JPS599526A - Temperature measuring device - Google Patents

Abstract

PURPOSE:To measure temperatures, by using two light beams having different wavelength, making both light beams pass the same light transmitting path, varying only the intensity of the light beam with one wavelength in response to a tempeature by a tempeature sensor, and comparing the ratio of the intensities of the split light beams and the quotients before the light beams are inputted to the temperature sensor. CONSTITUTION:Parts of light beams having wavelengths of lambda1 and lambda2 are split by a light splitter 54. One group of light beams is inputted to a light source monitoring light receiving element 60 through an optical fiber 56, and the light beams are transduced into electric signals by a signal processing part 61. The other group of the light beams is inputted to a light receiving element 59 through a temperature sensor 57 and an optical fiber 58, and the light beams are transduced into electric signals by the signal processor 61. The electric signals corresponding to the light beams of lambda1 and lambda2 which are received by the light receiving element 59 are made to be V1lambda1 and V1lambda2. The electric signals received by the light receiving elements 60 are made to be V2lambda1 and V2lambda2. Said electric signals are amplified by an amplifier 62, and the division operations of the signals are alternately performed by a divider 45. The results of both divisions are held by a sample and hold amplifiers 44 and 44'. The division operations are performed by a second divider 45' again. The result is amplified by an amplifier 63 and inputted to a display part 64, and the temperature can be displayed. Thus the functuation in the characteristics of the light transmitting path of an optical temperature sensor can be compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature measuring device in which an optical signal emitted from a sensor at a light temperature is transmitted via an optical fiber or the like.

When transmitting an analog quantity from an optical temperature sensor via an optical transmission line, the transmission characteristics of the optical transmission line fluctuate due to temperature changes and bending stress, making accurate temperature measurement difficult, so compensate for this fluctuation. However, it is necessary to improve measurement accuracy.

Figure 1 shows an example of a temperature measuring device that compensates for such transmission characteristic fluctuations. 1 Light emitted from a light source 1 using a halogen lamp, for example, becomes a parallel beam at a lens 2, and then passes through a filter 3 and a dichroic composite mirror. At 4,5°6, the visible light is removed, and only the ultraviolet light is focused by the lens 7 onto the end face core of the optical fiber 8, and the visible light with the spectrum indicated by the emission wavelength on the right side of . ,,! Emits light rays. This visible light passes through the optical fiber 8 again and is divided into parts by the beam splitter 10;
1, the interference filters 12 and 13 take out only the visible light rays with emission wavelengths a and c shown in FIG.
．． 15 to a photodetector 16.17. The optical signal is converted into an electric signal by the photodetector 16, and then A/D converted by the A/D converter multiplexer 20 via the preamplifiers 18 and 19. (2) a: light intensity of wavelength a) is calculated and input to the microcomputer 21; Read-only memo IJ
The relationship between the temperature and the relative intensity I c / I a of the radiation wavelength shown in ) in Fig. 2 is written in the (ROM) 22, which is converted into temperature information by the microcomputer and then converted into D/A conversion. The image is displayed via the device 24. Here, the relative intensities I c /I a of wavelengths a and C are taken.
The second light passes through the optical connector 39 and reaches the temperature detection section 40 . The detection unit 40 includes a semiconductor device such as Ga, As, CdTe, etc., and light passes through this semiconductor.
The light passes through an optical fiber and an optical connector 41, enters a photodetector 42, and is converted into an electrical signal. After passing through the light receiving circuit 43 and amplifying it in the sample-and-hold amplifier 44, the λ1. Light intensity of λ,■λ3. ■Ratio of λ2■λ+
/Iλ, is determined. Here, semiconductors such as GaAs and CdTe have temperature dependence in the wavelength range in which they absorb light. As shown by curve P in Figure 4 (6), the wavelength of the absorption edge of a semiconductor changes depending on the temperature.
For example, when light emitting diode light of a suitable wavelength shown by curve Q is used, the light intensity of the light emitting diode passing through the semiconductor has temperature dependence as shown in FIG. 4(c). Therefore, the compensation method used in these devices, however, is not applicable to temperature measuring devices using optical temperature sensors based on other principles. The compensation method in the device shown in FIG. 1 is applicable only to optical temperature sensors that utilize temperature changes in the emission spectrum of fluorescent substances, and the compensation method in the device shown in FIG. It is applicable only to optical temperature sensors based on the principle of using wavelengths whose intensity is temperature-dependent and wavelengths whose intensity is not temperature-dependent. However, in an optical temperature sensor using the principle of natural birefringence or multiwave interference, such a = 5- compensation method cannot be applied because there is no wavelength range in which the intensity of transmitted light does not have temperature dependence.

The present invention is intended to eliminate the above-mentioned drawbacks, and aims to provide a temperature measurement device that can compensate for fluctuations in optical transmission path characteristics even when an optical temperature sensor based on another principle is used. .

This is achieved by comprising means for calculating the temperature by comparing the change in the intensity of light of one wavelength depending on the temperature.

