JPH03287030A - Optical fiber radiation thermometer - Google Patents

Abstract

PURPOSE:To secure the optical path to a body to be measured even in a narrow place and a place where measurement environment is inferior and to accurately measure the temperature and emissivity at the same time by transmitting two spectral radiation brightness signals which differ in conditions from the body to be measured to a photodetector by using an optical fiber. CONSTITUTION:The optical fiber 2 transmits the radiation brightness from the body 1 to be measured to the detector 3. The best spectral radiation conditions (wavelength and polarization) for the body 1 to be measured can be selected by the detector 3 and two spectral radiation conditions are easily obtained. A parameter input part 41 inputs the parameter of the relational equation between two known spectral emissivity values which correspond to the two selected spectral radiation conditions and are characteristic to the body to be measured to an arithmetic part 5 and a parameter input part 42 inputs the parameter of a black body furnace calibration function showing the relation between the spectral radiation brightness signal of the detector 3 and real temperature to the arithmetic part 5. The arithmetic part 5 finds the real emissivity on the emissivity function which is the function between the two corresponding spectral emissivity values from the two spectral radiation brightness signals to find the real temperature at the same time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an optical fiber radiation temperature measurement device that simultaneously measures the temperature and emissivity of an object whose emissivity changes during the manufacturing process of ferrous and non-ferrous metals using an optical fiber. Regarding.

[Conventional technology]

Conventional radiation temperature measurement requires the emissivity of the object to be measured to be known, but in the manufacturing process of ferrous and non-ferrous metals,
At present, the emissivity of the object to be measured may change, and for this reason, conventional radiation thermometers are not sufficiently reliable. Moreover, the measurement environment is poor, and accurate temperature measurements cannot be expected in small spaces. To address these issues,
Various improvement measures have been proposed, but none of them provide a fundamental solution to the actual emissivity change.

For example, a two-color thermometer is only valid under the assumption that the ratio between the two spectral emissivities is constant.

Furthermore, there is a method (Japanese Patent No. 1,368,788) that utilizes a specular reflection effect on the surface of the object to be measured using a reference radiation source, but there is a concern that the roughness of the surface of the object to be measured changes.

Therefore, accurate measurements are often difficult.

[Problem to be solved by the invention]

Generally, the emissivity is determined by the conditions defined by the measurement system, such as the wavelength, and the physical conditions of the non-measured object, such as the material. Therefore, even if we consider only the conditions of the measurement system, the wavelength, directionality (angle)
, it is possible to define an infinite number of emissivities with different polarization components, and if the effects of the material to be measured, processing conditions, surface roughness, degree of redox, thermal history, temperature, etc. are taken into account, the emissivity can be varied. Determined by parameters. That is, emissivity cannot be set easily. Furthermore, if the emissivity changes due to changes in the physical conditions of the object to be measured, setting the emissivity becomes extremely difficult. Furthermore, in a narrow place or a place where the measurement environment is poor, a normal lens system cannot secure an optical path to the object to be measured. The present invention has been devised to solve the above-mentioned problems, and the present invention has been devised to solve the above-mentioned problems. Focusing on the fact that the relationship between spectral emissivity is unique to the physical conditions of the object to be measured, we aimed to accurately determine temperature and emissivity at the same time by determining the relationship between two spectral emissivities in advance. It is something.

[Means to solve the problem]

The optical fiber radiation thermometer of the present invention includes an optical fiber means for transmitting two types of spectral radiance signals that differ in at least one condition among the wavelength, polarization state, and measurement angle among thermal radiation from an object to be measured; A means for photoelectrically converting the transmitted spectral radiance signal by a photodetector, a means for manually inputting parameters defining a relational expression specific to the object to be measured between two spectral emissivities corresponding to the spectral radiance, and two spectral radiance signals. The calculation means calculates the temperature and emissivity of the object to be measured from the relational expression between the radiance signal and the spectral emissivity, and the means outputs the obtained temperature and emissivity. This method is characterized in that the temperature and emissivity of the object to be measured are simultaneously determined by solving a known relational expression specific to the object to be measured.

