A method for correcting the response of a polarized remote sensor in the short-wave infrared band to background radiation

Abstract

This invention discloses a method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band. The method includes: first, establishing a remote sensor response function based on the sensor's absolute spectral responsivity, target spectral radiance, and background radiation; dividing the test temperature into multiple temperature levels and obtaining the background radiation response using polynomial fitting; measuring the background radiation responsivity using an integrating sphere and a vacuum high-low temperature environment simulation test system to obtain the equivalent blackbody temperature; obtaining the corresponding in-band weighted radiance using the ratio of the background radiation response signal to the equivalent spectral responsivity at a known reference temperature; calculating the total background radiation response using the evaluated weighted spectral radiance and the instrument's internal equivalent spectral responsivity; and analyzing the accuracy of the background radiation polarization response correction using a combined uncertainty assessment method. This invention can be used to eliminate background radiation, increase the dynamic range of the detection system, and improve the system's signal-to-noise ratio and measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of remote sensor calibration data processing technology, and in particular to a method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band. Background Technology

[0002] In recent years, driven by international demands in fields such as Earth observation, atmospheric sounding, and planetary exploration, polarization remote sensing technology has entered a stage of wide spectral coverage, large dynamic range observation, and high-precision detection. To achieve effective detection of distant, weak targets, high-sensitivity cooled infrared detectors are often used. These detectors are particularly sensitive to heat sources, and the impact of background radiation on the system is even more pronounced. The resulting polarization response characteristics are difficult to ignore, significantly affecting the efficiency and accuracy of polarization calibration. This has become a bottleneck limiting the improvement of short-wave infrared band calibration accuracy in polarization remote sensors.

[0003] Background radiation typically refers to the radiant energy received by an instrument's detection system from non-observed targets. Background radiation directly increases the background noise and dynamic range drift of polarization remote sensors in the short-wave infrared band, thus affecting the sensor's response measurements. The impact of background radiation on infrared detection becomes more pronounced as the target signal weakens and detector performance improves. Although the radiation response of infrared channel detectors is almost linear in the room temperature range, research shows that under vacuum calibration, the infrared channel exhibits significant nonlinear characteristics at both low and high temperatures. Accurate low-temperature target calibration is crucial for cloud microphysical parameter inversion. In Earth observation and weak space target detection, target radiation is weak, and the detector response is low; in these cases, background radiation becomes the dominant factor limiting the improvement of the system's short-wave infrared signal-to-noise ratio and polarization measurement accuracy.

[0004] Compared to visible light systems, shortwave infrared systems passively receive thermal radiation from targets, resulting in more complex background radiation characteristics. This includes not only external background radiation but also stray radiation generated by the system's own structure, i.e., internal background radiation. The sources of internal background radiation are complex and can be broadly categorized into three types based on the radiation source: optical elements, structural elements, and background radiation from the uncooled parts of the detector. The surfaces of optical elements and mechanical structures, as well as the uncooled parts of the detector, all generate thermal radiation, which is received by the detector after multiple reflections, refractions, or diffractions. Radiation from optical elements is mainly related to material type and temperature; radiation from mechanical structures is mainly related to material emissivity, temperature, and transmission path; and radiation from the uncooled parts of the detector is mainly related to material type and temperature.

[0005] Based on the analysis of domestic and international background radiation research, the main research methods for background radiation in detection systems currently include software modeling analysis and the BAT (built-and-test) method. Software modeling analysis refers to modeling the generation process of background radiation signals based on the principles of infrared physics, quantifying various factors affecting the radiation characteristics of the target, and simulating background radiation signals under different environments. Current methods mainly include Monte Carlo methods, ray tracing methods, and region methods. This method is widely used due to its low cost, lack of limitations in equipment and test site conditions, and ability to achieve accurate and detailed analysis at both the system and component levels. Its disadvantage lies in the inability to verify its accuracy and effectiveness; in reality, the field environment is much more complex than the simulated environment, and it is impossible to obtain accurate target radiation characteristics through simulation.

[0006] For measuring background radiation response, the BAT method is mainly used. This involves establishing a measurement model of the target's infrared radiation characteristics and then testing and correcting the model through on-site radiation measurement experiments. This is the most direct way to obtain the target's true radiation characteristics. Relatively complete measurement systems have been developed abroad. For example, the Arnold Center in Tennessee, California, accurately measures the background radiation of infrared systems under low-temperature and vacuum conditions. However, this experimental testing method is difficult to implement and has significant errors.

