CN112665748B - Split type spectrum thermometer for near space detection and atmospheric temperature inversion method - Google Patents
Split type spectrum thermometer for near space detection and atmospheric temperature inversion method Download PDFInfo
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Abstract
The invention discloses a split type spectrum thermometer for near space detection and an atmospheric temperature inversion method.A main optical structure of the spectrum thermometer is designed into a split type structure and comprises a light receiving subsystem and a spectrum detection subsystem, wherein the same calibration subsystem does not exist independently and is coupled in the spectrum detection subsystem; and a split type spectrum temperature meter is used as a detection carrier, a near space atmospheric temperature inversion method based on minimization of a synthetic spectrum cyclic difference value is provided, the atmospheric temperature of the near space is accurately inverted from actually observed image data, and the method can be applied to networking observation of a temperature field in the top area of the near space.
Description
Technical Field
The invention relates to the field of near space detection, in particular to a spectrum thermometer and an atmospheric temperature inversion method.
Background
The research of the adjacent space (generally, 20-100 km of the space above the earth) gradually draws attention of people, the temperature is an important basic state parameter of the top area of the adjacent space, and the temperature can be used for researching the dynamic process of various scales of the area, evaluating the long-term climate change of the earth and guaranteeing the space environment. Therefore, accurate and long-term observation of temperature has always been one of the important tasks in this field.
At present, various technical means have been developed to observe the temperature of the top area of the adjacent space, including not only a plurality of satellite-borne instruments specially used for observing global temperature field distribution, but also high-precision ground-based instruments such as a fluorescence laser radar and a meteor radar for active remote sensing, and in addition, some passive remote sensing instruments based on the spectrum technology start to implement wide-range networking observation with their flexibility. The combination of multiple detection means makes great progress in many scientific problems and application fields.
With the continuous and deep research, the effective large-scale and high-density networking observation on the temperature field is an important development trend in order to further promote the scientific research and application level in the near space field. However, the traditional structure of the instrument for detecting airglow rotation temperature based on the principle of the spectrophotometer has great limitation, and cannot completely meet the requirement of networking observation, thereby preventing effective and wide application in networking observation.
Disclosure of Invention
The invention aims to: aiming at the limitations of temperature detection in the top area of the near space on the technology, method and data inversion and the application requirements of the passive optical remote sensing technology in large-scale high-density networking, one of the purposes of the invention is to provide a split type spectrum thermometer for detecting the near space, which consists of a light receiving subsystem and a spectrum detection subsystem, and is provided with a same-machine calibration system, so that the sensitivity, the optical structure, the performance stability of the instrument and the accuracy of temperature inversion are improved, and the split type spectrum thermometer has strong applicability to the external field observation environment due to the flexible structural characteristics;
the invention also aims to provide a near space atmospheric temperature inversion method based on synthetic spectrum difference value circulation by taking a split type spectrum temperature instrument as a detection carrier, and the near space atmospheric temperature inversion method can accurately invert the near space atmospheric temperature from actually observed image data, thereby providing a brand-new and more practical technical means for networking observation of a temperature field at the top of the near space.
The technical scheme is as follows: the invention provides a split type thermometer for detecting a near space, which is characterized in that a main optical structure is designed into a split type structure and mainly comprises a light receiving subsystem and a spectrum detection subsystem, wherein a same-machine calibration subsystem does not exist independently but is coupled in the spectrum detection subsystem.
The light receiving subsystem comprises a light inlet cylinder, a plurality of first shading rings embedded in the inner wall of the light inlet cylinder, a Fresnel lens and an optical fiber light cone, wherein the Fresnel lens and the optical fiber light cone are arranged in the light inlet cylinder; the diameter of the inner ring through hole of the first shading ring is gradually reduced from top to bottom, and the formed inclination angle is the same as the observation solid angle of the light receiving subsystem; the large end face of the optical fiber light cone faces the Fresnel lens, and the small end face of the optical fiber light cone is far away from the Fresnel lens and is connected with the light guide pipe; the light inlet tube of the light receiving subsystem is matched with the Fresnel lens and the large end face of the optical fiber light cone to form an observation solid angle of +/-11 degrees to +/-15 degrees in the zenith direction. The diameter of the circular projection plane of the airglow layer corresponding to the zenith direction of the observation solid angle is about 36 km-52 km, and the design can ensure higher horizontal spatial resolution of the temperature field and simultaneously has the temperature disturbance quantity caused by detecting small-scale gravity waves.
The spectrum detection subsystem comprises a dome integrating sphere, an annular lighting optical fiber, a main light path shading cylinder and an imaging system which are sequentially arranged from top to bottom; the top end of the main light path shading cylinder is clamped with a field diaphragm, the middle part of the main light path shading cylinder is fixed with a main lens, the bottom end of the main light path shading cylinder is clamped with a narrow-band interference filter, and the inner wall of the main light path shading cylinder is embedded with a plurality of second shading rings; a plurality of second shading rings are arranged above and below the main lens, and the inclination angle formed by inner ring through holes of the upper shading ring and the lower shading ring is the same as the solid angle of the main light path; annular illumination optic fibre is equipped with first connection port and second connection port, and the light pipe passes through first connection port and links to each other with annular illumination optic fibre, and the second connection port is connected with optic fibre, and the other end and the calibration lamp of optic fibre link to each other.
