JP6762011B2 - An imaging device and imaging method that quantitatively displays the magnetic field distribution in color using a magneto-optical imaging plate. - Google Patents

Description

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

(Magnetic field invisible to the eye)
Magnetic fields are used in various industrial fields such as magnetic recording media (eg, hard disks and videotapes) and electromagnetic heaters. The magnetic field itself cannot be seen directly with the eyes, but when iron sand is sprinkled around the magnet, you can see the pattern of iron sand particles lined up along the lines of magnetic force.

(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 visible (iron sand in the above example). The method using a magneto-optical microscope that has already been developed also magnetically transfers the magnetic field distribution to a film having a large magneto-optical effect called a magneto-transfer film (for example, a bismuth-substituted garnet film (Patent Document 1)) to obtain a polarized image. It is a method of visualizing as (see, for example, Non-Patent Documents 1 to 3). This method is expected to be an excellent method capable of measuring easily, with high spatial resolution, and in real time.

(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). A typical method among these methods is a method called "orthogonal detector method" in which the polarizer and the detector are shifted by approximately 90 degrees to observe the magnetic film. When the incident light having a light intensity I ₀ passes through the magnetic film and the analyzer, the light intensity I is as follows, depending on the Faraday rotation angle θ _F , the angler θ _P, and the angler θ _{A of the} analyzer. It is expressed 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 the contrast with respect to the Faraday rotation angle θ _F as shown by the above mathematical formula (Equation 1), so that it is obtained by this method. The contrast of the image (for example, the brightness shown in black and white grayscale on the image) does not directly represent the strength of the magnetic field.

(Prior art for quantitative measurement of magnetic field distribution)
Therefore, in order to obtain an image of a quantitative magnetic field distribution, a 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), or the present inventors have already proposed " 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 coping method (calibration of a black-and-white image using the relationship between the light intensity I and the magnetic field H), the calibration curve of Joose et al. (Formula 2 below) is known (Non-Patent Document 3). In Equation 2, c is the fitting parameter and _Ms is the saturation magnetization.

However, when calibrating using this formula 2, information such as incident light intensity I ₀ , background image I ₁ , and fitting parameter c is also required. It is unrealistic to calculate the magnetic field by applying this calibration curve at all points (x, y) on the image because a huge amount of calculation and time are required. Therefore, in reality, there is no choice but to obtain all the magnetic fields on the image measured using the parameters (fitting parameter c described above) obtained for only one point (for example, (x ₁ , y ₁ )). Therefore, if the irradiation light has unevenness (spots) or the light intensity I changes during the measurement, a correct value cannot be obtained. Further, as is clear from Equation 2, since it is necessary to perform a calculation such as subtracting the light intensity I by the background image I ₁ or dividing by the incident light intensity I ₀ , the magnetic field strength after the calculation is ignored. There is too much noise to be added (that is, the SN ratio of the magnetic field strength (signal) after calculation becomes worse).

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

However, the reconstructed image information contains more unnecessary noise than 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 a polarized image consisting of three images many times (several tens to 100 times).

Japanese Patent No. 3743440

Takayuki Ishibashi, "Quantitative Observation of Magnetic Field Distribution with a Magnetic Optical Microscope and Its Sensitivity", Optical Society of Japan, Optical Society of Japan, Vol. 42, No. 1 (2013), p. 13-19 Takato Machi, "Magnetic Flux Observation of Superconducting Wires with a Magnetic Optical Microscope", Applied Physics, Japan Society of Applied Physics, Vol. 82, No. 2 (2013), p. 117-122 Ch. Joose et al., "Thickness and roughness of density of magnetic flux penetration and critic current densities in YBa2Cu307-d thin films," P. 235-252

The present invention has been made in view of such circumstances, and imaging that simply and easily quantitatively measures and displays the magnetic field distribution without requiring a huge amount of calculation / time and noise reduction processing at the calibration stage. It is an object of the present invention to provide an apparatus and an imaging method. In other words, it is an object of the present invention to provide an apparatus and method for quantitatively color-displaying a magnetic field distribution using an MO imaging plate provided with a magnetic transfer film.

