CN111595458B - Thermal infrared imager radiometric calibration method and device - Google Patents
Thermal infrared imager radiometric calibration method and device Download PDFInfo
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Abstract
The invention relates to a thermal infrared imager radiometric calibration method, a device, equipment, a system and a computer storage medium, wherein the method comprises the following steps: acquiring thermal infrared imager response charge numbers corresponding to different black body temperatures at the same exposure time, and acquiring thermal infrared imager response charge numbers corresponding to different black body temperatures at each exposure time by adjusting the exposure time; fitting the thermal infrared imager response charge number corresponding to the same black body temperature at each exposure time to obtain the charge flux density corresponding to the current black body temperature, and further obtain the charge flux densities corresponding to different black body temperatures; and fitting the charge flux densities corresponding to the different blackbody temperatures to obtain a radiation calibration coefficient. The radiometric calibration coefficient obtained by the invention does not depend on the exposure time of the thermal infrared imager any more, and meanwhile, full-pixel calibration is adopted in the calibration process, so that the non-uniform correction preparation work before measurement is eliminated, and the early preparation time of measurement is greatly reduced.
Description
Technical Field
The invention relates to the technical field of infrared testing, in particular to a thermal infrared imager radiometric calibration method, device, equipment, system and computer readable storage medium.
Background
Radiometric calibration of the thermal infrared imager is the basis for realizing quantitative measurement of the thermal infrared imager, and laboratory radiometric calibration is to calculate radiometric calibration coefficients including Gain coefficients Gain and Offset values by using algorithms according to a radiance value L and an imaging digital quantization value DN measured by different thermal infrared imagers. The currently common laboratory radiometric calibration process is shown in fig. 1, a certain exposure time of a thermal infrared imager is set, the thermal infrared imager is subjected to non-uniform correction, a radiation brightness value L of a black body is calculated by taking a black body radiation source as a standard through the temperature and the emissivity of the black body, the black body is imaged by the thermal infrared imager, and a gray value (DN value) of the black body imaged on the thermal infrared imager is recorded. And changing the temperature of the black body, and recording the one-to-one correspondence between the plurality of groups of radiation brightness values L and the gray value DN. A typical variation of the measured charge quantity as a function of the exposure time is given in fig. 2. Ideally, the amount of accumulated charge increases linearly with increasing exposure time. It can be observed that the detected charge flux (i.e., slope) increases with increasing black body temperature, but the intercept does not change, as it depends only on the bias level of the readout circuit. Therefore, through linear fitting, the radiometric calibration coefficients Gain, Offset can be obtained, and finally the functional relationship between L and DN is obtained:
L＝Gain*DN+Offset
where Gain is the Gain factor and Offset is the Offset value.
The traditional thermal imager radiometric calibration needs longer preparation time before the measurement of the thermal imager, mainly due to the following two points:
1. different thermal imagers' exposure times correspond to a set of calibration parameters, and therefore, it is necessary to obtain calibration results for several exposure times and to perform radiometric calibration for several exposure times. Because the exposure time of the thermal imager needs to be changed according to the radiation intensity of the target in the testing process of the thermal imager, calibration before testing is difficult to ensure that the exposure time of the calibrated thermal imager is matched with the exposure time used in the testing process. This is very disadvantageous for real-time acquisition of quantitative data of thermal imagers, as well as for fast quantitative measurements of thermal imagers.
2. The traditional thermal infrared imager radiometric calibration is divided into relative calibration and absolute calibration, namely, before black body calibration is carried out, non-uniform correction is carried out on an imaging surface of the thermal imager by a one-point or two-point correction method, then absolute radiometric calibration is carried out on the corrected thermal imager, and the calibration work of the thermal imager is completed by calculating the relation between an imaging gray value and an entrance pupil radiometric value. Due to the existence of the non-uniform correction process, the preparation work of the radiation calibration in the early stage is greatly increased. Meanwhile, in order to ensure the consistency of the calibration state and the measurement state, the thermal infrared imager also needs to be subjected to non-uniform correction before quantitative measurement is carried out, so that the preparation working time of the thermal infrared imager in the early stage of measurement is greatly increased. When rapid measurement of a dynamic target, a non-cooperative target, and the like is performed, the problem seriously affects the reflecting ability of the measurement target and is not favorable for rapid measurement.
