JP2017133862A - Magnetic field measurement device, magnetic field measurement apparatus, magnetic field measurement system, and magnetic field measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and apparatus for improving the convenience in magneto-optical imaging.SOLUTION: A magnetic field measurement device includes: a magnetic transfer element 13 having a magnetic transfer film 13a for producing a magneto-optical effect; and a surface light source 11 that generates irradiation light and emits the irradiation light from a light emission surface 11a. The light emission surface 11a of the surface light source 11 is bonded to the magnetic transfer element 13. The magnetic field measurement device further includes a linear polarization plate 12 and a linear polarization plate 14. The linear polarization plate 12 is inserted into a gap between the magnetic transfer element 13 and the surface light source 11, and the linear polarization plate 14 is disposed so as to face the linear polarization plate 12 with respect to the magnetic transfer element 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic field measurement device, a magnetic field measurement apparatus, a magnetic field measurement system, and a magnetic field measurement method, and more particularly to a technique for measuring a magnetic field using a magneto-optic effect.

  Magneto-optical imaging using a magnetic transfer film is known as a method for nondestructively measuring a spatial magnetic field. The magnetic transfer film is configured as a film that is easily magnetized by a magnetic field and exhibits a magneto-optical effect (for example, a Faraday effect). A magnetic field distribution is converted into a light intensity distribution using a magneto-optical effect (for example, rotation of the polarization plane) generated according to the magnetic field at the position at each position of the magnetic transfer film, and this light intensity distribution is optically converted. By observing, information on the magnetic field distribution can be obtained. In this method, it is possible to observe the magnetization distribution and the current distribution by observing the magnetic field distribution generated by the magnetization and the current. For example, a Bi-substituted magnetic garnet film is used as the magnetic transfer film. Magneto-optical imaging using a magnetic transfer film is known, for example, from Non-Patent Document 1 and Patent Documents 1 to 3.

  It is desirable that magneto-optical imaging can be easily performed. Non-Patent Document 1 and Patent Documents 1 to 3 described above disclose a method using a polarization microscope in magneto-optical imaging. However, if magneto-optical imaging can be performed with an apparatus having a simpler configuration, convenience in magneto-optical imaging is achieved. It is more preferable because it can be improved.

  Moreover, it is desirable that the magnetic field measuring device used for measuring the spatial magnetic field is small. By downsizing the magnetic field measuring device, it becomes easy to arrange the magnetic field measuring device at a position where a spatial magnetic field measurement is desired. Such a situation similarly applies to a magnetic field measuring device including a magnetic transfer film and magneto-optical imaging using the magnetic field measuring device.

Akimasa Kosaka, Masayuki Naganuma, Mitsuharu Aoyagi, Tsukasa Kobayashi, S. Niratisairak, Tatsuo Nomura, Takayuki Ishibashi, "Preparation and Evaluation of Y3-XBiXFe5O12 Magnetic Transfer Film Using Organometallic Decomposition Method", Journal of the Magnetics Society of Japan, The Magnetic Society of Japan, 2011, Vol. 35, No. 3, p. 194-198

JP 2009-43964 A JP 2005-291707 A JP 2005-292163 A

  Therefore, an object of the present invention is to achieve at least one of improvement in convenience in magneto-optical imaging and miniaturization of a magnetic field measurement device.

  Other objects and novel features of the present invention will be readily apparent to those skilled in the art from the following disclosure.

  In one aspect of the present invention, a magnetic field measurement device includes a magnetic transfer element including a magnetic transfer film that exhibits a magneto-optical effect, and a surface light source that generates irradiation light and emits the irradiation light from a light emitting surface. The light emitting surface of the surface light source is bonded to the magnetic transfer element.

  In another aspect of the present invention, the apparatus includes the above-described magnetic field measurement device and an imaging device that captures an image of the magnetic field measurement device and generates a magnetic field distribution image indicating the distribution of the magnetic field at each position of the magnetic transfer film.

  In still another aspect of the present invention, a magnetic field measurement apparatus includes: an optical fiber; a probe that is bonded to the first end of the optical fiber and includes the magnetic field measurement device described above; a light source that generates excitation light; and a light detection device. It has. A phosphor is used as a surface light source of the magnetic field measuring device. Excitation light is incident on the phosphor of the magnetic field measurement device, and measurement light, which is light that has passed through the magnetic transfer element among irradiation light generated by the phosphor, is incident on one end of the optical fiber and propagates through the optical fiber. The light is emitted from the other end of the optical fiber and enters the light detection device.

In still another aspect of the present invention, a magnetic field measurement system includes a magnetic field measurement device, a beam splitter, a first circularly polarizing plate, a second circularly polarizing plate, a first imaging device, a second imaging device, and an arithmetic operation. The magnetic field measurement device includes a magnetic transfer element including a magnetic transfer film that exhibits a magneto-optical effect, and a surface light source that generates irradiation light and emits the irradiation light from a light emitting surface. The light emitting surface of the surface light source is bonded to the magnetic transfer element. The beam splitter generates a first beam and a second beam from the beam of measurement light emitted from the magnetic transfer element. The first beam is incident on the first imaging device via the first circularly polarizing plate, and the second beam is incident on the second imaging device via the second circularly polarizing plate. The first imaging device captures the first beam to generate a first captured image, and the second imaging device captures the second beam to generate a second captured image. The arithmetic device generates a difference image between the first captured image and the second captured image as a magnetic field distribution image indicating a magnetic field distribution at each position of the magnetic transfer film.

In still another aspect of the present invention, a magnetic field measurement method includes a magnetic transfer element including a magnetic transfer film that exhibits a magneto-optical effect, and a surface light source that generates irradiation light and emits the irradiation light from a light emitting surface. , A step of arranging a magnetic field measurement device in which a light emitting surface of a surface light source is bonded to a magnetic transfer element, and imaging the magnetic field measurement device with irradiation light generated by the surface light source being incident on the magnetic transfer element And a step of generating a magnetic field distribution image showing a magnetic field distribution at each position of the magnetic transfer film.

  According to the present invention, at least one of improvement in convenience in magneto-optical imaging and miniaturization of a magnetic field measurement device can be achieved.

It is a side view which shows the structure of the magnetic field measuring device of one Embodiment of this invention. It is a top view which shows the direction of the transmission axis of two linearly-polarizing plates of the magnetic field measuring device of FIG. It is a conceptual diagram which shows the magnetic field measurement using the magnetic field measuring device of FIG. It is a figure which shows the relationship between the magnetic field of the film thickness direction of a magnetic transfer film, and a Faraday rotation angle. The relationship between the intensity of measurement light and the magnetic field in the film thickness direction when the angle θ (the angle between the plane perpendicular to the transmission axis of one linearly polarizing plate and the transmission axis of the other linearly polarizing plate) is 0 ° is shown. It is a graph. It is a graph which shows the relationship between the intensity | strength of the measurement light and the magnetic field of a film thickness in case the angle (theta) exists in the range of (alpha) _FS <= (theta) <= 90 degree- (alpha) _FS . Angle theta between the transmission axes of the two linear polarization plate is a graph showing the relationship between magnetic field intensity and the film thickness direction of the measuring light if the range of -α _{FS <θ <α FS.} It is a graph which shows the relationship between the intensity | strength of measurement light in case saturation saturation Faraday rotation angle (alpha) _FS is large, and the magnetic field of a film thickness direction. It is a side view which shows the modification of a magnetic field measuring device. It is a side view which shows the structure of the magnetic field measuring device of other embodiment of this invention. It is a conceptual diagram which shows the magnetic field measurement using the magnetic field measuring device of FIG. It is a side view which shows the other modification of a magnetic field measuring device. It is a conceptual diagram which shows the magnetic field measurement using the magnetic field measuring device of FIG. It is a side view which shows the further another modification of a magnetic field measuring device. It is a side view which shows the further another modification of a magnetic field measuring device. It is a system configuration figure showing the composition of the magnetic field measurement system in one embodiment of the present invention. It is sectional drawing which shows the structure of the probe used in the magnetic field measurement system of this embodiment. It is sectional drawing which shows the other structure of the probe used in the magnetic field measurement system of this embodiment. It is sectional drawing which shows the further another structure of the probe used in the magnetic field measurement system of this embodiment. It is a system block diagram which illustrates the modification of a magnetic field measurement system. It is a system block diagram which illustrates the other modification of a magnetic field measurement system. It is a system block diagram which shows the structure of the magnetic field measurement system in other embodiment of this invention. It is a conceptual diagram which shows the operation | movement which acquires a magnetic field distribution image with the magnetic field measurement system of this embodiment.

