Magnetic field source position detection method

Abstract

To provide a magnetic field source position detection method capable of improving detection accuracy while maintaining the portability of a diamond sensor.SOLUTION: A magnetic field source position detection method includes: a fluorescence intensity acquisition step of two-dimensionally scanning a sample in a state where excitation light from a laser light source is guided by an optical fiber and applied to a diamond, and acquiring intensity of fluorescence emitted from the diamond; and a position detection step of detecting a position of a magnetic field source in the sample on the basis of a change amount of the fluorescence intensity in the same direction as a scanning direction of the excitation light with respect to the acquired fluorescence intensity. The position detection step includes calculating a differential value only in the same direction as the scanning direction of the excitation light for a distribution image of the acquired two-dimensional fluorescence intensity, obtaining the square of the calculated differential value, and detecting the position of the magnetic field source in the sample on the basis of the obtained result.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for detecting the position of a magnetic field source, and particularly to a method for detecting the position of a magnetic field source using a diamond sensor using an optical fiber.

Background Art

[0002] As a diamond sensor using an optical fiber, for example, the one described in Non-Patent Document 1 below is known. Specifically, as shown in FIG. 2(a) of Non-Patent Document 1, a laser light source that generates excitation light, a diamond having an NV (Nitrogen-Vacancy) center, a microwave source that irradiates the diamond with microwaves and sweeps them, and a detector that detects the intensity of fluorescence emitted from the diamond by the irradiation of the excitation light. And the excitation light output from the laser light source is guided to the diamond by an optical fiber. In such a diamond sensor having such a structure, the position of the magnetic field source is detected based on the amount of change in the detected fluorescence intensity.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Recently, with the expansion of the application of diamond sensors, the development of easily portable diamond sensors has been demanded. However, the diamond sensor using the above-mentioned optical fiber has a problem that it is difficult to apply for portability for the following reasons. That is, when the magnetic field source to be detected is scanned using the diamond sensor, the optical fiber also vibrates slightly due to the influence of minute vibrations or the like. As a result, a large background noise is generated, and the detection accuracy deteriorates. In addition, in order to maintain the detection accuracy, for example, a method of firmly fixing the optical fiber is considered, but when the optical fiber is fixed, a new problem of hindering the portability of the diamond sensor occurs.

[0005] The present invention has been made to solve such technical problems, and an object thereof is to provide a method for detecting the position of a magnetic field source capable of enhancing the detection accuracy while maintaining the portability of a diamond sensor.

Means for Solving the Problems

[0006] The method for detecting the position of a magnetic field source according to the present invention includes a fluorescence intensity acquisition step of guiding excitation light from a light source through an optical fiber, irradiating a diamond, and two-dimensionally scanning a sample in a state where the diamond is irradiated, and acquiring the intensity of fluorescence emitted from the diamond; and a position detection step of detecting the position of the magnetic field source in the sample based on the amount of change in the fluorescence intensity in the same direction as the scanning direction of the excitation light with respect to the acquired fluorescence intensity.

[0007] In the method for detecting the position of a magnetic field source according to the present invention, since the position of the magnetic field source is detected based on the amount of change in the fluorescence intensity in the same direction as the scanning direction of the excitation light, it is possible to reduce the background noise caused by minute vibrations of the optical fiber. Moreover, since it is not necessary to fix the optical fiber, the portability of the diamond sensor can be ensured. As a result, it is possible to enhance the detection accuracy of the position of the magnetic field source while maintaining the portability of the diamond sensor.

[0008] In the magnetic field source position detection method according to the present invention, in the position detection step, it is preferable to calculate a differential value only in the same direction as the scanning direction of the excitation light for the acquired two-dimensional fluorescence intensity distribution image, and detect the position of the magnetic field source in the sample based on the calculated differential value. By doing so, background noise due to minute vibrations of the optical fiber can be reduced, so that the detection accuracy of the position of the magnetic field source can be improved.

[0009] Further, in the magnetic field source position detection method according to the present invention, in the position detection step, it is preferable to obtain the square of the calculated differential value or the absolute value of the calculated differential value, and detect the position of the magnetic field source in the sample based on the obtained result. By doing so, background noise due to minute vibrations of the optical fiber can be further reduced, so that the detection accuracy of the position of the magnetic field source can be further improved.

