Optically pumped magnetic sensor

Abstract

This optically pumped magnetic sensor comprises: a laser unit that includes a laser element and a support member; a cell unit that includes a cell in which an alkali metal is enclosed; a photodetector; and a support that defines a space in an optical path of a laser light in which at least a portion of the laser element side is located. The support member has a first surface perpendicular to an optical axis of the laser element. The support has a second surface perpendicular to the optical axis of the laser element. The support member and the support are shaped such that the support member is movable relative to the support in a direction perpendicular to the optical axis of the laser element and in a state in which the first surface and the second surface face each other. The support member and the support are fixed to each other in a state in which the first surface and the second surface face each other.

Description

Optically Pumped Magnetic Sensor

[0001] The present disclosure relates to an optically pumped magnetic sensor.

[0002] An optically pumped magnetic sensor including a laser unit including a laser element that emits laser light, a cell unit including a cell filled with an alkali metal, and a photodetector that detects the laser light emitted from the laser element and passing through the cell is known (see, for example, Patent Document 1).

[0003] U.S. Patent No. 10955495

[0004] In the optically pumped magnetic sensor as described above, the detection sensitivity of the magnetic field may decrease due to some cause.

[0005] An object of the present disclosure is to provide an optically pumped magnetic sensor capable of suppressing a decrease in the detection sensitivity of a magnetic field.

[0006] The optically pumped magnetic sensor according to one aspect of the present disclosure is [1] "a laser unit including a laser element that emits laser light and a support member that supports the laser element, a cell unit including a cell filled with an alkali metal, a photodetector that detects the laser light emitted from the laser element and passing through the cell, and a support that defines a space in which at least a portion on the laser element side of the optical path of the laser light from the laser element to the cell is located, the support member has a first surface perpendicular to the optical axis of the laser element, the support has a second surface perpendicular to the optical axis of the laser element, the support member and the support are shaped such that the support member is movable in a direction perpendicular to the optical axis of the laser element with respect to the support in a state where the first surface and the second surface face each other, and the first surface and the second surface are fixed to each other in a state where they face each other", an optically pumped magnetic sensor.

[0007] In the above-described optically excited magnetic sensor, a laser element that emits laser light is supported by a support member, and the space in which at least the portion of the laser light path on the laser element side is located is defined by a support body. The support member and the support body have a shape such that the support member can move relative to the support body in a direction perpendicular to the optical axis of the laser element, with the first and second surfaces perpendicular to the optical axis of the laser element facing each other. This allows the position of the optical axis of the laser element to be adjusted in a direction perpendicular to the optical axis of the laser element during the manufacturing of the optically excited magnetic sensor. As a result, an optically excited magnetic sensor can be obtained in which the support member and the support body are fixed relative to each other in a state in which the laser light emitted from the laser element travels appropriately through the cell to the photodetector. Therefore, the above-described optically excited magnetic sensor can suppress a decrease in the detection sensitivity of the magnetic field.

[0008] One aspect of the present disclosure is an optically excited magnetic sensor, which may be [2] "the optically excited magnetic sensor described in [1] above, wherein each of the support member and the support body is made of resin." With this optically excited magnetic sensor, since the materials of the support member and the support body are non-magnetic materials, a decrease in magnetic field detection sensitivity caused by the materials of the support member and the support body can be suppressed. On the other hand, since the materials of the support member and the support body are resin, it is difficult to achieve high mechanical precision with respect to them. However, as described above, since it is possible to fix the support member and the support body to each other after adjusting the position of the optical axis of the laser element, a decrease in magnetic field detection sensitivity caused by the mechanical precision of the support member and the support body can be suppressed.

[0009] One aspect of the present disclosure is the optically excited magnetic sensor described in [1] or [2] above, wherein each of the first and second surfaces extends to surround the laser element when viewed from a direction parallel to the optical axis of the laser element. With this optically excited magnetic sensor, the position of the optical axis of the laser element in a direction perpendicular to the optical axis of the laser element can be stably adjusted during the manufacture of the optically excited magnetic sensor.

[0010] One aspect of the optically excited magnetic sensor of this disclosure is [4] "the optically excited magnetic sensor according to [3] above, wherein the outer edge of the second surface is located outside the outer edge of the first surface when viewed from the direction parallel to the optical axis of the laser element." With this optically excited magnetic sensor, the position adjustment of the optical axis of the laser element in a direction perpendicular to the optical axis of the laser element can be performed more stably during the manufacture of the optically excited magnetic sensor.

[0011] One aspect of the present disclosure is an optically excited magnetic sensor, which may be [5] "an optically excited magnetic sensor according to any one of [1] to [4] above, wherein the support member and the support body are fixed to each other with the first surface and the second surface in contact with each other." With this optically excited magnetic sensor, the position of the optical axis of the laser element in a direction perpendicular to the optical axis of the laser element can be stably adjusted during the manufacture of the optically excited magnetic sensor.

[0012] One aspect of the present disclosure is a photo-excited magnetic sensor, which may be [6] "a photo-excited magnetic sensor according to any one of [1] to [5] above, wherein the support supports the cell unit and the photodetector." The photo-excited magnetic sensor allows for a simplification of the support structure of the cell unit and the photodetector.

