CN114295226A - Calibration method for improving thermal imager temperature measurement resolution ratio based on frame accumulation - Google Patents
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Abstract
The invention relates to a temperature calibration method for improving resolution of a thermal imager based on frame accumulation, which comprises the steps of collecting infrared image frame sequences corresponding to different temperatures of a black body instrument by using the thermal imager to be calibrated, calculating the mean value of all pixel points in an infrared image after frame accumulation, fitting an approximate true value calibration equation with the set value of the black body instrument, further accumulating and averaging multiple measured values of the same pixel point in the infrared image frame sequences respectively, and fitting a calibration equation set of all pixel points in the thermal imager with the approximate true value. The frame accumulation technology is applied to temperature calibration of the thermal imager, random errors of temperature measurement of the thermal imager are reduced, and meanwhile, system errors of temperature measurement of the thermal imager are restrained.
Description
Technical Field
The invention relates to the technical field of thermal imager temperature calibration, and particularly provides a calibration method for improving thermal imager temperature measurement resolution based on frame accumulation.
Background
The infrared thermal imager has the advantages of visualization, non-contact, high temperature measurement speed and the like, and is widely applied to the fields of industry, aerospace and medicine. The thermal infrared imager measures the infrared energy radiated by an object, measures the accurate value of the surface temperature of the object, and presents the difference of the surface temperature of a human body through certain processing. The wide application places higher requirements on the measurement precision.
In the angle analysis of measurement, the thermal infrared imager is used as a measurement system, random errors and system errors exist, the measurement precision of the system is influenced, and the thermal infrared imager needs to be calibrated to improve the measurement precision. The existing calibration mode takes the temperature of the black body instrument as the basis of calibration, simultaneously considers the influence caused by the angle and the distance of the thermal imager, namely the influence of system errors, does not process the influence of random noise and each temperature point on the measurement result, loses part of measurement precision, and when in measurement, the black body instrument consumes long time when reaching thermal balance, is inconvenient to carry, and influences the measurement efficiency.
Disclosure of Invention
The invention aims to provide a calibration method for improving the temperature measurement resolution of a thermal imager based on frame accumulation, which improves the resolution of the thermal imager, improves the temperature measurement precision of the thermal imager, and also improves the sensitivity of temperature difference identification on the surface of a measured object.
The technical scheme of the invention is as follows: the frame accumulation technology is applied to temperature calibration of the thermal imager, the random error of thermal imager temperature measurement is reduced, the system error of thermal imager temperature measurement is restrained, the measurement result of each pixel point is calibrated, the system error caused by spatial distribution of the pixel points is further restrained, the resolution of the thermal imager is improved, the temperature measurement precision of the thermal imager is improved, the sensitivity of surface temperature difference identification of a measured object is also improved, and the method specifically comprises the following steps:
s1: setting a temperature value of the black body instrument, and acquiring infrared image frame sequences corresponding to different black body instrument temperatures by using a thermal imager to be calibrated;
s2: performing frame accumulation processing on the infrared image frame sequence at each temperature, and calculating the mean value of all pixel points in the infrared image after frame accumulation to serve as a value to be calibrated;
s3: fitting an approximate true value calibration equation by taking the set value of the blackbody instrument as a true value, and solving the approximate true value of the value to be calibrated;
s4: accumulating and averaging multiple measured values of the same pixel point in the infrared image frame sequence at each temperature respectively to serve as a value to be calibrated of the pixel point;
s5: fitting the calibration equation of each pixel point by taking the approximate truth value as a true value so as to obtain a final calibration equation set;
s6: and acquiring the infrared image frame sequence with the same frame number during measurement, accumulating and averaging multiple measured values of the same pixel point respectively, and substituting the accumulated values into a calibration equation set to obtain a calibrated measurement result.
Further, the result of the continuous imaging of the thermal imager may be a sequence of infrared image frames, or a sequence of temperature value matrices formed by temperature values corresponding to each pixel point.
Further, frame accumulation technology is used for carrying out frame accumulation processing on the infrared image frame sequence collected by the thermal imager, and the result after frame accumulation is used for participating in the subsequent calculation process.
Further, an approximate true value calibration equation is calculated, and a blackbody instrument is used for setting the value T0As a true value, the mean value of all pixel points in the infrared image
Performing least square fitting as a value to be calibrated to obtain a true-approximation calibration straight line Y-kX + b, wherein k and b are correction coefficients, X is the value to be calibrated, Y is a true-approximation value, and substituting the infrared image mean values to obtain a true-approximation value TsThe calibration process inhibits the system error of thermal imager temperature measurement and improves the measurement precision.
