Wide-field dynamic magnetic imaging device and method

Abstract

A wide-field dynamic magnetic imaging device and method. The wide-field dynamic magnetic imaging device comprises: a probe assembly (1), comprising a diamond (101) containing NV centers; a microwave magnetic field assembly (2) configured to generate a uniform microwave field and a uniform bias magnetic field in the vicinity of the diamond (101), so as to regulate the spin energy level of the diamond (101) and the quantum state evolution process; a laser modulation assembly (3) configured to output an initial uniform pulsed laser to excite the diamond (101) to emit fluorescence; a fringe light modulation assembly (4) configured to modulate the initial uniform pulsed laser to output a fringe pulsed laser, causing the fluorescence emitted by the diamond (101) to be fringe fluorescence, or to modulate the fluorescence emitted by the diamond (101) into fringe fluorescence; a fluorescence detection assembly (5) configured to perform spatial imaging on the fringe fluorescence to obtain magnetic field information of a sample under test (7), thereby obtaining an initial magnetic image of said sample (7); and a data processing assembly (6) configured to perform Fourier transform and inverse Fourier transform on the initial magnetic image to obtain a first magnetic image.

Description

Wide-field dynamic magnetic imaging apparatus and method TECHNICAL FIELD

[0001] At least one embodiment of the present disclosure relates to the field of wide-field quantum magnetic imaging, and more particularly to a wide-field dynamic magnetic imaging apparatus and method. BACKGROUND

[0002] NV color centers are atomic-scale point defects in diamond, which have been applied in biological systems, integrated circuits, material science, earth science, positioning and navigation, quantum information and other fields due to their strong performance at room temperature. Quantum diamond microscopes use optical initialization and readout of NV electron spin states to measure the spatial distribution images of multiple physical parameters (such as vector magnetic field) in parallel. Due to the small size of NV color centers, they can be placed near the sample to be measured, thereby performing high spatial resolution magnetic field measurement.

[0003] Quantum diamond microscope technology has developed rapidly in the past decade, and the measurement time bandwidth has gradually developed from static magnetic field measurement (DC) to dynamic magnetic field imaging (kHz). In order to obtain a wide-field magnetic field image, quantum diamond microscope technology uses a camera (such as an electron-coupled device CCD, or a complementary metal oxide semiconductor CMOS, etc.) to collect NV color center fluorescence carrying electromagnetic signals. The readout speed of the camera also determines the upper limit of the time resolution of the quantum diamond microscope (~10 ms), which limits the detection capability of the technology for high-frequency dynamic signals. In order to meet the needs of dynamic magnetic imaging, in recent years, researchers have used a lock-in camera in a quantum diamond microscope for fluorescence collection and imaging, achieving a time resolution of up to 0.4 ms. However, the lock-in camera requires high NV fluorescence intensity, and the time resolution is highly dependent on the fluorescence intensity. For example, in this work, in order to achieve a time resolution of 0.4 ms, a high NV color center density (about 0.1-1 ppm) and a thickness of 40 microns are used, so the spatial resolution is much greater than the optical diffraction limit. This makes it difficult to apply this technology to weak light scenarios. For example, under the requirement of high spatial resolution, the thickness of the NV color center is only tens of nanometers to microns, and the number of photoelectrons caused by the NV color center fluorescence on the millisecond time scale is difficult to meet the detection threshold of the lock-in camera, so it is difficult to achieve sub-millisecond to microsecond scale time resolution measurement of high-frequency dynamic signals under the requirement of high spatial resolution.

[0004] In existing quantum diamond microscope technology, under the requirement of high spatial resolution, the thickness of the NV color center is only tens of nanometers to microns, and the number of photoelectrons caused by the NV color center fluorescence on the millisecond time scale is difficult to meet the detection threshold of the lock-in camera, so it is difficult to achieve sub-millisecond to microsecond scale time resolution measurement of high-frequency dynamic signals under the requirement of high spatial resolution.

[0005] SUMMARY

[0006] To solve the above and other problems in the prior art, the present disclosure provides a wide-field dynamic magnetic imaging device and method, which can achieve time-resolved measurement of high-frequency dynamic signals on the sub-millisecond to microsecond scale under the requirement of high spatial resolution.

[0007] According to one aspect of the present disclosure, a wide-field dynamic magnetic imaging device is provided, comprising:

[0008] A probe assembly comprising a diamond containing NV color centers;

[0009] A microwave magnetic field assembly configured to generate a uniform microwave field and a uniform bias magnetic field near the diamond to regulate the spin energy level and quantum state evolution process of the diamond;

[0010] A laser modulation assembly configured to output an initial uniform pulsed laser to excite the diamond to emit fluorescence, the fluorescence including magnetic field information of a sample to be measured;

[0011] A stripe light modulation assembly configured to modulate the initial uniform pulsed laser to output a stripe pulsed laser, so that the fluorescence emitted by the diamond is stripe fluorescence; or directly modulate the fluorescence emitted by the diamond into stripe fluorescence;

[0012] A fluorescence detection assembly configured to spatially image the stripe fluorescence to obtain the magnetic field information of the sample to be measured, and further obtain an initial magnetic image of the sample to be measured; and

[0013] A data processing assembly configured to perform Fourier transform and inverse Fourier transform processing on the initial magnetic image to obtain a first magnetic image;

[0014] The initial magnetic image includes a two-dimensional real space image obtained by superimposing a plurality of sub-two-dimensional real space images obtained at different times, and the first magnetic image includes a plurality of the sub-two-dimensional real space images corresponding to the different times respectively.

[0015] According to the embodiment of the present disclosure, the uniform microwave field and the uniform bias magnetic field are generated near the diamond containing NV centers contained in the probe assembly by setting the microwave magnetic field assembly, so as to regulate the spin energy level of the diamond and the quantum state evolution process; the initial uniform pulsed laser is output by setting the laser modulation assembly, so as to excite the diamond to emit fluorescence, and the fluorescence includes the magnetic field information of the sample to be measured; the initial uniform pulsed laser is modulated by setting the stripe light modulation assembly, so as to output the stripe pulsed laser, so that the fluorescence emitted by the diamond is stripe fluorescence; or the stripe light modulation assembly modulates the fluorescence emitted by the diamond into stripe fluorescence; the stripe fluorescence is spatially imaged by setting the fluorescence detection assembly, so as to obtain the magnetic field information of the sample to be measured, and then obtain the initial magnetic image of the sample to be measured; and the data processing assembly is set to perform Fourier transform and inverse Fourier transform processing on the initial magnetic image, so as to obtain the first magnetic image; the initial magnetic image includes a two-dimensional real space image obtained by superimposing a plurality of sub-two-dimensional real space images obtained at a plurality of time points, and the first magnetic image includes a plurality of sub-two-dimensional real space images corresponding to a plurality of time points respectively. Through the cooperation between each component in the wide-field dynamic magnetic imaging device, the time-resolved measurement of the high-frequency dynamic signal in the sub-millisecond to microsecond scale under the requirement of high spatial resolution is realized. BRIEF DESCRIPTION OF DRAWINGS

[0016] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure, taken in conjunction with the accompanying drawings, in which:

[0017] FIG. 1 schematically shows an experimental sequence diagram of Fourier k-space encoding to realize high-speed signal acquisition in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure;

[0018] FIG. 2 schematically shows a working principle diagram of a probe assembly in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure;

[0019] FIG. 3 schematically shows a relative position diagram of a diamond containing NV centers and a uniform radiation structure in a probe assembly in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure;

[0020] FIG. 4 schematically shows a block diagram of a microwave magnetic field assembly in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure;

[0021] FIG. 5 schematically shows a block diagram of a laser modulation assembly in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure;

[0022] FIG. 6 schematically shows a block diagram of a stripe light modulation assembly in a wide-field dynamic magnetic imaging device according to another embodiment of the present disclosure;

[0023] FIG. 7 schematically shows a principle diagram of a stripe light modulation component modulating out stripe light in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure;

[0024] FIG. 8 schematically shows a block diagram of a fluorescence detection component in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure;

[0025] FIG. 9 schematically shows a light path diagram of stripe fluorescence generation and collection in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure;

[0026] FIG. 10 schematically shows a light path diagram of stripe fluorescence generation and collection in a wide-field dynamic magnetic imaging device according to another embodiment of the present disclosure;

[0027] FIG. 11 schematically shows a working principle diagram of a temperature control component in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure;

[0028] FIG. 12 schematically shows a positional relationship diagram of a position adjustment component and a probe component, and a sample to be measured in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure;

[0029] FIG. 13 schematically shows a flowchart of a wide-field dynamic magnetic imaging method according to an embodiment of the present disclosure; and

[0030] FIG. 14 schematically shows a flowchart of performing Fourier transform and inverse Fourier transform processing on an initial magnetic image by using a data processing component to obtain a first magnetic image in a wide-field dynamic magnetic imaging method according to an embodiment of the present disclosure.

