JPH05142051A - Two-color multiple radiation thermometer - Google Patents

Abstract

PURPOSE:To measure the temperature of radiation with high accuracy even when an oxide film is growing on the surface of an object to be measured, by comparing the changing ratio with time of the power ratio of the emissivity or of the spectral emissivity ratio, and selecting the band of the minimum changing ratio. CONSTITUTION:A photoelectric conversion part divides the radiant light from an object to be measured to a first measuring band of wavelengths lambda1 and lambda1x, and a second measuring band of wavelengths lambda2 and lambda2x, and measures luminous temperatures S1, S1x and S2, S2x of the two wavelengths in the bands, respectively. The power ratio of the emissivity is calculated according to an equation 1, II in an operational block 301, 302 from the luminous temperatures of the two wavelengths in each band. In the equations, C2 is a second constant of Plank. Then, each power ratio of the emissivity is converted to the spectral emissivity ratio epsilon1/epsilon2/epsilon1x, epsilon1/epsilon2/epsilon2x in a converting block 501, 502, and the temperature T is calculated in a calculating block 401, 402 using the emissivity ratio. A measuring band is selected in a wavelength band selecting block 100. A selector 101 switches the temperature to the temperature T calculated for the measuring band of the smaller change with time of the power ratio of the emissivity, and this temperature T is output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-color multi-type radiation thermometer, and in particular, it receives thermal radiation energy of two different wavelengths from a thermal radiator in a plurality of wavelength bands and outputs the surface temperature of the thermal radiator. The present invention relates to a two-color multi-type radiation thermometer that can measure the surface temperature of a heat radiator with non-contact and with high accuracy.

[0002]

2. Description of the Related Art First, the principle meanings of symbols used in the following description will be clarified.

Temperature measurement wavelengths: λ ₁ , λ ₂ , ... λ _i [μm] Proximity wavelengths of the above wavelengths: λ _1x , λ _2x , ... λ _ix [μm] _Magnitude relationship of the above wavelengths λ ₁ < λ _1x <λ ₂ <λ _2x <... <λ _i <λ _ix Spectral emissivity at temperature measurement wavelength λ _i : ε _i [μm] Proximity spectral emissivity at near wavelength λ _ix : ε _ix [μm] Thermal object Surface true temperature: T [K] Thermal object surface Luminance temperature at wavelength λ _i : Si [K] Thermal object surface Luminance temperature at wavelength λ _ix : Six [K] Radiant (Plank) second constant C2: 1.4388 × 10 ⁴ [ μm ・ K]

Radiation thermometers, which measure the surface temperature of a thermal object by applying the radiation temperature measurement technique, are widely used. These radiation thermometers have a single-color thermometer with one wavelength used for measurement and two radiation thermometers.
There are two two-color thermometers. Not only a monochromatic thermometer but also a two-color thermometer that uses two wavelengths causes a large measurement error when the emissivity of the measurement target changes.

In the two-color thermometer, when the spectral emissivities at the two wavelengths to be measured are substantially equal or a certain proportional relationship is established, there is no problem in temperature measurement accuracy, but the surface state of the thermal object is an oxidation reaction. When the spectral emissivity deviates from the above relation, the measurement accuracy becomes significantly worse (a monochromatic radiation thermometer has a larger error than this).

Therefore, there has been a demand for a two-color thermometer capable of measuring the surface temperature of a heat object in response to changes in the spectral emissivity.

Japanese Patent Publication No. 3-4855 discloses an improved two-color thermometer which corrects the emissivity and is used as a radiation thermometer which solves this measurement accuracy problem. In addition, the improved form 2
Radiant temperature measurement technology that is virtually the same as the color thermometer, Tanaka, DP
Dewitt's Theory of a New Radiation Thermometry
Method and an Experimental Study Using Galvanneal
ed Steel Specimens ”(Proceedings of the Society of Instrument and Control Engineers, Vol. 25, No. 10, p. 1031/1037, 1989 10
TRACE (Thermometry Re-esta)
blished by Automatic Compensation of Emissivity)
There is a law.

Since the improved radiation thermometer and the TRACE method basically employ the same calculation method, the former method will be mainly described.

In Japanese Examined Patent Publication No. 3-4855, T is deleted from the formula of the spectral emissivity represented by the following formulas (1) and (2) obtained by using the Wien approximation rule, and the following formula (3) is obtained. Are seeking. The ratio (Kuramasu number) of the power of the wavelength of the spectral emissivity, which is the left side of the equation (3), is called the emissivity exponentiation ratio for convenience of explanation.

Note that the following equation is separated by two wavelengths λ for simplicity.
The case of ₁ and λ ₂ is shown, but two adjacent wavelengths λ
_{The same} holds true for ₁ and λ _1x .

Ε ₁ = exp {(C 2 / λ ₁ ) (1 / T-1 / S 1)} (1) ε ₂ = exp {(C 2 / λ ₂ ) (1 / T-1 / S 2)} (2) ε ₁ ^{λ 1} / ε ₂ ^λ ₂ = exp {C 2 (1 / S 2 −1 / S 1)} (3) (left side: emissivity power ratio)

In the above equation, the brightness temperatures S1 and S2 are 2
Since it is obtained as the output of the wavelength detector, the value of the emissivity exponentiation ratio can be obtained by calculating the right side of the equation (3).