[0007] Currently, domestic research on background radiation mainly focuses on simulation analysis, and a comprehensive background radiation measurement system has not yet been established. Among the few domestic reports of experimental methods, Chang Songtao et al. from the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, proposed a method for measuring the internal background radiation of a cooled infrared system based on the principle of radiometric calibration. This method calculates the internal background radiation of the system by calibrating the infrared detector and combining the results of the infrared system's radiometric calibration. However, this method does not provide a quantitative analysis of the background radiation. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies and solve the problems of increased background noise and dynamic range drift in the shortwave infrared band of polarization remote sensors caused by background radiation, this invention provides a method for correcting the background radiation response of shortwave infrared band polarization remote sensors. This method enables accurate measurement and correction of background radiation in the shortwave infrared band of polarization remote sensors, reducing the impact of background radiation on the measurement results in the shortwave infrared band.

[0009] This invention is achieved through the following technical solution:

[0010] A method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band includes the following steps:

[0011] Step (1) is based on the response of the shortwave infrared band of the polarization remote sensor and its absolute spectral responsivity R(λ). k ), target spectral radiance L(λ) k), and background radiation response F bkg (λ k The relationship between λ and λ is used to establish the response function S(λ) of the polarization remote sensor. k );

[0012] Step (2) divides the test temperature of each channel of the polarization remote sensor into multiple temperature levels and uses polynomial fitting to obtain the background radiation response of each channel;

[0013] Step (3): The background radiation response is measured using a spectrally tunable integrating sphere as a reference light source and a vacuum high and low temperature environment simulation test system. The radiation inside the instrument is simulated by using the spectrally tunable integrating sphere as a reference light source to obtain the equivalent blackbody temperature.

[0014] Step (4): Using multiple temperature points of the vacuum high and low temperature environment simulation test system, under the condition of a known reference temperature, obtain the in-band weighted radiance L corresponding to the ratio of the background radiation response signal to the background radiation equivalent spectral responsivity at the known reference temperature. m (λ j );

[0015] Step (5): Calculate the total background radiation response F using the evaluated weighted spectral radiance and the instrument's internal radiation equivalent spectral responsivity. bkg (λ);

[0016] Step (6) uses the combined uncertainty assessment method to analyze the accuracy of the background radiation polarization response correction.

[0017] Further, in step (1), the response function S(λ) of the polarization remote sensor k )for:

[0018]

[0019] Where, λ k Let λ be the k-th channel of the polarization remote sensor, where k is the channel number of the polarization remote sensor. min and λ max For a polarization remote sensor to have the shortest and longest wavelengths of response, L(λ) k R(λ) represents the spectral radiance of the k-th channel at wavelength λ. k F represents the absolute spectral responsivity of the k-th channel at wavelength λ. bkg (λ k ) represents the background radiation response of the k-th channel of the polarization remote sensor with wavelength λ.

[0020] Furthermore, in step (2), the background radiation response of each polarization channel of the polarization remote sensor is divided into multiple temperature levels, with temperature t. i The background radiation response at time F bkg (λk ,t i )express:

[0021]

[0022] Among them, L Int (λ k ,t i R(λ) represents the spectral radiance of the radiation inside the instrument. k B(t0) represents the absolute spectral responsivity at the initial temperature point t0. i t represents the fitting coefficient. i Let i be a temperature point, and i be the temperature point number.

[0023] Further, step (3) includes: first, based on the original spectrum S observed in the cold air... DS That is, the count value and the instrument spectral response function R(λ) k Approximate calculation of the instrument's internal radiation equivalent spectral response. That is, the radiation value; then, The energy of the integrated band is obtained by integrating the corresponding band; finally, the temperature of a blackbody with the same energy is estimated by interpolation, as shown in equation (3):

[0024]

[0025] Among them, S DS and S ICT L represents the instrument output signal when cold air and the reference light source are incident, respectively. ICT R(λ) represents the spectral radiance of the inner blackbody. k ) is the instrument's spectral response function, and <·> indicates taking the mean value.

[0026] Further, step (4) includes: dividing the operating environment temperature of the k-th channel of the polarization remote sensor into multiple temperature levels according to the actual operating environment temperature changes, assuming that the temperature t of temperature point j is... j Given a reference temperature, the background radiation response signal F(λ) of the polarization remote sensor k ,t j ) and temperature t j Equivalent spectral responsivity δ under background radiation bkg (λ k ,t j The ratio of ) to the in-band weighted radiance L of the corresponding m-th channel m (λ j They are approximately equal, as shown in formula (4):

[0027]

[0028] Furthermore, in step (5), the total background radiation response Fbkg (λ k The weighted radiance L corresponding to all known temperature points m (λ j ) and background radiation responsivity δ bkg (λ k ,t j ) represents, as shown in formula (5):

[0029]

[0030] Furthermore, in step (6), based on the measurement method and mathematical model B = f(x1, x2…x) of the background radiation... n Determine the input quantity x. i Uncertainty u(x) arising from the measurand i The background radiation polarization response correction accuracy is analyzed using the combined uncertainty assessment method, taking into account the background radiation polarization response and its propagation rate. The measured quantity is the background radiation responsivity and temperature, among other parameters.

