Novel medium-wave thermal infrared imager calibration device and calibration method

Abstract

The invention relates to a novel medium-wave thermal infrared imager calibration device and calibration method, and relates to the field of measurement, the novel medium-wave thermal infrared imager calibration device comprises a black body controller, a black body, a medium-wave thermal infrared imager, a collimation laser, a laser measurement system, an endoscope, a focusing lens and a photoelectric detector, the medium-wave thermal infrared imager is placed on one side of the heating end of the black body; an endoscope is placed at the position where the input end is aligned with the medium-wave thermal infrared imager and the output end is aligned with the black body, a beam splitter is placed outside the input end of the endoscope, a collimation laser is placed in the direction of 45 degrees of the normal of a reflecting surface of the beam splitter, and a laser measurement system is placed in the direction of 45 degrees of the normal of a transmission surface of the beam splitter; the medium-wave thermal infrared imager calibration device has the advantages that the influence of the absorption effect of environmental atmosphere transmission on calibration of the medium-wave thermal infrared imager is basically eliminated, and the measurement uncertainty caused by calibration in the use process of the medium-wave thermal infrared imager is effectively reduced.

Description

Technical Field

[0001] The invention relates to the field of measurement technology, and in particular to a novel calibration device and calibration method for a medium-wave infrared thermal imager. Background Art

[0002] Thermal imagers are important equipment in optical radiation characteristics testing. Laboratory calibration of thermal imagers is an important step in converting raw measurement data (grayscale value) into radiation characteristics data (radiant brightness) with physical meaning in optical radiation characteristics testing. The accuracy of calibration directly affects the measurement uncertainty during the use of thermal imagers. The more accurate the calibration, the smaller the measurement uncertainty.

[0003] In laboratory calibration, black bodies are usually used as standard sources for infrared radiation calibration. In order to avoid damage to the thermal imager by the black body, the thermal imager needs to be placed at a certain distance from the black body. However, the ambient atmosphere between the black body and the thermal imager absorbs optical radiation. In the traditional laboratory infrared radiation calibration of thermal imagers, due to the lack of corresponding measurement methods and devices, the influence of the above absorption on the thermal imager calibration is not eliminated or weakened. Especially for the radiation calibration of medium-wave infrared thermal imagers, the typical band range of medium-wave infrared thermal imagers is 3.7μm to 4.8μm, and there is a main absorption peak of carbon dioxide (about 4.3μm) in this band. Carbon dioxide is a relatively high-content gas in the atmosphere. In recent years, the global average carbon dioxide content has been close to 420ppm, and the carbon dioxide content will be higher when the indoor population is dense and the ventilation is long. According to calculations, when a medium-wave infrared thermal imager is used for radiation calibration 1 meter away from the black body, the carbon dioxide content in the ambient atmosphere is 420ppm, and the error caused by atmospheric transmission is about 6.4%.

[0004] Therefore, in view of the above shortcomings, it is necessary to provide a new medium-wave infrared thermal imager calibration device and calibration method. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The technical problem to be solved by the present invention is to solve the problem that the absorption effect of ambient atmospheric transmission causes errors in the calibration of a medium-wave infrared thermal imager.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention provides a novel medium-wave infrared thermal imager calibration device, comprising a blackbody controller, a blackbody, a medium-wave infrared thermal imager, a collimating laser, a laser measurement system, a cavity mirror, a focusing lens and a photoelectric detector. The blackbody controller is connected to the blackbody through a cable, and the medium-wave infrared thermal imager is placed on one side of the heating end of the blackbody; the cavity mirror is placed at a position where the input end is aligned with the medium-wave infrared thermal imager and the output end is aligned with the blackbody, a beam splitter is placed outside the input end of the cavity mirror, a collimating laser is placed in the direction of 45° of the normal of the reflection surface of the beam splitter, and a laser measurement system is placed in the direction of 45° of the normal of the transmission surface of the beam splitter; a focusing lens and a photoelectric detector are placed in sequence outside the output end of the cavity mirror.

[0009] As a further illustration of the present invention, preferably, the cavity mirror comprises an input cavity mirror and an output cavity mirror, both the input cavity mirror and the output cavity mirror are plano-concave high-reflection mirrors, and the output cavity mirror and the concave parts of the output cavity mirror are arranged opposite to each other.

