Two-dimensional magnetic field imaging method and system based on diamond nv color center

Abstract

The application discloses a two-dimensional magnetic field imaging method based on diamond NV color centers, comprising the following steps: generating a rough scanning path according to a region to be measured, controlling a displacement scanning unit to drive a diamond NV color center detection unit to move point by point, locking and triggering collection after reaching a position; obtaining the light detection magnetic resonance spectrum of each measuring point through light excitation and microwave sweep, and calculating the magnetic field information; identifying an abnormal region according to the rough scanning result and generating a fine scanning path, and performing fine scanning on the abnormal region; periodically returning to a reference point to collect a reference spectrum line during the scanning process, and compensating for the drift of the current batch of measuring points, and finally matching the compensated magnetic field information with coordinate information to generate a two-dimensional magnetic field distribution map. The application can improve the positioning accuracy, measurement stability and imaging reliability of two-dimensional magnetic field imaging.

Description

Technical Field

[0001] This invention relates to the field of quantum sensing and precision measurement technology, and in particular to a two-dimensional magnetic field imaging method and system based on diamond NV color centers. Background Technology

[0002] Diamond nitrogen-vacancy (NV) centers are solid-state defect systems with excellent quantum spin properties, enabling highly sensitive detection of physical quantities such as magnetic fields, temperature, and electric fields at room temperature. Among them, the magnetic field measurement technology of diamond NV centers based on the principle of optically probed magnetic resonance (ODMR) has received widespread attention in recent years in fields such as micro-nano magnetic characterization, electronic device testing, biomagnetic signal detection, industrial non-destructive testing, and basic scientific research due to its advantages such as not requiring low temperature and high vacuum conditions, high spatial resolution, and minimal disturbance to the measured object. For the visualization characterization of the magnetic field distribution in the test area, it is usually necessary to use a displacement platform to drive the diamond NV center probe or the sample to be tested to scan point by point, and combine optical excitation, microwave frequency sweep and fluorescence detection to obtain the ODMR spectrum of each measurement point, and then reconstruct a two-dimensional magnetic field distribution map.

[0003] However, existing two-dimensional magnetic field imaging schemes based on diamond NV centers still have some shortcomings in practical applications. First, the scanning motion and spectral line acquisition mostly adopt an open-loop motion control mode, without real-time coordinate feedback and precise positioning determination mechanisms. This makes them prone to misalignment of coordinate data and magnetic field data due to stepper motor step loss and mechanical jamming. Furthermore, there is no clear timing synchronization design between motion and acquisition, which easily leads to problems such as premature acquisition before the motion is in place or starting motion before the acquisition is completed, directly resulting in decreased imaging accuracy and insufficient data reliability. Second, there is a lack of effective drift compensation mechanisms. During long-term, large-area scanning, the resonance peaks of ODMR spectral lines are significantly shifted due to multiple factors such as ambient temperature fluctuations, laser power drift, and microwave source frequency offset. Most existing devices lack periodic reference correction and drift compensation designs, resulting in a significant increase in magnetic field calculation errors in the later stages of scanning, poor overlap of images from multiple scans, and an inability to meet the requirements for long-term stable measurement. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, one objective of this invention is to propose a two-dimensional magnetic field imaging method and system based on diamond NV centers. Through closed-loop motion-acquisition control, hardware-level timing synchronization, periodic drift compensation, and full-process quantitative calibration, this method significantly improves the measurement accuracy, stability, and reliability of the imaging system while ensuring low cost and ease of implementation.

[0005] In a first aspect, the present invention proposes a two-dimensional magnetic field imaging method based on diamond NV color centers, the method comprising the following steps: S1. Coarse Scan Parameter Setting and Path Generation: Set the coarse scan area and coarse scan step parameters according to the range of the area to be measured, and preset the reference point position for drift compensation to generate a list of first target coordinates for full-range coarse scan. S2. Measurement point movement and position acquisition: The control displacement scanning unit drives the diamond NV color center detection unit to move sequentially along the first target coordinate list, and acquires the current position information in real time during the movement; S3. Position determination and lock trigger: The current position information is compared with the corresponding target coordinates. After determining that the target is in position, the displacement scanning unit is controlled to enter the lock state and the acquisition trigger signal is output. S4. Spectral line acquisition: In response to the acquisition trigger signal, the optical excitation unit is controlled to provide excitation light to the diamond NV color center detection unit, the microwave excitation unit is controlled to perform frequency sweep, and the fluorescence signal generated by the diamond NV color center detection unit is acquired to obtain the optical detection magnetic resonance spectrum of the current measurement point. S5. Coarse Scan Result Processing and Abnormal Region Identification: The optical detection magnetic resonance spectrum of the current measurement point is processed to obtain the magnetic field information of the current measurement point; after obtaining the magnetic field information of the measurement points corresponding to the first target coordinate list, abnormal regions are identified based on the coarse scan results, and a second target coordinate list for fine scanning is generated based on the boundary of the abnormal regions. S6. Fine scanning of abnormal areas: The control displacement scanning unit drives the diamond NV color center detection unit to perform fine scanning of the abnormal areas along the second target coordinate list, and performs current position acquisition, positioning determination, lock triggering, optical detection magnetic resonance spectrum acquisition and magnetic field information acquisition for each target coordinate in the second target coordinate list in sequence. S7. Reference point revisit and drift compensation: After completing the scanning of each predetermined batch of measurement points during the fine scanning process, the displacement scanning unit is controlled to return to the reference point position and the photodetector magnetic resonance spectrum of the reference point is re-acquired in order to compensate for the drift of the photodetector magnetic resonance spectrum of the current batch of measurement points. S8. Data Matching and Imaging Output: Match the compensated magnetic field information of each measuring point with the corresponding coordinate information to generate a two-dimensional magnetic field distribution map.

[0006] Preferably, the method for obtaining the magnetic field information in steps S5, S6, and S7 is as follows: To eliminate common-mode interference from ambient temperature and crystal stress in magnetic field measurements, a model is built based on the effective Hamiltonian operator: (1); in, This is a Hamiltonian operator whose eigenvalues ​​correspond to the energies of the electron spin levels in the diamond NV color center. For zero-field splitting parameters, For temperature, This refers to the transverse splitting factor caused by localized stress in the crystal. It is a spin vector operator. , Let be the components of the electron spin operator in the three coordinate axes. Electron gyromagnetic ratio, The vector of the magnetic field to be measured; The acquired optically detected magnetic resonance (OMR) spectrum was subjected to noise reduction filtering. The center frequencies of the two resonance peaks were then extracted from the filtered OMR spectrum using a multi-peak Lorentz fitting algorithm. and ,in, This is to detect the center frequency of the higher-frequency resonance peak in the optical magnetic resonance spectrum. For the center frequency of the lower-frequency resonance peak, the Lorentz fitting function is in the form of: (2); in, For microwave frequencies, To fit the fluorescence intensity, For baseline offset, For the first The amplitude of each peak For the first The center frequency of each peak Half-height and half-width; Extracted resonance peak frequencies and known , Substitute into formula (1) to calculate the magnetic field strength at that point. : (3).

