Magnetic flux leakage detection device based on minimum sampling period

Abstract

The invention relates to a magnetic flux leakage detection device based on a minimum sampling period. The magnetic flux leakage detection device comprises a magnetizer, a diamond block containing an NV color center, a laser module, a microwave module, a photoelectric detector, a data acquisition module, a data processing module and a main control module. Wherein the data acquisition module samples according to a minimum sampling period, at least one group of paired magnetic characterization frequencies is acquired in the period, the total sampling frequency is greater than or equal to 3 times, the data processing module calculates the microwave center frequency of temperature drift suppression through the paired frequencies, and the rest of sampling data and the center frequency are subtracted to obtain magnetic field noise reduction characterization data. The device has the advantages that while the temperature drift suppression effect is kept, the magnetic measurement sampling rate and the detection speed are greatly improved, the signal acquisition precision is optimized, the magnetic flux leakage sensing capability is enhanced, the device adapts to detection of various to-be-detected objects such as planes and circumferential surfaces, the software and hardware implementation difficulty is low, and the detection efficiency and universality are both good.

Description

Technical Field

[0001] This invention belongs to the field of magnetic flux leakage detection technology, specifically relating to a magnetic flux leakage detection device based on the minimum sampling period. Background Technology

[0002] In recent years, the research and application of solid-state spin center systems in the field of quantum precision detection have developed rapidly. Among them, diamond nitrogen-vacancy (NV) centers, due to their stable quantum spin characteristics at room temperature, have become the core carrier for precise magnetic field sensing. The diamond NV center sensing method based on optically probed magnetic resonance (ODMR) technology has been widely used in high-sensitivity magnetic field measurement, providing a new technical path for magnetic flux leakage detection in the field of nondestructive testing. Magnetic flux leakage detection, as an important branch of nondestructive testing, achieves defect identification and condition assessment by detecting the magnetic field signal leaked at defects in ferromagnetic test objects. It plays an irreplaceable role in industrial manufacturing, equipment maintenance, and other fields. Combining diamond NV center quantum sensing technology with magnetic flux leakage detection can break through the sensitivity bottleneck of traditional magnetic flux leakage detection and achieve precise detection of micro- and nano-scale defects.

[0003] The core of diamond NV center magnetic field sensing based on ODMR technology is to quantize the magnetic field by utilizing the linear correlation between the external magnetic field and the spin resonance frequency of the NV center, and its ground state energy level. Corresponding to a pair of left and right microwave resonant frequencies, the difference between these frequencies is positively correlated with the external magnetic field, and it can effectively suppress the spin resonant frequency drift caused by temperature changes. Therefore, it has become a key means in the existing technology to eliminate temperature errors and calculate magnetic field values. However, this traditional data processing method has significant technical defects: it is necessary to collect the two pairs of resonant frequencies separately, and only by performing a double-point sampling can an effective magnetic field value be calculated. This results in the magnetic field sampling rate being only half that of the frequency sampling rate, which greatly limits the speed and bandwidth of magnetic field measurement.

[0004] In scenarios such as rapid defect screening on industrial production lines and real-time non-destructive monitoring of high-speed equipment, the requirements for speed and dynamic response capabilities in magnetic flux leakage (MFL) detection are extremely high. Low magnetic field sampling rates cannot meet the needs for rapid and accurate measurement, becoming a core technological barrier for the large-scale application of diamond NV center quantum sensing technology in the field of MFL detection. Meanwhile, the magnetization devices in traditional MFL detection are prone to magnetic field interference to the sensing probe. The MFL signal at some defects in the test object is weak and easily affected by the ambient magnetic field, further reducing the efficiency and accuracy of detection. Conventional ODMR signal detection methods also suffer from high noise and low resonant frequency capture efficiency, making it difficult to match the measurement accuracy requirements under high sampling rates. Therefore, improving the magnetic field sampling rate of the diamond NV center sensing structure while maintaining temperature suppression and ensuring measurement accuracy, and optimizing the magnetic excitation, magnetic focusing, and signal detection stages of MFL detection, has become a key research direction for promoting the practical application of quantum sensing technology in the field of non-destructive testing.

[0005] Patent CN119023703A discloses a non-destructive testing method and a magnetic flux leakage detection device based on the minimum sampling period. By combining a diamond NV color center that can generate a wide-field fluorescence signal with a wide-field camera for sensing and detection, a dual working mode of rapid inspection and fine imaging is designed. For defect-free areas, rapid inspection electrical signals are quickly screened by averaging / taking extreme values. For suspected defect areas, the two-dimensional imaging mode is switched to obtain the defect morphology, realizing the combination of wide-field rapid detection and accurate defect imaging. This solves the problems of small coverage area and low computational efficiency caused by redundancy of wide-field detection data in traditional diamond NV color center detection. However, the problem of limited magnetic field sampling rate still exists. It does not optimize the sampling and data processing method for the spin resonance frequency of NV color centers. The magnetic field sampling rate is still half of the frequency sampling rate, which cannot meet the high requirements of magnetic field measurement speed and bandwidth in industrial rapid inspection scenarios. At the same time, it does not solve the technical problem of temperature drift interference on resonance frequency measurement and high sampling rate.

[0006] Patent CN119534461A discloses a defect detection method and device based on NV color centers. This invention preprocesses the fluorescent electrical signal of diamond NV color center magnetic flux leakage detection to filter out abnormal signals, optimizes the signal by combining high-pass filtering and wavelet denoising, and then determines the defect location by signal-to-noise ratio and establishes a formula to calculate the depth and width of the defect, thus realizing quantitative defect detection based on NV color centers. This effectively improves the reliability of detection data and the accuracy of defect identification, thereby solving the problems of traditional NV color center defect detection being only qualitative, the detection signal being easily interfered with, and quantitative detection relying on expensive vision equipment. However, it still has the problem of limited magnetic field sampling rate. It uses fixed frequency microwave for magnetic flux leakage detection, does not optimize the sampling method of resonant frequency and data processing logic, and the magnetic field sampling rate is still half of the frequency sampling rate. The measurement speed is difficult to match the needs of high-speed detection scenarios, and the magnetic field sampling rate is not improved while ensuring temperature suppression effect.

[0007] In summary, the traditional magnetic field sampling rate is only half that of the standard sampling rate, resulting in low measurement efficiency. There is an urgent need for a better magnetic flux leakage detection device based on the minimum sampling period to improve measurement efficiency. Summary of the Invention

[0008] The present invention aims to solve the problem of low detection efficiency in the current field of nondestructive testing.