[0031] In the above figures, the meaning of the reference signs is as follows: 1 - probe assembly; 101 - diamond containing NV color centers; 102 - uniform radiation structure; 2 - microwave magnetic field assembly; 201 - microwave source; 202 - microwave beam splitter; 203 - microwave switch; 204 - microwave combiner; 205 - microwave amplifier; 206 - isolator; 207 - impedance matching; 208 - magnetic field source; 3 - laser modulation assembly; 301 - laser; 302 - first half-wave plate; 303 - acousto-optic modulator set; 304 - lens set; 3041 - first convex lens; 3042 - second convex lens; 305 - beam shaper; 306 - second half-wave plate; 307 - first reflection assembly; 3071 - first mirror; 3072 - second mirror; 4 - fringe light modulation assembly; 401 - digital micromirror device; 402 - first lens; 403 - filter; 404 - second lens; 5 - fluorescence detection assembly; 501 - imaging lens; 502 - multi-stage filter; 503 - fluorescence detector; 6 - data processing assembly; 7 - sample to be measured; 8 - substrate; 9 - temperature control assembly; 901 - temperature monitor; 902 - temperature control box; 903 - temperature controller; 10 - objective lens; 11 - first focusing lens; 12 - third mirror; 13 - dichroic mirror; 14 - achromatic lens; 15 - position adjustment assembly; 151 - Z-axis position adjustment device; 152 - two-axis position adjustment device; 153 - three-axis position adjustment device; 1531 - three-axis large-range position adjustment device; 1532 - three-axis small-range position adjustment device. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood, however, that the description which follows is merely exemplary and is not intended to limit the scope of the present disclosure. In the following detailed description of the embodiments of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. However, it would be apparent to one skilled in the art that the embodiments of the present disclosure can be practiced without these specific details. In other instances, well-known structures and functions have been described in detail in order to avoid obscuring aspects of the present disclosure.

[0033] The terms used herein are merely used to describe specific embodiments and are not intended to limit the present disclosure. The terms "include", "comprise" and the like used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0034] All terms used herein, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art unless otherwise defined. It should be noted that the use of any terms herein should not be interpreted as excluding the use of any other terms.

[0035] In the case of using expressions similar to "at least one of A, B, and C, etc.", it should generally be interpreted that the meaning of the expression is at least one of A, B, and C (for example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, a system having B alone, a system having C alone, a system having both A and B, a system having both A and C, a system having both B and C, and / or a system having A, B, and C, etc.).

[0036] In the existing quantum diamond microscope technology, under the requirement of high spatial resolution, the thickness of the NV color center is only tens of nanometers to microns, at this time the number of photoelectrons caused by the NV color center fluorescence in the millisecond time scale is difficult to meet the detection threshold of the phase-locked camera, and it is difficult to realize the time resolution measurement of sub-millisecond to microsecond scale of high-frequency dynamic signal under the requirement of high spatial resolution.

[0037] Therefore, the present disclosure provides a wide-field dynamic magnetic imaging device, which generates a uniform microwave field and a uniform bias magnetic field near a diamond containing an NV color center included in a probe assembly by setting a microwave magnetic field assembly, so as to regulate the spin energy level and quantum state evolution process of the diamond; an initial uniform pulsed laser is output by setting a laser modulation assembly, so as to excite the diamond to emit fluorescence, and the fluorescence includes magnetic field information of a sample to be measured; a stripe light modulation assembly is set to modulate the initial uniform pulsed laser, so as to output stripe pulsed laser, so that the fluorescence emitted by the diamond is stripe fluorescence; or the stripe light modulation assembly modulates the fluorescence emitted by the diamond into stripe fluorescence; a fluorescence detection assembly is set to perform spatial imaging on the stripe fluorescence, so as to obtain the magnetic field information of the sample to be measured, and then obtain an initial magnetic image of the sample to be measured; and a data processing assembly is set to perform Fourier transform and inverse Fourier transform processing on the initial magnetic image, so as to obtain a first magnetic image; the initial magnetic image includes a two-dimensional real space image obtained by superimposing a plurality of sub-two-dimensional real space images obtained at a plurality of time points, and the first magnetic image includes a plurality of sub-two-dimensional real space images corresponding to a plurality of time points respectively. Through the mutual cooperation between each component in the wide-field dynamic magnetic imaging device, the present disclosure realizes the time resolution measurement of sub-millisecond to microsecond scale of high-frequency dynamic signal under the requirement of high spatial resolution.

[0038] According to some embodiments of the present disclosure, the wide-field dynamic magnetic imaging device comprises a probe assembly, a microwave magnetic field assembly, a laser modulation assembly, a striped light modulation assembly, a fluorescence detection assembly, and a data processing assembly. The probe assembly comprises a diamond containing NV centers; the microwave magnetic field assembly is configured to generate a uniform microwave field and a uniform bias magnetic field near the diamond to regulate the spin energy level and quantum state evolution process of the diamond; the laser modulation assembly is configured to output an initial uniform pulsed laser to excite the diamond to emit fluorescence, the fluorescence comprising magnetic field information of the sample to be measured; the striped light modulation assembly is configured to modulate the initial uniform pulsed laser to output striped pulsed laser, so that the fluorescence emitted by the diamond is striped fluorescence; or the striped light modulation assembly directly modulates the fluorescence emitted by the diamond into striped fluorescence. The fluorescence detection assembly is configured to spatially image the striped fluorescence to obtain the magnetic field information of the sample to be measured, and further obtain an initial magnetic image of the sample to be measured; and the data processing assembly is configured to perform Fourier transform and inverse Fourier transform processing on the initial magnetic image to obtain a first magnetic image.

[0039] According to some embodiments of the present disclosure, the initial magnetic image comprises a two-dimensional real space image obtained by superimposing a plurality of sub-two-dimensional real space images obtained at different times, and the first magnetic image comprises a plurality of sub-two-dimensional real space images corresponding to the different times respectively.

[0040] According to some embodiments of the present disclosure, by setting the microwave magnetic field assembly to generate a uniform microwave field and a uniform bias magnetic field near the diamond containing NV centers contained in the probe assembly to regulate the spin energy level and quantum state evolution process of the diamond; setting the laser modulation assembly to output an initial uniform pulsed laser to excite the diamond to emit fluorescence, the fluorescence comprising magnetic field information of the sample to be measured; setting the striped light modulation assembly to modulate the initial uniform pulsed laser to output striped pulsed laser, so that the fluorescence emitted by the diamond is striped fluorescence; or the striped light modulation assembly directly modulates the fluorescence emitted by the diamond into striped fluorescence; setting the fluorescence detection assembly to spatially image the striped fluorescence to obtain the magnetic field information of the sample to be measured, and further obtain an initial magnetic image of the sample to be measured; and setting the data processing assembly to perform Fourier transform and inverse Fourier transform processing on the initial magnetic image to obtain a first magnetic image; the initial magnetic image comprises a two-dimensional real space image obtained by superimposing a plurality of sub-two-dimensional real space images obtained at different times, and the first magnetic image comprises a plurality of sub-two-dimensional real space images corresponding to the different times respectively. The time-resolved measurement of sub-millisecond to microsecond scale of high-frequency dynamic signal under the requirement of high spatial resolution is achieved.

[0041] According to some embodiments of the present disclosure, the time resolution is limited by the signal acquisition speed. Taking wide-field imaging as an example, the shooting speed of the camera determines the time interval between two adjacent pictures, and therefore the highest time resolution of imaging is the frame rate of the camera. In order to obtain a dynamic image with high time resolution, the number of pixel points collecting light signals can be reduced, thereby reducing the readout time, but this will reduce the imaging field of view, resulting in a decrease in the flux of wide-field imaging, which is not conducive to the imaging requirements of a large field of view. In order to retain the advantage that the flux of wide-field imaging is much larger than that of scanning imaging, while improving the time resolution of imaging, a non-uniform illumination method can be used to encode images of different time periods at different positions in the k-space, and then the dynamic image information is reconstructed through Fourier transform and spatial filtering.

[0042] The core component of wide-field imaging is a microscope system, which is a linear translation invariant system. The imaging process can be described by a point spread function, which can be represented by formula (1):

[0043] wherein, represents the light field intensity distribution on the image plane, which represents the fluorescence distribution image of the sample obtained by the microscope system, represents the light field intensity distribution of the light emitted by the sample surface. For NV-based wide-field magnetic imaging, fluorescence is emitted by NV centers, so the fluorescence intensity is related to the spatial distribution of NV centers, and PSF represents the point spread function of the microscope system, represents a convolution operation.

