JP3932680B2 - Radiation thermometer with optical loss compensation function and its temperature measurement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation thermometer having a transmission loss compensation function and a temperature measuring method thereof.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, radiation thermometers that measure the temperature of an object surface in a non-contact manner using a phenomenon in which the amount of radiated light (radiant light) changes in accordance with changes in the object temperature have been used. For example, in the 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 a single sensor without contact.
[0003]
Furthermore, an apparatus capable of precisely measuring the temperature of a minute part has been developed by combining such a radiation thermometer and an optical fiber and transmitting the radiation light through the optical fiber. In this radiation thermometer using an optical fiber, as schematically shown in FIG. 4, a condenser lens 2 is installed in the vicinity of a measurement location 1 (for example, a turbine blade), and the light condensed by the condenser lens is collected. The temperature is guided to the light receiving element 4 through the optical fiber 3 and the temperature is calculated from the output. In this figure, 5 is a light receiving circuit, 6 is an arithmetic circuit, and 7 is an output device.
[0004]
[Problems to be solved by the invention]
In a radiation thermometer using an optical fiber, the transmission loss of the optical fiber changes due to temperature change, bending, and aging. Therefore, even with a thermometer that has been calibrated (corrected) precisely at the time of manufacture, if it is subject to temperature changes, bending, or changes over time, it cannot be measured accurately, and it must be reassembled and recalibrated. There is a problem that is not applicable to long-term continuous measurement.
[0005]
The present invention has been developed to solve such problems. That is, an object of the present invention is to provide a radiation thermometer having a transmission loss compensation function capable of compensating for transmission loss of an optical fiber in use, thereby enabling continuous measurement for a long time, and a method for measuring the temperature. There is to do.
[0006]
[Means for Solving the Problems]
A partial reflection coating is applied to the back surface of the condenser lens (2) in advance, and pulse light having a predetermined light quantity P having a wavelength reflected by the coating when the radiation thermometer is used is input from the outside through an optical fiber and guided to the condenser lens. As a result, the light reflected by the back surface of the lens receives a transmission loss for the round trip of the optical fiber, and is added to the normal measurement light for measurement. Accordingly, it is possible to calculate the light quantity ΔS of the reflected light that has received the transmission loss for the round trip of the pulsed light from the changes S1 and S2 of the received light amount due to the presence or absence of the pulsed light, and from this, calculate the transmittance Tr of the optical fiber to compensate the transmission loss. be able to. The present invention is based on such a novel principle.
[0007]
According to the present invention, a condensing lens (2) for condensing radiated light from a high-temperature object (1) having a partially reflective coating on the back surface, and an optical fiber (3) for transmitting the collected light And a photoelectric conversion device (10) that converts the transmitted light amount into an electrical signal and calculates the temperature T of the high-temperature object therefrom, and the photoelectric conversion device is a light receiving element (4) that converts the transmitted light into a current signal. ), A light receiving circuit (5) that converts the current signal into a voltage signal, a light emitting element (12) that emits light of a predetermined light amount P having a wavelength reflected by the partial reflection coating, and light emitting the light emitting element in a pulsed manner A driving circuit (13) to be coupled, an optical coupling element (14) for coupling the light emitting element and the light receiving element to an optical fiber, a sampling circuit (15) for acquiring a received light signal in synchronization with ON / OFF of the light emitting element, Light receiving circuit in timing And an arithmetic circuit (16) to compensate for transmission losses et voltage signals S1, S2, wherein the partially reflective coating is selectively reflective coating specific wavelengths .lambda.1, light of the light emitting element (12) Is a pulsed light with a wavelength λ1, and the partial reflection coating reflects only the light with the wavelength λ1 among the radiated light from the high temperature object (1), and the radiation temperature having a transmission loss compensation function, A total is provided.
[0009]
Moreover, according to this invention, it has a condensing lens (2) in the vicinity of a high temperature object (1), and the light condensed with this condensing lens is made into a light receiving element (4) 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, a partial reflection coating is applied to the back surface of the condensing lens, and pulse light having a predetermined light amount P having a wavelength reflected by the partial reflection coating is applied to the condensing lens. As shown in (2), it is made incident on the optical fiber, the transmission loss is compensated from the change S1 and S2 in the amount of received light depending on the presence or absence of pulsed light, and the partial reflection coating is a coating that selectively reflects a specific wavelength λ1. And the pulsed light is pulsed light having a wavelength λ1, and the partial reflection coating reflects only the light having the wavelength λ1 among the radiated light from the high-temperature object (1). Provided by It is.
[0010]
According to the apparatus and method of the present invention, the light emitting element (12), the drive circuit (13), and the optical coupling element (14) are used to transmit pulsed light having a predetermined light amount P having a wavelength reflected by the coating when the radiation thermometer is used. Is led to the back surface of the condenser lens (2), and the reflected light from the lens back surface is collected by the optical coupling element (14), the sampling circuit (15), the light receiving element (4) and the light receiving circuit (5). The transmission loss ΔS for the round trip of the pulsed light can be calculated by the arithmetic circuit (16) from the change S1, S2 of the received light amount due to the presence or absence of the pulsed light. Tr can be calculated to compensate for transmission loss.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to a common member and the overlapping description is abbreviate | omitted.
