Thermal infrared imager measurement angle compensation method

Abstract

The invention discloses a thermal infrared imager measurement angle compensation method, and belongs to the technical field of infrared temperature measurement, and the method comprises the steps: determining a target object needing temperature measurement, carrying out the temperature measurement of the target object based on the initial measurement angle of a thermal infrared imager and the target object, and obtaining a reference temperature; setting an angle range and a preset value, taking the preset value as an interval, selecting a plurality of measurement angles in the angle range, rotating the target object, obtaining measurement temperatures of the target object by the thermal infrared imager under the plurality of measurement angles, and defining the measurement temperatures as first measurement temperatures; converting the first measurement temperature based on the Planck's law of radiation to obtain radiation power; and calculating a compensation coefficient of each measurement angle, compensating the radiation power based on the compensation coefficients to obtain standard radiation power, and converting the standard radiation power into a compensated target temperature based on a preset temperature radiation quantity relation table. According to the invention, the temperature measurement precision of the thermal infrared imager is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of infrared thermal imagers, and in particular relates to a measurement angle compensation method for an infrared thermal imager. Background Art

[0002] In the field of infrared temperature measurement technology, infrared thermal imagers are widely used in industrial inspection, medical diagnosis, environmental monitoring and other fields because they can quickly and accurately perform non-contact temperature measurement. However, the temperature measurement accuracy of infrared thermal imagers is affected by many factors, one of which is the measurement angle.

[0003] Traditional infrared temperature measurement technology usually ignores the impact of the measurement angle on the temperature measurement accuracy, or only provides some basic correction functions, which often cannot meet the needs of high-precision measurement. In addition, due to the lack of effective measurement angle compensation methods, users often need to rely on experience or complex manual correction processes when measuring at non-vertical angles.

[0004] In order to improve the temperature measurement accuracy of infrared thermal imagers at non-vertical angles, an effective measurement angle compensation method is needed. This method should be able to automatically adjust the temperature reading according to the actual measurement angle to compensate for the temperature measurement error caused by angle deviation. Summary of the invention

[0005] In order to solve the above problems, the present invention provides an infrared thermal imager measurement angle compensation method to solve the problems in the prior art.

[0006] In order to achieve the above-mentioned invention object, the present invention proposes an infrared thermal imager measurement angle compensation method, comprising:

[0007] Step S1: determining a target object that needs temperature measurement, measuring the temperature of the target object based on an initial measurement angle between the infrared thermal imager and the target object, and obtaining a reference temperature;

[0008] Step S2: setting an angle range and a preset value, within the angle range, selecting a plurality of measuring angles within the angle range at intervals of the preset value, rotating the target object, obtaining the measured temperature of the target object by the infrared thermal imager at the plurality of measuring angles, and defining the measured temperature as a first measuring temperature;

[0009] Step S3: converting the first measured temperature to obtain radiation power based on Planck's radiation law;

[0010] Step S4: Calculate the compensation coefficient of each of the measurement angles, compensate the radiation power based on the compensation coefficient to obtain the standard radiation power, and convert the standard radiation power into a compensated target temperature based on a preset temperature radiation relationship table.

[0011] Further, obtaining the radiation power comprises the following steps:

[0012] The radiation power S(T i ), the first formula is: Wherein, λ is the wavelength of the infrared thermal imager for temperature measurement, λ1 and λ2 are the preset upper and lower wavelength limits, c1 and c2 are Planck constants, T i The first measured temperature.

[0013] Further, calculating the compensation coefficient of the measurement angle includes the following steps:

[0014] The measured angles are fitted based on a second formula to obtain a compensation coefficient ε(θ) of each of the measured angles, wherein the second formula is: Wherein, k1, k2, k3 and k4 are fitting parameters of the exponential model, and θ is the measurement angle.

[0015] Further, obtaining the standard radiation power includes the following steps:

[0016] The standard radiation power S(T0) is obtained based on the third formula, and the third formula is: Among them, S(T am ) is the target object at the ambient temperature T am The radiated power under .

