Magnetic shield device

Abstract

A magnetic shield device 1 comprises: a body part 13 that is an enclosure that forms an internal magnetically-shielded space 10 and comprises body-part magnetic shield members 11, 12 that are formed from one or more layers of a body-part magnetic shield material that provides a shield to magnetism from the outside; and an opening part 14 that is formed in the body part 13, connects the magnetically-shielded space 10 with the outside, and also allows a person to enter and exit. The magnetic shield device 1 also comprises a magnetism reduction means (30, 40, 61, 62, 63) that reduces infiltration of magnetism from the outside into the magnetically-shielded space 10 through the opening part 14.

Description

Magnetic shielding device

[0001] The present invention relates to a magnetic shielding device capable of shielding from external magnetic fields and housing a magnetic sensor and a test subject inside.

[0002] Conventionally, biomagnetic measurements using magnetic sensors, such as those used in magnetoencephalography (MEG), have employed SQUIDs (Superconducting Quantum Interference Devices), which are highly sensitive magnetic sensors capable of detecting weak magnetic fields. When using such highly sensitive magnetic sensors, a magnetic shielding device that shields against external magnetic fields is used, for example, as disclosed in Patent Document 1 (JP 2007-311523). In recent years, optical pumping magnetometers (OPMs, hereinafter referred to as OPM sensors) have been proposed as a highly sensitive magnetic sensor to replace SQUIDs. Unlike SQUIDs, OPM sensors do not require refrigerants such as liquid helium and have the advantage of achieving magnetic sensitivity comparable to SQUIDs at room temperature, and their application to various biomagnetic measurements (e.g., MEG) is being studied. Because OPM sensors require an even lower magnetic field environment compared to conventional sensors as an operating condition, they must be used within a magnetic shielding device that sufficiently blocks (reduces) external magnetic fields, including the Earth's magnetic field, and the residual magnetic field within the magnetic shielding device must be maintained below a certain value.

[0003] The magnetic field entering a magnetic shielding device from the outside tends to be strongest through the openings that serve as entrances and exits. Therefore, various measures have been taken to improve the structure of the doors that close these openings in order to reduce the internal residual magnetic field. For example, Patent Document 2 (JP-A-6-021680) proposes a method of using pneumatic pressure to press each permalloy layer so that they are uniformly connected across the surface when the door of a multilayer magnetic shielding device is closed. Patent Document 3 (JP-A-2006-352024) discloses a method of connecting the pressing parts of the door of a multilayer magnetic shielding device to apply uniform pressure simultaneously, while also pressing each layer with an elastic body.

[0004] JP 2007-311523 A, JP H06-021680 A, JP 2006-252024 A

[0005] Here, the present inventors have focused on magnetic leakage from the door portion that closes the opening of a magnetic shield device as in the above-mentioned Patent Document 2 and Patent Document 3, and have found that when countermeasures are implemented in the structure of the door portion, the device itself becomes expensive, or the operability of the device deteriorates (for example, the door becomes heavy and the opening and closing performance deteriorates). Then, in order to reduce the intruding magnetic field from the opening and reduce the residual magnetic field inside the shield device, the inventors conceived of reducing the magnetic field in the vicinity of the opening, and as a result of extensive and intensive studies, the present invention has been accomplished.

[0006] Accordingly, an object of the present invention is to provide a magnetic shield apparatus having a magnetic shield space capable of accommodating a magnetic sensor and a subject therein, which can more effectively reduce the intrusion of external magnetism from an opening through which a person can enter and exit.

[0007] What achieves the above object is as follows. A magnetic shield apparatus including a magnetic shield space capable of accommodating a magnetic sensor and a subject therein, the magnetic shield apparatus comprising: a casing-shaped main body portion including a main body magnetic shield member made of one or more layers of main body magnetic shield material that shields magnetism from the outside, and having the magnetic shield space formed therein; and an opening portion formed in the main body portion, communicating the magnetic shield space with the outside, and allowing a person to enter and exit, wherein the magnetic shield apparatus further includes a magnetism reducing unit that reduces intrusion of external magnetism from the opening portion into the magnetic shield space.

[0008] A magnetic shield apparatus of the present invention includes a casing-shaped main body portion that includes a main body magnetic shield member made of one or more layers of main body magnetic shield material that shields magnetism from the outside and has a magnetic shield space formed therein, and an opening portion that is formed in the main body portion, communicates the magnetic shield space with the outside, and allows a person to enter and exit, and the magnetic shield apparatus further includes a magnetism reducing unit that reduces intrusion of external magnetism from the opening portion into the magnetic shield space. This makes it possible to more effectively reduce the intrusion of external magnetism from the opening through which a person can enter and exit.

[0009] Figure 1 is a schematic perspective view showing an embodiment of the magnetic shielding device of the present invention. Figure 2 is a schematic cross-sectional view taken along line A-A in Figure 1. Figure 3 is a schematic cross-sectional view taken along line B-B in Figure 2. Figure 4 is a schematic cross-sectional view taken along line D-D in Figure 3. Figure 5 is a schematic enlarged cross-sectional view of section C in Figure 2. Figure 6 is a schematic cross-sectional view showing another embodiment of the magnetic shielding device of the present invention. Figure 7 is a schematic cross-sectional view showing yet another embodiment of the magnetic shielding device of the present invention. Figure 8 is a schematic enlarged cross-sectional view showing yet another embodiment of the magnetic shielding device of the present invention. Figure 9 is a schematic enlarged cross-sectional view showing yet another embodiment of the magnetic shielding device of the present invention. Figure 10 is a schematic cross-sectional view showing yet another embodiment of the magnetic shielding device of the present invention.

