JP7393648B2 - Temperature measuring device and temperature measuring method - Google Patents

Description

The present invention relates to a temperature measuring device and a temperature measuring method.

Radiation thermometry is a method of determining the temperature of a target object by detecting the thermal radiation emitted by the object according to its temperature using a measuring device such as a radiation thermometer. It is a remote temperature measurement method that can measure temperature. Today, many industries, including the steel industry, use such radiation thermometry methods.

In particular, in the steel industry, during the manufacturing process, water or other materials that have the property of absorbing thermal radiation in the near-infrared band are placed on the optical path between the object to be measured, such as a steel sheet material, and a measurement device such as a radiation thermometer. Absorbers such as fats and oils are often present. In such a case, a part of the thermal radiation from the object to be measured is absorbed by the absorber, causing a measurement error and making it impossible to accurately measure the temperature of the object to be measured.

Therefore, in order to suppress the measurement error caused by the absorber existing on the optical path as described above, the present inventors have developed a spectroscopic analysis of the absorber of interest, for example, as disclosed in Patent Document 1 below. We have proposed a two-color radiation thermometer that uses two wavelengths with the same transmittance as measurement wavelengths. In general, a two-color radiation thermometer observes thermal radiation from an object at two different wavelengths, and its measurement principle is that the ratio of the radiance at the two wavelengths changes depending on the temperature. However, when an absorber is present on the optical path, there is a problem in that the absorber attenuates the thermal radiation differently at two wavelengths, causing an error. Therefore, in the two-color radiation thermometer disclosed in Patent Document 1, by making the spectral absorption coefficients of the absorber at the two wavelengths used for measurement the same, the influence of attenuation of thermal radiation light is suppressed, This allows for accurate temperature measurements.

JP2019-23635A

Thermal radiation from an object changes monotonically as the temperature increases or decreases, but with a radiation thermometer, the temperature of the object being observed decreases, and the amount of thermal radiation to be observed increases when a photodetector (for example, an infrared sensor ), the output from the photodetector becomes unstable and the output changes irregularly in response to increases and decreases in temperature, making accurate temperature measurement impossible. Therefore, in a typical monochromatic radiation thermometer, a measurement lower limit temperature is set as the lower limit temperature at which accuracy of measurement temperature can be ensured. In view of this situation, the present inventors discovered that a technology for lowering the minimum measurement temperature while ensuring the accuracy of temperature measurement results in a two-color radiation thermometer was needed, and the above-mentioned patent Regarding the two-color radiation thermometer disclosed in Document 1, we conducted a study to widen the usable temperature range.

Therefore, the present invention was conceived based on the knowledge obtained from the above study, and an object of the present invention is to lower the minimum measurement temperature while ensuring the accuracy of temperature measurement. An object of the present invention is to provide a temperature measuring device and a temperature measuring method that can perform the following steps.

The temperature measuring device of the present invention uses a two-color radiation thermometer to measure the temperature of an object to be measured. A light receiving unit that receives thermal radiation from the measurement target in a state where it can exist on the optical path to the target, and a first optical filter that detects the spectral radiance of the thermal radiation received by the light receiving unit. generating a first luminance signal by measuring through the light receiving section, and setting the spectral radiance of the thermal radiation received by the light receiving section so that the spectral transmittance of the first optical filter and the absorber are the same. a detection unit that generates a second brightness signal by measuring through a second optical filter, and a temperature calculation unit that calculates the temperature of the measurement target from the first brightness signal and the second brightness signal. and a dichromatic ratio obtained by dividing the first luminance signal by the second luminance signal is a predetermined value of about 1 at the lower measurement limit temperature of the temperature measuring device, and When the relationship between the transmission wavelength width of the first optical filter and the amount of change in the dichroic ratio is obtained under the condition that the spectral transmittances of the first optical filter and the second optical filter are the same, In the relationship between the transmission wavelength width of the first optical filter and the amount of change in the dichroic ratio, the transmission wavelength width and center wavelength of the first optical filter and the second optical filter are determined based on the condition that becomes an inflection point. Set.

The temperature measuring method of the present invention uses a two-color radiation thermometer to measure the temperature of an object to be measured. A light receiving unit that receives thermal radiation from the measurement target in a state where it can exist on the optical path to the target, and a first optical filter that detects the spectral radiance of the thermal radiation received by the light receiving unit. generating a first luminance signal by measuring through the light receiving section, and setting the spectral radiance of the thermal radiation received by the light receiving section so that the spectral transmittance of the first optical filter and the absorber are the same. a detection unit that generates a second brightness signal by measuring through a second optical filter, and a temperature calculation that calculates the temperature of the object to be measured from the first brightness signal and the second brightness signal. A predetermined value such that the dichromatic ratio obtained by dividing the first luminance signal by the second luminance signal using a temperature measuring device having Under the condition that the spectral transmittances of the first optical filter and the second optical filter are the same, the relationship between the transmission wavelength width of the first optical filter and the amount of change in the dichroic ratio is obtained. and the transmission wavelength width of the first optical filter and the second optical filter based on a condition that becomes an inflection point in the relationship between the transmission wavelength width of the first optical filter and the amount of change in the dichroic ratio. and setting a center wavelength.

As explained above, according to the present invention, in a two-color radiation thermometer, it is possible to lower the minimum measurement temperature while ensuring accuracy of temperature measurement.