[0009] The present invention solves the above-mentioned technical problems through the following technical means:

[0010] A magnetic flux leakage detection device based on a minimum sampling period includes a magnetizer, a diamond block, a photodetector, and a light source, as well as a data acquisition module, a data processing module, and a main control module. The signal acquisition end of the photodetector faces the fluorescence output surface of the diamond block. The data acquisition module, data processing module, and main control module are electrically connected in sequence. The diamond block contains an NV color center, and two pairs of magnetic characterization frequencies of the NV color center are set as two selectable data sampling points. The data acquisition module samples analog data and is configured to repeatedly sample the data sampling points according to the minimum sampling period. In each minimum sampling period, at least one pair of magnetic characterization frequencies are sampled, and the total number of samplings is not less than three. The data processing module is used to perform independent calculations on the sampled data obtained in each minimum sampling period. The independent calculation process includes: calculating the microwave center frequency used to suppress temperature drift using a pair of magnetic characterization frequencies, subtracting the other sampled data from the microwave center frequency in sequence, obtaining the difference value, and using it as the magnetic field noise reduction characterization data output in the minimum sampling period.

[0011] By adding data acquisition, processing, and main control modules, and relying on the minimum sampling period design, the temperature drift suppression center frequency is calculated only through a pair of magnetic characterization frequencies within a single cycle. The magnetic field data is obtained by subtracting the remaining sampling data from this center frequency. This not only preserves the temperature drift suppression effect but also breaks the traditional limitation of "two pair of frequency samplings are required for one magnetic field value," significantly improving the magnetic measurement sampling rate and thus significantly increasing the speed of non-destructive testing of magnetic flux leakage. At the same time, it achieves coordinated control of each module and efficient data processing.

[0012] Preferably, it also includes a microwave module and a lock-in amplifier. The microwave module is used to output frequency-modulated microwaves, and its microwave radiating end is arranged close to the periphery of the diamond block. The lock-in amplifier is located inside the main control module and is used for data demodulation.

[0013] The frequency-modulated microwave output from the microwave module can precisely control the spin state of the NV color center. The lock-in amplifier demodulates the data, converting the optical fluorescence signal into a high signal-to-noise ratio electrical error signal, thereby improving the magnetic field sensitivity and dynamic response capability of the NV color center sensor and making the sampling data more accurate.

[0014] Preferably, it also includes a frequency tracking module located inside the main control module. This frequency tracking module is used to lock the microwave frequency output by the microwave module to the spin resonant frequency of the NV color center.

[0015] The frequency tracking module can automatically and instantly lock the microwave frequency to the spin resonance frequency of the NV color center, eliminating the need for periodic spectrum scanning to find the resonance point. The resonance frequency drift caused by magnetic field changes can be quickly compensated, and the microwave frequency value can be directly used as a continuous magnetic field reading, enabling the sampling rate to break through to the kHz or even MHz level, further improving the real-time performance and continuity of the detection.

[0016] Preferably, the data acquisition module alternately samples two data sampling points, which is defined as a sampling period. The duration of the minimum sampling period is not greater than a preset time T, and the temperature change amplitude of the non-actively heated environment within the preset time T is not higher than 0.1K.

[0017] The minimum sampling period is limited to no more than a preset time T. Within this preset time, the temperature change amplitude of the non-actively heated environment is no higher than 0.1K. At this time, the center frequency shift caused by temperature can be ignored, and the temperature noise during this period can be regarded as the same value. Temperature interference can be effectively eliminated by subtraction. While maintaining a high sampling rate, the accuracy of magnetic field measurement is ensured, achieving a balance between sampling speed and detection accuracy.

[0018] Preferably, a set of paired magnetic characterization frequencies used to determine the microwave center frequency for suppressing temperature drift are the first two sampled data within each minimum sampling period. Subsequent sampled data within the same minimum sampling period are simultaneously subtracted from the microwave center frequency at the end of the acquisition to obtain magnetic field noise reduction characterization data.

[0019] The first two sampled data within the minimum sampling period are used as the paired magnetic characterization frequencies for calculating the center frequency. After subsequent sampled data are collected, the difference between the magnetic field data and the center frequency is calculated immediately. There is no need to wait for all samples within the period to be completed before unified calculation, which greatly shortens the output delay of magnetic field data, improves the real-time performance of data processing, and makes the feedback of magnetic flux leakage detection results faster, making it suitable for high-speed detection conditions.

[0020] Preferably, the selected sampling points are the same from the start of the second sampling to the end of each minimum sampling period.

[0021] Within the minimum sampling period, the same sampling point is selected from the second sampling onwards, with only one out-of-point sampling at the beginning of the period. This simplifies the design of the data acquisition program and the judgment of sampling rules, reduces the complexity of hardware control, and ensures that the calculation benchmark of subsequent magnetic field data remains consistent. No additional absolute value conversion or other operations are required, reducing the number of data processing steps, improving computational efficiency, and ensuring the consistency of output data.

[0022] Preferably, the magnetic characterization frequency is the spin resonance frequency of the NV color center or the microwave frequency corresponding to the point of maximum slope on the ODMR spectrum.

[0023] Not only can the spin resonance frequency of the NV color center be selected, but the microwave frequency at the point of maximum slope on the ODMR spectrum can also be selected to adapt to the frequency identification and sampling requirements under different detection scenarios, thereby improving the versatility and adaptability of the device. Moreover, the frequency characteristics at the point of maximum slope are more obvious, making it easier to quickly capture sampling data.

[0024] Preferably, it also includes a magnetizer for focusing the leakage magnetic field, wherein the diamond block is located within the focusing magnetic field of the magnetizer.

[0025] The magnetic field amplifies the leakage magnetic field at the defect, enhancing the device's ability to detect weak leakage magnetic fields and expanding the measurement range. At the same time, it can effectively shield the interference of external environmental magnetic fields, reduce the influence of stray environmental magnetic fields on NV color center sensing, and further improve the signal-to-noise ratio and accuracy of magnetic field measurement.

[0026] Preferably, the magnetic focusing direction of the magnetizer is parallel to the axis of the NV color center.

[0027] This arrangement allows the external magnetic field to activate the two NV color centers. The energy levels are symmetrically separated, and the ODMR spectrum presents two symmetrical resonance peaks, which facilitates the accurate identification of the difference between the magnetic characterization frequency and the calculated frequency, making the measurement results of the magnetic field size more accurate and reducing the detection error caused by the asymmetry of energy level splitting.