Further, from the equations (1) and (2), the equation (4) expressing the true temperature T of the surface of the heat object is obtained. By applying the ratio of the spectral emissivity to the equation (4), T can be obtained. You can ask.

T = (λ ₂ −λ ₁ ) / {(λ ₁ λ ₂ / C 2) ln (ε ₁ / ε ₂ ) + λ ₂ / S 1 −λ ₁ / S 2} (4)

On the other hand, the correlation function f between the spectral emissivity ratio and the emissivity exponentiation ratio as shown in equation (5) is determined in advance by measurement.

In measuring the temperature, the spectral emissivity ratio is obtained from the emissivity exponential ratio calculated by the equation (3) by the correlation function f, and the true temperature T is calculated by the equation (4) using the spectral emissivity ratio. To do. As described above, the old two-color radiation thermometer calculates the spectral emissivity ratio as 1 or a constant value, and does not correspond to the change in spectral emissivity.

Ε ₁ / ε ₂ = f (ε ₁ ^{λ 1} / ε ₂ ^λ ₂ ) ... (5)

When the measurement method using the above equations is applied to a thermal body whose surface state changes due to an oxidation reaction or the like, temperature measurement can be performed with high accuracy by selecting a "dull" measurement wavelength with respect to the surface change. It is possible.

[0019]

However, in the measurement technique disclosed in the above publication, the measurement accuracy is significantly deteriorated when the emissivity power ratio of the selected wavelength changes sensitively to the change of the surface state. There is a problem.

Hereinafter, this problem will be described in detail.

As a specific example in which the spectral emissivity of the selected wavelength is sensitively changed by the change of the surface state of the heat object, when the surface is oxidized and a semitransparent (at the measurement wavelength) oxide film is formed on the surface. There is. In this case, the semi-transparent film formed on the surface causes optical interference and the spectral emissivity is drastically reduced. In this case, the emissivity exponential ratio also drops sharply (sudden change).
To do.

Such a sudden change in the emissivity is described by Makino et al. In “Heat Transfer 1986”, vol.
2, Hemishere, (1986), PP. 577-582
From the experiments and model calculations of the optical interference theory, when surface oxidation occurs, a drop in the spectral emissivity spectrum (hereinafter referred to as a valley) appears in the short wavelength region, and this valley moves in the long wavelength direction as the oxidation progresses. Confirmed as a characteristic change.

13 to 17 are schematic diagrams showing an example of characteristic changes in the spectral emissivity spectrum.

In the figure, the horizontal axis is the spectral wavelength λ, and the vertical axis is the emissivity ε.
And the portion indicated as valley is the valley of the spectral emissivity spectrum.

FIGS. 13 to 17 show how the spectral emissivity spectrum of a metal such as stainless steel changes as the oxide film is formed on the surface.

FIG. 13 shows a low temperature state before the oxide film is formed,
FIG. 14 shows a stage where an oxide film is not formed yet while being heated to a medium temperature, FIG. 15 is a stage where an oxide film starts to be formed when heated to a medium temperature, and FIG. 16 shows an oxide film growing at the same temperature. FIG. 17 shows the respective spectra at the stage where the thick oxide film was formed by heating to the high temperature.

It is considered that the reason why the above-mentioned valleys occur is mainly due to the optical interference due to the oxide film. The Makino et al. Obtained the spectral emissivity spectrum by the model calculation based on the interference theory, and calculated the experimental result with the calculated result. It is reported that they compare well with each other.

Therefore, it is explained that the phenomenon that the spectral emissivity spectrum changes appears because the radiant energy in the spectral wavelength band on the order of the thickness of the oxide film or less is selectively trapped in the oxide film. That is, because the radiation that is specifically selected causes interference or multiple reflections in the oxide film, remarkable energy attenuation occurs, and as the oxide film thickness increases, the specific selection wavelength band moves, so that the valley is short. It is considered to move from wavelength to long wavelength.

When such a spectral emissivity spectrum changes with time, the emissivity ratio changes, so that the old type 2
It goes without saying that a measurement error occurs in the color radiation thermometer, and it is also difficult to calculate the equation used in the improved two-color thermometer, and thus a measurement error similarly occurs.

The reason is that in the calculation of the improved two-color thermometer using the two adjacent wavelengths λ ₁ and λ _1x , the correlation between the two spectral emissivities ε ₁ and ε _1x is set as a regression function from the experimental data off-line. This is because it is difficult to return to that situation, although it must be decided. This will be briefly described below.

_{Assuming that} the measured data of the spectral emissivity ε ₁ and ε _1x is the data during the movement of the valley from the short wavelength to the long wavelength as in the spectral emissivity spectrum described above, the emissivity ε
The correlation between ₁ and ε _1x changes from “positive correlation” to “negative correlation” to “positive correlation”.

This can be easily understood by following the changes in the values of the emissivity ε ₁ and ε _1x corresponding to the approaching two wavelengths λ ₁ and λ _1x in FIGS. 13 to 17. That is, "vall
Short wavelength side of "ey" part (where the spectral slope is negative)
When is between wavelengths λ ₁ and λ _1x , the magnitude relationship between the emissivity ε ₁ and ε _1x is reversed, and the positive and negative signs of the correlation are reversed.

