JPH07167713A - Multi-wavelength radiation thermometer - Google Patents

Abstract

PURPOSE:To eliminate the influences of the irregular distribution of a spectral emissivity in a visual field for measurement thereby to measure temperatures highly accurately, by distributing an optical fiber from a side where a heat radiation light enters to divergent optical fibers. CONSTITUTION:A spectral means 13 is constituted of an optical fiber 14 and a plurality of spectral filters 16a-16d of different wavelengths. The optical fiber 14 is divided to a plurality of divergent optical fibers 15a-15d at a side where a heat radiation light 12 is emitted from the optical fiber 4. Moreover, the optical fiber 14 is tuniformly distributed from a side 14a where the heat radiation light enters the optical fiber 14 to the divergent optical fibers 15a-15d. The heat radiation light 21 detected from a visual field 11a for measurement is distributed from the entering side 14a to each divergent optical fiber 15a-15d proportionally. Even when a spectral emissivity is irregularly distributed in the visual field 11a, it is avoided that the heat radiation light of a specific spectral emissivity is partially transmitted to any of the divergent optical fibers 15a-15d. Temperatures accordingly be obtained with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-wavelength radiation thermometer, and more particularly to measuring the surface temperature of an object to be measured whose thermal emissivity is unknown or changes, such as the surface of a galvanized steel sheet. It relates to a multi-wavelength radiation thermometer used.

[0002]

2. Description of the Related Art A radiant temperature measuring method for measuring the radiance of thermal radiation emitted from an object to be measured is capable of quickly measuring the surface temperature without contacting the object to be measured with a thermometer. Therefore, it is widely used in industry.

However, in the object to be measured in the manufacturing process of steel or the like, the emissivity necessary for the radiation temperature measuring method is unknown, or the emissivity varies due to phase transformation, alloying, oxidation, change in surface roughness, etc. Therefore, there is a problem that it is difficult to apply the radiation thermometry or the temperature measurement accuracy is extremely low.

As measures against the above-mentioned fluctuation of the emissivity, the following two methods have been conventionally proposed. First
Method, the reflectance ρ of the object to be measured is measured using a reference thermal radiation source or light source, and the emissivity ε of the object to be measured is determined from the relationship where the sum of the reflectance ρ and the emissivity ε is constant. It is a method of measuring the temperature. However, in the case of the device used for this method, since the reference heat radiation source or light source is installed near the measured object, it can be applied to the general manufacturing process where the measurement environment is severe due to high temperature, dust, vibration, etc. Difficult,
There is also a problem that a lot of maintenance work is required to maintain accuracy. In addition, since the standard heat radiation source or an auxiliary device such as a light source and a large lens are equipped, the size of the entire device becomes relatively large and the price becomes relatively high, so that there is a problem that it can be applied only in a limited field. It was

The second method is to measure the spectral radiances of two different wavelengths with respect to the thermal radiation emitted from the same object to be measured, and to calculate the ratio of the two spectral radiances corresponding to these two spectral radiances. Is a method of obtaining temperature assuming that is constant (two-color temperature measurement method). However, this spectral emissivity changes depending on the temperature, material, surface properties, etc. of the object to be measured, and therefore the ratio of the spectral emissivity also fluctuates, which makes it difficult to measure temperature with high accuracy.

To address these problems, a radiation temperature measuring method using multiple wavelengths has been proposed (Japanese Patent Laid-Open No. 5-231).
944). FIG. 7 is a block configuration diagram schematically showing an apparatus used in a conventional radiation temperature measuring method using multiple wavelengths, and 11 in the figure denotes an object to be measured. The right side of the measurement object 11 surface is the lens 12 is arranged as a light receiving means, on the right side of the light receiving lens 12 differs from the optical fiber 22 as spectroscopic means, such as transmission wavelength lambda ₁ to [lambda] ₄ 4
Individual spectral (narrow band) filters 16a to 16d are provided. To the right of the spectral filters 16a to 16d, photodetectors 17a to 17d using Ge photodiodes or the like as detecting / amplifying means, amplifiers 18a to 18d, and an AD converter 19 are sequentially arranged, and to the right of the AD converter 19. Is provided with a computer 20 as an arithmetic processing means, and photodetectors 17a to 17d and amplifiers 18a to 1 are provided.
8d, the AD converter 19, and the computer 20 are electrically connected to each other.

