JPH03197828A - Temperature measuring method by infrared camera - Google Patents

Abstract

PURPOSE:To easily detect a defective part by switching a 1st and a 2nd temperature measurement range and picking up images before and after heating, and detecting a heat image part which has high heat data projecting from the periphery from the deviation value heat image between two composite heat images. CONSTITUTION:Each measurement range for obtaining a heat image by the infrared camera is divided into four measurement range without overlapping with each other, which are switched to pick up the infrared heat images of an object to be measured before and after the heating, thereby obtaining heat image effective ranges D - A in the respective measurement ranges. Then the heat image data in the ranges D - A are processed by a personal computer by superimposition, subtraction, etc., and the result is displayed on a CRT display device. Then the heat image part which has high heat data projecting from the periphery is detected as a defect from the deviation value heat image between the two composite heat images obtained by composition.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for capturing images of a measurement target with a large temperature difference using an infrared camera and obtaining a thermal image of the measurement target before and after heating using a desired temperature resolution. This invention relates to a temperature measurement method using an infrared camera that can easily detect defective parts with high temperature resolution by signal processing a thermal image obtained by switching between a plurality of temperature measurement ranges.

[Prior Art] When the inside of a pipe or the like is corroded and thinned, one method for diagnosing this thinning from the outside is to measure temperature using an infrared camera. In this method, first, the surface of the object to be measured, such as a pipe, is heated uniformly. Then, the surface temperature of the pipe increases due to this heating, but if there is a thinned part in the vibrator, the temperature rise in the defective part with thinner wall is larger than that in the normal part with thicker wall due to the difference in heat capacity, and the two There will be temperature differences between the parts. Therefore, by measuring the temperature of the surface of the vibrator after heating with an infrared camera, it is possible to determine where the thinned portion is and the degree of thinning based on the temperature difference.

Figure 9(a) shows - Temperature A11 measured by an infrared camera inside the membrane.
1 is a configuration diagram of a fixed device, 1 is an infrared camera, 2 is a personal computer (hereinafter referred to as a personal computer), 3 is a CRT display that can normally display in color, and 4 is a vibrator for all regular holidays. In addition, an example is shown in which a large temperature difference has already occurred in the vibrator 4 due to radiant heat from the sun before it is heated for AP1.

FIG. 9(b) is a diagram showing an example of the temperature distribution determined by the temperature measuring device shown in FIG. 9(a), where the horizontal axis represents the position of the vibrator surface and the vertical axis represents the al constant temperature. In the same figure, the temperature of the surface of the vibrator is 28℃ at the highest and 20℃ at the lowest, that is, 8℃.
The temperature distribution is based on the temperature difference in degrees Celsius, and naturally the temperature is highest at the center of the surface where sunlight irradiates perpendicularly to the vibrator surface, and the temperature gradually decreases toward the periphery.

[Problems to be Solved by the Invention] The infrared camera used in the conventional infrared temperature measuring device as described above has thermal pixels equivalent to one screen (for example, about 256 x 2 O 3) displayed on a CRT display, and has a low temperature resolution. When set to a desired value (for example, the highest resolution is 0.01°C, and the following values can be set to any value such as 0.02°C, 0.03°C, 0.04°C, etc.), each thermal pixel emits infrared light. Based on the amount of light received, temperature information (for example, 8-bit data after quantization, data with values from 0 to 255) is provided in a temperature range determined by the set temperature resolution from the specified lower limit of the measurement temperature.

Therefore, the 'tM r1 resolution is the highest of 0.01℃/bi
If t, the measurable temperature range is 0.01℃ x 25B
It becomes -2,56℃. Now set the lower limit of API constant temperature to 2
If it is 0°C, the temperature measurement range will be 20°C to 22.55°C. However, since the temperature difference in the measurement in FIG. 9(b) is 8° C., one measurement cannot cover the entire range of the vibrator temperature.

In order to cover the entire pipe temperature range in one measurement, if the temperature resolution is lowered to, for example, 0.04°C/bit,
A temperature range of 0.04°C x 25B -10.24°C can be covered.

Therefore, if there is a large temperature difference in the apl constant object,
Even if we try to improve the temperature resolution of an infrared camera to make it easier to detect defects, it is not possible to measure the entire object due to the limited amount of temperature information per thermal pixel of the infrared camera (usually 8 bits). When the temperature range is widened, the temperature resolution decreases, making it difficult to detect defects.

