JP2018136217A - Magnetometric sensor and magnetic field measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetometric sensor with which it is possible to have a high spatial resolution.SOLUTION: Provided is a magnetometric sensor including: a test object arrangement unit for arranging a test object; a gas cell storage unit for storing a plurality of two-dimensionally arranged gas cells; a plurality of two-dimensionally arranged optical prisms for inputting light to the gas cells; a plurality of two-dimensionally arranged polarimeters having a polarized light separation element for separating the light having passed through the gas cells into a first polarized light and a second polarized light and an optical detector for detecting the first polarized light or the second polarized light. The gas cells store a medium for causing the optical characteristic of light to change in accordance with the magnitude of a magnetic field, the gas cell storage unit is provided between the test object arrangement unit and the plurality of optical prisms, the plurality of optical prisms are provided between the gas cell storage unit and the plurality of polarimeters, and the polarimeters are configured so that the polarization direction of incident light in the polarized light separation element is changeable.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a magnetic sensor and a magnetic field measurement device.

  An optical pumping type magnetic field measuring apparatus is known as a magnetic field measuring apparatus that detects a magnetic field emitted from a living heart or the like. The optical pumping type magnetic field measuring apparatus includes a magnetic sensor for irradiating a gas cell filled with an alkali metal gas with linearly polarized light and measuring the magnetic field according to the rotation angle of the polarization plane of the light transmitted through the gas cell. (For example, refer to Patent Document 1).

Japanese Patent Laying-Open No. 2015-62020

  In the magnetic sensor as described above, it is desirable to bring the plurality of gas cells as close as possible in order to increase the spatial resolution. However, in the magnetic sensor described in Patent Document 1, when a plurality of gas cells are arranged in the direction in which light is emitted from the light source (Z-axis direction), the light sources may be in the way to bring the plurality of gas cells closer. It can be difficult. Further, in the magnetic sensor described in Patent Document 1, when a plurality of gas cells are arranged in a direction (X-axis direction) orthogonal to the direction in which light is emitted from the light source, the photodetector (PD) is an obstacle. Thus, it may be difficult to bring a plurality of gas cells close to each other.

  One of the objects according to some aspects of the present invention is to provide a magnetic sensor that can have high spatial resolution. Another object of some aspects of the present invention is to provide a magnetic field measurement apparatus including the magnetic sensor.

The magnetic sensor according to the present invention is
A subject placement section for placing the subject;
A gas cell accommodating portion for accommodating a plurality of gas cells arranged two-dimensionally;
A plurality of optical prisms arranged in a two-dimensional manner by making light incident on the gas cell;
A plurality of two-dimensionally arranged elements, each having a polarization separation element that separates light transmitted through the gas cell into first polarized light and second polarized light, and a photodetector that detects the first polarized light or the second polarized light The polarimeter of
Including
The gas cell contains a medium that changes the optical properties of light according to the magnitude of the magnetic field;
The gas cell housing portion is provided between the subject placement portion and the plurality of optical prisms,
The plurality of optical prisms are provided between the gas cell housing portion and the plurality of polarimeters,
The polarimeter is configured to change the polarization direction of incident light in the polarization separation element.

  In such a magnetic sensor, there is no light source or photodetector between the plurality of gas cells, and the plurality of gas cells can be brought close to each other. Therefore, such a magnetic sensor can have high spatial resolution.

In the magnetic sensor according to the present invention,
The gas cell accommodating portion is
A first reflector that reflects light reflected by the optical prism in a first direction so as to pass through the first gas cell of the plurality of gas cells;
A second reflecting plate that reflects light reflected by the first reflecting plate and transmitted through the first gas cell toward a second direction inclined with respect to the first direction so as to pass through the first gas cell;
May be accommodated.

  In such a magnetic sensor, for example, the rotation angle of the polarization plane of light can be increased and high sensitivity can be achieved as compared with the case where light passes through the first gas cell only once.

In the magnetic sensor according to the present invention,
The first reflecting plate may reflect the light reflected by the second reflecting plate and transmitted through the first gas cell toward the polarimeter.

  In such a magnetic sensor, a reflecting plate for reflecting light toward the first gas cell, and a reflecting plate for reflecting light transmitted through the first gas cell toward the polarimeter, and a common reflecting plate, can do.

In the magnetic sensor according to the present invention,
The first reflecting plate and the second reflecting plate may include a phase compensation film that reflects light transmitted through the first gas cell while maintaining a phase difference between P-polarized light and S-polarized light.

  Such a magnetic sensor can detect the rotation angle of the polarization plane of light with high sensitivity.

In the magnetic sensor according to the present invention,
The second reflecting plate may be provided between the first gas cell and a second gas cell among the plurality of gas cells.

  In such a magnetic sensor, a reflector that reflects light toward the first gas cell and a reflector that reflects light toward the second gas cell can be used as a common reflector.

In the magnetic sensor according to the present invention,
Light may be incident on a third gas cell of the plurality of gas cells from a third direction orthogonal to the second direction.

  In a magnetic field measurement apparatus including such a magnetic sensor, components in two directions of the magnetic field can be measured.

In the magnetic sensor according to the present invention,
Supporting the polarimeter, including a support portion provided with an opening,
The polarimeter may have an insertion portion that is rotatably inserted into the opening.

  In such a magnetic sensor, the polarimeter can be rotated about the central axis of the opening, and the polarization direction of incident light in the polarization separation element can be changed.

In the magnetic sensor according to the present invention,
The polarimeter is provided with a slot,
The elongated hole may be provided with a screw for fixing the polarimeter to the support portion.

  In such a magnetic sensor, for example, when the gas cell is deteriorated and the gas cell is replaced, the polarimeter is rotated by removing the screw from the elongated hole and inserting the screw into the elongated hole again at a desired position. Can be fixed to the support portion.

In the magnetic sensor according to the present invention,
The medium may be a gaseous alkali metal.

  In such a magnetic sensor, the polarization plane of the light transmitted through the gas cell can be changed according to the magnitude of the magnetic field by interacting with the magnetic field to which the alkali metal is applied.

The magnetic field measurement apparatus according to the present invention is
A magnetic sensor according to the present invention is included.

  Such a magnetic field measurement apparatus can include the magnetic sensor according to the present invention.

The side view which shows typically the magnetic field measuring device which concerns on this embodiment. The figure which shows the structural example of the processing apparatus of the magnetic field measuring apparatus which concerns on this embodiment. The top view which shows typically the 1st magnetic sensor which concerns on this embodiment. Sectional drawing which shows the 1st magnetic sensor which concerns on this embodiment typically. Sectional drawing which shows the 1st magnetic sensor which concerns on this embodiment typically. Sectional drawing which shows the 1st magnetic sensor which concerns on this embodiment typically. Sectional drawing which shows the 1st magnetic sensor which concerns on this embodiment typically. Sectional drawing which shows the 1st magnetic sensor which concerns on this embodiment typically. The perspective view which shows typically the 1st magnetic sensor which concerns on this embodiment. Sectional drawing which shows the 1st magnetic sensor which concerns on this embodiment typically. The top view which shows typically the 1st magnetic sensor which concerns on this embodiment. The top view which shows typically the 2nd magnetic sensor which concerns on this embodiment. Sectional drawing which shows the 2nd magnetic sensor which concerns on this embodiment typically. The figure for demonstrating the model used for the experiment example. The figure for demonstrating the model used for the experiment example. The table | surface which shows a calculation result.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are essential constituent requirements of the present invention.

