JPH0447777B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pressure measuring device for measuring pressure in minute parts such as blood vessels.

BACKGROUND OF THE INVENTION Conventionally, it has been extremely difficult to measure pressure in minute parts, and the detection part to be measured needs to be of a certain size. A semiconductor pressure sensor can be used when the detection area is about a few mm, but if you want to measure an even smaller area, such as when measuring blood pressure in a blood vessel, an even smaller sensor is required. It has been impossible to measure with conventional pressure sensors. However, since it would be extremely useful to be able to measure pressure in minute areas, such a pressure sensor has been desired.

Purpose of the Invention The present invention has been made in view of the actual situation of conventional pressure sensors, and is a novel optical fiber sensor that uses an optical fiber as a sensor to reliably measure pressure in minute areas such as inside blood vessels. The purpose is to provide a pressure measuring device.

Structure and Effects of the Invention The first invention of the present application includes a light source, a polarizing beam splitter that transmits the light provided by the light source, and a cladding on the tip side that is thinly formed and has a reflective film on the end face, and can be used as a sensor. An optical fiber, a sealed cylindrical probe that includes a sensor section at the tip of the optical fiber and has an axial opening on the side facing the thin clad surface of the optical fiber, and an opening in the probe. A pressure vibrating membrane that covers the optical fiber and has a reflective surface on the inside and changes the distance from the cladding surface of the optical fiber depending on the pressure. The present invention includes a photoelectric converter disposed on the reflected output side that is reflected again by the beam splitter, and a signal processing section that measures the pressure in the sensor section based on the signal intensity of the photoelectric converter. In a second aspect of the invention, the sensor portion includes a sealed cylindrical probe that includes an optical fiber tip sensor portion and has an opening on the side surface, and a pressure vibrating membrane that covers the opening of the probe.
The probe is characterized by being constructed by providing a material with a large photoelastic constant that is filled into the probe and whose refractive index changes depending on pressure.

According to the first or second invention of the present application having such characteristics, the sensor section is constituted by an optical fiber, and the optical fiber is returned to the light source side by attenuation of the reflected light. Since pressure is measured, the sensor portion can be configured to be extremely small. Therefore, it is possible to directly and accurately measure the pressure of a portion that requires measurement even in the case of a minute measurement target such as inside a blood vessel.

DESCRIPTION OF EMBODIMENTS FIG. 1 is a principle diagram of a sensor section of a pressure measuring device according to the present application. The pressure measuring device according to the invention uses an optical fiber 1 as a sensor. As is well known, an optical fiber has a core 2 that allows light to pass through.
It has a structure covered with a cladding 3 having a lower refractive index. In the present invention, only the cladding 3 at the tip of the optical fiber 1 used as a sensor is cut off as close as possible to the core 2 as shown in the figure, and
As shown in the figure, a reflective film 4 such as a metal film that totally reflects light is provided on the tip end surface of the optical fiber 1. The structure is such that the amount of light transmitted through the core 2 changes depending on the pressure applied to the cut section 3a of the cladding 3. The optical fiber 1 is assumed to be driven by a laser light source, and a detector capable of detecting the light intensity of the reflected light is provided. Then, the laser light transmitted from the laser oscillator through the core 2 is reflected by the reflective film 4, passes through the core 2 again, and is applied to the reflected light intensity detector, but at that time, the laser light is applied to the cross section 3a of the cladding 3. The intensity of reflected light changes depending on the pressure. Therefore, it is possible to detect the pressure applied to the cross section 3a of the cladding 3 based on the intensity of the reflected light.

FIG. 2 is a configuration diagram of a pressure measuring device using an optical fiber pressure sensor according to the first invention of the present application.
In this embodiment, a He--Ne laser 10, for example, is used as a light source, and its output is applied to a polarizing beam splitter 11. The polarizing beam splitter 11
It is arranged in a direction in which the laser output of the He--Ne laser 10 is transmitted, and the transmitted output is applied to the optical fiber 13 via the condenser lens 12. Optical fiber 13 may be a multimode fiber or a single mode fiber. Now, this optical fiber 13 is made into a multi-mode fiber with a cladding diameter of about 150 μm, and the cladding is machined by cutting a few mm, for example, about 2 mm at the tip, as a pressure sensor as described above, and a reflective film 14 is provided on the tip surface. put. Then, the tip probe portion is inserted into a pressure measurement region, for example, a blood vessel as shown.
On the other hand, a photoelectric converter 15 is provided at a position where the reflected light that has passed through the optical fiber 13 is reflected again by the polarizing beam splitter 11. The photoelectric converter 15 converts an optical signal into an electrical signal, and its output is given to a signal processing section 16. The signal processing section 16 is configured to extract light intensity as a signal corresponding to pressure. Here, the sensor portion at the tip of the optical fiber 13 is inserted into a cylindrical metal probe 17 having a diameter of approximately 300 μmφ, as shown in the end view in FIGS. 3a and 3b. The metal probe 17 is the third
As shown in Figure a, an opening 17a parallel to the axis is provided in a portion of the optical fiber 13 facing the cross section of the cladding. Then, cover this opening 17a,
A pressure vibrating membrane 18 on which a metal such as aluminum is vapor-deposited is provided on the side opposite to the cut surface of the cladding of the optical fiber 13. Further, the gap between the optical fiber 13 and the metal probe 17 is filled with a liquid having a refractive index slightly lower than that of the cladding, such as alcohol 19, and the metal probe 17 is sealed with a resin 20 provided at the bottom of the metal probe 17. Then the pressure vibrating membrane 1
8 is constructed so that the distance between the aluminum vapor deposited film on its back surface and the cut surface of the cladding of the optical fiber 13 can be easily changed by external pressure.

