JP2005308455A - Electromagnetic field detecting element and electromagnetic field detector using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic field detecting element capable of accurately controlling the height from a measuring level. <P>SOLUTION: The detecting element has an optical fiber 21 for magnetic field measurement for detecting a magnetic field radiated from a measuring object and a plurality of optical fibers 22 for height measurement for measuring the displacement of distance from the tip end to the measuring object. To the tip end of the optical fiber 21 for magnetic field measurement, an MO crystal 24 coated with a mirror thin film 25 is provided on one end surface. Around the optical fiber 21 for magnetic field measurement, a plurality of optical fibers 22 for height measurement are arranged. The optical fiber 21 for magnetic field measurement and the optical fibers 22 for height measurement are fixed in one in a state that each tip end surface are aligned in the same plane. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an element for detecting a magnetic field and an electric field generated from a printed circuit board on which components are mounted, an MCM (multichip module), and the like, and a measuring apparatus including the element.

  A so-called EMI (Electro Magnetic Interference) problem is known in which electromagnetic waves radiated from an electronic device cause harm to other electronic devices. In designing electronic devices, EMI countermeasures are generally taken. In this EMI (Electro Magnetic Interference) countermeasure, it is important to specify the source of the electromagnetic field. When specifying the generation source of an electromagnetic field in a printed circuit board or MCM, a sensor capable of detecting an electric field or a magnetic field is used. For example, a magnetic field generation source is specified by measuring a near magnetic field radiated from a mounted component using a sensor capable of detecting a magnetic field.

  In the magnetic field measurement, a loop coil sensor having a loop detection area of about 10 cm to 1 mm is generally used (Non-Patent Documents 1 and 2). Loop coil sensors include those made of printed circuit board materials and those made of ceramics, which are already commercially available. Recently, although limited to a certain direction, a thin film loop sensor having a resolution of 100 μm or less has been reported.

  In addition, a magnetic field detection element using a crystal (MO crystal) having a magneto-optic effect and an optical fiber has been proposed (Non-Patent Documents 3 to 5). FIG. 7 schematically shows the configuration of a magnetic field detection element in which a magneto-optical crystal is bonded to the tip of an optical fiber. In this magnetic field detection element, a magneto-optic (MO) crystal 14 having a mirror thin film 15 formed on one end face is provided at the tip of an optical fiber 11 having a core region 12 and a cladding region. The surface of the magneto-optic (MO) crystal 14 opposite to the surface on which the mirror thin film 15 is provided is fixed to the end surface of the optical fiber 11.

In this magnetic field detection element, the light propagating in the core region 12 in the direction of the tip portion reaches the mirror thin film 15 through the MO crystal 14 and is reflected there. The reflected light from the mirror thin film 15 again enters the core region 12 through the MO crystal 14 and propagates in the core region 12 in the direction opposite to the tip. At this time, in the MO crystal 14, the polarization angle of light passing therethrough changes according to the magnitude of the magnetic field from the outside (magneto-optic effect). Therefore, the external magnetic field intensity can be measured by detecting the change in the polarization angle of the reflected light from the mirror thin film 15 by the analyzer.
Naoki Tamaki, Norio Masuda, Toshihide Kuriyama, Masahide Tago, Togane Kiyoshi, Masahiro Yamaguchi, Kenichi Arai: IEICE Technical Report, EMCJ2002-6, pp.31-34 (Apr.2002) Naoki Tamaki, Norio Masuda, Kazuyoshi Ishizaka: Material of IEEJ Magnetics Study Group, MAG-00-137, pp.25-30 (2000-06) Masahiro Tsuchiya, Atsushi Yamazaki, Shinichi Wakana, Hayato Kishi: Journal of Japan Society of Applied Magnetics, Vol.26, No.3, pp.128-134 (2002) S. Wakana, E. Yamazaki, M. Iwanami, S. Hoshino, M. Kishi, and M. Tsuchiya: Jpn. J. Appl. Phys. Vol. 42 (2003) pp. 6637-6640. M. Iwanami, S. Hoshino, M. Kishi, and M. Tsuchiya: Proc. 2003.IEEE Symp. On Electromagnetic Compatibility, pp.347-352 (Aug.2003).

  Since the current loop coil sensor has low resolution, it is difficult to accurately specify the generation source of the electromagnetic field in the printed circuit board or the MCM. Recently, printed circuit boards and MCMs tend to be miniaturized, and for this reason, sensors with higher resolution are required.

