JP7518334B2 - Temperature Measurement Method - Google Patents

Description

The present invention relates to a temperature measurement method.

Radiation thermometry is a method of determining the temperature of an object by detecting the thermal radiation emitted by the object according to its temperature using a measuring device such as a radiation thermometer, and is a remote temperature measurement method that can measure temperature quickly and without contact. Today, radiation thermometry is used in many industries, including the steel industry.

For example, the following Patent Document 1 discloses a technology that uses radiation thermometry to measure the surface temperature of a cast piece being cast by a continuous casting machine.

JP 2014-36988 A

The radiation thermometer used in the above-mentioned Patent Document 1 is a so-called "monochromatic radiation thermometer" that calculates the temperature of an object to be measured based on the energy intensity of thermal radiation light at a certain wavelength of interest. However, because a monochromatic radiation thermometer derives temperature from the energy intensity in the measurement field of view, the measurement field of view is often missing at the edges (corners) of the object (hereinafter simply referred to as "missing field of view"), resulting in temperature measurement errors (more specifically, errors caused by underestimating the temperature of the corners).

In addition, in an actual production line at a steelworks, the radiation thermometer needs to be placed at least 3 to 4 m away from the target object, and the circular measurement diameter of a monochromatic radiation thermometer is about 40 to 50 mm. On the other hand, when monitoring the temperature during production, it is important to accurately measure the temperature of the steel end, and with a measurement diameter in the range described above, the temperature near the corners drops, making it impossible to accurately measure the temperature of the steel end.

The present invention has been made in consideration of the above problems, and the object of the present invention is to provide a temperature measurement method that can measure the temperature of an object more accurately while suppressing temperature measurement errors at the ends of the object.

In order to solve the above problems, according to one aspect of the present invention, there is provided a temperature measurement method for detecting thermal radiation light in the near-infrared band emitted by a red-hot steel material , which is a measurement object, and measuring the temperature of the red-hot steel material based on the detection result of the radiance of the thermal radiation light, the method detecting the thermal radiation light of the red-hot steel material using a two-color radiation thermometer having a light-receiving unit that receives the thermal radiation light of the red-hot steel material , a detection unit that detects the thermal radiation light received by the light-receiving unit, and a position control mechanism that changes the relative positional relationship between the red-hot steel material and the light-receiving unit to cause the light-receiving unit to measure the distribution of the thermal radiation light in the width direction of the red-hot steel material, the two-color radiation thermometer detecting the thermal radiation light of the red- hot steel material and measuring the temperature distribution along the width direction of the red- hot steel material including the vicinity of the end portion of the red-hot steel material , The temperature measurement method includes a predetermined minimum amount of radiated light, which is the minimum amount of radiated light required for temperature calculation within the circular measurement field of view of the two-color radiation thermometer, and the position control mechanism changes the relative positional relationship between the red-hot steel material and the light-receiving unit until the amount of radiated light detected within the circular measurement field of view of the two-color radiation thermometer becomes less than the minimum amount of radiated light, and when an area occupied by something other than the red-hot steel material exists within the circular measurement field of view of the two-color radiation thermometer, the measurement result of the temperature of the red-hot steel material is output in correspondence with a center position calculated from the center position and radius of the circular measurement field of view of the two-color radiation thermometer and the end position of the red-hot steel material within the circular measurement field of view .
In order to solve the above problems, according to another aspect of the present invention, there is provided a temperature measurement method for detecting thermal radiation light in the near infrared band emitted by a red-hot steel material as a measurement object, and measuring the temperature of the red-hot steel material based on the detection result of the radiance of the thermal radiation light, the method comprising: a two-color radiation detector having a light receiving unit that receives the thermal radiation light from the red-hot steel material ; a detection unit that detects the thermal radiation light received by the light receiving unit; and a position control mechanism that changes the relative positional relationship between the red-hot steel material and the light receiving unit to cause the light receiving unit to measure the distribution of the thermal radiation light in the width direction of the red-hot steel material. The present invention provides a temperature measurement method in which a two-color radiation thermometer is used to detect the thermal radiation light of the red-hot steel material , and a temperature distribution along the width direction of the red- hot steel material including the vicinity of the end of the red-hot steel material is measured, and if there is an area within the circular measurement field of view of the two-color radiation thermometer that is occupied by something other than the red-hot steel material, the measurement result of the temperature of the red-hot steel material is output in correspondence with a center of gravity position calculated from the center position and radius of the circular measurement field of view of the two-color radiation thermometer and the end position of the red-hot steel material within the circular measurement field of view .

It is preferable that the two-color radiation thermometer has a specified minimum amount of radiated light, which is the minimum amount of radiated light required for temperature calculation within the circular measurement field of the two-color radiation thermometer, and the position control mechanism changes the relative positional relationship between the red-hot steel material and the light-receiving unit until the amount of radiated light detected within the circular measurement field of the two-color radiation thermometer becomes less than the minimum amount of radiated light.

The position control mechanism may be an angle control mechanism that changes the angle between a surface normal direction of the red-hot steel material and an optical axis of the light receiving portion.

The angle control mechanism may change the angle between the surface normal direction and the optical axis of the light receiving unit by rotating a mirror, which is arranged at an angle to the surface normal direction between the red-hot steel and a light-guiding optical system that guides the thermal radiation light to the detection unit, by a predetermined angle with the longitudinal direction of the red-hot steel as the rotation axis.

The position control mechanism may be a drive mechanism that moves the light receiving unit along the width direction of the red-hot steel material .

The two-color radiation thermometer is a two-color radiation thermometer that can independently output the radiance of the thermal radiation light at each of two wavelengths of interest, and when scanning the temperature distribution in the width direction of the red-hot steel material , if something other than the red-hot steel material is located within the circular measurement field of view of the radiance of the two-color radiation thermometer, the two-color radiation thermometer may measure the temperature of the red -hot steel material using the radiance of the thermal radiation light at each of the two wavelengths of interest, and when the red-hot steel material occupies the circular measurement field of view, the two-color radiation thermometer may measure the temperature of the red-hot steel material using the radiance of the thermal radiation light at either one of the two wavelengths of interest.

When the distance from the two-color radiation thermometer to the red-hot steel material is H [mm], the size of the measurement diameter of the two-color radiation thermometer is D _L [mm], and the width of the red-hot steel material is W [mm], the two-color radiation thermometer is a two-color radiation thermometer that can independently output the radiance of the thermal radiation light at each of two wavelengths of interest, and has, as the position control mechanism, an angle control mechanism that changes the angle between the surface normal direction of the red-hot steel material and the optical axis of the light receiving unit, and when scanning the temperature distribution in the width direction of the red-hot steel material , the magnitude of the angle between the surface normal direction of the red-hot steel material and the optical axis of the light receiving unit is expressed as follows: |φ|=|tan ⁻¹ [{(W/2)−(D _L When the angle between the surface normal direction of the red-hot steel material and the optical axis of the light receiving unit exceeds a value represented by |φ|=|tan −1 [{(W/2)−(D L /2)}/H]|, the two-color radiation thermometer may measure the temperature of the red-hot steel material using the radiance of the thermal radiation light at each of the two wavelengths of interest, and when the magnitude of the angle between the surface normal direction of the red-hot steel material and the optical axis of the light receiving unit is equal to or smaller than a value represented by |φ|=|tan ⁻¹ [{(W/2)−(D _L /2)}/H]|, the two-color radiation thermometer may measure the temperature of the red-hot steel material using the radiance of the thermal radiation light at either one of the two wavelengths of interest.

The dichroic radiation thermometer may calculate a dichroic ratio by dividing one of the measurement data of the radiance at two wavelengths of interest by the other, and use the calculated dichroic ratio to calculate the temperature of the red-hot steel material based on a relationship between the dichroic ratio and temperature.

The two-color radiation thermometer may measure the thermal radiation light of the red-hot steel at two wavelengths at which the spectral absorption coefficient of the absorber is identical to each other, with an absorber having a wavelength-dependent spectral absorption coefficient in the near-infrared band being present at least in part on the light path, generate measurement data indicating the detection results of the radiance of the thermal radiation light at the two wavelengths, and calculate the temperature of the red-hot steel based on the generated measurement data corresponding to the two wavelengths and a relationship equation between spectral radiance and temperature.

The detection unit may include a branching optical element that branches the thermal radiation light of the red-hot steel into two optical paths, a first detection element that detects the branched thermal radiation light at one of the two wavelengths, a second detection element that detects the branched thermal radiation light at the other of the two wavelengths, a first optical filter that is provided between the branching optical element and the first detection element and transmits the thermal radiation light of one of the two wavelengths, and a second optical filter that is provided between the branching optical element and the second detection element and transmits the thermal radiation light of the other of the two wavelengths.

As the two types of wavelengths, two types of wavelength bands of a predetermined width including wavelengths at which the spectral absorption coefficients of the absorber are the same are selected, and the two types of wavelength bands may be selected so that the apparent spectral absorption coefficients calculated by weighting the spectral absorption coefficients of the absorber with the spectral radiance of the temperature to be measured are equal to each other.

The two-color radiation thermometer may further calculate a thickness of the absorber using the blackbody radiance at either of the two wavelengths calculated using the temperature of the red-hot steel, the measured radiance of the thermal radiation light, the spectral absorption coefficient of the absorber at the two wavelengths, the reflectance of the thermal radiation light at the interface of the absorber with the red-hot steel, the reflectance of the thermal radiation light at the interface of the absorber opposite to the red-hot steel side , and the setting conditions in the measurement unit.

The absorbent may be at least one of water, oil, solution, glass, or resin.

The near infrared band may be 940 nm to 1350 nm.

As described above, the present invention makes it possible to measure the temperature of an object more accurately while suppressing temperature measurement errors at the ends of the object.

FIG. 1 is a graph showing the relationship between wavelength and spectral radiance. FIG. 1 is a graph showing the relationship between temperature and dichroic ratio. FIG. 1 is a graph showing the relationship between temperature and dichroic ratio. FIG. 1 is a graph showing the relationship between temperature and dichroic ratio. FIG. 11 is a graph showing the relationship between temperature and the attenuation rate of spectral radiance. FIG. 11 is a graph showing the relationship between temperature and the attenuation rate of spectral radiance. FIG. 11 is an explanatory diagram for explaining the influence of water on a monochromatic radiation thermometer. FIG. 2 is an explanatory diagram showing the wavelength dependence of the spectral absorption coefficient of water. FIG. 11 is an explanatory diagram for explaining the influence of water on a monochromatic thermometer. FIG. 1 is an explanatory diagram showing the relationship between blackbody radiance and wavelength and temperature. FIG. 11 is an explanatory diagram for explaining a change in the dichroic ratio caused by a water film. FIG. 2 is an explanatory diagram showing the spectral absorption coefficient of water, which is an example of an absorber. FIG. 11 is an explanatory diagram for explaining a combination of wavelengths of a two-color radiation thermometer that is not affected by water. FIG. 11 is an explanatory diagram for explaining a combination of wavelengths of a two-color radiation thermometer that is not affected by water. FIG. 11 is an explanatory diagram for explaining a combination of wavelengths of a two-color radiation thermometer that is not affected by water. FIG. 2 is an explanatory diagram for explaining weighting coefficients according to the spectral absorption coefficient and the spectral radiance of water. FIG. 2 is an explanatory diagram for explaining weighting coefficients according to the spectral absorption coefficient and the spectral radiance of water. FIG. 1 is an explanatory diagram showing the wavelength dependence of the spectral radiance of a high-temperature object. FIG. 2 is an explanatory diagram showing how the dichroic ratio changes depending on the spectral absorption coefficient of water. FIG. 11 is an explanatory diagram for explaining a method for calculating the thickness of a water film. FIG. 11 is a graph showing the relationship between the thickness of the water film and the spectral transmittance. FIG. 2 is an explanatory diagram illustrating a schematic example of a configuration of a temperature measuring device according to the embodiment; FIG. 2 is an explanatory diagram illustrating a schematic example of a configuration of a temperature measuring device according to the embodiment; 2 is an explanatory diagram showing a schematic example of the configuration of a measurement unit included in the temperature measurement device according to the embodiment; FIG. 2 is an explanatory diagram showing a schematic example of the configuration of a measurement unit included in the temperature measurement device according to the embodiment; FIG. 10 is a graph showing an example of the relationship between the center wavelength of an optical filter and a temperature measurement error. FIG. 4 is an explanatory diagram showing a schematic example of the configuration of a detection unit in the measurement unit according to the embodiment; FIG. 4 is an explanatory diagram showing a schematic example of the configuration of a detection unit in the measurement unit according to the embodiment; FIG. 4 is an explanatory diagram showing a schematic example of the configuration of a detection unit in the measurement unit according to the embodiment; FIG. 4 is a block diagram showing an example of the configuration of a calculation processing unit included in the temperature measuring device according to the embodiment. FIG. 13 is a block diagram showing another example of the configuration of the arithmetic processing unit included in the temperature measuring device according to the embodiment. FIG. FIG. 2 is a block diagram showing an example of a hardware configuration of the temperature measuring device according to the embodiment. 4 is an explanatory diagram for explaining a temperature measuring method according to the embodiment. FIG. 4 is an explanatory diagram for explaining a temperature measuring method according to the embodiment. FIG. 4 is an explanatory diagram for explaining a temperature measuring method according to the embodiment. FIG. 4 is an explanatory diagram for explaining a temperature measuring method according to the embodiment. FIG. 4 is an explanatory diagram for explaining a temperature measuring method according to the embodiment. FIG. FIG. 11 is an explanatory diagram for explaining a method of calculating a center of gravity position. FIG. 4 is an explanatory diagram showing a temperature measuring method in the embodiment. FIG. 4 is a graph showing the results of temperature measurements in the examples. FIG. 4 is a graph showing the results of temperature measurements in the examples.