[0010] Furthermore, in the magnetic field source position detection method according to the present invention, in the fluorescence intensity acquisition step, it is preferable to two-dimensionally scan the sample with an external magnetic field applied in the scanning direction of the excitation light. By doing so, the signal-to-noise ratio can be increased, so that the detection accuracy of the position of the magnetic field source can be further improved.

Advantages of the Invention

[0011] According to the present invention, it is possible to improve the detection accuracy of the position of the magnetic field source while maintaining the portability of the diamond sensor.

Brief Description of the Drawings

[0012]

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[0013] Hereinafter, embodiments of the magnetic field source position detection method according to the present invention will be described with reference to the drawings. Prior to the description of the embodiments, the configuration of the diamond sensor used in the magnetic field source position detection method will be described.

[0014] [Regarding the Configuration of the Diamond Sensor] The diamond sensor 1 used in the magnetic field source position detection method of the present embodiment is a diamond sensor using an optical fiber, and is a device for two-dimensionally scanning a sample and detecting the position of a magnetic field source in the sample. Here, the "magnetic field source" refers to, for example, foreign matter in the sample. Therefore, the detection of the position of the magnetic field source in the sample has the same meaning as the detection of foreign matter in the sample. By using such a technique, it is possible to confirm the presence or absence of defective products in the product and easily identify the occurrence position of the defective products.

[0015] FIG. 1 is a schematic diagram showing the configuration of the diamond sensor used in the magnetic field source position detection method according to the embodiment. As shown in FIG. 1, the diamond sensor 1 mainly includes an excitation light irradiation unit 2, a sensor unit 3 in which a diamond 31 is disposed, a microwave source 6, an external magnetic field 7, a sample stage 8, a detection unit 4, and a control unit 5.

[0016] The excitation light irradiation unit 2 includes a laser light source 21 that generates excitation light to irradiate the diamond 31, a first lens 22 that guides the excitation light output from the laser light source 21 to the optical fiber 23, an optical fiber 23 that guides the excitation light to the diamond 31 side, an optical fiber 24 connected to the optical fiber 23 via a fiber coupler (not shown), and a second lens 25 and a third lens 26 optically connected to the optical fiber 24. The laser light source 21 is controlled by the control unit 5 and outputs, for example, green excitation light (i.e., laser light).

[0017] The sensor unit 3 has a microwave irradiation substrate 32 on which the diamond 31 is disposed. The diamond 31 has a plurality of NV centers and emits fluorescence when irradiated with excitation light.

[0018] The microwave source 6 is controlled by the control unit 5 and irradiates and sweeps the diamond 31 with a frequency-variable microwave. The external magnetic field 7 is composed of a permanent magnet and serves to improve the responsiveness to the magnetic field by applying a magnetic field of, for example, about 2 to 3 mT to the position of the diamond 31. Further, by adjusting the direction of the polarity of the external magnetic field 7, a magnetic field can be applied to the sample 100 placed on the sample stage 8 in a predetermined direction (for example, the X direction). Note that the sample 100 is, for example, a product, etc., and the magnet drawn on the sample 100 indicates the magnetic field source 101.

[0019] The sample stage 8 is for placing and fixing the sample 100 and is disposed below the diamond 31. The sample stage 8 has a rectangular base 81 and an XY stage 82 disposed on the upper surface of the base 81 and movable in the X-axis direction and the Y-axis direction with respect to the base 81. The sample 100 is placed on the upper surface of the XY stage 82 and can move in the X-axis direction and the Y-axis direction as the XY stage 82 moves. The distance between the upper surface of the XY stage 82 and the bottom surface of the diamond 31 can be adjusted as necessary and is, for example, 0.8 mm.

[0020] The detection unit 4 includes an optical fiber 41 connected to the optical fibers 23 and 24 via an optical fiber coupler (not shown), an optical fiber 45 connected to the optical fiber 41 via a first mirror 42, a filter 43, and a second mirror 44, a photodetector 46 that detects the light guided by the optical fiber 45, and a voltmeter 47.

