JP2018028519A - Imaging device and imaging method for quantitatively displaying in color magnetic field distribution using magnetooptic imaging plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device and an imaging method which do not require a lot of calculations and noise reduction processing in calibration step and are able to quantitatively measure and calculate a magnetic field distribution in a simple and easy fashion.SOLUTION: An imaging device 10 comprises: light sources 1, 2 capable of emitting visible light having a plurality of different spectra; a polarizer 6; an MO imaging plate 7; and an analyzer 9. A measurement target 8 is arranged on a surface 7b of the plate 7 opposite a light incident surface 7a. The plate 7 is provided with a magnetic transfer film exhibiting high magnetic field dependence with respect to at least one of the spectra of the visible light. The device 10 can obtain a calibration curve of a magnetic field intensity H around the plate 7 and a RGB value corresponding to the magnetic field intensity H. A color image 19 of a measurement target 8 can be observed by reflected light through the analyzer 9, and the magnetic field intensity of the measurement target 8 can quantitatively be displayed or measured using the color image 19 and a color bar 16, etc.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus and an imaging method for quantitatively displaying a magnetic field distribution using a magneto-optical imaging technique including a magnetic transfer film, and more particularly to an apparatus for displaying (visualizing) a magnetic field distribution in a color corresponding to its intensity. And a method.

(Magnetic field invisible to eyes)
Magnetic fields are used in various industrial fields such as magnetic recording media (for example, hard disks and video tapes) and electromagnetic heaters. Although the magnetic field itself cannot be seen directly with the eyes, when iron sand is scattered around the magnet, it is possible to see a pattern of sand iron particles aligned along the magnetic field lines.

(Visualization of magnetic field distribution using magnetic transfer film)
In order to observe the magnetic field distribution in this way, the magnetic field may be replaced with something that is visible (in the above example, iron sand). A method using a magneto-optical microscope that has already been developed also magnetically transfers a magnetic field distribution to a film having a large magneto-optical effect called a magnetic transfer film (for example, a bismuth-substituted garnet film (Patent Document 1)), and a polarized image. (For example, refer nonpatent literatures 1-3.). This method is expected as an excellent method that allows simple, high spatial resolution and real-time measurement.

(Quantitative measurement of magnetic field distribution)
It is also possible to quantitatively measure the magnetic field distribution by quantitatively measuring the magneto-optical effect (Non-patent Document 1). In these methods, a method called “orthogonal analyzer method” in which the magnetic film is observed by shifting the polarizer and the analyzer by approximately 90 degrees is representative. When the incident light having the light intensity I ₀ passes through the magnetic film and the analyzer, the intensity I of the light depends on the Faraday rotation angle θ _F , the polarizer angle θ _P, and the analyzer angle θ _A as follows: Represented by a mathematical formula.

in this way. Since the magnetic transfer film is magnetized according to the magnetic field distribution, the magnetic field distribution is converted into light intensity by the Faraday effect. However, in the orthogonal analyzer method, the light intensity I is proportional to the square of cosine (that is, non-linear) with respect to the Faraday rotation angle θ _F as shown in the above equation (Equation 1). The contrast of the image (for example, the brightness indicated by the black and white gray scale on the image) does not directly represent the strength of the magnetic field.

(Prior art for quantitative measurement of magnetic field distribution)
For this reason, in order to obtain a quantitative magnetic field distribution image, the black and white image is calibrated using the relationship between the light intensity I and the magnetic field H (Non-Patent Documents 2 and 3). It is necessary to use a known magneto-optical imaging method such as “circular polarization modulation method” (Non-Patent Document 1).

First, in the former countermeasure (calibration of a black and white image using the relationship between the light intensity I and the magnetic field H), a calibration curve by Jos et al. (Formula 2 below) is known (Non-Patent Document 3). In Equation 2, c is a fitting parameter, and M _s is saturation magnetization.

However, when the calibration is performed using Formula 2, information such as the incident light intensity I ₀ , the background image I ₁ , and the fitting parameter c is also required. Note that calculating the magnetic field by applying this calibration curve to all points (x, y) on the image requires an enormous amount of calculation and time, and is unrealistic. Therefore, in practice, all magnetic fields on the image measured using a parameter (the above-described fitting parameter c) obtained for only one point (for example, (x ₁ , y ₁ )) can only be obtained. For this reason, if the irradiation light is uneven (spots) or the light intensity I changes during measurement, a correct value cannot be obtained. Further, as apparent from Equation 2, since it is necessary to subtract the light intensity I from the background image I ₁ or to divide by the incident light intensity I ₀ , the calculated magnetic field intensity is ignored. Noise that cannot be performed is added (that is, the SN ratio of the magnetic field strength (signal) after the calculation is deteriorated).

In the latter countermeasure (the circular polarization modulation method proposed by the present inventors), an apparatus in which a liquid crystal element for polarization modulation is incorporated in an ordinary magneto-optical microscope is used. The voltage applied to the liquid crystal element is changed by applying a voltage, and three optical images of right circularly polarized light (RCP), linearly polarized light (LP), and left circularly polarized light (LCP) are measured. Next, at all points on the image, one image is obtained that is “reconstructed” with the rotation angle θ and ellipticity η obtained from the light intensities I _RCP , I _LP , and I _LCP of the pixels at the same position. The calculation of the rotation angle θ and the ellipticity η at the time of this reconstruction is executed by the following mathematical formulas 3 and 4.

  However, in the reconstructed image information, unnecessary noise increases compared to a normal optical image due to the above calculation of the rotation angle θ and the ellipticity η. In order to reduce this noise, it is necessary to take three polarized images many times (several tens to 100 times).