After diligent studies, the present inventors have conducted diligent studies, and the only polarized image showing the magnetic field distribution finally processed by the prior art is the brightness of light (light intensity, in other words, a black-and-white grayscale image). Focusing on the fact that it was only expressed in, I wondered if this polarized image could be displayed in color. By doing so, it was thought that the color display could express a slight change of state of the polarized image, and that this could be appropriately matched with the magnetic field strength. Then, specifically, they have found a means and a process for selectively incident light having a plurality of spectra having different magnetic field dependence from a light source onto a magnetic field imaging plate including a magnetic transfer film, and have completed the present invention. It was.

That is, the present invention has, for example, the following configurations and features.
(Aspect 1)
A light source capable of irradiating visible light with multiple different wavelength spectra,
A polarizer that transmits the visible light emitted from the light source and
An MO imaging plate that reflects the visible light transmitted from the polarizer and reflects it.
An detector that transmits the light reflected from the plate and
It is an imaging device that quantitatively displays the magnetic field distribution of the object to be measured in color.
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 that exhibits high magnetic field dependence on at least one of the visible light spectra.
The imaging device is
A calibration device that acquires a calibration curve of the magnetic field strength around the plate and the RGB value corresponding to the magnetic field strength, and
A device for creating and displaying a color-magnetic field strength correspondence display from the calibration curve obtained by the calibration device is further provided, and
The color image of the object to be measured can be observed by the reflected light through the analyzer, and the magnetic field intensity of the object to be measured is quantitatively measured by using the color image and the color-magnetic field strength correspondence display. An imaging device characterized in that it can be displayed or measured.
(Aspect 2)
An imaging unit capable of capturing the color image transmitted through the analyzer and
A display unit that displays the color image obtained from the imaging unit, and
The imaging apparatus according to aspect 1, further comprising.
(Aspect 3)
The color-magnetic field strength correspondence display is a color bar represented by a plurality of representative values of the magnetic field strength and colors corresponding to the representative values, and the color bar is displayed by the display unit or another display means. imaging apparatus according to state-like 2, characterized in that the.
(Aspect 4)
The color-magnetic field strength correspondence display is a magnetic field strength display pointer, and
The magnetic field strength display pointer is
A pointer unit that can be freely moved on the color image displayed on the display unit at the request of the operator.
When the pointer unit is placed at a desired position on the color image, the local RGB value at that position is read, and the RGB value is substituted into the relational expression based on the calibration curve to correspond to the RGB value. It is equipped with a corresponding magnetic field strength calculation unit that calculates the magnetic field strength, and
The imaging apparatus according to aspect 2 or 3, wherein the magnetic field strength or the magnetic field strength and the RGB value obtained by the corresponding magnetic field strength calculation unit are displayed by the display unit or another display means.
(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)
It is an imaging method that quantitatively displays the magnetic field distribution of the object to be measured in color.
The step of selecting multiple spectra of different visible light emitted from a light source,
A step of preparing 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.
A step of inputting and reflecting the visible light from the light source to the plate through a polarizing element and transmitting the reflected light from the plate to the analyzer.
A step of obtaining a calibration curve between the magnetic field strength in the plate and the RGB value obtained from the reflected light.
A step of arranging the object to be measured on a surface opposite to the light incident surface of the plate,
Steps to create and display a color-magnetic field strength correspondence display from the calibration curve,
Including and
The color image of the object to be measured can be observed by the reflected light through the analyzer, and the magnetic field intensity of the object to be measured is quantitatively measured by using the color image and the color-magnetic field strength correspondence display. An imaging method characterized in that it can be displayed or measured.
(Aspect 8)
A step of photographing the object to be measured from the plate side through the analyzer, and
A step of displaying the imaged color image of the object to be measured on the display unit, and
The imaging method according to aspect 7, wherein
(Aspect 9)
The color-magnetic field strength correspondence display is a color bar represented by a plurality of representative values of the magnetic field strength and colors corresponding to the representative values, and the color bar is used as the display unit or another display means. imaging method according to state-like 8, further comprising the step of displaying Te.
(Aspect 10)
The color-magnetic field strength correspondence display is a magnetic field strength display pointer, and
The magnetic field strength display pointer includes a pointer unit that can freely move on the color image displayed on the display unit at the request of the operator, 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 used. The magnetic field strength calculation step to calculate the corresponding magnetic field strength and
The imaging method according to aspect 8 or 9, 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 calculation step by 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 plate is an MO imaging plate including a magnetic transfer film made of magnetic garnet.