[0031]

[0032] In the formula, r(x) i ,x j ) represents the input quantity x i and x j The correlation coefficient, Input quantity x i The sensitivity coefficient.

[0033] The advantages of this invention are:

[0034] A background radiation measurement method based on environmental simulation experiments was adopted. By utilizing the fine adjustment function of the environmental simulation experiment system, the real working environment of the remote sensor was simulated, and the background radiation response was measured and calibrated. This effectively solved the problem of increased background noise and dynamic range drift in the shortwave infrared band of the polarization remote sensor caused by background radiation, and reduced the impact of background radiation on the measurement results of the shortwave infrared band of the polarization remote sensor. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the background radiation test of the present invention;

[0036] Figure 2 This is a flowchart of the background radiation correction method of the present invention;

[0037] Figure 3 This is a flowchart of the temperature control design for the vacuum high and low temperature environment simulation test system of the present invention;

[0038] Figure 4This is a diagram showing the effect of shortwave infrared band background radiation correction of the polarization remote sensor of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0040] This invention proposes a method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band. Based on the relationship between the response of the polarization remote sensor in the shortwave infrared band and its absolute spectral responsivity, target spectral radiance, and background radiation response, a response function of the polarization remote sensor is established. The test temperature is divided into multiple temperature levels, and polynomial fitting is used to obtain the background radiation response of each channel. The background radiation response is measured using a spectrally tunable integrating sphere reference light source and a vacuum high and low temperature environment simulation test system. The spectrally tunable integrating sphere reference light source is used to simulate the internal radiation of the instrument to obtain the equivalent blackbody temperature. The ratio of the background radiation response signal to the equivalent spectral responsivity of the background radiation at a known reference temperature is used to obtain the corresponding in-band weighted radiance. The total background radiation response is calculated using the evaluated weighted spectral radiance and the equivalent spectral responsivity of the instrument's internal radiation. The accuracy of the background radiation polarization response correction is analyzed using a combined uncertainty assessment method.

[0041] like Figure 1 As shown, the calibration device for a short-wave infrared polarization calibration method for polarization remote sensors based on background radiation correction according to the present invention includes an integrating sphere 1, a vacuum high and low temperature environment simulation test system 2, a spectral radiance meter 3, and a short-wave infrared polarization remote sensor under test 4. The integrating sphere 1 serves as the light source, employing a wide-band light source such as a tungsten bromide lamp, a halogen tungsten lamp, or a white laser, with a spectral range covering the short-wave infrared band. By utilizing the spectral distribution characteristics of the integrating sphere, a verification band interval for the calibration results is selected to verify the calibration results under different dynamic ranges of the remote sensor. The heat sink temperature of the vacuum high and low temperature environment simulation test system 2 can be adjusted to accommodate the temperature and vacuum requirements of high and low temperature tests in thermal vacuum environments for different applications. The spectral radiance meter 3 is an integrating sphere radiance monitoring unit, with a spectral range covering the short-wave infrared band, used to monitor the radiance value of the light source. The short-wave infrared polarization remote sensor under test 4, with a spectral range covering the short-wave infrared band, is used to conduct background radiation measurement experiments.

[0042] like Figure 2 As shown, the shortwave infrared band background radiation response correction method for a polarization remote sensor according to the present invention specifically includes the following steps:

[0043] Step (1) is based on the response of the shortwave infrared band of the polarization remote sensor and its absolute spectral responsivity R(λ). k ), target spectral radiance L(λ) k ), and background radiation response F bkg (λk The relationship between λ and λ is used to establish the response function S(λ) of the polarization remote sensor. k )for:

[0044]

[0045] Where, λ k Let λ be the k-th channel of the polarization remote sensor, where k is the channel number of the polarization remote sensor. min and λ max For a polarization remote sensor to have the shortest and longest wavelengths of response, L(λ) k R(λ) represents the spectral radiance of the k-th channel at wavelength λ. k F represents the absolute spectral responsivity of the k-th channel at wavelength λ. bkg (λ k ) represents the background radiation response of the k-th channel of the polarization remote sensor with wavelength λ.