[0021] The filter 43 is configured to transmit only the red fluorescence emitted from the diamond 31 and not to transmit other light. The photodetector 46 has, for example, a photodiode that converts the emission intensity of the diamond 31 into a voltage intensity, detects the fluorescence guided by the optical fiber 45, and outputs the detected fluorescence signal to the control unit 5. The voltmeter 47 converts the voltage signal (analog signal) of the photodiode into a digital signal in order to send it to the control unit 5, and outputs the converted signal to the control unit 5.

[0022] The control unit 5 is constituted by, for example, a microcomputer that combines a CPU (Central Processing Unit) that executes operations, a ROM (Read Only Memory) as a secondary storage device that records a program for the operations, and a RAM (Random Access Memory) as a temporary storage device that stores the progress of the operations and temporary control variables. By executing the stored program, it performs control over each component constituting the diamond sensor 1 and calculations related to the position detection of the magnetic field source 101.

[0023] For example, the control unit 5 is electrically connected to the laser light source 21 and the microwave source 6, respectively, and controls their operation timings, outputs, operation times, etc. Also, the control unit 5 detects the position of the magnetic field source 101 in the sample 100 based on the fluorescence signal detected by the photodetector 46. More specifically, the control unit 5 detects the position of the magnetic field source 101 in the sample 100 based on the change amount of the fluorescence intensity detected by the photodetector 46.

[0024] [Regarding the process leading to the present invention] Here, the background of the present invention will be described.

[0025] The inventor of the present application utilized the diamond sensor 1 using the above-described optical fiber and scanned the sample 100 two-dimensionally. As a result, the position of the magnetic field source 101 in the sample 100 could not be detected. The reason is considered to be that the fluctuation of the intensity of the entire two-dimensional fluorescence image obtained is large. More specifically, when scanning two-dimensionally using the diamond sensor 1, the optical fibers 23, 24, 41, and 45 vibrate slightly due to the influence of minute vibrations generated. When the optical fibers 23, 24, 41, and 45 vibrate, the efficiency of the fluorescence emitted from the diamond 31 reaching the detection unit 4 changes. Therefore, the fluctuation of the background intensity becomes large. In other words, the background noise is large due to the minute vibration of the optical fiber. As a result, it is considered that the detection accuracy is adversely affected. Here, the background refers to the sample.

[0026] In order to improve the detection accuracy of the diamond sensor 1, it is necessary to reduce the background noise caused by the minute vibration of the optical fiber. As described above, in order to suppress the minute vibration of the optical fiber, a method of firmly fixing the optical fiber is considered. However, when the optical fiber is fixed, a new problem of hindering the portability of the diamond sensor occurs.

[0027] Therefore, as a result of intensive research by the inventor of the present application, it has been found that the accuracy of detecting the position of the magnetic field source can be improved by detecting the position of the magnetic field source in the sample based on the amount of change in the fluorescence intensity in the same direction as the scanning direction of the excitation light with respect to the obtained fluorescence intensity, and the present invention has been completed.

[0028] [Regarding the method for detecting the position of a magnetic field source according to an embodiment] In order to realize the above, the method for detecting the position of a magnetic field source according to the present embodiment includes a fluorescence intensity acquisition step and a position detection step.

[0029] First, in the fluorescence intensity acquisition step, the laser light source 21 irradiates the diamond 31 with excitation light according to the command of the control unit 5. The excitation light is, for example, green laser light with a wavelength of 532 nm, and its power is, for example, 2 mW. Then, the green excitation light is guided by the first lens 22, the optical fiber 23, and the optical fiber 24, passes through the second lens 25 and the third lens 26, and is irradiated onto the diamond 31.

[0030] When the green excitation light is irradiated, red fluorescence is emitted from the NV center of the diamond 31. The emitted red fluorescence and a part of the green excitation light are guided to the filter 43 via the optical fiber 24, the optical fiber 41, and the first mirror 42. Since the filter 43 is configured to transmit only the red fluorescence emitted from the diamond 31 and not transmit other light, the red fluorescence passes through the filter 43, while the green excitation light and other light are cut off. Then, the red fluorescence that has passed through the filter 43 is further guided to the photodetector 46 by the second mirror 44 and the optical fiber 45.