The preferred embodiment of the present invention will be described in detail below with reference to the attached drawings. Note that in this specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals to avoid redundant description.

(Investigations by the present inventors regarding radiation thermometers)
<Principles of Radiation Thermometry and Objectives of the Invention>
Before describing the temperature measuring method according to the embodiment of the present invention, the principle of radiation thermometry, which is the focus of the present invention, will be briefly described, and the object of the present invention will be described.

As mentioned above, radiation thermometry is a method of finding the temperature of an object by detecting the thermal radiation emitted by the object according to its temperature. The spectral radiance L of a black body, which is an ideal radiator, is expressed by the following formula (1) as a function of temperature and wavelength according to Planck's black body radiation law.

In the above formula (1),
T: temperature [K]
λ: wavelength [nm]
c ₁ : the first constant of blackbody radiation, 1.19×10 ²⁰ [W·m ⁻² ·nm ⁴ ]
_c2 : second constant of blackbody radiation, 1.44 x ¹⁰⁷ [nm·K]
It is.

Here, when the radiator is red-hot steel or when observing thermal radiation of a short wavelength, if λT is sufficiently smaller than _c2 , the above formula (1) can be approximated as the following formula (2).

The spectral radiance of an actual object is smaller than that of a blackbody as described above, and the spectral radiance L of an actual object is expressed by the following equation (3) using the material's inherent spectral emissivity.

In the above formula (3), ε(λ) is the spectral emissivity at the observation wavelength λ [nm], and the other formulas are the same as those in the above formulas (1) and (2).

In radiation thermometry, the observed wavelength λ is determined by the detector, so the spectral radiance L is a function of the temperature T and the emissivity ε. Figure 1 shows the relationship between the observed wavelength λ and the spectral radiance L when the temperature T is changed to several temperatures.

Therefore, radiation thermometry using a general monochromatic radiation thermometer (also called monochromatic radiation thermometry) involves first determining the spectral emissivity, then measuring the spectral radiance of the thermal radiation from the object being measured at one observation wavelength to determine the temperature. In other words, with general monochromatic radiation thermometry, if the spectral emissivity of the object being measured is unknown, it is not possible to perform accurate temperature measurement. Also, if there is an absorber on the optical path from the object to be measured to the radiation thermometer and the observed light is attenuated, temperature measurement errors will occur unless the amount of attenuation by the absorber can be quantitatively determined.

On the other hand, in addition to the monochromatic radiation thermometer using a monochromatic radiation thermometer, there is also a method of measuring temperature using a two-color thermometer. A two-color radiation thermometer (hereinafter also simply referred to as a two-color thermometer) is a measuring instrument that observes thermal radiation light at two different observation wavelengths. As is clear from the above formula (3), if the spectral emissivity is the same at the two wavelengths λ ₁ and λ ₂ , the ratio of the spectral radiance L at the two wavelengths (i.e., the dichroic ratio) becomes a function of temperature only, so that the temperature can be measured without knowing the spectral emissivity of the object to be measured in advance (the radiation thermometry using a two-color thermometer will be described in detail below). When wavelengths close enough to be considered to have the same spectral emissivity (for example, wavelengths λ ₁ =1 μm and λ ₂ =1.2 μm in FIG. 1) are selected, it can be seen that the dichroic ratio R is a function of temperature T, as shown in FIG. 2. Such a two-color radiation thermometer has the characteristic that it is not affected by defects in the field of view of the detector or by light attenuation caused by obstacles in the optical path (e.g., floating dust or mist, dirt on the observation window, etc.).

On the other hand, as mentioned earlier, with typical monochromatic radiation thermometry, there is a lack of field of view, which leads to temperature measurement errors at the edges (corners) of the object. Such temperature measurement errors arise because the temperature is derived based on the energy intensity in the measurement field of view, so by using a two-color radiation thermometer with the characteristics described above, it is possible to measure the temperature of the object more accurately while suppressing temperature measurement errors at the edges of the object.

<Findings Obtained by the Inventors>
Next, the principle of the two-color radiation thermometer will be briefly explained, and then the findings obtained by the inventors will be explained in detail with reference to Figures 3 to 17. Figures 3 to 17 are explanatory diagrams for explaining the findings obtained by the inventors.

[About the principle of two-color radiation thermometer]
A two-color radiation thermometer is a measurement device that determines the temperature T of an object to be measured by using the ratio of spectral radiances L( _λ1 , T) and L( _λ2 , T) of two wavelengths _λ1 and _λ2 . The two spectral radiances observed using the above formula (3) can be expressed as the following formulas (4) and (5).

Here, if the spectral emissivities at the two wavelengths _λ1 and _λ2 are equal to each other (ε( _λ1 ) = ε( _λ2 ) = ε), the dichroic ratio R, defined as the ratio obtained by dividing the above formula (4) by formula (5), is expressed as the following formula (6).

Here, in the above formula (6), R _λ and Λ are as shown in the following formulas (6a) and (6b).

Equation (6) above shows that the dichroic ratio R is a function of temperature T.
Now, consider measuring the temperature of a measurement object using a two-color thermometer. In this case, when setting the two wavelengths λ ₁ and λ ₂ used for temperature measurement, attention is paid to how the dichroic ratio R changes when two wavelengths close to each other (e.g., 1200 nm and 1250 nm) are selected and when two wavelengths separated by a certain distance (e.g., 1200 nm and 1300 nm) are selected. Such a change can be obtained by substituting the two wavelengths λ ₁ and λ ₂ into the above formulas (6) to 6(b).

The obtained changes are shown in Fig. 3. In Fig. 3, the horizontal axis represents temperature T [°C], and the vertical axis represents the dichroic ratio R calculated based on formula (6).
As is clear from Fig. 3, the dichroic ratio R increases monotonically with temperature T. It can also be seen that the closer the two selected wavelengths are to each other, the more gradual the change in the dichroic ratio R. A gradual change in the dichroic ratio R (in other words, the temperature gradient of the dichroic ratio) means that even if the temperature T changes significantly, the amount of change in the dichroic ratio R is small. In other words, when the two selected wavelengths are close to each other, the amount of change in the dichroic ratio is small even if the temperature changes, and the temperature measurement sensitivity decreases.

From this fact, it can be seen that when measuring temperature using a two-color thermometer, it is preferable that the temperature corresponding to the difference between the two selected wavelengths is equal to or greater than the temperature resolution of the two-color thermometer, and it is even more preferable that the temperature range to be measured is such that a significant slope is obtained in the correspondence relationship between the dichroic ratio R and temperature as shown in Figure 3. The wavelength difference corresponding to such temperature resolution varies depending on the two-color thermometer used, but for example, it is preferable that the absolute value of the difference between the two selected wavelengths, |λ ₁ - λ ₂ |, is 100 nm or more.

[Findings Obtained by the Inventors]
The principle of the two-color thermometer that is the focus of the embodiments of the present invention has been briefly described above.
Now, in the above formula (3), the spectral radiance L was calculated for a single-color thermometer (measurement wavelength λ=1.55 μm) and a two-color thermometer (measurement wavelength _λ1 =0.90 μm, _λ2 =1.55 μm) to estimate the temperature of the corner of the red-hot steel plate. In this case, the temperature of the measurement object was set to 800° C., and the lower limit temperature of the thermometer (determined by the minimum radiance at which the amount of light detection works correctly) was set to 600° C. In addition, the separation distance between the thermometer and the measurement object was set to 3000 mm, the measurement field of view was set to a circular spot with a diameter of 36 mm, and the ratio of the area measured other than the measurement object to the measurement area was derived as the attenuation rate.

First, the relationship between the derived two-color ratio (λ ₁ /λ ₂ ) and temperature in the two-color radiation thermometer is shown in FIG. 4. Using the results shown in FIG. 4, consider measuring the temperature of a corner of red-hot steel with both a single-color thermometer and a two-color thermometer. When the corner comes into the measurement field of view of the thermometer, a defect occurs, and the observed radiation light attenuates even if the temperature is the same, resulting in the temperature measurement result shown in FIG. 5A. That is, when trying to measure the corner of red-hot steel, with a single-color thermometer, if the temperature of the corner is 800° C., the temperature becomes 680° C. at an attenuation rate of 85% (when measuring the range from the edge of the steel to a position 7.5 mm toward the center of the steel). This result means that the measurement error is 120° C. at an attenuation rate of 85%. On the other hand, with a two-color thermometer, the temperature measurement result is 800° C. as shown in FIG. 5A, and it is clear that the correct temperature can be measured. This result shows that even if 85% of the area within the measurement field of view is other than the object to be measured, accurate measurement is possible as long as radiance equivalent to 600°C or higher is detected.

As shown in Figure 5B, when the corner temperature is set to 900°C and the same calculation is performed, the radiance increases, and it is possible to accurately measure the temperature up to an attenuation rate of 93% (when measuring the range from the very edge of the steel material to a position 4.4 mm toward the center of the steel material).

These results show that the higher the temperature of the object to be measured, the more accurately the temperature of the corner can be measured using a two-color thermometer. The various photodetectors provided in the radiation thermometer have a minimum value (hereinafter simply referred to as the "minimum radiation amount") for the amount of radiation light that can be detected (brightness). The two-color thermometer outputs an accurate temperature when each detector set for two wavelengths detects radiation light equal to or greater than the minimum radiation amount, and measurement errors occur when the amount of radiation light detected is less than the minimum radiation amount. The higher the temperature of the object to be measured, the greater the absolute amount of thermal radiation, and the corner can be measured to the edge. In addition, with a two-color thermometer, if the amount of radiation light detected within the measurement field of view is equal to or greater than the minimum radiation amount, the temperature of the object to be measured can be measured with high accuracy. This is the first finding obtained by the inventors.

Next, as shown in FIG. 6, a steel plate in a high temperature state (temperature T, emissivity ε) is taken as an example of a measurement object, and further findings obtained by the inventors are described in detail using a case in which water, an example of an absorber, exists as a water film on the steel plate.

For example, in the continuous casting and hot rolling processes of the steel manufacturing process, the temperature of red-hot steel moving along a conveying line is frequently measured. However, in the area where the slab is pulled out of the continuous casting machine and between the rolling stands in the hot rolling process, cooling water may be stagnant on the steel or the evaporated cooling water may hang around as steam. As for the scattering of light by steam on the light path, if the two wavelengths observed are not far apart, the thermal radiation light will show almost the same attenuation even at different wavelengths, so a two-color pyrometer can be applied. On the other hand, if the water stagnant on the steel forms a water film, the spectral absorptance of water shows strong wavelength dependence in the near-infrared band suitable for radiation temperature measurement, so the water acts as an absorber with unknown attenuation characteristics. As a result, the assumption that the attenuation of thermal radiation light occurs in the same way at the two wavelengths does not hold, and a two-color radiation thermometer cannot be used appropriately. Water is transparent in the visible light band with wavelengths of approximately 800 nm or less, but in short wavelength bands such as the visible light band, thermal radiation light is not emitted until the object being measured becomes very hot, so the temperature range of the object being measured is limited to high temperatures.

In addition, in the steel manufacturing process described above, in addition to water, glass, solutions present on the steel plate, and oils, fats, and resins present on the steel plate also have non-uniform spectral absorptance in the near-infrared band (i.e., they show strong wavelength dependence) and function as absorbers.

The situation in which an absorber is present in the optical path between the object being measured and the radiation thermometer in radiation thermometry can occur not only in the steel manufacturing process described above, but also in various other measurement environments.

The inventors conducted extensive research to solve these problems and realize a two-color radiation thermometer that can accurately measure the temperature of an object to be measured, even when thermal radiation is detected when an absorber is present on the optical path from the object to be measured to the radiation thermometer. As a result, they were able to obtain the findings described in detail below.

