JP2005291946A - Optical fiber sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber sensor capable of measurement rapidly by using a wavelength dispersion type spectrograph. <P>SOLUTION: The optical fiber sensor 1 includes a sensor system 10 for applying incoherent light comprising a white light source 5 to a diaphragm sensor section 3 via a coupler 4; the wavelength dispersion type spectrograph 30 in which return light from the diaphragm sensor section 3 enters via the coupler 4; and a signal processing system 40 in which a return light signal is inputted. In the optical fiber sensor 1, one of pressure, force, temperature, and flow rate from the return light signal to the diaphragm sensor section 3 is measured. When an A/D converter 42 for converting the return light signal to a digital signal and a D/A converter 43 for displaying a pressure value are connected to an electronic computer 41 by a serial or parallel interface, pressure and force can be measured speedily with high resolution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical fiber sensor that can be used for measuring blood pressure and force.

Conventionally, an optical fiber sensor used for blood pressure measurement or the like includes a pressure sensor (see Patent Document 1) that uses a diaphragm that also serves as a mirror in a sensor unit, a low-coherence light source such as a halogen lamp, a photodetector, and the like. It is composed of
In the case of using a diaphragm serving as a pressure sensor as a so-called Fabry-Perot interferometer, two measurement methods are known.
In the first conventional measurement method, an interferometer equivalent to the interferometer of the pressure sensor is provided on the detector side, one of the two mirrors constituting the interferometer is mechanically scanned, and the time domain In this method, stripes are formed to determine the optical path length difference and the pressure is determined. For this mechanical scanning, an actuator using a piezoelectric element or the like has been used (for example, see Non-Patent Document 1).

  The second conventional measuring method is a method of detecting displacement due to the pressure of the diaphragm as a spatial stripe. The spatial fringes are input to the spectroscope as return light through a coupler provided in the optical fiber sensor, and the cavity length of the Fabry-Perot resonator is measured. And a pressure can be calculated | required from cavity length (for example, refer nonpatent literatures 2 and 3).

JP 2000-35369 A (FIG. 1) K. Fritsch, R. N. Poorman, “Fiber-linked interferometric pressure sensor”, (1987), Rev. Sci. Instrum., Vol.58, No.9, pp.1655-1659 V. Bhatia and 3 others, “Wavelength-tracked white lightinterferometry for highly sensitive strain and temperature measurements”, (1996), ELECTRONICS LETTERS, Vol.32, No.3, pp.247-249 Roger A. Wolthuis and 5 others, “Development of Medical Pressure and Temperature Sensors Employing Optical Spectrum Modulation”, (1991), IEEE TRANSACTION ON BIOMEDICAL ENGINEERING, Vol.38, No.10, pp.974-981

  However, although the conventional measurement method in the first time domain can perform relatively high-speed sampling, it requires mechanical scanning of the mirror, and there are problems in accuracy and long-term stability.

  In addition, the conventional measurement method in the second spatial region can detect displacement due to pressure applied to the diaphragm without using mechanical scanning of the mirror itself. For this reason, there is a problem that high-speed sampling is difficult due to the use of a spectroscope although it is highly accurate as a detection system for pressure, force, speed, etc. using a diaphragm and is stable in the long term.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an optical fiber sensor that uses a wavelength dispersion spectroscope and can perform quick measurement.