This state is specifically shown in FIGS. 18 and 19. It is understood that there is a completely opposite correlation between the valley before passing (FIG. 18) and after passing (FIG. 19).

"Steelmaking Research No. 339" by Tanaka et al. (1
990) 63-67, the ε ₁ -ε ₂ graph as schematically shown in FIG. 20 is not monovalent, and a loop is formed, but this loop is also caused by oxide film radiation interference. It is estimated that

As described above, since the correlation regression graph of the emissivity ε ₁ and ε _1x cannot be simply determined, there is a problem that a measurement error is unavoidable even in the case of the improved two-color thermometer. is there.

Actually, when the temperature of the stainless steel sheet (SUS430) whose surface oxidation is in progress is measured by the improved two-color thermometer, the maximum value of the measurement error is about 15 ° C. in the temperature range of about 600 ° C. and the standard deviation. Was about 5 ° C.

The temperature during the progress of such surface oxidation and surface alloying is an important process parameter in the steel process, for example. Therefore, it is a big problem that there is an error in the radiation temperature measurement value, and the appearance of a more accurate thermometer is desired, and the temperature measurement error is ± 5 ° C (the maximum error value is within 5 ° C). Is the required measurement accuracy.

As a conventional radiation temperature measuring technique, US
It is disclosed that PAT 4417822 is used together with a laser to correct the emissivity by using the reflectance of the laser beam from the surface of the object to be measured. However, this technique requires a complicated device for laser application. In addition to being expensive, it is necessary to take offline data on the reflectance measurement by the laser. However, since this data reflects a complex phenomenon involving surface light scattering phenomena, it is doubtful whether this offline data can be used online.
In addition, there is a problem that the temperature measurement error is large because an error occurs in the online measurement value of the reflectance.

In addition, US PAT 4561786 includes:
A radiation thermometry technique using the apparatus shown in FIG. 21 is disclosed.

In this technique, a radiant wave is condensed by a lens 213, and a secondary calculation for obtaining the "ratio" and the "difference" of the output of the detector 211 of the two-color observation wavelength separated by the rotation filter 215 is executed. However, the temperature calculation method is put into practical use by utilizing these calculated values.

In the figure, 251 is a holding circuit 245, 247.
Is a division calculation block that performs division between the outputs W1 and W2 of the above, and its output is a "ratio". Also, 259 is
It is a differential amplifier that performs subtraction between the outputs of the holding circuits 255 and 257, and its output is the “difference”. In addition, S1
S4 is a timing signal for synchronizing the rotational position of the rotary filter 215 with the control system, 217 is a first wavelength spectral filter, 219 is a second wavelength spectral filter, and
41 and 243 are amplifiers.

The division block 251 and the differential amplifier 2
Each output value from 59 is converted into linearization circuits 253 and 26.
1 and the resistance values R1, R2, R3, and R4 are adjusted and set for each measurement object, and the calculated temperature value is displayed on the meter 275.

In this system, the linearizer 25 described above is used.
3, 261, the adjustment of the resistances R1 to R4 is determined by trial and error depending on the material to be measured, and therefore the calculation method has no theoretical base generated as a result of trial and error.
No factual or theoretical description is given.

According to this method, it is said that temperature measurement can be performed with high accuracy (± 5 ° C.) on aluminum whose surface is undergoing surface change. However, in order to obtain such high measurement accuracy, trial and error is required. It is estimated that it took a considerable amount of time (setting data is not disclosed).

Therefore, since the apparatus of the above-mentioned system has no theoretical base, it takes a long time for trial and error to measure the temperature of metals other than aluminum, and therefore it is not versatile. is there.

The present invention has been made in order to solve the above-mentioned conventional problems. Even if the emissivity fluctuates remarkably due to the change of the surface condition of the object to be measured by oxidation or the like, the temperature can be accurately measured. It is an object of the present invention to provide a practical double multiplex radiation thermometer capable of measuring the.

[0047]

DISCLOSURE OF THE INVENTION The present invention is directed to a spectroscopic means for splitting into _two different wavelengths λ ₁ and λ ₂ for a plurality of different wavelength bands, and a luminance for two wavelengths λ ₁ and λ ₂ for each wavelength band. From the photoelectric conversion means for measuring the temperatures S1 and S2 and the brightness temperatures S1 and S2 of two wavelengths obtained online for each wavelength band, the emissivity exponential ratio ε1 ^λ1 / ε2 is calculated by the following equation.
Exponentiation ratio calculating means for calculating ^λ2 , and ε1 _λ1 / ε2 ^λ2 = exp {C2 (1 / S2 −1 / S1)} (C2: second constant of Plank) ε1 ^λ1 / ε2 ^λ2 previously measured and stored The emissivity ratio calculating means for converting the emissivity ratio ε 1 / ε 2 by the correlation function f of the following equation, and ε 1 / ε 2 = f (ε ¹ λ ¹ / ε 2 λ ² ) using the above spectral emissivity ratio ε 1 / ε 2 Temperature calculation means for executing color temperature calculation to calculate a measurement temperature, and monitoring the time variation of the emissivity exponential ratio or the spectral emissivity ratio for each wavelength band, and based on the time variation, a specific wavelength band is determined. The above-described object is achieved by including a wavelength band selection unit for selecting and outputting the measured temperature calculated for the selected specific wavelength band.

