CN111781584A - Based on target radiation O2Passive distance measuring method of absorption correlation K distribution method - Google Patents
Based on target radiation O2Passive distance measuring method of absorption correlation K distribution method Download PDFInfo
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Abstract
The invention discloses a target radiation-based O2A passive distance measurement method of an absorption correlation K distribution method relates to the technical field of distance measurement methods. The method comprises the following steps: s1 establishing O based on related K distribution method2An absorption coefficient database; s2, acquiring environment and target measurement data necessary for passive distance measurement by using environmental parameter sensors such as temperature, air pressure and altitude and a detection tracking system capable of measuring the zenith angle of the target; s3 establishing an atmosphere non-uniform path O based on a curved earth model2A relation model of absorption efficiency and atmospheric non-uniform path length; s4 collecting object O through spectrum detection tracking system2Radiation spectrum near the A absorption band and resolving O on the target radiation transmission path2The absorption efficiency. The method fully utilizes a line-by-line integration method to calculate the absorption coefficientThe accuracy and the rapidity of the related K distribution method ensure the accuracy, the stability and the real-time performance of the passive distance measurement method.
Description
Technical Field
The invention relates to the technical field of distance measuring methods, in particular to a method based on target radiation O2A passive ranging method of an absorption correlation K distribution method.
Background
O2The passive absorption ranging technique is a technique using O in atmosphere2Monocular passive distance measurement technology for passively acquiring target distance by absorbing near-infrared radiation of target by A absorption band, Restprff, J.P.S. OKSI company and Edwards air force base [ Restprff, J.P.Passive ranging using multi-color in front detectors.NavalSurface Weaps Center in 2000]Together with new usable gas absorption bands, mainly comprising O2762nm absorption band, CO22.0 μm and 4.3 μm absorption bands and O34.7 μm and 9.6 μm absorption bands, and the characteristics of these absorption bands, such as ranging sensitivity, minimum error, etc., were compared. Hasson, first proposed in 2002, utilizes O in pairs from a theoretical point of view2MoleculeThe concept of passive ranging of absorption peaks was analyzed and the feasibility of the method was verified using Fabry-Perot interferometer with high spectral resolution [ Victor H.Hasson, Christopher R.Dupuis. Passioning with high throughput the Earth's tomosphere. proceedings of SPIE,2002](ii) a In 2005, doctor m.r.hawks proposed O2The average absorptivity of 762nm absorption band is used for measuring passive distance measurement, and on the basis of analyzing the theory of using average absorptivity of 762nm band to make distance measurement, the O mode based on band mode is established2The method is characterized in that a random distribution model of average absorption rate is adopted, an ABB-Bomen MR 254 Fourier spectrometer is used for developing a distance measurement experiment on the tail flame of the solid rocket engine, and the feasibility of the distance measurement method is proved through experiments.
Ansderson on r.ansderson at technical college of american university of air force in 2010 for utilizing O2The problem that the 762nm absorption band distance measurement is easy to saturate is solved2690nm absorption band, analysis comparing the absorption characteristics and range finding capability of the two absorption bands, and then using ABB-Bomen MR-304 Fourier spectrometer, a series of static and dynamic tests were carried out in which the maximum measurement error in a tracking probe with a maximum probe distance of about 90km for up to 90s in a Falcon9 launch vehicle observation test<5% average measurement error<3％。
While a series of important research results are obtained abroad, O-based research results have been obtained by many colleges and universities and scientific research institutions in China2Theoretical research and preliminary test verification are carried out by the absorption passive ranging technology, and the university of north and middle schools is based on O2The action mechanism of the passive distance measurement with the absorption characteristic is studied in detail and O is studied2The dependence relationship between the absorption coefficient and the temperature and the pressure is established, and the average O based on an Elsasser belt model and a random Malkmus belt model is constructed2And (5) a transmittance calculation model. The general radiation atmospheric transmission software (CART) simulation analysis of different spectral resolution of the measuring equipment to O is carried out by the Anhui optical machine2The influence of the A-band absorption rate measurement precision and the farthest measuring range is obtained through simulation analysis: for ranging by using absorption peak, the higher the measurement spectral resolution, the closer the distance to reach absorption saturation, and the spectral resolutionThe lower, the farther away absorption saturation is reached; the university of electronic technology utilizes Modtran software to establish a database of transmittance, path length and zenith angle to solve O2The maximum measuring range of the absorption passive distance measurement is limited by absorption saturation.