FIG. 1 is an overall configuration diagram of a radiation thermometer according to the present invention. As shown in this 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 electrical signal and calculates a temperature T of a high-temperature object therefrom. Is done.
The condenser lens 2 is installed in the vicinity of the high temperature object 1 (for example, a turbine blade), and condenses the radiated light from the high temperature object 1 on the end face of the optical fiber 3. The condensing lens 2 is shown as a single convex lens in this figure, but may be a compound lens composed of two or more lenses. Moreover, although the protective glass of the condensing lens 2 is not shown in this figure, such protective glass may be used.
Furthermore, according to the present invention, the partial reflection coating 2a is applied to the back surface (right side surface in the figure) of the condenser lens 2. The partial reflection coating 2a preferably selectively reflects a specific wavelength λ1, but the present invention is not limited to this, and may reflect a wide range of wavelengths.
The optical fiber 3 transmits light collected 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, for example, and has flexibility.
[0012]
The photoelectric conversion device 10 includes a light receiving element 4, a light receiving circuit 5, a light emitting element 12, a drive circuit 13, an optical coupling element 14, a sampling circuit 15, and an arithmetic circuit 16, as shown in the figure.
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 light receiving amount of light transmitted through the optical fiber 3 can be converted into a voltage signal (voltage level) by the combination of the light receiving element 4 and the light receiving circuit 5, and this voltage signal is processed by an appropriate arithmetic circuit. Thus, the temperature of the high-temperature object 1 can be calculated as in the conventional case.
[0013]
The light emitting element 12 emits light having a predetermined light amount P having a wavelength reflected by the partial reflection coating 2a. When the partial reflection coating 2a selectively reflects a specific wavelength λ1, this wavelength may be set to the same wavelength λ1, but the partial reflection coating 2a reflects a wide range of wavelengths. In this case, any wavelength may be used as long as it is in a narrow wavelength range.
The drive circuit 13 causes the light emitting element 12 to emit light in pulses. Further, the optical coupling element 14 couples the light emitting element 12 and the light receiving element 4 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 through the optical fiber 3, and simultaneously receive the reflected light and transmitted light and measure the amount of light received by the light receiving element 4. can do.
[0014]
The sampling circuit 15 acquires a light reception signal from the light receiving element 4 in synchronization with ON / OFF of the light emitting element 12. Further, the arithmetic circuit 16 compensates for transmission loss from the voltage signals S1, S2 from the light receiving circuit at each ON / OFF timing of the light emitting element 12.
[0015]
FIG. 2 is a principle diagram of the present invention. In (A), if the transmittance of the partial reflection coating 2a is Tr2 with respect to the light amount S0 of the radiated light from the high temperature object 1, the light amount of the radiated light input to the optical fiber 3 is Tr2 × S0. Further, assuming that the transmittance of the optical fiber 3 is Tr, the light quantity S2 measured by the light receiving element 4 is Tr2 * S0 * Tr, and S0 = S2 / (Tr2 * Tr). . (Equation 1) holds. That is, since the transmittance Tr2 of the partial reflection coating 2a is known from the measurement at the time of manufacture, if the transmittance Tr of the optical fiber 3 is known, the amount of emitted light S0 can be calculated and the transmission loss can be compensated. Recognize.
[0016]
In FIG. 2 (B), the above-mentioned radiation thermometer (light emitting element 12, drive circuit 13, optical coupling element 14) guides the pulsed light of a predetermined light amount P having a wavelength reflected by the partial reflection coating 2a to the condenser lens 2. Then, the light quantity P × Tr multiplied by the transmittance Tr of the optical fiber 3 is incident on the partial reflection coating 2a. If the reflectance of the partial reflection coating 2a is Fr, the light quantity P × Tr × Fr is reflected. P × Tr ² × Fr = ΔS. Multiplied by the transmittance Tr of the optical fiber 3. . The light quantity of (Expression 2) is added to the transmitted light quantity S2 of (A), and is measured by the light receiving element 4 as the light quantity S1. Therefore, S2 + .DELTA.S = S1. . The relationship of (Formula 3) is established. Here, since S2, S1, and P are known or measurable, and the reflectance Fr of the partially reflective coating 2a is also known from the measurement at the time of manufacture, the transmittance Tr of the optical fiber 3 is actually measured from Equation 2. Can do.
[0017]
By using FIG. 2 and (Equation 1) to (Equation 3) described above, the pulsed light of the predetermined light quantity P is incident on the optical fiber so as to be guided to the condenser lens 2, and the change S1 in the amount of received light due to the presence or absence of the pulsed light. , S2 can compensate for transmission loss. That is, the light emitting element 12, the drive circuit 13, and the optical coupling element 14 guide the pulsed light having a predetermined light quantity P having a wavelength reflected by the coating when the radiation thermometer is used to the back surface of the condenser lens 2 through the optical fiber. The coupling element 14, the sampling circuit 15, the light receiving element 4 and the light receiving circuit 5 add and measure the reflected light from the back surface of the lens to the transmitted light amount S2 of the condenser lens, and change in the received light amount S1, S2 depending on the presence or absence of pulsed light. From the calculation circuit 16, the transmission loss ΔS for the round trip of the pulsed light can be calculated (Equation 3). From this, the optical fiber transmittance Tr can be calculated (Equation 2), and the transmission loss can be compensated (Equation 1). This can be displayed on a CRT or the like by the output device 7 or output to another control device or the like.