[0017] Further, obtaining the first measured temperature comprises the following steps:

[0018] A plurality of measurements are performed at the same measurement angle to obtain a plurality of second measurement temperatures, and an average value of the second measurement temperatures is used as the first measurement temperature corresponding to the measurement angle.

[0019] Furthermore, the number of measurements at the same measurement angle is 3 times.

[0020] Furthermore, the initial measurement angle is an angle between the normal direction of the thermal imager and the surface of the object being measured.

[0021] Furthermore, the angle range is 0-70°.

[0022] Furthermore, the upper wavelength limit and the lower wavelength limit are 8 μm and 14 μm respectively.

[0023] Furthermore, the preset value is 5 degrees.

[0024] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0025] The present invention obtains an accurate reference temperature by measuring the target object at an initial measurement angle to provide a reference for subsequent angle compensation. The present invention measures the temperature at multiple preset angles and collects measurement data at different angles to provide comprehensive information for the compensation algorithm. The temperature data is converted into radiation power to provide a unified comparison standard for measurement results under different conditions. The error caused by the measurement angle is accurately corrected by calculating the compensation coefficient and applying it to the radiation power. The present invention can also correct the infrared temperature measurement results at different angles, so that accurate and reliable results can be obtained in temperature measurements under different actual scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flowchart of a method for compensating an angle of measurement of an infrared thermal imager according to the present invention;

[0027] Figure 2 This is a diagram showing how the compensation coefficient of the present invention varies with angle. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first xx script may be referred to as a second xx script, and similarly, a second xx script may be referred to as a first xx script.

[0030] like Figure 1 As shown, a method for measuring angle compensation of an infrared thermal imager includes:

[0031] S1: Determine a target object that needs temperature measurement, measure the temperature of the target object based on an initial measurement angle between the infrared thermal imager and the target object, and obtain a reference temperature.

[0032] Specifically, assume that the target object is a black body, which is a perfect radiator that can emit radiation in a specific way that depends only on its temperature and has nothing to do with the shape, material, color, etc. The radiation characteristics of a black body are described by Planck's radiation law, which states that the radiation emittance (radiant power) of a black body is proportional to the fourth power of its temperature and is related to the wavelength of the radiation.

[0033] If the normal direction of the infrared thermal imager is perpendicular to the surface of the target object, the angle of the infrared thermal imager at this time is recorded as the initial measurement angle. Table 1 shows the temperature displayed by the thermal imager at the initial measurement angle before the measurement angle between the infrared thermal imager and the black body is corrected.

[0034] Table 1 Temperature displayed by thermal imager before angle correction

[0035]

[0036]

[0037] Fix the infrared thermal imager at the initial measurement angle and ensure that its visual axis (normal direction) is perpendicular to the surface of the target object, which means that the thermal imager faces the surface of the object directly without any angle tilt, ensuring that the reference temperature T0 is obtained without any angle error. The reference temperature will be used as the reference for subsequent measurements and compensation.

[0038] S2: setting an angle range and a preset value, within the angle range, selecting multiple measurement angles within the angle range with the preset value as an interval, rotating the target object, obtaining the measured temperature of the target object by the infrared thermal imager at the multiple measurement angles, and defining the measured temperature as the first measurement temperature.

[0039] Specifically, the angle range is set to 0-70°, the preset value is 5 degrees, the target object is placed on a bracket that can rotate around the central axis, and the target object is rotated to adjust the angle between it and the infrared thermal imager. Starting from the initial normal direction (0° angle), the infrared thermal imager or the target object is gradually adjusted to change within the preset angle range, and a measurement point is set every 5° to record the first measurement temperature [T1, T2, ..., Tn] of the thermal imaging. When the infrared thermal imager performs temperature measurement, the change of the measurement angle will cause the radiation emissivity of the object surface to change. This is because the observed surface area and surface characteristics (such as roughness and shape) of the target object at different angles may be different, which will cause errors in the measured temperature of the infrared thermal imager.

[0040] In order to reduce the influence of these errors on the measurement results, the actual measured temperature, ie, the first measured temperature, needs to be compensated to obtain a value closer to the real temperature of the object, ie, the target temperature.

[0041] S3: Convert the first measured temperature to obtain radiation power based on Planck's radiation law.

