CN101806627A - Method for measuring influence of background factors to infrared temperature measurement - Google Patents

Abstract

The invention discloses a method for measuring the influence of background factors on infrared temperature measurement. Store the calibration experiment data in the software system that measures the influence of background factors on infrared temperature measurement; start the black body, infrared thermal imaging components, industrial computer and measurement software system; when the black body is constant at a certain temperature T, the software system collects it through the image acquisition card And display the thermal image video. At this time, adjust the parameters of the infrared thermal imaging component. After the thermal image is clear, save the thermal image in bmp format; open the saved thermal image, select the black body area in the thermal image, and the system reads the average gray level of the black body , and then call the database to find the calibration gray level corresponding to the T temperature, and then calculate the difference between the average gray level and the calibration gray level. The difference quantitatively reflects the influence of the background environment on the infrared temperature measurement. The invention can quantitatively measure the influence of the background on the infrared temperature measurement during the actual temperature measurement, and this result can be applied to the temperature measurement compensation, and finally the accuracy of the temperature measurement can be improved.

Description

A Measuring Method of Influence of Background Factors on Infrared Temperature Measurement

technical field

The invention relates to a radiation temperature measurement method and an infrared thermal imaging temperature measurement method, in particular to a method for measuring the influence of background factors on infrared temperature measurement.

Background technique

All objects with a temperature higher than absolute zero in nature emit infrared radiation. Infrared temperature measurement is to measure the temperature of an object by receiving the radiant energy emitted by the object. The previous data are qualitatively indicating that the external background environment has an impact on infrared temperature measurement, because the actual temperature measurement, the object is in a certain background environment, so the radiation caused by the background will inevitably affect the accuracy of temperature measurement after entering the infrared temperature measurement instrument sex. If the influence of the background on the infrared temperature measurement during the actual temperature measurement can be quantitatively measured, corresponding compensation can be carried out, and the accuracy of temperature measurement can be improved in the end.

Contents of the invention

The purpose of the present invention is to provide a method for measuring the influence of background factors on infrared temperature measurement. Any object with a temperature higher than absolute zero emits infrared radiation. After receiving the infrared radiation, the infrared focal plane array undergoes signal processing and finally synthesizes a "thermal image". ", the present invention is to quantitatively measure the influence of the background on infrared temperature measurement by using the gray scale change of the thermal image.

The technical solution adopted in the present invention is that the measuring method comprises:

a) Carry out the temperature grayscale calibration experiment, and pre-store the calibration experiment data in the form of a database in the software system that measures the influence of the background environment on infrared temperature measurement;

b) Starting step: to start the black body, infrared thermal imaging components, industrial computer and measurement software system;

c) Image acquisition step: when the black body is constant at a certain temperature T, the software system collects the black body image through the image acquisition card, displays the thermal image video according to the software system, adjusts the parameters of the infrared thermal imaging component, and after the thermal image is clear, it is displayed in bmp format save the thermal image;

d) Measurement steps: Open the saved thermal image, select the black body area in the thermal image with the left mouse button, the system reads the average gray level of the black body, then calls the database to find the calibration gray level corresponding to the T temperature, and then calculates the average gray level and calibration The difference in gray scale, the difference quantitatively reflects the influence of the background environment on infrared temperature measurement;

e) End step: used to stop the measuring device.

The beneficial effects that the present invention has are:

The present invention takes the black body as the measured object, and uses thermal imaging components to measure the gray scale corresponding to the black body at the same temperature in the laboratory calibration environment and the field environment. Due to the particularity of the black body, the ambient temperature has no influence on the gray scale of the image, and the influencing factors It is only the background where the black body is located. Therefore, only the gray level difference of the black body in the two environments is required, and the influence of the background on infrared temperature measurement can be obtained quantitatively.

The invention can quantitatively measure the influence of the background on the infrared temperature measurement during the actual temperature measurement, and this result can be applied to the temperature measurement compensation, and finally the accuracy of the temperature measurement can be improved.

Description of drawings

Figure 1 is a schematic diagram of the device for measuring the influence of background on infrared temperature measurement.

Figure 2 is the black body image collected by the thermal imaging component.

Among them, 1. Infrared thermal imaging component, 2. Industrial computer, 3. Blackbody, 4. Background area, 5. Blackbody area.

Detailed ways

Black bodies have certain particularities in radiation temperature measurement, that is, for black bodies, the impact of changes in ambient temperature on the output signal of the infrared detector is zero, and the image grayscale does not change when reflected on the thermal image. The proof process is as follows:

Formula (1) is the basic formula of an infrared temperature measurement system:

V _s =K[εf(T ₀ )+(1-ε)f(T _u )]...(1)

In the formula, V _s is the voltage signal output by the infrared detector, K is a constant, ε is the emissivity of the object, T ₀ is the real temperature of the object surface, and T _u is the ambient temperature at that time.

