JP2023008303A - Pressure sensor and pressure sensor device - Google Patents

Abstract

To provide a pressure sensor allowing detection even when applied pressure is small.SOLUTION: A pressure sensor includes: a housing having a communicated opening; a magnetic film generating the Faraday effect capable of modulating the optical rotation angle of linear polarization by changing a magnetic field; an optical fiber capable of irradiating the magnetic film with the linear polarization to receive return light from the magnetic film and arranged on one side of the opening; an elastic film arranged to be separated at a predetermined interval from the magnetic film on the other side of the opening and having at least a part displaced corresponding to applied pressure; a moisture-proof film formed on the surface of the elastic film on the side opposite to the magnetic film side and capable of preventing moisture from permeating into the elastic film; and a magnetic body arranged on the surface of the elastic film on the side of the magnetic film and capable of changing the magnetic field in the magnetic film corresponding to the displacement of the elastic film.SELECTED DRAWING: Figure 2

Description

The present invention relates to pressure sensors and pressure sensor devices.

So far, an optical micro pressure sensor has been developed in which a Faraday element and a total reflection mirror are arranged at the tip of an optical fiber, and a silicon diaphragm with a magnet attached is arranged further outside (see, for example, Patent Document 1).

According to the conventional pressure sensor device, it is possible to detect the pressure in the narrow portion, and it can be manufactured at low cost.

Japanese Patent Application No. 2021-014906

However, in the conventional pressure sensor, since the diaphragm is made of silicon, the amount of displacement when pressure is applied to the diaphragm is relatively small, and it is difficult to accurately detect minute pressure. rice field.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pressure sensor capable of accurately detecting pressure even when the applied pressure is small.

A pressure sensor according to an embodiment of the present disclosure includes a housing having a communicating opening, a magnetic film that generates a Faraday effect that modulates the optical rotation angle of linearly polarized light due to a change in magnetic field, and linearly polarized light to the magnetic film. An optical fiber that is incident and receives return light from the magnetic film and is arranged on one side of the opening, and an optical fiber that is arranged on the other side of the opening at a predetermined distance from the magnetic film and is applied an elastic film at least partially displaced according to applied pressure; a moisture-proof film formed on the surface of the elastic film on the side opposite to the magnetic film side and preventing permeation of moisture into the elastic film; and a magnetic body arranged on the surface of the elastic film on the film side and changing the magnetic field in the magnetic film according to the displacement of the elastic film.

In the pressure sensor according to one embodiment of the present disclosure, the elastic membrane preferably contains resin.

In the pressure sensor according to one embodiment of the present disclosure, the resin is preferably polyimide.

In the pressure sensor according to an embodiment of the present disclosure, it is preferable that the magnetic material includes a powder magnet.

In the pressure sensor according to one embodiment of the present disclosure, the magnetic substance preferably has a particle size of 1 to 20 μm.

In the pressure sensor according to an embodiment of the present disclosure, the magnetic substance preferably contains at least one of SmCo and NdFeB.

In the pressure sensor according to one embodiment of the present disclosure, the moisture-proof film preferably contains a ferromagnetic metal thin film.

In the pressure sensor according to one embodiment of the present disclosure, the film thickness of the moisture-proof film is preferably 10 to 100 nm.

In the pressure sensor according to an embodiment of the present disclosure, the magnetic body preferably has a convex structure protruding toward the magnetic film.

The pressure sensor according to an embodiment of the present disclosure preferably has a second elastic film on the magnetic film.

The pressure sensor according to an embodiment of the present disclosure preferably further includes a reflective film arranged on the magnetic film and reflecting incident light from the light source toward the light source.

A pressure sensor device according to an embodiment of the present disclosure is optically connected to a light emitting unit including a light source and the pressure sensor via an optical fiber, and the pressure applied to the pressure sensor is controlled based on the return light. and a detection signal generator for outputting a detection signal corresponding to the detection signal.

A pressure sensor according to an embodiment of the present disclosure can provide a pressure sensor that can accurately detect pressure even when the applied pressure is small.