[0007] Preferably, in step S7: S71: Before the scan starts, the displacement scanning unit moves the diamond NV color center detection unit to the reference point, collects the zero magnetic field reference spectrum, and extracts the center frequency of its resonance peak amplitude by fitting the formula (2). ; S72: Record start time After each batch of measurement points is scanned, the scanning process is paused. The displacement scanning unit drives the diamond NV color center detection unit back to the reference point, and sequentially executes the current position acquisition, positioning determination, and lock-off triggering. The optical detection magnetic resonance spectrum of that point is then re-acquired to obtain the current reference frequency. ; S73: Record the current moment Calculate the drift slope : (4); S74: Let the first The original measurement frequency of each measuring point is The time of its collection is , of which The first measuring point is the measuring point for this batch, the [number]th ... Frequency after drift compensation correction at each measuring point for: (5); S75: Adjust the frequency Substitute into formula (3) to recalculate the magnetic field strength, replace the original uncorrected result, and update the storage; S76: Update baseline parameters , This will serve as the baseline spectral line for the next batch of measurement points.

[0008] Preferably, in step S2: The spatial mapping matrix model is ,in, For the first Spatial coordinate vector of each sampling point This is the control pulse vector for the stepper motor. This is a diagonal matrix of pulse displacement conversion coefficients; In step S3, the positioning determination adopts a positioning criterion based on the infinite norm: (6); in, For real-time coordinates, For the target coordinates, This is the mechanical tolerance threshold, only when The control displacement scanning unit enters the locked state and outputs a data acquisition trigger signal.

[0009] Preferably, in step S1, the displacement scanning unit is controlled to perform an X-shaped coarse scan along the two diagonals of the area to be measured; magnetic field data is collected at preset intervals along the X-shaped coarse scanning path; abnormal areas where the rate of change of magnetic field strength exceeds a preset threshold are identified based on the coarse scanning results; and in step S5, a reciprocating S-shaped fine scanning path is generated based on the boundary of the abnormal area to perform a line-by-line fine scan of the abnormal area.

[0010] Preferably, before performing S1, a quantitative calibration and error correction step is included. The quantitative calibration and error correction step includes: placing the diamond NV color center detection unit in the uniform magnetic field region of a standard uniform magnetic field source, setting different standard magnetic field values ​​in sequence and acquiring the corresponding photodetector magnetic resonance spectra, and establishing a magnetic field strength-frequency offset calibration curve; during the scanning imaging process, linearly correcting the calculated magnetic field strength according to the calibration curve, and repeatedly measuring the same measurement point a number of times, using the average value and standard deviation σ of each measurement result as the statistical basis, eliminating abnormal measurement values ​​that exceed the range of the average value ±3σ, and then taking the average value of the remaining valid data as the final measurement result.

[0011] Secondly, the present invention proposes a two-dimensional magnetic field imaging system based on diamond NV centers, which applies any of the above-mentioned two-dimensional magnetic field imaging methods based on diamond NV centers. The system includes: a displacement scanning unit, a host control unit, a light excitation unit, a light signal transmission and collection unit, a data acquisition unit, a motion control unit, a microwave excitation unit, a diamond NV center detection unit, and a microwave loading unit. The diamond NV color center detection unit is fixedly mounted on the displacement execution end of the displacement scanning unit, and the microwave loading unit is mounted around the diamond NV color center detection unit. The output terminal of the photoexcitation unit is connected to the input terminal of the optical signal transmission and collection unit. The output terminal of the optical signal transmission and collection unit is optically coupled to the diamond NV color center detection unit. The optical signal transmission and collection unit is also connected to the fluorescence detection component. The electrical signal output terminal of the fluorescence detection component is connected to the data acquisition unit. The output of the microwave excitation unit is connected to the microwave loading unit via a microwave amplification component. The motion control unit is driven and connected to the displacement scanning unit, and is communicatively connected to the upper control unit. It is used to drive the displacement scanning unit to move the diamond NV color center detection unit and upload the current position information in real time. The data acquisition unit is communicatively connected to the upper control unit and is used to control the microwave excitation unit to perform frequency sweep after receiving the acquisition trigger signal, and to acquire the fluorescence electrical signal output by the fluorescence detection component to obtain the optical detection magnetic resonance spectrum. The upper control unit uses any of the above-mentioned two-dimensional magnetic field imaging methods based on diamond NV color centers to control the generation of two-dimensional magnetic field images.

[0012] The beneficial effects of this invention are: By setting a closed-loop control process of current position acquisition—position determination—lock-off trigger—spectral line acquisition, the displacement scanning unit performs photodetector magnetic resonance spectral line acquisition only after the measurement point is in position. This reduces the problem of misalignment between measurement point coordinates and magnetic field information caused by asynchronous scanning motion and acquisition, improving the positioning accuracy and data consistency of two-dimensional magnetic field imaging. At the same time, by identifying abnormal areas and generating fine scanning paths after coarse scanning, the imaging resolution of key areas can be guaranteed while taking into account the overall scanning efficiency, thereby improving the practicality of two-dimensional magnetic field imaging. (2) A reference point revisit and drift compensation mechanism is set up during the fine scanning process. By periodically re-acquiring the optically detected magnetic resonance spectrum of the reference point, the drift correction of the spectrum of the current batch of measurement points can be performed. This can reduce the resonance peak position shift caused by factors such as ambient temperature fluctuations, light source drift, and microwave frequency drift, thereby improving the stability and repeatability of the magnetic field calculation results under long-term and large-scale scanning conditions. Furthermore, this invention obtains magnetic field information by processing the optically detected magnetic resonance spectrum, and then matches the compensated magnetic field information with the corresponding coordinate information to generate a two-dimensional magnetic field distribution map, which is beneficial to improving the reliability and visualization effect of the imaging results. (3) Quantitative calibration and error correction are performed before scanning. By establishing a magnetic field strength-frequency offset calibration curve and combining repeated measurements, outlier removal, and averaging, the quantitative accuracy and reliability of the magnetic field measurement results can be improved. Therefore, this invention, while ensuring the feasibility of the technical solution, takes into account the positioning accuracy, measurement stability, scanning efficiency, and quantitative measurement capability of two-dimensional magnetic field imaging, and is suitable for two-dimensional magnetic field imaging applications in the fields of quantum sensing and precision measurement. Attached Figure Description

[0013] In the attached diagram: Figure 1 This is a flowchart of a two-dimensional magnetic field imaging method based on diamond NV color centers proposed in this invention; Figure 2 This is a diagram of the "three-level" structure of the diamond NV color center proposed in this invention; Figure 3 This is a schematic diagram of the optical path of the diamond NV color center using an optical fiber circulator proposed in this invention; Figure 4 This is a diagram of the two-dimensional magnetic field imaging system based on diamond NV color centers proposed in this invention; Figure 5 The ODMR image is obtained by fitting the method proposed in this invention; Figure 6 This is a magnetic field color temperature image generated based on the method proposed in this invention.

