Field Calibration Device and Method for Large Aperture Infrared Optoelectronic System

Abstract

The present invention relates to the technical field of infrared radiation calibration, and particularly relates to an outdoor calibration device and method suitable for large-aperture infrared optoelectronic systems. The outdoor calibration device includes a calibration light source, a reference board, a temperature measurement module, and a calculation module. The exit of the calibration light source is located at the entrance pupil of the infrared optoelectronic system, with a size smaller than the entrance pupil diameter of the infrared optoelectronic system, and the radiant intensity is adjustable. The reference board completely blocks the field of view of the infrared optoelectronic system and is provided with a light inlet, allowing only the radiation of the calibration light source to enter the infrared optoelectronic system through the light inlet. The emissivity on the side of the reference board facing the infrared optoelectronic system is uniform. The temperature measurement module is used to monitor the temperature of the reference board in real time. The calculation module is used to determine the thermal radiation of the reference board based on the temperature and emissivity of the reference board, and then add the radiation of the calibration light source as the incident radiation to achieve the calibration of the infrared optoelectronic system. The present invention can reduce the measurement difficulty of outdoor calibration of large-aperture infrared optoelectronic systems, reduce costs, and improve measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of infrared radiation calibration, and particularly to an outdoor calibration device and method suitable for large-aperture infrared optoelectronic systems, and an infrared radiation measurement method. Background Art

[0002] Measuring the infrared radiation of a flying target by using a calibrated infrared optoelectronic system is a direct means to obtain the true radiation characteristics of the flying target. The measurement accuracy of infrared radiation depends on the radiation calibration accuracy and the measurement accuracy of atmospheric transmittance. With the development of ground-based infrared radiation measurement technology, the aperture of infrared optoelectronic system (such as telescope, etc.) equipment for measurement is getting larger and larger, and the measurement accuracy requirement is also getting higher and higher. The traditional direct extended source and large-aperture infrared collimator calibration methods have poor mobility, great measurement difficulty, low accuracy and high cost, and it is difficult to meet the requirements of outdoor calibration of large-aperture (aperture exceeding 1000mm) equipment. Therefore, it is necessary to provide an outdoor calibration device and method for large-aperture infrared optoelectronic systems. Summary of the Invention

[0003] Based on the problems of great difficulty and low accuracy in outdoor calibration of large-aperture infrared optoelectronic systems, embodiments of the present invention provide an outdoor calibration device and method suitable for large-aperture infrared optoelectronic systems, which can reduce the measurement difficulty of outdoor calibration of large-aperture infrared optoelectronic systems, reduce costs, and improve measurement accuracy.

[0004] In a first aspect, embodiments of the present invention provide an outdoor calibration device suitable for large-aperture infrared optoelectronic systems, including: a calibration light source, a reference plate, a temperature measurement module and a calculation module;

[0005] The exit of the calibration light source is located at the entrance pupil of the infrared optoelectronic system, with a size smaller than the entrance pupil aperture of the infrared optoelectronic system, and the radiation luminance is adjustable;

[0006] The reference plate completely blocks the field of view of the infrared optoelectronic system and is provided with a light inlet, and only the radiation of the calibration light source enters the infrared optoelectronic system through the light inlet; the emissivity on the side of the reference plate facing the infrared optoelectronic system is uniform;

[0007] The temperature measurement module is installed on the reference plate and is used to monitor the temperature of the reference plate in real time;

[0008] The calculation module is used to determine the thermal radiation of the reference plate based on the temperature and emissivity of the reference plate, and then add the radiation of the calibration light source as the incident radiation to realize the calibration of the infrared optoelectronic system.

[0009] Optionally, the calculation module is further used to obtain infrared image grayscale data output by the infrared optoelectronic system, and to calibrate the infrared optoelectronic system based on the incident radiation brightness of the calibration light source and the reference plate and the corresponding infrared image grayscale data.

[0010] Optionally, the calibration light source includes a high-temperature cavity blackbody and a collimator;

[0011] The temperature of the high-temperature cavity blackbody is adjustable; the exit port of the collimator matches the light entrance port of the reference plate; the radiation of the high-temperature cavity blackbody enters the incident port of the collimator through a pinhole aperture and finally enters the infrared photoelectric system.

[0012] Optionally, the external field calibration device further includes:

[0013] Bottom adjustment platform and raised platform;

[0014] The calibration light source is arranged on the bottom adjustment platform, and the bottom adjustment platform is arranged on the elevation platform. The bottom adjustment platform is used to fine-tune the position and posture of the collimator to achieve alignment of the collimator with the optical axis of the infrared photoelectric system.