1 is a schematic configuration diagram of a pressure sensor device according to Example 1 of the present disclosure; FIG. (a) and (b) are cross-sectional views of the pressure sensor according to Example 1 of the present disclosure, where (a) shows a state before pressure is applied, and (b) shows a state after pressure is applied. indicates (a) is an enlarged view of area A in FIG. 2(a), and (b) is an enlarged view of area B in FIG. 2(b). 4 is a graph showing the relationship between the pressure applied to the elastic membrane and the amount of deformation of the elastic membrane in the pressure sensor according to Example 1 of the present disclosure. 5 is a graph showing the relationship between the amount of deformation of the elastic film and the magnetic field intensity of the magnetic film in the pressure sensor according to Example 1 of the present disclosure. (a) and (b) are cross-sectional views of a pressure sensor according to Example 2 of the present disclosure, (a) showing a state before pressure is applied to the elastic membrane, and (b) showing pressure applied to the elastic membrane. is applied.

A pressure sensor and a pressure sensor device according to the present invention will be described below with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to those embodiments, but extends to the invention described in the claims and equivalents thereof.

[Example 1]
First, a pressure sensor device according to Example 1 of the present disclosure will be described. FIG. 1 shows a schematic configuration diagram of a pressure sensor device 1000 according to Example 1 of the present disclosure.

The pressure sensor device 1000 has a light emitting section 10 , a circulator 20 , a first optical element 30 , an optical path section 40 , a pressure sensor 101 and a detection signal generating section 60 . An optical path between the light emitting section 10 , the circulator 20 , the first optical element 30 , the optical path section 40 and the detection signal generating section 60 is composed of a PANDA (Polarization-maintaining AND Absorption-reducing) fiber 80 . An optical path between the optical path section 40 and the pressure sensor 101 is formed by the optical fiber 3 . The optical fiber 3 may have a configuration similar to that of the PANDA fiber 80 . The outer diameter of the PANDA fiber 80 is 125 μm in one example. The optical path between the first optical element 30, the optical path section 40, the pressure sensor 101, and the detection signal generating section 60 is a polarization maintaining type light beam such as a bow-tie fiber and an elliptical jacket fiber. It may be formed by fibers.

The light emitting section 10 has a light emitting element 11 , an isolator 12 and a polarizer 13 . The light emitting element 11 is, for example, a semiconductor laser or a light emitting diode. Specifically, a Fabry-Perot laser, a superluminescence diode, or the like can be used as the light emitting element 11 .

The isolator 12 transmits the light incident from the light emitting element 11 to the circulator 20 side, which is a light branching section, and prevents the light incident from the circulator 20 from transmitting to the light emitting element 11 side. to protect The isolator 12 is, for example, a polarization dependent optical isolator. However, the isolator 12 is not limited to such an example, and may be a polarization independent optical isolator.

The polarizer 13 is an optical element for linearly polarized light emitted from the light emitting element 11, and its type is not particularly limited. The first linearly polarized light obtained by the polarizer 13 is incident on the first optical element 30 via the circulator 20 .

The circulator 20 transmits the first linearly polarized light emitted from the light emitting section 10 to the first optical element 30, and branches the second linearly polarized light emitted from the first optical element 30 to the detection signal generating section 60. It is an optical branching part. Circulator 20 may be formed by, for example, a Faraday rotator, a half-wave plate, a polarizing beam splitter, and a reflective mirror.

The first optical element 30 is, for example, a half-wave plate arranged to have an azimuth angle of 22.5 degrees with respect to the plane of polarization of the first linearly polarized light incident from the circulator 20 . The first optical element 30 rotates the plane of polarization of the first linearly polarized light incident from the circulator 20 by 45 degrees and outputs the first linearly polarized light to the optical path section 40 . The first linearly polarized light whose plane of polarization is rotated 45 degrees by the first optical element 30 is divided into a first linearly polarized light CW1 that is P-polarized light and a second linearly polarized light CCW1 that is S-polarized light orthogonal to the first linearly polarized light CW1. include.

Also, the first optical element 30 rotates the plane of polarization of the second linearly polarized light, which is the linearly polarized light incident from the optical path section 40 , by 45 degrees, and outputs the second linearly polarized light to the circulator 20 .

