Magnetic field sensor device

Abstract

To provide a magnetic field sensor device with high detection sensitivity.SOLUTION: A magnetic field sensor device 1 comprises: a light emission part 10 emitting incident light which is straight polarization light; a modulation element 11 modulating the incident light to alternately emit first incident light having a first polarization plane and second incident light having a second polarization plane differing in phase from the first polarization plane; a magnetic field sensor element 15 emitting first return light and second return light, which are straight polarization light, obtained by rotating the polarization planes of the first incident light and the second incident light emitted from the modulation element 11 in accordance with a magnetic field to be applied; and a detection signal generation part 20 separating the first return light and the second return light into a P polarization component and an S polarization component, and generating, from the P polarization component and the S polarization component, a detection signal according to a magnetic field in which the magnetic field sensor element is arranged.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] An interferometric optical magnetic field sensor device is known that places a magnetic field sensor element 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 a Faraday rotator (see, for example, Patent Document 1). The interferometric optical magnetic field sensor device described in Patent Document 1 uses a detection signal from which a DC component corresponding to the reference light intensity has been removed, and therefore can increase the signal-to-noise ratio of the detection signal corresponding to the magnetic field to be detected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-126007 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is a demand for a magnetic field sensor device with higher detection sensitivity than the optical magnetic field sensor device described in Patent Document 1.

[0005] The present invention is intended to solve such problems, and has an object to provide a magnetic field sensor device with high detection sensitivity. [Means for solving the problem]

[0006] The magnetic field sensor device of the present invention comprises a light emitting unit that emits incident light, which is linearly polarized light; a modulation element that modulates the incident light and alternately emits first incident light having a first polarization plane and second incident light having a second polarization plane that is out of phase with the first polarization plane; a magnetic field sensor element that emits first return light and second return light, which are linearly polarized light obtained by rotating the polarization planes of the first incident light and second incident light incident from the modulation element in accordance with an applied magnetic field; and a detection signal generation unit that separates each of the first return light and second return light into a P-polarized component and an S-polarized component, and generates a detection signal from the P-polarized component and the S-polarized component that corresponds to the magnetic field in which the magnetic field sensor element is placed.

[0007] Furthermore, in the magnetic field sensor device according to the present invention, it is preferable that the detection signal generation unit includes a polarization separation element that separates each of the first and second return lights into a P-polarized component and an S-polarized component, a first photoelectric conversion element that photoelectrically converts the P-polarized component of the first and second return lights to output a first P-polarized signal and a second P-polarized signal, a second photoelectric conversion element that photoelectrically converts the S-polarized component of the first and second return lights to output a first S-polarized signal and a second S-polarized signal, a first subtraction circuit that subtracts at least a portion of the wavelength component of the second P-polarized signal from at least a portion of the wavelength component of the first P-polarized signal to generate a first differential signal, a second subtraction circuit that subtracts at least a portion of the wavelength component of the second S-polarized signal from at least a portion of the wavelength component of the first S-polarized signal to generate a second differential signal, and a detection signal generation circuit that generates a detection signal based on the first differential signal and the second differential signal and outputs the generated detection signal.

[0008] Furthermore, the magnetic field sensor device according to the present invention preferably further comprises an optical element disposed between the modulation element and the magnetic field sensor element, which rotates the first polarization plane and the second polarization plane by 45 degrees.

[0009] Furthermore, in the magnetic field sensor device according to the present invention, it is preferable that the modulation element modulates the incident light so that the phase difference between the first polarization plane and the second polarization plane becomes 90 degrees.

[0010] Furthermore, the magnetic field sensor device of the present invention further includes a first division circuit that divides the first differential signal by the effective value of the first differential signal to generate a first divided signal, and a second division circuit that divides the second differential signal by the effective value of the second differential signal to generate a second divided signal, and it is preferable that the detection signal generation circuit generates the detection signal from the first divided signal and the second divided signal.

[0011] Furthermore, in the magnetic field sensor device according to the present invention, it is preferable that the modulation element modulates the incident light at a predetermined modulation period, the detection signal generation unit further includes a lock-in amplifier which receives the reference signal, the first P polarized signal, the second P polarized signal, the first S polarized signal, and the second S polarized signal, each having a period equal to the modulation period, and extracts a first P extraction signal, a second P extraction signal, a first S extraction signal, and a second S extraction signal, which are modulated wavelength components corresponding to the modulation periods of the first P polarized signal, the second P polarized signal, the first S polarized signal, and the second S polarized signal, and the first subtraction circuit subtracts the second P extraction signal from the first P extraction signal to generate a first differential signal, and the second subtraction circuit subtracts the second S extraction signal from the first S extraction signal to generate a second differential signal.

