JPS6280529A - Optical system pressure measuring instrument - Google Patents

Abstract

PURPOSE:To measure pressure with high precision and high reliability even when an optical component in sue varies in optical characteristics by making the 1st and the 2nd photodetection fiber bundles different in the quantity of incident light, and receiving individually and converting their projection light beams photoelectrically. CONSTITUTION:Light projected by a light source 8 through a projection fiber 12 is converged by a lens 22 held in a hole 21 for projection, and projected on a pressure receiving diaphragm 2 as a converged, parallel, or diverged light having a small angle of divergence. The light reflected by the pressure receiving diaphragm 2 forms a light spot 25A at a detection terminal 25 as input terminals 23A and 24A of the 1st and the 2nd photodetection fiber bundles 23 and 24. The boundary between the input terminals is positioned at a place crossing the direction (arrow A) of the movement of the light spot 25A formed at the detection terminal 25 with the reflected light by the displacement of the pressure receiving diaphragm 2. Then, projection light beams from photodetection fiber bundles 23 and 24 are received and converted photoelectrically the photodetectors 26 and 27 for measurement such as pin photodiodes, and calculated by a converting circuit 28 according to a specified expression to obtain a ratio, outputting a signal corresponding to differential pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical pressure measuring device that measures pressure or differential pressure using light.

[Conventional technology]

Figures 3 and 4 are from Instrumentation, 1984, Vol. 27,
&4. Pages 29 to 33, shows a conventional pressure measuring device of this type described in "All-optical differential pressure/pressure transmitter using optical fiber". In the figure, reference numeral 1 denotes a sensor body having a chamber with a vertical cross-sectional shape such as a circular or elliptical shape, and 2 denotes a chamber inside the sensor body 1, a first chamber 3A and a second chamber 3B.
It is a flat pressure receiving diaphragm that is separated into two parts and supported by the sensor main body 1, and at least the surface on the second chamber 3B side has a reflective surface to prevent the difference between the first chamber 3A and the second chamber 3B. Deformed by pressure difference. 4 is a first capillary communicating with the first chamber 3A, and 5 is a second capillary communicating with the second chamber 3B.
This is the capillary. 4A and 5A are sealing diaphragms provided at the ends of the first and second capillaries 4.5, respectively, which allow the transparent incompressible liquid to pass through the first and second capillaries.
It is sealed in capillaries 4 and 5 and first and second chambers 3A and 3B.

The first and second capillaries 4 and 5 have a measuring pressure pA introduced through seal diaphragms 4A and 5A, respectively.
This is for guiding pB to the pressure receiving diaphragm 2 via an incompressible fluid. 6 is an optical fiber bundle,
It is held in the sensor main body 1, and the − side surface side, that is, the detection end 6A is arranged to face the center portion of the pressure receiving diaphragm 2 via the second chamber 3B.

As shown in FIG. 4, the detection end 6A includes a light-emitting optical fiber 6B that emits light toward the pressure-receiving diaphragm 2 and a light-receiving optical fiber 6C that receives reflected light from the pressure-receiving diaphragm 2. are arranged alternately in a line. Further, the other end surface side of the optical fiber bundle 6 is separated into a light-emitting optical fiber 6B and a light-receiving optical fiber 6C. 7
1 is a sensor section, which is composed of the above-mentioned components 1 to 6.

8 is a light source using a light emitting element such as a light emitting diode, 9 is a beam splitter that splits the light from the light source 8, and 10 is a monitor light receiver using a light receiving element such as a bin photodiode. splitter 9
This is for monitoring the intensity of the light from the light source 8 by receiving the light reflected by the light source 8. Reference numeral 11 denotes a light emitting circuit having a light source 8 and a monitoring light receiver 10, which changes the voltage applied to the light source 8 according to the amount of light received by the monitoring light receiver 10, and adjusts the intensity of the light emitted from the light source 8. is constant. Reference numeral 12 denotes a light projection fiber, which propagates the light from the light source 8 that has passed through the beam splitter 9, and guides it to the sensor section 7. A light receiving fiber 13 guides the light emitted from the sensor section 7 to a measuring light receiver 14, which will be described later. 14 is a measurement light receiver such as a bin photodiode that receives the light emitted from the light receiving fiber 13 and converts it photoelectrically; 15 is a measurement light receiver that converts the photoelectrically converted signal by the measurement light receiver 14 and sends it to the pressure receiving diaphragm 2; mosquito\
This is a conversion circuit that outputs a pressure-electric conversion signal proportional to the differential pressure value. Note that the output end of the light emitting fiber 12 and the input end of the bundle of light emitting optical fibers 6B and the input end of the light receiving fiber 13 and the output end of the bundle of light receiving optical fibers 6C are optically connected by optical connectors (not shown). has been done. Reference numeral 16 denotes a processing section, which is composed of components shown by reference numerals 8 to 11, 14, and 15.