[0028] Preferably, the magnetizer is a ring-shaped magnetizer with a magnetizing gap.

[0029] The advantages of this invention are: (1) Significantly improved sampling rate: Abandoning the traditional mode of “two pairs of frequency sampling to calculate one magnetic field value”, by setting the minimum sampling period, only one pair of magnetic characterization frequencies are used in a single period to calculate the temperature drift suppression center frequency, and the remaining sampling data are subtracted from the center frequency to obtain effective magnetic field data. While retaining the temperature drift suppression effect, the magnetic sampling rate is no longer limited to half of the frequency sampling rate, thus achieving a core improvement in detection speed and adapting to the needs of rapid non-destructive testing scenarios; (2) More accurate sampling data: On the one hand, by using the time limit of the minimum sampling period, the temperature change within the period is ensured to be negligible, and the temperature drift interference can be uniformly eliminated, thus solving the problem of spin resonance frequency drift caused by temperature; on the other hand, it can be equipped with a lock-in amplifier and frequency tracking module to realize signal noise reduction and real-time microwave frequency locking, breaking through the noise bottleneck of direct optical detection, and making the resonance frequency sampling more accurate, thus ensuring the accuracy of magnetic field measurement from both data processing and signal acquisition dimensions. (3) Strong real-time performance: The design of the operation logic of calculating the center frequency of the first two sampling data and the real-time difference of the subsequent sampling data greatly shortens the output delay of magnetic field data and improves the real-time feedback capability of the detection results; at the same time, the rule of sampling at different points once per cycle and sampling at the same points for the rest simplifies the program design and hardware control logic of data acquisition, reduces the extra steps of data processing, reduces the difficulty of software and hardware implementation of the device, and improves the stability of operation. (4) Enhanced magnetic field sensing: The addition of a magnetic concentrator and optimization of its design in conjunction with the NV color center not only amplifies the weak leakage magnetic field at the defect, expanding the magnetic field measurement range of the device, but also effectively detects the leakage magnetic field generated by the tiny defect; it also shields the interference of the external environment magnetic field, reducing measurement errors caused by environmental factors. At the same time, the design of the magnetic concentrator direction being parallel to the NV color center axis allows the ODMR spectrum to present a symmetrical single peak, avoiding the sampling chaos of multiple peak superposition, and further improving the detection accuracy in weak magnetic field scenarios. (5) More flexible sampling: On the one hand, it expands the selection range of magnetic characterization frequencies, supports two sampling methods: NV color center spin resonance frequency and ODMR spectrum maximum slope point frequency, and adapts to different algorithm recognition requirements and detection conditions; on the other hand, it designs a ring-shaped magnetizer structure, which can realize single-probe full-circumference detection of tubular, columnar, rope-shaped and other circumferential objects. At the same time, planar objects can be adapted to L-shaped magnetizers, taking into account the detection requirements of different detection surfaces such as plane and curved surfaces, and greatly expanding the actual application scenarios of the device. Attached Figure Description

[0030] Figure 1 This is a system diagram of a magnetic flux leakage detection device based on the minimum sampling period according to a first embodiment of the present invention; Figure 2 The ODMR spectrum of the first embodiment of the present invention is a frequency-modulated spectrum with only one pair of peaks; Figure 3 A partial view of an L-shaped magnetic flux leakage detection device based on the minimum sampling period according to a second embodiment of the present invention; Figure 4 This is a partial view of a leakage magnetic flux detection device based on the minimum sampling period according to the third embodiment of the present invention, which has a ring-shaped magnetic concentrator.

[0031] In the picture: 1. Magnetizer; 2. Diamond block; 3. Laser module; 4. Microwave module; 41. Microwave radiator; 5. Photodetector; 51. Transimpedance amplifier; 6. Data acquisition module; 7. Data processing module; 8. Main control module; 9. Sample; 10. Magnetizer. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1: This embodiment provides a magnetic flux leakage detection device based on the minimum sampling period. (See attached document.) Figure 1 It includes a magnetizer 1, a diamond block 2, a laser module 3, a microwave module 4, a photodetector 5, a data acquisition module 6, a data processing module 7, and a main control module 8.

[0034] The working principle of the device of the present invention is as follows: For defect detection of ferromagnetic sample 9, by magnetizing it, when there is a defect on its surface, the magnetic field will leak at the defect, that is, the so-called leakage magnetic field. The strength of the leakage magnetic field is related to the defect state. By measuring whether there is a leakage magnetic field on the surface of sample 9, it can be determined whether there is a defect. The defect state can also be determined to a certain extent based on the strength of the leakage magnetic field.

[0035] Therefore, when testing sample 9, magnetizer 1 is needed to magnetize the surface of sample 9. See details... Figure 1 Magnetizer 1 can be a permanent magnet or an electromagnet. In this embodiment, a pair of magnets with opposite magnetic poles are placed near the surface of sample 9 to magnetize the sample. This structure enables the magnetizer 1 to form a controllable magnetic wire loop with the test object, and precisely controls the magnetic field within the detection area of ​​the test object. This ensures effective magnetization of the ferromagnetic test object, generating a stable and detectable leakage magnetic field at the defect, while effectively avoiding magnetic field interference to the diamond block 2 sensing core and other electrical modules of the device. This reduces detection errors caused by magnetic interference from the hardware level and lays the foundation for accurate detection of leakage magnetic field.