It can be seen that the catalyst is based on O2The absorbed passive ranging technology is a novel passive ranging technology with high precision and long range, and is bound to become a key point and a hot point for researching the passive ranging technology in the future, and is also a breakthrough point for realizing the wide application of the passive ranging technology in the military field. But accurately measuring the target radiation spectrum in the spectrum detection system and completing O2After the absorption efficiency is extracted, quickly and accurately resolving the target distance corresponding to the average absorption rate is the basis for realizing real-time passive ranging; the target distance can be solved in real time and mainly depends on O on any path under any condition2Fast resolution of absorption efficiency.
The K distribution method (KD) is a method for calculating the average absorption rate in a certain wave number range, and transforms the complex integral of the wave number space into the simple Gaussian integral of the absorption coefficient space in a mode of rearrangement of the absorption coefficient, thereby realizing the high-efficiency and high-precision solution of the average absorption rate; compared with the traditional belt mode method, the CKD method not only has good precision, but also can be directly used for solving the problem of atmospheric scattering which cannot be solved by the belt mode method.
Due to the advantages of the CKD method in resolving precision and resolving efficiency, the CKD method becomes the key point of research of scholars at home and abroad, and is widely applied in the fields of planet atmosphere research, remote sensing detection, radiation analysis and the like. Tsun analyzes the multiple scattering problem of the golden star atmosphere near infrared band by using a CKD method; caliot uses improved algorithm of correlation K distribution method to remote high temperature H2O-CO2-COThe infrared spectrum of the mixed gas is analyzed, and the remote sensing discrimination of the thermal jet flow is successfully realized; the stone Guangdong jade and Zhanghua greatly improve the calculation efficiency of the related K distribution method and simultaneously provide the basic idea of solving the non-uniform path by the CKD method; the method of using the CKD method for the remote detection of the high-temperature tail jet flame is applied to the YixueMei and Liulinhua, so that the calculation efficiency of the gas radiation characteristic is greatly improved; weak and reasonable et al successfully realize the rapid calculation of the optical transmittance of the water vapor wide absorption band by using the CKD method, and the continuous improvement of the CKD algorithm and the successful application of the CKD algorithm in various fields enable the advantages of good calculation accuracy and high efficiency of the CKD algorithm to further become a hotspot concerned by students.
The method fully utilizes the advantage of the average absorption rate calculated by the correlation K distribution method, and quickly and accurately establishes the O on the non-uniform path in the actual atmosphere on the basis of the curved surface earth model2A mathematical model of average absorption rate and path length; is O2Further applications of the absorption passive ranging technique provide some theoretical support.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a passive distance measurement method based on a target radiation O2 absorption correlation K distribution method, which has the advantages of rapidness, accuracy, robustness, long distance measurement, high and stable distance measurement precision and solves the problems in the background art.
In order to achieve the purpose, the invention provides the following technical scheme: based on target radiation O2The passive distance measurement method of the absorption correlation K distribution method comprises the following steps:
s1, establishing O based on related K distribution method2An absorption coefficient database;
s2, acquiring environment and target measurement data necessary for passive distance measurement by using environmental parameter sensors such as temperature, air pressure and altitude and a detection tracking system capable of measuring the zenith angle of the target;
s3, establishing an atmosphere non-uniform path O based on a curved earth model2A relation model of absorption efficiency and atmospheric non-uniform path length;
s4, collecting the target O through the spectrum detection tracking system2Radiation near the A absorption bandEmission spectroscopy and resolving O on the target radiation transmission path2The absorption efficiency.