Disclosure of Invention
The present invention is directed to a method, an apparatus, a device, a system, and a computer readable storage medium for radiometric calibration of a thermal infrared imager, which are provided to overcome one or more of the above-mentioned drawbacks of the prior art, such that calibration parameters are no longer dependent on the exposure time of the thermal infrared imager.
In order to solve the technical problem, a first aspect of the present invention provides a thermal infrared imager radiometric calibration method, including the following steps:
s1, acquiring thermal infrared imager response charge numbers corresponding to different black body temperatures in the same exposure time, and acquiring thermal infrared imager response charge numbers corresponding to different black body temperatures in each exposure time by adjusting the exposure time;
s2, fitting the thermal infrared imager response charge number corresponding to the same black body temperature under each exposure time to obtain the charge flux density corresponding to the current black body temperature, and further obtain the charge flux densities corresponding to different black body temperatures;
and S3, fitting the charge flux densities corresponding to the different black body temperatures to obtain a radiation calibration coefficient.
In the thermal infrared imager radiometric calibration method according to the present invention, preferably, the number of the response charges of the thermal infrared imager obtained in step S1 is the number of the response charges of a single pixel, the radiometric calibration coefficient obtained in step S3 is the radiometric calibration coefficient of a single pixel, and the method further includes the steps executed after step S3 of: s4, constructing a calibration parameter matrix of the thermal infrared imager by using the radiometric calibration coefficient of a single pixel, and obtaining a calibration fitting formula for inverting the radiation temperature.
In the thermal infrared imager radiometric calibration method according to the present invention, preferably, in step S2, the charge flux density corresponding to the current black body temperature is obtained by fitting according to the following formula:
countsi,j(k,n)＝Fi,j(n)*ET(k)+Coff(n)；
wherein ET (k) is the exposure time of the kth group, countsi,j(k, n) is the number of the thermal infrared imager response charges corresponding to the nth black body temperature under the k exposure time group, Fi,j(n) is the fitted charge flux density corresponding to the nth blackbody temperature, CoffAnd (n) is a bias term obtained by fitting.
In the thermal infrared imager radiometric calibration method according to the present invention, preferably, the radiometric calibration coefficient is obtained by fitting according to the following formula in step S3:
Fi,j(n)＝Gi,jLbb(n)+Oi,j；
wherein G isi,jIs the gain coefficient of the (i, j) th pixel, Oi,jIs the offset value, L, of the (i, j) th pixelbb(n) is the radiance calculated from the nth blackbody temperature, Fi,jAnd (n) is the charge flux density corresponding to the nth blackbody temperature obtained by fitting.
In the thermal infrared imager radiometric calibration method according to the present invention, preferably, the calibration fitting formula of the thermal infrared imager constructed in the step S4 is:
wherein L isbbFor radiance, F is the charge flux density matrix of the thermal infrared imager, Gi,jIs the gain coefficient of the (i, j) th pixel, Oi,jThe offset values of the (i, j) th pixel are i 1,2, …, M, j 1,2, …, N, M and N are the number of rows and columns of pixels in the thermal infrared imager, respectively.
In a second aspect of the present invention, there is provided a thermal infrared imager radiometer device, comprising:
the data acquisition unit is used for acquiring thermal infrared imager response charge numbers corresponding to different blackbody temperatures in the same exposure time and acquiring thermal infrared imager response charge numbers corresponding to different blackbody temperatures in each exposure time by adjusting the exposure time;
the flux density fitting unit is used for fitting the thermal infrared imager response charge number corresponding to the same black body temperature under each exposure time to obtain the charge flux density corresponding to the current black body temperature and further obtain the charge flux densities corresponding to different black body temperatures;
and the calibration parameter fitting unit is used for fitting the charge flux densities corresponding to the different blackbody temperatures to obtain a radiometric calibration coefficient.