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

For example, when an image pickup 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 method of the prior art, it is expressed only in black and white 256 gradations at the maximum. Although it is not possible, even if an image pickup device having the same resolution is used by the method of the present invention, the state of the object to be measured can be expressed by a color gradation of up to about 17 million (that is, 256 cubes) gradation. In other words, in the present invention, even if a camera having the lowest resolution is used, minute changes / differences in the spectrum of the reflected light from the magnetic film indicating the object to be measured can be reliably captured and expressed.

It is the schematic which showed the imaging apparatus which concerns on this invention (Example 1). It is a figure which showed an example of the cross-sectional structure of the MO imaging plate. It is a chromaticity distribution map which showed the plot point of the calibration data and the calibration curve. It is a figure which showed an example of the color bar created and displayed by this invention. It is a flowchart explaining each step of the imaging method of this invention (Example 3). It is a flowchart explaining the detail of the calibration step of the imaging method of Example 3. It is a figure which showed the state of the magnetic field distribution of the object to be measured, which was displayed using the imaging apparatus (white light source) of Example 5. It is a figure which showed the modification of the MO imaging plate and its magneto-optical property.

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

(Overview of the device of the present invention)
FIG. 1 is a schematic view showing an example of an imaging device (hereinafter, also simply referred to as “device”) 10 of the present invention. In this embodiment, two light sources, the first and second light sources 1 and 2, are provided as the 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 a second light having a wavelength spectrum of a second color (for example, yellow) different from that of the first color.

(Simultaneous incident 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, and is emitted from both light sources 1 and 2. The dripping light enters the beam splitter 3. More specifically, the light from one light source (for example, the first light source 1) is incident on the first surface (outer surface) 3a of the beam splitter 3 and is separated into a component 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) 3b 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. Suddenly, it will be incident on the MO imaging plate 7 described later.

(Magnetic Optical (MO) Imaging Plate)
The transmitted light component of the first light and the reflected light component of the second light are linearly polarized when they pass through the polarizer 6, and then the MO (magneto-optcal, meaning "magneto-optics") imaging plate 7 (hereinafter referred to as "magnetic optics"). , Simply referred to as "MO plate") incident on one side surface 7a. When the device 10 of the present invention is used, a magnetic field distribution is provided on 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). The light to be measured 8 (magnetic material) is connected (contacted or close to), and the light incident on and reflected on the MO plate 7 and the MO plate 7 is also affected by a local magnetic field, as will be described later. As the reflected light, a color image showing the light that has passed through the analyzer 9 and an object (including the object to be measured 8) around the light is acquired by an imaging unit 11 such as a camera.

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

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

(Example of composition of MO imaging plate)
As shown in FIG. 2, the compositions of the substrate 71, the base layer 72, the magnetic transfer film 73, and the reflective film 74 adopted in Example 1 are a glass plate, Nd ₂ Bi _{1 Fe4} Ga ₁ O ₁₂ , and Nd, respectively. ₁ Bi ₂ Fe ₅ O ₁₂ , and Ag, but are not necessarily limited to these compositions. From the experience of the present inventors, the thickness of the substrate 71 is preferably 50 μm to 3 mm. Further, the base layer 72 is preferably 30 to 300 nm, more preferably 100 to 150 nm. The thickness of the magnetic transfer film 73 is preferably 100 nm to 10 μm, more preferably 600 to 800 nm. As will be described later, for the magnetic transfer film 73, it is preferable to select a material having high magnetic field dependence and wavelength dependence for a specific color. From this point of view, in addition to the above-mentioned Nd ₁ Bi ₂ Fe ₅ O ₁₂ (Bi2NIG), 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 one of Nd, Y, Lu or a combination of these rare earth elements.

(Modified example of composition of MO imaging plate)
Instead of the above-mentioned glass substrate, the substrate 71 may be, for example, a substrate made of GGG (Gadolinium Gallium Garnet) or a substrate made of other materials. 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.

The color image information of the object 8 to be measured acquired by the image pickup unit 11 is stored in the memory 14 by the CPU 13 in the personal computer 12 connected to the image pickup unit 11 and is displayed by the display 15a and the like. The unit 15 makes it possible to display the state of the MO plate 7 (color reflected on) covering a part or all of the object 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 USB.

It should be noted that, with only the components described above, it is only possible to 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 cannot be made.

