A method for switching sensitivity of an NV color center magnetic sensor and a nondestructive testing device

Abstract

The present application relates to metal flaw detection technical field, especially a kind of NV color center magnetic sensor sensitivity switching method and nondestructive testing device, including detection optical fiber, diamond NV color center being connected at one end of detection optical fiber, microwave antenna being set at the outside of diamond NV color center, and radio frequency transmission line being connected with microwave antenna;Magnetizer is set at the periphery of probe assembly;Bicolor sheet is set at the end of detection optical fiber away from diamond NV color center;Light intensity modulator is installed in the reflection side of bicolor sheet;532nm laser is connected with light intensity modulator;Microwave module, microwave signal is output to probe assembly;Photoelectric detection module, including photoelectric diode being installed in the transmission side of bicolor sheet, and filter sheet being located between bicolor sheet and photoelectric diode and carrying out stray light filtering;Host computer;The frequency and power of microwave source are changed by the parameter fed back by photoelectric diode in detection working time period, and then the sensitivity of NV color center magnetic sensor is changed, and the current working environment is matched.

Description

Technical Field

[0001] The present invention relates to the technical field of metal flaw detection, and in particular to a sensitivity switching method of an NV color center magnetic sensor and a nondestructive testing device. Background Art

[0002] An NV color center (Nitrogen-Vacancy Center) is an atomic-level defect structure in diamond crystals, consisting of a nitrogen atom (N) and an adjacent vacancy. As a point defect in the diamond lattice, it possesses unique quantum mechanical and optical properties, leading to its important applications in numerous cutting-edge scientific fields.

[0003] The Chinese patent application number CN202111054892.X discloses metal non-destructive testing equipment, methods and storage media, including an NV color center sensor probe, which is arranged at a position to be tested on the object to be tested; a control device, which is connected to the NV color center sensor probe and is used to provide excitation to the NV color center sensor probe so that the NV color center sensor probe generates a fluorescence signal, and collects the fluorescence signal, and determines the damage condition of the object to be tested based on the fluorescence signal; the equipment provides excitation to the NV color center sensor probe arranged at the measuring position of the object to be tested so that the NV color center sensor probe generates a fluorescence signal, collects the fluorescence signal generated by the NV color center sensor probe, and determines the damage condition of the object to be tested based on the fluorescence signal generated by the NV color center sensor probe; the equipment has the advantages of small size, low cost, and can detect deep defects of the object to be tested.

[0004] However, the metal nondestructive flaw detection equipment disclosed in the above-mentioned Chinese patent is the same as the existing nondestructive testing equipment in that the sensitivity is generally fixed. Sensitivity is an unchangeable property of the sensor since its manufacture. However, in actual work, it is often necessary to select a sensor with appropriate sensitivity in advance according to the actual usage situation, and it cannot be changed thereafter. However, due to the different materials and shapes of the equipment, NV color center sensors with different sensitivities are required, and it is impossible to customize sensors with different sensitivities according to different objects. Therefore, a sensitivity switching method of an NV color center magnetic sensor and a nondestructive testing device are proposed to solve the above problems. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to solve the technical problem of fixed sensor sensitivity.

[0006] The above technical problem is solved by the following technical solution: The present invention proposes the following technical solution: a sensitivity switching method of an NV color center magnetic sensor, comprising:

[0007] Setting initial microwave parameters: setting initial microwave frequency and initial microwave power, the microwave source outputs the initial microwave frequency and initial microwave power, and the microwave acts on the NV color center magnetic sensor simultaneously with the external excitation light;

[0008] Obtain the number of outliers in the test results: Scan the surface of the object to be tested using the NV color center magnetic sensor and obtain the number of outliers N based on the outlier detection algorithm;

[0009] Adjust the sensitivity of the NV color center magnetic sensor: determine whether the initial number of outliers N falls within the reasonable number of outliers {N1, N2} in the comparison module. If N is less than N1, adjust the initial microwave power to increase the sensitivity of the NV color center magnetic sensor. If N is greater than N2, adjust the initial microwave power to reduce the sensitivity of the NV color center magnetic sensor.

