Temperature measurement device, temperature measurement method, and program

Abstract

To more accurately measure a temperature distribution in the widthwise direction of a measurement object even when there exists an absorber, on an optical path for measuring the measurement object, which absorbs heat radiation light from the measurement object and has wavelength dependency in a spectral absorption coefficient.SOLUTION: A temperature measuring device pertaining to the present invention comprises: a measurement unit for measuring the heat radiation light of a measurement object in two kinds of wavelengths with which the spectral absorption coefficients of an absorber are identical for both and generating measurement data that indicates the detection result of radiance of heat radiation light in the two kinds of wavelengths; and a computation processing unit for calculating the temperature of the measurement object on the basis of the measurement data corresponding to the two kinds of wavelengths and a relational expression between spectral radiance and temperature. The measurement unit includes a light receiving unit for receiving the heat radiation light of the measurement object, a detection unit for detecting the received heat radiation light, and a position control mechanism for changing the relative positional relationship between the measurement object and the light receiving unit and causing the distribution of heat radiation light in the widthwise direction of the measurement object to be measured by the light receiving unit.SELECTED DRAWING: Figure 14A

Description

Technical Field

[0001] The present invention relates to a temperature measuring device, a temperature measuring method, and a program.

Background Art

[0002] Radiation thermometry is a method of knowing the temperature of an object by detecting the thermal radiation light emitted by the object according to its temperature with a measuring instrument such as a radiation thermometer, and is a remote temperature measurement method capable of measuring temperature non-contact and at high speed. Today, such radiation thermometry is used in many industries including the steel industry.

[0003] For example, in Patent Document 1 below, a technique for measuring the surface temperature of a slab being cast by a continuous casting machine by radiation thermometry is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, as described in detail below, in the above radiation thermometry, when an absorber such as water exists on the optical path between the measurement object and the measurement device, part of the thermal radiation light from the measurement object is absorbed by the absorber, resulting in a measurement error, and there is a problem that the temperature of the measurement object cannot be accurately measured. In Patent Document 1 above, a method of performing temperature measurement after expelling water and vapor on the optical path by gas purge is proposed. However, such a method always requires the supply of purge gas, and moreover, it is difficult to expel water and vapor existing on the slab.

[0006] In addition, for example, when manufacturing slabs or hot-rolled steel sheets in the steel industry, in order to manufacture higher-quality products, it is important to perform uniform temperature control along the width direction of the product. Therefore, there is a demand for a technology capable of measuring the temperature distribution in the width direction of the object to be measured.

[0007] Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to absorb thermal radiation light from a measurement object on the optical path for measuring the measurement object, and even when there is an absorber having a wavelength dependence in the spectral absorption coefficient, to provide a temperature measurement device, a temperature measurement method, and a program capable of more accurately measuring the temperature distribution in the width direction of the measurement object.

Means for Solving the Problems

[0008] In order to solve the above problems, according to one aspect of the present invention, there is provided an apparatus for measuring the temperature of a measurement object by detecting the thermal radiation light in the near-infrared band emitted by the measurement object in a state where an absorber having a wavelength dependence of the spectral absorption coefficient in the near-infrared band is present in at least a part of the optical path. The apparatus includes: a measurement unit that measures the thermal radiation light of the measurement object at two wavelengths at which the spectral absorption coefficients of the absorber are the same as each other, and generates measurement data indicating detection results of the radiation luminance of the thermal radiation light at the two wavelengths; and an arithmetic processing unit that calculates the temperature of the measurement object based on the measurement data corresponding to the two wavelengths generated by the measurement unit and a relational expression between the spectral radiation luminance and the temperature. The measurement unit includes: a light receiving unit that receives the thermal radiation light from the measurement object; 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 measurement object 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 measurement object. The position control mechanism is an angle control mechanism that changes the angle formed by the surface normal direction of the measurement object and the optical axis of the light receiving unit. The arithmetic processing unit further calculates the thickness of the absorber using the blackbody radiation luminance at any one of the two wavelengths calculated using the temperature of the measurement object, the measured radiation luminance of the thermal radiation light, the spectral absorption coefficients 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 side opposite to the measurement object side, and the angle formed by the surface normal direction of the measurement object and the optical axis of the light receiving unit. Further, as the two types of wavelengths, two wavelength bands each having a predetermined width and including wavelengths at which the spectral absorption coefficients of the absorber are the same as each other are selected, and the two wavelength bands are selected such that apparent spectral absorption coefficients calculated by weighted-averaging the spectral absorption coefficients of the absorber with the spectral radiance at the measurement target temperature are equal to each other. A temperature measuring device is provided.

[0010] The angle control mechanism may change the angle formed by the surface normal direction and the optical axis of the light receiving unit by rotating a mirror provided obliquely with respect to the surface normal direction between the measurement object 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 measurement object as the rotation axis.

[0012] The detection unit includes a branching optical element that branches the thermal radiation light of the measurement object 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 provided between the branching optical element and the first detection element and transmitting the thermal radiation light at one of the two wavelengths, and a second optical filter provided between the branching optical element and the second detection element and transmitting the thermal radiation light at the other of the two wavelengths. It is preferable to have these components. of It is preferable to have a second optical filter provided between the branching optical element and the second detection element and transmitting the thermal radiation light at the other of the two wavelengths.

[0013] The arithmetic processing unit preferably calculates a dichromatic ratio obtained by dividing one of the measurement data corresponding to the two wavelengths by the other, approximates that the spectral emissivities are equal to each other between the two wavelengths, and calculates the temperature of the measurement object based on the relational expression between the calculated dichromatic ratio and the temperature using the calculated dichromatic ratio.

[0016] Based on the center in the width direction of the measurement object, when the width of the measurement object is represented as W and the size along the width direction of the measurement field of the radiant luminance of the thermal radiation light is represented as DL, the arithmetic processing unit may calculate the thickness of the absorber in the range of -(W / 2 - DL / 2) to +(W / 2 - DL / 2).

[0017] The absorber may be at least one of water, oil and fat, solution, glass or resin.

[0018] The near-infrared band may be 940 nm to 1350 nm.

[0019] In order to solve the above problems, according to another aspect of the present invention, there is provided a method for measuring the temperature of a measurement object by detecting the near-infrared band thermal radiation light emitted by the measurement object in a state where an absorber having a wavelength dependence on the spectral absorption coefficient in the near-infrared band is present in at least a part of the optical path, and based on the detection result of the radiation luminance of the thermal radiation light. The method includes a light receiving unit that receives the thermal radiation light from the measurement object, 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 measurement object 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 measurement object. The position control mechanism is an angle control mechanism that changes the angle formed by the surface normal direction of the measurement object and the optical axis of the light receiving unit. The method further includes a step of measuring the thermal radiation light of the measurement object at two wavelengths at which the spectral absorption coefficients of the absorber are the same, and generating measurement data indicating the detection results of the radiation luminance of the thermal radiation light at the two wavelengths; and a step of calculating the temperature of the measurement object based on the generated measurement data corresponding to the two wavelengths and the relational expression between the spectral radiation luminance and the temperature. In the step of calculating the temperature of the measurement object, the blackbody radiation luminance at any one of the two wavelengths calculated using the temperature of the measurement object, the radiation luminance of the measured thermal radiation light, the spectral absorption coefficients 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 side opposite to the measurement object side, and the angle formed by the surface normal direction of the measurement object and the optical axis of the light receiving unit are used to further calculate the thickness of the absorber. Further, as the two types of wavelengths, two wavelength bands each having a predetermined width and including wavelengths at which the spectral absorption coefficients of the absorber are the same as each other are selected, and the two wavelength bands are selected such that apparent spectral absorption coefficients calculated by weighted-averaging the spectral absorption coefficients of the absorber with the spectral radiance at the measurement target temperature are equal to each other. A temperature measurement method is provided.

[0020] In order to solve the above problems, according to still another aspect of the present invention, the near-infrared band thermal radiation light emitted by the object to be measured is measured at two wavelengths at which the spectral absorption coefficients of the absorber having wavelength dependence in the near-infrared band are the same as each other in a state where the absorber is present in at least a part of the optical path, and measurement data indicating the detection result of the radiation luminance of the thermal radiation light is output. It includes a light receiving unit that receives the thermal radiation light from 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 the light receiving unit to measure the distribution of the thermal radiation light in the width direction of the object to be measured by the light receiving unit. The position control mechanism is an angle control mechanism that changes the angle formed by the surface normal direction of the object to be measured and the optical axis of the light receiving unit. Furthermore, as the two types of wavelengths, two wavelength bands each having a predetermined width and including wavelengths at which the spectral absorption coefficients of the absorber are the same as each other are selected, and the two wavelength bands are selected such that apparent spectral absorption coefficients calculated by weighted-averaging the spectral absorption coefficients of the absorber with the spectral radiance at the measurement target temperature are equal to each other. A program for realizing an arithmetic processing function of calculating the temperature of the object to be measured based on the measurement data corresponding to the two wavelengths and the relational expression between the spectral radiance and the temperature on a computer capable of acquiring data from the measurement unit. The arithmetic processing function further calculates the thickness of the absorber using the blackbody radiation luminance at any one of the two wavelengths calculated using the temperature of the object to be measured, the radiation luminance of the measured thermal radiation light, the spectral absorption coefficients of the absorber at the two wavelengths, the reflectance of the thermal radiation light at the interface of the absorber on the object to be measured side, the reflectance of the thermal radiation light at the interface of the absorber opposite to the object to be measured side, and the angle formed by the surface normal direction of the object to be measured and the optical axis of the light receiving unit. A program is provided.

Advantages of the Invention

[0021] As described above, according to the present invention, even when an absorber that absorbs the thermal radiation light from the object to be measured and has wavelength dependence in the spectral absorption coefficient exists on the optical path for measuring the object to be measured, it is possible to more accurately measure the temperature distribution in the width direction of the object to be measured.

Brief Description of the Drawings

[0022]

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Mode for Carrying Out the Invention

[0023] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0024] (Regarding the principle of radiation thermometry and the object of the present invention) Prior to the description of the temperature measurement device and the temperature measurement method according to the embodiments of the present invention, the principle of the radiation thermometry method that the present invention focuses on will be briefly described, and the object of the present invention will be explained.

[0025] As described above, the radiation thermometry method is a method of detecting the thermal radiation light emitted by an object according to its temperature to know the temperature of the object. The spectral radiance L of a blackbody, which is an ideal radiator, is expressed by the following formula (1) as a function of temperature and wavelength according to Planck's blackbody radiation law.

[0026]

Equation

[0027] In the above formula (1), T: Temperature [K] λ: Wavelength [nm] c1: First constant of blackbody radiation, 1.19×10 20 [W·m -2 ·nm 4 c2: Second constant of blackbody radiation, 1.44×10 7 [nm·K] is.

[0028] Here, when the radiator is a red-hot steel material or when observing short-wavelength thermal radiation light, if λT is sufficiently smaller than c2, the above formula (1) can be approximated as the following formula (2).