[0012] Furthermore, in the magnetic field sensor device according to the present invention, it is preferable that the modulation element emits the first incident light and the second incident light in response to an input of a modulation signal whose period is the modulation period.

[0013] Furthermore, in the magnetic field sensor device according to the present invention, it is preferable that the lock-in amplifier receives a modulated signal as a reference signal. [Effects of the Invention]

[0014] The magnetic field sensor device according to the present invention can increase the detection sensitivity. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram showing a magnetic field sensor device according to an embodiment; [Figure 2]2 is a diagram showing the polarization planes of the first incident light and the second incident light emitted from the modulation element shown in FIG. 1, and the polarization planes of the first incident light and the second incident light emitted from the first optical element shown in FIG. 1. FIG. [Figure 3] FIG. 2 is a circuit diagram of the detection signal generating circuit shown in FIG. [Figure 4] FIG. 10 is a circuit block diagram of a signal generating unit according to a first modified example. [Figure 5] FIG. 10 is a circuit block diagram of a signal generating unit according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0016] The magnetic field 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 the embodiments, but extends to the inventions set forth in the claims and their equivalents.

[0017] (Configuration and Function of Magnetic Field Sensor Device According to the Embodiment) FIG. 1 is a block diagram showing a magnetic field sensor device according to an embodiment.

[0018] The magnetic field sensor device 1 is an interference-type optical magnetic field sensor device having a light-emitting unit 10, a modulation element 11, a circulator 12, a first optical element 13, an optical path unit 14, a magnetic field sensor element 15, and a detection signal generation unit 20. The optical paths between the light-emitting unit 10, the modulation element 11, the circulator 12, the first optical element 13, the optical path unit 14, the magnetic field sensor element 15, and the detection signal generation unit 20 are formed by a PANDA (Polarization-Maintaining and Absorption-Reducing) fiber 16. The outer diameter of the PANDA fiber 16 is, for example, 125 μm. Note that the optical paths between the first optical element 13, the optical path unit 14, the magnetic field sensor element 15, and the detection signal generation unit 20 may also be formed by a polarization-maintaining optical fiber such as a bow-tie fiber or an elliptical jacket fiber.

[0019] The light-emitting unit 10 includes a light-emitting element 10a, an isolator 10b, and a polarizer 10c. The light-emitting element 10a is, for example, a semiconductor laser or a light-emitting diode, and emits incident light that enters the magnetic field sensor element 15 via the circulator 12, the first optical element 13, and the optical path unit 14. Specifically, a Fabry-Perot laser, a superluminescence diode, or the like can be preferably used as the light-emitting element 10a.

[0020] The isolator 10b protects the light emitting element 10a by transmitting the light incident from the light emitting element 10a to the circulator 12 and not transmitting the light incident from the circulator 12 to the light emitting element 10a side. The isolator 10b is, for example, a polarization-dependent optical isolator, but may also be a polarization-independent optical isolator. The polarizer 10c is an optical element for converting the light emitted by the light emitting element 10a into linearly polarized light, and its type is not particularly limited. The input light, which is linearly polarized light obtained by the polarizer 10c, is incident on the modulation element 11.

[0021] The modulation element 11 is a ferroelectric liquid crystal (FLC), and is optically connected to the light emitting section 10 so that input light is incident from the light emitting section 10. The modulation element 11 includes a pulse signal and has a predetermined modulation period T M In response to the input of a modulation signal having a modulation period T M The modulation element 11 modulates the incident light with a first polarization plane and a second polarization plane that is 90 degrees out of phase with the first polarization plane, at a modulation period T M Half period T M / 2 alternates between firing.

[0022] The duty ratio of the modulation signal input to the modulation element 11 is 50%. M Since the duty ratio of the modulated signal is 50%, the pulse width of the pulse signal included in the modulated signal is the modulation period T M Half period T M / 2. When no pulse signal included in the input modulation signal is applied to the modulation element 11, the modulation element 11 transmits the input light incident from the light-emitting unit 10 without modulating it and outputs it to the circulator 12 as first input light. On the other hand, when a pulse signal included in the input modulation signal is applied to the modulation element 11, the modulation element 11 modulates the input light incident from the light-emitting unit 10, rotates the plane of polarization of the incident light by 90 degrees, and outputs the incident light with the rotated plane of polarization to the circulator 12 as second input light.