  In a magnetic field detection element including a magneto-optic crystal at the tip of an optical fiber, the resolution is basically determined by the core diameter of the optical fiber, so that the resolution can be higher than that of a loop coil sensor. However, this magnetic field detection element has the following problems.

  In the magnetic field distribution measurement, the measurement surface is scanned with the magnetic field detection element. At that time, the distance between the magnetic field detection element and the measurement surface (the height of the magnetic field detection element from the measurement surface) needs to be kept constant. In order to perform magnetic field distribution measurement with higher spatial resolution, it is necessary to control the distance between the measurement surface and the detection element with high accuracy and keep the height of the magnetic field detection element during scanning as constant as possible. In particular, since wiring formed on a printed circuit board, MCM, or the like has a complicated shape, more accurate height control is required when measuring the magnetic field distribution of such wiring. . However, in the conventional magnetic field measurement using the magnetic field detection element, such a high level is obtained only by scanning the magnetic field detection element by relative movement between the magnetic field detection element and the stage to which the measurement object is fixed. Accurate height control cannot be performed. Further, the magnetic field detection element itself is not configured to detect the height. For this reason, it has been difficult to measure the magnetic field distribution with high resolution.

  The objective of this invention is providing the electromagnetic field detection element which can control the height from a measurement surface with high precision, and an electromagnetic field measuring apparatus using the same.

  In order to achieve the above object, an electromagnetic field detection element of the present invention includes a first optical fiber provided with an optical crystal for detecting an electromagnetic field radiated from an object to be measured, and a tip portion from the first optical fiber. A second optical fiber for measuring a variation in the distance to the object to be measured, and the first and second optical fibers are aligned so that the end surfaces of the respective distal end portions are the same surface. It is characterized by being fixed integrally in the state.

  In the above configuration, the distance from the end surface of the tip of the first optical fiber to the measurement object corresponds to the height from the measurement surface of the electromagnetic field detection element. Since the end surface of the distal end portion of the second optical fiber is configured to be the same surface as the end surface of the distal end portion of the first optical fiber, the object to be measured is measured from the end surface of the distal end portion of the second optical fiber. By measuring the distance up to, it is possible to know the height of the electromagnetic field detection element from the measurement surface. Thus, in the present invention, the displacement of the distance from the electromagnetic field detection element to the measurement object can be measured using the second optical fiber. Therefore, based on the result of the displacement measurement, it is possible to control the distance from the electromagnetic field detection element to the measurement object to be constant.

  Also, the resolution of the electromagnetic field detection element of the present invention is basically determined by the core diameter of the first optical fiber as in the case of the conventional magnetic field detection element, so that the electromagnetic field can be generated with higher spatial resolution than the loop coil sensor. It is possible to measure.

  Further, the resolution (displacement resolution) of the distance displacement measurement using the second optical fiber depends on the light source to be used. For example, when a semiconductor laser having a wavelength of 840 nm is used, it may be 0.1 μm or less. Is possible. Therefore, even if the object to be measured has a complicated shape (small step) such as wiring formed on a printed circuit board or MCM, the height control according to the shape (step) is performed. It is possible to carry out with high precision.

  The electromagnetic field measurement apparatus of the present invention is connected to a support portion that supports the electromagnetic field detection element, a stage to which a measurement target is fixed, and a first optical fiber that constitutes the electromagnetic field detection element, A first measurement unit that measures an electromagnetic field radiated from the measurement object via the first optical fiber and a second optical fiber that constitutes the electromagnetic field detection element are connected, and the second light A second measurement unit that measures a displacement of a distance from the tip of the electromagnetic field detection element to the measurement object via a fiber; and the electromagnetic field detection element scans the measurement object, and the scanning is performed. Is a control unit that controls the movement of the stage so that the distance from the tip of the electromagnetic field detection element to the measurement object is constant based on the amount of displacement detected by the second measurement unit It is characterized by having.

  According to said structure, it is possible to scan on a measurement surface with a magnetic field detection element in the state where the distance from the front-end | tip of an electromagnetic field detection element to a measurement object was always fixed.