[0010] The magnetic shielding device of the present invention will be described using the embodiments shown in the drawings. As shown in Figures 1 to 4, the magnetic shielding device 1 of the present invention is a magnetic shielding device 1 that has a magnetic shielding space 10 inside which a magnetic sensor and a subject can be housed, and comprises a housing-shaped main body 13 which has a magnetic shielding space 10 formed inside which a magnetic shielding space 10 is formed, and an opening 14 formed in the main body 13 which connects the magnetic shielding space 10 to the outside and into which a person can enter and exit, and further comprises a magnetic reduction means for reducing the intrusion of external magnetism into the magnetic shielding space 10 from the opening 14.

[0011] The magnetic shielding device 1 is for shielding (reducing or blocking) external magnetic fields. In this embodiment, the magnetic shielding device 1 comprises a housing-shaped main body 13, and a magnetic shielding space 10 is formed inside the main body 13 (inside the innermost magnetic shielding member 11). Measuring jigs or the like (not shown) may be installed in the magnetic shielding space 10.

[0012] The main body portion 13 of the magnetic shielding device 1 is equipped with one or more layers of magnetic shielding members (magnetic shielding members for the main body). Specifically, the main body portion 13 of the magnetic shielding device 1 in this embodiment is equipped with two layers of magnetic shielding members for the main body 11 and 12, comprising an innermost layer of magnetic shielding member for the main body (a housing-shaped innermost layer shield wall portion composed of the innermost layer of magnetic shielding members for the main body) 11 that defines the magnetic shielding space 10, and an outer layer of magnetic shielding member for the main body (a housing-shaped outer layer shield wall portion composed of the outer layer of magnetic shielding members for the main body) 12 that surrounds the innermost layer of magnetic shielding member for the main body 11 and is adjacent to the innermost layer of magnetic shielding member for the main body 11 at a predetermined distance to the outside. The magnetic shield space 10 defined by the innermost magnetic shielding member for the main body (the innermost shield wall portion in the shape of a housing, composed of the innermost magnetic shielding member for the main body) 11 is set appropriately according to the use and purpose of the magnetic shielding device 1, but for example, as shown in Figure 2, it is preferable that the depth dimension L1 is about 2000 mm and the width dimension W1 is about 2000 mm.

[0013] Although not described in detail here, it is preferable that the magnetic shielding members for each main body (innermost shield wall and outermost shield wall) 11, 12 are constructed to have as few gaps as possible in order to prevent magnetic intrusion. Furthermore, it is preferable that the magnetic shielding members for each main body (innermost shield wall and outermost shield wall) 11, 12 have a structure with as few openings as possible, but openings may be provided as needed (for example, for pulling in various measuring cables, etc.).

[0014] In this embodiment, each magnetic shielding member 11, 12 for the main body is composed of a plate-shaped member formed from a high-permeability material. Examples of materials that constitute such magnetic shielding members 11, 12 for the main body (magnetic shielding material for the main body) include iron and permalloy, with permalloy having a relatively high nickel content (e.g., permalloy C) or a material having a permeability of 100,000 H / m or more being particularly preferred. Furthermore, the thickness of the magnetic shielding members 11, 12 for the main body (the thickness of the plate-shaped member constituting the magnetic shielding members 11, 12 for the main body) is preferably 1 to 2 mm.

[0015] In this embodiment, the magnetic shielding device 1 is equipped with two layers of magnetic shielding members 11 and 12 for the main body. However, in the magnetic shielding device, the number of layers of magnetic shielding members for the main body may be increased depending on the surrounding magnetic environment. For example, it is preferable that the number of layers of magnetic shielding members for the main body in the magnetic shielding device be 3 to 4.

[0016] Furthermore, although not described in detail here, it is preferable that the innermost magnetic shielding member 11 for the main body is supported by the bottom wall portion of the outer magnetic shielding member 12 for the main body via a base 15, and that there are no support columns or other supports in the lateral direction or on the ceiling. It is also preferable that the innermost magnetic shielding member 11 for the main body is supported in a state that is vibrationally insulated from the outer magnetic shielding member 12 for the main body (a state in which vibrations from the outside or the outer magnetic shielding member 12 for the main body are less likely to be transmitted).

[0017] The magnetic shielding device 1 has a main body portion 13 and is equipped with an opening 14 that allows a person to enter and exit, connecting the magnetic shielding space 10 to the outside. The size of the opening 14 is set appropriately according to the use and purpose of the magnetic shielding device 1, but it is preferably large enough for an average person to easily pass through. For example, as shown in Figures 2 and 3, it is preferable that the height dimension H2 is about 2000 mm and the width dimension W2 is about 900 mm.

