JPH03200027A - Radiation thermometer - Google Patents

Abstract

PURPOSE:To remove the influence of an optical loss in an optical path and to highly accurately find out the temperature of a target to be measured by inputting a photometeric value and a background emitting light value to an arithmetic means and resolving unknown quantities based upon relation among th unknown unquantities, the photometeric value and the background emitting light value by using an emissivity, the optical loss in the optical path as unknown quantities in addition to the temperature of the target. CONSTITUTION:The background emitting light values Eblambda1, Eblambda2, Eblambda3 of respec tive wavelengths are applied by a background emitting light measuring means BGRM or a background emitting light value inputting means BGRI. Referenced light measuring values Mlambda1 to Mlambda3, reflected light measuring values Rlambda3 to Rlambda3, emitted light measuring values Elambda1 to Elambda3, and background emitting light values Eblambda1 to Eblambda3 are inputted to the arithmetic means TC. The means TC includes the emissivity and the optical loss in the optical path as unknown quantities in addition to the temperature of the target TG to be measured and finds out the unknown quantities based upon the relation among respective photometric values, the background emitting light value and respective unknown quantities to calculate the temperature of the target TG.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radiation thermometer that receives infrared light or other light emitted from an object to be measured and determines the temperature of the object from the amount of received light. be.

C. Prior Art] Radiation thermometers that measure radiation from an object to be measured and determine the temperature of the object based on the photometric value are generally known. Factors other than object temperature may affect the photometric value of synchrotron radiation.
For example, the emissivity of the object to be measured, the background radiation from a radiation source other than the object to be measured, etc. affect the photometric value of the radiation. and,
In order to determine the temperature of the object to be measured, it is necessary to investigate the influence of factors other than the temperature of the object.

Conventionally, a radiation thermometer that takes these points into account to determine the temperature of an object to be measured is disclosed, for example, in Japanese Patent Application Laid-Open No. 63-30.
As shown in Japanese Patent Laid-open No. 5227 or Japanese Patent Application Laid-Open No. 63-305228, an irradiation means for irradiating two or more or three or more reference beams with different wavelengths toward an object to be measured, and a side beam for irradiating reference beams of each of the wavelengths. a reference light photometer that emits light, a reflected light photometer that measures the reflected light of the reference light of each wavelength reflected by the object to be measured, and a radiance photometer that measures the radiance from the object to be measured for each wavelength. Based on predetermined assumptions regarding the relationship between the means, emissivity, measured reflection information value, and unknown coefficient, the temperature of the object to be measured is calculated from the photometric values of each of the photometric means, excluding the influence of emissivity. A device equipped with a calculation means is known. According to this radiation thermometer, when the emissivity of the object to be measured is unknown, its influence can be removed. Furthermore, these publications disclose that when the value of the background radiation is known or is a value measured by a measuring means, the temperature of the object to be measured can be calculated by removing the influence of the background radiation. There is.

[Problem to be solved by the invention]

However, as factors that affect the photometric value of synchrotron radiation,
In addition to the emissivity and background radiation mentioned above, optical loss in the optical path may be a problem. In other words, optical loss occurs when measuring in an atmosphere that absorbs infrared rays, when there is a field of view missing in the measurement system, or when the lens is dirty. In such cases, the above-mentioned optical loss affects the photometric value of synchrotron radiation, and the extent of this optical loss is unknown, so conventional radiation thermometers cannot eliminate errors caused by optical loss. The problem remained that it could not be done.

The present invention has been made in view of the above, and is a radiation thermometer that can eliminate the effects of emissivity and background radiation as well as the effects of optical loss, and can accurately determine the temperature of a measured object. The purpose is to provide

[Means to solve the problem]

In order to achieve the above object, the present invention provides a radiation thermometer that measures the temperature of a measured object based on the measurement of emitted light from the measured object under conditions where optical loss occurs in the optical path. illumination means for irradiating reference light including the above wavelengths toward the object to be measured; reference light metering means for measuring the reference light for each of the wavelengths; and reflection of the reference light reflected by the object to be measured. reflected light photometry means for measuring light according to each of the wavelengths; synchrotron radiation photometry means for measuring the emitted light from the object to be measured according to each wavelength; Background radiation value supply means for supplying;
Each photometric value obtained by each of the photometric means and the background radiation value obtained by the background radiation value supplying means are input, and these values and the temperature of the object to be measured, which is an unknown quantity, are input.
The apparatus is equipped with calculation means for calculating the temperature of the object to be measured by solving the unknown quantity based on the relationship between the emissivity and the above-mentioned optical loss.