Further optimizing the technical solution, the step S1 includes the following steps:
s1.1, reading in O in HITRAN molecule database2Line information of 430 lines of the A absorption band under standard conditions;
s1.2, determining and selecting temperature sampling points and air pressure sampling points in the atmospheric temperature and air pressure range;
s1.3, calculating 430 spectral line broadening under different temperature and air pressure (T, P) combinations by using a line-by-line integration method and a spectral line intensity calculation method under a non-standard condition, and then carrying out line-intensity superposition on each wavenumber in a specified wavenumber range;
s1.4, rearranging the line intensity distribution of the spectral lines superposed in the S1.3 by using a correlation K distribution method, calculating an accumulation probability distribution curve of the line intensity of the spectral lines in the spectral band and sampling;
s1.5, combining the absorption coefficients and the probability distributions at the sampling points of the cumulative probability distribution curves of all temperature and air pressure (T, P) combinations into an absorption coefficient database which is inquired according to the temperature and the air pressure and can be solved by plugging values.
Further optimizing the technical solution, the standard conditions in step S1.1 are temperature 296K, air pressure 101325Pa, and the spectral line information includes spectral line center frequency, spectral line intensity, self-broadening half-width, air-broadening half-width, and air-broadening temperature-dependent index.
Further optimizing the technical scheme, in the step S1.3, extrapolation is performed according to the following formula by theory according to the relationship between the spectral line parameter in the standard state and the spectral line parameter in the non-standard state:
in the formula: sV(P0,T0) Is the linear strength of a single O2 molecule in a standard state; t is0And P0Respectively temperature and air pressure under standard conditions; t and P are respectively the temperature and the air pressure under the nonstandard condition needing to be calculated; q (T)0) Andq (T) is the total internal partition function under standard and non-standard conditions, respectively, which can be solved by fitting a cubic polynomial of the total internal partition function to temperature.
Q(T)＝a+bT+cT2+dT3
The values of the coefficient term and constant term of the polynomial in the formula can be determined according to O2Molecular and temperature queries.
Further optimizing the technical solution, the step S2 includes the following steps:
s2.1, acquiring a zenith angle theta of the target by using an imaging type spectrum detection tracking system;
and S2.2, acquiring the ambient temperature T, the atmospheric pressure P and the altitude H at the position of the detection system by using an environmental sensor.
Further optimizing the technical solution, the step S3 includes the following steps:
s3.1, dividing the appointed non-uniform target radiation transmission path by using a curved earth model in combination with the environmental parameters and the target zenith angle measured in the step S2, and solving the length and the average altitude of each segmented path;
s3.2, solving the average temperature, the average air pressure and the O of each segmented path in the step S3.1 by utilizing the change rule of the atmospheric temperature and the atmospheric pressure along with the altitude and an ideal gas equation2Average concentration of molecules;
s3.3, solving O determined by the average temperature and the average pressure of each subsection path in the step S3.2 by utilizing table look-up interpolation fitting of the absorption coefficient database under different temperature and pressure combinations established in the step S1.52The absorption coefficient;
s3.4, using the beer law of absorption and O of each segment2Average concentration of molecules, O2The absorption coefficient and the path length are accumulated to calculate O corresponding to different distance lengths2And obtaining a mathematical model of the relation between the O2 absorption efficiency and the path length on the specified path.
Further optimizing the technical solution, the step S4 includes the following steps:
s4.1, the imaging type spectrum detection tracking system obtains target radiationAfter atmospheric transmission attenuation2A absorption band (12850 cm)-1-13170cm-1) Measured spectral data Iv of a certain spectral resolution within the range;
s4.2, calculating average O in the absorption band A by using the measured spectrum data2Absorption efficiency AO2。
S5, average O obtained in step S4.22Absorption efficiency AO2S3.4 passive distance measurement mathematical model inversion average O by interpolation fitting method2Absorption efficiency AO2The corresponding target distance.
Compared with the prior art, the invention provides a target radiation-based O2The passive ranging method of the absorption correlation K distribution method has the following beneficial effects:
1. the target-based radiation O2The passive distance measurement method based on the absorption correlation K distribution method provides a distance measurement method based on target radiation O2The passive ranging technology of the absorption and correlation K distribution method fully utilizes the accuracy of calculating an absorption coefficient by a line-by-line integration method and the rapidity of the correlation K distribution method, and ensures the accuracy, stability and instantaneity of the passive ranging method.
2. The target-based radiation O2The passive distance measurement method of the absorption correlation K distribution method can be used for not only a foundation fixed or mobile platform, but also a space-based and other moving platforms; the method can be combined with an infrared search tracking system, a photoelectric alarm system or a photoelectric countermeasure system to form a photoelectric passive alarm system with target two-dimensional space position and three-dimensional distance measurement, and has important application prospects in the aspects of air-to-air countermeasure, remote back-leading early warning and the like.