[0031] Subsequently, the microwave source 6 irradiates and sweeps the microwave irradiation substrate 32 with microwaves according to the command of the control unit 5. When the microwaves are swept, the electron spin of the NV center causes optically detected magnetic resonance, and the red fluorescence emitted from the diamond 31 rapidly weakens. That is, at the resonance frequency, the intensity of the red fluorescence rapidly decreases. The photodetector 46 detects the red fluorescence and outputs the intensity of the detected fluorescence to the control unit 5.

[0032] Next, the positions of the sample 100 and the diamond 31 are relatively moved, and while two-dimensionally scanning the sample 100 with the excitation light through the diamond 31, the fluorescence emitted from the diamond 31 is detected. In the present embodiment, the sensor unit 3 in which the diamond 31 is disposed is fixed, and the sample 100 is scanned by moving the sample 100. However, the sample 100 may be scanned by fixing the sample 100 and moving the sensor unit 3, or the sample 100 may be scanned by moving both the sample 100 and the sensor unit 3. Note that, compared with the case of moving the sample 100, the detection field of view can be made wider by moving the sensor unit 3.

[0033] In the present embodiment, the sample 100 is scanned with the excitation light by moving the XY stage 82. Specifically, the sample 100 is moved in the X direction of the XY stage 82 with respect to the diamond 31. For example, as indicated by the arrow in FIG. 2, the excitation light is scanned from one end to the other end of the sample 100 along the X direction of the XY stage 82. Then, after reaching the other end of the sample 100, the position of the sample 100 is adjusted by the XY stage 82 so that the excitation light is shifted in the Y direction of the XY stage 82 and returned to one end of the sample 100. By repeating such an operation, the fluorescence emitted from the diamond 31 is detected while continuously scanning the entire main surface of the sample 100 with the laser light.

[0034] Note that the scanning of the excitation light and the acquisition of the fluorescence intensity are performed under the control of the control unit 5 according to, for example, the flowchart shown in FIG. 3.

[0035] First, in step S101, the control unit 5 starts the scanning of the excitation light with the scanning count N set to 0 (zero). In step S102 following step S101, the control unit 5 moves the Y-direction stage to the scanning start point. At this time, y = 0. As the Y-direction stage is moved, the sample 100 placed on the XY stage 82 also moves.

[0036] In step S103 following step S102, the control unit 5 moves the X-direction stage to the scanning start point. At this time, x = 0. As the X-direction stage is moved, the sample 100 placed on the XY stage 82 also moves.

[0037] In step S104 following step S103, fluorescence intensity is acquired. At this time, the detection unit 4 detects the fluorescence emitted from the diamond 31 at the scanning start point (x = 0, y = 0) and acquires the intensity of the detected fluorescence.

[0038] In step S105 following step S104, the control unit 5 moves the stage by Δx in the X direction and sets x to x + Δx. In step S106 following step S105, the control unit 5 determines whether x > x_max. x_max is a numerical value preset based on, for example, the dimension of the sample 100 in the X direction and is stored in the control unit 5.

[0039] If it is determined that x is less than or equal to x_max, the process returns to step S104 described above, and fluorescence acquisition is performed at the point (x = x + Δx, y = 0). On the other hand, if it is determined in step S106 that x is greater than x_max, the process proceeds to step S107 described above.

[0040] In step S107, the control unit 5 moves the stage by Δy in the Y direction and sets y to y + Δy. In step S108 following step S107, the control unit 5 determines whether y > y_max. y_max is a numerical value preset based on, for example, the dimension of the sample 100 in the Y direction and is stored in the control unit 5.

[0041] If it is determined that y is less than or equal to y_max, the process returns to step S103 described above, and then fluorescence acquisition is performed at the point (x = x + Δx, y = y + Δy) (step S104). On the other hand, if it is determined in step S108 that y is greater than y_max, the process proceeds to step S109 described above.

[0042] In step S109, the control unit 5 counts the number of scans and sets N to N+1. In step S110 following step S109, the control unit 5 determines whether N==N_max. N_max is a numerical value preset based on the dimensions of the entire sample 100 etc., and is stored in the control unit 5 in advance. In step S110, if it is determined that N!=N_max, the process returns to step S102, and the above-described steps S102 to S109 are repeatedly executed. On the other hand, if it is determined in step S110 that N==N_max, the process proceeds to step S111.