  As described above, according to the present invention, the bottom surface (surface on the measurement object side) of the magneto-optic crystal or electro-optic crystal provided at the tip of the fiber is brought very close to the surface of the measurement object, and the interval is set. Since the electromagnetic field can be detected in a constant state, measurement with higher spatial resolution than the conventional one can be performed. Therefore, the near magnetic field radiated from the external pin of the LSI package mounted on the printed circuit board or the MCM or the wiring on the LSI chip can be accurately detected.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 schematically shows a configuration of a magnetic field detection element according to an embodiment of the present invention. This magnetic field detection element is for detecting a near magnetic field radiated from a printed circuit board or MCM mounted on an electronic device, and has a configuration including a single magnetic field measuring optical fiber 21 and a plurality of high magnetic fields. And an optical fiber 22 for measurement. The optical fiber 21 for magnetic field measurement is located in the center, and the optical fiber 22 for height measurement is bundled so as to surround it. As the magnetic field measurement optical fiber 21, for example, an existing single mode optical fiber or a core expansion fiber having a fiber diameter of 125 μm and a core diameter of about 10 μm (wavelength 1.55 μm) can be used. As the height measuring optical fiber 22, for example, an existing multimode optical fiber having a fiber diameter of 125 μm and a core diameter of about 50 μm can be used.

  The magnetic field measuring optical fiber 21 and the height measuring optical fiber 22 are bonded and fixed by a fixing portion 23 in a state in which their respective distal end portions are aligned. A glass capillary may be used for the fixing portion 23. The end faces of the tip portions of the magnetic field measurement optical fiber 21 and the height measurement optical fiber 22 are fixed, and are chamfered by optical polishing. A crystal (MO crystal) 24 having a magneto-optic effect is provided in a region including the tip of the magnetic field measurement optical fiber 21 at the center of this surface, and the surface of the MO crystal 24 in contact with the tip of the fiber. A dielectric multilayer mirror 25 is provided on the opposite side of the surface. The MO crystal 24 and the dielectric multilayer mirror 25 are also fixed by adhesion.

  In the magnetic field detection element configured as described above, the magnetic field measurement optical fiber 21 is connected to the magnetic field measurement system 26. The plurality of height measuring optical fibers 22 include an irradiation optical fiber and a light receiving optical fiber, and both are connected to the micro displacement meter 27. According to this configuration, the magnetic field distribution on the measurement surface is measured using the magnetic field measurement optical fiber 21 and at the same time, the height measurement optical fiber 22 is used to measure from the tip of the magnetic field detection element to the measurement surface. The distance displacement (height displacement) is measured.

  In addition, it is desirable to arrange | position so that the end surface (surface in which light injects) of irradiation optical fiber, and the end surface (surface in which light injects) of light receiving optical fiber adjoins. By arranging in this way, the reflected light from the measurement surface when the measurement surface is irradiated with light from the irradiation optical fiber can be efficiently received by the light receiving optical fiber.

  Next, the configuration of a magnetic field measurement apparatus including the above-described magnetic field detection element will be described. FIG. 2 shows a schematic configuration of the magnetic field measuring apparatus. This magnetic field measuring apparatus has a magnetic field measuring system 26 having a magnetic field detecting element unit 50 composed of a magnetic field detecting element having the structure shown in FIG.

  The magnetic field measurement system 26 includes a laser light source 51, fiber amplifiers (FA) 52a and 52b, a polarization controller 53, an optical fiber 54, an optical circulator 55, an analyzer 56, a photodetector 57, a spectrum analyzer 58, a data collection / control device. 59 and XYZ stage 60.

  Laser light from the laser light source 51 is supplied to the polarization controller 53 via the FA 52a. The FA 52a is a well-known FA and optically amplifies the laser light from the laser light source 51. The polarization controller 53 controls the polarization state of the incident laser light. The laser light having a certain polarization state output from the polarization controller 53 is supplied to the optical circulator 55 through the optical fiber 54.

  The optical circulator 55 is connected to the magnetic field measurement optical fiber 21 of the magnetic field detection element unit 50, and supplies laser light input via the optical fiber 54 to the magnetic field measurement optical fiber 21. The optical circulator 55 supplies the laser light input from the magnetic field measurement optical fiber 21 to an analyzer 56 provided on a path different from the path from the laser light source 51. As described above, the optical circulator 55 has an input port to which laser light from the laser light source 51 is input, an input / output port for the magnetic field detection element unit 50, and an output port to the analyzer 56.