1. First, a magnetic field measurement apparatus according to this embodiment will be described with reference to the drawings. FIG. 1 is a side view schematically showing a magnetic field measuring apparatus 1 according to this embodiment. In FIG. 1, an X axis, a Y axis, and a Z axis are illustrated as three axes orthogonal to each other.

As shown in FIG. 1, the magnetic field measuring apparatus 1 is a device that measures a cardiac magnetic field emitted from the heart of a subject (living body) 9 as a measurement target, a cerebral magnetic field emitted from the brain of the subject (living body) 9, or the like. It is. The magnetic field measurement apparatus 1 can measure a magnetic field in a nondestructive manner. The magnetic field measurement apparatus 1 includes a magnetic sensor according to the present invention. Below, the magnetic field measuring device 1 containing the 1st magnetic sensor 100 and the 2nd magnetic sensor 200 as a magnetic sensor which concerns on this invention is demonstrated. Furthermore, the magnetic field measurement device 1 includes a processing device 2 (see FIG. 2), a base 3, and a magnetic shield device 6.

  The second magnetic sensor 200 is a sensor for measuring a weak magnetic field (magnetic field to be measured) such as a cardiac magnetic field or a brain magnetic field to be measured and an environmental magnetic field, and is used as a magnetocardiograph or a magnetoencephalograph. . The first magnetic sensor 100 is a sensor for mainly measuring an environmental magnetic field such as an external magnetic field (magnetic noise). The magnetic sensors 100 and 200 include, for example, an optical pumping type magnetic sensor, a SQUID (Superducting Quantum Interface Device) type magnetic sensor, a flux gate magnetic sensor, an MI sensor, a Hall element, and the like.

  The height direction (vertical direction in FIG. 1) of the magnetic field measuring apparatus 1 is defined as the Z-axis direction. The Z-axis direction is the vertical direction. The directions in which the upper surfaces of the base 3 and the table 4 extend are defined as the X-axis direction and the Y-axis direction. The X axis direction and the Y axis direction are horizontal directions, and the X axis direction and the Y axis direction are orthogonal to each other. The height direction (left-right direction in FIG. 1) of the subject 9 in the lying state is defined as the X-axis direction.

  The base 3 is disposed on the bottom surface inside the magnetic shield device 6 (main body portion 6a), and extends along the X-axis direction (movable direction of the subject 9) to the outside of the main body portion 6a. . The table 4 includes an X-axis direction table 4a, a Z-axis direction table 4b, and a Y-axis direction table 4c. On the base 3, an X-axis direction table 4a that moves along the X-axis direction by an X-axis direction linear motion mechanism 3a is installed. On the X-axis direction table 4a, a Z-axis direction table 4b that is moved up and down along the Z-axis direction by a lifting device (not shown) is installed. On the Z-axis direction table 4b, there is installed a Y-axis direction table 4c that moves on the rail along the Y-axis direction by a Y-axis direction linear motion mechanism (not shown). The table 4 is a subject placement unit for placing the subject 9. The table 4 constitutes the magnetic sensors 100 and 200.

  The magnetic shield device 6 includes a rectangular tube-shaped main body 6a having an opening 6c. The inside of the main body 6a is hollow, and the cross-sectional shape of a plane passing through the Y-axis direction and the Z-axis direction (a plane perpendicular to the X-axis direction in the YZ cross section) is approximately a quadrangle. When measuring the cardiac magnetic field, the subject 9 is accommodated inside the main body 6a while lying on the table 4. The main body 6a extends in the X-axis direction and functions as a passive magnetic shield by itself.

  The magnetic sensors 100 and 200 are disposed inside the main body 6 a of the magnetic shield device 6. The magnetic shield device 6 suppresses a situation in which an external magnetic field such as geomagnetism flows into the space where the magnetic sensors 100 and 200 are disposed. That is, the magnetic shield device 6 makes the space in which the magnetic sensors 100 and 200 are disposed a significantly lower magnetic field than the external magnetic field, and the influence of the external magnetic field on the second magnetic sensor 200 is suppressed.

  The base 3 protrudes in the + X-axis direction from the opening 6c of the main body 6a. As for the size of the magnetic shield device 6, for example, the length in the X-axis direction is about 200 cm, and one side of the opening 6c is about 90 cm. Then, the subject 9 lying on the table 4 can move in and out of the magnetic shield device 6 along the X-axis direction along the base 3 together with the table 4 from the opening 6c.

The processing device 2 (see FIG. 2) is a device that receives electric signals from the magnetic sensors 100 and 200 and measures a magnetic field such as a cardiac magnetic field and a brain magnetic field. When a magnetic field or a residual magnetic field is generated by the electrical signal generated by the processing device 2 and detected by the second magnetic sensor 200, noise is generated. Therefore, it is preferable that the processing device 2 is installed at a location away from the opening 6c of the magnetic shield device 6 so that the generated magnetic field and the remaining magnetic field are difficult to reach the second magnetic sensor 200.

  The main body 6a of the magnetic shield device 6 is formed of a ferromagnetic material having a relative magnetic permeability of, for example, several thousand or more, or a high conductivity conductor. As the ferromagnetic material, for example, permalloy, ferrite, or iron, chromium, or cobalt-based amorphous material can be used. As the high conductivity conductor, for example, aluminum or the like having a magnetic field reduction effect by an eddy current effect can be used. It is also possible to form the main body 6a by alternately laminating ferromagnetic materials and high conductivity conductors.

  Correction coils (Helmholtz coils) 6 b are installed at the ends of the main body 6 a and the base 3 on the + X axis direction side and the −X axis direction side. The correction coil 6b has a frame shape and is arranged so as to surround the main body 6a. The correction coil 6b is a coil for correcting an inflow magnetic field flowing into the internal space of the main body 6a. The inflow magnetic field refers to a magnetic field in which an external magnetic field passes through the opening 6c and enters the internal space. The inflow magnetic field is strongest in the X-axis direction with respect to the opening 6c. The correction coil 6 b generates a magnetic field so as to cancel the inflow magnetic field by the current supplied from the processing device 2.

  The second magnetic sensor 200 is fixed to the ceiling of the main body 6a via the support member 7. In the illustrated example, the second magnetic sensor 200 is located closer to the subject 9 than the first magnetic sensor 100. When measuring the cardiac magnetic field of the subject 9, the X-axis direction table 4 a and the Y-axis direction table 4 c are moved so that the chest 9 a that is the measurement position in the subject 9 faces the second magnetic sensor 200. The Z-axis direction table 4b is raised so that the chest 9a approaches the second magnetic sensor 200.

  The first magnetic sensor 100 is fixed to the ceiling of the main body 6a via a support member 7. In the illustrated example, the first magnetic sensor 100 is separated from the second magnetic sensor 200 and is located farther from the subject 9 than the second magnetic sensor 200. The magnetic sensors 100 and 200 are configured to include a common table 4. The detailed configuration of the magnetic sensors 100 and 200 will be described later.

  FIG. 2 is a diagram illustrating a configuration example of the processing device 2. As illustrated in FIG. 2, the processing device 2 includes an operation unit 110, a display unit 112, a storage unit 114, and a calculation unit 116.