Japanese Patent No. 3743440

Takayuki Ishibashi, “Quantitative Observation of Magnetic Field Distribution in Magneto-Optical Microscope and High Sensitivity”, Optics, Japan Optical Society, Vol. 42 No. 1 (2013), p. 13-19 Takato Machi, “Flux Observation of Superconducting Wires Using Magneto-Optical Microscope”, Applied Physics, Japan Society of Applied Physics, Vol. 82 No. 2 (2013), p. 117-122 Ch. Jose, et al., “Thickness and roughness dependency of magnetic flux penetration and critical currents in YBa2Cu307-d thin films,” Physic. 235-252

  The present invention has been made in view of such circumstances, and does not require enormous computation, time, and noise reduction processing at the calibration stage, and performs imaging that quantitatively measures and displays a magnetic field distribution simply and easily. An object is to provide an apparatus and an imaging method. In other words, an object of the present invention is to provide an apparatus and a method for quantitatively displaying the magnetic field distribution using an MO imaging plate having a magnetic transfer film.

  As a result of intensive studies, the inventors of the present invention have only a light image (the intensity of light, in other words, a black-and-white grayscale image), which is a polarization image showing a magnetic field distribution finally processed by the prior art. Focusing on the fact that it was only expressed in, I thought whether this polarized image could be displayed in color. Then, it was considered that the color display can express a slight change in the state of the polarization image, and can appropriately correspond to this. Specifically, a means and process for selectively allowing light having a plurality of spectra having different magnetic field dependencies to enter a magnetic field imaging plate including a magnetic transfer film from a light source have been found, and the present invention has been completed. It was.

That is, the present invention includes, for example, the following configurations and features.
(Aspect 1)
A light source capable of emitting visible light having a plurality of different wavelength spectra;
A polarizer that transmits the visible light emitted from the light source;
An MO imaging plate that receives and reflects the visible light transmitted from the polarizer;
An analyzer that transmits light reflected from the plate;
An imaging apparatus for quantitatively displaying the magnetic field distribution of an object to be measured, comprising:
The object to be measured is arranged on a surface opposite to the light incident surface of the plate,
The plate is provided with a magnetic transfer film showing high magnetic field dependence for at least one of the visible light spectrum, and
The imaging device comprises:
A calibration device for obtaining a calibration curve of the magnetic field intensity around the plate and the RGB value corresponding to the magnetic field intensity;
A device for creating and displaying a color-magnetic field strength correspondence display from the calibration curve obtained by the calibration device, and
A color image of the object to be measured can be observed by the reflected light through the analyzer, and the magnetic field strength of the object to be measured is quantitatively determined using the color image and the color-magnetic field strength correspondence display. An imaging apparatus capable of displaying or measuring.
(Aspect 2)
An imaging unit capable of imaging the color image transmitted through the analyzer;
A display unit for displaying the color image obtained from the imaging unit;
The imaging apparatus according to aspect 1, further comprising:
(Aspect 3)
The color-magnetic field strength correspondence display is a color bar expressed by a plurality of representative values of the magnetic field strength and a color corresponding to the representative value, and the color bar is displayed on the display unit or another display means. The imaging apparatus according to aspect 1 or 2, wherein
(Aspect 4)
The color-magnetic field strength correspondence display is a magnetic field strength display pointer, and
The magnetic field strength display pointer
A pointer unit that can freely move on the color image displayed on the display unit according to an operator's request;
When the pointer portion is arranged at a desired position on the color image, a local RGB value at the position is read, and the RGB value is substituted into a relational expression based on the calibration curve to correspond to the RGB value. A corresponding magnetic field strength calculating unit for calculating the magnetic field strength, and
The imaging apparatus according to aspect 2 or 3, wherein the magnetic field intensity or the magnetic field intensity and the RGB value obtained by the corresponding magnetic field intensity calculation unit are displayed on the display unit or another display unit.
(Aspect 5)
The imaging apparatus according to any one of aspects 1 to 4, wherein the light source includes a plurality of monochromatic light sources.
(Aspect 6)
The imaging apparatus according to any one of aspects 1 to 4, wherein the light source includes at least a single white light source.
(Aspect 7)
An imaging method for quantitatively displaying the magnetic field distribution of an object to be measured,
Selecting different spectra of visible light emitted from a light source;
Providing an MO imaging plate provided with a magnetic transfer film that exhibits a higher magnetic field dependence for at least one of the spectra than for the remaining spectra;
Reflecting the visible light from the light source to the plate through a polarizer and transmitting the reflected light from the plate to the analyzer;
Obtaining a calibration curve between the magnetic field strength at the plate and the RGB values obtained from the reflected light;
Placing the object to be measured on a surface opposite to the light incident surface of the plate;
Creating and displaying a color-magnetic field strength correspondence display from the calibration curve;
Including, and
A color image of the object to be measured can be observed by the reflected light through the analyzer, and the magnetic field strength of the object to be measured is quantitatively determined using the color image and the color-magnetic field strength correspondence display. An imaging method characterized by being capable of displaying or measuring.
(Aspect 8)
Imaging the object to be measured from the plate side through the analyzer;
Displaying the color image of the measured object on the display unit;
The imaging method according to aspect 7, wherein
(Aspect 9)
The color-magnetic field strength correspondence display is a color bar expressed by a plurality of representative values of the magnetic field strength and colors corresponding to the representative value, and the color bar is displayed on the display unit or another display means. The imaging method according to aspect 7 or 8, further comprising a step of displaying.
(Aspect 10)
The color-magnetic field strength correspondence display is a magnetic field strength display pointer, and
The magnetic field intensity display pointer includes a pointer unit that can freely move on the color image displayed on the display unit according to an operator's request; and
When the pointer portion is arranged at a desired position on the color image, the local RGB value at the position is read, the RGB value is substituted into the relational expression based on the calibration curve, and the RGB value is set. A magnetic field strength calculating step for calculating a corresponding magnetic field strength;
The imaging method according to claim 8 or 9, further comprising a step of displaying the magnetic field intensity or the magnetic field intensity and the RGB value obtained in the magnetic field intensity calculating step on the display unit or another display means. .
(Aspect 11)
An MO imaging plate that can be used in any of the imaging apparatus according to Aspects 1 to 6 or the imaging method according to Aspects 7 to 10,
The MO imaging plate, wherein the plate includes a magnetic transfer film made of magnetic garnet.