It is a graph diagram for explaining the spectral transmission characteristics of water and wavelength selection of a two-color radiation thermometer. FIG. 2 is a graph diagram showing the relationship between temperature and dichroic ratio when an optical filter having the transmission characteristics shown in FIG. 1 is used. It is a table showing an example of conditions for center wavelengths and transmission wavelength widths of two types of wavelength bands. FIG. 2 is a graph diagram showing an example of the relationship between the spectral transmission characteristics of water and the transmission wavelength width of an optical filter. FIG. 2 is a graph diagram showing an example of the relationship between the spectral transmission characteristics of water and the transmission wavelength width of an optical filter. FIG. 2 is a graph diagram showing an example of the relationship between the spectral transmission characteristics of water and the transmission wavelength width of an optical filter. FIG. 2 is a graph diagram showing an example of the relationship between the spectral transmission characteristics of water and the transmission wavelength width of an optical filter. FIG. 2 is a graph diagram showing an example of the relationship between the spectral transmission characteristics of water and the transmission wavelength width of an optical filter. FIG. 2 is a graph diagram showing the relationship between temperature and dichroic ratio for each transmission wavelength width of an optical filter on the short wavelength side. FIG. 2 is a graph diagram showing the relationship between the transmission wavelength width of an optical filter on the short wavelength side and the amount of change in dichroic ratio per 100°C. It is an explanatory view showing typically an example of composition of a temperature measurement device concerning the same embodiment. It is an explanatory view showing typically an example of composition of a temperature measurement device concerning the same embodiment. It is an explanatory view showing typically an example of composition of a measuring part with which a temperature measuring device concerning the same embodiment is provided. FIG. 2 is a block diagram schematically showing an example of the configuration of a calculation processing unit included in the temperature measurement device according to the embodiment. It is a flowchart which showed an example of the flow of the temperature measurement method implemented by the temperature measurement device concerning the same embodiment. FIG. 2 is a block diagram showing an example of the hardware configuration of an arithmetic processing unit included in the temperature measuring device according to the embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that, in this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals and redundant explanation will be omitted.

(Regarding studies conducted by the inventors)
Before explaining the temperature measuring device and temperature measuring method according to the embodiment of the present invention, please refer to FIGS. 1 to 6 for further study contents using the two-color radiation thermometer disclosed in Patent Document 1. I will explain while doing so.
FIG. 1 is a graph for explaining the spectral transmission characteristics of water and wavelength selection of a two-color radiation thermometer, and FIG. 2 shows the temperature and temperature when using an optical filter having the transmission characteristics shown in FIG. FIG. 3 is a graph diagram showing the relationship with the dichromatic ratio. FIG. 3 is a table showing an example of conditions for the center wavelength and transmission wavelength width of two types of wavelength bands. 4A to 4E are graphs showing an example of the relationship between the spectral transmission characteristics of water and the transmission wavelength width of an optical filter. FIG. 5 is a graph showing the relationship between temperature and dichroic ratio using the transmission wavelength width of the optical filter on the short wavelength side as a parameter. FIG. 6 is a graph showing the relationship between the transmission wavelength width of the optical filter on the short wavelength side and the amount of change in dichroic ratio per 100°C.

Regarding the two-color radiation thermometer shown in Patent Document 1, the present inventors have conducted extensive studies on a method for lowering the minimum measurement temperature while ensuring temperature measurement accuracy. The two-color radiation thermometer used here has two optical bandpass filters (hereinafter also simply referred to as "optical filters") and two photodetectors (InGaAs elements) corresponding to the two optical bandpass filters. According to the principle of the two-color radiation thermometer shown in Patent Document 1, two wavelengths near the wavelength 1200 nm and near the wavelength 1300 nm at which the spectral transmittance of water is equal are selected, and these two wavelengths are The settings are made to perform measurements using the .

In such a two-color radiation thermometer, when the transmission wavelength width of the two optical filters is 20 nm, two different transmission wavelength bands are set, as shown by a dashed line and a broken line in FIG. The effective transmittance (average transmittance) of water, which is an absorber, is the same in the wavelength band (indicated by a dashed line) and the wavelength band on the longer wavelength side (indicated by a broken line). Here, in FIG. 1, the width 20 nm indicated by w1 is the width of the transmission wavelength band of the optical filter on the short wavelength side, and the width 20 nm indicated by w2 is the width of the transmission wavelength band of the optical filter on the long wavelength side. It is.

Figure 2 shows the spectral radiance obtained by dividing the spectral radiance in the shorter wavelength band by the spectral radiance in the longer wavelength band in a two-color radiation thermometer that has an optical filter as shown in Figure 1. The relationship between dichroic ratio and temperature is shown. From FIG. 2, it can be seen that as the temperature decreases, the value of the two-color ratio also decreases. From this result, in order to lower the measurement minimum temperature, it is necessary to balance the spectral radiance on the short wavelength side and the spectral radiance on the long wavelength side so that the dichroic ratio at the measurement minimum temperature is close to 1. It has become clear that it is desirable, and for this purpose, it is important to improve the transmission wavelength width of the optical filter.

In order to improve the transmission wavelength width of an optical filter, if we consider widening the transmission wavelength width on the short wavelength side and the long wavelength side, as is clear from Figure 1, the transmission wavelength width in the short wavelength side wavelength band is When the width is expanded toward shorter wavelengths, it includes a region where the spectral transmittance of water increases rapidly. On the other hand, in the wavelength band on the long wavelength side, when the transmission wavelength width is expanded to the longer wavelength side, a region where the spectral transmittance of water decreases is included. If the transmission wavelength width is simply widened due to the characteristic of the wavelength dependence of the spectral transmittance of water, it is not possible to realize an optical filter in which the transmittance of water becomes equal.

In addition, in Figure 2, the dichroic ratio near 500°C, which is the lowest measurement temperature that can ensure the accuracy of temperature measurement results, is approximately 0.45, so the radiance in the wavelength band on the short wavelength side is It can be seen that the radiance is less than half that of the wavelength band on the wavelength side. In addition, as shown in Figure 2, the dichroic ratio decreases monotonically as the temperature of the measurement target decreases, so the decrease in radiance due to the decrease in the temperature of the measurement target is due to the long wavelength It can be seen that the wavelength band on the short wavelength side is more noticeable than the wavelength band on the side. Therefore, when the temperature of the object to be measured falls (in other words, when trying to lower the measurement minimum temperature), the photodetector that detects the thermal radiation in the short wavelength band changes to the longer wavelength band. It can be seen that the amount of light becomes insufficient before the photodetector detects thermal radiation in the wavelength band.

In addition, even considering that in the spectral luminance characteristics of blackbody radiation, the radiance located on the longer wavelength side increases more rapidly than the radiance located on the shorter wavelength side, the transmission wavelength of the optical filter It can be seen that when widening the width, the transmission wavelength width on the short wavelength side should be given more priority than on the long wavelength side.