[0015] Optionally, the aperture of the collimator is determined by:

[0016] Determine the radiation brightness range of the target to be measured reaching the entrance pupil of the infrared photoelectric system;

[0017] Determining the radiation brightness range emitted by the high-temperature cavity-type blackbody;

[0018] Establishing a relationship between the equivalent radiant brightness of the high-temperature cavity blackbody and the reference plate at the entrance pupil of the infrared photoelectric system and the radiant brightness emitted by the high-temperature cavity blackbody;

[0019] Based on the established relationship and the radiation brightness range of the high-temperature cavity-type blackbody emission, the equivalent radiation brightness range corresponding to different aperture values ​​of the collimator is calculated;

[0020] The aperture value is selected so that the corresponding equivalent radiation brightness range covers the radiation brightness range of the target to be measured reaching the entrance pupil of the infrared photoelectric system.

[0021] Optionally, the reference plate is a lens cover covering the incident port of the infrared photoelectric system.

[0022] Optionally, the light entrance is located in one of the four quadrants of the reference plate.

[0023] Second aspect, an embodiment of the present invention further provides a field calibration method applicable to a large-aperture infrared optoelectronic system, which is implemented by using the field calibration device described in any one of the above. The method includes the following steps:

[0024] Adjust the radiation luminance of the calibration light source based on the measurement requirements to obtain multiple groups of different incident radiation luminances and corresponding infrared image gray-scale data; wherein, the incident radiation luminance is the equivalent radiation luminance of the incident radiation provided by the calibration light source and the reference plate at the entrance pupil of the infrared optoelectronic system.

[0025] Fit the obtained multiple groups of data to obtain a calibration relationship L = b×DN + a; wherein, L represents the incident radiation luminance, DN is the gray value of the pixel of the infrared image, and a and b are calibration coefficients.

[0026] Third aspect, an embodiment of the present invention further provides a field calibration method applicable to a large-aperture infrared optoelectronic system, which is implemented by using the field calibration device described in any one of the third to fifth items above. The method includes the following steps:

[0027] S1. Adjust the high-temperature cavity blackbody and the collimator so that the high-temperature cavity blackbody is located at the focal plane of the collimator, and the collimator is aligned with the optical axis of the infrared optoelectronic system.

[0028] S2. Set each integration time and temperature measurement point according to the measurement requirements.

[0029] S3. Set the working temperature of the high-temperature cavity blackbody according to the temperature measurement point. After the temperature is stable, obtain the corresponding infrared image gray-scale data according to the set integration time and calculate the incident radiation luminance; wherein, the incident radiation luminance is the equivalent radiation luminance of the incident radiation provided by the calibration light source and the reference plate at the entrance pupil of the infrared optoelectronic system.

[0030] S4. Repeat step S3 to obtain multiple groups of incident radiation luminances and infrared image gray-scale data corresponding to the temperature measurement points.

[0031] S5. Based on the obtained multiple groups of data, calibrate the infrared optoelectronic system at the corresponding integration time to obtain a calibration relationship L = b×DN + a; wherein, L represents the incident radiation luminance, DN is the gray value of the pixel of the image at a fixed luminance, and a and b are calibration coefficients.

[0032] Fourth aspect, an embodiment of the present invention further provides an infrared radiation measurement method, which is implemented by using an infrared optoelectronic system. Before measurement, the infrared optoelectronic system is field-calibrated by using the method described in any one of the above.

[0033] The embodiments of the present invention provide an outdoor calibration device and method applicable to large-aperture infrared optoelectronic systems, and an infrared radiation measurement method. When performing outdoor calibration, the present invention completely blocks the background radiation of the external environment with a reference plate, allowing only the radiation of the reference plate and the calibration light source to enter the infrared optoelectronic system. The infrared radiation emitted by the calibration light source and the thermal radiation of the reference plate itself are equivalent to the incident radiation provided by a large-aperture radiation source, and corresponding calibration is carried out. The present invention can achieve the calibration of a large-aperture infrared optoelectronic system by using a calibration light source with a smaller aperture, and isolates the background radiation interference introduced by the external environment, avoiding the influence of environmental changes on the calibration results, and can complete relatively accurate outdoor calibration under the condition of simple operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 It is the calibration principle diagram of an outdoor calibration device applicable to a large-aperture infrared optoelectronic system provided by an embodiment of the present invention;

[0036] Figure 2 It is the schematic diagram of the calibration light source and the support structure provided by an embodiment of the present invention;

[0037] Figure 3 It is the schematic diagram of a reference plate structure provided by an embodiment of the present invention;

[0038] Figure 4 It is the schematic diagram of the method steps of an outdoor calibration device applicable to a large-aperture infrared optoelectronic system provided by an embodiment of the present invention;

[0039] Figure 5 It is the schematic diagram of the method steps of another outdoor calibration device applicable to a large-aperture infrared optoelectronic system provided by an embodiment of the present invention;