Embodiments of the present invention will be described below with reference to the drawings. In each figure, parts common to the previously cited figures are given the same reference numerals. In FIG. 5, different wavelengths λ1. λ
, the light emitting elements 33 and 34 are caused to emit light by the drive section 32. An example of the light emitting element driving section 32 is shown in FIG. The pulse generator 31 generates a pulse -6=, and the pulse is directly applied to one light emitting element drive circuit 51, but the other light emitting element drive circuit 52 is
A pulse is applied after passing through the inverter 53. As a result, the circuit 51 for driving the light emitting element 33 and the circuit 52 for driving the light emitting element 34 are operated alternately to cause each light emitting element 33 and 34 to emit light alternately.

The light emitted from the light emitting elements 33, 34 is transmitted to the optical fiber 35.
36 and enters into one optical fiber 38 at an optical multiplexer 37. Next, in the optical splitter 54, the 1.41ii of the λ1 and λ2 lights enters the optical fiber 58 different from the optical fiber 55, and the light receiving element 5
9 and is converted into an electrical signal by the signal processing section 61. FIG. 7 shows an example of a signal processing section. Light receiving element 59
received at λ1. The electric signal for the light of λ2 is
, λ1. (2), λ, and λ1. which is received by the light receiving element 60 for the light source element UT. The electric signal for the light of λ is v2λ, respectively.
1. ■, λ2. The electrical signal is amplified by an amplifier 62 and then input to a divider 45 .

Divisions of V1λ1/■, λ and ■, λ1α, λ are performed alternately.

This is because the lights of λ1 and λ2 are alternately incident on the light receiving element 59 and the light receiving element 60 for monitoring the light source.

The results of both divisions are held in sample-and-hold amplifiers 44 and 44', and the results of both divisions are input again to the second divider 45'. Holding of the division result is performed by a signal from the light emitting element driving section 32. As a result, (V+λUα, λ
+)/(Vtλv%λ2) is output from the divider 45'. This output is amplified by an amplifier 63.

/l'tN= light is reflected by the filter 66. That is, the filter 66 has a characteristic of transmitting light of λ and reflecting light of λ2. The light of λ incident on the transparent solid 67 (having an optically parallel plane) causes multiwave interference, and a part of the incident light becomes reflected light and the transparent solid 67
I'm going to emit it. The intensity of this emitted light changes depending on the temperature of the optical parallel plane solid 67. The reflected lights λ and λ2 have their optical paths bent by the beam splitter 10, pass through the mirror 11 and the lens 65, and then pass through the detection end 57.
It enters into a different optical fiber 58 than when it entered.

FIG. 9 is an example of an optical temperature sensor based on the principle of natural birefringence. In FIG. 9, the parallel beam emitted from the lens 65 passes through a polarizing beam splitter 68, becomes linearly polarized light, passes through a wavelength plate 69, and is given a phase difference. It is reflected by the reflective film 71, travels again through the optically anisotropic crystal 70 in the opposite direction to the incident light, and is further given a phase difference within the optically anisotropic crystal.

Extract the vibration component (S component) of the light in the direction, Mira 11,
The light passes through the lens 65 and enters the optical fiber 58 different from the one that entered the detection end 57 . At this time.

The retardation provided by the wave plate 69 has almost no temperature dependence, but the retardation provided by the optically anisotropic crystal 7o has temperature dependence. However, the phase difference given to the light of λ1 has a temperature dependence, but the S component of λ2 has almost no temperature dependence.

By adopting the above configuration, output fluctuation of one light emitting element,
Measurement errors due to variations in optical loss characteristics of optical fibers can be compensated for. The reason for this will be explained below. In FIG. 5, the intensity of the light of λ1 emitted from the light emitting element 33 is 1λ1. With the light receiving element 59, the bar 35.
Optical multiplexer 37, optical fiber 38. The optical loss at the optical branch -i-, M(T), represents the temperature dependence of the optical intensity at the temperature sensor 57. Bλ1. Dλl and Iλ1 each have time dependence. On the other hand, if the intensity of the light λ received by the light-receiving element 60 for monitoring the light source is 2λ, 2, λ1 is given by 2λ,=Cλ, i) λ11λ1 (2). Here, C20 is the optical loss from outputting the optical splitter 54 to passing through the optical fiber 56 and entering the light receiving element 60 for monitoring the light source.

Similarly, the intensity of the light of wavelength λ2 emitted from the light emitting element 34 is determined as ■λ2. Light receiving element 59. Light receiving element 60 for light source monitor
The intensity of the light of λ received at is 11λ, respectively.

If I-I, ■1λ, = 13λ2Dλ, ■λ2(3) I2λ2=Cλ
, I) λ, ■λ2 (4) is given. Here, Bλ
1+Cλ2. As in the case of λ, Dλ is the loss of the optical transmission path for the light of λt. The right side of equation (6) is
The temperature dependence of the temperature detection end is detected, and light source fluctuations,
Loss fluctuations in the optical transmission line are eliminated. From this,
It can be seen that by adopting this configuration, accurate temperature measurement is possible regardless of variations in the light source and variations in loss in the optical transmission line.