[0029]

Equation

[0030] The spectral radiance of an actual object is smaller than the spectral radiance of a blackbody as described above, and the spectral radiance L of an actual object is expressed by the following formula (3) using the spectral emissivity specific to the substance.

[0031]

Equation

[0032] Here, in the above formula (3), ε(λ) is the spectral emissivity at the observation wavelength λ [nm], and for other literal formulas, it is the same as in the above formulas (1) and (2).

[0033] In radiation thermometry, since the observation wavelength λ is determined by the detector, the spectral radiance L is a function of the temperature T and the emissivity ε. Therefore, a general radiation thermometry method (also called monochromatic radiation thermometry) is a method of measuring the spectral radiance of thermal radiation light from the object to be measured at one observation wavelength after grasping the spectral emissivity in advance and obtaining the temperature. In other words, in a general monochromatic radiation thermometry method, when the spectral emissivity of the object to be measured is unknown, accurate temperature measurement cannot be performed. Also, when an absorber exists on the optical path from the object to be measured to the radiation thermometer and the observed light is attenuated, if the attenuation amount by the absorber cannot be quantitatively specified, a temperature measurement error will occur.

[0034] On the other hand, in radiation thermometry, in addition to the monochromatic radiation thermometry method using a monochromatic radiation thermometer, there is also a temperature measurement method using a two-color thermometer. A two-color radiation thermometer (hereinafter simply referred to as a two-color thermometer) is a measuring device that observes thermal radiation light at two different observation wavelengths. As is clear from referring to the above formula (3), when the spectral emissivities are the same at two wavelengths λ1 and λ2, the ratio of the spectral radiances L at the two wavelengths becomes a function only of the temperature, so the temperature can be measured without knowing the spectral emissivity of the object to be measured in advance (the radiation thermometry method using a two-color thermometer will be described in detail below). Such a two-color radiation thermometer also has the characteristic that it is not affected by these obstacles even for light attenuation caused by detector dead spots or obstacles on the optical path (for example, floating dust or mist, dirt on the observation window, etc.).

[0035] For example, in the continuous casting process and hot rolling process of the steel manufacturing process, it is frequently necessary to measure the temperature of red-hot steel materials moving on the conveying line. However, at the location where the slab is withdrawn from the continuous caster or between the rolling stands in the hot rolling process, cooling water may remain on the steel material, or the evaporated cooling water may accumulate as steam. Regarding the light scattering by steam on the optical path, if the two wavelengths to be observed are not widely separated, even for different wavelengths, the thermal radiation light shows almost the same attenuation. Therefore, a two-color thermometer can be applied. On the other hand, when stagnant water forms a water film on the steel material, in the near-infrared band suitable for radiation thermometry, the spectral absorptivity of water shows strong wavelength dependence. As a result, water functions as an absorber with unknown attenuation characteristics. Consequently, the assumption that the attenuation of thermal radiation light occurs similarly at two wavelengths does not hold, and a two-color radiation thermometer cannot be used appropriately. Water is transparent in the visible light band with a wavelength of about 800 nm or less. However, in a short-wavelength band such as the visible light band, thermal radiation light is not emitted unless the measurement object reaches a high temperature. Therefore, the temperature range of the measurement object is limited to high temperatures.

[0036] In addition, in the steel manufacturing process as described above, in addition to water, glass, solutions present on the steel plate, and oils, fats, and resins present on the steel plate also do not have a uniform spectral absorptivity in the near-infrared band (that is, they show strong wavelength dependence) and function as absorbers.

[0037] The situation where an absorber exists on the optical path between the measurement object and the radiation thermometer in radiation thermometry can occur not only in the steel manufacturing process as described above but also in various other measurement environments.

[0038] As a result of earnestly studying to solve such problems and realizing a two-color radiation thermometer capable of accurately measuring the temperature of a measurement object even when detecting thermal radiation light in a state where an absorber exists on the optical path from the measurement object to the radiation thermometer, the present inventors were able to obtain the following findings, which will be described in detail below. Therefore, as a result of further study based on the obtained findings, the present inventors conceived of a temperature measurement device and a temperature measurement method according to an embodiment of the present invention as described below.

[0039] In addition, in the steel manufacturing process as described above, water is sprayed onto the high-temperature steel material to cool the high-temperature steel material. The amount of water present on the surface of the steel material is considered an important operating factor that affects the amount of heat extraction from the steel material. The inventors of the present invention have found that by using the temperature measuring device and temperature measuring method according to the embodiment of the present invention as described below, it is possible to obtain a more accurate temperature of the measurement object, and thus it is possible to more accurately calculate the thickness of water (i.e., the absorber) present on the optical path from the measurement object to the radiation thermometer.

[0040] (Regarding the findings obtained by the inventors of the present invention) Next, after briefly explaining the principle of the two-color radiation thermometer, the findings obtained by the inventors of the present invention will be described in detail with reference to FIGS. 1 to 13. FIGS. 1 to 13 are explanatory diagrams for explaining the findings obtained by the inventors of the present invention.

[0041] (Regarding the principle of the two-color radiation thermometer) The two-color radiation thermometer is a measuring device that specifies the temperature T of the measurement object by using the ratio of the spectral radiance L(λ1,T) and L(λ2,T) of two wavelengths λ1 and λ2. When expressing the two spectral radiance observed using the above formula (3), it becomes as follows in formulas (4) and (5).

[0042] [Number]

[0043] Here, assuming that the spectral emissivities are equal to each other (ε(λ1)=ε(λ2)=ε) at the two wavelengths λ1 and λ2, the two-color ratio R defined as the ratio of dividing the above formula (4) by formula (5) is expressed as follows in formula (6).

[0044] [Number]

[0045] Here, in the above formula (6), R λ and Λ are as shown in the following formulas (6a) and (6b).

[0046] [Number]

[0047] The above formula (6) indicates that the dichromatic ratio R is a function of the temperature T. Now, consider measuring the temperature of a measurement object using a two-color thermometer. In this case, when setting the two wavelengths λ1 and λ2 used for temperature measurement, pay attention to how the dichromatic ratio R changes when two wavelengths close to each other (for example, wavelengths 1200 nm and 1250 nm) are selected, and when two wavelengths separated to a certain extent (for example, 1200 nm and 1300 nm) are selected. Such a change pattern can be obtained by substituting the above two types of wavelengths λ1 and λ2 into the above formulas (6) to (6b).

[0048] The obtained change pattern is shown in FIG. 1. In FIG. 1, the horizontal axis is the temperature T [°C], and the vertical axis is the dichromatic ratio R calculated based on formula (6). As is clear from FIG. 1, the dichromatic ratio R increases monotonically with respect to the temperature T. Also, it can be seen that the closer the two selected wavelengths are to each other, the gentler the change pattern of the dichromatic ratio R. The fact that the change pattern of the dichromatic ratio R (in other words, the temperature gradient of the dichromatic ratio) is gentle means that even if the temperature T changes greatly, the change amount of the dichromatic ratio R is small. In other words, when the two selected wavelengths are close to each other, even if the temperature changes, the change amount of the dichromatic ratio is small, so the sensitivity of temperature measurement will decrease.

[0049] From such facts, 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 higher than the temperature resolution of the two-color thermometer. More preferably, the temperature range to be measured is such that a significant slope can be obtained in the correspondence relationship between the two-color ratio R and the temperature as shown in FIG. 1. The wavelength difference corresponding to such a temperature resolution varies depending on the two-color thermometer used. For example, it is preferable that the absolute value |λ1 - λ2| of the difference between the two selected wavelengths is 100 nm or more.

[0050] <Regarding the findings obtained by the present inventors> Above, the principle of the two-color thermometer focused on in the embodiments of the present invention has been briefly described. Next, as illustrated in FIG. 2, as an example of the object to be measured, a steel plate in a high-temperature state (temperature T, emissivity ε) is taken, and as an example, the case where water, which is an example of an absorber, exists as a water film on such a steel plate will be taken as an example, and the further findings obtained by the present inventors will be described in detail.

[0051] Water, which is an example of an absorber, is transparent up to near the long-wavelength end of the visible light band (near wavelength 800 nm), but at 800 nm or more belonging to the near-infrared band, it becomes a translucent body having a strong wavelength dependence, for example, as shown in FIG. 3. Also, as is clear from Lambert-Beer's law, the thicker the water film, the more the amount of light in the near-infrared band absorbed by water increases, and thus the spectral transmittance becomes a small value.

[0052] In order to avoid the influence of water in the radiation thermometry method, a method of measuring temperature in a band of 800 nm or less where there is almost no light absorption by water can be considered. Actually, a "water film transmission type radiation thermometer (single-wavelength radiation thermometer)" with an observation wavelength of 800 nm is commercially available. However, thermal radiation rapidly decreases toward the short-wavelength side. For a radiation thermometer with an observation wavelength of 800 nm, the temperature of the object to be measured needs to be at least 650 °C or higher.

[0053] Also, as described above, if there is steam, which is a scattering medium, even if the water is transparent, it is difficult to accurately measure the temperature by monochromatic radiation thermometry. Here, a specific example where the measurement becomes inaccurate when performing single-wavelength radiation thermometry in the wavelength band of 800 nm or more where water absorbs light is shown. For example, at a wavelength of 1300 nm, the intensity of light attenuates according to the spectral transmittance shown in FIG. 3 depending on the thickness of the water. Calculating the influence of such attenuation on the temperature measurement value results in the graph shown in FIG. 4. In FIG. 4, the horizontal axis represents the thickness of the water film [mm], and the vertical axis represents the temperature measurement error [°C]. As is clear from FIG. 4, even if the thickness of the water is only about 2 mm, a temperature measurement error of about 30 °C occurs. Therefore, in an actual measurement environment where the thickness of the water is unknown, it is extremely difficult to accurately measure the temperature when using a monochromatic radiation thermometer.

[0054] Subsequently, the reason why the temperature of the object to be measured needs to be at least 650 °C or more with a radiation thermometer having an observation wavelength of 800 nm will be described with reference to FIG. 5, which is an explanatory diagram showing the relationship between blackbody radiation luminance, wavelength, and temperature.

[0055] In FIG. 5, the horizontal axis represents temperature, and the vertical axis represents blackbody spectral radiation luminance. As shown in FIG. 5, the blackbody spectral radiation luminance monotonically increases as the temperature increases. Here, the detection limit of the sensor used in a general radiation thermometer is thermal radiation with a blackbody spectral radiation luminance of about 1. Therefore, focusing on the curve with an observation wavelength of 800 nm in FIG. 5, the intersection of the straight line represented by "blackbody spectral radiation luminance = 1" and the curve with an observation wavelength of 800 nm is about 650 °C.