[0042] Specifically, the temperature measured by the infrared thermal imager is converted into radiation power through Planck's radiation law. The radiation power describes the radiation characteristics of a black body in thermal equilibrium. However, since most objects are not ideal black bodies, a correction factor needs to be introduced to correct the radiation power in order to improve the accuracy of the temperature measured by the infrared thermal imager.

[0043] S4: Calculate the compensation coefficient for each measurement angle, compensate the radiation power based on the compensation coefficient, obtain the standard radiation power, and convert the standard radiation power into a compensated target temperature based on a preset temperature radiation relationship table.

[0044] Specifically, before calculating the compensation coefficient, a correction coefficient needs to be introduced. The correction coefficient is the influence of the radiation size source on the temperature measurement of the infrared thermal imager. It is the ratio of the difference between the actual measured radiation power and the ambient radiation power to the difference between the normal measured radiation power and the ambient radiation power. The compensation coefficient at different angles is obtained by fitting the actual measured temperature and the correction coefficient, such as Figure 2 As shown in FIG. 1 , the compensation coefficient varies with angle.

[0045] Through experiments or theoretical calculations, a relationship table between multiple temperatures and radiation powers is established. This relationship table usually contains standard radiation power values ​​at different temperatures within a specific wavelength range. The value closest to the measured standard radiation power is found in the relationship table, or the target temperature corresponding to the measured radiation power is calculated using an interpolation method.

[0046] Furthermore, the relationship between the angle and the emissivity can be obtained through Table 1 and the aforementioned process, and then the temperature compensation is performed according to the actual measured angle. Table 2 is the result after the thermal imager corrects the temperature of each first point in Table 1 using the correction model.

[0047] Table 2 Results after angle correction

[0048]

[0049] The results show that the corrected target temperature is more accurate and closer to the actual blackbody temperature, that is, the accuracy of the measurement results of the corrected infrared temperature measuring device is significantly improved.

[0050] The present invention can obtain an accurate reference temperature by measuring the target object at an initial measurement angle to provide a reference for subsequent angle compensation. By measuring the temperature at multiple preset angles, measurement data at different angles can be collected to provide comprehensive information for the compensation algorithm. The temperature data can be converted into radiation power to provide a unified comparison standard for measurement results under different conditions. By calculating the compensation coefficient and applying it to the radiation power, the error caused by the measurement angle can be accurately corrected. The present invention can also correct the infrared temperature measurement results at different angles, so that accurate and reliable results can be obtained in temperature measurements in different actual scenarios.

[0051] As a preferred technical solution of the present invention, obtaining the radiation power includes the following steps:

[0052] The radiation power S(T i ), the first formula is: Where λ is the wavelength of the infrared thermal imager for temperature measurement, λ1 and λ2 are the preset upper and lower wavelength limits, c1 and c2 are Planck constants, and T i is the first measured temperature.

[0053] Specifically, the upper and lower wavelength limits are 8 μm and 14 μm respectively, and the Planck constant c1 = 2πhc 2 , c2=hc / k, c is the speed of light, h is the Planck coefficient, and k is the Boltzmann constant. Using Planck's radiation law, the radiation power of the target object at multiple measurement temperatures can be calculated more accurately because it takes into account the relationship between temperature and wavelength.

[0054] Calculating the compensation factor for the measured angle includes the following steps:

[0055] The measured angle is fitted based on the second formula to obtain the compensation coefficient ε(θ) of each measured angle. The second formula is: Wherein, k1, k2, k3 and k4 are the fitting parameters of the exponential model, and θ is the measurement angle.

[0056] Specifically, the present invention selects an exponential model as a fitting model for the compensation coefficient, because the exponential relationship can well describe the relationship between the measurement angle and the radiation intensity. The least squares method or other optimization algorithms are used to determine the model parameters k1, k2, k3 and k4 according to the collected data, so that the error between the compensation coefficient predicted by the model and the actual measurement value is minimized. The fitted compensation coefficient is applied to the measurement results of the infrared thermal imager to correct the errors at different measurement angles.