  In the following, various embodiments of the present invention will be described. In the following description, it should be noted that the same or corresponding components may be referred to by the same or corresponding reference numerals. It should also be noted that in the accompanying drawings, the dimensions of members may be illustrated at a ratio different from the actual ratio of dimensions in order to facilitate understanding of the invention.

  FIG. 1 is a side view showing a configuration of a magnetic field measurement device 1 according to an embodiment of the present invention. The magnetic field measuring device 1 of this embodiment is a magnetic field sensor used in magnetic field optical imaging, and includes a surface light source 11, a linearly polarizing plate 12, a magnetic transfer element 13, and a linearly polarizing plate 14. The magnetic field measuring device 1 is configured as a structure in which a linearly polarizing plate 12, a magnetic transfer element 13, and a linearly polarizing plate 14 are laminated and integrated. Specifically, the linear polarizing plate 12 is bonded to the surface light source 11, and the magnetic transfer element 13 is bonded to the linear polarizing plate 12. Further, the linear polarizing plate 14 is bonded to the magnetic transfer element 13. The magnetic transfer element 13 is provided between the linearly polarizing plates 12 and 14.

  The surface light source 11 generates irradiation light that irradiates the magnetic transfer element 13 and emits it from the light emitting surface 11a. The light emitting surface 11 a of the surface light source 11 is bonded to the magnetic transfer element 13 with the linearly polarizing plate 12 interposed therebetween. That is, the irradiation light emitted from the light emitting surface 11 a is incident on the magnetic transfer element 13 through the linear polarizing plate 12.

  As the surface light source 11, for example, an electroluminescence light source (EL light source) that generates light using electroluminescence can be used. By using an electroluminescence light source as the surface light source 11, the thickness of the surface light source 11 can be reduced, which is preferable.

  As will be described in detail in an embodiment described later, a phosphor may be used as the surface light source 11. When a phosphor is used as the surface light source 11, irradiation light can be generated by irradiating the magnetic transfer element 13 by supplying excitation light without supplying electricity to the surface light source 11. Therefore, the use of the phosphor as the surface light source 11 is suitable for use in an environment where it is difficult to use electricity, for example, an environment where explosion proofing is required or an electrical wiring is difficult.

  The linearly polarizing plate 12 is configured to pass linearly polarized light whose polarization plane is in a specific direction. The linearly polarizing plate 12 is inserted between the surface light source 11 and the magnetic transfer element 13, and linearly polarized irradiation light whose polarization plane is in a specific direction is incident on the magnetic transfer element 13.

  The magnetic transfer element 13 includes a substrate 13a and a magnetic transfer film 13b formed on one main surface of the substrate 13a. As the magnetic transfer film 13b, a magnetic film that exhibits a large Faraday effect is preferably used. In one embodiment, as the magnetic transfer film 13b, a magnetic film having in-plane magnetization (that is, a magnetization easy axis is parallel to the film surface) may be used. In this case, the magnetization (and Faraday rotation angle) is proportional to the magnetic field, which is preferable for obtaining a good image in magneto-optical imaging.

  In order to improve the sensitivity of magneto-optical imaging, a magnetic film having a perpendicular magnetization (that is, an easy axis of magnetization perpendicular to the film surface) and a small residual magnetization is used as the magnetic transfer film 13b. It is preferable. Also in this case, the magnetization (and the Faraday rotation angle) has a proportional relationship with the magnetic field, and the saturation magnetic field becomes small, so that the increase amount of the Faraday rotation angle with respect to the magnetic field becomes large. When a magnetic film having a perpendicular magnetization and a small residual magnetization is used as the magnetic transfer film 13b, the coercive force is small and a labyrinth magnetic domain is easily formed. However, it is preferable to use a magnetic film having a sufficiently small magnetic domain width.

In one preferred embodiment, the magnetic transfer film 13b, the magnetic garnet film, e.g., films formed by Bi-substituted iron garnet _{(Y 3-X Bi X Fe} 5 O 12) is used. A thin film formed of Bi-substituted magnetic garnet has in-plane magnetization and can be suitably used as the magnetic transfer film 13b. In addition, Bi-substituted magnetic garnet may be replaced with other elements that replace yttrium (Y) (for example, lutetium (Lu), ytterbium (Yb), neodymium (Nd), lead (Pb)), and / or iron (Fe). A material to which other elements to be substituted (for example, gallium (Ga) or aluminum (Al)) are added may be used as the magnetic transfer film 13b.

In another embodiment, a thin film formed of (Nd, Bi) ₃ Fe ₅ O ₁₂ or a thin film formed of (Nd, Bi) ₃ (Fe, Ga) ₅ O ₁₂ is used as the magnetic transfer film 13b. May be. A thin film formed of (Nd, Bi) ₃ Fe ₅ O ₁₂ has a perpendicular coercive force and a small coercive force and residual magnetization, and is suitable for use as the magnetic transfer film 13b. In addition, (Nd, Bi) ₃ (Fe, Ga) ₅ O ₁₂ also has a low coercive force and residual magnetization while having a perpendicular magnetization in the range where the Ga content is small, and the magnetic transfer film 13b Suitable for use.

  In order to obtain a good image in magneto-optical imaging, the magnetic transfer film 13b is preferably formed so as to have a granular structure with extremely small crystal grains. In the magnetic transfer film 13b having a granular structure, since a large magnetic domain is unlikely to be generated, an image due to the presence of the magnetic domain is hardly generated regardless of the magnetic field. As an example, the grain size of the crystal grains of the magnetic transfer film 13b is preferably about 50 nm. The magnetic transfer film 13b having such a structure can be formed using, for example, an organic metal deposition (MOD) method.

The substrate 13a is formed of a material suitable for forming the magnetic transfer film 13b. When a magnetic garnet film is used as the magnetic transfer film 13b, for example, a gadolinium gallium garnet (Gd ₃ Ga ₅ O ₁₂ ) single crystal substrate may be used as the substrate 13a, or a glass substrate may be used. Also good. The use of a glass substrate as the substrate 13a is preferable in that the area of the magnetic transfer element 13 can be easily increased.

  The linearly polarizing plate 14 is configured to pass linearly polarized light having a specific plane of polarization. The linearly polarizing plate 14 is provided so as to face the linearly polarizing plate 12 with the magnetic transfer element 13 interposed therebetween. The linearly polarizing plate 14 selectively emits linearly polarized light whose polarization plane has a specific direction out of the light that has passed through the magnetic transfer element 13. Light emitted from the linear polarizing plate 14 is used as measurement light used for generating an image in magneto-optical imaging.

  FIG. 1 shows a structure in which the magnetic transfer film 13 b of the magnetic transfer element 13 is bonded to the linearly polarizing plate 12 and the substrate 13 a is bonded to the linearly polarizing plate 14. The magnetic transfer film 13b may be bonded to the linearly polarizing plate 14, and the substrate 13a may be bonded to the linearly polarizing plate 12. However, from the viewpoint of making the magnetic transfer film 13b closer to a desired position for measuring the magnetic field distribution, the magnetic transfer film 13b is preferably provided on the side closer to the surface light source 11, and therefore the magnetic transfer film 13b is linearly polarized light. A structure joined to the plate 12 is preferable.

  FIG. 2 is a plan view showing directions of the transmission axis of the linear polarizing plate 12 and the transmission axis of the linear polarizing plate 14. In FIG. 2, the direction of the transmission axis of the linear polarizing plate 12 is indicated by a broken line arrow 12a, and the direction of the transmission axis of the linear polarizing plate 14 is indicated by an arrow 14a. The transmission axis of the linear polarizing plate 12 is defined in a direction parallel to the X-axis direction.

  In the present embodiment, as illustrated in FIG. 2, the transmission axis of the linear polarizing plate 12 and the transmission axis of the linear polarizing plate 14 are directed in different directions. In FIG. 2, the angle between the plane perpendicular to the transmission axis of the linear polarizer 12 and the transmission axis of the linear polarizer 14 (that is, the plane perpendicular to the plane of polarization of the linearly polarized light passing through the linear polarizer 12 and the straight line) The angle between the polarization planes of linearly polarized light passing through the polarizing plate 14 is shown as “θ”. As will be discussed in detail later, the angle θ has a suitable range.

