Magnetic field sensor head, pressure sensor head, magnetic field sensor device, and pressure sensor device

Abstract

To provide a magnetic field sensor head capable of suppressing a decrease in measurement accuracy due to a magnetic field applied from a magnetic body arranged in the vicinity of a Faraday rotator.SOLUTION: A magnetic field sensor head 50a includes: an optical element 52 having a first surface and a second surface, which diverges incident light incident on the first surface and emits it from the second surface, and which focuses return light incident on the second surface and emits it from the first surface; a Faraday rotator 54 that is disposed so that the incident light emitted from the second surface is incident thereon and the return light is emitted to the second surface, and that rotates polarization planes of the incident light and the return light by a rotation angle according to an applied magnetic field when the incident light and the return light pass through; a mirror element 55 that emits the return light to the Faraday rotator in response to an incidence of the incident light from the Faraday rotator; a magnetic body 57 that applies a magnetic field to the Faraday rotator; and a compensation element 53 that is arranged so that the incident light is emitted to the Faraday rotator and the return light is incident from the Faraday rotator, and that compensates for the rotation angle.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a magnetic field sensor head, a pressure sensor head, a magnetic field sensor device, and a pressure sensor device. [Background technology]

[0002] An interference-type optical magnetic field sensor device is known that has a magnetic field sensor element with a Faraday rotator disposed at the tip of an optical fiber, and photoelectrically converts light transmitted through the magnetic field sensor element to generate a detection signal corresponding to the magnetic field applied to the Faraday rotator (see, for example, Patent Document 1). The interference-type optical magnetic field sensor device described in Patent Document 1 uses a detection signal from which the DC component corresponding to the reference light intensity has been removed, thereby increasing the signal-to-noise ratio of the detection signal and improving the detection accuracy of the magnetic field.

[0003] Also known is a pressure sensor device that includes a magnetic body, a magnetic field sensor element disposed close to the magnetic body, and a pressure sensor having a pressure-receiving element that holds the magnetic body so that the distance between the magnetic field sensor element and the magnetic body changes in response to the application of pressure (see, for example, Patent Document 2). The pressure sensor device described in Patent Document 2 can be manufactured more easily than a pressure sensor device that uses a Fabry-Perot resonator, and therefore the manufacturing cost can be reduced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-126007 A [Patent Document 2] JP 2022-118688 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the pressure sensor device described in Patent Document 2, the Faraday rotator is placed in close proximity to the magnetic material, which may result in various noises caused by the magnetic field applied from the magnetic material to the Faraday rotator, resulting in a decrease in measurement accuracy.

[0006] The present invention is devised to solve such problems, and has an object to provide a magnetic field sensor head that can suppress a decrease in measurement accuracy caused by a magnetic field applied from a magnetic body placed in close proximity to a Faraday rotator. [Means for solving the problem]

[0007] The magnetic field sensor head of the present invention has a first surface and a second surface, and comprises an optical element that diverges incident light incident on the first surface and emits it from the second surface, and focuses returning light incident from the second surface and emits it from the first surface; a Faraday rotator that is arranged so that incident light emitted from the second surface enters and emits returning light to the second surface, and that rotates the polarization planes of the incident light and the returning light by a rotation angle corresponding to an applied magnetic field when the incident light and the returning light pass through; a mirror element that emits returning light to the Faraday rotator in response to the incident light being incident from the Faraday rotator; a magnetic body that applies a magnetic field to the Faraday rotator; and a compensation element that is arranged so that incident light exits the Faraday rotator and returning light enters from the Faraday rotator, and that compensates for the rotation angle.

[0008] Furthermore, in the magnetic field sensor head according to the present invention, it is preferable that the Faraday rotator is made of a soft magnetic material, and the compensation element is made of a hard magnetic material.

[0009] Furthermore, in the magnetic field sensor head according to the present invention, the magnetization direction of the compensation element is preferably opposite to the magnetization direction of the magnetic body that applies a magnetic field to the Faraday rotator.

[0010] Furthermore, in the magnetic field sensor head according to the present invention, the compensating element preferably compensates for the amount of shift of the rotation angle due to a change in temperature.

[0011] Furthermore, in the magnetic field sensor head according to the present invention, it is preferable that the absolute values ​​of the shift amounts due to temperature changes in the rotation angles of the polarization planes of the Faraday rotator and the compensation element are equal to each other, and that the rotation directions of the polarization planes of the Faraday rotator and the compensation element are opposite to each other.

[0012] Furthermore, in the magnetic field sensor head according to the present invention, the compensation element preferably compensates for a rotation angle caused by a magnetic field applied from the magnetic body.

[0013] Furthermore, in the magnetic field sensor head of the present invention, the absolute value of the rotation angle of the polarization plane when the incident light and the returned light pass through the compensation element is equal to the absolute value of the rotation angle of the polarization plane when the incident light and the returned light pass through the Faraday rotator when a magnetic field applied from a magnetic material is applied to the Faraday rotator, and it is preferable that the rotation directions of the polarization planes of the Faraday rotator and the compensation element are opposite.

[0014] Furthermore, in the magnetic field sensor head according to the present invention, the compensation element is preferably disposed between the optical element and the Faraday rotator.

[0015] Furthermore, the magnetic field sensor head according to the present invention preferably further comprises a transmission element disposed between the compensation element and the Faraday rotator, for transmitting the incident light and the return light.

[0016] Furthermore, in the magnetic field sensor head according to the present invention, the compensation element is preferably disposed opposite the first surface.

[0017] Furthermore, the magnetic field sensor head according to the present invention preferably further comprises a pressure-receiving element that holds the magnetic body so that the distance between the Faraday rotator and the magnetic body changes in response to the application of pressure.

[0018] In addition, the pressure sensor head of the present invention has an optical element having a first surface and a second surface, which diverges incident light incident on the first surface and emits it from the second surface, and focuses returning light incident from the second surface and emits it from the first surface; a Faraday rotator arranged so that the incident light emitted from the second surface is incident on and emits returning light to the second surface, and which rotates the polarization planes of the incident light and the returning light when the incident light and the returning light pass through the Faraday rotator by a rotation angle corresponding to an applied magnetic field; a mirror element that emits returning light to the Faraday rotator in response to the incident light being incident from the Faraday rotator; a magnetic body that applies a magnetic field to the Faraday rotator; a compensation element arranged so that the incident light is emitted to the Faraday rotator and the returning light is incident from the Faraday rotator, which compensates for the rotation angle; and a pressure-receiving element that holds the magnetic body so that the distance between the Faraday rotator and the magnetic body changes in response to the application of pressure.