The optical path section 40 has a first beam splitter 41 , a second beam splitter 42 , a first optical path 43 , a second optical path 44 and a second optical element 45 .

The first beam splitter 41 emits the first linearly polarized light CW<b>1 to the first optical path 43 and the second linearly polarized light CCW<b>1 to the second optical path 44 . The first beam splitter 41 receives the third linearly polarized light CW2 from the second optical path 44 and the fourth linearly polarized light CCW2 from the first optical path 43 . The third linearly polarized light CW2 and the fourth linearly polarized light CCW2 are polarization components of the second linearly polarized light emitted to the first optical element 30 that are orthogonal to each other.

The second beam splitter 42 receives the first linearly polarized light CW<b>1 from the first optical path 43 and the second linearly polarized light CCW<b>1 from the second optical path 44 . The second beam splitter 42 also emits the third linearly polarized light CW2 to the second optical path 44 and the fourth linearly polarized light CCW2 to the first optical path 43 .

The first beam splitter 41 and the second beam splitter 42 split incident light into a P-polarized component and an S-polarized component, and synthesize and emit the P-polarized component and the S-polarized component. The first beam splitter 41 and the second beam splitter 42 are, for example, prism beam splitters. However, it is not limited to such an example, and the first beam splitter 41 and the second beam splitter 42 may be planar beam splitters or wedge beam splitters.

The first optical path 43 guides the first linearly polarized light CW1 introduced from the first beam splitter 41 to the second beam splitter 42, and directs the fourth linearly polarized light CCW2 introduced from the second beam splitter 42 to the first beam splitter 43. 41. The second optical path 44 guides the second linearly polarized light CCW2 introduced from the first beam splitter 41 to the second beam splitter 42, and directs the third linearly polarized light CW2 introduced from the second beam splitter 42 to the first beam splitter 44. 41.

The first optical path 43 is a PANDA fiber with one end optically connected to the first beam splitter 41 and the other end optically connected to the second beam splitter 42 . The second optical path 44 is a PANDA fiber with one end optically connected to the first beam splitter 41 and the other end optically connected to the second beam splitter 42 . The first optical path 43 and the second optical path 44 may be polarization-maintaining fibers such as bow-tie fibers and elliptical jacket fibers. A second optical element 45 is arranged in the second optical path 44 .

The second optical element 45 has a first quarter-wave plate 46 , a second quarter-wave plate 47 and a 45-degree Faraday rotator 48 .

The first quarter-wave plate 46 is a quarter-wave plate 46 arranged with its optical axis tilted 45 degrees with respect to the slow and fast axes of the PANDA fiber forming the second optical path 44 . 4) A wave plate. The first quarter-wave plate 46 converts linear polarization to circular polarization and circular polarization to linear polarization.

The second quarter-wave plate 47 is a quarter-wave plate whose optical axis is inclined by -45 degrees with respect to the slow axis and fast axis of the PANDA fiber forming the second optical path 44. is. A second quarter-wave plate 47 converts the circularly polarized light from the 45 degree Faraday rotator 48 into linearly polarized light and converts the linearly polarized light into circularly polarized light.

The 45-degree Faraday rotator 48 is a Faraday rotator that changes the phase of circularly polarized light incident from each of the first quarter-wave plate 46 and the second quarter-wave plate 47 .

In the 45-degree Faraday rotator 48, the phase of the second linearly polarized light CCW1 emitted from the second quarter-wave plate 47 is the second linearly polarized light incident on the first quarter-wave plate 46. The phase of the circularly polarized light incident from the first quarter-wave plate 46 is changed so that it is 45 degrees out of phase with the polarized light CCW1. Also, the 45-degree Faraday rotator 48 changes the phase of the third linearly polarized light CW2 emitted from the first quarter-wave plate 46 to that of the third linearly polarized light CW2 incident on the second quarter-wave plate 47. Change the phase of the circularly polarized light so that it is -45 degrees out of phase.

The pressure sensor 101 is arranged at the tip of the optical fiber 3 and optically connected to the second beam splitter 42 via the optical fiber 3 . The pressure sensor 101 receives the linearly polarized light emitted from the light emitting unit 10 as incident light, and emits return light corresponding to the pressure applied when the incident light is incident through the optical fiber 3 . .