In addition, the two-color radiation thermometer as disclosed in Patent Document 1 includes a photodetector for detecting spectral radiance in a wavelength band on the short wavelength side, and a photodetector for detecting spectral radiance in a wavelength band on the long wavelength side. The same optical element (for example, an InGaAs element) is used as a photodetector for detecting the . Therefore, it is efficient to determine the transmission wavelength widths of the two wavelength bands so that the dichromatic ratio is approximately 1 at the lower measurement limit temperature, which is the lower limit temperature that can ensure the accuracy of temperature measurement results. I understand. In other words, it is important to balance the spectral radiance detected in the wavelength band on the short wavelength side and the spectral radiance detected in the wavelength band on the long wavelength side. In order to maximize the efficiency of the (same) photodetector used in each wavelength band, the spectral radiance detected in the short wavelength band and the long wavelength band are It can be seen that it is desirable that the detected spectral radiances be approximately the same. In other words, the dichroic ratio obtained by dividing the spectral radiance detected in the wavelength band on the short wavelength side by the spectral radiance detected in the wavelength band on the long wavelength side is set to a predetermined value of approximately 1. It turns out that it is desirable to do so.

Note that the desirable dichroic ratio is "about 1" because the optical filters used in the wavelength band on the short wavelength side and the wavelength band on the long wavelength side can be constructed by obtaining commercially available optical filters, for example. However, in such a case, it is assumed that a combination (configuration) of optical filters with an accurate dichroic ratio of "1" does not exist on the market and cannot be obtained. Therefore, although we aim to configure the dichromatic ratio to be "1", it does not have to be strictly "1", and may deviate somewhat from "1" as long as it is within the allowable range of temperature measurement accuracy. It can be said.

In addition, in the above explanation, the dichroic ratio obtained by dividing the spectral radiance in the wavelength band on the short wavelength side by the spectral radiance in the wavelength band on the long wavelength side was explained, but the wavelength band on the long wavelength side The same thing can be said by using the dichroic ratio obtained by dividing the spectral radiance of by the spectral radiance of the wavelength band on the short wavelength side. In other words, as the measurement minimum temperature approaches, when calculating the dichroic ratio, the radiance located in the denominator approaches a small value faster than the radiance located in the numerator. Division becomes unstable. Therefore, as in the above explanation, it is understood that it is important to balance the radiance in the wavelength band on the short wavelength side and the radiance in the wavelength band on the long wavelength side.

Based on the above findings, the present inventors conducted a simulation regarding the center wavelength (center transmission wavelength) and transmission wavelength width of each optical filter when the transmission wavelength width of the optical filter was widened in stages. In this simulation, the dichroic ratio in the two wavelength bands is set to 1 at the minimum measurement temperature based on the above knowledge, and based on the principle of the two-color radiation thermometer shown in Patent Document 1, the spectroscopy of water in the two wavelength bands is A condition was set that the transmittance (more precisely, the average transmittance in the transmission wavelength width) should be the same. Then, as initial conditions, the center wavelength of the optical filter on the short wavelength side is set to 1200 nm, the center wavelength of the optical filter on the long wavelength side is set to 1300 nm, and the filter characteristics of the optical filter on the short wavelength side are kept as fixed as possible. , while satisfying the above-mentioned conditions that the dichroic ratio in the two wavelength bands is 1 and the spectral transmittance is the same, the filter characteristics (transmission wavelength width and center wavelength) of the optical filter on the long wavelength side are changed. This was simulated.

The obtained results are shown in FIG. 3. Furthermore, among the seven patterns of simulation conditions shown in FIG. 3, simulation results for five patterns (patterns B to F) are shown in FIGS. 4A to 4E, respectively. In addition, in FIG. 3, the unit of all numerical values is nm.

As in the example shown in Figure 1, if the transmission wavelength width is the same for the two wavelengths, at the lower measurement limit temperature, the amount of light in the shorter wavelength band is relatively insufficient, and as shown in Figure 2. As shown, the two-color ratio is 0.45 (about 1/2). In order to set the dichroic ratio to a predetermined value of approximately 1, the transmission wavelength width of the optical filter on the short wavelength band side is adjusted in the direction of widening, and the transmission wavelength width of the optical filter on the long wavelength band side is adjusted to be twice that of the optical filter on the long wavelength band side. You can see that it is sufficient to do this. In the results shown in FIG. 3, in patterns A to D, the transmission wavelength width of the optical filter on the short wavelength side is changed to that of the optical filter on the long wavelength side without changing the center wavelength of the optical filter on the short wavelength side from 1200 nm. This satisfies the above-mentioned condition that the spectral transmittance is the same between the optical filter on the short wavelength side and the optical filter on the long wavelength side. Note that the center wavelength of the optical filter on the longer wavelength side is slightly shifted toward the shorter wavelength side in order to satisfy the condition that the spectral transmittance of water is the same in the two wavelength bands. As shown in FIGS. 4A to 4C, each wavelength band did not include many regions where the spectral transmittance of water changed significantly, and the effective transmittance of each optical filter could be easily adjusted.

On the other hand, in Patterns E to G, simply adjusting the transmission wavelength width and center wavelength of the optical filter on the longer wavelength side will not result in a dichroic ratio of approximately 1 in the above two wavelength bands. Since it was not possible to find a solution that satisfied the condition that the spectral transmittance of water is the same, it was necessary to shift the center wavelength of the optical filter on the shorter wavelength side to the longer wavelength side. As a result, the transmission wavelength width of the optical filter on the short wavelength side is no longer exactly twice the transmission wavelength width of the optical filter on the long wavelength side. In addition, in pattern E shown in FIG. 4D, the transmission wavelength bands of the two optical filters are very close to each other, and in pattern F shown in FIG. 4E, a part of the transmission wavelength bands of the two optical filters overlap. .