  The operation unit 110 is used to input information necessary for processing performed by the arithmetic unit 116 (such as various instructions such as a magnetic field measurement start instruction and measurement conditions). For example, a button switch, a lever switch, a dial switch, or the like. Various switches, a touch panel, a keyboard, a mouse, and the like may be used.

  The display unit 112 displays the processing result of the calculation unit 116 as characters, graphs, tables, animations, and other images. For example, the display unit 112 may be an LCD (Liquid Crystal Display) or an EL display (Electroluminescence display). Good. In addition, you may make it implement | achieve the function of the operation part 110 and the display part 112 with one touchscreen type display.

The storage unit 114 is for storing programs, data, and the like for the arithmetic unit 116 to perform various processes. For example, various types such as a ROM (Read Only Memory), a flash ROM, and a RAM (Random Access Memory). IC (In
(tegrated circuit) It is comprised with recording media, such as a memory, a hard disk, and a memory card. The storage unit 114 is used as a work area of the calculation unit 116, and temporarily stores calculation results and the like executed by the calculation unit 140 according to various programs. Furthermore, the memory | storage part 130 may memorize | store the data which require long-term preservation | save among the data produced | generated by the process of the calculating part 140. FIG.

  The calculation unit 116 is realized by, for example, a microprocessor such as a CPU (Central Processing Unit), and performs a magnetic field calculation process. Specifically, the calculation unit 116 acquires the first measurement value of the first magnetic sensor 100 and the second measurement value of the second magnetic sensor 200, and estimates the environmental magnetic field in the measurement target space based on the first measurement value. And the calculation process which extracts a measurement object magnetic field by subtracting this from a 2nd measured value is performed. Thereby, in the magnetic field measurement apparatus 1, the influence of the environmental magnetic field (magnetic noise) in the measurement target space in which the second magnetic sensor 200 is arranged is reduced, and the biomagnetic field such as the cardiac magnetic field and the brain magnetic field to be measured is more Accurate measurement is possible.

2. Magnetic sensor 2.1. First Magnetic Sensor Next, the first magnetic sensor 100 according to the present embodiment will be described with reference to the drawings. The first magnetic sensor 100 is, for example, a sensor for estimating an environmental magnetic field (magnetic noise) in a measurement target space where the second magnetic sensor 200 (see FIG. 1) is arranged. In addition, the 1st magnetic sensor 100 may be a sensor for detecting the magnetic field (cardiac magnetic field) of measurement object with an environmental magnetic field (magnetic noise).

  FIG. 3 is a plan view schematically showing the first magnetic sensor 100 (hereinafter also simply referred to as “magnetic sensor 100”) according to the present embodiment. 4 is a cross-sectional view taken along line IV-IV in FIG. 3 schematically showing the magnetic sensor 100 according to the present embodiment. FIG. 5 is a cross-sectional view taken along line VV in FIG. 3 schematically showing the magnetic sensor 100 according to the present embodiment. 6 is a cross-sectional view taken along the line VI-VI in FIG. 3 schematically showing the magnetic sensor 100 according to the present embodiment. 3 to 6 illustrate the X axis, the Y axis, and the Z axis as three axes orthogonal to each other.

  As shown in FIGS. 3 to 6, the magnetic sensor 100 includes a light source 10, an optical component 20, reflectors 31, 32, 33, 34, 35, 36, 37, a gas cell 40, and a gas cell storage unit 50. , Container 60, support portion 70, and polarimeter 80. Further, as shown in FIG. 1, the magnetic sensor 100 includes a table 4 that is a subject placement unit for placing the subject 9. For the sake of convenience, in FIG. 3, the seventh reflector 37, the gas cell storage unit 50, and the support unit 70 are omitted from illustration (however, the opening 74 provided in the support unit 70 is illustrated). ). Moreover, illustration of the table 4 is abbreviate | omitted in FIGS.

  As shown in FIGS. 3 and 4, the light source 10 emits laser light 12 having a wavelength corresponding to an absorption line of cesium (Cs), for example. The wavelength of the laser beam 12 is, for example, 894 nm corresponding to the D1 line. The light source 10 is, for example, a tunable laser, and the laser light 12 is continuous light having a certain amount of light. In the example illustrated in FIG. 4, the light source 10 is provided on the −X axis direction side of the optical component 20.

  The laser beam 12 emitted from the light source 10 enters the polarizing plate 14. The laser beam 12 that has passed through the polarizing plate 14 is linearly polarized light. The laser beam 12 that has become linearly polarized light enters the optical component 20. The polarization plane of the laser beam 12 (electric field vibration plane) is, for example, parallel or perpendicular to the XY plane. If the laser beam 12 emitted from the light source 10 is linearly polarized light, the polarizing plate 14 may not be provided. Although not shown, the laser beam 12 may be incident on the optical component 20 via a collimator lens.

  The optical component 20 has a plurality of optical prisms 22 arranged two-dimensionally. That is, the plurality of optical prisms 22 are arranged such that a predetermined plane (a surface parallel to the XY plane in the illustrated example) passes through the plurality of optical prisms 22. The plurality of optical prisms 22 are provided between the gas cell housing 50 and the plurality of polarimeters 80. The optical prism 22 causes the laser beam 12 to enter the gas cell 40.

  The first optical prisms 22a, 22b, 22c, 22d, 22e, 22f, and 22g among the plurality of optical prisms 22 reflect a part of the incident laser light 12 and a part of the incident laser light 12 (others). It is a half mirror that transmits a part of it. The second optical prisms 22h, 22i, and 22j among the plurality of optical prisms 22 are mirrors (reflecting plates) that reflect all (almost all) the incident laser light 12.

  The normal lines (not shown) of the reflecting surfaces of the optical prisms 22a, 22d, 22g, and 22j exist, for example, in a plane parallel to the XY plane and are inclined by 45 ° with respect to the Y axis. The normal lines (not shown) of the reflecting surfaces of the optical prisms 22b, 22c, 22e, 22f, 22h, and 22i exist in a plane parallel to the XZ plane, for example, and are inclined at a predetermined angle with respect to the Z axis. . In the present invention, the “predetermined angle” is, for example, 2 ° or more and 5 ° or less, and preferably 3 °.

  The laser beam 12 emitted from the light source 10 and traveling in the + X-axis direction first enters the first optical prism 22a. The first optical prism 22a reflects a part of the incident laser light 12 and advances it in the + Y-axis direction, transmits a part of the incident laser light 12 and advances it in the + X-axis direction.

  The laser beam 12 transmitted through the first optical prism 22a and traveling in the + X-axis direction is incident on the first optical prism 22b as shown in FIG. The first optical prism 22b reflects a part of the incident laser light 12 and advances it at a predetermined angle with respect to the Z axis, and transmits a part of the incident laser light 12 to advance in the + X axis direction. . The light reflected by the first optical prism 22 b enters the first gas cell 41 of the plurality of gas cells 40 through the first reflector 31.

  The plurality of gas cells 40 are classified into, for example, a first gas cell 41, a second gas cell 42, a third gas cell 43, a fourth gas cell 44, and a fifth gas cell 45.

  The laser beam 12 transmitted through the first optical prism 22b and traveling in the + X-axis direction is incident on the first optical prism 22c. The first optical prism 22c reflects a part of the incident laser light 12 and advances it at a predetermined angle with respect to the Z axis, and transmits a part of the incident laser light 12 to advance in the + X axis direction. . The light reflected by the first optical prism 22 c enters the second gas cell 42 of the plurality of gas cells 40 via the third reflector 33.