In the thermal infrared imager radiometric calibration device according to the present invention, preferably, the thermal infrared imager radiometric calibration device further includes: and the radiation temperature inversion unit is used for constructing a calibration parameter matrix of the thermal infrared imager by using the radiation calibration coefficient of a single pixel, and obtaining a calibration fitting formula for inverting the radiation temperature.
In a third aspect of the present invention, there is provided a thermal infrared imager radiometer device, comprising: at least one processor, at least one memory and a computer program stored in the memory, which when executed by the processor, implement the method as previously described.
In a fourth aspect of the present invention, a thermal infrared imager radiometric calibration system is provided, which includes the thermal infrared imager radiometric calibration device as described above and a thermal infrared imager connected thereto.
In a fifth aspect of the invention, a computer-readable storage medium is provided, on which a computer program is stored, which, when being executed by a processor, carries out the method as set forth above.
The implementation of the thermal infrared imager radiometric calibration method, the device, the equipment, the system and the computer readable storage medium has the following beneficial effects:
1. the charge flux density calibration method improves the traditional method of adopting different calibration curves at different exposure times into one calibration curve, can be suitable for any exposure time, and greatly reduces the quantitative processing process of data;
2. the invention adopts full-pixel calibration in the calibration process, eliminates the non-uniform correction preparation work before measurement, greatly reduces the early preparation time of measurement, and is beneficial to the rapid quantitative measurement of the thermal imager and the expansion of the infrared quantitative measurement temperature range.
Drawings
FIG. 1 illustrates a prior art thermal infrared imager radiometric calibration process;
FIG. 2 is a graph of a typical variation of measured charge quantity as a function of exposure time;
FIG. 3 is a flow chart of a thermal infrared imager radiometric calibration method in accordance with a preferred embodiment of the present invention;
FIG. 4 is a graph showing the results of a charge-exposure time fit;
FIG. 5 is a schematic diagram of charge flux density versus black body temperature;
fig. 6 is a block diagram of a thermal infrared imager radiometer calibration apparatus according to a preferred embodiment of the present invention.
Detailed Description
In order to make the objects, 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 drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The radiometric calibration method of the thermal infrared imager provided by the invention can be used for quickly calibrating pixels one by one in real time and is designed to be closely matched with the physical performance of the thermal infrared imager so as to correct the influence in different dynamic ranges. The method of the present invention does not rely on observing the function of the change in digital level versus black body temperature, or the function of radiation change over a band of wavelengths, which is characterized by charge flux density in counts/mus, representing the exposure time dependent sensitivity of thermal infrared imager readings. Meanwhile, in the early calibration process, pixel-by-pixel calibration data is preferably acquired to replace the non-uniform correction before measurement, so that the preparation working time before measurement is greatly saved.
Referring to fig. 3, a flowchart of a radiometric calibration method of a thermal infrared imager according to a preferred embodiment of the present invention is shown. As shown in fig. 3, the thermal infrared imager radiometric calibration method provided by this embodiment includes the following steps:
first, in step S1, a data obtaining step is performed to obtain corresponding thermal infrared imager response charge numbers of different blackbody temperatures at the same exposure time, and then the corresponding thermal infrared imager response charge numbers of different blackbody temperatures at each exposure time are obtained by adjusting the exposure time.
In this step, the black body is placed in front of a thermal infrared imager as a radiation standard. Firstly, the exposure time of the thermal infrared imager is kept unchanged, the temperature of a black body is changed, and the response charge number of the thermal infrared imager is obtained. And then changing the exposure time of the thermal infrared imager, repeating the steps, and acquiring the response charge number of the thermal infrared imager corresponding to different blackbody temperatures under each exposure time.