[0019] Also, a magnetic field sensor device according to the present invention comprises: a light-emitting unit that emits incident light; an optical fiber optically connected to the light-emitting unit; a magnetic field sensor head that is disposed at the tip of the optical fiber and emits return light in response to an applied pressure when the incident light is incident via the optical fiber; and a detection signal generating unit that is optically connected to the magnetic field sensor head via the optical fiber and outputs a detection signal in response to the pressure applied to the magnetic field sensor head based on the return light, the magnetic field sensor head having a first surface and a second surface, and disperses the incident light incident on the first surface and emits it from the second surface, and disperses the return light incident on the second surface. The optical element includes an optical element that focuses light and emits it from a first surface, a Faraday rotator that is arranged so that incident light that has exited from the second surface enters the Faraday rotator and emits returned light to the second surface, and that rotates the polarization planes of the incident light and the returned light by a rotation angle corresponding to an applied magnetic field when the incident light and the returned light pass through the Faraday rotator, a mirror element that emits returned light to the Faraday rotator in response to the incident light being incident from the Faraday rotator, a magnetic body that applies a magnetic field to the Faraday rotator, and a compensation element that is arranged so that the incident light exits the Faraday rotator and the returned light enters the Faraday rotator and that compensates for the rotation angle.

[0020] Also, a pressure sensor device according to the present invention includes a light emitting unit that emits incident light, an optical fiber optically connected to the light emitting unit, a pressure sensor head that is disposed at the tip of the optical fiber and emits return light corresponding to an applied pressure when the incident light is incident via the optical fiber, and a detection signal generating unit that is optically connected to the pressure sensor head via the optical fiber and outputs a detection signal corresponding to a pressure applied to the pressure sensor head based on the return light, the pressure sensor head having a first surface and a second surface, an optical element that diverges the incident light incident on the first surface and emits it from the second surface, and focuses the return light incident from the second surface and emits it from the first surface, and a detection signal generating unit that outputs a detection signal corresponding to the pressure applied to the pressure sensor head based on the return light. the Faraday rotator is arranged so that incident light is incident on the second surface and returns light to the second surface, and when the incident light and the returned light are transmitted through the Faraday rotator, the Faraday rotator rotates the polarization planes of the incident light and the returned light by a rotation angle corresponding to an applied magnetic field; a mirror element that emits returned light to the Faraday rotator in response to the incident light being incident from the Faraday rotator; a magnetic body that applies a magnetic field to the Faraday rotator; a compensation element that is arranged so that incident light is output to the Faraday rotator and returned light is incident from the Faraday rotator, and that compensates for the rotation angle; and a pressure-receiving element that holds the magnetic body so that the distance between the Faraday rotator and the magnetic body changes in response to the application of pressure. Effect of the Invention

[0021] The magnetic field sensor head according to the present invention can suppress a decrease in measurement accuracy caused by a magnetic field applied from a magnetic body arranged in the vicinity of a Faraday rotator. [Brief description of the drawings]

[0022] [Figure 1] 1 is a block diagram showing a magnetic field sensor device according to a first embodiment. [Diagram 2] 2 is an enlarged cross-sectional view of a portion indicated by dashed line A in FIG. [Diagram 3] 3A is a diagram showing an example of a magnetization curve of the compensation element shown in FIG. 2, and FIG. 3B is a diagram showing an example of a magnetization curve of the Faraday rotator shown in FIG. [Figure 4]3 is a diagram showing the amount of shift in the Faraday rotation angle due to temperature change in each of the compensation element shown in FIG. 2 and the Faraday rotator shown in FIG. 2 to which a magnetic field is applied from a magnetic body. [Diagram 5] 3 is a diagram showing changes in the Faraday rotation angle of incident light sequentially passing through the compensating element and the Faraday rotator shown in FIG. 2, and of returned light sequentially passing through the Faraday rotator and the compensating element. [Figure 6] 3(a) is an oblique view (part 1) of the pressure-receiving element shown in FIG. 2, (b) is an oblique view (part 2) of the pressure-receiving element shown in FIG. 2, and (c) is an oblique cross-sectional view of the pressure-receiving element along line BB in (a). [Figure 7] FIG. 2A is a diagram showing the pressure sensor when no pressure is applied, and FIG. 2B is a diagram showing the pressure sensor when pressure is applied. [Figure 8] FIG. 11 is a block diagram showing a magnetic field sensor device according to a second embodiment. [Figure 9] 9 is an enlarged cross-sectional view of a portion indicated by dashed line C in FIG. 8. [Figure 10] 10(a) is an oblique view (part 1) of the retaining element shown in FIG. 9, (b) is an oblique view (part 2) of the retaining element shown in FIG. 9, and (c) is an oblique cross-sectional view of the retaining element along line DD in (a). [Figure 11] 13 is a diagram showing the relationship between the magnetic field of a compensation element in the magnetic field sensor head according to the first modified example and the magnetic field applied to a Faraday rotator from a magnetic body. FIG. [Figure 12] 13 is a diagram showing changes in the Faraday rotation angle of incident light that is transmitted successively through a compensation element and a Faraday rotator, and of returned light that is transmitted successively through the Faraday rotator and a compensation element, in a magnetic field sensor head according to a first modified example. FIG. [Figure 13] FIG. 13(a) is a diagram showing a magnetic field sensor head according to a second modified example, and FIG. 13(b) is a diagram showing a magnetic field sensor head according to a third modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, a magnetic field sensor device and a magnetic field sensor head according to the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to the embodiments, but extends to the inventions described in the claims and their equivalents.

[0024] (Configuration and Functions of the Magnetic Field Sensor Device According to the First Embodiment) FIG. 1 is a block diagram showing a magnetic field sensor device according to the first embodiment.