[0040] In the figure: 1: Infrared optoelectronic system; 11: Infrared focal plane array; 2: Reference plate; 21: Light inlet; 3: Collimator; 31: Small aperture diaphragm; 4: High-temperature cavity blackbody; 5: Bottom adjustment platform; 6: Pad high platform. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] As described above, with the development of ground-based infrared radiation measurement technology, the aperture of infrared optoelectronic systems (such as telescopes) used for measurement is getting larger and larger, and the measurement accuracy requirements are also getting higher and higher. Traditional direct extended source and large-aperture infrared collimator calibration methods both require large-aperture radiation sources, with poor mobility, high measurement difficulty, low accuracy, and high cost, and it is difficult to meet the requirements of field calibration. In view of this, the present invention proposes a method of using a small-aperture calibration light source combined with a reference plate to be equivalent to a large-aperture radiation source, so as to simplify the operation difficulty and isolate the interference of the external environment on calibration, thereby reducing the calibration difficulty of large-aperture infrared optoelectronic systems (referred to as infrared optoelectronic systems) and improving the calibration accuracy at the same time.

[0043] The following describes the specific implementation methods of the above concepts.

[0044] The embodiment of the present invention provides an external field calibration device applicable to a large-aperture infrared optoelectronic system, including a calibration light source, a reference plate 2, a temperature measurement module, and a calculation module;

[0045] Among them, the exit of the calibration light source is located at the entrance pupil of the infrared optoelectronic system 1, with a size smaller than the entrance pupil aperture of the infrared optoelectronic system 1, and the radiant intensity of the calibration light source is adjustable;

[0046] The reference plate 2 completely blocks the field of view of the infrared optoelectronic system 1, and an incident light port 21 is opened on the reference plate 2, and only the radiation of the calibration light source enters the infrared optoelectronic system 1 through the incident light port 21; the emissivity on the side of the reference plate 2 facing the infrared optoelectronic system 1 is uniform;

[0047] The temperature measurement module is installed on the reference plate 2 for real-time monitoring of the temperature of the reference plate 2;

[0048] The calculation module is used to determine the thermal radiation of the reference plate 2 based on the temperature and emissivity of the reference plate 2, and then add the determined thermal radiation to the radiation of the calibration light source as the incident radiation to achieve the calibration of the infrared optoelectronic system. The calibration process is to determine the corresponding relationship between the radiant intensity at the entrance pupil of the infrared optoelectronic system and the gray-scale data of the infrared image output by the infrared optoelectronic system.

[0049] In the above embodiments, the calibration light source and the reference plate 2 are equivalent to an integral large-aperture radiation source. The radiation luminance emitted by the calibration light source is adjustable, and the thermal radiation provided by the reference plate 2 is calculated based on the emissivity of the reference plate 2 itself and the real-time temperature. The emissivity of the reference plate 2 can be accurately measured in advance, and the actual thermal radiation provided by the reference plate 2 is only related to its temperature. At the same time, the reference plate 2 only allows the infrared radiation emitted by the calibration light source to pass through, isolating the interference of external environmental changes. During calibration, only accurate and measurable background radiation (i.e., the thermal radiation of the reference plate 2) is considered, improving the calibration accuracy. Moreover, the reference plate 2 is large enough to completely cover the field of view area of the infrared optoelectronic system 1, and the aperture of the calibration light source does not need to be designed very large. A small-aperture calibration light source can be used to achieve the field calibration of a large-aperture infrared optoelectronic system, without relying on a large-aperture calibration light source, nor the need for operations such as scanning. The calibration process is simple, easy to implement, and low in cost.

[0050] It should be noted that to ensure that the calibrated infrared optoelectronic system can be used to measure the infrared radiation characteristics of the target to be measured, the equivalent radiation luminance range of the incident radiation jointly provided by the calibration light source and the reference plate 2 at the entrance pupil of the infrared optoelectronic system should be able to cover the radiation luminance range of the target to be measured reaching the entrance pupil of the infrared optoelectronic system. More preferably, the adjustable range of the calibration light source is made to cover the radiation luminance range of the target to be measured reaching the entrance pupil of the infrared optoelectronic system, because compared with the thermal radiation provided by the reference plate, the radiation emitted by the calibration light source is easier to regulate. The radiation luminance range of the target to be measured reaching the entrance pupil of the infrared optoelectronic system can be determined by means such as estimation.

[0051] Optionally, the temperature measurement module includes at least one high-precision temperature sensor, and the temperature sensor is preferably arranged outside the reference plate 2 for easy installation.

[0052] Optionally, the calculation module is further configured to obtain the infrared image gray-scale data output by the infrared optoelectronic system, and calibrate the infrared optoelectronic system based on the incident radiation luminance of the calibration light source and the reference plate received at the entrance pupil of the infrared optoelectronic system 1 and the corresponding infrared image gray-scale data.