The detection signal generator 60 has a third beam splitter 61, a first light receiving element 62, a second light receiving element 63, and a signal processing circuit 70, and receives the second linearly polarized light split by the circulator 20. do. The detection signal generation unit 60 separates the second linearly polarized light into an S-polarized component and a P-polarized component, receives the S-polarized component and the P-polarized component, converts them into electrical signals, and differentially amplifies them, thereby generating pressure sensor signals. A detection signal Ed corresponding to the pressure applied to 101 is output.

The third beam splitter 61 is a polarizing beam splitter (PBS) of prism type, planar type, wedge substrate type, optical waveguide type, or the like. The component 65 is separated.

Each of the first light receiving element 62 and the second light receiving element 63 is, for example, a PIN photodiode. The first light receiving element 62 receives the S polarized light component 64 and the second light receiving element 63 receives the P polarized light component 65 . Each of the first light-receiving element 62 and the second light-receiving element 63 photoelectrically converts the received light and outputs an electrical signal corresponding to the amount of received light. The signal processing circuit 70 differentially amplifies the electrical signal representing the S-polarized component and the electrical signal representing the P-polarized component, thereby outputting a detection signal Ed corresponding to the pressure applied to the pressure sensor 101 .

Next, a pressure sensor according to Example 1 will be described. 2A and 2B show cross-sectional views of the pressure sensor 101 according to Example 1 of the present disclosure. FIG. 2(a) shows the state before pressure is applied, and FIG. 2(b) shows the state after pressure is applied.

The pressure sensor 101 has a housing 1 , a magnetic film 2 that is a Faraday rotator, an optical fiber 3 , an elastic film 4 , a moisture-proof film 5 and a magnetic body 6 . The pressure sensor 101 is arranged at the tip of the optical fiber 3 which is a PANDA fiber. is emitted.

The housing 1 has openings that communicate with each other. The housing 1 may, for example, comprise a tubular structure. The housing 1 can be made of silicon, for example. However, it is not limited to such an example. The housing 1 may include a convex portion 1a that protrudes toward the inner periphery. By providing the convex portion 1a, even when pressure is applied to the elastic film 4, it is possible to prevent the housing 1 from being displaced. Also, an adhesive 8 may be used to fix the housing 1 to the optical fiber 3 .

The magnetic film 2 produces the Faraday effect that modulates the optical rotation angle of linearly polarized light by changing the magnetic field. The magnetic film 2 is a granular film having a structure in which nano-order magnetic particles are dispersed in a dielectric. The magnetic film 2 is arranged on the end face of the quarter-wave plate 31 and is a magnetic field sensor element for detecting a magnetic field. As for the magnetic particles, for example, a metal compound such as an oxide may be formed in a small portion such as the outermost layer. It is dispersed alone in the thin film without being formed. The distribution of the magnetic particles in the magnetic film 2 may not be completely uniform, and may be slightly biased. The magnetic film 2 has optical transparency because the magnetic particles are present in the dielectric with a size smaller than the wavelength of light.

The magnetic film 2 is not limited to a single layer, and may be a multilayer film in which granular films and dielectric films are alternately laminated. By forming the magnetic film 2 as a multi-layered granular film, a larger Faraday rotation angle can be obtained by multiple reflection within the granular film.

The dielectric of the magnetic film 2 is preferably a fluoride (metal fluoride) such as magnesium fluoride (MgF ₂ ), aluminum fluoride (AlF ₃ ), yttrium fluoride (YF ₃ ). Dielectrics include tantalum oxide (Ta ₂ O ₅ ), silicon dioxide (SiO ₂ ), titanium dioxide (TiO ₂ ), niobium pentoxide (Nb ₂ O ₅ ), zirconium dioxide (ZrO ₂ ), hafnium dioxide ( HfO ₂ ), and oxides such as aluminum trioxide (Al ₂ O ₃ ). Fluorides are preferable to oxides for good phase separation between the dielectric and the magnetic particles, and magnesium fluoride, which has a high transmittance, is particularly preferable.