Wherein the aperture range of the Fresnel lens is 200-500 mm.
Preferably, the light receiving subsystem is used for receiving light and transmitting the light out through the light guide pipe; the received light guided out by the light guide pipe is transmitted to the annular illumination optical fiber, and the light beam is introduced into the dome integrating sphere along the outlet at the tail end of the annular illumination optical fiber, so that a circular plane light source with uniform intensity is obtained at the field diaphragm 11 through repeated diffuse scattering for many times; the light source enters the shading cylinder, the plane divergent light source at the field diaphragm 11 is converted into parallel light beams with different angles entering the narrow-band interference filter 14, and then the parallel light beams pass through the narrow-band interference filter to be imaged.
Preferably, the small end face of the optical fiber taper is connected with the optical fiber end cap, the tail end of the optical fiber end cap is connected with a light guide pipe with free length, and the joint of the optical fiber end cap and the light guide pipe is positioned at the bottom end of the light inlet cylinder and sealed in the light inlet cylinder. Wherein, the length of light pipe can carry out freely adjusting according to actual need.
Preferably, the number of the first shading rings is 6-10, and the number of the second shading rings is 8-10. First anti-dazzling ring is from last to locating in advance a light section of thick bamboo inner wall down in proper order, and second anti-dazzling ring is from last to setting gradually down in anti-dazzling inner wall.
The imaging system comprises an imaging lens and a CCD sensor, and the imaging system converges parallel light beams with different angles after penetrating through the narrow-band interference filter on an imaging surface of the CCD sensor. The whole imaging system is arranged below the narrow-band interference filter, and meanwhile, the imaging lens and the narrow-band interference filter need to be tightly buckled, so that light leakage is avoided.
The external part of the spectrum detection subsystem is provided with a housing with a heat insulation layer, the side wall of the housing is provided with a refrigerating device, and the outer wall of the shading cylinder is provided with a temperature and humidity sensor. Wherein, a filter wheel is arranged between the shading cylinder and the imaging system along the horizontal direction, and the filter wheel is positioned on the axis of the air outlet of the refrigerating device; the filter wheel is used for placing a plurality of narrow-band interference filters, and the filter wheel is rotated in the observation process to realize the switching of different filters. Meanwhile, the narrow-band interference filter is ensured to achieve the optimal constant temperature effect, and heat below the CCD sensor is effectively brought back to an air inlet of the refrigerating device through circulation of the air channel.
Further, install electronic filter wheel additional between light path shading cylinder and imaging lens, wherein can place the multi-disc narrowband interference filter and rotate the switching in observing, can satisfy and use the demand that the multichannel surveyed even of binary channels.
A commonly used method in the prior art to improve the detection capability is to use a better performing CCD camera. According to the technical scheme, the split structure is adopted, the volume of the light receiving subsystem can be adjusted according to actual needs, the light transmission quantity is increased, meanwhile, the limitation requirement on the CCD camera is reduced, the cost is greatly improved, and the split structure is beneficial to networking observation of a large number of devices. The invention adopts a light cone, an optical fiber and a dome integrating sphere to realize the accurate coupling of the light receiving subsystem and the spectrum detection subsystem.
The invention also provides a near space atmospheric temperature inversion method based on the minimization of the synthetic spectrum cyclic difference value, which can accurately invert the atmospheric temperature of the near space from the actually observed image data and can be applied to networking observation of the temperature field of the top area of the near space.
The atmospheric temperature inversion process based on single synthesis spectrum difference circulation under different atmospheric temperatures comprises the following steps:
(1) firstly, different atmospheric temperatures T are adjusted A-i As input parameters of the forward model, input T A-i Then, the forward model FWD-MDL module outputs different temperatures T A-i Corresponding analog simulation images are calculated, and each forward synthetic spectrum S is calculated F-i ；
(2) Inputting the detected actual observation result OBS-RES into an inversion algorithm RV-AGM, and outputting an actual synthesized spectrum S through calculation R ；
(3) Each forward synthesized spectrum S F-i With the actual synthetic spectrum S R Making difference to obtain forward and actual synthetic spectrum S F-i And S R And averaging the absolute values of all point-by-point differences to obtain a set of differences Df F-i ；
(4) Take Df F-i Minimum difference Df in (1) min And determining Df min The corresponding numerical value of the serial number i is T corresponding to the value of i A-i Namely the near space atmospheric temperature obtained by single synthesis spectrum difference circulation.