[0010] Determine the sensitivity of the NV color center magnetic sensor: Repeat the microwave power adjustment until the number of outliers N falls into the reasonable number interval of outliers {N1, N2}, then the microwave power setting is completed and the sensitivity setting of the NV color center magnetic sensor is completed.

[0011] In a preferred embodiment of the sensitivity switching method of the NV color center magnetic sensor of the present invention, obtaining the initial microwave frequency specifically includes the following steps:

[0012] The ODMR pattern of the NV color center magnetic sensor is measured under zero magnetic field; the microwave frequency corresponding to the point with the maximum slope on the spectrum line is determined as the initial microwave frequency.

[0013] As a preferred embodiment of the method for switching the sensitivity of the NV color center magnetic sensor of the present invention, the method for adjusting the sensitivity of the NV color center magnetic sensor further comprises the following steps:

[0014] The initial microwave frequency is adjusted so that the number of outliers N falls within the reasonable number range of outliers {N1, N2}.

[0015] As a preferred implementation of the NV color center magnetic sensor sensitivity switching method of the present invention: when the microwave power is in the range of 10dbm-16dbm and the number of outliers N is still less than N1, the microwave power is no longer adjusted, and the initial microwave frequency is adjusted to change until the number of outliers N falls into the reasonable number range of outliers {N1, N2}.

[0016] The beneficial effect of the NV color center magnetic sensor sensitivity switching method of the present invention is that the frequency and power of the microwave source are changed by monitoring the parameters fed back by the photodiode during the working time period, thereby changing the sensitivity of the NV color center magnetic sensor to match the current working environment.

[0017] Another object of the present invention is to provide a non-destructive testing device, which aims to solve the problem that the sensitivity of conventionally designed NV color center magnetic measurement equipment cannot be changed.

[0018] To solve the above technical problems, the present invention further provides the following technical solutions: a non-destructive testing device, comprising an NV color center magnetic sensor sensitivity switching method; comprising:

[0019] A probe assembly includes a detection optical fiber, a diamond NV color center connected to one end of the detection optical fiber, a microwave antenna arranged outside the diamond NV color center, and a radio frequency transmission line connected to the microwave antenna;

[0020] a magnetizing assembly, comprising a magnetizer disposed on the periphery of the probe assembly;

[0021] A dual-color plate is provided at one end of the detection optical fiber away from the diamond NV color center;

[0022] A laser module comprising a light intensity modulator mounted on the reflective side of the dichroic plate and a nm laser connected to the light intensity modulator;

[0023] A microwave module, used for outputting microwave signals to the probe assembly;

[0024] A photoelectric detection module, comprising a photodiode mounted on the transmission side of the dichroic plate, and a filter located between the dichroic plate and the photodiode for filtering out stray light;

[0025] The host is electrically connected to the photodiode and the microwave module.

[0026] As a preferred embodiment of the nondestructive testing device of the present invention, the microwave module includes a microwave circulator arranged at an end of the radio frequency transmission line away from the microwave antenna, a microwave amplifier connected to the microwave circulator, and a microwave source connected to the microwave amplifier.

[0027] As a preferred solution of the nondestructive testing device of the present invention, the magnetizer is a permanent magnet or an energized coil.

[0028] As a preferred solution of the non-destructive testing device of the present invention, a probe cover is provided on the outer surface of the magnetizer.

[0029] As a preferred solution of the nondestructive testing device of the present invention, the host further comprises a microwave automatic control module for automatically adjusting the microwave power and / or microwave frequency of the microwave module.

[0030] As a preferred solution of the nondestructive testing device of the present invention, a signal noise reduction module is provided inside the host.

[0031] The beneficial effect of the nondestructive testing device of the present invention is that nondestructive testing of an object can be achieved through the redesigned nondestructive testing device, and the sensitivity of the sensor can be changed by changing the power and frequency of the microwave source. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention. Obviously, the drawings described below only relate to some embodiments of the present invention, and are not intended to limit the present invention.