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FIG. 1 is a schematic diagram of a foundation and space-based exploration scheme of the present invention;
FIG. 2 is a flow chart of a passive ranging method according to the present invention;
FIG. 3 present invention O2A, an absorption coefficient curve diagram in an absorption band along with the change of wave number and cumulative probability;
FIG. 4 is a schematic diagram of an absorption coefficient database on Gaussian integral nodes with different pressures and different temperatures in the present invention;
FIG. 5 is O calculated by software simulation and the method of the present invention under different atmospheric modes2A mean absorbance contrast plot;
FIG. 6O with model and method of the invention2The average absorption rate and the relative error curve thereof are shown schematically;
FIG. 7 is a schematic diagram of an original image and three-dimensional gray scale distribution of the target at 740 nm;
FIG. 8 is a schematic diagram of an external field experimental data point and a resolving curve of the method of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Please refer to fig. 1-8: the invention discloses a target radiation-based O2The passive distance measurement method of the absorption correlation K distribution method comprises the following steps:
s1, establishing O based on related K distribution method2An absorption coefficient database;
s2, acquiring environment and target measurement data necessary for passive distance measurement by using environmental parameter sensors such as temperature, air pressure and altitude and a detection tracking system capable of measuring the zenith angle of the target;
s3, establishing an atmosphere non-uniform path O based on a curved earth model2A relation model of absorption efficiency and atmospheric non-uniform path length;
s4, collecting the target O through the spectrum detection tracking system2Radiation spectrum near the A absorption band and resolving O on the target radiation transmission path2The absorption efficiency.
Referring to FIG. 1, a passive distance measuring system for ground or space-based is based on light from a ground or space-based distance measuring system when measuring distance of an airborne or ground emitting target with self-radiationThe spectrum real-time detection device (a hyperspectral imager, a multispectral imager or a Fourier transform spectrometer and the like can be adopted) and the target tracking and positioning device are used for tracking and positioning the target O2Measuring the absorption band A, the spectral data of the spectral band nearby the absorption band A and the target zenith angle; meanwhile, an environmental parameter detection device in the ranging system acquires environmental parameters (atmospheric temperature, atmospheric pressure and altitude) during target spectrum acquisition in real time.
Referring to fig. 2, the following steps of the passive ranging method are explained with reference to the flowchart of the passive ranging method of the present invention:
S1O based on correlation K distribution method2And establishing an absorption coefficient database.
S1.1, reading O in HITRAN2010 molecular database2The molecule has an absorption band at A (12850 cm)-1-13170cm-1) Spectral line information (spectral line center frequency, spectral line intensity, self-broadening half-width, air-broadening temperature-dependent index, etc.) of 430 spectral lines under standard conditions (temperature 296K, air pressure 101325 Pa);
s1.2, determining and selecting temperature sampling points and air pressure sampling points in the atmospheric temperature and air pressure range; because the radiation of the measured target may pass through different altitudes of the atmosphere during transmission, the difference of temperature and air pressure at different altitudes of the atmosphere can cause O2The absorption coefficient of the molecule is different, and the O at different altitudes2The difference in molecular concentration also results in O at the atmosphere at different altitudes2The absorption efficiency is greatly different, so that the temperature sampling points and the air pressure sampling points with proper quantity are selected in the temperature and air pressure ranges in the atmosphere, and the established O is ensured2The absorption coefficient database can meet the calculation requirements of absorption coefficients at different positions in the atmosphere;
s1.3, calculating 430 spectral line broadening under different temperature and air pressure (T, P) combinations by using a line-by-line integration method and a spectral line intensity calculation method under a non-standard condition, and then carrying out line-intensity superposition on each wavenumber in a specified wavenumber range;
extrapolating according to the relation between the spectral line parameters under the standard state and the spectral line parameters under the non-standard state by theory according to the following formula:
in the formula: sV(P0,T0) Is a single O2Linear strength of the molecule in the standard state; t is0And P0Respectively temperature and air pressure under standard conditions; t and P are respectively the temperature and the air pressure under the nonstandard condition needing to be calculated; q (T)0) And Q (T) is the total internal partition function under standard and non-standard conditions, respectively, which can be solved by fitting cubic polynomial of the total internal partition function and temperature;
Q(T)＝a+bT+cT2+dT3(2)
the values of the coefficient term and constant term of the polynomial in the formula can be determined according to O2The molecular and temperature query is obtained;