Further, the atmospheric temperature inversion process based on single synthesis spectrum difference circulation under different filter temperatures comprises the following steps:
(1) at atmospheric temperature T A-i On the basis of the determination, different filter temperatures T are first determined F-j As input parameters of the forward model, input T F-j Then, the forward modeling FWD-MDL module outputs different filter temperatures T F-j Corresponding analog simulation images are calculated, and each forward synthetic spectrum S is calculated simultaneously F-j ；
(2) Inputting the detected actual observation result OBS-RES into an inversion algorithm RV-AGM, and outputting an actual synthesized spectrum through calculation;
(3) each forward-calculated synthesized spectrum S F-j With the actual synthetic spectrum S R Difference is made to obtain forward and actual synthesized spectrum S F-j And S R To obtain a set of difference values Df F-j ；
(4) Take Df F-j Minimum difference value Df in min And determining Df min The corresponding numerical value of the serial number j, the value of j corresponds to T F-j Namely the temperature of the optical filter obtained by the single synthesis spectrum difference circulation.
The invention relates to an atmospheric temperature inversion process based on multiple cycles of a synthetic spectrum difference, which comprises the following steps:
(1) t obtained by single circulation of different filter temperatures F-j As a given filter temperature T F Brought into the flow of single circulation of different atmospheric temperatures, thereby calculating the atmospheric temperature T A And at a fixed T A Based on the temperature of the filter, the cyclic calculation of different filter temperatures is performed again, so as to obtain a new filter temperature T F-new ；
(2) Calculating T F-new And T F Difference value Δ T of F (ii) a When Δ T F Less than or equal to a set threshold value P stop Then the loop is terminated, corresponding to T A Namely the near space atmospheric temperature obtained by final inversion; when Δ T F Greater than a set threshold value P stop Then, the second cycle is started and T is used F-new Substituted T F The initial value is obtained, and the new delta T is obtained after a plurality of cycles F Less than or equal to the threshold value P stop Finally, an accurate near space atmospheric temperature T is obtained A 。
Has the beneficial effects that:
1) compared with the same type of instrument for detecting the temperature of the top area of the adjacent space, the split type structural design provided by the invention has the advantages that the light receiving subsystem can greatly improve the light receiving capability, improve the sensitivity of temperature detection and enable the structure of the spectrum detection subsystem to be more compact, so that the overall stability and reliability of the system are improved;
2) the invention utilizes the combination of the round top integrating sphere, the annular illumination optical fiber and the pen-shaped calibration lamp in the spectrum detection subsystem to realize the on-line quick calibration of multiple parameters such as flat field coefficient, image center, spectral line position and the like, and provides real-time calibration parameters for forward modeling and inversion, thereby improving the precision and accuracy of temperature detection;
3) the split structure provided by the invention also enables the observation mode to be more flexible, the adjustable light receiving subsystem realizes the observation of the field angle range and the change of the direction, the outfield adaptability is stronger, the development and maintenance cost is reduced, and a more practical means is provided for large-scale high-density networking observation;
4) according to the invention, a plurality of layers of shading rings and dome integrating spheres are respectively added in each subsystem, so that the stray light interference is eliminated, and the imaging quality is improved;
5) the same-machine calibration system is arranged to provide real-time important parameters such as a flat field coefficient, a graph center position, an optical filter wavelength variation with temperature and the like for forward modeling and inversion, so that the accuracy of data inversion is improved;
6) the forward model of the split-type spectrum thermometer comprehensively considers atmospheric parameters and parameters of each instrument, can accurately simulate and simulate an observation result, and provides a basis for inversion.
7) According to the inversion process of the atmospheric temperature in the near space, the influence caused by small changes of the atmospheric temperature and the temperature of the optical filter is considered at the same time, and the accuracy and the reliability of temperature inversion are improved by a method of synthesizing the spectral difference for multiple cycles.
Drawings
Fig. 1 is a schematic diagram of the optical structure of the split-type spectrothermometer of the present invention.
Fig. 2 is a schematic diagram of the optical-mechanical design of the spectrum detection subsystem of the split-type spectrum thermometer of the present invention.
FIG. 3 is an atmospheric temperature inversion process based on a single synthesis spectral difference cycle at different atmospheric temperatures according to the present invention.
FIG. 4 is an atmospheric temperature inversion process based on a single synthesis spectral difference cycle at different filter temperatures according to the present invention.
FIG. 5 is an atmospheric temperature inversion process based on multiple cycles of the composite spectral difference of the present invention.
FIG. 6 is a block diagram of the forward model sub-modules of the present invention.
FIG. 7 is a flow chart of the present invention for raw image data pre-processing.
FIG. 8 is a photograph of the optical structure of the internal body of the split-type spectrothermometer spectral detection subsystem.
Fig. 9 is a photograph of the split-type spectrothermometer with the spectral detection subsystem enclosed in the housing.
In the figure: 1. the system comprises a light receiving subsystem, a spectrum detection subsystem, a light inlet cylinder, a first shading ring, a second shading ring, a third shading ring, a fourth shading ring, a fifth shading ring, a sixth shading ring, a third shading ring, a fourth, a fifth, a fourth, a fifth, a fourth and a fourth, a fourth and a fifth, a fourth and a fourth, a fourth and a fifth, a fourth and a fourth, a fifth, a fourth and a fourth, a fourth and a fourth, a fourth and a fourth, a.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
As shown in fig. 1, the optical structure of the main body of the split-type spectrum thermometer of the present invention is designed as a split-type structure, and mainly includes two subsystems: a light receiving subsystem 1 and a spectrum detection subsystem 2. The on-machine scaling subsystem is not self-contained but is coupled into the spectral detection subsystem 2.
