JPS58139038A - Temperature measuring device using optical fiber - Google Patents

Abstract

PURPOSE:To provide a high-precise photo thermometer, by a method wherein light transmitting a photo temperature sensor is separated into an output, corresponding to a wavelength having transmissivity depending on temperature, and an output, corresponding to a wavelength having transmissivity not depending on temperature, by means of an optical BPE to find a ratio between the two electric output signals. CONSTITUTION:Light from a light source 1 using a luminous diode enters a photo temperature sensor 3 through an optical fiber 2. Light passing through the sensor 3 is connected to bundle fibers 7 and 7', which are branched into two parts, through an optical fiber 4 by a photo connector 6, and is further joined, in order, to optical BPF8, 8' corresponding to wavelengths lambda1 and lambda2, photoelectric converters 5, 5', and amplifiers 9, 9', and the outputs of the amplifiers 9, 9' are inputted to a divider 10. The BPF8 is a BPF centering around a wavelength lambda1 having transmissivity, depending on temperature, of a light transmitting the sensor 3, and the BPF8' is a BPF which has a wavelength lambda2 having transmissivity hardly depending on temperature. This permits temperature of a spot where the sensor 3 is located to be high-precisely measured by means of the output of the divider 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature measuring device using an optical fiber, and more specifically, to a temperature measuring device using an optical temperature sensor and an optical fiber serving as a signal transmission path.

Conventionally, there has been a device of this type as shown in FIG.

In other words, the light from the light source passes through the optical fiber
The light is applied to an optical temperature sensor 3 made of a semiconductor crystal or an amorphous material such as Aa, and the light that has passed through the optical temperature sensor 3 is inputted to a photoelectric conversion device j via an optical fiber. The light transmittance of the optical temperature sensor J changes depending on the wavelength of the light and changes depending on the temperature. Figure 2 shows an example of the relationship between the wavelength dependence of such an optical temperature sensor and the temperature. The wavelength λ is plotted on the axis, the transmittance is plotted on the vertical axis, and temperature [Tt] is used as a parameter. From this figure, the wavelength λ
It can be seen that the transmittance changes with changes in temperature T1 at 1, λ, and λJ. Now, the wavelength of light from light source l is λJ&
If C is selected, the light transmittance in the edge light temperature sensor 3 changes within the range where the temperature changes from T/ to TJ. If the intensity of the light entering the optical fiber JK from the light source is known, the light transmittance at the optical temperature sensor JK can be calculated by measuring the intensity of the light entering the photoelectric conversion device JK, thus , the temperature of the optical temperature sensor J can be known.

However, in the case of conventional devices such as those mentioned above.

Optical fiber, optical temperature sensor 3. The mutual coupling efficiency of optical fibers changes, or the optical fibers.

When the amount of light incident on the photoelectric conversion device S changes due to a change in transmission loss due to the bending of the sensor, it is impossible to distinguish between that change and the change in the amount of incident light due to a temperature change of the optical temperature sensor J, making it impossible to obtain an accurate measurement value. The disadvantage was that it was not possible to do so.

This invention was made in order to eliminate one or more of the drawbacks of the conventional devices, and provides a temperature needle side device using an optical fiber that eliminates measurement errors caused by changes in coupling efficiency between optical members constituting the device. The purpose is to provide

It is also an object of the present invention to provide a type of optical fiber with different wavelength passbands on the output end face of the optical fiber on the receiving side.
``It is proposed to provide a temperature measuring device using an optical fiber, which includes band-pass filters and processes light incident on a photoelectric conversion device from one of the filters as a signal light and the other as a reference light.

When the light passes through the temperature sensor, the output voltage corresponding to the first wavelength λ/ whose transmittance depends on −gK and the transmittance at temperature Kfi and The present invention is characterized by means for determining the ratio between the output voltage and the output voltage corresponding to the independent wavelength λ.

This invention will be explained in detail below using one drawing.