[0013] One aspect of the present disclosure is the optically excited magnetic sensor according to any one of [1] to [6] above, further comprising a lens unit including a collimating lens disposed on the optical path, wherein the support has a housing portion on which the lens unit is disposed, the lens unit and the support have a shape such that the lens unit is movable relative to the support in the direction of extension of the optical path with respect to the support, with the outer surface of the lens unit and the inner surface of the housing portion facing each other, and the outer surface and the inner surface are fixed to each other with respect to each other. With this optically excited magnetic sensor, the position of the collimating lens can be adjusted in the direction of extension of the optical path of the laser light during the manufacture of the optically excited magnetic sensor. As a result, an optically excited magnetic sensor can be obtained in which the lens unit and the support are fixed to each other in a state in which the laser light emitted from the laser element is appropriately collimated. This suppresses the spreading of the laser light emitted from the laser element, and the laser light travels appropriately through the cell to the photodetector, thereby suppressing a decrease in the detection sensitivity of the magnetic field.

[0014] One aspect of the present disclosure is the photo-excited magnetic sensor described in [7] above, wherein the lens unit further includes a cylindrical holder, the collimating lens is disposed within the holder, and the outer surface of the lens unit is the outer surface of the holder. With this photo-excited magnetic sensor, the position of the collimating lens and the fixing of the lens unit to the support can be performed via the holder, thereby suppressing contamination, damage, etc., of the collimating lens.

[0015] One aspect of the optically excited magnetic sensor of this disclosure is [9] "the optically excited magnetic sensor according to any one of [1] to [8] above, wherein the first surface is located on the second surface side of the laser element in a direction parallel to the optical axis of the laser element." With this optically excited magnetic sensor, physical interference between the laser element and the support during the manufacturing of the optically excited magnetic sensor can be reliably suppressed.

[0016] One aspect of the present disclosure is an optically excited magnetic sensor according to any one of [1] to [9] above, further comprising:

[10] "a control board on which a connector is mounted that is electrically and physically connected to external wiring, the laser unit supports the laser element in an electrically connected state to the laser element, and further comprising: a rigid wiring board fixed to the support member, and a flexible wiring board stretched between the rigid wiring board and the control board." With this optically excited magnetic sensor, even if an external force acts on the control board via the external wiring, the external force is less likely to reach the rigid wiring board, thereby suppressing misalignment of the optical axis of the laser element caused by the external force.

[0017] One aspect of the present disclosure is the optically excited magnetic sensor described in

[10] , wherein the support member has an opening formed therein, the opening is located on the opposite side of the rigid wiring board from the laser element, and the laser element is included when viewed from a direction parallel to the optical axis of the laser element. With this optically excited magnetic sensor, when the cell in the cell unit is heated by the heater, the heat is less likely to be transferred to the laser element via the support member, thereby suppressing a decrease in the output characteristics of the laser element caused by heat.

[0018] According to this disclosure, it is possible to provide an optically excited magnetic sensor that can suppress the decrease in magnetic field detection sensitivity.

[0019] Figure 1 is a perspective view of an example of an optically excited magnetic sensor. Figure 2 is another perspective view of the optically excited magnetic sensor shown in Figure 1. Figure 3 is a cross-sectional view of the optically excited magnetic sensor shown in Figure 1. Figure 4 is a cross-sectional view of the optically excited magnetic sensor along the line IV-IV shown in Figure 3. Figure 5 is a cross-sectional view of a portion of the optically excited magnetic sensor shown in Figure 1. Figure 6 is a perspective view of the laser unit shown in Figure 1. Figure 7 is another perspective view of the laser unit shown in Figure 1. Figure 8 is a plan view of a portion of an modified optically excited magnetic sensor.

[0020] An example of this disclosure will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted. [Configuration of the optically excited magnetic sensor]

[0021] As shown in Figures 1 to 4, the optically excited magnetic sensor 1 comprises a laser unit 2, a lens unit 3, a mirror 4, a polarizing unit 5, a cell unit 6, a photodetector 7, a unit support member 8, and a support body 9. The laser unit 2 includes a laser element 21. The lens unit 3 includes a collimating lens 31. The polarizing unit 5 includes a polarizing element 51. The cell unit 6 includes a cell 61. The unit support member 8 supports the polarizing unit 5. The support body 9 supports the laser unit 2, the lens unit 3, the mirror 4, the cell unit 6, the photodetector 7, and the unit support member 8. The support body 9 supports the polarizing unit 5 via the unit support member 8.

[0022] In the optically excited magnetic sensor 1, the laser light L emitted from the laser element 21 of the laser unit 2 passes through the collimating lens 31 of the lens unit 3, is reflected by the mirror 4, and then sequentially passes through the polarizing element 51 of the polarizing unit 5 and the cell 61 of the cell unit 6 before entering the photodetector 7. In other words, in the optically excited magnetic sensor 1, the lens unit 3, mirror 4, and polarizing unit 5 are arranged in this order on the optical path P of the laser light L from the laser element 21 to the cell 61. The lens unit 3 is located on the optical path P1 from the laser element 21 to the mirror 4. The polarizing unit 5 is located on the optical path P2 from the mirror 4 to the cell 61.

[0023] Hereinafter, the direction parallel to the optical path P1 will be referred to as the Z-axis direction, the direction parallel to the optical path P2 which is perpendicular to the optical path P1 will be referred to as the X-axis direction, and the direction perpendicular to the optical paths P1 and P2 will be referred to as the Y-axis direction. The Z-axis direction is parallel to the optical axis A1 of the laser element 21. The X-axis direction is parallel to the optical axis A2 of the polarizing element 51. The optical path P1 is coaxial with the optical axis A1, and the optical path P2 is coaxial with the optical axis A2. In the optically excited magnetic sensor 1, laser light L is emitted from the laser element 21 to one side in the Z-axis direction, and the laser light L is reflected by the mirror 4 to one side in the X-axis direction.