In the light receiving subsystem 1, the upper part mainly comprises a light inlet tube 3 and 6-10 first light-shielding rings 4 embedded into the inner wall of the light inlet tube, wherein the light inlet tube 3 is made of a cylindrical aluminum shell, the first light-shielding rings 4 are made of blackened anodized aluminum, the diameters of through holes of the inner rings are sequentially reduced from top to bottom, and the formed inclination angle is the same as an observation solid angle of equipment, so that stray light outside the observation solid angle of an observation field can be effectively shielded. A large-caliber Fresnel lens 5 is fixed at the joint of the middle part of the light inlet tube 3 and is used for converging light beams in an observation field angle into an optical fiber light cone 6 at the rear end imaging surface of the Fresnel lens 5; the large end face of the optical fiber light cone 6 is arranged upwards and corresponds to the Fresnel lens 5, the small end face of the optical fiber light cone is arranged downwards and is connected with an optical fiber end cap 7, and the tail end of the optical fiber end cap 7 is connected with a light pipe 8 with free length. The optical fiber end cap 7 is used for coupling the optical fiber light cone 6 with the light guide pipe 8, so that the light beam collection efficiency is improved. The connection part of the optical fiber end cap 7 and the light pipe 8 is positioned at the bottom end of the light inlet cylinder 3 and sealed in the light inlet cylinder 3.
The light receiving subsystem 1 is designed to greatly improve the integral light receiving capability of the instrument and simultaneously not influence the structure of a spectrum detection end. The light receiving subsystem 1 is actually a luminosity light receiving system, and an imaging light path design is not needed, wherein the light inlet cylinder 3 is matched with the Fresnel lens 5 and the large end face of the optical fiber light cone 6 to form an observation solid angle of about +/-11 degrees in the zenith direction.
Furthermore, the Fresnel lens 5 is characterized in that it can be produced at low cost with a large clear diameter, the diameter to be used according to the invention being at least greater than that of the Fresnel lens
200mm, and has high transmittance in the near infrared band, and the special structure can make the focal length shorter than the diameter of the lens, thus saving the space of the optical structure, and because the light receiving subsystem 1 does not need imaging, the imaging quality of the Fresnel lens 5 is not too high. The diameter of the large port of the optical fiber light cone 6 can be as high as
40mm, the light transmission efficiency is more than 75%, and the design of the taper can greatly increase the numerical aperture of the optical fiber and increase the solid angle of incident light.
In the spectrum detection subsystem 2, a dome integrating sphere 9 is arranged at the top, and the outlet end of the lower part of the dome integrating sphere is tightly jointed with an annular illumination optical fiber 10, the combined purpose of the two components is to transmit the received light guided out by the light guide pipe 8 to the annular illumination optical fiber 10 and introduce the light beam into the dome integrating sphere 9 along the outlet of the tail end of the illumination optical fiber, so that a circular plane light source with uniform intensity is obtained at the field diaphragm 11 through the action of repeated diffuse scattering.
The field diaphragm 11 is clamped at the top of the main light path shading cylinder 21, and the middle part thereof fixes the main lens 13, the bottom end thereof clamps the narrow-band interference filter 14, and the inner wall thereof is embedded with 8 to 10 second shading rings 12. The whole main body light path aims at converting a plane divergent light source at a field stop 11 into parallel light beams with different angles entering a narrow-band interference filter 14, wherein the light path is divided into an upper part and a lower part by a main lens 13, and the inclination angles of the upper part and the lower part formed by a second shading ring 12 are the same as the solid angle of the main body light path, so that stray light outside the solid angle of the field stop can be effectively shielded.
The imaging lens 15 and the CCD sensor 16 are combined to form an imaging system, and the purpose is to converge the parallel light beams of different angles after passing through the narrow-band interference filter 14 onto the imaging surface of the CCD sensor 16. The whole imaging system is arranged below the narrow-band interference filter 14, and meanwhile, the imaging lens 15 and the narrow-band interference filter 14 need to be tightly buckled, so that light leakage is avoided.
The spectral detection subsystem 2 is designed to achieve detection of the intensity of the target spectral line of each item in the light source using as simple an optical structure and a small volume as possible. The uniform plane light source is formed at the field diaphragm 11, the uniformity is at least over 97 percent, although the uniformity of the plane light source generated by the hemispherical dome integrating sphere is not as high as that of the whole spherical integrating sphere (99.5 percent), the invention completely meets the requirements. The light receiving capability of the light receiving subsystem is greatly improved, so that the light receiving subsystem can be used in the spectrum detection subsystem
A narrow-band interference filter 14 with the aperture of 25mm, a CCD sensor 16 with a smaller image surface and a large-aperture (F #0.95) imaging lens 15 of a C-bayonet, so that the whole optical structure is very compact.
