JP2000046656A - Radiation thermometer having light receiving loss compensation function and temperature measuring method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate for a light receiving loss due to a deposit on lens surface. SOLUTION: The preset light quantity P of pulse light is introduced to a condenser lens 2 via an optical fiber 3, using a light emitting element 12, a drive circuit 13 and an optically coupled element 14, and a reflected light quantity ΔS due to a deposit on lens surface is added to the transmitted light quantity S2 of the condenser lens 2 for measurement, using the optically coupled element 14, a sampling circuit 15, a light receiving element 4 and a light receiving circuit 5. Then, an arithmetic operation circuit 16 calculates a reflected light quantity ΔSA from the changes S1 and S2 of a light receiving quantity due to the existence and non-existence of pulse light, and the reflectance Rf of the deposit is found from the value of ΔS. Furthermore, the transmission factor Tr of the lens surface is found from a relationship between the reflectance Rf and the transmission factor Tr, thereby making compensation for the receiving light loss.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation thermometer having a light-receiving loss compensation function and a method for measuring the temperature.

[0002]

2. Description of the Related Art Radiation thermometers that measure the temperature of the surface of an object in a non-contact manner by using the phenomenon that the amount of radiation light (radiation light) changes in accordance with a change in the temperature of the object have been used. For example, in temperature measurement of a turbine blade such as a gas turbine, there is an advantage that a large number of turbine blades rotating at a high temperature can be measured by one sensor in a non-contact manner.

Further, there has been developed an apparatus capable of precisely measuring the temperature of a minute portion by combining such a radiation thermometer with an optical fiber and transmitting the emitted light through the optical fiber. In this radiation thermometer using an optical fiber, as schematically shown in FIG. 3, a condenser lens 2 is installed near a measurement point 1 (for example, a turbine blade), and light collected by the condenser lens is collected. It is led to the light receiving element 4 via the optical fiber 3,
The temperature is calculated from the output. In addition,
In this figure, 5 is a light receiving circuit, 6 is an arithmetic circuit, and 7 is an output device.

[0004]

Purging air or the like is usually supplied to the surface of the condenser lens 2 to prevent foreign matter from adhering. However, since the combustion gas and purge air supplied to the turbine blade 1 contain impurities, the impurities adhere to the surface of the condenser lens during use, and the light transmittance gradually decreases. There is. In this case, the measured temperature is displayed lower than the actual temperature because the amount of radiation light received decreases. Therefore, even if the measurement location (turbine blade) is overheated to a temperature higher than the allowable temperature, it is displayed low. There was a problem that could cause damage. In other words, it is a major problem that the adhesion state of the particles on the lens surface is unknown.

The present invention has been made to solve such a problem. That is, an object of the present invention is to provide a radiation thermometer having a light-receiving loss compensation function capable of compensating for a light-receiving loss due to a deposit on a lens surface, and a method of measuring the temperature.

[0006]

By guiding a pulse light of a predetermined light amount P to a condenser lens (2) via an optical fiber, the amount of light reflected by the substance adhering to the surface thereof becomes equal to the transmitted light amount S2 of the condenser lens. Since the addition is measured, the amount of reflected light ΔS can be calculated from the changes S1 and S2 in the amount of received light depending on the presence or absence of the pulsed light, and the reflectance Rf of the attached matter can be calculated therefrom.
Further, since the reflectance and the transmittance on the lens surface have a substantially constant relationship, the light receiving loss can be compensated by obtaining the transmittance Tr on the lens surface from this relationship. The present invention is based on such a new principle.

According to the present invention, a condensing lens (2) for condensing light emitted from a high-temperature object (1), an optical fiber (3) for transmitting condensed light, and a light amount for transmitted light A photoelectric conversion device (10) for converting the transmitted light into a current signal; and a photoelectric conversion device (10) for converting the transmitted light into a current signal. A light receiving circuit (5) for converting to a voltage signal, a light emitting element (12) for emitting a predetermined amount of light P having a wavelength λ1, a driving circuit (13) for causing the light emitting element to emit light in pulses, a light emitting element and a light receiving element Optical coupling element (14) for coupling optical fiber to optical fiber
And a sampling circuit (15) for acquiring a light receiving signal in synchronization with ON / OFF of the light emitting element, and an arithmetic circuit (16) for compensating light receiving loss from the voltage signals S1, S2 from the light receiving circuit at each timing. A radiation thermometer having a light reception loss compensation function is provided.