[0024] The support 9 includes a first portion 91 and a second portion 92. The first portion 91 and the second portion 92 are integrally formed from a non-magnetic resin (for example, a heat-resistant resin such as PPS or PEEK as a base material and free of magnetic materials, or a flame-retardant resin such as ABS or POM as a base material and free of magnetic materials). In other words, the support 9 is made of resin. The first portion 91 has a rectangular plate shape, for example, with the Y-axis direction as the thickness direction. The second portion 92 has a rectangular plate shape, for example, with the Z-axis direction as the thickness direction. The first portion 91 is located on one side of the second portion 92 in the Z-axis direction. The second portion 92 protrudes on one side of the main surface 91a of the first portion 91 in the Y-axis direction. The main surface 91a is the main surface on one side in the Y-axis direction. A recess 93 is formed in the second portion 92. The recess 93 opens into the main surface 92a of the second portion 92. The main surface 92a is the main surface on the other side in the Z-axis direction. The recess 93 extends to one side of the second portion 92 in the Y-axis direction and the other side in the X-axis direction.

[0025] A recess 94 is formed in the support 9. The recess 94 opens into the main surface 91a of the first portion 91. The recess 94 includes a plurality of housing portions 95, 96, 97, 98, and 99. A lens unit 3 is arranged in housing portion 95. A mirror 4 is arranged in housing portion 96. A unit support member 8 supporting a polarization unit 5 is arranged in housing portion 97 so as to intersect perpendicularly with the optical path P2. A cell unit 6 is arranged in housing portion 98. A photodetector 7 is arranged in housing portion 99. The recess 94 is formed as a continuous structure so that the optical path of the laser light L from the laser element 21 to the photodetector 7 can be located within the recess 94. Housing portion 95 opens to the bottom surface of the recess 93 via the second portion 92. As a result, the support 9 defines a space S in which the portion Pa of the optical path P on the laser element 21 side is located.

[0026] The laser unit 2 includes a laser element 21, a laser support member (support member) 22, a rigid wiring board 23, a flexible wiring board 24, and a submount 25. The laser support member 22 is made of a non-magnetic resin (for example, a heat-resistant resin such as PPS or PEEK as the base material and free of magnetic materials, or a flame-retardant resin such as ABS or POM as the base material and free of magnetic materials). The laser support member 22 has a rectangular plate shape, for example, with the Z-axis direction as the thickness direction. The laser support member 22 has a first surface 22a which is a plane perpendicular to the optical axis A1 of the laser element 21. The first surface 22a is one end face in the Z-axis direction. A groove 26 is formed in the laser support member 22. The groove 26 opens to the first surface 22a. The groove 26 extends in the Y-axis direction, and one end 26a of the groove 26 reaches one side of the laser support member 22 in the Y-axis direction.

[0027] One end 24a of the flexible wiring board 24 is electrically and physically connected to the rigid wiring board 23. The rigid wiring board 23 and one end 24a of the flexible wiring board 24 are fixed on the bottom surface of the groove 26. The flexible wiring board 24 extends outside the groove 26 via one end 26a of the groove 26. The submount 25 is fixed on the rigid wiring board 23 within the groove 26. The laser element 21 is fixed on the submount 25 within the groove 26. In this way, the laser element 21, the rigid wiring board 23, one end 24a of the flexible wiring board 24, and the submount 25 are housed within the groove 26. The laser element 21 is electrically connected to the rigid wiring board 23 via wiring (not shown) provided on the submount 25 and a wire (not shown) stretched between the wiring and the rigid wiring board 23. The laser element 21 emits linearly polarized laser light L to one side in the Z-axis direction. The laser element 21 is, for example, a vertical-cavity surface-emitting laser element. As described above, in the laser unit 2, the rigid wiring board 23 supports the laser element 21 while being electrically connected to it, and is fixed to the laser support member 22. In other words, in the laser unit 2, the laser element 21 is supported by the laser support member 22.

[0028] The laser support member 22 is positioned within a recess 93 of the support body 9 and is fixed to the second surface 9a, which is the bottom surface of the recess 93. The second surface 9a is perpendicular to the optical axis A1 of the laser element 21. In the optically excited magnetic sensor 1, the laser support member 22 and the support body 9 are fixed to each other by a plurality of bolts 27, with the first surface 22a of the laser support member 22 and the second surface 9a of the support body 9 in contact with each other. With the laser support member 22 and the support body 9 fixed to each other, the laser element 21 is exposed to the space S defined by the support body 9. In the optically excited magnetic sensor 1, during manufacturing, the position of the optical axis A1 of the laser element 21 is adjusted in a direction perpendicular to the optical axis A1 of the laser element 21 (i.e., "any direction perpendicular to the optical axis A1", including the X-axis and Y-axis directions), and with this position adjusted, the laser support member 22 and the support body 9 are fixed to each other by a plurality of bolts 27. Each bolt 27 is made of a non-magnetic resin (for example, a heat-resistant resin such as PPS or PEEK as the base material and free of magnetic materials, or a flame-retardant resin such as ABS or POM as the base material and free of magnetic materials).

[0029] The lens unit 3 includes a collimating lens 31 and a cylindrical holder 32. The collimating lens 31 is positioned inside the holder 32 and fixed to the inner surface of the holder 32 by adhesive. The collimating lens 31 collimates the laser light L emitted from the laser element 21. In the optically excited magnetic sensor 1, the holder 32 and the support 9 are fixed to each other by adhesive, with the outer surface 32a of the holder 32 and the inner surface 95a of the housing 95 in contact with each other. In the optically excited magnetic sensor 1, during manufacturing, the position of the collimating lens 31 is adjusted in the direction of extension of the optical path P1 of the laser light L (i.e., the Z-axis direction), and in that state, the holder 32 and the support 9 are fixed to each other by adhesive. The holder 32 is made of a non-magnetic resin (for example, a heat-resistant resin such as PPS or PEEK as the base material and not containing magnetic materials, or a flame-retardant resin such as ABS or POM as the base material and not containing magnetic materials).