  Since the intensity of the measurement light emitted from each position of the magnetic field measurement device 1 having the above configuration depends on the magnetic field at each position of the magnetic transfer film 13b, the magnetic field is measured by imaging the magnetic field measurement device 1 with the imaging device 2. A distribution image (an image showing a magnetic field distribution) can be acquired. FIG. 3 is a conceptual diagram showing magnetic field measurement using the magnetic field measurement device 1 of the present embodiment. FIG. 3 illustrates a case where the magnetic field measurement device 1 is used for measuring the distribution of the magnetic field generated by the magnetic field generation source 3 as an example.

  As shown in FIG. 3, the magnetic field measurement device 1 is installed at a position where measurement of the magnetic field distribution is desired. When measuring the magnetic field distribution, the surface light source 11 is operated to generate irradiation light. The generated irradiation light is incident on the magnetic transfer film 13 b of the magnetic transfer element 13 through the linearly polarizing plate 12. The linearly polarized irradiation light is incident on the magnetic transfer film 13 b of the magnetic transfer element 13.

Due to the Faraday effect of the magnetic transfer film 13b, the polarization plane of the irradiated light rotates while the irradiated light passes through the magnetic transfer film 13b in the film thickness direction (Z-axis direction in FIG. 3). The rotation angle of the polarization plane at each position of the magnetic transfer film 13b, that is, the Faraday rotation angle α is the magnetic field at each position of the magnetic transfer film 13b, more strictly, the film thickness direction at each position of the magnetic transfer film 13b (see FIG. It depends on the magnetic field H _Z 3 in the Z-axis direction). Figure 4A shows an example of the dependency of the Faraday rotation angle α in the thickness direction to the magnetic field H _Z. The Faraday rotation angle α is saturated when the magnetic field H _{Z at} each position of the magnetic transfer film 13b is sufficiently large. In FIG. 4A, α _FS is the absolute value (saturated Faraday rotation angle) when the Faraday rotation angle α is saturated, and H _FS is the absolute value of the magnetic field H _{Z at which} the Faraday rotation angle is saturated. Note that the direction of rotation of the polarization plane (sign of Faraday rotation angle α) depends on the direction of the magnetic field H _Z , and when the direction of the magnetic field H _Z is reversed, the direction of rotation of the polarization plane is also reversed.

  Due to the rotation of the polarization plane while passing through the magnetic transfer film 13b in the film thickness direction (Z-axis direction in FIG. 3), the Faraday rotation angle α at each position of the magnetic transfer film 13b is changed from each position of the linear polarizer 14b. That is, measurement light having an intensity depending on the magnetic field Hz at each position of the magnetic transfer film 13b is emitted. Therefore, an image reflecting the intensity depending on the magnetic field Hz at each position of the magnetic transfer film 13b, that is, a magnetic field distribution image can be obtained by imaging the measurement light emitted from the linear polarizing plate 14 with the imaging device 2. .

In order to establish a one-to-one correspondence between the magnetic field H _{Z in the} film thickness direction and the intensity of the measurement light, the angle θ (that is, the plane perpendicular to the transmission axis of the linear polarizer 12 and the linear polarizer 14 The angle between the transmission axes is preferably in the range of the following formula (1).
α _FS ≦ θ ≦ 90 ° −α _FS (1)
Here, α _FS is the rotation angle of the polarization plane when a sufficiently large magnetic field is applied and the rotation of the polarization plane is saturated, that is, the saturation Faraday rotation angle. Hereinafter, the reason why it is preferable that the angle θ is in the range of the expression (1) will be discussed.

In a general optical system, a pair of polarizers whose angle between transmission axes is 90 ° is often used. This corresponds to setting the angle θ to 0 ° in the arrangement of the linearly polarizing plates 12 and 14 in FIG. However, when the angle between the transmission axes of the linearly polarizing plates 12 and 14 is set to 90 °, that is, when the angle θ is set to 0 °, the light is emitted from the magnetic field measuring device 1 as shown in FIG. 4B. that the intensity of the measuring light will depend on the absolute value of the magnetic field H _Z independently of the direction of the magnetic field H _Z. This is because, as is also shown in the graph of FIG. 4A, when a magnetic field Hz orientation to reverse while the magnitude of the magnetic field H _Z (absolute value) in the same, even α Faraday rotation angle, the size It is because it becomes the opposite direction while keeping it the same. In particular, the intensity of the measuring light, the magnetic field _{H Z} is in the range of _{-H FS <H Z <+ H} FS, generally, proportional to sin ² (γH _Z d) with respect to the magnetic field _{H Z.} Here, γ is a Verde constant, and d is the film thickness of the magnetic transfer film 13b. Therefore, by setting the angle θ to 90 °, it is impossible to identify the orientation of the magnetic field H _Z from the intensity of the measuring light. This is from the resulting magnetic field distribution image which means that it can not grasp the direction of the magnetic field H _Z.

On the other hand, as shown in FIG. 4C, when the angle θ is set in the range of the expression (1), the range of the magnetic field H _Z that does not saturate the Faraday rotation angle α (ie, −H _FS <H _Z <+ H of _FS range), it is possible to widen the range of one-to-one correspondence is established between the magnetic field H _Z and the intensity of the measuring light. This, for a wide range of the magnetic field H _Z, from the intensity of the measuring light, it means that the magnetic field H _Z, can be identified, including its orientation. Thus, the angle θ by setting the range of the equation (1) above, it is possible to obtain a magnetic field distribution image which can grasp the direction of the magnetic field H _Z. Furthermore, the magnetic field at each position of the magnetic transfer film 13b can be specified from the luminance at each position in the magnetic field distribution image.

Incidentally, as illustrated in FIG. 4D, when a -α _{FS <θ <α FS} is the magnetic field H _Z for one-to-one correspondence relationship between the magnetic field H _Z and the intensity of the measuring light is established and ranges, so that the range of the established non field H _Z is present. If the range field H _Z can take is known, it may set the angle theta as -α _{FS <θ <α FS} is established. However, for certain of the magnetic field H _Z, including orientation, the angle θ is preferably in the range defined by the above formula (1).

As shown in FIG. 4E, when the saturation Faraday rotation angle α _FS is large (more specifically, when the sum of the angle θ and the saturation Faraday rotation angle α _FS exceeds 90 °), the magnetic field H _Z In the range where the absolute value of is large, there may be a case where the correspondence relationship between the magnetic field _HZ and the intensity of the measurement light does not become a one-to-one relationship. In FIG. 4E, when the magnetic field H _Z is in the range of −H _FS <H _Z <H ₁ (<0) and (0 <) H ₂ <H _Z <H _FS , the field H _Z and the intensity of the measurement light are The correspondence relationship is not a one-to-one relationship. However, such setting, it is possible to enhance the sensitivity in the measurement of small magnetic fields H _Z, is rather preferable.

  One of the advantages of the magnetic field measurement device 1 of the present embodiment is that magneto-optical imaging can be easily performed. In the present embodiment, the magnetic field measuring device 1 configured as a structure in which the surface light source 11, the linearly polarizing plate 12, the magnetic transfer element 13, and the linearly polarizing plate 14 are integrated is installed in a space for measuring the magnetic field distribution. A magnetic field distribution image can be obtained simply by photographing the magnetic field measuring device 1 with the imaging device 2 while the surface light source 11 is operated.

  FIG. 5 is a side view showing a modification of the magnetic field measurement device 1 of the present embodiment. In the magnetic field measurement device 1 illustrated in FIG. 5, a reflecting plate 15 is bonded to the back surface 11 b (surface facing the light emitting surface 11 a) of the surface light source 11. In such a configuration, since the light emitted from the back surface of the surface light source 11 is reflected by the reflecting plate 15, it is possible to increase the intensity of irradiation light applied to the magnetic transfer element 13. Such a configuration is suitable for effectively using the light generated by the surface light source 11 for magnetic field measurement.

  FIG. 6 is a side view showing a configuration of a magnetic field measurement device 1A according to another embodiment of the present invention. A magnetic field measurement device 1 </ b> A illustrated in FIG. 6 includes a circularly polarizing plate 16 instead of the pair of linearly polarizing plates 12 and 14. The circularly polarizing plate 16 is an optical element having a function of generating circularly polarized light from incident light, and most typically includes a laminated linearly polarizing plate and a quarter wavelength plate.