In addition, in the steel manufacturing process described above, water is sprayed onto the hot steel to cool it down, and the amount of water present on the surface of the steel is considered to be an important operational factor that determines the amount of heat extracted from the steel. The inventors have come to the realization that by using a temperature measuring device and a temperature measuring method according to an embodiment of the present invention as described below, it is possible to obtain a more accurate temperature of the object to be measured, and therefore to more accurately calculate the thickness of the water (i.e., absorber) present on the optical path from the object to be measured to the radiation thermometer.

Water, an example of an absorber, is transparent up to the long wavelength end of the visible light band (near 800 nm wavelength), but becomes semi-transparent with strong wavelength dependency at wavelengths above 800 nm in the near infrared band, as shown in Figure 7. Also, as is clear from the Beer-Lambert law, the thicker the water film, the more light in the near infrared band is absorbed by the water, and the smaller the spectral transmittance becomes.

In order to avoid the influence of water in radiation thermometry, a method of measuring temperature at wavelengths below 800 nm, where water barely absorbs light, has been considered, and in fact, "water-film-penetrating radiation thermometers (single-wavelength radiation thermometers)" with an observation wavelength of 800 nm are commercially available. However, thermal radiation has the characteristic of decreasing rapidly as the wavelength becomes shorter, and a radiation thermometer with an observation wavelength of 800 nm requires that the temperature of the object being measured be at least 650°C or higher.

As mentioned above, if steam, which is a scattering medium, is present, it is difficult to perform accurate temperature measurement using monochromatic radiation thermometry, even if the water is transparent. Here, we will show a specific example of inaccurate measurement when performing monochromatic radiation thermometry in the wavelength band of 800 nm or more, where water absorbs light. For example, at a wavelength of 1300 nm, the light intensity attenuates according to the spectral transmittance shown in Figure 7 depending on the thickness of the water. When the effect of such attenuation on the measured temperature is calculated, it is as shown in Figure 8. In Figure 8, the horizontal axis is the thickness of the water film [mm], and the vertical axis is the temperature measurement error [°C]. As is clear from Figure 8, even if the thickness of the water is only about 2 mm, a temperature measurement error of about 30°C will occur. Therefore, in an actual measurement environment where the thickness of the water is unknown, it is extremely difficult to perform accurate temperature measurement using a monochromatic radiation thermometer.

Next, we will explain why the temperature of the object to be measured must be at least 650°C for a radiation thermometer with an observation wavelength of 800 nm, with reference to Figure 9, which shows the relationship between blackbody radiance, wavelength, and temperature.

In Figure 9, the horizontal axis is temperature and the vertical axis is blackbody spectral radiance. As shown in Figure 9, blackbody spectral radiance increases monotonically as temperature increases. Here, the detection limit of the sensor used in a typical radiation thermometer is thermal radiation with a blackbody spectral radiance magnitude of about 1. Therefore, if we focus on the curve for an observation wavelength of 800 nm in Figure 9, the intersection point between the straight line representing "blackbody spectral radiance = 1" and the curve for an observation wavelength of 800 nm is approximately 650°C.

As explained above, when using a two-color radiation thermometer, it is preferable to set the distance between the two wavelengths at least 100 nm. Therefore, to realize a two-color radiation thermometer in a wavelength band where water is transparent, it is preferable to set the short wavelength side of the observation wavelength to around 800 nm - 100 nm = 700 nm. In such a case, as shown in Figure 9, the lower limit temperature measurement of the two-color radiation thermometer will be about 740°C. Also, as shown in Figure 9, if the observation wavelength is set to, for example, 1000 nm, it will be possible to measure temperatures from 500°C, and if the observation wavelength is set to, for example, 1200 nm, it will be possible to expand the lower limit temperature measurement to around 400°C.

Therefore, from the above findings, it can be seen that in order to ensure a wide measurement temperature range, it is sufficient to set the observation wavelength on the longer wavelength side. However, when a two-color radiation thermometer is constructed using two observation wavelengths of 800 nm or more, as is clear from Figure 7, this wavelength band becomes a band in which the spectral absorptance of water shows a significant wavelength dependency. The two types of spectral radiance L observed in this wavelength band, taking into account the absorption of water as an absorber, are expressed by the following formulas (7) and (8).

Here, in the above formulas (7) and (8), τ ₁ is the spectral transmittance of water at wavelength λ ₁ , and τ ₂ is the spectral transmittance of water at wavelength λ _2. The spectral transmittance τ of water is a function of the spectral absorption coefficient of water, the thickness of the water, and the interface reflectance determined from the refractive indexes of both at the interface between water and air (details will be described below). In this case, if the interface reflection is omitted, the spectral transmittances τ ₁ and τ ₂ of water can be expressed as τ ₁ =exp(-α ₁ ×t) and τ ₂ =exp(-α ₂ ×t), respectively. Here, α ₁ is the spectral absorption coefficient of water at wavelength λ ₁ , α ₂ is the spectral absorption coefficient of water at wavelength λ ₂ , and t is the thickness of the water film.

In the above equations (7) and (8), when the amounts of attenuation due to absorption differ between the two wavelengths _λ1 and _λ2 due to the wavelength dependence of the spectral absorption coefficient of water as shown in FIG. 7, the terms _τ1 and _τ2 due to water absorption will not cancel out in the relationship between the dichroic ratio and temperature defined in equation (6).

For example, in a two-color thermometer focusing on wavelengths of 1000 nm and 1100 nm, the dichroic ratio changes as shown in Figure 10 when there is no water and when thermal radiation light is observed passing through water. For example, if the true temperature of the object being measured is 700°C, as is clear from Figure 10, when a 5 mm thick water film is present, the apparent temperature is approximately 640°C, and when a 10 mm thick water film is present, the apparent temperature is approximately 590°C. In actual temperature measurements, where the thickness of the water film changes irregularly, the presence of water, which acts as an absorber, can cause significant temperature measurement errors.

As a result of further investigations based on the above findings, the inventors have come to the conclusion that, in order to accurately measure the temperature of an object to be measured by a dichroic radiation thermometer even when an absorber is present on the light path, it is sufficient to cancel out the terms τ ₁ and τ ₂ caused by absorption by the absorber in the above formulas (7) and (8) when calculating the dichroic ratio R. In order to cancel out the terms caused by absorption by the absorber, two observation wavelengths at which the spectral absorptance of the absorber is equal are selected, and the temperature of the object to be measured is measured.

Figure 11 is a graph showing the wavelength dependence of the spectral absorption coefficient of water, which is an example of an absorber, where the horizontal axis of Figure 11 is wavelength and the vertical axis is the spectral absorption coefficient. As a result of examining Figure 11 based on the above findings, the inventors came to the conclusion that the observation wavelength of the two-color radiation thermometer should be selected based on the technical concept described below.

○How to select observation wavelengths – Part 1
In order to specify two wavelengths having the same spectral absorption coefficient, attention should be paid to the spectrum of the spectral absorption coefficient as shown in Fig. 11, and attention should be paid to the number of intersections between a straight line represented by (spectral absorption coefficient = any constant) (in other words, a straight line parallel to the horizontal axis in the spectrum as shown in Fig. 11) and a curve corresponding to the spectrum of the spectral absorption coefficient. In this case, two wavelengths having the same spectral absorption coefficient should be appropriately selected from a wavelength band in which the number of intersections between the curve and the straight line is two or more.

For example, in the case of water shown in FIG. 12A, there are two wavelength bands in which the number of intersections is two or more:
(1) A wavelength band from the other intersection (near a wavelength of 940 nm) of a line (a line represented by a spectral absorption coefficient ≒ 0.02) tangent to a saddle of the spectrum near a wavelength of 1070 to 1080 nm to the other intersection (near a wavelength of 1130) of a line (a line represented by a spectral absorption coefficient ≒ 0.05) tangent to a peak near a wavelength of 970 to 980 nm: a first wavelength selection region. (2) A wavelength band from the other intersection (near a wavelength of 1155 nm) of a line (a line represented by a spectral absorption coefficient ≒ 0.11) tangent to a saddle of the spectrum near a wavelength of 1260 nm to the other intersection (near a wavelength of 1300 nm) of a line (a line represented by a spectral absorption coefficient ≒ 0.13) tangent to a peak near a wavelength of 1190 nm: a second wavelength selection region.

Using these two wavelength selection regions as a guide, two wavelengths with the same spectral absorption coefficient can be selected. In this case, as explained above, it is preferable to select two wavelengths with a wavelength difference of, for example, about 100 nm so that the temperature corresponding to the difference between the two wavelengths is equal to or greater than the temperature resolution of the two-color radiation thermometer.

Based on the above technical concept, for example, in FIG. 12B, two wavelengths, 1000 nm and 1130 nm, can be selected from the first wavelength selection region. Also, for example, in FIG. 12C, two wavelengths, 1190 nm and 1300 nm, can be selected from the second wavelength selection band. Note that this wavelength combination is merely an example, and wavelengths can be appropriately selected from the two types of wavelength selection regions based on the above technical concept.

Such a two-color radiation thermometer that uses a specific spectrum (a specific wavelength in a narrow band where the wavelength bandwidth can be ignored) can be realized by using a narrow-band optical interference filter and installing the narrow-band optical interference filter in the two-color radiation thermometer. Such narrow-band optical interference filters with a half-width of about 10 nm are commercially available, and it is also possible to manufacture narrow-band optical interference filters using known technology. Such wavelength selection filters will be explained again below.

○How to select observation wavelengths – Part 2
Generally, radiation thermometers rarely observe narrow-band spectral radiance that can be regarded as a specific single wavelength as described above. This is because, when the observation wavelength band is narrow, the absolute amount of light detected by the radiation thermometer becomes small, which reduces the detection sensitivity and increases the minimum measurement temperature. When measuring thermal radiation light of a finite wavelength bandwidth rather than a narrow band using a general wavelength selection filter or the like, the two observation wavelengths as described above can be selected as follows.

In other words, when the bandwidth of the observed wavelength cannot be ignored as in the above 1, instead of using a simple average of the absorption coefficients of the observed band as the effective spectral absorption coefficient, it is sufficient to obtain an averaged spectral absorption coefficient weighted by the spectral radiance that has wavelength dependency according to the temperature of the object to be measured, and use this for processing. In other words, this method is a method of selecting an observation band having a finite bandwidth so that the "apparent spectral absorption coefficients" calculated by weighting the spectral absorption coefficients of the absorbers by the spectral radiance of the temperature of the object to be measured are equal to each other. Below, this selection method will be specifically explained with reference to Figures 13A and 13B.

As a specific example, consider the selection of two wavelengths with a bandwidth of 40 nm starting from the first wavelength selection region shown in FIG. 12B.
First, the observation wavelength on the short wavelength side of the first wavelength selection region is fixed to 980 nm to 1020 nm, which is a bandwidth of 40 nm. In the wavelength range of 980 nm to 1020 nm, the effective spectral absorption coefficient α _eff is expressed as the following formula (9) using the spectral absorption coefficient α(λ) at wavelength λ and a weighting coefficient w(λ) determined from Planck's blackbody radiation formula, taking into account the wavelength dependency of the spectral radiance.

Here, assuming that the temperature of the measurement object is 900° C., a weighting factor w(λ) is calculated by normalizing the wavelength dependency of the spectral radiance L. The weighting factor w(λ) obtained is shown by a dashed line in FIG. 13A. In the example shown in FIG. 13A, the average value of the spectral absorption coefficient weighted by such a weighting factor was 4.2×10 ⁻² [1/mm]. In contrast, when the spectral absorption coefficient was averaged (simple averaged) with a uniform weight without considering the wavelength dependency of the spectral radiance L, the average value was 4.3×10 ⁻² [1/mm].

Next, for the observation wavelengths on the long wavelength side of the first wavelength selection region, a wavelength band around 1130 nm is selected so that the spectral absorption coefficient weighted and averaged with the spectral radiance at 900°C is 4.2×10 ⁻² [1/mm], which is the same as the weighted spectral absorption coefficient on the short wavelength side, as described above. As a result, as shown in FIG. 13B, the wavelengths from 1100 nm to 1140 nm met this condition. The simple average of the spectral absorption coefficients in the wavelength band shown in FIG. 13B was 4.1×10 ⁻² [1/mm].

13A and 13B, the value of the apparent spectral absorption coefficient (effective absorption coefficient) changes by 0.2×10 ⁻² [1/mm] depending on whether or not the wavelength dependency of the spectral radiance L of the object to be measured is taken into consideration. Conversely, if a simple average of the spectral absorption coefficients in the observation band is used to estimate the apparent spectral absorption coefficient, a discrepancy of about 0.2×10 ⁻² [1/mm] will occur in the effective spectral absorption coefficient when a high-temperature object is actually measured.

In the above explanation, the weighting coefficient based on the spectral radiance was calculated assuming that the object to be measured was 900°C. However, as shown in FIG. 14, for example, if the temperature range is about 200°C, the spectral radiance does not change significantly. Therefore, if the approximate temperature of the object to be measured can be predicted based on past operational data, etc., it is possible to assign a weighting coefficient based on the spectral radiance.