The present invention is also the same as the wavelength band selecting means, in that the time rate of change of the emissivity exponentiation ratio or the spectral emissivity ratio is compared and the wavelength band having the smallest change rate is selected. The above-mentioned problems are achieved.

In the present invention, the wavelength band selecting means compares the absolute values of the emissivity exponential ratio or the spectral emissivity ratio and selects the wavelength band having the minimum absolute value. Similarly, the above-mentioned object is achieved.

According to the present invention, when the wavelength band is 3 or more, the wavelength band selection means is arranged so that the wavelength band selecting means has a wavelength range 2 or a wavelength range longer than the wavelength band in which the time variation of the emissivity exponentiation ratio or the spectral emissivity ratio is maximum. By selecting the second and subsequent wavelength bands, the above-mentioned problem is similarly achieved.

[0051]

First, the principle of the present invention will be described. However, here, the spectral two wavelengths are λ _i and λ _ix, and the brightness temperature of each wavelength is S
i, Six and emissivity ε _i , ε _ix (i = 1, 2, ...)
It is written as. i indicates different wavelength bands.

As described above, in the improved two-color thermometer, the emissivity exponentiation ratio is obtained from the brightness temperatures S1 and S1x by the equation (3), and the emissivity exponentiation ratio is calculated as two spectral emissivities ε ₁ and ε _1x.
Is applied to the function of the equation (5) determined as a regression function from experimental data, and the emissivity ratio: ε ₁ / ε _1x is obtained as a function value of the function, and the emissivity ratio is calculated as )
The temperature T is calculated by applying the formula to the two-color temperature calculation formula.

However, when this emissivity ratio has a specific surface oxide film thickness, it greatly fluctuates due to radiation interference,
When this fluctuation occurs, the above correlation function f becomes, for example, a divalent function, which causes a problem in calculation processing.

The inventors of the present invention anticipate the time zone of occurrence of such emissivity fluctuation by a method supported by experiments and theories, eliminate the temperature calculation result in that time zone, and eliminate the time zone of exclusion. By compensating for the temperature calculation results in different wavelength bands, we have made it possible to measure temperature with high accuracy even when emissivity changes.

FIG. 1 is a schematic diagram showing a change in spectral emissivity based on the above experiment and theory.

FIG. 1A shows the time variation of ε ₁ and ε _1x , and FIG. 1B shows the time variation of the emissivity ratio ε ₁ / ε _1x .
(C) is a time variation of ε _2, ε _2x, Figure 1 (D) is the time variation of the emissivity ratio ε ₂ / ε _2x, a diagram showing respectively.

Here, the spectral wavelength is λ ₁ <λ _1x <λ ₂ <λ
_2x , λ ₁ and λ _1x , and λ ₂ and λ _2x are near wavelengths, and measurement bands (wavelength bands) are configured by these two adjacent wavelengths.

Specifically, when the radiation photoelectric element is selected from Si and Ge, λ ₁ = 1.00 μ, λ _1x = 1.05 μ, and λ ₂ = 1.60.
It is possible to set μ, λ _2x = 1.65μ, etc.

Ε ₁ and ε _1x are the near wavelengths λ ₁ and λ _1x described above.
Since it is the spectral emissivity of, it shows almost the same time change,
When a microscopic physical property change of the surface such as surface oxidation progresses, the microscopic change causes a sensitive change.

FIG. 1A shows an example in which surface oxidation is in progress.
The effect of radiant light interference due to the oxide film appears in time earlier from λ _{1 having} a smaller wavelength, and ends in time earlier. Therefore, as shown in the figure, ε ₁ and ε _1x are fluctuation graphs that are slightly deviated in the time axis direction, so that the time timing at which ε ₁ = ε _1x as shown by A and A ′ in the figure Therefore, the time variation of the emissivity ratio ε ₁ / ε _1x becomes as shown in FIG. 1 (B).

The emissivity ratio is 1 at the time timings A and A'above, and a rapid change in the emissivity occurs before and after that time, so that the emissivity ratio changes significantly.

On the other hand, in the two wavelengths λ ₂ and λ _{2x of} the measurement band separated from the measurement band composed of λ ₁ and λ _1x ,
Similar changes are observed at timing later than (A) and (B). This is shown in FIGS. 1 (C) and (D).

The time difference between the sudden change in emissivity in FIGS. 1A and 1B and the sudden change in FIGS. 1C and 1D depends on the thickness of 1.00 μm. The oxide film grows 1.
It is determined by the time difference until it reaches about 60μ. This time difference depends on the time of the oxidation reaction, but it was on the order of several seconds when the stainless steel sheet was oxidized in the atmosphere.

In the conventional improved two-color system, as shown in FIG.
In the time zone Z1 or the timing zone Z2 in which the emissivity ratio is 1 or more described in (D), and ε in the time zones of the timing zone Z10 or the timing zone Z20 in which the emissivity ratio before and after the fluctuation is large. ₁ /
There is a problem that the measurement error becomes large when the temperature is calculated using ε _1x or ε ₂ / ε _2x .

According to the present invention, as the emissivity ratio, ε ₂ / ε _{2x in} which the fluctuation does not occur is used in the timing zone Z1 and the timing zone Z10, and the fluctuation is already completed and stabilized in the timing zone Z2 and the timing zone Z20. The temperature was calculated by using ε ₁ / ε _1x .