According to the present invention, a condenser lens (2) is provided in the vicinity of the high-temperature object (1), and light condensed by the condenser lens is received by a light-receiving element (3) via an optical fiber (3). In the temperature measurement method for calculating the temperature T of the high-temperature object from the received light amount according to 4), a pulse light of a predetermined light amount P is incident on an optical fiber so as to be guided to the condenser lens (2), and the presence or absence of the pulse light is determined. A temperature measuring method is provided, wherein light receiving loss is compensated from changes in received light amount S1, S2.

According to the apparatus and method of the present invention, the light emitting element (12), the driving circuit (13) and the optical coupling element (14).
As a result, the pulse light of the predetermined light amount P is guided to the condenser lens (2) via the optical fiber, and the optical coupling element (14), the sampling circuit (15), the light receiving element (4), and the light receiving circuit (5)
, The amount of reflection .DELTA.S reflected by the substance adhering to the lens surface is added to the amount of transmission S2 of the condenser lens and measured.
6), the change in the amount of received light S1, S depending on the presence or absence of the pulse light
2 to calculate the amount of reflected light ΔS, calculate the reflectance Rf of the attached matter from this, and obtain the transmittance Tr of the lens surface from the relationship between the reflectance and the transmittance of the lens surface to compensate for the light reception loss. it can.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, common members are denoted by the same reference numerals, and redundant description is omitted. FIG. 1 is an overall configuration diagram of a radiation thermometer according to the present invention. As shown in the figure, the radiation thermometer of the present invention comprises a condenser lens 2, an optical fiber 3, and a photoelectric conversion device 10 that converts a transmitted light amount into an electric signal and calculates a temperature T of a high-temperature object from the electric signal. Is done. The condenser lens 2 is installed near the hot object 1 (for example, a turbine blade).
The light emitted from the optical fiber 3 is focused on the end face of the optical fiber 3. Although the condensing lens 2 is shown as a single convex lens in this figure, it may be a compound lens composed of two or more lenses. Further, although the protective glass of the condenser lens 2 is not shown in this figure, such a protective glass may be used. The optical fiber 3 transmits the light condensed by the condenser lens 2 to the photoelectric conversion device 10.
The optical fiber 3 is formed by bundling a plurality of (for example, three) ultrafine fiber wires having a diameter of about 0.4 mm, and has flexibility and low transmission loss.

As shown in the figure, the photoelectric conversion device 10 includes a light receiving element 4, a light receiving circuit 5, a light emitting element 12, a driving circuit 13,
Optical coupling element 14, sampling circuit 15, and arithmetic circuit 1
Consists of six. The light receiving element 4 converts the light transmitted through the optical fiber 3 into a current signal. The light receiving circuit 5 converts the current signal converted by the light receiving element 4 into a voltage signal. Therefore, the combination of the light receiving element 4 and the light receiving circuit 5 allows the optical fiber 3
Can be converted into a voltage signal (voltage level), and the voltage signal is processed by an appropriate arithmetic circuit to calculate the temperature of the high-temperature object 1 as in the related art. it can.

The light emitting element 12 emits light having a predetermined light amount P having a wavelength λ1. The drive circuit 13 causes the light emitting element 12 to emit light in a pulse shape. Further, the optical coupling element 14 is
And the light receiving element 4 are coupled to the optical fiber 3. With this configuration, it is possible to irradiate the condenser lens 2 with pulsed light from the light emitting element 12 via the optical fiber 3 and simultaneously receive the reflected light and the transmitted light together, and measure the amount of light received by the light receiving element 4 can do.

The sampling circuit 15 acquires a light receiving signal from the light receiving element 4 in synchronization with ON / OFF of the light emitting element 12. Further, the arithmetic circuit 16 determines whether the light emitting element 12 is ON / OFF.
The light receiving loss is compensated from the voltage signals S1 and S2 from the light receiving circuit at each OFF timing.

FIG. 2 shows the principle of the present invention. (A) shows the definition of the transmittance Tr. As shown in this figure,
Assuming that the amount of light transmitted through the condenser lens 2 is S2 with respect to the amount S0 of light emitted from the high-temperature object 1, Tr = S2 / S0
. . (Equation 1) defines the transmittance Tr. When there is no attached matter on the lens surface, S2 = S0 and Tr = 1.0, and as the amount of attached matter increases, the transmittance Tr decreases as exemplified in (D). Further, since the light quantity S2 of the transmitted light can be measured by the above-mentioned radiation thermometer (the light receiving element 4 and the light receiving circuit 5), if the transmittance Tr is known, the light quantity S0 of the emitted light can be calculated, and the light receiving loss can be compensated. We can see that we can do it.