Here, the effect of the difference in effective absorption coefficient, 0.2×10 ⁻² [1/mm], between the case where the spectral absorption coefficient is corrected by the weighting coefficient and the case where the spectral absorption coefficient is not corrected, on the accuracy of the dichroic radiation thermometer is examined. For example, in a situation where thermal radiation light is measured through a water film having a thickness of 10 mm, the dichroic ratio R was calculated based on the above formula (6) for each of the cases where the spectral absorption coefficients of water at two wavelengths are equal to each other ^and are 4.2×10 ⁻² [1/mm], and the spectral absorption coefficient on the short wavelength side is 4.3×10 ⁻² [1/mm] and the spectral absorption coefficient on the long wavelength side is 4.1×10 −2 [1/mm]. The obtained results are shown in FIG. 15. In the results shown in FIG. 15, the dichroic ratios in the above two cases had a difference equivalent to a temperature difference of about 20° C. Therefore, when the observation wavelength has a width (when the observation wavelength is formed from a finite band), it is desirable to select two wavelength bands so that the spectral absorption coefficients of the absorbers averaged using weighting based on the spectral characteristics of the thermal radiation light exactly match each other.

Thus, according to the second observation wavelength selection method, when radiation thermometry is performed using observation wavelengths having a finite bandwidth, the spectral absorption coefficient is corrected so that the light intensity attenuation is equal between wavelengths in the two-color radiation thermometer. Since such correction of the spectral absorption coefficient makes it possible to further reduce measurement errors, it is more preferable to perform the correction process of the spectral absorption coefficient described in the second observation wavelength selection method even when a narrowband observation wavelength is selected based on the first observation wavelength selection method. In this case, it is preferable to determine the effective value α _eff of the spectral absorption coefficient in consideration of the wavelength dependency of the spectral radiance as described above.

When estimating the effective absorption coefficient of the observation wavelength band, the spectral data related to the spectral absorption coefficient may be weighted and averaged using the spectral transmittance characteristics of the wavelength selection filter and the spectral sensitivity characteristics of the photodetector built into the radiation thermometer as weights in addition to the spectral characteristics of the thermal radiation of the measurement target. In this case, the numerator of the relational expression shown in formula (9) will include terms related to the spectral transmittance characteristics of the wavelength selection filter and terms related to the spectral sensitivity characteristics of the photodetector built into the radiation thermometer. By further utilizing the spectral transmittance characteristics and spectral sensitivity characteristics to perform a weighted average of the spectral absorption coefficient, it is possible to perform a correction that is closer to the actual one, taking into account the distribution of the spectral absorption coefficient, and it is possible to further improve accuracy.

In addition, in the above-mentioned second observation wavelength selection method, the bandwidths of the two observation wavelengths are set to be the same for processing, but the bandwidths of the two observation wavelengths may be different. For example, in the near-infrared band, the longer the wavelength, the greater the spectral radiance, so the observation bandwidth on the longer wavelength side may be narrower than the shorter wavelength side.

Next, the inventors will explain their findings regarding a method for measuring the thickness of the water film located above the surface of the object to be measured, along with the temperature of the object to be measured, with reference to Figures 16 and 17.

If we consider the situation shown in Figure 6 more precisely as a situation in which cooling water is flowing over the top surface of red-hot steel material, which is an example of an object to be measured, then such a situation can be modeled as shown in Figure 16.

If the temperature of the red-hot steel is high, the water on the upper surface of the steel goes into a film boiling state, and a layer of water vapor is formed between the steel surface and the water film as shown in FIG. 16, and the water film floats from the surface of the steel. In this case, the radiation thermometer is supposed to view the steel, which is the object of measurement, from diagonally above the steel in the vertical direction as shown in FIG. 16. Inside the water film, the light radiated from the steel is absorbed according to the thickness t of the water film, and the radiance attenuates. More specifically, when the angle between the optical axis of the radiation thermometer and the surface normal direction of the object of measurement is θ ₀ , inside the water film, the light radiated from the steel advances at an angle θ ₁ that satisfies the relationship (n _a · sin θ ₀ = n _w · sin θ ₁ ) expressed by Snell's law. Therefore, the radiance of the light radiated from the steel attenuates according to the optical path length (t/cos θ ₁ ). Furthermore, at the interface between the water film and the water vapor layer, and at the interface between the water film and the air layer, interfacial reflection occurs with reflectances ρ ₁ and ρ ₂ , respectively. The radiation resulting from such absorption by the water film and interfacial reflection at the water film interface is measured by a radiation thermometer. Here, water vapor, which is a gas, has optical properties that are completely different from those of liquid water, and is almost transparent in the wavelength band of 940 nm to 1650 nm. In other words, it can be considered that there is no absorption of radiation in the water vapor layer shown in FIG. 16.

The effective spectral transmittance τ ₁ in the above formula (7) is expressed by the following formula (10) using the interface reflection loss at the interface of the water film and the spectral absorption coefficient α ₁ at the wavelength λ ₁ inside the water film.

In addition, the reflectances _ρ1 and _ρ2 at the water film interface are _ρ1 = _ρ2 due to the relationship of the refractive indexes of the layers as described above, so the reflectance values are rewritten as ρ= _ρ1 = _ρ2 . At angles other than θ=0°, it is necessary to consider the reflectance ρ separately as the reflectance _ρp of the p-polarized component and the reflectance _ρs of the s-polarized component. Therefore, the above formula (10) is transformed into the following formula (11). Here, in the following formula (11), the reflectances _ρp and _ρs at the water film/air interface are expressed, for example, as the following formulas (12) and (13).

Here, n _v is the refractive index of water vapor (n _v =1.00), n _w is the refractive index of water (n _w =1.33), and n _a is the refractive index of air (n _a =1.00). In this technology, the wavelengths λ ₁ and λ ₂ are selected so that the spectral absorption coefficient α ₁ at the wavelength λ ₁ and the spectral absorption coefficient α ₂ at the wavelength λ ₂ are equal to each other, and the reflectances ρ _p and ρ _s are constants determined only by the refractive index and refraction angle of each layer, as in the above formulas (12) and (13). Therefore, even if formula (8) is used instead of formula (7), the value of the transmittance τ ₂ is equal to the value of the transmittance τ ₁ .

When the temperature T of the steel material to be measured is determined based on the dichroic ratio shown in the above formula (6), the transmittance τ ₁ at wavelength λ ₁ is calculated by modifying the above formula (4) as shown in the following formula (14). Here, in the following formula (14), the numerator is the radiance value observed by the radiation thermometer, and the denominator corresponds to the radiance value radiated from a black body at temperature T. Also, in the following formula (14), the spectral emissivity ε (λ ₁ ) of the steel material is a stable value of about 0.8 in the wavelength band of λ ₁ = 1.1 μm to 1.3 μm.

Next, by substituting the above equation (10) into the above equation (7) and solving for the thickness t of the water film, we obtain the following equation (15).

In the above formula (15), the spectral absorption coefficient _α1 of water may be a value obtained in a previously conducted experiment or the like. For example, when the combination of wavelengths _λ1 and _λ2 is (1100 nm, 1130 nm), 0.0428 mm ^-1 may be used as the spectral absorption coefficient _α1 of water. Also, when the combination of wavelengths _λ1 and _λ2 is (1190 nm, 1300 nm), 0.129 mm ^-1 may be used as the spectral absorption coefficient _α1 of water.

Therefore, when the temperature T of the steel material to be measured is obtained, the transmittance _τ1 is calculated based on the above formula (14), and the thickness t of the water film can be calculated from the above formula (15) by using the obtained transmittance _τ1 , the measurement value of the radiance obtained by the radiation thermometer, the refractive index of each medium as shown in FIG. 16, the spectral absorption coefficient α of water as described above, and the installation angle θ of the radiation thermometer.

Here, regarding the above formula (15), how the thickness t of the water film changes with the decrease in the spectral transmittance τ was calculated for each of the cases where the angles θ ₀ =0°, 30°, and 45°, and the results obtained are shown in FIG. 17 below. In addition, in the above formula (15), as the spectral absorption coefficient α ₁ of water, α ₁ =0.129 mm ^-1 , which is the value at the wavelength λ ₁ =1.19 μm, was used, and the value shown in FIG. 16 was used for the refractive index. As is clear from FIG. 17, it can be seen that the thickness of the water film increases as the spectral transmittance τ decreases. In addition, since the optical path length of the radiation light in the water film changes depending on the installation angle θ ₀ of the radiation thermometer, the relationship between the spectral transmittance and the water film thickness shown in FIG. 17 also changes slightly depending on the installation angle θ ₀ .

Even in a situation where the surface of red-hot high-temperature steel is covered with film-boiling water, if an accurate temperature T can be obtained by radiation thermometry using a two-color radiation thermometer as shown in the above findings, it is possible to accurately calculate the thickness of the water film. This is the second finding obtained by the inventors.

Based on this finding, the inventors conducted further studies and came up with a more preferable temperature measuring device, as described below, which performs radiation thermometry based on the second finding. In the more preferable temperature measuring device described below, it is possible to accurately measure the temperature of the object to be measured by radiation thermometry using a two-color radiation thermometer, even when measurements are performed in a band in which the spectral absorption coefficient of the absorber has wavelength dependency in order to lower the minimum measurement temperature. In addition, by obtaining the temperature of the object to be measured more accurately, it is possible to more accurately calculate the thickness of the absorber, such as a water film, that covers the surface of the object to be measured.

(Embodiment)
<Configuration of temperature measuring device>
Next, the overall configuration of the temperature measuring device 10, which is an example of a two-color radiation thermometer used in the temperature measuring method according to the embodiment of the present invention, will be described in detail with reference to Figures 18A and 18B. Figures 18A and 18B are explanatory diagrams showing an example of the overall configuration of the temperature measuring device 10 according to the present embodiment.

The temperature measuring device 10 according to this embodiment is a device that detects thermal radiation light in the near-infrared band emitted by a measurement object, and measures the temperature of the measurement object based on the detection result of the radiance of the thermal radiation light. A more preferable temperature measuring device 10 is a device that detects thermal radiation light in the near-infrared band emitted by a measurement object in a state where an absorber having a wavelength-dependent spectral absorption coefficient in the near-infrared band is present at least partially on the light path, and measures the temperature of the measurement object based on the detection result of the radiance of the thermal radiation light. Here, examples of absorbers having a wavelength-dependent spectral absorption coefficient in the near-infrared band include at least one of water, oil, solution, glass, and resin.

In addition, in this embodiment, the near-infrared band is focused on the band of 800 nm to 1600 nm, and particularly preferably, the band of 940 nm to 1350 nm. The reason why the lower limit of the particularly preferred wavelength band is set to 940 nm is that, as shown in FIG. 7, water becomes a semi-transparent body with strong wavelength dependency at wavelengths of 800 nm or more (particularly 940 nm or more) which belong to the near-infrared band. The reason why the upper limit of the particularly preferred wavelength band is set to 1350 nm is that, as also shown in FIG. 7, water becomes opaque at 1350 nm or more when the water film thickness is 10 mm or more.

Such a temperature measuring device 10 mainly includes a measuring unit 101, a calculation processing unit 103, and a memory unit 105, as shown in FIG. 18A, for example.

The measurement unit 101 measures the magnitude of the emitted thermal radiation (observation light) from a measurement object that emits thermal radiation in the near-infrared band, such as a steel plate at a high temperature. In a particularly preferred temperature measurement device 10, the measurement unit 101 measures the thermal radiation of the measurement object at two wavelengths at which the absorber has the same spectral absorption coefficient, and generates measurement data that indicates the detection results of the radiance of the thermal radiation at these two wavelengths.

These measurement units 101 correspond to an optical system consisting of various lenses/lens groups and sensors such as photodetectors in a two-color radiation thermometer, for example. A more detailed configuration of the measurement units 101 will be described later. Furthermore, the two types of wavelengths measured by the measurement units 101 in a particularly preferred temperature measurement device 10 are preset in accordance with the two types of "observation wavelength selection methods" described above.

The measurement unit 101 measures the magnitude of the thermal radiation light from the measurement object and generates measurement data indicating the detection result of the radiance of the thermal radiation light, and outputs the generated measurement data to the calculation processing unit 103 described later.

The arithmetic processing unit 103 is realized by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a communication device, etc. The arithmetic processing unit 103 performs overall control of the measurement processing performed by the measurement unit 101. The arithmetic processing unit 103 also performs arithmetic processing to calculate the temperature of the measurement object based on the measurement data measured by the measurement unit 101. More specifically, the arithmetic processing unit 103 calculates the temperature of the measurement object based on the measurement data corresponding to two types of wavelengths generated by the measurement unit 101 and the relational equation between spectral radiance and temperature derived from Planck's blackbody radiation formula as described above. Information regarding the temperature of the measurement object calculated by the arithmetic processing unit 103 is output as an image via a display screen, etc., output as a printed matter via a printer, etc., or output as data itself.