Therefore, in one example of the present invention, in order to achieve the above-mentioned object of the present invention, the magnetic field strength and the display color corresponding to the color image 19 correspond to the magnetic field distribution of the object 8 to be measured (in addition to the color image 19). Color-magnetic field strength correspondence displays 16 and 17 (hereinafter, also referred to as "color bar 16" and "pointer 17") are also displayed on the display unit 15 (for example, on the display 15a). It can be displayed on.

(Color bar)
First, as an example, the 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 is further provided with a calibration electromagnet 21, a voltage applying unit 22 for applying a voltage V to the electromagnet 21, a magnetic field strength measuring unit 23, and a light intensity measuring 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 makes it possible to 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 thereof, and a coil 21b is spirally wound around the core 21a so that both ends of the coil 21b are connected to the voltage applying portion 22. You may. A commercially available regulated DC power supply may be used as the voltage applying unit 22 and the voltage adjusting unit 25. By changing the current flowing through the coil 21b by the voltage adjusting unit 25, the voltage value V applied to the electromagnet 21 can be arbitrarily changed. The voltage application unit 22 and the personal computer 12 may be connected to store the data of the voltage value V set and applied as described above in the memory 14 by the command of the CPU 13. The voltage applying unit 22 and the personal computer 12 can be connected via an interface 12a such as USB, and the magnetic field strength measuring unit 23 or the light intensity measuring unit 24, which will be described later, is connected to the personal computer 12. May be the same means / method.

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

Further, the light intensity measuring unit 24 may use a commercially available optical spectroscope, or may be a measuring instrument having the functions of the above-mentioned imaging unit 11. The light intensity measuring 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 by 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 8 to be measured). That is, instead of the object 8 to be measured, the calibration electromagnet 21 is brought into contact with or close to the MO plate 7. The magnetic field strength measuring unit 23 measures the magnetic field strength H of the electromagnet 21 applied at a certain voltage value V. The light intensity measuring unit 24 acquires optical characteristic data (for example, wavelength spectrum I (λ)) of light that has been reflected from the MO plate 7 that is in contact with or close to the electromagnet 21 and has passed through the analyzer 9.

As described above, the wavelength spectrum I (λ), the magnetic field intensity H, and the set voltage value V data 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 by the instruction of the CPU 13. It is stored in 14. After that, the voltage adjusting unit 25 changes the voltage value V applied to the electromagnet 21, and the wavelength spectrum I (λ), the magnetic field strength H, and the voltage value V data corresponding to the voltage value V at that time are obtained. It is acquired by the calibration devices 22 to 25, and is transmitted and stored in the memory 14 by a command of the CPU 13. This measurement operation is repeated a plurality of times (preferably 5 times or more, more preferably 10 times or more to improve 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 a wavelength spectrum I (λ) at each magnetic field strength 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 an RGB value.

Further, the apparatus 10 of the present invention is also provided with a calibration curve calculation unit 27, and from the correspondence relationship between the RGB value obtained by the RGB calculation unit 26 and the magnetic field strength H, a chromaticity distribution map (xy color) described later Plot each data obtained during calibration (that is, the magnetic field strength H and the corresponding RGB values (more specifically, the x and y values obtained from the RGB values)) on the map (degree map) ( See FIG. 3).

The magnetic field strength (for example, +1, +0.5, 0, -0.5, -1, all units are [koe]) is also shown next to some plot points in FIG. Further, the horizontal axis x and the vertical axis y of the chromaticity distribution map (CIE1931) shown in FIG. 3 are calculated by the ratio of the tristimulus values (color mixing amount of the three stimuli) (color mixing ratio of the three stimuli). From these plots, a calibration curve (for example, a fitting curve) of the magnetic field strength H and the RGB values (more specifically, the values of x and y) can be calculated. The mathematical formula information of the obtained calibration curve is also stored in the memory 14.

Further, in the device 10 of the present invention, a color bar creating unit 28 is also provided. The color bar creation unit 28 creates and calculates basic information for displaying the color bar 16 by using mathematical formula information related to the calibration curve stored in the memory 14. For example, the color bar display unit 16 determines the maximum and minimum magnetic field strengths H _max and H _min (for example, +1 kOe and -1 kOe) for display, and sets the maximum value H _max and the minimum value H _min . The number n of regions dividing the range of (for example, n = 11) is determined. When n = 11, in addition to the region of the maximum value H _{max and} the region of the minimum value H _min , the magnetic field strength H of 9 points (9 partition regions) evenly divided between these is acquired (total). The magnetic field strength H at 11 points (11 regions) can be obtained).