[0018] The magnetic shielding device 1 includes magnetic shielding members 31 and 32 for protruding parts, made of one or more layers of magnetic shielding material for protruding parts, as a magnetic reduction means to reduce the intrusion of external magnetism from the opening 14, and a tunnel or sleeve-shaped cylindrical protrusion 30 that protrudes outward from the opening 14 and communicates with the magnetic shielding space 10 through the opening 14. In other words, the magnetic shielding device 1 includes a cylindrical protrusion 30 that protrudes outward from the opening 14 and communicates with the magnetic shielding space 10 through the opening 14, and includes magnetic shielding members 31 and 32 for protruding parts, made of one or more layers of magnetic shielding material for protruding parts, provided on the cylindrical protrusion 30 and shielding with external magnetism. The cylindrical protrusion (tunnel or sleeve-shaped protrusion) 30 can be imagined as, for example, the tunnel-shaped entrance of an igloo, an ice dwelling of the Inuit (Eskimo), or a structure such as a "windbreak room (entrance hood)" found in cold regions. In this embodiment, the protrusion 30 has a rectangular tubular shape with an upper surface 34, a lower surface 35, and a pair of side surfaces 36, 36, with one end connected to the opening 14 and the other end open to the outside. The shape of the protrusion is not limited to the example shown, and for example, it may be cylindrical overall, or part of the upper surface or side surfaces may be curved (arch-shaped). In this embodiment, the protrusion is integrally provided with the main body of the magnetic shielding device, but the protrusion may be detachably provided with the main body of the magnetic shielding device. In other words, the magnetic reduction means of the magnetic shielding device may include a cylindrical protrusion component (sleeve for magnetic shielding device) equipped with a magnetic shielding member for the protrusion made of one or more layers of magnetic shielding material for the protrusion that shields from external magnetism, and by detachably attaching the protrusion component to the opening of the main body, a protrusion that protrudes outward from the opening may be formed. This makes it possible to reconfigure an existing magnetic shielding room (main body having an opening for a magnetic shielding device) as a magnetic shielding device equipped with the above-described protrusion.

[0019] The protruding portion 30 of the magnetic shielding device 1 is provided with one or more layers of magnetic shielding members (magnetic shielding members for the protruding portion). Specifically, the protruding portion 30 of the magnetic shielding device 1 in this embodiment is provided with two layers of magnetic shielding members for the protruding portion 31 and 32, comprising an innermost layer of magnetic shielding member for the protruding portion (a cylindrical innermost layer shield wall portion composed of the innermost layer magnetic shielding member for the protruding portion) 31 that defines the internal space 33 of the protruding portion, and an outer layer of magnetic shielding member for the protruding portion (a cylindrical outer layer shield wall portion composed of the outer layer magnetic shielding member for the protruding portion) 32 that surrounds the innermost layer magnetic shielding member for the protruding portion 31 and is adjacent to the innermost layer magnetic shielding member for the protruding portion 31 at a predetermined distance to the outside. The internal space 33 of the protruding portion, defined by the innermost magnetic shielding member for the protruding portion (a cylindrical innermost shield wall portion composed of the innermost magnetic shielding member for the protruding portion) 31, is, for example, large enough for an average person to easily pass through. For instance, as shown in Figure 4, the height dimension H3 is approximately 2000 mm and the width dimension W3 is approximately 800 to 900 mm. However, such an internal space of the protruding portion can be made to an appropriate size and ratio depending on the purpose and function of the magnetic shielding device, such as inspection (machine) or treatment.

[0020] In this embodiment, each magnetic shielding member 31, 32 for the protruding portion is composed of a plate-shaped member formed from a high-permeability material. The material constituting such magnetic shielding members 31, 32 for the protruding portion (magnetic shielding material for the protruding portion) is the same as the material constituting the magnetic shielding members 11, 12 for the main body (magnetic shielding material for the main body) described above, and examples include iron and permalloy. In particular, permalloy with a relatively high nickel content (for example, permalloy C) or a material with a magnetic permeability of 100,000 H / m or more is preferred. Furthermore, the thickness of the magnetic shielding members 31, 32 for the protruding portion (the thickness of the plate-shaped member constituting the magnetic shielding members 31, 32 for the protruding portion) is preferably 1 to 2 mm.

[0021] In this embodiment, the magnetic shielding device 1 is equipped with two layers of magnetic shielding members 31 and 32 for protruding parts. However, in the magnetic shielding device, the number of layers of magnetic shielding members for protruding parts may be increased or decreased depending on the surrounding magnetic environment. For example, the number of layers of magnetic shielding members for protruding parts in the magnetic shielding device is preferably 1 to 3.

[0022] In a magnetic shielding device 1 equipped with such a protrusion 30, external magnetic fields, including the Earth's magnetic field, can be reduced by the protrusion 30 (in other words, the magnetic field near the opening 14 can be reduced), thereby reducing the magnetic field that penetrates into the interior of the magnetic shielding device 1 (magnetic shielding space 10) from the opening 14. Furthermore, by reducing the magnetic field near the opening 14 in the magnetic shielding device 1, it becomes possible to secure a wide area with a flat magnetic field distribution inside the magnetic shielding device 1 (magnetic shielding space 10).

[0023] As shown in Figure 2, the magnetic shielding device 1 of this embodiment may include, as a magnetic reduction means, a door magnetic shielding member 41 made of one or more layers of door magnetic shielding material that shields against external magnetism, and a door (opening door) 40 provided at the opening 14 so as to be able to open and close the opening 14. In other words, the magnetic shielding device 1 may include, at the opening 14, a door (opening door) 40 provided so as to be able to open and close the opening 14, and as a magnetic reduction means, a door magnetic shielding member 41 made of one or more layers of door magnetic shielding material that shields against external magnetism. This makes it possible to reduce the magnetic field (magnetism) that enters the inside of the magnetic shielding device 1 (magnetic shielding space 10) from the opening 14 not only at the protruding part 30 but also at the door (opening door) 40. Although not described in detail, the door (opening door) 40 may be a hinged door type as shown in Figure 2, or it may be a sliding door type.