The incident end 24 side of the thermal radiation light 21 in the optical fiber 22 is formed in such a manner that a plurality of single-core optical fibers 23 are bundled into one, while the emitting end side of the thermal radiation light 21 in the optical fiber 22 is formed. Branch optical fibers 25a to 25d are formed, and each of the branch optical fibers 25a to 25d is a mode in which a plurality of single-core optical fibers 23 are divided into four from the incident end 24 side and bundled.

When the temperature of the hot-dip galvanized steel sheet is measured online, for example, in the alloying process using the multi-wavelength radiation thermometer constructed in this way, first the thermal radiation 21 emitted from the object to be measured 11 is measured. The light-receiving lens 12 focuses the light on the incident end 24 of the optical fiber 22. Then, the thermal radiation light 21 is divided into four in the optical fiber 22, and after being emitted from the branch optical fibers 25a to 25d, the transmission wavelength λ ₁
[Lambda] ₄ is spectrally separated by different spectral filters 16a to 16d. The respective lights separated into the wavelengths λ _{1 to} λ ₄ are detected by the photodetectors 17a to 17d and converted into electric signals, then amplified by the amplifiers 18a to 18d, and further converted from analog signals to digital signals by the AD converter 19. After being converted to a signal, the measured spectral radiance L
As ₁ ⁰ ~L ₄ ⁰ is input to the computer 20.

[0009] Then the measured spectral radiance L ₁ ⁰ ~L ₄ ⁰ corresponding to the four spectral emissivity ε ₁ ~ε ₄ unique to the measurement object 11 two unknown constants α _0, α ₁ and the wavelength Set as a function of λ _{1 to} λ ₄ . Next, the unknown constants α ₀ and α ₁
Substituting an initial value to, to calculate the spectral radiance L ₁ '~L _4' by means of a computer 20, the measured spectral radiation and the spectral radiance L ₁ on the calculation '~L _4' luminance L ₁ ⁰ ~L ₄ ^The temperature and the emissivity are obtained based on the constants α ₀ and α ₁ when the difference from ⁰ becomes a predetermined value or less.

[0010]

In the above-mentioned multi-wavelength radiation thermometer, a measurement field of view 11a of a predetermined size is required on the surface of the object 11 to be measured, and this size detects the heat radiation light 21. For example, in the case of using a Ge (germanium) photodiode, a measurement field of view 11a having a diameter of about 30 mm is required.

On the other hand, the surface of the object to be measured 11 may not have a uniform emissivity, and therefore the measurement field of view 11
The a does not always have a uniform emissivity as a whole. For example, in the case of hot-dip galvanized steel sheet in the alloying treatment step, Fe
(Iron) and Zn (zinc) plated on the surface of the steel sheet are diffused on the plated surface to form Fe-Zn compounds at various ratios and grow. This alloying rate is influenced by not only the treatment temperature but also the concentration of trace elements such as P (phosphorus) and Si (silicon) contained in the steel sheet and the thickness of Zn plating.
These concentration and thickness distributions may not be macroscopically uniform. Further, as shown in FIG. 4, it is known that the spectral emissivity is higher in A when alloying is progressing and lower in B when not alloying. Therefore, as shown in FIG. 8, in the measurement visual field 11a during the alloying process, there may be a case where the portion 26 having a relatively high alloying degree or emissivity and the portion 27 having a relatively low emissivity are unevenly distributed. .

On the other hand, in the conventional optical fiber 22, the single-core fiber 23 arranged on the incident end 24 side of the optical fiber 22 is randomly distributed to the branch optical fibers 25a to 25d.