[0014] In the diagram: 100-Displacement scanning unit, 200-Upper control unit, 300-Optical excitation unit, 400-Optical signal transmission and collection unit, 500-Data acquisition unit, 600-Motion control unit, 700-Microwave excitation unit, 800-Diamond NV color center detection unit, 900-Microwave loading unit. Detailed Implementation

[0015] Example 1: Reference Figure 1 A two-dimensional magnetic field imaging method based on diamond NV color centers includes the following steps: S1. Coarse Scan Parameter Setting and Path Generation: Set the coarse scan area and coarse scan step parameters according to the range of the area to be measured, and preset the reference point position for drift compensation to generate a list of first target coordinates for full-range coarse scan. In this embodiment: the displacement scanning unit is controlled to perform an X-shaped coarse scan along the two diagonals of the area to be measured; magnetic field data is collected at preset intervals along the X-shaped coarse scan path; and abnormal areas where the rate of change of magnetic field strength exceeds a preset threshold are identified based on the coarse scan results. S2. Measurement point movement and position acquisition: The control displacement scanning unit drives the diamond NV color center detection unit to move sequentially along the first target coordinate list, and acquires the current position information in real time during the movement; In this embodiment: The spatial mapping matrix model is ,in, For the first Spatial coordinate vector of each sampling point This is the control pulse vector for the stepper motor. This is a diagonal matrix of pulse displacement conversion coefficients; In step S3, the positioning determination adopts a positioning criterion based on the infinite norm: (6); in, For real-time coordinates, For the target coordinates, This is the mechanical tolerance threshold, only when The control displacement scanning unit enters the locked state and outputs a data acquisition trigger signal.

[0016] S3. Position determination and lock trigger: The current position information is compared with the corresponding target coordinates. After determining that the target is in position, the displacement scanning unit is controlled to enter the lock state and the acquisition trigger signal is output. S4. Spectral line acquisition: In response to the acquisition trigger signal, the optical excitation unit is controlled to provide excitation light to the diamond NV color center detection unit, the microwave excitation unit is controlled to perform frequency sweep, and the fluorescence signal generated by the diamond NV color center detection unit is acquired to obtain the optical detection magnetic resonance spectrum of the current measurement point. S5. Coarse Scan Result Processing and Abnormal Region Identification: The optical detection magnetic resonance spectrum of the current measurement point is processed to obtain the magnetic field information of the current measurement point; after obtaining the magnetic field information of the measurement points corresponding to the first target coordinate list, abnormal regions are identified based on the coarse scan results, and a second target coordinate list for fine scanning is generated based on the boundary of the abnormal regions. In this embodiment: To eliminate common-mode interference from ambient temperature and crystal stress in magnetic field measurements, a model is built based on the effective Hamiltonian operator: (1); in, This is a Hamiltonian operator whose eigenvalues ​​correspond to the energies of the electron spin levels in the diamond NV color center. For zero-field splitting parameters, For temperature, This refers to the transverse splitting factor caused by localized stress in the crystal. It is a spin vector operator. , Let be the components of the electron spin operator in the three coordinate axes. Electron gyromagnetic ratio, The vector of the magnetic field to be measured; The acquired optically detected magnetic resonance (OMR) spectrum was subjected to noise reduction filtering. The center frequencies of the two resonance peaks were then extracted from the filtered OMR spectrum using a multi-peak Lorentz fitting algorithm. and ,in, This is to detect the center frequency of the higher-frequency resonance peak in the optical magnetic resonance spectrum. For the center frequency of the lower-frequency resonance peak, the Lorentz fitting function is in the form of: (2); in, For microwave frequencies, To fit the fluorescence intensity, For baseline offset, For the first The amplitude of each peak For the first The center frequency of each peak Half-height and half-width; Extracted resonance peak frequencies and known , Substitute into formula (1) to calculate the magnetic field strength at that point. : (3).

[0017] In this embodiment: a reciprocating S-shaped fine scanning path is generated based on the boundary of the abnormal region to perform a line-by-line fine scanning of the abnormal region.

[0018] S6. Fine scanning of abnormal areas: The control displacement scanning unit drives the diamond NV color center detection unit to perform fine scanning of the abnormal areas along the second target coordinate list, and performs current position acquisition, positioning determination, lock triggering, optical detection magnetic resonance spectrum acquisition and magnetic field information acquisition for each target coordinate in the second target coordinate list in sequence. S7. Reference point revisit and drift compensation: After completing the scanning of each predetermined batch of measurement points during the fine scanning process, the displacement scanning unit is controlled to return to the reference point position and the photodetector magnetic resonance spectrum of the reference point is re-acquired in order to compensate for the drift of the photodetector magnetic resonance spectrum of the current batch of measurement points. In this embodiment: S71: Before the scan starts, the displacement scanning unit moves the diamond NV color center detection unit to the reference point, collects the zero magnetic field reference spectrum, and extracts the center frequency of its resonance peak amplitude by fitting the formula (2). ; S72: Record start time After each batch of measurement points is scanned, the scanning process is paused. The displacement scanning unit drives the diamond NV color center detection unit back to the reference point, and sequentially executes the current position acquisition, positioning determination, and lock-off triggering. The optical detection magnetic resonance spectrum of that point is then re-acquired to obtain the current reference frequency. ; S73: Record the current moment Calculate the drift slope : (4); S74: Let the first The original measurement frequency of each measuring point is The time of its collection is , of which The first measuring point is the measuring point for this batch, the [number]th ... Frequency after drift compensation correction at each measuring point for: (5); S75: Adjust the frequency Substitute into formula (3) to recalculate the magnetic field strength, replace the original uncorrected result, and update the storage; S76: Update baseline parameters , As the reference spectral line for the next batch of measurement points S8. Data Matching and Imaging Output: Match the compensated magnetic field information of each measuring point with the corresponding coordinate information to generate a two-dimensional magnetic field distribution map.

[0019] In this embodiment: before executing S1, a quantitative calibration and error correction step is also included. The quantitative calibration and error correction step includes: placing the diamond NV color center detection unit in the uniform magnetic field region of a standard uniform magnetic field source, setting different standard magnetic field values ​​in sequence and acquiring the corresponding photodetector magnetic resonance spectrum, and establishing a magnetic field strength-frequency offset calibration curve; during the scanning imaging process, linearly correcting the calculated magnetic field strength according to the calibration curve, and repeatedly measuring the same measurement point a number of times, using the average value and standard deviation σ of each measurement result as the statistical basis, eliminating abnormal measurement values ​​that exceed the range of the average value ±3σ, and then taking the average value of the remaining valid data as the final measurement result.