[0053] The above embodiments use the calculation module to obtain corresponding data for calibration, which can achieve automatic calculation and processing.

[0054] Furthermore, to achieve full-automatic calibration, the calculation module is further configured to generate a control instruction and send it to the calibration light source to adjust the radiation luminance emitted by the calibration light source. The calibration light source responds to the control instruction for adjustment.

[0055] Optionally, the calibration light source includes a high-temperature cavity-type blackbody 4 and a collimator 3;

[0056] The temperature of the high-temperature cavity blackbody 4 is adjustable; the exit of the collimator 3 matches the light inlet 21 of the reference plate 2; the radiation emitted by the high-temperature cavity blackbody 4 enters the entrance of the collimator 3 through the small aperture diaphragm 31, passes through the exit of the collimator 3 and the light inlet 21 of the reference plate 2, and finally enters the infrared optoelectronic system.

[0057] Using the high-temperature cavity blackbody 4 and the collimator 3 as the calibration light source, by adjusting the temperature of the high-temperature cavity blackbody 4, the intensity of the infrared radiation it emits can be adjusted, so as to accurately determine the radiation luminance of the calibration light source at the entrance pupil of the infrared optoelectronic system 1. The high-temperature cavity blackbody 4 has a large adjustable range, and moreover, the technologies of the high-temperature cavity blackbody 4 and the collimator 3 are relatively mature and the cost is low.

[0058] Furthermore, the calculation module can also be used to determine the radiation of the calibration light source based on the temperature, emissivity of the high-temperature cavity blackbody 4 and the transmittance of the collimator 3.

[0059] Figure 1 The calibration principle of an outdoor calibration device applicable to a large-aperture infrared optoelectronic system provided by an embodiment of the present invention is shown. The incident radiation is equal to the radiation of the calibration light source plus the thermal radiation of the reference plate 2. The expression of the equivalent radiation illuminance of the incident radiation at the entrance pupil of the infrared optoelectronic system 1 is:

[0060]

[0061] Among them, Ω IFOV is the instantaneous field of view solid angle, corresponding to the infrared focal plane array 11 in the infrared optoelectronic system, A c is the exit area of the collimator 3 (i.e., the area of the exit), A o is the entrance pupil area of the infrared optoelectronic system, L bb (T bb ) is the integrated radiation luminance of the high-temperature cavity blackbody 4 in the measurement band range of the infrared optoelectronic system. For the convenience of representation, it is abbreviated as L Figure 1 in bb , T bb represents the temperature of the high-temperature cavity blackbody 4, L bb (T bb ) can be calculated according to Planck's formula, L bkg (T bkg ) is the integrated radiation luminance of the reference plate 2 in the measurement band range of the infrared optoelectronic system, abbreviated as L Figure 1 in bkg , T bkg represents the temperature of the reference plate 2, τ c represents the transmittance of the collimator 3, Figure 1 in, Ω cis the emission field solid angle of the high temperature cavity black body 4, corresponding to the incident port of the collimator 3, f is the focal length of the collimator 3, and F is the focal length of the infrared optoelectronic system 1, which can be used to calculate the instantaneous field solid angle Ω IFOV .

[0062] In some other embodiments, the calibration light source may also be implemented by using a surface source black body, and the position of the surface source black body corresponds to the position of the exit port of the calibration light source.

[0063] Alternatively, if Figure 2 As shown, the field calibration device also includes: a bottom adjustment platform 5 and a raised platform 6; the bottom adjustment platform 5 and the raised platform 6 are supporting structures for the calibration light source; the calibration light source is arranged on the bottom adjustment platform 5, and the bottom adjustment platform 5 is arranged on the raised platform 6, and the bottom adjustment platform 5 is used to fine-tune the position and posture of the collimator 3 to achieve alignment of the collimator with the optical axis of the infrared photoelectric system.

[0064] The calibration light source is set up using the bottom adjustment platform 5 and the elevation platform 6, and the calibration light source is set up in a suitable position, which is conducive to the rapid disassembly and assembly of the field calibration device. During calibration, the calibration light source and its supporting structure in the field calibration device are installed in front of the incident port of the infrared photoelectric system. After the calibration is completed, they can be disassembled and moved without occupying the space of the working environment of the infrared photoelectric system. The calculation module in the field calibration device can be integrated into the controller of the infrared photoelectric system, or it can be set separately. Further preferably, the bottom adjustment platform 5 cooperates with the three ball head feet of the parallel light tube 3, and the whole can realize five-dimensional adjustment, with an adjustment accuracy of 1mm in the horizontal and vertical directions, an adjustment range of 50mm, and a reset accuracy of less than 10mm; the adjustment accuracy of the azimuth and pitch directions is 1″, the adjustment range is 5°, and the reset accuracy is better than 2′.

