JP3318162B2 - Infrared thermal imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared thermal imaging apparatus, and more particularly to an infrared thermal imaging apparatus capable of real-time partial emissivity correction.

[0002]

2. Description of the Related Art Infrared thermal imaging devices that display a temperature distribution measured based on infrared energy emitted from an object to be measured as a thermal image are used in many application fields such as research and development, facility maintenance diagnosis and monitoring, and volcano monitoring. Have been. When measuring the temperature by using infrared energy is performed by obtaining the black body radiation energy W ₀ substantial temperature of the measurement object.

[0003] When the surface temperature of the infrared sensor to obtain the infrared energy is to be saturated at ambient temperature T _a, and the surface temperature of the measurement object is to be T _0, the black body radiation energy W ₀ This expression Can be represented by W ₀ = (1 / ε) ｛W− (1−ε) W _a ｝ W is the infrared energy obtained by the infrared sensor,
W _a is almost exactly be estimated from the ambient temperature data,
By specifying the emissivity ε, it is possible to know the blackbody radiant energy and thus the infrared energy of the measurement object.

FIG. 2 is an explanatory diagram of temperature measurement by an infrared thermal imaging device. It is assumed that the measurement object 102 has a surface temperature T ₀ and an emissivity ε. Radiation infrared energy 203 emitted by the measurement object 102 itself at the surface temperature T ₀
Is εW ₀ , where the black body radiation amount corresponding to the surface temperature T ₀ is W ₀ .

On the other hand, if the radiant infrared energy 201 due to the environmental temperature (T _a ) is W _a , the reflected infrared energy 2 due to the environmental temperature reflected by the measuring object 102 is 2
02 W _a -εW _a, that is, _{{(1-ε) W a} }.
Therefore, the incident infrared energy 204 incident on the infrared camera 101 is expressed by the following equation (1).

[0006]

W = εW ₀ + {(1−ε) W _a }

The W ₀ obtained from the above is the above-mentioned _value. By designating the emissivity ε, the infrared energy of the object to be measured can be known, and the surface temperature can be known based on the infrared energy. The process of setting the emissivity ε and grasping the infrared energy and thus the surface temperature is emissivity correction. Incidentally, the emissivity ε mentioned above take different values depending on the wavelength, thus W, both the W ₀ and W _a becomes different depending on the wavelength. The blackbody condition is ε = 1.

The conventional infrared thermal imaging apparatus has an energy-temperature conversion table for each emissivity, and when an emissivity is designated and input from the outside, incident infrared energy is converted into temperature data subjected to emissivity correction by the temperature conversion table. It converted and stored in the memory, and displays as the temperature distribution in the predetermined temperature range, and character display by converting the black body radiation amount W ₀ of the temperature data.

Such a temperature conversion table includes a surface temperature T ₀ of an object to be measured, T _0, and a minimum temperature T of the observed temperature.
The relationship between the output voltage difference of the infrared sensor at _min and the output voltage difference written in a storage medium such as a ROM is generally used.
₀ is required.

In the conventional emissivity correction method for an infrared thermal imaging apparatus, emissivity correction is performed in real time on the entire screen of a frame, or partial emissivity correction is performed on a still image once. Was going by either.

[0011]

The emissivity correction by the above-mentioned conventional infrared thermal imaging apparatus does not cause a large problem in the case of a measurement object having a relatively uniform temperature distribution, but the temperature distribution is partially reduced. In the case of measurement objects that are significantly different from each other, for example, if the target is one where components with different emissivity are mixedly arranged, such as a component mounted printed circuit board, it is necessary to perform full screen correction as in the past The true temperature cannot be measured for a portion of the measurement target other than the portion of the emissivity that matches the correction value set for the entire screen of the frame.

Therefore, for a portion that does not match such a correction value, the same measurement is repeated a number of times equal to the number of portions, or a partial image is corrected once by making a still image, so that the former is used. Causes an increase in the number of measurements, and in the latter case, it is necessary to generate a still image for each correction including heat generation and endothermic phenomena that change with time. Is required.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide an infrared thermal imaging apparatus which enables real-time partial correction of emissivity, and significantly reduces processing time required for emissivity correction.