  Specifically, a circularly polarizing plate 16 is bonded to the light emitting surface 11 a of the surface light source 11, and the magnetic transfer element 13 is bonded to the circularly polarizing plate 16. In the structure of FIG. 6, the magnetic transfer element 13 is bonded to the light emitting surface 11 a of the surface light source 11 via the circularly polarizing plate 16. In the structure of FIG. 6, the magnetic transfer film 13 b of the magnetic transfer element 13 is bonded to the circularly polarizing plate 16, but the substrate 13 a may be bonded to the circularly polarizing plate 16. However, it is preferable that the magnetic transfer film 13b is provided on the side close to the surface light source 11 from the viewpoint of making the magnetic transfer film 13b closer to the position where the measurement of the magnetic field distribution is desired, so that the magnetic transfer film 13b is circularly polarized. A structure joined to the plate 16 is preferable.

  Also in the magnetic field measurement device 1A of the second embodiment, the intensity of the measurement light emitted from each position of the magnetic field measurement device 1A depends on the magnetic field at each position of the magnetic transfer film 13b. By picking up an image by 2, a magnetic field distribution image (an image showing the magnetic field distribution) can be obtained. FIG. 7 is a conceptual diagram showing magnetic field measurement using the magnetic field measurement device 1A of the present embodiment. FIG. 7 illustrates a case where the magnetic field measurement device 1 </ b> A is used for measuring the distribution of the magnetic field generated by the magnetic field generation source 3 as an example.

  As shown in FIG. 7, the magnetic field measurement device 1A is installed at a position where measurement of the magnetic field distribution is desired. When measuring the magnetic field distribution, the surface light source 11 is operated to generate irradiation light. The generated irradiation light enters the magnetic transfer film 13 b of the magnetic transfer element 13 through the circularly polarizing plate 16. Circularly polarized irradiation light is incident on the magnetic transfer film 13 b of the magnetic transfer element 13. In the following description, it is assumed that the circularly polarizing plate 16 generates clockwise circularly polarized light for convenience. However, it should be noted that a magnetic field distribution image can be obtained by the same principle even when the circularly polarizing plate 16 generates counterclockwise circularly polarized light.

In the present embodiment, the circular circular dichroism (the property that absorption coefficients of clockwise circularly polarized light and counterclockwise circularly polarized light are different) of the magnetic transfer film 13b and the phenomenon that the absorption coefficient depends on the magnetic field are used. . When clockwise circularly polarized light is incident on the magnetic transfer film 13b, clockwise circularly polarized light and counterclockwise circularly polarized light are generated in the magnetic transfer film 13b by the Faraday effect of the magnetic transfer film 13b. The intensity of right-handed circularly polarized light and left-handed circularly polarized light generated at each position of the magnetic transfer film 13b is the intensity of the magnetic field at each position of the magnetic transfer film 13b, more strictly, the thickness direction of the magnetic field (Z-axis in FIG. 3). It depends on the magnetic field H _Z direction).

  Here, because of the circular polarization dichroism, the absorption coefficient in the magnetic transfer film 13b differs between the clockwise circularly polarized light and the counterclockwise circularly polarized light. As a result, the measurement light emitted from each position of the magnetic transfer film 13b. Is dependent on the magnetic field Hz at each position of the magnetic transfer film 13b. Therefore, an image reflecting the intensity depending on the magnetic field Hz at each position of the magnetic transfer film 13b, that is, a magnetic field distribution image can be obtained by imaging the measurement light emitted from the linear polarizing plate 14 with the imaging device 2. .

  The magnetic field measurement device 1A illustrated in FIG. 6 also has an advantage that the magneto-optical imaging can be easily performed similarly to the magnetic field measurement device 1 illustrated in FIG. In the embodiment of FIG. 6, the magnetic field measuring device 1 </ b> A configured as a structure in which the surface light source 11, the circularly polarizing plate 16, and the magnetic transfer element 13 are integrated is installed in a space for measuring the magnetic field distribution, and the surface light source A magnetic field distribution image can be obtained simply by photographing the magnetic field measurement device 1 </ b> A with the imaging device 2 in a state in which 11 is operated.

  FIG. 8 shows a modification of the magnetic field measurement device. The magnetic field measuring device of the modified example is referred to by reference numeral “1B”. In the magnetic field measurement device 1A shown in FIG. 6, the circularly polarized light generated by the circularly polarizing plate 16 is incident on the magnetic transfer element 13 as irradiation light. However, in the magnetic field measurement device 1B shown in FIG. A configuration in which circularly polarized light is extracted from the emitted light by the circularly polarizing plate 16 is employed.

  Specifically, the magnetic transfer element 13 is bonded to the light emitting surface 11 a of the surface light source 11, and the circularly polarizing plate 16 is bonded to the magnetic transfer element 13. In the structure of FIG. 8, the magnetic transfer element 13 is directly bonded to the light emitting surface 11 a of the surface light source 11. In FIG. 8, the magnetic transfer film 13b of the magnetic transfer element 13 is bonded to the light emitting surface 11a of the surface light source 11, and the substrate 13a is bonded to the circularly polarizing plate 16, but the substrate 13a is bonded to the light emitting surface 11a and magnetically. The transfer film 13 b may be bonded to the circularly polarizing plate 16.

  Also for the magnetic field measurement device 1B of FIG. 8, the intensity of the measurement light emitted from each position of the magnetic field measurement device 1B depends on the magnetic field at each position of the magnetic transfer film 13b. By doing so, a magnetic field distribution image (image showing the magnetic field distribution) can be obtained. FIG. 9 is a conceptual diagram showing magnetic field measurement using the magnetic field measurement device 1B of the present embodiment. FIG. 9 illustrates a case where the magnetic field measurement device 1B is used for measuring the distribution of the magnetic field generated by the magnetic field generation source 3 as an example. In the following description, it is assumed that the circularly polarizing plate 16 generates clockwise circularly polarized light for convenience. However, it should be noted that a magnetic field distribution image can be obtained by the same principle even when the circularly polarizing plate 16 generates counterclockwise circularly polarized light.

  As shown in FIG. 9, the magnetic field measurement device 1B is installed at a position where measurement of the magnetic field distribution is desired. When measuring the magnetic field distribution, the surface light source 11 is operated to generate irradiation light. The generated irradiation light is incident on the magnetic transfer film 13 b of the magnetic transfer element 13. Irradiation light incident on the magnetic transfer film 13b includes various polarized light.

In the present embodiment, the circular circular dichroism (the property that absorption coefficients of clockwise circularly polarized light and counterclockwise circularly polarized light are different) of the magnetic transfer film 13b and the phenomenon that the absorption coefficient depends on the magnetic field are used. . When the irradiation light is incident on the magnetic transfer film 13b, right-handed circularly polarized light and left-handed circularly polarized light are generated in the magnetic transfer film 13b due to the Faraday effect of the magnetic transfer film 13b. The intensity of right-handed circularly polarized light and left-handed circularly polarized light generated at each position of the magnetic transfer film 13b is the intensity of the magnetic field at each position of the magnetic transfer film 13b, more strictly, the thickness direction of the magnetic field (Z-axis in FIG. 3). It depends on the magnetic field H _Z direction).

  Here, because of the circular polarization dichroism, the absorption coefficient in the magnetic transfer film 13b differs between right-handed circularly polarized light and left-handed circularly polarized light. As a result, in the light emitted from each position of the magnetic transfer film 13b, The intensity of clockwise circularly polarized light depends on the magnetic field Hz at each position of the magnetic transfer film 13b.

  The light emitted from the magnetic transfer film 13 b is incident on the circularly polarizing plate 16. As a result, the clockwise circularly polarized component of the light emitted from the magnetic transfer film 13b is emitted from the circularly polarizing plate 16 as measurement light. As described above, the intensity of the clockwise circularly polarized light emitted from each position of the magnetic transfer film 13b depends on the magnetic field Hz at each position of the magnetic transfer film 13b, and as a result, is emitted from the circularly polarizing plate 16. The intensity of the measurement light also depends on the magnetic field Hz at each position of the magnetic transfer film 13b. Therefore, by imaging the measurement light emitted from the circularly polarizing plate 16 with the imaging device 2, an image reflecting the intensity depending on the magnetic field Hz at each position of the magnetic transfer film 13b, that is, a magnetic field distribution image can be obtained. .

  The magnetic field measurement device 1B illustrated in FIG. 8 can easily perform magneto-optical imaging similarly to the magnetic field measurement device 1 illustrated in FIG. 1 and the magnetic field measurement device 1A illustrated in FIG. Has the advantage. In the embodiment of FIG. 8, the magnetic field measurement device 1 </ b> B configured as a structure in which the surface light source 11, the magnetic transfer element 13, and the circularly polarizing plate 16 are integrated is installed in a space for measuring the magnetic field distribution. A magnetic field distribution image can be obtained simply by photographing the magnetic field measurement device 1 </ b> B with the imaging device 2 in a state in which 11 is operated.