In order to achieve the above object, an optical fiber sensor of the present invention includes a sensor system, a wavelength dispersion spectrometer, and a signal processing system. The sensor system includes a white light source, a coupler connected to the white light source, and the coupler. An optical fiber connected to the optical fiber, and a diaphragm sensor part disposed at the tip of the optical fiber, the diaphragm sensor part comprising a diaphragm unit, a spacer part, and a half mirror layer provided on the tip surface of the optical fiber And a total reflection layer provided on the inner surface of the diaphragm unit. The signal processing system includes an electronic computer and an A / D converter. The signal processing system includes an electronic computer and an A / D converter. / D converter connected with serial or parallel interface, and light incident on optical fiber from white light source via coupler The return light due to the phase shift of the reflected light from the half mirror layer and the total reflection layer is incident on the wavelength dispersion spectrometer, and the return light signal is output from the wavelength dispersion spectrometer to the signal processing system. The displacement of the diaphragm sensor unit is detected based on the interference characteristics of the return light signal due to the displacement generated by the external pressure to the diaphragm sensor unit, and any one of pressure, force, and temperature is measured from this displacement. It is characterized by.
According to this configuration, the return light from the diaphragm sensor unit is made incident on the wavelength dispersive spectrometer, and any one of pressure, force, and temperature can be detected at high speed by the signal processing system.

In the above configuration, preferably, the first sensor including the optical fiber and the diaphragm sensor portion is embedded in the support member along the longitudinal direction, and the diaphragm sensor portion faces the window portion opened to the side of the support member. A second sensor comprising an optical fiber and a diaphragm sensor portion embedded along the longitudinal direction in the support member, the diaphragm sensor portion being disposed exposed at the tip of the support member, the first and first The displacement of each diaphragm sensor unit is detected based on the interference light characteristic of the return light signal generated by the external pressure applied to each diaphragm sensor unit of the sensor No. 2, and the flow velocity is detected based on the pressure difference obtained from each displacement.
According to this configuration, the two diaphragm sensor units are arranged on the support member, the return light spectrum from the diaphragm sensor unit is made incident on the wavelength dispersive spectrometer, and the flow rate is increased by the pressure difference in the signal processing system. Can be detected.

  The optical fiber sensor of the present invention preferably further includes a D / A converter that converts any one of the measured pressure, force, temperature, and flow velocity into an analog signal, and the D / A converter and the electronic computer are serially connected. Alternatively, they are connected by a parallel interface. According to this configuration, the return light spectrum from the diaphragm sensor unit is made incident on the wavelength dispersion spectrometer, and the pressure, force, temperature, and flow velocity can be detected and displayed at high speed by the signal processing system.

  In the above configuration, the signal processing system preferably calculates the peak wavelength of the return optical signal by a linear interpolation method near the peak wavelength. According to this configuration, the peak wavelength can be measured with higher resolution. Therefore, the resolution of any of pressure, force, temperature, and flow rate calculated using the peak wavelength is improved.

  In the above configuration, the white light source is preferably a white LED. As a result, it is smaller and lighter than the halogen lamp, and the optical fiber sensor can be reduced in size and power consumption. In addition, since it has a long life, it is not necessary to replace a light bulb as in a halogen lamp, and convenience is improved.

  Further, the optical fiber sensor more preferably includes a temperature measurement system in the vicinity of the diaphragm sensor unit, and performs temperature correction of the pressure or force to be measured. This temperature measuring system preferably includes a thermocouple or a temperature measuring optical fiber sensor. According to this configuration, it is possible to accurately measure the temperature in the vicinity of the diaphragm sensor unit, and it is possible to accurately correct the measured values of pressure and force by this temperature measurement, and the accuracy is improved.

  ADVANTAGE OF THE INVENTION According to this invention, the optical fiber sensor which can be measured rapidly using a wavelength dispersion type | mold spectrometer can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding members are denoted by the same reference numerals.
First, an optical fiber sensor according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing a configuration of an optical fiber sensor according to a first embodiment of the present invention. In FIG. 1, the optical fiber sensor 1 includes a sensor system 10, a spectroscope 30, and a signal processing system 40.

The sensor system 10 includes an optical fiber 2, a sensor including a diaphragm sensor unit 3 connected to the tip of the optical fiber, a coupler 4, and a white light source 5, and light emitted from the white light source 5. Is incident on the diaphragm sensor unit 3 through the coupler 4 and the optical fiber 2, and the return light 6 from the diaphragm sensor unit 3 is incident on the spectroscope 30.
The white light source 5 is incoherent light, and for example, a halogen lamp can be used. Further, a white light emitting diode (white LED) is preferably used. Since the white LED is small and light and has a long life, the optical fiber sensor can be miniaturized.