The optical fiber probe constructed in this way is inserted into a blood vessel as shown in Figure 2, and He-Ne
The laser 10 is operated and laser light is applied to the optical fiber 13 via the polarizing beam splitter 11 and the condensing lens 12. Then, the laser light is transmitted through the optical fiber 13, becomes randomly polarized light, and is applied to the probe section inside the blood vessel. and optical fiber 13
The reflected light is reflected by the reflective film 14 applied to the end face of the polarizing beam splitter 11 via the optical fiber 13 and the condensing lens 12. Then, a part of the component is reflected by the polarizing beam splitter 11 and applied to the photoelectric converter 15. An electrical signal with a signal level corresponding to the intensity of the reflected laser light is obtained from the photoelectric converter 15, and the signal is transmitted to the signal processing section 16, where the intensity of the reflected light returning through the optical fiber 13 is measured. . Here, the pressure vibrating membrane 18 vibrates through the opening 17a provided in the metal probe 17 due to changes in the pressure around the probe section, in this case blood pressure, and the pressure vibrates the pressure vibrating membrane 18 and the optical fiber 13. The gap with the cladding changes. If this gap is wide, the pressure vibration membrane 18
However, as the gap becomes narrower, the amount of light absorbed increases accordingly, so if the intensity of the reflected light is detected by the photoelectric converter 15, the pressure inside the blood vessel can be detected. becomes possible.

In this embodiment, the clad part of the sensor part of the optical fiber 13 is cut as close as possible to the core of the optical fiber 13, but it may be cut until it comes into contact with the core, or the clad part of the sensor part of the optical fiber 13 may be cut until it comes into contact with the core. It is also possible to construct an optical fiber sensor section by connecting only the optical fiber section using another optical fiber with a thin cladding layer.

FIG. 4 shows a sectional view of the tip probe portion of an optical fiber pressure sensor showing an embodiment of the second invention of the present application. In the present invention, instead of changing the amount of light absorbed leaking from the cladding layer, a material having a large photoelastic constant is provided in contact with the cladding shoulder, and pressure is detected by the change in the refractive index. This embodiment is similar to the embodiment shown in FIG. 2 in that the He-Ne laser light source 10 is used to provide laser light to the end face of the optical fiber via the polarizing beam splitter 11 and the condensing lens 12. Since it is the same as that, the overall configuration diagram is omitted.
In this embodiment, the optical fiber 30 is a multi-mode optical fiber, and only the sensor portion at the tip is made of a fiber with an extremely thin cladding layer, for example, a fiber with a core diameter of
In the case of 50 μm, another optical fiber 31 with a cladding diameter of about 60 μm is connected to the tip end surface of the optical fiber 30 as shown. Then, as in the embodiment shown in FIG. 3a, the sensor optical fiber 31 is housed in the metal probe 32, and
The inside is filled with a material having a large photoelastic constant whose refractive index changes depending on pressure, such as liquid crystal 33. It is assumed that a reflective film 34 is provided on the tip end surface of the optical fiber 31 in the same manner as in the embodiment described above. In this case as well, an opening 3 is formed on one side of the metal probe 32 as shown in the figure.
2a, a pressure vibrating membrane 35 for separating the liquid crystal 33 from the outside and transmitting pressure, and a resin 36 for sealing the metal probe 32.

In this embodiment as well, if laser light is applied from the He-Ne laser 10 to the end face of the optical fiber 30 via the polarizing beam splitter 11 and the condensing lens 12,
Laser light is applied to the optical fiber 31 of the sensor section and is reflected by the reflective film 34 on the end face thereof. Then, the reflected light is again condensed by the condenser lens 12 via the optical fibers 31 and 30 and returned to the polarizing beam splitter 11, and a part of it is converted into an electrical signal by the photoelectric converter 15. At that time, optical fiber 3
A portion of the laser light transmitted through the liquid crystal 1 leaks into the liquid crystal 33 through the cladding layer. By the way, metal probe 3
The refractive index of the liquid crystal 33 in the liquid crystal 2 fluctuates depending on the external pressure transmitted via the pressure vibrating membrane 35.
Therefore, the amount of light leaking to the liquid crystal 33 while traveling back and forth through the optical fiber 31 varies based on the pressure. Therefore, the pressure at the part where the metal probe 32 is inserted can be measured by converting the reflected light into an electrical signal by the photoelectric converter 15 and measuring the intensity of the reflected light by the signal processing unit 16. It becomes possible.