The material of the magnetic particles is not particularly limited as long as it produces the Faraday effect. Examples of the material of the magnetic particles include ferromagnetic metals such as iron (Fe), cobalt (Co), nickel (Ni), and alloys thereof. Examples of alloys of Fe, Co and Ni include FeNi alloys, FeCo alloys, FeNiCo alloys, and NiCo alloys. The Faraday rotation angles per unit length of Fe, Co and Ni are two to three orders of magnitude larger than those of magnetic garnets applied to conventional Faraday rotators.

The magnetic film 2 is not limited to the above-described granular film, and any material having optical transparency and Faraday effect may be used, such as conventional magnetic garnet crystals, ferrite, cobalt ferrite, and the like.

It is preferable to further have a reflecting film 7 arranged on the magnetic film 2 and reflecting the incident light from the light source toward the light source. The reflective film 7 is formed on the magnetic film 2 and reflects the light transmitted through the magnetic film 2 toward the magnetic film 2 . As the reflective film 7, for example, a silver (Ag) film, a gold (Au) film, an aluminum (Al) film, or a dielectric multilayer mirror can be used. In particular, an Ag film with high reflectance and an Au film with high corrosion resistance are preferable because the manufacturing process is simple. The thickness of the reflective film 7 may be any size that ensures a sufficient reflectance of 98% or more. By reciprocating light in the magnetic film 2 using the reflective film 7, the Faraday rotation angle can be increased.

The optical fiber 3 allows the linearly polarized light to enter the magnetic film 2 and receives the return light from the magnetic film 2 . The optical fiber 3 may be arranged on one side of the opening of the housing 1 . The optical fiber 3 has a core 32 and a clad 33 . The core 32 is preferably formed by adding germanium dioxide (GeO ₂ ) to silicon dioxide, for example, so that the core 32 has a higher refractive index than the clad 33 made of silicon oxide (SiO ₂ ).

A quarter-wave plate 31 is provided at the tip of the optical fiber 3 . The quarter wave plate 31 is disposed with its optical axis inclined by 45 degrees with respect to the slow axis and fast axis of the optical fiber 3 optically connecting the second beam splitter 42 to the quarter wave plate 31 . wave plate. The quarter-wave plate 31 converts the polarization state of linearly polarized incident light into circularly polarized light, and converts the polarized state of return light incident from the magnetic film 2 as circularly polarized light into linearly polarized light.

The elastic film 4 is arranged at a predetermined distance from the magnetic film 2 on the other side of the opening of the housing 1, which is the side opposite to the side on which the optical fiber 3 is arranged. Moreover, the elastic film 4 is configured such that at least a portion thereof is displaced according to the applied pressure. The elastic membrane 4 preferably contains a resin. For example, polyimide can be used as the resin. However, it is not limited to such an example, and the elastic film 4 may be made of another resin.

By forming the elastic film 4 from a resin such as polyimide, the amount of displacement of the elastic film 4 can be increased even when the pressure applied to the elastic film 4 is small. However, if the resin has moisture permeability, it may expand or contract depending on the external environment, which may cause a problem of unstable zero point in pressure detection. Therefore, in the pressure sensor 101 according to Example 1, the moisture-proof film 5 is provided on the elastic film 4 . The moisture-proof film 5 is formed on the surface of the elastic film 4 opposite to the magnetic film 2 side. By arranging the moisture-proof film 5 on the elastic film 4 , it is possible to prevent permeation of moisture from the external environment to the elastic film 4 .

The moisture-proof film 5 preferably contains a ferromagnetic metal thin film. As the ferromagnetic metal thin film, for example, a thin film containing at least one metal selected from the metal group consisting of iron, cobalt, and nickel can be used. By including the ferromagnetic metal thin film in the moisture-proof film 5, the magnetic material 6 such as a powder magnet can be attracted to the elastic film 4, as will be described later.

The film thickness of the moisture-proof film 5 is preferably 10 to 100 nm. The elastic membrane 4 should be displaced in response to the applied pressure. Even if the moisture-proof film 5 is formed of a ferromagnetic metal thin film, the elastic film provided with the moisture-proof film 5 can be curved according to the displacement of the elastic film 4 if the film thickness is about 10 to 100 nm. Even when pressure is applied to 4, the elastic membrane 4 can be bent.