[0036] See Figure 1Diamond block 2 is the core sensing component of the leakage magnetic field detection device based on the minimum sampling period of this invention. Specifically, diamond block 2 is a diamond grain containing a single NV color center (i.e., nitrogen-vacancy color center) without other redundant color center structures and only one NV axis. This design ensures that the ODMR spectrum corresponding to diamond block 2 has only a pair of split resonance peaks, which can accurately match the sampling requirements of two paired magnetic characterization frequencies, avoid frequency signal interference caused by multi-axial color centers, and improve the accuracy of magnetic field detection. The physical dimensions of the diamond block 2 are approximately 200 μm in length, height, and width. It has a micron-level grain structure (the specific dimensions can be adjusted according to the actual detection scenario, as long as it contains a single NV color center and has only one NV axis, which can effectively achieve the effects of excitation light, microwave, and leakage magnetic field). It is small in size and has high sensing sensitivity, and can be arranged close to the detection surface of the object under test, so as to accurately capture the weak leakage magnetic field signal at the defect. At the same time, it is fixed to the end face of the optical fiber by optical adhesive (or other fixing methods that do not affect signal transmission). The optical fiber is the excitation light transmission accessory of the laser module 3. The excitation light output by the laser module 3 is connected to the other end of the optical fiber through a coupler and transmitted to the surface of the diamond block 2 along the entire path of the optical fiber. The excitation light of 532 nm (which is the conventional and efficient excitation light wavelength for initializing the spin state of the diamond NV color center, or other excitation light wavelengths that can effectively initialize the spin state of the NV color center and induce it to produce detectable photofluorescence) is selected to achieve efficient and directional irradiation of the NV color center, so as to ensure the stable initialization of the spin state of the NV color center. Diamond block 2 is positioned within the range of the excitation magnetic field generated by magnetizer 1, with its sensing area directly facing the magnetization surface of magnetizer 1. It can directly receive the leakage magnetic field generated at the defect location of the test object. Simultaneously, diamond block 2 is within the microwave radiation range of microwave module 4. The microwave radiator 41 of microwave module 4 is positioned close to the periphery of diamond block 2, ensuring that the microwave signal fully covers the sensing area of ​​diamond block 2, guaranteeing a stable spin resonance transition between the NV color center and the microwave signal. The fluorescence output surface of diamond block 2 faces the signal acquisition end of the photodetector. The photoluminescence generated under the combined effects of excitation light and microwaves can be directly transmitted to the acquisition area of ​​photodetector 5.

[0037] Laser module 3 is the core component for excitation light output in the leakage magnetic field detection device based on the minimum sampling period of this invention. Its core function is to output excitation light of a specific wavelength to the diamond block 2, thereby effectively initializing the spin states of the NV color centers within the diamond block 2 and providing photoexcitation conditions for the generation of photofluorescence. (See also...) Figure 1 In this example, the basic configuration of laser module 3 is to output laser light with a wavelength of 532nm. This wavelength is an optimal parameter for adapting to the quantum properties of diamond NV centers, and can efficiently initialize the spin state of the NV centers to... Ground state. The laser module includes at least a light source that outputs excitation light of the corresponding wavelength to meet the basic output requirements of the excitation light. For optimization needs in different detection scenarios, it can also integrate functional devices such as power modulation, collimation and beam expansion, polarization control, filtering, and timing control as needed to achieve multi-dimensional adjustment of the excitation light and adapt to leakage magnetic field detection scenarios with different sensitivity and accuracy requirements. The output end of the laser module 3 is connected to one end of the transmission optical fiber via a coupler. The other end of the optical fiber is bonded and fixed to the diamond block 2 with optical adhesive. After the excitation light is output from the laser module 3, it is directionally transmitted along the entire path of the optical fiber to the light-receiving surface of the diamond block 2, achieving efficient and precise irradiation of the NV color centers within the diamond block 2, avoiding excitation light loss during transmission, and ensuring the optical excitation effect. The laser module 3 is also electrically connected to the main control module 8 of the device and is centrally controlled by the main control module 8. The integrated laser driver and TEC driver (thermoelectric cold driver) in the main control module 8 provide stable operation for the laser module 3, enabling functions such as starting and stopping the laser module 3, power adjustment, and monitoring its operating status. This ensures the stability and continuity of the excitation light output and adapts to the high-frequency sampling rhythm of the data acquisition module 6. Furthermore, the excitation light output rhythm of the laser module 3 coordinates with the microwave radiation from the microwave module 4. Together, they act on the diamond block 2, causing the NV color center to generate stable photoluminescence under dual light and microwave excitation. This provides a reliable fluorescence source for the signal acquisition of the photodetector 5 and is a crucial optical excitation basis for the device's magnetic field sensing. Its output state can be adjusted in real time by the main control module 8 according to detection requirements.

[0038] Microwave module 4 is the microwave signal output component of the leakage magnetic field detection device based on the minimum sampling period of this invention. Its core function is to radiate microwave signals to the diamond block 2, which, in conjunction with the excitation light output from laser module 3, act on the NV color center to achieve resonant transitions of the spin states of the NV color center, providing microwave excitation conditions for optically detected magnetic resonance (ODMR) magnetic field sensing. For details, please refer to [link to relevant documentation]. Figure 1The microwave module 4 includes at least two core components: a microwave source and a microwave radiator 41. It can also integrate supporting devices such as a microwave amplifier and a microwave circulator according to signal adjustment requirements. The center frequency of its output microwave signal is preferably 2.87 GHz (this frequency is a conventional reference frequency adapted to the spin resonance of the diamond NV color center; it can be adjusted up or down according to the intensity change of the leakage magnetic field of the defect in the test object, and can be adjusted accordingly in actual use). The microwave radiator 41 of the microwave module 4 is arranged close to the periphery of the diamond block 2, and the microwave radiation range can fully cover the sensing area of ​​the diamond block 2, ensuring that the microwave signal can fully interact with the NV color center within the diamond block 2. The microwave signal output from the microwave source can be amplified by the microwave amplifier and prevented from reverse transmission by the microwave circulator before being directionally radiated to the diamond block 2 by the microwave radiator 41, reducing microwave signal transmission loss and ensuring the resonance transition effect. Microwave module 4 is bidirectionally electrically connected to main control module 8 and is centrally controlled by main control module 8. Main control module 8 can adjust the output frequency and power of microwave module 4 in real time according to detection requirements. Its microwave radiation rhythm is coordinated with the excitation light output of laser module 3, and the two act synchronously on diamond block 2, causing the NV color center to undergo spin resonance transition under dual excitation of light and microwave, and generate stable photoluminescence, providing a basis for signal acquisition by photodetector 5. The frequency-modulated microwave output by microwave module 4 can make the ODMR spectrum of NV color center show obvious "zero-crossing" spin resonance frequency characteristics, which facilitates the data acquisition module 6 to accurately identify two pairs of magnetic characterization frequency sampling points. Its real-time adjustable microwave frequency can be adapted to the alternating sampling rhythm of the two magnetic characterization frequencies by data acquisition module 6, providing a stable and continuous frequency sampling basis for magnetic field noise reduction characterization data calculation by data processing module 7.

