JPS58132637A - Pressure measuring device employing optical fiber - Google Patents

Abstract

PURPOSE:To prevent the loss of an optical fiber and connector from entering as an error and to enable to perform a high-precise measurement, by a method wherein a pressure gauge employs a photo pressure sensor, which has transmissivity and reflecting rate changing with a pressure and a wavelength dependency, and consists of a two-wavelength system. CONSTITUTION:An emitting light having wavelengths lambda1 and lambda2 are combined together by a photo composing device 12, and is introduced to a photo pressure sensor 4 through an optical fiber 15 for entering. The sensor 4 converts an incident light into a parallel light by means of a micro lens 21, and after the light passes through a dichroic mirror 20 attached to a diaphragm 5, it is combined with an optical fiber 16 by a micro lens 22 to lead it to a photo electric converter 6. The electric signal of the converter 6 is converted into a DC signal by sample holding amplifiers 17 and 18 synchronizing with driver circuits 8 and 9, and is divided by a divider 19. The division removes an error produced due to a transmission loss and a connector loss, which results in being capable of performing a precise measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure measuring device using an optical fiber that takes advantage of the fact that the transmittance or reflectance of light changes with pressure.

Conventionally, there has been a device for this purpose as shown in FIG.

In FIG. 1, 1 is a light source, 2 and 3 are bundle fibers, 4 is an optical pressure sensor, 5 is a diaphragm, 6 is a photoelectric conversion device, and 7 is a pressure.

Next, the operation will be explained. The output light from light source 1 is 2
The light is inserted into one of the branched fiber bundles 2, guided to the optical pressure sensor 4, and irradiated onto the diaphragm 5. The reflected light from the diaphragm 5 is received by the other bundle fiber 3 which is split into two. When a pressure T is applied to the optical pressure sensor 4 from the outside, the position of the diaphragm 5 changes depending on the magnitude of the pressure, and as a result, the amount of light received by the bundle fiber 3 changes. The reflected light received by the optical fiber 3 is guided to a photoelectric conversion device 6 and converted into an electrical signal. By measuring the magnitude of this electrical signal, the pressure cuff can be determined from K.

Conventional pressure measurement devices using optical fibers are configured as described above, so if the transmission loss of the optical fiber changes or the coupling efficiency of the optical connector changes, the output electrical signal changes and the pressure increases. This has the disadvantage that it cannot be distinguished from those caused by fluctuations, resulting in large measurement errors.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and uses an optical pressure sensor whose light transmittance or reflectance changes depending on pressure and has wavelength dependence. It is an object of the present invention to provide a pressure measurement device using an optical fiber that measures pressure with high precision by signal processing an electrical output signal for light having a wavelength longer than that. Hereinafter, this invention will be explained with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention. Second
In the figure, the same reference numerals as in FIG. 1 indicate the same components,
8 and 9 are driving circuits for light sources, 10 is a light source that emits light with a wavelength λ1, 11 is a light source that emits light with a wavelength λ, 12 is an optical multiplexer, 13 and 14 are optical fibers, and 15 and 16 are input lights, respectively. An optical fiber for output, 17 and 18 a sample and hold amplifier, and 19 a divider. Note that the optical system is shown as a double line, and the electrical system is shown as a single line.

FIG. 3 shows an example of the configuration of the optical pressure sensor 4, where 5 is a diaphragm, 20 is a diaphragm, 20 is a diaphragm, 20 is a diaphragm through which light with a wavelength λ is transmitted,
21 and 22 are collimating and condensing microlenses, and 23 is a case of the optical pressure sensor 4.

Next, the principle of operation of the above embodiment of the present invention will be explained. In FIG. 2, light emitted from a light source 10 that emits light with a wavelength λ and a light source 11 that emits light with a wavelength λ are respectively inserted into optical fibers 13 and 14 and combined by an optical multiplexer 12. As the light sources 10 and 11, for example, a light emitting diode or a laser diode is used, and these are alternately pulse-driven by drive circuits 8 and 9. These lights are guided to the optical pressure sensor 4 by an optical fiber 15 for incidence.