  According to the present invention, the finally obtained magnetic field distribution image is displayed in two or more colors (color gradation), and the correspondence between the color and the magnetic field strength (color bar) is also shown. Therefore, the sign and size of the magnetic field can be determined easily and intuitively with the naked eye. Further, in the method of the present invention, it is only necessary to calibrate the relationship between the intensity of the magnetic field and the color (RGB value) (that is, there is no need for subtraction or division as described above in the calibration processing of the prior art). Is simple. In other words, in the method of the present invention, it is not necessary to calibrate the relationship between the intensity of the magnetic field and the intensity of light (light intensity, black and white brightness) required in the prior art. No problems such as processing and noise occur.

  For example, if the imaging device (8-bit camera) having the lowest resolution is used to express the magnetic field state (magnetic field strength) of the object to be measured by the prior art method, it is expressed only in 256 gray levels at maximum. However, even if an image pickup apparatus having the same resolution is used in the method of the present invention, the state of the object to be measured can be expressed with a color gradation of a maximum of about 17 million (that is, the cube of 256) gradation. In other words, in the present invention, even if a camera having the lowest resolution is used, a minute change / difference in the spectrum of reflected light from the magnetic film indicating the object to be measured can be reliably captured and expressed.

1 is a schematic diagram showing an imaging apparatus according to the present invention (Example 1). It is the figure which showed an example of the cross-sectional structure of MO imaging plate. It is a chromaticity distribution diagram showing plot points of calibration data and calibration curves thereof. It is the figure which showed an example of the color bar produced and displayed by this invention. 10 is a flowchart illustrating each step of the imaging method of the present invention (Example 3). 10 is a flowchart illustrating details of a calibration step of the imaging method according to the third embodiment. It is the figure which showed the mode of the magnetic field distribution of the to-be-measured object displayed using the imaging device (white light source) of Example 5. FIG. It is the figure which showed the modification of MO imaging plate, and its magneto-optical characteristic.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings, but the present invention is not limited to the following specific embodiments. In each figure, the same numerals are used for the same or corresponding members.

(Outline of the device of the present invention)
FIG. 1 is a schematic view showing an example of an imaging apparatus (hereinafter also simply referred to as “apparatus”) 10 of the present invention. In this embodiment, two light sources, first and second light sources 1 and 2, are provided as light sources. The first light source 1 is a monochromatic light source (for example, a blue LED) that emits first light having a wavelength spectrum of a certain first color (for example, blue). On the other hand, the second light source 2 is a monochromatic light source (for example, a yellow LED) that emits second light having a wavelength spectrum of a second color (for example, yellow) different from the first color.

(Simultaneous incidence of multiple lights with different color components)
In the example shown in FIG. 1, the second light source 2 is arranged so that the light emitted from the light source 2 travels in a direction orthogonal to the light irradiation direction of the first light source 1. The struck light enters the beam splitter 3. More specifically, light from one light source (for example, the first light source 1) enters the first surface (outer surface) 3a of the beam splitter 3 and is divided into components of transmitted light and reflected light. Among them, the transmitted light component of the first light (blue light) is emitted from the second surface (inner surface) 3 b and passes through the diffuser 4, the lens 5, and the polarizer 6 in this order.

  On the other hand, the other light source (for example, the second light source 2) is oriented so that the second light emitted from the light source 2 first enters the second surface (inner surface) 3b of the beam splitter 3. Therefore, the reflected light component of the second light (yellow light) reflected by the second surface 3b also passes through the diffuser 4, the lens 5, and the polarizer 6 in this order in the same manner as the transmitted light component of the first light. Then, the light enters the MO imaging plate 7 described later.

(Magnetic optics (MO) imaging plate)
The transmitted light component of the first light and the reflected light component of the second light are linearly polarized when passing through the polarizer 6, and then MO (magneto-optcal, meaning “magneto-optic”) imaging plate 7 (hereinafter referred to as “optical optics”). , Simply referred to as “MO plate”). When using the apparatus 10 of the present invention, one side surface 7b of the MO plate 7 (the surface opposite to the surface 7a on which the composite light from the light sources 1 and 2 is incident) had a magnetic field distribution. The object to be measured 8 (magnetic material) is connected (contacted or approached), and the MO plate 7 and the light incident and reflected on the MO plate 7 are also affected by a local magnetic field, as will be described later. As the reflected light, a color image indicating light that has passed through the analyzer 9 and objects around the light (including the object 8 to be measured) is acquired by an imaging unit 11 such as a camera.

(Analyzer)
The analyzer 9 is arranged in a state substantially orthogonal to the polarizer 6 so that the signal of the reflected light (due to the Faraday rotation) can be acquired with high contrast by the imaging unit 11 described above. This measurement method is called the orthogonal analyzer method.

(Cross-sectional structure of MO imaging plate)
Here, FIG. 2 shows an example of a cross-sectional structure of the MO plate 7. In the MO plate 7, a magnetic transfer film 73 made of bismuth-substituted garnet, a base layer 72 that assists in forming the film 73 on the substrate 71, and a reflective film 74 are disposed on the substrate 71. The MO plate 7 is brought into contact with or close to the measured object 8 such that the reflective film 74 side faces the measured object 8 and the substrate 71 side faces the incident light from the light sources 1 and 2.