The detailed configuration of the calculation processing unit 103 will be described later.

The memory unit 105 is realized by, for example, a RAM or a storage device provided in the temperature measuring device 10 according to this embodiment. The memory unit 105 stores various parameters and data such as the spectral absorption coefficient of the absorber of interest, the spectral radiance of the measurement object obtained by analyzing past operation data, and a weighting coefficient used to correct the spectral absorption coefficient. In addition to these data, the memory unit 105 appropriately records various parameters and intermediate processing progress that need to be saved when the temperature measuring device 10 according to this embodiment performs some processing, or various databases and programs. The measurement unit 101 and the calculation processing unit 103 can freely read and write data from the memory unit 105.

The measurement unit 101, the calculation processing unit 103, and the storage unit 105 may be realized inside one measurement device as one function of, for example, a two-color radiation thermometer, as shown in FIG. 18A. The measurement unit 101, the calculation processing unit 103, and the storage unit 105 may be distributed and implemented in multiple devices, as shown in FIG. 18B. In the example shown in FIG. 18B, the functions of the measurement unit 101 and the storage unit 105 are realized inside a measurement unit that functions as, for example, a two-color radiation thermometer, and the functions of the calculation processing unit 103 and the storage unit 105 are realized inside a calculation processing device such as a personal computer, various servers, various process computers, etc. In FIG. 18B, the storage unit 105 is realized as the storage units 105a and 105b in the measurement unit and the calculation processing device, respectively, but the storage unit 105 may be realized only inside the measurement unit, or only inside the calculation processing device.

<Configuration of measurement unit 101>
Next, a detailed description will be given of an example of the configuration of the measurement unit 101 according to this embodiment with reference to Fig. 19 to Fig. 21. Fig. 19 is an explanatory diagram showing a schematic example of the configuration of the measurement unit provided in the temperature measurement device according to this embodiment. Figs. 20 to 21 are explanatory diagrams showing a schematic example of the configuration of a position control mechanism in the measurement unit according to this embodiment.

The measuring unit 101 according to this embodiment corresponds to the optical system in a two-color radiation thermometer, and operates under the control of the calculation processing unit 103 to measure the thermal radiation light in the near-infrared band emitted by the object to be measured. As shown in FIG. 19, the measuring unit 101 has a light receiving unit 111 that receives the thermal radiation light from the object to be measured, a detection unit 113 that detects the thermal radiation light received by the light receiving unit 111, and a position control mechanism 115 that changes the relative positional relationship between the object to be measured and the light receiving unit 111 to cause the light receiving unit 111 to measure the distribution of the thermal radiation light in the width direction of the object to be measured.

In the measurement unit 101 according to this embodiment, the light receiving unit 111 and the detection unit 113 as described above may be optically connected by various known optical transmission mechanisms. Examples of such optical transmission mechanisms include various known optical fibers OF. By connecting the light receiving unit 111 and the detection unit 113 by an optical transmission mechanism such as an optical fiber OF, it becomes possible to arrange the light receiving unit 111 separately from the detection unit 113, which further improves the convenience of using the temperature measurement device according to this embodiment.

As shown in FIG. 19, the light receiving unit 111 has a light receiving lens 121 that receives the thermal radiation light from the object to be measured, and a connection coupler 123 for connecting the thermal radiation light from the object to be measured that has passed through the light receiving lens 121 to the optical fiber OF. The light receiving lens 121 and the connection coupler 123 function as a light guiding optical system that guides the thermal radiation light to the detection unit 113.

The specific configuration of the light receiving unit 111 according to this embodiment is not particularly limited. For example, in FIG. 19, a single biconvex lens is illustrated as the light receiving lens 121, but the light receiving lens 121 may be a lens group composed of multiple optical elements. Furthermore, the lens used for the light receiving lens 121 is not particularly limited, and known optical elements such as spherical lenses and aspherical lenses can be used as appropriate. The connection coupler 123 and the optical fiber OF are also not particularly limited, and various known connection couplers and optical fibers can be used.

The thermal radiation light from the object to be measured is converted into a nearly parallel beam by the light receiving lens 121 of the light receiving unit 111 and reaches the connection coupler 123. The connection coupler 123 connects the thermal radiation light guided from the light receiving lens 121 to one end of the optical fiber OF. The thermal radiation light from the object to be measured that is received by the light receiving unit 111 and then transmitted by the optical fiber OF is guided to the detection unit 113.

As illustrated in FIG. 20, the detection unit 113 includes a connection coupler 151 optically connected to the optical fiber OF, a beam splitter 153, optical filters 155a, 155b, focusing lenses 157a, 157b, and sensors 159a, 159b.

The thermal radiation light from the object to be measured that passes through the connection coupler 151 is guided to the beam splitter 153, which is an example of a branching optical element. The beam of thermal radiation light that reaches the beam splitter 153 is branched into two optical paths by the beam splitter 153.

As shown in FIG. 20, an optical filter 155a, which is an example of a first optical filter, is provided on one of the optical paths after the branching, and an optical filter 155b, which is an example of a second optical filter, is provided on the other optical path after the branching.

The optical filters 155a and 155b function as wavelength selection filters, and select the wavelength of the thermal radiation light to transmit the thermal radiation light having a specific wavelength to the downstream sensors 159a and 159b. Any known optical filters can be used for the optical filters 155a and 155b, as long as they can transmit light of two preset wavelengths (observation wavelengths). As explained in the knowledge regarding the "method of selecting the observation wavelength" above, the optical filters 155a and 155b may be narrow-band wavelength selection filters or general-band (having a finite bandwidth) wavelength selection filters.

The thermal radiation of one of the two observation wavelengths that is transmitted through optical filter 155a is focused by focusing lens 157a onto sensor 159a, which is an example of a first detection element. The thermal radiation of the other of the two observation wavelengths that is transmitted through optical filter 155b is focused by focusing lens 157b onto sensor 159b, which is an example of a second detection element.

The sensors 159a and 159b detect the spectral radiance of the thermal radiation light from the object to be measured, guided by the condenser lenses 157a and 157b, respectively, and generate the obtained luminance signal data. Then, the sensors 159a and 159b each output the obtained luminance signal to the calculation processing unit 103. Such luminance signals correspond to the measurement data indicating the detection result of the radiance of the thermal radiation light.

Here, the sensors 159a and 159b are not particularly limited, and any known sensor may be used as long as it is suitable for the two types of wavelengths described above for detecting thermal radiation light. Examples of such sensors (photodetectors) include a detection element using Si and a detection element using InGaAs.

In FIG. 20, the focusing lenses 157a and 157b are shown as a single biconvex lens, but the focusing lenses 157a and 157b may be a lens group made up of a plurality of lenses. The lenses used for the focusing lenses 157a and 157b are not particularly limited, and well-known optical elements such as spherical lenses and aspherical lenses can be used as appropriate.

Here, in a more preferred temperature measuring device 10 in this embodiment, one of the combinations of two observation wavelengths (i.e., the transmission wavelengths of the optical filters 155a and 155b) is selected to be, for example, 1190 nm from the second wavelength selection region shown in FIG. 12A. In this case, the other wavelength is selected from the vicinity of 1300 nm. Here, as is clear from FIG. 12A, in this wavelength band, the spectral absorption coefficient of water increases as the wavelength becomes longer.

The spectral absorption coefficient at a wavelength selected from around 1300 nm must match the spectral absorption coefficient at a wavelength of 1190 nm. If they do not match, the principle explained above will not hold true, and as the degree of match decreases, temperature measurement errors will occur.

In the following, the occurrence of temperature measurement errors in the more preferred temperature measuring device 10 was confirmed by the following test.
That is, five types of wavelength selection filters with a half-width of the transmission band of about 10 nm and center wavelengths of the transmission band of 1300.0 nm, 1301.8 nm, 1303.2 nm, 1304.2 nm, and 1304.7 were prepared, and the difference in temperature indication value between the presence and absence of water as an absorber on a measurement object at 900° C. was investigated. The obtained results are shown in FIG.

As is clear from Figure 21, if a wavelength selection filter with a center wavelength of 1303.2 nm is used, the temperature measurement value does not change regardless of the presence or absence of water. This is because the spectral absorption coefficient of water (the spectral transmittance when radiation passes through water) at wavelengths of 1190 nm and 1303.2 nm exactly matches. In other words, by selecting such a center wavelength, it is possible to measure the temperature without being affected by water at all.

On the other hand, if the central wavelength of the transmission band of the wavelength selection filter is shifted from 1303.2 nm to the long wavelength side by 1 nm, the mismatch in the spectral transmittance of water will cause a temperature measurement error of about 10°C when the thickness of the water film is 2.5 mm, and a temperature measurement error of about 20°C when the thickness of the water film is 5 mm. As is clear from these results, it is preferable that the transmission wavelength band (central wavelength) of the wavelength selection filter used as the optical filters 155a and 155b is selected according to the expected thickness of the water film and the required accuracy of the temperature measurement error. For example, if a water film with a maximum thickness of about 5 mm is expected, it is preferable that the transmission wavelength of the wavelength selection filter is selected with an accuracy of about ±0.5 nm. Also, if it is desired to keep the temperature measurement error within the range of ±10°C, it is preferable that the width of the transmission wavelength band of the wavelength selection filter is about 1.0 nm.

Returning to FIG. 19 again, the position control mechanism 115 according to this embodiment will be described.
As mentioned above, the position control mechanism 115 according to this embodiment is a mechanism that changes the relative positional relationship between the measurement object and the light receiving unit 111, and causes the light receiving unit 111 to measure the distribution of thermal radiation light in the width direction of the measurement object. This makes it possible for the temperature measuring device 10 according to this embodiment to measure the temperature distribution in the width direction, including the corner portions, of the measurement object of interest.

When a minimum amount of radiation light, which is the minimum amount of radiation light required for temperature calculation within the measurement field of view, is specified in advance for the sensors 159a and 159b used in the measurement, it is preferable that the position control mechanism 115 changes the relative positional relationship between the measurement object and the light receiving unit 111 for the sensors 159a and 159b until the amount of radiation light detected within the measurement field of view becomes less than the minimum amount of radiation light. This makes it possible for the temperature measuring device 10 according to this embodiment to more accurately measure the temperature distribution in the width direction, including the corners, of the measurement object of interest.

The position control mechanism 115 according to this embodiment will be described in more detail below with reference to Figures 22A to 23.

The position control mechanism 115 according to this embodiment may be a drive mechanism that moves the light receiving unit 111 along the width direction of the measurement object, as shown, for example, in FIG. 22A. In FIG. 22A, the direction perpendicular to the paper surface is the longitudinal direction of the measurement object, the direction normal to the surface of the measurement object is the thickness direction of the measurement object, and the direction perpendicular to both the longitudinal direction and the thickness direction is the width direction of the measurement object. In this case, the drive mechanism functioning as the position control mechanism 115 moves the light receiving unit 111 along the width direction of the measurement object, thereby changing the relative positional relationship between the light receiving unit 111 and the measurement object, and it becomes possible to measure the temperature distribution in the width direction of the measurement object of interest.

Such a driving mechanism is not particularly limited, and various known driving mechanisms, such as actuators, can be used as appropriate.

The position control mechanism 115 according to this embodiment may be an angle control mechanism that changes the angle between the surface normal direction of the measurement object and the optical axis of the light receiving unit 111. For example, in FIG. 22B, the direction perpendicular to the paper surface is the longitudinal direction of the measurement object, the surface normal direction of the measurement object is the thickness direction of the measurement object, and the direction perpendicular to both the longitudinal direction and the thickness direction is the width direction of the measurement object. In this case, a rotation axis is provided in a direction parallel to the longitudinal direction, and the light receiving unit 111 rotates around the rotation axis within a range of -φ° to +φ°, changing the relative positional relationship between the light receiving unit 111 and the measurement object, making it possible to measure the temperature distribution in the width direction of the measurement object of interest.

Here, the rotation angle φ corresponds to the angle between the optical axis of the light receiving unit 111 and the surface normal direction of the measurement object. The magnitude of the rotation angle φ is not particularly limited, and may be set appropriately depending on the width of the measurement object and the installation height of the light receiving unit 111 (height from the surface of the measurement object). However, if the magnitude |φ| of the rotation angle φ exceeds 45°, the energy of the thermal radiation light received by the light receiving unit 111 may become too small, so the magnitude |φ| of the rotation angle φ is preferably 0° or more and 45° or less. Note that such a rotation angle φ corresponds to the angle θ ₀ in the model shown in FIG. 16.

