, the point target calibration model is:

[0035] E = a4·DN 4 + a3·DN 3 + a2·DN 2 + a1·DN + a0;

[0036] Wherein, E is the actual calibration beam illuminance value or the theoretically inverted calibration beam illuminance value, a0, a1, a2, a3, and a4 are calibration coefficients fitted using a fourth-order nonlinear model, and DN is the gray value of the point target.

[0037] In step five, the conversion equation is:

[0038]

[0039] Wherein, M' is the magnitude of the calibration beam, E obj is the calibration beam illuminance value, and E0 is the calibration beam illuminance value corresponding to the zero magnitude.

[0040] Furthermore, the calculation method of the photometric measurement deviation ΔM of the point target includes:

[0041] ΔM = M - M0;

[0042] Wherein, M is the theoretical calibration beam magnitude, and M0 is the actual calibration beam magnitude corresponding to M.

[0043] In step six, the optimized point target calibration model is:

[0044] DN = 28.337M 4 -718.21M 3 +6789.1M 2 -28528M + 48921;

[0045] Wherein, DN is the gray value of the point target, and M is the theoretical calibration beam magnitude.

[0046] The present invention also provides a low-illuminance calibration device for spatial point targets, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the low-illuminance calibration test method for spatial point targets are implemented.

[0047] The beneficial effects of the present invention are:

[0048] By adopting the method of simulating the imaging of spatial point targets, using the irradiance of the light source system as the test object, and attenuating and splitting the light in a fixed ratio, the present invention can perform low-illuminance calibration tests on the optoelectronic device to be tested. At the same time, by establishing the relationship between the target magnitude and the gray value DN of the point target through the optimized point target calibration model, the measurement error factors can be reduced, and finally, high-precision calibration coefficients and reliable photometric quantitative measurement capabilities under low-illuminance conditions can be obtained.

[0049] Since the targets in space - based observation conditions are generally at a relatively long distance and their shapes are generally point - like, the combination method of "light - attenuation sheet + beam splitter" disclosed in the present invention can ensure the measurement accuracy under low - illumination conditions through the test beam measured by a micro - illuminance meter. At the same time, it can simulate and calculate the calibration parameter characteristics of the optoelectronic device to be measured under different imaging sizes and different photometric states of the point target, ensuring the accuracy in space - based measurement and providing a reliable solution for the high - precision calibration of space - based observation cameras. Brief Description of the Drawings

[0050] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0051] Figure 1 It is a schematic diagram of a space point - target low - illumination calibration device adopted by a space point - target low - illumination calibration test method. Detailed Embodiment

[0052] As Figure 1 shown, the embodiment of the present invention provides a space point - target low - illumination calibration test method, including:

[0053] Step 1: Adjust the optical axis of the collimator to be parallel to the optical axis of the optoelectronic device to be measured placed in the darkroom, and confirm that the outgoing light of the collimator covers the entire aperture of the optoelectronic device to be measured; Place a beam splitter on the parallel optical axis of the collimator and the optoelectronic device to be measured, and use the beam splitter to divide the outgoing light of the collimator into a calibration beam and a test beam; Place a light - attenuation sheet on the calibration - beam optical path between the optoelectronic device to be measured and the beam splitter to obtain the relationship function between the test - beam illuminance value and the light - source - system brightness value and the relationship function between the test - beam illuminance value and the calibration - beam illuminance value.

[0054] Step 2: Set the initial state of calibration - data acquisition according to the dynamic range of the optoelectronic device to be measured, collect and store the output signal of the optoelectronic device to be measured when there is no radiation input from the light - source system as the background - noise data.

[0055] Step 3: After removing the background - noise data, select a star - point target board corresponding to the through - light aperture, place it between the beam splitter and the collimator to simulate a space point target, select a light - attenuation sheet (preferably an OD3 light - attenuation sheet) to simulate a space dim - weak point target, make the imaging size of the detector in the optoelectronic device to be measured less than 80 pixels to simulate the measured state of a space low - illumination point target; Place a micro - illuminance meter on the test - beam optical path, the micro - illuminance meter records the real test - beam illuminance value, and obtain the real calibration - beam illuminance value based on the relationship function between the test - beam illuminance value and the calibration - beam illuminance value.

[0056] Determine the center of the point target using a two-dimensional Gaussian distribution template. Combine the center of the point target and use the annular region method to estimate the gray value of the point target. Fit multiple groups of point target gray values and the true calibration beam illuminance value to obtain the calibration coefficient of the optoelectronic device to be measured, and obtain the point target calibration model.