[0039] The photodetector 5 is the fluorescence signal conversion component of the leakage magnetic field detection device based on the minimum sampling period of this invention. Its core function is to collect the photofluorescence generated by the diamond block 2 under the dual action of excitation light and microwave, and convert the optical signal into an analog electrical signal that can be sampled and processed by subsequent modules. It is a key component connecting optical sensing and electrical data processing. The signal acquisition end of the photodetector 5 is arranged close to the fluorescence output surface of the diamond block 2, and the acquisition range accurately covers the fluorescence emission area of ​​the diamond block 2. The photofluorescence can be directly transmitted to the acquisition end of the photodetector 5 through spatial light, or an optical lens can be added between the two according to the detection requirements to achieve efficient collection of fluorescence, reduce fluorescence signal transmission loss, and ensure the integrity and sensitivity of signal acquisition. The photodetector 5 includes a transimpedance amplifier 51, which is electrically linked with the photodetector 5. It can directly convert the weak fluorescence current signal output by the photodetector 5 into a stable voltage signal, complete the preliminary conditioning of the analog electrical signal, and solve the problems of easy interference and low amplitude of the current signal after optical signal conversion. The signal output terminal of photodetector 5 is electrically connected to the analog signal input terminal of data acquisition module 6. The fluorescent voltage analog signal, conditioned by transimpedance amplifier 51, can be directly transmitted to data acquisition module 6. The signal acquisition rate of photodetector 5 matches the sampling rhythm of data acquisition module 6, enabling real-time response to changes in fluorescence output of diamond block 2 and meeting the high sampling rate detection requirements of the device. The intensity of the acquired fluorescent analog signal is correlated with the spin state of the NV color center, accurately reflecting the matching state between the microwave frequency and the spin resonance frequency of the NV color center, providing a true and effective original signal basis for subsequent magnetic characterization frequency sampling and magnetic field noise reduction characterization data calculation. Photodetector 5 is centrally powered and monitored by main control module 8. Main control module 8 can control its working status in real time, ensuring continuous and stable operation of photodetector 5 during high-frequency sampling of the device, avoiding signal acquisition errors caused by device malfunction, and ensuring the sensing stability of the entire detection system.

[0040] The data acquisition module 6, as the core sampling unit of the magnetic flux leakage detection device, is electrically connected to the photodetector 5 and the data processing module 7. Upstream, it receives the analog data output by the photodetector 5, and downstream, it transmits the sampled digital data to the data processing module 7 for processing. It is a key component for realizing high sampling rate magnetic measurement of the device.

[0041] The input signal to the data acquisition module 6 comes from the analog electrical signal output by the photodetector 5 after the diamond block 2 undergoes photofluorescence. Module 6 pre-sets two paired magnetic characterization frequencies of the NV color center within the diamond block 2 as two selectable data sampling points. These magnetic characterization frequencies can be the spin resonance frequency of the NV color center or the microwave frequency corresponding to the point of maximum slope on the ODMR spectrum. These two sampling points provide the basis for subsequently obtaining the center frequency for temperature drift suppression. (See reference...) Figure 2Before sampling, a specific NV axis can be selected as the sampling axis as needed. Figure 2 In the ODMR spectrum shown, the spin resonance frequency of this sampling axis is represented as a "zero crossing point" in the figure. Let the "zero crossing point" on the left be the first data sampling point (i.e., point A), and the "zero crossing point" on the right be the second data sampling point (i.e., point B).

[0042] Module 6 is configured to repeatedly sample the two data sampling points mentioned above according to the minimum sampling period, and sets two hard requirements for the sampling process of each minimum sampling period: first, at least one pair of magnetic characterization frequencies must be sampled within the period to meet the calculation requirements of the microwave center frequency; second, the total number of samplings within the period must be no less than three, which is different from the traditional sampling mode and realizes the improvement of magnetic sampling rate.

[0043] Module 6 can be adapted to various sampling rules. In order to better demonstrate the sampling rules of the present invention, this embodiment provides two sampling rule examples.

[0044] Example 1: This rule is the preferred sampling rule within the minimum sampling period. Its core feature is a single out-of-range sampling + remaining same-range sampling: After setting the total number of samplings in the minimum sampling period, only one sampling point of the two paired magnetic characterization frequencies is sampled once (the order of this out-of-range sampling is not fixed and can occur at any sampling stage within the period), while the other sampling point is sampled for all remaining times. For example, if the minimum sampling period has a total of 10 samplings, the first sampling point can be sampled only once and the second sampling point 9 times, or the second sampling point can be sampled only once and the first sampling point 9 times. Under this rule, there is only one sampling operation at different points, and all other samplings are concentrated on the same side of the sampling points.

[0045] Example 2: This rule is a general sampling rule within the minimum sampling period. Its core feature is that both sampling points are sampled multiple times, with flexible allocation of the sampling counts. After setting the total number of samples for the minimum sampling period, multiple samples are taken from each of the two paired magnetic characterization frequencies. The sampling count n for one sampling point is 1 < n < total sampling count - 1, and the sampling count for the other sampling point is the total sampling count - n. The order of these multiple samplings for the two sampling points is not fixed; they can be continuous or spaced out. For example, if the minimum sampling period has 10 total samples, the first sampling point can be sampled 2-8 times, and the second sampling point 8-2 times. Under this rule, both sampling points undergo multiple sampling operations, resulting in multiple sets of paired data combinations that can be used to calculate the center frequency. The triggering order of the sampling points is not fixed and can be flexibly set. It also supports setting the first two samples within each minimum sampling period as the paired magnetic characterization frequencies for calculating the center frequency, and the same sampling point can be consistently selected from the second sampling to the end of the sampling process, adapting to the fast computation requirements of data processing module 7.

[0046] The sampling period, sampling rules, and sampling triggering of the data acquisition module 6 are all uniformly controlled by the main control module 8. It forms a time-series coordination with the excitation light output of the laser module 3 and the microwave signal radiation of the microwave module 4 to ensure that the sampling process is synchronized with the photoluminescence generation process of the NV color center, thus ensuring the accuracy of the sampling data.