[0024] Furthermore, it is preferable that the main body 13 of the magnetic shielding device 1 is equipped with two or more layers (two layers in this embodiment) of magnetic shielding members 11 and 12 for the main body, and the door (door for opening) 40 is equipped with a door magnetic shielding member 41 with fewer layers than the main body 13 (one layer in this embodiment). This makes it possible to lighten the door (door for opening) 40. In particular, as in this embodiment, when the opening 14 is relatively large (large enough for an average person to easily pass through), if the door (door for opening) 40 that can open and close such an opening 14 has the same layer configuration as the main body 13, the weight of the door (door for opening) 40 may become several hundred kg (for example, about 300 kg), which increases the cost of constructing a structure to support such a door (for example, a hinge and the frame member that supports it), and the structure related to the door may deform over time, potentially increasing magnetic leakage (intrusion), so the effect of lightening the door is significant.

[0025] The door magnetic shielding member 41 is composed of a plate-shaped member made of a high-permeability material. The material used to make up such a door magnetic shielding member 41 (door magnetic shielding material) is similar to that used for the main body magnetic shielding members 11 and 12 (main body magnetic shielding material) and the protruding magnetic shielding members 31 and 32 (protruding magnetic shielding material), including iron and permalloy. Particularly preferred are permalloy with a relatively high nickel content (e.g., permalloy C) or a material with a permeability of 100,000 H / m or more. Furthermore, the thickness of the door magnetic shielding member 41 (the thickness of the plate-shaped member constituting the door magnetic shielding member 41) is preferably 1 to 2 mm.

[0026] Furthermore, as shown in Figure 6, the magnetic shielding device 1a may include a second door (protruding door) magnetic shielding member 51 made of one or more layers of magnetic shielding material for a second door (protruding door) that shields against external magnetism, and a second door (protruding door) 50 provided that can open and close the opening on the opposite side of the opening 14 of the protruding portion 30. In other words, as in the magnetic shielding device 1a, the opening 14 may include a second door (protruding door) 50 provided that can open and close the opening of the protruding portion 30 (the opening on the opposite side of the opening 14), and the magnetic shielding means may include a second door (protruding door) magnetic shielding member 51 made of one or more layers of magnetic shielding material that shields against external magnetism. This makes it possible to reduce the magnetic field (magnetism) entering the inside of the magnetic shielding device 1a (magnetic shielding space 10) from the opening 14 not only in the protruding portion 30 but also in the second door (protruding door) 50. Although not described in detail here, the second door (projecting door) 50 may be a hinged door type as shown in Figure 6, or it may be a sliding door type.

[0027] Furthermore, it is preferable that the main body portion 13 of the magnetic shielding device 1a is equipped with two or more layers (two layers in this embodiment) of magnetic shielding members 11 and 12 for the main body portion, and the second door (protruding door) 50 is equipped with a magnetic shielding member 51 for the second door (protruding door) which has fewer layers than the main body portion 13 (one layer in this embodiment). This makes it possible to construct the second door (protruding door) 50 to be relatively lightweight, thereby suppressing cost increases and deformation over time.

[0028] The second door magnetic shielding member 51 is composed of a plate-shaped member made of a high-permeability material. The material constituting the second door magnetic shielding member 51 (second door magnetic shielding material) is the same as the material constituting the main body magnetic shielding members 11 and 12 (main body magnetic shielding material) and the material constituting the protruding magnetic shielding members 31 and 32 (protruding magnetic shielding material) described above, and includes iron and permalloy, with permalloy having a relatively high nickel content (for example, permalloy C) or a material having a magnetic permeability of 100,000 H / m or more being particularly preferred. Furthermore, the thickness of the second door magnetic shielding member 51 (the thickness of the plate-shaped member constituting the second door magnetic shielding member 51) is preferably 1 to 2 mm.

[0029] Furthermore, as shown in Figure 7, the magnetic shielding device 1b does not necessarily have to be provided with a door (opening door) or a second door (protruding door) as a means of reducing magnetism.

[0030] The magnetic reduction means of the magnetic shielding device 1 includes compensation coils in the protruding portion 30 that are orthogonal to each other and face each other in at least one of the following directions: the direction perpendicular to the opening 14 (X direction), the width direction of the opening 14 (Y direction), and the height direction of the opening 14 (Z direction). As shown in Figures 2 to 4, the magnetic shielding device 1 of this embodiment includes three pairs of compensation coils that are orthogonal to each other and face each of the three directions X, Y, and Z described above: compensation coils 61, 61 that face each other in the direction perpendicular to the opening 14 (X direction), compensation coils 62, 62 that face each other in the width direction of the opening 14 (Y direction), and compensation coils 63, 63 that face each other in the height direction of the opening 14 (Z direction). In the following, the pairs of compensation coils 61, 61, 62, 62, and 63, 63 may be simply referred to as 61, 62, and 63.