Tsuge's motion will be explained. The pressure for measurement acts on the pressure receiving diaphragm 2 from the first chamber 3A side, and the pressure for measurement P
B acts on the pressure receiving diaphragm 2 from the second chamber 3B side. The pressure receiving diaphragm 2 deforms in accordance with the pressure difference between the two input measuring pressures and PB. On the other hand, a part of the emitted light from the light source 8 that is modulated and driven by the light emitting circuit 11 of the processing section 16 is reflected by the beam splitter 9 and enters the monitor receiver 10, and the rest passes through the beam splitter 9 and is projected. The light enters the optical fiber 12. Since the output of the monitor light receiver 10 is proportional to the intensity of the emitted light from the light source 8, the light emitting circuit 11 controls the light source 8 based on the output of the monitor light receiver 10 so that the intensity of the light emitted from the light source 8 is constant.
control. On the other hand, the emitted light incident on the light projection fiber 12 is guided to the detection end 6A of the optical fiber bundle 6 via an optical connector (not shown) and the light projection optical fiber 6B, and irradiates the pressure receiving diaphragm 2. This irradiation light is reflected by the reflecting surface of the pressure receiving diaphragm 2 and is transferred to the light receiving optical fiber 6C.
, 1 is input to the measurement light receiver 14 via an optical connector (not shown) and a light receiving fiber 13.Here, the pressure receiving diaphragm 2 receives two input measuring pressures proportional to the pressure difference of PB. The sensing end 6 of the optical fiber bundle 6 is displaced.
The distance to A changes. Since the irradiated light from the light-emitting optical fiber 6B becomes diverging light, the intensity Ir of the reflected light incident on the light-receiving optical fiber 6C is expressed by the following equation.

Ir (X Since the intensity Io of the light emitted from the light emitting optical fiber 6B is controlled to be a constant value, unless the optical characteristics of the light emitting fiber 12 etc. change, the intensity Io of the light emitted from the light emitting optical fiber 6B is a constant value.
The intensity Ir of the incident light C, that is, the intensity of the output light of the light receiving fiber 13 that is approximately equal to this intensity 1r is measured by the measuring light receiver 14.
By detecting the distance, the distance can be calculated backwards.

Therefore, the conversion circuit 15 is a photoelectric converter 4 of the measurement light receiver 14.
Measuring pressure PAIPB proportional to distance based on No. 8
Outputs a signal according to the differential pressure. In other words, the relationship between the distance and the pressure difference between two people and PB can be determined by measuring the relationship between the known differential pressure and the L value in advance and obtaining a relational expression, and this obtained relational expression can be converted. It may be incorporated into the conversion circuit 5 in advance. The reason for using the optical fiber bundle 6 as the detection end 6A is to improve the stability and reliability of pressure measurement.
The sensitivity of the sensor section 7 can be adjusted by arranging the light receiving light 7 and the eyeper 6C.

[Problem that the invention seeks to solve]

Since the conventional optical pressure measuring device is configured as described above, it must always output an output signal as an absolute value according to the differential pressure across the diaphragm. Loss in optical fiber, loss in receiving fiber,
It was necessary to maintain the optical characteristics such as the reflection characteristics of the pressure receiving diaphragm at a constant level at all times, which made the circuit configuration complicated. There were problems such as a lack of accuracy and reliability in pressure measurement, such as changes in the length of the line or the position of the wiring affecting the pressure measurement value. This invention aims to solve the above problems. The aim of the present invention is to obtain a highly accurate and highly reliable optical pressure measuring device in which even if the optical characteristics of the optical elements used change, this change does not affect the measured pressure value. purpose.