  Also in the present embodiment, as shown in FIGS. 10A and 10B, the reflector 15 may be bonded to the back surface 11b of the surface light source 11 (the surface facing the light emitting surface 11a). In such a configuration, since the light emitted from the back surface of the surface light source 11 is reflected by the reflecting plate 15, it is possible to increase the intensity of irradiation light applied to the magnetic transfer element 13. Such a configuration is suitable for effectively using the light generated by the surface light source 11 for magnetic field measurement.

  The above-described magnetic field measurement devices 1, 1A, 1B have a simple structure of a laminated body in which plate-like structures are laminated, and also have an advantage of being easily miniaturized. One suitable application that makes use of the advantages of the magnetic field measuring devices 1, 1A, 1B is a probe for measuring a magnetic field. Hereinafter, embodiments of a probe for measuring a magnetic field and a magnetic field measurement system including the probe will be described.

  FIG. 11 is a system configuration diagram showing the configuration of the magnetic field measurement system 20 in one embodiment. The magnetic field measurement system 20 includes a probe 21, an optical fiber 22, and a measurement light processing unit 23.

  FIG. 12 is a cross-sectional view showing the configuration of the probe 21. The probe 21 includes the magnetic field measurement device 1, a sleeve 41, a lens 42, a concave mirror 43, and a filter 44.

  As described above, the magnetic field measuring device 1 includes the surface light source 11, the linearly polarizing plate 12, the magnetic transfer element 13, and the linearly polarizing plate 14. However, in the present embodiment, a phosphor is used as the surface light source 11. In FIG. 12, the phosphor used as the surface light source 11 is indicated by reference numeral 11A. FIG. 12 shows an embodiment in which the magnetic field measurement device 1 having the configuration shown in FIG. 1 is used in the probe 21, but the magnetic field measurement device 1A having the configuration shown in FIG. The magnetic field measurement device 1B having the configuration shown in FIG. 8 may be used. Also in this case, it is preferable that a phosphor is used as the surface light source 11.

  The sleeve 41 is a cylindrical hollow structure, and a lens 42 is attached to one end thereof, and a concave mirror 43 (concave mirror) is attached to the other end. In the internal space of the sleeve 41, the magnetic field measuring device 1 and the filter 44 are accommodated. The magnetic field measuring device 1 is provided so as to be positioned on the optical axis of the lens 42, and is positioned between the lens 42 and the concave mirror 43. The filter 44 is provided so as to surround the periphery of the magnetic field measurement device 1. The filter 44 has a wavelength characteristic that selectively passes excitation light that excites the phosphor 11 </ b> A of the magnetic field measurement device 1. In the present embodiment, since blue light is used as the excitation light, a blue transmission filter that selectively transmits blue light is used as the filter 44.

  Returning to FIG. 11, the optical fiber 22 is used to connect the probe 21 and the measurement light processing unit 23. One end of the optical fiber 22 is optically connected to the probe 21, and the other end is optically connected to the measurement light processing unit 23.

  The measurement light processing unit 23 generates excitation light that excites the phosphor 11 </ b> A of the magnetic field measurement device 1 of the probe 21 and calculates the magnetic field at the position of the magnetic field measurement device 1 from the measurement light emitted from the magnetic field measurement device 1. . Specifically, the measurement light processing unit 23 includes a laser diode 31, a lens 32, a blue reflection mirror 33, a lens 34, a photodiode 35, an interface 36, and an arithmetic device 37.

  The laser diode 31 generates excitation light that excites the phosphor 11 </ b> A of the magnetic field measurement device 1. In the present embodiment in which blue light is used as the excitation light, a blue laser diode is used as the laser diode 31.

  The lens 32 collimates the excitation light generated by the laser diode 31 into parallel light. The blue reflection mirror 33 reflects the excitation light emitted from the lens 32 and enters the lens 34. As will be described later, the blue reflection mirror 33 is formed so as to pass the measurement light while reflecting the excitation light which is blue light. The lens 34 makes the excitation light reflected by the blue reflection mirror 33 incident on the optical fiber 22, collimates the measurement light emitted from the optical fiber 22 into parallel light, and emits it toward the blue reflection mirror 33. The measurement light emitted from the lens 34 passes through the blue reflection mirror 33 and enters the photodiode 35.

  The photodiode 35 is used as a light detection device that converts measurement light incident thereon into an electrical signal and outputs the electrical signal. The electrical signal output from the photodiode 35 has a signal level corresponding to the intensity of the measurement light.

  The interface 36 performs digital-analog conversion on the electrical signal received from the photodiode 35 and generates digital measurement data corresponding to the signal level of the electrical signal. The signal level of the electrical signal received from the photodiode 35 is the intensity of the measurement light output from the magnetic field measurement device 1, that is, the position where the magnetic field measurement device 1 is provided (more precisely, the position of the magnetic transfer film 13b). Corresponds to the intensity of the magnetic field.

  The computing device 37 calculates the magnetic field at the position where the magnetic field measuring device 1 is provided based on the digital measurement data received from the interface 36.

  Next, magnetic field measurement using the magnetic field measurement system 20 will be described. The magnetic field measurement system 20 of this embodiment is configured to measure a magnetic field at a position where the magnetic field measurement device 1 of the probe 21 is provided. The magnetic field measurement system 20 measures the magnetic field by the following operation.

  Referring to FIG. 11, when measuring the magnetic field, the laser diode 31 generates excitation light that excites the phosphor 11 </ b> A of the magnetic field measurement device 1. The generated excitation light is indicated by reference numeral 24 in FIG. As described above, in the present embodiment, the excitation light 24 is blue light. The excitation light 24 is collimated into parallel light by the lens 32, reflected by the blue reflecting mirror 33, further collected by the lens 34, and incident on one end of the optical fiber 22. The excitation light 24 incident on the optical fiber 22 is transmitted to the probe 21 by the optical fiber 22.

  As shown in FIG. 12, the excitation light 24 transmitted to the probe 21 is emitted from the other end of the optical fiber 22, enters the lens 42 of the probe 21, and is collimated into parallel light by the lens 42. The excitation light 24 emitted from the lens 42 is supplied to the phosphor 11 </ b> A of the magnetic field measurement device 1, and the light generated by the phosphor 11 </ b> A by excitation by the excitation light 24 is used as irradiation light that is irradiated to the magnetic transfer element 13. . Specifically, a portion of the excitation light 24 emitted from the lens 42 in the vicinity of the optical axis of the lens 42 is directly incident on the magnetic field measurement device 1 and used for excitation of the phosphor 11A. On the other hand, the portion of the lens 42 away from the optical axis passes through the filter 44 and enters the concave mirror 43. The excitation light 24 reflected by the concave mirror 43 is incident on the phosphor 11A of the magnetic field measuring device 1 and used for exciting the phosphor 11A. The filter 44 plays a role of preventing light that has not entered the lens 42 from entering measurement light emitted from the magnetic field measurement device 1 from entering the concave mirror 43. Irradiation light generated by the phosphor 11 </ b> A has a wavelength longer than that of the excitation light 24.

  Irradiation light generated by the phosphor 11 </ b> A is incident on the magnetic transfer element 13 via the linearly polarizing plate 12 and further incident on the linearly polarizing plate 14. Light emitted from the linear polarizing plate 14 is used as the measurement light 25. The intensity of the measurement light 25 depends on the magnetic field at the position of the magnetic transfer film 13 b of the magnetic transfer element 13. The measurement light 25 enters the lens 42 and further enters the optical fiber 22. The measurement light 25 incident on the optical fiber 22 is transmitted to the measurement light processing unit 23 by the optical fiber 22.

  Referring again to FIG. 11, the measurement light 25 transmitted to the measurement light processing unit 23 is emitted from the optical fiber 22, is incident on the lens 34 of the measurement light processing unit 23, and is collimated to parallel light by the lens 34. . The measurement light 25 emitted from the lens 34 passes through the blue reflection mirror 33 and enters the photodiode 35. If the material of the phosphor 11A is appropriately selected, the wavelength of the irradiation light incident on the magnetic transfer element 13, that is, the wavelength of the measurement light 25 is set so that the measurement light 25 passes through the blue reflection mirror 33. Is possible. Here, a part of the excitation light 24 may be scattered inside the probe 21 and returned to the measurement light processing unit 23 via the optical fiber 22, but the excitation returned to the measurement light processing unit 23. Since the light 24 is reflected by the blue reflection mirror 33, it does not enter the photodiode 35.