[0023] The circulator 12 is an optical branching unit that transmits the first incident light and the second incident light emitted from the light emitting unit 10 to the first optical element 13, and branches the first returned light and the second returned light emitted from the first optical element 13 to the detection signal generating unit 20. The first incident light and the second incident light are also simply referred to as incident light, and the first returned light and the second returned light are also simply referred to as returned light. In one example, the circulator 12 is formed by a Faraday rotator, a half-wave plate, a polarizing beam splitter, and a reflecting mirror.

[0024] The first optical element 13 is also simply referred to as an optical element, and in one example is a half-wave plate arranged so that its azimuth angle is 22.5 degrees with respect to the plane of polarization of the first incident light incident from the circulator 12. The first optical element 13 is optically connected to the modulation element 11 via the circulator 12, rotates the planes of polarization of the first incident light and second incident light incident from the circulator 12 by 45 degrees, and outputs the incident light to the optical path section 14. The first optical element 13 is also optically connected to the optical path section 14, rotates the planes of polarization of the first returning light and second returning light, which are linearly polarized light incident from the optical path section 14, by 45 degrees, and outputs the light to the circulator 12.

[0025] FIG. 2 is a diagram showing the polarization planes of the first incident light and the second incident light emitted from the modulation element 11 and the polarization planes of the first incident light and the second incident light emitted from the first optical element 13. As shown in FIG.

[0026] The modulation element 11 receives a modulation signal having a modulation period T M Half period T MThe modulation element 11 transmits the incident light without modulating it over a modulation period T / 2, and outputs the first incident light, which is S-polarized light, to the first optical element 13 via the circulator 12. The modulation element 11 is configured to modulate the first incident light over a modulation period T / 2, in which a pulse signal included in the input modulation signal is applied. M Half period T M 1. The second incident light, which is P-polarized light, is output to the first optical element 13 via the circulator 12. The second incident light is P-polarized light.

[0027] The first optical element 13 is configured to receive the first incident light at a modulation period T M Half period T M / 2, the first optical element 13 rotates the polarization plane of the first incident light and outputs linearly polarized light at 45 degrees to the optical path section 14. Also, the first optical element 13 rotates the polarization plane of the first incident light over a modulation period T M Half period T M / 2, and outputs 135-degree linearly polarized light to the optical path section 14. The first optical element 13 rotates the polarization plane of the second incident light over a modulation period T M Half period T M The light is emitted to the optical path section 14 every 1 / 2.

[0028] The first and second incident lights, whose polarization planes are rotated 45 degrees by the first optical element 13, each have a first linearly polarized light CW1 that is P-polarized and a second linearly polarized light CCW1 that is S-polarized and perpendicular to the first linearly polarized light CW1. The first linearly polarized light CW1 possessed by the first and second incident lights has the same polarization direction. On the other hand, the second linearly polarized light CCW1 possessed by the first and second incident lights has the opposite polarization direction.

[0029] The optical path section 14 has a first beam splitter 14a, a second beam splitter 14b, a first optical path 14c, a second optical path 14d, and a second optical element 14e, and is optically connected to the modulation element 11 via the circulator 12 and the first optical element 13.

[0030] The first beam splitter 14a outputs the first linearly polarized light CW1 to the first optical path 14c and outputs the second linearly polarized light CCW1 to the second optical path 14d. Furthermore, the first beam splitter 14a receives the third linearly polarized light CW2 from the second optical path 14d and the fourth linearly polarized light CCW2 from the first optical path 14c. The third linearly polarized light CW2 and the fourth linearly polarized light CW2 are orthogonal polarization components of the returning light output to the first optical element 13.

[0031] The second beam splitter 14b receives the first linearly polarized light CW1 from the first optical path 14c and the second linearly polarized light CCW1 from the second optical path 14d. The second beam splitter 14b also outputs the third linearly polarized light CW2 to the second optical path 14d and outputs the fourth linearly polarized light CCW2 to the first optical path 14c.

[0032] The first beam splitter 14a and the second beam splitter 14b separate the incident light into a P-polarized component and an S-polarized component, and then combine and output the P-polarized component and the S-polarized component. The first beam splitter 14a and the second beam splitter 14b are, for example, prism-type beam splitters, but may also be planar-type beam splitters or wedge-type beam splitters.