[0014]

To achieve the above object, the present invention has the following means. That is, a first configuration of the infrared thermal imaging apparatus of the present invention is an infrared thermal imaging apparatus that generates a thermal image of a measurement target based on infrared energy acquired by an infrared two-dimensional sensor, and generates a thermal image. Correction part drawing means for drawing, as a television image, a correction part of the measurement object which partially performs emissivity correction necessary for the correction, and a predetermined temperature upper limit value in emissivity correction necessary for generating a thermal image of the correction part Correction coefficient calculation means for obtaining a correction coefficient necessary for emissivity correction based on the temperature lower limit value and infrared energy corresponding to the environmental temperature data and storing the correction coefficient for each pixel; And a partial emissivity correction means for correcting the emissivity for the corrected portion for each pixel.

A second configuration of the infrared thermal imaging apparatus according to the present invention has a configuration in which both the partial correction and the entire correction for each frame of the measurement object can be executed in the first configuration. .

[0016]

Next, the present invention configured as described above will be described. In the infrared thermal imaging apparatus of the present invention, the correction coefficient required for the emissivity correction is used for the correction operation in one frame unit in the conventional infrared thermal image, but the correction part is targeted for the pixel unit in the dedicated storage medium. A correction coefficient including a correction coefficient necessary for generating a thermal image is registered in pixel units, thereby enabling emissivity correction in pixel units.
As a result, partial corrections with different emissivities can be made in real time, and a remarkable reduction in the number of processing steps is ensured.

[0017]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. The embodiment shown in FIG. 1 generates an infrared camera 1 as an infrared two-dimensional sensor that acquires two-dimensional thermal image data of a measurement object, and generates a thermal image of the measurement object based on infrared energy acquired by the infrared camera 1. And a processor 20 for displaying.

The processor 20 includes a D / A converter 5 and a monitor TV 6 which constitute a correction portion drawing means capable of drawing a correction portion as a television image in addition to the entire image.
A graphic controller 10, a timing generator 7 constituting a correction coefficient calculating means for storing a correction coefficient necessary for emissivity correction in pixel units, a memory 8 for subtraction data and a memory 9 for multiplication data, and a partial emissivity correction means Temperature conversion table 2, subtractor 3, multiplier 4, environmental temperature sensor 13, and data 15 for converting environmental temperature (T _a ) detected by environmental temperature sensor 13 to corresponding radiant infrared energy (W _a ), and keyboard 15 Inverse temperature conversion table 14 for storing a table including data for converting the temperature input from the camera into radiant infrared energy, a CPU 12 having a built-in thermal image processing program and commonly included in each of the above-described units, and each of the above-described units Keyboard 1 for setting operation of configuration and necessary conditions for emissivity correction
1, and the CPU bus 11 is also shown in FIG.

Next, with respect to the operation of the present embodiment, the operation when the partial emissivity of the object to be measured is corrected will be described. The infrared camera 1 receives incident infrared energy W over a predetermined range of the measurement object by a two-dimensional array of infrared light receiving elements or a two-dimensional change of a received light beam by optical operation.
Is converted to digital data and supplied to the temperature conversion table 2 of the processor 20.

The temperature conversion table 2 registers data for converting infrared energy into a corresponding temperature, whereby the surface temperature T ₀ of the measuring object 102 is obtained from the output of the infrared camera 1 under the control of the CPU 12. . The data converted to the temperature by the temperature conversion table 2 is processed by the subtractor 3 and the multiplier 4 in accordance with the display temperature range, converted into image data by the graphic controller 10, and then converted into a D / A converter. 5 is output to the monitor TV 6 and displayed.

The subtraction data required for the subtraction processing in the subtractor 3 is read out from the subtraction data memory 8 and the multiplication data required for the multiplication processing in the multiplier 4 is read out from the multiplication data memory 9 by the CPU 12 and provided. Is done. These subtraction data and multiplication data are registered for each emissivity ε, and in the case of emissivity = 1, that is, in the case of a black body, the display lower limit value of the temperature is used as the subtraction data, and the multiplication data is calculated so that the display upper limit value becomes the maximum. When the emissivity is less than 1, subtraction data and multiplication data are obtained by calculation. This calculation is performed using Equation 1 described above.

In equation 1, when ε = 1, the incident infrared energy 204 (W) is equal to the black body radiation amount W ₀ of the measurement object 102, and the subtraction data and the multiplication data within the display temperature range are registered. Is done.

Next, when the emissivity ε is less than 1, subtraction data and multiplication data obtained by performing the following calculation based on Equation 1 are registered. When the display lower limit of the temperature is T _min in the setting of the keyboard 15, the corresponding radiant infrared energy W _min is obtained from the reverse temperature conversion table 13. Further, the environmental temperature T _a acquired by the environmental temperature sensor 13
_Is obtained from the reverse temperature conversion table 14.