[0047] The core idea of ​​this embodiment is that temperature changes more slowly than magnetic field. It is assumed that the temperature is constant or changes very little within a short period of time. This means that the influence of temperature on the measurement process can be regarded as uniform during this period. In traditional technology, a temperature drift removal step is performed for each sampled data (two consecutive sampled data are grouped together, and the accurate magnetic measurement characterization data that suppresses temperature drift can be obtained by calculating the frequency difference). Although this can achieve extremely high measurement accuracy, it also greatly reduces the magnetic measurement sampling rate. Considering that the temperature change is minimal or constant within a short time interval, a short sampling period with a constant temperature can be set. All sampled data within this short sampling period share a frequency that suppresses temperature drift. This scheme takes this frequency as the center frequency. When calculating this center frequency, two sampling frequencies are used, which will cause one of the sampling frequencies to become invalid (invalidity only means that it cannot be used to obtain noise-reduced magnetic field characterization data again. In fact, it is because the noise-reduced magnetic field characterization data obtained from the two sampling data are equivalent, so one of the two must be chosen, resulting in the invalidation of one sampling frequency). However, other sampled data within this period can obtain magnetic field noise reduction characterization data based on the same center frequency. This short sampling period is also the minimum sampling period.

[0048] In this embodiment, the minimum sampling period is no greater than the preset time T = 0.01s (in this embodiment, the preset time is set to 0.01s. If the detection environment is a temperature-stable working condition, the sampling period T can be appropriately widened according to the actual temperature change). Under this period limit, the temperature change amplitude in the non-active heating environment is only about 0.1K, and the center frequency shift can be ignored. Temperature noise can be regarded as a constant value, providing hardware support for the temperature interference suppression algorithm of the subsequent data processing module 7.

[0049] The data processing module 7 is electrically connected to the data acquisition module 6 to receive sampled data. Simultaneously, it is under the unified control of the main control module 8. After processing, it transmits the effective magnetic field characterization data back to the main control module 8 for display and analysis. The input signal to the data processing module 7 is the NV color core magnetic characterization frequency sampled data acquired and transmitted by the data acquisition module 6 according to the minimum sampling period. Independent calculation logic is executed for the sampled data within each minimum sampling period, ensuring that the calculation results of each period do not interfere with each other, thus guaranteeing the real-time performance and independence of the magnetic field data. The data processing module 7 first extracts a pair of magnetic characterization frequencies from the sampled data of a single minimum sampling period (in this embodiment, the first two sampled data within that period are selected). It then calculates the microwave center frequency used to suppress temperature drift using a core method of summation and averaging. In practical applications, if the summation result is processed with fixed parameters through multiplication, division, addition, or subtraction, or if only a summation operation is performed, it still falls within the scope of the center frequency calculation of the data processing module 7 and does not affect the core effect of temperature drift suppression.

[0050] After calculating the microwave center frequency, the data processing module 7 sequentially subtracts all remaining sampled data within the minimum sampling period from the single center frequency. The resulting difference is the final output magnetic field noise reduction characterization data for that period, replacing the traditional method of subtracting the left and right resonant frequencies pairwise. This maximizes the utilization of sampled data while preserving the temperature drift suppression effect, thereby improving the magnetic sampling rate. The data processing module 7 adapts to the fast sampling rules of the data acquisition module 6. When the data acquisition module 6 uses the first two sampled data within a period as paired magnetic characterization frequencies, the data processing module 7 can immediately complete the center frequency calculation after receiving the first two sampled data. When subsequent sampled data is received from the data acquisition module 6, the difference operation is completed synchronously, and the magnetic field data is output. There is no need to wait for all samples within the period to be completed before performing unified calculations, significantly shortening the data processing delay and improving the output speed of the magnetic field data.

[0051] The data processing module 7 is compatible with various sampling rules of the data acquisition module 6. Whether it is the preferred "single-time different-point sampling + remaining same-point sampling" rule or the "multiple flexible allocation of sampling from two sampling points" rule, the data processing module 7 can accurately extract one set of paired magnetic characterization frequencies to calculate the center frequency and uniformly perform subtraction processing on all remaining sampled data. Moreover, for the sampling rule of "fixing the same sampling point from the second sampling onwards", the data processing module 7 does not need to perform additional processing such as absolute value conversion on the subtraction results, simplifying the calculation process and ensuring the consistency and uniformity of the output data. The data processing module 7 transmits all magnetic field noise reduction characterization data obtained in each minimum sampling period to the main control module 8 in real time. The main control module 8 completes subsequent operations such as data display, external transmission, and spectrum plotting, and simultaneously receives calculation instructions from the main control module 8 for control, realizing collaborative work with other modules of the device.

[0052] The main control module 8 is the core component for global control and data interaction of the leakage magnetic field detection device based on the minimum sampling period. It undertakes the core functions of centralized management and control of all modules of the device, data aggregation and processing, human-machine interaction, and external data transmission. It is the central control hub that ensures the coordinated operation of all components of the device. The main control module 8 has built-in core hardware such as a processor, power supply circuit, laser driver, and TEC driver (thermoelectric cold driver). The processor is the core of the module's operation and control, responsible for issuing various control commands, secondary processing of sampled data, and external data transmission. The power supply circuit provides stable and adjustable power to all power-consuming modules of the device (laser module 3, microwave module 4, photodetector 5, etc.), realizing centralized management and control of the power supply of each module. The laser driver and TEC driver are specially configured for laser module 3 to ensure stable power and wavelength of the excitation light output and avoid the impact of abnormal light source operation on the spin state initialization of the NV color center. The main control module 8 is bidirectionally electrically connected to all functional modules of the device, issuing working instructions to each module and receiving real-time feedback on working status, realizing fully automated control of the entire process: for the laser module 3, it controls its opening and closing, excitation light power adjustment, and working sequence to ensure that the excitation light output and microwave radiation are coordinated; for the microwave module 4, it regulates its microwave frequency and output power to adapt to the requirements of magnetic characterization frequency sampling and frequency tracking; for the data acquisition module 6, it sets the sampling frequency and sampling trigger timing and monitors its sampling status; for the data processing module 7, it configures the sampling period threshold and synchronizes the calculation rhythm; at the same time, it monitors the working status of auxiliary components such as the photodetector 5 and the transimpedance amplifier 51, and promptly feeds back fault signals to ensure the stable operation of the device.

[0053] The main control module 8 is the core of the device's data aggregation. It receives magnetic field noise reduction characterization data transmitted from the data processing module 7 in real time, organizes and temporarily stores the data, and then realizes the visualization output of the magnetic field data through the data display and human-machine interaction unit. At the same time, it supports operators to adjust the detection parameters (such as sampling frequency) in real time through the human-machine interaction interface to adapt to the needs of different test objects and different detection scenarios. In addition, the main control module 8 can be connected to a host computer to realize remote transmission of detection data, spectrum drawing, historical data storage and analysis, and expand the device's data analysis and management capabilities. The main control module 8, designed to meet the core requirements of high sampling rate and real-time performance of the device, possesses precise module coordination and scheduling capabilities. It can synchronously control the excitation light output of the laser module 3 and the microwave frequency modulation of the microwave module 4 according to the sampling rhythm of the data acquisition module 6 and the calculation rhythm of the data processing module 7, ensuring the time synchronization of the entire process of optical excitation, microwave radiation, signal sampling, and data processing without significant delay. At the same time, within the minimum sampling period (≤0.01s), it achieves high-speed response and precise coordination of each module, ensuring the detection accuracy and stability of the device at high sampling rates, and meeting the high-frequency detection needs of scenarios such as rapid industrial screening and real-time monitoring of high-speed equipment.