Used for temperature calculation of each of the above measurement bands,
The formulas corresponding to the formulas (3) to (5) are shown below.

[0067] _{^{ε 1 λ1 / ε 1x λ1x =}} exp {C2 (1 / S1x-1 / S1)} ... (3-1) ε 2 λ2 / ε 2x λ2x = exp {C2 (1 / S2x-1 / S2) } (3-2) T = (λ _1x −λ ₁ ) / {(λ ₁ λ _1x / C 2) ln (ε ₁ / ε _1x ) + λ _1x / S 1 −λ ₁ / S _1x } (4-1) T = (λ _2x −λ ₂ ) / {(λ ₂ λ _2x / C 2) ln (ε ₂ / ε _2x ) + λ _2x / S 2 −λ ₂ / S _2x } (4-2) ε ₁ / ε _1x = f _{^{1 (ε 1 λ1 / ε 1x}} λ 1x) ... (5-1) ε 2 / ε 2x = f 2 (ε 2 λ2 / ε 2x λ2x) ... (5-2)

As described above in detail, in the present invention, 2
Since it is possible to apply two-color radiation thermometry to a measurement band composed of wavelengths over a plurality of wavelength bands, for example, because an oxide film grows over time on the steel plate surface,
Even when the valley of the spectral emissivity spectrum moves from the low wavelength side to the long wavelength side as shown in FIGS. 13 to 17,
The measurement band can be selected in a wavelength band in which no valley exists.

Therefore, since the temperature can be measured by the two-color thermometer always using the measurement band with no change in emissivity, highly accurate temperature measurement can be performed even when the surface condition of the object to be measured changes with time. It will be possible.

[0070]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 2 is a block diagram including a partial cross-sectional view showing a main part of a two-color multiplex type radiation thermometer according to the first embodiment of the present invention, and FIG. 3 is an enlarged plan view showing an infrared transmission filter disk. FIG. 4 is a diagram showing the sensitivity of the photoelectric element, FIG. 5 is a block diagram showing an outline of the signal processing unit, and FIG. 6 is a block diagram showing an outline of a wavelength band selection block.

The two-color multiple radiation thermometer of this embodiment is shown in FIG.
The two-color double system is provided with the photoelectric conversion unit shown in FIG. 4 and the signal processing unit shown in FIG.

The photoelectric conversion section has a lens 2 for condensing the light emitted from the object to be measured (heat radiating body) 1 and the lens 2.
An infrared transmission filter disk 3 for spectrally splitting the radiated light condensed by the first measurement band having wavelengths λ ₁ and λ _1x and a second measurement band having wavelengths λ ₂ and λ _2x , and the filter disk 3 A photoelectric element 5 for photoelectrically converting the radiated light of the first measurement band, which has been dispersed in Step 1, and a conversion circuit 6 for converting signals from the photoelectric element 5 into brightness temperature signals S1 and S1x,
A photoelectric element 7 for photoelectrically converting the radiation of the second measurement band,
A conversion circuit 8 for converting a signal from the photoelectric element 7 into brightness temperature signals S2 and S2x is provided.

In the filter disk 3, a λ ₁ transmission filter 31, a λ _1x transmission filter 31x, a λ ₂ transmission filter 32, and a λ _2x transmission filter 32x are arranged in this order at equal intervals.
The filter discs 3 are arranged one by one, and when the filter disc 3 is rotated by the motor 33, the spectrum of each wavelength is divided twice for each rotation.

Further, projections 34 for detecting the rotational position of the filter are attached around the filter disk 3 at regular intervals, and when the projections 34 are detected by the filter rotational position detection sensor 35, a timing signal generating circuit. 36
A timing signal is generated by the above, and the timing signal is sent to the conversion circuits 5 and 6 to control the radiation receiving operation of the conversion circuits 5 and 6.

Further, the photoelectric element 5 has two adjacent wavelengths λ ₁ and λ _1x.
Both of them have a photosensitivity characteristic as shown on the left side of FIG.
The photoelectric element 7 adjacent two wavelengths lambda _2, has a light-receiving sensitivity characteristics as shown in FIG right to both lambda _2x, wavelength lambda _1, lambda _1x
And a second measurement band having wavelengths λ ₂ and λ _2x are sufficiently separated from each other.

The signal processing section shown in FIG. 5 has the brightness temperatures S 1 (corresponding to λ ₁ ) and S 1x output from the conversion circuit 6.
(Corresponding to λ _1x ) is used to calculate the emissivity exponential ratio from the equation (3-1), and the correlation between the equation (3-1) calculation block 301 and the experimentally determined equation (5-1). From the regression equation, the emissivity ratio (ε ₁ / ε _1x ) is calculated using the emissivity exponentiation ratio (5-1) Formula calculation block 501 and the two-color temperature calculation formula (4-) using the calculated emissivity ratio. 1) calculates the temperature T from the equation (4-1) below calculation block 401, corresponding to the luminance temperature S2 (lambda ₂ output from the converting circuit 8), S2x
Perform similar calculations for (corresponding to λ _2x ) (3-2)
Expression calculation block 302 and expression calculation block 5 (5-2)
02 and a (4-2) formula calculation block 402.

The temperature T output from each of the calculation blocks 401 and 402 is input to the selector 101, and the temperature T calculated for the two wavelengths of either one of the measurement bands is output.

