Infrared radiation characteristics measurement method for removing stray radiation

Abstract

This invention belongs to the field of infrared radiation measurement technology, and particularly relates to a method for measuring infrared radiation characteristics by removing stray radiation. This invention obtains calibration coefficients from a large-aperture infrared optical imaging system that has already been calibrated in a high-low temperature chamber. Patch-type temperature sensors are installed at both ends of the large-aperture infrared optical imaging system. Combined with an infrared radiation measurement principle model, stray radiation caused by temperature inhomogeneity in the large-aperture optical imaging system can be calculated and eliminated, thereby improving the accuracy of infrared radiation characteristic measurements under target range conditions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of infrared radiation measurement, and particularly relates to an infrared radiation characteristic measurement method for removing stray radiation. BACKGROUND

[0002] Target infrared radiation characteristic measurement technology is one of main methods for obtaining target radiation luminance and other characteristic parameters in a target range. In the target range environment, continuous change of ambient temperature, direct sunlight on an infrared optical imaging system, and heat dissipation of electronic devices such as detectors during operation, can cause the phenomenon of non-uniform temperature distribution of the large-aperture infrared optical imaging system, and the temperature difference changes continuously with the progress of the system operation process. The large-aperture infrared optical imaging system belongs to a heat-sensitive system, and the heat radiation generated by the system itself will enter the detector after internal reflection and transmission, forming stray radiation, which causes the image gray level to drift with the change of system temperature, and seriously affects the measurement accuracy of the infrared radiation characteristic. The conventional method for eliminating stray radiation is to collect the ambient temperature and combine the large-aperture infrared optical imaging system which has been calibrated in a high-low temperature chamber to eliminate this part of stray radiation. However, the temperature distribution of the large-aperture infrared optical imaging system is non-uniform, especially under the condition of direct sunlight, the local temperature can be very high, and the use of a single ambient temperature to represent the temperature of the system is not accurate, which seriously reduces the measurement accuracy of the infrared radiation characteristic in the target range. SUMMARY

[0003] Therefore, the present application aims to provide an infrared radiation characteristic measurement method for removing stray radiation, so as to solve the problem that the non-uniform temperature distribution of the large-aperture infrared optical imaging system in the target range caused by factors such as ambient temperature and direct sunlight seriously affects the accuracy of the infrared radiation measurement. The present application can calculate and eliminate the stray radiation caused by the change of system temperature, and further improve the accuracy of the infrared radiation characteristic measurement under the target range environment.

[0004] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0005] The present application provides an infrared radiation characteristic measurement method for removing stray radiation, which specifically comprises the following steps:

[0006] S1: After calibrating the large-aperture infrared optical imaging system in a high-low temperature test chamber, temperature sensors are arranged at both ends of the large-aperture infrared optical imaging system under the ambient temperature in the field environment, and the temperature sensors are used to collect the temperature of the mechanical housing of the large-aperture infrared optical imaging system;

[0007] S2: assuming that the temperature of the mechanical housing changes uniformly, the mechanical housing is divided into n microelements along the optical axis direction, and the temperature difference between adjacent microelements is calculated;

[0008] S3: obtaining the target image gray scale of the radiation temperature T target

[0009] S4: inverting the equivalent blackbody radiation luminance of the target based on the target image gray scale, to realize the infrared radiation characteristic measurement of removing the self thermal radiation of the large-aperture infrared optical imaging system.

[0010] Further, in step S1, the specific operation of calibrating the large-aperture infrared optical imaging system is: placing the large-aperture infrared optical imaging system and the surface source blackbody into a high-low temperature test box, adjusting the positions of the large-aperture infrared optical imaging system and the surface source blackbody, so that the optical axis of the large-aperture infrared optical imaging system coincides with the central normal line of the effective radiation surface of the surface source blackbody, the surface source blackbody covers the entrance pupil and the field of view of the large-aperture infrared optical imaging system, and the temperature of the surface source blackbody and the working temperature in the high-low temperature test box are changed respectively, to complete the radiation calibration of the large-aperture infrared optical imaging system under different environmental temperatures.

[0011] Further, in step S2, the temperature difference of the adjacent microelements is calculated:

[0012]

[0013] wherein, T amb1 and T amb2 are the temperature values collected by the temperature sensors respectively located at both ends of the large-aperture infrared optical imaging system, T amb1 T amb2 , ΔT amb is the temperature difference of the adjacent microelements, and n is the number of the microelements, and n is greater than or equal to 2.

[0014] Further, in step S2, ΔT amb T amb1 ≤0.01.

[0015] Further, in step S1, the calibration formula is:

[0016]

[0017] wherein, h is the output image gray scale, t int is the detector integration time, L(T) is the radiation luminance incident to the large-aperture infrared optical imaging system when the blackbody temperature is T L(T ​​​​​​amb ) is the ambient temperature, T amb is the stray light brightness, G response is the response gain of the large-aperture infrared optical imaging system, G stray is the stray light gain, h det1 and h det2 are all response biases.