Figure 5 shows the relationship between the dichroic ratio and temperature for each transmission wavelength width of the optical filter on the short wavelength side, obtained from the simulation results when using the optical filters shown in patterns B to F in Figure 3. shows. As is clear from FIG. 5, it can be seen that as the transmission wavelength width of the optical filter on the short wavelength side widens, the slope of the curve showing the relationship between dichroic ratio and temperature becomes smaller. A decrease in the slope of the curve means that the amount of change in the two-color ratio will decrease even when the temperature changes significantly, which means that the sensitivity of the two-color radiation thermometer will decrease. It means. Therefore, it can be seen that in order to ensure the accuracy of temperature measurement, the transmission wavelength width of the optical filter on the short wavelength side should not be too wide.

Therefore, FIG. 6 shows the results obtained by simulating the relationship between the transmission wavelength width of the optical filter on the short wavelength side and the amount of change in dichroic ratio per 100° C.
Looking at FIG. 6, as the transmission wavelength width of the optical filter on the short wavelength side increases, the amount of change in the dichroic ratio decreases, but especially when the transmission wavelength width of the optical filter on the short wavelength side becomes 90 nm. It can be seen that the amount of change in the two-color ratio decreases rapidly with the position as the boundary. In this case, it can be said that the point where the transmission wavelength width of the optical filter on the short wavelength side is 90 nm is the inflection point of the amount of change in dichroic ratio per 100°C.

Looking at the table shown in Figure 3, it can be seen that until the inflection point, where the transmission wavelength width of the optical filter on the short wavelength side is 90 nm (pattern D in Figure 3), the center of the optical filter on the short wavelength side is By setting the transmission wavelength width of the optical filter on the short wavelength side to twice the transmission wavelength width of the optical filter on the long wavelength side without changing the wavelength from 1200 nm, it is possible to select an optical filter that satisfies the conditions. Ta.

Therefore, while ensuring the sensitivity of the two-color radiation thermometer, the two-color radiation temperature is It can be seen that when measuring temperature using a meter, it is most efficient to set the transmission wavelength width of the optical filter on the short wavelength side to 90 nm and the transmission wavelength width of the optical filter on the long wavelength side to 45 nm.

Based on the above findings, the present inventors have determined that the dichroic ratio is a predetermined value of approximately 1 in the two wavelength bands, and the spectral transmittance of water is the same. While widening the transmission wavelength width of the optical filter on the wavelength side and keeping the filter characteristics of the optical filter on the short wavelength side fixed, search for the transmission wavelength width and center wavelength of the optical filter on the long wavelength side that satisfy the conditions. By doing so, we came up with the idea that it is possible to set an appropriate transmission wavelength width for an optical filter.

In the above explanation, water was used as an example of an absorber, but absorbers other than water (e.g., oil, solution, glass, resin, etc.) may exist on the optical path between the measurement target and the object. Similar measures can be taken in cases where the

(About how to set the transmission wavelength width of the optical filter in a two-color radiation thermometer)
Based on the above knowledge, the present inventors came up with a method for setting the transmission wavelength width of an optical filter when lowering the minimum measurement temperature required for a two-color radiation thermometer. Below, a method for setting the transmission wavelength width of an optical filter in a two-color radiation thermometer discovered by the present inventors will be explained.

In this method, first, as a solution condition, "the dichroic ratio is a predetermined value of about 1 in two wavelength bands, and the spectral transmittance is the same" is determined.
Next, for example, as initial values, the center wavelength of the optical filter on the short wavelength side is set to 1200 nm, and the center wavelength of the optical filter on the long wavelength side is set to 1300 nm.
Then, while maintaining the above conditions, the transmission wavelength width of the optical filter on the short wavelength side is appropriately widened, as shown in FIG. 3, for example.

Then, in order to satisfy the above conditions, the transmission wavelength width and center wavelength of the optical filter on the long wavelength side are inevitably determined. If the transmission wavelength width and center wavelength of the optical filter on the long wavelength side that can satisfy the above conditions cannot be determined, the center wavelength of the optical filter on the long wavelength side is shifted to the shorter wavelength side.

By repeating such experiments, determining the conditions for the optical filter and determining the dichroic ratio each time, we can determine the transmission wavelength width of the optical filter on the short wavelength side and the amount of change in the dichroic ratio, as shown in Figure 6. You can find the relationship between

As a result, it is possible to know the inflection point in the relationship between the transmission wavelength width of the filter on the short wavelength side and the amount of change in the dichroic ratio. The transmission wavelength width and center wavelength of an optical filter can be determined, and by using such an optical filter, the lower limit of the measured temperature can be lowered while ensuring the accuracy of the temperature measurement result.

<About the configuration of the temperature measuring device>
Below, first, the overall configuration of the temperature measuring device 10 according to the embodiment of the present invention will be described in detail with reference to FIGS. 7A and 7B. 7A and 7B are explanatory diagrams showing an example of the overall configuration of the temperature measuring device 10 according to this embodiment.

In the temperature measuring device 10 according to the present embodiment, an absorber having wavelength-dependent spectral transmittance in the near-infrared band absorbs thermal radiation in the near-infrared band emitted by the object to be measured, and the absorber absorbs the thermal radiation light in the near-infrared band to the object to be measured. This device uses a two-color radiation thermometer to measure the temperature of an object that may be present on the road. Here, examples of the absorber whose spectral absorption coefficient has wavelength dependence in the near-infrared band include at least one of water, water vapor, fats and oils, solutions, glass, and resins. Further, in this embodiment, the near-infrared band is particularly focused on the band from 940 nm to 1350 nm. The reason why the lower limit is set to 940 nm is that water becomes a semitransparent substance with strong wavelength dependence at wavelengths of 800 nm or more (particularly 940 nm or more) belonging to the near-infrared band. Moreover, the reason why the upper limit is set to 1350 nm is that at 1350 nm or more, water becomes opaque when the water film thickness is 10 mm or more.

The temperature measuring device 10 mainly includes a measuring section 101, an arithmetic processing section 103, and a storage section 105, as shown in FIG. 7A, for example.

The measurement unit 101 measures thermal radiation (observation) emitted from an object to be measured that emits thermal radiation 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. measuring the size of light). More specifically, the measurement unit 101 measures the thermal radiation of the measurement target at two different wavelengths at which the spectral transmittance of the absorber is the same, and calculates the radiance of the thermal radiation at these two wavelengths. Generate measurement data showing the detection results.