As the angle adjustment mechanism as shown in FIG. 22B, for example, various known swivel mechanisms using actuators or the like may be applied, or various imaging lenses such as imaging lenses with a tilt mechanism or imaging lenses with a tilt mechanism and a shift mechanism may be used.

In addition, as an angle control mechanism for changing the angle between the surface normal direction of the measurement object and the optical axis of the light receiving unit 111, for example, a mechanism using a rotating mirror as shown in FIG. 23 can be used. In FIG. 23, the direction perpendicular to the paper surface is the width direction of the measurement object, the surface normal direction of the measurement object is the thickness direction of the measurement object, and the direction perpendicular to both the longitudinal direction and the thickness direction is the longitudinal direction of the measurement object. In the example shown in FIG. 23, a mirror M is provided between the light guide optical system (i.e., the light receiving mirror 121 and the connection coupler 123) in the light receiving unit 111 and the measurement object, at an angle with respect to the surface normal direction of the measurement object, and the surface normal direction of the measurement object and the optical axis connecting the light receiving lens 121 and the connection coupler 123 are set to be perpendicular to each other.

At this time, the angle between the surface normal direction of the measurement object and the optical axis of the light receiving unit 111 can be changed by rotating the mirror M by a predetermined angle around the optical axis connecting the light receiving lens 121 and the connection coupler 123 (in other words, the longitudinal direction of the measurement object) as the axis of rotation. This changes the relative positional relationship between the light receiving unit 111 and the measurement object, making it possible to measure the temperature distribution in the width direction of the measurement object of interest.

23, the magnitude of the rotation angle around the rotation axis of the mirror M is not particularly limited, and may be set appropriately depending on the width of the object to be measured and the installation height of the light receiving unit 111 (height from the surface of the object to be measured). However, if the rotation angle exceeds 45°, the energy of the thermal radiation light received by the light receiving unit 111 may become too small, so the rotation angle is preferably between 0° and 45°.

The angle adjustment mechanism shown in FIG. 23 can be realized by using a known driving mechanism, such as an actuator, and various known mirrors.

In addition, in the measurement unit 101 according to this embodiment, the position control mechanism 115 may be a combination of a drive mechanism as shown in FIG. 22A and an angle adjustment mechanism as shown in FIG. 22B or FIG. 23.

Here, the moving speed in the width direction of the drive mechanism as shown in FIG. 22A and the rotation speed of the angle adjustment mechanism as shown in FIG. 22B and FIG. 23 are not particularly limited. However, if the measurement object is moving, for example, on a conveyor line, it is preferable to determine the moving speed and rotation speed so as to synchronize with the movement timing of the measurement object, taking into account the conveying speed of the measurement object, and it is also preferable to synchronize the detection rate (measurement period) of the sensors 159a and 159b in the detection unit 113 with the conveying speed of the measurement object.

A brief explanation of an example of the configuration of the measurement unit 101 according to this embodiment has been given above with reference to Figures 19 to 23.

<Example of the configuration of the arithmetic processing unit 103>
Next, a configuration example of the arithmetic processing unit 103 according to this embodiment will be described with reference to Fig. 24 and Fig. 25. Fig. 24 is a block diagram showing a configuration example of the arithmetic processing unit 103 according to this embodiment, and Fig. 25 is a block diagram showing a configuration example of the arithmetic processing unit 103 in a more preferable temperature measuring device 10 according to this embodiment.

As shown in FIG. 24, the calculation processing unit 103 according to this embodiment mainly includes a measurement control unit 171, a data acquisition unit 173, a temperature calculation unit 175, a result output unit 177, and a display control unit 179.

The measurement control unit 171 is realized by, for example, a CPU, a ROM, a RAM, an input device, an output device, a communication device, etc. The measurement control unit 171 is a processing unit that comprehensively controls the functions of the temperature measuring device 10 according to this embodiment. In addition, the measurement control unit 171 controls the operation of the measurement unit 101 so as to measure thermal radiation light from the measurement object at two types of wavelengths as described above. Furthermore, the measurement control unit 171 can also output various setting values such as measurement conditions of thermal radiation light including device placement conditions to the temperature calculation unit 175 and thickness calculation unit 177 as necessary.

The data acquisition unit 173 is realized by, for example, a CPU, a ROM, a RAM, a communication device, etc. The data acquisition unit 173 acquires the luminance signals at the two wavelengths generated by the measurement unit 101, and outputs them to the temperature calculation unit 175 described below. The data acquisition unit 173 may also associate the acquired luminance signals at the two wavelengths with time information regarding the date and time when the luminance signals were acquired, and store the associated information in the storage unit 105 as history information.

The temperature calculation unit 175 is realized by, for example, a CPU, a ROM, a RAM, etc. The temperature calculation unit 175 uses the luminance signals at two types of wavelengths output from the data acquisition unit 173 to calculate a dichroic ratio (in other words, a ratio of spectral radiances) by dividing one luminance signal by the other luminance signal. The temperature calculation unit 175 also calculates the temperature of the measurement object using the calculated dichroic ratio and a relational expression between the dichroic ratio and temperature.

When the temperature calculation unit 175 calculates the dichroic ratio R, there is no particular limitation as to which of the luminance signals of the two wavelengths _λ1 and _λ2 should be used as the denominator and which of the luminance signals should be used as the numerator, as long as the reference luminance signal is not changed during the calculation process.

The temperature calculation unit 175 outputs information about the temperature T of the object to be measured calculated as described above to the result output unit 177, which will be described later.

The result output unit 177 is realized by, for example, a CPU, a ROM, a RAM, an output device, a communication device, etc. The result output unit 177 outputs information related to the temperature T of the object to be measured output from the temperature calculation unit 175 to the user of the temperature measurement device 10. Specifically, the result output unit 177 associates data corresponding to the temperature measurement result with time data related to the date and time when the data was generated, and outputs the data to various servers or control devices, or outputs the data as paper media using an output device such as a printer. In addition, the result output unit 177 may output data corresponding to the judgment result to various information processing devices such as an externally provided computer, or may output the data to various recording media.

When the result output unit 177 outputs data corresponding to the temperature measurement result to an output device such as a display provided in the temperature measuring device 10 or to a display of various external devices, the result output unit 177 cooperates with the display control unit 179 described later to output the judgment result.

The display control unit 179 is realized by, for example, a CPU, a ROM, a RAM, an output device, a communication device, etc. The display control unit 179 performs display control when data corresponding to the temperature measurement results and the thickness calculation results are displayed on various display devices such as a display. This allows the user of the temperature measuring device 10 to immediately grasp the measurement results regarding the temperature of the measurement object and the calculation results regarding the thickness of the absorbent body.

Moreover, in this embodiment, the more preferable calculation processing unit 103 of the temperature measuring device 10 mainly includes a measurement control unit 171, a data acquisition unit 173, a display control unit 179, a temperature calculation unit 181, a thickness calculation unit 183, and a result output unit 185, as shown in FIG. 25.

Here, the measurement control unit 171, data acquisition unit 173, and display control unit 179 in the more preferred temperature measurement device 10 have the same configuration as the calculation processing unit 103 shown in FIG. 24 and provide the same effects, so detailed description will be omitted below.

The temperature calculation unit 181 is realized by, for example, a CPU, a ROM, a RAM, etc. The temperature calculation unit 181 uses the luminance signals at two types of wavelengths output from the data acquisition unit 173 to calculate a dichroic ratio (in other words, a ratio of spectral radiances) by dividing one luminance signal by the other luminance signal. The temperature calculation unit 181 also calculates the temperature of the measurement object using the calculated dichroic ratio and a relational expression between the dichroic ratio and temperature.

As is clear from the above formula (6), the dichroic ratio R can be calculated by dividing one of the luminance signals at two wavelengths by the other luminance signal. On the other hand, in the more preferable temperature measuring device 10 of this embodiment, the absorption of thermal radiation light by the absorber is taken into account as shown in the above formulas (7) and (8), so that the dichroic ratio R is expressed by the following formula (16) when the above formulas (7) and (8) are used to derive the formula in the same way as formula (6).

As is clear from the findings described above, in the measuring unit 101 according to this embodiment, the spectral radiance is measured at wavelengths where the spectral absorption coefficients of the absorbers are the same. Therefore, the terms related to the absorption by the absorber shown in the first term of the middle side of the above formula (16) cancel each other out in the numerator and denominator, resulting in a value of 1. Therefore, R _λ and Λ on the right side of the above formula (16) are the same as those in the above formulas (6a) and (6b).

Here, R _λ and Λ shown in formula (6a) and formula (6b) are constants determined from the measurement conditions obtainable from the measurement unit 101. Therefore, the temperature calculation unit 181 can calculate the temperature T of the object to be measured by using the calculated dichroic ratio R and the relational expression (leftmost side=rightmost side) in the above formula (16).

When the temperature calculation unit 181 calculates the dichroic ratio R, there is no particular limitation as to which of the luminance signals of the two wavelengths _λ1 and _λ2 should be used as the denominator and which of the luminance signals should be used as the numerator, as long as the reference luminance signal is not changed during the calculation process.

Furthermore, the temperature calculation unit 181 may directly calculate the temperature using the above formulas (7) and (8) without using the dichroic ratio R represented by the above formula (16). That is, if the emissivity ε at the two wavelengths λ ₁ and λ ₂ are known, the unknowns in the above formulas (7) and (8) are the temperature T and the thickness t of the water film. Therefore, the temperature calculation unit 175 can calculate the temperature T by solving the simultaneous equations by solving the simultaneous equations of the above formulas (7) and (8). Furthermore, even if the emissivity ε at the two wavelengths λ ₁ and λ ₂ is unknown, if the emissivity ε at the wavelength λ ₁ and the emissivity ε at the wavelength λ ₂ are equal to each other, it is possible to directly calculate the temperature T by solving the simultaneous equations of the above formulas (7) and (8). Here, the method of solving the simultaneous equations is not particularly limited, and for example, if it is possible to solve it analytically, it may be solved analytically, it may be solved by numerical calculation, or it may be solved as an optimum value problem.

The temperature calculation unit 181 outputs information about the temperature T of the object to be measured calculated as described above to the thickness calculation unit 183 and the result output unit 185, which will be described later.

The thickness calculation unit 183 is realized by, for example, a CPU, a ROM, a RAM, etc. The thickness calculation unit 183 further calculates the thickness of the absorber using the blackbody radiance at one of the two wavelengths calculated from the obtained temperature of the measurement object, the radiance of the measured thermal radiation light, the spectral absorption coefficient of the absorber at the two wavelengths, the reflectance of the thermal radiation light at the interface of the absorber on the measurement object side, the reflectance of the thermal radiation light at the interface of the absorber on the measurement unit 101 side, and the setting conditions of the measurement unit 101 at the time of measurement.

More specifically, the thickness calculation unit 183 calculates the transmittance τ based on the above formula (14) using the measured values of the luminance signals (spectral radiance) at two types of wavelengths output from the data acquisition unit 173 and the temperature T of the measurement object calculated by the temperature calculation unit 181. Furthermore, the thickness calculation unit 183 calculates the thickness t of the absorber based on the above formula (15) using the obtained transmittance τ, the reflectances ρ _p and ρ _s of the thermal radiation light in the absorber, the spectral absorption coefficient α of the absorber, and the installation conditions of the light receiving unit 111 in the measurement unit 101 (specifically, the angle θ between the surface normal direction of the measurement object and the optical axis of the light receiving unit 111).

The thickness calculation unit 183 outputs information regarding the thickness t of the absorbent body calculated as described above to the result output unit 185, which will be described later.

The result output unit 185 is realized by, for example, a CPU, a ROM, a RAM, an output device, a communication device, etc. The result output unit 185 outputs information on the temperature T of the measurement object output from the temperature calculation unit 181 and information on the thickness t of the absorbent body output from the thickness calculation unit 183 to the user of the temperature measurement device 10. Specifically, the result output unit 185 outputs data corresponding to the temperature measurement results and the thickness calculation results to various servers or control devices, or outputs the data as paper media using an output device such as a printer, in association with time data on the date and time when the data was generated. In addition, the result output unit 185 may output data corresponding to the judgment result to various information processing devices such as an externally provided computer, or may output the data to various recording media.

In addition, when the result output unit 185 outputs data corresponding to the temperature measurement results and the thickness calculation results to an output device such as a display provided in the temperature measuring device 10 or to a display of various external devices, the result output unit 185 works in cooperation with the display control unit 179 to output the judgment results.

The above shows an example of the functions of the arithmetic processing unit 103 according to this embodiment. Each of the above components may be configured using general-purpose parts and circuits, or may be configured using hardware specialized for the function of each component. In addition, the functions of each component may all be performed by a CPU or the like. Therefore, it is possible to change the configuration used as appropriate depending on the technical level at the time of implementing this embodiment.