  The laser beam 12 transmitted through the first optical prism 22c and traveling in the + X-axis direction is incident on the second optical prism 22h. The second optical prism 22h reflects the incident laser beam 12 and advances it at a predetermined angle with respect to the Y axis. The light reflected by the second optical prism 22 h enters the fourth gas cell 44 of the plurality of gas cells 40 via the fourth reflector 34.

  As shown in FIG. 3, the laser beam 12 reflected by the first optical prism 22a and traveling in the + Y-axis direction is incident on the first optical prism 22d. The first optical prism 22d transmits a part of the incident laser light 12 and travels in the + Y-axis direction, reflects a part of the incident laser light 12 and travels in the + X-axis direction.

  The laser beam 12 reflected by the first optical prism 22d and traveling in the + X-axis direction is incident on the first optical prism 22e as shown in FIG. The first optical prism 22e reflects a part of the incident laser light 12 and advances it at a predetermined angle with respect to the Z axis, and transmits a part of the incident laser light 12 to advance in the + X axis direction. . The light reflected by the first optical prism 22 e enters the fourth gas cell 44 via the fourth reflector 34.

  The laser beam 12 transmitted through the first optical prism 22e and traveling in the + X-axis direction is incident on the first optical prism 22f. The first optical prism 22f reflects a part of the incident laser light 12 and advances it at a predetermined angle with respect to the Z axis, and transmits a part of the incident laser light 12 to advance in the + X axis direction. . The light reflected by the first optical prism 22 f enters the third gas cell 43 among the plurality of gas cells 40.

  The laser beam 12 transmitted through the first optical prism 22f and traveling in the + X-axis direction is incident on the second optical prism 22i. The second optical prism 22i is advanced by a predetermined angle with respect to the Z axis. The light reflected by the second optical prism 22 i enters the third gas cell 43.

  The laser beam 12 transmitted through the first optical prism 22d and traveling in the + Y-axis direction is incident on the first optical prism 22g. The first optical prism 22g transmits a part of the incident laser light 12 and travels in the + Y axis direction, reflects a part of the incident laser light 12 and travels in the + X axis direction.

  Although not shown, two first optical prisms and one second optical prism are provided on the + X axis direction side of the first optical prism 22g. The laser beams 12 reflected by the two first optical prisms enter the third gas cell 43, respectively. The laser beam 12 reflected by the second optical prism is incident on the fifth gas cell 45 among the plurality of gas cells 40 via the sixth reflector 36.

  The laser beam 12 transmitted through the first optical prism 22g and traveling in the + Y-axis direction is incident on the second optical prism 22j. The second optical prism 22j reflects the incident laser beam 12 and advances it in the + X-axis direction.

  Although not shown, two first optical prisms and one second optical prism are provided on the + X axis direction side of the second optical prism 22j. The laser beam 12 reflected by one of the first optical prisms enters the fifth gas cell 45 via the sixth reflector 36. The laser beam 12 reflected by the other first optical prism enters the first gas cell 41 via the first reflecting plate 31. The laser beam 12 reflected by the second optical prism enters the second gas cell 42 via the third reflector 33.

  In the illustrated example, the laser beam 12 of one optical path is separated into 12 optical paths by the optical prism 22. The reflectance of the optical prism 22 is set, for example, so that the intensity of the laser beam 12 in each optical path is the same. The number of optical paths that the laser beam 12 separates is not particularly limited, and can be changed depending on the number of optical prisms 22.

The reflectors 31, 32, 33, 34, 35, 36, and 37 reflect the laser light 12 reflected by the optical prism 22. The reflection plates 31 to 37 maintain the phase difference between the P-polarized light and the S-polarized light (the phase difference between the P-polarized component and the S-polarized component) while maintaining the phase difference between the P-polarized light and the S-polarized light. And b) a phase compensation film 38 for reflection. The phase compensation film 38 constitutes a reflecting surface of the reflecting plates 31 to 37. The phase compensation film 38 is, for example, a dielectric multilayer film such as a silicon oxide film, a titanium oxide film, or a magnesium fluoride film. The portions other than the phase compensation film 38 of the reflectors 31 to 37 are configured by, for example, a metal layer.

  As shown in FIG. 4, the first reflector 31 reflects the laser light 12 reflected by the optical prism 22 in the first direction A <b> 1 so as to pass through the first gas cell 41. The laser beam 12 incident on the first reflecting plate 31 exists, for example, in a plane parallel to the XZ plane, and travels at a predetermined angle with respect to the Z axis. In the example shown in FIG. 4, the first reflecting plate 31 reflects the laser light 12 reflected by the first optical prism 22b. The normal line (not shown) of the reflecting surface of the first reflecting plate 31 exists, for example, in a plane parallel to the XZ plane and is inclined by 45 ° with respect to the Z axis. The laser beam 12 traveling in the first direction A1 is, for example, light that exists in a plane parallel to the XZ plane and travels in a direction inclined by a predetermined angle with respect to the X axis. The laser beam 12 incident on the first reflecting plate 31 is, for example, P-polarized light or S-polarized light with respect to the reflecting surface of the first reflecting plate 31. The first reflector 31 is provided on the −X axis direction side of the first gas cell 41.

  The second reflecting plate 32 is inclined in the second direction inclined with respect to the first direction A1 so that the laser beam 12 reflected by the first reflecting plate 31 and transmitted through the first gas cell 41 is transmitted through the first gas cell 41 again. Reflect toward A2. The reflecting surface of the second reflecting plate 32 is, for example, parallel to the YZ plane. The laser beam 12 traveling in the second direction A2 exists, for example, in a plane parallel to the XZ plane, and travels in a direction inclined by a predetermined angle with respect to the X axis. The second reflector 32 is provided on the + X axis direction side of the first gas cell 41. The second reflector 32 is provided between the first gas cell 41 and the second gas cell 42.

  The first reflector 31 further reflects the laser light 12 reflected by the second reflector 32 and transmitted through the first gas cell 41 toward the polarimeter 80. The first reflecting plate 31 is, for example, present in a plane parallel to the XZ plane, reflects the laser light 12 in a direction inclined by a predetermined angle with respect to the Z axis, and enters the polarimeter 80.

  For example, the third reflector 33 is provided symmetrically with the first reflector 31 with respect to a plane parallel to the YZ plane and passing through the center of the second reflector 32. In the example shown in FIG. 4, the third reflecting plate 33 reflects the laser light 12 reflected by the first optical prism 22c. The third reflector 33 reflects the incident laser beam 12 so as to pass through the second gas cell 42. The third reflector 33 is provided on the + X axis direction side of the second gas cell 42.

  The second reflecting plate 32 reflects the laser beam 12 reflected by the third reflecting plate 33 and transmitted through the second gas cell 42 so as to pass through the second gas cell 42 again. The third reflector 33 further reflects the laser light 12 reflected by the second reflector 32 and transmitted through the second gas cell 42 toward the polarimeter 80.