[0044] Under the condition of uniform illumination, the light field intensity of the light emitted by the sample is only related to the spatial distribution of NV centers and the population of quantum states. In the context of magnetic imaging applications, the population is related to the external magnetic field B(t). Here, the two factors are combined and denoted as Assuming that the illumination intensity of the excitation light is I0, and the fluorescence collection efficiency of the microscope system for NV is a, then the light field intensity of the light emitted by the sample can be represented by formula (2):

[0045] In this case, due to the slow readout of the camera, the fluorescence distribution caused by dynamic magnetic signals at different times will be accumulated in one picture (i.e., the initial magnetic image), and therefore the time resolution is low.

[0046] If non-uniform excitation light is used to illuminate NV centers, the light field intensity of the fluorescence emitted by the sample is linearly related to the distribution of NV centers and the light field intensity distribution of the illumination light, and this linear relationship satisfies formula (3):

[0047] Substituting equation (3) into equation (1) and performing Fourier transform, equation (4) can be obtained:

[0048] where OTF represents the optical transfer function of the microscope system, which is the Fourier transform of the point spread function OTF = FFT{PSF}, and OTF represents the limitation of the information amount passing through the microscope system, only allowing low-frequency information to pass through the system and high-frequency information to be truncated.

[0049] Now, the excitation light illuminates the NV centers in the form of cosine, and the excitation light field intensity can be expressed as equation (5):

[0050] where I c0 and φ represent the average intensity and initial phase of the cosine illumination fringe, respectively, represent the magnitude and direction of the spatial frequency of the cosine fringe, and the modulus is the inverse of the fringe period. Through Fourier transform, the expression of the cosine fringe in the frequency domain is equation (6):

[0051] Therefore, are the δ functions at three positions in the frequency domain. Substituting equation (6) into equation (4), the spectral information of the image plane fluorescence image is obtained, and the spectral information of the image plane fluorescence image satisfies equation (7):

[0052] Equations (6) and (7) show that the effect of cosine fringe illumination light is to copy the spectral information of the fluorescence image into three parts in the frequency domain, and the expressions are equations (8), (9) and (10):

[0053] One of the copies has a zero frequency position at the origin of the frequency domain, and the other two copies have zero frequency positions at and The frequency domain signal at each position contains complete spectral information of the fluorescence image.

[0054] As can be seen from equation (7), cosine fringe illumination can move the image spectral information to a specified position in k-space (i.e., the frequency domain), so that the image information at different times can be encoded to different positions in k-space by adjusting the magnitude and direction of the fringe spatial frequency, thereby realizing time-resolved imaging of dynamic images.

[0055] The adjustable grating is generated by a digital micromirror device (DMD) 401 to modulate the fringe illumination light, and the rapid switching of the fringes is realized by electrical pulses, so that the image information at a specified moment can be acquired at a speed much higher than the frame rate of the camera, thereby realizing high-time-resolution dynamic magnetic imaging and breaking through the limitation of the time resolution of the quantum diamond microscope by the readout speed of the camera.

[0056] FIG. 1 schematically shows an experimental sequence diagram of Fourier k-space encoding to realize high-speed signal acquisition in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure.

[0057] According to some embodiments of the present disclosure, in order to acquire dynamic magnetic images with high time resolution, the fluorescence measurement uses an electron-coupled device or a complementary metal-oxide semiconductor camera used by a general quantum diamond microscope as a fluorescence detector. The fringe pattern in FIG. 1 represents a schematic diagram of a two-dimensional grating pattern loaded by a digital micromirror device, and the switching of the fringe pattern is controlled by a trigger signal. The microwave pulse is represented by a shaded square, and π / 2 represents the length of the microwave pulse. As shown in FIG. 1, m fringe images are switched in the process of exposure of one frame of camera picture, and all NV center fluorescence counts generated during exposure are collected into one image. This image can be represented by formula (11):

[0058] wherein represents the mth cosine fringe illumination light played in time sequence, represents the spatial distribution and quantum state population of NV centers at each different moment (t m = mΔt), which records the spatial magnetic field information recorded by NV centers at different moments. Fourier transform of formula (11) gives the frequency domain signal represented by formula (12):

[0059] Formula (11) and formula (12) represent that the magnetic field images collected at different moments can be superimposed in the same image. Although the magnetic field images at different moments cannot be distinguished in the real space, the spectral information of the images at different moments is separable in the k-space, so the images at different moments can be distinguished in the frequency domain.

[0060] According to some embodiments of the present disclosure, in the magnetic imaging pulse sequence in FIG. 1, three different magnetic field measurement pulse sequences are listed, namely Ramsey sequence, Rabi oscillation and continuous wave spectrum sequence. During the signal measurement process, different sequences can be selected to match the measurement of different signals. In general, the quantum state of the NV center is initialized by laser and microwave, the quantum state of the NV center evolves to the final state under the action of the magnetic field to be measured, and then the quantum state population is read out by laser to obtain the magnetic field information. Different magnetic fields result in different NV center populations, and thus different NV center fluorescence intensities. Through wide-field imaging, the magnetic field size at different positions can be obtained, and fast fluorescence signal reading can obtain the relationship between the magnetic field and time.

[0061] The principle of magnetic field measurement will be described below taking the three sequences as examples.

[0062] Ramsey sequence: laser initialization pulse-π / 2 microwave pulse-free evolution-π / 2 microwave pulse-laser readout pulse. First, the laser pulse initializes the NV center to the |0> state, and then the π / 2 microwave pulse flips the NV to the state, and then the NV freely evolves under the external magnetic field B(t) to accumulate the phase θ=2πγB(t m )τ, where γ=2.8MHz / G is the gyromagnetic ratio of the NV center, B(t m ) is the external magnetic field at time t m , and τ is the free evolution time. After the free evolution is completed, the NV center is prepared to the state, and then a π / 2 microwave pulse flips the NV to the cos(θ / 2)|0>+ie iθ sin(θ / 2)|1> state, and finally the laser pulse reads out the population of the NV center in the |0> state ρ 00 =(1+cosθ) / 2.

[0063] Rabi oscillation sequence: laser initialization pulse-variable length microwave pulse-laser readout pulse. This method can be used to measure the spatial distribution of high frequency electromagnetic field strength in the order of hundreds of MHz to GHz. By initializing the NV to the |0> state, then applying the measured field to drive the energy level resonance of the NV center, the fluorescence of the NV center will change with the length of the driving field, and the frequency of the Rabi oscillation is v=γB1, where B1 is linearly related to the microwave magnetic field

[0064] Continuous wave spectrum sequence: continuous laser and continuous microwave are applied at the same time. According to the Zeeman effect, the external magnetic field causes the NV energy level to split, and the |±1> energy level interval is Δv=2γB NV . Therefore, by measuring the resonance spectrum, the energy level of the NV center can be determined, and the magnetic field B NV along the NV axis direction at this time can be obtained.

[0065] According to an embodiment of the present disclosure, according to formula (12), the frequency domain signals of the magnetic images at different times are encoded in different regions of the k-space, so that the image reconstruction can be performed in combination with the spatial filtering of the frequency domain, and the inverse solution process includes steps 1-4.

[0066] In step 1, a two-dimensional real space image is collected, and the fluorescence image is collected according to the experimental sequence shown in FIG. 1, and finally a plurality of cosine stripe encoded accumulated fluorescence images, i.e., initial magnetic images, are obtained.

[0067] In step 2, the initial magnetic image is subjected to Fourier transform to obtain a frequency domain signal, and a two-dimensional k-space image is obtained. The theoretical expression of step 2 is formula (12).

[0068] In step 3, the image frequency domain signals at different times in the two-dimensional k-space image are separated, and a k-space filter is constructed for each time image, the center position of which is , and the width W satisfies , that is, the filter width is less than or equal to the spatial frequency difference between the two stripes with the closest period and direction, so as to ensure that the separated signal is not disturbed by other direction stripes; after the k-space filter is applied to all cosine stripes, M two-dimensional k-space frequency domain signals are obtained, representing the frequency domain signals at different times.

[0069] In step 4, the zero frequency position of the two-dimensional frequency domain signal corresponding to each stripe is moved from to the origin of the two-dimensional k-space, and then inverse Fourier transform is performed to obtain a real space image encoded by each stripe, i.e., a two-dimensional real space magnetic field image corresponding to the time, that is, a first magnetic image including a plurality of sub-two-dimensional real space images corresponding to a plurality of times.

[0070] FIG. 2 schematically shows a working principle diagram of a probe assembly in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure.

[0071] According to some embodiments of the present disclosure, as shown in FIG. 2, the probe assembly 1 further includes a uniform radiation structure 102 configured to provide a microwave field to change the spin quantum state of the NV color center in the diamond 101.

[0072] According to some embodiments of the present disclosure, the microwave field is provided by setting the uniform radiation structure 102 to change the spin quantum state of the NV color center in the diamond 101.