The same-machine calibration subsystem is composed of a pen-shaped calibration lamp 18, an optical fiber 17, an annular illumination optical fiber 10, a dome integrating sphere 9 and a field diaphragm 11 in sequence. Wherein the port of the optical fiber 17 entering the annular illumination fiber 10 and the port of the light pipe 8 entering the annular illumination fiber 10 are separately arranged. The calibration system aims to lead the calibration light beam emitted by the pen-shaped calibration lamp 18 into the annular illumination optical fiber 10 through the optical fiber 17, and then form a uniform plane light source at the field diaphragm 11 through multiple repeated diffuse scattering actions of the dome integrating sphere 9, so that the calibration system is used for the subsequent system calibration process. The pencil lamp 18 generally uses an Ne lamp as a light source, and has a wide linear spectrum in the near infrared band that can be used by the system.
As shown in fig. 2, on the basis of the completion of the optical structure design in fig. 1, the optical-mechanical structure needs to be designed according to the actual situation. After fully considering the aspects of heat dissipation of the CCD sensor 16, precise temperature control of the narrow-band interference filter 14, heat insulation of the spectrum detection subsystem 2, and overall shock resistance, etc., the optical-mechanical structure shown in fig. 2 is designed to be applied to the spectrum detection subsystem 2. The inner wall of a housing 19 formed by an aluminum shell with a heat insulation layer is additionally provided with a sealing heat insulation layer made of vacuum cotton, and meanwhile, the side wall of one side is additionally provided with a semiconductor TEC air conditioner 20 with the weight not higher than 80W, the common radiating fin of the air conditioner is positioned in the shell, one half of the common radiating fin is positioned in an external space, and the temperature control precision needs to be within +/-0.5K. The air outlet of the semiconductor TEC air conditioner 20 faces the narrow-band interference filter 14 and the imaging lens 15, which not only ensures the temperature control of the narrow-band interference filter 14, but also prevents the temperature drift caused by the heat transferred from the CCD sensor 16 to the imaging lens 15 and then transferred to the narrow-band interference filter 14 as much as possible. A temperature and humidity sensor 22 is additionally arranged on the outer side wall of a main light path shading cylinder 21 in the area adjacent to the narrow-band interference filter 14 to monitor real-time temperature and humidity. The CCD sensor 16 is packaged inside a scientific grade CCD camera and can be refrigerated below ambient temperature by at least 40 c, thereby greatly reducing dark noise. If two channels or even multiple channels are needed for detection, an electric filter wheel 24 is additionally arranged between the light path shading cylinder 21 and the imaging lens 15, wherein multiple narrow-band interference filters 14 can be placed and switched in rotation during observation. In addition, if a chemical moisture absorption material is used in the space of the aluminum housing 19 with a heat insulating layer having good sealing performance, the chemical moisture absorption material can be replaced for a long time. The light receiving subsystem 1 needs to be fixed and protected according to actual conditions when an external field is observed.
The following describes a specific embodiment of the actual temperature detecting process according to the present invention with reference to fig. 1 and 2:
the method can invert the atmospheric temperature of the near space by detecting the spectral intensity.
On the basis of comprehensively considering the characteristics of the invention and the characteristics of the airglow spectrum to be detected, the split-type spectral thermometer is designed with three near-infrared channels to acquire and realize the detection of the temperature, namely the airglow O 2 Atmospheric molecule rotation spectral band of (0-1) band, P-branch and Q-branch vibration spectral bands of OH (6-2) Meinel band. Wherein, selecting O 2 The wavelength of 6 pairs of spectral lines of the (0-1) band is distributed between 864.7-867.8 nm, the average radiation intensity is 500-800 Rayleigh (R), and the peak radiation intensity is near the height of 94 km. For the Meinel band spectrum of hydroxyl OH, two bands of P and Q branches of OH (6-2) are supposed to be adopted, wherein 3 pairs of lines selected by the P branch are distributed in the range of 839.9-846.6 nm, 3 pairs of lines of the Q branch are distributed in the range of 834.3-836.5 nm, and the average radiation intensity exceeds 1000R.
The split-type spectral thermometer is based on the basic principle of a spectrophotometer, and the general technology of the instrument utilizes the rule that the peak transmittance of a narrow-band interference filter changes along with the incident light angle. The law of the central wavelength of the narrow-band interference filter varying with the incident beam angle can be expressed by the following formula:
wherein λ is the central transmittance of the filter varying with angle, λ 0 Is the peak transmittance at normal incidence, θ is the angle of incidence of the beam, μ 0 Is the refractive index of air, μ is the optical filterThe refractive index of the sheet. As can be seen from equation (1), as the incident angle θ increases, the center wavelength shifts to a short wavelength, and the peak transmittance decreases.