(Example of composition of MO imaging plate)
Substrate 71 employed in Example 1, the base layer 72, the composition of the magnetic transfer film 73 and the reflective film 74, as shown in FIG. 2, respectively, a glass _{plate, Nd 2 Bi 1 F e4 Ga} 1 O 12, Nd _{Although it is 1} Bi ₂ Fe ₅ O ₁₂ and Ag, it is not necessarily limited to these compositions. From the experience of the inventors, the thickness of the substrate 71 is preferably 50 μm to 3 mm. Further, the underlayer 72 is preferably 30 to 300 nm, and more preferably 100 to 150 nm. The thickness of the magnetic transfer film 73 is preferably 100 nm to 10 μm, and more preferably 600 to 800 nm. As the magnetic transfer film 73, as described later, it is preferable to select a material having high magnetic field dependency and wavelength dependency with respect to a specific color. From this viewpoint, in addition to Nd ₁ Bi ₂ Fe ₅ O ₁₂ (Bi2NIG) described above, RE _3-x Bi _x Fe ₅ O ₁₂ (where x is 0 <x <3 (more preferably, 1 <x <3 )) Is preferred. Here, RE means any of Nd, Y, and Lu, or a combination of these rare earth elements.

(Modification of MO imaging plate composition)
For example, a substrate made of GGG (Gadolinium Gallium Garnet) or another material may be used as the substrate 71 in place of the glass substrate. Further, since the metal of the reflective film 74 is relatively easily damaged, a protective film (not shown) such as TiN may be additionally formed.

  Information on the color image of the DUT 8 acquired by the imaging unit 11 is stored in the memory 14 by the CPU 13 in the personal computer 12 connected to the imaging unit 11 from the imaging unit 11, and is provided with a display 15 a and the like. The unit 15 can display the state of the MO plate 7 (color reflected on the MO plate 7 that covers part or all of the object to be measured 8 (magnetic material) (for example, in the frame 18 in FIG. 1). . The display unit 15 is connected to the personal computer 12 via an interface 12b such as a USB.

  It should be noted that only the components described above can only observe the state (color image 19) corresponding to the magnetic field strength (distribution) of the object 8 to be measured through the MO plate 7, and quantitative observation of the magnetic field distribution. And quantitative measurements are not possible.

  Therefore, in an example of the present invention, in order to achieve the above-described object of the present invention, the magnetic field distribution and the display color corresponding to the color image 19 in addition to the color image 19 are determined. The display unit 15 (for example, on the display 15a) also includes color-magnetic field strength correspondence displays 16 and 17 (hereinafter also referred to as “color bar 16” and “pointer 17”). Can be displayed.

(Color bar)
First, as an example, means and processing for displaying the color bar 16 will be described in detail.

(Configuration of calibration equipment)
As shown in FIG. 1, the apparatus 10 of the present invention further includes a calibration electromagnet 21, a voltage application unit 22 that applies a voltage V to the electromagnet 21, a magnetic field strength measurement unit 23, and a light intensity measurement unit 24. ing. A voltage adjusting unit 25 is built in or connected to the voltage applying unit 22, and the voltage adjusting unit 25 can change the voltage value V applied to the electromagnet 21.

  As a more specific configuration example, the electromagnet 21 is provided with an iron core 21a in the center, a coil 21b is spirally wound around the electromagnet 21, and both ends of the coil 21b are connected to the voltage application unit 22. May be. As the voltage application unit 22 and the voltage adjustment unit 25, a commercially available DC stabilized power supply may be used. The voltage value V applied to the electromagnet 21 can be arbitrarily changed by changing the current flowing through the coil 21b by the voltage adjusting unit 25. The voltage application unit 22 and the personal computer 12 may be connected, and the data of the voltage value V set and applied as described above may be stored in the memory 14 in accordance with an instruction from the CPU 13. The voltage application unit 22 and the personal computer 12 can be connected via an interface 12a such as a USB. A connection between the magnetic field strength measurement unit 23 or the light intensity measurement unit 24 and the personal computer 12, which will be described later. May be the same means and method.

  Further, as the magnetic field strength measurement unit 23, for example, a non-contact type gauss meter may be used, and the magnetic field strength H generated near the electromagnet 21 when the voltage V is applied to the electromagnet 21 as described above is measured. Can do. The voltage application unit 22 and the personal computer 12 may be connected, and the magnetic field strength H data measured as described above may be stored in the memory 14 according to a command from the CPU 13.

  The light intensity measurement unit 24 may use a commercially available optical spectrometer, or may be a measurement device that combines the functions of the imaging unit 11 described above. Note that the light intensity measurement unit 24 and the personal computer 12 may be connected, and the wavelength spectrum I (λ) measured as described above may be stored in the memory 14 according to a command from the CPU 13.

  These configurations are used in the calibration stage before using the apparatus 10 of the present invention (before observing the actual object to be measured 8). That is, the calibration electromagnet 21 is brought into contact with or close to the MO plate 7 instead of the DUT 8. The magnetic field strength measurement unit 23 measures the magnetic field strength H of the electromagnet 21 applied with a certain voltage value V. The light intensity measurement unit 24 acquires optical characteristic data (for example, wavelength spectrum I (λ)) of light reflected from the MO plate 7 in contact with or close to the electromagnet 21 and passed through the analyzer 9.

  As described above, the wavelength spectrum I (λ), the magnetic field intensity H, and the set voltage value V acquired by the light intensity measuring unit 24, the magnetic field intensity measuring unit 23, and the voltage applying unit 22 are stored in memory according to instructions from the CPU 13. 14 is stored. Thereafter, the voltage value V applied to the electromagnet 21 is changed by the voltage adjusting unit 25, and the wavelength spectrum I (λ), the magnetic field strength H, and the voltage value V corresponding to the voltage value V at that time are obtained. Acquired by the calibration devices 22 to 25 and transmitted / stored in the memory 14 according to a command from the CPU 13. This measurement operation is repeated a plurality of times (preferably 5 times or more, more preferably 10 times or more in order to increase the accuracy of the color bar 16).