The optical pressure sensor 4 is configured, for example, as shown in FIG. After passing through the dichroic mirror 20, the light is coupled to the optical phino (16) by the condensing dichroic lens 22 and guided to the photoelectric conversion device 6. When external pressure T is applied to the diaphragm 5,
The diaphragm 5 is displaced, and the dichroic mirror 20 is also displaced accordingly. The dichroic mirror 20 transmits light with wavelength λ and reflects light with wavelength λ, so the transmittance for light with wavelength C does not depend on pressure;
The light transmittance of decreases with increasing pressure. Therefore,
Light with wavelength λ can be used as reference light, and light with wavelength λ can be used as signal light. The electrical signal (pulse) obtained by the photoelectric conversion device 6 is converted into a DC signal by a sample-and-hold amplifier 17.18 synchronized with a drive circuit 1188.9, and divided by a divider 19. Each party fiber 15°160
Changes in transmission loss due to bending and changes in optical funector loss change in the same way for both wavelengths λ and λ, so
These error factors can be removed by the above division, and pressure can be measured with high accuracy. Figure 4 shows the transmission characteristics of the dichroic mirror 20.

This shows an example of reflection characteristics. Curve shown by solid line■
indicates the transmission characteristics, and the dotted curve (■) indicates the reflection characteristics.

FIGS. 5(a) to 5(h) are waveform diagrams for explaining the operation of the embodiment shown in FIG. 2, showing changes in electrical signals and light intensity at various parts. The symbols (a) to (h) in FIG. 5 and the symbols (a) to (h) in FIG. 2 correspond to each other. In FIG. 5, (a) is a pulse waveform of light with wavelength λ1, and (b) is a pulse waveform of light with wavelength λ1.
, (c) is the optical fiber 15 for incidence.
(d) is the pulse waveform of the light propagating inside the optical fiber 16 for output, (e) is the electrical output waveform of the output of the photoelectric conversion device 6, (f), (g) are the electrical signal waveforms of the outputs of the sample-and-hold amplifiers 17 and 18, respectively, and (h) is the output waveform of the divider 19.

In the above embodiment, a light emitting diode or a semiconductor laser is used as the light source 10.11, but a halogen lamp, a tungsten lamp, a gas laser, or the like may also be used. Furthermore, in the above embodiment, there are two types of light sources, namely, the light source 10 that emits light with wavelength λ1 and the light source 10 that emits light with wavelength λ! The case has been described in which the light source 11 that emits light of wavelength λ, is used.

A light source that simultaneously emits λ may also be used. An example of this is shown in FIG.

In FIG. 6, 24 is a halogen lamp, a tungsten lamp, a light emitting diode, etc. with a wavelength of λ1. 25 is an optical demultiplexer; 25 is an optical demultiplexer;
6.27 represents a short optical fiber. In this method, an optical demultiplexer 25 splits light with a wavelength λ1 whose transmitted light intensity does not change with pressure and light with a wavelength λ whose transmitted light intensity depends on pressure, and the light of each wavelength is independently photoelectronized. The pressure is measured by converting and dividing them.

Also, instead of the optical demultiplexer 250, an optical demultiplexer and a wavelength λ1゜λ
, may be used in combination with an optical wavelength bandpass filter. The simplest and cheapest embodiment of this method is shown in Section 7.
As shown in the figure.

In FIG. 7, 28.29 is a bundle fiber branched into two, and 30.31 is a wavelength λ.

represents a wavelength bandpass filter for wavelength λ.

Further, 32 is an optical connector, which operates as a kind of optical distributor.

8(a) to 8(f) are characteristic diagrams and waveform diagrams for explaining the operation of the embodiment of FIG. 7. FIG. 8(a) is a spectrum diagram of the light source 24, and FIG. 8(b) is a wavelength λ1 of the dichroic ink mirror 20 included in the optical pressure sensor 4.
．． The transmission and reflection characteristics with respect to λ are similar to those shown in FIG. Figure 8(C) shows the wavelength bandpass filter 30.3.
1, Figure 8(d).