The magnetic body 6 is arranged on the surface of the elastic film 4 on the magnetic film 2 side. For example, as shown in FIG. 2( a ), when the moisture-proof film 5 is formed on the elastic film 4 and the moisture-proof film 5 contains a magnetic material, the magnetic body 6 is in contact with the moisture-proof film 5 . It is attracted by the magnetic force acting therebetween and can be placed on the elastic membrane 4 . Even if the moisture-proof film 5 does not contain a magnetic material, if the elastic film 4 contains a magnetic material, the magnetic force between the magnetic material contained in the elastic film 4 and the magnetic body 6 is generated. It works so that the magnetic body 6 can be placed on the elastic film 4 .

Also, the magnetic body 6 changes the magnetic field in the magnetic film 2 according to the displacement of the elastic film 4 . It is preferable that the magnetic body 6 includes a powder magnet. The powder magnet that constitutes the magnetic body 6 preferably has a particle size of 1 to 20 μm. The powder magnet that constitutes the magnetic body 6 preferably contains at least one of SmCo (samarium cobalt) and NdFeB (neodymium).

By forming the magnetic body 6 using a powder magnet, the magnetic body 6 can also be deformed according to the deformation of the elastic film 4 . FIG. 3(a) shows an enlarged view of area A in FIG. 2(a), and FIG. 3(b) shows an enlarged view of area B in FIG. 2(b). It is assumed that the magnetic body 6 is arranged on the surface 4 a of the elastic film 4 . For example, it is assumed that powder magnets (6a, 6b, 6c, 6d) are arranged on the surface 4a of the elastic film 4. FIG. At this time, the powder magnets (6a, 6b, 6c, 6d) can move freely on the surface 4a of the elastic membrane 4. FIG. As shown in FIG. 3B, when pressure is applied to the elastic membrane 4, the surface 4b of the elastic membrane 4 is curved. In this case, when the magnetic body 6 comprises powder magnets, the powder magnets (6a, 6b, 6c, 6d) can move along the curved surface 4b. It is possible to maintain a state of close contact with the film 4 .

As shown in FIG. 2(b), when a pressure P1 is applied to the elastic membrane 4 provided with the moisture-proof membrane 5 from the outside of the elastic membrane 4, the elastic membrane 4 moves toward the inside of the housing 1 toward the central portion. is curved like a dent. By bending the elastic film 4 toward the inside of the housing 1 , the top portion 6T of the magnetic body 6 is displaced in the direction of the magnetic film 2 . For example, as shown in FIG. 2A, when the distance from the top portion 6T of the magnetic body 6 to the surface 2a of the magnetic film 2 is d1 before pressure is applied to the elastic film 4, As shown in 2(b), when the pressure P1 is applied to the elastic film 4, the distance from the top portion 6T of the magnetic body 6 to the surface 2a of the magnetic film 2 changes to d2. Here, by applying the pressure P1 to the elastic film 4, the top portion 6T of the magnetic body 6 approaches the surface 2a of the magnetic film 2, so that d2 becomes a value smaller than d1. In this case, as shown in FIG. 2A, if the intensity of the magnetic field on the surface 2a of the magnetic film 2 generated by the magnetic body 6 is H1 before the pressure is applied to the elastic film 4, then FIG. As shown in b), when the pressure P1 is applied to the elastic film 4, the strength of the magnetic field on the surface 2a of the magnetic film 2 changes to H2. A change in magnetic field strength in the magnetic film 2 causes a change in the magnitude of the detected Faraday rotation angle. Therefore, the pressure applied to the elastic membrane 4 can be calculated from the magnitude of the Faraday rotation angle.

Next, a specific measurement example of applied pressure will be described. FIG. 4 is a graph showing the relationship between the pressure applied to the elastic membrane 4 and the amount of deformation of the elastic membrane 4 in the pressure sensor 101 according to Example 1 of the present disclosure. As can be seen from FIG. 4, when the pressure applied to the elastic membrane 4 is increased, the amount of deformation of the elastic membrane 4 increases substantially proportionally. For example, the deformation amount is 6 [μm] when the applied pressure is 150 [mmHg], and the deformation amount is 12 [μm] when the applied pressure is 300 [mmHg].