  Further, the apparatus 10 of the present invention is further provided with an RGB calculation unit 26, and the RGB calculation unit 26 calls the wavelength spectrum I (λ) at each magnetic field intensity H stored in the memory 14, and this wavelength spectrum I The RGB value corresponding to (λ) is calculated and stored in the memory 14. That is, the color information of the MO plate 7 observed at each magnetic field strength H at the time of calibration is obtained as RGB values.

  The apparatus 10 of the present invention is also provided with a calibration curve calculation unit 27. From the correspondence between the RGB values obtained by the RGB calculation unit 26 and the magnetic field strength H, a chromaticity distribution diagram (xy color) described later is provided. On the scale diagram), each data obtained at the time of calibration (that is, the magnetic field strength H and the corresponding RGB value (more specifically, x and y values obtained from the RGB value)) are plotted ( (See FIG. 3).

  In addition, the magnetic field strength (for example, +1, +0.5, 0, −0.5, −1, and the unit is all [kOe]) is also shown next to some plot points in FIG. Also, the horizontal axis x and the vertical axis y of the chromaticity distribution diagram (CIE1931) shown in FIG. 3 are calculated by the ratio of tristimulus values (mixture amount of triprimary stimuli) (mixture ratio of triprimary stimuli). From these plots, a calibration curve (for example, a fitting curve) of the magnetic field strength H and RGB values (more specifically, x and y values) can be calculated. The mathematical information of the obtained calibration curve is also stored in the memory 14.

Furthermore, in the apparatus 10 of the present invention, a color bar creating unit 28 is also provided. The color bar creating unit 28 creates and calculates basic information for displaying the color bar 16 using mathematical formula information related to the calibration curve stored in the memory 14. For example, the color bar display unit 16 determines maximum and minimum magnetic field strengths H _max and H _min (for example, +1 kOe and −1 kOe) for display, and the maximum value H _max and the minimum value H _min . The number n (for example, n = 11) of regions that divide the range is determined. In the case of n = 11, in addition to the maximum value H _max region and the minimum value H _min region, the magnetic field strengths H of nine points (9 partition regions) that are equally divided between these are acquired (total) Magnetic field intensity H of 11 points (11 regions) is obtained).

Nine points (9 areas) inside the color bar 16 are acquired so as to equally divide the maximum value H _max and the minimum value H _min from the viewpoint of visibility and accuracy of the display of the color bar 16. However, it is not necessarily limited to this. For example, the vicinity of the magnetic field strength H that is actually easily observed may be finely and unevenly divided. The RGB values (color information) corresponding to the magnetic field strengths H are calculated using the obtained magnetic field strengths H and the calibration curve described above. By calculating in this way, a bar representative value (correspondence between each magnetic field intensity H and the corresponding RGB value) indicating each divided region of the color bar 16 is obtained.

  The color bar 16 is obtained by the color bar creating unit 28, and thereafter, the data of the bar representative value stored in the memory 14 is read to display the color bar 16 at a predetermined location on the display 15a of the display unit 15. It can be done. An example of the color bar 16 created and displayed as described above is shown in FIG. The color bar 16 is not only configured to be displayed on the display 15a of the display unit 15 (see FIG. 1), but also display means (for example, a separate display device or display not shown) different from the display unit 15. You may make it display on. Another display means includes paper displayed by printing, and the color (color image) that can be observed with the naked eye on the analyzer 9 is compared with the color bar 16 printed on the paper. The magnetic field strength H can also be measured.

(Magnetic field strength pointer)
Further, in the apparatus 10 according to another embodiment (embodiment 2) of the present invention, instead of the above-described color bar 16 (or in addition to the above-described color bar 16), a magnetic field strength display pointer 17 (see FIG. 1). ) May be available. The magnetic field strength display pointer 17 is a pointer portion (for example, a pointer portion that can freely move on the color image 19 of the MO plate 7 displayed on the display portion 15 in response to an operator's request (operation of means such as a mouse not shown). (Arrow) 17a may be provided.

  When the pointer portion 17a is placed or clicked at a desired position on the color image 19, the corresponding magnetic field strength calculating portion 29 reads a local RGB value at the desired position and sends this RGB value according to an instruction from the CPU 13. The magnetic field strength H corresponding to this RGB value can be calculated by substituting it into the relational expression based on the above-mentioned calibration curve (information forming the calibration curve is stored in the memory 14). Further, the magnetic field strength H can be displayed on the display unit 15 as described later or stored in the memory 14.

  The magnetic field strength H calculated by the corresponding magnetic field strength calculating unit 29 may be quantitatively displayed on the frame 17b (or other desired location on the display 15a) near the pointer unit 17a. . In addition to the magnetic field intensity H at the position where the pointer portion 17a is arranged (or clicked), a frame 17c for displaying the RGB value at that position may also be provided. In the case of the second embodiment, the local magnetic field strength H at an arbitrary position on the color image 19 of the MO plate 7 is more quantitatively compared with the case of only the color bar 16 of the first embodiment. It becomes possible to display clearly.

(Imaging method of the present invention)
Next, a method for quantitatively displaying the magnetic field distribution of the DUT 8 using the apparatus 10 of the present invention will be described with reference to the flowchart shown in FIG.

  First, the optical system of the apparatus 10 of the present invention is set as follows (steps S1 and S2).

  In step S1, in order to determine the color tone of the color bar 16, the wavelength spectra of the first light and the second light irradiated from the light sources 1 and 2 toward the MO plate 7 and the DUT 8 are selected. In other words, the light incident on the targets 7 and 8 from the light sources 1 and 2 is set so as to have a plurality (at least two or more) of different color components (wavelength spectrum components) (step S1).