Therefore, the split-type spectral thermometer provided by the project needs to select a proper optical filter, multiple spectral lines can be sequentially filtered out by utilizing different beam angles through designing an imaging light path, and the intensity is acquired through the CCD camera. The detection mode of the instrument is as follows: near-infrared radiation emitted by a gas glow layer in the top area of the near space enters the split type spectrum thermometer through the atmospheric window, corresponding spectral line intensity can be filtered by the optical filter through different incident light angles, and finally intensity values of different spectral lines are obtained on a CCD image surface and used for inverting temperature. The solid angle of the air-borne planar array antenna facing the sky is about +/-11 degrees to +/-15 degrees, and the diameter of the circular projection plane of the airglow layer corresponding to the zenith direction is about 36km to 52 km. In addition, the observation mode of the passive optical remote sensing does not have the spatial resolution in the vertical direction, but the final observation temperature is the average temperature in a certain horizontal range and a certain thickness area on the approximate fixed height because the height of the airglow layer is relatively stable and the thickness of the main radiation layer is about 3-6 km.
The method for inverting the atmospheric temperature of the near space according to the invention is described in detail below with reference to the accompanying drawings and the specific embodiments:
as shown in fig. 3, the atmospheric temperature inversion process based on single synthesis spectrum difference cycle at different atmospheric temperatures of the present invention is as follows:
the explanation is made in a left-to-right manner from top to bottom. First, different atmospheric temperatures T are given A-i As input parameter for the forward model, T A-i In the range of T A-1 To T A-N Typically, the interval is 0.1K from 110K to 300K, but the range can be expanded if desired, and the interval can be adjusted according to the calculation speed requirement. At input T A-i Then, the forward model FWD-MDL module outputs different temperatures T through calculation A-i Corresponding simulationTrue image, calculating forward synthetic spectrum S F-i . On the other hand, the actual observation result OBS-RES of a certain detection is input into an inversion algorithm RV-AGM, and an actual synthesized spectrum is output through calculation, and only one actual synthesized spectrum exists for each detection. Then, each forward synthesized spectrum S is F-i With the actual synthetic spectrum S R Making difference so as to obtain forward and actual synthetic spectrum S F-i And S R Wherein the difference is made point by point, and the absolute values of all point by point differences are averaged to obtain a set of differences Df F-i ：
Based on Df F-i The minimum difference Df can be obtained by circular comparison min And determining Df min The corresponding numerical value of the serial number i, at this time, the value of i corresponds to T A-i Namely the near space atmospheric temperature obtained by single synthesis spectrum difference circulation.
However, the atmospheric temperature T obtained by a single cycle of synthetic spectral differences A-i The temperature cannot be directly used as the inversion temperature, because all instrument parameters in the current forward model are ideal parameters, and in actual observation, the accuracy of the final synthesized spectrum is affected by the small change of all instrument parameters in a complex environment, and especially, the parameters of the optical filter have great difference along with the change of the temperature, so the flow calculation of fig. 4 needs to be performed on the basis of the completion of the flow of fig. 3.
As shown in fig. 4, the atmospheric temperature inversion process based on single synthesis spectrum difference cycle at different filter temperatures according to the present invention is as follows:
after the flow of FIG. 3, the atmospheric temperature T A-i It has been determined that the input standard molecular spectral data has also been determined. At this time, different filter temperatures T are given first F-j As input parameter of the forward model, the filter temperature T F-j In the range of T F-1 To T F-N Generally, the interval is 0.1K, which is taken from 21.0K to 23.0K, but the range can be expanded if necessary, and the interval can be adjusted according to the calculation speed requirement. At input T F-j Then, the forward model FWD-MDL module outputs different filter temperature T through calculation F-j Corresponding analog simulation images are calculated, and each forward synthetic spectrum S is calculated F-j . On the other hand, the actual observation result OBS-RES of a certain detection is input into an inversion algorithm RV-AGM, and an actual synthesized spectrum is output through calculation, and only one actual synthesized spectrum exists for each detection. Then, each forward synthesized spectrum S F-j And the actual synthetic spectrum S R Making difference so as to obtain forward and actual synthetic spectrum S F-j And S R The difference value of (1) is obtained by averaging the absolute values of all point-by-point difference values, and the calculation method is the same as that of (1), thereby obtaining a group of difference values Df F-j . Based on Df F-j The minimum difference Df can be obtained by circular comparison min And determining Df min Corresponding to the numerical value of the serial number j, at this time, the value of j corresponds to T F-j Namely the temperature of the optical filter obtained by the single synthesis spectrum difference circulation.
After the flow of FIG. 4, although the filter temperature T is F-j Is determined, but at this time T F-j Since the temperature of the filter is different from the temperature assumed when the flow of FIG. 3 is started, T calculated in the flow of FIG. 3 A-i Is no longer completely accurate. To obtain more accurate results, we need to repeat the flow of fig. 3 and 4, so as to implement multiple loop calculations. The specific flow is shown in fig. 5.