  The magnetic field detection element unit 50 is configured to support the magnetic field detection element shown in FIG. 1 above the measurement object 61 arranged on the XYZ stage 60. In the magnetic field detection element, the laser light incident on the magnetic field measurement optical fiber 21 propagates in the magnetic field measurement optical fiber 21 in the direction of the tip, passes through the MO crystal 24, reaches the mirror thin film 25, and is reflected there. Is done. The reflected light from the mirror thin film 25 again passes through the MO crystal 24 and then propagates in the magnetic field measuring optical fiber 21 toward the optical circulator 55. At this time, if a magnetic field is generated at the site of the measurement object 61 facing the tip of the optical fiber 21 for measuring magnetic field 21, the polarization angle of the laser light passing through the MO crystal 24 depends on the magnitude of the magnetic field. Change.

  The analyzer 56 is for changing the change in the polarization angle of the laser light (reflected light from the mirror thin film 25) supplied from the optical circulator 55 to change the light intensity. The laser light that has passed through the analyzer 56 is supplied to the photodetector 57 via the FA 52b. The FA 52b is a well-known FA and optically amplifies the laser beam from the analyzer 56. The light detector 57 detects the light intensity of the laser light amplified by the FA 52b. The laser beam supplied from the optical circulator 55 is passed through the analyzer 56, and the light intensity of the transmitted light is detected by the photodetector 57, so that the polarization angle corresponding to the change in the external magnetic field intensity generated in the MO crystal 24. Detect changes. The output (electric signal) of the photodetector 57 is supplied to the spectrum analyzer 58. The spectrum analyzer 58 detects the frequency component of the signal supplied from the photodetector 57.

  The minute displacement meter 27 is an optical fiber displacement meter, and is connected to the height measuring optical fiber 22 of the magnetic field detection element of the magnetic field detection element unit 50. The micro displacement meter 27 irradiates the measurement object 61 with the irradiation laser light through the irradiation optical fiber of the height measurement optical fiber 22 and reflects from the measurement object 61 through the light receiving optical fiber. Receives light. In this case, the amount of reflected light from the measurement object 61 varies depending on the distance from the tip of the magnetic field detection element to the measurement surface. Therefore, by detecting this change in the amount of reflected light, the displacement of the distance (height) from the tip of the magnetic field detection element to the measurement object 61 can be measured.

  The data collection / control device 59 controls the overall operation of the magnetic field measurement device. The data collection / control device 59 collects each data (magnetic field measurement result and height measurement result) from the spectrum analyzer 58 and the micro displacement meter 27 and an XYZ stage. 60 movement control is performed.

  Next, the operation of the magnetic field measuring apparatus described above will be specifically described.

  When measuring the magnetic field distribution of the measurement object 61, the data collection / control device 59 collects data from the spectrum analyzer 58 while controlling the movement of the XYZ stage 60 in the XY direction and is supplied from the micro displacement meter 27. Based on the height measurement result, the movement of the XYZ stage 60 in the Z direction is controlled so that the distance from the magnetic field detection element to the measurement object 61 is kept constant.

  When a magnetic field is generated at the portion of the measurement object 61 that faces the tip of the magnetic field measurement optical fiber 21, the polarization angle of the laser light that passes through the MO crystal 24 changes according to the magnitude of the magnetic field. Therefore, if a magnetic field distribution is generated in the measurement object 61, a change corresponding to the magnetic field distribution is detected in the photodetector 57 by scanning the magnetic field detection element on the measurement object 61.

  Further, when the height of the magnetic field detection element from the measurement surface (the distance from the tip of the magnetic field detection element to the measurement site of the measurement object 61) changes due to the unevenness of the surface of the measurement object 61, the micro displacement meter 27 The amount of change (displacement) is detected at. When the displacement is detected by the minute displacement meter 27, the data collection / control device 59 controls the movement of the XYZ stage 60 in the Z direction according to the displacement. Thereby, the distance (height from the measurement surface) from the tip of the magnetic field detection element to the measurement surface is kept constant.

  According to the above operation, the magnetic field detection element can be scanned on the measurement object 61 with the height from the measurement surface of the magnetic field detection element kept constant. In addition, the bottom surface (mirror thin film 25) of the magneto-optic crystal 24 at the tip of the magnetic field measurement optical fiber 21 can be brought very close to the measurement object, and the magnetic field component can be resolved with a resolution that can be determined by the core diameter of the magnetic field measurement optical fiber 21. Can be detected. As a result, the magnetic field distribution can be measured with high resolution and high accuracy.