[0079] Also, ₁ epsilon emissivity power ratio from the computing block 301 and ³⁰² λ1 / ε _1x λ1x and ε ^₂ λ2 / ε
_2x ^λ2x are respectively input to the wavelength band selection block 100, and a specific wavelength band, that is, a measurement band is selected based on the time variation of these emissivity ratios, and the selection signal is output to the selector 101 to obtain the emissivity. Temperature T calculated for the measurement band with the smaller power ratio fluctuation over time
And the temperature T is output.

The wavelength band selection block 100 has a configuration shown in FIG. 6 (A) or FIG. 6 (B) described below. In addition, in the present embodiment, even if both are used,
Also, either one may be used.

The wavelength band selection block 100 of FIG.
Is for outputting a selection signal by using the time rate of change of emissivity power ratio, the calculation block 110 for differentiating the ^{ε ₁} λ1 / ε _1x λ1x, operation block 110 for differentiating the ^{ε ₂} λ2 / ε _2x λ2x ' And a comparator 111 which compares the calculation results of these two blocks 110 and 110 'and outputs a signal for selecting the measurement block with the smaller change rate.

The wavelength band selection block 100 shown in FIG. 6B.
Is, epsilon ₁ and ^.lambda.1 / epsilon _1x calculation block 120 which calculates the absolute value of ^Ramuda1x, the computation block 120 'for calculating the absolute value of ^{ε ₂} λ2 / ε _2x λ2x, these two blocks 120,12
It is composed of a comparator 121 which compares the calculation result of 0'and outputs a signal for selecting the smaller measurement band.

The function of the wavelength band selection block 100 described above will be described below with reference to FIG.

Valleys, which are emissivity lowering portions due to radiated light interference, occur in the order of ε ₁ → ε _1x → ε ₂ → ε _2x due to the size relationship of wavelengths. This decrease in emissivity cannot be detected by a conventional two-color radiation thermometer.

In this embodiment, in the case of the first measurement band, the brightness temperatures S1 and S1x are used to calculate the emissivity power ratio in the calculation block 301, and the emissivity ratio is calculated in the calculation block 501 using the emissivity power ratio. ε ₁ / ε _1x can be obtained.
Similarly, in the case of the second measurement band, the brightness temperatures S2, S2x
Can be used to calculate the emissivity power ratio in the calculation block 302 and the value can be used to calculate the emissivity ratio ε ₂ / ε _2x in the calculation block 502.

As can be inferred from FIG. 1, the timing zone in which the spectral emissivity suddenly changes due to the oxide film formation is in the above-mentioned 2
It can be detected with sufficient accuracy by observing the temporal change of the two emissivity ratios. Specifically, as shown in FIG. (B)
As shown in, it can be detected from the magnitude of the absolute value of the emissivity power ratio.

Therefore, when the surface condition of the object to be measured corresponds to the timing zone Z1 or Z10 in FIG. 1, the second measurement band is used, and conversely, the timing zone Z2 or Z2 is used.
When 20 is supported, the temperature calculation result calculated using the first measurement band can be selected by the selector 101 and output.

According to the two-color multiplex radiation thermometer of this embodiment described in detail above, the two adjacent wavelengths λ ₁ and λ _{1x of} the first measurement band are used.
In addition, the temperature can be calculated independently for each of the adjacent two wavelengths λ ₂ and λ _2x of the second measurement band,
Since it is possible to selectively output the temperature calculated for the measurement band in which the time variation of the emissivity ratio of the wavelength is small, for example, an oxide film is generated on the surface of the object 1 to be measured, and the oxide film grows with time to form a film. Even if the thickness increases, it is possible to select an appropriate measurement band, execute the temperature calculation, and output the temperature. Therefore, highly accurate temperature measurement can always be performed.

FIG. 7 is a block diagram corresponding to FIG. 2 showing the outline of the photoelectric conversion portion of the second embodiment according to the present invention, and FIG. 8 shows the light receiving sensitivity of the photoelectric element used in the second embodiment. It is a diagram showing.

In this embodiment, instead of the photoelectric elements 5 and 7, there is a light receiving sensitivity characteristic as shown in FIG. 8 which is sensitive to four wavelengths λ ₁ , λ _1x , λ ₂ and λ _2x indicated by reference numeral 9 in the figure. Instead of the photoelectric element and the conversion circuit blocks 6 and 8, the brightness temperature signals S1 and S1x, which respectively correspond to the received light signals of these four wavelengths,
It is substantially the same as the first embodiment except that the conversion circuit block 10 for outputting S2 and S2x is provided.

FIG. 9 is a block diagram corresponding to FIG. 2 showing an outline of the photoelectric conversion section of the third embodiment according to the present invention.

The two-color multiple radiation thermometer of this embodiment is shown in FIG.
0 is a two-color triple system having a photoelectric conversion part shown in a perspective view of FIG. 0. In addition to the two-color double radiation thermometer of the first embodiment, a third measurement band composed of adjacent two wavelengths λ ₃ and λ _3x is also used. It is designed to be able to measure temperature.