[0057] Step 4: Adjust the exposure time to reduce the brightness value of the light source system until the detector no longer responds, obtain the extreme brightness value of the light source system, and acquire and record the output image of the optoelectronic device to be measured, the true test beam illuminance value recorded by the micro-illuminometer, the true calibration beam illuminance value, and the exit illuminance value of the collimator.

[0058] Step 5: Adjust the brightness value of the light source system within the extreme brightness value range of the light source system to make the true calibration beam illuminance value vary within a preset range. For example, adjust it between 1Mv and 7Mv, and calculate the effects under different brightness values of the light source system. Convert it to the true calibration beam magnitude through the conversion equation. At the same time, obtain multiple groups of point target gray values. Invert multiple groups of theoretical calibration beam illuminance values from the multiple groups of point target gray values through the point target calibration model, and convert them to the theoretical calibration beam magnitude through the conversion equation. Calculate the difference between the theoretical calibration beam magnitude and the true calibration beam magnitude to obtain the point target photometric measurement deviation of different photometric magnitudes.

[0059] Step 6: Swap the light passing aperture of the star point target board to change the imaging size on the image plane (preferably within the range of 5pixel - 80pixel), and repeat Step 5 until the average value of the point target photometric measurement deviation of different photometric magnitudes is less than the threshold. For example, the average value of ΔM calculated from more than 15 tests is less than 0.1Mv, obtain the stable calibration coefficient, optimize the point target calibration model through the stable calibration coefficient, and calculate the difference between the theoretical calibration beam magnitude and the true calibration beam magnitude under the optimized point target calibration model to obtain the point target photometric measurement deviation of different photometric magnitudes and different imaging sizes.

[0060] Step 7: Verify the low-light calibration test accuracy of the spatial point target through the point target photometric measurement deviation of different photometric magnitudes and different imaging sizes.

[0061] In Step 1, the relationship function between the test beam illuminance value and the brightness value of the light source system is:

[0062]

[0063] where E coll is the true test beam illuminance value, d0 is the light passing aperture of the star point target board, f is the focal length of the optoelectronic device to be measured, L0 is the brightness value of the light source system, and τ coll is the transmittance of the collimator.

[0064] The relationship function between the test beam illuminance value and the calibration beam illuminance value is:

[0065] E cal = E coll ·δ·β;

[0066] In the formula, E cal is the true calibration beam illuminance value, E coll is the true test beam illuminance value, δ is the attenuation coefficient of the optical attenuation sheet, and β is the splitting ratio of the beam splitter.

[0067] In step two, the output signal V of the optoelectronic device under test when there is no radiation input from the light source system is collected and stored as:

[0068] V = Φ·R V ;

[0069] Φ = E e0 ·A0;

[0070] Among them, Φ is the luminous flux incident on the optoelectronic device under test, R V is the responsivity of the optoelectronic device under test, A0 is the entrance pupil area of the optoelectronic device under test, and E e0 is the entrance pupil illuminance of the optoelectronic device under test, that is, the true calibration beam illuminance value.

[0071] In step three, the gray-scale distribution of the point target in the image is a two-dimensional Gaussian distribution. Therefore, the present invention uses a two-dimensional Gaussian distribution template to determine the center of the point target, and the calculation method is:

[0072]

[0073] Among them, G(x, y) is the gray-scale distribution of the point target, that is, the gray-scale value of any pixel point, B is the background gray-scale value, H is the difference between the gray-scale peak value of the point target area and the background gray-scale value, (x, y) is any point in the point target area of the image, (x0, y0) is the center of the point target, and R is the pixel radius of the point target area.

[0074] Theoretically, the star point to be measured is a completely isolated star image. The histogram of the pixel gray scale in the principle star image area is a Gaussian distribution. The detector is the average value of the distribution. A circular area around the target center can be used to estimate the gray scale of the point target. In step three, the method for estimating the gray scale value of the point target using the circular area method according to the center of the point target is:

[0075] According to the center of the point target, set the circular initial area of the point target r = 3 pixels;

[0076] Divide the circular initial area of the point target into four areas in the horizontal and vertical directions, and calculate the gray-scale standard deviation and average value of each area respectively;

[0077] Expand r by a step of 1 pixel each time and continue to solve the gray - scale standard deviation and average value of the four regions after expansion until the gray - scale standard deviation reaches the peak. The corresponding r range at this time is the point - target region;

[0078] Remove the background gray - scale average value in the region outside the point - target region, which is the gray - scale value of the point - target.

[0079] In step three, the point - target calibration model is:

[0080] E=a4·DN 4 +a3·DN 3 +a2·DN 2 +a1·DN+a0;

[0081] In the formula, E is the true calibration beam illuminance value or the theoretically inverted calibration beam illuminance value, a0, a1, a2, a3, a4 are calibration coefficients fitted by a fourth - order non - linear model, and DN is the gray - scale value of the point - target.