[0033] The first optical path 14c guides the first linearly polarized light CW1 introduced from the first beam splitter 14a to the second beam splitter 14b, and also guides the fourth linearly polarized light CCW2 introduced from the second beam splitter 14b to the first beam splitter 14a. The second optical path 14d guides the second linearly polarized light CCW2 introduced from the first beam splitter 14a to the second beam splitter 14b, and also guides the third linearly polarized light CW2 introduced from the second beam splitter 14b to the first beam splitter 14a.

[0034] The first optical path 14c is a PANDA fiber having one end optically connected to the first beam splitter 14a and the other end optically connected to the second beam splitter 14b. The second optical path 14d is a PANDA fiber having one end optically connected to the first beam splitter 14a and the other end optically connected to the second beam splitter 14b. The first optical path 14c and the second optical path 14d may be polarization-maintaining fibers such as bowtie fibers and elliptical jacket fibers. A second optical element 14e is disposed in the second optical path 14d.

[0035] The second optical element 14e has a first (1 / 4) wave plate 14f, a second (1 / 4) wave plate 14g, and a 45-degree Faraday rotator 14h.

[0036] The first (1 / 4) wave plate 14f 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 14d. The first (1 / 4) wave plate 14f converts linearly polarized light into circularly polarized light and also converts circularly polarized light into linearly polarized light.

[0037] The second (1 / 4) wave plate 14g 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 14d. The second (1 / 4) wave plate 14g converts the circularly polarized light from the 45-degree Faraday rotator 14h into linearly polarized light and also converts the linearly polarized light into circularly polarized light.

[0038] The 45-degree Faraday rotator 14h is a Faraday rotator that changes the phase of the circularly polarized light incident from each of the first (1 / 4) wave plate 14f and the second (1 / 4) wave plate 14g. The 45-degree Faraday rotator 14h changes the phase of the circularly polarized light so that the phase of the second linearly polarized light CCW1 output from the second (1 / 4) wave plate 14g is shifted by 45 degrees from the phase of the second linearly polarized light CCW1 that is linearly polarized and incident on the first (1 / 4) wave plate 14f. The 45-degree Faraday rotator 14h also changes the phase of the circularly polarized light so that the phase of the third linearly polarized light CW2 output from the first (1 / 4) wave plate 14f is shifted by −45 degrees from the phase of the third linearly polarized light CW2 that is incident on the second (1 / 4) wave plate 14g.

[0039] The magnetic field sensor element 15 is disposed at the tip of the PANDA fiber 16, optically connected to the second beam splitter 14b via the PANDA fiber 16, and optically connected to the modulation element 11 via the circulator 12, the first optical element 13, and the optical path section 14. The magnetic field sensor element 15 includes a quarter-wave plate optically connected to the second beam splitter 14b, a Faraday rotator optically connected to the quarter-wave plate, and a mirror element optically connected to the Faraday rotator. The quarter-wave plate is disposed with its optical axis tilted 45 degrees with respect to the slow and fast axes of the PANDA fiber 16, and converts the polarization state of the linearly polarized incident light into circularly polarized light and converts the polarization state of the circularly polarized return light incident from the Faraday rotator into linearly polarized light. The Faraday rotator is a granular film having a dielectric and nano-sized magnetic particles dispersed in the dielectric in a stable phase-separated state from the dielectric, and changes the phase of circularly polarized light by a Faraday rotation angle corresponding to an applied magnetic field. The magnetic field sensor element 15 receives linearly polarized light emitted from the light emitting unit 10 as incident light and also emits return light corresponding to the applied magnetic field when incident light is received via the optical fiber 16.

[0040] The detection signal generating unit 20 has a third beam splitter 21, a first photoelectric conversion element 22, a second photoelectric conversion element 23, a first subtraction circuit 24, a second subtraction circuit 25, and a detection signal generating circuit 26. The detection signal generating unit 20 separates each of the first returned light and the second returned light split by the circulator 12 into a P-polarized component and an S-polarized component, and generates a detection signal Ed corresponding to the magnetic field applied to the magnetic field sensor element 15 from the separated P-polarized component and S-polarized component.

[0041] The third beam splitter 21 is also called a polarization separation element and is a polarization beam splitter (PBS) of a prism type, a plane type, a wedge substrate type, an optical waveguide type, or the like, and splits the return light split by the circulator 12 into an S-polarized component P S and the P-polarized component P P The third beam splitter 21 splits the first returning light into a first P-polarized component P P1 and the first S-polarized component P S1 The second return light is separated into the second P-polarized component P P2 and the second S-polarized component P S2 and separate into.