(e) indicates the wavelength λ1. is the electrical output signal for the light of λ. FIG. 8 <1> represents the voltage after signal processing.

Note that the symbols (d), (e), and (f) in Fig. 8
The symbols (d), (e), and (f) in FIG. 7 correspond to each other.

The arrows in FIG. 8(d) indicate variations in loss due to the optical connector 32, and the arrows B indicate variations in the pressure cuff.

In FIG. 7, the spectral characteristics of the light source 24.

If the intensity is constant, only the electrical signal for light at wavelength λ varies with pressure. If a change in transmission loss occurs due to loss in the optical connector 32 or bending of the optical fiber 15, 16, etc., both lights will fluctuate in the same way. Therefore,
The ratio of the two signals depends only on pressure.

In each of the above embodiments, the dichroic ink mirror 2 is used as the wavelength-dependent optical element used in the optical pressure sensor 4.
The case where 0 is used is shown, but semiconductors, liquid crystals, colors, etc.
An optical element made of glass or the like may also be used.

Furthermore, in each of the above embodiments, a transmission type optical pressure sensor 4 has been described, but a reflection type can also be used as in the embodiments shown in FIGS. 9 and 11. Below, FIGS. 9 and 11 will be explained.

In FIG. 9, optical fiber 15. Micro lens 21
The light of wavelength λ2 that has been guided to the optical pressure sensor 4 via the dichroic mirror 20 is reflected by the dichroic mirror 20, is received by the same optical fiber 15, passes through the beam splinter 33, and is converted into an electrical signal by the photoelectric conversion device 6. Ru. On the other hand, the wavelength λ1
The light passes through the dichroic mirror 20, is reflected by the mirror 34 attached to the diaphragm 5, and is connected to the optical fiber 15. It is converted into an electrical signal by the photoelectric conversion device 6 via the beam splitter 33. Since the position of the mirror 34 changes depending on the external pressure T, the electrical signal for light of wavelength λ1 becomes a function of pressure.

On the other hand, the electrical signal for light with wavelength λ does not depend on pressure. Therefore, the light with the wavelength λ can be used as the signal light, and the light with the wavelength λ can be used as the reference light. Also, if you use this construction method,
As shown in Fig. 1θ, the dichroic mirror 20 and the wavelength λ1
It is also possible to integrate the mirror 34 for the mirror 34 .

Next, an embodiment using bundle fibers will be described with reference to FIG. One bundle fiber 2 branched into two
from wavelength λ1. λ, is sent to the optical pressure sensor 4. The optical pressure sensor 4 includes a dichroic mirror 20 that transmits light with a wavelength λ and reflects light with a wavelength λ, and a diaphragm 5 that is displaced by external pressure. A reflective film 35 is provided on the light incident surface of the diaphragm 5 . The light with a wavelength λ reflected by the dichroic mirror 20 and the light with a wavelength λ1 reflected by the diaphragm 5 are received by the other branched fiber bundle 3 and guided to the optical receiver. In the optical receiving section, for example, as shown in FIG.
<28.29, and a trap is installed at the tip of each branch so that only the wavelength λ can pass through, and the signal for the wavelength C and the signal for the wavelength λ can be extracted independently by the photoelectric conversion device 6. There is. Since the dichroic mirror 20 is configured not to move due to pressure, the signal at wavelength λ depends on pressure, but the signal at wavelength λ does not depend on pressure. Therefore, if these signals are processed, highly accurate pressure measurement can be performed. In addition, in FIG. 11, we have described an example of a configuration using the dichroic mirror 20 and the diaphragm 5, but when pressure is applied to a material such as liquid crystal, its reflection characteristics show wavelength dependence, so it is possible to use a structure similar to that described above. OJ's ability is to provide a two-wavelength pressure measurement device.