[0025] The magnetic field sensor device 1 includes a light emitting unit 10, a circulator 20, a first optical element 30, an optical path unit 40, a magnetic field sensor head 50a, and a detection signal generating unit 60, and is also referred to as a pressure sensor device. The optical paths between the light emitting unit 10, the circulator 20, the first optical element 30, the optical path unit 40, the magnetic field sensor head 50a, and the detection signal generating unit 60 are formed by a PANDA (Polarization-maintaining AND Absorption-reducing) fiber 80. The outer diameter of the PAND fiber 80 is 125 μm, for example. The optical paths between the first optical element 30, the optical path unit 40, the magnetic field sensor head 50a, and the detection signal generating unit 60 may be formed by a polarization-maintaining optical fiber such as a bow-tie fiber or an elliptical jacket fiber.

[0026] The light emitting section 10 includes 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, the light emitting element 11 may preferably be a Fabry-Perot laser, a superluminescence diode, or the like.

[0027] The isolator 12 transmits the light incident from the light emitting element 11 to the circulator 20 side, and does not transmit the light incident from the circulator 20 to the light emitting element 11 side, thereby protecting the light emitting element 11. The isolator 12 is, for example, a polarization-dependent optical isolator, and may also be a polarization-independent optical isolator.

[0028] The polarizer 13 is an optical element for converting the light emitted by the light emitting element 11 into linearly polarized light, and the type of the polarizer 13 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.

[0029] The circulator 20 is an optical branching unit that transmits the first linearly polarized light emitted from the light emitting unit 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 unit 60. The circulator 20 is formed by, for example, a Faraday rotator, a half-wave plate, a polarizing beam splitter, and a reflecting mirror.

[0030] The first optical element 30 is, for example, a half-wave plate arranged so that the azimuth angle is 22.5 degrees with respect to the polarization plane of the first linearly polarized light incident from the circulator 20. The first optical element 30 rotates the polarization plane of the first linearly polarized light incident from the circulator 20 by 45 degrees and emits the first linearly polarized light to the optical path section 40. The first linearly polarized light whose polarization plane has been rotated 45 degrees by the first optical element 30 has 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.

[0031] Moreover, 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 portion 40, by 45 degrees, and outputs the second linearly polarized light to the circulator 20.

[0032] The optical path section 40 includes 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 .

[0033] The first beam splitter 41 outputs the first linearly polarized light CW1 to the first optical path 43, and outputs the second linearly polarized light CCW1 to the second optical path 44. In addition, 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 CW2 are polarization components of the second linearly polarized light output to the first optical element 30 that are orthogonal to each other.

[0034] The second beam splitter 42 receives the first linearly polarized light CW1 from the first optical path 43 and the second linearly polarized light CCW1 from the second optical path 44. In addition, the second beam splitter 42 outputs the third linearly polarized light CW2 to the second optical path 44 and outputs the fourth linearly polarized light CCW2 to the first optical path 43.

[0035] The first beam splitter 41 and the second beam splitter 42 separate the incident light into a P-polarized component and an S-polarized component, and then combine 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-type beam splitters, but may also be flat-type beam splitters or wedge-type beam splitters.

[0036] 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 also guides the fourth linearly polarized light CCW2 introduced from the second beam splitter 42 to the first beam splitter 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 also guides the third linearly polarized light CW2 introduced from the second beam splitter 42 to the first beam splitter 41.

[0037] The first optical path 43 is a PANDA fiber having 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 having one end optically connected to the first beam splitter 41 and the other end optically connected to the second beam splitter 42. Note that the first optical path 43 and the second optical path 44 may be polarization maintaining fibers such as a bowtie fiber and an elliptical jacket fiber. A second optical element 45 is disposed in the second optical path 44.

[0038] The second optical element 45 has a first (¼) wave plate 46, a second (¼) wave plate 47, and a 45-degree Faraday rotator .

[0039] The first (1 / 4) wave plate 46 is a 1 / 4 wave plate whose optical axis is inclined at 45 degrees with respect to the slow axis and fast axis of the PANDA fiber forming the second optical path 44. The first (1 / 4) wave plate 46 converts linearly polarized light into circularly polarized light and also converts circularly polarized light into linearly polarized light.

[0040] The second (1 / 4) wave plate 47 is a 1 / 4 wave plate arranged with its optical axis tilted at -45 degrees with respect to the slow axis and fast axis of the PANDA fiber forming the second optical path 44. The second (1 / 4) wave plate 47 converts the circularly polarized light from the 45 degree Faraday rotator 48 into linearly polarized light, and also converts the linearly polarized light into circularly polarized light.

[0041] The 45-degree Faraday rotator 48 is a Faraday rotator that changes the rotation angle of the circularly polarized light incident from each of the first (¼) wave plate 46 and the second (¼) wave plate 47.

[0042] The 45-degree Faraday rotator 48 changes the rotation angle of the circularly polarized light incident from the first (¼) waveplate 46 such that the rotation angle of the second linearly polarized light CCW1 output from the second (¼) waveplate 47 is shifted by 45 degrees from the rotation angle of the second linearly polarized light CCW1, which is the linearly polarized light incident on the first (¼) waveplate 46. In addition, the 45-degree Faraday rotator 48 changes the rotation angle of the circularly polarized light such that the rotation angle of the third linearly polarized light CW2 output from the first (¼) waveplate 46 is shifted by −45 degrees from the rotation angle of the third linearly polarized light CW2 incident on the second (¼) waveplate 47.

[0043] The magnetic field sensor head 50a is a pressure sensor head that is disposed at the tip of a PANDA fiber 80, optically connected to the second beam splitter 42 via the PANDA fiber 80, and inserted into a relatively narrow place such as a patient's blood vessel. The magnetic field sensor head 50a receives linearly polarized light emitted by the light emitting unit 10 as incident light, and emits return light according to the applied pressure when incident light is received via the optical fiber 80.

[0044] The detection signal generating unit 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. The detection signal generating unit 60 splits 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 to output a detection signal Ed corresponding to the pressure applied to the magnetic field sensor head 50a. The third beam splitter 61 is a polarizing beam splitter (PBS) such as a prism type, a flat type, a wedge substrate type, or an optical waveguide type, and splits the second linearly polarized light split by the circulator 20 into an S-polarized component 64 and a P-polarized component 65.