  In the magnetic field detection element of the present embodiment described above, the resolution is determined in more detail by the beam diameter of light incident on the MO crystal 24 and the thickness of the MO crystal 24. When a single mode fiber is used for the optical fiber 21 for magnetic field measurement, the beam diameter is the core diameter of the fiber (about 10 μm), and is constant. Therefore, in order to obtain a high-resolution detection element, the thickness of the MO crystal 24 Need to be as thin as possible. According to the experiments so far, in the case of a measurement object having a wiring with a wiring width and a wiring interval of several tens of μm, if the thickness of the MO crystal 24 is set to 100 μm or less, the magnetic field from each wiring can be discriminated. Is possible. Currently, in mounting parts such as printed wiring and MCM, there are wiring widths and wiring intervals of several tens of μm. When detecting a magnetic field in such mounting parts, the thickness of the MO crystal 24 should be 100 μm or less. Is desirable.

  In addition, the higher the reflectance of the mirror thin film 25, the more light is detected by the photodetector of the magnetic field measurement system, and as a result, the detection sensitivity is improved. Therefore, it is desirable to use a mirror thin film 25 having a high reflectance.

  Next, specific production examples and measurement results of the magnetic field detection element of the present embodiment described above will be described.

(Example 1)
FIG. 3 is a diagram for explaining the configuration of the magnetic field detection element according to the first embodiment of the present invention. FIG. 3A is a schematic view of the vicinity of the tip of the magnetic field detection element as viewed from the side surface. (B) is a schematic diagram of the end surface of a front-end | tip part.

  First, a plurality of height measuring optical fibers 32 made of a multimode fiber are arranged around the magnetic field measuring optical fiber 31 made of a single mode fiber and temporarily fixed. Thereafter, the bundle of optical fibers is hardened with an adhesive 33 so as not to collapse. Then, after the tip of the fixed optical fiber bundle was optically polished, a mirror thin film 35 was formed on one surface in a region including the end surface of the optical fiber 31 for magnetic field measurement in the center of the processed surface. An MO crystal 34 having a thickness of 50 μm is bonded and fixed. In this way, the magnetic field detection element having the structure shown in FIG. 3 is obtained. In this example, a Bi-substituted YIG (yttrium iron garnet) thin film crystal was polished as the MO crystal 34 so that the magnetization direction was perpendicular to the surface. Further, as the mirror thin film 35, a dielectric mirror having a performance of 90% or higher reflectivity with respect to the wavelength of light used for magnetic field detection was used.

  The magnetic field detection element produced as described above was attached to the magnetic field measuring apparatus shown in FIG. The optical fiber 31 for magnetic field measurement was connected to the optical circulator 55 with a connector. The plurality of height measuring optical fibers 32 are examined so that irradiation and light receiving fibers can be alternately arranged (the position of the fiber can be easily known by entering light from one fiber end face). , Irradiation and light reception were bundled separately and connected to the micro displacement meter 27 with a connector. As the laser light source 51, a semiconductor laser light source having an oscillation wavelength of 1.55 μm and an output of 1 mW was used, and EDFAs were used as the FAs 52a and 52b.

  The laser light from the laser light source 51 is amplified to 10 mW by the FA 52 a and then adjusted to a constant polarization state by the polarization controller 53. The laser beam whose polarization state has been adjusted in this way is input to the magnetic field measurement optical fiber 31, and the reflected light from the mirror thin film 35 is detected by the photodetector 57 via the analyzer 56 and the FA 52b. In the photodetector 57, a change in the polarization angle corresponding to the external magnetic field intensity is detected as a change in the light intensity. The frequency component of the output signal of the photodetector 57 is detected by the spectrum analyzer 58.

  On the other hand, in the micro displacement meter 27, a semiconductor laser having an oscillation wavelength of 840 nm is used as a measurement light source (not shown), and the laser light from the semiconductor laser is applied to the measurement object 61 via each irradiation optical fiber. Irradiated. The reflected light from the measurement site of the measurement object 61 is received by a photodetector (not shown) through each light receiving optical fiber. The minute displacement meter 27 outputs a displacement measurement result corresponding to the amount of reflected light. The displacement measurement result is supplied to the data collection / control device 59 through the interface. In this case, the resolution in the displacement measurement can be 0.1 μm or less.

  The data collection / control device 59 performs control in the height direction based on the displacement measurement result from the micro displacement meter 27 to keep the distance from the tip of the magnetic field detection element to the measurement surface constant, and the magnetic field detection element. Is scanned on the measurement object 61. Thus, the magnetic field distribution on the measuring object 61 is detected.