[0033] Figure 1 This is a flow chart of sensitivity switching of the NV color center magnetic sensor in the present invention.

[0034] Figure 2 This is a schematic diagram of microwave power and NV color center sensitivity in the present invention.

[0035] Figure 3 This is the zero magnetic field ODMR spectrum diagram of the present invention.

[0036] Figure 4 It is a schematic diagram of the overall structure of a nondestructive testing device in the present invention.

[0037] Figure 5 Schematic diagram of the structure of the magnetization component in the present invention.

[0038] Figure 6 Schematic diagram of the structure of the probe assembly in the present invention.

[0039] In the figure: 1. Probe assembly; 111. Detection optical fiber; 112. RF transmission line; 113. Diamond NV color center; 114. Microwave antenna; 2. Magnetization assembly; 21. Probe cover; 22. Magnetizer; 3. 532nm laser; 4. Light intensity modulator; 5. Dichroic plate; 6. Filter; 7. Photodiode; 8. Main unit; 9. Signal noise reduction module; 10. Microwave source; 11. Microwave circulator; 12. Microwave amplifier. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to specific embodiments and the accompanying drawings.

[0041] The terms used in the present invention are those commonly used in the art in view of the functions of the present invention, but these terms may vary according to the intentions of those skilled in the art, precedents, or new technologies in the art. In addition, specific terms may be selected by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the present invention. Therefore, the terms used in the specification should not be understood as simple names, but rather as the meanings of the terms and the overall description of the present invention.

[0042] Example 1, with reference to Figures 1-6 This embodiment provides a sensitivity switching method for an NV color center magnetic sensor, including:

[0043] Set the initial microwave parameters: Set the initial microwave frequency and initial microwave power. The microwave source outputs the initial microwave frequency and initial microwave power. The microwave and the external excitation light act on the NV color center magnetic sensor at the same time.

[0044] Since there is a zero-field splitting energy D between the m_s=0 state and the m_s=±1 state of the NV color center magnetic sensor, usually D≈2.87 GHz‌, when the frequency of the microwave field matches the energy difference between the energy levels, a resonant transition will occur. The initial microwave frequency of the NV color center magnetic sensor is set according to this characteristic. Based on laboratory data, a frequency of 2.87GHz±400MHz can generally ensure that the NV color center magnetic sensor can detect normally and obtain test results. We can set any value as the initial microwave frequency here, such as 2.871GHz; the initial microwave power can generally be between -20dbm and 20dbm, depending on the detection requirements. If the accuracy requirements of the structure to be tested are high, it can be started at high power, otherwise it can be started at low power.

[0045] Obtain the number of outliers in the test results: Scan the surface of the object to be tested using the NV color center magnetic sensor and obtain the number of outliers N based on the outlier detection algorithm;

[0046] When using an NV color-center magnetic sensor to detect an object, if the sensitivity of the NV color-center magnetic sensor does not match the object, this usually manifests as a sudden change in the output value. In this case, an outlier detection algorithm is used to detect the number of sudden changes in the output value. Since the outlier detection algorithm is a conventional technology, it will not be described in detail here.

[0047] The value of microwave power is different for different measurement sensitivity requirements.

[0048] For example, we found in the experiment that Figure 2 As shown in the figure, when the microwave power is in the range of 10dBm-16dBm, the sensitivity of the NV color center magnetic sensor is the highest. Based on this data, in the abnormal value judgment step, if the initial microwave power is less than 10dBm or greater than 16dBm, if the number of abnormal values ​​N is less than N1, it means that the sensitivity of the NV color center magnetic sensor is not high enough. At this time, we adjust the microwave power to tend to the range of 10dBm-16dBm. If N is greater than N1, it means that the sensitivity of the NV color center magnetic sensor is too high. At this time, we adjust the microwave power to stay away from the range of 10dBm-16dBm. Considering the power consumption issue, it is sufficient to adjust it in the low power direction.

[0049] In specific implementation, the microwave power is changed by step adjustment, and each step adjustment span is 0.5dBm.