[0046] Step (2) divides the test temperature of each channel of the polarization remote sensor into multiple temperature levels, and uses polynomial fitting to obtain the background radiation response of each channel, with the temperature being t. i The background radiation response at time F bkg (λ k ,t i )express:

[0047]

[0048] Among them, L Int (λ k ,t i R(λ) represents the spectral radiance of the radiation inside the instrument. k B(t0) represents the absolute spectral responsivity at the initial temperature point t0. i t represents the fitting coefficient. i Let i be a temperature point, and i be the temperature point number.

[0049] Step (3) involves measuring the background radiation response using a spectrally tunable integrating sphere as a reference light source and a vacuum high and low temperature environment simulation test system. The radiation from the reference light source of the spectrally tunable integrating sphere is used to simulate the radiation within the instrument, thus obtaining the equivalent blackbody temperature. First, based on the original spectrum S observed in the cold air... DS That is, the count value and the instrument spectral response function R(λ) k Approximate calculation of the instrument's internal radiation equivalent spectral response. That is, the radiation value; then, The energy of the integrated band is obtained by integrating the corresponding band; finally, the temperature of a blackbody with the same energy is estimated by interpolation, as shown in equation (3):

[0050]

[0051] Among them, S DS and S ICT L represents the instrument output signal when cold air and the reference light source are incident, respectively. ICT R(λ) represents the spectral radiance of the inner blackbody. k ) is the instrument's spectral response function, and <·> indicates taking the mean value.

[0052] Step (4): Using the temperature points of the vacuum high and low temperature environment simulation test system, the working environment temperature of the k-th channel of the polarization remote sensor is divided into multiple temperature levels according to the actual working environment temperature changes. Assume that the temperature point numbered j is t. j Given a reference temperature, the background radiation response signal F(λ) of the polarization remote sensor k ,t j ) and temperature t j Equivalent spectral responsivity δ under background radiation bkg (λ k ,t j The ratio of ) to the in-band weighted radiance L of the corresponding m-th channel m (λ j They are approximately equal, as shown in formula (4):

[0053]

[0054] Step (5) utilizes the weighted radiance L corresponding to all known temperature points. m (λ j ) and background radiation responsivity δ bkg (λ k ,t j ), calculate the total background radiation response F bkg (λ), as shown in formula (5):

[0055]

[0056] Step (6) uses the combined uncertainty assessment method to analyze the accuracy of the background radiation polarization response correction. Based on the background radiation measurement method and mathematical model B = f(x1, x2…x…), the accuracy is further analyzed. n Determine the input quantity x. i Uncertainty u(x) arising from the measurand i The background radiation polarization response correction accuracy is analyzed using the combined uncertainty assessment method, taking into account the background radiation polarization response and its propagation rate. The measured quantity is the background radiation responsivity and temperature, among other parameters.

[0057]

[0058] In the formula, r(x) i ,xj ) represents the input quantity x i and x j The correlation coefficient, Input quantity x i The sensitivity coefficient.

[0059] like Figure 3 As shown, to achieve precise control of the stability and uniformity of the test environment temperature, a feedback automatic control method is adopted for temperature control, using a fuzzy adaptive fuzzy and PID composite control mode. Once the cavity shape and the radiation characteristics of the inner wall material are determined, the radiation energy depends only on the temperature. According to the Stefan-Boltzmann law, the full-wavelength radiation energy E of a real object's hemisphere is:

[0060] E=εσT 4 (7)

[0061] In the formula, ε is the emissivity, σ is the proportionality constant, and T is the temperature.

[0062] Differentiating both sides, we get:

[0063]

[0064] As can be seen from equation (8), temperature changes will lead to changes in radiation energy. Therefore, in the Fuzzy and PID composite feedback control algorithm, based on the characteristics of Fuzzy and PID control, Fuzzy control is used during dynamic processes, while PID control is automatically switched when the system approaches or is in a steady state.

[0065] like Figure 4 The image shown is a diagram illustrating the background radiation correction effect of the shortwave infrared band of the polarization remote sensor of this invention.

[0066] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. These embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art can make various substitutions and modifications, all of which should fall within the scope of the present invention.