Further, calculating a calibration equation of each pixel point, and calculating a N-frame mxn infrared image frame sequence T at each temperatureiN, (i ═ 1, 2.. N) of the same pixel point t(m,n)The N measured values t are averaged to obtain
As the value to be calibrated of the pixel point, the value is approximated to the true value TsAs a true value, performing least square fitting on the calibration equation of each pixel point to obtain a final calibration equation set
Wherein k is(m,n)，b(m,n)To calibrate the coefficients, x(m,n)For the value to be calibrated of a pixel point, y(m,n)For the pixel point calibration result, the system error caused by the spatial distribution of the pixel points is further inhibited, the resolution of the thermal imager is improved, the temperature measurement precision of the thermal imager is improved, and the sensitivity of the thermal imager for identifying the surface temperature difference of the measured object is also improved.
Furthermore, when the thermal imager is used for collecting the surface of the object, the infrared image frame sequences with the same frame number are collected, multiple measured values of the same pixel point are respectively accumulated and averaged, the measured values are substituted into a calibration equation set to obtain the measured result of each pixel point, and the sensitivity of the temperature difference identification of the surface of the measured object is improved.
The invention has the beneficial effects that: the frame accumulation technology is applied to temperature calibration of the thermal imager, random errors of temperature measurement of the thermal imager are reduced, and system errors of temperature measurement of the thermal imager are restrained at the same time.
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FIG. 1 is a flowchart of a thermal imager temperature resolution calibration method according to the present invention
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail below. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1, the present embodiment provides a calibration method for improving thermal resolution of a thermal imager based on frame accumulation, and the calibration method is applied to screening of human diseases, and the method includes the specific steps of:
s1: as the human body temperature is detected, the temperature value range of the black body instrument is set to be 30-45 ℃ during calibration (7 temperature values are set in the embodiment: 30 ℃, 34 ℃, 36 ℃, 38 ℃, 40 ℃, 42 ℃ and 45 ℃), and the thermal imager to be calibrated is used for collecting an infrared image frame sequence I with the resolution of m multiplied by N of 400 frames and the set temperature values of the black body instrumenti(i＝1,2,...N)；
S2: respectively carrying out N-frame accumulation processing on infrared image frame sequences collected at 7 temperatures to obtain infrared images after frame accumulation, and solving the average value of all pixel points in the infrared images
As the value to be calibrated, reducing the random error of the thermal imager in temperature measurement;
s3: takes 7 temperature values set by the blackbody instrument as true values T0Fitting a calibration equation Y between a value to be calibrated and a true value by using a least square method, wherein k and b are correction coefficients, X is the value to be calibrated, Y is an approximate true value, and the values of 7 temperatures are measured
Substituting the calibration equation to obtain a corresponding approximate true value IsInhibiting the system error of thermal imager temperature measurement;
s4: respectively calculating N frames of infrared image frame sequences I at the 7 temperaturesiMiddle and same pixel point t(m,n)The N measured values are subjected to frame accumulation to obtain
As the value to be calibrated of the pixel point;
s5: approximate truth value I corresponding to 7 temperaturessAs a true value, performing least square fitting to obtain a calibration equation corresponding to the m × n pixel points, thereby obtaining a final calibration equation set
Wherein k is(m,n)，b(m,n)To calibrate the coefficients, x(m,n)For the value to be calibrated of a pixel point, y(m,n)For the pixel point calibration result, the system error caused by the spatial distribution of the pixel points is further inhibited, the resolution of the thermal imager is improved, the temperature measurement precision of the thermal imager is improved, and the sensitivity of the thermal imager for identifying the surface temperature difference of the measured object is also improved;
s6: when the human body surface is measured, N frames of infrared image frame sequences at the same position are collected, the measured values of the same pixel points are accumulated and averaged and are substituted into a calibration equation set to obtain a measurement result, the measurement accuracy is improved, the sensitivity of identifying the surface temperature difference of the measured object is improved, and certain diseases causing uneven skin surface temperature distribution, such as breast tumor, lower limb deep venous thrombosis, arthritis and the like, can be screened better.
