Optical system and portable long-wave infrared atmospheric radiation temporal and spatial change rapid measurement device

Abstract

The invention discloses an optical system which comprises a first lens, an optical filter and a second lens which are sequentially arranged in the optical path transmission direction, and further discloses a measuring device which comprises the optical system, the lower end of a detector cold shield is connected with a transition block, the lower end of the transition block is connected with a supporting column, the lower end of the supporting column is connected with a shell, and a Dewar flask is arranged on the shell. A detector is arranged on the end face, located in the detector cold screen, of the transition block. A turntable and a turntable base are sequentially connected below the shell; the imaging optical system is integrated into the structure of the vacuum cavity of the refrigeration type long-wave focal plane infrared detector, so that the refrigeration type long-wave focal plane infrared detector has a large-view-field imaging function, and the measuring device is portable and can meet the requirement for rapidly measuring atmospheric radiation spatial and temporal distribution.

Description

Technical Field

[0001] The invention belongs to the technical field of long-wave infrared measurement, and in particular relates to an optical system and a portable device for quickly measuring the temporal and spatial changes of long-wave infrared atmospheric radiation. Background Art

[0002] The spatiotemporal variation of atmospheric radiation refers to the change of atmospheric radiation brightness over time at a given zenith angle, the spatial change of atmospheric radiation brightness with zenith angle, the change of atmospheric radiation over time at different zenith angles, etc. The spatiotemporal variation of atmospheric radiation will produce low-frequency fluctuations in radiation brightness, which will be superimposed on air-based and space-based targets such as celestial bodies, satellites, missiles, and aircraft as a changing background, reducing the measurement accuracy of the target. Therefore, in the fields of astronomical observation, military defense, etc., it is very necessary to quickly measure the spatiotemporal variation of atmospheric radiation. The main problems of traditional atmospheric radiation measurement devices including Fourier spectrometers and radiometers include: the measurement device is large in size and mass, not easy to carry, and can usually only measure the change of atmospheric radiation brightness over time at a given zenith angle at a slower rate; to obtain the change of atmospheric radiation brightness with zenith angle, it is necessary to scan the measurement optical path in the direction of the zenith angle, and it is impossible to obtain atmospheric radiation brightness data at different zenith angles at the same time, which greatly reduces the measurement efficiency and accuracy.

[0003] The existing Chinese patent CN108955874A provides a sky light background measurement device and method for narrow-band continuous infrared spectrum scanning. The infrared sky light background of the target sky area is measured by a scanning reflector. The device and method are mainly used to measure the sky light background in the near-infrared band. The function of the measurement optical path is focusing, and it has no spatial resolution capability. It can only measure the sky light background at a given zenith angle. The sky light background at different zenith angles needs to be guided into the measurement optical path by a scanning reflector. The obtained spatial distribution of atmospheric radiation is not from the same time, which reduces the efficiency and accuracy of the measurement of the spatial distribution of atmospheric radiation. Summary of the invention

[0004] The purpose of the present invention is to provide an optical system and a portable device for quickly measuring the temporal and spatial changes of long-wave infrared atmospheric radiation.

[0005] To achieve the above object, the present invention adopts the following technical solution: An optical system comprises a first lens, a filter and a second lens arranged in sequence along a light transmission direction, the distance between the first lens and the second lens is 20-30 mm, and the focal length range of the optical system is 40-50 mm.

[0006] Preferably, the central wavelength of the filter is 8-12 μm, the first lens is a meniscus lens, and the second lens has any shape, but is preferably a meniscus lens.