  Next, an MO plate 7 is prepared (selected) having a composition that exhibits a magnetic field dependence (influence of an external magnetic field) with high sensitivity for at least one of the color components of incident light set in step S1 (step). S2).

  The light having the color component set in step S1 is incident on the MO plate 7 prepared in step S2 through the lens 5 and the polarizer 6 (step S3). In this step S3, the analyzer 9 is connected to the MO plate 7 and the imaging unit 11 so that the reflected light from the MO plate 7 can be acquired through the analyzer 9 in the calibration step S4 and the imaging step S6 described later. It arrange | positions between the light intensity measurement parts 24. Here, the angle and position of the analyzer 9 are adjusted around 90 degrees with respect to the polarizer 6 (that is, the polarizer) so that the imaging signal can be obtained with high sensitivity (with high contrast). 6).

(Calibration process of the present invention)
After the setting of the optical system (steps S1 to S3), the following calibration work is performed (step S4) before quantitative observation of the actual measurement object 8.

  The magnetic field strength H in the vicinity of the MO plate 7 is gradually changed to obtain a calibration curve between the magnetic field strength H in the MO plate 7 and the RGB values of the reflected light (step S4).

  The specific process of step S4 will be described with reference to FIG. The calibration electromagnet 21 is connected (contacted or approached) to the MO plate 7 (step S41). The magnetic field intensity H generated in the electromagnet 21 and the adjacent MO plate 7 is measured by applying the voltage V to the electromagnet 21 using the voltage application unit 22 (step S42). Further, the wavelength spectrum I (λ) of the light reflected from the MO plate 7 whose magneto-optical effect has changed according to the magnetic field intensity H is measured through the analyzer 9 (step S43).

  Next, the voltage V applied to the electromagnet 21 is changed to change the magnetic field strength H near the MO plate 7 (step S44), and the magnetic field strength H around the MO plate 7 and the wavelength spectrum I (λ) of the reflected light are obtained. Measure (Steps S42 and S43). This operation is repeated a desired number of times (for example, N times).

  After this repetitive processing, a correspondence relationship between the magnetic field intensity H near the MO plate 7 based on the measurement data and the wavelength spectrum I (λ) of the reflected light corresponding thereto is obtained. The wavelength spectrum I (λ) can be converted into RGB values corresponding to the spectrum I (λ) (step S45). A calibration curve (magnetic field strength H-RGB value) can be calculated by plotting calibration data on a chromaticity distribution diagram based on the RGB values obtained in step S45 and obtaining a fitting curve (step S46). ).

  As described above, if the setting of the light source (incident light) (steps S1 to S3) and the calibration for displaying the color bar 16 (step S4) are executed, the actual observation of the arbitrary object 8 can be performed. (Steps S5 to S9 described later).

  First, the calibration electromagnet 21 used in step S4 is separated from the MO plate 7, and the object 8 to be actually observed is connected (contacted or approached) to the MO plate 7 in the apparatus 10 of the present invention. Set (step S5). Specifically, one surface of the object to be measured 8 is brought into surface contact (or proximity) with the surface 7 b of the MO plate 7.

  Next, the imaging unit 11 such as a camera is turned on, the reflected light of the MO plate 7 (that is, the color image of the object 8 to be measured) is imaged through the analyzer 9, and the captured color image data is transmitted to the personal computer 12. (Step S6).

  Thereafter, the CPU 13 of the personal computer 12 displays the color image data received from the imaging unit 11 in a predetermined frame 18 on the display 15a of the display unit 15 (step S7). The imaging data is stored in the memory 14 as necessary or by an input operation of the operator.

Next, the color bar 16 is displayed on the display 15a using the calibration curve obtained in step S4 (step S8). Specifically, the information (the maximum value H _max corresponding to the upper limit, the minimum value H _min corresponding to the lower limit, and the information constituting the display of the color bar 16 desired by the operator in the calibration curve (formula) stored in the memory 14, and By inputting a bar representative value corresponding to each scale, color information (RGB values) of each bar area can be calculated. The color bar 16 having a desired range or scale can be displayed in a frame on the display 15a from each bar representative value, each RGB value calculated in correspondence with this, and corresponding information (matrix data).

  Thereby, for example, the operator can display the color image 19 of the object to be measured 8 (more specifically, the MO plate 7 covered thereon) and the color bar 16 on the same display 15a. Therefore, for example, the color image 19 of the object 8 to be measured acquired from time to time (in real time) is quantitatively observed while being compared and contrasted with the color bar 16 in which the color and the magnetic field strength H are shown correspondingly. Is possible.

  Further, instead of (or in conjunction with) the display process (step S8) of the color bar 16 described above, the magnetic field strength display pointer 17 described in the second embodiment is displayed on the display 15a. While operating, the magnetic field strength H may be acquired and displayed more quantitatively at an arbitrary position (step S9).

  In step S9, first, the pointer 17 is displayed on the display 15a by the operator's operation (input operation to any input means not shown). The operator moves the pointer portion 17a to a desired measurement position on the color image 19 of the object 8 to be measured on the display 15a by operating an operation means such as a mouse (not shown). By clicking the mouse at the determined position of the pointer portion 17a (the click operation is not necessarily required, for example, the pointer portion 17a may be disposed on the image 19), the CPU 13 changes the color at the position. The corresponding magnetic field strength calculation unit 29 is instructed to acquire the RGB value information of the image 19.

  The corresponding magnetic field strength calculation unit 29 substitutes the acquired RGB value into the relational expression based on the calibration curve, and calculates the magnetic field strength H corresponding to the RGB value. The RGB value and the magnetic field strength H acquired and calculated in this way may be displayed on the frame 17b or the frame 17c on the display 15a. In addition, the data of the RGB value and the magnetic field strength H calculated and displayed as described above are stored in the memory 14 at each desired selection position of the color image 19 in response to an operator's request. Also good.