[0020] Example 2: A two-dimensional magnetic field imaging system based on diamond NV centers, applying any one of the schemes of the two-dimensional magnetic field imaging method based on diamond NV centers in Example 1, the system includes: a displacement scanning unit 100, a host control unit 200, a light excitation unit 300, a light signal transmission and collection unit 400, a data acquisition unit 500, a motion control unit 600, a microwave excitation unit 700, a diamond NV center detection unit 800, and a microwave loading unit 900; The diamond NV color center detection unit 800 is fixedly installed at the displacement execution end of the displacement scanning unit 100, and the microwave loading unit 900 is installed around the diamond NV color center detection unit 800. The output terminal of the optical excitation unit 300 is connected to the input terminal of the optical signal transmission and collection unit 400. The output terminal of the optical signal transmission and collection unit 400 is optically coupled to the diamond NV color center detection unit 800. The optical signal transmission and collection unit 400 is also connected to the fluorescence detection component. The electrical signal output terminal of the fluorescence detection component is connected to the data acquisition unit 500. The output of the microwave excitation unit 700 is connected to the microwave loading unit 900 via a microwave amplification component. The motion control unit 600 is driven and connected to the displacement scanning unit 100 and communicates with the upper control unit 200. It is used to drive the displacement scanning unit 100 to move the diamond NV color center detection unit 800 and upload the current position information in real time. The data acquisition unit 500 is communicatively connected to the upper control unit 200. After receiving the acquisition trigger signal, it controls the microwave excitation unit 700 to perform frequency sweep and acquires the fluorescence electrical signal output by the fluorescence detection component to obtain the optical detection magnetic resonance spectrum. Example 1 of application of the upper control unit 200: Control the generation of two-dimensional magnetic field imaging using any scheme of the two-dimensional magnetic field imaging method based on diamond NV color centers.

[0021] In an optional embodiment, the system is equipped with an infrared ranging unit in the Z-axis direction, which can adjust the probe position in the Z-axis direction according to the shape of the sample throughout the scanning process.

[0022] Example 3: To more clearly illustrate the implementation plan and its effects, we will use the attached diagram as an example: Reference Figure 4 This embodiment is based on a two-dimensional magnetic field imaging system using diamond NV color centers: The displacement scanning unit 100 uses a three-axis precision ball screw slide, with X-axis and Y-axis travel of 0-100mm and Z-axis travel of 0-50mm. The positioning accuracy can reach 0.01mm. Each axis of the slide is equipped with a two-phase hybrid stepper motor, which, together with the ball screw transmission mechanism, achieves precision displacement. The upper control unit 200 can be a regular desktop computer or a laptop computer, pre-installed with Windows or Linux operating system, Python 3.8 or above, and PyQt5, NumPy, SciPy, PySerial, Matplotlib and other dependent libraries, and runs a dedicated upper computer control program. The optical excitation unit 300 uses a 532nm single-mode fiber laser with an adjustable output power of 0-200mW. The output fiber is a single-mode polarization-maintaining fiber, and a matching laser power supply is used to achieve power control and stable output. The optical signal transmission and collection unit 400 adopts a three-port fiber optic circulator with a working wavelength covering 532nm and 600-800nm. Each port is an FC / APC interface with low insertion loss and an isolation greater than 50dB, ensuring unidirectional and efficient transmission of pump light and fluorescence. The data acquisition unit 500 uses a data acquisition card, specifically the RedPitaya125-14 open-source hardware development board, equipped with a dual-core ARM processor and a 14-bit high-speed ADC / DAC, with a sampling rate of 125MS / s, and communicates with the PC host computer via Ethernet. The core control unit of the motion control unit 600 uses an STM32F407IGT6 microcontroller, and the motion control unit 600 uses a digital stepper motor driver, which can set the microstepping parameters through a DIP switch; The microwave excitation unit 700 uses a programmable radio frequency microwave source with an output frequency range covering 2.8-3.0GHz, adjustable output power, and supports external triggering and programmable frequency sweeping functions. The microwave amplification component uses an RF power amplifier, operating in the 2-4GHz frequency band, with adjustable gain; The NV Diamond Color Center Detector 800 uses NV... - The ensemble diamond sample, measuring 2mm × 2mm × 0.5mm, with a nitrogen impurity concentration of approximately 1ppm, is fixed to the Z-axis slide end of a three-axis precision ball screw slide using a clamp. The fluorescence detection component uses a high-sensitivity silicon-based photodetector, paired with a low-noise preamplifier circuit, with a response wavelength covering 400-1000nm; the focusing lens uses an aspherical focusing lens to precisely focus the pump light onto the sensitive area of ​​the diamond NV color center, while efficiently collecting the fluorescence signal generated by excitation. The microwave loading unit 900 uses a small radio frequency coil wound with enameled copper wire, which is fixed on the probe fixture of the diamond NV color center to apply a uniform microwave field to the diamond NV color center. The connection method is as follows: The fiber optic output of the laser is connected to the first port of the fiber optic circulator via a fiber optic flange. The second port of the fiber optic circulator is connected to the fiber optic collimator via fiber optic cable. The light emitted from the collimator is focused onto the diamond NV color center by a focusing lens. The third port of the fiber optic circulator is connected to the optical input interface of the fluorescence detection component via fiber optic cable. The signal output of the fluorescence detection component is connected to the analog input channel of the data acquisition card via a coaxial shielded cable. The RF output of the microwave source is connected to the input of the microwave amplifier via an RF coaxial cable. The output of the microwave amplifier is connected to both ends of the coil via an RF cable. The programmable interface of the microwave source is connected to the control interface of the data acquisition card. In the motion control unit 600, the GPIO port of the STM32 microcontroller is connected to the signal input of the stepper motor driver, where the PUL pin outputs the stepper motor signal. The system outputs a pulse signal, a direction control signal from the DIR pin, and an enable signal from the ENA pin. The power output terminal of the stepper motor driver is connected to the two-phase winding of the stepper motor. The stepper motor is connected to the lead screw transmission mechanism of the slide platform via a coupling. The serial port pin of the STM32 microcontroller is connected to the USB interface of the PC host computer via a USB-to-serial module. Peripheral components such as an emergency stop button and status indicator lights are soldered onto the hardware circuit of the STM32 microcontroller. The two ends of the emergency stop button are connected to the interrupt pin of the microcontroller and ground, respectively. The data acquisition card is connected to the network port of the PC host computer via a network cable, or connected to a local area network on the same network segment as the PC host computer. The hardware modules of the entire system are integrated and fixed using an aluminum profile bracket. The optical components of the optical path are fixed using an optical adjustment bracket. The slide platform is fixed to the optical breadboard or equipment chassis via a base plate.