[0045] 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 an S-polarized component 64, and the second light receiving element 63 receives a P-polarized 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 light received. The signal processing circuit 70 differentially amplifies the electrical signal indicating the S-polarized component and the electrical signal indicating the P-polarized component, thereby outputting a detection signal Ed corresponding to the pressure applied to the magnetic field sensor head 50a.

[0046] FIG. 2 is an enlarged cross-sectional view of a portion indicated by dashed line A in FIG.

[0047] The magnetic field sensor head 50a has a quarter-wave element 51, an optical element 52, a compensation element 53, a Faraday rotator 54, a mirror element 55, a pressure-receiving element 56, and a magnetic body 57. The magnetic field sensor head 50a is disposed at the tip of a PANDA fiber 80, and emits return light in response to pressure applied to the pressure-receiving element 56 when incident light is incident via the optical path section 40 and the PANDA fiber 80. The optical element 52, the compensation element 53, the Faraday rotator 54, the mirror element 55, and the pressure-receiving element 56 have the same outer diameter.

[0048] The quarter-wave element 51 is a PANDA fiber whose optical axis is inclined at 45 degrees with respect to the slow and fast axes of the PANDA fiber 80 that optically connects to the second beam splitter 42, and whose length is one-fourth of the beat length. The quarter-wave element 51 functions as a polarization state switching element that switches the polarization state between linearly polarized light and circularly polarized light, similar to a quarter-wave plate. The quarter-wave element 51 converts the polarization state of the linearly polarized incident light into circularly polarized light, and also converts the polarization state of the return light that is incident as circularly polarized light from the Faraday rotator 54 into linearly polarized light.

[0049] The optical element 52 is, for example, a SELFOC (registered trademark) lens, has a first surface 521 and a second surface 522, and is disposed between the ¼ wavelength element 51 and the compensation element 53. The optical element 52 outputs the incident light Li incident from the ¼ wavelength element 51 to the compensation element 53, and outputs the return light Lr incident from the compensation element 53 to the ¼ wavelength element 51. The ¼ wavelength element 51 is bonded to the first surface 521 by an adhesive member 52a such that the core of the PANDA fiber forming the ¼ wavelength element 51 is positioned at the center of the first surface 521. The second surface 522 is disposed opposite to the first surface 521, and the compensation element 53, the Faraday rotator 54, and the mirror element 55 are disposed adjacent to each other in this order. The optical element 52 diverges the incident light Li incident on the first surface 521 and emits it from the second surface 522 , and focuses the return light Lr incident on the second surface 522 and emits it from the first surface 521 .

[0050] The compensation element 53 and the Faraday rotator 54 are formed of a bismuth-substituted rare-earth iron garnet (Bi-RIG) single crystal, and are Faraday rotators that rotate the polarization planes of the incident light Li and the returned light Lr. The compensation element 53 is a hard magnetic material, and the Faraday rotator 54 is a soft magnetic material. The compensation element 53 is disposed between the optical element 52 and the Faraday rotator 54. The Faraday rotator 54 is disposed between the compensation element 53 and the mirror element 55.

[0051] FIG. 3(a) is a diagram showing an example of the magnetization curve of the compensation element 53, and FIG. 3(b) is a diagram showing an example of the magnetization curve of the Faraday rotator 54. In FIGS. 3(a) and 3(b), the horizontal axis indicates the applied magnetic field [kOe], and the vertical axis indicates the magnetic flux density [T]. FIG. 3(a) was created using a sample having a square planar shape with a side of 5.4 [mm] and a thickness of 418 [μm]. FIG. 3(b) was created using a sample having a square planar shape with a side of 0.3 [mm] and a thickness of 80 [μm]. In FIG. 3(a), the waveform W101 shows the magnetization curve in the normal direction of the plane of the sample, and the waveform W102 shows the magnetization curve in the direction parallel to the extension direction of the plane of the sample. In FIG. 3(b), the waveform W201 shows the magnetization curve in the normal direction of the plane of the sample, and the waveform W202 shows the magnetization curve in the direction parallel to the extension direction of the plane of the sample.

[0052] 3(a), the compensating element 53 functions as a hard magnetic material having a large coercive force Hc and residual magnetic flux density Br when the magnetization direction is the normal direction. The coercive force Hc of the compensating element 53 is, for example, 500 [Oe], and the compensating element 53 is a magnetic material having a residual magnetic flux density Br while a magnetic field less than the coercive force Hc is applied. When a magnetic field equal to or greater than the coercive force Hc is applied to the compensating element 53, the magnetization direction is reversed, and the compensating element 53 becomes a magnetic material having a residual magnetic flux density of -Br.

[0053] 3(b), the Faraday rotator 54 functions as a soft magnetic body having a coercive force Hc of approximately zero. The Faraday rotator 54 is a magnetic body that changes the magnetic flux density in response to the magnetic field applied from the magnetic body 57.

[0054] FIG. 4 is a diagram showing the shift amount of the Faraday rotation angle due to the temperature change of the compensation element 53 and the Faraday rotator 54 to which a magnetic field is applied from the magnetic material 57. In FIG. 4, the dotted line L101 shows the shift amount of the Faraday rotation angle due to the temperature change of the compensation element 53, and the dotted line L102 shows the shift amount of the Faraday rotation angle due to the temperature change of the Faraday rotator 54. The straight line L101 was generated using a sample having a square planar shape with a side of 0.25 mm and a thickness of 78 μm. The straight line L102 was generated using a sample having a square planar shape with a side of 0.25 mm and a thickness of 88 μm, which is disposed 0.1 mm away from a permanent magnet with a magnetic flux density of 1.0 T. The magnetization directions of the samples used to generate the straight lines L101 and L102 are opposite to each other.

[0055] As indicated by dotted lines L101 and L102, the Faraday rotation angles of the compensating element 53 and the magnetic body 57 change linearly in response to temperature changes in the range of 22.5° C. to 42.0° C. The rate of change of the Faraday rotation angle of the compensating element 53 in response to temperature changes is almost independent of the area of ​​the compensating element 53 and increases as the thickness of the compensating element 53 increases.