Claims

1. A method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band, characterized in that, Includes the following steps: Step (1), based on the response of the shortwave infrared band of the polarization remote sensor and its absolute spectral responsivity R(λ) k ), target spectral radiance L(λ) k ), and background radiation response F bkg (λ k The relationship between λ and λ is used to establish the response function S(λ) of the polarization remote sensor. k ); λ represents the kth channel of the polarization remote sensor; k is the channel number of the polarization remote sensor. Step (2): Divide the test temperature of each channel of the polarization remote sensor into multiple temperature levels, and use polynomial fitting to obtain the background radiation response of each channel; Step (3): Measure the background radiation response using a spectrally tunable integrating sphere as a reference light source and a vacuum high and low temperature environment simulation test system. Use the spectrally tunable integrating sphere as a reference light source to simulate the radiation inside the instrument and obtain the equivalent blackbody temperature. Step (4): Using multiple temperature points of the vacuum high and low temperature environment simulation test system, under the condition of a known reference temperature, obtain the in-band weighted radiance L corresponding to the ratio of the background radiation response signal to the background radiation equivalent spectral responsivity at the known reference temperature. m (λ j ); j is the temperature point number, λ j Let be the wavelength at the j-th temperature point; Step (5): Calculate the total background radiation response F using the evaluated weighted spectral radiance and the instrument's internal radiation equivalent spectral responsivity. bkg (λ); Step (6) uses the combined uncertainty assessment method to analyze the accuracy of the background radiation polarization response correction.

2. The method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band according to claim 1, characterized in that, In step (1), the response function of the polarization remote sensor for: （1） in, Let λ be the k-th channel of the polarization remote sensor, where k is the channel number of the polarization remote sensor. min and λ max For polarization remote sensors, the shortest and longest wavelengths of response are required. R(λ) is the spectral radiance of the k-th channel at wavelength λ. k Let λ be the absolute spectral responsivity of the k-th channel at wavelength λ. Let λ be the background radiation response of the k-th channel of the polarization remote sensor.

3. The method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band according to claim 2, characterized in that, In step (2), the background radiation response of each polarization channel of the polarization remote sensor is divided into multiple temperature levels, with temperature t. i Background radiation response at time express: （2） Among them, L Int (λ k ,t i R(λ) represents the spectral radiance of the radiation inside the instrument. k B(t0) represents the absolute spectral responsivity at the initial temperature point t0. i t represents the fitting coefficient. i Let i be a temperature point, and i be the temperature point number.

4. The method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band according to claim 3, characterized in that, Step (3) includes: First, based on the original spectrum S observed in the cold air... DS That is, the count value and the instrument spectral response function R(λ) k Approximate calculation of the instrument's internal radiation equivalent spectral response. That is, the radiation value; then, The energy of the integrated band is obtained by integrating the corresponding band; finally, the temperature of a blackbody with the same energy is estimated by interpolation, as shown in equation (3): （3） Among them, S DS and S ICT L represents the instrument output signal when cold air and the reference light source are incident, respectively. ICT R(λ) represents the spectral radiance of the inner blackbody. k ) is the instrument's spectral response function, and <·> indicates taking the mean value.

5. The method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band according to claim 4, characterized in that, Step (4) includes: dividing the operating environment temperature of the k-th channel of the polarization remote sensor into multiple temperature levels according to the actual operating environment temperature changes, assuming that the temperature t of temperature point j is... j Given a reference temperature, the background radiation response signal of the polarization remote sensor With temperature t j Equivalent spectral response to background radiation The ratio of the in-band weighted radiance L of the corresponding m-th channel m (λ j They are approximately equal, as shown in formula (4): （4）。 6. The method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band according to claim 5, characterized in that, In step (5), the total background radiation response F bkg (λ k The weighted radiance L corresponding to all known temperature points m (λ j and background radiation responsivity This is represented as shown in formula (5): （5）。 7. The method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band according to claim 6, characterized in that, In step (6), based on the measurement method and mathematical model B=f(x1,x2…x) of the background radiation... n Determine the input quantity x. i Uncertainty u(x) arising from the measurand i The background radiation polarization response correction accuracy is analyzed using the combined uncertainty assessment method, where the measured quantity is the background radiation polarization response; the input quantities are parameters such as background radiation responsivity and temperature; the combined uncertainty u(B) is expressed by equation (6): （6） In the formula, r(x) i ,x j ) represents the input quantity x i and x j The correlation coefficient, Input quantity x i The sensitivity coefficient.

8. The method for correcting the background radiation response of a polarization remote sensor in the shortwave infrared band according to claim 3, characterized in that, Temperature control is achieved through automatic feedback control, employing a fuzzy adaptive Fuzzy and PID composite control mode. In the Fuzzy and PID composite feedback control algorithm, based on the characteristics of Fuzzy and PID control, Fuzzy control is used during dynamic processes; when the system approaches or reaches a steady state, it automatically switches to PID control.

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