That is, the two wavelengths λ ₁ and λ _{1x of} the first measurement band
The photoelectric conversion unit (the upper stage in the figure) for photoelectrically converting and outputting the brightness temperature signals S1 and S1x, and the two wavelengths λ ₂ and λ _2x of the second measurement band are photoelectrically converted by the same function as in the first embodiment. The brightness temperature signals S2 and S2x are converted and the third
The photoelectric conversion element 7 ′ photoelectrically converts the two wavelengths λ ₃ and λ _3x of the measurement band, and the conversion circuit block 8 ′ includes a photoelectric conversion unit (lower stage in the figure) that outputs the brightness temperatures S3 and S3x. The photoelectric conversion unit is preferably a compound eye type as shown in the drawing, but may be the one in which a filter is added to the first and second embodiments.

Although not shown, the signal processor of this embodiment is
A processing function for the third measurement band is added to the signal processing unit of the first embodiment so that measurement data can be selected from three measurement bands.

This embodiment has a higher measurement accuracy than the two-color double system such as the first embodiment. That is, in the case of the two-color double system, since the wavelength band selection block 100 cannot detect the timing zone unless the emissivity changes actually occur, a large error occurs at the time of switching the wavelength band. On the other hand, in the case of the two-color triple system, the timing zone can be detected in the wavelength band that is not related to the output, so that it is possible to avoid the occurrence of the error generation time associated with the switching.

This relationship will be specifically described with reference to FIGS. FIG. 11 shows the first measurement bands λ ₁ , λ _1x ,
Second measurement bands λ ₂ , λ _2x and third measurement bands λ ₃ , λ
FIG. 13 is a time chart showing the emissivity variation for each wavelength when 3 _× 3 separated wavelength bands are used, and FIG.
Is a select signal table output by the wavelength band selection block 100. In the table, ⊚ indicates the wavelength band to be selected, Δ indicates the wavelength band whose fluctuation is unknown, and × indicates the wavelength band that should not be selected.

As shown in the above table, in the case of the timing zone 10, the third measurement bands λ ₃ and λ _3x , which are two ahead of the wavelength band which is actually changing, are selected. First measurement bands λ ₂ , λ _2x that have already passed
And select 1st or 2nd in the case of timing zone 30
Select one of the measurement bands. As described above, according to the two-color triple method (the same applies to the case of four or more colors), the wavelength band of Δ can be prevented from being selected, so that the temperature can be measured with higher accuracy than the two-color double method. By the way, in the 2-color double system, △
It means that the temperature is calculated in the wavelength band where is not known when the emissivity fluctuation occurs.

Next, a specific example in which the present invention is actually applied will be described.

Off-line data was taken for a steel plate (made by Kawasaki Steel Co., Ltd.) in accordance with the above-mentioned Japanese Patent Publication No. 3-4855, and a regression function was created with the following first and second two-color measurement bands, and two-color double The system radiation thermometer was constructed.

First measurement band: (Si photoelectric element) λ ₁
= 1.00μ λ _1x = 1.05μ Second measurement band: (Ge photoelectric element) λ ₂ = 1.60μ λ _2x = 1.65μ

The method described in Japanese Patent Application No. 3-129828, which has already been filed, was used to create this regression function.

That is, one measurement band has two wavelengths λ ₁ , λ
₂ , the brightness temperature S at wavelengths λ ₁ and λ ₂
The ratio of the spectral emissivities ε ₁ and ε _{2 at} the wavelengths λ ₁ and λ ₂ was calculated by the following formula using 1 and S 2 and a constant A (where 0 ≦ A ≦ 1).

Ε ₁ / ε ₂ = [A · exp {C 2 (1 / S 2 −1 / S 1)}] ^{2 / (λ 1 + λ 2).}

Tables 1 and 2 show the results (maximum temperature error) of the temperature measurement according to the present invention using the above regression data and the same measurement with the thermometers of various types for comparison.

The object to be measured is stainless steel SUS304, Table 1 shows the case where the surface oxidation is in progress and the emissivity variation is remarkable, and Table 2 shows the case where the variation is relatively small in the temperature range other than that extracted in Table 1. Is the measurement result of. Number is 20 samples
Is the average value of.

The true temperature was measured with a thermocouple welded to the steel sheet, and ε was calculated using the true temperature during the progress of surface oxidation.
The qualitative judgment was made based on the tendency of change, and the case where ε change was remarkable was extracted.

In the case of the present invention, as is clear from Table 1 and Table 2, the temperature measurement error was within 5 ° C. at both emissivity fluctuations and other times, and its effectiveness was confirmed. It is expected that the two-color triple system will have higher accuracy.

[0108]

[Table 1]

[0109]

[Table 2]

Although the present invention has been specifically described above, it is needless to say that the present invention is not limited to the above-mentioned embodiments.

For example, the number of measurement bands is not limited to 2 or 3, and may be 4 or more.

Further, as shown in the embodiment, it is preferable that the measurement bands are composed of two adjacent wavelengths and the measurement bands are separated from each other. However, the present invention is not limited to this, and the two wavelengths which form the measurement band are included. Need not be in close proximity, and thus the measurement bands may partially overlap.

In the above embodiment, the case where the wavelength band selection block 100 selects the wavelength band based on the time variation of the emissivity exponentiation ratio has been described.
Emissivity ratio from ² ε ^₁ λ1 / ε _1x λ1x and ε ^₂ λ2 / ε _2x
^{It is also possible} to input ^λ2x and select the wavelength band based on the temporal variation of the emissivity ratio.