the single spectral line intensity only describes the line intensity of the spectral line at the center frequency of the single spectral line, but each spectral line has a certain spectral line width and can affect the absorption at other frequencies; meanwhile, 430 spectral lines exist in the whole wave number range of the absorption band, dozens of spectral lines exist even if the whole absorption band is not used and only a part of spectral bands are selected, so that the positions of all the spectral lines in the selected spectral bands and the linear functions of the spectral lines are required to be determined, and the monochromatic absorption coefficients can be accurately calculated;
in the formula
Is the absorption coefficient of line i at wavenumber v under non-standard conditions (T, P); v. of0iIs the wavenumber at the center of line i;
is the line intensity of the spectral line i under non-standard conditions; f (v-v)0i) Is a normalized spectral line expression. The linear expression of the spectral line of molecular absorption is mainly highThe gaussian profile, the lorentz profile and the Voigt profile in between can be looked up from the relevant literature, while also considering the truncation of the line wing contribution. The spectral line type expression in the invention is selected in three types of line type expressions according to the standard of the ratio of Doppler half width and Lorentz half width of each spectral line under the non-standard condition, and the line wing truncation is selected to be equal wave number truncation;
the monochromatic absorption coefficients of all spectral lines in the selected spectral range are accumulated to obtain the monochromatic absorption coefficients on each wave number sampling point;
s1.4, rearranging the monochromatic absorption coefficients superposed in the step (3) by using a correlation K distribution method, calculating an accumulated probability distribution curve of the monochromatic absorption coefficients in the spectrum and sampling, for example, a supplementary explanation can be given by referring to a means in the prior art, please refer to FIG. 3;
with reference to fig. 3, the absorption coefficient which changes drastically with the wave number is transformed into a smooth curve irrelevant to the wave number by the correlated K distribution method through the ordered rearrangement of the absorption coefficient, so that the complex integral of the wave number space can be replaced by simple gaussian integral, and the average absorption rate of the absorption band under a certain temperature and pressure combination can be rapidly and accurately solved;
the average transmittance in the absorption band can be resolved with higher accuracy by a small amount of gaussian integration of the single-level smooth increasing curve in fig. 3(b), as shown in equation (4):
in the formula: n is the number of Gaussian integration points; k (g)j) The value of the absorption coefficient at the jth Gaussian integration point; Δ gjFor the cumulative probability density width at the jth Gaussian integration point, in mathematical terms, k (g)j) And Δ gjCurve function values and interval widths corresponding to jth integration intervals of the integrated curve respectively;
s1.5, so that the absorption coefficient curve which is monotonously and smoothly increased under the combination of all temperature sampling points and all air pressure sampling points is calculated and sampled on the Gaussian integration point, the temperature and the air pressure can be establishedPressing O as an index2An absorption coefficient database.
S2, respectively acquiring the atmospheric temperature T at the passive ranging system by using the environmental parameter detection device and the target tracking and positioning devicerAtmospheric pressure PrAltitude HrAnd target zenith angle theta0。
S3, establishing an atmosphere non-uniform path O based on a curved earth model2The model of the relationship between the absorption efficiency and the atmospheric non-uniform path length comprises the following operation steps:
s3.1, dividing the appointed non-uniform target radiation transmission path by using a curved surface earth model in combination with the environmental parameters and the target zenith angle measured in the second step, and solving the length and the average altitude of each segmented path;
s3.2, solving the average temperature, the average air pressure and the O of each segmented path by utilizing the change rule of the atmospheric temperature and the atmospheric pressure along with the altitude and an ideal gas equation2Average concentration of molecules;
s3.3, solving O determined by the average temperature and the average pressure of each subsection path by utilizing the table look-up interpolation fitting of the absorption coefficient database under the combination of different temperatures and pressures2The absorption coefficient;
s3.4, using the beer law of absorption and O of each segment2Average concentration of molecules, O2The absorption coefficient and the path length are accumulated to calculate O corresponding to different distance lengths2Absorption efficiency, and thus O on the designated path2A mathematical model of the absorption efficiency versus path length;
s4, collecting the target O through the imaging type spectrum detection tracking system2Radiation spectrum near the a absorption band and resolving O2 absorption efficiency on the target radiation transmission path, comprising the following steps:
s4.1, the imaging type spectrum detection and tracking system obtains O after the target radiation is attenuated by atmospheric transmission2A absorption band (12850 cm)-1-13170cm-1) Measured spectral data Iv of a certain spectral resolution within the range;
s4.2, calculating the average in the A absorption band by using the measured spectrum dataAll are O2Absorption efficiency
S5, utilizing average O on the acquired target radiation transmission path length2Absorption efficiency AO2And on the inclined path O2The relation curve of the average absorption rate and the path length can be inverted into an average O by an interpolation fitting method2Absorption efficiency
The corresponding target distance.