  As an example of the magnetic field measurement data, FIG. 4 shows an example when the control in the height direction is not performed, and FIG. 5 shows an example when the control in the height direction is performed. In these examples, a printed circuit board having a microstrip structure wiring bent four times with a wiring width of 80 μm is used as the measurement object 61, and a signal with a signal power of 15 dBm and a frequency of 10 MHz is supplied to the wiring from the wiring. The resulting magnetic field was measured. The vertical axis is the normalized output signal of the photodetector 57, and the unit is “dB”. On the horizontal axis, the position (μm) in the scanning direction is plotted. The four central peaks correspond to the strength of the magnetic field generated in each of the wirings bent four times. Comparing the magnetic field measurement data of FIG. 4 and FIG. 5, in the example of FIG. 5 (with control in the height direction), an even magnetic field distribution is obtained, whereas in the example of FIG. Without control), the magnetic field distribution is greatly collapsed. This means that the magnetic field distribution can be measured more accurately by controlling the height direction.

(Example 2)
FIG. 6 is a diagram for explaining the configuration of the magnetic field detection element according to the second embodiment of the present invention, in which (a) is a schematic view of the vicinity of the tip of the magnetic field detection element as viewed from the side, (B) is a schematic diagram of the end surface of a front-end | tip part.

  First, a magnetic field measuring optical fiber 41 made of a core expansion fiber having a tip core diameter of 20 μm is supported in a state passing through the center of a glass capillary 46 having an inner diameter of 0.9 mm. Next, a plurality of height measuring optical fibers 42 made of multimode fibers are inserted into the glass capillary 46 and temporarily fixed so as to surround the magnetic field measuring optical fiber 41. Thereafter, the adhesive 43 is poured into the gap portion of the optical fiber of the glass capillary 46 to harden the optical fiber bundle so as not to collapse. At this time, the tip portions of the magnetic field measurement optical fiber 41 and the height measurement optical fiber 42 are set to protrude about 50 μm from the end of the glass capillary 46.

  Subsequently, after the tip of the fixed optical fiber bundle is optically polished, a mirror thin film 45 is formed on one surface in a region including the end surface of the optical fiber 41 for magnetic field measurement in the center of the processed surface. The MO crystal 44 having a thickness of 50 μm is fixed by adhesion. In this way, the magnetic field detection element having the structure shown in FIG. 6 is obtained. In this example, a Bi-substituted YIG (yttrium iron garnet) thin film crystal was polished as the MO crystal 44 so that the magnetization direction was parallel to the surface. Further, as the mirror thin film 45, a dielectric mirror having a performance of 90% or higher reflectivity with respect to light having a wavelength used for magnetic field detection was used.

  The magnetic field detection element produced as described above was attached to the magnetic field measuring apparatus shown in FIG. The optical fiber 41 for magnetic field measurement was connected to the optical circulator 55 with a connector. The plurality of height measuring optical fibers 42 were examined so that the irradiation and light receiving fibers could be alternately arranged, and then the irradiation and light receiving fibers were bundled separately and connected to the micro displacement meter 27 with a connector. As the laser light source 51, a semiconductor laser light source having an oscillation wavelength of 1.55 μm and an output of 1 mW was used, and EDFAs were used as the FAs 52a and 52b.

  The laser light from the laser light source 51 is amplified to 10 mW by the FA 52 a and then adjusted to a constant polarization state by the polarization controller 53. The laser light whose polarization state is adjusted in this way is input to the optical fiber 41 for magnetic field measurement, and the reflected light from the mirror thin film 45 is detected by the photodetector 57 via the analyzer 56 and the FA 52b. In the photodetector 57, a change in the polarization angle corresponding to the external magnetic field intensity is detected as a change in the light intensity. The frequency component of the output signal of the photodetector 57 is detected by the spectrum analyzer 58.

  On the other hand, in the micro displacement meter 27, a semiconductor laser having an oscillation wavelength of 840 nm is used as a measurement light source (not shown), and the laser light from the semiconductor laser is applied to the measurement object 61 via each irradiation optical fiber. Irradiated. The reflected light from the measurement site of the measurement object 61 is received by a photodetector (not shown) through each light receiving optical fiber. In this way, the displacement measurement is performed by the micro displacement meter 27, and the result is supplied to the data collection / control device 59 through the interface. In this case, the resolution in displacement measurement can be 0.1 μm or less.