[0023] Reference Figure 2 The core working principle of the system is based on optically detected magnetic resonance (ODMR) technology for diamond NV centers. Diamond's crystal structure consists of tetrahedral unit cells made up of carbon atoms, with each unit cell containing eight carbon atoms. A diamond NV center is formed when one of these carbon atoms is replaced by a nitrogen atom, creating a lattice vacancy at an adjacent position. The stable defect structure formed by the nitrogen atom and the vacancy results in a negatively charged NV center. - The color center consists of six electrons, forming a triplet system with spin S=1. Its energy level structure is mainly divided into the triplet ground state. 3 A2, triplet excited state 3 E and singlet metastable states, where the triplet ground state is determined by m s =0 and m s =±1 state composition, m under zero magnetic field s =+1 and m s The -1 energy level is degenerate, and the zero-field splitting parameter D is approximately 2.87 GHz. When the diamond NV color center is irradiated with 532 nm pump light, the electrons in the ground state are excited to the excited state. Electrons with spin 0 will spontaneously transition back to the ground state, emitting red fluorescence in the 637 nm-800 nm range. Electrons with spin ±1 will partially decay to a metastable state through intersystem crossing, and then non-radiatively transition back to the ground state. s The process does not produce fluorescence in the ground state of m = 0. Continuous pump light irradiation will continuously polarize electrons to m. s The spin state = 0 completes the initialization of the diamond NV center spin system, at which point the fluorescence intensity reaches a stable state. When a microwave field matching the energy level difference is applied, m s Electrons with a value of 0 will be excited to m s The ±1 state leads to a decrease in fluorescence intensity. By continuously scanning the microwave frequency and simultaneously recording the corresponding fluorescence intensity, the ODMR spectrum showing the fluorescence intensity changing with the microwave frequency can be obtained, and a resonance absorption peak will appear on the spectrum. When an external magnetic field is present, the degenerate energy level of the ground state of the diamond NV color center undergoes Zeeman splitting, m s =+1 and m s When the energy level = -1 separates, the corresponding resonance absorption peak splits, and the center frequencies of the two resonance peaks shift symmetrically relative to the zero-field splitting frequency.

[0024] The optical path of the system is as follows Figure 3As shown, the workflow is as follows: After the laser is started, it outputs a stable 532nm linearly polarized pump light. The pump light is transmitted through a single-mode fiber to the first port of the fiber circulator. Based on the unidirectional transmission characteristics of the fiber circulator, the optical signal is output from the second port. After passing through the fiber collimator and focusing lens, it is focused onto the diamond NV center, performing continuous optical polarization and spin initialization on the diamond NV center. The 600-800nm ​​red fluorescence generated by the excited diamond NV center is collected by the same focusing lens and collimator and coupled into the second port of the fiber circulator. The fluorescence signal cannot be transmitted back to the first port and can only be output from the third port, transmitted to the fluorescence detection component. The photodiode in the fluorescence detection component converts the fluorescence signal into a weak current signal, which is converted into a voltage signal by the built-in low-noise preamplifier circuit and amplified, and output to the analog acquisition channel of the data acquisition card, completing the entire process of optical signal transmission, excitation, collection and photoelectric conversion. This all-fiber optical path design does not require complex spatial optical path adjustment, greatly improving the stability and portability of the system.

[0025] To achieve closed-loop control of the entire motion-acquisition process, hardware-level timing synchronization, and periodic drift compensation, the STM32 microcontroller lower-level program in this embodiment is developed in C language using the KeilMDK development environment. The program sets independent 32-bit signed pulse counters for the X, Y, and Z axes respectively. After system power-on, the user sets the range of the area to be measured (X: 0-100mm, Y: 0-100mm, coarse scan step: 5mm, fine scan step: 0.5mm, etc.) through the graphical interface of the PC host computer. The first stage is the X-shaped coarse scan. The PC host computer generates a list of target coordinates for the X-shaped path: uniformly discrete points on the two diagonals of the rectangular area, with approximately [missing information - likely a reference to a specific point on each diagonal]. Side length / step number of points. The host computer sends movement commands (format "G00X%Y%Z%f%Z%f%r%n") to the STM32 microcontroller via UART serial port. The STM32 microcontroller's built-in three-axis coordinate real-time acquisition and upload module executes the following process: Independent 32-bit signed pulse counters are set for each of the X / Y / Z three-axis stepper motors. The microcontroller outputs one step pulse to each stepper motor driver, and the pulse counter of the corresponding axis synchronously increments (forward) or decrements (reverse) according to the direction of motion; the pre-stored pulse count-physical coordinate conversion coefficient... The three-axis pulse count is converted into the current coordinates in real time according to the formula: , , The current three-axis coordinate data is cyclically sent to the PC via serial port at a fixed frequency of 10Hz-20Hz, with the format "X + value Y + value Z + value". The PC continuously receives the real-time coordinates uploaded by the STM32. And when compared with the current target coordinates Perform a comparison. The comparison is based on the positioning criterion shown in formula (6): when When the time is right, it is determined to be in place. In this embodiment... mm. After the ODMR acquisition and magnetic field calculation are completed at the measurement points on each X-shaped path, the system generates a roughness magnetic field heat map in real time. The gradient analysis identifies the area where the magnetic field intensity change exceeds the preset threshold. In this embodiment, the threshold is 0.1 mT / mm, and the area is marked as the boundary of the abnormal area. Second stage: S-shaped fine scanning. For the identified abnormal area, in this embodiment, the abnormal area is X: 30-50mm, Y: 40-60mm. The host computer automatically generates a target coordinate list of the S-shaped fine scanning path. The S-shaped path is reciprocating: after the X-axis moves from the beginning end (30mm) of the abnormal area to the end end (50mm), the Y-axis advances by one fine advance unit (0.5mm in this embodiment). The X-axis then moves back from the end end to the beginning end, and repeats until the entire abnormal area is covered (Y from 40mm to 60mm, a total of 41 rows). The positioning determination of each measurement point is also based on formula (6) to ensure the spatial positioning accuracy of each sampling point.