[Means for solving problems]

The optical pressure measuring device according to the present invention is characterized in that the light transmitted from the light source is converted into one of convergent light, parallel light, and diffused light with a small diffusion angle by the light projecting means, and the reflecting surface is displaced by the pressure for measurement. The projected light beams form a light spot on the incident surface of the light receiving means consisting of the first and second optical waveguide means via the reflecting surface, and the amount of light corresponding to the displacement of the reflecting surface is transmitted to the first The output light from the first and second optical waveguides is individually received by each light receiving element and photoelectrically converted, and a predetermined formula is calculated based on these photoelectrically converted signals. The conversion means calculates the ratio and outputs it as a pressure-electrical conversion signal at a level corresponding to the magnitude of the measurement pressure.

[For production]

The optical pressure measuring device in this invention has a measuring pressure k
The amount of light incident on the first and second optical waveguide means of the light receiving means is controlled by utilizing the fact that the light spot reflected from the reflecting surface that is displaced and formed on the incident surface of the light receiving means moves due to the displacement of the reflecting surface. the converting means individually receives and photoelectrically converts the emitted light from the first and second optical waveguide means, calculates the ratio according to a predetermined value based on these photoelectrically converted signals, and outputs the ratio. As a result, a pressure-electric conversion signal of the pressure measurement result is output in a form in which components affected by changes in the optical characteristics of the optical element used are eliminated.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings. FIG. 1 shows the overall cross-sectional structure of one embodiment of the present invention,
In the figure, symbols 1.2.3A, 3B, 4A, and 5A.

4.5.8.12 are the same components as in the conventional example, and their explanation will be omitted. 20 is a light emitting circuit, which has a light source 8 and causes this light source 8 to emit light. Reference numeral 21 denotes nine light emitting holes provided in the sensor main body 1 and diagonally with respect to the surface of the pressure receiving diaphragm 2. It is maintained through etc. 22 is a lens held in the light projection hole 21;
The light emitted from the light projection fiber 12 is focused to produce convergent light,
The light is projected onto the pressure receiving diaphragm 2 via the second chamber 3B as parallel light or diffused light with a small diffusion angle.

Reference numeral 23 denotes a first light-receiving fiber bundle serving as a first optical waveguide means for transmitting the reflected light from the pressure-receiving diaphragm 2, and 24 a second light-receiving fiber bundle for transmitting the reflected light from the pressure-receiving diaphragm 2. A second light-receiving fiber bundle is used as a wave means. The first and second light-receiving fiber bundles 23°240 have the light-emitting fiber 12 at the input side end.
It is held in the sensor main body 1 so that the light projected and reflected by the pressure receiving diaphragm 2 is incident thereon. The detection end 25, which is the input end of the first and second light-receiving fiber bundles 23 and 24 exposed to the second chamber 3B side, is connected to the second chamber 3B.
As shown in the figure, the input end 23A of the first light-receiving fiber bundle 23 is formed by stacking optical fibers in a layered manner, and the input end 24A of the second light-receiving fiber bundle 24 is similarly formed by stacking optical fibers in a layered manner. The input end 23A is located closer to the output end of the light projecting fiber 12 than the input end 24A.

As shown by the dashed line in FIG. 2, the boundary between the input end 23A of the first light receiving fiber bundle and the input end 24A of the second light receiving fiber bundle is formed at the detection end 25 by the reflected light from the pressure receiving diaphragm 2. 25A is located at a position intersecting the direction in which the pressure receiving diaphragm 2 moves due to displacement (indicated by the arrow in FIG. 2). In this embodiment, the boundary of the detection end 25 is the light spot 25
It is located at a position substantially perpendicular to the direction in which A moves.