[0057] Obtaining the standard radiant power includes the following steps:

[0058] The standard radiation power S(T0) is obtained based on the third formula, which is: Among them, S(T am ) is the target object in the surrounding environment temperature T am The radiated power under .

[0059] Specifically, the ambient temperature of the target object can usually be obtained through a temperature sensor, and the corrected radiation power is calculated according to the measurement angle and the displayed temperature based on the third formula. This formula takes into account the change in radiation amount caused by the deviation of the measurement angle from the normal direction and the impact of changes in ambient temperature on the radiation amount, and incorporates them into the compensation calculation. The compensation process helps to reduce the error caused by non-vertical measurement angles, making the measurement results more reliable.

[0060] Obtaining the first measured temperature comprises the following steps:

[0061] Perform multiple measurements at the same measurement angle to obtain multiple second measurement temperatures, and use the average value of the second measurement temperatures as the first measurement temperature of the corresponding measurement angle.

[0062] Specifically, the target temperature is a temperature value obtained after angle compensation processing, and the number of measurements at the same measurement angle is 3 times.

[0063] It should be understood that, although each step in the flow chart of each embodiment of the present invention is shown in sequence according to the indication of the arrow, these steps are not necessarily performed in sequence according to the order indicated by the arrow. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be performed in other orders. Moreover, at least a portion of the steps in each embodiment may include a plurality of sub-steps or a plurality of stages, and these sub-steps or stages are not necessarily performed at the same time, but can be performed at different times, and the execution order of these sub-steps or stages is not necessarily performed in sequence, but can be performed in turn or alternately with at least a portion of other steps or sub-steps or stages of other steps.

[0064] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program. The above-mentioned program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0065] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

[0067] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for compensating an infrared thermal imager's measurement angle, characterized in that: The method comprises the following steps: Step S1: determining a target object that needs temperature measurement, measuring the temperature of the target object based on an initial measurement angle between the infrared thermal imager and the target object, and obtaining a reference temperature; Step S2: setting an angle range and a preset value, selecting a plurality of measuring angles within the angle range with the preset value as an interval, rotating the target object, obtaining the measured temperature of the target object by the infrared thermal imager at the plurality of measuring angles, and defining the measured temperature as a first measuring temperature; Step S3: converting the first measured temperature to obtain radiation power based on Planck's radiation law; Step S4: Calculate the compensation coefficient of each of the measurement angles, compensate the radiation power based on the compensation coefficient to obtain the standard radiation power, and convert the standard radiation power into a compensated target temperature based on a preset temperature radiation relationship table.

2. The method according to claim 1, characterized in that Obtaining the radiated power includes the following steps: The radiation power S(T i ), the first formula is: Wherein, λ is the wavelength of the infrared thermal imager for temperature measurement, λ1 and λ2 are the preset upper and lower wavelength limits, c1 and c2 are Planck constants, T i The first measured temperature.

3. The method according to claim 1, characterized in that Calculating the compensation coefficient of the measured angle comprises the following steps: The measured angles are fitted based on a second formula to obtain a compensation coefficient ε(θ) of each measured angle, wherein the second formula is: Wherein, k1, k2, k3 and k4 are fitting parameters of the exponential model, and θ is the measurement angle.

4. The method according to claim 3, characterized in that Obtaining the standard radiant power includes the following steps: The standard radiation power S(T0) is obtained based on the third formula, and the third formula is: Among them, S(T am ) is the target object at the ambient temperature T am The radiated power under .

5. The method according to claim 1, characterized in that Obtaining the first measured temperature comprises the following steps: A plurality of measurements are performed at the same measurement angle to obtain a plurality of second measurement temperatures, and an average value of the second measurement temperatures is used as the first measurement temperature corresponding to the measurement angle.

6. The method according to claim 5, characterized in that The number of measurements at the same measurement angle is 3.

7. The method according to claim 1, characterized in that The initial measurement angle is the angle between the normal direction of the thermal imager and the surface of the object being measured.

8. The method according to claim 1, characterized in that The angle range is 0-70°.

9. The method according to claim 1, characterized in that: The upper wavelength limit and the lower wavelength limit are 8 μm and 14 μm, respectively.

10. The method according to claim 5, characterized in that The preset value is 5 degrees.

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