[0018] Further, in step S3, the target image gray scale of the radiation temperature T target is obtained according to the calibration formula:

[0019] ;

[0020] wherein, is the target image gray scale of the radiation temperature T target , G i is the stray light gain of the first i block of microelements.

[0021] Further, in step S4, the calculation formula used for the inversion of the equivalent blackbody radiation brightness of the target based on the target image gray scale is:

[0022] ;

[0023] wherein, L ( T target ) is the equivalent blackbody radiation brightness of the target, is the stray light gain, n is the number of microelements, is the temperature sensitivity.

[0024] Further, the temperature sensor is a patch temperature sensor.

[0025] Compared with the prior art, the present application can achieve the following beneficial effects:

[0026] The infrared radiation characteristic measurement method for removing stray light of the present application can calculate the self thermal radiation of the infrared optical imaging system caused by temperature change by adding a patch temperature sensor, thereby eliminating the influence of stray light caused by non-uniform system temperature on the target gray scale and improving the accuracy of the target infrared radiation characteristic measurement. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 A schematic flowchart of the infrared radiation characteristic measurement method for removing stray radiation as described in the embodiments of the present invention;

[0029] Figure 2 A schematic diagram showing the location of the temperature sensor installed in a large-aperture infrared optical imaging system according to an embodiment of the present invention.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1. Incident radiation; 2. Temperature sensor; 3. Mechanical housing; 4. Optical lens assembly; 5. Infrared detector. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0034] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] like Figure 1 As shown, the present invention provides a method for measuring infrared radiation characteristics by removing stray radiation, specifically including the following steps:

[0038] S1: After calibrating the large-aperture infrared optical imaging system in a high and low temperature test chamber, temperature sensors 2 are installed at both ends of the large-aperture infrared optical imaging system under the ambient temperature of the external field. The temperature sensors 2 are used to collect the temperature of the mechanical shell 3 of the large-aperture infrared optical imaging system.

[0039] S2: Assume that the temperature of the mechanical housing 3 changes uniformly. Divide the mechanical housing 3 into n infinitesimal elements along the optical axis and calculate the temperature difference between adjacent infinitesimal elements.

[0040] S3: Based on the calibration formula obtained in step S1 and the calculation results in step S2, the radiation temperature T is obtained. target The grayscale of the target image;

[0041] The grayscale of the target image is obtained by recording the target image through a large-aperture infrared optical imaging system and interpreting the target image.

[0042] S4: Based on the grayscale of the target image, the equivalent blackbody radiance of the target is inverted to realize the measurement of the infrared radiation characteristics of the large-aperture infrared optical imaging system after removing its own thermal radiation.

[0043] It should be noted that the present invention obtains calibration coefficients through a large-aperture infrared optical imaging system that has been calibrated in a high and low temperature chamber, installs patch-type temperature sensors 2 at both ends of the large-aperture infrared optical imaging system, and combines the infrared radiation measurement principle model to calculate and eliminate stray radiation caused by the large-aperture optical imaging system with uneven temperature, thereby improving the accuracy of infrared radiation characteristic measurement under target range conditions.

[0044] Example 1

[0045] Step 1: Place the large-aperture infrared optical imaging system and the blackbody into the high and low temperature test chamber. Adjust the positions of the infrared optical imaging system and the blackbody to ensure they are parallel and aligned. The blackbody should cover the entrance pupil and field of view of the large-aperture infrared optical imaging system. Change the temperature of the blackbody and the temperature inside the high and low temperature test chamber to perform radiation calibration of the large-aperture infrared optical imaging system under different ambient temperatures, and obtain the response gain of the large-aperture infrared optical imaging system. G response Stray radiation gain G stray Response bias h det1 and h det2 The calibration model of incident radiance and output grayscale is obtained:

[0046] ;

[0047] in, h To output the grayscale of the image, t int For the detector integration time, L(T) The blackbody temperature is T At that time, the incident radiation brightness of a large-aperture infrared optical imaging system, L(T amb ) The ambient temperature is T amb stray radiation brightness at that time G response For the response gain of a large-aperture infrared optical imaging system, G stray For stray radiation gain, h det1 and h det2 All are response biases.

[0048] By obtaining at least three sets of blackbody temperatures T and at least three sets of ambient temperatures T amb The corresponding image gray level h is used to calculate the response gain of the large-aperture infrared optical imaging system using the least squares fitting method. G response Stray radiation gain G stray and response bias h det1 and h det2 。

[0049] Step 2: When measuring the target, patch-type temperature sensors 2 are installed at both ends of the large-aperture infrared optical imaging system to collect the temperature at both ends of the large-aperture infrared optical imaging system in real time, and the temperatures at both ends of the mechanical housing 3 are obtained respectively. T amb1 and T amb2 ( T amb1 ≤ T amb2 ).

[0050] like Figure 2 As shown, temperature sensor 2 is located at both ends of mechanical housing 3, and incident radiation 1 is imaged onto infrared detector 5 through optical lens group 4.