[0026] The PC host computer control program is developed using Python and features a graphical user interface built with PyQt5. The program utilizes the PySerial library to develop a serial communication module for sending commands and receiving coordinate data from the STM32 microcontroller; and a Socket communication module for Ethernet communication to send commands and receive raw ODMR data from the RedPitaya data acquisition card. After the user sets the start and end coordinates of the scanning area, step resolution, and Z-axis height through the UI, the program automatically generates a list of target coordinates for an S-shaped path, arranged in scanning order. After scanning starts, the program sends the first target coordinate movement command to the STM32, continuously receiving real-time coordinates and comparing them with the target coordinates. When the absolute values ​​of the differences in the X, Y, and Z axes are all less than a preset threshold (default 0.02mm), the slide is considered to be in position. Upon this determination, a lock command is sent to the host computer, simultaneously triggering the data acquisition card to start the ODMR scan via Ethernet. The data acquisition card uses GPIO trigger signals to ensure the slide is stationary before starting frequency scanning and data acquisition. After completing data acquisition and magnetic field calculation, the next target coordinate movement command is issued, and the process is repeated until the full area scan is completed. Before the scan starts, the slide is controlled to move to the reference point, the zero magnetic field ODMR reference spectrum is acquired, the center frequency of the reference resonance peak is extracted and stored; during the scan, after each preset number of scans is completed, the slide is automatically controlled to return to the reference point, the spectrum is reacquired and the peak position drift is calculated, and the ODMR spectrum acquired in the current batch is linearly corrected to effectively suppress the peak position drift caused by environmental factors. The standard magnetic field calibration curve is pre-stored, and the calculated magnetic field strength is linearly corrected based on the calibration curve during the scan; the same measurement point is measured repeatedly. In this embodiment, the number of times is 3 times, and the abnormal values ​​exceeding the 3σ range are removed. The average value is taken as the final measurement result. The original ODMR signal is subjected to noise reduction and filtering. The center frequencies of the two resonance peaks are extracted by multi-peak Lorentz fitting. Combined with the zero field splitting parameter, the crystal local stress correction term and the electron gyromagnetic ratio parameter, the magnetic field strength is calculated by substituting into formula (1) and formula (3) to obtain the magnetic field information of the corresponding measurement point. Finally, the coordinates of discrete measurement points and magnetic field strength data are gridded, and a continuous spatial magnetic field distribution surface is generated using a radial basis function interpolation algorithm. This surface is then converted into a two-dimensional magnetic field color temperature distribution map using color mapping rules. The map supports image scaling, translation, saving, and export of the original data.

[0027] This system supports multiple operating modes, including single-point ODMR measurement mode, automated two-dimensional scanning imaging mode, and dual-energy spectral measurement mode, to meet different experimental and measurement needs. In single-point ODMR measurement mode, the user can control the slide platform via a PC to move the diamond NV color center to the target measurement point. After setting the microwave sweep parameters, single or continuous ODMR signal acquisition is initiated. The PC displays the ODMR spectrum in real time, completing peak identification and magnetic field calculation, suitable for precise magnetic field measurement at fixed points and principle demonstration experiments. In automated two-dimensional scanning imaging mode, after the user sets the scanning area and step parameters, the system automatically completes point-by-point scanning, data acquisition, magnetic field calculation, and image generation of the entire area without manual intervention, suitable for visual imaging of the magnetic field distribution on the surface of the sample. In dual-energy spectral measurement mode, multiple sets of microwave parameters can be configured to complete ODMR measurements at the same measurement point with different powers and sweep frequency ranges, or multiple microwave sources can be expanded to achieve synchronous measurement of different frequency bands, further improving the accuracy and anti-interference capability of magnetic field measurement.

[0028] The py3diamond program on the PC host computer is divided into five core modules: UI module, motion control module, data acquisition module, signal processing module, and imaging visualization module. The UI module is built on PyQt5 and consists of three functional pages: the main page, the derivative analysis page, and the magnetocolor temperature map analysis page. Figure 5 As shown, the main page integrates ODMR parameter configuration, scan control, real-time spectral line display, and analysis result display functions; the derivative analysis page provides first and second derivative analysis functions for ODMR spectral lines, which can accurately identify the position and boundary of resonance peaks; the magnetic color temperature map analysis page is used to display the generated two-dimensional magnetic field color temperature distribution map, such as... Figure 6As shown, interactive viewing and data export functions are provided. The motion control module is developed based on Python's serial library, implementing serial communication configuration, connection, and disconnection. It can send motion control commands to the STM32 microcontroller and simultaneously parse the coordinate data uploaded by the microcontroller, realizing real-time monitoring and control of the slide position. The data acquisition module is developed based on Socket communication, realizing Ethernet communication with the RedPitaya data acquisition card. It can send acquisition and microwave control commands, and simultaneously receive raw ODMR data uploaded by the acquisition card, completing data caching and preprocessing. The signal processing module integrates algorithms such as digital filtering, multi-peak Lorentz fitting, derivative analysis, deep learning peak recognition, and magnetic field calculation. The Lorentz fitting algorithm can accurately fit the resonance peaks of ODMR spectra, extracting parameters such as peak center frequency, linewidth, and contrast. The derivative analysis algorithm calculates the first and second derivatives of the spectral lines to accurately locate the maximum slope point and peak boundary of the resonance peaks, improving the accuracy of peak recognition. The deep learning-assisted peak recognition algorithm uses a lightweight convolutional neural network model, which can accurately identify resonance peaks in low signal-to-noise ratio environments, improving the system's anti-interference capability. The magnetic field calculation algorithm accurately calculates the magnetic field strength value based on the extracted resonance peak frequency offset and the gyromagnetic ratio parameter, and evaluates the uncertainty of the calculation results. The imaging visualization module is developed based on the Matplotlib and NumPy libraries, realizing the gridding, interpolation, color mapping, and image generation of discrete magnetic field data, while also supporting image scaling, translation, and saving operations.

[0029] After receiving the raw ODMR data, the PC host computer first performs digital filtering and noise reduction processing (in this embodiment, a Savitzky-Golay filter is used, with a window width of 11 and a polynomial order of 3). The center frequencies of the two resonance peaks of the filtered spectrum are extracted using a multi-peak Lorentz fitting algorithm. and The Lorentz fitting function is in the form of: (2); in, Microwave frequency (unit: MHz). To fit the fluorescence intensity (unit: V). For baseline offset, For the first The amplitude of each peak For the first The center frequency of each peak The width at half maximum (WHM) is half the height. The system has already met the baseline standard before frequency sweep startup: under conditions without an external magnetic field (achieved through a magnetic shielding cylinder, residual magnetic field...). The baseline ODMR spectrum was collected, and the zero-field splitting parameters at the current temperature were obtained by fitting the data. The precise value. Then, for each measurement point, the extracted resonant frequency... and known , Substitute into formula (3) to calculate the magnetic field strength at that point. (Unit: G): (3); To further obtain information about the direction of the magnetic field, the vector angle can be calculated using the cosine projection relationship. Let the unit vector of the magnetic field direction be... ,in Polar angle ( arrive ), Azimuth ( arrive The direction of the magnetic field is then parallel to the first... NV axis unit vector The included angle satisfy: (7); In the NV coordinate system, the unit vectors of the directions of the four NV axes are respectively , , , By combining the frequency offsets measured along the four NV axes, the magnetic field vector can be solved inversely. The complete pointer.