FIG. 3 shows an embodiment of the present invention, in which a light source using a light emitting diode, an optical fiber made of a single core or a bundle fiber, and a light temperature of a semiconductor crystal or an amorphous material such as ()aAs are shown. Sensor J etc. are the same as those in FIG. The output end of the optical fiber tube is connected to a co-branched bundle fiber optic 7' via an optical connector 4, and further connected to optical bandpass filters t and t' corresponding to wavelengths λl and λJK, and photoelectric conversion devices 3 and 3'.
, amplifiers D and t' are connected in sequence, and amplifiers 9 .
The output of 9' is connected to a divider 10K.

Next, the operation will be explained, but before that, the characteristics of the main parts will be explained with reference to FIG. Figure (a) shows the spectrum when a light emitting diode is used as the light source, while Figure (b) shows the temperature dependence of the light absorption characteristics of the optical temperature sensor 3 made of semiconductor crystal. Figure (C) illustrates the relationship between the pass wavelength bands of the optical band pass filters z and t'.

In Figure 3, the spectrum of light from the light source l inserted into the optical fiber is as shown in Figure (a) K.
It is assumed that the wavelengths λl and λ- are included. The light inserted into the optical fiber is guided to the optical temperature sensor 3, and a case where a semiconductor crystal is used as the optical temperature sensor J will be explained. The semiconductor crystal is shown in Figure (b).
KAs shown, the optical fundamental absorption edge wavelength λg ('r)
The amount of absorption increases rapidly for light with a wavelength shorter than 2g(T). Also, generally 2g(T)
shifts to longer wavelengths as the temperature rises. Therefore, when light with a constant intensity in the spectrum including 2g(T) is incident on the optical temperature sensor 3, the transmitted light intensity decreases as the temperature rises. The light transmitted through the optical temperature sensor J is guided to a light receiving section by an optical fiber, and branched to a bundle fiber back 7' via an optical connector 6.

Furthermore, the signals K are converted into electrical signals by photoelectric conversion devices 3 and 3' through optical bandpass filters t and t', respectively.

The optical band-pass filter t is a band-pass filter whose transmittance of light passing through the optical temperature sensor J is centered at the first wavelength λl, which is temperature-dependent, as shown in FIG. The optical band-pass filter l' is a band-pass filter whose transmittance is centered at the th wavelength λ whose transmittance hardly depends on the temperature Kn. Therefore.

The electrical output signal of the photoelectric conversion device 3 corresponding to the wavelength λ/ changes according to the temperature of the optical temperature sensor J.

□　2　J　　　　　　　　　　　j　f, □□竺-1゜1-ka.

The number changes little with temperature. On the other hand, optical coupling losses in the optical connector 6 and optical temperature sensor 3, losses due to bending of optical fibers, fluctuations in output power from light source 1, etc. act in almost the same way on light of wavelengths λl and λ. Therefore, photoelectric conversion device S.

4 for each electrical output signal of j'. It will come to you in the same way. Therefore, the photoelectric conversion device S, ? If the electrical output signals of are amplified by the amplifiers t and t', respectively, and then divided by the divider 10, the temperature at the location where the optical temperature sensor 3 is placed can be accurately measured.

In the above embodiment, a light emitting diode was used as the light source, but other light sources such as a norogen lamp or a tungsten lamp may be used.

Further, in one or more embodiments, a semiconductor crystal is used as the optical temperature sensor, but other materials such as an amorphous body or chalcogen glass may be used.

Furthermore, in the above example, from the light temperature sensor 1
Although we have shown a configuration in which the transmitted light is guided to an optical connector using an optical fiber and the output light is co-branched using a bundle fiber, it is also possible to use an optical splitter using a beam splitter, an optical demultiplexer, etc. . When an optical demultiplexer is used, a configuration that does not require the optical bandpass filter in the above embodiments can be achieved. As shown in Fig. 3, the light from the optical fiber 13 is demultiplexed into wavelengths λl and λ by the wave splitter//, and the light with the wavelength λl passes through the optical fiber 13 to the photoelectric conversion device jK. The light of λ is input to the photoelectric conversion device 3' through the optical fiber /j' and converted into an electric signal.