[0050] Determine the sensitivity of the NV color center magnetic sensor: Repeat the microwave power adjustment until the number of outliers N falls into the reasonable number interval of outliers {N1, N2}, then the microwave power setting is completed and the sensitivity setting of the NV color center magnetic sensor is completed.

[0051] The number of outliers corresponds to the number of defects present on the tested part.

[0052] The method proposed in this example can be applied to places with different detection sensitivity requirements. For example, for the retrieval of cracks on the surface of a wheel, if the defect size required to be detected is above the millimeter level, the corresponding detection sensitivity is actually relatively low. At this time, if the equipment maintains high sensitivity, the number of detected abnormal values ​​will inevitably exceed the actual demand, and it is necessary to switch to low sensitivity mode; in addition to millimeter-level defects, small defects at the micron level will also be detected, which does not meet the requirements. However, if the defect size to be detected is above the micron level, if the equipment maintains low sensitivity, it will not be able to detect micron-level defects, and it is necessary to switch to high sensitivity mode.

[0053] Taking into account that microwave frequency can also affect measurement sensitivity, we can consider designing the initial microwave frequency. In a preferred embodiment, the initial microwave frequency is obtained by measuring the ODMR diagram of the NV color center magnetic sensor under zero magnetic field; finding the microwave frequency corresponding to the point with the maximum slope on the spectrum line; and using the microwave frequency corresponding to the point with the maximum slope on the spectrum line as the initial microwave frequency. This microwave frequency design can ensure that the NV color center magnetic sensor has a certain degree of initial measurement sensitivity.

[0054] Example 2, reference Figures 1 to 6 , which is the second embodiment of the present invention, is different from the previous embodiment in that it also includes further changing the measurement sensitivity by microwave frequency.

[0055] Specifically, obtaining the initial microwave frequency includes the following steps:

[0056] Measure the ODMR pattern of the NV color center magnetic sensor under zero magnetic field;

[0057] The microwave frequency corresponding to the point with the maximum slope on the spectrum line is determined as the initial microwave frequency.

[0058] Furthermore, adjusting the sensitivity of the NV color center magnetic sensor specifically includes the following steps:

[0059] The initial microwave frequency is adjusted so that the number of outliers N falls within the reasonable number range of outliers {N1, N2}.

[0060] The specific explanation is as follows:

[0061] Although microwave power has a greater impact on the sensitivity of NV color center magnetic sensors than microwave frequency, generally the power can be changed directly; however, microwave frequency can also affect the measurement sensitivity, as shown in the following figure. Figure 3 The microwave frequency corresponding to the point with the maximum slope in the graph has better measurement sensitivity. The NV color center magnetic sensor has the highest sensitivity at this point. Therefore, in the initial stage, we measured the ODMR graph at zero magnetic field. The ODMR graph, or optically detected magnetic resonance graph, is a spectrum that detects the magnetic resonance phenomenon of a material through optical means. Combining magnetic resonance technology and optical detection methods, it is mainly used to study the spin states, defect structures, or energy level characteristics of quantum systems in materials. The ODMR graph reflects the relationship between the optical signal (such as fluorescence intensity) and the magnetic field or frequency of the sample under the influence of a specific microwave frequency or magnetic field. When the applied magnetic field or microwave frequency matches the energy level transition of a specific spin state in the sample, resonant absorption is triggered, resulting in a change in fluorescence intensity, forming characteristic peaks or valleys in the graph. The optimal microwave frequency is determined from the ODMR graph. Subsequent measurements are performed at this optimal microwave frequency, and the sensitivity is adjusted by adjusting the microwave power. In subsequent measurements, if the sensitivity adjustment caused by changing the microwave power does not meet the required level, the microwave frequency can be adjusted during the measurement to further change the sensitivity.

[0062] Furthermore, when the microwave power is within the range of 10dBm-16dBm and the number of outliers N is still less than N1, the microwave power is no longer adjusted. At this time, the initial microwave frequency is adjusted until the number of outliers N falls into the reasonable number range of outliers {N1, N2}. This situation indicates that relying solely on power adjustment cannot meet the sensitivity requirements. At this time, it is necessary to adjust the microwave frequency for higher sensitivity.