Next, a modification of FIG. 5 will be described. FIG. 10 shows an example in which light of λ2 and light of λ2 are emitted alternately, but at the same time. The difference from FIG. 5 is that the light is transmitted to the light receiving element 59. Before entering the light receiving element 60 for monitoring the light source, the light of λ1 and λ2 are separated by an optical demultiplexer 72, and different light receiving elements 59, 59' for λ1 and λ2, and the light receiving element 60 for monitoring the light source are separated.
, 60' is the point where light is incident.

Although the configuration is such that the three lights emit light at the same time, the light is transmitted to the optical multiplexer 54.
In this method, the optical branching device 54 branches the light before the light enters the light receiving element 60, 60' for monitoring the light source. do not need. FIG. 13 shows a system in which the lights λ and λ are emitted alternately, but the configuration is such that the light entering the detection end 57 and the light exiting the detection end 57 are transmitted through the same optical fiber. The light emitted from the light emitting elements 33 and 34 is transmitted through the optical fiber 35.
, 36 , passes through the optical multiplexer 37 and the optical fiber 38 and enters the optical directional coupler 74 .

Here, a part of the light is branched, and the branched light passes through the optical fiber 56 and enters the light source monitoring light receiving element 6o. The other light emitted from the optical directional coupler 74 passes through the optical fiber 55, enters the temperature detection end 57, is reflected inside, enters the input light 7 eyeper 55 again, and changes the optical directionality. It reaches combiner 7+. Here, the light is transmitted from 14- to 15- to light-receiving element 6o for light source monitoring. It is shown in FIG. Fig. 15 uses the principle of natural birefringence, and Fig. 16 uses the principle of multiwave interference. In both figures, the light of λ is reflected by the filter 66 and returns without entering the optically anisotropic crystal 70 or the transparent solid 67 having optically parallel planes, but the light of λ1 passes through the filter 66 and is anisotropic. crystal 70 or transparent solid 67
The light enters and is reflected by the end face of the reflective film 71 or the transparent solid body 67 and returns.

As described above, the present invention uses two lights of different wavelengths, passes them through the same optical transmission path, changes only the intensity of the light of one wavelength at the temperature sensor depending on the temperature, and then inputs the light into the temperature sensor. The temperature is measured by calculating the ratio of the intensity of the light of each wavelength that has been split before splitting, and then comparing the quotients. Figure 1 shows a system diagram of an example of a temperature measuring device using a conventional optical temperature sensor, and Figure 2 (c) shows the temperature-dependent intensity for only one of the wavelengths based on the principle of A spectral diagram of excitation ultraviolet rays and synchrotron radiation showing the characteristics of the fluorescent substance used; Fig. 2 (c) is a diagram of the relationship between the light intensity of wavelengths a and c of synchrotron radiation and their ratio and temperature; Fig. 3 The figure is a systematic diagram of another conventional example, Figure 4 (g) is the temperature dependence of the absorption edge characteristics of the semiconductor used in it, and Figure 4 (b) is the dependence of the light intensity of light passing through the semiconductor based on it. FIG. 5 is a block diagram of an embodiment of the temperature measuring device according to the present invention, FIG. 6 is a system diagram of its light emitting element driving section, and FIG. 7 is a system diagram of its signal processing section. Fig. 8 is a system diagram showing one embodiment of the optical temperature sensor, Fig. 9 is a system diagram showing another embodiment, Fig. 10 is a system diagram showing another embodiment of the temperature measuring device, and Fig. 11. is a system diagram of a part of the signal processing 16 in the modified example, and FIGS. 12 to 14 are system diagrams of further different embodiments of the temperature measuring device, respectively. 1. ”
FIG. 6 is a reading diagram showing two embodiments of the optical temperature sensor used in the apparatus shown in FIGS. 13 and 14, respectively.

Part 64 Display part 67 Transparent solid having optically parallel planes 70 Optically anisotropic crystal 74
...Optical directional coupler.

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Claims (1)

[Claims] 1) A light emitting source that emits two lights of different wavelengths, a splitter that separates the lights into two parts, and a splitter that separates the lights into two parts, and the light of one part is guided to produce the intensity of the light of one wavelength. An optical temperature sensor that changes only the temperature depending on the temperature, and calculates the ratio of the intensity of one part of the light passing through the optical temperature sensor to the light intensity of the other part,
The temperature measuring device further comprises a step for calculating the temperature by comparing the ratio of the light beams of both wavelengths. ) The temperature measuring device according to claim 1, wherein the temperature sensor utilizes the temperature dependence of natural birefringence. 3i) A temperature measuring device according to claim 1, characterized in that the optical temperature sensor utilizes the temperature dependence of multiwave interference.