Background Art As well known to those skilled in the art, it is difficult to intercept a magnetic filed without being accompanied with an electric field unlike the electric field. However, it is possible to intercept the magnetic field using a superconductor and a ferromagnetic body.

In detail, since a line of magnetic force cannot penetrate through the superconductor, it does not exist in a space surrounded by the superconductor.

Additionally, in the case of using the ferromagnetic body, a space is partially shielded from the magnetic field by allowing the concentrated lines of magnetic force to pass through a bypass path outside the space after the line of magnetic force is concentrated at one point.

However, the use of the superconductor is disadvantageous in that the high-priced superconductor must be used to intercept the line of magnetic force and the superconductor must be used at very low temperatures so as to secure superconductivity, thus it's costs are very high to intercept the magnetic field using the superconductor. For example, a metal superconductor must be cooled to a liquid helium temperature of 4. 2 °K, and a ceramic high temperature superconductor must be cooled to a liquid nitrogen temperature of 198 °K.

Meanwhile, various technologies of intercepting the magnetic field using the ferromagnetic body have been developed. For example, the selection of a material concentrating the line of magnetic force and a magnetic focusing plate, and an intercepting structure having the bypass path capable of detouring the path of magnetic force have been developed by the present inventors.

As described above, various technologies of intercepting the magnetic field using magnetic materials have been developed and applied to precision instruments, sensors, and magnetic heads. However, these technologies cannot be applied to homogenize a disturbed magnetic field distribution, and particularly, it is impossible to apply the teclmologies to homogenize the magnetic field distribution of a surface or a plane.

Disclosure of the Invention Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an aspect of the present invention is to provide a fresnel structure, in which soft magnets, hard magnets, or superconductors with a shape of a plate, a sheet, a bar, or a net are arranged at regular intervals in a predetermined direction according to the degree of disturbance to remove a localized magnetic disturbance occurring in a plane, a surface, or a space to homogenize a magnetic field distribution.

It is another aspect of the present invention to provide a method of installing fresnel panels to remove a localized magnetic disturbance, in which the fresnel panels are installed in a polyhedral, a spherical, or a cylindrical body.

Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

The above and/or other aspects are achieved by providing a fresnel panel structure for homogenizing a magnetic field distribution, including two or more magnetic focusing members arranged in parallel at intervals of 1 to 100 mm. The magnetic focusing members are made of a magnetic material and having a plate or sheet, a thin film, a net, a bar, a pipe, or a powder shape. Additionally, the

magnetic material has a magnetic permeability of 2.0 or more, coercive magnetic field of 1.0 oersted or less, saturated magnetization of 10 gausses or more, and a Curie temperature of-269 C (liquid helium temperature of 4. 2 °K) or higher at a temperature range of-269 to 200C.

Furthermore, the above and/or other aspects are achieved by providing a method of installing a fresnel panel structure to remove a magnetic disturbance including attaching the fresnel panel structure to at least three faces of a hexahedral body including three pairs of opposite faces in such a way that the fresnel panel structure is attached to any one face of the two opposite faces of the hexahedral body. At this time, the fresnel panel structure includes two or more magnetic focusing members arranged in parallel at intervals of 1 to 100 mm.

Brief Description of the Drawings The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a perspective view illustrating fresnel panels according to the present invention; FIG. 2A illustrates a vertical component distribution of a magnetic field measured using a magnetometer at a height of 50 mm from a bottom at which the magnetic field is disturbed; FIG. 2B illustrates the vertical component distribution of the magnetic field measured using the magnetometer at a height of 5 mm from the bottom at which the magnetic field is disturbed of FIG. 2A after the fresnel panels are attached to the bottom; and FIG. 2C illustrates the vertical component distribution of the magnetic field measured using the magnetometer at a height of 50 mm from the bottom at which the magnetic field is disturbed of FIG. 2A after the fresnel panels are attached to the bottom.