[0030] The mirror 4 reflects the laser light L, which has been collimated by the collimating lens 31, to one side in the X-axis direction. In the optically excited magnetic sensor 1, the mirror 4 is fixed to the housing 96 with adhesive, with the mirror surface 4a of the mirror 4 forming a 45-degree angle with the Z-axis direction and the Y-axis direction, respectively, and parallel to the Y-axis direction.

[0031] The polarization unit 5 includes a polarizing element 51 and a holding member 52. The polarizing element 51 is held by the holding member 52 by being fixed to the holding member 52 with an adhesive. The polarizing element 51 emits the laser light L reflected by the mirror 4 as circularly polarized light to one side in the X-axis direction. As an example, the polarizing element 51 is a quarter-wave plate that converts the incident laser light L from linearly polarized to circularly polarized light and emits it. In the optically excited magnetic sensor 1, the holding member 52 and the unit support member 8 are engaged with each other and fixed to each other with an adhesive, and the unit support member 8 is fixed to the housing 97 with an adhesive. In the optically excited magnetic sensor 1, during manufacturing, the orientation of the polarization axis (i.e., the fast axis and the slow axis) of the polarizing element 51 is adjusted by rotating the holding member 52 with respect to the unit support member 8 with respect to the optical axis A2 of the polarizing element 51 as the center line, and in that state, the holding member 52 and the unit support member 8 are fixed to each other with an adhesive. Furthermore, the holding member 52 and the unit support member 8 are each made of a non-magnetic resin (for example, a heat-resistant resin such as PPS or PEEK as the base material and free of magnetic materials, or a flame-retardant resin such as ABS or POM as the base material and free of magnetic materials).

[0032] The unit support member 8 has a light-passing hole 8a, and the holding member 52 has a light-passing hole 52a (see Figure 4). The laser light L emitted from the polarizing element 51 passes through the light-passing hole 52a and the light-passing hole 8a in sequence.

[0033] The cell unit 6 includes a cell 61, a heater 62, a plurality of heat insulating members 63, and a cell case 64. The cell 61 is made of a material that is light-transmitting to laser light L (for example, glass, sapphire, etc.). Parts of the cell 61 that do not require light transmission to laser light L may be made of a material that is impermeable to laser light L (for example, silicon, etc.). The cell 61 is sealed with an alkali metal and an inert gas. As an example, the alkali metal is at least one of potassium, lithium, sodium, rubidium, and cesium, and the inert gas is at least one of helium, neon, argon, krypton, xenon, nitrogen, and hydrogen.

[0034] The heater 62 is positioned along the outer surface of the cell 61. In the photo-excited magnetic sensor 1, the heater 62 is positioned along the other surface of the outer surface of the cell 61 in the Y-axis direction. The heater 62 heats the cell 61 so that the alkali metals inside the cell 61 vaporize. As an example, the heater 62 is a sheet-like member containing a heating wire that generates heat when an electric current is applied. Multiple heat insulating members 63 cover the cell 61 and the heater 62. The cell case 64 houses the cell 61, the heater 62, and the multiple heat insulating members 63. In the photo-excited magnetic sensor 1, the cell case 64 includes a box-shaped main body 65 that opens on one side in the Y-axis direction, and a lid 66 that closes the opening of the main body 65. The main body 65 and the lid 66 are each made of a non-magnetic resin (for example, a heat-resistant resin such as PPS or PEEK as the base material and free of magnetic materials, or a flame-retardant resin such as ABS or POM as the base material and free of magnetic materials). In the photo-excited magnetic sensor 1, the main body 65 is fixed to the housing 98 with adhesive.

[0035] Multiple heat insulating members 63 have a pair of light-passing holes 63a and 63b facing each other in the X-axis direction, and the main body 65 has a pair of light-passing holes 65a and 65b facing each other in the X-axis direction (see Figure 4). The laser light L emitted from the polarizing element 51 passes sequentially through the light-passing hole 65a, the light-passing hole 63a, the cell 61, the light-passing hole 63b, and the light-passing hole 65b.

[0036] The photodetector 7 detects the laser light L emitted from the laser element 21 of the laser unit 2 and passing through the cell 61 of the cell unit 6. The photodetector 7 is configured to include, for example, a photodetector such as a photodiode. The photodetector 7 is fixed to the housing 99 with adhesive.

[0037] The photo-excited magnetic sensor 1 further comprises a coil 11, a control board 12, a connector 13, and a case 14. The coil 11 is arranged along the outer surface 6a of the cell unit 6. In the photo-excited magnetic sensor 1, the coil 11 is arranged along one surface in the Y-axis direction and both surfaces in the X-axis direction of the outer surface of the cell case 64. A portion of the coil 11 is arranged between the polarization unit 5 and the cell unit 6. The coil 11 generates a correction magnetic field, for example, so that the influence of magnetic fields other than the magnetic field being measured on the cell 61 approaches zero. As an example, the coil 11 is a sheet-like member that includes wiring that generates a magnetic field when energized.

[0038] The control board 12 is mounted on the main surface 92a of the second portion 92 of the support 9, spaced apart from the laser unit 2, so as to cover the recess 93 from the other side in the Z-axis direction. The other end 24b of the flexible wiring board 24 of the laser unit 2 is electrically and physically connected to the control board 12. In other words, the flexible wiring board 24 is stretched between the rigid wiring board 23 of the laser unit 2 and the control board 12. The control board 12 is electrically connected via wiring to the laser element 21 of the laser unit 2, as well as to the heater 62 and photodetector 7 of the cell unit 6. The connector 13 is mounted on the control board 12. External wiring for inputting and outputting electrical signals to and from the control board 12 is electrically and physically connected to the connector 13.