[0031] Although not described in detail here, the magnetic shielding device 1 is equipped with a power source (current source) for driving each of the compensation coils 61, 62, and 63. That is, each of the compensation coils 61, 62, and 63 of the magnetic shielding device 1 is connected to a power source (current source) not shown, and the current (compensation current) supplied by the power source (current source) can generate magnetic fields (compensation magnetic fields) that cancel out the external magnetic fields (magnetic fields from the outside) in the three directions X, Y, and Z, respectively, with respect to the opening 14. It is preferable that such a power source (current source) can supply each of the compensation coils 61, 62, and 63 with an independent current (individually set compensation current) in order to minimize the magnetic field near the opening 14 (magnetic field entering from the opening 14).

[0032] In a magnetic shielding device 1 equipped with such compensating coils 61, 62, and 63, external magnetic fields, including the Earth's magnetic field, can be reduced (cancelled) by the magnetic fields (compensating magnetic fields) generated by the compensating coils 61, 62, and 63 (in other words, the magnetic field near the opening 14 can be reduced). As a result, the magnetic field (magnetism) entering the interior of the magnetic shielding device 1 (magnetic shielding space 10) from the opening 14 can be reduced. Furthermore, by reducing the magnetic field near the opening 14 in the magnetic shielding device 1, it becomes possible to secure a wide area with a flat magnetic field distribution inside the magnetic shielding device 1 (magnetic shielding space 10).

[0033] Furthermore, when multiple (or multiple pairs of) compensation coils are provided, it is preferable that these compensation coils are non-interfering with each other; that is, the magnetic field (compensating magnetic field) generated by any one pair of compensation coils is not affected by the magnetic fields (compensating magnetic fields) generated by the other pairs of compensation coils. This can be achieved by arranging each compensation coil opposite to each other in mutually orthogonal directions, allowing each compensation coil to independently compensate for the external magnetic field.

[0034] In this embodiment, the protruding portion 30 of the magnetic shielding device 1 is equipped with two or more (in this case, two) layers of magnetic shielding members 31 and 32 for the protruding portion, and each compensation coil 61, 62, and 63 is arranged on the outside of the innermost layer of magnetic shielding member 31 for the protruding portion 30, and on the inside of the outer layer of magnetic shielding member 32 for the protruding portion that is adjacent to the innermost layer of magnetic shielding member 31 for the protruding portion 31 at a predetermined distance outward (see the arrangement of the compensation coils 62 facing each other in the Y direction shown in Figure 5). This makes it possible to gently distribute the magnetic field (compensating magnetic field) generated by each compensation coil 61, 62, and 63 within the protruding portion 30, and to more effectively reduce the intrusion of external magnetism from the opening 14.

[0035] In a magnetic shielding device, if the number of layers of magnetic shielding members for protruding parts is three or more, the compensation coil can be placed between each pair of adjacent layers of magnetic shielding members for protruding parts. However, it is preferable to place the compensation coil between the innermost layer of magnetic shielding member for protruding parts and an outer layer of magnetic shielding member for protruding parts that is adjacent to the innermost layer at a predetermined distance. This makes it possible to suppress the magnitude of the current flowing through the compensation coil to obtain the required magnetic field (compensation magnetic field) while making the distribution of the generated magnetic field (compensation magnetic field) gentler.

[0036] Furthermore, although not described in detail here, as shown in Figure 8, the compensation coils (Figure 8 shows the arrangement of compensation coils 62 facing each other in the Y direction) may be arranged inside the innermost magnetic shielding member 31 for the protruding portion 30 (i.e., inside the space 33 within the protruding portion). This makes it possible to generate an appropriate compensating magnetic field in each compensation coil with a smaller current.

[0037] Furthermore, although not described in detail here, as shown in Figure 9, the compensation coil (Figure 9 shows the arrangement of compensation coils 62 facing each other in the Y direction) may be arranged on the outside of the outermost magnetic shielding member 32 for the protruding portion 30 (i.e., on the outside of the protruding portion 30).

[0038] Furthermore, in the magnetic shielding device 1 of this embodiment, all three pairs of compensating coils 61, 62, and 63 are arranged in the same configuration (distributed between the innermost magnetic shielding member for protruding parts and the outer magnetic shielding member for protruding parts adjacent to the innermost magnetic shielding member for protruding parts at a predetermined distance to the outside). However, the configurations of each compensating coil 61, 62, and 63 may be different depending on the type of magnetic field (compensating magnetic field) to be generated by each compensating coil 61, 62, and 63.

[0039] Furthermore, in the magnetic shielding device 1, compensation coils 61, 62, 63 (and a door 40) are provided in the protruding portion 30, which allows the protruding length L of the protruding portion 30 to be made relatively small, thereby enabling the magnetic shielding device 1 to be miniaturized.

[0040] Although not described in detail here, the magnetic reduction means of the magnetic shielding device comprises at least one pair of compensating coils in the protruding portion that are orthogonal to each other and face each other in at least one direction perpendicular to the opening (X direction), the width direction of the opening (Y direction), and the height direction of the opening (Z direction). It is more preferable that the path length of the space inside the protruding portion from one end to the other end of the opening (the protruding length of the protruding portion) is 0.25 to 0.5 times the length of the long side of the opening (the larger of the width direction dimension and the height direction dimension of the opening, in this case the height direction dimension H2).

[0041] In a magnetic shielding device, it is not necessary to provide compensation coils in all three directions (X, Y, and Z) as in the magnetic shielding device 1 of the above-described embodiment. Compensation coils (one pair) may be provided in one direction, or compensation coils (two pairs) may be provided in any two directions. In a magnetic shielding device, the priority order for providing compensation coils to more effectively reduce the intrusion of external magnetism from the opening is Y direction, Z direction, and X direction.