This invention was made to solve this problem, and even if there is a large temperature difference in the API constant object, it is possible to create a thermal image of the entire IIFJ constant object without reducing the temperature resolution, and to locate the defective parts. The purpose is to obtain a temperature measurement method using an infrared camera that can easily detect temperature.

[Means for Solving the Problems] In the temperature measurement method using an infrared camera according to the present invention, when an infrared camera images a measurement object with a large temperature difference and obtains a thermal image thereof, depending on the desired temperature resolution, the temperature measurement method using an infrared camera When the temperature range of the entire object cannot be covered, a plurality of first temperature measurement ranges are set for dividing the temperature range and measuring each with a desired temperature resolution, and
A first composite thermal image is created by combining the effective thermal images obtained by switching and imaging each temperature measurement range, and then heating the entire surface to be measured to raise the temperature almost constant. in,
The plurality of first temperatures JFJ correspond to the temperature increase.
The same number of second temperature ΔIII constant ranges are set by shifting the constant ranges, and the effective thermal images obtained by switching and imaging each of the set second temperature ranges are synthesized. to create a second composite thermal image, and calculate a deviation value thermal image by subtracting thermal data of a first composite thermal image located at the same imaging position from the thermal data of the second composite thermal image; The apparatus is equipped with a signal processing means capable of detecting a defective part of the object to be measured by identifying a thermal image part having significantly higher thermal data than the average thermal data of the deviation value thermal image.

[Function] In this invention, when an infrared camera is used to image a measurement object with a large temperature difference and obtain a thermal image, the infrared camera is used when the temperature range of the entire measurement object cannot be covered depending on the desired temperature resolution. A signal processing means for processing a thermal image signal imaged by divides the temperature range and sets a plurality of first temperatures all+fixed ranges each with a desired temperature resolution. A first composite thermal image is created by combining the effective thermal images obtained by switching and imaging each temperature measurement range, and then heating the entire measurement target surface to raise the temperature almost constant. , the plurality of first temperatures 71117 corresponding to the temperature increase.
The same number of second temperature measurement ranges with shifted constant ranges are set, and the effective thermal images obtained by switching and imaging each of the set second temperature n1 constant ranges are synthesized to obtain a second composite thermal image. A deviation thermal image is calculated by subtracting the thermal data of the first synthetic thermal image at the same imaging position from the thermal data of the second synthetic thermal image, and A defective portion of the object to be measured is detected by identifying a thermal image portion having significantly higher thermal data than the average thermal data.

[Example] FIGS. 1(a) to 1(d) are diagrams showing measurement range divided imaging before heating and its thermal image effective range according to the present invention. In this embodiment, as in the case of the conventional example, the infrared camera 1
The temperature data of each pixel in the thermal image captured by
-2.5B℃. In this case, (a) and (b) in the same figure
, (c) and (d) are the measurement ranges for obtaining thermal images using an infrared camera, 20'' to 22.55℃, 22.58℃.
”~25.11'C125,12@~27.87℃
, 27, i38 ”~: Divide into four non-overlapping measurement ranges of 90.23°C, and sequentially switch the four divided measurement ranges to measure the object to be measured (in this example, vibrator 4).
), and the effective range of the thermal image in each measurement range is shown as DSC, B, and A, respectively. Then, the thermal image data within each thermal image effective range D-A is subjected to signal processing such as superposition and subtraction by the computer 2 as explained below, and the processing results are displayed on the CR7 display 3. .

FIGS. 2(a) and 2(b) are diagrams showing a composite image obtained by superimposing the thermal image effective ranges imaged by each Jl constant range in FIG. 1, and its cross-sectional thermal image data values. In the same figure (a), it is shown that the entire fixed holiday (7%) is covered by a composite image obtained by superimposing thermal image effective ranges A to D.

In addition, in FIG. 5B, the horizontal axis represents each thermal image position on the X-Y cross section of FIG. Therefore, this thermal image data value ignores the absolute value of temperature and uses the lower limit values of each temperature measurement range (20°C, 22.56°C, 25.12°C, 27.
68° C.) as the data value “0”, and the data value with the highest value of the binary 8-bit data measured from this lower limit value as “255” is shown as is.

Next, while the mutual positions of the infrared camera 1 and the δP1 constant object (the vibrator 4 in this example) are fixed, the Δp1 constant object is heated in order to detect a defective portion included in the measurement object.

It is desirable that this heating be performed so as to uniformly raise the temperature of the entire AFI target surface by a constant amount as much as possible.