  The fourth reflector 34 reflects the laser beam 12 reflected by the optical prism 22 so as to pass through the fourth gas cell 44. In the example shown in FIG. 6, the fourth reflecting plate 34 reflects the laser light 12 reflected by the second optical prism 22h (see FIG. 4). A normal line (not shown) of the reflecting surface of the fourth reflecting plate 34 exists, for example, in a plane parallel to the YZ plane, and is inclined 45 ° with respect to the Z axis. For example, the fourth reflecting plate 34 reflects the laser light 12 in a direction that is present in a plane parallel to the XY plane and inclined by a predetermined angle with respect to the Y axis. The fourth reflector 34 is provided on the −Y axis direction side of the fourth gas cell 44.

The fifth reflecting plate 35 reflects the laser beam 12 reflected by the fourth reflecting plate 34 and transmitted through the fourth gas cell 44 so as to pass through the fourth gas cell 44 again. The reflective surface of the fifth reflector 35 is, for example, parallel to the XZ plane. The fifth reflecting plate 35 reflects the laser light 12 in a direction that is present in a plane parallel to the XY plane and inclined by a predetermined angle with respect to the Y axis, for example. The fifth reflector 35 is provided on the + Y axis direction side of the fourth gas cell 44. The fifth reflector 35 is provided between the fourth gas cell 44 and the fifth gas cell 45.

  The fourth reflector 34 further reflects the laser beam 12 reflected by the fifth reflector 35 and transmitted through the fourth gas cell 44 toward the polarimeter 80. The fourth reflecting plate 34 is, for example, present in a plane parallel to the XZ plane, reflects the laser light 12 in a direction inclined by a predetermined angle with respect to the Z axis, and enters the polarimeter 80.

  For example, the sixth reflector 36 is provided symmetrically with the fourth reflector 34 with respect to a plane parallel to the XZ plane and passing through the center of the fifth reflector 35. The sixth reflector 36 reflects the incident laser beam 12 so as to pass through the fifth gas cell 45. The sixth reflector 36 is provided on the + Y axis direction side of the fifth gas cell 45.

  The fifth reflecting plate 35 reflects the laser beam 12 reflected by the sixth reflecting plate 36 and transmitted through the fifth gas cell 45 so as to pass through the fifth gas cell 45 again. The sixth reflector 36 further reflects the laser light 12 reflected by the fifth reflector 35 and transmitted through the fifth gas cell 45 toward the polarimeter 80.

  The seventh reflector 37 reflects the laser light 12 reflected by the optical prism 22 so as to pass through the third gas cell 43. Specifically, the seventh reflector 37 reflects the laser light 12 reflected by the optical prism 22 and transmitted through the third gas cell 43 so as to pass through the third gas cell 43 again. In the example shown in FIG. 5, the seventh reflector 37 reflects the laser beam 12 reflected by the optical prisms 22f and 22i. The reflection surface of the seventh reflection plate 37 is parallel to the XY axes, for example. In the illustrated example, the seventh reflecting plate 37 is provided on the −Z-axis direction side of the plurality of gas cells 40.

  Although not shown, the seventh reflector 37 may be provided only on the −Z axis direction side of each of the plurality of third gas cells 43. However, as shown in the figure, the number of components can be reduced by providing one seventh reflecting plate 37 on the −Z-axis direction side of the plurality of gas cells 40.

  A plurality of gas cells 40 are provided. The plurality of gas cells 40 are two-dimensionally arranged. That is, the gas cell 40 is disposed such that a predetermined plane (a plane parallel to the XY plane in the illustrated example) passes through the plurality of gas cells 40. The gas cell 40 has a structure sealed with a container such as quartz glass or borosilicate glass. In the illustrated example, the shape of the gas cell 40 is a cube.

  The gas cell 40 contains a medium 40a that changes the optical characteristics of light according to the magnitude of the magnetic field. Specifically, the medium 40a is a gaseous alkali metal. Examples of the alkali metal as the medium 40a include cesium (Cs), potassium (K), and rubidium (Rb).

When the laser beam 12 is irradiated to the alkali metal atoms accommodated in the gas cell 40, the alkali metal atoms are spin-polarized by optical pumping (the spin directions of the atoms are aligned). The direction of spin polarization is determined by the plane of polarization of the incident laser beam 12. In this state, when a magnetic field is applied to the gas cell 40, so-called precession occurs in which the spin direction of alkali metal atoms rotates around the magnetic field direction. The spin-polarized alkali metal atoms are relaxed by, for example, colliding with the inner wall of the gas cell 40. Steady spin polarization occurs by balancing the spin polarization of alkali metal atoms with its relaxation. Since this spin polarization has optical anisotropy (mainly linear dichroism), the polarization plane of the substantially incident laser beam 12 is rotated and emitted. The rotation angle changes according to the magnitude of the component obtained by projecting the applied magnetic field in the traveling direction of the laser beam 12.

  In the gas sensor 40, the laser beam 12 is incident from one side and emitted to the other side (first path) in the gas cell 40, and the laser beam 12 is incident again from the other side and emitted to one side (first). 2 paths), a so-called double path type magnetic sensor. In the gas cell 40, the first path and the second path are paths that do not overlap.

  The first gas cell 41 is a gas cell in which the laser beam 12 is incident from the −X-axis direction side and is emitted to the + X-axis direction side, and the laser beam 12 is incident again from the + X-axis direction and is emitted to the −X-axis direction side. It is. The second gas cell 42 is a gas cell in which the laser beam 12 is incident from the + X axis direction side and is emitted to the −X axis direction side, and the laser beam 12 is incident again from the −X axis direction and is emitted to the + X axis direction side. It is. In the third gas cell 43, the laser beam 12 enters from the + Z-axis direction side (from the third direction A3 orthogonal to the second direction A2), is emitted to the −Z-axis direction side, and again from the −Z-axis direction. 12 is a gas cell that enters and is ejected toward the + Z-axis direction. The fourth gas cell 44 is a gas cell in which the laser beam 12 is incident from the −Y axis direction side and is emitted to the + Y axis direction side, and the laser beam 12 is incident again from the + Y axis direction and is emitted to the −Y axis direction side. It is. The fifth gas cell 45 is a gas cell in which the laser beam 12 enters from the + Y-axis direction side and is emitted to the −Y-axis direction side, and the laser beam 12 enters again from the −Y-axis direction and is emitted to the + Y-axis direction side. It is.

  The first gas cell 41 and the second gas cell 42 are gas cells for detecting a component of the magnetic field in the substantially X-axis direction. The third gas cell 43 is a gas cell for detecting a component of the magnetic field in the substantially Z-axis direction. The fourth gas cell 44 and the fifth gas cell 45 are gas cells that detect a component of the magnetic field in the substantially Z-axis direction. The gas cells 41 and 42 can constitute a magnetic field gradient meter (gradometer) in a substantially X-axis direction. The plurality of gas cells 43 can constitute a magnetic field gradient meter in a substantially Z-axis direction. The gas cells 44 and 45 can constitute a magnetic field gradient meter in a substantially Y-axis direction.

  The gas cell housing part 50 houses the reflectors 31 to 36 and the gas cell 40. The gas cell storage unit 50 is provided between the table 4 (see FIG. 1) and the plurality of optical prisms 22. In the illustrated example, the gas cell housing 50 is provided on the −Z axis direction side of the optical component 20. The gas cell accommodating part 50 is a rectangular parallelepiped, for example. The gas cell housing part 50 is provided with a through hole 52 for allowing the laser light 12 to pass therethrough. Although the material of the gas cell accommodating part 50 is not specifically limited, For example, they are copper, aluminum, carbon, etc. with high heat conductivity. The gas cell 40 can be heated by heating the gas cell housing 50.