FIG. 5 is a graph showing the relationship between the deformation amount of the elastic film 4 and the magnetic field intensity of the magnetic film 2 in the pressure sensor 101 according to Example 1 of the present disclosure. From FIG. 5, it can be seen that the magnetic field intensity in the magnetic body 6 increases as the deformation amount of the elastic film 4 increases. For example, the magnetic field strength is 351 [Oe] when the deformation amount of the elastic film 4 is 6 [μm], and the magnetic field strength is 373 [Oe] when the deformation amount of the elastic film 4 is 12 [μm].

From the above measurement examples, the amount of deformation of the elastic film 4 is uniquely determined according to the pressure applied to the elastic film 4, and the amount of change in magnetic field strength in the magnetic film 2 can be calculated from the amount of deformation of the elastic film 4. can. First, the magnetic field strength in the magnetic film 2 before pressure is applied to the elastic film 4 is obtained. In the example shown in FIG. 5, the magnetic field strength is calculated to be 331 [Oe] when the deformation amount of the elastic film 4 is 0 [μm]. By using this value, the relationship between the applied pressure to the elastic film 4 and the amount of change in magnetic field strength in the magnetic film 2 can be obtained. For example, when a pressure of 150 [mmHg] is applied to the elastic film 4, the magnetic field strength in the magnetic film 2 changes from 331 [Oe] to 351 [Oe], so the amount of change in the magnetic field strength is 20 [Oe]. Since the Faraday rotation angle is determined based on the amount of change in the magnetic field strength in the magnetic film 2, the amount of change in the magnetic field strength is calculated from the Faraday rotation angle calculated by the detection signal generator 60, and from the calculated amount of change in the magnetic field strength, The applied pressure to the elastic membrane can be calculated.

Specifically, the circularly polarized light incident on the magnetic film 2 from the quarter-wave plate 31 passes through the magnetic film 2, is reflected by the reflecting film 7, passes through the magnetic film 2 again, and becomes return light. The return light that has passed through the magnetic film 2 is again incident on the quarter-wave plate 31 .

The circularly polarized light incident on the magnetic film 2 from the quarter-wave plate 31 changes its phase according to the magnetic field applied to the magnetic film 2 . The circularly polarized light reflected by the reflective film 7 further changes its phase according to the magnetic field applied to the magnetic film 2 . By using the pressure sensor 101, the pressure applied to the pressure sensor 101 is detected by detecting the amount of change in magnetic field strength in the magnetic film 2 that changes according to the distance between the magnetic film 2 and the magnetic body 6. can do.

The magnetic body 6 preferably has a convex structure projecting toward the magnetic film 2 . Further, the magnetic body 6 may be formed in a conical or pyramidal shape as shown in FIGS. 2(a) and 2(b). By forming the magnetic body 6 into a convex structure, the distance between the magnetic body 6 and the magnetic film 2 can be shortened, and the magnetic field strength in the magnetic film 2 can be increased. Sensitivity can be improved.

[Example 2]
Next, a pressure sensor according to Example 2 will be described. 6A and 6B show cross-sectional views of the pressure sensor 102 according to the second embodiment of the present disclosure. 6(a) shows the state before pressure is applied to the elastic membrane 4, and FIG. 6(b) shows the state after pressure is applied to the elastic membrane 4. FIG. The pressure sensor 102 according to the second embodiment differs from the pressure sensor 101 according to the first embodiment in that the second elastic film 9 is further provided on the magnetic body 6 . Since other configurations of the pressure sensor 102 according to the second embodiment are the same as those of the pressure sensor 101 according to the first embodiment, detailed description thereof will be omitted.

By providing the second elastic film 9 on the surface of the magnetic body 6 on the side of the magnetic film 2, the shape of the magnetic body 6 can be maintained even when the magnetic body 6 is formed of a powder magnet. The second elastic membrane 9 may be formed using the same material as the elastic membrane 4 .