FIG. 2 is a sectional view showing the structure of the diaphragm sensor used in the present invention. As shown in the drawing, in the diaphragm sensor unit 3, a diaphragm unit 20 and a spacer 21 are arranged so as to define an internal space with respect to the distal end surface of the optical fiber 2. A reflection layer, which will be described later, is formed on the inner surface of the diaphragm portion 3, and this internal space serves as a Fabry-Perot resonator 23.
Specifically, the reflective diaphragm unit 20 made of SiO ₂ or the like has a structure in which it is joined to a half mirror layer 2 a formed on the front end surface of the optical fiber 2 via a spacer 21. The reflective diaphragm unit 20 has a mesa portion 20a at the center, and the periphery thereof is a diaphragm 20b. A total reflection mirror layer 22 made of an Al film or the like is formed on the surface of the mesa portion 20a. As a result, the space between the half mirror layer 2 a and the total reflection mirror layer 22 becomes each of the reflection layers described above, which is a so-called Fabry-Perot resonator 23.
The light 24 propagating through the optical fiber is incident on the spectroscope 30 through the coupler as interference light of the light 25 reflected by the half mirror layer 2 a and the light 26 reflected by the total reflection mirror layer 22. . When pressure is applied to the diaphragm sensor unit 3, the mesa unit 20a is displaced. This displacement is a change in the sensor cavity length, which is the length of the Fabry-Perot resonator 23.
As a result, in the optical fiber sensor 1, the reflected light 26 in the reflective layer composed of the total reflection mirror layer 22 generated by deformation of the diaphragm sensor portion 3 due to external pressure, and the reflection composed of the half mirror layer 2a on the front end surface of the optical fiber. The pressure can be detected based on the interference light characteristic of the return optical signal due to the phase shift from the reflected light 25 at the layer.

Next, a wavelength dispersion spectroscope that detects return light from the sensor system will be described.
FIG. 3 is a diagram schematically showing the structure of the wavelength dispersion spectrometer 30 used in the present invention. The wavelength dispersive spectrometer 30 includes a diffraction grating 33 and a light detector 35 that detects the light intensity of each wavelength dispersed from the diffraction grating. The return light 6 enters the spectroscope 30 through the coupler 4 by the optical fiber 2 </ b> A, enters the collimator 32 through the slit 31, and enters the diffraction grating 33. Then, the light is distributed to the light detector 35 via the mirror 34. The light detector 35 can be a line sensor such as a CCD or MOS type image sensor.
Since the light dispersed in this way is incident on each pixel of the CCD line sensor 35 and amplified, the detection light corresponding to each wavelength is instantaneously measured as the spectrum of the return light 6. The spectrum of the return light 6 is output as a return light signal 30a to the signal processing system 40 via a serial or parallel high-speed interface.
Thereby, in the wavelength dispersion spectrometer 30 used in the present invention, incoherent light can be instantaneously measured.

  The control system 40 includes a control electronic computer 41 composed of a personal computer, a microprocessor, etc., a spectroscope A / D converter 42, a display D / A converter 43, and the like.

  The spectroscope A / D converter 42 converts the spectrum a of the return optical signal 30a of the analog signal output from the wavelength dispersion spectroscope 30 into a digital signal and becomes an output signal 42a. The output signal 42a is preferably output to the microprocessor 41 as a parallel interface or a parallel signal in order to increase the signal processing time.

  The microprocessor 41 computes the spectrum of the return optical signal 30a, which is a digital signal from the A / D converter for spectroscope 42, calculates the sensor cavity length, and calculates the pressure and the like from this calculated value. The pressure and other values thus obtained are output to the display device (not shown) as actual analog values by the display D / A converter 43. At this time, the output 43a from the microprocessor 41 to the display D / A converter 43 is preferably a parallel interface rather than a serial interface in order to increase the display speed. As for the relationship between the sensor cavity length and the pressure, data measured in advance may be stored in the memory unit of the microprocessor 41.