  The container 60 accommodates the optical component 20, the seventh reflection plate 37, and the gas cell storage unit 50. Although the material of the container 60 is not specifically limited, For example, it is a heat insulating ceramic, a plastic, glass, etc. As shown in FIG. 4, the container 60 may be provided with a window portion 62 that can transmit the laser light 12.

  The support part 70 is provided by closing the opening of the container 60. In the illustrated example, the support unit 70 is provided on the + Z-axis direction side of the optical component 20. The support unit 70 supports the polarimeter 80. Although the material of the support part 70 is not specifically limited, For example, it is a heat insulating ceramic, plastic, glass, etc. The support part 70 has a first surface 71 on the −Z axis side and a second surface 72 on the + Z axis side. The first surface 71 is, for example, a surface parallel to the XY plane. The second surface 72 has an inclined surface 73 inclined at a predetermined angle with respect to the first surface 71. A plurality of inclined surfaces 73 are provided.

  An opening 74 is provided in the support portion 70. The opening 74 is a through hole that penetrates the support portion 70 from the inclined surface 73 to the first surface 71. The shape of the opening 74 is, for example, a cylindrical shape. In the example shown in FIGS. 4 and 5, the central axis C of the opening 74 is parallel to the normal line (not shown) of the inclined surface 73 and parallel to the incident direction of the laser beam 12 incident on the polarimeter 80. is there. A plurality of openings 74 are provided according to the number of inclined surfaces 73. In the example shown in FIG. 3, the plurality of openings 74 are provided in a matrix.

  The polarimeter 80 is supported by the support unit 70. A plurality of polarimeters 80 are provided. The plurality of polarimeters 80 are two-dimensionally arranged. That is, the polarimeter 80 is arranged such that a predetermined plane (a plane parallel to the XY plane in the illustrated example) passes through the plurality of polarimeters 80.

  7 is a cross-sectional view taken along the line VII-VII in FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. The polarimeter 80 is provided with a long hole 90 as shown in FIGS. In the illustrated example, two elongated holes 90 are provided in one polarimeter 80. A long hole 92 is provided in the support portion 70. For example, when viewed from the direction of the central axis C of the opening 74, the long hole 90 and the long hole 92 overlap each other.

  The elongated holes 90 and 92 are provided with screws 94 for fixing the polarimeter 80 to the support portion 70. The head portion 95 of the screw 94 is in contact with the polarimeter 80. The screw 94 passes through the long hole 90 and is screwed into the long hole 92. The long hole 92 is a screw hole that is screwed into the screw 94. The head 95 of the screw 94 is brought into contact with the polarimeter 80, and the screw 94 passes through the long hole 90 and is screwed into the long hole 92, whereby the polarimeter 80 is fixed to the support portion 70. As shown in FIG. 7, the inner walls of the long holes 90 and 92 have portions that are not in contact with the screws 94.

  FIG. 9 is a perspective view schematically showing the polarimeter 80. 10 is a cross-sectional view taken along the line XX of FIG. As shown in FIGS. 9 and 10, the polarimeter 80 includes an insertion portion 81, a polarization separation element 82, a first photodetector 83, a second photodetector 84, and a substrate 85. Yes.

  The insertion portion 81 is inserted into an opening 74 provided in the support portion 70. With the screw 94 removed from the elongated holes 90 and 92, the insertion portion 81 is rotatably inserted into the opening 74. In a state where the screw 94 is removed from the elongated holes 90 and 92, the polarimeter 80 can rotate around the central axis C of the opening 74.

  The polarimeter 80 is provided with a through hole 86. The through hole 86 passes through the insertion portion 81. The laser beam 12 reflected by the reflecting plates 31, 33, 34, 36, and 37 enters the polarization separation element 82 through the through hole 86.

  The polarization separation element 82 separates the laser light 12 transmitted through the gas cell 40 into the first polarized light 12a and the second polarized light 12b. The first polarization 12a and the second polarization 12b are two polarization components orthogonal to each other. For example, the first polarized light 12a is P-polarized light, and the second polarized light 12b is S-polarized light. The first polarized light 12a and the second polarized light 12b travel in directions orthogonal to each other. The polarization separation element 82 is, for example, a polarization beam splitter, a Wollaston prism, or the like.

The polarimeter 80 can change the polarization direction of incident light in the polarization separation element 82. Specifically, in the state in which the screw 94 is removed from the elongated holes 90 and 92, the polarimeter 80 has an incident surface 82a of the polarization separating element 82 that is parallel to the central axis C (the incident direction of the laser beam 12 in the polarimeter 80). It is configured to be rotatable about an axis. Thereby, the polarimeter 80 can change the polarization direction of the incident light (laser light 12) in the polarization separation element 82, and can adjust the light quantity of the 1st polarization 12a and the light quantity of the 2nd polarization 12b. .

  The first photodetector 83 detects the first polarized light 12a. The second photodetector 84 detects the second polarized light 12b. Specifically, the photodetectors 83 and 84 detect the intensities of the two component linearly polarized light 12a and 12b orthogonal to each other. Thereby, the photodetectors 83 and 84 can detect the rotation angle of the polarization plane of the laser beam 12. And the processing apparatus 2 (refer FIG. 2) can calculate a magnetic field from the change of the rotation angle of the polarization plane of the laser beam 12. FIG. The rotation angle of the polarization plane is proportional to the magnitude of the magnetic field component projected in the traveling direction of the laser beam 12 in the gas cell 40. Therefore, the magnetic field measurement apparatus 1 including the magnetic sensor 100 can measure the magnetic field distribution of three-dimensional components that are substantially orthogonal to each other. The photodetectors 83 and 84 are, for example, photodiodes (PD).

  The substrate 85 supports the photodetectors 83 and 84. An integrated circuit (IC) may be mounted on the substrate 85.

  The magnetic sensor 100 has the following features, for example.

  In the magnetic sensor 100, a gas cell housing portion 50 that houses a plurality of gas cells 40 that are two-dimensionally arranged, a plurality of optical prisms 22 that are two-dimensionally arranged by making light incident on the gas cells 40, and the gas cells 40 are arranged. A plurality of polarimeters 80 having two-dimensionally arranged light detectors 83 and 84 for detecting the transmitted light, and the plurality of optical prisms 22 include the gas cell housing unit 50 and the plurality of polarimeters 80. Between. Therefore, in the magnetic sensor 100, the light source 10 or the photodetectors 83 and 84 do not exist between the plurality of gas cells 40, and the plurality of gas cells 40 can be brought close to each other (the interval between the plurality of gas cells 40 can be reduced). Therefore, the magnetic sensor 100 can have a high spatial resolution.

  Further, in the magnetic sensor 100, the gas cell storage unit 50 is provided between the subject placement unit 4 and the plurality of optical prisms 22. Therefore, in the magnetic sensor 100, for example, the distance between the subject placement unit 4 and the gas cell storage unit 50 is larger than when a plurality of optical prisms 22 are provided between the subject placement unit 4 and the gas cell storage unit 50. Can be reduced. Thereby, in the magnetic sensor 100, the space | interval of a test object and the gas cell 40 can be made small, and it can have a high sensitivity.