[For production]

The effects of the present invention will be specifically explained below. Let us now assume that two different spectral emissivities are EX'EY, and that the relationship between the two spectral emissivities is experimentally known and can be expressed as shown in FIG.

This relationship is expressed as the emissivity function of material A by the following equation (1).

E, = f (EX) (1) The subscripts X and Y represent measurement conditions with different wavelengths, measurement angles, or polarization components, and possible combinations thereof include, for example, 2-wavelength type, polarization type, and 2-wavelength polarization type. . The feature of the present invention is to detect the polarization components of two or more thermal radiations with different wavelengths or measurement angle conditions, and to select an arbitrary combination from them to determine the emissivity characteristic function that is most suitable for the object being measured. The purpose is to find temperature and emissivity using
The process will be explained below. First, when the radiometer is calibrated in a blackbody furnace, the relationship between the true temperature and the radiometer output is shown in FIG. 5 and can be expressed by equations (2) and (3).

That is, parameters A, B, and C are determined by calibration.

To; true temperature LX, Ly; radiometer output C
2; Second constants of radiation A, B, C; Parameters of blackbody furnace calibration function Exa, E
yo: true emissivity Figure 6 is the unknown true temperature T. and true emissivity EXO.

The output signal LY of the radiometer that includes information on both EYO and EYO can be expressed by equation 4) (5).

and = EXo−L, (λ,,To)
(4) LY=E,.・L, (
λy, 'ro) (5) Since the true temperature and emissivity are unknown at this point, given the assumed temperature T, (
2) Obtain the apparent radiance Lx' + Lv' from the formula. Therefore, the apparent emissivity can be calculated from equations (6) and (7).

The second feature of the present invention is to determine whether the apparent emissivity ExEy is the true emissivity E by referring to the emissivity characteristic function f held as prior knowledge.
xo5Ey. The purpose is to find a solution by performing operations that match the . To explain this using Figure 7, the apparent emissivity (E
x' ET) is the − pair of input signals (LX, L
y'') moves on the 0 curve when the assumed temperature T is changed.On the other hand, the true emissivity of Exo, Ey
. Since is on the f curve, the intersection with the 6th curve is the true emissivity to be determined, and the temperature T assumed at that time becomes the true temperature T0. These six curves and the f-function curve intersect at different positions if the true emissivity is different even if the true temperature T0 is the same.

Here, the combination of different measurement conditions that is optimal for the object to be measured means that the 6 curve and the f curve intersect stably. As shown in FIG. 8, as the slopes of the 6th curve and the f curve become closer, the intersection becomes unstable due to changes in emissivity, and the accuracy deteriorates.

Therefore, by optimally selecting a combination of measurement conditions that differ depending on the object to be measured, it is possible to always obtain a stable solution.

In this way, in the radiation thermometer of the present invention, by optimally selecting a combination of different measurement conditions among a plurality of spectral radiances from the detector, the optimal emissivity characteristic function for the object to be measured can be obtained and accurate Temperature measurement becomes possible.

[Examples] Hereinafter, the features of the present invention will be specifically explained based on Examples with reference to the drawings. FIG. 1 shows the configuration of the present invention, where 1 is an object to be measured, and 2 is an optical fiber for optically transmitting the radiance from the object to a detector 3. In FIG. The optimum combination of spectral emission conditions (wavelength, polarization) for the object to be measured can be selected using optical fibers or detectors. Examples include a two-wavelength type using a single mode fiber filter, and a polarizing type using a polarizing fiber and a polarizer. In the parameter input section 41 of No. 4, parameters of a relational expression representing the relationship between two known spectral emissivities specific to the object to be measured corresponding to the two selected spectral radiation conditions are input manually.

On the other hand, the parameter input section 42 inputs the parameters (ABC three constants) of the blackbody furnace calibration function that represents the relationship between the spectral radiance signal of the detector and the true temperature corresponding to the two selected spectral radiation conditions. In the part, the true emissivity on the emissivity characteristic function, which is a relational expression between the two corresponding spectral emissivities, is determined based on the two spectral radiance signals, and the true temperature is determined at the same time.