[0082] In step five, the conversion equation is:

[0083]

[0084] In the formula, M′ is the magnitude of the calibration beam, E obj is the calibration beam illuminance value, and E0 is the calibration beam illuminance value corresponding to the zero magnitude.

[0085] Among them, the calculation method of the point - target photometric measurement deviation ΔM includes:

[0086] ΔM=M - M0;

[0087] In the formula, M is the theoretical calibration beam magnitude, and M0 is the true calibration beam magnitude corresponding to M.

[0088] In step six, the optimized point - target calibration model is:

[0089] DN=28.337M 4 -718.21M 3 +6789.1M 2 -28528M + 48921;

[0090] Among them, DN is the gray - scale value of the point - target, and M is the theoretical calibration beam magnitude.

[0091] The present invention also provides a low - illuminance calibration device for spatial point - targets, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the method are implemented.

[0092] The following gives specific examples based on the method and device disclosed in the present invention.

[0093] Set the exposure time to 10ms, adjust the illumination of the light source system to 5Mv, select a star point target plate with a clear aperture of 0.14mm, and use a low-light illuminance meter to record the data, see Table 1.

[0094] Table 1

[0095]

[0096] The deviation obtained in this example is 0.02Mv, which is much smaller than 0.3Mv (magnitude), proving that the device and method disclosed in the present invention are reliable.

[0097] The beneficial effects of the embodiments of the present invention are:

[0098] The present invention adopts the method of simulating space point target imaging, taking the irradiance of the light source system as the test object and fixed-ratio attenuation spectroscopy, and can perform point target low-illuminance calibration test on the optoelectronic equipment to be tested. At the same time, the relationship between the target magnitude and the point target grayscale value DN is established through the optimized point target calibration model, which can reduce the measurement error factors and finally obtain high-precision calibration coefficients and reliable photometric quantitative measurement capabilities under low-illuminance conditions.

[0099] Since the targets in space-based observation conditions are generally far away and in point shape, the combination of "light attenuation plate + spectroscope" disclosed in the present invention can ensure the measurement accuracy under low illumination conditions through the test beam measured by a low-light illuminance meter; at the same time, the calibration parameter characteristics of the point target under different imaging sizes and different luminous intensity states of the optoelectronic device to be tested can be simulated and calculated, thereby ensuring the accuracy in space-based measurement and providing a reliable solution for high-precision calibration of space-based observation cameras.

[0100] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for low-light calibration test of a space point target, characterized in that: include: Step 1: Adjust the collimator to be parallel to the optical axis of the optoelectronic device to be tested built in the darkroom, and confirm that the output light of the collimator covers the entire aperture of the optoelectronic device to be tested; place a beam splitter on the parallel optical axis of the collimator and the optoelectronic device to be tested, and use the beam splitter to split the output light of the collimator into a calibration beam and a test beam; place an optical attenuation plate on the calibration beam optical path between the optoelectronic device to be tested and the beam splitter, and obtain the relationship function between the illumination value of the test beam and the brightness value of the light source system, and the relationship function between the illumination value of the test beam and the illumination value of the calibration beam; Step 2: Complete the initial state setting of calibration data acquisition according to the dynamic range of the optoelectronic device to be tested, and collect and store the output signal of the optoelectronic device to be tested when there is no radiation input from the light source system as background noise data; Step 3: After removing the background noise data, select a star point target plate of the corresponding aperture and place it between the beam splitter and the collimator to simulate a point target in space. Select a light decay plate to simulate a dark point target in space, so that the image plane imaging size of the detector in the optoelectronic device to be tested is less than 80 pixels. Place a low-light illuminance meter on the optical path of the test beam. The low-light illuminance meter records the real test beam illumination value. Based on the relationship function between the test beam illumination value and the calibration beam illumination value, the real calibration beam illumination value is obtained. The center of the point target is determined by a two-dimensional Gaussian distribution template. Combined with the center of the point target, the gray value of the point target is estimated by the annular area method. The calibration coefficient of the optoelectronic device to be tested is fitted by using multiple groups of point target gray values ​​and the illumination value of the real calibration beam to obtain the point target calibration model. Step 4: Adjust the exposure time, reduce the brightness value of the light source system, until the detector no longer responds, obtain the extreme brightness value of the light source system, obtain and record the output image of the optoelectronic device to be tested, the real test beam illumination value recorded by the micro-light meter, the real calibration beam illumination value, and the output light illumination value of the collimator; Step 5: Adjust the brightness value of the light source system within the extreme value range of the brightness of the light source system, so that the illumination value of the real calibration beam changes within the preset range, and convert it into the magnitude of the real calibration beam through the conversion equation; at the same time, obtain multiple groups of point target grayscale values, and invert multiple groups of theoretical calibration beam illumination values ​​from the multiple groups of point target grayscale values ​​through the point target calibration model, and convert them into the theoretical calibration beam magnitude through the conversion equation; calculate the difference between the theoretical calibration beam magnitude and the real calibration beam magnitude to obtain the photometric measurement deviation of point targets of different luminosity sizes; Step 6: Replace the aperture of the star point target plate, change the image size of the image plane, repeat step 5, until the average value of the photometric deviation of point targets of different photometric sizes is less than the threshold value, and obtain a stable calibration coefficient. Optimize the point target calibration model through the stable calibration coefficient, calculate the difference between the theoretical calibration beam magnitude and the actual calibration beam magnitude under the optimized point target calibration model, and obtain the photometric deviation of point targets of different photometric sizes and different imaging sizes; Step 7: Verify the accuracy of the low-illuminance calibration test of spatial point targets through the photometric measurement deviation of point targets with different luminosity and imaging sizes.