[0056] As described above, when using a two-color thermometer, it is preferable to separate the intervals between the two wavelengths by at least 100 nm or more. Therefore, in order 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 FIG. 5, the lower limit temperature of the measurement by the two-color thermometer becomes about 740°C. Further, as shown in FIG. 5, if the observation wavelength is set to 1000 nm, for example, temperature measurement from 500°C becomes possible, and if the observation wavelength is set to 1200 nm, for example, it becomes possible to widen the lower limit temperature of the measurement to around 400°C.

[0057] Therefore, from the above findings, it can be understood that in order to widely secure the measurement temperature range, the observation wavelength may be set to the longer wavelength side. However, when a two-color radiation thermometer is configured using two types of wavelengths of 800 nm or more of the observation wavelength, as is clear from FIG. 3, such a wavelength band becomes a band in which the spectral absorptance of water shows a remarkable wavelength dependence. The two types of spectral radiance L observed in such a wavelength band are represented by the following formulas (7) and (8) in consideration of the absorption of water as an absorber.

[0058]

Equation

[0059] Here, in the above formulas (7) and (8), τ1 is the spectral transmittance of water at wavelength λ1, and τ2 is the spectral transmittance of water at wavelength λ2. Further, the spectral transmittance τ of water is a function of the spectral absorption coefficient of water, the thickness of water, and the interface reflectance determined from the refractive indices of both at the interface between water and air (details will be described below). At this time, when the interface reflection is omitted, the spectral transmittances τ1 and τ2 of water can be expressed as τ1 = exp(-α1 × t) and τ2 = exp(-α2 × t), respectively. Here, α1 is the spectral absorption coefficient of water at wavelength λ1, α2 is the spectral absorption coefficient of water at wavelength λ2, and t is the thickness of the water film.

[0060] In the above formulas (7) and (8), when the attenuation amounts due to absorption are different from each other at two wavelengths λ1 and λ2 due to the wavelength dependence of the spectral absorption coefficient of water as shown in FIG. 3, in the relational expression between the dichroic ratio and temperature defined by formula (6), τ1 and τ2, which are terms due to the absorption of water, do not cancel out.

[0061] For example, in a two-color thermometer focusing on a wavelength of 1000 nm and a wavelength of 1100 nm, the dichroic ratio changes as shown in FIG. 6 when there is no water and when thermal radiation light is observed through water. For example, assuming that the true temperature of the measurement object is 700 °C, as is clear from FIG. 6, when there is a 5-mm-thick water film, the apparent temperature is about 640 °C, and when there is a 10-mm-thick water film, the apparent temperature is about 590 °C. In actual temperature measurement where the thickness of the water film changes irregularly, in this way, due to the presence of water as an absorber, a large temperature measurement error will occur.

[0062] As a result of further studies based on the above findings, the inventors have found that even when an absorber is present on the optical path, in order to accurately measure the temperature of the measurement object with a two-color thermometer, τ1 and τ2, which are terms due to the absorption by the absorber in the above formulas (7) and (8), should cancel out when calculating the dichroic ratio R. In order to cancel out the terms due to the absorption by the absorber, two observation wavelengths with equal spectral absorptivities of the absorber may be selected and the temperature of the measurement object may be measured.

[0063] FIG. 7 is a graph showing the wavelength dependence of the spectral absorption coefficient of water as an example of an absorber. The horizontal axis in FIG. 7 is the wavelength, and the vertical axis is the spectral absorption coefficient. As a result of examining FIG. 7 based on the above findings, the inventors have found that the observation wavelengths of the two-color thermometer may be selected based on the technical idea described below.

[0064] ○ Method for selecting observation wavelengths - Part 1 In order to identify two wavelengths with equal spectral absorption coefficients, one should focus on the spectrum of the spectral absorption coefficient as shown in Fig. 7, and pay attention to the number of intersections between the straight line represented by (spectral absorption coefficient = any constant) (in other words, a straight line parallel to the horizontal axis in the spectrum shown in Fig. 7) and the curve corresponding to the spectrum of the spectral absorption coefficient. At this time, from the wavelength band where the number of intersections between such a curve and the straight line is 2 or more, two wavelengths with equal spectral absorption coefficients can be appropriately selected.

[0065] For example, in the case of water shown in Fig. 8A, the wavelength bands where the number of intersections is 2 or more are the following two. (1) Wavelength band from the other intersection point (near wavelength 940 nm) of the straight line (the straight line represented by spectral absorption coefficient ≒ 0.02) that touches the saddle of the spectrum near wavelengths 1070 - 1080 nm to the other intersection point (near wavelength 1130) of the straight line (the straight line represented by spectral absorption coefficient ≒ 0.05) that touches the peak near wavelengths 970 - 980 nm: the first wavelength selection region (2) Wavelength band from the other intersection point (near wavelength 1155 nm) of the straight line (the straight line represented by spectral absorption coefficient ≒ 0.11) that touches the saddle of the spectrum near wavelength 1260 nm to the other intersection point (near wavelength 1300 nm) of the straight line (the straight line represented by spectral absorption coefficient ≒ 0.13) that touches the peak near wavelength 1190 nm: the second wavelength selection region

[0066] Using such two types of wavelength selection regions as a guide, two wavelengths with equal spectral absorption coefficients can be selected. At this time, as described 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 higher than the temperature resolution of the two-color thermometer.

[0067] Based on the above technical concept, for example, in FIG. 8B, two wavelengths, i.e., wavelength 1000 nm and wavelength 1130 nm, can be selected from the first wavelength selection region. Also, for example, in FIG. 8C, two wavelengths, i.e., wavelength 1190 nm and wavelength 1300 nm, can be selected from the second wavelength selection band. It should be noted that such a combination of wavelengths is merely an example, and based on the above technical concept, wavelengths can be appropriately selected from the two types of wavelength selection regions.

[0068] Such a two-color radiation thermometer using a specific spectrum (a specific wavelength in a narrow band with a negligible wavelength bandwidth) can be realized by using a narrow-band optical interference filter and installing such a narrow-band optical interference filter in the two-color radiation thermometer. Such a narrow-band optical interference filter can be obtained as a commercially available product if its half-value width is about 10 nm, or it is also possible to manufacture a narrow-band optical interference filter using known techniques. Such a wavelength selection filter will be described again below.

[0069] ○Regarding the method of selecting the observation wavelength - Part 2 Generally, a radiation thermometer rarely observes the spectral radiance in a narrow band 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, resulting in a decrease in detection sensitivity or an increase in the measurement lower limit temperature. When measuring thermal radiation light with a finite wavelength bandwidth rather than a narrow band using a general wavelength selection filter or the like, the above two observation wavelengths can be selected as follows.

[0070] That is, when the bandwidth of the wavelength to be observed cannot be ignored as in the above item 1, instead of using the simple average value of the absorption coefficient in the observation band as the effective spectral absorption coefficient, the spectral absorption coefficient weighted and averaged with the spectral radiance having a wavelength dependence according to the temperature of the measurement target may be obtained and used for the processing. That is, such a method is a method of selecting an observation band having a finite bandwidth so that the "apparent spectral absorption coefficients" calculated by weighted-averaging the spectral absorption coefficients of the absorber with the spectral radiance at the measurement target temperature are equal to each other. Hereinafter, with reference to FIGS. 9A and 9B, such a selection method will be specifically described.

[0071] As a specific example, consider the case of selecting two wavelengths with a bandwidth of 40 nm starting from the first wavelength selection region shown in FIG. 8B. First, the observation wavelength on the short-wavelength side of the first wavelength selection region is fixed to wavelengths 980 nm to 1020 nm where the bandwidth is 40 nm. In the range of wavelengths 980 nm to 1020 nm, the effective spectral absorption coefficient α eff is strictly expressed by the following formula (9) using the spectral absorption coefficient α(λ) at wavelength λ and the weighting coefficient w(λ) determined from Planck's blackbody radiation formula considering the wavelength dependence of the spectral radiance.

[0072] [Number]

[0073] Here, assuming that the temperature of the measurement object is 900 ° C, the weighting coefficient w(λ) obtained by normalizing the wavelength dependence of this spectral radiance L is calculated. The obtained weighting coefficient w(λ) is shown by a dashed line in FIG. 9A. In the example shown in FIG. 9A, the average value of the spectral absorption coefficients weighted by such a weighting coefficient is 4.2×10 -2 [1 / mm]. On the other hand, when the spectral absorption coefficients are averaged with a uniform weight (simple averaging) without considering the wavelength dependence of the spectral radiance L, it becomes 4.3×10 -2 [1 / mm].

[0074] Next, the observation wavelength on the long-wavelength side of the first wavelength selection region is such that the spectral absorption coefficient averaged with the weight of the spectral radiance at 900 °C is the same as the weighted spectral absorption coefficient on the short-wavelength side, which is 4.2×10 -2 [1 / mm]. Thus, a wavelength band around 1130 nm is selected. As a result, as illustrated in Fig. 9B, wavelengths from 1100 nm to 1140 nm met such conditions. The simple average of the spectral absorption coefficients in the wavelength band shown in Fig. 9B was 4.1×10 -2 [1 / mm].

[0075] In this way, depending on whether or not the wavelength dependence of the spectral radiance L of the measurement object is considered, the value of the apparent spectral absorption coefficient (effective absorption coefficient) changes by 0.2×10 -2 [1 / mm] in the examples shown in Figs. 9A and 9B. Conversely, if the simple average of the spectral absorption coefficients in the observation band is used when estimating the apparent spectral absorption coefficient, when actually measuring a high-temperature measurement object, there will be a discrepancy of about 0.2×10 -2 [1 / mm] in the effective spectral absorption coefficient.

[0076] In the above description, the weight coefficient based on the spectral radiance was calculated assuming that the measurement object was at 900 °C. However, as shown in Fig. 10 for example, if the temperature range is about 200 °C, the spectral radiance does not change significantly. Therefore, if the approximate temperature of the measurement object can be predicted based on past operation data etc., it becomes possible to give a weight coefficient based on the spectral radiance.

[0077] Here, the influence of the difference of 0.2×10 -2 [1 / mm] in the effective absorption coefficient between the case where the spectral absorption coefficient is corrected by the weight coefficient and the case where it is not corrected on the accuracy of the two-color thermometer is examined. For example, in the situation of measuring thermal radiation light through a water film with a thickness of 10 mm, when the spectral absorption coefficients of water at two wavelengths are equal to each other at 4.2×10 -2 [1 / mm], and when 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 -2For each case where it is [1 / mm], the two-color ratio R was calculated based on the above formula (6). The obtained results are shown in FIG. 11. In the results shown in FIG. 11, there was a deviation in the two-color ratio in the above two cases corresponding to a temperature difference of about 20°C. Therefore, when there is a width in the observation wavelength (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 averaged absorbers match exactly with each other by using the weighting based on the spectral characteristics of the thermal radiation light.