In this configuration, the background emitted light value supplying means may include background emitted light photometry means for measuring emitted light from objects around the object to be measured for each of the wavelengths, or The background radiation value input means is configured to input the value of the radiation light for each wavelength when the value is known.

[Effect]

According to the above configuration, the background radiation value is given by the background radiation value supply means, and the emissivity and optical loss are unknown together with the temperature of the object to be measured, and these, each of the photometric values, and the background radiation value are combined. The calculation means calculates the correct temperature of the object to be measured, excluding the influence of the background radiation value, emissivity, and optical loss.

〔Example〕

FIG. 1 shows the overall configuration of a radiation thermometer according to a first embodiment of the present invention. Each of the photometric means described later in this radiation thermometer measures light of three or more different n types of wavelengths, and the figure shows the case where n==3.

In this figure, the illumination means has n different wavelengths λi
It is composed of a light source section LS that generates a reference light including light of (i=1.2...,n), an injection fiber FBa, and an injection head OHa. The intermittent reference light is irradiated to the measurement location of the object to be measured TG through the injection fiber FBa and the injection head OHa. In addition, in order to calculate the reflectance, a signal corresponding to the reference light of each wavelength λ1 is output from the light source section LS to the monitor line,
1 and A/D conversion by the A/D converter ADC to obtain the reference light photometry value M(A1) for each wavelength. In the example shown in the figure, the reference light photometry value M (A1) for each wavelength is obtained. Three amplifiers Al, A2 . A3 is provided. A monitor line including these amplifiers Ai constitutes a reference light photometry means.

On the other hand, the light including the reflected light of the reference light irradiated onto the object to be measured TG from the injection head OHa, the background radiation light, and the emitted light from the object to be measured TG itself is transmitted to the measurement point of the object to be measured TG. The light is focused by a measurement head OHb arranged toward the light beam, and is sent to the optical branch BR through a measurement fiber FBb.

Then, this light is transmitted to the optical branching section BR□ with each wavelength λ□, λ2, . λ
3, each of which is separated by a photodetector S, , S2, which will be described later. It is converted into an electrical signal by S3. This signal consists of an alternating current component with a frequency f corresponding to the reflected light of the reference light, and a direct current component corresponding to the sum of the background emitted light and the emitted light from the object to be measured TG itself. Among these, the AC component is processed by DC cut capacitors C, C2, C3 and amplifiers ACA1, ACA2, . ACA3 and rectifier circuit RC1
, RC2゜RC3, and then Δ/D conversion by the A/D converter ADC, resulting in reflected light photometric values R(λt), R(A2), and R(A3). Ru. In addition, the DC component is processed by an amplifier DCA for each wavelength.
1. DCA2, DCA3, and sample-and-hold circuits SH1, SH2, SH for removing AC components
3, and is then A/D converted by the A/D converter ADC to obtain the synchrotron radiation photometry value E (A
1), E(A2).

E(A3).

In this way, in the system that measures the light focused by the measurement head OHb for each wavelength, the AC component extraction circuit constitutes the reflected light photometry means, and the DC component extraction circuit constitutes the emitted light photometry means. ing.

Also, if the temperature of the surrounding objects is sufficiently low compared to the temperature of the object to be measured TG, the background radiation can be ignored, but in case the background radiation cannot be ignored, the background radiation As a background radiation source value supply means for obtaining and supplying values,
A background radiation photometry means BGRM and a background radiation value input means BGRI are provided for measuring the background radiation for each of the wavelengths. If the values of the background radiation for each wavelength are known, input the values manually from the background radiation value input means BGRI; if not, enter the values manually from the background radiation photometry means BGRM.
The background radiation light measurement means BGRM or the background radiation value input means BGRI can be used to calculate the background radiation values Eb (λ
3) is given.