The invention is not the best known technology.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (6)
1. A calibration method for improving thermal resolution of a thermal imager based on frame accumulation is characterized in that: the frame accumulation technology is applied to temperature calibration of the thermal imager, the random error of thermal imager temperature measurement is reduced, the system error of thermal imager temperature measurement is restrained, the measurement result of each pixel point is calibrated, the system error caused by spatial distribution of the pixel points is further restrained, the resolution of the thermal imager is improved, the temperature measurement precision of the thermal imager is improved, the sensitivity of surface temperature difference identification of a measured object is also improved, and the method specifically comprises the following steps:
s1: setting a temperature value of the black body instrument, and acquiring infrared image frame sequences corresponding to different black body instrument temperatures by using a thermal imager to be calibrated;
s2: performing frame accumulation processing on the infrared image frame sequence at each temperature, and calculating the mean value of all pixel points in the infrared image after frame accumulation to serve as a value to be calibrated;
s3: fitting an approximate true value calibration equation by taking the set value of the blackbody instrument as a true value, and solving the approximate true value of the value to be calibrated;
s4: accumulating and averaging multiple measured values of the same pixel point in the infrared image frame sequence at each temperature respectively to serve as a value to be calibrated of the pixel point;
s5: fitting the calibration equation of each pixel point by taking the approximate truth value as a true value so as to obtain a final calibration equation set;
s6: and acquiring the infrared image frame sequence with the same frame number during measurement, accumulating and averaging multiple measured values of the same pixel point respectively, and substituting the accumulated values into a calibration equation set to obtain a calibrated measurement result.
2. The sequence of infrared image frames of claim 1, wherein: the result of the continuous imaging of the thermal imager can be an infrared image frame sequence or a temperature value matrix sequence formed by temperature values corresponding to all pixel points.
3. The infrared image of claim 1, wherein: and accumulating the infrared image frame sequence acquired by the thermal imager by using a frame accumulation technology.
4. The approximate truth calibration equation of claim 1 wherein: setting value T by blackbody instrument0As a true value, the mean value of all pixel points in the infrared image
Performing least square fitting as a value to be calibrated to obtain a true-approximation calibration straight line Y-kX + b, wherein k and b are correction coefficients, X is the value to be calibrated, Y is a true-approximation value, and substituting the infrared image mean values to obtain a true-approximation value TsThe calibration process inhibits the system error of thermal imager temperature measurement and improves the measurement precision。
5. The system of calibration equations of claim 1, wherein: for each temperature, N frames of m × N infrared image frame sequence TiN, (i ═ 1, 2.. N) of the same pixel point t(m,n)The N measured values t are averaged to obtain
As the value to be calibrated of the pixel point, the value is approximated to the true value TsAs a true value, performing least square fitting on the calibration equation of each pixel point to obtain a final calibration equation set
Wherein k is(m,n)，b(m,n)To calibrate the coefficients, x(m,n)For the value to be calibrated of a pixel point, y(m,n)For the pixel point calibration result, the system error caused by the spatial distribution of the pixel points is further inhibited, the resolution of the thermal imager is improved, the temperature measurement precision of the thermal imager is improved, and the sensitivity of the thermal imager for identifying the surface temperature difference of the measured object is also improved.
6. The measurement result of claim 1, wherein: when a thermal imager is used for collecting the surface of an object, the infrared image frame sequences with the same number of frames are collected, multiple measured values of the same pixel point are respectively accumulated and averaged, the measured values are substituted into a calibration equation set to obtain the measured result of each pixel point, and the sensitivity of the thermal imager to the surface temperature difference identification of the measured object is improved.
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| CN115005782A (en) * | 2022-06-06 | 2022-09-06 | 杭州新瀚光电科技有限公司 | Human health assessment method, system, terminal device and storage medium |
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| CN105466563A (en) * | 2014-09-09 | 2016-04-06 | 南京理工大学 | Infrared thermal imager inhomogeneity two-point correction module and method |
| CN111611544A (en) * | 2020-05-12 | 2020-09-01 | 中国科学院上海技术物理研究所 | Thermal imager warm water drainage monitoring method for airborne large-view-field area array swinging |
| CN112651903A (en) * | 2020-11-12 | 2021-04-13 | 苏州长风航空电子有限公司 | Thermal infrared imager image preprocessing system and preprocessing method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105466563A (en) * | 2014-09-09 | 2016-04-06 | 南京理工大学 | Infrared thermal imager inhomogeneity two-point correction module and method |
| CN111611544A (en) * | 2020-05-12 | 2020-09-01 | 中国科学院上海技术物理研究所 | Thermal imager warm water drainage monitoring method for airborne large-view-field area array swinging |
| CN112651903A (en) * | 2020-11-12 | 2021-04-13 | 苏州长风航空电子有限公司 | Thermal infrared imager image preprocessing system and preprocessing method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115005782A (en) * | 2022-06-06 | 2022-09-06 | 杭州新瀚光电科技有限公司 | Human health assessment method, system, terminal device and storage medium |
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