[0054] Example 2: This embodiment, based on Embodiment 1, adds a lock-in amplifier and a frequency tracking module, located inside the main control module 8 (not shown in the figure). Specifically, the main control module 8 integrates a lock-in demodulation module and a frequency tracking module to expand the functional units, realizing an integrated design of the device functions. When the lock-in demodulation module is integrated, it can cooperate with the frequency-modulated microwave output from the microwave module 4 to complete the demodulation processing of the fluorescence signal, converting the optical fluorescence signal into a high signal-to-noise ratio electrical error signal, improving the accuracy of the sampling data. When the frequency tracking module is integrated, a negative feedback control loop can be formed, instantly and automatically locking the microwave frequency output from the microwave module 4 to the spin resonant frequency of the NV color center. There is no need for periodic spectrum scanning, and the microwave frequency value can be directly used as a continuous magnetic field reading, increasing the sampling rate of the device to the kHz or even MHz level. At the same time, the control output data of this module can be synchronously transmitted to the data processing module 7 to optimize the calculation accuracy of the magnetic field characterization data.

[0055] The device is equipped with a lock-in amplifier. The output signal of the photodetector 5 will first be demodulated and noise-reduced by the lock-in amplifier before being transmitted to the data acquisition module 6. The data acquisition module 6 and the frequency tracking module form a data linkage. The data acquisition module 6 can receive the resonant frequency data it locks in, further optimize the accuracy of the average value calculation, and make the magnetic field characterization data more consistent with the actual leakage magnetic field situation.

[0056] Example 3: Based on Examples 1 and 2, see [link to example]. Figure 3 In Embodiment 3, a magnetic field concentrator 10 is added. The magnetic field concentrator 10 is a core auxiliary component for optimizing the leakage magnetic field of the leakage magnetic field detection device based on the minimum sampling period of this invention. Its core function is to concentrate the leakage magnetic field generated at the defect of the test object, shield external environmental magnetic field interference, and improve the device's detection capability and measurement accuracy for weak leakage magnetic fields. The magnetic field concentrator 10 is arranged around the diamond block 2, ensuring that the diamond block 2 is completely within the core area of ​​the magnetic field formed by the magnetic field concentrator 10. After the leakage magnetic field at the defect of the test object is concentrated by the magnetic field concentrator 10, it acts directionally on the NV color center sensing area within the diamond block 2, ensuring that the leakage magnetic field can be efficiently sensed by the NV color center. At the same time, the magnetic field concentrator 10 can shield external stray magnetic fields, avoiding interference from environmental magnetic fields on the NV color center magnetic field sensing, thus improving the signal-to-noise ratio of leakage magnetic field detection from a hardware perspective.

[0057] See Figure 3 The magnetic concentrator 10 consists of two L-shaped magnetic blocks arranged opposite each other to form a magnetic concentrating air gap, with one end of the L-shaped magnetic blocks forming the magnetic concentrating air gap being narrow. This structure is suitable for detecting magnetic leakage from planar test objects, accurately concentrating the magnetic leakage field at defects in the planar test object and increasing the local magnetic leakage field intensity. The magnetic concentrating direction of the magnetic concentrator 10 is parallel to the axis of the NV color center within the diamond block 2. When arranged in parallel, the concentrated magnetic leakage field can cause the two NV color centers to... The symmetrical separation of the ground-state spinon energy levels results in two symmetrical resonance peaks in the ODMR spectrum of the NV color center. This facilitates the precise identification of two paired magnetic characterization frequency sampling points by the data acquisition module 6, while ensuring the accuracy of frequency difference calculation and reducing magnetic field measurement errors caused by energy level splitting asymmetry. Furthermore, the magnetic focusing direction of the magnetizer 10 is at equal angles to the four NV axes of the diamond block 2. This is reflected in the ODMR spectrum as shown in the attached figure. Figure 2 As shown, it has only one pair of peaks, which can also be expressed as having only one pair of microwave resonant frequencies. In this case, the magnitude of the external magnetic field can be measured more accurately.

[0058] The magnetic focusing effect of the magnetizer 10 amplifies weak leakage magnetic field signals, effectively expanding the magnetic field measurement range of the device. This enables the device to accurately detect weak leakage magnetic fields at minute defects in the test object, improving the device's detection sensitivity and applicability. Its magnetic field shielding effect reduces the impact of environmental magnetic field fluctuations on the NV color center sensor. Combined with the temperature noise suppression algorithm of the data processing module 7, it achieves dual suppression of environmental magnetic field interference and temperature interference, further improving the accuracy of magnetic field measurement. Furthermore, the magnetizer 10 is a purely hardware structure, requiring no electrical connection to other electrical modules of the device (laser module 3, microwave module 4, main control module 8, etc.). It only needs to be spatially integrated with the diamond block 2 and the test object, making it highly adaptable and flexibly selectable according to the needs of the detection scenario. It does not change the working logic and collaborative relationship of the core modules of the device, adapting to the high sampling rate detection requirements of the device.

[0059] Example 4: Based on Embodiments 1, 2, and 3, this invention adds a magnetizer 10. (See attached document.) Figure 4 The only difference from Embodiment 3 is that the magnetic concentrator 10 in Embodiment 3 consists of two L-shaped magnetic blocks arranged opposite each other to form a magnetic concentrating air gap, while the magnetic concentrator 10 of this invention is a ring structure with a magnetic concentrating notch. This ring structure with a magnetic concentrating notch is a split design that can be spliced ​​up and down, making it easy to insert tubular, columnar, rope-shaped, or other circumferentially shaped objects to be tested into the inner hole of the ring. The diamond block 2 is placed in the magnetic concentrating notch of the ring magnetic concentrator, which can realize the synchronous detection of the leakage magnetic field of the entire circumferential surface of the object to be tested, without the need to arrange multiple sensor probes, thus greatly improving the detection efficiency of circumferentially shaped objects to be tested.