Next, pressure measurement of the optical fiber sensor according to the first embodiment of the present invention will be described. FIG. 4 is a flowchart showing the processing content of the pressure measurement of the optical fiber sensor according to the first embodiment of the present invention.
First, in step ST1, measurement parameters such as initialization of the spectroscope 30, exposure integration time of the CCD 35, and smoothing are set. In step ST2, pressure reference value calibration is performed, and the optical fiber sensor 1 is installed at a predetermined location where pressure measurement is performed. Here, the reference pressure can be zero when no pressure is applied.

  In step ST3, the integrated exposure of the spectrum in the CCD 35 is started. Then, after a predetermined time has elapsed, in step ST4, the integrated exposure of the spectrum in the CCD 35 is terminated.

  Next, in step ST5, the spectral data of the return light 6 is transferred from the spectroscope 30 to the microprocessor 41.

Subsequently, in step ST6, a plurality of peak wavelengths in the spectrum are detected. The sensor cavity length is calculated from these peak wavelengths. This sensor cavity length (d) may be calculated from the following equation.
d = (m / 2n) · λ ₀ = ((m−1) / 2n) · λ ₁
Here, m and m−1 are spectral peaks, λ ₀ and λ ₁ are wavelengths corresponding to the spectral peaks, and n is a refractive index of the inter-mirror material.

  In step ST7, a pressure value is calculated from the sensor cavity length to obtain pressure data. Next, in step ST8, the pressure data is transferred to the pressure display D / A converter 43, and the pressure is displayed on the display device.

  In step ST9, it is determined whether or not to continue the pressure measurement. When it is determined that the measurement is continued, the process returns to step ST2 to perform pressure measurement.

On the other hand, when it is determined in step ST9 that the pressure measurement is finished, the pressure measurement is finished.
In this way, pressure measurement can be performed by the optical fiber sensor 1.

  Thereby, in the optical fiber sensor 1 of the present invention, the acquisition time can be shortened by using the wavelength dispersion spectroscope 30 for the return light spectrum from the sensor. Further, if the data is transferred to the microprocessor at a high speed by the parallel interface of the spectroscope A / D converter 42, the processing time required for pressure measurement can be further shortened.

Next, a modification of the optical fiber sensor according to the first embodiment of the present invention will be described. FIG. 5 is a flowchart showing the processing content of the pressure measurement of the optical fiber sensor according to the modification of the first embodiment of the present invention.
This processing content is different from the processing content of the optical fiber sensor according to the first embodiment in that step ST8 in FIG. 4 is changed to steps ST11 to ST13. That is, pressure data is obtained in step ST7, and then in step ST11, the display of the cavity length, pressure value, etc. is displayed on the monitor.
In step ST12, a pressure waveform graph display or the like is output to the monitoring display device. Subsequently, in step ST13, the pressure value, the graph and the like are stored in the memory.
Subsequent steps ST9 and subsequent steps are the same as the processing contents of the optical fiber sensor according to the first embodiment, and thus description thereof is omitted.
Such processing contents can be performed by software operating on the operating system (OS) using the personal computer 41. Further, when the microprocessor 41 is used, the program software including the above processing contents can be directly operated on the microprocessor 41 so that it can be processed at a higher speed.