[0007] A portable long-wave infrared atmospheric radiation temporal and spatial variation rapid measurement device comprises the above optical system, wherein the filter is located at the top of the detector cold screen, the second lens is located at the light blocking ring of the detector cold screen, the lower end of the detector cold screen is connected to a transition block, a shell is provided below the transition block, and the shell is a cylindrical structure with a closed opening at one end and a closed opening at the other end. The transition block is connected to the open end of the shell through a support column. A Stirling refrigeration module is arranged in the shell. The cold end of the Stirling refrigeration module is connected to the lower end surface surrounded by the support column in the transition block. A Dewar flask is arranged on the open end of the shell. The transition block is located in the detector cold screen and the detector is installed on the end surface; the transition block ensures uniform cooling of the detector; the transition block is made of Al2O3 ceramic material with high thermal conductivity; The support column, transition block, and detector cold shield are all located in the Dewar flask; preferably, the support column is made of Kevlar fiber material, which is light in weight, high in strength, and low in thermal conductivity. The support column fixes the transition block and prevents the heat from the Dewar shell from being transferred to the transition block, thereby preventing cold leakage; A turntable and a turntable base are connected in sequence below the closed end of the shell; the turntable can make the measuring device rotate along the zenith angle direction; The end of the Dewar flask away from the Stirling refrigeration module is provided with a window frame. The first lens is located in the window frame. The first lens and the shell cooperate to seal both ends of the Dewar flask, providing a vacuum-tight space. The outer side of the window frame is connected with an annular air knife through a thread. The threaded connection can be used as an air outlet during calibration. Preferably, a temperature control module is provided at the threaded connection between the annular air knife and the window frame for measuring the surface temperature of the first lens to make its temperature uniform.

[0008] A dust cover is provided on the top of the annular wind knife, and the dust cover and the annular wind knife are connected via a magnet.

[0009] The side wall of the dust cover is provided with an air outlet, and the inner surface of the dust cover is a gray body. The gray body is a slightly oxidized metal, and the gray body is used as the inner surface for the external field calibration of the measuring device to ensure that the calibration does not exceed the dynamic range of the detector.

[0010] The annular air knife, temperature control module, turntable, and detector are all electrically connected to a processor module, and the processor module is used to collect and process detector data; control the air volume and temperature of the air knife and the rotation of the turntable. After collecting the temperature of the threaded connection, the temperature control module transmits the temperature to the processor, and controls the air volume and air temperature of the air knife by comparing it with the set temperature, thereby controlling the temperature of the first lens surface and the inner surface of the dust cover, and then achieving calibration.

[0011] The method for measuring atmospheric radiation using the above-mentioned rapid measurement device comprises the following steps: Step 1: Before the measurement begins, close the dust cover, control the Stirling refrigeration module to cool the Dewar flask and the internal components, use the wind knife to make the surface of the first lens and the inner surface of the dust cover reach the specified temperature, and start calibration; Step 2: Open the dust cover and point the measuring device to any azimuth, zenith angle 7.5° position. There is no need to scan the sky area. The atmospheric radiation measuring device can quickly measure the atmospheric radiation from the positive zenith to the zenith angle of 15° at the same time.

[0012] The optical system of the present invention adopts three optical elements, including two lenses and an infrared filter. The infrared filter is placed between the two lenses. Taking into full consideration the difficulty of production and processing, mechanical adjustment and manufacturing cost, a certain distance (20-30mm) should be left between the first lens and the second lens. In order to facilitate the installation and adjustment of the filter and the detector cold screen, and to match the field of view, in order to improve the resolution of the system, the F number should be controlled in a smaller range (generally less than 2.5). Finally, the focal length range of the optical system is set to 40-50mm.