[0042] It is preferable that each compensation coil is large enough to be reasonably disposed in the magnetic shield apparatus (protruding portion). For example, as shown in FIGS. 2 to 4, it is preferable that the compensation coils are provided along the outer peripheral edges of the top surface portion 34, the bottom surface portion 35, and the side surface portion 36 of the protruding portion 30. Thereby, a uniform magnetic field (compensation magnetic field) can be generated in each compensation coil.

[0043] Further, in the magnetic shield apparatus, it is also effective to provide a magnetic sensor in the vicinity of the opening of the main body portion, and to actively control at any time the magnitude of the magnetic field (compensation magnetic field) generated in each compensation coil (in other words, the magnitude of the current (compensation current) passed through each compensation coil) according to the magnetic field detected by the magnetic sensor.

[0044] Although not illustrated, the magnetic reduction means of the magnetic shield apparatus may include compensation coils that face each other in at least one of mutually orthogonal directions perpendicular to the opening (X direction), the width direction of the opening (Y direction), and the height direction of the opening (Z direction), at the opening or outside the opening. For example, a frame body having no magnetic shielding property may be provided outside the opening of the magnetic shield apparatus, and the compensation coils may be arranged on the frame body.

[0045] Further, as in a magnetic shield apparatus 1c shown in FIG. 10, the protruding portion 30 may be bent. Specifically, in the magnetic shield apparatus 1c, the protruding portion 30 has bent portions 37, 37, and the openings of the protruding portion 30 on the side opposite to the opening 14 (in this example, both of the two openings) do not exist in front of the opening 14 (the openings do not exist when the outer edge of the opening 14 is extended outward in the direction perpendicular to the opening 14). Thereby, the magnetic field in the vicinity of the opening 14 can be further reduced, and the magnetic field (magnetism) entering the interior of the magnetic shield apparatus 1 (magnetic shield space 10) from the opening 14 can be further reduced.

[0046] When the bent portion 37 is provided on the protruding portion 30 as in the magnetic shield apparatus 1c of the present example, the compensation coils 61, 62 (and 63 (not shown)) on the protruding portion 30 are preferably disposed closer to the opening 14 side than the bent portion 37.

[0047] The magnetic shield device of the present invention is preferably a magnetic shield device for biomagnetic measurement used in biomagnetic measurement (for example, magnetoencephalography), and more preferably a magnetic shield device for biomagnetic measurement using an OPM sensor that can accommodate an OPM sensor (not shown) and a subject (not shown) whose biomagnetism is to be measured by the OPM sensor inside thereof.

[0048] The magnetic shield device of the present invention includes a casing-shaped main body portion that includes a main body magnetic shield member made of one or more layers of main body magnetic shield material that shields magnetism from the outside, and has a magnetic shield space formed inside, and an opening portion that is formed in the main body portion, communicates the magnetic shield space with the outside, and allows a person to enter and exit, and the magnetic shield device further includes a magnetism reduction unit that reduces intrusion of external magnetism from the opening portion into the magnetic shield space. Thereby, the intrusion of external magnetism from the opening that allows a person to enter and exit can be more effectively reduced.

[0049] Further, the magnetic shield device of the present invention includes a casing-shaped main body portion that includes a main body magnetic shield member made of one or more layers of main body magnetic shield material that shields magnetism from the outside, and has a magnetic shield space formed inside, and an opening portion that is formed in the main body portion, communicates the magnetic shield space with the outside, and allows a person to enter and exit, and the magnetic shield device further includes a cylindrical protruding portion that protrudes outward from the opening portion and communicates with the magnetic shield space via the opening portion inside, and the protruding portion has a protruding portion magnetic shield member made of one or more layers of protruding portion magnetic shield material that shields magnetism from the outside. Thereby, the intrusion of external magnetism from the opening that allows a person to enter and exit can be more effectively reduced.

[0050] Furthermore, the magnetic shielding device of the present invention comprises a main body-shaped body part having a magnetic shielding space formed inside, and a magnetic shielding member for the main body part consisting of one or more layers of magnetic shielding material for the main body part that shields against external magnetism, and an opening formed in the main body part that connects the magnetic shielding space to the outside and allows a person to enter and exit, and further comprises at least one pair of compensation coils facing each other in at least one direction perpendicular to the opening, in the width direction of the opening, and in the height direction of the opening, either at the opening or outside the opening. This makes it possible to more effectively reduce the intrusion of external magnetism through the opening that allows a person to enter and exit.

[0051] The magnetic shielding device of the present invention is as follows: (1) A magnetic shielding device having a magnetic shielding space inside which a magnetic sensor and a subject can be housed, wherein the magnetic shielding device comprises a housing-shaped main body having a magnetic shielding member for the main body made of one or more layers of magnetic shielding material for the main body that shields from external magnetism, and the magnetic shielding space is formed inside the main body, and an opening formed in the main body that communicates the magnetic shielding space with the outside and allows a person to enter and exit, and further comprises a magnetic reduction means for reducing the intrusion of external magnetism into the magnetic shielding space from the opening.

[0052] This magnetic shielding device comprises a main body-shaped body part having a magnetic shielding member made of one or more layers of magnetic shielding material for the main body part that shields against external magnetism, and a magnetic shielding space formed inside the main body part, and an opening formed in the main body part that connects the magnetic shielding space to the outside and allows a person to enter and exit, and further, the magnetic shielding device comprises a magnetic reduction means that reduces the intrusion of external magnetism into the magnetic shielding space from the opening. This makes it possible to more effectively reduce the intrusion of external magnetism from the opening that allows a person to enter and exit.