[0065] Optionally, in the field calibration device, the aperture of the collimator 3 is determined by:

[0066] Determine the radiation brightness range of the target to be measured reaching the entrance pupil of the infrared photoelectric system;

[0067] Determine the brightness range of the radiation emitted by the high-temperature cavity blackbody 4 itself;

[0068] Establishing a relationship between the equivalent radiant brightness of the incident radiation provided by the high-temperature cavity blackbody 4 and the reference plate 2 at the entrance pupil of the infrared photoelectric system and the radiant brightness emitted by the high-temperature cavity blackbody 4;

[0069] Based on the established relationship and the radiation brightness range emitted by the high-temperature cavity blackbody 4, the equivalent radiation brightness range corresponding to different aperture values ​​of the collimator 3 is calculated;

[0070] Select the aperture value so that the corresponding equivalent radiance range covers the radiance range of the target to be measured reaching the entrance pupil of the infrared optoelectronic system.

[0071] Further, determining the radiance range of the target to be measured reaching the entrance pupil of the infrared optoelectronic system may include:

[0072] Based on the temperature range, surface emissivity, observation elevation angle of the infrared optoelectronic system, and atmospheric transmittance of the target to be measured, determine the radiance range of the target to be measured reaching the entrance pupil of the infrared optoelectronic system.

[0073] For example, if the temperature range of the target to be measured is 300K to 1000K, the surface emissivity of the target is 0.7, and the observation elevation angle of the infrared optoelectronic system is 45°, then the atmospheric transmittance in the 3.7μm to 4.8μm wavelength band is about 0.4. Furthermore, the radiance range of the target to be measured reaching the entrance pupil of the infrared optoelectronic system can be calculated as: 0.35W / (m 2 ·sr) to 929.21W / (m 2 ·sr).

[0074] Further, determining the radiance range emitted by the high-temperature cavity blackbody 4 may include:

[0075] Based on the temperature range and emissivity of the high-temperature cavity blackbody 4, determine the radiance range emitted by the high-temperature cavity blackbody 4.

[0076] For example, if the emissivity of the high-temperature cavity blackbody 4 is 0.99 and the temperature is continuously adjustable in the range of 50°C to 1200°C, according to Planck's formula, the radiance L b emitted by the high-temperature cavity blackbody 4 can be calculated to have a corresponding range of 2.74W / (m 2 ·sr) to 10642W / (m 2 ·sr).

[0077] Optionally, establish a relationship between the equivalent radiance of the radiation provided by the high-temperature cavity blackbody 4 and the reference plate 2 at the entrance pupil of the infrared optoelectronic system and the radiance emitted by the high-temperature cavity blackbody 4, which can be expressed as:

[0078]

[0079] Thus, the equivalent radiance ranges corresponding to different aperture values selected by the collimator 3 are shown in Table 1 below. When calculating, τ c = 0.9, the ambient temperature is 25°C, and the emissivity of the reference plate is 0.2.

[0080] Table 1 Equivalent radiance corresponding to different aperture values

[0081] Caliber (mm) <![CDATA[L (W / (m 2 ·sr))]]> 100 0.25～71.18 200 0.30～284.01 300 0.38～638.74 350 0.44～869.31 400 0.50～1135.35 450 0.57～1436.87

[0082] In the above manner, a calibration radiation source with a diameter of 400 mm can be obtained, which can ensure that the radiation luminance of the calibration radiation source (including the high-temperature cavity blackbody 4 and the reference plate 2) received by the infrared optoelectronic system is closest to covering the radiation luminance range of the target to be measured reaching the entrance pupil of the infrared optoelectronic system.

[0083] The infrared optoelectronic system uses a calibration light source with a smaller diameter, which can not only save hardware costs but also be convenient for disassembly and assembly.

[0084] Optionally, the reference plate 2 is a lens cap that covers the entrance of the infrared optoelectronic system.

[0085] The reference plate 2 in the form of a lens cap is small in volume, easy to install, and can ensure that the reference plate completely blocks the field of view of the infrared optoelectronic system, and no radiation interference from the external environment enters.

[0086] Furthermore, as Figure 3 shown, the light entrance 21 is located in one of the four quadrants of the reference plate 2.

[0087] The infrared optoelectronic system is a symmetric structure, and calibration can also be achieved by incident light from one quadrant of the infrared optoelectronic system without scanning. This helps to simplify the calibration process. For example, one quadrant area of the reference plate 2 can be set as a detachable structure to facilitate the replacement of calibration light sources with different diameters and the corresponding light entrances 21 adapted thereto.

[0088] Optionally, a coating with uniform emissivity is coated on the side of the reference plate 2 facing the infrared optoelectronic system.