  The measurement light 25 incident on the photodiode 35 is converted into an electrical signal, and the electrical signal is supplied to the interface 36. The electrical signal output from the photodiode 35 has a signal level corresponding to the intensity of the measurement light.

  Digital measurement data corresponding to the signal level of the electrical signal is generated from the electrical signal supplied to the interface 36 by digital-analog conversion. The signal level of the electric signal is the intensity of the measurement light output from the magnetic field measurement device 1, that is, the magnetic field intensity at the position where the magnetic field measurement device 1 is provided (more precisely, the position of the magnetic transfer film 13b). It corresponds. Based on the digital measurement data, the arithmetic unit 37 calculates the magnetic field at the position where the magnetic field measurement device 1 is provided.

  In the configuration illustrated in FIG. 11, since the photodiode 35 is used to measure the intensity of the measurement light 25, a magnetic field distribution image cannot be obtained. However, as will be described later, a magnetic field distribution image can be obtained by using an imaging element such as a CCD (charge carrying device) or a CMOS (complementary metal oxide semiconductor) sensor instead of the photodiode 35.

  One of the advantages of the magnetic field measurement system 20 shown in FIG. 11 is that irradiation light to be irradiated to the magnetic transfer element 13 can be generated by the phosphor 11 </ b> A without supplying electricity to the probe 21. Such a configuration is suitable for measuring a magnetic field in an environment where electricity cannot be used (for example, an environment where explosion protection is required).

  FIG. 13 illustrates a modification of the configuration of the probe. In the probe 21 </ b> A illustrated in FIG. 13, a cone mirror 43 </ b> A (a mirror having a reflective surface having a cone shape or a part of a cone shape) is used instead of the concave mirror 43. The configuration of FIG. 13 is suitable for bringing the position where the magnetic field measurement device 1 is disposed closer to the end of the probe 21A (end of the sleeve 41). In the configuration of FIG. 11 using the concave mirror 43, it is necessary to arrange the magnetic field measuring device 1 so that the phosphor 11 </ b> A is located in the vicinity of the focal point of the concave mirror 43. It is necessary to secure a distance. On the other hand, when the cone mirror 43A is used, the distance between the magnetic field measurement device 1 and the cone mirror 43A can be reduced, and therefore the position where the magnetic field measurement device 1 is disposed is brought closer to the end of the probe 21A. Can do. Such a configuration is suitable for measuring the magnetic field by positioning the magnetic field measuring device 1 as close as possible to the position where the magnetic field is to be measured.

  FIG. 14 illustrates another modification of the configuration of the probe. In the probe 21B illustrated in FIG. 14, a scatterer 43B is used instead of the concave mirror 43 and the cone mirror 43A. In the configuration of FIG. 14, the scatterer 43 </ b> B is disposed so as to surround the magnetic field measurement device 1. Of the beam of the excitation light 24 emitted from the lens 42, a portion in the vicinity of the optical axis of the lens 42 is directly incident on the magnetic field measuring device 1 and used for exciting the phosphor 11A. On the other hand, the portion of the lens 42 away from the optical axis passes through the filter 44 and enters the scatterer 43B. The scatterer 43B is configured to generate irregular reflection, and the light incident on the phosphor 11A of the magnetic field measuring device 1 out of the excitation light 24 scattered by the scatterer 43B is used for exciting the phosphor 11A. The On the other hand, in the configuration using the scatterer 43B, the magnetic field measuring device 1 can be brought closer to the end of the probe 21B (end of the sleeve 41), and the distance to the cone mirror 43A can be made closer. Such a configuration is suitable for measuring the magnetic field by positioning the magnetic field measuring device 1 as close as possible to the position where the magnetic field is to be measured.

  FIG. 15 is a system configuration diagram illustrating a modification of the magnetic field measurement system. The magnetic field measurement system 20A illustrated in FIG. 15 is configured to obtain a magnetic field distribution image using a probe. Specifically, the magnetic field measurement system 20A illustrated in FIG. 15 has a configuration similar to that of the magnetic field measurement system 20 illustrated in FIG. 11, but the magnetic field measurement system illustrated in FIG. In the system 20 </ b> A, the measurement light processing unit 23 </ b> A uses an imaging device, more specifically, a CCD 38 instead of the photodiode 35. In addition, a lens 39 for allowing the measurement light 25 to enter the light receiving surface of the CCD 38 is provided.

  The measurement light 25 emitted from the optical fiber 22 is incident on the lens 34 of the measurement light processing unit 23A, and is collimated into parallel light by the lens 34. The measurement light 25 emitted from the lens 34 passes through the blue reflection mirror 33 and enters the lens 39. The lens 39 collects the measurement light 25 and enters the CCD 38. The CCD 38 images the measurement light 25 incident on the CCD 38. The imaging signal output from the CCD 38 is supplied to the interface 36 and converted into digital measurement data. The computing device 37 generates a magnetic field distribution image from the digital measurement data. In addition, the arithmetic unit 37 may calculate the magnetic field at each position of the magnetic field measurement device 1 from the luminance at each position of the magnetic field distribution image (the luminance of each pixel).

  In the magnetic field measurement system 20A having such a configuration, the magnetic field at the position of the magnetic field measurement device 1 of the probe (probe 21B in FIG. 15) (strictly, the position of the magnetic transfer film 13b of the magnetic transfer element 13 of the magnetic field measurement device 1). Can be obtained. Further, if the arithmetic unit 37 performs image processing on the magnetic field distribution image, the magnetic field at each position of the magnetic field measurement device 1 can be specified from the luminance at each position of the magnetic field distribution image (the luminance of each pixel). is there.

  15 shows the configuration of the magnetic field measurement system 20A in which the probe 21B shown in FIG. 14 is used, but the probes 21 and 21A shown in FIGS. 12 and 13 are used. Also good.

  FIG. 16 illustrates another modification of the magnetic field measurement system. The magnetic field measurement system 50 illustrated in FIG. 16 is configured to transmit the excitation light 24 and the measurement light 25 through separate optical fibers. In the configuration in which the excitation light 24 and the measurement light 25 have different wavelengths and the excitation light 24 and the measurement light 25 are transmitted by different optical fibers, optical fibers having suitable characteristics can be used. This is effective for reducing attenuation of the excitation light 24 and the measurement light 25 in the optical fiber.

  Specifically, the magnetic field measurement system 50 illustrated in FIG. 16 includes a probe 21 </ b> B, two optical fibers 22 a and 22 b, and a measurement light processing unit 51.

  The configuration of the probe 21B is as described above. However, in this embodiment, the excitation light 24 is incident on the lens 42 from the optical fiber 22a, and the measurement light 25 is incident on the optical fiber 22b from the lens 42.

  The measurement light processing unit 51 includes an excitation light generation unit 52, a measurement light receiving unit 53, an interface 57, and a calculation device 58.

  The excitation light generation unit 52 includes a laser diode 54 and lenses 55 and 56. The laser diode 54 generates excitation light 24 that excites the phosphor 11 </ b> A of the magnetic field measurement device 1. In the present embodiment in which blue light is used as the excitation light 24, a blue laser diode is used as the laser diode 54. The lens 55 collimates the excitation light generated by the laser diode 54 into parallel light. The lens 56 makes the excitation light 24 collimated by the lens 55 incident on the optical fiber 22a.

  The measurement light receiving unit 53 includes a blue cut filter 53a, a lens 53b, and a CCD 53c. When the excitation light 24 is scattered inside the probe 21B and returns to the measurement light processing unit 51 via the optical fiber 22b, the blue cut filter 53a removes the excitation light 24 that has returned to the measurement light processing unit 51. . The lens 53b condenses the measurement light 25 emitted from the optical fiber 22b and enters the CCD 53c. The CCD 53c images the measurement light 25 incident on the CCD 53c. The imaging signal output from the CCD 53c is supplied to the interface 57 and converted into digital measurement data. The computing device 58 generates a magnetic field distribution image from the digital measurement data. In addition, the calculation device 58 may calculate the magnetic field at each position of the magnetic field measurement device 1 from the luminance at each position of the magnetic field distribution image (the luminance of each pixel).