[0013] The rapid measurement device of the present invention abandons the use of a flat lens as a sealing window in the prior art, and creatively uses a first lens as a sealing window. For the atmospheric radiation measurement device, the outer side of the sealing window lens is an air environment, and the inner side is a vacuum environment. The air pressure on the inner and outer sides of the sealing window lens is different, resulting in an air pressure difference. The air pressure difference will apply pressure to the sealing window lens from the outside to the inside, and the window frame of the lens will also be subjected to atmospheric pressure to squeeze the edge of the lens, causing the lens sealing window to deform. At the same time, since the cold screen and the detector in the vacuum chamber require low-temperature refrigeration, due to radiation heat exchange and weak heat conduction, the temperature of the lens sealing window will be lower than the ambient temperature, but higher than the temperature of the optical element on the cold screen. Therefore, the optical design of the lens needs to comprehensively consider the influence of air pressure and temperature gradient on aberration. Since the pressure direction is from outside to inside and the thermal expansion direction is from inside to outside, the first lens in the present invention adopts a meniscus lens to balance the influence of the internal and external pressure difference and the deformation caused by thermal expansion; the edge of the meniscus lens adopts a flat plate structure, which is convenient for airtight connection with the window frame, ensuring airtightness and imaging quality.

[0014] The detector cold screen in the rapid measurement device of the present invention is designed as an aperture stop of the optical system. A filter and a second lens are installed on the detector cold screen. The detector cold screen also has the function of suppressing stray light. The inner wall of the detector cold screen is blackened to absorb infrared stray light. A light blocking ring is arranged on the inner wall of the detector cold screen. The light blocking ring has a lens clamping mechanism, and the second lens can be installed inside the cold screen. The second lens is both an imaging component of the optical system and a component that suppresses infrared stray light. The inner surface of the dust cover is a gray body, made of a lightly oxidized metal material, and the emissivity is controlled between 0.2 and 0.4 to ensure that the standard source and the sky radiation brightness are not too different during calibration, which exceeds the dynamic range. A wind knife with a refrigeration function is installed on the outside of the window frame through a threaded connection to send cold air to the lens sealing window to cool it and ensure uniform temperature. During calibration, the magnetic dust cover and the wind knife end face are seamlessly combined, and cold air is sent to the sealing window (first lens) and the dust cover at the same time through the wind knife, so that the sealing window (first lens) and the inner surface of the dust cover (calibration source) are cooled and have the same temperature.

[0015] The device of the present invention integrates the imaging optical system into the structure of the vacuum cavity of the refrigerated long-wave focal plane infrared detector, so that it has a large field of view imaging function. The measuring device is portable and can meet the needs of quickly measuring the spatiotemporal distribution of atmospheric radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the structure of the optical system of the present invention; Figure 2 It is a structural schematic diagram of the rapid measurement device of the present invention; Figure 3 The first lens, the Dewar flask and the temperature distribution inside the lens of the present invention; Figure 4 This is a structural deformation diagram of the first lens and the Dewar flask of the present invention; Figure 5 The original optical path and the point diagram after deformation of the device of the present invention; (a) is the original optical path point diagram, and (b) is the point diagram after deformation caused by pressure; Figure 6 The point diagram with and without temperature gradient under the combined influence of internal and external pressure difference and thermal expansion, where (a) is without temperature gradient and (b) is with temperature gradient; Description of reference numerals: In the figure: 1. First lens; 2. Filter; 3. Second lens; 4. Detector; 5. Transition block; 6. Stirling cooling module; 7. Window frame; 8. Detector cold screen; 9. Support column; 10. Turntable; 11 Turntable base; 12. Dust cover; 13. Annular air knife; 14 Processor module; 15. Temperature control module; 16. Dewar flask; 17. Shell. DETAILED DESCRIPTION

[0018] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise" and "center" are used herein. The directions or positional relationships indicated by "clockwise", "counterclockwise", etc. are based on the directions or positional relationships shown in the drawings and are only for the convenience of describing the present application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, they should not be understood as limiting the present application.

[0019] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0020] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0021] An optical system such as Figure 1 As shown, it includes a first lens 1, a filter 2 and a second lens 3 arranged in sequence along the light transmission direction, the distance between the first lens 1 and the second lens 3 is 20-30mm, and the focal length range of the optical system is 40-50mm. The central wavelength of the filter 2 is 8-12μm, and the first lens 1 and the second lens 3 are both meniscus lenses.