[0053] Furthermore, the above embodiments may also be as follows: (2) The magnetic shielding device according to (1) above, wherein the magnetic reduction means comprises a cylindrical projection that protrudes outward from the opening and communicates internally with the magnetic shield space through the opening, and the projection comprises a magnetic shielding member for the projection made of one or more layers of magnetic shielding material for the projection that shields from external magnetism.

[0054] Furthermore, the magnetic shielding device of the present invention is as follows: (3) A magnetic shielding device having a magnetic shielding space inside which a magnetic sensor and a subject can be housed, wherein the magnetic shielding device comprises a housing-shaped main body having a magnetic shielding member for the main body made of one or more layers of magnetic shielding material for the main body that shields against external magnetism, and an opening formed in the main body that communicates the magnetic shielding space with the outside and allows a person to enter and exit, wherein the magnetic shielding device further comprises a cylindrical projection that protrudes outward from the opening and communicates with the magnetic shielding space inside via the opening, wherein the projection has a magnetic shielding member for the projection made of one or more layers of magnetic shielding material for the projection that shields against external magnetism.

[0055] This magnetic shielding device comprises a main body made of one or more layers of magnetic shielding material for the main body that shields against external magnetic fields, a housing-like main body with a magnetic shielding space formed inside, and an opening formed in the main body that connects the magnetic shielding space to the outside and allows a person to enter and exit. Furthermore, the magnetic shielding device comprises a cylindrical projection that protrudes outward from the opening and communicates with the magnetic shielding space through the opening, and the projection has a magnetic shielding member for the projection made of one or more layers of magnetic shielding material for the projection that shields against external magnetic fields. This makes it possible to more effectively reduce the intrusion of external magnetic fields through the opening that allows a person to enter and exit.

[0056] Furthermore, the above embodiments may also be as follows: (4) The magnetic shielding device according to (2) or (3) above, wherein the projection is a cylindrical projection having an internal space through which a person can pass. (5) The magnetic shielding device according to any one of (2) to (4) above, wherein the magnetic shielding device comprises a door provided in the opening so as to be able to open and close the opening, and the door has a magnetic shielding member for the door made of one or more layers of magnetic shielding material for doors that shields magnetism from the outside. (6) The magnetic shielding device according to (5) above, wherein the main body comprises two or more layers of magnetic shielding material for the main body, and the door has fewer layers of magnetic shielding material for the door than the main body. (7) The magnetic shielding device according to any one of (2) to (6) above, wherein the magnetic shielding device comprises a projection door provided so as to be able to open and close the opening on the opposite side of the projection from the opening, and the projection door has a magnetic shielding member for the projection door made of one or more layers of magnetic shielding material for projection doors that shields magnetism from the outside. (8) The magnetic shielding device according to (7), wherein the main body comprises two or more layers of magnetic shielding members for the main body, and the protruding door comprises fewer layers of magnetic shielding members for the protruding door than the main body. (9) The magnetic shielding device according to any one of (1) to (8), wherein the magnetic shielding device comprises at least one pair of compensating coils facing each other in at least one direction perpendicular to the opening, in the width direction of the opening, and in the height direction of the opening, at the opening or outside the opening. (10) The magnetic shielding device according to any one of (2) to (8), wherein the magnetic shielding device comprises at least one pair of compensating coils facing each other in at least one direction perpendicular to the opening, in the width direction of the opening, and in the height direction of the opening, at the protruding portion. (11) The magnetic shielding device according to (10), wherein the compensating coils are disposed inside the innermost layer of the magnetic shielding member for the protruding portion at the protruding portion.(12) The magnetic shielding device according to (10), wherein the protrusion comprises two or more layers of magnetic shielding members for the protrusion, and the compensating coil is disposed in the protrusion on the outside of the innermost layer of magnetic shielding members for the protrusion and on the inside of an outer layer of magnetic shielding members for the protrusion adjacent to the innermost layer of magnetic shielding members for the protrusion at a predetermined distance outward. (13) The magnetic shielding device according to any one of (2) to (8), wherein the magnetic shielding device comprises at least one pair of compensating coils in the protrusion that are orthogonal to each other and face each other in at least one direction perpendicular to the opening, in the width direction of the opening, and in the height direction of the opening, and the path length of the internal space of the protrusion from the opening to the opening on the opposite side of the opening is 0.25 to 0.5 times the larger of the width dimension and the height dimension of the opening.

[0057] Furthermore, the magnetic shielding device of the present invention is as follows: (14) A magnetic shielding device having a magnetic shielding space inside which a magnetic sensor and a subject can be housed, wherein the magnetic shielding device comprises a housing-shaped main body having a magnetic shielding member for the main body made of one or more layers of magnetic shielding material for the main body that shields from external magnetism, and the magnetic shielding space is formed inside, and an opening formed in the main body that communicates the magnetic shielding space with the outside and into which a person can enter and exit, and further comprises a magnetic shielding device having at least one pair of compensating coils facing each other in the opening or outside the opening in at least one of the following directions perpendicular to the opening, the width direction of the opening and the height direction of the opening.