FIGS. 3(a) to 3(d) are diagrams showing 4-1 fixed range divided imaging after heating and its thermal image effective range according to the present invention.

FIG. 3 shows an example in which a heat load is uniformly applied to the surface to be measured during the APL period before heating in FIG. In this case, each temperature measurement range of the infrared camera 1 is also shifted by 3 degrees to 23 degrees to 25.5 degrees.
5℃, 25.5B°~28.11℃, 28.12''~
3.0°C, 67°C, and 30.88' to 33.23°C, and each measurement range after the change is sequentially switched at high speed to capture an infrared thermal image of the object to be measured. Figure 3(a)-(d)
) shows each temperature measurement range after heating and the effective range of thermal images taken in each range, C and B.

A is shown respectively. In this example, the mutual positions of the infrared camera 1 and the vibrator 4 are fixed, so the
The thermal image effective range D-A in the figure is the same position of the vibrator 4.

FIGS. 4(a) and (b) are diagrams showing a composite image obtained by superimposing the effective range of thermal images captured by each measurement range in FIG. 3 and its cross-sectional thermal image data values, and the horizontal and vertical axes is exactly the same as in Figure 2.

FIGS. 5(a) and 5(b) are diagrams showing the process of subtracting the thermal image data of FIGS. 2(a) and (b) from the thermal image data of FIGS. 4(a) and (b). This subtraction processing is a signal processing performed to remove the influence of the temperature distribution that the measurement object had before heating, and to detect an abnormal temperature rise occurring from a defective part due to heating.

Figure 5 (a) shows that the thermal image data at the same position corresponding to Figure 2 (a) is subtracted from the thermal image data within the thermal image effective range for each measurement range in Figure 4 (a). A deviation value thermal image based on the difference value (deviation value) after processing is displayed. Also, the same figure (
In b), the thermal deviation value in the X-Y cross section of FIG. 3(a) is displayed. In this example, since the X-Y11'r position is fixed, it may be considered that the deviation value between the thermal image data of FIG. 4(b) and FIG. 2(b) is displayed. In this example,
If the surface to be measured is ideally heated so that it rises by 3 degrees Celsius uniformly, each temperature measurement range after heating is shifted by 3 degrees Celsius, so the deviation values after the above subtraction process will all be zero. . However, it is not easy to heat all the surfaces to be measured so that the temperature rises by 3 degrees Celsius uniformly, so if there is a normal part where the temperature increases from 3.1 degrees Celsius to 3.2 degrees Celsius, in this case, the above-mentioned subtraction process will be applied. The subsequent thermal deviation value is displayed on the CRT display unit 3 as a thermal image having temperature data of 0.1°C and 0.2°C. Therefore, if all the l1llJ constant objects are normal parts, the thermal deviation value after this subtraction process will be a value close to zero, or a value that does not change rapidly from a certain constant value. However, the temperature resolution in this case is thermal image data maintained at O, OL''C. Therefore, if this figure 5 (
In the deviation value thermal image shown in a), if there is a part where the thermal deviation value increases rapidly, this part can be estimated to be a defective part.

FIGS. 6(a) to 6(d) are diagrams showing superimposed composite images of the thermal image effective range for each flPj constant range before and after heating according to the present invention, and their cross-sectional thermal image data values, and show thinning defect areas. An example is shown in which . Figures (a) and (b)
) is a diagram showing a composite image obtained by superimposing the thermal image effective range D-A for each measurement range in the state before heating and its cross-sectional thermal image data. It is something. Figures (C) and (d) show the results for each δ1j constant range when the entire surface to be measured is uniformly heated by a heat load, and the temperature rise is large only in the internal defect area, and the other areas rise by 3°C. A superimposed composite image of the thermal image effective range and thermal image data values in the XY cross section of this composite image are shown. It can be seen that there is a defective part in the center of the effective thermal image range A in FIG. 2(c), and that the thermal image data value also increases at the corresponding position in FIG.

T57 Figures (a) and (b) are diagrams showing the subtraction process of the thermal image data in Figures 6 (e) and (d) from the thermal image data in Figures 6 (e) and (d), and show the process of subtracting the thermal image data in Figures 6 (a) and (b). Figure 5 (a) when there is no
) and (b). X-Yr in Figure 5(a)
Since there is no defective part in the Tr plane thermal image, the data deviation value in FIG. 3(b) is almost zero.