The nine points (nine areas) inside the color bar 16 are acquired so as to evenly 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 always limited to this. For example, the vicinity of the magnetic field strength H, which is easily observed, may be finely and unevenly divided. Using each of the obtained magnetic field strengths H and the above-mentioned calibration curve, RGB values (color information) corresponding to each magnetic field strength H are calculated. By calculating in this way, a bar representative value (corresponding relationship between each magnetic field strength H and the corresponding RGB value) indicating each divided region of the color bar 16 can be obtained.

The color bar 16 is obtained by the color bar creation unit 28, and then by reading out each data of the bar representative value stored in the memory 14, the color bar 16 is displayed at a predetermined position on the display 15a of the display unit 15. You can do it. FIG. 4 shows an example of the color bar 16 created and displayed as described above. The color bar 16 is not only configured to be displayed on the display 15a of the display unit 15 (see FIG. 1), but is also a display means different from the display unit 15 (for example, a separate display device or display (not shown)). It may be displayed in. Another display means includes paper displayed by printing, and by comparing a color (color image) observable with the naked eye on the analyzer 9 with a color bar 16 printed on the paper. , The magnetic field strength H can also be measured visually.

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

When the pointer unit 17a is placed or clicked at a desired position on the color image 19, the corresponding magnetic field strength calculation unit 29 reads the local RGB value at the desired position by the command of the CPU 13, and reads the RGB value. 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 (the 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 or stored in the memory 14 as described later.

Then, the magnetic field strength H calculated by the corresponding magnetic field strength calculation unit 29 may be quantitatively displayed on the frame 17b (or other desired location on the display 15a) near the pointer unit 17a. .. Further, a frame 17c for displaying the RGB value at the position where the pointer portion 17a is arranged (or clicked) as well as the magnetic field strength H may be provided at the same time. In the case of this Example 2, the local magnetic field strength H at an arbitrary position on the color image 19 of the MO plate 7 is more quantitative and more quantitative than the case of only the color bar 16 of the previous Example 1. It will be possible to display clearly.

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

First, the setting of the optical system of the apparatus 10 of the present invention is performed 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 emitted from the light sources 1 and 2 toward the MO plate 7 and the object 8 to be measured are selected. In other words, the light incident on the targets 7 and 8 from the light sources 1 and 2 is set to have a plurality (at least two or more) different color components (wavelength spectrum components) (step S1).

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

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 attached 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 is arranged between the light intensity measuring unit 24 and the light intensity measuring unit 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 image pickup unit 11 can obtain the spectral signal of the reflected light with high sensitivity (high contrast). It is preferable to orient it so as to be substantially orthogonal to 6.

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

The magnetic field strength H near 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 value 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 close to) the MO plate 7 (step S41). The magnetic field strength H generated in the electromagnet 21 and the MO plate 7 adjacent to the electromagnet 21 by applying a voltage V to the electromagnet 21 is measured by using the voltage applying unit 22 (step S42). Further, the wavelength spectrum I (λ) of the light reflected from the MO plate 7 whose magneto-optical effect changes according to the magnetic field strength H is measured through the analyzer 9 (step S43).

Next, the magnetic field strength H near the MO plate 7 is changed by changing the voltage V applied to the electromagnet 21 (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, S43). This operation is repeated a desired number of times (for example, N times).

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

If the setting of the light source (incident light at) (steps S1 to S3) and the calibration for displaying the color bar 16 (step S4) are executed as described above, the actual observation of the arbitrary object 8 to be measured can be performed. You can enter (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 to be measured 8 to be actually observed is connected (contacted or close 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 close to) the surface 7b of the MO plate 7.

Next, the power of the image pickup 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 to be measured 8) is imaged through the analyzer 9, and the imaged color image data is transmitted to the personal computer 12. (Step S6).

After that, 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 needed 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 constituting the display of the color bar 16 desired by the operator on the calibration curve (mathematical formula) stored in the memory 14 (maximum value H _max corresponding to the upper limit, minimum value H _min corresponding to the lower limit, and By inputting the bar representative value corresponding to each scale, the color information (RGB value) of each bar area can be calculated. From the representative value of each bar, each RGB value calculated corresponding to the representative value, and the corresponding information (matrix data), the color bar 16 having a desired range and scale can be displayed in the frame on the display 15a.