[0018]
FIG. 3 is a relationship diagram between the input wavelength and the intensity (light quantity) in the radiation thermometer of the present invention. In this figure, (A) is a coating in which the partial reflection coating 2a selectively reflects a specific wavelength λ1, and the light emitting subelement 12 emits light of a predetermined light quantity P of wavelength λ1. .
In this case, the light quantity S0 of the radiated light from the high-temperature object 1 is normally distributed over a wide range from, for example, a wavelength of 750 nm to 1550 nm, but the light having a specific wavelength λ1 (for example, around 1300 nm) is reflected by the coating 2a. Loss. However, since the loss region due to the coating 2a is very narrow compared to the entire wavelength region, there is almost no influence on the radiation thermometer, and since there is little loss in the entire wavelength region, highly accurate temperature measurement can be performed. In addition, since the coating 2a affects only the specific wavelength λ1, the coating 2a is used when other wavelengths (for example, λ2) are used for other purposes or when particularly high accuracy is required in a wavelength portion other than the wavelength λ1. Can be reduced to a level where there is little or almost no influence.
[0019]
FIG. 3B shows a case where the partial reflection coating 2a is a coating that uniformly reflects a wide range of wavelengths, and the light-emitting subelement 12 emits light of a predetermined light quantity P having a wavelength λ1.
In this case, the light amount S0 of the radiated light from the high-temperature object 1 is lost due to reflection of light in a wide range of wavelengths (for example, wavelengths from 750 nm to 1550 nm) by the coating 2a. However, if the reflectance (transmittance Tr) of the coating 2a is measured in advance, the temperature can be similarly measured by the method described above.
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 (100%). However, in an actual apparatus, the conversion gain η is known and included. The formula should be applied.
[0020]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. For example, the present invention can be applied to the measurement of the surface temperature of a general high-temperature object in addition to the gas turbine blade.
[0021]
【The invention's effect】
As described above, the radiation thermometer having the transmission loss compensation function and the temperature measurement method of the present invention have excellent effects such as being able to compensate for transmission loss due to deposits on the lens surface.
[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 relationship diagram between an input wavelength and intensity (light quantity) in the radiation thermometer of the present invention.
FIG. 4 is a schematic view of a conventional radiation thermometer using an optical fiber.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 High temperature object 2 Condensing lens 2a Partial reflection coating 3 Optical fiber 4 Light receiving element 5 Light receiving circuit 6 Arithmetic circuit 7 Output device 10 Photoelectric conversion device 12 Light emitting element 13 Drive circuit 14 Optical coupling element 15 Sampling circuit 16 Arithmetic circuit

Claims (2)

A condensing lens (2) for condensing the radiated light from the high-temperature object (1), an optical fiber (3) for transmitting the collected light, and a transmitted light amount. And a photoelectric conversion device (10) for converting the temperature into an electric signal and calculating the temperature T of the high-temperature object therefrom,
The photoelectric conversion device includes a light receiving element (4) that converts transmitted light into a current signal, a light receiving circuit (5) that converts the current signal into a voltage signal, and a predetermined light amount P having a wavelength reflected by the partial reflection coating. A light emitting element (12) that emits light, a drive circuit (13) that emits the light emitting element in pulses, an optical coupling element (14) that couples the light emitting element and the light receiving element to an optical fiber, and ON of the light emitting element A sampling circuit (15) that acquires a light reception signal in synchronization with / OFF, and an arithmetic circuit (16) that compensates for transmission loss from the voltage signals S1 and S2 from the light reception circuit at each timing ,
The partially reflective coating is a coating that selectively reflects a specific wavelength λ1, and the light of the light emitting element (12) is pulsed light having a wavelength λ1.
The radiation thermometer having a transmission loss compensation function, wherein the partial reflection coating reflects only light having the wavelength λ1 among radiation emitted from the high temperature object (1) . A condensing lens (2) is provided in the vicinity of the high temperature object (1), and the light condensed by the condensing lens is guided to the light receiving element (4) through the optical fiber (3). In the temperature measurement method for calculating the temperature T of
A partial reflection coating is applied to the back surface of the condensing lens, and pulsed light of a predetermined light amount P having a wavelength reflected by the partial reflection coating is incident on the optical fiber so as to be guided to the condensing lens (2). Compensate for transmission loss from the amount change S1, S2 ,
The partially reflective coating is a coating that selectively reflects a specific wavelength λ1, and the pulsed light is pulsed light having a wavelength λ1.
The temperature measurement method according to claim 1, wherein the partial reflection coating reflects only the light having the wavelength λ1 in the radiated light from the high temperature object (1) .

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