In addition, in any one of the first or more embodiments, a two-wavelength blade structure was described in which the transmitted light from the optical temperature sensor is co-branched in order to improve measurement accuracy. Wavelength λノ.

The wavelength λ/
It is possible to separate the electrical signal corresponding to the wavelength λJK from the electrical signal corresponding to the wavelength λJK. This has a configuration as shown in Fig. 6, and includes a drive circuit that mechanically displaces and replaces the optical bandpass filters S and t', and a pulse generation circuit/3.
．． The sample and hold circuit / $ and / 4" are connected in sequence, and the sample and hold circuit / $ and / l' are connected in sequence.
is inserted between the amplifier t and the divider 70, and the drive circuit/JK
In synchronization, electric signals corresponding to wavelengths λ and λJK are separated and divided by a divider by 5 io.

As described above, this invention has a simple configuration.

Highly accurate temperature measurement is possible by eliminating measurement errors due to changes in the characteristics of optical members.

[Brief explanation of drawings]

Fig. 7 is a block diagram of a conventional device, Fig. 2 is a characteristic diagram of a light temperature sensor, and Fig. 3 is a block diagram of an embodiment of the present invention. (C) is a spectral diagram of the light source, a characteristic diagram of the optical temperature sensor, and a characteristic diagram of the optical bandpass filter, respectively, and FIGS. J and 6 are configuration diagrams of other embodiments, respectively. l・・light source, ko, 41, / j, / &'・
・Optical fiber, 3... Optical temperature sensor, ! , j'・
- Photoelectric conversion device, 6... Optical connector, Ri, Ri'... Bundle fiber, t, t'... Optical bandpass filter,! , Te'... amplifier, io... divider, l/... optical demultiplexer. /Co...Drive circuit, 13...Pulse generator, /#. / II'...Sample hold circuit. In each figure, the same reference numerals indicate the same or corresponding parts. Agent Makoto Kuzuno - ・１・ 1 illustration 3 illustrations Homura 4 illustrations 5 illustrations party 6 illustrations

Claims (1)

[Claims] <i) A light temperature sensor that receives light from a light source through an optical fiber, and a light receiving section that receives the light that has passed through the light temperature sensor through the optical fiber. In the temperature measuring device, the light received by the light receiving section is
[Means for separating the sensor into a seventh wavelength λl band whose transmittance depends on temperature and a seventh wavelength λband whose transmittance does not depend on temperature Kfi; 1. A temperature measuring device using an optical fiber, comprising means for determining a ratio of electrical output signals. (g) The wavelength λ is placed at the output end of l pairs of bundle fibers that split the light transmitted through the optical temperature sensor into two.
Claim 1 comprising: optical bandpass filters that each pass a band of λ1; photoelectric conversion devices respectively coupled to these optical bandpass filters; and a divider for calculating the ratio of the outputs of these photoelectric conversion devices. A temperature measuring device using an optical fiber according to item 1. (3) An optical demultiplexer that separates the light transmitted through the optical temperature sensor into wavelength bands of λ and λ, and a pair of photoelectric conversions coupled to the optical output of the optical demultiplexer via an optical fiber. 2. A temperature measuring device using an optical fiber according to claim 1, comprising a divider for determining the ratio of the electrical output signals of these photoelectric conversion devices. (4I) A school band pass filter that is movably arranged between the output end of the optical fiber that guides the light that has passed through the optical temperature sensor and the single charging conversion device and that passes the light with wavelengths λl and λ, respectively; A driving means for replacing and driving the optical bandpass filter, and synchronizing with this driving means, the wavelengths λl, λ1
2. A temperature measuring device using an optical fiber according to claim 1, comprising: means for separating electrical output signals corresponding to the light; and means for determining a ratio of the separated electrical output signals.