Preferably, this step may convert the black body temperature into radiant brightness for storage when recording data. The data can be recorded as the response charge number of the thermal infrared imager detector under the radiation brightness conditions of different exposure times and different black bodies.
Specifically, since the output level of the thermal infrared imager is in direct proportion to the black body radiation brightness, for comparison, firstly the planck formula converts the black body temperature into the black body radiation brightness as follows:
in the formula: wλ: spectral radiant exitance, unit: w.cm-2·μm-1；
λ: wavelength, unit: mu m;
C1: first radiation constant 3.7415 × 104, unit: w.cm-2·μm4；
C2: second radiation constant 1.4388 × 104, unit: μ m.K;
t: absolute temperature, unit: K.
therefore, the radiant exitance of the black body in the infrared thermal imager imaging band delta lambda is the integral of the band:
in the formula: wΔλ: wave band radiation emittance, unit: w.cm-2；
ελ: spectral emissivity
λ1: lower limit of infrared thermal imager imaging band, unit: mu m;
λ2: upper limit of imaging band of thermal infrared imager, unit: and mu m.
For a black body, the spectral emissivity ελConsidered a constant, the above equation can be written as:
in the formula Wbbε is a constant for the degree of radiation extraction.
Therefore, the temperature of the black body can be converted into the radiance of the black body in the imaging band of the thermal infrared imager by the following formula:
more preferably, the number of response charges of each pixel on the detector of the thermal infrared imager needs to be read during recording.
Taking a certain calibration test as an example, the black body temperature, i.e., the radiation brightness, is set to be a group a, the exposure time is set to be a group B, and calibration test data for a certain (i, j) pixel is as follows. i 1,2, …, M, j 1,2, …, N, M and N are the number of rows and columns of pixels in the thermal infrared imager, respectively.
TABLE 1 calibration raw data record Table (Single Pixel)
For the thermal infrared imager with the pixel number of the detector being M multiplied by N, the data of more than M multiplied by N groups of tables are required to be acquired aiming at the whole pixels of the thermal infrared imager.
Subsequently, in step S2, a flux density fitting step is performed to fit the number of electric charges responded to the thermal infrared imager corresponding to the same black body temperature at each exposure time, so as to obtain the electric charge flux density corresponding to the current black body temperature, and further obtain the electric charge flux densities corresponding to different black body temperatures.
FIG. 4 is a diagram showing the result of charge-exposure time fitting. The thermal infrared imager radiometric calibration method of the invention firstly reads different black body temperatures (T)bb,1，Tbb,2，Tbb,3，Tbb,4…), the thermal infrared imager responds to the relationship between the number of charges and the exposure time of the thermal infrared imager. Theoretically, the number of charges received by the detector of the thermal infrared imager at the same blackbody temperature is in linear relation with the exposure time, and C in the graphoffThe bias parameter represents the scaling, i.e., the magnitude of the dark current noise in response to the amount of charge. The slope of each line in the graph represents the number of charges passing through the detector of the thermal infrared imager per unit time, i.e., the charge flux density corresponding to different blackbody temperatures, in counts/μ s. And then the radiometric calibration parameter can be obtained by the functional fitting of the charge flux density F and the black body temperature. The charge flux density F depends on the radiant energy received by the thermal infrared imager in unit time, namely is in direct proportion to the radiant power received by the entrance pupil of the thermal infrared imager, and further is in direct proportion to the radiant brightness L received by the entrance pupil of the thermal infrared imagerIIn direct proportion, the imaging system of the thermal infrared imager needs to be covered by the black body in the calibration process, so that the entrance pupil radiance of the thermal infrared imager is the radiance L of the black bodybb。
Preferably, the charge flux density corresponding to the current black body temperature is obtained in step S2 by fitting the following equation:
countsi,j(k,n)＝Fi,j(n)*ET(k)+Coff(n)；
wherein ET (k) is the exposure time of the kth group, countsi,j(k, n) is the number of the thermal infrared imager response charges corresponding to the nth black body temperature under the k exposure time group, Fi,j(n) is the fitted charge flux density corresponding to the nth blackbody temperature, CoffAnd (n) is a bias term obtained by linear fitting. k is 1,2, …, B, n is 1,2, …, a. The parameters with i, j subscripts all correspond to the (i, j) th pixel.