FIG. 5 is an atmospheric temperature inversion process based on multiple cycles of the composite spectral difference of the present invention. T obtained by single circulation of the flow of FIG. 4 F-j As a given filter temperature T F Brought into the flow of fig. 3, thereby calculating the atmospheric temperature T A And at a fixed T A Based on the above, the loop calculation of fig. 4 is performed again, thereby obtaining a new filter temperature T F-new . At this time, T is calculated F-new And T F Difference value Δ T of F ＝|T F-new -T F L. If Δ T F Less than a set threshold value P stop (in general, P is taken stop 0.1K), the loop is terminated, at which point the corresponding T A Namely the near space atmospheric temperature obtained by the final inversion. If Δ T F Still greater than the set threshold value P stop Then the second cycle is started and T is used F-new Substituted T F The initial value is that after a plurality of cycles, an accurate near space atmospheric temperature T is obtained A 。
FIG. 6 is a block diagram of the forward model sub-modules of the present invention. In both the flow charts of fig. 3 and fig. 4, a forward model is required to be used to calculate the synthesized spectrum, so that the forward model directly affects the accuracy of the final temperature inversion result. As shown in fig. 6, the forward model is mainly composed of 4 submodules, namely, an airglow spectral radiation submodule, an atmospheric radiation transmission submodule, an optical system submodule and a CCD detector submodule.
The airglow spectrum emission submodule mainly comprises a standard database of airglow emission lines, generally from the international HITRAN molecular spectrum database, and different versions can be used, such as HITRAN02 or HITRAN08, which contain the most common airglow emission component O 2 OH and O atoms.
The atmospheric radiation transmission submodule generally uses universal open source software such as ARTS and the like for calculating the absorption and loss of the airglow luminescence spectral line in a propagation path.
The optical sub-module of the optical system is complex, and based on the optical structure of the split-type spectrum thermometer shown in fig. 1 and 2, the sub-module is composed of a light receiving sub-system, an optical fiber coupling system, a co-machine calibration system, an optical filter model and an imaging optical system. The optical fiber coupling system needs to take the coupling efficiency and the whole transmittance of an optical fiber device into consideration, the same-machine calibration system needs to take the parameters of a dome integrating sphere and a calibration lamp into consideration, the optical filter model needs to take various optical filter parameters into consideration, the imaging optical system needs to take the optical distortion parameters and Modulation Transfer Function (MTF) values into consideration, and the specific parameters need to be obtained through laboratory calibration.
The CCD detector sub-module needs to take into account the responsivity obtained by the calibration and the noise model. When all calibration parameters, the atmospheric temperature T are used A Temperature T of the optical filter F After all the images are input into the four sub-modules, forward images can be simulated through computer programming. The calculation of the synthesized spectrum is required to calculate an average value of gray values of all pixels in each circle by taking the center of the image as a base point and taking one pixel or bin as a radius interval based on the forward image, so as to obtain a curve which takes the center pixel as an origin and extends to the edge of the image, and this is the synthesized spectrum.
Before the inversion processes of fig. 3, 4 and 5 are executed, data preprocessing is required to be performed on the observation acquired raw image, as shown in fig. 7. Firstly, removing cosmic rays from an acquired original image by using a threshold method, wherein a reasonable threshold is set, all pixel points exceeding the threshold are considered as abnormal signals caused by strong cosmic rays, and the abnormal signals are replaced by the average value of 8 surrounding pixels. The second step is to remove background noise, close the CCD shutter before each actual shooting, shoot a dark noise image once with the same exposure time, and subtract the dark noise image from the image after the first step, thereby obtaining an effective signal image which can be used for carrying out the actual inversion process. And thirdly, calculating the synthesized spectrum through the calibration parameters, wherein the calculation method is the same as the last step of the figure 6.
The embodiments not described in detail can be easily implemented by using the prior art.
Claims (10)
1. The utility model provides a split type spectrum thermometer for approaching space is surveyed which characterized in that: comprises a light receiving subsystem (1) and a spectrum detection subsystem (2);
the light receiving subsystem (1) comprises a light inlet cylinder (3), a plurality of first shading rings (4) embedded in the inner wall of the light inlet cylinder, a Fresnel lens (5) and an optical fiber light cone (6) which are arranged inside the light inlet cylinder, wherein the optical fiber light cone (6) is positioned below the Fresnel lens (5); the diameter of an inner ring through hole of the first shading ring (4) is gradually reduced from top to bottom, and the formed inclined angle is the same as the observation solid angle of the light receiving subsystem (1); the large end face of the optical fiber light cone (6) faces the Fresnel lens (5), and the small end face of the optical fiber light cone is far away from the Fresnel lens and is connected with the light guide pipe (8);
the spectrum detection subsystem comprises a dome integrating sphere (9), an annular illuminating optical fiber (10), a main light path shading cylinder (21) and an imaging system which are sequentially arranged from top to bottom; the top end of the main light path shading cylinder is provided with a field diaphragm (11), the middle part of the main light path shading cylinder is fixed with a main lens (13), the bottom end of the main light path shading cylinder is provided with a narrow-band interference filter (14), and the inner wall of the main light path shading cylinder is embedded with a plurality of second shading rings (12); second shading rings are arranged above and below the main lens, and the inclination angle formed by inner ring through holes of the upper shading ring and the lower shading ring is the same as the solid angle of the main light path;
annular illumination optic fibre (10) are equipped with first connection port and second connection port, and light pipe (8) link to each other with annular illumination optic fibre (10) through first connection port, and the second connection port is connected with optic fibre (17), and the other end of optic fibre links to each other with calibration lamp (18).