Reference numeral 26 denotes a first measurement light receiver as a photoelectric conversion effect type optical sensor such as a bin photodiode, which is arranged at a position to receive the emitted light of the first light receiving fiber bundle 23; This is a second measuring light receiver, which is a photoelectric conversion effect type optical sensor such as a bin photodiode, and is arranged at a position to receive the light emitted from the light receiving fiber bundle 24. 28 is a conversion circuit, which has first and second measurement light receivers 26.27, and a current IA flowing through each of the first and second measurement light receivers 26.27.
A predetermined calculation is performed based on l I B to determine the ratio, and a pressure-electric conversion signal corresponding to the differential pressure P is output.

Note that, for example, the conversion circuit 28 is composed of a measurement light receiver 26, 27 and an arithmetic circuit that performs calculations based on the output current of the calculation light receiver 26, 27.

29 is a sensor section, and symbols 1.2, 4.5.3A, 3
B.

It is composed of components indicated by 4A and 5A. Reference numeral 30 denotes a processing section, which is composed of components indicated by reference numerals 8, 20, and 26 to 28. In addition, the first and second chambers 3A
, 3B and the first and second capillaries 4 and 5 are filled with a non-pressure translucent liquid (not shown).

Next, the operation of this embodiment will be explained. Processing section 30
The modulated radiation from the light source 8 modulated and driven by the light emitting circuit 20 enters the projection fiber 12, is transmitted to the output end, and then is radially emitted again.

This emitted light is focused by the projection lens 22, becomes, for example, parallel light, and is irradiated onto the reflective surface of the pressure receiving diaphragm 2 in the form of a light spot. This irradiation light is applied to the pressure receiving diaphragm 2.
The light received by the spot is specularly reflected and reaches the detection end 25. The position of the reflected light spot 25A formed on the detection end 25 by this K corresponds to the position of the pressure receiving diaphragm 2, that is, the pressure difference between the two measurement pressures and PB.

For example, in the case of differential pressure O, that is, pA-pB,
25A is the input end 23A, 24A of the first and second light-receiving fiber bundles.
divided into equal parts. In the case of 2 people>Ps, the pressure receiving diaphragm 2 is pushed and deformed toward the second chamber 3B by the pressure difference, and the reflected light spot 25A becomes the second chamber 3B as shown in the second position.
The input end 23A of the first light receiving fiber bundle is closer to the input end 23A of the first light receiving fiber bundle than the input end 24A of the first light receiving fiber bundle. Pa<PB
In the case of , contrary to the case of PA>PB, Fig. 2C
) 25A is the second light receiving 7
Move to the input end 24A side of the Aipapander.

As described above, the amount of light incident on the first and second light-receiving fiber bundles 23 and 24 differs depending on the position of the reflected light spot 25A at the detection end 25. Each beam incident on the first and second light receiving fiber bundles 23 and 24 is optically transmitted to the rear tube 1 and the second measurement light receiver 26.
．． The light is received at 27, respectively. As a result of this light reception, currents I A l I B are obtained by the measurement light receivers 26 and 27, respectively.

Here, the pressure for measurement pA, the differential pressure of pB 222 people - pB
It is shown as

In equation (2), the numerator (iA-iB) indicates a value that depends on the position of the reflected light spot 25A at the detection end 25, and the denominator (IA+tB) indicates the total power effective for measurement. That is, the denominator is the error component due to the influence of fluctuations in the optical characteristics of optical elements such as the light source 8, the light emitting fiber 12, the lens 22, and the reflecting surface of the pressure receiving diaphragm 2, and the absolute total power when the fluctuations in optical characteristics are not affected. (The numerator is the same as the denominator, including error components due to fluctuations in optical properties and reflected light spora)
25A, which is influenced by the position of the detection end 25. Therefore, as shown in equation (2), by taking the ratio of the two, the common error component affected by the fluctuation of the optical characteristics of the optical elements mentioned above is eliminated, and the reflected light spoiler with respect to the absolute total power is 25A. A value corresponding to the position at the detection end 25 is obtained. The calculation on the right side of equation (2) is performed by the conversion circuit 24. The conversion circuit 28 incorporates a circuit that performs an arithmetic expression obtained by actually measuring the known differential pressure applied to the pressure receiving diaphragm 2 and the calculated value of equation (2). It outputs a pressure-electrical conversion signal with a value proportional to the differential pressure P.