[0063] Example 3, reference Figures 1 to 6 , which is the third embodiment of the present invention, further provides a nondestructive testing device, which applies a sensitivity switching method of an NV color center magnetic sensor; comprising:

[0064] The probe assembly 1 includes a detection optical fiber 111, a diamond NV center 113 connected to one end of the detection optical fiber 111, a microwave antenna 114 arranged outside the diamond NV center 113, and a radio frequency transmission line 112 connected to the microwave antenna 114.

[0065] The magnetizing assembly 2 includes a magnetizer 22 disposed on the periphery of the probe assembly 1; preferably, the magnetizer 22 is a permanent magnet or an energized coil.

[0066] The dichroic plate 5 is arranged at the end of the detection optical fiber 111 away from the diamond NV color center 113 .

[0067] The laser module includes a light intensity modulator 4 installed on the reflection side of the dichroic plate 5 and a 532nm laser 3 connected to the light intensity modulator 4.

[0068] The microwave module is used to output microwave signals to the probe assembly 1 .

[0069] The photoelectric detection module includes a photodiode 7 mounted on the transmission side of the dichroic plate 5, and a filter 6 located between the dichroic plate 5 and the photodiode 7 to filter out stray light;

[0070] The host 8 is electrically connected to the photodiode 7 and the microwave module.

[0071] In another example, a microwave module includes a microwave circulator 11 disposed at one end of a radio frequency transmission line 112 away from a microwave antenna 114, a microwave amplifier 12 connected to the microwave circulator 11, and a microwave source 10 connected to the microwave amplifier 12. The microwave source 10 generates a microwave signal, the microwave amplifier 12 amplifies the microwave power, and the microwave circulator 11 prevents reverse transmission of the microwave signal.

[0072] In another example, the magnetizer 22 is a permanent magnet or a powered coil.

[0073] In another example, a probe cover 21 is provided on the outer surface of the magnetizer 22. The probe cover 21 can isolate the magnetizer 22 and prevent the magnetizer 22 from being affected by the external environment.

[0074] In another example, the main unit 8 further includes a microwave automatic control module for automatically adjusting the microwave power and / or microwave frequency of the microwave module. Compared with manual adjustment, controlling the microwave module through the microwave automatic control module is simpler and more labor-saving.

[0075] In another example, a signal noise reduction module 9 is provided inside the host 8. The signal noise reduction module 9 can filter the data to avoid the influence of abnormal data.

[0076] Usage process: 532nm laser 3, light intensity modulator 4 and dichroic plate 5 are set on the same straight line, 532nm laser 3 emits laser, which is modulated by light intensity modulator 4 and then irradiates dichroic plate 5, and is reflected into the optical fiber; microwave source 10, microwave circulator 11 and microwave amplifier 12 are connected by radio frequency line; radio frequency line can stably transmit microwaves; the other end of dichroic plate 5 is connected to filter 6, and the other end of filter 6 is connected to photodiode 7; light penetrating dichroic plate 5 is filtered by filter 6 for stray light and then received by photodiode 7, and converted into electrical signal, so that host 8 can receive light data; photodiode 7 is connected to host 8 through data line; host 8 receives electrical signal converted by photodiode 7, and electrical signal is then received by host 8 for subsequent processing, and the number N of abnormal values ​​is obtained based on abnormal value detection algorithm; the initial abnormal value is judged. Whether the number of constant values ​​N falls into the reasonable number interval of outliers {N1, N2} in the comparison module, if N is less than N1, the microwave power of the microwave source 10 is adjusted to improve the sensitivity of the NV color center magnetic sensor; if N is greater than N2, the microwave power of the microwave source 10 is adjusted to reduce the sensitivity of the NV color center magnetic sensor; repeat the adjustment of the microwave power of the microwave source 10 until the number of outliers N falls into the reasonable number interval of outliers {N1, N2}, then the sensitivity of the NV color center magnetic sensor meets the detection sensitivity of the object, thereby obtaining the non-destructive testing data of the object, when the microwave power is in the range of 10dbm-16dbm, and N is still less than N1, then start to adjust the size of the initial microwave frequency until the number of outliers N falls into the reasonable number interval of outliers {N1, N2}, and the sensitivity adjustment of the NV color center magnetic sensor is completed.