FIG. 2B shows the definition of the reflectance Rf. The above-mentioned radiation thermometer (light emitting element 12, driving circuit 1
3. When the predetermined amount of pulse light P is guided to the condenser lens 2 by the optical coupling element 14), a part ΔS thereof is reflected. In this case, the light receiving element 4 measures the light amount S1 obtained by adding the transmitted light amount S2 and the reflected light amount ΔS of (A). Therefore,
S2 + ΔS = S1. . If the relationship of (Equation 2) is satisfied and the reflectance Rf is defined as ΔS / P, Rf = (S1−S2)
/ P. . (Equation 3) holds. Where S2, S1, P
Since each is known or measurable, the reflectance R
f can be measured.

FIGS. 2C and 2D show transmittance Tr and reflectance R.
It is a figure showing relation of f. As shown in (C), the light incident on the attached matter is transmitted, reflected or absorbed, and the amount of absorbed light is usually small.
Tr + k · Rf = 1. . (Equation 4) holds. Where k
Is a correction coefficient, which can be regarded as substantially constant (Equation 6), but strictly, it is better to measure in advance as a function of the reflectance Rf (Equation 7). Equation 5 is a modification of equation 4.

By using the above-described FIG. 2 and (Equation 1) to (Equation 7), the pulse light of a predetermined light amount P is
And the light reception loss can be compensated from the changes S1 and S2 in the amount of received light depending on the presence or absence of pulsed light. That is, the light emitting element 12, the driving circuit 13, and the optical coupling element 14 guide the pulse light of a predetermined light amount P to the condenser lens 2 via the optical fiber, and the optical coupling element 14, the sampling circuit 15, the light receiving element 4, and the light receiving circuit 5, the amount of reflected light ΔS due to the adhering substance on the lens surface is added to the amount of transmitted light S2 of the condenser lens and measured. (Equation 2), the reflectance Rf of the attached matter is calculated from this (Equation 3), and the reflectance Rf of the lens surface is further calculated.
By calculating the transmissivity Tr of the lens surface from the relationship between (Equation 4 and 5) and the transmissivity Tr (Equations 4 and 5), the light receiving loss can be compensated using Equation 1, and this is displayed on a CRT or the like by the output device 7, Alternatively, it can be output to another control device or the like.

It is preferable that the light emitting element 12 emits light having a predetermined light amount P having a wavelength λ1. The influence of the wavelength λ1 can be suppressed to a negligible level by using, for example, one having sufficiently small transmission loss of the optical fiber. Further, when another wavelength λ2 is used for other purposes, mutual influence can be eliminated. In the above description, the conversion gain η in the photoelectric conversion of the light receiving element 4 and the light emitting element 12 is ignored (assumed to be 100%). However, in an actual apparatus, such a conversion gain η is known and included. It is good to apply an expression.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, the present invention can be applied to surface temperature measurement of general high-temperature objects other than gas turbine blades.

[0020]

As described above, the radiation thermometer having the light-receiving loss compensation function of the present invention and the temperature measuring method thereof can compensate for the light-receiving loss due to the attachment on the lens surface.
And so on.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a radiation thermometer according to the present invention.

FIG. 2 is a principle diagram of the present invention.

FIG. 3 is a schematic diagram of a conventional radiation thermometer using an optical fiber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot object 2 Condensing lens 3 Optical fiber 4 Light receiving element 5 Light receiving circuit 6 Arithmetic circuit 7 Output device 10 Photoelectric converter 12 Light emitting element 13 Drive circuit 14 Optical coupling element 15 Sampling circuit 16 Arithmetic circuit

Claims (2)

[Claims] A condenser lens for condensing light emitted from a high-temperature object, an optical fiber for transmitting condensed light, and converting the transmitted light amount into an electric signal. And a photoelectric conversion device (10) for calculating the temperature T of the high-temperature object, wherein the photoelectric conversion device converts the transmitted light into a current signal, and converts the current signal into a voltage signal. Light emitting circuit (5), a light emitting element (12) for emitting light of a predetermined light amount P of wavelength λ1, a driving circuit (13) for emitting the light emitting element in a pulse shape, and an optical fiber connecting the light emitting element and the light receiving element. Optical coupling element (14) for coupling and ON / OF of light emitting element
Sampling circuit (1
5) and a radiation thermometer having a light-receiving loss compensation function, comprising: an arithmetic circuit (16) for compensating for light-receiving loss from the voltage signals S1, S2 from the light-receiving circuit at each timing. 2. A condensing lens (2) near a high-temperature object (1), and the light condensed by the condensing lens is guided to a light receiving element (4) via an optical fiber (3). In a temperature measurement method for calculating a temperature T of a high-temperature object from a received light amount, a pulse light of a predetermined light amount P is incident on an optical fiber so as to be guided to a condenser lens (2), and a change S1, A method for measuring temperature, wherein light receiving loss is compensated from S2.