Therefore, the distribution state of the spectral emissivity of the object 11 to be measured, the size of the measurement visual field 11a, the shape of the single-core optical fiber 23 in the optical fiber 22, the distribution state to the branch optical fibers 25a to 25d, and the like. If the above conditions are overlapped, there is a problem that the thermal radiation light 21 from the portion 27 (FIG. 8) having a low emissivity may be unevenly distributed to any of the branched optical fibers 25a to 25d.

In such a case, there is a problem that the temperature cannot be obtained by the above calculation method.

The present invention has been made in view of the above problems, and it is possible to evenly distribute the thermal radiation light from the measurement visual field to any of the branch optical fibers, and to measure the temperature, material, To provide a multi-wavelength radiation thermometer that can eliminate these effects even when the surface state is biased and the distribution of the spectral emissivity in the measurement field is biased, and therefore the temperature can be obtained with high accuracy. It is an object.

[0016]

In order to achieve the above object, a multi-wavelength radiation thermometer according to the present invention comprises a light receiving means for receiving thermal radiation light emitted from an object to be measured, and the received heat. Spectral means for spectrally splitting the radiated light into N (N is an integer of 3 or more) thermal radiation lights, and detection / amplification means for converting the spectrally divided thermal radiation light into a spectral radiance signal. And a multi-wavelength radiation thermometer including arithmetic processing means for obtaining the temperature of the object to be measured from the spectral radiance signal, wherein the spectroscopic means includes an optical fiber and N spectral filters each having a different wavelength. It is configured that the thermal radiation light output side of the optical fiber is divided into N branch optical fibers, while the optical fiber is evenly distributed from the thermal radiation light input side to each branch optical fiber side. It is set to.

[0017]

According to the multi-wavelength radiation thermometer of the present invention, the spectroscopic means is composed of an optical fiber and N spectral filters each having a different wavelength, and the thermal radiation emission side of the optical fiber has N branched lights. While being divided into fibers, since the optical fiber is evenly distributed from the heat radiation light incident side to each of the branched optical fibers, the heat radiation light received from the measurement field of view is input from the incident light side of the optical fiber. Even if the distribution of the spectral emissivity in the measurement field of view is biased, the thermal radiation light from a specific spectral emissivity will be distributed evenly to each of the branched optical fibers. Therefore, it is possible to eliminate the biased transmission to the above, and therefore the accurate spectral emissivity can be obtained by calculation, and the temperature can be obtained with high accuracy.

[0018]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of a multi-wavelength radiation thermometer according to the present invention will be described below with reference to the drawings. It should be noted that components having the same functions as those of the conventional example are designated by the same reference numerals. FIG. 1 is a block diagram schematically showing an embodiment of a multi-wavelength radiation thermometer according to the present invention, in which 14 is an optical fiber and 16a to 16d are spectral filters. The configuration of the multi-wavelength radiation thermometer shown in FIG. 1 is the same as that of the conventional multi-wavelength radiation thermometer except for the optical fiber 14. Therefore, detailed description thereof will be omitted here, and the points different from the conventional one will be described. Only its configuration will be described.

FIG. 2 is a sectional view schematically showing the optical fiber 14 according to the embodiment. (A) is an optical fiber on the incident side of thermal radiation, (b) is a first branched optical fiber, and (c) is. ) Indicates the second branch optical fiber, (d) indicates the third branch optical fiber, and (e) indicates the fourth branch optical fiber.
The incident side 14a of the optical fiber 14 has a single-core optical fiber 23.
(FIG. 1) is a single-core optical fiber 23a ₁ , 23b ₁ , 23c
₁ , 23d ₁ , 23a ₂ , 23b ₂ , ... Are arranged in this order so as to rotate outward from the center (FIG. 2).
(A)). On the other hand, the branch optical fiber 15a is the optical fiber 1
4 from the incident side 14a to the single-core optical fibers 23a ₁ and 23a
₂ , only ... are taken out and bound (Fig. 2
(B)). Similarly, the branch optical fiber 15b is connected from the incident side 14a of the optical fiber 14 to the single-core optical fiber 23b ₁ ,
23b _2, ... only it is being bundled taken (Fig. 2
(C)), and the branch optical fiber 15c is the optical fiber 14
From the incident side 14a of the single-core optical fibers 23c ₁ and 23c
₂ , ... Only are taken out and bundled (FIG. 2 (d)), and the branched optical fiber 15d is the incident side 14 of the optical fiber 14.
Only the single-core optical fibers 23d ₁ , 23d ₂ , ... Are taken out from a and bundled (FIG. 2 (e)).