The measurement unit 101 is an optical system that includes various lenses/lens groups in a two-color radiation thermometer, an optical filter that satisfies the transmission wavelength width conditions as described above, and a sensor such as a photodetector. This corresponds to A more detailed configuration of the measurement unit 101 will be explained below. Further, the two types of wavelengths measured by the measurement unit 101 are set in advance to two wavelengths at which the spectral transmittance of the absorber is the same using the optical filter as described above.

When the measurement unit 101 measures the magnitude of thermal radiation of the object to be measured and generates measurement data indicating the detection result of the radiance of the thermal radiation, the measurement unit 101 sends the generated measurement data to an arithmetic processing unit 103, which will be described later. Output.

The arithmetic processing unit 103 is realized by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a communication device, and the like. The calculation processing unit 103 performs overall control of the measurement processing performed by the measurement unit 101. Further, the arithmetic processing unit 103 performs arithmetic processing for calculating the temperature of the object to be measured based on the measurement data measured by the measurement unit 101. More specifically, the arithmetic processing unit 103 calculates the radiance measurement data corresponding to the two types of wavelength bands generated by the measurement unit 101 and the spectral radiance and temperature derived from Planck's blackbody radiation equation. The temperature of the object to be measured is calculated based on the relational expression between The information regarding the temperature of the object to be measured calculated by the arithmetic processing unit 103 is outputted as an image via a display screen or the like, outputted as a printed matter via a printer or the like, or outputted as data itself.

Note that the detailed configuration of the arithmetic processing unit 103 will be explained in detail below.

The storage unit 105 is realized, for example, by a RAM, a storage device, or the like included in the temperature measuring device 10 according to the present embodiment. The storage unit 105 stores various information such as the spectral absorption coefficient of the absorber of interest, the spectral radiance of the measurement target obtained by analyzing past operation data, and weighting coefficients used to correct the spectral absorption coefficient. parameters, data, etc. are stored. In addition to these data, the storage unit 105 also stores various parameters that need to be saved when the temperature measuring device 10 according to the present embodiment performs some processing, the progress of the processing, etc. Various databases, programs, etc. are recorded as appropriate. This storage unit 105 allows the measuring unit 101, the arithmetic processing unit 103, and the like to freely read/write data.

These measuring section 101, arithmetic processing section 103, and storage section 105 may be realized inside one measuring device as, for example, a function of a two-color radiation thermometer, as schematically shown in FIG. 7A. Further, the measurement section 101, the arithmetic processing section 103, and the storage section 105 may be distributed and implemented in a plurality of devices, for example, as shown in FIG. 7B. In the example shown in FIG. 7B, the functions of the measurement unit 101 and the storage unit 105 are realized inside a measurement unit that functions as a two-color radiation thermometer, and the functions of a personal computer, various servers, various process computers, etc. A case is illustrated in which the functions of the arithmetic processing unit 103 and the storage unit 105 are implemented inside the processing device. Note that in FIG. 7B, the storage section 105 is realized as storage sections 105a and 105b in the measurement unit and the arithmetic processing device, respectively, but the storage section 105 may be realized only inside the measurement unit, It may be implemented only inside the arithmetic processing device.

<About the configuration example of the measurement section>
Next, a configuration example of the measurement unit 101 according to the present embodiment will be described in detail with reference to FIG. 8. FIG. 8 is an explanatory diagram schematically showing an example of the configuration of a measuring section included in the temperature measuring device according to the present embodiment.

The measurement unit 101 according to the present embodiment corresponds to the optical system in a two-color radiation thermometer, and operates under the control of the arithmetic processing unit 103 to measure heat in the near-infrared band emitted by an object to be measured. Measure synchrotron radiation. As schematically shown in FIG. 8, this measurement unit 101 performs measurement in a state where an absorber whose spectral transmittance in the near-infrared band is wavelength-dependent may exist on the optical path to the measurement target. It has a light receiving section 111 that receives thermal radiation from the object, and a detecting section 113 that detects the thermal radiation received by the light receiving section 111.

In the measuring section 101 according to the present embodiment, the light receiving section 111 and the detecting section 113 as described above may be optically connected by various known optical transmission mechanisms. Examples of such a light transmission mechanism include various known optical fibers OF. By connecting the light receiving section 111 and the detecting section 113 using a light transmission mechanism such as an optical fiber OF, it becomes possible to arrange the light receiving section 111 separately from the detecting section 113, and according to the present embodiment. The convenience of using the temperature measuring device is further improved.

As shown in FIG. 8, the light receiving unit 111 includes a light receiving lens 121 that receives thermal radiation from the object to be measured, and connects the thermal radiation from the object to be measured that has passed through the light receiving lens 121 to an optical fiber OF. It has a connection coupler 123 for. The light-receiving lens 121 and the connection coupler 123 function as a light-guiding optical system that guides thermal radiation to the detection section 113.

Here, the specific configuration of the light receiving section 111 according to this embodiment is not particularly limited. For example, in FIG. 8, one 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 any known optical element such as a spherical lens or an aspherical lens may 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.

Thermal radiation from the object to be measured, which has absorbers (in FIG. 8, water) of various thicknesses on at least a portion of its surface, is converted into a substantially parallel beam by the light receiving lens 121 of the light receiving unit 111, and connected. It reaches the coupler 123. The connection coupler 123 connects the thermal radiation guided from the light receiving lens 121 to one end of the optical fiber OF. Thermal radiation from the object to be measured is received by the light receiving section 111 and then transmitted through the optical fiber OF, and is guided to the detecting section 113.

As illustrated in FIG. 8, 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, condensing lenses 157a and 157b, and a sensor. 159a, 159b.

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

As shown in FIG. 8, on one optical path after the branching, an optical filter 155a, which is an example of a first optical filter that transmits light in a wavelength band on the short wavelength side, is provided. An optical filter 155b, which is an example of a second optical filter that transmits light in a wavelength band on the long wavelength side, is provided on one optical path.