Thereby, for example, the operator can display the color image 19 of the object to be measured 8 (more specifically, the MO plate 7 overlying the object 8) and the color bar 16 on the same display 15a. Therefore, for example, the color image 19 of the object to be measured 8 acquired at any time (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 combination 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, and this is displayed. The magnetic field strength H may be acquired and displayed more quantitatively at an arbitrary position while operating (step S9).

In step S9, first, the pointer 17 is displayed on the display 15a by an operator's operation (input operation to any input means of a keyboard (not shown)). The operator moves the pointer unit 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 operating means such as a mouse (not shown). By clicking the mouse at the determined position of the pointer unit 17a (the click operation is not always necessary, for example, the pointer unit 17a may be simply arranged on the image 19), the CPU 13 has 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 this RGB value. The RGB values acquired and calculated in this way and the magnetic field strength H may be displayed on the frame 17b or the frame 17c on the display 15a. In addition, in response to the request of the operator, the data of the RGB values calculated and displayed as described above and the magnetic field strength H are stored in the memory 14 at each desired selected position of the color image 19. May be good.

(Other variants (number of monochromatic light sources))
In Example 1 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 provided. Not necessarily limited to the above embodiment, three or more light sources (not shown) may be prepared to simultaneously provide three or more incident lights having different color components (wavelength spectra). As a result, the color image 19 of the object 8 to be measured, which is captured by the imaging unit 11 and displayed by the display unit 15, has 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 more colorfully by the gradation using three or more colors in the region from the minimum value H _min to the maximum value H _max .

(Modification using a 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, a blue LED and a yellow LED) corresponding to these color components are used. Although prepared, a single white light source may be used. As a result, the device configuration can be made simpler, smaller, and cheaper.

However, the structure and composition of the MO plate 7 (particularly, the magnetic transfer film 73) exhibiting highly wavelength-dependent characteristics that react extremely sensitively only to two or more color components (wavelength spectra) contained in the white light source. Must be selected or manufactured.

When one of the MO plates 7 manufactured by the present inventors is used, there is a wavelength dependence corresponding to two colors of blue and yellow, and when the magnetic field strength H is changed, the wavelength spectrum of yellow is obtained. Only 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 imaged 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 object to be measured 8 displayed by 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 imaged by placing the ferrite magnet under the MO plate 7 is shown on the left side of the image. Some areas in FIG. 7 are enlarged, and the enlarged areas, the corresponding color bars 16 bars, and their representative values 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 or adjusted. Therefore, in order to change the color or the like of the color bar 16. It is necessary to positively adjust and improve the composition and structure of the MO plate 7 side to which light is irradiated, not the light source side. Actually, at present, it is difficult to newly create the structure of the magnetic transfer film 73 (garnet film) of the MO plate 7, so that the color display of the color bar 16 when a white light source is used is displayed. The options are expected to be narrower than when using a combination of multiple monochromatic light sources.

The present inventors manufactured several types of MO plates 7 (Test Examples 1 to 5) by changing the composition of the magnetic transfer film 73 and the substrate 71, and evaluated the magneto-optical characteristics. FIG. 8 shows an example of the evaluation result. In FIG. 8, the horizontal axis represents the wavelength and the vertical axis represents the car rotation angle. 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 (Bi2.5 NIG) 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 (Bi2.5 NIG 0.5G) 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 F _e5 O ₁₂ (Bi2.5 NIG) and a substrate 71 made of GGG was used. In Test Example 4, an MO plate 7 having a magnetic transfer film 73 made of Nd _0.5 Bi _2.5 F _e4.0 Ga _1.0 O ₁₂ (Bi2.5 NIGG) and a glass substrate 71 was used. In Test Example 5, it was used _{Y 0.5 Bi 2.5 F e5 O 12} MO plate 7 having a magnetic transfer film 73 and the glass substrate 71 made of (Bi2.5YIG).

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

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

As described above, the magnetic field is 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 simple and quantitative observation of the magnetic field generated from these products.

According to the present invention, the image of the magnetic field distribution finally obtained is displayed by two or more colors (gradation), and the correspondence relationship (color bar) between the color and the magnetic field strength can also be shown. Therefore, the sign and magnitude of the magnetic field can be easily and intuitively determined with the naked eye. Further, in the method of the present invention, the process is simple because it is only necessary to calibrate the relationship between the strength of the magnetic field and the color (RGB value). In other words, in the method of the present invention, it is not necessary to calibrate the relationship between the magnetic field intensity and the light intensity required in the prior art, so that problems such as enormous processing in the calibration stage and noise do not occur. ..