[0073] According to some embodiments of the present disclosure, the uniform microwave field generated by the uniform radiation structure 102 has a range of 100 microns, and the uniformity of the microwave field can reach more than 95%, so as to ensure that the NV color centers are affected equally, and improve the accuracy of the spin quantum state of the NV color center in the diamond 101.

[0074] According to some embodiments of the present disclosure, as shown in FIG. 2, the substrate 8 is arranged below the sample 7 to be measured, and the substrate 8 is configured to support the sample 7 to be measured.

[0075] FIG. 3 schematically shows the relative position of the diamond containing NV color centers and the uniform radiation structure in the probe assembly of the wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure.

[0076] According to some embodiments of the present disclosure, as shown in FIG. 3, the diamond containing NV color centers is arranged at a position symmetric to the center of the uniform radiation structure.

[0077] According to some optional embodiments of the present disclosure, the uniform radiation structure 102 is a waveguide, and the uniform distribution of the microwave field in the diamond containing NV color centers can be achieved by setting the shape of the waveguide.

[0078] According to some embodiments of the present disclosure, the surface of the diamond 101 containing NV color centers is flat, and contains a plurality of NV color centers, and the plurality of NV color centers form a thin layer inside the diamond 101; the depth difference between two adjacent NV color centers is less than 10 microns, and the distance between the two adjacent NV color centers in the horizontal direction is less than the optical diffraction limit.

[0079] According to some embodiments of the present disclosure, the surface of the diamond 101 containing NV color centers is flat, which can improve the accuracy of sensing the external magnetic field. Moreover, the diamond 101 containing NV color centers has no surface structure, i.e., the diamond 101 has fewer internal defects and impurities, which reduces the interference with the quantum state. Marking the specific position of the diamond 101 (for example, the position of the NV color center center) can improve the accuracy of identifying the sensing area, and facilitate the initialization, manipulation and reading of the quantum state of the NV color center.

[0080] According to some embodiments of the present disclosure, by setting the depth difference between two adjacent NV centers to be less than 10 microns, the distance between two adjacent NV centers in the horizontal direction is less than the optical diffraction limit, and all NV centers in the diamond 101 satisfy this arrangement, the uniformity and consistency of quantum sensing are improved. When the depth difference between all NV centers is less than 10 microns, all NV centers are affected by the diamond lattice similarly, further enhancing the uniformity of sensing. When the horizontal distance between all NV centers is less than the optical diffraction limit of the system, a smaller spot can be used to excite multiple NV centers individually or simultaneously, thereby improving the resolution and sensitivity of optical measurement. All NV centers satisfying this arrangement also improve the efficiency of microwave field manipulation, so that the microwave field can act more uniformly on all NV centers.

[0081] According to some embodiments of the present disclosure, when a plurality of NV centers are formed in a certain density and arrangement within the diamond 101, they can constitute a two-dimensional thin layer. The thin layer can be located near the surface of the diamond 101 or at a certain depth inside the diamond 101. Due to the optical and quantum properties of NV centers, the thin layer composed of NV centers also exhibits similar properties. For example, the thin layer can exhibit strong fluorescence under laser pumping, and its fluorescence characteristics can be regulated by controlling factors such as temperature. Since the spin state of the NV center can be manipulated and detected by laser and microwave, the thin layer can be used as a two-dimensional quantum bit array for various quantum information processing tasks.

[0082] FIG. 4 schematically shows a block diagram of a microwave magnetic field component in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure.

[0083] According to some embodiments of the present disclosure, as shown in FIG. 4, the microwave magnetic field component 2 includes a microwave source 201, a microwave beam splitter 202, a microwave switch 203, a microwave combiner 204, a microwave amplifier 205, an isolator 206, an impedance matching 207, and a magnetic field source 208. The microwave source 201 is configured to generate an initial microwave of a specific frequency and power; the microwave beam splitter 202 is configured to divide the initial microwave into two paths of equal power and a phase difference of 90°; the microwave switch 203 is configured to control the on-off of the transmission path of the two first microwaves; the microwave combiner 204 is configured to combine the two first microwaves into a second microwave; the microwave amplifier 205 is configured to amplify the power of the second microwave to obtain a third microwave, which enters the uniform radiation structure 102; the isolator 206 is configured to avoid the reflection of the third microwave into the microwave amplifier 205; the impedance matching 207 is configured to reduce the loss in the transmission process of the third microwave; and the magnetic field source 208 is configured to provide a uniform bias magnetic field.

[0084] According to some embodiments of the present disclosure, the generated microwave field and the bias magnetic field are regulated by setting the microwave magnetic field assembly 2 to ensure that there is a uniform microwave field and a uniform bias magnetic field environment near the diamond 101. According to the frequency and power requirements of the target uniform microwave field, a suitable microwave source 201 capable of generating the frequency and power of the target uniform microwave field is selected, and the initial microwave of a specific frequency and power includes the frequency and power of the target uniform microwave field. The frequency range of the initial microwave is usually between 300 MHz and 300 GHz.

[0085] According to some embodiments of the present disclosure, the uniform microwave field is in the diamond NV color center region; the direction of the bias magnetic field is along the direction of the NV color center axis.

[0086] According to some embodiments of the present disclosure, as shown in FIG. 4, the microwave switch 203 includes a first microwave switch 2031 and a second microwave switch 2032, and the on-off of the transmission path of the two first microwaves is controlled by the microwave switch 203, which can realize flexible control of the microwave signal transmission. The power of the second microwave is amplified by the microwave amplifier 205 to obtain the third microwave, which ensures that the power of the third microwave can generate the power required by the target uniform microwave field after entering the uniform radiation structure 102. The third microwave is prevented from reflecting into the microwave amplifier by the isolator 206, and the microwave amplifier 205 is also prevented from being damaged. The impedance matching 207 ensures that the impedance change encountered by the microwave signal in the transmission process is minimized, reducing the loss in the transmission process of the third microwave. The impedance matching 207 is arranged at the end of the entire line of the microwave magnetic field assembly 2, which plays a role in protecting the microwave line.

[0087] According to some embodiments of the present disclosure, the impedance matching 207 refers to the characteristic impedance of the connected transmission line being equal to and having the same phase as the internal resistance of the microwave source 201, or the characteristic impedance of the transmission line being equal to and having the same phase as the size of the connected load impedance (i.e. the uniform radiation structure), to ensure the maximum power transmission of the microwave signal and reduce the reflection loss of the microwave signal.

[0088] According to some embodiments of the present disclosure, the microwave source 201 includes any one of a semiconductor device and a resonant cavity; the magnetic field source 208 includes any one of a coil and a large volume permanent magnet. The microwave source 201 generates a spatially uniform microwave field near the diamond 101; the magnetic field source 208 generates a spatially uniform bias magnetic field near the diamond 101. The uniform range of the bias magnetic field is on the order of 1 millimeter, and the uniformity of the uniform bias magnetic field can reach more than 95%; the uniform microwave field generated by the uniform radiation structure 102 has a range of 100 microns, and the uniformity of the microwave field can reach more than 95%, and the uniformity of the microwave field within 500 microns is about 99.5%.

[0089] Figure 5 schematically shows a block diagram of a laser modulation assembly in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure.

[0090] According to some embodiments of the present disclosure, as shown in Figure 5, the laser modulation assembly 3 comprises a laser 301, a first half-wave plate 302, an acousto-optic modulator group 303, a lens group 304, and a beam shaper 305. The laser 301 is configured to output an initial continuous laser; the first half-wave plate 302 is configured to regulate the polarization direction of the initial continuous laser to obtain a first continuous laser; the acousto-optic modulator group 303 is configured to modulate the first continuous laser to obtain an initial pulsed laser, so as to improve the on-off ratio of the initial pulsed laser; the lens group 304 is configured to adjust the beam diameter of the initial pulsed laser; and the beam shaper 305 is configured to convert the beam of the initial pulsed laser into a flat-top beam with uniform light intensity distribution, so as to output an initial uniform pulsed laser.

[0091] According to some embodiments of the present disclosure, the initial continuous laser is a linearly polarized Gaussian beam, having a Gaussian light intensity distribution and a linearly polarized polarization state, and the laser power of the initial continuous laser is in the order of 1-5 W; the acousto-optic modulator (AOM) group is a structure in which multiple acousto-optic modulators are cascaded, and the acousto-optic modulator group can control the on-off of the transmission path of the first continuous laser through an external modulation signal, thereby obtaining the initial pulsed laser; the lens group 304 comprises a first convex lens 3041 and a second convex lens 3042, the back focal surface of the first convex lens 3041 coincides with the front focal surface of the second convex lens 3042, forming a confocal relationship, so that the incident near-parallel laser beam is adjusted in beam diameter by the lens group 304 and then exits in the same near-parallel state, and the exit beam diameter is equal to the product of the incident beam diameter and the ratio of the focal length of the second convex lens 3042 to the first convex lens 3041, and the beam diameter is adjusted by selecting a suitable focal length; and the beam shaper 305 is a kind of diffractive optical element, such as a flat-top beam shaper, which converts the initial pulsed laser into the initial uniform pulsed laser, and the light intensity of the initial uniform pulsed laser is uniformly distributed.