[0043] In step S111, the control unit 5 ends the scanning of the excitation light and stores the data output from the detection unit 4 (i.e., the fluorescence intensity of each acquired point).

[0044] Then, in the position detection step following the fluorescence intensity acquisition step, based on the amount of change in the fluorescence intensity in the same direction as the scanning direction of the excitation light with respect to the acquired fluorescence intensity, the position of the magnetic field source 101 in the sample 100 is detected. At this time, the control unit 5 first calculates the differential value only in the same direction as the scanning direction of the excitation light for the acquired two-dimensional fluorescence intensity distribution image (i.e., the two-dimensional magnetic field distribution image). Then, the control unit 5 obtains the square of the calculated differential value, and based on the obtained result, detects the position of the magnetic field source 101 in the sample 100.

[0045] Hereinafter, the position detection step will be described in detail with reference to FIG. 4. The process shown in FIG. 4 is performed, for example, under the control of the control unit 5.

[0046] First, in step S201, the control unit 5 sets i to 0 (zero) and starts detection. In step S202 following step S201, the control unit 5 sets i to i + 1 and calculates the derivative value only in the X direction of the i-th image. Here, the "i-th image" is, for example, the image of the fluorescence intensity of each point obtained in the fluorescence intensity acquisition step. For example, the control unit 5 takes the image of the fluorescence intensity of the point (x = 0, y = 0) sequentially obtained in the fluorescence intensity acquisition step, the image of the fluorescence intensity of the point (x = x + Δx, y = 0), the image of the fluorescence intensity of the point (x = x + Δx, y = y + Δy)... as the first image, the second image, the third image... and calculates the derivative value only in the X direction for each image of the fluorescence intensity.

[0047] In step S203 following step S202, the control unit 5 calculates the square of the derivative value calculated in step S202. In step S204 following step S203, the control unit 5 determines whether i == N_acc. N_acc is the number of integration times and is set based on, for example, the total number of points obtained in the fluorescence intensity acquisition step.

[0048] Then, in step S204, if it is determined that i!= N_acc, the process returns to step S202, and the calculation of the derivative value only in the X direction for the next image of the fluorescence intensity (step S202) and the calculation of the square of the calculated derivative value (step S203) are respectively executed. On the other hand, if it is determined in step S204 that i == N_acc, the process proceeds to step S205.

[0049] In step S205, the control unit 5 removes noise by performing an additive average on the data for the number of integration times N_acc. In step S206 following step S205, the control unit 5 performs image processing by binarizing using 1 / 2 of the maximum intensity value I_max as a threshold. Thereby, the detection is completed (step S207).

[0050] Here, based on FIG. 5, the calculation of the differential value (differentiation process) in step S202 will be described. FIG. 5 is a schematic diagram of a two-dimensional fluorescence intensity distribution for explaining the calculation of the differential value. The schematic diagram of the two-dimensional fluorescence intensity distribution shown in FIG. 5 is the one obtained in the above-described fluorescence intensity acquisition step, that is, a two-dimensional magnetic field distribution image (also referred to as a distribution image of two-dimensional fluorescence intensity). Note that c in FIG. 5 ij represents the fluorescence intensity of each point (x i , y j ). Also, the fluorescence intensity is proportional to the magnetic field intensity.

[0051] For example, when calculating the differential value only in the X direction (the scanning direction of the excitation light) with respect to the two-dimensional magnetic field distribution image, the difference between adjacent points in the X direction is taken, and the differential value of the point (x i , y j ) is calculated as c'ij as follows. That is, c' ij = (c i(j+1) - c i(j-1) ) / Δx = c i(j+1) - c i(j-1) (here, Δx = 1). Mathematically, Δx = 2 is appropriate, but in the subsequent processing, the coefficient part affecting the whole has no meaning (that is, it does not affect the results such as the SNR), so it is processed with only a simple difference with Δx = 1. Therefore, for example, when x = 2 and y = 2, c' 22 = c 23 - c 21 .