[0077] Finally, it should be pointed out that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways without departing from the scope of the present invention.

Claims

1. A sensitivity switching method for an NV color center magnetic sensor, characterized in that: include: Setting initial microwave parameters: setting initial microwave frequency and initial microwave power, the microwave source outputs the initial microwave frequency and initial microwave power, and the microwave acts on the NV color center magnetic sensor simultaneously with the external excitation light; Obtain the number of outliers in the test results: Scan the surface of the object to be tested using the NV color center magnetic sensor and obtain the number of outliers N based on the outlier detection algorithm; Adjust the sensitivity of the NV color center magnetic sensor: determine whether the initial number of outliers N falls within the reasonable number of outliers {N1, N2} in the comparison module. If N is less than N1, adjust the initial microwave power to increase the sensitivity of the NV color center magnetic sensor. If N is greater than N2, adjust the initial microwave power to reduce the sensitivity of the NV color center magnetic sensor. Determine the sensitivity of the NV color center magnetic sensor: Repeat the microwave power adjustment until the number of outliers N falls within the reasonable number interval {N1, N2}. The microwave power setting is completed, and the sensitivity setting of the NV color center magnetic sensor is completed. The method of adjusting the sensitivity of the NV color center magnetic sensor further includes the following steps: Adjust the initial microwave frequency so that the number of outliers N falls within the reasonable number interval of outliers {N1, N2}; When the microwave power is within the range of 10dBm-16dBm and the number of outliers N is still less than N1, the microwave power is no longer adjusted. At this time, the initial microwave frequency is adjusted until the number of outliers N falls into the reasonable number range of outliers {N1, N2}.

2. A sensitivity switching method for an NV color center magnetic sensor according to claim 1, characterized in that: Obtaining the initial microwave frequency specifically includes the following steps: Measure the ODMR pattern of the NV color center magnetic sensor under zero magnetic field; The microwave frequency corresponding to the point with the maximum slope on the spectrum line is determined as the initial microwave frequency.

3. A nondestructive testing device, characterized in that: A sensitivity switching method for an NV color center magnetic sensor according to any one of claims 1 to 2 is applied; comprising: A probe assembly (1) comprises a detection optical fiber (111), a diamond NV color center (113) connected to one end of the detection optical fiber (111), a microwave antenna (114) arranged outside the diamond NV color center (113), and a radio frequency transmission line (112) connected to the microwave antenna (114); A magnetizing assembly (2) comprising a magnetizer (22) disposed on the periphery of the probe assembly (1); A two-color plate (5) is arranged at one end of the detection optical fiber (111) away from the diamond NV color center (113); A laser module comprising a light intensity modulator (4) mounted on the reflection side of the dichroic plate (5), and a 532nm laser (3) connected to the light intensity modulator (4); A microwave module, used for outputting microwave signals to the probe assembly (1); A photoelectric detection module comprises a photodiode (7) mounted on the transmission side of the dichroic plate (5), and a filter (6) located between the dichroic plate (5) and the photodiode (7) for filtering stray light; A host (8) is electrically connected to the photodiode (7) and the microwave module, and the host (8) further includes a microwave automatic control module for automatically adjusting the microwave power and / or microwave frequency of the microwave module; A signal noise reduction module (9) is provided inside the host (8).

4. A nondestructive testing device according to claim 3, characterized in that: The microwave module comprises a microwave circulator (11) arranged at one end of the radio frequency transmission line (112) away from the microwave antenna (114), a microwave amplifier (12) connected to the microwave circulator (11), and a microwave source (10) connected to the microwave amplifier (12).

5. A nondestructive testing device according to claim 4, characterized in that: The magnetizer (22) is a permanent magnet or an energized coil.

6. A nondestructive testing device according to claim 5, characterized in that: The outer surface of the magnetizer (22) is provided with a probe cover (21).

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