An optical fiber sensor according to a second embodiment of the present invention will be described.
FIG. 6 is a diagram showing a peak wavelength correction method used for the optical fiber sensor according to the second embodiment of the present invention. In the figure, the horizontal axis represents wavelength (nm), and the vertical axis represents return light intensity (arbitrary scale). In the figure, one peak of the return light 6 from the optical fiber sensor is shown. As shown in the figure, the peak can be corrected by approximating the peak with a polygonal line, interpolating with two straight lines close to the peak, and setting the wavelength at the intersection as the peak wavelength. When the vertical axis is the y axis and the horizontal axis is the x axis, and the two straight lines to be interpolated are y = a ₁ x + b ₁ and y = a ₂ x + b ₂ , the peak wavelength at the intersection is x = become _{(b 2 -b 1) / (} a 1 -a 2). Such a correction can be calculated by the microprocessor 41 of the control system. According to this peak wavelength correction method, the accuracy can be improved by about 10 times the wavelength resolution of the spectrometer.

Next, an optical fiber sensor according to a third embodiment of the present invention will be described.
Although the optical fiber sensor 1 according to the present invention has been described exclusively for the case of a pressure sensor, the product of the pressure and the cross-sectional area of the diaphragm portion 3 is a force applied to the diaphragm sensor portion 3, so Can be used. As a result, in the optical fiber sensor, based on the characteristics of the interference light of the return light based on the phase shift of the reflected light at the reflection layer and the front end surface of the optical fiber generated by the deformation of the diaphragm sensor unit 3 due to external pressure, Furthermore, force can be detected.

Next, an optical fiber sensor according to a fourth embodiment of the present invention will be described.
By utilizing the fact that the internal space between the diaphragm sensor portion 3 of the optical fiber sensor 1 and the front end surface of the optical fiber 2 is sealed, the thermal expansion or contraction of air or the like enclosed in the internal space is caused. It is also possible to know the temperature outside the optical fiber sensor 1 by detecting the change in the atmospheric pressure by the optical fiber sensor 1. In this way, the optical fiber sensor 1 can be used as a temperature sensor.
As a result, in the optical fiber sensor, the temperature is changed from the pressure based on the characteristics of the interference light of the return light caused by the phase shift of the reflection layer generated by the deformation of the diaphragm sensor portion due to the external pressure and the reflected light at the tip surface of the optical fiber. Can be detected.

Next, an optical fiber sensor according to a fifth embodiment of the present invention will be described.
FIG. 7 is a perspective view showing a fifth embodiment of the optical fiber sensor according to the present invention. In FIG. 7, the optical fiber sensor 80 is composed of a first sensor 84 and a second sensor 86 embedded in a support member 81.
Similar to the sensor 1 of the first embodiment, the first sensor 84 includes the optical fiber 2 and the diaphragm sensor unit 3 disposed at the tip thereof, and extends in the longitudinal direction within the support member 81. The diaphragm sensor unit 3 is arranged facing a window that opens to the side of the support member 81. The second sensor 86 includes an optical fiber 82 and a diaphragm sensor portion 83 disposed at the tip of the optical fiber 82. The second sensor 86 is embedded in the support member 81 along the longitudinal direction, and the diaphragm sensor portion 3 is supported by the support member. 81 is exposed and arranged on the front end surface. The support member 81 can be applied to a guide wire or a catheter. Further, the optical fibers 2 and 82 and the diaphragm sensor units 3 and 83 used for the first and second sensors 84 and 86 may be the same.

According to the optical fiber sensor 80 having such a configuration, when the guide wire 81 is inserted into a patient's blood vessel or the like, the first and second diaphragm sensor units 3 and 83 can measure blood pressure at two locations on the blood vessel. It can be measured simultaneously. Thus, the blood flow velocity V in the blood vessel can be calculated based on the difference between the pressures detected by the first and second diaphragm sensor units 3 and 83. That is, when the intravascular pressure by the first diaphragm sensor unit 3 is P and the viscosity of blood is ρ, the pressure due to the flow velocity acting on the distal end surface of the guide wire 81 is expressed by the following equation:
P + (ρV ₂ ) / 2
It is requested from.
Therefore, the blood flow velocity V in the blood vessel can be detected based on the pressure difference detected by the first diaphragm sensor unit 3 and the second diaphragm sensor unit 83. In this way, the first diaphragm sensor unit 3 and the second diaphragm sensor unit 83 can be used as a flow velocity sensor. Of course, a catheter or the like may be used as the support member instead of the guide wire 81.