When the temperature of the hot-dip galvanized steel sheet is measured online, for example, in the alloying process using the multi-wavelength radiation thermometer configured as described above, first, the thermal radiation light 21 emitted from the object to be measured 11 is measured. The light receiving lens 12 collects the light at the incident end 24 of the optical fiber 14. Then, the thermal radiation light 21 is divided into four in the optical fiber 14, is emitted from the branch optical fibers 15a to 15d, and is then spectrally divided by the spectral filters 16a to 16d having different transmission wavelengths λ. The respective lights separated into the wavelengths λ _{1 to} λ ₄ are detected by the photodetectors 17a to 17d and converted into electric signals, then amplified by the amplifiers 18a to 18d, and further converted into digital signals by the AD converter 19. after being inputted into the computer 20 as measured spectral radiance L ₁ ⁰ ~L ₄ ^0.

Next, the temperature T'and the unknown constant α ₀ ′ for each wavelength λ _{1 to} λ ₄ shown by the spectral emissivity function of the following equation ₁ ,
Input α ₁ ′ to the computer 20 as an initial value.
These initial values are selected and calculated from the ranges of temperature and emissivity assumed in the alloying process and used.

[0022]

[Equation 1]

Next, using the above initial values, the spectral radiances L _{1 to} L ₄ , the temperature T, and the unknown constant α are calculated by the following equation 2.
₀ and α ₁ are calculated.

[0024]

[Equation 2]

Then, the spectral radiances L _{1 to} L obtained by the calculation
₄ and to calculate the difference S between the measured spectral radiance L ₁ ⁰ ~L ₄ ^0,
Further, the calculated temperature T and the constants α ₀ and α _1, and the initial value temperature T ′ and the constants α ₀ ′ and α for each wavelength λ _{1 to} λ _4.
Calculate the sum of squares C of the difference from ₁ '. Next, for example, S ≦
The conditions of 0.001 and C ≦ 0.01 are set, and the computer 20 determines whether or not these conditions are simultaneously satisfied. When these conditions are not satisfied at the same time, for example, T ′ = T ′ + 0.5 × (T−T ′), α ₀ ′ = α
₀ ′ + 0.5 × (α ₀ −α ₀ ′), α ₁ ′ = α ₁ ′ +
Enter 0.5 (α ₁ −α ₁ ′) as a new initial value,
The above calculation is repeated. On the other hand, if the above conditions are satisfied at the same time, the calculation is terminated, and the temperature T obtained at this time is set as the measured temperature.

The results of measuring the temperature of the galvanized steel sheet during the alloying process using the multi-wavelength radiation thermometer shown in FIG. 1 will be described below. The measurement conditions are shown below. The measurement visual field 11a was set to have a diameter of about 20 mm.
Further, as the optical fiber 14, 160 single-core optical fibers 23 are used, and as shown in FIG. 2, the optical fiber 14 is divided into 40 pieces from the incident side 14a to the branch optical fibers 15a to 15d side and is evenly distributed. I used one. On the incident side 14a of the optical fiber 14, 160 single-core optical fibers 23 are bundled with resin at a filling rate of approximately 90%.
The size of a is approximately 1.5 mm in diameter. The spectral filters 16a, 16b, 16c and 16d used had transmission wavelengths λ of 1.3, 1.5, 1.6 and 1.7 μm, respectively. Further, the evaluation was performed by the temperature measurement error of the multi-wavelength radiation thermometer when the true temperature was 500 ° C.
As a comparative example, a multi-wavelength radiation thermometer incorporating a conventional optical fiber was used.