[0042] The first photoelectric conversion element 22 and the second photoelectric conversion element 23 are, for example, PIN photodiodes. P1 and the second P polarization component P P2 The second photoelectric conversion element 23 receives the first S-polarized component P S1 and the second S-polarized component P S2 The first photoelectric conversion element 22 receives the first P-polarized component P P1 and the second P polarization component P P2 The first polarized component P P1 and the second P polarization component P P2 The first polarized signal I P1 and the second P-polarized signal I P2 to the first subtraction circuit 24. The second photoelectric conversion element 23 outputs the first S-polarized component P S1 and the second S-polarized component P S2 The first S-polarized component P S1 and the second S-polarized component P S2SThe first S-polarized signal I S1 and the second S-polarized signal I S2 is output to the second subtraction circuit 25.

[0043] The first subtraction circuit 24 subtracts the first P polarized signal I input from the first photoelectric conversion element 22. P1 and the second P-polarized signal I P2 a memory for storing a first P polarization signal I P1 from the second P-polarized signal I P2 The first subtraction circuit 24 subtracts the first P polarized signal I P1 from the second P-polarized signal I P2 The first P-polarized signal I P1 and the second P-polarized signal I P2 The first differential signal D1 is generated by subtracting the first differential signal D1 from the first differential signal D2, and the generated first differential signal D1 is output to the detection signal generation circuit 26.

[0044] 1st P polarization signal I P1 The voltage signal E corresponding to P1 is expressed by equation (1), and the second P-polarized signal I P2 The voltage signal E corresponding to P2 is expressed by equation (2). The first P polarized signal I P1 The voltage signal E corresponding to P1 The second P-polarized signal I is expressed by equation (2) P2 The voltage signal E corresponding to P2 The first differential signal D1 generated by subtracting E0 from E0 is expressed by equation (3). In equations (1) to (3), E0 is the light intensity of the incident light.

[0045]

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[0046] The second subtraction circuit 25 subtracts the first S-polarized signal I input from the first photoelectric conversion element 22. S1 and the second S-polarized signal I S2 a memory for storing a first S-polarized signal I S1 from the second S-polarized signal I S2The first subtraction circuit 24 subtracts the first S-polarized signal I from the first S-polarized signal I. S1 from the second S-polarized signal I S2 The first S-polarized signal I is obtained by subtracting S1 from the second S-polarized signal I S2 The second differential signal D2 is generated by subtracting the first differential signal D1 from the second differential signal D2, and the generated second differential signal D2 is output to the detection signal generation circuit 26.

[0047] First S-polarized signal I S1 The voltage signal E corresponding to S1 is expressed by equation (4), and the second S-polarized signal I S2 The voltage signal E corresponding to S2 is expressed by equation (5). The first S-polarized signal I S1 The voltage signal E corresponding to S1 The second S-polarized signal I is expressed by equation (5) S2 The voltage signal E corresponding to S2 The second differential signal D2 generated by subtracting E0 from E0 is expressed by equation (6). In equations (4) to (6), E0 is the light intensity of the incident light.

[0048]

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[0049] FIG. 3 is a circuit diagram of the detection signal generating circuit 26. As shown in FIG.

[0050] The detection signal generating circuit 26 includes a third detection operational amplifier 26a, a third detection resistor 26b, a fourth detection resistor 26c, a fifth detection resistor 26d, and a sixth detection resistor 26e. The non-inverting input terminal of the third detection operational amplifier 26a is connected to one end of the third detection resistor 26b and the fourth detection resistor 26c, and the inverting input terminal of the third detection operational amplifier 26a is connected to one end of the fifth detection resistor 26d and the sixth detection resistor 26e. The output terminal of the third detection operational amplifier 26a is connected to the other end of the sixth detection resistor 26e and outputs a detection signal Ed. The other end of the third detection resistor 26b is connected to one output terminal of the second detection operational amplifier 32a, the other end of the fourth detection resistor 26c is grounded, and the other end of the fifth detection resistor 26d is connected to the output terminal of the first detection operational amplifier 31a.

[0051] The detection signal generating circuit 26 generates a detection signal Ed by subtracting the second differential signal D2 input from the second subtraction circuit 25 from the first differential signal D1 input from the first subtraction circuit 24, and outputs the generated detection signal Ed.