The optical filters 155a, 155b function as wavelength selection filters, select the wavelength of the thermal radiation, and transmit the thermal radiation having a specific wavelength to the subsequent sensors 159a, 159b. Sensor 159a is an example of a first photodetector, and sensor 159b is an example of a second photodetector. The sensor 159a measures the spectral radiance of thermal radiation of the object to be measured to generate a brightness signal, and the sensor 159b measures the spectral radiance of the thermal radiation of the object to generate a brightness signal. By dividing , the dichromatic ratio can be obtained.

The filter characteristics of these two optical filters 155a and 155b are appropriately set according to the method described above.

That is, the optical filters 155a, 155b are set so that the spectral transmittance (average spectral transmittance in the transmission wavelength width) of water, which is an absorber, is the same, and the transmission of the optical filters 155a, 155b is set to be the same. Each of the wavelength widths is set in advance so that the dichromatic ratio calculated using the measurement data generated from the sensors 159a and 159b is 1 at the minimum measurement temperature required for the temperature measurement device.

Thermal radiation belonging to the shorter wavelength band that has passed through the optical filter 155a is focused onto the sensor 159a by the focusing lens 157a. Further, the thermal radiation belonging to the wavelength band on the long wavelength side that has passed through the optical filter 155b is focused onto the sensor 159b by the condensing lens 157b.

The sensors 159a and 159b detect the spectral radiance of the thermal radiation from the measurement object guided by the condensing lenses 157a and 157b, respectively, and generate data of the obtained brightness signals. Thereafter, each of the sensors 159a and 159b outputs the obtained luminance signal to the arithmetic processing section 103. This brightness signal corresponds to measurement data indicating the detection result of the radiance of thermal radiation light. In this embodiment, the measurement data output from the sensor 159a will be conveniently referred to as first measurement data, and the measurement data output from the sensor 159b will be conveniently referred to as second measurement data.

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

In FIG. 8, the condensing lenses 157a and 157b are schematically illustrated using one biconvex lens, but these condensing lenses 157a and 157b are a lens group composed of a plurality of lenses. It's okay. Further, the lenses used for these condensing lenses 157a and 157b are not particularly limited, and known optical elements such as spherical lenses and aspheric lenses can be appropriately used.

Here, it is assumed that, for example, the center wavelength=1200 nm is selected as one of the two observation wavelength combinations (that is, the transmission wavelengths of each of the optical filters 155a and 155b). In this case, the other center wavelength will be selected from around 1300 nm. Furthermore, when the center wavelength as described above is selected, the transmission wavelength width of the optical filter 155a is preferably 90 nm, for example, and the transmission wavelength width of the optical filter 155b is preferably 45 nm, for example.

The configuration example of the measuring section 101 according to the present embodiment has been briefly described above with reference to FIG. 8.

<About the configuration example of the arithmetic processing unit 103>
Next, a configuration example of the arithmetic processing unit 103 according to the present embodiment will be described with reference to FIG. 9. FIG. 9 is a block diagram showing a configuration example of the arithmetic processing unit 103 according to this embodiment.

As illustrated in FIG. 9, the calculation processing unit 103 according to the present embodiment includes a measurement control unit 171, a data acquisition unit 173, a temperature calculation unit 175, a result output unit 177, and a display control unit 179. Prepare for the Lord.

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, and the like. The measurement control unit 171 is a processing unit that centrally controls the functions of the temperature measurement device 10 according to the present embodiment. Furthermore, the measurement control unit 171 controls the operation of the measurement unit 101 so as to measure the thermal radiation from the object to be measured at the two types of wavelengths as described above. Further, the measurement control section 171 can also output various setting values such as measurement conditions for thermal radiation light to the temperature calculation section 175 as necessary.

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

The temperature calculation unit 175 is realized by, for example, a CPU, ROM, RAM, or the like. The temperature calculating section 175 calculates the temperature of the measurement object using the luminance signals at two types of wavelengths output from the data acquiring section 173. Further, the temperature calculation unit 175 uses the luminance signals at two types of wavelengths output from the data acquisition unit 173 to calculate a dichromatic ratio (in other words, a spectral radiation The brightness ratio) is calculated. Further, the temperature calculation unit 175 calculates the temperature of the measurement target object using the calculated two-color ratio and the relational expression between the two-color ratio and the temperature.

As disclosed in Patent Document 1, the dichroic ratio R can be calculated by dividing one of the luminance signals at two wavelengths by the luminance signal of the other wavelength. On the other hand, in the temperature measuring device 10 according to the present embodiment, absorption of thermal radiation by the absorber is taken into consideration, as shown in the following equations (1) and (2). Therefore, the dichroic ratio R is expressed by the following equation (3) when the equation is derived in the same manner as in Patent Document 1 using the following equations (1) and (2).

Here, in the above equations (1) and (2), τ ₁ is the spectral transmittance of water at wavelength λ ₁ , and τ ₂ is the spectral transmittance of water at wavelength λ ₂ . 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 index of both water and air at the interface. In this case, if interface reflection is omitted, the spectral transmittances τ ₁ and τ ₂ of water can be expressed as τ ₁ =exp(-α ₁ ×t) and τ ₂ =exp(-α ₂ ×t), respectively. can. Here, α ₁ is the spectral absorption coefficient of water at wavelength λ ₁ , α ₂ is the spectral absorption coefficient of water at wavelength λ ₂ , and t is the thickness of the water film.

As previously explained, 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 with each other using the optical filters 155a and 155b whose filter characteristics are appropriately set. has been done. Therefore, the term related to absorption by the absorber shown in the first term on the middle side of the above equation (3) cancels each other in the numerator and denominator, and has a value of 1. Therefore, R _λ and Λ on the right side of the above equation (3) are as shown in the following equations (4a) and (4b).

Here, R _λ and Λ shown in equations (4a) and (4b) are constants determined from measurement conditions that can be obtained from the measurement unit 101. Therefore, the temperature calculation unit 175 can calculate the temperature T of the measurement target using the calculated two-color ratio R and the relational expression (leftmost side = rightmost side) in the above equation (3). It becomes possible.