For example, take the numbers in Table 1According to which, for each set of radiance data, a fitting is performed using the corresponding data, the countsi,j(k, n) and ET (k) are data in the table, coexisting in the B group data corresponding to one, Fi,j(n) and CoffAnd (n) is the data calculated by fitting. Thereby, the charge flux densities corresponding to different blackbody temperatures can be obtained, and since the blackbody temperature can be converted into the radiant luminance representation, the charge flux densities corresponding to different radiant luminances can also be obtained as shown in table 2 below.
Table 2 charge flux density calculation
Finally, in step S3, a calibration parameter fitting step is performed to fit the charge flux densities corresponding to the different blackbody temperatures to obtain radiometric calibration coefficients.
Preferably, the radiometric calibration coefficients are fitted in step S3 by the following formula:
Fi,j(n)＝Gi,jLbb(n)+Oi,j；
wherein G isi,jIs the gain coefficient of the (i, j) th pixel, Oi,jIs the offset value, L, of the (i, j) th pixelbb(n) is the radiance calculated from the nth blackbody temperature, Fi,jAnd (n) is the charge flux density corresponding to the nth blackbody temperature obtained by fitting.
G abovei,jAnd Oi,jFor the radiometric calibration coefficients, data fitting may be performed to obtain the charge flux densities corresponding to different radiances in table 2.
The invention provides an improved radiometric calibration data processing method aiming at the requirements of rapid and real-time quantitative measurement of a thermal infrared imager, replaces the traditional relative radiometric calibration process, and reduces the data processing time occupied by relative radiometric calibration and the introduced uncertainty. Meanwhile, a charge flux density calibration method is introduced according to the charge number of the pixel, and the traditional method of adopting different calibration curves for different exposure times is improved into a calibration curve which can be suitable for any exposure time, so that the quantitative processing process of data is greatly reduced.
More preferably, the number of the response charges of the thermal infrared imager obtained in step S1 is the number of the response charges of a single pixel, the radiometric scaling coefficient obtained in step S3 is the radiometric scaling coefficient of a single pixel, and the method of the present invention further includes the steps executed after step S3 of:
s4, constructing a calibration parameter matrix of the thermal infrared imager by using the radiometric calibration coefficient of a single pixel, and obtaining a calibration fitting formula for inverting the radiation temperature. That is to say, the calibration process is generalized to the full pixels of the thermal infrared imager, the calibration parameters are updated to be in the form of two-dimensional matrix data, taking the thermal infrared imager with the number of pixels of M × N as an example, the calibration fitting formula of the thermal infrared imager constructed in the step S4 is as follows:
wherein L isbbFor radiance, F is the charge flux density matrix of the thermal infrared imager, Gi,jIs the gain coefficient of the (i, j) th pixel, Oi,jThe offset values of the (i, j) th pixel are i 1,2, …, M, j 1,2, …, N, M and N are the number of rows and columns of pixels in the thermal infrared imager, respectively.
Wherein the scaling parameter matrix is:
where Gain is the Gain factor and Offset is the Offset value.
The above formula can be used to calculate the inversion from the number of charges responded by the thermal infrared imager to the radiance of the entrance pupil.
On the basis, the charge flux density and the black body temperature can be fitted to obtain a fitting formula for inversion from the response charge number of the thermal infrared imager to the radiation temperature. FIG. 5 is a schematic diagram showing the relationship between the charge flux density and the black body temperature. The abscissa in fig. 5 represents the black body temperature for calibration, and the ordinate represents the charge flux density. The curve reflects the calibration result of radiometric calibration, does not contain exposure time parameters, and is suitable for the inversion of the radiation temperature of the thermal infrared imager under various different exposure time conditions.