[0010] As a further illustration of the present invention, preferably, one side of the concave surface of the input cavity mirror is aligned with the receiving mirror surface of the medium-wave infrared thermal imager, and one side of the concave surface of the output cavity mirror is aligned with the heating end surface of the black body.

[0011] As a further illustration of the present invention, preferably, the concave side of the input cavity mirror and the output cavity mirror is coated with a 1580nm reflective film, and the flat side is coated with a 1580nm anti-reflection film; the center positions of the input cavity mirror and the output cavity mirror are both located on the collimated laser optical axis.

[0012] As a further illustration of the present invention, preferably, the laser measurement system includes a beam shaping module, a measuring laser and a measuring laser controller, the measuring laser controller is electrically connected to the measuring laser to change the current of the measuring laser, the measuring laser changes the output laser wavelength by changing the current, and the beam shaping module is located between the beam splitter and the measuring laser to change the central wavelength of the output laser.

[0013] The present invention also provides a novel calibration method for a medium-wave infrared thermal imager calibration device, comprising the following steps:

[0014] Ⅰ. Build a calibration device, where the effective side length of the black body heating end surface is not less than the aperture of the medium-wave infrared thermal imager lens;

[0015] Ⅱ. Set the initial temperature of the black body, turn on the medium-wave infrared thermal imager to receive the image of the heating end face of the black body, and after the temperature of the black body stabilizes, adjust the medium-wave infrared thermal imager so that the central field of view is aligned with the center position of the heating end face of the black body;

[0016] Ⅲ. Turn on the collimating laser mirror, adjust the input cavity mirror and the output cavity mirror until the mirror surfaces are relatively parallel so that the input cavity mirror and the output cavity mirror form an optical resonant cavity; turn on the measuring laser through the measuring laser controller, adjust the optical axis direction of the laser output from the laser measuring system to coincide with the optical axis of the collimating laser, then turn off the collimating laser and adjust the position of the focusing lens so that the transmitted light spot is focused on the target surface of the photodetector;

[0017] IV. Taking the reference voltage as the initial voltage, an additional voltage is loaded on the reference voltage to make the laser output by the measuring laser show periodic changes within a wavelength range; the photodetector receives and completes the AD conversion to obtain an optical power measurement result of a laser wavelength scan; after completing a laser wavelength scan, the output voltage of the measuring laser controller is set back to the initial reference voltage, and the above process is repeated to obtain the measurement results of multiple laser wavelength scans distributed in time sequence.

[0018] V. Keep the initial temperature of the black body unchanged, the medium-wave infrared thermal imager collects infrared images at a certain frequency, and completes multiple laser wavelength scans at a speed not lower than the infrared image acquisition frequency to obtain the corresponding measurement results; then change the black body temperature, and repeat the above process after the temperature stabilizes, to obtain the measurement images of the medium-wave infrared thermal imager at different black body temperatures and the laser wavelength scanning measurement results at the corresponding time.

[0019] VI. Align the measured medium-wave infrared measurement image and the laser wavelength scanning measurement result on the time axis, and process them in sequence in combination with the distance value between the black body and the medium-wave infrared thermal imager to calculate the apparent medium-wave infrared radiation brightness; finally, establish the functional relationship between the apparent medium-wave infrared radiation brightness corresponding to different black body temperatures and the measured black body average grayscale value to complete the calibration.

[0020] As a further illustration of the present invention, preferably, the average gray value of the black body is read by using infrared image processing software, and the medium-wave infrared radiation brightness corresponding to different temperatures is calculated using Planck's formula.

[0021] As a further illustration of the present invention, preferably, the laser wavelength scanning curve is read by using spectral processing software, the wavelength scanning ring-down time in one cycle is calculated using the oscillation time calculation formula, the carbon dioxide content is calculated by the device concentration measurement formula based on the laser cavity ring-down spectroscopy technology, and the content is substituted into the atmospheric transmission calculation software to obtain the atmospheric transmittance.

[0022] As a further illustration of the present invention, preferably, the apparent mid-wave infrared radiation brightness L′ m for:

[0023] L′ m =L m ·t m

[0024] in

[0025] L m is the brightness of medium-wave infrared radiation corresponding to different temperatures;

[0026] t m is the atmospheric transmittance.

[0027] As a further illustration of the present invention, preferably, the functional relationship between the apparent mid-wave infrared radiation brightness and the measured black body average gray value is:

[0028] L′ m = k·DN m +b

[0029] in

[0030] k is the gain coefficient;

[0031] b is the compensation value.