  Further, in the magnetic sensor 100, the polarimeter 80 is configured to be able to change the polarization direction of incident light in the polarization separation element 82. Therefore, in the magnetic sensor 100, when a known magnetic field is applied, the intensity (light quantity) of the first polarization 12a detected by the first photodetector 83 and the second polarization detected by the second photodetector 84 are detected. It is possible to change the way the light is incident on the polarization separation element 82 so that the intensity (light quantity) of 12b becomes a predetermined value. Therefore, the magnetic sensor 100 can detect the magnetic field more accurately.

In the magnetic sensor 100, the gas cell housing 50 reflects the laser light 12 reflected by the optical prism 22 in the first direction A <b> 1 so as to pass through the first gas cell 41, and the first reflection. A second reflecting plate 32 that reflects the laser beam 12 reflected by the plate 31 and transmitted through the first gas cell 41 in a second direction A2 inclined with respect to the first direction A1 so as to pass through the first gas cell 41; , To accommodate. Therefore, in the first gas cell 41, the laser beam 12 is incident from one side and emitted to the other side (first path), and the laser beam 12 is incident again from the other side and emitted to one side (second). Route). Thus, in the 1st gas cell 41, the laser beam 12 permeate | transmits (passes) twice, and a 1st path | route and a 2nd path | route do not overlap. Therefore, in the magnetic sensor 100, the rotation angle of the polarization plane of the laser light 12 can be increased and the sensitivity can be higher than when the laser light 12 passes through the first gas cell 41 only once, for example. .

  In the magnetic sensor 100, the first reflecting plate 31 reflects the laser light 12 reflected by the second reflecting plate 32 and transmitted through the first gas cell 41 toward the polarimeter 80. Therefore, in the magnetic sensor 100, a reflecting plate for reflecting the laser light 12 toward the first gas cell 41, and a reflecting plate for reflecting the laser light 12 transmitted through the first gas cell 41 toward the polarimeter 80; Can be used as a common reflector (first reflector 31). Therefore, in the magnetic sensor 100, a reflecting plate for reflecting the laser beam 12 toward the first gas cell 41, and a reflecting plate for reflecting the laser beam 12 transmitted through the first gas cell 41 toward the polarimeter 80 The number of parts can be reduced as compared with the case of providing them as separate reflectors.

  In the magnetic sensor 100, the first reflecting plate 31 and the second reflecting plate 32 have the phase compensation film 38 that reflects the laser light 12 transmitted through the first gas cell 41 while maintaining the phase difference between the P-polarized light and the S-polarized light. Have. Therefore, the magnetic sensor 100 can detect the rotation angle of the polarization plane of the laser light 12 with high sensitivity. For example, when the laser light 12 is reflected by the reflectors 31 and 32, the extinction ratio decreases if the phase difference between the P-polarized light and the S-polarized light is different between the laser light 12 before being reflected and the laser light 12 after being reflected. However, the rotation angle of the polarization plane of the laser beam 12 may not be detected with high sensitivity. In the magnetic sensor 100, such a problem can be avoided.

  In the magnetic sensor 100, the second reflecting plate 32 is provided between the first gas cell 41 and the second gas cell 42. Therefore, in the magnetic sensor 100, a reflector that reflects the laser light 12 toward the first gas cell 41 and a reflector that reflects the laser light 12 toward the second gas cell 42 are used as a common reflector (second reflection). Plate 32). Therefore, in the magnetic sensor 100, when the reflecting plate that reflects the laser beam 12 toward the first gas cell 41 and the reflecting plate that reflects the laser beam 12 toward the second gas cell 42 are provided as separate reflecting plates. In comparison, the number of parts can be reduced.

  In the magnetic sensor 100, the laser beam 12 enters the third gas cell 43 from the third direction A3 orthogonal to the second direction A2. Therefore, the magnetic field measuring apparatus including the magnetic sensor 100 can measure the two-direction components of the magnetic field.

  The magnetic sensor 100 includes a support portion 70 that supports the polarimeter 80 and is provided with an opening 74, and the polarimeter 80 has an insertion portion 81 that is rotatably inserted into the opening 74. Therefore, in the magnetic sensor 100, the polarimeter 80 can be rotated about the central axis C of the opening 74, and the polarization direction of the incident light in the polarization separation element 82 can be changed.

  In the magnetic sensor 100, a long hole 90 is provided in the polarimeter 80, and a screw 94 that fixes the polarimeter 80 to the support unit 70 is provided in the long hole 90. Therefore, in the magnetic sensor 100, for example, when the gas cell 40 is deteriorated and the gas cell 40 is replaced, the screw 94 is removed from the long hole 90, the polarimeter 80 is rotated, and the screw 90 is again screwed into the long hole 90 at a desired position. The polarimeter 80 can be fixed to the support portion 70 by inserting 94. In the magnetic sensor 100, since the hole provided in the polarimeter 80 is the long hole 90, the polarimeter 80 can be fixed to the support unit 70 at a desired position by rotating the polarimeter 80. In the magnetic sensor 100, since the polarimeter 80 is provided on the most + Z-axis direction side of the magnetic sensor 100, the polarimeter 80 can be easily rotated.

As shown in FIG. 11, the long hole 90 may have an arcuate outer edge centered on the central axis C when viewed from the central axis C direction. Thereby, in the magnetic sensor 100, the polarimeter 80 can be more reliably rotated to fix the polarimeter 80 to the support portion 70 at a desired position.

  In the magnetic sensor 100, the medium 40a accommodated in the gas cell 40 is a gaseous alkali metal. Therefore, the magnetic sensor 100 can change the polarization plane of the light transmitted through the gas cell 40 according to the magnitude of the magnetic field by interacting with the magnetic field to which the alkali metal is applied.

  In the magnetic sensor 100, the normal lines of the reflecting surfaces of the optical prisms 22b, 22c, 22e, 22f, 22h, and 22i exist in a plane parallel to the XZ plane, and are inclined at a predetermined angle with respect to the Z axis. The predetermined angle is not less than 2 ° and not more than 5 °. Therefore, the magnetic sensor 100 can have high sensitivity. For example, when the predetermined angle is smaller than 2 °, the double pass effect is weakened and the sensitivity may be lowered. When the predetermined angle is larger than 5 °, the volume of the gas cell 40 is reduced by the increase in the size of the reflectors 31, 33, 34, and 36, and the sensitivity may be lowered.

  Although not shown, the magnetic sensor 100 may not have one of the first photodetector 83 and the second photodetector 84. When the correlation between the light intensity detected by the photodetector 83 and the rotation angle of the polarization plane is known, the rotation angle of the polarization plane of the laser light 12 can be detected even in the above-described form. .

2.2. Second Magnetic Sensor Next, the second magnetic sensor 200 according to the present embodiment will be described with reference to the drawings. The second magnetic sensor 200 is a sensor for detecting a magnetic field (cardiac magnetic field) to be measured.

  FIG. 12 is a plan view schematically showing the second magnetic sensor 200 according to this embodiment. FIG. 13 is a cross-sectional view taken along line XIII-XIII of FIG. 12 schematically showing the second magnetic sensor 200 according to the present embodiment. For the sake of convenience, in FIG. 12, the seventh reflector 37, the gas cell storage unit 50, and the support unit 70 are omitted from illustration (however, the opening 74 provided in the support unit 70 is illustrated). ). 12 and 13, the table 4 is not shown. 12 and 13 illustrate the X axis, the Y axis, and the Z axis as three axes orthogonal to each other.