[0022] like Figure 2As shown, the rapid measuring device of the present invention comprises the above optical system, the filter 2 is located at the top of the detector cold shield 8, the second lens 3 is located at the light blocking ring of the detector cold shield 8, the lower end of the detector cold shield 8 is connected to a transition block 5, a shell 17 is provided below the transition block, and the shell 17 is a cylindrical structure with an opening closed at one end and a closed opening at the other end. The transition block 5 is connected to the open end of the housing 17 through the support column 9, the cold end of the Stirling cooling module 6 is connected to the lower end surface surrounded by the support column in the transition block 5, and the filter 2 is fixed on the detector cold screen 8 together with the second lens 3 as the aperture stop of the imaging light path to limit the external stray light from entering the imaging light path; The detector 4 is arranged on the end surface of the transition block 5 located in the detector cold shield 8; the transition block 5 ensures uniform cooling of the detector 4; the transition block 5 is made of Al2O3 ceramic material with high thermal conductivity; the detector 4 adopts a focal plane detector; the full field angle of the imaging optical path is greater than 10°, and the full field of view can achieve diffraction-limited imaging; The support column 9, the transition block 5, and the detector cold shield 8 are all located in the Dewar flask 16; the support column 9 is made of Kevlar fiber material, which is light in weight, high in strength and low in thermal conductivity. The support column fixes the transition block and prevents the heat from the outer shell of the Dewar flask 16 from being transferred to the transition block 5, thereby preventing cold leakage; The lower part of the closed end of the housing 17 is connected in sequence to a turntable 10 and a turntable base 11; the turntable 10 can make the measuring device rotate along the zenith angle direction; The end of the Dewar flask 16 away from the Stirling refrigeration module 6 is provided with a window frame 7. The first lens 1 is located in the window frame 7; the first lens 1 is used as a sealing window, and the meniscus protrudes outward, and can withstand a maximum of 1 standard atmospheric pressure and a certain temperature gradient. This structural design can balance the effects of pressure and temperature on imaging quality; the cooperation of the first lens 1 and the shell 17 realizes the sealing of both ends of the Dewar flask 16, providing a vacuum-tight space; The outer side of the window frame 7 is connected with an annular air knife 13 by threads. The threaded connection can be used as an air outlet during calibration. The threaded connection between the annular air knife 13 and the window frame 7 is provided with a temperature control module 15 for controlling the surface temperature of the first lens 1 to make it uniform.

[0023] A dust cover 12 is provided at the top of the annular wind knife 13, and the dust cover 12 and the annular wind knife 13 are connected via a magnet.

[0024] The side wall of the dust cover 12 is provided with an air outlet, and the inner surface of the dust cover 12 is a gray body. The gray body is a slightly oxidized metal, and the gray body is used as the inner surface for the external field calibration of the measuring device to ensure that the calibration does not exceed the dynamic range of the detector.

[0025] The annular air knife 13 , the temperature control module 15 , the turntable 10 , and the detector 4 are all electrically connected to a processor module 14 , and the processor module 14 is used for collecting and processing data from the detector 4 ; and controlling the air volume and temperature of the annular air knife 13 and the rotation of the turntable 10 .

[0026] The method for measuring using the above measuring device comprises the following steps: Step 1: Before the measurement starts, the dust cover 12 is closed, the Stirling refrigeration module 6 is controlled to cool the Dewar flask 16 and the internal components, and the annular air knife 13 is used to make the first lens surface 1 and the inner surface of the dust cover 12 reach the specified temperature, and the calibration is started; the calibration is started; Step 2: Open the dust cover 12, point the measuring device to any azimuth, and point to the zenith angle of 7.5°. There is no need to scan the sky area. The atmospheric radiation measuring device can simultaneously and quickly measure the atmospheric radiation from the positive zenith to the zenith angle of 15°.