[0051] Step 3: According to T amb1 and T amb2 The mechanical casing 3 of the large-aperture infrared optical imaging system is divided into equal parts along the optical axis. n Block microelement ( n ≥2), assuming the temperature of the mechanical casing 3 of the large-aperture infrared optical imaging system changes uniformly, the temperature difference between adjacent micro-elements is obtained as follows:

[0052] :

[0053] This requires ΔT amb / T amb1 ≤0.01.

[0054] Step 4: Obtain the radiation temperature according to the calibration formula. T target The target image grayscale is:

[0055] ;

[0056] in, G i For the first i The stray radiation gain of the block microelement, and Due to Δ T amb Since it is a tiny quantity, the stray radiation of the infinitesimal element is:

[0057] ;

[0058] in,

[0059] ;

[0060] L / T is the temperature sensitivity, obtained by differentiating Planck's formula with respect to temperature. λ 1, λ [2] represents the response band range of the infrared detector 5. T For temperature, c 1 is the first radiation constant. c 2 is the second radiation constant. c 1 = (3.7415 ± 0.0003 × 10) 8 (W·m 2 ·μm 4 ), c 2 = (1.4388 ± 0.0002) × 10 4 (μm 4 ·K), λ This represents the wavelength of the incident radiation 1. Therefore:

[0061] ;

[0062] Finally, the target's equivalent blackbody radiation brightness L ( T target This can be obtained through inversion:

[0063] .

[0064] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0065] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method of measuring the properties of infrared radiation with removal of stray radiation, characterized in that: Specifically comprising the following steps: S1: after calibrating the large-aperture infrared optical imaging system in a high-low temperature test box, temperature sensors are arranged at two ends of the large-aperture infrared optical imaging system under an environmental temperature in a field, and the temperature sensors are used to collect the temperature of a mechanical shell of the large-aperture infrared optical imaging system; S2: assuming that the temperature of the mechanical shell changes uniformly, the mechanical shell is equally divided into n microelements along an optical axis direction, and the temperature difference between adjacent microelements is calculated; S3: based on the calibration formula obtained in step S1 and the calculation result of step S2, obtain the target image gray scale with a radiation temperature of T target ; S4: the equivalent blackbody radiation brightness of a target is inversed based on the gray scale of a target image, and infrared radiation characteristic measurement of the large-aperture infrared optical imaging system after removing its own thermal radiation is realized.

2. The stray radiation removed infrared radiation property measurement method of claim 1, wherein: In step S1, the specific operation of calibrating the large-aperture infrared optical imaging system is as follows: the large-aperture infrared optical imaging system and a surface source blackbody are placed in a high-low temperature test box, the position of the large-aperture infrared optical imaging system and the surface source blackbody is adjusted, the optical axis of the large-aperture infrared optical imaging system is made to coincide with the central normal line of the effective radiation surface of the surface source blackbody, the surface source blackbody covers the entrance pupil and the field of view of the large-aperture infrared optical imaging system, the temperature of the surface source blackbody and the working temperature in the high-low temperature test box are changed respectively, and the radiation calibration of the large-aperture infrared optical imaging system under different environmental temperatures is completed.

3. The stray radiation removed infrared radiation property measurement method of claim 1, wherein: In step S2, the temperature difference between adjacent microelements is calculated as follows: ； wherein, T amb1 and T amb2 are temperature values respectively collected by temperature sensors located at two ends of the large-aperture infrared optical imaging system, T amb1 ≤ T amb2 , In step S1, the calibration formula is as follows: amb is a temperature difference between adjacent microelements, and n is a number of the microelements, and n is greater than or equal to 2.

4. The stray radiation removed infrared radiation property measurement method of claim 3, wherein: In step S2, In step S4, the calculation formula used for inverting the equivalent blackbody radiation brightness of a target based on the gray scale of a target image is as follows: amb / T amb1 ≤0.

01.

5. The stray radiation removed infrared radiation property measurement method of claim 1, wherein: The temperature sensor is a patch temperature sensor. ； wherein, h is the output image gray level, t int is the detector integration time, ​ is the blackbody temperature, T is the radiance incident to the large aperture infrared optical imaging system, ​ amb ) is the ambient temperature, T amb is the stray radiation radiance, G response is the response gain of the large aperture infrared optical imaging system, G stray is the stray radiation gain, h det1 and h det2 are both response offsets.

6. The stray radiation removed infrared radiation property measurement method of claim 5, wherein: In step S3, the radiation temperature is obtained according to the calibration formula T target The target image gray scale is: ； wherein, is the target image gray level, target at a radiation temperature of T G i is the stray light gain of the i block of microcells.

7. The stray radiation removed infrared radiation property measurement method of claim 3, wherein: ​ ； wherein L T target is the equivalent blackbody radiation luminance targeted, is the stray light gain, n is the number of microcells, is the temperature sensitivity.​ 8. The stray radiation removed infrared radiation property measurement method of claim 1, wherein: ​

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