[0092] According to some optional embodiments of the present disclosure, the laser 301 generates an initial continuous laser with a power in the order of 1 W and a wavelength of 532 nm; the acousto-optic modulator group is a structure in which three acousto-optic modulators are cascaded, and the acousto-optic modulator group can make the overall on-off ratio as high as 10 7 :1, thereby improving the efficiency of converting the first continuous laser into the initial pulsed laser and reducing the loss of the first continuous laser signal; and the uniformity of the initial uniform pulsed laser is about 90%.

[0093] Figure 6 schematically shows a block diagram of a fringe light modulation assembly in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure.

[0094] According to some embodiments of the present disclosure, as shown in FIG. 6, the stripe light modulation assembly 4 comprises a digital micromirror device 401, 4f optical systems 402, 404, and a filter 403. The digital micromirror device 401 is configured to diffract the initial uniform pulsed laser into a plurality of beams of parallel light propagating in different directions; the 4f optical systems 402, 404 are configured to convert the plurality of beams of parallel light into stripe light, which presents a two-dimensional distribution of light and dark stripes on the output plane; the filter 403 is arranged in the 4f optical systems 402, 404, and the filter 403 is configured to filter out stray light in the plurality of beams of parallel light.

[0095] According to some embodiments of the present disclosure, a digital micromirror device (DMD) is an array of tiny mirrors, each of which can be independently tilted to two different angles (e.g., +12° and -12°), thereby reflecting light to two different directions. When parallel light is incident on the DMD, by controlling the tilting angle of each mirror, a binary grating can be formed. This binary grating is like a two-dimensional black-and-white chessboard, where the white part represents that light can pass through, and the black part represents that light is blocked, therefore, the DMD has two states of “on” and “off”, the micro-mirror of the DMD is in the “on” state to allow light to pass through, and the micro-mirror of the DMD is in the “off” state to block light.

[0096] According to some embodiments of the present disclosure, the 4f optical systems 402, 404 comprise two lens assemblies of a first lens 402 and a second lens 404, the focal lengths of the first lens 402 and the second lens 404 are equal, both are f, and the distance between the first lens 402 and the second lens 404 is 2f; the digital micromirror device 401 is located at the front focal plane of the first lens 402, and the filter 403 is located at the back focal plane of the first lens 402. The first lens 402 performs Fourier transform on the plurality of beams of parallel light propagating in different directions, and forms a spectrum plane containing spatial spectrum information at the back focal plane of the first lens 402; the filter 403 filters out stray light in the plurality of beams of parallel light, and filters out multi-order diffracted light in the plurality of beams of parallel light; the second lens 404 images the finally formed stripe light to the output plane, and the stripe light presents a two-dimensional distribution of light and dark stripes on the output plane.

[0097] According to some embodiments of the present disclosure, when parallel light passes through the first lens 402, it forms a Fourier transform spectrum of the light field at the back focal plane of the first lens 402 (i.e., at a distance f from the first lens 402). This transform contains the spatial frequency information of the light field; the filter 403 can modify the Fourier transform spectrum, thereby changing the spatial distribution of the light field; the second lens 404 converts the filtered Fourier transform spectrum back into a light field, thereby producing the desired two-dimensional fringe light distribution on the output plane. The shape, direction, and contrast of these fringes can be controlled by adjusting the pattern of the DMD and the design of the filter 403.

[0098] According to some embodiments of the present disclosure, the fringe light modulation assembly 4 can modulate uniform light into fringe structured light with a fringe contrast greater than 50%. The fringe light modulation assembly 4 can also achieve rapid switching of different fringes at a switching rate of up to 50 kHz, thereby providing a time resolution of 20 microseconds for dynamic wide-field magnetic imaging. The fringe light modulation assembly 4 can be placed after the excitation modulation assembly 3 to modulate the generated fringe excitation light, or placed before the fluorescence detection assembly 5 to achieve fringe modulation of fluorescence.

[0099] FIG. 7 schematically shows a principle diagram of fringe light modulation by a fringe light modulation assembly in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure.

[0100] According to some embodiments of the present disclosure, as shown in FIG. 7, parallel light is incident on a digital micromirror device, a binary grating is generated by the digital micromirror device 401 to diffract the incident light into multiple beams of parallel light propagating in different directions, and then Fourier space filtering is performed by the 4f optical system 402, 404 and the filter 403 to produce a two-dimensional fringe light distribution on the output plane.

[0101] According to some embodiments of the present disclosure, assuming that the propagation direction of light is always in the z direction, the light field distribution of the parallel incident light can be described as a uniformly distributed light field E0 in the xy plane. The DMD is placed at the front focal plane of the first lens 402 and loaded with a grating pattern. The micro-mirrors in the open state reflect the incident light into the subsequent optical path. At the same time, the loaded grating distribution causes the incident light to diffract, causing the light exiting the DMD to propagate in multiple directions.

[0102] The following describes the fringe generation process using a grating in the y direction as an example. A coordinate system x’Oy’ is defined on the grating optical surface, and it is assumed that the period of the loaded grating in the y’ direction is T y , and the width of each slit is D. The transmittance function of the DMD can be described as formula (13):

[0103] where N' is the maximum number of grating periods that can be accommodated by the DMD optical surface, the specific value is related to the size and direction of the grating period; a(x', y') is the aperture function of the DMD light transmission surface, the size is the product of the resolution MxN of the DMD and the pixel period Δd, and the expression of a(x', y') is formula (14): where rect(x') is a one-dimensional rectangular function.

[0104] Formula (13) indicates that the grating loaded by the DMD is a plurality of rectangular slits distributed along the y direction, and the light emitted after the incident light irradiates the grating will be diffracted to different positions in the y direction. The light field obtained at the focal plane of the first lens 402 is the Fourier transform of the grating pattern, that is, the spatial spectrum information. The light field can be obtained by Fourier transform of formula (13), and the transform process can be represented as formula (15):

[0105] where T(u, v) is the light field distribution at the focal plane of the first lens 402; A(u, v) is the Fourier transform of the DMD light transmission aperture; A(u, v) can be represented as formula (16):

[0106] In order to generate a stripe light, a filter 403 is placed at the back focal plane of the first lens 402, which removes the high diffraction order and retains the ±1 order and 0 order to enter the subsequent optical path, and the filtered light field distribution can be represented as formula (17):

[0107] where T(u, v)' is the filtered light field distribution.

[0108] The light field distribution T(x, y) formed at the back focal plane (i.e. the output plane) of the second lens 404 is the Fourier transform of formula (17), and T(x, y) can be represented as formula (18):

[0109] where a(x, y) is, and a(x, y) can be represented as formula (19):

[0110] According to formula (18), the distribution of light intensity at the back focal plane of the second lens 404 can be obtained |T(x, y)| 2 , |T(x, y)| 2 can be represented as formula (20):

[0111] According to some embodiments of the present disclosure, since the DMD is a planar array of multiple micromirrors, when receiving parallel light irradiation, the micromirror array acts as a two-dimensional grating, resulting in interference and diffraction of the outgoing light. Therefore, the outgoing light contains not only the target fringe light described above, but also multi-order diffracted light caused by the periodic structure of the pixels. In order to ensure that the target fringe light is not disturbed, it is necessary to filter out other multi-order diffracted light. The formation principle of multi-order diffracted light is described first, and then the filtering method of multi-order diffracted light is described.

[0112] Assuming that the side length of the DMD pixel is d and the pixel period is Δd, the transmittance function of the DMD can be represented as formula (21):

[0113] Where a(x', y') is the aperture function of the DMD light transmission surface, the expression is given by formula (14); rect(x' / d, y' / d) is a two-dimensional rectangular function, indicating that the shape of a single pixel is a square of dxd, and the center position is the origin of the planar coordinate system (x', y'); the convolution operation indicates that the pixels are distributed at different positions on the DMD optical surface, q(x', y') represents the position distribution function of the DMD pixel array, which can be represented as formula (22):

[0114] After passing through the first lens 402, the image obtained on the back focal plane of the first lens 402 is the Fourier transform of the DMD optical surface pattern, and the complex amplitude of the light field on the focal plane is represented by formula (23): Where A(f x ,f y ) and sinc(f x d, f y d) can be represented by formulas (24) and (25) respectively: x y

[0115] According to the Fourier transform of the rectangular function, formula (24) is processed, and the Fourier transform of the rectangular function can be represented by formula (26):

[0116] According to the Fourier transform formula (26) of the rectangular function, formula (24) is processed to obtain formula (27): x y 2 sinc(MΔdf x ,NΔdf y )(27).​​​​

[0117] Using the Fourier transform of the Dirac comb function, i.e., formula (28):

[0118] Based on the Fourier transform of the Dirac comb function (28), we can obtain formula (29):

[0119] Therefore, formula (29) indicates that multi-level diffraction light caused by the DMD pixel structure is obtained on the back focal plane of the first lens 402, and the intensity of each level of diffraction light is modulated by single-slit diffraction caused by micro-image elements.