The above reference light photometry values M(λ,) to M(A3), reflected light photometry values R(λ□) to R(A3), and synchrotron radiation photometry values E(A1)
~E(A3) and background radiation value Eb(A1) ~Eb(
A3) is input to the calculation means TC. In addition to the temperature of the object to be measured TG, the calculation means TC also includes the emissivity and the optical loss in the optical path as unknowns, and based on the relationship between each of the above-mentioned photometric values and background emitted light values and each unknown, as will be described later. The unknown quantity is determined by the calculation principle and solution method as shown in the following, and the temperature of the object to be measured TG is calculated. The calculated value is input to the display section DSP and the output section oP, and is displayed and output in an analog or digital manner.

As shown in FIG. 2, for example, the light source section LS is configured to emit a reference light emitted from a halogen lamp 1 and condensed by a reflector 2 at a frequency f using a chopper 4 driven by a motor 3 to emit the reference light into an injection fiber. While sending it to FBa, the reference light reflected by glass or half mirror 5 is separated into each wavelength through branching fiber 6 and optical filter 7.8.9, photoelectrically converted by photodetectors s11 s21 s3, and sent to the monitor line. The structure is such that it can be output.

Alternatively, as shown in Fig. 3 or 4, the semiconductor laser diodes 11, 12, 13 for each wavelength are
4, the reference beams of frequency f emitted from these diodes 11, 12.13 are collected and sent to the injection fiber FBa, while the output section connected to each diode 11, 12.13 is connected to the reference beam. The structure may be such that a corresponding signal is output to a monitor line.

In addition, the optical branching unit BR includes optical filters 21, 22, and 23 that branch the end of the measurement fiber FBb and transmit only light of a predetermined wavelength of each branched light, as shown in FIG. 5, for example. Through the photodetector S, S2.
The structure is such that light is received by S. Alternatively, as shown in FIG. 6, the light passing through the measurement fiber FBb is divided into wavelengths by a lens 24 and a diffraction grating 25, and the light is divided into wavelengths by a photodetector s1. s2. Alternatively, as shown in FIG.
．． Divided into each wavelength by 28, optical filter 29.30
．． The structure may be such that the light is received by the photodetector S□r 82 * 33 through 31.

Next, the calculation principle and solution method for temperature, etc. to which the present invention is applied will be explained.

Principles of calculating temperature etc. Assuming that the object to be measured is a black body with temperature T, the luminous flux of light with wavelength λ emitted from the object per unit area and unit solid angle, that is, the spectral radiance L (λ, T) is given by Blank's formula. Assuming that the optical system of the device has a measurement area ΔA1 and a measurement solid angle ΔΩ, the photometric value of the emitted light is E. (λ, T), the relationship between this and the spectral radiance (λ, T) is expressed using polar coordinates (r, θ, φ) as shown in the following equation (11).

Eo (λ, T) = Ce-body f f, g J,)
, S (λ) − L (λ, T) cosθ −s
inθ・d λ d θ dA ・・
・(1) Here, S (λ) is the overall spectral sensitivity of the photodetector and optical filter, and Ce is the photoelectric conversion coefficient regarding the DC signal of the measuring device, which is specifically determined by blackbody calibration measurement. It is a constant. Therefore, the above E corresponds to the photometric value of emitted light from a black body at temperature T. The values of (λ, T) can be prepared in advance.

By the way, since the actual object to be measured TG is not a black body, the photometric value of the emitted light is related to the emissivity and is also affected by the background radiation. Furthermore, if there is gas such as water vapor in the atmosphere between the object to be measured TG and the measurement head OHb, which causes infrared absorption, or if there is a lack of field of view or dirt in the measurement system, the measurement wavelength Optical loss occurs in the area.

In this case, if the emissivity of the measured object TG at each wavelength is (λi), the reflectance is ρ (λi), and the optical loss is α (λi), then the synchrotron radiation photometric value E (λi) The following equation (2) holds true for .

E (λ i) = α (λ i) [ε (λ i)
−EO(λ i .

T)+ρ(λi)・Eb(λi)] ...(2) When the object to be measured TG is a non-transparent object in the measurement wavelength range, the relationship between emissivity and reflectance is ε(λi) +ρ(λ1)
=1...(3).

Also, as shown in Figure 8, light of wavelength λ with unit light intensity is incident on the object to be measured TG, and the light is reflected at various angles (θ, ψ) with light intensity Ir (θ, ψ, λ). Suppose that
The hemispherical reflectance ρ(λ) is expressed by the following equation (4).