[0032] (III) Beneficial effects

[0033] The above technical solution of the present invention has the following advantages:

[0034] Through the calibration device and calibration method designed by the present invention, the carbon dioxide content in the transmission path during the radiation calibration process can be obtained online in real time, effectively reducing the impact of atmospheric transmission on the measurement results. Preliminary estimates show that the error caused by atmospheric transmission can be reduced to less than 0.1%, which can be regarded as basically eliminating the impact of atmospheric transmission on the calibration of medium-wave infrared radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is the optical path diagram of the calibration device of the present invention;

[0036] Figure 2 It is a flow chart of the calibration method of the present invention.

[0037] In the figure: 1. Blackbody controller; 11. Cable; 2. Blackbody; 3. Medium-wave infrared thermal imager; 31. Tripod; 4. Collimating laser; 41. Beam splitter; 5. Laser measurement system; 51. Beam shaping module; 52. Measuring laser; 53. Measuring laser controller; 6. Cavity mirror; 61. Input cavity mirror; 62. Output cavity mirror; 7. Focusing lens; 8. Photodetector. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] A new type of calibration device for medium-wave infrared thermal imagers, such as Figure 1 As shown, it includes a blackbody controller 1, a blackbody 2, a medium-wave infrared thermal imager 3, a collimating laser 4, a laser measuring system 5, a cavity mirror 6, a focusing lens 7 and a photoelectric detector 8. The blackbody controller 1 is connected to the blackbody 2 through a cable 11, and the medium-wave infrared thermal imager 3 is placed on the side of the heating end of the blackbody 1; the cavity mirror 6 is placed at a position where the input end is aligned with the medium-wave infrared thermal imager 3 and the output end is aligned with the blackbody 2, a beam splitter 41 is placed outside the input end of the cavity mirror 6, the collimating laser 4 is placed in the direction of 45° of the normal line of the reflection surface of the beam splitter 41, and the laser measuring system 5 is placed in the direction of 45° of the normal line of the transmission surface of the beam splitter 41.

[0040] like Figure 1 As shown, the blackbody controller 1 is mainly used to control the heating temperature of the blackbody 2. The blackbody 2 is a rectangular surface source standard blackbody, and the effective side length of the heating end face (for example, 300mm) should not be less than the lens aperture of the medium-wave infrared thermal imager 3 (for example, 100mm). The collimated laser 4 is a helium-neon laser, and the output laser center wavelength is 632.8nm. The collimated laser 4 is provided to calibrate the placement of the laser measurement system 5, cavity mirror 6, focusing lens 7 and photodetector 8 to ensure that the optical axis is in a straight line. The photodetector 8 is a gain-adjustable indium gallium arsenic detector, which can measure wavelengths covering 800nm ​​to 1700nm and has a high measurement sensitivity.

[0041] like Figure 1 As shown, the laser measurement system 5 includes a beam shaping module 51, a measuring laser and a measuring laser controller 53. The measuring laser controller 53 is electrically connected to the measuring laser 52. The measuring laser controller 53 changes the current of the measuring laser 52 by adjusting the output voltage and the voltage timing waveform. The measuring laser 52 is a butterfly DFB laser, and the output laser center wavelength is 1580nm. The output laser wavelength can be changed by changing the input current. The beam shaping module 51 is located between the beam splitter 41 and the measuring laser 52. The beam shaping module 51 is composed of a group of lenses with adjustable spacing to change the center wavelength of the output laser.

[0042] like Figure 1As shown, the cavity mirror 6 includes an input cavity mirror 61 and an output cavity mirror 62. The input cavity mirror 61 and the output cavity mirror 62 are both plano-concave high-reflection mirrors with exactly the same structure. The concave parts of the output cavity mirror 61 and the output cavity mirror 62 are arranged opposite to each other. The planes of the input cavity mirror 61 and the output cavity mirror 62 are coated with a 1580nm anti-reflection film, and the concave surfaces are coated with a 1580nm reflective film, and the reflectivity is better than 0.9999. The inner concave surface of the output cavity mirror 62 is aligned with the horizontal position of the heating end surface of the black body 2, and the inner concave surface of the input cavity mirror 61 is aligned with the position of the receiving end surface of the lens of the medium-wave infrared thermal imager 3.

