CN-121995281-A - Wide-field magnetic field imaging method based on sparse sampling and Bayesian estimation

CN121995281ACN 121995281 ACN121995281 ACN 121995281ACN-121995281-A

Abstract

The application provides a wide-field magnetic field imaging method based on sparse sampling and Bayesian estimation, which belongs to the field of magnetic field imaging and comprises the following steps of constructing an NV color center system to measure and record magnetic field information to be measured, selecting a small number of discrete sampling points to measure magnetic field intensity data of the NV color center system in an imaging view field of a detected area, constructing an error correlation function among pixel points in the detected area, establishing a Bayesian estimation model, taking the magnetic field intensity data of the small number of discrete sampling points as observables, predicting the magnetic field intensity of unmeasured pixel points in a whole view field to obtain a preliminarily reconstructed magnetic field distribution image, selecting a plurality of reference points in the detected area to obtain a nominal magnetic field value and an actually measured magnetic field value, and calibrating the preliminarily reconstructed magnetic field distribution image in a mean value proportion correction mode.

Inventors

Tian Jiazhao
CHANG XINYU
Duan Bogun
ZHANG HAO
Li Kangze
LIU KEQING
LIAO TINGYU
XIAO LIANTUAN

Assignees

太原理工大学

Dates

Publication Date: 20260508
Application Date: 20260122

Claims (9)

1.A wide-field magnetic field imaging method based on sparse sampling and Bayesian estimation is characterized by comprising the following steps: Step S1, constructing a diamond magnetic field detection system containing an NV color center, optically exciting a detected area, and applying a dynamic decoupling sequence matched with an alternating current magnetic field signal to be detected, so that the NV color center spins record magnetic field information to be detected in an evolution process; S2, selecting a small number of discrete sampling points in an imaging view field of a measured area, measuring NV fluorescent signals or population numbers of the sampling points, and converting a measurement result into magnetic field intensity data based on a phase accumulation model; S3, constructing an error correlation function among pixel points in a detected area, constructing a Bayesian estimation model, taking magnetic field intensity data of a small number of discrete sampling points as observables, and predicting the magnetic field intensity of unmeasured pixel points in a full view field to obtain a preliminarily reconstructed magnetic field distribution image; and S4, selecting a plurality of reference points in the detected area, acquiring a nominal magnetic field value and an actually measured magnetic field value, and calibrating the preliminarily reconstructed magnetic field distribution image by adopting a mean value proportion correction mode to acquire a corrected magnetic field imaging result.
2. The method for imaging a wide field magnetic field based on sparse sampling and Bayesian estimation as set forth in claim 1, wherein the diamond magnetic field detection system containing the NV color center constructed in the step S1 is a two-level model, and the total Hamiltonian amount H (t) of the two-level subspace of the NV color center under the interaction appearance is expressed as: ; Wherein, the In the form of a bubble-benefit matrix, For the amount of detuning between the microwave frequency and the two energy level difference, For the interaction item of the alternating magnetic field to be measured and the spin, Controlling the pulse Hamiltonian quantity for microwaves; Interaction item of alternating magnetic field and spin to be measured Expressed as: ; Wherein, the Is the coupling strength of the alternating magnetic field, Is the angular frequency of the alternating magnetic field; Under ideal conditions, NV spin phase accumulation when Ramsey measurements are performed on NV spins using a kinetic decoupling sequence The approximation is: ; Wherein, the For measuring time.
3. The method for wide-field magnetic field imaging based on sparse sampling and Bayesian estimation as set forth in claim 2, wherein in step S2, the population of each sampling point is measured, and the measurement result is converted into magnetic field intensity data based on a phase accumulation model: ; Wherein, the For the gyromagnetic ratio of the NV electron spins, a conversion from the frequency quantity to the magnetic field amplitude quantity is achieved.
4. The wide-field magnetic field imaging method based on sparse sampling and Bayesian estimation as set forth in claim 2, wherein: spreading noise from static non-uniformities And time-varying dynamic noise The common components are as follows: ; static non-uniform spreading noise Obeying the mean value of 0 and standard deviation of Of the probability density of The method comprises the following steps: ; Dynamic noise Meets Ornstein-Uhlenbeck procedure: ; Wherein, the For the time infinitesimal of the time, As a function of the time constant of the correlation, For the noise diffusion constant, To obey to Is a random variable of (a).
5. The method of claim 1, wherein the Bayesian estimation model in step S3 constructs an optimal linear unbiased predictor by defining an error correlation between the sampling points and the points to be predicted, which predicts the magnetic field strength Expressed as: ; Wherein, the For the two-dimensional coordinates of the pixel to be predicted, To be at the sampling point set The measured magnetic field strength vector of the magnetic field, Is a correlation matrix with dimension of n×n, and its element is composed of It is given that, As a correlation vector of dimension n x 1, For a column vector with all 1's components, Is the overall mean value obtained according to the maximum likelihood estimation.
6. The method for wide-field magnetic field imaging based on sparse sampling and Bayesian estimation as set forth in claim 5, wherein the correlation matrix is By distance function The decision, the distance function is defined as: ; Wherein, the For the i-th sample point, For the j-th sample point, For the value of the ith sample point on the kth coordinate component, 、 Are all the weight coefficients of the two-dimensional space model, The value range is [1, 2].
7. The wide-field magnetic field imaging method based on sparse sampling and Bayesian estimation as set forth in claim 6, wherein: and (3) with By maximizing the sample likelihood function determination, the likelihood function L is expressed as: ; Wherein, the As a whole variance of the values of the variance, And optimizing likelihood functions to obtain optimal correlation parameters for determinant of the correlation matrix.
8. The method for imaging a wide-field magnetic field based on sparse sampling and Bayesian estimation as set forth in claim 7, wherein the mean value correction in the step S4 adopts a proportional correction mode, and the specific implementation steps are as follows: selecting a plurality of reference points in the region to be measured Obtaining nominal magnetic field of each reference point And the average value obtained by measurement Arbitrary coordinates Post-correction magnetic field strength at Expressed as: ; Wherein, the The uncorrected magnetic field strength is estimated for bayesian.
9. The method for wide-field magnetic field imaging based on sparse sampling and Bayesian estimation according to any of claims 1-8, wherein the method can be used for a wide-field magnetic field imaging platform based on NV color center, a scanning type NV magnetometer, a superconducting quantum interference device and a magnetic field sensing platform.