[0120] To obtain the target fringe light, excess diffraction orders should be removed, retaining only the highest intensity zero diffraction order. Therefore, a low-pass filter, i.e., filter 403, can be placed at the back focal plane of the first lens 402 to filter out the high diffraction orders. Simultaneously, to ensure that the ±1st order of the target fringe light is not filtered out, the width W of the low-pass filter should be... f W needs to be satisfied f >2λf1 / T y .

[0121] Figure 8 schematically illustrates a block diagram of a fluorescence detection component in a wide-field dynamic magnetic imaging apparatus according to an embodiment of the present disclosure.

[0122] According to some embodiments of this disclosure, as shown in FIG8, the fluorescence detection assembly 5 includes: an imaging lens 501, a multi-stage filter 502, and a fluorescence detector 503. The imaging lens 501 is configured to focus fluorescence to form a fluorescence image; the multi-stage filter 502 is configured to filter out stray light signals and laser light reflected from the surface of the diamond 101; the fluorescence detector 503 is configured to convert the fluorescence signal into an electrical signal in order to obtain the magnetic field information of the sample 7 to be tested.

[0123] According to some embodiments of this disclosure, by using the imaging lens 501 in the fluorescence detection component 5 to focus the fluorescence emitted by the diamond 101 to form a fluorescence image; by using the multi-stage filter 502 to filter out stray light signals and laser light reflected from the surface of the diamond 101; and by using the fluorescence detector 503 configured to convert the fluorescence signal into an electrical signal, the magnetic field information of the sample 7 to be tested can be obtained.

[0124] According to some embodiments of this disclosure, the fluorescence detector 503 is able to distinguish the spatial location of NV color centers based on fluorescence signals.

[0125] According to some optional embodiments of this disclosure, the fluorescence detector 503 includes either an electronically coupled device or a complementary metal-oxide-semiconductor, and the multi-stage filter 502 includes three 900-nanometer short-pass filters.

[0126] FIG. 9 schematically shows a light path diagram of the generation and collection of the stripe fluorescence in the wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure.

[0127] According to some embodiments of the present disclosure, as shown in FIG. 9, the laser 301 generates an initial continuous laser, the first half-wave plate 302 adjusts the polarization direction of the initial continuous laser to obtain a first continuous laser, the first continuous laser is modulated by the acousto-optic modulator group 303 to output an initial pulsed laser, the lens group 304 adjusts the beam diameter of the initial pulsed laser, and the initial pulsed laser with the adjusted beam diameter is converted into an initial uniform pulsed laser with uniform light intensity by the beam shaper 305; the second half-wave plate 306 adjusts the polarization direction of the initial uniform pulsed laser; the initial uniform pulsed laser with the changed polarization direction is reflected to the digital micromirror device 401 by the first reflection assembly 307, the digital micromirror device 401 diffracts the initial uniform pulsed laser into a plurality of parallel lights propagating in different directions, and the micromirrors of the DMD introduce the parallel lights into the 4f optical system 402, 404 when the micromirrors are in an "on" state, the parallel lights are converted into stripe lights by the 4f optical system 402, 404 and the filter 403, and a two-dimensional distribution of bright and dark stripes is presented on the output plane. The filter 403 filters out high-order diffracted light, and the remaining 0th-order and ±1st-order light passes through the second lens 404, the first focusing lens 11 and the third mirror 12 in turn, is then reflected into the objective lens 10 by the dichroic mirror 13, and finally forms stripe light illumination on the plane where the NV color center thin layer of the diamond 101 is located. The illumination range of the finally formed stripe excitation light is greater than 200 microns, and the stripe contrast is greater than 40%.

[0128] According to some embodiments of the present disclosure, the stripe light is a stripe pulsed laser, the NV color center in the diamond 101 absorbs the stripe light, emits stripe fluorescence, the stripe fluorescence is collected after passing through the objective lens 10, is then transmitted into the imaging lens 501 by the dichroic mirror 13, passes through the multi-stage optical filter 502, and is finally collected on the target surface of the fluorescence detector 503.

[0129] According to some optional embodiments of the present disclosure, the first lens 402 is a Fourier lens; the dichroic mirror 13 is a 600-nanometer long-wave pass dichroic mirror; the multi-stage optical filter 502 is a 900-nanometer short-pass filter. The first reflection assembly 307 includes two mirrors, i.e., the first mirror 3071 and the second mirror 3072, or the first reflection assembly 307 includes one mirror; and the filter 403 is a low-pass filter.

[0130] FIG. 10 schematically shows a light path diagram of the generation and collection of the stripe fluorescence in the wide-field dynamic magnetic imaging device according to another embodiment of the present disclosure.

[0131] According to some embodiments of the present disclosure, as shown in FIG. 10, the laser 301 generates initial continuous laser, the first half-wave plate 302 adjusts the polarization direction of the initial continuous laser to obtain the first continuous laser, the first continuous laser is modulated by the acousto-optic modulator group 303 to output the initial pulsed laser, the lens group 304 adjusts the beam diameter of the initial pulsed laser, and the initial pulsed laser with the adjusted beam diameter is converted into initial uniform pulsed laser with uniform light intensity distribution by the beam shaper 305; the second half-wave plate 306 adjusts the polarization direction of the initial uniform pulsed laser; the initial uniform pulsed laser with the changed polarization direction is reflected by the first reflection assembly 307 in turn, and then focused by the first focusing lens 11 to output the focused pulsed laser, the focused pulsed laser is reflected by the dichroic mirror 13 into the objective lens 10, focused at the pupil plane of the objective lens 10, then passes through the objective lens and exits as parallel light, and finally forms uniform excitation illumination at the plane where the 12 diamond NV color center thin layer is located. The finally formed uniform excitation illumination range is greater than 200 microns, and the uniformity in the range of 200 microns is greater than 90%.

[0132] According to some embodiments of the present disclosure, the NV color center in the diamond 101 absorbs the uniform excitation light to generate fluorescence, the emitted fluorescence is collected by the objective lens 10, enters the achromatic lens 14 after passing through the dichroic mirror 13, then adjusts the light advancing direction after passing through the third mirror 12, and is incident on the digital micromirror device 401 at a suitable angle. The digital micromirror device 401 is located at the focal plane of the first lens 402, and loads a pattern to modulate the structured light of the wide-field fluorescence distribution of the NV color center. The micromirror of the DMD in the "on" state introduces the outgoing light into the first lens 402, and a filter 403 is placed at the focal plane of the first lens 402 to filter out high-order diffracted light, and the remaining 0th and ±1st order light passes through the second lens 404 to output the stripe fluorescence. The stripe fluorescence passes through the combination of the imaging lens 501 and the multi-stage optical filter 502, and is finally collected on the target surface of the fluorescence detector 503.

[0133] According to some embodiments of the present disclosure, the combination of the objective lens 10 and the imaging lens 501 forms a conjugate plane between the NV color center thin layer plane of the diamond 101 and the target surface of the fluorescence detector 503, and the counts accumulated by each fluorescence detection unit on the target surface of the fluorescence detector 503 are converted into the planar distribution of the NV color center fluorescence.

[0134] According to some optional embodiments of the present disclosure, the first lens 402 is an achromatic Fourier lens; the imaging lens 501 is an achromatic imaging lens; the dichroic mirror 13 is a 600 nanometer long-wave pass dichroic mirror; the multi-stage optical filter 502 is a 900 nanometer short-pass filter; and the first reflection assembly 307 includes a mirror.

[0135] According to some embodiments of the present disclosure, the Fourier lens can transform an incident light wave into a linear combination of monochromatic plane waves of different frequencies, which corresponds to the Fourier transform in mathematics; the achromatic Fourier lens has the ability to eliminate or reduce chromatic aberration while maintaining the basic function of the Fourier lens; the achromatic imaging lens is an optical element specially used for imaging, and its main function is to improve the imaging quality by eliminating or reducing chromatic aberration.

[0136] According to some embodiments of the present disclosure, by setting the first lens 402 as an achromatic Fourier lens and the imaging lens 501 as an achromatic imaging lens, the chromatic aberration of the collected fringe fluorescence is reduced, and the imaging quality of the fringe fluorescence is improved.