[0039] Case 14 houses the various parts of the photo-excited magnetic sensor 1. In the photo-excited magnetic sensor 1, case 14 includes a box-shaped main body 15 that opens to the other side in the Z-axis direction, and a lid 16 that closes the opening of the main body 15. Both the main body 15 and the lid 16 are made of a non-magnetic resin (for example, a heat-resistant resin such as PPS or PEEK as the base material and free of magnetic materials, or a flame-retardant resin such as ABS or POM as the base material and free of magnetic materials). In the photo-excited magnetic sensor 1, the control board 12 can be accessed by removing the lid 16 from the main body 15. Note that the case 14 is not shown in Figures 1 and 2.

[0040] The optically excited magnetic sensor 1, configured as described above, is used, for example, in the following way when measuring the magnetic field of a target object. First, with the external wiring electrically and physically connected to the connector 13, the optically excited magnetic sensor 1 is placed near the target object. Next, with the cell 61 heated by the heater 62, and alkali metal vaporized inside the cell 61, linearly polarized laser light L is emitted from the laser element 21. The linearly polarized laser light L emitted from the laser element 21 is collimated by the collimating lens 31 and reflected by the mirror 4. The laser light L reflected by the mirror 4 is converted into circularly polarized light by the polarizing element 51. The circularly polarized laser light L emitted from the polarizing element 51 passes through the cell 61 and is detected by the photodetector 7.

[0041] At this time, the alkali metal vaporized in cell 61 is excited by irradiation with circularly polarized laser light L, resulting in a spin-polarized state. Here, the spin-polarized state of the alkali metal changes according to the magnetic field of the object being measured, and the intensity of the laser light L incident on the photodetector 7 changes according to the spin-polarized state of the alkali metal. Therefore, it becomes possible to measure the magnetic field of the object being measured based on the intensity of the laser light L detected by the photodetector 7. [Configuration of laser unit and lens unit]

[0042] As shown in Figures 5 to 7, the laser support member 22 of the laser unit 2 is fixed to the support body 9. The laser support member 22 and the support body 9 are shaped such that the laser support member 22 can move relative to the support body 9 in a direction perpendicular to the optical axis A1 of the laser element 21, with the first surface 22a and the second surface 9a facing each other, and are fixed to each other with the first surface 22a and the second surface 9a facing each other. The phrase "shape such that the laser support member 22 can move relative to the support body 9 in a direction perpendicular to the optical axis A1 of the laser element 21 with respect to the support body 9 with respect to the optical axis A1 of the laser element 21" means "a shape such that, regardless of whether the first surface 22a and the second surface 9a are in contact with each other, when the laser support member 22 and the support body 9 are not fixed to each other, the laser support member 22 can move relative to the support body 9 in a direction perpendicular to the optical axis A1 of the laser element 21, with one of the first surface 22a and the second surface 9a acting as a guide surface and the other of the first surface 22a and the second surface 9a acting as a guided surface."

[0043] In the optically excited magnetic sensor 1, the laser support member 22 and the support body 9 are fixed to each other with their first surface 22a and second surface 9a in contact with each other. The first surface 22a and the second surface 9a each extend to surround the laser element 21 when viewed from a direction parallel to the optical axis A1 of the laser element 21. The outer edge 9E of the second surface 9a is located outside the outer edge 22E of the first surface 22a when viewed from a direction parallel to the optical axis A1 of the laser element 21.

[0044] The laser support member 22 is formed with a pair of through holes 22c and a pair of receiving holes 22d. Each through hole 22c and each receiving hole 22d penetrate the laser support member 22 in a direction parallel to the optical axis A1 of the laser element 21. As an example, the pair of through holes 22c are located at a pair of corner portions of the rectangular plate-shaped laser support member 22, and the pair of receiving holes 22d are located at the other pair of corner portions of the rectangular plate-shaped laser support member 22. A bolt 27 is inserted into each through hole 22c through a washer 28. The tip of the bolt 27 is screwed into each screw hole 9b formed in the support 9 so as to correspond to each through hole 22c. The inner diameter of the through hole 22c is sufficiently larger than the outer diameter of the bolt 27. A pin of a jig is inserted into each receiving hole 22d from the side opposite to the first surface 22a during the manufacture of the photoexcited magnetic sensor 1. The jig is a device for adjusting the position of the optical axis A1 of the laser element 21 in a direction perpendicular to the optical axis A1 of the laser element 21, and is used during the manufacture of the photoexcited magnetic sensor 1. During the manufacture of the photoexcited magnetic sensor 1, the position of the optical axis A1 of the laser element 21 is adjusted by the jig so that the laser light L emitted from the laser element 21 properly travels to the photodetector 7 through the cell 61, and the laser support member 22 is fixed to the support 9 by a plurality of bolts 27 with the position of the optical axis A1 of the laser element 21 adjusted. Note that each receiving hole 22d only needs to open at least on the surface of the laser support member 22 on the side opposite to the first surface 22a.

[0045] In the photoexcited magnetic sensor 1, the difference between the inner diameter of the through hole 22c and the outer diameter of the bolt 27 corresponds to an adjustment margin for adjusting the position of the optical axis A1 of the laser element 21 in a direction perpendicular to the optical axis A1 of the laser element 21. Within the range of the adjustment margin, the outer surface of the laser support member 22 does not physically interfere with the inner surface of the recess 93 (that is, a space is formed around the outer surface of the laser support member 22), and the outer edge portion of the washer 28 is located outside the through hole 22c.