Best Mode for Carrying Out the Invention With reference to FIG. 1, a fresnel panel structure for homogenizing a magnetic field distribution according to the present invention includes two or more magnetic focusing members with a width (a) of 0.1 to 10 mm arranged in parallel at intervals of 1 to 100 mm. At this time, a length of each of the magnetic focusing members is not limited. The magnetic focusing members are made of a magnetic material and have a plate or sheet, a thin film, a net, a bar, a pipe, or a powder shape. Additionally, the magnetic material has a magnetic permeability of 2.0 or more, coercive magnetic field of 1.0 oersted or less, saturated magnetization of 10 gausses or more, and a Curie temperature of-269 C (liquid helium temperature of 4. 2 °IL) or higher at a temperature range of-269 to 200 C.

Meanwhile, the magnetic material is selected from the group consisting of metals such as Fe, Fe-Si, permalloys, super permalloys, permendurs, mumetals, and molly-permalloys, soft magnets such as MnZn ferrite, NiZn ferrite, CuZn ferrite, and garnet-based ceramics, superconductors such as ceramic-based superconductors, intermetallic compound superconductors, and metal-nonmetal compound superconductors, and hard magnets. Additionally, each of the magnetic focusing members may include a mixture of the magnetic material with organics or nonmagnetic materials.

A plurality of fresnel panels are put on a bottom at which the magnetic field is disturbed so as to homogenize a disturbed magnetic field distribution, as shown in FIG. 1. At this time, each of the fresnel panels is preferably positioned in such a way that a short axis of the fresnel panel is positioned north and south of a geomagnetic field, and a long axis of the fresnel panel is positioned east and west of the geomagnetic field.

Meanwhile, a shape and a size of the fresnel panel consisting of the magnetic material depend on a disturbance state of the magnetic field. In other words, when the magnetic field is severely disturbed, the magnetic material with high magnetic permeability (I1) is used to homogenize the magnetic field. At this time, a ratio of a width (a) of one fresnel panel to an interval (g) between the two adjacent fresnel panels must be large, and a length of the fresnel panel must be as

long as possible. On the other hand, when the magnetic field is weakly disturbed, the magnetic material with low magnetic permeability is used to homogenize the magnetic field, and the ratio of the width (a) of one fresnel panel to the interval (g) between the two fresnel panels must be small. In this regard, the length of the fresnel panel is not important.

FIGS. 2A to 2C illustrate a vertical component distribution of a magnetic field measured by a magnetometer in the case of using a fresnel structure of FIG. 1.

Referring to FIG. 2A, there is illustrated a magnetic field distribution measured at a point of a building's floor without installing the fresnel structure on the floor according to the first embodiment of the present invention. In this regard, the magnetic field distribution is measured to be a size of 2 m X 2 m, and a vertical component (Bz) of a magnetic flux density (B) of the magnetic field is measured using a magnetic flux density measuring device provided with a fluxgate-type sensor (manufactured by EMO Co. , device name: magnetometer, model name: geomag 101). The vertical component of the magnetic flux density ranges from 235 to 352 mG at a height of 50 mm from the floor. At this time, a maximum deviation is 177 mG. Furthermore, the vertical component of the magnetic flux density ranges from 310 to 325 mG, and the maximum deviation is 15 mG at a height of 500 mm from the floor. Through the above description, it can be seen that the maximum value of the magnetic flux density is decreased but the minimum value of the magnetic flux density is increased with a distance between a measured position of the magnetic flux density and the floor increasing, thereby the magnetic disturbance at a predetermined height from the floor is reduced in comparison with the disturbance at a surface of the floor. In this regard, the magnetic disturbance on the surface of the floor is caused by reinforcing bars with ferromagnetic property positioned in the floor.