[0030] When performing long-stroke, large-area fine scanning (e.g., scanning more than 30 lines or total time exceeding 30 minutes), the system automatically executes the drift compensation process. The specific steps are as follows: (1) Before scanning starts, control the slide to move to the physical reference point (coordinate origin). Zero-magnetic-field ODMR reference lines were acquired, and the center frequencies of their resonance peak amplitudes were extracted using Lorentz fitting. Record the start time (Time via PC system, unit: s); (2) After completing the preset number of rows (10 rows in this embodiment) of S-shaped scanning, the system pauses the scanning process and sends the command "HOME" to the STM32 microcontroller to return to the reference point. After the slide returns to the reference point and completes the positioning judgment according to formula (6), the ODMR spectrum of that point is re-acquired to obtain the current reference frequency. Record the current moment (3) Calculate the drift slope according to formula (4). (4) Since the last drift correction (i.e., since...) arrive (between) all the measuring points that have been collected, let the first one be... The original measurement frequency of each measuring point is The time of its collection is Then, linear correction is performed according to formula (6): (5); in, The corrected frequency (unit: MHz). The elapsed time from the start point to the measurement point (in seconds). (5) The corrected frequency Substitute into formula (3) to recalculate the magnetic field strength, replace the original uncorrected result, and update the storage. (6) Update the reference parameters: Let , The subsequent scans continued. This correction mechanism is based on the physical fact that changes in ambient temperature are approximately linear over a short period of time, effectively eliminating system errors introduced by factors such as gradual temperature changes, laser power fluctuations, and microwave source frequency drift. Experimental verification showed that during a 2-hour continuous scan, the peak drift of this system decreased from over 2MHz without compensation to below 400kHz, a drift reduction of 80%, and a significant improvement in imaging overlap.

[0031] The complete workflow is as follows: After the system is powered on, the hardware initialization of the laser, microwave source, data acquisition card, and STM32 microcontroller is completed. Initial Z-axis focusing is performed via the PC host computer, and the standard magnetic field calibration process is executed to generate a magnetic field strength-frequency offset calibration curve. The user sets the scanning area, step resolution, scanning speed, drift correction cycle, and microwave sweep frequency parameters via the PC host computer, which automatically generates a target coordinate list for the S-shaped path. The scanning process is initiated, and the PC host computer sends the first target coordinate movement command to the STM32 microcontroller, which drives the slide to move towards the target coordinate. During the movement, the STM32 microcontroller uploads the current coordinates of the slide in real time, and the PC host computer continuously compares the current coordinates with the target coordinates until the target position is determined. After the target position is determined, the PC host computer sends a lock command to the STM32 microcontroller. The STM32 microcontroller locks the motor and sends a hardware trigger signal to the data acquisition card via GPIO. The data acquisition card then initiates ODMR scanning, completing the synchronous acquisition of fluorescence and microwave signals. The PC processes the acquired ODMR data, performing peak fitting, drift correction, magnetic field calculation, and error correction, and storing the coordinates of the current measurement point in association with the magnetic field strength. After the magnetic field calculation is completed, the PC sends a movement command to the STM32 microcontroller for the next target coordinate, repeating the above steps until all measurement points are scanned. During the scanning process, after each preset number of rows is scanned, the reference point drift correction process is automatically executed to correct the acquired data. After the full area scan is completed, the PC integrates and processes all measurement point data to generate a two-dimensional magnetic field color temperature distribution map of the area to be measured, completing the entire measurement process.

[0032] To verify the performance indicators of the system of this invention, a comprehensive performance test was conducted on the completed imaging system. The test content included four core indicators: spatial resolution, magnetic field sensitivity, measurement uncertainty, and positioning accuracy. In the spatial resolution test, the scanning step resolution was set to 1 mm, and a standard magnetic sample was scanned and imaged. The system could clearly distinguish magnetic field features at 1 mm intervals, achieving a spatial resolution of 1 mm. Reducing the step resolution can further improve the spatial resolution capability, balancing scanning efficiency and resolution requirements. In the magnetic field sensitivity test, ODMR signals from fixed points were continuously acquired, the time-domain fluctuations of the magnetic field solution results were recorded, and the magnetic field noise power spectral density was calculated. The integral calculation was performed within the frequency range of 100-1000 Hz, and the measured magnetic field sensitivity of the system reached [value missing]. Superior The design specifications are as follows. In the magnetic field detection uncertainty test, a standard uniform magnetic field is generated using a triaxial Helmholtz coil. The probe is placed within the uniform magnetic field region, and multiple repeated measurements are performed. Statistical analysis of the measurement results shows that the Type A uncertainty of the magnetic field measurement is 0.05 mT, indicating high measurement accuracy. In the coordinate positioning accuracy test, a marker pen is fixed on the slide, and the slide is controlled to execute a preset scanning path, drawing the motion trajectory on paper. The trajectory dimensions are measured using a high-precision measuring tool, and the single-step movement distance is repeatedly tested. The Type A uncertainty of the slide's single-step movement distance is 0.05 mm, demonstrating excellent positioning accuracy and motion repeatability, ensuring the accuracy of the scanning position.

Claims

1. A two-dimensional magnetic field imaging method based on diamond NV color centers, characterized in that, The method steps are as follows: S1. Coarse Scan Parameter Setting and Path Generation: Set the coarse scan area and coarse scan step parameters according to the range of the area to be measured, and preset the reference point position for drift compensation to generate a list of first target coordinates for full-range coarse scan. S2. Measurement point movement and position acquisition: The control displacement scanning unit drives the diamond NV color center detection unit to move sequentially along the first target coordinate list, and acquires the current position information in real time during the movement; S3. Position determination and lock trigger: The current position information is compared with the corresponding target coordinates. After determining that the target is in position, the displacement scanning unit is controlled to enter the lock state and the acquisition trigger signal is output. S4. Spectral line acquisition: In response to the acquisition trigger signal, the optical excitation unit is controlled to provide excitation light to the diamond NV color center detection unit, the microwave excitation unit is controlled to perform frequency sweep, and the fluorescence signal generated by the diamond NV color center detection unit is acquired to obtain the optical detection magnetic resonance spectrum of the current measurement point. S5. Coarse Scan Result Processing and Abnormal Region Identification: The optical detection magnetic resonance spectrum of the current measurement point is processed to obtain the magnetic field information of the current measurement point; after obtaining the magnetic field information of the measurement points corresponding to the first target coordinate list, abnormal regions are identified based on the coarse scan results, and a second target coordinate list for fine scanning is generated based on the boundary of the abnormal regions. S6. Fine scanning of abnormal areas: The control displacement scanning unit drives the diamond NV color center detection unit to perform fine scanning of the abnormal areas along the second target coordinate list, and performs current position acquisition, positioning determination, lock triggering, optical detection magnetic resonance spectrum acquisition and magnetic field information acquisition for each target coordinate in the second target coordinate list in sequence. S7. Reference point revisit and drift compensation: After completing the scanning of each predetermined batch of measurement points during the fine scanning process, the displacement scanning unit is controlled to return to the reference point position and the photodetector magnetic resonance spectrum of the reference point is re-acquired in order to compensate for the drift of the photodetector magnetic resonance spectrum of the current batch of measurement points. S8. Data Matching and Imaging Output: Match the compensated magnetic field information of each measuring point with the corresponding coordinate information to generate a two-dimensional magnetic field distribution map.