[0137] FIG. 11 schematically shows a working principle diagram of a temperature control component in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure.

[0138] According to some embodiments of the present disclosure, as shown in FIG. 11, the above-mentioned wide-field dynamic magnetic imaging device further comprises a temperature control component 9, which comprises a temperature monitor 901, a temperature control box 902, and a temperature controller 903. The temperature monitor 901 is configured to monitor the temperature of the surface of the diamond 101; the temperature control box 902 is configured to place the probe component 1; and the temperature controller 903 is configured to control the temperature inside the temperature control box 902 to be stable at a target temperature.

[0139] According to some embodiments of the present disclosure, by setting the temperature control component 9 to control the temperature inside the temperature control box 902, and then control the temperature of the surface of the diamond 101, the temperature of the surface of the diamond 101 is stabilized at the target temperature, and the stability of the target temperature is ensured to be within ±0.01 degrees Celsius. By controlling the temperature of the surface of the diamond 101 to be stable at the target temperature, the temperature of the NV color center in the diamond 101 is also controlled to be stable at the target temperature. When the NV color center is in a stable temperature environment, the spin energy level structure can maintain its stability, maintain a long spin coherence time, and improve the accuracy of quantum state optical initialization, reading and quantum state manipulation.

[0140] According to some optional embodiments of the present disclosure, the target temperature is about 30°C.

[0141] FIG. 12 schematically shows a positional relationship diagram of a position adjusting component, a probe component, and a sample to be measured in a wide-field dynamic magnetic imaging device according to an embodiment of the present disclosure.

[0142] According to some embodiments of the present disclosure, the wide-field dynamic magnetic imaging device described above further comprises a position adjusting assembly 15, which comprises a Z-axis position adjusting device 151, a two-axis position adjusting device 152, and a three-axis position adjusting device 153. The Z-axis position adjusting device 151 is configured to adjust the position of the objective lens 10; the two-axis position adjusting device 152 is configured to adjust the position of the probe assembly 1; and the three-axis position adjusting device 153 is configured to adjust the position of the sample 7 to be measured. The distance between the probe assembly 1 and the sample 7 to be measured is adjusted by adjusting the two-axis position adjusting device 152 and the three-axis position adjusting device 153.

[0143] According to some embodiments of the present disclosure, as shown in FIG. 12, the probe assembly 1 is mounted on the two-axis position adjusting device 152, which is located between the objective lens 10 and the sample 7 to be measured. The two-axis position adjusting device 152 can adjust the position of the probe assembly 1 in the X-axis direction and the Y-axis direction, i.e., the position of the probe assembly 1 in the xy plane. The objective lens 10 is mounted on the Z-axis position adjusting device 151, which controls the objective lens 10 to focus on the NV color center plane, thereby realizing wide-field fluorescence imaging and reading of the NV color center. The sample 7 to be measured is mounted on the three-axis position adjusting device 153, which can adjust the position of the sample 7 to be measured and the substrate 8 in the X-axis, Y-axis, and Z-axis directions.

[0144] According to some embodiments of the present disclosure, the three-axis position adjusting device 153 comprises a three-axis large-range position adjusting device 1531 and a three-axis small-range position adjusting device 1532. The single-axis stroke of the three-axis small-range position adjusting device 1532 is on the order of several hundred micrometers, and the resolution (adjustment accuracy) is 1 nanometer; the single-axis stroke of the Z-axis position adjusting device 151, the two-axis position adjusting device 152, and the three-axis large-range position adjusting device 1531 is on the order of tens of millimeters, and the resolution (adjustment accuracy) is 10 micrometers. The adjustment accuracy of the three-axis small-range position adjusting device 1532 is greater than that of the three-axis large-range position adjusting device 1531. The three-axis large-range position adjusting device 1531 can enable the sample 7 to be measured and the substrate 8 to move in a large range; and the three-axis small-range position adjusting device 1532 performs nanoscale spatial positioning through a nanometer piezoelectric displacement stage, thereby improving the spatial position adjustment accuracy of the sample 7 to be measured and the substrate 8.

[0145] According to some embodiments of the present disclosure, the wide-field dynamic magnetic imaging device performs the following procedure for experimental measurement: first, install the diamond 101 containing NV color centers and the sample 7 to be measured; then adjust the positions of the diamond 101 containing NV color centers and the sample 7 to be measured so that the NV color center plane is moved to the focal plane of the objective lens 10; adjust the external magnetic field so that the magnetic field direction coincides with the NV axis direction; then perform a coherence time measurement to find NV color centers with properties meeting the experimental requirements. After determining the test area, experimental data acquisition is performed. Before all experiments are completed, after each time-resolved k-space encoding data acquisition is completed, NV color center position calibration is performed, and after calibration is completed, the experiment continues. Repeat the above experimental process until the experiment is completed, and use the data processing assembly 6 to process the data.

[0146] According to some embodiments of the present disclosure, the data processing assembly 6 includes a computer workstation with a GPU operation unit. The image reconstruction process in data processing includes: first, Fourier transform each time superimposed real space image, resolve the spectral information of the image collected at each time point in k-space, move each spectrum to the k-space origin, then apply a filter 403 to sort the signals, and finally reconstruct the real space image at each time point by inverse Fourier transform, completing image reconstruction.

[0147] According to some embodiments of the present disclosure, during the specific experimental measurement process of the wide-field dynamic magnetic imaging device, a computer-controlled square wave sequence generator is used as a clock source to time-synchronize and control each component in the system. After the experiment starts, the square wave sequence generator sends out square wave pulses, while controlling the following components in the system: controlling the acousto-optic modulator group 303 in the laser modulation assembly 3 to control the laser switch; controlling the digital micromirror device 401 in the stripe light modulation assembly 4 to switch different direction stripe patterns; controlling the fluorescence detector 503 in the fluorescence detection assembly 5 to collect fluorescence; and controlling the microwave switch 203 in the microwave magnetic field assembly 2 to control the output microwave field. The acousto-optic modulator group 303, the digital micromirror device 401, the fluorescence detector 503, and the microwave switch 203 are combined in a certain time sequence to collect corresponding fluorescence signals, realizing high time-resolved k-space encoding experimental data acquisition based on stripe light modulation.

[0148] According to some embodiments of the present disclosure, by combining pulsed laser, microwave field, magnetic field, and pulse sequence, the magnetic field information is encoded in the NV color center quantum state, and the quantum state fluorescence signal is read out by laser pulse.

[0149] FIG. 13 schematically shows a flowchart of a wide-field dynamic magnetic imaging method according to an embodiment of the present disclosure.

[0150] Another aspect of the present disclosure also provides a wide-field dynamic magnetic imaging method using the wide-field dynamic magnetic imaging device described above, as shown in FIG. 13, the wide-field dynamic magnetic imaging method includes operation S101 to operation S105.

[0151] In operation S101, the initial uniform pulsed laser is output by the laser modulation assembly 3 to excite the diamond 101 containing NV color centers to emit fluorescence, and the fluorescence includes the magnetic field information of the sample 7 to be measured.

[0152] In operation S102, the initial uniform pulsed laser is modulated by the stripe light modulation assembly 4 to output the stripe pulsed laser, so that the fluorescence emitted by the diamond 101 is stripe fluorescence; or the fluorescence emitted by the diamond 101 is modulated into stripe fluorescence.

[0153] In operation S103, the uniform microwave field and the uniform bias magnetic field are generated at the position of the diamond 101 by the microwave magnetic field assembly 2 to regulate the spin energy level and quantum state evolution process of the diamond 101.

[0154] In operation S104, the stripe fluorescence is spatially imaged by the fluorescence detection assembly 5 to obtain the magnetic field information of the sample 7 to be measured, and then the initial magnetic image of the sample 7 to be measured is obtained.

[0155] In operation S105, the initial magnetic image is subjected to Fourier transform and inverse Fourier transform processing by the data processing assembly 6 to obtain the first magnetic image.

[0156] According to some embodiments of the present disclosure, the initial magnetic image includes a two-dimensional real space image obtained by superimposing a plurality of sub-two-dimensional real space images obtained at a plurality of time instants, and the first magnetic image includes a plurality of sub-two-dimensional real space images corresponding to the plurality of time instants, respectively.

[0157] According to some embodiments of the present disclosure, the initial uniform pulsed laser is output by the laser modulation assembly 3 to excite the diamond 101 containing NV color centers to emit fluorescence, and the fluorescence includes the magnetic field information of the sample 7 to be measured; the initial uniform pulsed laser is modulated by the stripe light modulation assembly 4 to output the stripe pulsed laser, so that the fluorescence emitted by the diamond 101 is stripe fluorescence; or the fluorescence emitted by the diamond 101 is modulated into stripe fluorescence; the uniform microwave field and the uniform bias magnetic field are generated at the position of the diamond 101 by the microwave magnetic field assembly 2 to regulate the spin energy level and quantum state evolution process of the diamond 101; the stripe fluorescence is spatially imaged by the fluorescence detection assembly 5 to obtain the magnetic field information of the sample 7 to be measured, and then the initial magnetic image of the sample 7 to be measured is obtained; the initial magnetic image is subjected to Fourier transform and inverse Fourier transform processing by the data processing assembly 6 to obtain the first magnetic image; and the time-resolved measurement of the high-frequency dynamic signal on the sub-millisecond to microsecond scale under the requirement of high spatial resolution is realized.