Description

Wide-field magnetic field imaging method based on sparse sampling and Bayesian estimation Technical Field The application relates to the technical field of quantum precision measurement and magnetic field imaging, in particular to a wide-field magnetic field imaging method based on sparse sampling and Bayesian estimation. Background The nitrogen-vacancy (NV) colour centre is a point defect structure in the diamond lattice, with a triplet ground state of spin s=1, with zero field cleavage of about d=2pi×2.88GHz. By means of optical pumping and microwave control, initialization, coherent control and optical reading of the NV spin state can be achieved, and therefore high-sensitivity detection of physical quantities such as an external magnetic field, an external electric field, an external temperature and an external strain can be achieved. In the field measurement aspect, the magnetometer based on the NV color center is widely applied to the nano-scale condensed state system research, geological and mineral sample imaging, biological magnetic signal detection, integrated circuit current and defect diagnosis and other directions. The existing space resolution magnetic imaging mainly comprises two types, namely scanning imaging based on a single NV probe, realizing nanoscale resolution by keeping a minimum detection distance, but needing point-by-point scanning, and long imaging time, and wide-field imaging based on an NV set, realizing rapid imaging by parallel reading of a camera, wherein the spatial resolution is limited by an optical diffraction limit and a distance between an NV layer and a sample. In many application scenarios where both high resolution and high speed are required, there is still a significant conflict between traditional point scanning and full-sampling wide-field imaging in terms of acquisition time, data volume and complexity of subsequent processing, so development of a novel imaging strategy that can still achieve high-quality reconstruction under a limited number of sampling points is highly needed. Disclosure of Invention In order to solve the technical problems, the application provides a wide-field magnetic field imaging method based on sparse sampling and Bayesian estimation, which realizes magnetic field distribution reconstruction with high spatial resolution and high structural similarity on the premise of greatly reducing the number of sampling points, and can further reduce system errors through reference point correction, thereby improving imaging efficiency and reliability. The technical scheme adopted by the application is that the wide-field magnetic field imaging method based on sparse sampling and Bayesian estimation comprises the following steps: Step S1, constructing a diamond magnetic field detection system containing an NV color center, optically exciting a detected area, and applying a dynamic decoupling sequence matched with an alternating current magnetic field signal to be detected, so that the NV color center spins record magnetic field information to be detected in an evolution process; S2, selecting a small number of discrete sampling points in an imaging view field of a measured area, measuring NV fluorescent signals or population numbers of the sampling points, and converting a measurement result into magnetic field intensity data based on a phase accumulation model; S3, constructing an error correlation function among pixel points in a detected area, constructing a Bayesian estimation model, taking magnetic field intensity data of a small number of discrete sampling points as observables, and predicting the magnetic field intensity of unmeasured pixel points in a full view field to obtain a preliminarily reconstructed magnetic field distribution image; and S4, selecting a plurality of reference points in the detected area, acquiring a nominal magnetic field value and an actually measured magnetic field value, and calibrating the preliminarily reconstructed magnetic field distribution image by adopting a mean value proportion correction mode to acquire a corrected magnetic field imaging result. Further, the diamond magnetic field detection system containing the NV color center constructed in the step S1 is a two-level model, and the total hamiltonian H (t) of the two-level subspace of the NV color center under the interaction state is expressed as: ; Wherein, the In the form of a bubble-benefit matrix,For the amount of detuning between the microwave frequency and the two energy level difference,For the interaction item of the alternating magnetic field to be measured and the spin,Controlling the pulse Hamiltonian quantity for microwaves; Interaction item of alternating magnetic field and spin to be measured Expressed as: ; Wherein, the Is the coupling strength of the alternating magnetic field,Is the angular frequency of the alternating magnetic field; Under ideal conditions, NV spin phase accumulation when Ramsey measurements are performed on NV spins