[0046] As shown in Figures 5 and 6, the first surface 22a of the laser support member 22 is located on the second surface 9a side of the support 9 than the laser element 21 in a direction parallel to the optical axis A1 of the laser element 21. In other words, the laser element 21 does not protrude from the first surface 22a. In the optically excited magnetic sensor 1, the entire laser element 21 is located within the groove 26. The groove 26 includes multiple widened portions 22f that are widened outward at multiple locations around the rigid wiring board 23. The multiple widened portions 22f are used as introduction points for adhesive to fix the rigid wiring board 23, to which one end 24a of the flexible wiring board 24 is connected, within the groove 26 during the manufacturing of the optically excited magnetic sensor 1. Because the laser support member 22 (the inner wall surface of the groove 26) is spaced apart from the laser element 21 in the multiple widened portions 22f, even if the laser support member 22 is affected by the heat due to the temperature rise of the support 9, it is possible to suppress the heat effect from reaching the laser element 21.

[0047] As shown in Figures 5 and 7, an opening 22b is formed in the laser support member 22. The opening 22b is located on the opposite side of the laser element 21 from the rigid wiring board 23. In the optically excited magnetic sensor 1, the opening 22b opens to the bottom surface of the groove 26 and to the surface of the laser support member 22 opposite to the first surface 22a. The opening 22b contains the laser element 21 when viewed from a direction parallel to the optical axis A1 of the laser element 21. In other words, the laser element 21 is located inside the outer edge of the opening 22b when viewed from a direction parallel to the optical axis A1 of the laser element 21.

[0048] As shown in FIG. 5, the holder 32 of the lens unit 3 is fixed to the support 9. The holder 32 and the support 9 are shaped such that the holder 32 is movable in the extending direction of the optical path P1 with respect to the support 9 with their outer surface 32a and inner surface 95a facing each other, and they are fixed to each other with their outer surface 32a and inner surface 95a facing each other. The phrase "shaped such that the holder 32 is movable in the extending direction of the optical path P1 with respect to the support 9 with their outer surface 32a and inner surface 95a facing each other" means "when the holder 32 and the support 9 are not fixed to each other regardless of whether the outer surface 32a and the inner surface 95a are in contact with each other, with one of the outer surface 32a and the inner surface 95a as the guiding surface and the other as the guided surface, the holder 32 is movable in the extending direction of the optical path P1 with respect to the support 9".

[0049] In the photoexcitation magnetic sensor 1, the holder 32 and the support 9 are fixed to each other by an adhesive with their outer surface 32a and inner surface 95a in contact with each other. The housing portion 95 includes a widened portion 95b widened outwardly at the side of the holder 32. The widened portion 95b is used as an introduction portion for the adhesive for fixing the holder 32 to the housing portion 95 during the manufacture of the photoexcitation magnetic sensor 1. [Operation and Effect]

[0050] In the optically excited magnetic sensor 1, a laser element 21 that emits laser light L is supported by a laser support member 22, and the space S located in the optical path P of the laser light L on the laser element 21 side is defined by a support body 9. In this configuration, the laser support member 22 and the support body 9 have a shape that allows the laser support member 22 to move relative to the support body 9 in a direction perpendicular to the optical axis A1 of the laser element 21 (at least in the X-axis and Y-axis directions in the optically excited magnetic sensor 1), with the first surface 22a and the second surface 9a, which are perpendicular to the optical axis A1 of the laser element 21, facing each other. This allows the position of the optical axis A1 of the laser element 21 to be adjusted in a direction perpendicular to the optical axis A1 of the laser element 21 during the manufacturing of the optically excited magnetic sensor 1. As a result, an optically excited magnetic sensor 1 can be obtained in which the laser support member 22 and the support body 9 are fixed relative to each other in a state in which the laser light L emitted from the laser element 21 travels appropriately to the photodetector 7 via the cell 61. Therefore, the optically excited magnetic sensor 1 can suppress a decrease in magnetic field detection sensitivity.

[0051] In the optically excited magnetic sensor 1, the laser support member 22 and the support body 9 are both made of resin. As a result, the materials of the laser support member 22 and the support body 9 are non-magnetic, which suppresses a decrease in magnetic field detection sensitivity caused by the materials of the laser support member 22 and the support body 9. On the other hand, because the materials of the laser support member 22 and the support body 9 are resin, it is difficult to achieve high mechanical precision. However, as described above, since it is possible to fix the laser support member 22 and the support body 9 to each other after adjusting the position of the optical axis A1 of the laser element 21, a decrease in magnetic field detection sensitivity caused by the mechanical precision of the laser support member 22 and the support body 9 can be suppressed.

[0052] In the optically excited magnetic sensor 1, the first surface 22a and the second surface 9a each extend to surround the laser element 21 when viewed from a direction parallel to the optical axis A1 of the laser element 21. As a result, the region where the laser support member 22 and the support 9 face each other (the surface contact region in the optically excited magnetic sensor 1) exists in almost all directions centered on the laser element 21. Therefore, during the manufacturing of the optically excited magnetic sensor 1, the position adjustment of the optical axis A1 of the laser element 21 in a direction perpendicular to the optical axis A1 can be stably performed.

[0053] In the optically excited magnetic sensor 1, the outer edge 9E of the second surface 9a is located outside the outer edge 22E of the first surface 22a when viewed from a direction parallel to the optical axis A1 of the laser element 21. As a result, the entire first surface 22a becomes a region facing the second surface 9a (a surface contact region in the optically excited magnetic sensor 1), which allows for more stable adjustment of the position of the optical axis A1 of the laser element 21 in a direction perpendicular to the optical axis A1 of the laser element 21 during the manufacturing of the optically excited magnetic sensor 1.