In this embodiment, only the sensor section is constructed using another optical fiber with a thin cladding layer, but similarly to the embodiment of the first invention, a normal optical fiber is used to form the cladding section at the tip that becomes the sensor. The cladding of the sensor section may be made thinner by cutting or etching so that its cross section and the liquid crystal come into contact with each other. Moreover, instead of the liquid crystal 33, a mixture of glycerin and gelatin, plastic, etc. can also be used.

Furthermore, in the first and second inventions described above, a multimode fiber is used as the optical fiber, but it is also possible to use a single mode optical fiber, and a light emitting diode may be used as the light source instead of a laser light source. It is also possible to use non-coherent light sources such as.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the basic structure of the optical fiber pressure sensor according to the present invention, and FIG. 2 is a block diagram showing the structure of an embodiment of the pressure measuring device according to the first invention of the present invention using this optical fiber sensor. , FIG. 3a is a cross-sectional view showing the tip of an optical fiber used as a pressure sensor, FIG. 3b is a cross-sectional view of the optical fiber, and FIG. 4a is an optical fiber pressure measuring device according to the second invention of the present application. FIG. 4B is a sectional view showing the tip of the embodiment, and FIG. 1, 13, 30, 31...optical fiber, 2...
Core, 3...Clad, 3a...Cross section, 10...
He-Ne laser, 11...Polarizing beam splitter, 12...Condenser lens, 14, 34...Reflection film, 15...Photoelectric converter, 16...Signal processing unit,
17, 32...metal probe, 17a, 32a...
...Opening, 18, 35...Pressure vibration membrane, 19...
Alcohol, 33...LCD.

Claims (1)

[Scope of Claims] 1. A light source configured as a sensor, comprising a light source, a polarizing beam splitter that transmits light provided by the light source, and a thin cladding on the tip side and a reflective film on the end face. a cylindrical probe that includes a tip sensor portion of the optical fiber and is sealed with an axial opening on the side facing the thin clad surface of the optical fiber; and an opening of the probe. a pressure vibrating membrane that covers the optical fiber and has a reflective surface on the inside and changes the distance from the cladding surface of the optical fiber according to pressure; a photoelectric converter that is placed on the reflected output side that is reflected again by the polarizing beam splitter and converts the reflected light into an electrical signal; and a signal processing unit that measures the pressure of the sensor unit based on the signal intensity of the photoelectric converter. An optical fiber pressure measuring device comprising: 2. Claim 1, wherein the optical fiber is constructed by cutting the cladding at the tip of an optical fiber whose cladding diameter is larger than the core diameter.
Optical fiber pressure measuring device as described in . 3. The optical fiber pressure measuring device according to claim 1, wherein the optical fiber has another optical fiber having a cladding diameter slightly larger than the core diameter connected to the tip end thereof as a sensor fiber. 4. Any one of claims 1 to 3, wherein the light source is a laser light source.
The fiber optic pressure measuring device described in Section 1. 5. a light source, a polarizing beam splitter that transmits the light provided by the light source, an optical fiber having a thin cladding on the tip side and having a reflective film on its end face and configured as a sensor; and the optical fiber. a sealed cylindrical probe that includes a tip sensor section and has an opening on its side; a pressure vibrating membrane that covers the opening of the probe; and a pressure vibrating membrane that is filled in the probe and changes its refractive index depending on the pressure. A material having a large photoelastic constant is placed on the reflection output side where the light is reflected at the end face of the optical fiber, transmitted in the opposite direction through the optical fiber, and reflected again by the polarization beam splitter, and converts the reflected light into an electrical signal. An optical fiber pressure measuring device comprising: a photoelectric converter; and a signal processing section that measures pressure in a sensor section based on a signal intensity of the photoelectric converter. 6. Claim 5, wherein the optical fiber is constructed by cutting the cladding at the tip of an optical fiber whose cladding diameter is larger than the core diameter.
Optical fiber pressure measuring device as described in . 7. The optical fiber pressure measuring device according to claim 5, wherein the optical fiber has a distal end connected to another optical fiber having a cladding diameter slightly larger than the core diameter as a sensor fiber. 8. Any one of claims 5 to 7, wherein the light source is a laser light source.
The fiber optic pressure measuring device described in Section 1. 9. Claims 5 to 8, wherein the material having a large photoelastic constant is liquid crystal.
The optical fiber pressure measuring device according to any one of the above items.