[0060] In summary, the device of the present invention has the following advantages: (1) Significantly improved sampling rate: Abandoning the traditional mode of “two pairs of frequency sampling to calculate one magnetic field value”, by setting the minimum sampling period, only one pair of magnetic characterization frequencies are used in a single period to calculate the temperature drift suppression center frequency, and the remaining sampling data are subtracted from the center frequency to obtain effective magnetic field data. While retaining the temperature drift suppression effect, the magnetic sampling rate is no longer limited to half of the frequency sampling rate, thus achieving a core improvement in detection speed and adapting to the needs of rapid non-destructive testing scenarios; (2) More accurate sampling data: On the one hand, by using the time limit of the minimum sampling period, the temperature change within the period is ensured to be negligible, and the temperature drift interference can be uniformly eliminated, thus solving the problem of spin resonance frequency drift caused by temperature; on the other hand, it can be equipped with a lock-in amplifier and frequency tracking module to realize signal noise reduction and real-time microwave frequency locking, breaking through the noise bottleneck of direct optical detection, and making the resonance frequency sampling more accurate, thus ensuring the accuracy of magnetic field measurement from both data processing and signal acquisition dimensions. (3) Strong real-time performance: The design of the operation logic of calculating the center frequency of the first two sampling data and the real-time difference of the subsequent sampling data greatly shortens the output delay of magnetic field data and improves the real-time feedback capability of the detection results; at the same time, the rule of sampling at different points once per cycle and sampling at the same points for the rest simplifies the program design and hardware control logic of data acquisition, reduces the extra steps of data processing, reduces the difficulty of software and hardware implementation of the device, and improves the stability of operation. (4) Enhanced magnetic field sensing: The addition of a magnetic concentrator and optimization of its design in conjunction with the NV color center not only amplifies the weak leakage magnetic field at the defect, expanding the magnetic field measurement range of the device, but also effectively detects the leakage magnetic field generated by the tiny defect; it also shields the interference of the external environment magnetic field, reducing measurement errors caused by environmental factors. At the same time, the design of the magnetic concentrator direction being parallel to the NV color center axis allows the ODMR spectrum to present a symmetrical single peak, avoiding the sampling chaos of multiple peak superposition, and further improving the detection accuracy in weak magnetic field scenarios. (5) More flexible sampling: On the one hand, it expands the selection range of magnetic characterization frequencies, supports two sampling methods: NV color center spin resonance frequency and ODMR spectrum maximum slope point frequency, and adapts to different algorithm recognition requirements and detection conditions; on the other hand, it designs a ring-shaped magnetizer structure, which can realize single-probe full-circumference detection of tubular, columnar, rope-shaped and other circumferential objects. At the same time, planar objects can be adapted to L-shaped magnetizers, taking into account the detection requirements of different detection surfaces such as plane and curved surfaces, and greatly expanding the actual application scenarios of the device.

[0061] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Terms such as "upper," "lower," "left," "right," "front," and "rear" used in the invention are merely for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A magnetic flux leakage detection device based on minimum sampling period, comprising a magnetizer, a diamond block, a photodetector, and a light source, characterized in that, It also includes a data acquisition module, a data processing module, and a main control module; the signal acquisition end of the photodetector faces the fluorescence output surface of the diamond block; the data acquisition module, data processing module, and main control module are electrically connected in sequence; the diamond block contains an NV color center, and the two pairs of magnetic characterization frequencies of the NV color center are set as two selectable data sampling points; the data acquisition module samples the analog data and is configured to repeatedly sample the data sampling points according to the minimum sampling period, and in each minimum sampling period, at least one pair of magnetic characterization frequencies are sampled and acquired, and the total number of samplings is not less than three; the data processing module is used to perform independent calculations on the sampled data obtained in each minimum sampling period. The independent calculation process includes: using a pair of magnetic characterization frequencies to calculate the microwave center frequency used to suppress temperature drift, subtracting the other sampled data from the microwave center frequency in sequence, obtaining the difference value, and using it as the magnetic field noise reduction characterization data output in the minimum sampling period.

2. The magnetic flux leakage detection device based on the minimum sampling period according to claim 1, characterized in that, It also includes a microwave module and a lock-in amplifier. The microwave module is used to output frequency-modulated microwaves, and its microwave radiating end is arranged close to the periphery of the diamond block. The lock-in amplifier is located inside the main control module and is used for data demodulation.

3. The magnetic flux leakage detection device based on the minimum sampling period according to claim 1, characterized in that, It also includes a frequency tracking module, located inside the main control module, which is used to lock the microwave frequency output by the microwave module to the spin resonance frequency of the NV color center.

4. The magnetic flux leakage detection device based on the minimum sampling period according to claim 1, characterized in that, The data acquisition module alternately samples two data sampling points, which is defined as a sampling period. The duration of the minimum sampling period is not greater than a preset time T, and the temperature change amplitude of the non-actively heated environment within the preset time is not higher than 0.1K.

5. The magnetic flux leakage detection device based on the minimum sampling period according to claim 1, characterized in that, A set of paired magnetic characterization frequencies used to determine the microwave center frequency for suppressing temperature drift consists of the first two sampled data within each minimum sampling period. Subsequent sampled data within the same minimum sampling period are simultaneously subtracted from the microwave center frequency at the end of the acquisition to obtain the magnetic field noise reduction characterization data.

6. The magnetic flux leakage detection device based on the minimum sampling period according to claim 5, characterized in that, Within each minimum sampling period, the selected sampling points are the same from the start of the second sampling to the end of the sampling.

7. The magnetic flux leakage detection device based on minimum sampling period according to claim 1, characterized in that, The magnetic characterization frequency is the spin resonance frequency of the NV color center or the microwave frequency corresponding to the point of maximum slope on the ODMR spectrum.

8. The magnetic flux leakage detection device based on the minimum sampling period according to claim 1, characterized in that, It also includes a magnetizer for focusing the leakage magnetic field, with the diamond block located within the focusing magnetic field of the magnetizer.

9. A magnetic flux leakage detection device based on minimum sampling period according to claim 8, characterized in that, The magnetic focusing direction of the magnetizer is parallel to the axis of the NV color center.

10. A magnetic flux leakage detection device based on minimum sampling period according to claim 1, characterized in that, The magnetizer is a ring-shaped magnetizer with a magnetizing gap.

Images