In the above embodiment, even if the current obtained by amplifying the current I A '' I D using a linear amplifier is input into the corresponding term of Equation (2) and the calculation on the right side of Equation (2) is performed, good.

Further, in the above embodiment, when using modulated light, the conversion circuit 28 may input a modulated signal from the light emitting circuit 20 and perform sampling in synchronization with the frequency 9 phase of the modulated light. Furthermore, the light emitted from the light source 8 need not be modulated light but may be continuous light.

In the above embodiment, the lens 22 is used for the purpose of obtaining a light spot, but the divergence angle of the light emitted from the projection fiber 12 is /h.
If not, the lens 22 is not necessary. In addition, although equation (2) is shown to obtain the differential pressure P, it may also be the case that the differential pressure p=
In the case of pB-pA, it may be or.

Furthermore, although differential pressure measurement was explained in the above embodiment,
Of course, it can be applied to simply measuring pressure.

Further, the seal diaphragms 4A, 5A and the compressible liquid are not necessarily required, and an optical pressure measuring device may be used, for example, to directly apply air pressure to the pressure receiving diaphragm.

Furthermore, a fiber bundle can be used instead of the light projecting fiber 12, and one optical fiber can be used in each of the first and second fiber bundles 23, 24.

Furthermore, the first and second measurement light receivers 26.2
As 7, a photoconductive effect type optical sensor may be used.Although the current IAolB was used in the above embodiment, the current IA,
Flow IB through a resistor, take out the voltage value VB, and use the voltage VB instead of the currents IA and IB to perform similar calculations such as equation (2) to obtain the pressure-electric conversion signal. You may obtain .

Furthermore, if the influence of external light is small, continuous light may be used instead of modulated light.

[Effects of the Invention] As described above, according to the present invention, the reflected light from the reflecting surface displaced by the measuring pressure is reflected by the two-path light receiving means at an amount of light corresponding to the displacement, and is emitted from the light receiving means. Since the structure is configured to calculate the ratio based on the signal obtained by photoelectrically converting each light according to a predetermined formula and output it, it is possible to eliminate the influence of the measured value due to fluctuations in the optical characteristics of the optical elements used. This has the effect of always providing high precision and high reliability.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional configuration diagram showing one embodiment of the present invention, Fig. 2 is a front view showing various states of the reflected light spot formed at the detection end of Fig. 1, and Fig. 3 is a conventional optical system. FIG. 4 is a cross-sectional configuration diagram showing the pressure sensor device, and FIG. 4 is a diagram showing the configuration of the detection end of FIG. 3. In the figure, 2 is a pressure receiving diaphragm, 4A and 5A are seal diaphragms, 8 is a light source, 12 is a light emitting fiber, 2
0 is a light emitting circuit, 22 is a lens, 23 is a first optical waveguide, 24 is a second optical waveguide, 25 is a detection end, 23A is an input end of the first optical waveguide, and 24A is a second optical waveguide. The input end of the wave means, 25A is a reflected light spot, 26 is a first measurement light receiver, 27 is a second measurement light receiver, and 28 is a conversion circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] a displacement means that has a reflective surface and is displaced together with the reflective surface due to measurement pressure; a light projection means that has a light source that transmits and emits light from the light source and projects it onto the reflective surface; a light receiving means for transmitting the light reflected by the surface; and a converting means for receiving the light emitted from the light receiving means and converting it into a pressure-electrical conversion signal having a level corresponding to the magnitude of the measuring pressure. In the optical pressure sensor device, the light projecting means projects one of convergent light, parallel light, and diffused light with a small diffusion angle, and the light projecting causes a light spot to be formed on the incident surface via the reflective surface. The light receiving means formed includes first and second optical waveguide means, and the boundary between the incident surfaces of the first and second optical waveguide means forms the light spot on the incident surface due to the displacement of the reflective surface. The converting means receives the emitted light from the first and second optical waveguide means individually with each light receiving element, photoelectrically converts the received light, and converts the output light based on the photoelectrically converted signal. An optical pressure measuring device characterized in that it calculates a ratio according to a predetermined formula and outputs the result.