The invention can respectively carry out quantitative processing on each pixel of the thermal infrared imager detector in a laboratory before leaving the factory to obtain the calibration curve of different pixels, and because each pixel is provided with one calibration result independently, the thermal infrared imager does not need to be subjected to non-uniform correction in the measurement and calibration process, the preparation working time of the test is greatly reduced, and the measurement speed is improved. After the calibration test is finished, the calibration data can carry out quantitative processing on the measurement data of the thermal infrared imager at any exposure time, and the exposure time is not limited by the calibration data any more, so that the exposure time can be adjusted at will during measurement, the workload brought by the predetermined exposure time is greatly reduced, the scene dynamic range of the use of the calibration data is improved, and the real-time quantitative processing of the thermal infrared imager can be realized.
Based on the same inventive concept, the embodiment of the invention also provides a thermal infrared imager radiation calibration device. Fig. 6 is a block diagram of an infrared thermal imager radiometer calibration apparatus according to a preferred embodiment of the present invention. As shown in fig. 6, this embodiment provides a thermal infrared imager radiometer assembly 600 including at least: a data acquisition unit 601, a flux density fitting unit 602 and a scaling parameter fitting unit 603.
The data obtaining unit 601 is configured to obtain thermal infrared imager response charge numbers corresponding to different blackbody temperatures at the same exposure time, and then obtain thermal infrared imager response charge numbers corresponding to different blackbody temperatures at each exposure time by adjusting the exposure time.
The invention firstly puts the black body in front of the thermal infrared imager as the radiation standard. Firstly, the exposure time of the thermal infrared imager is kept unchanged, the temperature of a black body is changed, and the response charge number of the thermal infrared imager is obtained. And then changing the exposure time of the thermal infrared imager, repeating the steps, and acquiring the response charge number of the thermal infrared imager corresponding to different blackbody temperatures under each exposure time.
Preferably, the data acquisition unit 601 may convert the black body temperature into radiant brightness for storage when recording data. The data can be recorded as the response charge number of the thermal infrared imager detector under the radiation brightness conditions of different exposure times and different black bodies.
Specifically, the temperature of the black body can be converted into the radiance of the black body at the imaging band of the thermal infrared imager by the following formula:
more preferably, the number of response charges of each pixel on the detector of the thermal infrared imager needs to be read during recording.
The flux density fitting unit 602 is configured to fit the number of electric charges responded by the thermal infrared imager corresponding to the same black body temperature at each exposure time to obtain an electric charge flux density corresponding to the current black body temperature, and further obtain electric charge flux densities corresponding to different black body temperatures.
Preferably, the flux density fitting unit 602 fits the current blackbody temperature to obtain the charge flux density corresponding to the current blackbody temperature by the following formula:
countsi,j(k,n)＝Fi,j(n)*ET(k)+Coff(n)；
wherein ET (k) is the exposure time of the kth group, countsi,j(k, n) is the number of the thermal infrared imager response charges corresponding to the nth black body temperature under the k exposure time group, Fi,j(n) is the fitted charge flux density corresponding to the nth blackbody temperature, CoffAnd (n) is a bias term obtained by linear fitting. k is 1,2, …, B, n is 1,2, …, a. The parameters with i, j subscripts all correspond to the (i, j) th pixel.
And the calibration parameter fitting unit 603 is configured to fit the charge flux densities corresponding to the different blackbody temperatures to obtain a radiometric calibration coefficient.