Turning to FIGS. 2B and 2C, there is illustrated a magnetic field distribution measured at a point of a building's floor in the case of applying the fresnel structure to the floor according to the second and third embodiment of the present invention. Oriented electrical steel sheets with initial magnetic permeability (, ui) of 1600 and thickness of 0.35 mm are processed into the fresnel panels with a width of 48 mm and a length of 500 mm, and the fresnel panels are

arranged on the floor in such a way that an interval between the two adjacent fresnel panels is 5 mm. In FIG. 2B, there is illustrated a variation of the magnetic flux density measured at a height of 5 mm from the floor on which the fresnel panels are arranged, and the magnetic flux density ranges from 348 to 378 mG at this height. At this time, the maximum deviation is 30 mG. Additionally, in FIG. 2C, there is illustrated a variation of the magnetic flux density measured at a height of 50 mm from the floor on which the fresnel panels are arranged. The magnetic flux density ranges from 345 to 360 mG, and the maximum deviation is 15 mG at this height. A detailed description will be given of a magnetic flux density distribution difference before and after the arrangement of the fresnel panels on the floor. The maximum value of the magnetic flux density is 360 mG at a height of 50 mm from the floor, which is increased by 8 mG in comparison with the maximum value of 352 mG at the surface of the floor. Further, the minimum value of the magnetic flux density is 345 mG at a height of 50 mm from the floor, which is increased by 110 mG in comparison with the minimum value of 235 mG at the surface of the floor. Accordingly, the maximum deviation between the maximum and minimum values of the magnetic flux density is reduced from 177 mG to 15 mG by 162 mG. This means that the magnetic disturbance is greatly reduced from 177 mG to 15 mG. Moreover, the maximum deviation at a height of 500 mm from the floor is reduced from 15 mG to 1 mG after the fresnel panels are arranged on the floor, which means that the magnetic disturbance at a height of 500 mm from the floor is almost removed by the fresnel panels.

Through the above description, it can be seen that the magnetic disturbance is greatly reduced by the fresnel panels, and is scarcely observed at a height of 500 mm or higher from the floor. That is to say, the fresnel panels effectively intercept the magnetic disturbance.

According to the present invention, at least two magnetic focusing members are arranged in parallel at intervals of 1 to 100 mm in each of the fresnel panels, and the fresnel panels are attached to at least three inner faces of a hexahedral body including three pairs of opposite faces to remove the magnetic disturbance and homogenize the magnetic field.

In detail, the fresnel panels must be attached to at least three faces of the

hexahedral body as a way to be attached to any one face of the two opposite faces of the hexahedral body so as to homogenize a magnetic field distribution in the hexahedral body.

When a factor causing the magnetic disturbance is apparently revealed, the magnetic field distribution is homogenized by attaching the fresnel panels to a face of the hexahedral body positioned near the factor causing the magnetic disturbance.

In other words, when the factor causing the magnetic disturbance is positioned outside any one face of the hexahedral body, the magnetic field distribution is homogenized by attaching the fresnel panels to the inner side of the face. On the other hand, when the factor causing the magnetic disturbance is positioned outside a corner between the two adjacent faces to affect the two adjacent faces, the fresnel panels must be attached to the inner sides of the two faces to homogenize the magnetic field distribution. Additionally, when it is not known where the factor causing the magnetic disturbance is positioned, the fresnel panels must be attached to the inner sides of all faces of the hexahedral body.

As well, the fresnel panels may be installed in various polyhedral bodies such as a tetrahedron, an octahedron, and a dodecahedron in the same manner as the case of the hexahedral body. In the case of a cylindrical body, the fresnel panels may be selectively attached to inner sides of lateral and bottom faces, to inner sides of lateral and top faces, or to inner sides of lateral, bottom, and top faces of the cylindrical body so as to homogenize the magnetic field distribution in the cylindrical body.

Industrial Applicability As described above, a magnetic field homogenizing structure of the present invention is advantageous in that a homogenizing effect is an excellent 95 % or more unlike a conventional magnetic field intercepting material or structure which does not effectively remove a magnetic disturbance. Furthermore, a method of installing a fresnel structure according to the present invention has an advantage of a localized magnetic disturbance suppressing effect of 95 % or more.

Moreover, the fresnel structure of the present invention effectively suppresses a

magnetic disturbance in any shape of a body, beit localized or broad, and removes the magnetic disturbance of a floor at which a magnetic field is disturbed in an efficiency of 95 % or more.

The present invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.