The passive distance measurement method realizes the following model analysis and experimental verification of the process:
according to the law that the absorption coefficient on the Gaussian node changes with the pressure and the temperature; sequentially calculating the distribution of absorption coefficients corresponding to the pressure and temperature at different altitudes from sea level to the top of the atmospheric layer, and extracting the absorption coefficient values at corresponding Gaussian integration points to make a two-dimensional absorption coefficient list as shown in FIG. 4; at the moment, the absorption coefficient on the corresponding Gaussian integration point is calculated according to the temperature and pressure interpolation on the path point, so that the consumption of data on resources can be greatly reduced, and the calculation efficiency of a program is improved.
According to the prefabricated absorption coefficient database and the relation model of the average absorption rate on the non-uniform path and the path length, the average absorption rate curve on the corresponding path can be quickly and accurately given under the condition that the path starting point information is known. For the adaptability of the passive ranging method, average absorption rate curves of inclined paths with the same starting point altitude of 0km and the zenith angle of 45 degrees under 6 standard atmospheric modes are calculated respectively; wherein the path length is 50km, and the temperature and pressure information at the starting point of the path in six standard atmospheric modes is shown in table 1, the calculation result is shown in fig. 5:
TABLE 1 pressure (hPa) and temperature information (K) at the origin of the inclined path
MLS, MLW, TM, SLS, SLW, 1976USS in table 1 represent six atmospheric modes of the Modtran software, latitude summer, mid-latitude winter, tropical, northern subarea summer, northern subarctic winter, and 1976us standard atmosphere, respectively;
as can be seen from fig. 5: o is2The mathematical model of the average absorption rate and the path length can accurately give the O of the set path in six typical atmospheric modes2The average absorption rate curve proves that the mathematical model can adapt to the inclined path conditions of different altitudes and zenith angles without adjustment; meanwhile, the relative error on the inclined path is basically not more than 2% and less than the software simulation result; overall, the mathematical model calculates O2The absorption efficiency errors are increased at the beginning section, and are rapidly reduced and gradually become smooth after reaching a maximum value; meanwhile, the relative error does not increase along with the increase of the path length, which shows that the absolute error of the average absorption rate does not increase along with the increase of the path length, so that O is ensured2The method absorbs the ranging precision of passive ranging, and simultaneously has the advantage that the passive ranging technology is better than other passive ranging technologies.
Foreign scholars Hawks was directed to O in 20062The relation problem of the average absorption rate and the path proposes that a relation model of the average absorption rate and the path length is established by utilizing a random distribution model and a curved surface earth model in a belt mode method, and the model function is a numerical implicit function as the model function established by the invention; however, the model not only contains special functions such as incomplete gamma function, Bessel function and error function which are complex to calculate, but also contains four undetermined parameters, and a plurality of distance points on a required path and O corresponding to the distance points need to be predicted before each use2Absorption efficiency so that the undetermined parameter can be determined by fitting to map O on the desired path2An absorption efficiency curve; not only does this require a lot of time, but also there is a certain difficulty in practical application, and fig. 6 shows O plotted by two mathematical models on a 10km altitude and 89 degree zenith angle path in the MLS atmospheric mode2Absorption efficiency curve.