When the emissivity ε is less than 1, by using these radiant infrared energies and substituting W ₀ = W _min and W _a = W _Ta into Equation 1, the infrared camera corresponding to the lower temperature limit T _min is obtained. The infrared energy W ₁ to be input to ₁ is expressed by the following equation (2).

[0025]

## EQU2 ## W ₁ = εW _min + (1−ε) W _Ta

Similarly, the infrared energy W ₂ to be input to the infrared camera 1 corresponding to the display upper limit value T _max of the temperature.
Is obtained by the following equation (3).

[0027]

## EQU3 ## W ₂ = εW _max + (1−ε) W _Ta

As for the emissivity ε, each time a drawing target area set by the operator using the keyboard 15 is used as drawing data by the CPU bus 11 and the graphic controller 10 and further drawn on the monitor TV 6 through the D / A converter 5. Is set to The emissivity ε is determined in advance by the CPU 12 based on the value of the emissivity ε.
₁ and W ₂ are obtained.

W ₁ and W ₂ obtained in this manner
Is again converted into a temperature in the temperature conversion table ₂ to obtain a lower limit temperature T ₁ and an upper limit temperature T ₂ for correction. Among these data, the lower limit temperature T ₁ is stored in the subtraction data memory 8 as subtraction data. This is shown by Equation 4. Further, the multiplication data is obtained by Expression 5.

[0030]

[Equation 4] Subtraction data = Lower limit temperature (T ₁ )

[0031]

## EQU5 ## Multiplied data = 255 / [upper limit temperature (T ₂ ) −lower limit temperature (T ₁ )]

[Mathematical formula-see original document] Equation 5 is a case where the input data has a 16-bit configuration and the display data has an 8-bit configuration. In this way, under the emissivity set for each drawing area, a correction coefficient for display to be applied to the conversion temperature belonging to that drawing area can be determined. That is,
Equations 4 and 5 mean that the input temperature data to be subjected to the emissivity correction exceeds the lower limit temperature T ₁ by using Equation 4, and then, by using Equation 5, with respect to the displayed 8 bits, , To determine how many quantization steps are assigned to the temperature data.

The subtraction data memory 8 and the multiplication data memory 9 store the thus obtained subtraction data and multiplication data as correction coefficients at the addresses corresponding to the pixels. At the time of the actual measurement, the timing signal generated by the timing generator 7 is supplied to the subtraction data memory 8 and the multiplication data memory 9, and both of these memories store the subtraction data and the multiplication data as correction coefficients for each address, that is, for each pixel. The two memories supply the subtraction data to the subtractor 3 and the multiplication data to the multiplier 4, so that the emissivity correction for each pixel can be performed in real time for each drawing target area.

In the above-described embodiment, the case where the partial correction is performed has been described as an example. However, it is easy to correct the emissivity based on the uniform emissivity for one frame of the total thermal image. Clearly what can be done.

[0035]

As described above, according to the infrared thermal imaging apparatus of the present invention, the partial correction of the emissivity is performed in real time for each pixel, so that the man-hour required for the partial emissivity correction can be significantly reduced. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of temperature measurement by an infrared thermal imaging device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Infrared camera 2 Temperature conversion table 3 Subtractor 4 Multiplier 5 D / A converter 6 Monitor TV 7 Timing generator 8 Subtraction data memory 9 Multiplication data memory 10 Graphic controller 11 CPU bus 12 CPU 13 Environmental temperature sensor 14 Reverse temperature conversion Table 15 keyboard 20 processor

Claims (2)

(57) [Claims] An infrared thermal imaging apparatus for generating a thermal image of a measurement object based on infrared energy obtained by an infrared two-dimensional sensor, and partially performing emissivity correction required for generating a thermal image. Correction portion drawing means for drawing a correction portion of the measurement object as a television image, and corresponding to predetermined temperature upper limit value, temperature lower limit value, and environmental temperature data in emissivity correction necessary for generating a thermal image of the correction portion. A correction coefficient calculating means for obtaining a correction coefficient necessary for emissivity correction based on the infrared energy and storing the correction coefficient for each pixel; and correcting the emissivity for each pixel in real time by the correction coefficient stored for each pixel. An infrared thermal imaging apparatus comprising: a partial emissivity correction unit that performs correction on a portion. 2. The infrared thermal imaging apparatus according to claim 1, wherein both the partial correction and the entire correction for each frame of the measurement object can be executed.