  Hereinafter, in the second magnetic sensor 200 according to the present embodiment, members having the same functions as the constituent members of the first magnetic sensor 100 according to the present embodiment described above will be denoted by the same reference numerals, and detailed description thereof will be given. Omitted.

  As shown in FIGS. 12 and 13, the second magnetic sensor 200 is different from the first magnetic sensor 100 described above in that the plurality of gas cells 40 are all the third gas cells 43.

  In the second magnetic sensor 200 (hereinafter also simply referred to as “magnetic sensor 200”), sixteen third gas cells 43 are provided. In the example shown in FIG. 12, 16 gas cells 43 are provided in a matrix. The second magnetic sensor 200 is a sensor for detecting a component of the magnetic field in the substantially Z-axis direction.

3. Experimental Example An experimental example is shown below to describe the present invention more specifically. The present invention is not limited by the following experimental examples.

As an experimental example, tracking calculation of each light beam (laser light) was performed. The normal vector of the reflector N, the unit vectors in the traveling direction of the incident light and k _in, the unit vector k _out of the traveling direction of the reflected light is given by the following formula (1). Based on the following formula (1), the traveling direction of the light beam incident on each polarimeter was calculated.

k _out = k _in +2 (−k _in · N) N (1)

  14 and 15 are diagrams for explaining a model used in the experimental example. 14 and 15 illustrate the X axis, the Y axis, and the Z axis as three axes orthogonal to each other.

As shown in FIGS. 14 and 15, the incident directions of the light beams k ₁₀ , k ₂₀ , k ₃₀ , k ₄₀ , and k ₅₀ are all in a plane parallel to the XZ plane, and the traveling direction is relative to the Z axis. It is assumed that it is tilted 3 °. The light beams k ₁₀ , k ₂₀ , k ₃₀ , and k ₄₀ are reflected in the order of the first reflector R 1, the second reflector R 2, and the first reflector R 1, and enter the polarimeter P. The light beam k ₅₀ was set reflected by the second reflector R2, is incident on the polarimeter P. The reflecting surface of the first reflecting plate R1 is inclined 45 ° with respect to the Z axis.

FIG. 16 is a table showing calculation results. The luminous fluxes k ₁₀ , k ₂₀ , k ₃₀ and k ₄₀ were reflected three times, and the luminous flux k ₅₀ was reflected once, but the polarimeter incident light vectors were the same. Therefore, it was found that the incident light beams k ₁₀ , k ₂₀ , k ₃₀ , k ₄₀ , and k ₅₀ are incident on the polarimeter P from the same direction. Thereby, it turned out that the attitude | position of each polarimeter P can be unified. Therefore, for example, in the magnetic sensor 100, the layout can be easily changed. That is, the layout can be easily changed by changing the positions of the optical prism 22, the gas cell 40, and the reflectors 31 to 36 without changing the orientation of the polarimeter 80.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 1 ... Magnetic field measuring apparatus, 2 ... Processing apparatus, 3 ... Base, 3a ... X-axis direction linear motion mechanism, 4 ... Table, 4a ... X-axis direction table, 4b ... Z-axis direction table, 4c ... Y-axis direction table, 6 DESCRIPTION OF SYMBOLS Magnetic shielding apparatus, 6a ... Main body part, 6b ... Correction coil, 6c ... Opening part, 7 ... Supporting member, 9 ... Subject, 9a ... Chest part, 10 ... Light source, 12 ... Laser light, 12a ... First polarized light, 12b 2nd polarization, 14 ... Polarizing plate, 20 ... Optical component, 22 ... Optical prism, 22a, 22b, 22c, 22d, 22e, 22f, 22g ... 1st optical prism, 22h, 22i, 22j ... 2nd optical prism, 31 ... 1st reflector, 32 ... 2nd reflector, 33 ... 3rd reflector, 34 ... 4th reflector, 35 ... 5th reflector, 36 ... 6th reflector, 37 ... 7th reflector, 38 ... phase compensation film, 40 ... gas cell, 41 ... first gas cell , 42 ... the second gas cell, 43 ... the third gas cell, 44 ... the fourth gas cell, 45 ... the fifth ... gas cell, 50 ... the gas cell housing part, 52 ... the through hole, 60 ... the container, 62 ... the window part, 70 ... the support part , 71 ... First surface, 72 ... Second surface, 73 ... Inclined surface, 74 ... Opening, 80 ... Polarimeter, 81 ... Insertion part, 82 ... Polarization separation element, 82a ... Incident surface, 83 ... First light detection , 84 ... second photodetector, 85 ... substrate, 86 ... through hole, 90, 92 ... long hole, 94 ... screw, 95 ... head, 100 ... first magnetic sensor, 110 ... operation unit, 112 ... display , 114 ... storage unit, 116 ... calculation unit, 200 ... second magnetic sensor

Claims (10)

A subject placement section for placing the subject;
A gas cell accommodating portion for accommodating a plurality of gas cells arranged two-dimensionally;
A plurality of optical prisms arranged in a two-dimensional manner by making light incident on the gas cell;
A plurality of two-dimensionally arranged elements, each having a polarization separation element that separates light transmitted through the gas cell into first polarized light and second polarized light, and a photodetector that detects the first polarized light or the second polarized light The polarimeter of
Including
The gas cell contains a medium that changes the optical properties of light according to the magnitude of the magnetic field;
The gas cell housing portion is provided between the subject placement portion and the plurality of optical prisms,
The plurality of optical prisms are provided between the gas cell housing portion and the plurality of polarimeters,
The polarimeter is a magnetic sensor configured to change a polarization direction of incident light in the polarization separation element. In claim 1,
The gas cell accommodating portion is
A first reflector that reflects light reflected by the optical prism in a first direction so as to pass through the first gas cell of the plurality of gas cells;
A second reflecting plate that reflects light reflected by the first reflecting plate and transmitted through the first gas cell toward a second direction inclined with respect to the first direction so as to pass through the first gas cell;
Houses a magnetic sensor. In claim 2,
The first reflection plate is a magnetic sensor that reflects light reflected by the second reflection plate and transmitted through the first gas cell toward the polarimeter. In claim 2 or 3,
The first reflector and the second reflector have a phase compensation film that reflects light transmitted through the first gas cell while maintaining a phase difference between P-polarized light and S-polarized light. In any one of Claims 2 thru | or 4,
The second reflector is a magnetic sensor provided between the first gas cell and a second gas cell of the plurality of gas cells. In any one of Claims 2 thru | or 5,
A third gas cell of the plurality of gas cells is a magnetic sensor in which light enters from a third direction orthogonal to the second direction. In any one of Claims 1 thru | or 6,
Supporting the polarimeter, including a support portion provided with an opening,
The polarimeter has a magnetic sensor having an insertion portion that is rotatably inserted into the opening. In claim 7,
The polarimeter is provided with a slot,
The long hole is provided with a screw for fixing the polarimeter to the support portion. In any one of Claims 1 thru | or 8,
The magnetic sensor, wherein the medium is a gaseous alkali metal.   A magnetic field measurement apparatus comprising the magnetic sensor according to claim 1.