[0078] Thus, according to the method for selecting the second observation wavelength, when performing radiation thermometry using an observation wavelength consisting of a finite bandwidth, correction of the spectral absorption coefficient is performed so that equivalent light quantity attenuation occurs between wavelengths in a two-color thermometer. By performing such correction of the spectral absorption coefficient, it becomes possible to further reduce the measurement error. Therefore, even when selecting a narrow-band observation wavelength based on the method for selecting the first observation wavelength, it is more preferable to perform the correction process of the spectral absorption coefficient described in the method for selecting the second observation wavelength. At this time, as described above, it is preferable to determine the effective value α eff of the spectral absorption coefficient in consideration of the wavelength dependence of the spectral radiance.

[0079] When estimating the effective absorption coefficient of the observation wavelength band, in addition to the spectral characteristics of the thermal radiation of the measurement object, the spectral transmittance characteristics of the wavelength selection filter, the spectral sensitivity characteristics of the photodetector built in the radiation thermometer, etc. may be weighted, and the spectral data related to the spectral absorption coefficient may be weighted and averaged. In this case, terms related to the spectral transmittance characteristics of the wavelength selection filter and terms related to the spectral sensitivity characteristics of the photodetector built in the radiation thermometer will be added to the numerator part of the relational expression shown in formula (9). By further using the spectral transmittance characteristics and spectral sensitivity characteristics to perform weighted averaging of the spectral absorption coefficient, it becomes possible to perform a correction in a form closer to the actual situation considering the distribution of the spectral absorption coefficient, and it becomes possible to further improve the accuracy.

[0080] In addition, in the above-described method for selecting the second observation wavelength, the case where the bandwidths of the two observation wavelengths are made the same for processing has been described, but the bandwidths of the two observation wavelengths may be different. For example, in the near-infrared band, since the spectral radiance increases as the wavelength becomes longer, the observation bandwidth on the long-wavelength side may be made narrower than that on the short-wavelength side.

[0081] Next, findings regarding a method for measuring the thickness of a water film located above the surface of a measurement object, conceived by the present inventors, in conjunction with the temperature of the measurement object, will be described with reference to FIGS. 12 and 13.

[0082] Considering more precisely the situation shown in FIG. 2 as a situation where cooling water is flowing on the upper surface of a red-hot steel material as an example of a measurement object, such a situation can be modeled as shown in FIG. 12.

[0083] If the temperature of the red-hot steel material is high, the water located on the upper surface of the steel material is in a film boiling state, and a layer of water vapor as shown in FIG. 12 is formed between the steel material surface and the water film, and the water film floats from the surface of the steel material. In such a case, the radiation thermometer is assumed to look at the steel material, which is the measurement object, obliquely upward in the vertical direction of the steel material as shown in FIG. 12. Inside the water film, the light radiated from the steel material is absorbed according to the thickness t of the water film, and the radiance decays. More specifically, when the angle formed by the optical axis of the radiation thermometer and the surface normal direction of the measurement object is θ0, inside the water film, the relationship represented by Snell's law (n a ·sinθ0=n w·sinθ1), the light radiated from the steel material travels at an angle θ1 that satisfies this condition. Therefore, the radiance of the light radiated from the steel material decreases according to the optical path length (t / cosθ1). Also, at the interface between the water film and the water vapor layer, and at the interface between the water film and the atmosphere layer, interface reflections with reflectivities ρ1 and ρ2 occur respectively. The radiation light resulting from such absorption by the water film and interface reflection at the water film interface is measured by a radiation thermometer. Here, the gaseous water vapor has completely different optical properties from liquid water. In the wavelength band of 940 nm to 1650 nm, water vapor is almost transparent. That is, it can be considered that there is no absorption of the radiation light in the water vapor layer shown in Fig. 12.

[0084] The effective spectral transmittance τ1 in the above formula (7) is expressed as follows in formula (10) by the interface reflection loss at the interface of the water film and the spectral absorption coefficient α1 at wavelength λ1 inside the water film.

[0085]

Equation

[0086] Also, the reflectivities ρ1 and ρ2 at the water film interface are such that ρ1 = ρ2 from the refractive index relationships in the above layers, so the value of such reflectivity is re-designated as ρ = ρ1 = ρ2. Such reflectivity ρ, except at θ = 0°, is the reflectivity ρ of the p-polarized component p and the reflectivity ρ of the s-polarized component s and it is necessary to consider them separately. Therefore, the above formula (10) is transformed as follows in formula (11). Here, in the following formula (11), the reflectivities ρ p , ρ s are expressed as follows in formulas (12) and (13) at the water film / atmosphere interface, for example.

[0087]

Equation

[0088] Here, n v is the refractive index of water vapor (nv = 1.00), and n w is the refractive index of water (n w = 1.33), and n a is the refractive index of the atmosphere (n a = 1.00). In this technology, the wavelengths λ1 and λ2 are selected such that the spectral absorption coefficient α1 at wavelength λ1 and the spectral absorption coefficient α2 at wavelength λ2 are equal to each other. Also, the reflectivities ρ p , ρ s are constants determined only by the refractive index and the refractive angle of each layer as shown in the above equations (12) and (13). Therefore, even when equation (8) is used instead of equation (7), the value of the transmittance τ2 is equal to the value of the transmittance τ1.

[0089] Based on the dichroic ratio shown in the above equation (6), when the temperature T of the steel material, which is the object to be measured, is obtained, the transmittance τ1 at wavelength λ1 is calculated as follows by transforming the above equation (4) into the following equation (14). Here, in the following equation (14), the numerator is the radiance value observed by the radiation thermometer, and the denominator corresponds to the radiance value radiated from a blackbody at temperature T. Also, in the following equation (14), the spectral emissivity ε(λ1) of the steel material is a stable value of about 0.8 in the wavelength band of λ1 = 1.1 μm to 1.3 μm.

[0090] Next, substituting the above equation (10) into the above equation (7) and solving for the thickness t of the water film, the following equation (15) can be obtained.

[0091]

Equation

[0092] Here, in the above equation (15), the spectral absorption coefficient α1 of water may be a value obtained from 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 It may be used.

[0093] Therefore, when the temperature T of the steel material, which is the object to be measured, is obtained, the transmittance τ1 is calculated based on the above formula (14). By using the obtained transmittance τ1, the measured value of the radiant luminance obtained by the radiation thermometer, the refractive index of each medium as shown in, for example, Fig. 12, the spectral absorption coefficient α of water as described above, and the installation angle θ of the radiation thermometer, the thickness t of the water film can be calculated from the above formula (15).

[0094] Here, regarding the above formula (15), how the thickness t of the water film changes with respect to the decrease in the spectral transmittance τ was calculated for each of the cases where the angle θ0 = 0°, 30°, and 45°, and the obtained results are shown in Fig. 13 below. In the above formula (15), as the spectral absorption coefficient α1 of water, the value at the wavelength λ1 = 1.19 μm is α1 = 0.129 mm. -1 Using this, the refractive index was the value shown in Fig. 12. As is clear from Fig. 13, it can be seen that when the spectral transmittance τ decreases, the thickness of the water film increases. Also, since the optical path length of the radiant light in the water film changes according to the installation angle θ0 of the radiation thermometer, the relationship between the spectral transmittance and the water film thickness shown in Fig. 13 also changes slightly according to the installation angle θ0.

[0095] Thus, even in a situation where the surface of a red-hot high-temperature steel material is covered with film-boiling water, if an accurate temperature T can be obtained by the radiation thermometry method using a two-color radiation thermometer as shown in the above findings, it becomes possible to accurately calculate the thickness of the water film.

[0096] The inventors' findings have been described in detail above with reference to FIGS. 1 to 13. As a result of further studies based on such findings, the inventors conceived of a temperature measurement device and a temperature measurement method as described below that perform radiometric temperature measurement based on the above findings. In the temperature measurement device and the temperature measurement method described below, even when measurement is performed in a band where the spectral absorption coefficient of the absorber has wavelength dependence in order to lower the measurement lower limit temperature, the temperature of the measurement object can be accurately measured by a radiometric temperature measurement method using a two-color radiometer. Further, by obtaining the temperature of the measurement object more accurately, it becomes possible to more accurately calculate the thickness of an absorber such as a water film covering the surface of the measurement object.

[0097] (Embodiment) <Configuration of Temperature Measurement Device> Subsequently, with reference to FIGS. 14A and 14B, the overall configuration of the temperature measurement device 10 according to an embodiment of the present invention will be described in detail. FIGS. 14A and 14B are explanatory diagrams showing an example of the overall configuration of the temperature measurement device 10 according to the present embodiment.

[0098] The temperature measurement device 10 according to the present embodiment 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 wavelength dependence in the spectral absorption coefficient exists in at least a part of the optical path in the near-infrared band, and measures the temperature of the measurement object based on the detection result of the radiation luminance of the thermal radiation light. Here, examples of the absorber having wavelength dependence in the spectral absorption coefficient in the near-infrared band include at least any one of water, fats and oils, solutions, glass, or resin. Further, in the present embodiment, the near-infrared band is particularly focused on the band of 940 nm to 1350 nm. The reason for setting the lower limit to 940 nm is that, as shown in FIG. 3, water becomes a semi-transparent body having strong wavelength dependence at 800 nm or more (particularly 940 nm or more) belonging to the near-infrared band. The reason for setting the upper limit to 1350 nm is that, as also shown in FIG. 3, water becomes opaque at 1350 nm or more when the water film thickness is 10 mm or more. This temperature measurement device 10 mainly includes, for example, as shown in FIG. 14A, a measurement unit 101, an arithmetic processing unit 103, and a storage unit 105.

[0099] The measurement unit 101 measures the magnitude of the thermal radiation light (observation light) emitted by a measurement object that emits thermal radiation light belonging to the near-infrared band (for example, a band of 940 nm to 1350 nm), such as a steel plate in a high-temperature state. More specifically, the measurement unit 101 measures the thermal radiation light of the measurement object at two wavelengths where the spectral absorption coefficients of the absorbers are the same, and generates measurement data indicating the detection results of the radiation luminance of the thermal radiation light at these two wavelengths.

[0100] This measurement unit 101 corresponds to an optical system composed of various lenses / lens groups and sensors such as photodetectors in a two-color radiation thermometer, for example. The more detailed configuration of the measurement unit 101 will be described again below. Also, the two wavelengths measured by the measurement unit 101 are preset in accordance with the two "methods for selecting observation wavelengths" described above.

[0101] When the measurement unit 101 measures the magnitude of the thermal radiation light of the measurement object and generates measurement data indicating the detection results of the radiation luminance of the thermal radiation light, the generated measurement data is output to an arithmetic processing unit 103 described later.

[0102] The arithmetic processing unit 103 is implemented 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 carried out by the measurement unit 101. Further, the arithmetic processing unit 103 performs arithmetic processing for calculating 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 expression between the spectral radiance and the 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 or the like, output as a printed matter via a printer or the like, or output as the data itself.

[0103] Details of such an arithmetic processing unit 103 will be described in detail again below.