2. The two-dimensional magnetic field imaging method based on diamond NV color centers according to claim 1, characterized in that, The methods for obtaining magnetic field information in steps S5, S6, and S7 are as follows: To eliminate common-mode interference from ambient temperature and crystal stress in magnetic field measurements, a model is built based on the effective Hamiltonian operator: （1）； in, This is a Hamiltonian operator whose eigenvalues ​​correspond to the energies of the electron spin levels in the diamond NV color center. For zero-field splitting parameters, For temperature, This refers to the transverse splitting factor caused by localized stress in the crystal. It is a spin vector operator. , Let be the components of the electron spin operator in the three coordinate axes. Electron gyromagnetic ratio, The vector of the magnetic field to be measured; The acquired optically detected magnetic resonance (OMR) spectrum was subjected to noise reduction filtering. The center frequencies of the two resonance peaks were then extracted from the filtered OMR spectrum using a multi-peak Lorentz fitting algorithm. and ,in, This is to detect the center frequency of the higher-frequency resonance peak in the optical magnetic resonance spectrum. For the center frequency of the lower-frequency resonance peak, the Lorentz fitting function is in the form of: （2）； in, For microwave frequencies, To fit the fluorescence intensity, For baseline offset, For the first The amplitude of each peak For the first The center frequency of each peak Half-height and half-width; Extracted resonance peak frequencies and known , Substitute into formula (1) to calculate the magnetic field strength at that point. : （3）。 3. The two-dimensional magnetic field imaging method based on diamond NV color centers according to claim 2, characterized in that, In step S7: S71: Before the scan starts, the displacement scanning unit moves the diamond NV color center detection unit to the reference point, collects the zero magnetic field reference spectrum, and extracts the center frequency of its resonance peak amplitude by fitting the formula (2). ; S72: Record start time After each batch of measurement points is scanned, the scanning process is paused. The displacement scanning unit drives the diamond NV color center detection unit back to the reference point, and sequentially executes the current position acquisition, positioning determination, and lock-off triggering. The optical detection magnetic resonance spectrum of that point is then re-acquired to obtain the current reference frequency. ; S73: Record the current moment Calculate the drift slope : （4）； S74: Let the first The original measurement frequency of each measuring point is The time of its collection is , of which The first measuring point is the measuring point for this batch, the [number]th ... Frequency after drift compensation correction at each measuring point for: （5）； S75: Adjust the frequency Substitute into formula (3) to recalculate the magnetic field strength, replace the original uncorrected result, and update the storage; S76: Update baseline parameters , This will serve as the baseline spectral line for the next batch of measurement points.

4. The two-dimensional magnetic field imaging method based on diamond NV color centers according to claim 1, characterized in that, In step S2: The spatial mapping matrix model is ,in, For the first Spatial coordinate vector of each sampling point This is the control pulse vector for the stepper motor. This is a diagonal matrix of pulse displacement conversion coefficients; In step S3, the positioning determination adopts a positioning criterion based on the infinite norm: （6）； in, For real-time coordinates, For the target coordinates, This is the mechanical tolerance threshold, only when The control displacement scanning unit enters the locked state and outputs a data acquisition trigger signal.

5. The two-dimensional magnetic field imaging method based on diamond NV color centers according to claim 1, characterized in that: In step S1, the displacement scanning unit is controlled to perform an X-shaped coarse scan along the two diagonals of the area to be measured; magnetic field data is collected at preset intervals along the X-shaped coarse scan path; abnormal areas where the rate of change of magnetic field strength exceeds a preset threshold are identified based on the coarse scan results; in step S5, a reciprocating S-shaped fine scan path is generated based on the boundary of the abnormal area to perform a line-by-line fine scan of the abnormal area.

6. The two-dimensional magnetic field imaging method based on diamond NV color centers according to claim 1, characterized in that, Before executing S1, a quantitative calibration and error correction step is also included. The quantitative calibration and error correction step includes: placing the diamond NV color center detection unit in the uniform magnetic field region of a standard uniform magnetic field source, setting different standard magnetic field values ​​in sequence and acquiring the corresponding photodetector magnetic resonance spectra, and establishing a magnetic field strength-frequency offset calibration curve; during the scanning imaging process, linearly correcting the calculated magnetic field strength according to the calibration curve, and repeatedly measuring the same measurement point a number of times, using the average value and standard deviation σ of each measurement result as the statistical basis, eliminating abnormal measurement values ​​that exceed the range of the average value ±3σ, and then taking the average value of the remaining valid data as the final measurement result.

7. A two-dimensional magnetic field imaging system based on diamond NV color centers, characterized in that: The system using the two-dimensional magnetic field imaging method based on diamond NV centers as described in any one of claims 1-6 comprises: a displacement scanning unit (100), a host control unit (200), a photoexcitation unit (300), a photosignal transmission and collection unit (400), a data acquisition unit (500), a motion control unit (600), a microwave excitation unit (700), a diamond NV center detection unit (800), and a microwave loading unit (900). The diamond NV color center detection unit (800) is fixedly disposed at the displacement execution end of the displacement scanning unit (100), and the microwave loading unit (900) is disposed around the diamond NV color center detection unit (800); The output end of the photoexcitation unit (300) is connected to the input end of the optical signal transmission and collection unit (400), the output end of the optical signal transmission and collection unit (400) is optically coupled to the diamond NV color center detection unit (800), the optical signal transmission and collection unit (400) is also connected to the fluorescence detection component, and the electrical signal output end of the fluorescence detection component is connected to the data acquisition unit (500). The output of the microwave excitation unit (700) is connected to the microwave loading unit (900) via a microwave amplification assembly; The motion control unit (600) is driven and connected to the displacement scanning unit (100) and communicates with the host control unit (200) to drive the displacement scanning unit (100) to move the diamond NV color center detection unit (800) and upload the current position information in real time. The data acquisition unit (500) is communicatively connected to the upper control unit (200) and is used to control the microwave excitation unit (700) to perform frequency sweep after receiving the acquisition trigger signal, and to acquire the fluorescence electrical signal output by the fluorescence detection component to obtain the optical detection magnetic resonance spectrum. The upper control unit (200) uses the two-dimensional magnetic field imaging method based on diamond NV color centers as described in any one of claims 1-6 to control the generation of two-dimensional magnetic field images.

Images