Next, an optical fiber sensor according to a sixth embodiment of the present invention will be described.
FIG. 8 is a block diagram showing a configuration of a temperature correction system used in the optical fiber sensor according to the sixth embodiment of the present invention. As shown in the figure, the temperature correction system 50 includes a temperature sensor 51 disposed in the vicinity of the sensor 3 of the optical fiber sensor 1, a signal amplification circuit 52 for the temperature sensor, and an A / D converter 53 for the temperature sensor. ing. Since the other configuration is the same as that of the optical fiber sensor 1 according to the first embodiment of the present invention, the description thereof is omitted.
The output 54 of the temperature sensor A / D converter 53 shown in the figure is output to the microprocessor 41 of the control system 40. The temperature sensor 51 can use a thermocouple having an outer diameter smaller than that of the optical fiber. The temperature correction may be performed after step ST7 in the flowcharts shown in FIGS.
According to this configuration, the accurate temperature in the vicinity of the diaphragm sensor unit 3 of the optical fiber sensor 1 is measured by the temperature sensor 51 disposed in the vicinity of the diaphragm sensor unit 3 of the optical fiber sensor 1. For this reason, it is possible to correct the pressure with respect to the temperature change by measuring the relationship between the temperature and the pressure in advance.

FIG. 9 is a block diagram showing another configuration of the optical fiber sensor according to the sixth embodiment of the present invention.
The optical fiber sensor 60 differs from the optical fiber sensor 1 according to the first embodiment in that the temperature of the optical fiber for temperature measurement can be switched by an optical switch 61 in the vicinity of the diaphragm sensor unit 3 of the optical fiber sensor. The sensor 62 is provided. The optical switch 61 is inserted on the coupler 4 side of the fiber 2.
When the optical switch 61 is connected to the diaphragm sensor unit 3 of the optical fiber sensor, the optical fiber sensor 1 according to the first embodiment is operated. On the other hand, when the optical switch 61 is connected to the optical fiber temperature sensor 62, it is input to the spectroscope 30 via the coupler 4. The spectrum of the optical fiber temperature sensor 62 measured by the spectroscope 30 is connected to the control system 40 via an interface such as an A / D converter, and the temperature is calculated by the microprocessor 41.
According to this configuration, the accurate temperature of the diaphragm sensor unit 3 of the optical fiber sensor is measured by the optical fiber temperature sensor 62 disposed in the vicinity of the diaphragm sensor unit 3 of the optical fiber sensor. For this reason, it is possible to correct the pressure with respect to the temperature change by measuring the relationship between the temperature and the pressure in advance.

FIG. 10 is a block diagram showing still another configuration of the optical fiber sensor according to the sixth embodiment of the present invention.
The optical fiber sensor 70 is different from the optical fiber sensor 60 according to the sixth embodiment of FIG. 9 in that an optical switch 61 is not used and a light source 75 and a coupler 74 are used so that the temperature can be constantly measured. And a spectroscope 76 and the like. For this reason, the optical fiber temperature sensor 62 is always connected to the spectroscope 76 via the coupler 74. The spectrum of the optical fiber temperature sensor 62 measured by the spectroscope 76 is connected to the control system 40 via an interface such as an A / D converter, and the microprocessor 41 constantly calculates the temperature. According to this configuration, the accurate temperature of the diaphragm sensor unit 3 of the optical fiber sensor is constantly measured by the optical fiber temperature sensor 62 disposed in the vicinity of the diaphragm sensor unit 3 of the optical fiber sensor. For this reason, by measuring the relationship between temperature and pressure in advance, it is possible to instantaneously correct pressure with respect to temperature change.