[0089] Through the coating, it can be ensured that the thermal radiation performance provided by the reference plate 2 to the infrared optoelectronic system 1 is stable. The emissivity can be measured by special equipment and can be quantified during calibration calculation.

[0090] As Figure 4 shown, the present invention also provides a field calibration method applicable to a large-aperture infrared optoelectronic system, which is implemented by using the field calibration device described in any one of the above embodiments, and includes the following steps:

[0091] Step 400, adjusting the radiation luminance of the calibration light source based on the measurement requirements to obtain multiple groups of different incident radiation luminances and the corresponding infrared image gray-scale data; wherein, the incident radiation luminance is the equivalent radiation luminance of the incident radiation provided by the calibration light source and the reference plate at the entrance pupil of the infrared optoelectronic system;

[0092] Step 402, fit the obtained multiple sets of data to obtain the calibration relationship L = b × DN + a; where L represents the incident radiation brightness, DN is the gray value of the infrared image pixel measured by the infrared photoelectric system, that is, the corresponding infrared image gray data, and a and b are calibration coefficients. The calibration coefficients a and b are determined by fitting (such as least squares fitting), and the calibration can be completed.

[0093] By adopting the above embodiment, by adjusting the calibration light source so that the range of incident radiation brightness variation covers the brightness range required for measurement, the corresponding infrared image grayscale data is obtained, and calibration can be completed within the brightness range required for measurement to obtain the required calibration relationship.

[0094] like Figure 5 As shown, the present invention also provides an outdoor calibration method applicable to a large-aperture infrared optoelectronic system, which is implemented by using an outdoor calibration device as described in some of the above embodiments, wherein the calibration light source includes a high-temperature cavity black body 4 and a collimator 3, and the method includes the following steps:

[0095] Step 500, adjusting the high temperature cavity black body 4 and the collimator 3, so that the high temperature cavity black body 4 is located at the focal plane of the collimator 3, and the collimator 3 is aligned with the optical axis of the infrared photoelectric system;

[0096] Step 502: according to the measurement requirements, set each integration time and temperature measurement point for the infrared photoelectric system; the temperature measurement point can be set according to the radiation brightness range of the target to be measured reaching the entrance pupil of the infrared photoelectric system. If the infrared image measured by the infrared photoelectric system is saturated at a certain temperature, the temperature can be taken as the maximum temperature and the ambient temperature can be taken as the minimum temperature. The temperature measurement points are set at equal intervals within this range.

[0097] Step 504: according to the measuring point, the working temperature of the high-temperature cavity black body 4 is set. After the temperature is stable, the corresponding infrared image grayscale data is obtained according to the set integration time, and the current incident radiation brightness is calculated; wherein the incident radiation brightness is the equivalent radiation brightness of the incident radiation provided by the calibration light source and the reference board at the entrance pupil of the infrared photoelectric system; if the temperature measuring points corresponding to multiple integration times are repeated, the integration time can be switched after the temperature of the high-temperature cavity black body 4 is stable to respectively collect the corresponding infrared image grayscale data, so as to save the time required for calibration;

[0098] Step 506, repeating step 504 to obtain multiple groups of incident radiation brightness and infrared image grayscale data corresponding to the temperature measurement points; the brightness range of the obtained multiple groups of different incident radiation brightness and infrared image grayscale data should be able to cover the radiation brightness range of the target to be measured reaching the entrance pupil of the infrared photoelectric system;

[0099] Step 508: Based on the obtained multiple sets of data, the infrared photoelectric system is calibrated at the corresponding integration time to obtain a calibration relationship L=b×DN+a; wherein L represents the incident radiation brightness, DN is the grayscale value of the image pixel at a fixed brightness, and a and b are calibration coefficients.

[0100] The method of the above embodiment is executed for an embodiment in which the calibration light source includes a high-temperature cavity black body 4 and a parallel light tube 3, so that the calibration light source is aligned with the optical axis of the infrared photoelectric system, and the calibration is performed after the grayscale of the detector target surface of the infrared photoelectric system is uniform, thereby improving the calibration accuracy. The specific data values ​​and data volume used in the calibration process can be adjusted according to actual needs. Preferably, at least 5 groups of data points are set at equal intervals within the radiation brightness range of the target to be measured reaching the entrance pupil of the infrared photoelectric system, and each group of data points includes the incident radiation brightness and the grayscale of the infrared image to ensure that the calibration relationship obtained is accurate. The calculation content in the above steps can be implemented using the calculation module of the field calibration device, or it can be implemented using the controller of the infrared photoelectric system (such as a host computer, etc.).