As described above, the present invention has very high industrial applicability and industrial applicability.

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

Claims (11)

A light source capable of irradiating visible light with multiple different wavelength spectra,
A polarizer that transmits the visible light emitted from the light source and
An MO imaging plate that reflects the visible light transmitted from the polarizer and reflects it.
An detector that transmits the light reflected from the plate and
It is an imaging device that quantitatively displays the magnetic field distribution of the object to be measured in color.
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 that exhibits high magnetic field dependence on at least one of the visible light spectra.
The imaging device is
A calibration device that acquires a calibration curve of the magnetic field strength around the plate and the RGB value corresponding to the magnetic field strength, and
A device for creating and displaying a color-magnetic field strength correspondence display from the calibration curve obtained by the calibration device is further provided, and
The color image of the object to be measured can be observed by the reflected light through the analyzer, and the magnetic field intensity of the object to be measured is quantitatively measured by using the color image and the color-magnetic field strength correspondence display. An imaging device characterized in that it can be displayed or measured. An imaging unit capable of capturing the color image transmitted through the analyzer and
A display unit that displays the color image obtained from the imaging unit, and
The imaging apparatus according to claim 1, further comprising. The color-magnetic field strength correspondence display is a color bar represented by a plurality of representative values of the magnetic field strength and colors corresponding to the representative values, and the color bar is displayed by the display unit or another display means. The imaging apparatus according to claim 2 , wherein the imaging apparatus is used. The color-magnetic field strength correspondence display is a magnetic field strength display pointer, and
The magnetic field strength display pointer is
A pointer unit that can be freely moved on the color image displayed on the display unit at the request of the operator.
When the pointer unit is placed at a desired position on the color image, the local RGB value at that position is read, and the RGB value is substituted into the relational expression based on the calibration curve to correspond to the RGB value. It is equipped with a corresponding magnetic field strength calculation unit that calculates the magnetic field strength, and
The imaging apparatus according to claim 2 or 3, wherein the magnetic field strength or the magnetic field strength and the RGB value obtained by the corresponding magnetic field strength calculation unit are displayed by the display unit or another display means. The imaging apparatus according to any one of claims 1 to 4, wherein the light source includes a plurality of monochromatic light sources. The imaging apparatus according to any one of claims 1 to 4, wherein the light source includes at least a single white light source. It is an imaging method that quantitatively displays the magnetic field distribution of the object to be measured in color.
The step of selecting multiple spectra of different visible light emitted from a light source,
A step of preparing 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.
A step of inputting and reflecting the visible light from the light source to the plate through a polarizing element and transmitting the reflected light from the plate to the analyzer.
A step of obtaining a calibration curve between the magnetic field strength in the plate and the RGB value obtained from the reflected light.
A step of arranging the object to be measured on a surface opposite to the light incident surface of the plate,
Steps to create and display a color-magnetic field strength correspondence display from the calibration curve,
Including and
The color image of the object to be measured can be observed by the reflected light through the analyzer, and the magnetic field intensity of the object to be measured is quantitatively measured by using the color image and the color-magnetic field strength correspondence display. An imaging method characterized in that it can be displayed or measured. A step of photographing the object to be measured from the plate side through the analyzer, and
A step of displaying the imaged color image of the object to be measured on the display unit, and
7. The imaging method according to claim 7. The color-magnetic field strength correspondence display is a color bar represented by a plurality of representative values of the magnetic field strength and colors corresponding to the representative values, and the color bar is used as the display unit or another display means. The imaging method according to claim 8 , further comprising a step of displaying the image. The color-magnetic field strength correspondence display is a magnetic field strength display pointer, and
The magnetic field strength display pointer includes a pointer unit that can freely move on the color image displayed on the display unit at the request of the operator, 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 used. The magnetic field strength calculation step to calculate the corresponding magnetic field strength and
The imaging according to claim 8 or 9, 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 calculation step by the display unit or another display means. Method. An MO imaging plate that can be used in any of the imaging apparatus according to claims 1 to 6 or the imaging method according to claims 7 to 10.
The plate is an MO imaging plate including a magnetic transfer film made of magnetic garnet.