As explained in detail above, the present invention uses an optical pressure sensor in which the transmittance or reflectance of light changes depending on pressure and is wavelength dependent, and configures an optical pressure measuring device using a two-wavelength method. Since loss in the optical fiber or optical connector is not introduced as a measurement error, pressure can be measured with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional optical fiber applied pressure measuring device, FIG. 2 is a block diagram showing an embodiment of the present invention,
FIG. 3 is a configuration diagram showing an example of the optical pressure sensor used in the embodiment of FIG. 2, and FIG. 4 is a diagram showing the wavelength λ1 of the dichroic mirror also used in the optical pressure sensor. Transmission 2 for λ
Reflection characteristic diagrams, FIGS. 5(a) to (h) are waveform diagrams of optical pulses or electric pulses at various parts for explaining the operation of the embodiment of FIG. 2, and FIGS. 6 and 7 are diagrams of other parts of the invention. FIGS. 8(a) to 8(f) are characteristic diagrams of main parts for explaining the operation of the embodiment shown in FIG. FIG. 9 is a configuration diagram showing still another embodiment of the present invention, and FIG. 1O is a diagram showing another configuration example of the optical pressure sensor used in the embodiment shown in FIG. 9.
FIG. 11 is a configuration diagram showing still another embodiment of the present invention. In the figure, 2 and 3 are fibers, 4 is an optical pressure sensor, 5 is a diaphragm, 6 is a photoelectric conversion device, 1 is pressure, and 8
．． 9 is a drive circuit, 10.11 is a wavelength λ1. 12 is an optical multiplexer, 13 to 16 are optical fibers,
ILlB is a sample and hold amplifier, 19 is a divider, 2
0 is a dichroic mirror, 21 and 22 are microphone lenses, 23 is a pressure sensor case, and 24 is a wavelength λ8. λ2
25 is an optical demultiplexer 426°2T is a short optical fiber, 28.29 is a bundle fiber, and 30.31 is a wavelength λ1. 32 is an optical connector, 33 is a beam splitter, 34 is a mirror, and 35 is a reflective film. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Makoto Kuzuno - (1 other person) Figure 1 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 b j+

Claims (1)

[Scope of Claims] (1) A light source that generates light of two wavelengths; an optical pressure sensor whose transmission or reflection characteristics with respect to pressure are wavelength-dependent; an optical fiber as a signal transmission path that is incident on the sensor; a photoelectric conversion device that receives transmitted light or reflected light from the optical pressure sensor and converts it into an electrical signal;
1. A pressure measurement device using an optical fiber, comprising a signal processing circuit that processes one of two electrical signals as a signal light and the other as a reference light. (21) A pressure measuring device using an optical fiber according to claim (1), characterized in that two types of light emitters each emitting light of a different wavelength are used as the light source. (3) Light source As claimed in claim 1, the method uses a device that emits light of two wavelengths together and separates the light into the respective wavelengths using a wavelength bandpass filter for both wavelengths in the optical receiving section. (Pressure measurement device using an optical fiber as described in Section 11. (4) An optical pressure sensor is constructed using a dichroic mirror and a diaphragm that transmit light of one wavelength and reflect light of the other wavelength. A pressure measuring device using an optical fiber according to claim (1), characterized in that (5) an optical pressure sensor is constructed using a semiconductor and a diaphragm whose transmittance is wavelength dependent. A pressure measuring device using an optical fiber according to Claim No. A pressure measuring device using an optical fiber according to claim 11. (7) a dichroic mirror that transmits light of one wavelength and reflects light of the other wavelength; A pressure measuring device using an optical fiber according to claim (1), characterized in that it uses an optical pressure sensor composed of a mirror that reflects light and a diaphragm. (8) A light source The output electric signals of the photoelectric conversion device for two wavelengths are converted into DC signals by a sample-and-hold amplifier synchronized with the driving circuit of the light source, and the ratio of the signals for each of the wavelengths is determined by a signal processing circuit. Claim No. 1 characterized in that it seeks (
A pressure measuring device using an optical fiber as described in the above section.