  The data collection / control device 59 performs control in the height direction based on the displacement measurement result from the micro displacement meter 27 to keep the distance from the tip of the magnetic field detection element to the measurement surface constant, and the magnetic field detection element. Is scanned on the measurement object 61. Thus, the magnetic field distribution on the measuring object 61 is detected.

  Also in this embodiment, when the control in the height direction is not performed, the magnetic field measurement data as shown in FIG. 4 is obtained, and when the control in the height direction is performed, the magnetic field as shown in FIG. Measurement data was obtained. From this result, it is understood that the magnetic field distribution can be measured more accurately by controlling the height direction.

  The configuration and operation of the embodiment described above are merely examples, and can be changed as appropriate without departing from the spirit of the invention. For example, the number of optical fibers for magnetic field measurement is one, but a plurality of optical fibers may be used. In this case, setting for performing magnetic field detection with each magnetic field measuring optical fiber is required. From the viewpoint of obtaining higher resolution at a lower cost, the configuration with one optical fiber for measuring the magnetic field is most desirable.

  Further, the position of the magnetic field measuring optical fiber may not be the center. However, if the position of the optical fiber for magnetic field measurement is greatly deviated from the center, it is difficult to determine which part of the measurement object is being measured when performing a measurement operation as a probe. Normally, since the magnetic field is detected at the center of the magnetic field detection element, it is desirable to place the optical fiber for magnetic field measurement in the center.

  Further, the number of irradiation optical fibers and light receiving optical fibers constituting the height measuring optical fiber may be one each in principle. However, in order to obtain high detection accuracy, each optical fiber is composed of a plurality of fibers. It is desirable to do. In this case, the irradiation optical fiber and the light receiving optical fiber may correspond “one to one” or “one to many”. From the viewpoint of efficiently receiving the reflected light, it is desirable that the irradiation optical fiber and the light receiving optical fiber correspond to each other “one-to-one” and are arranged adjacent to each other.

  In addition, the measurement surface is irradiated with the irradiation light from the irradiation optical fiber, and the reflected light is received using the light receiving optical fiber to measure the height. The light receiving unit may be configured by a single common fiber, and the height may be measured from the phase difference between the reflected light from the end face of the fiber tip and the reflected light from the surface of the measurement object. In this case, a single optical fiber for height measurement can be formed.

  In the above-described embodiment, a magnetic field is detected. However, an electric field detection element can be configured by replacing the MO crystal provided at the tip of the optical fiber for magnetic field measurement with an electro-optic crystal. In an electric field measuring optical fiber having an electro-optic crystal at the tip, incident laser light propagates in the fiber in the direction of the tip, passes through the electro-optic crystal, reaches the mirror thin film, and is reflected there. The reflected light from the mirror thin film again passes through the electro-optic crystal and then propagates in the fiber in the direction opposite to the tip. At this time, if an electric field is generated at the portion of the measurement object facing the tip of the optical fiber for electric field measurement, the degree of polarization of the laser light passing through the electro-optic crystal changes according to the magnitude of the electric field. . Specifically, the phase difference of the polarization component of the laser light changes due to the external electric field, and a part of the linearly polarized light becomes circularly polarized light. An electric field measurement can be performed by detecting a change in the degree of polarization according to an externally applied electric field using an analyzer. For this electric field measurement, the same measuring device (in this case, an electric field measuring device) as the configuration shown in FIG. 2 is used.

  The detection element may include a magnetic field measurement optical fiber, an electric field measurement optical fiber, and a height measurement optical fiber. In this case, the magnetic field and electric field can be measured with one probe.

  Furthermore, instead of the magnetic field measurement optical fiber, an electromagnetic field measurement optical fiber having a two-layer crystal part of an MO crystal and an electro-optic crystal at the tip may be used. In this case as well, the magnetic field and electric field can be measured with a single probe. However, since the crystal part is thicker than that of the single-layer structure, the resolution is lowered accordingly.