FIG. 2 schematically shows an embodiment of the calculation section. The radiance from the object to be measured (1) is transmitted through the optical fiber (2) and becomes two spectral radiance signals Lx and LY by the detector (3). The calculation requires a parameter 12 of a relational expression that expresses the relationship between two known spectral emissivities specific to the object to be measured, and a blackbody furnace calibration parameter 13 that expresses the relationship between the spectral radiance signal and the true temperature.

The parameters 12 and 13 may be input using a keyboard or the like, or stored internally and automatically retrieved. The calculation begins by giving the assumed temperature T of 14 and calculating the apparent black body spectral radiance signal L Obtain as ε'8 and ε' above. On the other hand, the emissivity characteristic function 19 representing the relationship specific to the measured object between the two spectral emissivities corresponding to the spectral radiation conditions is the true emissivity (εxo' ε
,. ) is shown by a curve f in 21 two-dimensional planes as possible combinations. That is, the assumed temperature T at which the true emissivity that exists on this curve can be taken is the true temperature T. will be shown. Therefore, while changing the assumed temperature T by 20,
2, the true temperature To can be obtained by finding a hypothetical temperature at which the apparent emissivity matches the true emissivity on the curve f.

Figure 3 shows examples of optical fiber combinations for securing the optical path and selecting spectral radiation conditions (polarization, wavelength).

In the configuration shown in column (A), a polarizer 30 is provided at the tip of the fiber to convert the polarized light into P-polarized light and S-polarized light, which are then optically transmitted through two single mode fibers 31 and 32. In the configuration shown in column (B), a half mirror 33 is attached to the fiber tip to separate two optical paths, and each
Passing through polarizing fiber 34 and S polarizing fiber 35, (C)
In the configuration shown in the column, a filter 36 is provided at the rear end of the fiber 37 to separate the light into two wavelengths. In the configuration shown in column (D), the half mirror 40 provided at the tip of the fiber
The light is separated into two wavelengths using single mode fibers 38 and 39 that transmit a predetermined wavelength into two optical paths.

Furthermore, by providing a plurality of fibers with different measurement angles in the configuration shown in FIG. 1, the measurement angle conditions can be changed.

〔Effect of the invention〕

As mentioned above, according to the present invention, an optical path can be secured by using an optical fiber in a narrow place or a place with a bad environment, and at the same time polarization and wavelength selection can be performed using the fiber, and two spectral radiation conditions can be achieved. can be easily obtained. On the other hand, since the calculation is performed based on the emissivity characteristic function unique to the measured object, which has been determined experimentally in advance, it is possible to obtain a reasonable true temperature and emissivity. By combining wavelength, polarization, and angle), it is possible to select the optimal emissivity characteristic function that matches the emissivity change process of the object being measured, making it possible to measure temperature with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the general configuration of the present invention, FIG. 2 is a diagram schematically explaining an embodiment, FIG. 3 is a configuration diagram showing an embodiment using optical fibers, and FIGS. 4 to 8 are FIG. 2 is a diagram for explaining the present invention in detail. In the figure, 1... object to be measured, 2... optical fiber, 3...
・Detector, 4...Parameter input section. (B) Entering Y (C) Figure X Figure true temperature T. Figure Figure EX Figure Figure Figure EX

Claims (1)

[Claims] 1. Optical fiber means for transmitting two types of spectral radiance signals that differ in at least one of the wavelength, polarization state, and measurement angle of thermal radiation from the object to be measured; means for photoelectric conversion by a detector; means for inputting parameters that define a relational expression specific to the object to be measured between two spectral emissivities corresponding to the spectral radiance; calculation means for calculating the temperature and emissivity of the object to be measured from the relational expression;
It has a means for outputting the obtained temperature and emissivity, and the calculation means calculates the temperature and emissivity of the object to be measured by solving a known relational expression specific to the object to be measured between the two spectral emissivities. An optical fiber radiation thermometer characterized by simultaneous measurement.