FIG. 6(a) showsShown are the mean absorbance curves simulated by the Modtran software and plotted with a model of the mode. The tape model calculates O at 60 equally spaced distance points from simulation by software2And the absorption efficiency is used as predicted data, and then an undetermined parameter value in the model function is obtained by using the model function through a fitting method, so that an average absorption rate curve on the path is drawn. Since the entire process requires a plurality of pieces of software and the data processing amount is large, the curve in fig. 6(a) takes more than 1min, and thus the method is suitable for post-processing of data. FIG. 6(b) is a graph of the method of the present invention with knowledge of only the position of the detection system and weather information; o over a distance of 300km when the step length of the sub-path is 1km2The absorption efficiency curve takes 1.34s in total, which is much less time than the band mode model.
The accuracy of the band mode model is better than that of the method of the invention at the beginning of the path in terms of accuracy, but the accuracy is comparable at a distance. The accuracy of the model with the mode is superior to that of the method of the invention because the model curve is restricted by more known distance points on the path; if the number of constrained known distance points is reduced, the accuracy of the model is necessarily affected, but the method of the present invention is not affected thereby. Through comparison of the two models, the model function established by the correlation K distribution method is proved to be concise, the calculation efficiency is greatly improved while better precision is ensured, and the calculation time is shortened.
In order to examine the preliminary effect of the inventive method in actual ranging, four target points of different distances were set up here. The altitude of the position where the imaging spectrometer is erected is 0.08km, the temperature is 10 degrees, the pressure is 1018hPa, and the zenith angle of a connecting line path of the target detector is 90 degrees; because the positions of the target points are different and the measurement time span is large, the temperature, the pressure and the zenith angle are the average values in the period of time, and small errors exist between the actual values when the target points are measured; the original image of the target at 740nm collected by the spectrometer and its three-dimensional gray scale distribution map are shown in fig. 7.
Referring to FIG. 8, an experiment is shownO of four experimental points in the course2Absorption efficiency and O calculated according to spectrometer position information and path zenith angle information model2Absorption efficiency curve. As can be seen from the figure: all experimental points are distributed closely to the model curve, and only the information of altitude, temperature, pressure and path inclination angle at the measurement system is used for resolving O2The absorption efficiency curve can accurately reflect the change relation between the real absorption rate and the distance, and the data processing of the example only takes 0.191 s.
The invention has the beneficial effects that: the invention provides a target-based radiation O2The passive ranging technology of the absorption and correlation K distribution method fully utilizes the accuracy of calculating an absorption coefficient by a line-by-line integration method and the rapidity of the correlation K distribution method, and ensures the accuracy, stability and instantaneity of the passive ranging method. The longest time and the largest calculation amount in the present invention is O using the line-by-line integration algorithm and the correlation K distribution algorithm in step S12Establishing an absorption coefficient database; o in any subsequent measurement state2Establishment of mathematical model of relation between absorption efficiency and path length and measurement according to O2The average absorbance can be instantaneously inverted for target distance. Therefore, the invention can be used for not only the foundation fixing or moving platform, but also the space base and other moving platforms; the method can be combined with an infrared search tracking system, a photoelectric alarm system or a photoelectric countermeasure system to form a photoelectric passive alarm system with target two-dimensional space position and three-dimensional distance measurement, and has important application prospects in the aspects of air-to-air countermeasure, remote back-leading early warning and the like.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (7)
1. Based on target radiation O2The passive distance measurement method of the absorption correlation K distribution method is characterized by comprising the following steps of:
s1, establishing correlation-basedO of K distribution method2An absorption coefficient database;
s2, acquiring environment and target measurement data necessary for passive distance measurement by using environmental parameter sensors such as temperature, air pressure and altitude and a detection tracking system capable of measuring the zenith angle of the target;
s3, establishing an atmosphere non-uniform path O based on a curved earth model2A relation model of absorption efficiency and atmospheric non-uniform path length;
s4, collecting the target O through the spectrum detection tracking system2Radiation spectrum near the A absorption band and resolving O on the target radiation transmission path2The absorption efficiency.