Note that when the temperature calculation unit 175 calculates the dichromatic ratio R, it is particularly important to determine which of the two wavelengths λ ₁ and λ ₂ the luminance signal is used as the denominator and which luminance signal is used as the numerator. The present invention is not limited to this, and it is sufficient that the reference luminance signal is not changed during the calculation process.

Further, the temperature calculation unit 175 may directly calculate the temperature using the above equations (1) and (2) without using the two-color ratio R expressed by the above equation (3). That is, if the emissivity ε at two types of wavelengths λ ₁ and λ ₂ is known, the two unknowns in the above equations (1) and (2) are the temperature T and the water film thickness t. Therefore, the temperature calculation unit 175 can calculate the temperature T by combining the above equations (1) and (2) and finding a solution to the simultaneous equations. Furthermore, even if the emissivity ε at the two wavelengths λ ₁ and λ ₂ is unknown, if the emissivity ε at the wavelength λ ₁ and the emissivity ε at the wavelength λ ₂ are equal to each other, the above formula can be similarly obtained. It is possible to directly calculate the temperature T by combining (1) and equation (2). Here, the method of solving the simultaneous equations is not particularly limited; for example, if it can be solved analytically, it may be solved analytically, it may be solved by numerical calculation, or it may be solved as an optimal value problem. It's okay.

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

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

In addition, the result output unit 177 outputs data corresponding to the temperature measurement result to an output device such as a display provided in the temperature measuring device 10 or a display of various devices provided externally. , outputs the measurement results in cooperation with a display control section 179, which will be described later.

The display control unit 179 is realized by, for example, a CPU, ROM, RAM, output device, communication device, etc. The display control unit 179 performs display control when displaying data corresponding to the temperature measurement results on various display devices such as a display. Thereby, the user of the temperature measuring device 10 can grasp the measurement result regarding the temperature of the object to be measured on the spot.

An example of the functions of the arithmetic processing unit 103 according to this embodiment has been described above. Each of the above components may be constructed using general-purpose members and circuits, or may be constructed using hardware specialized for the function of each component. Further, the functions of each component may be entirely performed by a CPU or the like. Therefore, it is possible to change the configuration to be used as appropriate depending on the technical level at the time of implementing this embodiment.

Note that 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 to implement it in a personal computer or the like. Further, a computer-readable recording medium storing such a computer program can also be provided. 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.

The configuration of the temperature measuring device 10 according to this embodiment has been described in detail above with reference to FIGS. 7A to 9.

<About temperature measurement method>
Next, an example of the flow of the temperature measurement method performed by the temperature measurement device 10 according to the present embodiment will be briefly described with reference to FIG. 10. FIG. 10 is a flowchart showing an example of the flow of the temperature measurement method according to the present embodiment.

In the temperature measurement method according to the present embodiment, first, under the control of the measurement control unit 171 of the arithmetic processing unit 103, the measurement unit 101 including an optical filter whose transmission wavelength width is appropriately set is used to separate the object from the measurement target. Thermal radiation of is measured (step S101). The generated measurement data is output to the data acquisition section 173 of the arithmetic processing section 103.

The data acquisition unit 173 of the arithmetic processing unit 103 outputs the measurement data output from the measurement unit 101 to the temperature calculation unit 175.

The temperature calculation unit 175 first calculates the dichromatic ratio R using measurement data in two wavelength bands obtained from the first measurement data and the second measurement data, respectively (step S103). Subsequently, the temperature calculation unit 175 outputs the temperature of the measurement object based on the relational expression showing the relationship between the two-color ratio and the temperature and the calculated two-color ratio R (step S105). Thereafter, the temperature calculation section 175 outputs the obtained information regarding the temperature of the measurement object to the result output section 177.

After that, the result output unit 177 that has acquired the information regarding the temperature of the measurement target outputs the acquired information regarding the temperature of the measurement target as a measurement result (step S107).

Thereby, in the temperature measurement method according to the present embodiment, it is possible to measure the temperature of the object to be measured while suppressing instability of the temperature measurement result.

An example of the flow of the temperature measurement method according to the present embodiment has been briefly described above with reference to FIG.

<About hardware configuration>
Next, with reference to FIG. 11, the hardware configuration of the arithmetic processing unit 103 included in the temperature measuring device 10 according to this embodiment will be described in detail. FIG. 11 is a block diagram for explaining the hardware configuration of the arithmetic processing unit 103 according to this embodiment.

The arithmetic processing unit 103 mainly includes a CPU 901, a ROM 903, and a RAM 905. The arithmetic processing unit 103 further includes a bus 907, an input device 909, an output device 911, a storage device 913, a drive 915, a connection port 917, and a communication device 919.

The CPU 901 functions as a central processing device and control device, and controls the entire operation or a part of the operation within the arithmetic processing unit 103 according to various programs recorded in the ROM 903, RAM 905, storage device 913, or removable recording medium 921. do. The ROM 903 stores programs, calculation parameters, etc. used by the CPU 901. The RAM 905 temporarily stores programs used by the CPU 901 and parameters that change as appropriate during program execution. These are interconnected by a bus 907 constituted by an internal bus such as a CPU bus.

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

The input device 909 is, for example, an operation means operated by a user such as a mouse, a keyboard, a touch panel, a button, a switch, a lever, or the like. Further, the input device 909 may be, for example, a remote control means (so-called remote control) using infrared rays or other radio waves, or an external connection device 923 such as a PDA that is compatible with the operation of the temperature measuring device 10. It's okay. Further, the input device 909 includes, for example, an input control circuit that generates an input signal based on information input by the user using the above-mentioned operating means and outputs it to the CPU 901. By operating the input device 909, the user can input various data to the temperature measuring device 10 and instruct processing operations.

The output device 911 is configured of a device that can visually or audibly notify the user of the acquired information. Examples of 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, and facsimiles. The output device 911 outputs, for example, results obtained by various processes performed by the arithmetic processing unit 103. Specifically, the display device displays the results obtained by various processes performed by the arithmetic processing unit 103 in text or images. On the other hand, the audio output device converts an audio signal consisting of reproduced audio data, audio data, etc. into an analog signal and outputs the analog signal.