As Example 1, an optical fiber sensor 1 according to the present invention was manufactured. The main part will be described with reference to FIG.
In the sensor system 10, a halogen lamp (LS-1 manufactured by Ocean Optics, USA) or a white LED (manufactured by Nichia Corporation, NSPW300BS) was used as an illumination light source. The diameter of the optical fiber 2 is 125 μm, and the tip thereof is a ZnS or Cr half mirror layer 2a. The diaphragm portion 3 is made of SiO _{2 and} has a diameter of 125 μm. Moreover, Al was used as the total reflection mirror layer. The spacer layer 21 was made of polyimide and its thickness was 2 μm.

  The wavelength-dispersion spectrometer 30 (USB2000 manufactured by Ocean Optics, USA) is a Zernitaner spectrometer, and the photodetector 35 is a CCD line sensor (Sony, ILX511). The data output interface was USB (Universal Serial Bus).

  In the control system 40, signal processing was performed using a personal computer (Latitude C400, manufactured by Dell) 41 and a 12-bit A / D converter 42 for a spectroscope built in the wavelength dispersion spectroscope 30.

Next, pressure was measured by the optical fiber sensor 1 of the example. The sampling period for measurement is 70 Hz.
11 and 12 are graphs showing the pressure dependence of the return light spectrum according to Example 1, and a halogen lamp and a white LED are used, respectively. The horizontal axis of the figure indicates the wavelength (nm), and the vertical axis indicates the return light intensity (arbitrary scale). As can be seen from the figure, when the pressure is changed from −100 mmHg to 400 mmHg every 50 mmHg, the peak due to the interference fringes generated in the return light from the diaphragm sensor unit 3 changes.

  FIG. 13 is a graph showing the relationship between the cavity length and the pressure measured in Example 1. A halogen lamp was used for the measurement. In the figure, the horizontal axis represents pressure (mmHg), and the vertical axis represents cavity length (nm). As can be seen from the figure, the cavity length decreases as the pressure increases.

  Instead of the personal computer 41, a 28 MHz microprocessor 41 (manufactured by Renesas Technology, SH / 7045F) was used. In addition, so-called parallel signal processing was performed with a 12-bit A / D converter for spectroscope (AD9200, manufactured by Analog Devices) and a 16-bit display D / A converter 43 (manufactured by Burr Brown, DAC7644). Other than that, the optical fiber sensor 1 according to the present invention was manufactured in the same manner as in Example 1. The sampling period of the measurement was 500 Hz, which was about 7 times as high as that of Example 1.

  As is clear from the above examples and comparative examples, the optical fiber sensor of the present invention operates faster than the optical fiber sensor using the conventional spectroscope.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. Absent. In the above-described embodiment, the pressure sensor has been mainly described, but it can also be used for a force sensor, a temperature sensor, a flow rate sensor, and the like.

It is a schematic diagram which shows the structure of the optical fiber sensor by 1st Embodiment concerning this invention. It is sectional drawing which shows the structure of the diaphragm sensor part used for this invention. It is a figure which shows typically the structure of the spectrometer used for this invention. It is a flowchart which shows the processing content of the pressure measurement of the optical fiber sensor which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the processing content of the pressure measurement of the optical fiber sensor which concerns on the modification of the 1st Embodiment of this invention. It is a figure which shows the correction method of the peak wavelength used for the optical fiber sensor which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows 5th Embodiment of the optical fiber sensor by this invention. It is a block diagram which shows the structure of the temperature correction system used for the optical fiber sensor which concerns on the 6th Embodiment of this invention. It is a block diagram which shows another structure of the optical fiber sensor which concerns on the 6th Embodiment of this invention. It is a block diagram which shows another structure of the optical fiber sensor which concerns on the 6th Embodiment of this invention. It is a figure which shows the pressure dependence of the return light spectrum by Example 1. FIG. It is a figure which shows the pressure dependence of the return light spectrum by Example 1. FIG. FIG. 3 is a diagram showing the relationship between the cavity length and pressure measured in Example 1.