It is possible to create a computer program for implementing each function of the arithmetic processing unit according to this embodiment as described above, and to install it in a personal computer or the like. It is also possible to provide a computer-readable recording medium on which such a computer program is stored. The recording medium is, for example, a magnetic disk, an optical disk, a magneto-optical disk, or a flash memory. The computer program may also be distributed, for example, via a network, without using a recording medium.

The configuration of the temperature measuring device 10 according to this embodiment has been described in detail above with reference to Figures 18A to 25.

Depending on the width of the object being measured, it may not be possible to measure the temperature across the entire width of the object using only one temperature measuring device 10. In such cases, by installing multiple temperature measuring devices 10 according to this embodiment along the width of the object, it is possible to measure the temperature across the entire width of the object.

<Hardware configuration>
Next, a hardware configuration of the temperature measuring device 10 according to the embodiment of the present invention will be described in detail with reference to Fig. 26. Fig. 26 is a block diagram for explaining the hardware configuration of the temperature measuring device 10 according to the embodiment of the present invention.

The temperature measuring device 10 mainly includes a CPU 901, a ROM 903, and a RAM 905. The temperature measuring device 10 further includes a host bus 907, a bridge 909, an external bus 911, an interface 913, a measuring unit 101, an input device 915, an output device 917, a storage device 919, a drive 921, a connection port 923, and a communication device 925.

The CPU 901 functions as a central processing device and control device, and controls all or part of the operation within the temperature measuring device 10 in accordance with various programs recorded in the ROM 903, RAM 905, storage device 919, or removable recording medium 927. The ROM 903 stores programs and calculation parameters used by the CPU 901. The RAM 905 temporarily stores programs used by the CPU 901 and parameters that change appropriately during program execution. These are interconnected by a host bus 907 consisting of an internal bus such as a CPU bus.

The host bus 907 is connected to an external bus 911, such as a PCI (Peripheral Component Interconnect/Interface) bus, via a bridge 909.

As described above, the measurement unit 101 detects the thermal radiation from the object to be measured and measures the magnitude of the spectral radiance.

The input device 915 is, for example, an operating means operated by the user, such as a mouse, keyboard, touch panel, button, switch, or lever. The input device 915 may also be, for example, a remote control means (so-called remote control) that uses infrared rays or other radio waves, or an external connection device 929 such as a mobile phone or PDA that supports the operation of the temperature measuring device 10. The input device 915 is further composed of, for example, an input control circuit that generates an input signal based on information input by the user using the above operating means and outputs it to the CPU 901. The user of the temperature measuring device 10 can input various data to the temperature measuring device 10 and instruct processing operations by operating this input device 915.

The output device 917 is composed of devices capable of visually or audibly notifying the user of acquired information. Such devices include display devices such as CRT display devices, liquid crystal display devices, plasma display devices, EL display devices, and lamps, audio output devices such as speakers and headphones, printers, mobile phones, facsimiles, etc. The output device 917 outputs, for example, the results obtained from the various processes performed by the temperature measuring device 10. Specifically, the display device displays the results obtained from the various processes performed by the temperature measuring device 10 in text or images. On the other hand, the audio output device converts audio signals consisting of reproduced voice data, acoustic data, etc. into analog signals and outputs them.

The storage device 919 is a data storage device configured as an example of a storage unit of the temperature measuring device 10. The storage device 919 is configured, for example, with a magnetic storage device such as a hard disk drive (HDD), a semiconductor storage device, an optical storage device, or a magneto-optical storage device. This storage device 919 stores the programs and various data executed by the CPU 901, as well as various data acquired from the outside.

The drive 921 is a reader/writer for recording media, and is built into the temperature measuring device 10 or attached externally. The drive 921 reads information recorded on a removable recording medium 927, such as a magnetic disk, optical disk, magneto-optical disk, or semiconductor memory, and outputs the information to the RAM 905. The drive 921 can also write information to a removable recording medium 927, such as a magnetic disk, optical disk, magneto-optical disk, or semiconductor memory, that is mounted on the drive 921. The removable recording medium 927 is, for example, a DVD medium, an HD-DVD medium, or a Blu-ray (registered trademark) medium. The removable recording medium 927 may also be a CompactFlash (registered trademark) (CompactFlash: CF), a flash memory, or an SD memory card (Secure Digital memory card), etc. The removable recording medium 927 may also be, for example, an integrated circuit card (IC card) equipped with a non-contact IC chip or an electronic device.

The connection port 923 is a port for directly connecting a device to the temperature measuring device 10. Examples of the connection port 923 include a USB (Universal Serial Bus) port, an IEEE 1394 port, and a SCSI (Small Computer System Interface) port. Other examples of the connection port 923 include an RS-232C port, an optical audio terminal, and an HDMI (High-Definition Multimedia Interface) port. By connecting an external connection device 929 to this connection port 923, the temperature measuring device 10 can directly obtain various data from the external connection device 929 or provide various data to the external connection device 929.

The communication device 925 is, for example, a communication interface configured with a communication device for connecting to the communication network 931. The communication device 925 is, for example, a wired or wireless LAN (Local Area Network), Bluetooth (registered trademark), or a communication card for WUSB (Wireless USB). The communication device 925 may also be a router for optical communication, a router for ADSL (Asymmetric Digital Subscriber Line), or a modem for various communications. This communication device 925 can transmit and receive signals, for example, between the Internet and other communication devices in accordance with a predetermined protocol such as TCP/IP. The communication network 931 connected to the communication device 925 is configured with a network connected by wire or wirelessly, and may be, for example, the Internet, a home LAN, infrared communication, radio wave communication, or satellite communication.

The above shows an example of a hardware configuration capable of realizing the functions of the temperature measuring device 10 according to an embodiment of the present invention. Each of the above components may be configured using general-purpose parts, or may be configured using hardware specialized for the function of each component. Therefore, the hardware configuration used can be changed as appropriate depending on the technical level at the time of implementing this embodiment.

(Temperature measurement method)
Next, the temperature measuring method according to this embodiment will be described with reference to Fig. 27 to Fig. 31. Fig. 27 to Fig. 31 are explanatory diagrams for explaining the temperature measuring method according to this embodiment.

As mentioned above, the temperature measurement method according to this embodiment is a method of detecting thermal radiation light in the near infrared band emitted by the object to be measured, and measuring the temperature of the object to be measured based on the detection result of the radiance of the thermal radiation light. More specifically, in the temperature measurement method according to this embodiment, a two-color radiation thermometer having a light receiving unit that receives the thermal radiation light of the object to be measured, a detection unit that detects the thermal radiation light received by the light receiving unit, and a position control mechanism that changes the relative positional relationship between the object to be measured and causes the light receiving unit to measure the distribution of the thermal radiation light in the width direction of the object to be measured is used to detect the thermal radiation light of the object to be measured and measure the temperature distribution along the width direction of the object to be measured. By using a two-color radiation thermometer, it is possible to suppress the occurrence of temperature errors due to the lack of a field of view of the radiation thermometer even at the corners of the object to be measured, and the temperature of the object to be measured can be measured more accurately while suppressing temperature measurement errors at the ends of the object.

In addition, by using the more preferable temperature measuring device 10 in this embodiment, it is possible to measure the temperature of the object to be measured more accurately even if an absorbent such as water is present between the object to be measured and the light receiving unit 111.

In the temperature measurement method according to the present embodiment, as shown in FIG. 27, the position control mechanism 115 is used to change the relative positional relationship between the light receiving unit 111 and the object to be measured, thereby making it possible to measure the temperature distribution in the width direction of the object to be measured. In this case, in order to more accurately measure the temperature of the corner of the object to be measured by the temperature measurement device 10, it is preferable that the position control mechanism 115 changes the relative positional relationship between the object to be measured and the light receiving unit 111 so that the object to be measured exists until the amount of radiation light actually detected becomes less than the minimum amount of radiation light, after previously specifying the minimum amount of radiation light, which is the minimum amount of radiation light required for temperature calculation, within the measurement field of the two-color radiation thermometer as shown in FIG. 27. In other words, it is preferable that the position control mechanism 115 controls the position of the light receiving unit 111 so that the amount of radiation light from the area occupied by the object to be measured within the measurement field of view is equal to or greater than the minimum amount of radiation light, as shown in the lower left diagram of FIG. 27. This makes it possible to more accurately measure the temperature of the object to be measured.

In addition, the position where something other than the measurement object is present within the measurement field of view of the temperature measuring device 10 can be regarded as the starting position of a corner portion in the width direction of the measurement object, and the corner portion of the measurement object can be considered to be up to the end of the measurement object in the width direction. Furthermore, a position where nothing other than the measurement object is present within the measurement field of view can be regarded as an area other than the corner portion in the width direction of the measurement object.

In the two-color radiation thermometer (temperature measuring device 10) described above, the radiance of the thermal radiation light at each of the two wavelengths of interest can be set to be output independently of each other, and the following control can be performed while scanning the temperature distribution in the width direction of the object to be measured.

For example, as shown in FIG. 28, when something other than the object to be measured is located within the range of the measurement field of the radiance of the two-color radiation thermometer, the temperature measuring device 10 measures the temperature of the object to be measured using the radiance of the thermal radiation light at each of the two wavelengths of interest (in other words, in the two-color mode in which it functions as a two-color radiation thermometer), and when the object to be measured occupies the range of the measurement field of view, the temperature measuring device 10 may measure the temperature of the object to be measured using the radiance of the thermal radiation light at one of the two wavelengths of interest (in other words, in the monochromatic mode in which it functions as a monochromatic radiation thermometer). As a result, in corners where temperature measurement errors are likely to occur, temperature measurement is performed in the two-color mode, which allows more accurate temperature measurement, while in areas other than the corners of the object to be measured where temperature measurement errors are relatively suppressed, temperature measurement can be performed in the monochromatic mode, which has a relatively small computational load.

In addition, it is also possible to perform a control similar to that shown in FIG. 28 while paying attention to the angle between the optical axis of the light receiving unit 111 and the surface normal direction of the measurement object in the angle control mechanism shown in FIG. 22B or FIG. 23. Here, as shown in the schematic diagram of FIG. 29, the distance from the temperature measuring device 10 to the measurement object (more specifically, the distance from the light receiving unit 111 to the measurement object. It can also be considered as the installation height of the light receiving unit 111) is H [mm], the width of the measurement object is W [mm], and the size of the measurement diameter of the temperature measuring device 10 is D _L [mm]. As shown in the schematic diagram of FIG. 29, the size |φ| of the angle φ when the end of the measurement diameter coincides with the position of the corner part of the measurement object can be expressed as |φ|=|tan ^-1 [{(W/2)-(D _L /2)}/H]| from the geometric relationship shown in FIG. 29. As a result, when the temperature measuring device 10 is scanning the temperature distribution in the width direction of the object to be measured, if the angle φ between the surface normal of the object to be measured and the optical axis of the light receiving unit 111 exceeds the value expressed by |φ| = |tan ^-1 [{(W/2) - (D _L /2)}/H]|, something other than the object to be measured will be present inside the measurement diameter, and the temperature measuring device 10 will function in a two-color mode and measure the temperature of the object to be measured using the radiance of the thermal radiation light at each of the two wavelengths of interest. On the other hand, when the magnitude of the angle φ between the surface normal direction of the object to be measured and the optical axis of the light receiving unit 111 is equal to or less than the value expressed by |φ| = |tan ^-1 [{(W/2) - (D _L /2)}/H]|, there is nothing other than the object to be measured inside the measurement diameter, so the temperature measuring device 10 may function in a monochromatic mode and measure the temperature of the object to be measured using the radiance of the thermal radiation light at either one of the two wavelengths of interest.

When controlling the switching between the two-color mode and the monochromatic mode as described above, it is preferable that the wavelength of the thermal radiance used in the monochromatic mode is a wavelength that is not easily affected by absorbers such as water.

The temperature of the object measured according to the method described above is a temperature calculated based on information obtained from the entire measurement field of view. However, when outputting the obtained temperature, it is important to associate the temperature with the position in the width direction of the object. Therefore, in the temperature measurement method according to this embodiment, when outputting the temperature of the object, it is preferable to identify the center of gravity of the area occupied by the object in the measurement field of view of the temperature measurement device 10, and output the obtained measurement result in association with the identified center of gravity. By outputting the temperature measurement result in association with the center of gravity of the area occupied by the object in the measurement field of view, it is possible to more accurately grasp the temperature distribution along the width direction of the object.

As shown in FIG. 30A, when the entire measurement field of view of the temperature measuring device 10 is occupied by the measurement object, the center of gravity of the area occupied by the measurement object in the measurement field of view is equal to the center of the measurement field of view.

On the other hand, as shown in FIG. 30B, when an area other than the measurement object is occupied within the measurement field of view of the temperature measuring device 10, the position of the center of gravity of the area occupied by the measurement object within the measurement field of view will be different from the center position of the measurement field of view. Therefore, it is preferable that the temperature calculation unit 181 in the calculation processing unit 103 of the temperature measuring device 10 according to this embodiment calculates the position of the center of gravity of the area occupied by the measurement object within the measurement field of view as follows, and associates it with the obtained measurement result.