FIG. 5 shows the measured spectral radiance L _i ⁰ and the transmission wavelength λ.
FIG. 4 is a curve diagram showing the relationship between the curve A, when the degree of alloying in the entire measurement field of view is high, the curve B, in the case of low alloying degree in the whole measurement field of view, and the curve C, the degree of alloying in the measurement field of view. There is a bias, and the optical fiber of the comparative example is used, the wavelength is 1.3 μm.
In the case where the thermal radiation light of the part having a low alloying degree is deviated into the branched optical fiber of FIG. 3 and is dispersed, the curve D shows the case where the alloying degree in the measurement visual field is deviated using the optical fiber of the embodiment. Is shown.

FIG. 4 is a curve diagram showing the relationship between the spectral emissivity ε _i and the transmission wavelength λ. Curve A shows a high degree of alloying in the entire measurement field of view, and curve B shows a degree of alloying in the entire measurement field of view. Is low, the curve C has a bias in the degree of alloying in the measurement field,
Further, when the optical radiation of the comparative example is used and the branching optical fiber having a wavelength of 1.3 μm disperses the thermal radiation light of the portion having a low alloying degree, the curve D has an uneven alloying degree in the measurement visual field. It shows a case where the light is dispersed using the optical fiber of the embodiment. These curves are obtained from the quotient of the measured spectral radiance L _i ⁰ shown in FIG. 5 and the blackbody spectral radiance at 500 ° C. (FIG. 3) that was previously obtained.

As is apparent from FIG. 4, the spectral emissivity ε _i
Is high at all wavelengths λ when the curve A has a high degree of alloying of the entire measurement visual field 11a, and is low at all wavelengths λ when the degree of alloying of the entire measurement visual field 11a is low. In these cases, similar results are obtained in both the examples and the comparative examples. On the other hand, as shown in FIG.
In the case of the embodiment, if there is a deviation in the degree of alloying, the curve A
A curve D is obtained which is between the curve B and the curve B, and this value is proportional to the area ratio of the alloying degree. On the other hand, in the comparative example, the wavelength of 1.3 μm is substantially the same as the curve B, and the other wavelengths are substantially the same as the curve A (curve C).

Further, when the degree of alloying of the measurement visual field 11a is uneven, in the case of the embodiment, the temperature measurement error range with respect to the true temperature of 500 ° C. is ± 15 ° C., and in the case of the comparative example,
The calculation was impossible and the temperature could not be measured.

As is clear from the above results and explanation, in the multi-wavelength radiation thermometer according to this embodiment, the measurement field of view 1
When the thermal radiation light 21 received from 1a can be uniformly distributed from the incident light side 14a of the optical fiber 14 to the respective branch optical fibers 15a to 15d, and the spectral emissivity ε _i distribution of the measurement visual field 11a is biased. However, it is possible to prevent the thermal radiation light 21 from being biasedly transmitted to any one of the branched optical fibers 15a to 15d, and therefore an accurate spectral emissivity can be calculated, and the temperature can be accurately determined. You can ask.

FIG. 6 is a sectional view schematically showing another embodiment of the optical fiber. In the figure, 34a shows the incident side of the thermal radiation light in the optical fiber 34. On the incident side 34a of the optical fiber 34, the single-core optical fibers 23a, 23b, 2
3c and 23d are arranged in one lump 35, and this lump 35 is further arranged so as to spread over the entire incident side 34a. On the other hand, only the single-core optical fibers 23a, 23b, 23c, and 23d are respectively taken out and bundled into four branch optical fibers (not shown). With the optical fiber 34 thus configured, the same effect as that of the above-described embodiment can be obtained, and the smaller measurement field of view 11a is obtained.
The case of (FIG. 1) can also be dealt with.

The arrangement of the single-core optical fibers 23 in the optical fiber 14 is not limited to that of the above embodiment, but the size of the measurement visual field 11a and the measurement visual field 1
An even allocation method can be set based on the degree of deviation of the emissivity distribution in 1a, the size and shape of the single-core optical fiber 23, and the like.