2. The split-type spectroscopic thermometer for close proximity space detection of claim 1, wherein: the received light guided out by the light guide pipe (8) is transmitted to the annular illumination optical fiber (10), and the light beam is introduced into the dome integrating sphere (9) along the outlet at the tail end of the annular illumination optical fiber (10), so that a circular plane light source with uniform intensity is obtained at the field diaphragm (11) through repeated diffuse scattering; the light source enters the shading cylinder (21), the plane divergent light source at the field diaphragm (11) is converted into parallel light beams with different angles entering the narrow-band interference filter (14), and then the parallel light beams penetrate through the narrow-band interference filter (14) to be imaged.
3. The split-type spectroscopic thermometer for close proximity space detection of claim 1, wherein: the small end face of the optical fiber light cone (6) is connected with the optical fiber end cap (7), the tail end of the optical fiber end cap (7) is connected with the light guide pipe (8), and the joint of the optical fiber end cap (7) and the light guide pipe (8) is located at the bottom end of the light inlet cylinder (3) and sealed in the light inlet cylinder.
4. The split-type spectroscopic thermometer for close proximity space detection of claim 1, wherein: the imaging system comprises an imaging lens (15) and a CCD sensor (16), and the imaging system converges parallel light beams with different angles after transmitting through the narrow-band interference filter (14) on an imaging surface of the CCD sensor (16).
5. The split-type spectroscopic thermometer for close proximity space detection of claim 1, wherein: the light inlet cylinder (3) of the light receiving subsystem is matched with the Fresnel lens (5) and the large end face of the optical fiber light cone (6) to form an observation solid angle of +/-11 degrees to +/-15 degrees in the zenith direction.
6. The split-type spectroscopic thermometer for close space detection as set forth in claim 1, wherein: the number of the first shading rings is 6-10, and the number of the second shading rings is 8-10.
7. The split-type spectroscopic thermometer for close proximity space detection of claim 1, wherein: a cover shell (19) with a heat insulation layer is arranged outside the spectrum detection subsystem, a refrigerating device (20) is installed on the side wall of the cover shell, and a temperature and humidity sensor (22) is installed on the outer wall of the shading cylinder; a filter wheel (24) is arranged between the shading cylinder (21) and the imaging system, and the filter wheel is positioned on the axis of an air outlet of the refrigerating device.
8. An atmospheric temperature inversion method based on the split-type spectrum thermometer for adjacent space detection of any one of claims 1 to 7, characterized in that: the inversion method comprises the following steps:
(1) will vary the atmospheric temperature T A-i As input parameters of the forward model, input T A-i Then, the forward model outputs different temperatures T A-i Corresponding analog simulation images are calculated, and each forward synthetic spectrum S is calculated F-i ；
(2) Inputting the detected actual observation result into an inversion algorithm, and outputting an actual synthesized spectrum S by calculation R ；
(3)Each forward synthesized spectrum S F-i With the actual synthetic spectrum S R Making difference to obtain forward and actual synthetic spectrum S F-i And S R And averaging the absolute values of all point-by-point differences to obtain a set of differences Df F-i ；
(4) Take Df F-i Minimum difference value Df in min And determining Df min The corresponding numerical value of the serial number i is T corresponding to the value of i A-i Namely the near space atmospheric temperature obtained by single synthesis spectrum difference circulation.
9. The atmospheric temperature inversion method according to claim 8, characterized in that: the inversion method further comprises the following steps:
(1) different filter temperatures T F-j As input parameters of the forward model, input T F-j Then, the forward model outputs different filter temperatures T F-j Corresponding analog simulation images are calculated, and each forward synthetic spectrum S is calculated F-j ；
(2) Inputting the actual detected observation result into an inversion algorithm, and outputting an actual synthesized spectrum through calculation;
(3) each forward synthesized spectrum S F-j With the actual synthetic spectrum S R Difference is made to obtain forward and actual synthesized spectrum S F-j And S R To obtain a set of difference values Df F-j ；
(4) Take Df F-j Minimum difference value Df in min And determining Df min The corresponding numerical value of the serial number j, the value of j corresponds to T F-j Namely the temperature of the optical filter obtained by the single synthesis spectrum difference circulation.
10. The atmospheric temperature inversion method of claim 9, wherein: the inversion method further comprises the following steps:
(1) t obtained by single circulation of different filter temperatures F-j As a given filter temperature T F Brought into the flow of single circulation of different atmospheric temperatures, thereby calculating the atmospheric temperature T A And is combined withAt a fixed T A Based on the temperature of the filter, the cyclic calculation of different filter temperatures is performed again, so as to obtain a new filter temperature T F-new ；
(2) Calculating T F-new And T F Difference value Δ T of F (ii) a When Δ T F Less than or equal to a set threshold value P stop Then the loop is terminated, corresponding to T A Namely the near space atmospheric temperature obtained by the final inversion; when Δ T F Greater than a set threshold value P stop Then, the second cycle is started and T is used F-new Substituted T F The initial value is obtained, and the new delta T is obtained after a plurality of cycles F Less than or equal to the threshold value P stop 。
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