[0043] The present invention also provides a novel calibration method for a medium-wave infrared thermal imager calibration device, such as Figure 2 As shown, the following steps are included:

[0044] Ⅰ. Build a calibration device and place the medium-wave infrared thermal imager 3 at a distance of 1 meter from the heating end surface of the black body 2.

[0045] Ⅱ. Turn on the black body 2 through the switch on the black body controller 1, and set the initial temperature of the black body 2 to 50°C. Turn on the medium-wave infrared thermal imager 3 until it runs stably, and the medium-wave infrared thermal imager 3 can receive the image of the heating end face of the black body 2. After the temperature of the black body 2 is stable, adjust the azimuth axis and pitch axis of the tripod 31 to align the central field of view of the medium-wave infrared thermal imager 3 with the central position of the heating end face of the black body 2.

[0046] III. Adjust the lens of the medium-wave infrared thermal imager 3 for focusing, turn on the collimating laser 4, adjust the input cavity mirror 61 and the output cavity mirror 62 so that the center positions of the input cavity mirror 61 and the output cavity mirror 62 fall on the collimating laser optical axis at the same time; adjust the mirror surfaces of the input cavity mirror 61 and the output cavity mirror 62 again so that the two mirror surfaces are relatively parallel, so that the input cavity mirror 61 and the output cavity mirror 62 form an optical resonant cavity.

[0047] The measuring laser 52 is turned on by the measuring laser controller 53, and the optical axis direction of the laser output by the measuring laser system 5 is adjusted so that the measuring laser optical axis coincides with the collimating laser optical axis. After the optical axes coincide, the collimating laser 4 is turned off. The position of the focusing lens 7 is adjusted so that the transmitted light spot is focused on the target surface of the photodetector 8. In the process of adjusting the focused light spot, a larger gain is used first, and a smaller gain is used after the light intensity gradually increases.

[0048] IV. Through the measurement laser controller 53, with a voltage value of 100mV as the initial reference voltage, an additional voltage in the shape of a triangular wave is loaded on the reference voltage, and the voltage peak is 0.5mV. The additional voltage can make the central wavelength of the laser output by the measurement laser 52 present a periodic change in the free spectrum range. Then, the reference voltage is gradually increased with a fixed voltage of 5mV, the peak value and waveform of the additional voltage are maintained unchanged, and the measurement lasers with different central wavelengths are output in sequence. Finally, under the action of the measurement lasers with different central wavelengths mentioned above, the photodetector 8 receives the transmission light intensity after focusing and completes the AD conversion to obtain a series of optical power measurement results.

[0049] The above process is a laser wavelength scan. After completing a laser wavelength scan, the reference voltage is reset to the initial reference voltage by measuring the laser controller 53 again, and the above process is repeated to obtain the measurement result of the second laser wavelength scan. By repeating the above process, the measurement results of multiple laser wavelength scans can be obtained in chronological order.

[0050] V. Keep the initial set temperature of black body 2 unchanged, and use medium-wave infrared thermal imager 3 to collect infrared images at a frequency of 10 Hz. At the same time, complete multiple laser wavelength scans at a frequency of 10 Hz to obtain corresponding measurement results. Through black body controller 1, gradually increase the temperature of black body 2 in steps of 10°C. After the second set temperature of 60°C stabilizes, keep the measurement frequency unchanged at 10 Hz, and use medium-wave infrared thermal imager 3 to collect infrared images again. At the same time, keep the measurement frequency unchanged at 10 Hz and complete multiple laser wavelength scans. Repeat the above process to obtain medium-wave infrared measurement images of black body 2 at different temperatures, as well as the laser wavelength scanning measurement results at the corresponding time.

[0051] VI. The measurement data generated during the calibration process are mainly divided into three categories: the medium-wave infrared measurement image of blackbody 2, the laser wavelength scanning measurement results, and auxiliary information. The three types of measurement data are aligned on the time axis, and the three types of measurement data at different measurement times are processed in turn. Among them, the auxiliary information is the distance between the heating end face of blackbody 2 and the medium-wave infrared thermal imager 3. The distance remains unchanged at different times and is always 1 meter.

[0052] The processing of the medium-wave infrared measurement image is as follows: Use infrared image processing software to read the average gray value of black body 2, which are DN1, DN2...DN m ; Using Planck's formula, we can get the brightness of mid-wave infrared radiation corresponding to different temperatures, which are L1, L2...L m .