[0027] The measuring device of the present invention is used to analyze the temperature distribution and detect the structural deformation caused by pressure and temperature. Figure 3 and 4 As shown in the figure, analysis shows that due to refrigeration, there is a large temperature gradient between the first lens (284.36±0.8K), the filter (106K), and the second lens (93K). The surface of the first lens also has an uneven refractive index caused by the temperature gradient. There is a pressure difference inside and outside the vacuum cavity, which causes the lens sealing window to be subjected to inward pressure, causing the lens to deform. The superposition of multiple factors leads to the deterioration of imaging quality, which must be considered in the design of the measurement device.

[0028] from Figure 5 It can be seen that the shape and size of the spot diagram slightly increase due to the pressure, but still within the diffraction limit. Figure 5 and Figure 6 It can be seen that the effects of pressure and thermal expansion will offset each other, resulting in the effect of deformation on aberration being negligible. However, the uneven temperature of the lens sealing window caused by the combined effects of refrigeration and external ambient temperature will still seriously affect the imaging quality. The external ambient temperature changes at any time, so the temperature gradient will also change. Therefore, the present invention provides an annular wind knife and a temperature control module to control the temperature of the first lens to ensure the imaging effect.

Claims

1. An optical system, characterized in that: The optical system comprises a first lens, a filter and a second lens which are arranged in sequence along the transmission direction of the optical path. The distance between the first lens and the second lens is 20-30 mm, and the focal length range of the optical system is 40-50 mm.

2. An optical system according to claim 1, characterized in that: The central wavelength of the filter is 8-12 μm, and the first lens and the second lens are both meniscus lenses.

3. A portable device for rapid measurement of temporal and spatial changes of long-wave infrared atmospheric radiation, characterized in that: The optical system comprises the optical system as claimed in claim 1 or 2, wherein the filter is located at the top of the detector cold screen, the second lens is located at the light blocking ring of the detector cold screen, the lower end of the detector cold screen is connected to a transition block, a shell is provided below the transition block, the shell is a cylindrical structure with an opening closed at one end and the other end closed, the transition block is connected to the open end of the shell through a support column, a Stirling refrigeration module is provided in the shell, and the cold end of the Stirling refrigeration module is connected to the lower end surface surrounded by the support column in the transition block, A Dewar flask is provided on the open end of the shell. A detector is provided on the end surface of the transition block located inside the detector cold shield; The support column, transition block, and detector cold shield are all located in the Dewar flask; The lower part of the closed end of the shell is connected with a turntable and a turntable base in sequence; The end of the Dewar flask away from the Stirling refrigeration module is provided with a window frame. The first lens is located in the window frame.

4. A portable long-wave infrared atmospheric radiation spatiotemporal variation rapid measurement device according to claim 3, characterized in that: The outer side of the window frame is connected with an annular wind knife through threads.

5. A portable long-wave infrared atmospheric radiation spatiotemporal variation rapid measurement device according to claim 4, characterized in that: A dust cover is provided on the top of the annular wind knife, and the dust cover and the annular wind knife are connected via a magnet.

6. A portable long-wave infrared atmospheric radiation spatiotemporal variation rapid measurement device according to claim 5, characterized in that: The side wall of the dust cover is provided with an air outlet, the inner surface of the dust cover is a gray body, the dust cover is made of a lightly oxidized metal material with an emissivity of 0.2-0.4, and is used for calibrating the measuring device.

7. A portable long-wave infrared atmospheric radiation spatiotemporal variation rapid measurement device according to claim 6, characterized in that: A temperature control module is provided at the threaded connection between the annular wind knife and the window frame, which is used to measure the temperature of the first lens surface and the dust cover.

8. A portable long-wave infrared atmospheric radiation spatiotemporal variation rapid measurement device according to claim 7, characterized in that: The annular air knife, temperature control module, turntable and detector are all electrically connected to a processor module, and the processor module is used for collecting and processing detector data; controlling the air volume and temperature of the air knife and the rotation of the turntable.

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