Explanation of symbols

1, 60, 70, 80: Optical fiber sensors 2, 2A, 82: Optical fiber 2a: Half mirror layer (reflection layer)
3, 83: Diaphragm sensor unit 4, 74: Coupler 5, 75: Light source 6: Return light 10: Sensor system 20: Reflective diaphragm unit 20a: Mesa unit 20b: Diaphragm unit 21: Spacer 22: Total reflection mirror layer (reflection) layer)
23: Fabry-Perot resonator 24: Light propagating through the optical fiber 25: Light reflected by the half mirror layer 26: Light reflected by the total reflection mirror layer 30, 76: Spectrometer (wavelength dispersion type spectrometer)
30a: Return light signal 31: Slit 32: Collimator 33: Diffraction grating 34: Mirror 35: Photo detector (CCD)
40: signal processing system 41: control computer (personal computer, microprocessor)
42: Spectrometer A / D converter 42a: Output signal 43: Display D / A converter 43a: Output signal from microprocessor 50: Temperature correction system 51: Temperature sensor (thermocouple)
52: Signal amplification circuit 53: A / D converter for temperature sensor 54: Output 61: Optical switch 62: Optical fiber temperature sensor 81: Support member (guide wire)
81b: Opened window portion 84: First sensor 85: Second sensor

Claims (7)

An optical fiber sensor having a sensor system, a wavelength dispersion spectrometer, and a signal processing system,
The sensor system includes a white light source, a coupler connected to the white light source, an optical fiber connected to the coupler, and a diaphragm sensor unit disposed at the tip of the optical fiber,
The diaphragm sensor unit includes a diaphragm unit, a spacer unit, a half mirror layer provided on the tip surface of the optical fiber, and a total reflection layer provided on the inner surface of the diaphragm unit. It has an internal space for the tip surface,
The signal processing system includes an electronic computer and an A / D converter, and the electronic computer and the A / D converter are connected by a serial or parallel interface.
The return light due to the phase shift of the reflected light in the half mirror layer and the total reflection layer due to the light incident on the optical fiber from the white light source through the coupler is incident on the wavelength dispersion spectrometer.
The return optical signal is output from the wavelength dispersive spectrometer to the signal processing system,
The signal processing system detects the displacement of the diaphragm sensor unit based on the interference characteristics of the return light signal due to the displacement generated by the external pressure to the diaphragm sensor unit, and any one of pressure, force, and temperature is detected from this displacement. An optical fiber sensor, characterized in that The first sensor comprising the optical fiber and the diaphragm sensor part is embedded along the longitudinal direction in the support member, and the diaphragm sensor part is disposed facing the window part opened to the side of the support member,
Furthermore, it comprises a second sensor consisting of an optical fiber and a diaphragm sensor part embedded along the longitudinal direction in the support member, and the diaphragm sensor part is arranged exposed at the tip of the support member,
The displacement of each diaphragm sensor unit is detected based on the interference light characteristic of the return light signal generated by the external pressure to each diaphragm sensor unit of the first and second sensors, and the flow velocity is detected by the difference in pressure obtained from each displacement. The optical fiber sensor according to claim 1, wherein:   Furthermore, a D / A converter that converts any one of the measured pressure, force, temperature, and flow velocity into an analog signal is provided, and the D / A converter and the electronic computer are connected by a serial or parallel interface. The optical fiber sensor according to claim 1.   The said signal processing system correct | amends and calculates the peak wavelength of the peak wavelength of the return optical signal from the said diaphragm sensor part by the linear interpolation method of the peak wavelength vicinity, It is any one of Claims 1-3 characterized by the above-mentioned. Fiber optic sensor.   The optical fiber sensor according to claim 1, wherein the white light source is a white LED.   The optical fiber sensor according to any one of claims 1 to 5, further comprising a temperature measurement system in the vicinity of the diaphragm sensor unit and performing temperature correction of the pressure to be measured.   The optical fiber sensor according to claim 6, wherein the temperature measurement system includes a thermocouple or a temperature measurement optical fiber sensor.

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