[0058] This magnetic shielding device comprises a main body-shaped housing-like body part having a magnetic shielding space formed inside, and a magnetic shielding member for the main body part consisting of one or more layers of magnetic shielding material for the main body part that shields against external magnetic fields, and an opening formed in the main body part that connects the magnetic shielding space to the outside and allows a person to enter and exit. Furthermore, the magnetic shielding device comprises at least one pair of compensating coils that are perpendicular to each other and facing each other in at least one direction perpendicular to the opening, in the width direction of the opening, and in the height direction of the opening, either in the opening or outside the opening. This makes it possible to more effectively reduce the intrusion of external magnetic fields through the opening that allows a person to enter and exit.

Claims

1. A magnetic shielding device comprising a magnetic shielding space capable of housing a magnetic sensor and a subject inside, wherein the magnetic shielding device comprises a housing-shaped main body portion having a magnetic shielding member for the main body portion made of one or more layers of magnetic shielding material for the main body portion that shields against external magnetism, and having the magnetic shielding space formed inside, and an opening formed in the main body portion that communicates the magnetic shielding space with the outside and allows a person to enter and exit, and further comprising a magnetic reduction means for reducing the intrusion of external magnetism into the magnetic shielding space from the opening.

2. The magnetic shielding device according to claim 1, wherein the magnetic reduction means comprises a cylindrical projection that protrudes outward from the opening and communicates internally with the magnetic shield space through the opening, and the projection comprises a magnetic shielding member for the projection made of one or more layers of magnetic shielding material for projections that shields from external magnetism.

3. A magnetic shielding device comprising a magnetic shielding space capable of housing a magnetic sensor and a subject inside, wherein the magnetic shielding device comprises a housing-shaped main body having a magnetic shielding member for the main body made of one or more layers of magnetic shielding material for the main body that shields against external magnetism, and an opening formed in the main body that communicates the magnetic shielding space with the outside and allows a person to enter and exit, and further comprises a cylindrical projection that protrudes outward from the opening and communicates with the magnetic shielding space inside through the opening, wherein the projection has a magnetic shielding member for the projection made of one or more layers of magnetic shielding material for the projection that shields against external magnetism.

4. The magnetic shielding device according to claim 2 or 3, wherein the projection is a cylindrical projection having an internal space through which a person can pass.

5. The magnetic shielding device according to any one of claims 2 to 4, wherein the magnetic shielding device comprises a door provided in the opening so as to be able to open and close the opening, and the door has a door magnetic shielding member made of one or more layers of door magnetic shielding material that shields against magnetism from the outside.

6. The magnetic shielding device according to claim 5, wherein the main body comprises two or more layers of magnetic shielding members for the main body, and the door comprises fewer layers of magnetic shielding members for the door than the main body.

7. The magnetic shielding device according to any one of claims 2 to 6, wherein the magnetic shielding device comprises a protruding door provided to open and close an opening on the opposite side of the protruding portion from the opening, and the protruding door has a magnetic shielding member for the protruding door made of one or more layers of magnetic shielding material for the protruding door that shields from external magnetism.

8. The magnetic shielding device according to claim 7, wherein the main body comprises two or more layers of magnetic shielding members for the main body, and the protruding door comprises fewer layers of magnetic shielding members for the protruding door than the main body.

9. The magnetic shielding device according to any one of claims 1 to 8, further comprising at least one pair of compensating coils facing each other in at least one of the following directions: perpendicular to the opening, in the width direction of the opening, and in the height direction of the opening, located in orthogonal to each other, in the opening or outside the opening.

10. The magnetic shielding device according to any one of claims 2 to 8, wherein the magnetic shielding device comprises at least one pair of compensating coils in the protruding portion that are orthogonal to each other and face each other in at least one direction perpendicular to the opening, in the width direction of the opening, and in the height direction of the opening.

11. The magnetic shielding device according to claim 10, wherein the compensation coil is disposed inside the innermost layer of the magnetic shielding member for the protruding portion at the protruding portion.

12. The magnetic shielding device according to claim 10, wherein the protruding portion comprises two or more layers of magnetic shielding members for the protruding portion, and the compensating coil is disposed on the outside of the innermost layer of magnetic shielding member for the protruding portion and on the inside of an outer layer of magnetic shielding member for the protruding portion adjacent to the innermost layer of magnetic shielding member for the protruding portion at a predetermined distance outward from the innermost layer of magnetic shielding member for the protruding portion.

13. The magnetic shielding device according to any one of claims 2 to 8, wherein the protruding portion comprises at least one pair of compensating coils that are orthogonal to each other and face each other in at least one direction perpendicular to the opening, in the width direction of the opening, and in the height direction of the opening, and the path length of the internal space of the protruding portion from the opening to the opening on the opposite side of the opening is 0.25 to 0.5 times the larger of the width dimension and the height dimension of the opening.

14. A magnetic shielding device comprising a magnetic shielding space capable of housing a magnetic sensor and a subject inside, wherein the magnetic shielding device comprises a housing-shaped main body portion having a magnetic shielding member for the main body portion made of one or more layers of magnetic shielding material for the main body portion that shields against external magnetism, and having the magnetic shielding space formed inside, and an opening formed in the main body portion that communicates the magnetic shielding space with the outside and allows a person to enter and exit, and further comprising at least one pair of compensating coils facing each other in the opening or outside the opening in at least one of the following directions perpendicular to the opening, in the width direction of the opening, and in the height direction of the opening.

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