2. The method according to claim 1, characterized in that In step 1, the relationship function between the test beam illumination value and the light source system brightness value is: Among them, E coll is the actual test beam illumination value, d0 is the aperture of the star point target plate, f is the focal length of the optoelectronic device to be tested, L0 is the brightness value of the light source system, τ coll is the collimator transmittance; The relationship function between the test beam illumination value and the calibration beam illumination value is: E cal =E coll ·d·b; In the formula, E cal is the real calibration beam illumination value, E coll is the actual test beam illumination value, δ is the attenuation coefficient of the light attenuator, and β is the splitting ratio of the beam splitter.

3. The method according to claim 1, characterized in that In step 2, the output signal V of the photoelectric device to be tested when there is no radiation input from the light source system is collected and stored as: V=Φ·R V ; Φ=E e0 ·A0; Where Φ is the luminous flux incident on the optoelectronic device to be tested, R V is the responsivity of the optoelectronic device to be tested, A0 is the entrance pupil area of ​​the optoelectronic device to be tested, E e0 It is the entrance pupil illuminance of the optoelectronic device to be tested, that is, the actual illuminance value of the calibration beam.

4. The method according to claim 1, characterized in that In step 3, the calculation method for determining the center of the point target using a two-dimensional Gaussian distribution template is: Among them, G(x,y) is the grayscale distribution of the point target, that is, the grayscale value of any pixel, B is the background grayscale value, H is the difference between the grayscale peak value of the point target area and the background grayscale value, (x, y) is any point in the point target area in the image, (x0, y0) is the center of the point target, and R is the pixel radius of the point target area.

5. The method according to claim 4, characterized in that In step 3, the method of estimating the gray value of the point target using the annular area method according to the center of the point target is: According to the center of the point target, set the circular initial area of ​​the point target r = 3 pixels; The initial circular area of ​​the point target is divided into four areas in the horizontal and vertical directions, and the grayscale standard deviation and average value of each area are calculated respectively; Expand r by increasing the step size by 1 pixel each time and continue to solve the grayscale standard deviation and average value of the four expanded areas until the grayscale standard deviation reaches the peak value. At this time, the corresponding r range is the point target area; The gray value of the point target is obtained by removing the average background gray value in the area outside the point target area.

6. The method according to claim 5, characterized in that In step 3, the point target calibration model is: <h2 style=";text-align:left;direction:ltr">E=a4·DN<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> +a3·DN<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +a2·DN<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +a1·DN+a0; Where E is the real calibration beam illumination value or the inverted theoretical calibration beam illumination value, a0, a1, a2, a3, a4 are the calibration coefficients fitted by the fourth-order nonlinear model, and DN is the point target gray value.

7. The method according to claim 1, characterized in that In step 5, the conversion equation is: Where M′ is the magnitude of the calibration beam, E obj is the calibration beam illumination value, and E0 is the calibration beam illumination value corresponding to the sporadic level.

8. The method according to claim 1, characterized in that The calculation method of the point target photometric measurement deviation ΔM includes: ΔM=M-M0; Where M is the theoretical calibration beam magnitude, and M0 is the real calibration beam magnitude corresponding to M.

9. The method according to claim 1, characterized in that In step six, the optimized point target calibration model is: <h2 style=";text-align:left;direction:ltr">DN = 28.337M<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> -718.21M<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +6789.1M<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> -28528M+48921; Among them, DN is the gray value of the point target, and M is the theoretical calibration beam magnitude.

10. A low-light calibration device for a spatial point target, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method according to any one of claims 1 to 9 when executing the computer program.

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