[0053] The processing of the laser wavelength scanning measurement results is as follows: the laser wavelength scanning curve is read using the cavity ring-down spectroscopy data processing software; the wavelength scanning ring-down time under one cycle is calculated using the ring-down time calculation formula; the carbon dioxide content is calculated using the gas concentration measurement formula based on the laser cavity ring-down spectroscopy technology, which are C1, C2...C m Based on the laser cavity ring-down spectroscopy technology, the device constructed according to the parameters in the embodiment is used to measure the carbon dioxide content, and its measurement accuracy is about 10ppm.

[0054] Finally, the carbon dioxide content is substituted into the atmospheric transmission calculation software, and the atmospheric transmittances in the measurement band range of the medium-wave infrared thermal imager 3 are obtained as t1, t2…t m The apparent mid-wave infrared radiation brightness L' is calculated by the following formula m :

[0055] L′ m =L m ·t m

[0056] in

[0057] L m is the brightness of medium-wave infrared radiation corresponding to different temperatures;

[0058] t m is the atmospheric transmittance.

[0059] VII. Establish the apparent mid-wave infrared radiation brightness L′1, L′2, ... L′ corresponding to different blackbody temperatures m Compared with the measured black body average gray value DN1, DN2...DN m A linear function between:

[0060] L′ m = k·DN m +b

[0061] in

[0062] k is the gain coefficient;

[0063] b is the compensation value.

[0064] The gain coefficient k and compensation value b are obtained through calculation. At this point, the laboratory radiation calibration of the medium-wave infrared thermal imager is completed.

[0065] In summary, the present invention is based on the laser cavity ring-down spectroscopy technology, and through real-time online accurate measurement of the carbon dioxide content in the ambient atmosphere on the transmission path of the medium-wave infrared thermal imager during the laboratory calibration process, combined with the calibration data processing method, it basically eliminates the influence of the absorption effect of the ambient atmosphere transmission on the calibration of the medium-wave infrared thermal imager, and effectively reduces the measurement uncertainty caused by calibration during the use of the medium-wave infrared thermal imager. It solves the problem that in the current laboratory radiation calibration of the medium-wave infrared thermal imager, the carbon dioxide in the ambient atmosphere has a large absorption effect on the medium-wave infrared radiation but is not deducted, thereby increasing the measurement uncertainty of the radiation calibration of the medium-wave infrared thermal imager.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A novel medium-wave infrared thermal imager calibration device, characterized in that: The invention comprises a black body controller (1), a black body (2), a medium-wave infrared thermal imager (3), a collimating laser (4), a laser measuring system (5), a cavity mirror (6), a focusing lens (7) and a photoelectric detector (8). The black body controller (1) is connected to the black body (2) via a cable (11). The medium-wave infrared thermal imager (3) is placed on one side of the heating end of the black body (2). The cavity mirror (6) is placed at a position where the input end is aligned with the medium-wave infrared thermal imager (3) and the output end is aligned with the black body (2). A beam splitter (41) is placed outside the input end of the cavity mirror (6). The collimating laser (4) is placed in a direction of 45° to the normal of the reflection surface of the beam splitter (41). The laser measuring system (5) is placed in a direction of 45° to the normal of the transmission surface of the beam splitter (41). The focusing lens (7) and the photoelectric detector (8) are placed in sequence outside the output end of the cavity mirror (6).

2. A novel medium-wave infrared thermal imager calibration device according to claim 1, characterized in that: The cavity mirror (6) comprises an input cavity mirror (61) and an output cavity mirror (62); the input cavity mirror (61) and the output cavity mirror (62) are both plano-concave high-reflection mirrors; and the concave parts of the output cavity mirror (61) and the output cavity mirror (62) are arranged facing each other.

3. A novel medium-wave infrared thermal imager calibration device according to claim 2, characterized in that: One side of the concave surface of the input cavity mirror (61) is aligned with the receiving mirror surface of the medium-wave infrared thermal imager (3), and one side of the concave surface of the output cavity mirror (62) is aligned with the heating end surface of the black body (2).

4. The novel medium-wave infrared thermal imager calibration device according to claim 3 is characterized in that: The concave side of the input cavity mirror (61) and the output cavity mirror (62) is coated with a 1580nm reflection film, and the flat side is coated with a 1580nm anti-reflection film; the center positions of the input cavity mirror (61) and the output cavity mirror (62) are both located on the collimated laser optical axis.