(Other variations (number of monochromatic light sources))
In the first embodiment described above, it is assumed that two monochromatic light sources 1 and 2 are prepared and two incident lights having different color components (wavelength spectra, for example, a blue component and a yellow component) are simultaneously given. The present invention is not necessarily limited to the above-described embodiment, and three or more light sources (not shown) may be prepared to provide three or more incident lights having different color components (wavelength spectra) at the same time. Thereby, the color image 19 of the DUT 8 imaged by the imaging unit 11 and displayed by the display unit 15 is obtained with a color distribution (gradation) of three or more colors corresponding to the settings of these monochromatic light sources. The display of the color bar 16 can also be displayed in a more colorful manner by gradation using three or more colors from the minimum value H _min to the maximum value H _max .

(Modification using white light source)
In Example 1 described above, in order to obtain incident light having two or more different color components, two or more monochromatic light sources 1 and 2 (for example, blue LEDs and yellow LEDs) corresponding to these color components are used. Although prepared, a single white light source may be used. Thereby, the apparatus configuration can be made simpler, smaller, and less expensive.

  However, the structure and composition of the MO plate 7 (particularly, the magnetic transfer film 73) exhibiting a highly wavelength-dependent characteristic that reacts with high sensitivity only to two or more color components (wavelength spectrum) contained in the white light source. Must be selected or manufactured.

  When one of the MO plates 7 manufactured so far by the present inventors is used, there is a wavelength dependency corresponding to two colors of blue and yellow, and when the magnetic field intensity H is changed, the wavelength spectrum of the yellow of them is changed. However, the magnetic field optical properties change more sensitively than for the remaining blue wavelength spectrum. Therefore, when the magnetic field strength H of the MO plate 7 is gradually changed, the color image 19 of the MO plate 7 captured through the analyzer 9 appears to change from blue to yellow according to the magnetic field strength H.

  FIG. 7 shows the state of the magnetic field distribution of the DUT 8 displayed using the apparatus 10 of the fifth embodiment. A ferrite magnet (right image) is used as the object 8 to be measured, and a color image 19 captured by placing it under the MO plate 7 is shown on the left side of the image. Several areas in FIG. 7 are enlarged, and this enlarged area, the bar of the color bar 16 corresponding to this enlarged area, and its representative value are shown.

  In the case of the fifth embodiment as described above, the light source is a white light source, and the color component (wavelength spectrum) of the incident light cannot be selected / adjusted. It is necessary to positively adjust and improve the composition and structure on the MO plate 7 side irradiated with light, not on the light source side. Actually, since it is difficult to create a new structure of the magnetic transfer film 73 (garnet film) of the MO plate 7 at present, the color display of the color bar 16 when using a white light source is used. The options are expected to be narrower than when a combination of a plurality of monochromatic light sources is used.

The inventors changed the composition of the magnetic transfer film 73 and the substrate 71, manufactured several types of MO plates 7 (Test Examples 1 to 5), and evaluated the magneto-optical characteristics. FIG. 8 shows an example of the evaluation result. FIG. 8 shows the wavelength on the horizontal axis and the Kerr rotation angle on the vertical axis. In Test Example 1, an MO plate 7 having a magnetic transfer film 73 made of Nd ₁ Bi _2.5 Fe ₅ O ₁₂ (Bi2.5NIG) and a substrate 71 made of GGG was used.

Similarly, in Test Example 2, an MO plate 7 having a magnetic transfer film 73 made of Nd _0.5 Bi _{2.5 Fe4.5} Ga _0.5 O ₁₂ (Bi2.5NIG0.5G) and a substrate 71 made of GGG was used. In Test Example 3, an MO plate 7 having a magnetic transfer film 73 made of Nd _0.5 Bi _2.5 Fe ₅ O ₁₂ (Bi2.5NIG) and a substrate 71 made of GGG was used. In Test Example 4, an MO plate 7 having a magnetic transfer film 73 and a glass substrate 71 made of Nd _0.5 Bi _{2.5 Fe 4.0} Ga _1.0 O ₁₂ (Bi2.5NIGG) was used. In Test Example 5, an MO plate 7 having a magnetic transfer film 73 made of Y _0.5 Bi _2.5 Fe ₅ O ₁₂ (Bi2.5YIG) and a glass substrate 71 was used.

  From this result, in the case of Test Examples 4 and 5 using the glass substrate 71, the reflected light of the MO plate 7 exhibits large Kerr rotation angle peaks in the vicinity of about 500 nm and about 550 nm, whereas GGG In the case of Test Examples 1 to 3 for the single crystal substrate, it was found that a broader Kerr rotation angle peak was developed over a wide range from about 500 nm to about 650 nm.

  In other words, from FIG. 8, by adjusting and combining the color component (wavelength spectrum) of the light emitted from the monochromatic light source and the magneto-optical characteristic (rotation angle spectrum) of the MO plate 7, it is possible to cover various color combinations. It was found that the magnetic field distribution of the measurement object 8 and the color bar 16 can be displayed in color. More specifically, from the result of FIG. 8, when using any of a plurality of monochromatic light sources (LEDs) and Test Examples 1 to 5, at least blue (450 nm), green (530 nm), yellow (590 nm) It was found that the magnetic field distribution of the object to be measured 8 and the color bar 16 can be displayed with a combination of colors such as red (650 nm).

  As described above, magnetic fields are used in various industrial fields such as magnetic recording media such as hard disks and electromagnetic heaters. In addition, there are many industrial products in which a magnetic field (electromagnetic wave) is generated by an electric current, and there is a high demand for simply and quantitatively observing the magnetic field generated from these products.