[0104] The storage unit 105 is implemented by, for example, a RAM or a storage device included in the temperature measurement device 10 according to the present embodiment. The storage 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, etc., and the weighting coefficient used for correcting the spectral absorption coefficient. In addition to these data, the storage unit 105 appropriately records various parameters, the intermediate progress of processing, etc. that need to be saved when the temperature measurement device 10 according to the present embodiment performs some processing, or various databases, programs, etc. This storage unit 105 enables the measurement unit 101, the arithmetic processing unit 103, etc. to freely perform data read / write processing.

[0105] As schematically shown in Fig. 14A, these measurement unit 101, arithmetic processing unit 103, and storage unit 105 may be implemented inside a single measuring device as one function of, for example, a two-color radiation thermometer. Further, as shown in Fig. 14B for example, the measurement unit 101, arithmetic processing unit 103, and storage unit 105 may be dispersedly implemented in a plurality of devices. In the example shown in Fig. 14B, the functions of the measurement unit 101 and the storage unit 105 are implemented inside a measurement unit that functions as a two-color radiation thermometer, for example, and the functions of the arithmetic processing unit 103 and the storage unit 105 are implemented inside an arithmetic processing device such as a personal computer, various servers, and various process computers. Note that in Fig. 14B, the storage unit 105 is implemented as storage units 105a and 105b in the measurement unit and the arithmetic processing device respectively, but the storage unit 105 may be implemented only inside the measurement unit or only inside the arithmetic processing device.

[0106] <Configuration example of measurement unit> Subsequently, with reference to Figs. 15 to 18, a configuration example of the measurement unit 101 according to the present embodiment will be described in detail. Fig. 15 is an explanatory diagram schematically showing an example of the configuration of the measurement unit included in the temperature measuring device according to the present embodiment. Fig. 16 is a graph showing an example of the relationship between the center wavelength of the optical filter and the temperature measurement error. Figs. 17A and 17B are explanatory diagrams schematically showing an example of the configuration of the detection unit in the measurement unit according to the present embodiment. Fig. 18 is an explanatory diagram schematically showing an example of the configuration of the detection unit in the measurement unit according to the present embodiment.

[0107] The measurement unit 101 according to this embodiment corresponds to the optical system in a two-color radiation thermometer, operates under the control of the arithmetic processing unit 103, and measures the thermal radiation light in the near-infrared band emitted by the measurement object. As schematically shown in FIG. 15, this measurement unit 101 includes a light receiving unit 111 that receives the thermal radiation light from the measurement object, 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 measurement object and the light receiving unit 111 and causes the light receiving unit 111 to measure the distribution of the thermal radiation light in the width direction of the measurement object.

[0108] 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 light transmission mechanisms. Examples of such light transmission mechanisms include various known optical fibers OF. By connecting the light receiving unit 111 and the detection unit 113 by a light transmission mechanism such as an optical fiber OF, it becomes possible to separately arrange the light receiving unit 111 from the detection unit 113, and the convenience when using the temperature measurement device according to this embodiment is further improved.

[0109] As shown in FIG. 15, the light receiving unit 111 includes a light receiving lens 121 that receives the thermal radiation light from the measurement object, and a connection coupler 123 for connecting the thermal radiation light from the measurement object 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.

[0110] Here, the specific configuration of the light receiving unit 111 according to the present embodiment is not particularly limited. For example, in FIG. 15, 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 a plurality of optical elements. Further, the lens used for the light receiving lens 121 is not particularly limited, and known optical elements such as a spherical lens or an aspherical lens can be appropriately used. 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.

[0111] Thermal radiation light from a measurement object in which absorbers (water in FIG. 15) of various thicknesses exist on at least a part of the surface becomes a substantially parallel light 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 measurement object received by the light receiving unit 111 and then transmitted by the optical fiber OF is guided to the detection unit 113.

[0112] As illustrated in FIG. 15, the detection unit 113 includes a connection coupler 151 optically connected to the optical fiber OF, a beam splitter 153, optical filters 155a and 155b, condenser lenses 157a and 157b, and sensors 159a and 159b.

[0113] The thermal radiation light from the measurement object that has passed through the connection coupler 151 is guided to a beam splitter 153, which is an example of a branching optical element. The light beam of the thermal radiation light that has reached the beam splitter 153 is branched into two optical paths by the beam splitter 153.

[0114] As shown in FIG. 15, an optical filter 155a, which is an example of a first optical filter, is provided on one of the optical paths after branching, and an optical filter 155b, which is an example of a second optical filter, is provided on the other optical path after branching.

[0115] The optical filters 155a and 155b function as wavelength selection filters, select the wavelength of the thermal radiation light, and transmit the thermal radiation light having a specific wavelength to the subsequent sensors 159a and 159b. For such optical filters 155a and 155b, as long as they can transmit light of two preset wavelengths (observation wavelengths), known ones can be used. Also, as described in the findings regarding the "method of selecting the observation wavelength", such optical filters 155a and 155b may be narrow-band wavelength selection filters or may be general-band (having a finite bandwidth) wavelength selection filters.

[0116] The thermal radiation light of one of the two observation wavelengths that has passed through the optical filter 155a is condensed by the condenser lens 157a onto the sensor 159a, which is an example of a first detection element. Also, the thermal radiation light of the other of the two observation wavelengths that has passed through the optical filter 155b is condensed by the condenser lens 157b onto the sensor 159b, which is an example of a second detection element.

[0117] The sensors 159a and 159b respectively detect the spectral radiance of the thermal radiation light from the measurement object guided by the condenser lenses 157a and 157b, and generate data of the obtained luminance signals. Then, each of the sensors 159a and 159b outputs the obtained luminance signal to the arithmetic processing unit 103. Such a luminance signal corresponds to measurement data indicating the detection result of the radiance of the thermal radiation light.

[0118] Here, the sensors 159a and 159b are not particularly limited, and as long as they are suitable for the two types of wavelengths as described above for detecting thermal radiation light, known ones can be used. Examples of such sensors (photodetectors) include, for example, a detection element using Si, a detection element using InGaAs, and the like.

[0119] In addition, in FIG. 15, the condenser lenses 157a and 157b are schematically illustrated using a single biconvex lens, but these condenser lenses 157a and 157b may be a lens group composed of a plurality of lenses. Further, the lenses used for these condenser lenses 157a and 157b are not particularly limited, and known optical elements such as spherical lenses and aspherical lenses can be appropriately used.

[0120] Here, as one of the combinations of two observation wavelengths (that is, the transmission wavelengths of the optical filters 155a and 155b respectively), for example, 1190 nm is selected from the second wavelength selection region shown in FIG. 8A. In this case, as the other wavelength, it will be selected from around 1300 nm. Here, as is clear from FIG. 8A, in such a wavelength band, the spectral absorption coefficient of water increases as the wavelength becomes longer.

[0121] The spectral absorption coefficient at the wavelength selected from around 1300 nm is required to be consistent with the spectral absorption coefficient at the wavelength of 1190 nm. If they do not match, the principle described above will not hold, and a temperature measurement error will occur as the degree of coincidence decreases.

[0122] Hereinafter, the state in which a temperature measurement error occurs was confirmed by the following test. That is, five types of wavelength selection filters with a half-value 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 nm were prepared, and the difference in the temperature indication values when water as an absorber was present and when it was not present on the measurement object at 900 °C was investigated. The obtained results are shown in FIG. 16.

[0123] As is clear from FIG. 16, it can be seen that for a wavelength selection filter with a central wavelength of 1303.2 nm, the temperature measurement value does not change regardless of the presence or absence of water. This is because the spectral absorption coefficient of water (spectral transmittance when the emitted light passes through water) exactly matches at wavelengths of 1190 nm and 1303.2 nm. That is, by selecting such a central wavelength, it becomes possible to measure the temperature without being affected by water at all.

[0124] On the other hand, when the central wavelength of the transmission band of the wavelength selection filter shifts 1 nm to the longer wavelength side from 1303.2 nm, due to the mismatch in the spectral transmittance of water, it can be seen that a temperature measurement error of approximately 10 °C occurs when the thickness of the water film is 2.5 mm, and a temperature measurement error of approximately 20 °C occurs when the thickness of the water film is 5 mm. As is clear from such results, the transmission wavelength band (central wavelength) of the wavelength selection filter used as the optical filters 155a and 155b is preferably selected according to the expected thickness of the water film, the accuracy required for the temperature measurement error, etc. For example, if a water film with a maximum thickness of about 5 mm is expected, the transmission wavelength of the wavelength selection filter is preferably 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, the width of the transmission wavelength band of the wavelength selection filter is preferably about 1.0 nm.

[0125] Returning to FIG. 15 again, the position control mechanism 115 according to the present embodiment will be described. As previously mentioned, the position control mechanism 115 according to the present 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 the thermal radiation light in the width direction of the measurement object. Thereby, in the temperature measurement device 10 according to the present embodiment, it becomes possible to measure the temperature distribution in the width direction of the measurement object of interest. Hereinafter, the position control mechanism 115 according to the present embodiment will be described more specifically with reference to FIGS. 17A to 18.

[0126] 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 schematically shown in FIG. 17A, for example. In FIG. 17A, 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 orthogonal to both the longitudinal direction and the thickness direction is the width direction of the measurement object. At this time, the drive mechanism functioning as the position control mechanism 115 moves the light receiving unit 111 along the width direction of the measurement object, so that the relative positional relationship between the light receiving unit 111 and the measurement object changes, and it becomes possible to measure the temperature distribution in the width direction of the measurement object of interest.

[0127] Such a drive mechanism is not particularly limited, and various known drive mechanisms such as an actuator can be appropriately used.

[0128] Further, the position control mechanism 115 according to this embodiment may be an angle control mechanism that changes the angle formed by the surface normal direction of the measurement object and the optical axis of the light receiving unit 111. For example, in FIG. 17B, 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 orthogonal to both the longitudinal direction and the thickness direction is the width direction of the measurement object. At this time, a rotation axis is provided in a direction parallel to the longitudinal direction, and the light receiving unit 111 rotates within the range of -φ° to +φ° about the rotation axis, so that the relative positional relationship between the light receiving unit 111 and the measurement object changes, and it becomes possible to measure the temperature distribution in the width direction of the measurement object of interest.

[0129] Here, the rotation angle φ corresponds to the angle formed by the optical axis of the light receiving unit 111 and the surface normal direction of the measurement object. Also, the magnitude of the rotation angle φ is not particularly limited and may be appropriately set according to the width of the measurement object and the installation height of the light receiving unit 111 (the height from the surface of the measurement object). However, when the magnitude |φ| of the rotation angle α exceeds 45°, the energy of the thermal radiation light received by the light receiving unit 111 may become too small. Therefore, 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 θ0 in the model shown in FIG. 12.

[0130] As an angle adjustment mechanism as shown in FIG. 17B, for example, various known pendulum mechanisms using an actuator or the like may be applied, or various imaging lenses such as an imaging lens having a tilt mechanism or an imaging lens having a tilt mechanism and a shift mechanism may be used.