Here, consider the case where there is an area occupied by the measurement target (the shaded arc portion in FIG. 31) as shown in FIG. 31. In this case, as shown in FIG. 31, the half angle of the arc is θ, the radius of the measurement field of view is r, the chord length is H, and half the chord length is h. In this case, the area S ₁ of the measurement field of view and the area S ₂ of the arc are expressed by formulas (21) and (22), respectively. Furthermore, from the geometrical relationship shown in FIG. 31, the following formulas (23) and (24) hold.

The parameter x in FIG. 31 can be calculated from the geometric relationship: "end position of the measurement object - (center position O of the measurement field of view - radius r of the measurement field of view)". It is also possible to specify in advance a relational expression that expresses the relationship between the attenuation rate expressed by "Equation (22)/Equation (21)" and the parameter x, and specify the value of the parameter x that corresponds to the attenuation rate of the actually measured radiance.

If the value of the parameter x during actual measurement can be specified as described above, the center of gravity position _XG of interest can be calculated from the following equation (25).

The temperature measurement method according to this embodiment has been described above with reference to Figures 27 to 31.

In addition, in the temperature measurement method according to this embodiment, multiple temperature measurement devices 10 may be installed near the corners of the object to be measured, and the temperature measurement results obtained from each temperature measurement device 10 may be evaluated to evaluate the temperature of the corners.

It is also possible to use a thermoviewer or the like capable of measuring thermal radiation at a specific wavelength as the temperature measuring device 10.

A temperature measuring device 10 according to the present invention (wavelength _λ1 = 1.2 μm, _λ2 = 1.3 μm, detector: InGaAs detector) was prepared, and a measurement object was a 2200 mm wide red-hot steel material heated to 900° C. or higher, and the temperature near its end was measured using a general monochromatic thermometer (wavelength λ = 0.8 μm, Si detector) and the temperature measuring device 10. The separation distance between each thermometer and the measurement object was 1174 mm for the monochromatic thermometer and 2000 mm for the temperature measuring device 10, so that the measurement diameter of both was 49 mm.

As shown diagrammatically in Figure 30, the state in which the edge of the measurement field of view of each thermometer is in contact with the corner portion is defined as a displacement amount = 0, and each thermometer is displaced in the direction shown in Figure 32. By displacing each thermometer in this way, a defect in the field of view occurs.

The results are shown in FIG.
As is clear from Figure 33, when a monochromatic thermometer is used, as soon as the displacement exceeds 0 and a visual field defect occurs, the temperature immediately drops, whereas with the temperature measuring device 10 of the present invention, it can be confirmed that the temperature can be measured with high accuracy from the time when a visual field defect occurs until the temperature is displaced by 29 mm.

Furthermore, a temperature measuring device 10 (wavelength _λ1 =1.2 μm, _λ2 =1.3 μm, detector: InGaAs detector) according to the present invention was prepared, and a general monochromatic thermometer (wavelength λ=1.0 μm, InGaAs detector) and the temperature measuring device 10 were used to measure the temperature of a slab during casting in a continuous casting machine. The results obtained are shown in FIG. 34. In FIG. 34, the measurement results obtained are output in association with the center of gravity position of the measurement field of view.

As is clear from Figure 34, up to the very edge of the 1,500 mm wide slab (a position around 750 mm in Figure 34), the single-color thermometer and the temperature measuring device 10 output almost the same temperature.

On the other hand, when focusing on the very edge, a typical single-color thermometer indicates a high temperature of 650 to 700°C even after passing the very edge, whereas the temperature measuring device 10 of the present invention indicates the lower limit temperature after passing the very edge. From these results, it was confirmed that the temperature measuring method using the temperature measuring device 10 of the present invention can accurately measure the temperature of the object to be measured.

The above describes in detail preferred embodiments of the present invention with reference to the attached drawings, but the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

REFERENCE SIGNS LIST 10 Temperature measuring device 101 Measurement unit 103 Arithmetic processing unit 105 Memory unit 111 Light receiving unit 113 Detection unit 121 Light receiving lens 123, 151 Connection coupler 153 Beam splitter 155a, 155b Optical filter 157a, 157b Condenser lens 159a, 159b Sensor 171 Measurement control unit 173 Data acquisition unit 175, 181 Temperature calculation unit 183 Thickness calculation unit 177, 185 Result output unit 179 Display control unit

Claims (15)

A temperature measurement method for detecting thermal radiation in the near infrared band emitted by a red-hot steel material as a measurement object, and measuring the temperature of the red-hot steel material based on a detection result of the radiance of the thermal radiation, comprising:
a two-color radiation thermometer having a light receiving unit that receives the thermal radiation light from the red-hot steel material, a detection unit that detects the thermal radiation light received by the light receiving unit, and a position control mechanism that changes the relative positional relationship between the red-hot steel material and the light receiving unit to cause the light receiving unit to measure the distribution of the thermal radiation light in the width direction of the red-hot steel material, detecting the thermal radiation light from the red-hot steel material and measuring the temperature distribution along the width direction of the red-hot steel material including the vicinity of the end portion of the red-hot steel material;
The two-color radiation thermometer has a minimum amount of radiation light required for temperature calculation within a circular measurement field of view of the two-color radiation thermometer, the minimum amount of radiation light being specified in advance,
the position control mechanism changes a relative positional relationship between the red-hot steel material and the light receiving unit until an amount of radiated light detected within the circular measurement field of the two-color radiation thermometer becomes less than the minimum amount of radiated light;
A temperature measurement method in which, when there is an area within the circular measurement field of view occupied by something other than the red-hot steel material, the measurement result of the temperature of the red-hot steel material is output in correspondence with a center of gravity position calculated from the center position and radius of the circular measurement field of view of the two-color radiation thermometer and the end position of the red-hot steel material within the circular measurement field of view. A temperature measurement method for detecting thermal radiation in the near infrared band emitted by a red-hot steel material as a measurement object, and measuring the temperature of the red-hot steel material based on a detection result of the radiance of the thermal radiation, comprising:
a two-color radiation thermometer having a light receiving unit that receives the thermal radiation light from the red-hot steel material, a detection unit that detects the thermal radiation light received by the light receiving unit, and a position control mechanism that changes the relative positional relationship between the red-hot steel material and the light receiving unit to cause the light receiving unit to measure the distribution of the thermal radiation light in the width direction of the red-hot steel material, detecting the thermal radiation light from the red-hot steel material and measuring the temperature distribution along the width direction of the red-hot steel material including the vicinity of the end portion of the red-hot steel material;
A temperature measurement method in which, when there is an area occupied by something other than the red-hot steel material within the circular measurement field of view of the two-color radiation thermometer, the measurement result of the temperature of the red-hot steel material is output in correspondence with a center of gravity position calculated from the center position and radius of the circular measurement field of view of the two-color radiation thermometer and the end position of the red-hot steel material within the circular measurement field of view of the two-color radiation thermometer. The two-color radiation thermometer has a minimum amount of radiation light required for temperature calculation within the circular measurement field of view of the two-color radiation thermometer, the minimum amount of radiation light being specified in advance,
3. The temperature measuring method according to claim 2, wherein the position control mechanism changes a relative positional relationship between the red-hot steel material and the light receiving unit until an amount of radiated light detected within the circular measurement field of view of the two-color radiation thermometer becomes less than the minimum amount of radiated light. The temperature measurement method according to any one of claims 1 to 3, wherein the position control mechanism is an angle control mechanism that changes the angle between the surface normal direction of the red-hot steel material and the optical axis of the light receiving unit. The temperature measurement method according to claim 4, wherein the angle control mechanism changes the angle between the surface normal direction and the optical axis of the light receiving unit by rotating a mirror that is disposed between the red-hot steel material and a light guide optical system that guides the thermal radiation light to the detection unit at an angle to the surface normal direction by a predetermined angle around the longitudinal direction of the red-hot steel material as a rotation axis. The temperature measurement method according to any one of claims 1 to 5, wherein the position control mechanism is a drive mechanism that moves the light receiving unit along the width direction of the red-hot steel material. The two-color radiation thermometer is a two-color radiation thermometer capable of independently outputting the radiance of the thermal radiation light at each of two wavelengths of interest,
When scanning the temperature distribution in the width direction of the red-hot steel material,
When something other than the red-hot steel material is located within the range of the circular measurement field of view of the radiance of the two-color radiation thermometer, the two-color radiation thermometer measures the temperature of the red-hot steel material using the radiance of the thermal radiation light at each of the two wavelengths of interest,
The temperature measurement method according to any one of claims 1 to 6, wherein, when the red-hot steel material occupies a range of the circular measurement field of view, the two-color radiation thermometer measures the temperature of the red-hot steel material using the radiance of the thermal radiation light at one of two wavelengths of interest. When the distance from the two-color radiation thermometer to the red-hot steel material is H [mm], the size of the measurement diameter of the two-color radiation thermometer is _DL [mm], and the width of the red-hot steel material is W [mm],
the two-color radiation thermometer is a two-color radiation thermometer capable of independently outputting the radiance of the thermal radiation light at each of two wavelengths of interest, and has, as the position control mechanism, an angle control mechanism that changes an angle between a surface normal direction of the red-hot steel material and an optical axis of the light receiving unit,
When scanning the temperature distribution in the width direction of the red-hot steel material,
When the magnitude of the angle between the surface normal direction of the red-hot steel material and the optical axis of the light receiving unit exceeds a value expressed by |φ|=|tan ⁻¹ [{(W/2)−(D _L /2)}/H]|, the two-color radiation thermometer measures the temperature of the red-hot steel material using the radiance of the thermal radiation light at each of two wavelengths of interest,
The temperature measurement method according to any one of claims 1 to 7, wherein when the magnitude of an angle between a surface normal direction of the red-hot steel material and an optical axis of the light receiving unit is equal to or smaller than a value expressed by |φ| = |tan ^-1 [{(W/2) - (D _L /2)}/H]|, the two-color radiation thermometer measures the temperature of the red-hot steel material using the radiance of the thermal radiation light at one of two wavelengths of interest. The two-color radiation thermometer is
Calculating a dichroic ratio by dividing one of the measurement data of the radiance at the two wavelengths of interest by the other;
The temperature measuring method according to any one of claims 1 to 8, further comprising the steps of: calculating the temperature of the red-hot steel material based on a relational expression between the dichroic ratio and temperature by utilizing the calculated dichroic ratio. The two-color radiation thermometer is
In a state where an absorber having a wavelength-dependent spectral absorption coefficient in the near-infrared band is present at least partially on the light path, the thermal radiation light of the red-hot steel is measured at two wavelengths at which the spectral absorption coefficient of the absorber is the same as each other, and measurement data is generated that indicates the detection results of the radiance of the thermal radiation light at the two wavelengths;
The temperature measurement method according to any one of claims 1 to 9, further comprising the step of calculating the temperature of the red-hot steel material based on the generated measurement data corresponding to the two types of wavelengths and a relational equation between spectral radiance and temperature. The detection unit is
A branching optical element that branches the thermal radiation light of the red-hot steel material into two optical paths;
a first detection element that detects the split thermal radiation light at one of the two types of wavelengths;
a second detection element that detects the split thermal radiation light at the other of the two wavelengths;
a first optical filter provided between the branching optical element and the first detection element, the first optical filter transmitting the thermal radiation light having one of the two types of wavelengths;
a second optical filter provided between the branching optical element and the second detection element, the second optical filter transmitting the thermal radiation light having the other wavelength of the two types of wavelengths;
The temperature measurement method according to claim 10, comprising: As the two types of wavelengths, two types of wavelength bands having a predetermined width including wavelengths at which the spectral absorption coefficients of the absorber are identical to each other are selected,
12. The temperature measurement method according to claim 10, wherein the two types of wavelength bands are selected such that apparent spectral absorption coefficients calculated by weighting the spectral absorption coefficient of the absorber with the spectral radiance of the temperature to be measured are equal to each other. The temperature measurement method according to any one of claims 10 to 12, wherein the two-color radiation thermometer further calculates a thickness of the absorber using a blackbody radiance at either of the two wavelengths calculated using the temperature of the red-hot steel, the measured radiance of the thermal radiation light, a spectral absorption coefficient of the absorber at the two wavelengths, a reflectance of the thermal radiation light at an interface of the absorber on the red-hot steel side, a reflectance of the thermal radiation light at an interface of the absorber on the opposite side to the red-hot steel side, and setting conditions in the detection unit. The temperature measurement method according to any one of claims 10 to 13, wherein the absorbent is at least one of water, oil, a solution, glass, and a resin. The temperature measurement method according to any one of claims 1 to 14, wherein the near infrared band is 940 nm to 1350 nm.

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