Further, in the above embodiment, the temperature calculation is executed for all the measurement bands, and the calculation result of the measurement band selected in the selection block 100 is output.
The temperature calculation may be executed only for the selected measurement band.

[0115]

As described above, according to the present invention,
Even if, for example, an oxide film is formed on the surface of the measurement target and its thickness increases and the surface state changes, the surface temperature of the measurement target can be measured with high accuracy.

[Brief description of drawings]

FIG. 1 is a time chart showing a temporal change of an emissivity and an emissivity ratio.

FIG. 2 is a block diagram showing a photoelectric conversion unit of a first embodiment according to the present invention.

FIG. 3 is an enlarged plan view showing a filter disc.

FIG. 4 is a diagram showing the light receiving sensitivity of a photoelectric element.

FIG. 5 is a block diagram showing a signal processing unit of the first embodiment.

FIG. 6 is a block diagram showing a configuration of a wavelength band selection block.

FIG. 7 is a block diagram showing a photoelectric conversion unit of a second embodiment.

FIG. 8 is a diagram showing the light receiving sensitivity of another photoelectric element.

FIG. 9 is a block diagram showing a photoelectric conversion unit of a third embodiment.

FIG. 10 is a perspective view showing an appearance of the photoelectric conversion unit.

FIG. 11 is a time chart showing changes in emissivity of a two-color triple system.

FIG. 12 is a chart showing the output timing of the selection signal of the wavelength band selection block.

FIG. 13 is a diagram showing an emissivity spectrum of a low temperature surface without an oxide film.

FIG. 14 is a diagram showing an emissivity spectrum of a medium-temperature surface without an oxide film.

FIG. 15 is a diagram showing an emissivity spectrum of a surface immediately after generation of an oxide film.

FIG. 16 is a diagram showing a surface emissivity spectrum during growth of an oxide film.

FIG. 17 is a diagram showing an emissivity spectrum of a surface after formation of a passive oxide film.

FIG. 18 is a diagram showing an emissivity spectrum of two adjacent wavelengths on a surface having no oxide film.

FIG. 19 is a diagram showing an emissivity spectrum of two adjacent wavelengths after generation of a surface oxide film.

FIG. 20 is a diagram showing a correlation of spectral emissivity of two wavelengths.

FIG. 21 is a block diagram showing a configuration of a conventional two-color radiation thermometer.

[Explanation of symbols]

1 ... Object to be measured, 3 ... Infrared filter disk, 4 ... Half mirror prism, 5, 7, 7 ', 9 ... Photoelectric element, 6, 8, 8', 10 ... Conversion circuit, 31 ... Wavelength λ ₁ transmission filter, 31x ... Wavelength λ _1x transmission filter, 32 ... Wavelength λ ₂ transmission filter, 32x ... Wavelength λ _2x transmission filter, 100 ... Wavelength band selection block, 101 ... Selector, 301 ... (3-1) Formula operation block, 302 ... (3 -2) Formula operation block, 401 ... (4-1) Formula operation block, 402 ... (4-2) Formula operation block, 501 ... (5-1) Formula operation block, 502 ... (5-2) Formula operation block .

Claims (4)

[Claims] _1. A spectroscopic means for separating into _two different wavelengths λ ₁ and λ ₂ for each of a plurality of different wavelength bands, and a brightness temperature S for the two wavelengths λ ₁ and λ ₂ for each wavelength band.
From the photoelectric conversion means for measuring 1 and S2 and the brightness temperatures S1 and S2 of two wavelengths obtained online for each wavelength band, the emissivity exponentiation ratio ε1 ^λ1 / ε2
Exponentiation ratio calculating means for calculating ^λ2 and ε1 _λ1 / ε2 ^λ2 = exp {C2 (1 / S2 −1 / S1)} (C2: second constant of Plank) ε1 ^λ1 / ε2 ^λ2 is measured and stored in advance. The emissivity ratio calculating means for converting into the emissivity ratio ε 1 / ε 2 by the correlation function f of the following equation, and ε 1 / ε 2 = f (ε ¹ λ ¹ / ε 2 λ ² ) using the above spectral emissivity ratio ε 1 / ε 2 Temperature calculation means for executing color temperature calculation to calculate the measured temperature, and monitoring the time variation of the emissivity exponentiation ratio or the spectral emissivity ratio for each wavelength band, and based on the time variation, a specific wavelength band is determined. A two-color multiplex type radiation thermometer, comprising: a wavelength band selecting means for selecting, and a measured temperature calculated for the selected specific wavelength band is output. 2. The wavelength band selection means according to claim 1, wherein the time change rates of the emissivity exponential ratio or the spectral emissivity ratio are compared with each other, and the wavelength band having the smallest change rate is selected. A two-color multi-type radiation thermometer. 3. The wavelength band selection means according to claim 1, wherein the absolute values of the emissivity exponentiation ratio or the spectral emissivity ratio are compared with each other, and the wavelength band having the smallest absolute value is selected. Characteristic 2-color multi-type radiation thermometer. 4. In claim 1, when the wavelength band is 3 or more, the wavelength band selection means has a lower wavelength side or a longer wavelength side than the wavelength band in which the time variation of the emissivity exponentiation ratio or the spectral emissivity ratio is maximum. A two-color multi-type radiation thermometer characterized by being adapted to select the second and subsequent wavelength bands.