[0131] Also, as an angle control mechanism for changing the angle formed by 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. 18 can be utilized. In FIG. 18, 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 orthogonal to both the longitudinal direction and the thickness direction is the longitudinal direction of the measurement object. In the example shown in FIG. 18, a mirror M is provided obliquely with respect to the surface normal direction of the measurement object between the light guiding optical system (that is, the light receiving mirror 121 and the connection coupler 123) in the light receiving unit 111 and 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 orthogonal to each other.

[0132] At this time, by rotating the mirror M by a predetermined angle with 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 rotation axis, the angle formed between the surface normal direction of the measurement object and the optical axis of the light receiving unit 111 can be changed. As a result, the relative positional relationship between the light receiving unit 111 and the measurement object changes, and it becomes possible to measure the temperature distribution in the width direction of the measurement object of interest.

[0133] Also in the example shown in FIG. 18, the magnitude of the rotation angle around the rotation axis of the mirror M is not particularly limited, and may be appropriately set according to the width of the measurement object and the installation height of the light receiving unit 111 (the height from the surface of the measurement object). However, when the magnitude of the rotation angle exceeds 45°, the energy of the thermal radiation light received by the light receiving unit 111 may become too small. Therefore, the magnitude of the rotation angle is preferably 0° or more and 45° or less.

[0134] An angle adjustment mechanism as shown in FIG. 18 can be realized by using, for example, a known drive mechanism such as an actuator and various known mirrors.

[0135] Further, in the measurement unit 101 according to the present embodiment, the position control mechanism 115 may be a combination of a drive mechanism as shown in FIG. 17A and an angle adjustment mechanism as shown in FIG. 17B or FIG. 18.

[0136] Here, the moving speed in the width direction in the drive mechanism as shown in FIG. 17A and the rotation speed in the angle adjustment mechanism as shown in FIGS. 17B and 18 are not particularly limited. However, when the measurement object is, for example, moving on a conveyance line, it is preferable to determine the moving speed and the rotation speed so as to be synchronized with the moving timing of the measurement object in consideration of the conveyance speed of the measurement object. Also, it is preferable to synchronize the detection frame rate of the sensors 159a and 159b in the detection unit 113 with the conveyance speed of the measurement object.

[0137] The configuration example of the measurement unit 101 according to the present embodiment has been briefly described above with reference to FIGS. 15 to 18.

[0138] <Regarding the configuration example of the arithmetic processing unit 103> Next, with reference to FIGS. 19 and 20, the configuration example of the arithmetic processing unit 103 according to the present embodiment will be described. FIG. 19 is a block diagram showing the configuration example of the arithmetic processing unit 103 according to the present embodiment, and FIG. 20 is an explanatory diagram for explaining the thickness calculation process in the arithmetic processing unit according to the present embodiment.

[0139] As illustrated in FIG. 19, the arithmetic processing unit 103 according to the present embodiment mainly includes a measurement control unit 171, a data acquisition unit 173, a temperature calculation unit 175, a thickness calculation unit 177, a result output unit 179, and a display control unit 181.

[0140] 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 measurement device 10 according to the present embodiment. Further, the measurement control unit 171 controls the operation of the measurement unit 101 so as to measure the thermal radiation light from the measurement object at two types of wavelengths as described above. Furthermore, the measurement control unit 171 can output various setting values such as the measurement conditions of the thermal radiation light including the arrangement conditions of the device to the temperature calculation unit 175 and the thickness calculation unit 177 as necessary.

[0141] 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 two types of wavelengths generated by the measurement unit 101 and outputs them to the temperature calculation unit 175 described later. Further, the data acquisition unit 173 may associate time information such as the date and time when the luminance signal was acquired with the acquired luminance signals at two types of wavelengths and store them in the storage unit 105 as history information.

[0142] 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 wavelengths output from the data acquisition unit 173 to calculate a dichromatic ratio (in other words, the ratio of spectral radiance) obtained by dividing one luminance signal by the other luminance signal. Further, the temperature calculation unit 175 calculates the temperature of the object to be measured by using the calculated dichromatic ratio and the relational expression between the dichromatic ratio and the temperature.

[0143] As is clear from the above formula (6), the dichromatic 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 present embodiment, as shown in the above formulas (7) and (8), since the absorption of the thermal radiation light by the absorber is considered, when the dichromatic ratio R is derived in the same manner as formula (6) by using the above formulas (7) and (8), it is represented by the following formula (16).

[0144]

Equation

[0145] As is clear from the findings described above, in the measurement unit 101 according to the present embodiment, the spectral radiance is measured at wavelengths where the spectral absorption coefficients of the absorbers are the same as each other. Therefore, the term related to the absorption by the absorber shown in the first term in the middle of the above formula (16) cancels out with each other in the numerator and denominator, and the value becomes 1. Therefore, R λ and Λ in the right side of the above formula (16) are the same as those in the above formulas (6a) and (6b).

[0146] Here, R λ and Λ shown in the above formulas (6a) and (6b) are constants determined from the measurement conditions that can be obtained from the measurement unit 101. Therefore, the temperature calculation unit 175 can calculate the temperature T of the object to be measured by using the calculated dichromatic ratio R and the relational expression (leftmost side = rightmost side) in the above formula (16).

[0147] In addition, when temperature calculation unit 175 calculates the dichroic ratio R, there is no particular limitation as to which of the two luminance signals of wavelengths λ1 and λ2 should be used as the denominator and which of the luminance signals should be used as the numerator, and it is sufficient that the reference luminance signal is not changed during the calculation process.

[0148] Furthermore, the temperature calculation unit 175 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 two types of wavelengths λ1 and λ2 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 above formulas (7) and (8). Furthermore, even if the emissivity ε at two types of wavelengths λ1 and λ2 is unknown, if the emissivity ε at the wavelength λ1 and the emissivity ε at the wavelength λ2 are equal to each other, it is possible to directly calculate the temperature T by solving the above formulas (7) and (8) simultaneously. 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.

[0149] The temperature calculation unit 175 outputs information relating to the temperature T of the object to be measured calculated as described above to a thickness calculation unit 177 and a result output unit 179, which will be described later.

[0150] The thickness calculation unit 177 is realized by, for example, a CPU, a ROM, a RAM, etc. The thickness calculation unit 177 further calculates the thickness of the absorber using the blackbody radiance at either 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 in the measurement unit 101 at the time of measurement.

[0151] More specifically, the thickness calculation unit 177 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 175. Further, the thickness calculation unit 177 uses the obtained transmittance τ, the reflectance ρ p , 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 formed between the surface normal direction of the measurement object and the optical axis of the light receiving unit 111) to calculate the thickness t of the absorber based on the above formula (15).

[0152] Here, as schematically shown in FIG. 20, with the center in the width direction of the measurement object as a reference, let the width of the measurement object be represented as W [mm], and the size along the width direction of the measurement field of the radiation luminance of the thermal radiation light be represented as DL [mm]. At this time, it is preferable that the thickness calculation unit 177 performs the calculation process of the thickness t of the absorber as described above in the range of -(W / 2 - DL / 2) to +(W / 2 - DL / 2). As is clear from FIG. 20, the position represented by (W / 2 - DL / 2) means the position where it has returned to the center in the width direction by the size of DL / 2 from the end position (W / 2) in the width direction of the measurement object. If an attempt is made to calculate the thickness t closer to the end of the measurement object than the position represented by (W / 2 - DL / 2), as is clear from FIG. 20, a part that is not the measurement object enters a part of the measurement field, resulting in a missing field. Due to such a missing field, an error may be superimposed on the calculated thickness t of the absorber.

[0153] The thickness calculation unit 177 outputs information regarding the thickness t of the absorber calculated as described above to the result output unit 179 described later.

[0154] The result output unit 179 is realized by, for example, a CPU, a ROM, a RAM, an output device, a communication device, etc. The result output unit 179 outputs information regarding the temperature T of the measurement object output from the temperature calculation unit 175 and information regarding the thickness t of the absorber output from the thickness calculation unit 177 to the user of the temperature measurement device 10. Specifically, the result output unit 179 associates data corresponding to the measurement result of the temperature and the calculation result of the thickness with time data regarding the date and time when the data was generated, etc., and outputs it to various servers and control devices, or uses an output device such as a printer to output it as a paper medium. Further, the result output unit 179 may output data corresponding to the determination result to various information processing devices such as a computer provided outside, or may output it to various recording media.

[0155] Also, when the result output unit 179 outputs data corresponding to the measurement result of the temperature and the calculation result of the thickness to an output device such as a display provided in the temperature measurement device 10 or a display provided in various devices provided outside, it outputs the determination result in cooperation with the display control unit 181 described later.

[0156] The display control unit 181 is realized by, for example, a CPU, a ROM, a RAM, an output device, a communication device, etc. The display control unit 181 performs display control when displaying data corresponding to the measurement result of the temperature and the calculation result of the thickness on various display devices such as a display. Thereby, the user of the temperature measurement device 10 can grasp on the spot the measurement result regarding the temperature of the measurement object and the calculation result regarding the thickness of the absorber.

[0157] As described above, an example of the functions of the arithmetic processing unit 103 according to the present embodiment has been shown. Each of the above components may be configured using general-purpose members and circuits, or may be configured using hardware specialized for the functions of each component. Also, all the functions of each component may be performed by a CPU or the like. Therefore, it is possible to appropriately change the configuration to be used according to the technical level at the time of implementing the present embodiment.

[0158] In addition, it is possible to create a computer program for realizing each function of the arithmetic processing unit according to the present embodiment as described above and install it on a personal computer or the like. Further, it is also possible to provide a computer-readable recording medium in which such a computer program is stored. The recording medium is, for example, a magnetic disk, an optical disk, a magneto-optical disk, a flash memory, or the like. Further, the above computer program may be distributed via a network, for example, without using a recording medium.

[0159] As described above, with reference to FIGS. 14A to 20, the configuration of the temperature measuring device 10 according to the present embodiment has been described in detail.

[0160] Note that depending on the size of the measurement object in the width direction of interest, it may not be possible to perform temperature measurement over the entire width direction of the measurement object using only one temperature measuring device 10. In such a case, by installing a plurality of temperature measuring devices 10 according to the present embodiment along the width direction of the measurement object, it becomes possible to perform temperature measurement over the entire width direction of the measurement object.

[0161] <Regarding the flow of the temperature measurement method> Subsequently, with reference to FIG. 21, an example of the flow of the temperature measurement method performed by the temperature measuring device 10 according to the present embodiment will be briefly described. FIG. 21 is a flowchart showing an example of the flow of the temperature measurement method according to the present embodiment.

[0162] As illustrated in FIG. 21, in the temperature measurement method according to the present embodiment, first, the measurement unit 101 of the temperature measurement device 10 measures the thermal radiation light from the measurement object at two wavelengths where the spectral absorption coefficient of the absorber is equal at each position in the width direction of the measurement object under the control of the measurement control unit 171 of the arithmetic processing unit 103 (step S101). Thereby, the measurement unit 101 generates two types of luminance signals regarding the intensity of the detected thermal radiation light (that is, spectral radiance luminance) and outputs them to the arithmetic processing unit 103.