  16 shows the configuration of the magnetic field measurement system 50 in which the probe 21B shown in FIG. 14 is used. The probes 21, 21A shown in FIGS. 12 and 13 are used. May be.

  FIG. 17 is a system configuration diagram showing a configuration of a magnetic field measurement system 70 in another embodiment. The magnetic field measurement system 70 of FIG. 17 is good by acquiring a magnetic field distribution image from each of the clockwise circularly polarized light and the counterclockwise circularly polarized light included in the measurement light emitted from the magnetic field measuring device, and synthesizing the magnetic field distribution image. The magnetic field distribution image is obtained. Hereinafter, the configuration of the magnetic field measurement system 70 will be described.

  The magnetic field measurement system 70 includes a magnetic field measurement device 1B, a non-polarizing beam splitter 71, circularly polarizing plates 72 and 73, imaging devices 74 and 75, and an image processing unit 76.

  The magnetic field measuring device 1 </ b> B includes a surface light source 11 and a magnetic transfer element 13. The surface light source 11 generates irradiation light that irradiates the magnetic transfer element 13 and emits it from the light emitting surface 11a. The light emitting surface 11 a of the surface light source 11 is bonded to the magnetic transfer element 13. That is, the irradiation light emitted from the light emitting surface 11 a enters the magnetic transfer element 13. The magnetic transfer element 13 includes a substrate 13a and a magnetic transfer film 13b formed on the substrate 13a. The details of the configuration of the magnetic transfer element 13 are as described above. FIG. 17 shows the configuration of the magnetic field measuring device 1B in which the magnetic transfer film 13b of the magnetic transfer element 13 is bonded to the light emitting surface 11a of the surface light source 11, but the substrate 13a is bonded to the surface light source 11. Also good. However, from the viewpoint of making the magnetic transfer film 13b closer to the position where the measurement of the magnetic field distribution is desired, it is preferable that the magnetic transfer film 13b be brought closer to the surface light source 11, and thus the magnetic transfer film 13b is bonded to the surface light source 11. The configuration is suitable.

  The non-polarizing beam splitter 71 reflects a part of the measurement light emitted from the magnetic transfer element 13 to separate the measurement light beam into two beams. The measurement light that has passed through the non-polarizing beam splitter 71 is incident on the circularly polarizing plate 72, and the measuring light reflected by the non-polarizing beam splitter 71 is incident on the circularly polarizing plate 73.

  The circularly polarizing plates 72 and 73 are configured such that the rotation directions of the polarization planes of the circularly polarized light emitted from each of them are the same. That is, the circularly polarizing plates 72 and 73 are both configured to emit clockwise circularly polarized light, or both are configured to emit counterclockwise circularly polarized light. Here, when the clockwise circularly polarized light is reflected, it becomes counterclockwise circularly polarized light, and when the counterclockwise circularly polarized light is reflected, it becomes clockwise circularly polarized light. Therefore, the circularly polarizing plates 72 and 73 both turn clockwise circularly polarized light. When configured to emit, the circularly polarizing plate 72 emits the clockwise circularly polarized component of the measurement light, and the circularly polarizing plate 73 outputs the counterclockwise circularly polarized component of the measuring light. Right-handed circularly polarized light having an intensity distribution corresponding to the intensity distribution is emitted.

  The imaging device 74 captures the measurement light emitted from the circularly polarizing plate 72 and obtains a captured image. Similarly, the imaging device 75 captures the measurement light emitted from the circularly polarizing plate 73 and captures the captured image. get. The imaging devices 74 and 75 generate captured image data corresponding to the acquired captured images and send the generated captured image data to the image processing unit 76.

  The image processing unit 76 includes an interface 77 and an arithmetic device 78. The interface 77 transfers the captured image data obtained by the imaging devices 74 and 75 to the arithmetic device 78. The computing device 78 generates a magnetic field distribution image from the captured images obtained by the imaging devices 74 and 75, respectively. In the present embodiment, the arithmetic device 78 generates a differential image of the captured image obtained by the imaging devices 74 and 75 from the transferred captured image data, and the differential image is finally obtained as a magnetic field distribution image. Used.

  FIG. 18 is a conceptual diagram showing an operation of obtaining a magnetic field distribution image by the magnetic field measurement system 70 of FIG. Hereinafter, the operation of the magnetic field measurement system 70 will be described on the assumption that the circularly polarizing plates 72 and 73 are both configured to emit clockwise circularly polarized light. However, those skilled in the art can easily understand that a magnetic field distribution image can be obtained by the same operation even when the circularly polarizing plates 72 and 73 are both configured to emit counterclockwise circularly polarized light. Like.

  When measuring the magnetic field distribution, the surface light source 11 is operated to generate irradiation light. The generated irradiation light is incident on the magnetic transfer film 13 b of the magnetic transfer element 13. The measurement light emitted from the magnetic transfer film 13b by the Faraday effect in the magnetic transfer film 13b includes information on the magnetic field at each position of the magnetic transfer film 13b.

  The beam of measurement light emitted from the magnetic transfer film 13 b is separated into two beams by the non-polarizing beam splitter 71. The beam of measurement light that has passed through the non-polarizing beam splitter 71 is incident on the imaging device 74 via the circularly polarizing plate 72, and the beam of measurement light reflected by the non-polarizing beam splitter 71 is passed through the circularly polarizing plate 73. The light enters the imaging device 75.

  The captured images acquired by the imaging devices 74 and 75 are both magnetic distribution images. Specifically, since the circularly polarizing plates 72 and 73 are both configured to emit clockwise circularly polarized light, they are obtained from the clockwise circularly polarized light component of the measurement light emitted from the magnetic transfer element 13. The magnetic distribution image 81 is generated by the imaging device 74, and the magnetic distribution image 82 obtained from the counterclockwise circularly polarized component of the measurement light emitted from the magnetic transfer element 13 is generated by the imaging device 75. The captured image data corresponding to the magnetic distribution image 81 generated by the imaging device 74 and the captured image data corresponding to the magnetic distribution image 82 generated by the imaging device 75 are transferred to the arithmetic device 78 of the image processing unit 76. The The computing device 78 calculates a difference image 83 of the magnetic distribution images 81 and 82 from the transferred captured image data. This difference image 83 is used as a magnetic distribution image finally obtained. In addition, by performing image processing on the finally obtained magnetic distribution image (difference image 83) by the arithmetic unit 78, the luminance of each magnetic field distribution image (the luminance of each pixel) can be calculated from the luminance of each pixel. It is also possible to specify the magnetic field at each position.

  According to such an operation, information on the magnetic field distribution included in the measurement light emitted from the magnetic transfer element 13 can be used more effectively, so that the detection sensitivity of the magnetic field distribution can be improved. In addition, noise due to uneven brightness of the surface light source 11 and position variation of the characteristics of the magnetic transfer film 13b can be canceled, so that the image quality of the magnetic field distribution image can be improved, or from the magnetic field distribution image The accuracy of the obtained magnetic field can be improved.

  In this embodiment, the rotation direction of the circularly polarized light emitted from the circularly polarizing plates 72 and 73 is such that the measurement light is reflected before the measurement light emitted from the magnetic transfer element 13 enters the circularly polarizing plate 72. Note that it should be determined according to the difference between the number of times the measurement light is reflected and the number of times the measurement light is reflected before the measurement light emitted from the magnetic transfer element 13 enters the circularly polarizing plate 73. I want to be. For example, if the difference between the number of times the measurement light is reflected before entering the circularly polarizing plate 72 and the number of times the measurement light is reflected before entering the circularly polarizing plate 73 is an odd number, The polarizing plates 72 and 73 are configured such that the rotation directions of the polarization planes of the circularly polarized light emitted from the polarizing plates 72 and 73 are the same. On the other hand, the difference between the number of times the measurement light is reflected before entering the circularly polarizing plate 72 and the number of times the measurement light is reflected before entering the circularly polarizing plate 73 is an even number (including zero). In this case, the circularly polarizing plates 72 and 73 are configured such that the rotation directions of the polarization planes of the circularly polarized light emitted from the circularly polarizing plates 72 and 73 are opposite to each other. By setting the rotation direction of the circularly polarized light emitted from the circularly polarizing plates 72 and 73 in this way, the clockwise circularly polarized light component and the counterclockwise circularly polarized light component of the measurement light emitted from the magnetic transfer element 13 are set. Can be acquired separately, and information on the magnetic field distribution included in the captured image can be used effectively.