In the example shown in FIGS. 6A and 6B, the example in which the second elastic film 9 is provided so as to cover the magnetic body 6 having a flat shape is shown. Not limited. That is, as shown in FIGS. 2A and 2B, the magnetic body 6 is formed to have a convex structure, and the magnetic body 6 having such a convex structure is covered with the second elastic film. A membrane 9 may be provided. With such a configuration, even when pressure is repeatedly applied to the elastic film 4, the convex structure of the magnetic body 6 can be maintained.

As shown in FIG. 6(b), when a pressure P2 is applied to the elastic film 4 provided with the moisture-proof film 5, the elastic film 4 is displaced so that the central portion thereof is depressed. Along with this, the surface central portion 6U of the magnetic body 6 is displaced in the direction of the magnetic film 2 . For example, as shown in FIG. 6A, when the distance from the surface center portion 6U of the magnetic body 6 to the surface 2a of the magnetic film 2 is d3 in the state before pressure is applied to the elastic film 4, As shown in FIG. 6B, when the pressure P2 is applied to the elastic film 4, the distance from the surface central portion 6U of the magnetic body 6 to the surface 2a of the magnetic film 2 changes to d4. Here, d4 is a value smaller than d3. In this case, assuming that the strength of the magnetic field on the surface 2a of the magnetic film 2 is H3 by the magnetic body 6 before applying pressure to the elastic film 4, as shown in FIG. ), when the pressure P2 is applied to the elastic film 4, the intensity of the magnetic field at the surface 2a of the magnetic film 2 changes to H4.

Also in the pressure sensor 102 according to the second embodiment, the Faraday rotation angle of the magnetic film 2 changes according to the change amount of the magnetic field strength. 4 can be calculated.

REFERENCE SIGNS LIST 1 housing 2 magnetic film 3 optical fiber 4 elastic film 5 moisture-proof film 6 magnetic body 7 reflective film 10 light emitting section 20 circulator 30 first optical element 40 optical path section 60 detection signal generating section 101, 102 pressure sensor

Claims (12)

a housing having a communicating opening;
a magnetic film that produces a Faraday effect that modulates the optical rotation angle of linearly polarized light by changing the magnetic field;
an optical fiber that causes linearly polarized light to enter the magnetic film, receives return light from the magnetic film, and is arranged on one side of the opening;
an elastic film disposed on the other side of the opening at a predetermined distance from the magnetic film and at least a portion of which is displaced according to the applied pressure;
a moisture-proof film formed on the surface of the elastic film on the side opposite to the magnetic film and preventing permeation of moisture into the elastic film;
a magnetic body arranged on the surface of the elastic film on the side of the magnetic film and changing the magnetic field in the magnetic film according to the displacement of the elastic film;
A pressure sensor comprising: 2. The pressure sensor according to claim 1, wherein said elastic membrane contains resin. 3. The pressure sensor according to claim 2, wherein said resin is polyimide. 4. The pressure sensor according to any one of claims 1 to 3, wherein said magnetic body includes a powder magnet. 5. The pressure sensor according to claim 4, wherein the magnetic material has a particle size of 1 to 20 μm. The pressure sensor according to any one of claims 1 to 4, wherein the magnetic material contains at least one of SmCo and NdFeB. 7. The pressure sensor according to any one of claims 1 to 6, wherein said moisture-proof film includes a ferromagnetic metal thin film. The pressure sensor according to any one of claims 1 to 7, wherein the moisture-proof film has a film thickness of 10 to 100 nm. 9. The pressure sensor according to claim 1, wherein said magnetic body has a convex structure projecting toward said magnetic film. 10. The pressure sensor according to claim 1, further comprising a second elastic film on said magnetic film. 11. The pressure sensor according to any one of claims 1 to 10, further comprising a reflecting film disposed on said magnetic film and reflecting incident light from a light source toward the light source. a light-emitting unit having a light source;
12. Optically connected to the pressure sensor according to any one of claims 1 to 11 through the optical fiber, and outputs a detection signal according to the pressure applied to the pressure sensor based on the return light a detection signal generator for
A pressure sensor device having

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