If the infrared temperature measurement system conducts temperature measurement experiments at different ambient temperatures T ₁ and T ₂ , and other experimental conditions remain unchanged, then formula (1) can be obtained

V _s1 ＝K[εf(T ₀ )+(1-ε)f(T ₁ )]...(2)

V _s2 ＝K[εf(T ₀ )+(1-ε)f(T ₂ )]...(3)

Subtract formula (2) from formula (3) to get

V'=K(1-ε)[f(T ₂ )-f(T ₁ )]...(4)

The above formula shows that in special cases such as the measured object is a black body (ε=1), then V'=0. Therefore, for a black body, the change of the ambient temperature has zero influence on the output signal of the thermal image. As far as the thermal image is concerned, the change of the gray scale of the image is 0, that is, the ambient temperature has no effect on the gray scale of the thermal image, and the only influencing factor is the location of the black body. Therefore, only the gray difference of the black body in the two environments is required, and the influence of the background on the infrared temperature measurement is obtained quantitatively.

a) Carry out the temperature grayscale calibration experiment in the laboratory, and store the calibration experiment data in the form of a database in the software system that measures the influence of the background environment on infrared temperature measurement. The so-called calibration is to establish a one-to-one correspondence between gray scale and temperature. The specific calibration process is: connect each instrument as shown in Figure 1: the image acquisition card is correctly installed in the PCI slot of the industrial computer, the lens of the infrared thermal imaging component 1 is aligned with the black body 3, and the output signal of the infrared thermal imaging component 1 is connected to the industrial computer 2. Turn on the input terminal of the internal acquisition card, turn on the power, start the black body 3, infrared thermal imaging component 1, industrial computer 2 and measurement software system, set the temperature of the black body, and record the current temperature grayscale data after it is stable; repeatedly change the temperature of the black body , after it stabilizes, record the next set of temperature grayscale data. From the above steps, the temperature grayscale calibration data can be obtained as shown in Table 1.

Table 1 Experimental data of the corresponding relationship between temperature and gray scale

After calibration, turn off the instrument and cut off the power. All subsequent steps are carried out under the on-site environment.

b) Start-up steps: connect each instrument as shown in Figure 1 and start the black body, infrared thermal imaging components, industrial computer and measurement software system;

c) Image acquisition step: set the blackbody temperature T, the thermal imaging component has been preheated in about 20 minutes, and the blackbody temperature has reached T and is constant. The software system collects the infrared image through the image acquisition card, which consists of the blackbody area 5 and the background area 4 Composition, according to the infrared image video displayed by the software system, adjust the parameters of the infrared thermal imaging component, and after the infrared image is clear, save the infrared image in bmp format (as shown in Figure 2);

d) Measurement steps: open the saved thermal image, select the black body area in the thermal image with the left mouse button, and select a certain area from the process of pressing the left mouse button and dragging until the left mouse button pops up. The rectangular area obtained, the system will automatically draw a rectangle to represent the area. The system calculates the average gray level H ₂ of the selected rectangular area on the black body, and then searches the calibration gray level H ₁ corresponding to the temperature of the black body T during calibration from the system database, and calculates the difference between the average gray level and the calibration gray level H ₁ -H ₂ , the difference quantitatively reflects the influence of the background environment on infrared temperature measurement;

e) End step: used to stop the measuring device and cut off the power supply.

The temperature resolution of the blackbody is 0.1°C, the temperature stability is ±(0.1-0.2)°C/30min, and the effective emissivity is 0.97±0.02.

The output of the infrared thermal imaging component is a PAL video signal with a field frequency of 50HZ.

The bit depth of the image acquisition card is 8 bits, the input is a PAL video signal, and the acquisition speed is 25 frames/second.

The temperature resolution of the blackbody is 0.1°C, the temperature stability is ±(0.1-0.2)°C/30min, and the effective emissivity is 0.97±0.02.

Claims (4)

1. A method for measuring the influence of background factors on infrared temperature measurement is characterized in that: the method for measuring comprises: a) Carry out the temperature grayscale calibration experiment, and pre-store the calibration experiment data in the form of a database in the software system that measures the influence of the background environment on infrared temperature measurement; b) Starting step: to start the black body, infrared thermal imaging components, industrial computer and measurement software system; c) Image acquisition step: when the black body is constant at a certain temperature T, the software system collects the black body image through the image acquisition card, displays the thermal image video according to the software system, adjusts the parameters of the infrared thermal imaging component, and after the thermal image is clear, it is displayed in bmp format save the thermal image; d) Measurement steps: Open the saved thermal image, select the black body area in the thermal image with the left mouse button, the system reads the average gray level of the black body, then calls the database to find the calibration gray level corresponding to the T temperature, and then calculates the average gray level and calibration The difference in gray scale, the difference quantitatively reflects the influence of the background environment on infrared temperature measurement; e) End step: used to stop the measuring device. 2. A method for measuring the influence of background factors on infrared temperature measurement according to claim 1, characterized in that: the temperature resolution of the blackbody is 0.1°C, and the temperature stability is ±(0.1～0.2)°C/30min , The effective emissivity is 0.97±0.02. 3. A method for measuring the influence of background factors on infrared temperature measurement according to claim 1, characterized in that: the output of the infrared thermal imaging component is a PAL video signal, and the field frequency is 50HZ. 4. a kind of background factor according to claim 1 measures the influence of infrared temperature measurement, it is characterized in that: the bit depth of described image acquisition card is 8bit, the input is PAL system video signal, and acquisition speed is 25 frames/second .

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