[0056] The rate of change of the Faraday rotation angle of the Faraday rotator 54 in response to temperature change is determined by the area and thickness of the Faraday rotator 54, the magnetic flux density of the magnetic body 57, and the distance between the Faraday rotator 54 and the magnetic body 57. The rate of change of the Faraday rotation angle of the Faraday rotator 54 in response to temperature change increases as the area of ​​the Faraday rotator 54 increases and as the thickness of the Faraday rotator 54 increases. The rate of change of the Faraday rotation angle of the Faraday rotator 54 in response to temperature change increases as the magnetic flux density of the magnetic body 57 increases and as the distance from the magnetic body 57 decreases.

[0057] In the magnetic field sensor head 50a, the compensating element 53, the Faraday rotator 54, and the magnetic body 57 are arranged so that the rates of change of the Faraday rotation angle of the compensating element 53 and the Faraday rotator 54 in response to temperature change are equal, and the magnetization directions of the compensating element 53 and the magnetic body 57 are opposite. In the magnetic field sensor head 50a, the rates of change of the Faraday rotation angle in response to temperature change are equal, and the magnetization directions of the compensating element 53 and the magnetic body 57 are opposite, so that the compensating element 53 can compensate for the shift amount of the Faraday rotation angle of the Faraday rotator 54 due to temperature change.

[0058] The mirror element 55 is formed on the Faraday rotator 54 and reflects the light transmitted through the Faraday rotator 54 toward the Faraday rotator 54. For example, a silver (Ag) film, a gold (Au) film, an aluminum (Al) film, or a dielectric multilayer mirror can be used as the mirror element 55. In particular, an Ag film having a high reflectance and an Au film having a high corrosion resistance are preferable because they are easy to form. The thickness of the mirror element 55 may be any thickness that can ensure a sufficient reflectance of 98% or more. For example, in the case of an Ag film, the thickness is preferably 50 nm or more and 200 nm or less. The Faraday rotation angle can be increased by using the mirror element 55 to make the light go back and forth within the Faraday rotator 54.

[0059] FIG. 5 is a diagram showing changes in the Faraday rotation angle of the incident light Li that is transmitted through the compensation element 53 and the Faraday rotator 54 in this order, and the returned light Lr that is transmitted through the Faraday rotator 54 and the compensation element 53 in this order.

[0060] The incident light Li and the return light Lr are transmitted through the compensation element 53, and the polarization plane of the light Li and the return light Lr is changed to −θ F (t) rotates, and passes through the Faraday rotator 54, changing the polarization plane to θ F (t) Rotate. θ F (t) is the amount of shift in the Faraday rotation angle that changes with temperature. The amount of shift θ of the rotation angle of the polarization plane of the Faraday rotator 54 and the compensation element 53 due to temperature change F The absolute values ​​of (t) are equal to each other. Furthermore, the directions of rotation of the polarization plane of the Faraday rotator 54 and the compensation element 53 are opposite to each other.

[0061] The incident light Li is transmitted through the compensation element 53 and changes its polarization plane to −θ F (t) The incident light Li then rotates its polarization plane to -θ F (t) By passing the light through the Faraday rotator 54 while rotating it, the polarization plane is changed to θ F (t) The light rotates, and the polarization plane returns to the state before passing through the compensating element 53.

[0062] The return light Lr is transmitted through the Faraday rotator 54 and changes its polarization plane to θ F (t) Rotate the polarization plane of the return light Lr by θ F (t) By transmitting the light through the compensation element 53 in the rotated state, the polarization plane is changed to −θ F (t) rotates, and the polarization plane returns to the state before passing through the Faraday rotator 54.

[0063] Figure 6(a) is a perspective view (part 1) of the pressure-receiving element 56, Figure 6(b) is a perspective view (part 2) of the pressure-receiving element 56, and Figure 6(c) is a perspective cross-sectional view of the pressure-receiving element 56 along line BB in Figure 6(a).

[0064] The pressure-receiving element 56 has a base 561, a support portion 562, and an elastic portion 563, and is formed by cutting silicon, which is capable of being micro-machined with high precision, using laser processing, etching processing, or the like.

[0065] The base 561 has a cylindrical shape with an outer diameter equal to the outer diameters of the compensating element 53, the Faraday rotator 54, and the mirror element 55. An opening 565 in which the magnetic body 57 is disposed is formed on one side of the base 561, and an elastic part 563 is disposed on the other side.

[0066] The support part 562 has a cylindrical shape, one end of which is connected to the center of the elastic part 563, and is disposed inside the base 561. The magnetic body 57 is disposed at the tip of the support part 562. The magnetic body 57 is disposed at the tip of the cylindrical support part, and is thereby disposed in close proximity to the Faraday rotator 54.

[0067] The elastic portion 563 has a spiral or helical shape and is disposed on the other side surface of the base 561, with a water-repellent film formed of a hydrophobic material such as a fluorine-based substance disposed on the outer surface. A single groove 564 extending in a spiral curve is formed between the elastic portions 563. The groove formed between the elastic portions 563 is formed so as to extend along an Archimedes' spiral having the center of the bottom surface of the support portion 562 as its origin. By forming the groove formed between the elastic portions 563 so as to extend along the Archimedes' spiral, the width of the elastic portions 563 becomes uniform.

[0068] When the elastic portion 563 is pressed from the outside, it bends toward the inside of the base 561. When the elastic portion 563 bends toward the inside of the base 561, it moves the support portion 562 arranged in the center of the elastic portion 563 toward the opening 585. When the support portion 562 moves toward the opening 585, the magnetic body 57 arranged at the tip of the support portion 562 moves in a direction approaching the Faraday rotator 54.

[0069] The magnetic body 57 is a thin-film permanent magnet having a circular planar shape that is the same shape as the diameter of the support portion 562. The magnetic body 57 is, for example, an iron-platinum (Fe-Pt) magnet. The magnetic body 57 may be a permanent magnet other than an iron-platinum magnet, such as a neodymium-iron-boron (Nd-Fe-B) magnet or a samarium-cobalt (Sm-Co) magnet. However, when the magnetic field sensor head 50a is inserted inside the human body, the magnetic body 57 is preferably an iron-platinum magnet that has little effect on the human body.