5. The calibration method of a novel medium-wave infrared thermal imager calibration device according to claim 1, characterized in that: The laser measurement system (5) comprises a beam shaping module (51), a measuring laser (52) and a measuring laser controller (53). The measuring laser controller (53) is electrically connected to the measuring laser (52) to change the current of the measuring laser (52). The measuring laser (12) changes the output laser wavelength by changing the current. The beam shaping module (51) is located between the beam splitter (41) and the measuring laser (52) to change the central wavelength of the output laser.

6. The calibration method of a novel medium-wave infrared thermal imager calibration device according to claim 1, characterized in that: The following steps are involved: Ⅰ. Build a calibration device, wherein the effective side length of the heating end surface of the black body (2) is not less than the lens aperture of the medium-wave infrared thermal imager (3); II. Setting the initial temperature of the black body (2), turning on the medium-wave infrared thermal imager (3) to receive the image of the heating end surface of the black body (2), and after the temperature of the black body (2) is stabilized, adjusting the medium-wave infrared thermal imager (3) so that the central field of view is aligned with the central position of the heating end surface of the black body (2); III. Turn on the collimating laser mirror (4), adjust the input cavity mirror (61) and the output cavity mirror (62) until the mirror surfaces are relatively parallel so that the input cavity mirror (61) and the output cavity mirror (62) form an optical resonant cavity; turn on the measuring laser (52) through the measuring laser controller (53), adjust the optical axis direction of the laser output from the laser measuring system (5) to coincide with the optical axis of the collimating laser, then turn off the collimating laser (4) and adjust the position of the focusing lens (7) so that the transmitted light spot is focused on the target surface of the photodetector (8); IV. Taking the reference voltage as the initial voltage, an additional voltage is loaded on the reference voltage so that the laser output by the measuring laser (52) shows periodic changes within a wavelength range; the photodetector (8) receives and completes AD conversion to obtain an optical power measurement result of a laser wavelength scan; after completing a laser wavelength scan, the output voltage of the measuring laser controller (53) is set back to the initial reference voltage, and the above process is repeated to obtain measurement results of multiple laser wavelength scans distributed in time sequence. V. Keeping the initial temperature of the black body (2) unchanged, the medium-wave infrared thermal imager (3) collects infrared images at a certain frequency, and completes multiple laser wavelength scans at a speed not lower than the infrared image collection frequency to obtain corresponding measurement results; then changing the temperature of the black body (2), repeating the above process after the temperature stabilizes, and obtaining measurement images of the medium-wave infrared thermal imager (3) at different black body (2) temperatures and the laser wavelength scanning measurement results at the corresponding time. VI. The measured medium-wave infrared measurement image and the laser wavelength scanning measurement result are aligned on the time axis, and are processed in sequence in combination with the distance value between the black body (2) and the medium-wave infrared thermal imager (3), and the apparent medium-wave infrared radiation brightness is calculated; finally, a functional relationship between the apparent medium-wave infrared radiation brightness corresponding to different black body temperatures and the measured black body average gray value is established to complete the calibration.

7. The calibration method of the novel medium-wave infrared thermal imager calibration device according to claim 6 is characterized in that: The average gray value of the black body (2) is read by infrared image processing software, and the medium-wave infrared radiation brightness corresponding to different temperatures is calculated using Planck's formula.

8. The calibration method of the novel medium-wave infrared thermal imager calibration device according to claim 7 is characterized in that: The laser wavelength scanning curve is read by using spectrum processing software, and the wavelength scanning ring-down time in one cycle is calculated using the oscillation time calculation formula. The carbon dioxide content is calculated using the device concentration measurement formula based on laser cavity ring-down spectroscopy technology and substituted into the atmospheric transmission calculation software to obtain the atmospheric transmittance.

9. The calibration method of the novel medium-wave infrared thermal imager calibration device according to claim 8 is characterized in that: Apparent mid-wave infrared radiation brightness L′ m for: L′ m =L m ·t m in L m is the brightness of medium-wave infrared radiation corresponding to different temperatures; t m is the atmospheric transmittance.

10. The calibration method of the novel medium-wave infrared thermal imager calibration device according to claim 9, characterized in that: The functional relationship between the apparent mid-wave infrared radiation brightness and the measured black body average gray value is: L′ m =k·DN m +b in k is the gain coefficient; b is the compensation value.

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