Preferably, the scaling parameter fitting unit 603 fits the radiation scaling coefficients by the following formula:
Fi,j(n)＝Gi,jLbb(n)+Oi,j；
wherein G isi,jIs the gain coefficient of the (i, j) th pixel, Oi,jIs the offset value, L, of the (i, j) th pixelbb(n) is the radiance calculated from the nth blackbody temperature, Fi,jAnd (n) is the charge flux density corresponding to the nth blackbody temperature obtained by fitting.
More preferably, the number of the response charges of the thermal infrared imager acquired by the data acquiring unit 601 is the number of the response charges of a single pixel, the radiometric scaling coefficient obtained by the scaling parameter fitting unit 603 is the radiometric scaling coefficient of a single pixel, and the device 600 further includes: and the radiation temperature inversion unit 604 is configured to construct a calibration parameter matrix of the thermal infrared imager by using the radiation calibration coefficient of a single pixel, and obtain a calibration fitting formula for inverting the radiation temperature.
The calibration fitting formula of the thermal infrared imager constructed by the radiation temperature inversion unit 604 is as follows:
wherein L isbbFor radiance, F is the charge flux density matrix of the thermal infrared imager, Gi,jIs the gain coefficient of the (i, j) th pixel, Oi,jThe offset values of the (i, j) th pixel are i 1,2, …, M, j 1,2, …, N, M and N are the number of rows and columns of pixels in the thermal infrared imager, respectively.
On the basis, the charge flux density and the black body temperature can be fitted to obtain a fitting formula for inversion from the response charge number of the thermal infrared imager to the radiation temperature.
The embodiment of the invention also provides equipment for executing the thermal infrared imager radiometric calibration method, which comprises the following steps: at least one processor, at least one memory and a computer program stored in the memory, which when executed by the processor, implement the thermal infrared imager radiometric calibration method as in the above embodiments.
The embodiment of the invention provides a thermal infrared imager radiometric calibration system which comprises the thermal infrared imager radiometric calibration equipment and a thermal infrared imager connected with the thermal infrared imager radiometric calibration equipment.
An embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the thermal infrared imager radiometric calibration method in the above embodiments is implemented.
The invention provides a new thermal infrared imager radiometric calibration method, by which calibration parameters do not depend on the exposure time of the thermal infrared imager any more, meanwhile, full-pixel calibration is adopted in the calibration process, non-uniform correction preparation work before measurement is eliminated, the early preparation time of measurement is greatly reduced, the working efficiency of the thermal infrared imager is improved, the calibration precision of the thermal infrared imager is improved, and the speed of a quantitative processing flow is improved. The infrared thermal image measurement of dynamic targets and non-cooperative targets is facilitated, high quantitative measurement precision is provided, and rapid quantitative measurement of a thermal imager and expansion of an infrared quantitative measurement temperature range are facilitated.
It should be understood that the principle of the thermal infrared imager radiometric calibration method and apparatus of the present invention is the same, and therefore the detailed description of the thermal infrared imager radiometric calibration method embodiment is also applicable to the thermal infrared imager radiometric calibration apparatus.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (9)
1. A thermal infrared imager radiometric calibration method is characterized by comprising the following steps:
s1, acquiring thermal infrared imager response charge numbers corresponding to different black body temperatures in the same exposure time, and acquiring thermal infrared imager response charge numbers corresponding to different black body temperatures in each exposure time by adjusting the exposure time;
s2, fitting the thermal infrared imager response charge number corresponding to the same black body temperature under each exposure time to obtain the charge flux density corresponding to the current black body temperature, and further obtain the charge flux densities corresponding to different black body temperatures;
s3, fitting the charge flux densities corresponding to the different black body temperatures to obtain a radiation calibration coefficient;
in the step S3, the radiometric calibration coefficient G is obtained by fitting the following formulai,jAnd Oi,j：
Fi,j(n)＝Gi,jLbb(n)+Oi,j；
Wherein G isi,jIs the gain coefficient of the (i, j) th pixel, Oi,jIs the offset value, L, of the (i, j) th pixelbb(n) is the radiance calculated from the nth blackbody temperature, Fi,jAnd (n) is the charge flux density corresponding to the nth blackbody temperature obtained by fitting.