[0052] The detection signal Ed generated by subtracting the second differential signal D2 expressed by the formula (6) from the first differential signal D1 expressed by the formula (3) is expressed by the formula (7).

[0053]

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[0054] (Actions and Effects of the Magnetic Field Sensor Device According to the Embodiment) The magnetic field sensor device 1 has a modulation element 11 that emits a first incident light and a second incident light, and can increase detection sensitivity by detecting the magnetic field applied to the magnetic field sensor element 15 using a first return light and a second return light corresponding to the first incident light and the second incident light, respectively.

[0055] The detection signal Ed generated by the magnetic field sensor device described in Patent Document 1 is expressed by equation (8).

[0056]

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[0057] As shown in equations (7) and (8), the magnetic field sensor device 1 can double the detection sensitivity compared to the magnetic field sensor device described in Patent Document 1.

[0058] (Modification of the magnetic field sensor device according to the embodiment) The magnetic field sensor device 1 is an interference-type optical magnetic field sensor device, but the magnetic field sensor device according to the embodiment may be a magnetic field sensor device other than an interference-type optical magnetic field sensor device as long as it has a modulation element 11. The circuit configuration of the detection signal generation unit 20 included in the magnetic field sensor device according to the embodiment is changed as appropriate depending on the type of the magnetic field sensor device.

[0059] Furthermore, in the magnetic field sensor device 1, an FLC is used as the modulation element 11, but the magnetic field sensor device according to the embodiment may have an element other than an FLC as the modulation element 11 as long as it can alternate the first incident light and the second incident light. The magnetic field sensor device according to the embodiment may have, for example, an LN modulator or a photoelastic modulator (PEM) as the modulation element 11.

[0060] Furthermore, in the magnetic field sensor device 1, the modulation element 11 modulates the incident light so that the first polarization plane of the first incident light and the second polarization plane of the second incident light differ by 90 degrees. However, in the magnetic field sensor device according to the embodiment, the modulation element 11 may modulate the incident light so that the first polarization plane of the first incident light and the second polarization plane of the second incident light differ by a predetermined angle other than 90 degrees. In the magnetic field sensor device 1, the modulation element 11 preferably modulates the incident light so that the angle between the first polarization plane and the second polarization plane is greater than 0 degrees and less than or equal to 180 degrees, and more preferably modulates the incident light so that the angle between the first polarization plane and the second polarization plane is greater than or equal to 60 degrees and less than or equal to 120 degrees.

[0061] Furthermore, in the magnetic field sensor device 1, a first optical element 13 that rotates the first polarization plane and the second polarization plane by 45 degrees is disposed between the modulation element 11 and the magnetic field sensor element 15. However, in the magnetic field sensor device according to the embodiment, the first optical element 13 may be omitted as long as the detection signal generation unit can generate a detection signal.

[0062] Furthermore, the magnetic field sensor device 1 calculates the detection signal Ed using a detection signal generating unit 20 having a third beam splitter 21 to a detection signal generating circuit 26, but the magnetic field sensor device according to the embodiment may calculate the detection signal Ed using a detection signal generating unit having a different configuration.

[0063] FIG. 4 is a circuit block diagram of a detection signal generating unit according to a first modified example.

[0064] The detection signal generation unit 30 differs from the detection signal generation unit 20 in that it has a lock-in amplifier 31, a first subtraction circuit 32, and a second subtraction circuit 33 instead of the first subtraction circuit 24 and the second subtraction circuit 25. The configurations and functions of the components of the detection signal generation unit 30 other than the lock-in amplifier 31, the first subtraction circuit 32, and the second subtraction circuit 33 are the same as the configurations and functions of the components of the detection signal generation unit 20 that are assigned the same reference numerals, so detailed description will be omitted here. The detection signal generation unit 30 can be arranged in the magnetic field sensor device 1 in place of the detection signal generation unit 20.