[0052] For reference, for example, when calculating the differential value only in the Y direction with respect to the two-dimensional magnetic field distribution image, the difference between adjacent points in the Y direction is taken, and the differential value of the point (x i , y j ) is calculated as c'ij as follows. That is, c' ij = (c (i+1)j - c (i-1)j ) / Δx = c (i+1)j - c (i-1)j (here, Δx = 1). Therefore, for example, when x = 2 and y = 2, c' 22 = c 32 - c 12 .

[0053] Also, for example, when calculating the differential values in the X and Y directions for a two-dimensional magnetic field distribution image, the differences between adjacent points in the X direction and adjacent points in the Y direction are taken, and the differential value c’ij of the point (x i , y j ) is calculated as follows. That is, c’ ij =={(c i(j+1) -c i(j-1) )+(c (i+1)j -c (i-1)j )} / Δx=(c i(j+1) -c i(j-1) )+(c (i+1)j -c (i-1)j ) (here, Δx = 1). Therefore, for example, when x = 2 and y = 2, c’ 22 =(c 23 -c 21 )+(c 32 -c 12 ).

[0054] In the magnetic field source position detection method according to this embodiment, since the position of the magnetic field source 101 in the sample 100 is detected based on the change amount of the fluorescence intensity in the same direction as the scanning direction of the excitation light, the background noise due to the minute vibration of the optical fibers 23, 24, 41, and 45 can be reduced. Moreover, since it is not necessary to fix the optical fibers 23, 24, 41, and 45, the portability of the diamond sensor 1 can be ensured. As a result, while maintaining the portability of the diamond sensor 1, the detection accuracy of the position of the magnetic field source 101 can be improved.

[0055] In particular, for the acquired two-dimensional fluorescence intensity distribution image, the differential value only in the same direction as the scanning direction of the excitation light is calculated, the square of the calculated differential value is obtained, and based on the obtained result, the position of the magnetic field source 101 in the sample 100 is detected. Therefore, the background noise due to the minute vibration of the optical fiber can be further reduced, and thus the detection accuracy of the position of the magnetic field source 101 can be further improved.

[0056] In addition, in the fluorescence intensity acquisition step, it is preferable to two-dimensionally scan the sample while applying an external magnetic field 7 in the scanning direction of the excitation light. Specifically, the direction of the polarity of the external magnetic field 7 is adjusted, and a magnetic field is applied to the sample 100 in the X direction. Then, with the magnetic field applied in the X direction, the sample 100 is scanned with the excitation light. By doing so, the signal-to-noise ratio can be increased (in other words, the signal-to-noise ratio can be improved), so that the detection accuracy of the position of the magnetic field source 101 can be further enhanced.

[0057] In addition, in the present embodiment, instead of calculating the square of the differential value (step S203), the absolute value of the calculated differential value may be obtained. Even in this case, the same operational effects can be obtained.

[0058] [Comparative Example and Example] The inventor of the present application conducted the following comparative examples and examples in order to verify the effects of the magnetic field source position detection method of the present embodiment.

[0059] [Comparative Example 1] In Comparative Example 1, based on the diamond sensor 1 shown in FIG. 1 above, changes were made as shown in FIG. 6. More specifically, in order to make the scanning of the excitation light easier, the optical fiber 24, the second lens 25, the third lens 26, the sensor unit 3 having the diamond 31, and the external magnetic field 7 were combined into one unit and integrated into the sensor head 9.

[0060] Next, using the diamond sensor 1 equipped with the sensor head 9, in accordance with the flowchart shown in FIG. 3 above, the foreign object 102 placed on the XY stage 82 was scanned (number of scans N = 9), the fluorescence emitted from the diamond 31 was detected, and a two-dimensional magnetic field distribution image was obtained. The foreign object 102 was, for example, a minute metal foil of 1 mm × 1 mm × 10 μm. Also, the distance between the upper surface of the XY stage 82 and the bottom surface of the diamond 31 was 0.8 mm.

[0061] Next, image processing was performed on the obtained two-dimensional magnetic field distribution image by the following conventional method, and the result is shown in FIG. 7(a).