The storage device 913 is a data storage device configured as an example of a storage section of the arithmetic processing section 103. The storage device 913 is configured of, for example, a magnetic storage device such as an HDD (Hard Disk Drive), a semiconductor storage device, an optical storage device, a magneto-optical storage device, or the like. This storage device 913 stores programs executed by the CPU 901, various data, and various data acquired from the outside.

The drive 915 is a reader/writer for recording media, and is either built into the arithmetic processing unit 103 or attached externally. The drive 915 reads information recorded on an attached removable recording medium 921 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory, and outputs it to the RAM 905. The drive 915 can also write records on a removable recording medium 921, such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory. The removable recording medium 921 is, for example, CD media, DVD media, Blu-ray (registered trademark) media, or the like. Further, the removable recording medium 921 may be a CompactFlash (registered trademark) (CF), a flash memory, an SD memory card (Secure Digital memory card), or the like. Furthermore, the removable recording medium 921 may be, for example, an IC card (Integrated Circuit card) equipped with a non-contact IC chip, an electronic device, or the like.

The connection port 917 is a port for directly connecting a device to the arithmetic processing unit 103. Examples of the connection ports 917 include a USB (Universal Serial Bus) port, an IEEE1394 port, a SCSI (Small Computer System Interface) port, an RS-232C port, and an HDMI (registered trademark) (High-Definition Mu ltimedia Interface) port, etc. By connecting the externally connected device 923 to this connection port 917, the arithmetic processing unit 103 can directly acquire various data from the externally connected device 923 or provide various data to the externally connected device 923.

The communication device 919 is, for example, a communication interface configured with a communication device for connecting to the communication network 925. The communication device 919 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 919 may be a router for optical communication, a router for ADSL (Asymmetric Digital Subscriber Line), a modem for various types of communication, or the like. This communication device 919 can transmit and receive signals, etc., to and from the Internet or other communication devices, for example, in accordance with a predetermined protocol such as TCP/IP. Further, the communication network 925 connected to the communication device 919 is configured by a wired or wirelessly connected network, and may be, for example, the Internet, a home LAN, an in-house LAN, infrared communication, radio wave communication, or satellite communication. It's okay.

An example of the hardware configuration capable of realizing the functions of the arithmetic processing unit 103 according to the embodiment of the present invention has been described above. Each of the above components may be constructed using general-purpose members, or may be constructed using hardware specialized for the function of each component. Therefore, it is possible to change the hardware configuration to be used as appropriate depending on the technical level at the time of implementing this embodiment.

Although preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea stated in the claims. It is understood that these also naturally fall within the technical scope of the present invention.

10 Temperature measuring device 101 Measuring unit 103 Arithmetic processing unit 105 Storage unit 111 Light receiving unit 113 Detecting 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 section 175 Temperature calculation section 177 Result output section 179 Display control section

Claims (4)

In a temperature measurement device that measures the temperature of a measurement target using a two-color radiation thermometer,
a light receiving unit that receives thermal radiation from the object to be measured, in a state where an absorber whose spectral transmittance in the near-infrared band is wavelength dependent may be present on the optical path to the object to be measured;
A first brightness signal is generated by measuring the spectral radiance of the thermal radiation light received by the light receiving section through a first optical filter, and the spectral radiance of the thermal radiation light received by the light receiving section is measured. , a detection unit that generates a second luminance signal by measuring through a second optical filter that is set so that the spectral transmittance of the first optical filter and the absorber are the same;
a temperature calculation unit that calculates the temperature of the measurement target from the first brightness signal and the second brightness signal;
has
The dichroic ratio obtained by dividing the first luminance signal by the second luminance signal is a predetermined value that is approximately 1 at the minimum measurement temperature of the temperature measuring device, and the first optical filter and the second luminance signal are When the relationship between the transmission wavelength width of the first optical filter and the amount of change in the dichroic ratio is obtained under the condition that the spectral transmittances of the two optical filters are the same,
In the relationship between the transmission wavelength width of the first optical filter and the amount of change in the dichroic ratio, the transmission wavelength width and center wavelength of the first optical filter and the second optical filter are determined based on a condition that becomes an inflection point. temperature measuring device. The center wavelength of the first optical filter set based on the conditions of the inflection point is 1200 nm,
The center wavelength of the second optical filter set based on the conditions of the inflection point is 1300 nm,
The transmission wavelength width of the first optical filter set based on the conditions of the inflection point is 90 nm,
The temperature measuring device according to claim 1, wherein the second optical filter has a transmission wavelength width of 45 nm, which is set based on the condition of the inflection point. The temperature measuring device according to claim 1 or 2, wherein the absorber is at least one of water, oil, solution, glass, or resin. In a temperature measurement method of measuring the temperature of a measurement target using a two-color radiation thermometer,
a light receiving unit that receives thermal radiation from the object to be measured, in a state where an absorber whose spectral transmittance in the near-infrared band is wavelength dependent may be present on the optical path to the object to be measured;
A first brightness signal is generated by measuring the spectral radiance of the thermal radiation light received by the light receiving section through a first optical filter, and the spectral radiance of the thermal radiation light received by the light receiving section is measured. , a detection unit that generates a second luminance signal by measuring through a second optical filter that is set so that the spectral transmittance of the first optical filter and the absorber are the same;
Using a temperature measuring device having a temperature calculation unit that calculates the temperature of the measurement target from the first brightness signal and the second brightness signal,
The dichroic ratio obtained by dividing the first luminance signal by the second luminance signal is a predetermined value that is approximately 1 at the minimum measurement temperature of the temperature measuring device, and the first optical filter and the second luminance signal are obtaining a relationship between the transmission wavelength width of the first optical filter and the amount of change in the dichroic ratio under the condition that the spectral transmittances of the two optical filters are the same;
In the relationship between the transmission wavelength width of the first optical filter and the amount of change in the dichroic ratio, the transmission wavelength width and center wavelength of the first optical filter and the second optical filter are determined based on a condition that becomes an inflection point. The steps to set
A temperature measuring method comprising:

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