ρ(λ) = (1/2π) f” f″I r (
θ, ψ.

λ) sinθ−dθdψ −(4) On the other hand, the photometry value M by the reference light photometry means and the reflected light photometry means
The apparent reflectance r(λi) obtained from (λi) and R(λi) is “(λ 1)=Cr −R(λ i
)/M(λ i)=α2 (λ') [(1/2π
) f fARI r(θ, ψ, λ) +
inθ−dθdψ1 (5). Here, Cr is a coefficient related to the charging conversion efficiency of the alternating current signal in the reflected light photometric means and the monitor signal in the reference light photometric means, and is a constant determined by calibration measurement of reflection. Let β(λi) be the ratio of the total reflected light to the hemispherical space and the actually measured reflected light, then β(λ+) = (f fARI r (θ, ψ, λ
)・tinθ−dθdψ) / (f:′cf:I r
(θψ, λ) Eye θ・dθdψ) r (λi)=α2 (λi)・β(λi)・ρ(λ)
...(6) holds true. Therefore, the emissivity is expressed by the following equation (7).

ε (λ1)=1− (1/α2 (λi)) (1
/β(λi)) ·r(λi) (7) By substituting the above equations (6) and (7) into equation (2), the following conditional equation (8) is obtained.

E(λl)=[α(λi)−(1/α(λ1))(1/
β(λi)) ・r(λi)]”E(7(λi, T)
+ (1/α(λI))(1/β(λi)) ・r(
λi) ・Eb(λi) ... (8) This conditional expression (8
) can be obtained for each n wavelength, so conditional expression (8
) is n, and the unknowns included in this are α(λ
i), β(λi), and T, so the unknowns cannot be solved as they are. Therefore, temperature, emissivity, optical loss, etc. can be determined by making reasonable assumptions and using approximate expressions to reduce the unknowns, as described below.

α(λ1) is expressed as a linear expression of wavelength λ (I≧0), 1/β(λ
l) is approximated by an m-order equation (m≧0) with wavelength λ, the linear equation has (/+1) unknowns corresponding to the number of coefficients from the 0th to the 1st-order, and the m-order equation has unknowns. Since the number of unknowns is (m+1) corresponding to the number of coefficients from the 0th order to the mth order, the number of unknowns including these and the temperature T is (AI+m+3).

Therefore, n such that n≧(l+m+3).

/, m is selected, the unknown quantity can be solved based on equation (8). As a specific example, assuming that m=1-〇, that is, α(λi) and 1/β(λi) are constant with respect to wavelength, α(λ1)=3° (=constant)... (9)1
/β(λ1)=bo (=constant) ...(lO)
far. Equation (9) means that the optical loss in the optical path is gray. Furthermore, using the equation (lO) means that the ratio of the measured reflectance to the hemispherical reflectance is constant with respect to wavelength, and it is already known that such an assumption is valid in temperature calculations. There is. If we introduce such an assumption, the unknowns are temperature T and a.

, bo, and the unknowns can be calculated by measuring three or more wavelengths. Although various specific solutions can be considered, two examples of solutions are shown below.

Example of solution when measuring light of three wavelengths When formula (8) is rewritten by substituting formulas (9) and (10), the following formula (11) is obtained.

E(λi) = (a6-c, 3-r (λ1))E,
(λi.

T) + c(, -r (λi)・Eb(λi)...(l
However, co=bO/a.

By solving three simultaneous equations obtained from equation (11) when n=3, the temperature T, etc. can be determined. In other words, from this simultaneous equation, a. .

If we eliminate c(, then we get (λI)(Eb(enter υ/E, (λt-Tnorl) - and (λsno(Eb(λ,)/Eo(λ21tonorl)...
・(12) becomes. Since EO(λ1.T) can be determined in advance, the temperature T that satisfies equation (I2) can be determined relatively easily by one-dimensional search or the like. Furthermore, if necessary, emissivity and optical loss may be calculated.

Solution example when measuring light with four or more wavelengths The assumptions in equations (9) and (10) are likely to include a certain degree of error. Furthermore, the photometric values also include measurement errors. Therefore, in order to reduce the influence of these errors on unknown variables such as temperature, the least squares method is introduced after setting n≧4. That is, an objective function for evaluating the deviation between the photometric value and the estimated value is considered, and a set of unknowns that minimizes the function is determined as a solution.