It is a schematic diagram which shows the structure of the magnetic field detection element which is one Embodiment of this invention. It is a block diagram which shows schematic structure of the magnetic field measuring apparatus provided with the magnetic field detection element shown in FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the structure of the magnetic field detection element which is 1st Example of this invention, (a) is the schematic diagram which looked at the front-end | tip part vicinity of the magnetic field detection element from the direction of the side surface, (b). It is a schematic diagram of the end surface of a front-end | tip part. It is a figure which shows an example of the magnetic field measurement data at the time of not performing control of a height direction. It is a figure which shows an example of the magnetic field measurement data at the time of performing control of a height direction. It is a figure for demonstrating the structure of the magnetic field detection element which is 2nd Example of this invention, (a) is the schematic diagram which looked at the front-end | tip part vicinity of the magnetic field detection element from the direction of the side surface, (b) It is a schematic diagram of the end surface of a front-end | tip part. It is a schematic diagram which shows schematic structure of the conventional magnetic field detection element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 54 Optical fiber 12 Core area | region 13 Clad area | region 14, 24, 34, 44 MO crystal 15, 25, 35, 45 Mirror thin film 21, 31, 41 Optical fiber for magnetic field measurement 22, 32, 42 Optical fiber for height measurement DESCRIPTION OF SYMBOLS 23 Fixed part 26 Magnetic field measurement system 27 Minute interference displacement meter 33, 43 Adhesive 46 Glass capillary 50 Magnetic field detection element part 51 Laser light source 52a, 52b Fiber amplifier 53 Polarization controller 55 Optical circulator 56 Analyzer 57 Photo detector 58 Spectrum analyzer 59 Data collection / control device 60 XYZ stage 61 Object to be measured

Claims (13)

A first optical fiber provided with an optical crystal for detecting an electromagnetic field generated from a measurement object at a tip portion;
A second optical fiber for measuring the displacement of the distance from the tip to the measurement object,
The electromagnetic field detection element, wherein the first and second optical fibers are integrally fixed in a state in which the end surfaces of the respective tip portions are aligned so as to be the same surface.   The electromagnetic field detection element according to claim 1, wherein the first optical fiber is a magnetic field measurement optical fiber in which the optical crystal is a magneto-optical crystal.   The electromagnetic field detection element according to claim 1, wherein the first optical fiber is an optical fiber for electric field measurement in which the optical crystal is an electro-optic crystal.   2. The electromagnetic field detection according to claim 1, wherein the first optical fiber includes a magnetic field measurement optical fiber in which the optical crystal is made of a magneto-optic crystal and an electric field measurement optical fiber in which the optical crystal is made of an electro-optic crystal. element. There are a plurality of the second optical fibers,
2. The electromagnetic field according to claim 1, wherein the first optical fiber is arranged at the center, and the plurality of second optical fibers are bundled and fixed so as to surround the first optical fiber. Detection element.   The electromagnetic field detection element according to claim 1, wherein the first optical fiber is a single mode optical fiber.   6. The electromagnetic field detection element according to claim 1, wherein the first optical fiber is a core expansion optical fiber in which a core at a tip portion of a single mode optical fiber is expanded.   The electromagnetic field detection element according to claim 1, wherein a thickness of the optical crystal is 100 μm or less.   The electromagnetic field detection element according to claim 1, wherein the first and second optical fibers are fixed by adhesion.   The glass capillary further has an inner diameter into which the first and second optical fibers can be inserted, and the first and second optical fibers are bonded and fixed in a state of being inserted into the glass capillary. Item 2. The electromagnetic field detection element according to Item 1.   The second optical fiber includes an irradiation optical fiber that irradiates the measurement target with laser light emitted from the end surface of the tip, and reflected light from the measurement target is incident from the end surface of the tip. The electromagnetic field detection element according to claim 1, comprising an optical fiber for receiving light.   The electromagnetic field detection element according to claim 11, wherein the irradiation optical fiber and the light receiving optical fiber are disposed adjacent to each other. A support portion for supporting the electromagnetic field detection element according to any one of claims 1 to 12,
A stage on which a measurement object is fixed;
A first measurement unit that is connected to a first optical fiber constituting the electromagnetic field detection element, and that measures an electromagnetic field radiated from the measurement object via the first optical fiber;
A second optical fiber constituting the electromagnetic field detection element is connected, and a second measurement for measuring a displacement of a distance from the tip of the electromagnetic field detection element to the measurement object via the second optical fiber. And
The measurement target is scanned with the electromagnetic field detection element, and during the scanning, the measurement target is measured from the tip of the electromagnetic field detection element based on the amount of displacement detected by the second measurement unit. An electromagnetic field measurement apparatus comprising: a control unit that performs movement control of the stage so that a distance to an object is constant.

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