[0163] Next, the data acquisition unit 173 of the arithmetic processing unit 103 acquires the luminance signals of the spectral radiance at two types of wavelengths output from the measurement unit 101, and outputs them to the temperature calculation unit 175 and the thickness calculation unit 177.

[0164] The temperature calculation unit 175 calculates the dichromatic ratio R by dividing one luminance signal by the other luminance signal using the acquired luminance signals at two wavelengths (step S103). Further, the temperature calculation unit 175 calculates the temperature T of the measurement object based on the relational expression showing the relationship between the dichromatic ratio R and the temperature T as shown in the above formula (9) and the calculated dichromatic ratio R (step S105). Thereafter, the temperature calculation unit 175 outputs information regarding the calculated temperature T of the measurement object to the thickness calculation unit 177 and the result output unit 179.

[0165] Also, the thickness calculation unit 177 calculates the thickness t of the absorber located on the upper surface of the measurement object based on the above formulas (14) and (15) using the acquired luminance signals at two wavelengths and the temperature T of the measurement object calculated by the temperature calculation unit 175 (step S107). Thereafter, the thickness calculation unit 177 outputs information regarding the calculated thickness t of the absorber to the result output unit 179.

[0166] The result output unit 179 outputs the temperature of the measurement object calculated by the temperature calculation unit 175 and the thickness of the absorber calculated by the thickness calculation unit 177 (step S109). Thereby, the user of the temperature measurement device 10 can grasp information regarding the temperature T of the measurement object and the thickness t of the absorber.

[0167] The flow of the temperature measurement method according to the present embodiment has been briefly described above with reference to FIG. 21.

[0168] (Regarding the hardware configuration) Next, with reference to FIG. 22, the hardware configuration of the temperature measurement device 10 according to the embodiment of the present invention will be described in detail. FIG. 22 is a block diagram for explaining the hardware configuration of the temperature measurement device 10 according to the embodiment of the present invention.

[0169] The temperature measurement device 10 mainly includes a CPU 901, a ROM 903, and a RAM 905. The temperature measurement device 10 further includes a host bus 907, a bridge 909, an external bus 911, an interface 913, a measurement 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.

[0170] The CPU 901 functions as a central processing device and a control device, and controls all or part of the operations within the temperature measurement device 10 according to various programs recorded in the ROM 903, the RAM 905, the storage device 919, or the removable recording medium 927. The ROM 903 stores programs, arithmetic parameters, etc. used by the CPU 901. The RAM 905 primary stores programs used by the CPU 901 and parameters that change as appropriate during program execution. These are interconnected by a host bus 907 constituted by an internal bus such as a CPU bus.

[0171] The host bus 907 is connected to an external bus 911 such as a PCI (Peripheral Component Interconnect / Interface) bus via the bridge 909.

[0172] As described above, the measurement unit 101 detects the thermal radiation light from the object to be measured and measures the magnitude of the spectral radiance.

[0173] The input device 915 is an operating means that can be operated by a user, such as a mouse, keyboard, touch panel, button, switch, and lever. Further, the input device 915 may be, for example, a remote control means (so-called remote control) using infrared rays or other radio waves, or an external connection device 929 such as a mobile phone or PDA corresponding to the operation of the temperature measuring device 10. Furthermore, the input device 915 is composed of, for example, an input control circuit that generates an input signal based on information input by the user using the above-described 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 or instruct a processing operation by operating this input device 915.

[0174] The output device 917 is composed of a device capable of notifying the acquired information to the user visually or aurally. 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, printer devices, mobile phones, facsimiles, and the like. The output device 917 outputs, for example, the results obtained by various processes performed by the temperature measuring device 10. Specifically, the display device displays the results obtained by various processes performed by the temperature measuring device 10 in text or image. On the other hand, the audio output device converts an audio signal composed of reproduced audio data, acoustic data, etc. into an analog signal and outputs it.

[0175] The storage device 919 is a data storage device configured as an example of the storage unit of the temperature measuring device 10. The storage device 919 is composed of, for example, a magnetic storage device such as an HDD (Hard Disk Drive), a semiconductor storage device, an optical storage device, or a magneto-optical storage device. This storage device 919 stores programs executed by the CPU 901, various data, and various data acquired from the outside.

[0176] Drive 921 is a reader / writer for a recording medium and is built into or externally attached to the temperature measuring device 10. Drive 921 reads information recorded on a removable recording medium 927 such as a mounted magnetic disk, optical disk, magneto-optical disk, or semiconductor memory and outputs it to the RAM 905. Further, Drive 921 can also write records to a removable recording medium 927 such as a mounted magnetic disk, optical disk, magneto-optical disk, or semiconductor memory. The removable recording medium 927 is, for example, a DVD medium, HD-DVD medium, Blu-ray (registered trademark) medium, etc. Also, the removable recording medium 927 may be a CompactFlash (registered trademark) (CompactFlash: CF), flash memory, or an SD memory card (Secure Digital memory card), etc. Further, the removable recording medium 927 may be, for example, an IC card (Integrated Circuit card) or an electronic device equipped with a non-contact type IC chip.

[0177] 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 IEEE1394 port, a SCSI (Small Computer System Interface) port, etc. Another example of the connection port 923 includes an RS-232C port, an optical audio terminal, an HDMI (High-Definition Multimedia Interface) port, etc. By connecting an external connection device 929 to this connection port 923, the temperature measuring device 10 can directly acquire various data from the external connection device 929 or provide various data to the external connection device 929.

[0178] The communication device 925 is a communication interface composed of, for example, a communication device for connecting to the communication network 931. The communication device 925 is, for example, a communication card for wired or wireless LAN (Local Area Network), Bluetooth (registered trademark), or WUSB (Wireless USB). Further, the communication device 925 may be a router for optical communication, a router for ADSL (Asymmetric Digital Subscriber Line), or a modem for various types of communication. This communication device 925 can transmit and receive signals in accordance with a predetermined protocol such as TCP / IP, for example, between the Internet and other communication devices. Also, the communication network 931 connected to the communication device 925 is composed of 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.

[0179] As described above, an example of the hardware configuration capable of realizing the functions of the temperature measurement device 10 according to the embodiment of the present invention has been shown. Each of the above-described components may be configured using general-purpose members, or may be configured by hardware specialized for the functions of each component. Therefore, it is possible to appropriately change the hardware configuration to be used according to the technical level at the time of implementing this embodiment.

[0180] (Summary) As described above, according to the temperature measurement device and the temperature measurement method according to the embodiment of the present invention, even when there is an absorber that absorbs the thermal radiation light from the measurement object on the optical path between the measurement object and has a wavelength dependence on the spectral absorption coefficient, two wavelengths with equal spectral absorption coefficients of the absorber are selected as the wavelengths for measurement. Further, in the measurement unit of the temperature measurement device according to the embodiment of the present invention, a mechanism capable of measuring the temperature distribution at each position in the width direction of the measurement object is provided. Therefore, it is possible to perform temperature measurement while removing the influence of the absorber on the optical path in the near-infrared band where light absorption by the absorber exists, and it is possible to more accurately measure the temperature of the measurement object at each position in the width direction of the measurement object.

[0181] Also, in the embodiment of the present invention, as described in the above "Method for Selecting Observation Wavelength - Part 2", even when the observation wavelength has a predetermined bandwidth, when measuring the measurement object, it is possible to make the effective spectroscopic absorption coefficients of the absorber in two observation wavelength bands the same. Thereby, even in a situation where the thickness of the absorber present on the optical path changes, it becomes possible to measure the temperature of the measurement object more accurately.

[0182] Furthermore, in the embodiment of the present invention, using the temperature of the measurement object measured more accurately, it becomes possible to more accurately calculate the thickness of the absorber present on the optical path from the measurement object to the radiation thermometer. Therefore, for example, in a process of spraying water on a high-temperature steel material for cooling, the amount of water on the steel plate that affects the heat extraction amount can be accurately monitored. As a result, if the temperature and the water film thickness are known simultaneously, it becomes possible to control the water cooling of the steel material with higher precision.

Example

[0183] (Example 1) In Example 1 shown below, in the continuous casting process of a steelworks, a temperature measuring device 10 equipped with a light receiving unit 111 having a rotating mirror mechanism as shown in FIG. 18 was used with a red-hot steel material moving on a conveying line as the measurement object, and the average surface temperature in the width direction of the red-hot steel material conveyed on the line and the average thickness of the water film that may exist on the red-hot steel material were measured. In this example, 1100 nm and 1130 nm were selected as the two wavelengths of interest. In addition, a generally used monochromatic radiation thermometer was separately installed on the conveying line to compare with the temperature output from the temperature measuring device 10. The obtained results are summarized in Table 1 below.

[0184]

Table 1

[0185] First, when there is almost no water film on the red-hot steel material, it can be seen that the temperature indicated by the temperature measuring device 10 (851.3 °C) and the temperature indicated by the monochromatic radiation thermometer (851.0 °C) are in a substantially consistent state. After that, when a water film comes to exist on the red-hot steel material, it can be seen that while the temperature indicated by the monochromatic radiation thermometer decreases to 828.0 °C, the temperature indicated by the temperature measuring device 10 does not change and remains at 853.3 °C.

[0186] On the other hand, it was found that as the amount of water existing on the red-hot steel material increases, the transmittance of near-infrared light decreases. Specifically, when there is almost no water film (when the average water film thickness is 0.5 mm), the transmittance of near-infrared light was 93.6%, whereas when there is a water film (when the average water film thickness is 3.0 mm), the transmittance of near-infrared light became 67.8%. From the transition of such transmittance, it is considered that the measurement results indicated by the monochromatic radiation thermometer in Table 1 above are due to the fact that as the transmittance of near-infrared light decreases, the energy of the thermal radiation light detected by the monochromatic radiation thermometer decreases. Therefore, it can be seen that the temperature indicated by the temperature measuring device 10 correctly reflects the surface temperature of the red-hot steel material of interest.

[0187] Also, using the temperature indicated by the temperature measuring device 10, the thickness of the water film was calculated for both the case where there is no water film and the case where there is a water film. Then, the calculation result when there is no water film was an average water film thickness = 0.5 mm, and the calculation result when there is a water film was an average water film thickness = 3.0 mm. From this result, it was found that even when it was recognized that there was no water film, actually, a water film with an average water film thickness of 0.5 mm existed.

[0188] (Example 2) Subsequently, an experiment was conducted to verify the measurement of the water film thickness using the temperature measuring device 10 according to the present invention. Since it is difficult to directly place water on the surface of a steel material heated to a high temperature and maintain a constant water film thickness, an experimental apparatus as shown in Fig. 23 was prepared. Fig. 23 is an explanatory diagram schematically showing the outline of the experimental apparatus used in Example 2.