- As an example, consider the following objective function F(T) that evaluates the deviation between the photometric value and the estimated value of synchrotron radiation based on Equation 111.

F (T) = Σ[fao Co”r (A1)lE
o(λi.

iCoIT) /E (λi)+Co@r (λi)・Eb
(λ i)/E(λ i) −1 2...(13
) a that minimizes F (T) for a certain value of T.

and co is F (T) is a. and 2 convex downwards about C8
Since it is a function of When aOr CO obtained in this way is written in the form of a vertical matrix, it becomes as shown in the following equation (14).

...(14) However, X1=E(λi, T)/E(A1)Yi=r
(λ i) (Eo(λ t, 'r)−Eb(
λ i) ) /E (λ 1) a of equation (14)
Substitute o and Co into equation (13) to calculate F (T). Minimize F(T) by repeating this calculation while changing T variously under physical constraints (0 x ε≦1, etc.) and machine constraints (temperature measurement range, etc.) Perform a one-dimensional search for the value of T. This value becomes the solution for T.

The calculation principle and the calculation shown in the solution example described above are performed by the calculation means TC shown in FIG.

Therefore, each photometric value of the reference light, reflected light, and radiation light for at least three wavelengths and the background radiation light are calculated by the calculation means TC.
If the temperature is inputted, not only the influence of background radiation and emissivity but also the influence of the above-mentioned optical loss are removed, and the temperature of the object to be measured TG can be determined with high accuracy.

〔Effect of the invention〕

As described above, according to the radiation thermometer of the present invention, the reference light, the reflected light of the reference light, and the emitted light from the object to be measured are each measured for each wavelength by the photometric means for three or more wavelengths,
These photometric values and the background radiation value obtained by the background radiation value supply means are input to the calculation means, and the unknowns and the above are The temperature of the object to be measured is calculated by solving the unknowns based on the relationship between the photometric value and the background radiation value, so in addition to the emissivity and background radiation, the influence of optical loss in the optical path is considered. The temperature of the object to be measured can be determined with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of the entire radiation thermometer according to the first embodiment of the present invention, FIGS. 2 to 4 are block diagrams showing various specific examples of the light source section, and FIGS. 5 to 7 The figure is a block diagram showing various specific examples of the light branching section, and FIG. 8 is an explanatory diagram of reflectance. LS...Light source section, A1. A2. A3...Amplifier, O
Ha...Injection head, OHb...Measuring head, BR
...Optical branch, cll C2) C3...DC cut capacitor, ACA engineering, ACA2, ACA3.
...Amplifier, RC□, RC2, RC3... Rectifier circuit,
D.C.A. DCA2, DCA3...Amplifier, SHl, SH2. SH3...Sample and hold circuit, Sl, S2
, S3... photodetector, TC... calculation means.

Claims (1)

[Scope of Claims] 1. A radiation thermometer that measures the temperature of a measured object based on the measurement of emitted light from the measured object under conditions where optical loss occurs in the optical path, the radiation thermometer having three or more different wavelengths. an illumination means for irradiating a reference light including a reference beam toward the object to be measured; a reference light metering means for measuring the reference light for each of the wavelengths; A reflected light photometer that measures light for each wavelength, a synchrotron radiation photometer that measures the emitted light from the object to be measured for each wavelength, and a background that supplies the value of background emitted light incident on the object to be measured from the surroundings. A synchrotron radiation value supplying means inputs each photometric value obtained by each of the photometric means and a background synchrotron radiation value obtained from the background radiation value supplying means, and calculates these values and the unknown temperature of the object to be measured; A radiation thermometer comprising: calculation means for calculating the temperature of an object to be measured by solving an unknown quantity based on the relationship between emissivity and the optical loss. 2. The radiation thermometer according to claim 1, wherein the background radiation value supplying means is a background radiation photometry means for measuring radiation from objects around the object for each of the wavelengths. 3. The background radiation value supplying means is a background radiation value inputting means for inputting the values for each wavelength of the radiation from objects surrounding the object when the values are already known. The radiation thermometer according to claim 1.