2. The thermal infrared imager radiometric calibration method according to claim 1, wherein the number of response charges of the thermal infrared imager obtained in step S1 is the number of response charges of a single pixel, the radiometric calibration coefficient obtained in step S3 is the radiometric calibration coefficient of a single pixel, the method further comprises the steps executed after step S3 of:
s4, constructing a calibration parameter matrix of the thermal infrared imager by using the radiometric calibration coefficient of a single pixel, and obtaining a calibration fitting formula for inverting the radiation temperature.
3. The thermal infrared imager radiometric calibration method according to claim 2, characterized in that the charge flux density corresponding to the current black body temperature is obtained in step S2 by fitting the following formula:
countsi,j(k,n)＝Fi,j(n)*ET(k)+Coff(n)；
wherein ET (k) is the exposure time of the kth group, countsi,j(k, n) is the number of the thermal infrared imager response charges corresponding to the nth black body temperature under the k exposure time group, Fi,j(n) is the fitted charge flux density corresponding to the nth blackbody temperature, CoffAnd (n) is a bias term obtained by fitting.
4. The thermal infrared imager radiometric calibration method according to claim 3, characterized in that the calibration fitting formula of the thermal infrared imager constructed in the step S4 is:
wherein L isbbFor radiance, F is the charge flux density matrix of the thermal infrared imager, Gi,jIs the gain coefficient of the (i, j) th pixel, Oi,jThe offset values of the (i, j) th pixel are i 1,2, …, M, j 1,2, …, N, M and N are the number of rows and columns of pixels in the thermal infrared imager, respectively.
5. A thermal infrared imager radiometric calibration device, comprising:
the data acquisition unit is used for acquiring thermal infrared imager response charge numbers corresponding to different blackbody temperatures in the same exposure time and acquiring thermal infrared imager response charge numbers corresponding to different blackbody temperatures in each exposure time by adjusting the exposure time;
the flux density fitting unit is used for fitting the thermal infrared imager response charge number corresponding to the same black body temperature under each exposure time to obtain the charge flux density corresponding to the current black body temperature and further obtain the charge flux densities corresponding to different black body temperatures;
the calibration parameter fitting unit is used for fitting the charge flux densities corresponding to the different black body temperatures to obtain a radiometric calibration coefficient;
the calibration parameter fitting unit obtains a radiometric calibration coefficient G by fitting according to the following formulai,jAnd Oi,j：
Fi,j(n)＝Gi,jLbb(n)+Oi,j；
Wherein G isi,jIs the gain coefficient of the (i, j) th pixel, Oi,jIs the offset value, L, of the (i, j) th pixelbb(n) is the radiance calculated from the nth blackbody temperature, Fi,jAnd (n) is the charge flux density corresponding to the nth blackbody temperature obtained by fitting.
6. The thermography radiometric calibration device of claim 5, further comprising: and the radiation temperature inversion unit is used for constructing a calibration parameter matrix of the thermal infrared imager by using the radiation calibration coefficient of a single pixel, and obtaining a calibration fitting formula for inverting the radiation temperature.
7. A thermal infrared imager radiometric calibration device comprising: at least one processor, at least one memory and a computer program stored in the memory, characterized in that the computer program realizes the method according to any one of claims 1 to 4 when the computer program is executed by the processor.
8. A thermographic radiometric calibration system, comprising the thermographic radiometric calibration device of claim 7 and a thermographic coupled thereto.
9. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the method according to any one of claims 1 to 4.
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| CN104316194A (en) * | 2014-09-24 | 2015-01-28 | 中国人民解放军63620部队 | Light adjusting-type infrared radiation calibration method |
| CN105241554A (en) * | 2015-09-29 | 2016-01-13 | 北京环境特性研究所 | Non-point source blackbody type radiation source under outfield condition and calibration method thereof |
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