  According to the present invention, the finally obtained magnetic field distribution image is displayed with two or more colors (gradation), and the correspondence between the color and the magnetic field strength (color bar) can also be shown. Therefore, the sign and size of the magnetic field can be determined easily and intuitively with the naked eye. In the method of the present invention, the processing is simple because it is only necessary to calibrate the relationship between the intensity of the magnetic field and the color (RGB value). In other words, in the method according to the present invention, it is not necessary to calibrate the relationship between the intensity of the magnetic field and the intensity of light, which has been required in the prior art. .

  Thus, the present invention has a very high industrial utility value and industrial applicability.

1 Light source (first light source)
2 Light source (second light source)
DESCRIPTION OF SYMBOLS 3 Beam splitter 4 Diffuser 5 Lens 6 Polarizer 7 MO imaging plate 8 Object to be measured 9 Analyzer 10 Imaging apparatus 11 Imaging part 12 Personal computer 13 CPU
14 Memory 15 Display unit 15a Display 16 Color-magnetic field strength display (color bar display unit, color bar)
17 color-magnetic field strength display (magnetic field strength pointer)
17a Pointer unit 17b, 17c, 18 Frame 19 Color image 21 Calibration electromagnet 22 Voltage application unit 23 Magnetic field intensity measurement unit 24 Light intensity measurement unit 25 Voltage adjustment unit 26 RGB calculation unit 27 Calibration curve calculation unit 28 Color bar creation unit 29 Magnetic field strength calculation unit 71 Substrate 72 Underlayer 73 Magnetic transfer film (magnetic transfer film layer)
74 Reflective film H Magnetic field intensity I (λ) Wavelength spectrum V Voltage value

Claims (11)

A light source capable of emitting visible light having a plurality of different wavelength spectra;
A polarizer that transmits the visible light emitted from the light source;
An MO imaging plate that receives and reflects the visible light transmitted from the polarizer;
An analyzer that transmits light reflected from the plate;
An imaging apparatus for quantitatively displaying the magnetic field distribution of an object to be measured, comprising:
The object to be measured is arranged on a surface opposite to the light incident surface of the plate,
The plate is provided with a magnetic transfer film showing high magnetic field dependence for at least one of the visible light spectrum, and
The imaging device comprises:
A calibration device for obtaining a calibration curve of the magnetic field intensity around the plate and the RGB value corresponding to the magnetic field intensity;
A device for creating and displaying a color-magnetic field strength correspondence display from the calibration curve obtained by the calibration device, and
A color image of the object to be measured can be observed by the reflected light through the analyzer, and the magnetic field strength of the object to be measured is quantitatively determined using the color image and the color-magnetic field strength correspondence display. An imaging apparatus capable of displaying or measuring. An imaging unit capable of imaging the color image transmitted through the analyzer;
A display unit for displaying the color image obtained from the imaging unit;
The imaging apparatus according to claim 1, further comprising:   The color-magnetic field strength correspondence display is a color bar expressed by a plurality of representative values of the magnetic field strength and a color corresponding to the representative value, and the color bar is displayed on the display unit or another display means. The imaging apparatus according to claim 1, wherein the imaging apparatus is configured as described above. The color-magnetic field strength correspondence display is a magnetic field strength display pointer, and
The magnetic field strength display pointer
A pointer unit that can freely move on the color image displayed on the display unit according to an operator's request;
When the pointer portion is arranged at a desired position on the color image, a local RGB value at the position is read, and the RGB value is substituted into a relational expression based on the calibration curve to correspond to the RGB value. A corresponding magnetic field strength calculating unit for calculating the magnetic field strength, and
The imaging apparatus according to claim 2 or 3, wherein the magnetic field intensity or the magnetic field intensity and the RGB value obtained by the corresponding magnetic field intensity calculation unit are displayed on the display unit or another display unit.   The imaging apparatus according to claim 1, wherein the light source includes a plurality of monochromatic light sources.   The imaging apparatus according to claim 1, wherein the light source includes at least a single white light source. An imaging method for quantitatively displaying the magnetic field distribution of an object to be measured,
Selecting different spectra of visible light emitted from a light source;
Providing an MO imaging plate provided with a magnetic transfer film that exhibits a higher magnetic field dependence for at least one of the spectra than for the remaining spectra;
Reflecting the visible light from the light source to the plate through a polarizer and transmitting the reflected light from the plate to the analyzer;
Obtaining a calibration curve between the magnetic field strength at the plate and the RGB values obtained from the reflected light;
Placing the object to be measured on a surface opposite to the light incident surface of the plate;
Creating and displaying a color-magnetic field strength correspondence display from the calibration curve;
Including, and
A color image of the object to be measured can be observed by the reflected light through the analyzer, and the magnetic field strength of the object to be measured is quantitatively determined using the color image and the color-magnetic field strength correspondence display. An imaging method characterized by being capable of displaying or measuring. Imaging the object to be measured from the plate side through the analyzer;
Displaying the color image of the measured object on the display unit;
The imaging method according to claim 7.   The color-magnetic field strength correspondence display is a color bar expressed by a plurality of representative values of the magnetic field strength and colors corresponding to the representative value, and the color bar is displayed on the display unit or another display means. The imaging method according to claim 7, further comprising a step of displaying. The color-magnetic field strength correspondence display is a magnetic field strength display pointer, and
The magnetic field intensity display pointer includes a pointer unit that can freely move on the color image displayed on the display unit according to an operator's request; and
When the pointer portion is arranged at a desired position on the color image, the local RGB value at the position is read, the RGB value is substituted into the relational expression based on the calibration curve, and the RGB value is set. A magnetic field strength calculating step for calculating a corresponding magnetic field strength;
10. The imaging according to claim 8, further comprising a step of displaying the magnetic field strength or the magnetic field strength and the RGB value obtained in the magnetic field strength calculating step on the display unit or another display means. Method. An MO imaging plate usable in any of the imaging apparatus according to claim 1 or 6 or the imaging method according to claims 7 to 10,
The MO imaging plate, wherein the plate includes a magnetic transfer film made of magnetic garnet.