2. A target radiation based O according to claim 12The passive distance measurement method of the absorption correlation K distribution method, wherein the step S1 includes the following steps:
s1.1, reading in O in HITRAN molecule database2Line information of 430 lines of the A absorption band under standard conditions;
s1.2, determining and selecting temperature sampling points and air pressure sampling points in the atmospheric temperature and air pressure range;
s1.3, calculating 430 spectral line broadening under different temperature and air pressure (T, P) combinations by using a line-by-line integration method and a spectral line intensity calculation method under a non-standard condition, and then carrying out line-intensity superposition on each wavenumber in a specified wavenumber range;
s1.4, rearranging the line intensity distribution of the spectral lines superposed in the S1.3 by using a correlation K distribution method, calculating an accumulation probability distribution curve of the line intensity of the spectral lines in the spectral band and sampling;
s1.5, combining the absorption coefficients and the probability distributions at the sampling points of the cumulative probability distribution curves of all temperature and air pressure (T, P) combinations into an absorption coefficient database which is inquired according to the temperature and the air pressure and can be solved by plugging values.
3. A target radiation based O according to claim 22The passive distance measurement method using the absorption correlation K distribution method is characterized in that the standard conditions in step S1.1 are 296K for temperature and 296K for air pressure101325Pa, and the spectral line information is spectral line center frequency, spectral line intensity, self-broadening half-width, air-broadening half-width and air-broadening temperature dependence index.
4. A passive distance measuring method based on the target radiation O2 absorption correlation K distribution method according to claim 2, wherein the extrapolation in step S1.3 is theoretically performed according to the following formula according to the relationship between the spectral parameters in the standard state and the spectral parameters in the non-standard state:
in the formula: sV(P0,T0) Is a single O2Linear strength of the molecule in the standard state; t is0And P0Respectively temperature and air pressure under standard conditions; t and P are respectively the temperature and the air pressure under the nonstandard condition needing to be calculated; q (T)0) And q (t) are the overall internal partition functions under standard and non-standard conditions, respectively, which can be solved by fitting cubic polynomials of the overall internal partition function to temperature.
Q(T)＝a+bT+cT2+dT3
The values of the coefficient term and constant term of the polynomial in the formula can be determined according to O2Molecular and temperature queries.
5. A target radiation based O according to claim 12The passive distance measurement method of the absorption correlation K distribution method is characterized in that the step S2 includes the following steps:
s2.1, acquiring a zenith angle theta of the target by using an imaging type spectrum detection tracking system;
and S2.2, acquiring the ambient temperature T, the atmospheric pressure P and the altitude H at the position of the detection system by using an environmental sensor.
6. A target radiation based O according to claim 12A passive distance measurement method of absorption correlation K distribution method is characterized in thatThe step S3 includes the following steps:
s3.1, dividing the appointed non-uniform target radiation transmission path by using a curved earth model in combination with the environmental parameters and the target zenith angle measured in the step S2, and solving the length and the average altitude of each segmented path;
s3.2, solving the average temperature, the average air pressure and the O of each segmented path in the step S3.1 by utilizing the change rule of the atmospheric temperature and the atmospheric pressure along with the altitude and an ideal gas equation2Average concentration of molecules;
s3.3, solving the O2 absorption coefficient determined by the average temperature and the average pressure of each segmented path in the step S3.2 by utilizing table look-up interpolation fitting of the absorption coefficient database under different temperature and pressure combinations established in the step S1.5;
s3.4, using the beer law of absorption and O of each segment2Average concentration of molecules, O2The absorption coefficient and the path length are accumulated to calculate O corresponding to different distance lengths2Absorption efficiency, and thus O on the designated path2A mathematical model of absorption efficiency versus path length.
7. A target radiation based O according to claim 12The passive distance measurement method of the absorption correlation K distribution method, wherein the step S4 includes the following steps:
s4.1, the imaging type spectrum detection and tracking system obtains O after the target radiation is attenuated by atmospheric transmission2A absorption band (12850 cm)-1-13170cm-1) Measured spectral data Iv of a certain spectral resolution within the range;
s4.2, calculating average O in the absorption band A by using the measured spectrum data2Absorption efficiency AO2。
S5, average O obtained in step S4.22Absorption efficiency AO2And step S3.4, inverting average O by using interpolation fitting method of passive distance measurement mathematical model2Absorption efficiency AO2The corresponding target distance.
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