[0101] Optionally, in step 500, when the collimator is aligned with the infrared photoelectric system, in order to obtain the maximum transmission efficiency, the secondary mirror and truss in the infrared photoelectric system should be avoided. First, the heights of the center of the secondary mirror of the infrared photoelectric system and the center of the collimator from the ground are measured to ensure that the collimator is roughly aligned with a quadrant of the infrared photoelectric system. Then, laser pens are placed on the light blocking ring on the inner wall of the collimator in parallel to the direction of the main optical axis. By adjusting the position of the collimator, the light spot of the laser pen is completely located on the primary mirror of the infrared photoelectric system without any obstruction, and the positions of the two can be considered aligned.

[0102] The calibration light source includes a collimator and a high-temperature cavity blackbody. When the high-temperature cavity blackbody is located at the aperture of the collimator, the high-temperature cavity blackbody is placed at the image plane of the incident port of the collimator. The high-temperature cavity blackbody has a pinhole wheel, and the hole on the pinhole wheel should be located at the focal plane of the collimator. First, select a larger hole, change the azimuth and pitch of the infrared photoelectric system, find the edge of the hole imaged, point the infrared photoelectric system to the center of the hole, and then use the same method to point the infrared photoelectric system to the center of the hole after changing to a smaller hole. Observe whether the grayscale value of the entire infrared image obtained by the infrared photoelectric system is uniform. If it is uniform, you can start to set the working temperature of the high-temperature cavity blackbody and perform radiation calibration.

[0103] In order to verify the effectiveness of the method of the present invention, in one embodiment, the operating temperatures of five high-temperature cavity black bodies are set to 201.0°C, 222.1°C, 242.2°C, 262.0°C and 281.0°C, and the incident radiation brightness L is calculated to be 8.6839, 11.5707, 14.9364, 18.8984 and 23.3534 W / m respectively. 2 / sr, the infrared image grayscale DN measured by the infrared optoelectronic system is 2132, 2314, 2517, 2751, 2991. According to the least squares fitting, the calibration relationship can be obtained as L = 0.0170 * DN - 27.8131.

[0104] When the working temperature of the high-temperature cavity blackbody is 212.0 °C, the measured infrared image grayscale DN is 2223. According to the above calibration relationship, the incident radiant intensity is 9.9779 W / m 2 / sr. And according to the calculation, the theoretical calculated value of the incident radiant intensity is 10.1106, and the measurement error is:

[0105]

[0106] When the working temperature of the high-temperature cavity blackbody is 232.2 °C, the measured infrared image grayscale DN is 2411. According to the above calibration relationship, the incident radiant intensity is 13.1739 W / m 2 / sr. According to the calculation, the theoretical calculated value of the incident radiant intensity is 13.1829, and the measurement error is:

[0107]

[0108] When the working temperature of the high-temperature cavity blackbody is 246.0 °C, the measured infrared image grayscale DN is 2624. According to the above calibration relationship, the incident radiant intensity is 16.7949 W / m 2 / sr. According to the calculation, the theoretical calculated value of the incident radiant intensity is 16.7937, and the measurement error is:

[0109]

[0110] It can be seen that the radiometric calibration accuracy of this method is better than 2%, meeting the requirements for general use.

[0111] The embodiment of the present invention also provides an infrared radiation measurement method implemented by an infrared optoelectronic system. Before measurement, the infrared optoelectronic system is field-calibrated using the field calibration method described in any of the above embodiments. After calibration, the calibration light source can be quickly disassembled without occupying the space of the working environment of the infrared optoelectronic system.

[0112] In summary, the present invention provides an outdoor calibration device and method applicable to large-aperture infrared optoelectronic systems. In the embodiments of the present invention, the incident radiation is calculated by treating the reference plate and the calibration light source as an integral large radiation source. Not only does it not rely on a large-aperture calibration light source, but it also solves the problem of the influence of environmental radiation during the calibration process, achieving higher-precision radiation calibration. At the same time, since the infrared optoelectronic system has a symmetric structure, the present invention proposes to calibrate by aligning the calibration light source with any quadrant of the infrared optoelectronic system without scanning, thereby simplifying the operation and reducing costs. In addition, the calibration light source is designed to ensure that each part can be quickly disassembled and installed. After calibration, it can be removed from the tower and placed, without occupying the space inside the tower.