[0054] In the optically excited magnetic sensor 1, the laser support member 22 and the support body 9 are fixed to each other with their first surface 22a and second surface 9a in contact with each other. This allows for stable adjustment of the position of the optical axis A1 of the laser element 21 in a direction perpendicular to the optical axis A1 of the laser element 21 during the manufacturing of the optically excited magnetic sensor 1.

[0055] In the optically excited magnetic sensor 1, the laser unit 2, lens unit 3, mirror 4, cell unit 6, and photodetector 7, as well as the polarization unit 5, are fixed to a unit support member 8, which is supported by a support 9. This simplifies the support structure of each part.

[0056] In the optically excited magnetic sensor 1, the holder 32 of the lens unit 3 and the support 9 are shaped such that the holder 32 can move relative to the support 9 in the direction of extension of the optical path P1, with the outer surface 32a of the holder 32 and the inner surface 95a of the housing 95 facing each other, and the outer surface 32a and inner surface 95a are fixed to each other in this position. This allows the position of the collimating lens 31 to be adjusted in the direction of extension of the optical path P1 (the Z-axis direction in the optically excited magnetic sensor 1) during the manufacturing of the optically excited magnetic sensor 1. As a result, an optically excited magnetic sensor 1 can be obtained in which the lens unit 3 and the support 9 are fixed to each other in a state where the laser light L emitted from the laser element 21 is appropriately collimated. This suppresses the spreading of the laser light L emitted from the laser element 21, and the laser light L travels appropriately through the cell 61 to the photodetector 7, thereby suppressing a decrease in the detection sensitivity of the magnetic field. In other words, by combining this with the adjustment of the two axes in the X-axis and Y-axis directions mentioned above, it is possible to irradiate laser light L in an appropriate state in all three axes. Furthermore, by separating the configuration into one that allows adjustment of two axes (X-axis and Y-axis) and one that allows adjustment of one axis (Z-axis), adjustment for irradiating the appropriate laser beam L becomes easier compared to a configuration that adjusts all three axes at once. In addition, since the collimating lens 31 is positioned within the holder 32 and the holder 32 and the support 9 are fixed to each other, the position of the collimating lens 31 and the fixing of the lens unit 3 to the support 9 can be performed via the holder 32. This prevents contact with the collimating lens 31 or direct stress from being applied to the collimating lens 31 when fixing the lens unit 3, thereby preventing contamination and damage to the collimating lens 31.

[0057] In the optically excited magnetic sensor 1, the first surface 22a of the laser support member 22 in the laser unit 2 is positioned on the second surface 9a side of the support 9 than the laser element 21 in a direction parallel to the optical axis A1 of the laser element 21. This ensures that physical interference between the laser element 21 and the support 9 during the manufacturing of the optically excited magnetic sensor 1 is reliably suppressed. In particular, in the optically excited magnetic sensor 1, the laser element 21, one end 24a of the rigid wiring board 23 and flexible wiring board 24, and the submount 25 are housed in the groove 26 of the laser support member 22. This means that physical interference between the components necessary for driving the laser element 21 and the support 9 is reliably suppressed, and because these components do not enter the space S of the support 9, it is possible to suppress the laser element 21 from being affected by the temperature rise of the support 9 when the cell 61 is heated by the heater 62 in the cell unit 6, thereby suppressing a decrease in the output characteristics of the laser element 21 and deterioration of each component due to heat.

[0058] In the optically excited magnetic sensor 1, a connector 13 that is electrically and physically connected to external wiring is mounted on the control board 12, and the flexible wiring board 24 of the laser unit 2 is stretched between the rigid wiring board 23 of the laser unit 2 and the control board 12. As a result, even if an external force acts on the control board 12 via the external wiring, or if stress acts on the control board 12 when the external wiring is attached to or detached from the connector 13, such external force and stress are less likely to reach the rigid wiring board 23, thereby suppressing the misalignment of the optical axis A1 of the laser element 21 caused by such external force and stress.

[0059] In the optically excited magnetic sensor 1, in the laser unit 2, the opening 22b formed in the laser support member 22 is located on the opposite side of the laser element 21 from the rigid wiring board 23, and includes the laser element 21 when viewed from a direction parallel to the optical axis A1 of the laser element 21. As a result, when the cell 61 in the cell unit 6 is heated by the heater 62, the heat is less likely to be transferred to the laser element 21 via the laser support member 22, thereby suppressing the decrease in the output characteristics of the laser element 21 caused by heat. [Modified example]

[0060] This disclosure is not limited to the example described above. For example, the laser support member 22 and the support body 9 may be fixed to each other with their first surface 22a and second surface 9a facing each other, or they may be fixed to each other with their first surface 22a and second surface 9a spaced apart from each other. As an example, as shown in Figure 8, a plurality of washer-shaped spacers 29 may be arranged between the first surface 22a and the second surface 9a, and each bolt 27 may be screwed into each screw hole 9b via each spacer 29. With this configuration, when the cell 61 in the cell unit 6 is heated by the heater 62, the heat is less likely to be transferred to the laser element 21 via the laser support member 22, thereby suppressing a decrease in the output characteristics of the laser element 21 due to heat. Furthermore, the laser support member 22 and the support body 9 may be roughly positioned by having one of the recesses and protrusions formed on the first surface 22a correspond to the other of the recesses and protrusions formed on the second surface 9a. In that case, fine adjustment during positioning is possible by making the diameter of the recess larger than the diameter of the protrusion corresponding to the recess. Furthermore, the laser support member 22 and the support body 9 may be fixed to each other with their first surface 22a and second surface 9a facing each other, and are not limited to surface contact but may be point contacts. In that case, it is preferable that the laser support member 22 and the support body 9 have multiple point contact points.