  Although various embodiments of the present invention have been specifically described above, the present invention should not be construed as being limited to the above-described embodiments. It will be apparent to those skilled in the art that the present invention may be practiced with various modifications.

DESCRIPTION OF SYMBOLS 1, 1A, 1B: Magnetic field measuring device 2: Imaging device 3: Magnetic field generation source 11: Surface light source 11A: Phosphor 11a: Light emitting surface 11b: Back surface 12: Linearly polarizing plate 12a: Broken line arrow 13: Magnetic transfer element 13a: Substrate 13b: Magnetic transfer film 14: Linear polarizing plate 14a: Arrow 15: Reflector 16: Circular polarizing plate 20, 20A: Magnetic field measurement systems 21, 21A, 21B: Probes 22, 22a, 22b: Optical fibers 23, 23A: Measurement light processing Unit 24: Excitation light 25: Measurement light 31: Laser diode 32: Lens 33: Blue reflection mirror 34: Lens 35: Photo diode 36: Interface 37: Computing device 38: CCD
39: Lens 41: Sleeve 42: Lens 43: Concave mirror 43A: Cone mirror 43B: Scattering body 44: Filter 50: Magnetic field measurement system 51: Measurement light processing unit 52: Excitation light generation unit 53: Measurement light receiving unit 53a: Blue cut Filter 53b: Lens 53c: CCD
54: Laser diode 55, 56: Lens 57: Interface 58: Computing device 70: Magnetic field measurement system 71: Non-polarizing beam splitter 72, 73: Circularly polarizing plate 74, 75: Imaging device 76: Image processing unit 77: Interface 78: Arithmetic devices 81 and 82: Magnetic distribution image 83: Difference image

Claims (20)

A magnetic transfer element comprising a magnetic transfer film exhibiting a magneto-optical effect;
A surface light source for generating irradiation light and emitting the irradiation light from a light emitting surface;
A magnetic field measuring device in which the light emitting surface of the surface light source is bonded to the magnetic transfer element. The magnetic field measurement device according to claim 1,
Furthermore,
A first linear polarizing plate;
A second linearly polarizing plate,
The first linear polarizing plate is inserted between the magnetic transfer element and the surface light source,
The second linearly polarizing plate is provided so as to face the first linearly polarizing plate across the magnetic transfer element. The magnetic field measurement device according to claim 2,
When the saturation Faraday rotation angle of the magnetic transfer film is α _FS , an angle θ formed by a plane perpendicular to the transmission axis of the first linear polarizing plate and the transmission axis of the second linear polarizing plate is as follows:
α _FS ≦ θ ≦ 90 ° -α _FS
Satisfying magnetic field measuring device. The magnetic field measurement device according to claim 2 or 3,
Furthermore, a magnetic field measuring device comprising a reflector that is bonded to a back surface of the surface light source facing the light emitting surface and reflects light emitted from the back surface of the surface light source. The magnetic field measurement device according to claim 1,
Furthermore,
A magnetic field measuring device comprising a circularly polarizing plate inserted between the magnetic transfer element and the surface light source. The magnetic field measurement device according to claim 1,
Furthermore,
A circularly polarizing plate,
The magnetic transfer element is provided between the circularly polarizing plate and the surface light source. The magnetic field measuring device according to any one of claims 1 to 6,
A magnetic field measuring device, wherein the surface light source comprises an electroluminescence light source. A magnetic field measuring device according to any one of claims 1 to 7,
The surface light source comprises a phosphor;
The magnetic field measuring device configured to receive the excitation light incident on the phosphor and generate the irradiation light by fluorescence. A magnetic field measuring device according to any one of claims 1 to 8,
An imaging device comprising: an imaging device that images the magnetic field measurement device and generates a magnetic field distribution image indicating a magnetic field distribution at each position of the magnetic transfer film. A first optical fiber;
A probe comprising the magnetic field measuring device according to claim 8 joined to a first end of the first optical fiber;
A measurement light processing unit joined to the second end of the first optical fiber,
The measurement light processing unit is
An excitation light generator that generates excitation light;
A light detection device,
The excitation light is incident on the phosphor of the magnetic field measurement device,
Of the irradiation light generated by the phosphor, measurement light that is light that has passed through the magnetic transfer element is incident on the first end of the first optical fiber, propagates through the first optical fiber, and travels through the first optical fiber. A magnetic field measurement system that is emitted from a second end of an optical fiber and is incident on the light detection device. The magnetic field measurement system according to claim 10,
In addition, including an arithmetic unit,
The light detection device includes an image sensor that images the measurement light,
The said arithmetic unit produces | generates the magnetic field distribution image which shows distribution of the magnetic field in the position of the said magnetic transfer film from the imaging signal output from the said image sensor. The magnetic field measurement system according to claim 10,
The excitation light is incident on the second end of the first optical fiber from the excitation light generation unit, propagates through the first optical fiber, and is emitted from the first end of the first optical fiber. A magnetic field measurement system incident on the phosphor. The magnetic field measurement system according to claim 10,
Furthermore,
Comprising a second optical fiber;
The excitation light is transmitted from the excitation light generator to the probe via the second optical fiber, and is incident on the phosphor of the magnetic field measurement device. The magnetic field measurement system according to claim 12,
The probe is
Furthermore,
A sleeve containing the magnetic field measuring device;
A lens,
A mirror provided at one end of the sleeve;
The magnetic field measuring device is located between the lens and the mirror;
The excitation light is incident on the lens from the first end of the first optical fiber, is incident on the mirror from the lens, is reflected by the mirror, and is incident on the phosphor of the magnetic field measurement device. system. The magnetic field measurement system according to claim 13,
The probe is
Furthermore,
A sleeve containing the magnetic field measuring device;
A lens,
A mirror provided at one end of the sleeve;
The magnetic field measuring device is located between the lens and the mirror;
The excitation light is incident on the lens from the excitation light generation unit via the second optical fiber, is incident on the mirror from the lens, is reflected by the mirror, and is incident on the phosphor of the magnetic field measurement device. Magnetic field measurement system. The magnetic field measurement system according to claim 12,
The probe is
Furthermore,
A sleeve containing the magnetic field measuring device;
A lens,
A scatterer,
The excitation light is incident on the lens from the first end of the first optical fiber, is incident on the scatterer from the lens, is scattered by the scatterer, and is incident on the phosphor of the magnetic field measurement device. Magnetic field measurement system. The magnetic field measurement system according to claim 13,
The probe is
Furthermore,
A sleeve containing the magnetic field measuring device;
A lens,
A scatterer,
The excitation light is incident on the lens from the excitation light generation unit through the second optical fiber, is incident on the scatterer from the lens, and is scattered by the scatterer to the phosphor of the magnetic field measurement device. Incident magnetic field measurement system. A magnetic field measuring device;
A beam splitter,
A first circularly polarizing plate;
A second circularly polarizing plate;
A first imaging device;
A second imaging device;
An arithmetic device,
The magnetic field measurement device includes:
A magnetic transfer element comprising a magnetic transfer film exhibiting a magneto-optical effect;
A surface light source for generating irradiation light and emitting the irradiation light from a light emitting surface;
The light emitting surface of the surface light source is bonded to the magnetic transfer element;
The beam splitter generates a first beam and a second beam from a beam of measurement light emitted from the magnetic transfer element;
The first beam is incident on the first imaging device via the first circularly polarizing plate,
The second beam is incident on the second imaging device via the second circularly polarizing plate,
The first imaging device captures the first beam to generate a first captured image,
The second imaging device captures the second beam to generate a second captured image;
The arithmetic device generates a difference image between the first captured image and the second captured image as a magnetic field distribution image indicating a magnetic field distribution at each position of the magnetic transfer film. The magnetic field measurement system according to claim 18,
The beam splitter transmits a part of the beam of measurement light emitted from the magnetic transfer element to generate the first beam, reflects a part to generate the second beam,
The magnetic field measurement system in which rotation directions of circularly polarized light emitted from the first circularly polarizing plate and the second circularly polarizing plate are the same. A magnetic transfer element including a magnetic transfer film that exhibits a magneto-optical effect; and a surface light source that generates irradiation light and emits the irradiation light from a light emitting surface, wherein the light emitting surface of the surface light source is the magnetic transfer element. Placing the magnetic field measuring device joined to the desired position;
Imaging the magnetic field measurement device in a state where the irradiation light generated by the surface light source is incident on the magnetic transfer element, and generating a magnetic field distribution image showing a magnetic field distribution at each position of the magnetic transfer film; A magnetic field measurement method.

Images