In each of the above embodiments, the case where the number of branch optical fibers is four has been shown, but in the case of another embodiment, the same can be applied to the case where the number of branch optical fibers is three or five or more.

[0035]

As described in detail above, in the multi-wavelength radiation thermometer according to the present invention, the spectroscopic means comprises an optical fiber and N spectroscopic filters having different wavelengths,
While the heat radiation light output side of the optical fiber is divided into N branch optical fibers, the optical fiber is evenly distributed from the heat radiation light input side to each of the branch optical fibers, so that light is received from the measurement visual field. It is possible to uniformly distribute the thermal radiation light from the incident light side of the optical fiber to each of the branched optical fibers, even if the distribution of the spectral emissivity in the measurement field of view is biased, from the specific emissivity It is possible to prevent the thermal radiated light from being biasedly transmitted to any one of the branched optical fibers, and therefore an accurate spectral emissivity can be calculated and a temperature can be calculated with high accuracy. it can.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing an embodiment of a multi-wavelength radiation thermometer according to the present invention.

FIG. 2 is a cross-sectional view schematically showing an optical fiber according to an embodiment, in which (a) is an incident side of a thermal radiation light of the optical fiber,
(B) is a first branch optical fiber, (c) is a second branch optical fiber, (d) is a third branch optical fiber,
(E) has shown the 4th branch optical fiber.

FIG. 3 is a curve diagram showing a blackbody spectral radiance at 500 ° C.

FIG. 4 is a curve diagram showing a relationship between a spectral emissivity ε _i and a transmission wavelength λ in a hot-dip galvanized steel sheet, where a curve A shows a high degree of alloying in the entire measurement visual field, and a curve B shows that in the entire measurement visual field. When the degree of alloying is low, the curve C has a bias in the degree of alloying within the measurement field of view, and a conventional optical fiber is used. In the case of biased spectral distribution, the curve D shows the case where the alloying degree in the measurement visual field is biased and spectrally analyzed using the optical fiber of the embodiment.

FIG. 5 is a curve diagram showing the relationship between measured spectral radiance L _i ⁰ and transmission wavelength λ, where curve A shows a high degree of alloying in the entire measurement visual field, and curve B shows a degree of alloying in the entire measurement visual field. Is low, the curve C has a bias in the degree of alloying within the measurement field of view, and the optical radiation of the comparative example is used. When spectrally dispersed, a curve D shows a case where the alloying degree in the measurement visual field is biased and is spectrally dispersed using the optical fiber of the embodiment.

FIG. 6 is a cross-sectional view schematically showing another embodiment of the optical fiber.

FIG. 7 is a conceptual diagram schematically showing an apparatus used in a conventional radiation temperature measuring method using multiple wavelengths.

FIG. 8 is a schematic diagram showing a state in which the alloying or emissivity distribution in the measurement field of view is biased and non-uniform.

[Explanation of symbols]

 11 measured object 12 light receiving lens 13 spectroscopic means 14 optical fiber 14a incident side 15a, 15b, 15c, 15d branched optical fiber 16a, 16b, 16c, 16d spectral filter 17a, 17b, 17c, 17d photodetector 18a, 18b, 18c , 18d amplifier 19 AD converter 20 computer 21 thermal radiation light

Claims (1)

[Claims] 1. A light receiving unit for receiving heat radiation light emitted from an object to be measured, and the received heat radiation light into N (N is an integer of 3 or more) heat radiation lights having different wavelengths. A spectroscopic means for spectroscopic analysis, and a detection / amplification means for converting the spectroscopic thermal radiation light into a spectral radiance signal,
In a multi-wavelength radiation thermometer including an arithmetic processing unit for obtaining the temperature of the object to be measured from the spectral radiance signal, the spectroscopic unit includes an optical fiber and N spectral filters each having a different wavelength. , The thermal radiation output side of the optical fiber is divided into N branch optical fibers, while the optical fibers are evenly distributed from the thermal radiation input side to each branch optical fiber side. Multiwavelength radiation thermometer.