[0062] The conventional method is different from the position detection step of the present embodiment in steps S202 and S203 shown in FIG. 4 above. Specifically, in the conventional method, instead of steps S202 and S203 shown in FIG. 4 above, between step 201 and step S204, steps such as "set i to i + 1 and calculate the average intensity I_mean of the entire i-th image", "calculate the difference between the intensity of each point and I_mean", and "calculate the absolute value of the intensity of each point" are provided in sequence. Note that steps S204 to S207 are the same as those of the present embodiment.

[0063] [Example 1] In Example 1, similar to Comparative Example 1, the foreign object 102 placed on the XY stage 82 was scanned (number of scans N = 9) using the diamond sensor 1 equipped with the sensor head 9, and a two-dimensional magnetic field distribution image was obtained. However, the position detection described in the present embodiment was performed on the obtained two-dimensional magnetic field distribution image. That is, in Example 1, position detection was performed on the obtained two-dimensional magnetic field distribution image using the flowchart shown in FIG. 4 above, and the result is shown in FIG. 7(b).

[0064] As can be seen by comparing FIG. 7(a) and FIG. 7(b), in the case of Comparative Example 1, the background noise was large and the foreign object 102 (i.e., the magnetic field source) could not be detected. However, in the case of Example 1, the foreign object 102 could be detected.

[0065] Also, as an index of the detection status, the detection performance was compared between Comparative Example 1 and Example 1 using the ratio (SN ratio) of the signal intensity of the foreign object to the background intensity (i.e., the degree of fluctuation of the signal intensity of the non-foreign object part). The SN ratio is calculated as S / N = (maximum value of the absolute value of the signal intensity of the foreign object) / (standard deviation of the signal intensity of the non-foreign object part). And the SN ratio of Comparative Example 1 was about 1. Therefore, in Comparative Example 1, since the signal intensity of the foreign object and the background intensity were almost equal, the position of the foreign object (in other words, the position of the magnetic field source) could not be specified. On the other hand, the SN ratio of Example 1 was 39.

[0066] From the results of Comparative Example 1 and Example 1, it was shown that the magnetic field source position detection method of the present embodiment can reduce background noise.

[0067] [Comparative Example 2, Comparative Example 3, Example 2, and Comparative Example 4] In addition, in order to clarify the effect of calculating only the differential value in the same direction as the scanning direction of the excitation light, the inventor of the present application conducted Comparative Example 2, Comparative Example 3, Example 2, and Comparative Example 4. In these comparative examples and examples, for the two-dimensional magnetic field distribution image obtained by the same method, image processing by the conventional method (Comparative Example 2), calculation of the differential value in the XY2 directions (Comparative Example 3), calculation of the differential value only in the X direction (that is, the same direction as the scanning direction of the excitation light) (Example 2), and calculation of the differential value only in the Y direction (Comparative Example 4) were performed, and the degree of fluctuation of the background intensity in each case was compared. Also, here, in order to compare only the background intensity, a two-dimensional magnetic field distribution image was obtained without placing a foreign object (that is, a magnetic field source), and the degrees of fluctuation of Comparative Example 2, Comparative Example 3, Example 2, and Comparative Example 4 were compared.

[0068] Specifically, first, using the diamond sensor 1 equipped with the above-described sensor head 9, in a state where no foreign object is placed on the XY stage 82 (that is, a state without the foreign object 102 shown in FIG. 6), scanning was performed according to the flowchart shown in FIG. 3 above (number of scans N = 1), fluorescence emitted from the diamond was detected, and a two-dimensional magnetic field distribution image was obtained.

[0069] Next, for the obtained two-dimensional magnetic field distribution image, those obtained by performing image processing by the above-described conventional method were used as Comparative Example 2, those obtained by calculating the differential values in the X and Y2 directions were used as Comparative Example 3, those obtained by calculating the differential value only in the X direction were used as Example 2, and those obtained by calculating the differential value only in the Y direction were used as Comparative Example 4.

[0070] FIG. 8(a) is a diagram showing the result of Comparative Example 2, FIG. 8(b) is a diagram showing the result of Comparative Example 3, FIG. 8(c) is a diagram showing the result of Example 2, and FIG. 8(d) is a diagram showing the result of Comparative Example 4. As can be seen by comparing these figures, when calculating the differential value only in the X direction for the two-dimensional magnetic field distribution image, the SN ratio could be increased and the background noise could be reduced.