[0065] The lock-in amplifier 31 receives the first P-polarized signal I from the first photoelectric conversion element 22. P1 and the second P-polarized signal I P2 is input, and the first S-polarized signal I is output from the second photoelectric conversion element 23. S1 and the second S-polarized signal I S2 The lock-in amplifier 31 also receives the modulated signal input to the modulation element 11 as a reference signal. The lock-in amplifier 31 receives the first P-polarized signal I P1 , the second P-polarized signal I P2 , the first S-polarized signal I S1 and the second S-polarized signal I S2The lock-in amplifier 31 extracts a modulated wavelength component corresponding to the frequency of the modulated signal I and outputs the extracted modulated wavelength component as a voltage signal. P1 The first P extracted signal V corresponding to the modulation wavelength component of P1 , and the second P-polarized signal I P2 The second P extracted signal V corresponding to the modulated wavelength component P2 to the first subtraction circuit 32. The lock-in amplifier 31 also outputs the first S-polarized signal I S1 The first S extracted signal V corresponding to the modulation wavelength component of S1 , and a second S-polarized signal I S2 The second S extracted signal V corresponding to the modulated wavelength component of S2 is output to the second subtraction circuit 33.

[0066] The first subtraction circuit 32 outputs the first P extraction signal V P1 and the second P extraction signal V P2 is input from the lock-in amplifier 31. The first subtraction circuit 32 subtracts the first P extraction signal V P1 The first PS extracted signal V P2 to obtain the first P extraction signal V P1 The first PS extracted signal V P2 The first subtraction circuit 32 subtracts the first difference signal D1 from the first difference signal D2 and outputs the generated first difference signal D1 to the detection signal generation circuit .

[0067] The second subtraction circuit 33 subtracts the first S extraction signal V S1 and the second S extraction signal V S2 is input from the lock-in amplifier 31. The second subtraction circuit 33 subtracts the first S extraction signal V S1 The second S extracted signal V S2 The first S extraction signal V S1 The second S extracted signal V S2 The second subtraction circuit 33 subtracts the second difference signal D2 from the detected signal. The second subtraction circuit 33 outputs the generated second difference signal D2 to the detected signal generation circuit .

[0068] The magnetic field sensor device according to the embodiment has a detection signal generating unit 30 that extracts modulated wavelength components using a lock-in amplifier 31, and therefore can reduce the noise level to about 1 / 10 of that of the magnetic field sensor device 1 that does not have a lock-in amplifier 31. The magnetic field sensor device according to the embodiment has a detection signal generating unit 30 that extracts modulated wavelength components using a lock-in amplifier 31, and therefore can significantly reduce the noise level and increase the detection sensitivity.

[0069] The lock-in amplifier 31 receives the modulated signal input to the modulation element 11 as a reference signal, but may also receive a signal having a predetermined frequency other than the modulated signal as a reference signal.

[0070] FIG. 5 is a circuit block diagram of a detection signal generating unit according to the second modification.

[0071] The detection signal generating unit 40 differs from the detection signal generating unit 20 in that it has a first division circuit 41 and a second division circuit 42. The configurations and functions of the components of the detection signal generating unit 40 other than the first division circuit 41 and the second division circuit 42 are the same as the configurations and functions of the components of the detection signal generating unit 20 that are assigned the same reference numerals, and therefore detailed description thereof will be omitted here. The detection signal generating unit 40 can be arranged in the magnetic field sensor device 1 in place of the detection signal generating unit 20.

[0072] The first division circuit 41 receives the first difference signal D1 from the first subtraction circuit 24. The first division circuit 41 extracts the DC component of the first difference signal D1, i.e., the first effective value M1, which is the effective value, from the first subtraction circuit 24. The first division circuit 41 divides the first difference signal D1 by the first effective value M1 to generate a first division signal R1, and outputs the generated first division signal R1 to the detection signal generation circuit 26. The first division signal R1 is expressed by equation (9).

[0073]

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[0074] The second division circuit 42 receives the second difference signal D2 from the second subtraction circuit 25. The second division circuit 42 extracts a second effective value M2, which is the effective value of the second difference signal D2, from the second subtraction circuit 25. The second division circuit 42 divides the second difference signal D2 by the second effective value M2 to generate a second division signal R2, and outputs the generated second division signal R2 to the detection signal generation circuit 26. The first division signal R1 is expressed by equation (10).

[0075]

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[0076] The detection signal generation circuit 26 generates a detection signal Ed by subtracting the second division signal R2 input from the second division circuit 41 from the first division signal R1 input from the first division circuit 41, and outputs the generated detection signal Ed. The detection signal Ed is expressed by equation (11).

[0077]

number

[0078] In the detection signal generation unit 40, the detection signal Ed does not include the intensity E0 of the incident light. Because the detection signal Ed does not include the intensity E0 of the incident light, it is not affected by fluctuations in the light intensity of the incident light emitted from the light emitting element 10a and fluctuations in light intensity due to optical loss in optical transmission paths such as the optical path unit 14. In the detection signal generation unit 40, the detection signal Ed is not affected by fluctuations in light intensity, so it is possible to detect the magnetic field applied to the magnetic field sensor element 15 with higher accuracy.