[0070] FIG. 7(a) is a diagram showing the magnetic field sensor head 50a in a state where no pressure is applied, and FIG. 7(b) is a diagram showing the magnetic field sensor head 50a in a state where pressure is applied.

[0071] In the magnetic field sensor head 50a, when pressure is applied from the outside of the elastic portion 563, the elastic portion 563 curves toward the inside of the base 561. In response to the elastic portion 563 curving toward the inside of the base 561, the magnetic body 57 moves in the direction of the Faraday rotator 54.

[0072] As the magnetic body 57 moves toward the Faraday rotator 54, the magnetic field H applied to the Faraday rotator 54 increases. The magnetic field H applied to the Faraday rotator 54 increases linearly with the decrease in the distance D between the Faraday rotator 54 and the magnetic body 57.

[0073] The circularly polarized light incident on the Faraday rotator 54 from the quarter-wave element 51 passes through the Faraday rotator 54, is reflected by the mirror element 55, and passes through the Faraday rotator 54 again to become returned light. The returned light transmitted through the Faraday rotator 54 is incident on the quarter-wave element 51 again.

[0074] The circularly polarized light incident on the Faraday rotator 54 from the quarter-wave element 51 changes its rotation angle in response to the magnetic field applied to the Faraday rotator 54. In addition, the circularly polarized light reflected by the mirror element 55 further changes its rotation angle in response to the magnetic field applied to the Faraday rotator 54.

[0075] (Functions and Effects of the Magnetic Field Sensor Device According to the First Embodiment) The magnetic field sensor device 1 can suppress a decrease in measurement accuracy caused by the magnetic field applied from the magnetic body 57 by using the compensating element 53 to compensate for the shift amount of the Faraday rotation angle of the Faraday rotator 54 caused by a change in temperature.

[0076] In addition, in the magnetic field sensor device 1, the compensation element 53 is formed from a hard magnetic material, so that the change in magnetic flux density due to the magnetic field applied from the magnetic material 57 is small, and the rotation of the polarization plane of the incident light Li and the returned light Lr in the Faraday rotator 54 can be compensated for with high precision.

[0077] In addition, in the magnetic field sensor device 1, the magnetization direction of the compensation element 53 is opposite to the magnetization direction of the magnetic body 57 that applies a magnetic field to the Faraday rotator 54, so that the compensation element 53 can compensate for the rotation of the polarization plane of the incident light Li and the returned light Lr in the Faraday rotator 54 due to the magnetic field applied from the magnetic body 57.

[0078] (Configuration and Functions of the Magnetic Field Sensor Device According to the Second Embodiment) FIG. 8 is a block diagram showing the magnetic field sensor device according to the second embodiment.

[0079] The magnetic field sensor device 2 differs from the magnetic field sensor device 1 in that it has a magnetic field sensor head 50b instead of the magnetic field sensor head 50a. The configurations and functions of the components of the magnetic field sensor device 2 other than the magnetic field sensor head 50b are the same as those of the magnetic field sensor device 1 with the same reference numerals, and therefore detailed description thereof will be omitted here.

[0080] FIG. 9 is an enlarged cross-sectional view of a portion indicated by dashed line C in FIG.

[0081] The magnetic field sensor head 50b differs from the magnetic field sensor head 50a in that it has a holding element 58 instead of the pressure-receiving element 56. The configurations and functions of the components of the magnetic field sensor head 50b other than the holding element 58 are the same as those of the magnetic field sensor head 50a with the same reference numerals, and therefore detailed description thereof will be omitted here.

[0082] Figure 10(a) is an oblique view (part 1) of the retaining element 58, Figure 10(b) is an oblique view (part 2) of the retaining element 58, and Figure 10(c) is an oblique cross-sectional view of the retaining element 58 along line DD in Figure 10(a).

[0083] The holding element 58 has a base 581, a support portion 582, and a holding portion 583, and is formed by cutting silicon using laser processing, etching processing, or the like, similarly to the pressure-receiving element 56.

[0084] Similar to the base 561, the base 581 has a cylindrical shape with an outer diameter equal to the outer diameters of the compensating element 53, the Faraday rotator 54, and the mirror element 55. An opening 585 in which the magnetic body 57 is disposed is formed on one side of the base 581, and a holder 583 is disposed on the other side.

[0085] The support part 582 has a cylindrical shape, one end of which is connected to the center of the holder 583, and is disposed inside the base 581. The magnetic body 57 is disposed at the tip of the support part 582. The magnetic body 57 is disposed at the tip of the cylindrical support part, and is thereby disposed in close proximity to the Faraday rotator 54.

[0086] Holding portion 583 has a circular planar shape, and is disposed so as to close the other side surface of base 581. At the center of holding portion 583, support portion 582 is disposed.

[0087] (Modification of the magnetic field sensor head according to the embodiment) In the magnetic field sensor heads 50a and 50b, the compensation element 53 compensates for the shift in the Faraday rotation angle due to temperature changes, but in the magnetic field sensor head of the embodiment, the compensation element 53 may also compensate for the Faraday rotation angle due to the magnetic field applied from the magnetic body 57.

[0088] Fig. 11 is a diagram showing the relationship between the magnetic field of the compensation element 53 in the magnetic field sensor head according to the first modification and the magnetic field applied to the Faraday rotator 54 from the magnetic body 57. In Fig. 11, the horizontal axis represents the magnetic field, and the vertical axis represents the magnetic flux density.

[0089] In the magnetic field sensor head according to the first modification, the magnetic field Hr of the compensation element 53 is equal to the magnetic field Hm applied from the magnetic body 57 to the Faraday rotator 54. The magnetic field Hr of the compensation element 53 is determined by adjusting the area and thickness of the compensation element 53. The magnetic field Hm applied from the magnetic body 57 to the Faraday rotator 54 is determined by adjusting the area and thickness of the Faraday rotator 54, the magnetic flux density of the magnetic body 57, and the separation distance between the Faraday rotator 54 and the magnetic body 57. The magnetic field sensor head according to the first modification can be mounted on either of the magnetic field sensor devices 1 and 2.