[0071] Furthermore, as the degree of fluctuation of the background intensity in Comparative Example 2, Comparative Example 3, Example 2, and Comparative Example 4, the present inventors calculated the standard deviation of the entire image respectively, and summarized the obtained results in Table 1.

[0072] [Table 1]

[0073] As shown in Table 1, it was found that only in the case of Example 2, the fluctuation of the background intensity (in other words, background noise) can be significantly reduced.

[0074] [Examples 3, 4, and 5] In Examples 3, 4, and 5, similar to Example 1, the present inventors used the diamond sensor 1 equipped with the sensor head 9 to scan the foreign matter 102 placed on the XY stage 82 according to the flowchart shown in FIG. 3 above (the number of scans N = 9), and obtained a two-dimensional magnetic field distribution image. Next, position detection was performed on the obtained two-dimensional magnetic field distribution image according to the flowchart shown in FIG. 9.

[0075] The flowchart of the position detection shown in FIG. 9 is the same as the steps S201, S202, S204, S205, and S207 of the flowchart shown in FIG. 4 above in steps S301, S302, S304, S305, and S307, but is different from the flowchart shown in FIG. 4 above in steps S303 and S306. Here, only the different steps S303 and S306 will be described.

[0076] The additional process in step S303 is divided into three patterns. The pattern in which no additional process is performed on the differential value calculated in step S302 (that is, the differential value calculated in step S302 remains as it is) is Example 3, the pattern in which the absolute value is taken for the differential value calculated in step S302 is Example 4, and the pattern in which the absolute value is taken for the differential value calculated in step S302 and the difference from the average value of the intensity of the entire image is taken is Example 5.

[0077] On the other hand, step S306 is a step of calculating the SN ratio based on the results of steps S301 to S305.

[0078] Then, in Examples 3, 4, and 5, the additional process in step S303 was changed to three patterns, and the respective SN ratios were calculated, and the detection performances (i.e., SN ratios) of these examples were compared. Also, for comparison, the SN ratios of Comparative Example 1 and Example 1 described above were also calculated respectively. The results are summarized in Table 2.

[0079]

Table 2

[0080] As shown in Table 2, compared with Comparative Example 1, all of Examples 1, 3 to 5 had the effect of improving the SN ratio, and it was found that Example 1 had the most significant effect of improving the SN ratio.

[0081] As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention described in the claims.

Explanation of Reference Numerals

[0082] 1: Diamond sensor, 2: Excitation light irradiation unit, 3: Sensor unit, 4: Detection unit, 5: Control unit, 6: Microwave source, 7: External magnetic field, 8: Sample stage, 9: Sensor head, 21: Laser light source, 22: First lens, 23, 24, 41, 45: Optical fiber, 25: Second lens, 26: Third lens, 31: Diamond, 32: Microwave irradiation substrate, 42: First mirror, 43: Filter, 44: Second mirror, 46: Photodetector, 47: Voltmeter, 81: Base, 82: XY stage, 100: Sample, 101: Magnetic field source

Claims

1. A fluorescence intensity acquisition step of guiding excitation light from a light source through an optical fiber, irradiating a diamond, and two-dimensionally scanning a sample in a state where the diamond is irradiated, and acquiring the intensity of fluorescence emitted from the diamond; A position detection step of detecting the position of a magnetic field source in the sample based on the amount of change in the fluorescence intensity in the same direction as the scanning direction of the excitation light with respect to the acquired fluorescence intensity; A magnetic field source position detection method characterized by including the above.

2. The magnetic field source position detection method according to claim 1, wherein in the position detection step, a differential value only in the same direction as the scanning direction of the excitation light is calculated with respect to the acquired two-dimensional fluorescence intensity distribution image, and the position of the magnetic field source in the sample is detected based on the calculated differential value.

3. The magnetic field source position detection method according to claim 2, wherein in the position detection step, the square of the calculated differential value or the absolute value of the calculated differential value is obtained, and the position of the magnetic field source in the sample is detected based on the obtained result.

4. The magnetic field source position detection method according to any one of claims 1 to 3, wherein in the fluorescence intensity acquisition step, the sample is two-dimensionally scanned with an external magnetic field applied in the scanning direction of the excitation light.

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