[0079] Although the detection signal generating unit 40 does not have the lock-in amplifier 31, the detection signal generating unit according to the embodiment may have the lock-in amplifier 31 in addition to the first division circuit 41 and the second division circuit 42. By having the lock-in amplifier 31 in addition to the first division circuit 41 and the second division circuit 42, the detection signal generating unit according to the embodiment can further reduce the noise level and increase the detection sensitivity. [Explanation of symbols]

[0080] 1. Magnetic field sensor device 10 Light-emitting part 11 Modulation element 12 Circulator 13 First optical element (optical element) 14 Optical path section 15 Magnetic field sensor element 20, 30, 40 Detection signal generation unit 21 Third beam splitter 22 First photoelectric conversion element 23 Second photoelectric conversion element 24, 32 First subtraction circuit 25, 33 Second subtraction circuit 26 Detection signal generation circuit

Claims

1. a light emitting unit that emits incident light that is linearly polarized light; a modulation element that modulates the incident light and alternately outputs a first incident light having a first polarization plane and a second incident light having a second polarization plane that is out of phase with the first polarization plane; a magnetic field sensor element that outputs first return light and second return light, which are linearly polarized light obtained by rotating the polarization planes of the first incident light and the second incident light that are incident from the modulation element in accordance with an applied magnetic field; a detection signal generating unit that separates each of the first return light and the second return light into a P-polarized component and an S-polarized component, and generates a detection signal corresponding to a magnetic field in which the magnetic field sensor element is disposed, from the P-polarized component and the S-polarized component; A magnetic field sensor device comprising:

2. The detection signal generation unit a polarization splitter that splits each of the first return light and the second return light into a P-polarized component and an S-polarized component; a first photoelectric conversion element that photoelectrically converts the P-polarized components of the first returned light and the second returned light to output a first P-polarized signal and a second P-polarized signal; a second photoelectric conversion element that photoelectrically converts the S-polarized components of the first returned light and the second returned light to output a first S-polarized signal and a second S-polarized signal; a first subtraction circuit that subtracts at least a portion of the wavelength component of the second P-polarized signal from at least a portion of the wavelength component of the first P-polarized signal to generate a first difference signal; a second subtraction circuit that subtracts at least a portion of the wavelength component of the second S-polarized signal from at least a portion of the wavelength component of the first S-polarized signal to generate a second difference signal; a detection signal generating circuit that generates the detection signal based on the first differential signal and the second differential signal and outputs the generated detection signal; The magnetic field sensor device according to claim 1 , wherein

3. The magnetic field sensor device according to claim 2 , further comprising an optical element disposed between the modulation element and the magnetic field sensor element, for rotating the first polarization plane and the second polarization plane by 45 degrees.

4. 3. The magnetic field sensor device according to claim 2, wherein the modulation element modulates the incident light so that the phase difference between the first polarization plane and the second polarization plane is 90 degrees.

5. a first division circuit that divides the first difference signal by an effective value of the first difference signal to generate a first divided signal; a second divider circuit that divides the second difference signal by an effective value of the second difference signal to generate a second divided signal, The magnetic field sensor device according to claim 2 , wherein the detection signal generating circuit generates the detection signal from the first divided signal and the second divided signal.

6. the modulation element modulates the incident light at a predetermined modulation period; the detection signal generation unit further includes a lock-in amplifier that receives a reference signal whose period is the modulation period, the first P polarized signal, the second P polarized signal, the first S polarized signal, and the second S polarized signal, and extracts a first P extracted signal, a second P extracted signal, a first S extracted signal, and a second S extracted signal, which are modulated wavelength components corresponding to the modulation periods of the first P polarized signal, the second P polarized signal, the first S polarized signal, and the second S polarized signal; the first subtraction circuit subtracts the second P extraction signal from the first P extraction signal to generate a first difference signal; 6. The magnetic field sensor device according to claim 2, wherein the second subtraction circuit subtracts the second S extraction signal from the first S extraction signal to generate a second difference signal.

7. The magnetic field sensor device according to claim 6 , wherein the modulation element emits the first incident light and the second incident light in response to an input of a modulation signal whose period is a modulation period.

8. The magnetic field sensor device according to claim 7 , wherein the lock-in amplifier receives the modulated signal as the reference signal.

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