However, since the X-Y cross-sectional thermal image in Figure 7(a) includes a defective part, the thermal difference value in Figure 7(b) includes abnormal temperature increases in addition to the average temperature increase. shown. Therefore, the presence of a defective portion can be detected from this abnormally increased value.

FIGS. 8(a) and 8(b) are diagrams showing the difference in the size of data indicating defective portions between the method according to the present invention and the conventional method. In the same figure (a), the thermal deviation value according to the present invention is 0.0
The defect is clearly shown with a temperature resolution of 1°C, but in the same figure (b), the thermal image data value obtained by the conventional method is 0.04.
It is shown that detection of defects is difficult due to the temperature resolution of °C.

In the above embodiment, an example of a temperature measurement method using an infrared camera for the purpose of detecting a defective part of an object to be measured was shown. It is clear that it can be used as a temperature measurement method using a general infrared camera, which measures the temperature distribution of the entire object to be measured by combining the divided thermal images taken by multiple divided temperature aPI fixed ranges, if desired. It is.

[Effects of the Invention] As described above, according to the present invention, when an infrared camera images an object to be measured with a large temperature difference and obtains a thermal image thereof, the temperature range of the entire object is fixed depending on the desired temperature resolution. When the temperature range of the object to be measured cannot be covered before and after heating, a plurality of first and second temperature ranges δIIJ are set to divide the temperature range of the object to be measured before and after heating, respectively, and each temperature is measured with the desired temperature resolution. 2 each temperature 1
After switching the TP1 constant range and capturing the image, the synthesized 2
Deviation value of two composite thermal images Thermal image areas with high thermal data that stand out from the surroundings are detected as defective areas from the thermal image, so it is possible to measure objects with large temperature differences with high temperature resolution, which was previously impossible. Therefore, it is possible to easily detect defective parts.

[Brief explanation of drawings]

Figures 1 (a) to (d) are diagrams showing the measurement range divided imaging before heating according to the present invention and its thermal image effective range, and Figure 2 (a)
) and (b) are diagrams showing a composite image in which the thermal image effective ranges imaged by each 71P+fixed range in FIG. 1 are superimposed, and the cross-sectional thermal image data values thereof. FIGS. 3(a) to 3(d) are diagrams showing the Δt1 constant range divided imaging after heating and the effective thermal image range thereof according to the present invention. Figures 4 (a) and (b) are diagrams showing a composite image obtained by superimposing the effective thermal image range taken by each measurement range in Figure 3 and its cross-sectional thermal image data, and Figures 5 (a) and ( b) is a diagram showing the subtraction process of the thermal image data of Figures 2 (a) and (b) from the thermal image data of TS4 Figures (a) and (b), and Figures 6 (a) to (d) are from this book. Figures 7(a) and 7(b) are diagrams showing superimposed composite images of the effective thermal image range for each measurement range before and after heating and their cross-sectional thermal image data values before and after heating according to the invention, and FIGS. 6(c) and ( Figures 8(a) and 8(b) show the subtraction process of the thermal image data from the thermal image data of d), and Figures 8(a) and 8(b) show defective parts according to the method according to the present invention and the conventional method. Figure 9(a) is a diagram showing the difference in data size, and Figure 9(a) is a configuration diagram of a temperature measuring device using an infrared camera inside the membrane. FIG. 3 is a diagram showing an example of temperature distribution. In the figure, 1 is an infrared camera, 2 is a computer, and 3 is a C
RT display, 4 is a pipe.

Claims (1)

[Claims] When capturing an object to be measured with a large temperature difference and obtaining a thermal image using an infrared camera, if the temperature range of the entire object cannot be covered depending on the desired temperature resolution, the temperature range can be divided and the desired temperature can be obtained for each object. A first composite thermal image is created by setting a plurality of first temperature measurement ranges for measuring with resolution, and synthesizing the effective thermal images obtained by switching and imaging each of the set first temperature measurement ranges. Then, with the entire surface to be measured heated to a nearly constant temperature rise, the same number of second temperature measurement ranges are set by shifting the plurality of first temperature measurement ranges corresponding to the temperature rise. A temperature measurement range is set, and a second composite thermal image is created by combining the effective thermal images obtained by switching and imaging each of the second temperature measurement ranges set, and creating a second composite thermal image. A deviation value thermal image is calculated by subtracting the thermal data of a first composite thermal image located at the same imaging position from the thermal data of 1. A method for measuring temperature using an infrared camera, characterized in that a defective part of an object to be measured is detected by identifying a thermal image part having a heat image.