[0189] In the experimental apparatus shown in Fig. 23, the temperature of the steel plate was maintained at 908°C. With the thickness of the water in the petri dish set at 5 mm or 10 mm, the petri dish was fixed at a position 10 cm above the steel plate. Then, when the installation angle θ of the temperature measurement device 10 was set at 0° or 30°, the temperature of the steel plate was measured by the temperature measurement device 10, and the thickness of the water in the petri dish was calculated based on the above formula (15). The obtained results are summarized in Table 2 below.

[0190]

Table 2

[0191] As is clear from the results shown in Table 2, for the steel plate temperature, a value close to the actual temperature of the steel plate is indicated, showing that the temperature measurement device 10 is operating properly. Also, as is clear from the results shown in Table 2, as the thickness of the water in the petri dish increases, the spectral transmittance decreases. Further, as the installation angle θ increases, the optical path length in the water becomes longer. Therefore, even with the same water thickness, it can be seen that the spectral transmittance decreases and the observed radiance attenuates. However, under any conditions, the calculated value of the water thickness shows a value almost equal to the set value, revealing that the temperature measurement device 10 can accurately measure the thickness of the water film.

[0192] From such findings, it has become clear that by using the temperature measurement device according to the present invention, even when there is an absorber that absorbs the thermal radiation light from the measurement object on the optical path for measuring the measurement object and has a wavelength dependence in the spectral absorption coefficient, it is possible to more accurately measure the temperature distribution in the width direction of the measurement object.

[0193] (Example 3) In an actual continuous casting machine, the temperature measuring device according to the present invention was installed at a location in the center of the line, and the temperature measuring device was rotated in the slab width direction to measure the temperature of the slab. The slab width W of the slab flowing on the line of the continuous casting machine was 2200 mm. In addition, the size DL of the measurement field of view of the temperature measuring device along the slab width direction was 56 mm at the slab end position, and 1100 nm and 1130 nm were selected as the two wavelengths at which the temperature measuring device was focused.

[0194] Also, for comparison, a general monochromatic radiation thermometer (measurement wavelength set to 1000 nm) was used to measure the temperature of the slab. The obtained results are shown in Table 3 and FIG. 24 below.

[0195]

Table 3

[0196] As is clear from Table 3 and FIG. 24, the temperature measuring device according to the present invention showed a higher temperature at the center of the width where the water film thickness was thick compared to a general monochromatic thermometer, and showed almost the same temperature as the monochromatic thermometer at other positions.

[0197] Also, using the spectral transmittance of the water film derived from the water film thickness shown by the temperature measuring device according to the present invention and the temperature shown by the temperature measuring device according to the present invention, the spectral radiance after attenuation by the water film was calculated, and the obtained spectral radiance after attenuation was converted to temperature. This converted temperature corresponds to the temperature that a monochromatic thermometer that measures the spectral radiance after attenuation would show.

[0198] As is clear from Table 3, the converted temperatures at positions other than the +1100 mm position are almost the same as the temperatures shown by the monochromatic thermometer, and it was confirmed that the slab temperature and the water film thickness can be accurately measured even when the installation angle (measurement angle) of the temperature measuring device changes.

[0199] In addition, when measuring the position at +1100 nm (the outermost edge portion), the spectral radiance decays due to missing visual fields. As is clear from Table 3, at the outermost edge portion, although the actual thickness of the water film was 0 mm, it can be seen that the thickness of the water film was overestimated. From such results, it can be understood that it is preferable not to calculate the thickness of the water film for the outermost edge portion.

[0200] As described above, the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that those having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims, and it is naturally understood that these also belong to the technical scope of the present invention.

Explanation of Signs

[0201] 10 Temperature measuring device 101 Measuring unit 103 Arithmetic processing unit 105 Storage 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 Condensing lens 159a, 159b Sensor 171 Measurement control unit 173 Data acquisition unit 175 Temperature calculation unit 177 Thickness calculation unit 179 Result output unit 181 Display control unit

Claims

1. An apparatus for measuring the temperature of a measurement object by detecting the thermal radiation light in the near-infrared band emitted by the measurement object in a state where an absorber having a wavelength dependence on the spectral absorption coefficient exists in at least a part of the optical path in the near-infrared band, measuring the thermal radiation light of the measurement object at two wavelengths at which the spectral absorption coefficients of the absorber are the same as each other, and generating measurement data indicating detection results of the radiation luminance of the thermal radiation light at the two wavelengths, a measurement unit; an arithmetic processing unit that calculates the temperature of the measurement object based on the measurement data corresponding to the two wavelengths generated by the measurement unit and a relational expression between spectral radiation luminance and temperature; comprising: the measurement unit includes: a light receiving unit that receives the thermal radiation light of the measurement object; a detection unit that detects the thermal radiation light received by the light receiving unit; a position control mechanism that changes the relative positional relationship between the measurement object and the light receiving unit and causes the light receiving unit to measure the distribution of the thermal radiation light in the width direction of the measurement object; having: the position control mechanism is an angle control mechanism that changes the angle formed by the surface normal direction of the measurement object and the optical axis of the light receiving unit; the arithmetic processing unit further calculates the thickness of the absorber using the blackbody radiation luminance at any one of the two wavelengths calculated using the temperature of the measurement object, the measured radiation luminance of the thermal radiation light, the spectral absorption coefficients 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 side opposite to the measurement object side, and the angle formed by the surface normal direction of the measurement object and the optical axis of the light receiving unit; as the two wavelengths, two wavelength bands having a predetermined width including wavelengths at which the spectral absorption coefficients of the absorber are the same as each other are selected; the two wavelength bands are selected such that the apparent spectral absorption coefficients calculated by weighting the spectral absorption coefficient of the absorber with the spectral radiation luminance of the measurement object temperature are equal to each other, a temperature measuring device.

2. The temperature measuring device according to claim 1, wherein the angle control mechanism rotates a mirror provided obliquely with respect to the surface normal direction between the object to be measured and a light guiding optical system that guides the thermal radiation light to the detection unit by a predetermined angle around the longitudinal direction of the object to be measured, thereby changing the angle formed by the surface normal direction and the optical axis of the light receiving unit.

3. The detection unit includes: a branching optical element that branches the thermal radiation light of the object to be measured 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 provided between the branching optical element and the first detection element, which transmits the thermal radiation light at one of the two wavelengths; a second optical filter provided between the branching optical element and the second detection element, which transmits the thermal radiation light at the other of the two wavelengths; The temperature measuring device according to claim 1 or 2, comprising:

4. The arithmetic processing unit: calculates a dichromatic ratio by dividing one of the measurement data corresponding to the two wavelengths by the other; approximates that the spectral emissivities are equal to each other between the two wavelengths, and calculates the temperature of the object to be measured based on the relationship between the calculated dichromatic ratio and the temperature using the dichromatic ratio. The temperature measuring device according to any one of claims 1 to 3.

5. When the center in the width direction of the object to be measured is used as a reference, the width of the object to be measured is represented as W, and the size along the width direction of the measurement field of the radiant luminance of the thermal radiation light is represented as DL, The arithmetic processing unit calculates the thickness of the absorber in the range of -(W / 2 - DL / 2) to +(W / 2 - DL / 2). The temperature measuring device according to any one of claims 1 to 4.

6. The temperature measuring device according to any one of claims 1 to 5, wherein the absorber is at least one of water, oil, solution, glass, or resin.

7. The temperature measuring device according to any one of claims 1 to 6, wherein the near-infrared band is 940 nm to 1350 nm.

8. A method for measuring the temperature of an object to be measured by detecting the thermal radiation light in the near-infrared band emitted by the object to be measured in a state where an absorber having a wavelength dependence on the spectral absorption coefficient exists in at least a part of the optical path in the near-infrared band, and measuring the temperature of the object to be measured based on the detection result of the radiant luminance of the thermal radiation light. A light receiving unit that receives the thermal radiation light of the measurement object, 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 measurement object and the light receiving unit so that the light receiving unit measures the distribution of the thermal radiation light in the width direction of the measurement object. The position control mechanism is an angle control mechanism that changes the angle formed by the surface normal direction of the measurement object and the optical axis of the light receiving unit. The measurement unit measures the thermal radiation light of the measurement object at two wavelengths at which the spectral absorption coefficients of the absorber are the same, and generates measurement data indicating the detection results of the radiation luminance of the thermal radiation light at the two wavelengths. Calculating the temperature of the measurement object based on the generated measurement data corresponding to the two wavelengths and the relational expression between the spectral radiation luminance and the temperature. Including In the step of calculating the temperature of the measurement object, the blackbody radiation luminance at any one of the two wavelengths calculated using the temperature of the measurement object, the radiation luminance of the measured thermal radiation light, the spectral absorption coefficients 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 side opposite to the measurement object side, and the angle formed by the surface normal direction of the measurement object and the optical axis of the light receiving unit are used to further calculate the thickness of the absorber. As the two wavelengths, two wavelength bands having a predetermined width including wavelengths at which the spectral absorption coefficients of the absorber are the same are selected. The two wavelength bands are selected such that the apparent spectral absorption coefficients calculated by weighted-averaging the spectral absorption coefficients of the absorber with the spectral radiation luminance of the measurement target temperature are equal to each other. Temperature measurement method.

9. The thermal radiation light in the near-infrared band emitted by the object to be measured is measured at two wavelengths where the spectral absorption coefficient of the absorber having a wavelength dependence in the near-infrared band is the same for each other, in a state where the absorber is present in at least a part of the optical path, and measurement data showing the detection result of the radiation luminance of the thermal radiation light is output. It has a light receiving unit that receives the thermal radiation light from 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 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 object to be measured. The position control mechanism is an angle control mechanism that changes the angle formed by the surface normal direction of the object to be measured and the optical axis of the light receiving unit. As the two wavelengths, two wavelength bands with a predetermined width including wavelengths where the spectral absorption coefficients of the absorber are the same for each other are selected, and the two wavelength bands are selected so that the apparent spectral absorption coefficients calculated by weighted-averaging the spectral absorption coefficient of the absorber with the spectral radiation luminance at the temperature of the object to be measured are equal to each other. To a computer capable of acquiring data from the measurement unit, A program for realizing an arithmetic processing function for calculating the temperature of the object to be measured based on the measurement data corresponding to the two wavelengths and the relational expression between the spectral radiation luminance and the temperature, The arithmetic processing function further calculates the thickness of the absorber using the blackbody radiation luminance at any one of the two wavelengths calculated using the temperature of the object to be measured, the radiation luminance of the measured thermal radiation light, the spectral absorption coefficients of the absorber at the two wavelengths, the reflectance of the thermal radiation light at the interface of the absorber on the object to be measured side, the reflectance of the thermal radiation light at the interface of the absorber on the side opposite to the object to be measured side, and the angle formed by the surface normal direction of the object to be measured and the optical axis of the light receiving unit. Program.

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