[0061] Furthermore, the laser support member 22 and the support body 9 may be fixed to each other by fixing means used in place of the multiple bolts 27 or by fixing means used together with the multiple bolts 27. For example, the laser support member 22 and the support body 9 may be fixed to each other with an adhesive. In that case, the adhesive may be placed between the first surface 22a and the second surface 9a. Similarly, the fixing method described in the above example may be any other fixing method as long as a magnetic material is not used.

[0062] Furthermore, the first surface 22a and the second surface 9a do not necessarily extend to surround the laser element 21 when viewed from a direction parallel to the optical axis A1 of the laser element 21. For example, the first surface 22a and the second surface 9a may be separated into multiple regions arranged around the laser element 21 when viewed from a direction parallel to the optical axis A1 of the laser element 21. Also, the outer edge 9E of the second surface 9a does not necessarily have to be located outside the outer edge 22E of the first surface 22a when viewed from a direction parallel to the optical axis A1 of the laser element 21. For example, at least a part of the outer edge 9E of the second surface 9a may be located inside the outer edge 22E of the first surface 22a when viewed from a direction parallel to the optical axis A1 of the laser element 21.

[0063] Furthermore, if the space S is defined by the support 9 in such a way that the laser element 21 remains exposed to the space S within the range of adjustment for adjusting the position of the optical axis A1 of the laser element 21 in a direction perpendicular to the optical axis A1 of the laser element 21, then at least a portion of the laser element 21 may protrude from the first surface 22a of the laser support member 22.

[0064] Furthermore, the laser support member 22 and the support body 9 may each be made of a non-magnetic material other than resin (for example, ceramic). Also, the unit support member 8 to which the lens unit 3, mirror 4, cell unit 6, photodetector 7, and polarizing unit 5 are fixed may be supported by a support body separate from the support body 9. Also, the shape of the holder 32 of the lens unit 3 does not have to be cylindrical; for example, it may be rectangular. Also, the lens unit 3 does not have to include the holder 32; for example, the collimating lens 31 may be directly fixed to the housing 95.

[0065] 1...Optical excitation magnetic sensor, 2...Laser unit, 3...Lens unit, 6...Cell unit, 7...Photodetector, 9...Support, 9a...Second surface, 9E...Outer edge, 12...Control board, 13...Connector, 21...Laser element, 22...Laser support member (support member), 22a...First surface, 22b...Aperture, 22E...Outer edge, 23...Rigid wiring board, 24...Flexible wiring board, 31...Collimating lens, 32...Holder, 32a...Outer surface, 61...Cell, 95...Housing section, 95a...Inner surface, A1...Optical axis, L...Laser light, P...Optical path, Pa...Part, S...Space.

Claims

1. A photo-excited magnetic sensor comprising: a laser unit including a laser element that emits laser light and a support member that supports the laser element; a cell unit including a cell containing an alkali metal; a photodetector that detects the laser light emitted from the laser element and passing through the cell; and a support that defines a space in which at least the portion of the optical path of the laser light from the laser element to the cell on the laser element side is located, wherein the support member has a first surface perpendicular to the optical axis of the laser element, the support has a second surface perpendicular to the optical axis of the laser element, and the support member and the support are shaped such that the support member can move relative to the support in a direction perpendicular to the optical axis of the laser element with respect to the support, with the first and second surfaces facing each other, and the first and second surfaces are fixed to each other with respect to each other.

2. The photo-excited magnetic sensor according to claim 1, wherein each of the support member and the support body is formed of resin.

3. The optically excited magnetic sensor according to claim 1, wherein each of the first and second surfaces extends to surround the laser element when viewed from a direction parallel to the optical axis of the laser element.

4. The optically excited magnetic sensor according to claim 3, wherein the outer edge of the second surface is located outside the outer edge of the first surface when viewed from the direction parallel to the optical axis of the laser element.

5. The photo-excited magnetic sensor according to claim 1, wherein the support member and the support body are fixed to each other with the first surface and the second surface in contact with each other.

6. The photo-excited magnetic sensor according to claim 1, wherein the support supports the cell unit and the photodetector.

7. The optically excited magnetic sensor according to claim 1, further comprising a lens unit including a collimating lens disposed on the optical path, wherein the support has a housing portion in which the lens unit is disposed, and the lens unit and the support have a shape such that the lens unit is movable relative to the support in the direction extending the optical path with respect to the support, with the outer surface of the lens unit and the inner surface of the housing portion facing each other, and the outer surface and the inner surface are fixed to each other with respect to each other.

8. The optically excited magnetic sensor according to claim 7, wherein the lens unit further includes a cylindrical holder, the collimating lens is disposed within the holder, and the outer surface of the lens unit is the outer surface of the holder.

9. The optically excited magnetic sensor according to claim 1, wherein the first surface is located on the second surface side of the laser element in a direction parallel to the optical axis of the laser element.

10. The optically excited magnetic sensor according to any one of claims 1 to 9, further comprising a control board on which connectors are mounted for electrical and physical connection to external wiring, wherein the laser unit further includes a rigid wiring board fixed to the support member and supporting the laser element in an electrically connected state to the laser element, and a flexible wiring board stretched between the rigid wiring board and the control board.

11. The optically excited magnetic sensor according to claim 10, wherein the support member has an opening formed therein, the opening is located on the opposite side of the rigid wiring board from the laser element, and includes the laser element when viewed from a direction parallel to the optical axis of the laser element.

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