[0113] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0114] Those of ordinary skill in the art can understand that all or part of the steps for implementing the above method embodiments can be completed by hardware related to program instructions. The foregoing program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps including the above method embodiments; and the foregoing storage medium includes various media such as ROM, RAM, magnetic disk or optical disc that can store program codes.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. And these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An outdoor calibration device applicable to a large-aperture infrared optoelectronic system, characterized in that, Including: A calibration light source, a reference plate, a temperature measurement module and a calculation module; The exit of the calibration light source is located at the entrance pupil of the infrared optoelectronic system, with a size smaller than the entrance pupil diameter of the infrared optoelectronic system, and the radiant intensity is adjustable; The reference plate completely blocks the field of view of the infrared optoelectronic system and is provided with a light entrance, and only the radiation of the calibration light source enters the infrared optoelectronic system through the light entrance; the emissivity on the side of the reference plate facing the infrared optoelectronic system is uniform; The temperature measurement module is installed on the reference plate and is used to monitor the temperature of the reference plate in real time; The calculation module is used to determine the thermal radiation of the reference plate based on the temperature and emissivity of the reference plate, and then add the radiation of the calibration light source as the incident radiation to calibrate the infrared optoelectronic system; The calibration light source includes a high-temperature cavity blackbody and a collimator; The temperature of the high-temperature cavity blackbody is adjustable; the exit of the collimator matches the light entrance of the reference plate; the radiation of the high-temperature cavity blackbody enters the entrance of the collimator through a small-aperture diaphragm and finally enters the infrared optoelectronic system; The aperture of the collimator is determined by the following method: Determine the range of radiant intensity of the target to be measured reaching the entrance pupil of the infrared optoelectronic system; Determine the range of radiant intensity emitted by the high-temperature cavity blackbody; Establish a relationship between the equivalent radiant intensity of the high-temperature cavity blackbody and the reference plate at the entrance pupil of the infrared optoelectronic system and the radiant intensity emitted by the high-temperature cavity blackbody; Based on the established relationship and the range of radiant intensity emitted by the high-temperature cavity blackbody, calculate the range of equivalent radiant intensity corresponding to different aperture values of the collimator; Select the aperture value so that the corresponding range of equivalent radiant intensity covers the range of radiant intensity of the target to be measured reaching the entrance pupil of the infrared optoelectronic system.

2. The field calibration device according to claim 1, wherein: The calculation module is further used to obtain the infrared image gray-scale data output by the infrared optoelectronic system, and calibrate the infrared optoelectronic system based on the incident radiant intensity of the calibration light source and the reference plate and the corresponding infrared image gray-scale data.

3. The external field calibration device according to claim 1, characterized in that It further includes: A bottom adjustment platform and a pad platform; The calibration light source is arranged on the bottom adjustment platform, the bottom adjustment platform is arranged on the pad platform, and the bottom adjustment platform is used to finely adjust the position and attitude of the collimator to align the collimator with the optical axis of the infrared optoelectronic system.

4. The field calibration device according to claim 1, wherein The reference plate is a lens cap that covers the entrance of the infrared optoelectronic system.

5. The field calibration device according to any one of claims 1 to 4, wherein The light entrance is located in one of the four quadrants of the reference plate.

6. An outdoor calibration method applicable to large-aperture infrared optoelectronic systems, characterized in that, Implemented by using the field calibration device according to any one of claims 1-5, the method includes the following steps: Adjust the radiant intensity of the calibration light source based on the measurement requirements to obtain multiple groups of different incident radiant intensities and corresponding infrared image gray-scale data; wherein, the incident radiant intensity is the equivalent radiant intensity of the incident radiation provided by the calibration light source and the reference plate at the entrance pupil of the infrared optoelectronic system; Multiple groups of data obtained by fitting are used to obtain a calibration relationship L = b×DN + a, where L represents the incident radiance, DN is the gray value of the pixels in the infrared image, and a and b are calibration coefficients.

7. An outdoor calibration method applicable to large-aperture infrared optoelectronic systems, characterized in that, This is achieved by using the field calibration device described in any one of claims 1 - 3. The method includes the following steps: S1. Adjust the high - temperature cavity blackbody and the collimator, and place the high - temperature cavity blackbody at the focal plane of the collimator. Align the collimator with the optical axis of the infrared optoelectronic system. S2. Set each integration time and temperature measurement points according to the measurement requirements. S3. Set the operating temperature of the high - temperature cavity blackbody according to the temperature measurement points. After the temperature stabilizes, obtain the corresponding infrared image gray - level data according to the set integration time, and calculate the incident radiance. Here, the incident radiance is the equivalent radiance of the incident radiation provided by the calibration light source and the reference plate at the entrance pupil of the infrared optoelectronic system. S4. Repeat step S3 to obtain multiple groups of incident radiance and infrared image gray - level data corresponding to the temperature measurement points. S5. Based on the multiple groups of data obtained, calibrate the infrared optoelectronic system at the corresponding integration time to obtain a calibration relationship L = b×DN + a, where L represents the incident radiance, DN is the gray value of the pixels in the image under a fixed brightness, and a and b are calibration coefficients.

8. An infrared radiation measurement method implemented by an infrared optoelectronic system, characterized in that: Before measurement, the infrared optoelectronic system is field - calibrated by using the method described in any one of claims 6 or 7.

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