[0090] FIG. 12 is a diagram showing the change in the Faraday rotation angle of the incident light Li, which passes successively through the compensation element 53 and the Faraday rotator 54, and the returned light Lr, which passes successively through the Faraday rotator 54 and the compensation element 53, in the magnetic field sensor head of the first modified example.

[0091] The incident light Li and the return light Lr are transmitted through the compensation element 53, and the polarization plane of the light Li and the return light Lr is changed to −θ Fr The light is then rotated and transmitted through the Faraday rotator 54, changing the polarization plane to θ Fm Rotate. θ Fr and θ Fm The rotation angle θ when the incident light Li and the return light Lr pass through the compensation element 53 is equal to each other. Fr The absolute value of is equal to the absolute value of the rotation angle when the incident light Li and the returned light Lr pass through the Faraday rotator 54 when the magnetic field applied from the magnetic body 57 is applied to the Faraday rotator 54. The directions of rotation of the polarization planes of the Faraday rotator 54 and the compensation element 53 are opposite to each other.

[0092] The incident light Li is transmitted through the compensation element 53 and changes its polarization plane to −θ Fr Then, the incident light Li rotates its polarization plane to −θ Fr By passing the light through the Faraday rotator 54 in a rotated state, the polarization plane is changed to θ Fm The polarization plane is rotated and returns to the state it was in before passing through the compensating element 53 .

[0093] The return light Lr is transmitted through the Faraday rotator 54 and changes its polarization plane to θ Fm Then, the polarization plane of the return light Lr is rotated by θ Fm By passing the light through the compensation element 53 in the rotated state, the polarization plane is changed to −θ Fr The plane of polarization is rotated back to the state it was in before passing through the Faraday rotator 54.

[0094] In the magnetic field sensor head of the first modified example, the compensation element 53 compensates for the Faraday rotation angle of the Faraday rotator 54 due to the magnetic field applied from the magnetic body 57, so that the magnetic field applied from the outside can be detected with high accuracy without being affected by the magnetic field applied from the magnetic body 57.

[0095] Furthermore, in the magnetic field sensor heads 50a and 50b, the compensation element 53 is disposed adjacent to the Faraday rotator 54, but in the magnetic field sensor head according to the embodiment, the compensation element 53 may be disposed away from the Faraday rotator 54.

[0096] FIG. 13(a) is a diagram showing a magnetic field sensor head according to a second modified example, and FIG. 13(b) is a diagram showing a magnetic field sensor head according to a third modified example.

[0097] The magnetic field sensor head 50c according to the second modification is different from the magnetic field sensor head 50a in that it has a transmission element 59. The configurations and functions of the components of the magnetic field sensor head 50c other than the transmission element 59 are the same as those of the magnetic field sensor head 50a with the same reference numerals, and therefore detailed description thereof will be omitted here. The magnetic field sensor head according to the second modification can be mounted on either the magnetic field sensor device 1 or 2.

[0098] The transmitting element 59 is formed of a light-transmitting member such as glass that transmits the incident light Li and the returned light Lr, and is disposed between the compensating element 53 and the Faraday rotator 54. The thickness of the transmitting element 59 is set so that the distance between the compensating element 53 and the magnetic body 57 is such that the magnetic field applied from the magnetic body 57 to the compensating element 53 is smaller than the holding force of the compensating element 53. The transmitting element 59 outputs the incident light Li incident from the compensating element 53 to the Faraday rotator 54. The transmitting element 59 also outputs the returned light Lr incident from the Faraday rotator 54 to the compensating element 53.

[0099] The magnetic field sensor head 50c can make the separation distance between the compensating element 53 and the magnetic body 57 longer than that of the magnetic field sensor head 50a by disposing the transmission element 59 between the compensating element 53 and the Faraday rotator 54. By making the separation distance between the compensating element 53 and the magnetic body 57 longer, the magnetic field sensor head 50c can reduce the risk of the magnetization direction of the compensating element 53 being reversed when a magnetic field exceeding the coercive force Hc of the compensating element 53 is applied from the magnetic body 57 to the compensating element 53.

[0100] The magnetic field sensor head 50d according to the third modification is different from the magnetic field sensor head 50a in the positional relationship between the optical element 52 and the compensation element 53. The configuration and function of the magnetic field sensor head 50d other than the positional relationship between the optical element 52 and the compensation element 53 are the same as the configuration and function of the magnetic field sensor head 50a, so detailed description will be omitted here. The magnetic field sensor head according to the third modification can be mounted on either the magnetic field sensor device 1 or 2.

[0101] The optical element 52 is disposed between the compensation element 53 and the Faraday rotator 54 such that a first surface 521 of the optical element 52 faces the compensation element 53. The optical element 52 outputs the incident light Li incident from the compensation element 53 to the Faraday rotator 54. In addition, the optical element 52 outputs the return light Lr incident from the Faraday rotator 54 to the compensation element 53.

[0102] The compensation element 53 is disposed between the ¼ wavelength element 51 and the optical element 52. The compensation element 53 outputs the incident light Li incident from the ¼ wavelength element 51 to the optical element 52. The compensation element 53 also outputs the return light Lr incident from the optical element 52 to the ¼ wavelength element 51.

[0103] The magnetic field sensor head 50c can make the separation distance between the compensating element 53 and the magnetic body 57 longer than that of the magnetic field sensor head 50a by disposing the compensating element 53 between the 1 / 4 wavelength element 51 and the optical element 52. By making the separation distance between the compensating element 53 and the magnetic body 57 longer, the magnetic field sensor head 50c can reduce the risk of the magnetization direction of the compensating element 53 being reversed due to a magnetic field exceeding the holding force Hc of the compensating element 53 being applied from the magnetic body 57 to the compensating element 53. [Explanation of symbols]

[0104] 1, 2 Magnetic field sensor device 10 Light emitting unit 20 Circulator 30 First optical element 40 Optical path section 50a, 50b, 50c, 50d Magnetic field sensor head 51 1 / 4 wavelength element 52 Optical Elements 53 Compensation element 54 Faraday Rotator 55 Mirror element 56 Pressure receiving element 57 Magnetic material 58 Retaining element 60 Detection signal generator

Claims

1. an optical element having a first surface and a second surface, diverging incident light incident on the first surface and emitting the same from the second surface, and converging return light incident on the second surface and emitting the same from the first surface; a Faraday rotator that is disposed so that the incident light emitted from the second surface is incident thereon and the returned light is emitted from the second surface, and that rotates the polarization planes of the incident light and the returned light by a rotation angle according to an applied magnetic field when the incident light and the returned light are transmitted through the Faraday rotator; a mirror element that emits the return light to the Faraday rotator in response to the incident light from the Faraday rotator; a magnetic body that applies a magnetic field to the Faraday rotator; a compensation element that is disposed so that the incident light is emitted to the Faraday rotator and the return light is incident from the Faraday rotator, and that compensates for the rotation angle; A magnetic field sensor head comprising:

2. the Faraday rotator is a soft magnetic material, 2. The magnetic field sensor head of claim 1, wherein the compensation element is a hard magnetic material.

3. the magnetization direction of the compensation element is opposite to the magnetization direction of the magnetic body that applies a magnetic field to the Faraday rotator; 3. The magnetic field sensor head according to claim 2.

4. 4. The magnetic field sensor head according to claim 1, wherein the compensation element compensates for a shift amount of the rotation angle due to a change in temperature.

5. the absolute values ​​of the shift amounts of the rotation angles of the polarization plane of the Faraday rotator and the compensation element due to temperature change are equal to each other, 5. The magnetic field sensor head of claim 4, wherein the Faraday rotator and the compensating element rotate the plane of polarization in opposite directions.

6. 4. The magnetic field sensor head according to claim 1, wherein the compensation element compensates for the rotation angle caused by the magnetic field applied from the magnetic body.

7. an absolute value of a rotation angle of the polarization plane when the incident light and the return light pass through the compensation element is equal to an absolute value of a rotation angle of the polarization plane when the incident light and the return light pass through the Faraday rotator when a magnetic field applied from the magnetic body is applied to the Faraday rotator, 7. The magnetic field sensor head of claim 6, wherein the Faraday rotator and the compensating element rotate the plane of polarization in opposite directions.

8. The magnetic field sensor head of claim 1 , wherein the compensation element is disposed between the optical element and the Faraday rotator.

9. 9. The magnetic field sensor head according to claim 8, further comprising a transmission element disposed between said compensation element and said Faraday rotator, said transmission element transmitting said incident light and said return light.

10. The magnetic field sensor head according to claim 1 , wherein the compensation element is disposed opposite the first surface.

11. 2. The magnetic field sensor head according to claim 1, further comprising a pressure-receiving element that holds the magnetic body so that a distance between the Faraday rotator and the magnetic body changes in response to application of pressure.

12. an optical element having a first surface and a second surface, diverging incident light incident on the first surface and emitting the same from the second surface, and converging return light incident on the second surface and emitting the same from the first surface; a Faraday rotator that is disposed so that the incident light emitted from the second surface is incident thereon and the returned light is emitted from the second surface, and that rotates the polarization planes of the incident light and the returned light by a rotation angle according to an applied magnetic field when the incident light and the returned light are transmitted through the Faraday rotator; a mirror element that emits the return light to the Faraday rotator in response to the incident light from the Faraday rotator; a magnetic body that applies a magnetic field to the Faraday rotator; a compensation element that is disposed so that the incident light is emitted to the Faraday rotator and the return light is incident from the Faraday rotator, and that compensates for the rotation angle; a pressure-receiving element that holds the magnetic body so that a distance between the Faraday rotator and the magnetic body changes in response to application of pressure; A pressure sensor head comprising:

13. A light emitting unit that emits incident light; an optical fiber optically connected to the light emitting unit; a magnetic field sensor head disposed at a tip of the optical fiber, the magnetic field sensor head emitting return light in response to an applied pressure when the incident light is incident through the optical fiber; a detection signal generating unit that is optically connected to the magnetic field sensor head via the optical fiber and outputs a detection signal corresponding to a pressure applied to the magnetic field sensor head based on the return light, and the magnetic field sensor head includes: an optical element having a first surface and a second surface, diverging incident light incident on the first surface and emitting the same from the second surface, and converging return light incident on the second surface and emitting the same from the first surface; a Faraday rotator that is disposed so that the incident light emitted from the second surface is incident thereon and the returned light is emitted from the second surface, and that rotates the polarization planes of the incident light and the returned light by a rotation angle according to an applied magnetic field when the incident light and the returned light are transmitted through the Faraday rotator; a mirror element that emits the return light to the Faraday rotator in response to the incident light from the Faraday rotator; a magnetic body that applies a magnetic field to the Faraday rotator; a compensation element that is disposed so that the incident light is emitted to the Faraday rotator and the return light is incident from the Faraday rotator, and that compensates for the rotation angle; A magnetic field sensor device comprising:

14. A light emitting unit that emits incident light; an optical fiber optically connected to the light emitting unit; a pressure sensor head that is disposed at a tip of the optical fiber and that emits return light corresponding to an applied pressure when the incident light is incident through the optical fiber; a detection signal generating unit that is optically connected to the pressure sensor head via the optical fiber and outputs a detection signal corresponding to a pressure applied to the pressure sensor head based on the return light, and the pressure sensor head includes: an optical element having a first surface and a second surface, diverging incident light incident on the first surface and emitting the same from the second surface, and converging return light incident on the second surface and emitting the same from the first surface; a Faraday rotator that is disposed so that the incident light emitted from the second surface is incident thereon and the returned light is emitted from the second surface, and that rotates the polarization planes of the incident light and the returned light by a rotation angle according to an applied magnetic field when the incident light and the returned light are transmitted through the Faraday rotator; a mirror element that emits the return light to the Faraday rotator in response to the incident light from the Faraday rotator; a magnetic body that applies a magnetic field to the Faraday rotator; a compensation element that is disposed so that the incident light is emitted to the Faraday rotator and the return light is incident from the Faraday rotator, and that compensates for the rotation angle; a pressure-receiving element that holds the magnetic body so that a distance between the Faraday rotator and the magnetic body changes in response to application of pressure; A pressure sensor device comprising:

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