[0158] FIG. 14 schematically shows a flowchart of processing the initial magnetic image by Fourier transform and inverse Fourier transform using a data processing component to obtain a first magnetic image in a wide-field dynamic magnetic imaging method according to an embodiment of the present disclosure.

[0159] According to some embodiments of the present disclosure, as shown in FIG. 14, processing the initial magnetic image by Fourier transform and inverse Fourier transform using a data processing component 6 to obtain a first magnetic image includes operation S201 to operation S203.

[0160] In operation S201, the initial magnetic image is processed by Fourier transform to obtain a frequency domain signal, which is represented in the form of a two-dimensional k-space image.

[0161] In operation S202, the image frequency domain signals at different time instants are obtained according to the two-dimensional k-space image.

[0162] In operation S203, the image frequency domain signals are processed by inverse Fourier transform to obtain a first magnetic image.

[0163] According to some embodiments of the present disclosure, in operation S202, the image frequency domain signals at different time instants are separated from the two-dimensional k-space image according to the two-dimensional k-space image, and a k-space filter is constructed for each image at a time instant, with a center position of and a width W satisfying that is, the filter width is less than or equal to the spatial frequency difference between the two most similar stripes in the period and direction, so as to ensure that the separated signals are not disturbed by the stripes in other directions; after applying the k-space filter to all cosine stripes, M two-dimensional k-space frequency domain signals are obtained, representing the frequency domain signals at different time instants, that is, the image frequency domain signals at different time instants are obtained.

[0164] According to some embodiments of the present disclosure, in operation S203, for the obtained image frequency domain signals at different time instants, the zero frequency position of the two-dimensional frequency domain signal corresponding to each stripe is moved from to the origin of the two-dimensional k-space, and then inverse Fourier transform is performed to obtain a real space image encoded by each stripe, that is, a two-dimensional real space magnetic field image corresponding to the time instant, that is, the first magnetic image including a plurality of sub-two-dimensional real space images corresponding to a plurality of time instants.

[0165] According to some embodiments of the present disclosure, k-space is an abstract space (three-dimensional space or two-dimensional plane) in which data points represent spatial frequency information of an image. Spatial frequency k is described by three components Kx, Ky, Kz, which correspond to a three-dimensional frequency space. In two-dimensional images, we usually only concern the two components Kx and Ky. Each point in k-space corresponds to a combination of sinusoidal waves of different frequencies, phases, and directions in the image. Therefore, the data in k-space can be regarded as a representation of the image in the frequency domain. When we acquire an image, it is actually a two-dimensional matrix composed of a series of pixel values. These pixel values represent the brightness or grayscale information of the image in the spatial domain. To analyze the frequency content of the image, we can perform a two-dimensional Fourier transform on the image. This process converts the pixel values of the image into complex-valued frequency coefficients, which describe the magnitude and phase of different frequency components in the image. The result of the transformation is a two-dimensional k-space image. In the k-space image, low-frequency components (corresponding to large-scale structures in the image) are usually located in the central region, while high-frequency components (corresponding to edges and details in the image) are distributed in the edge region. By analyzing the k-space image, we can better understand the frequency distribution and characteristics of the image. At the same time, we can also use k-space data to optimize the reconstruction process of the image, improve the resolution and contrast of the image, etc.

[0166] Those skilled in the art can understand that the features described in various embodiments and / or claims of the present disclosure can be combined or / and integrated in various combinations, even if such combinations are not explicitly described in the present disclosure. In particular, the features described in various embodiments and / or claims of the present disclosure can be combined and / or integrated in various combinations without departing from the spirit and teachings of the present disclosure. All these combinations and / or integrations fall within the scope of the present disclosure.

[0167] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes, and are not intended to limit the scope of the present disclosure. Although each embodiment is described above separately, this does not mean that the measures in each embodiment cannot be advantageously combined. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A wide-field dynamic magnetic imaging apparatus, wherein, The application relates to a magnetic field imaging device and a method thereof. The device comprises: a probe assembly comprising a diamond containing NV color centers; a microwave magnetic field assembly configured to generate a uniform microwave field and a uniform bias magnetic field near the diamond to regulate spin energy levels and quantum state evolution of the diamond; a laser modulation assembly configured to output initial uniform pulsed laser to excite the diamond to emit fluorescence, the fluorescence comprising magnetic field information of a sample to be measured; a fringe light modulation assembly configured to modulate the initial uniform pulsed laser to output fringe pulsed laser so that the fluorescence emitted by the diamond is fringe fluorescence, or directly modulate the fluorescence emitted by the diamond into fringe fluorescence; a fluorescence detection assembly configured to spatially image the fringe fluorescence to obtain magnetic field information of the sample to be measured, and then obtain an initial magnetic image of the sample to be measured; and a data processing assembly configured to perform Fourier transform and inverse Fourier transform on the initial magnetic image to obtain a first magnetic image.

2. The wide-field dynamic magnetic imaging device of claim 1, wherein, The initial magnetic image comprises a two-dimensional real space image obtained by superimposing a plurality of sub-two-dimensional real space images obtained at different time points, and the first magnetic image comprises a plurality of sub-two-dimensional real space images corresponding to the plurality of time points respectively. The diamond containing NV color centers has a smooth surface and contains a plurality of NV color centers, and the plurality of NV color centers form a thin layer in the interior of the diamond.

3. The wide-field dynamic magnetic imaging device of claim 2, wherein, The depth difference between adjacent two NV color centers is less than 10 microns, and the distance between adjacent two NV color centers in the horizontal direction is less than the optical diffraction limit. The laser modulation assembly comprises: a laser configured to output initial continuous laser; a first half-wave plate configured to regulate the polarization direction of the initial continuous laser to obtain first continuous laser; an acousto-optic modulator group configured to modulate the first continuous laser to obtain initial pulsed laser to improve the on-off ratio of the initial pulsed laser; a lens group configured to adjust the beam diameter of the initial pulsed laser; and 4. The wide-field dynamic magnetic imaging apparatus of claim 3, wherein, a beam shaper configured to convert the beam of the initial pulsed laser into a flat-top beam with uniform light intensity to output the initial uniform pulsed laser. The fringe light modulation assembly comprises: a digital micromirror device configured to diffract the initial uniform pulsed laser into a plurality of parallel beams propagating in different directions; a 4f optical system configured to convert the plurality of parallel beams into fringe light, the fringe light showing a two-dimensional distribution of bright and dark stripes on an output plane; and 5. The wide-field dynamic magnetic imaging apparatus of any one of claims 1-4, wherein, a filter provided in the 4f optical system, the filter being configured to filter out stray light in the plurality of parallel beams. The fluorescence detection assembly comprises: an imaging lens configured to focus the fluorescence to form a fluorescence image; a multi-stage filter configured to filter out stray light signals and laser reflected by the surface of the diamond; and 6. The wide-field dynamic magnetic imaging device of claim 5, wherein, a fluorescence detector configured to convert the fluorescence signals into electrical signals to obtain the magnetic field information of the sample to be measured. The probe assembly further comprises:

7. The wide-field dynamic magnetic imaging apparatus as claimed in claim 6, wherein, a uniform radiation structure configured to provide a microwave field to change the spin quantum state of the NV color centers in the diamond. The microwave magnetic field assembly comprises: a microwave source configured to generate initial microwaves with a specific frequency and power; a microwave splitter configured to split the initial microwave into two paths of first microwave with equal power and 90° phase difference; a microwave switch configured to control the transmission path of the two paths of first microwave; a microwave combiner configured to combine the two paths of first microwave into a second microwave; a microwave amplifier configured to amplify the power of the second microwave to obtain a third microwave, the third microwave entering the uniform radiation structure; an isolator configured to avoid the third microwave from reflecting into the microwave amplifier; an impedance matching configured to reduce the loss in the transmission process of the third microwave; and a magnetic field source configured to provide a uniform bias magnetic field.

8. The wide-field dynamic magnetic imaging apparatus of claim 7, wherein, Further comprising a temperature control assembly, comprising: a temperature monitor configured to monitor the temperature of the diamond surface, a temperature control box configured to place the probe assembly; and a temperature controller configured to control the temperature inside the temperature control box to be stable at a target temperature.

9. A wide-field dynamic magnetic imaging method using the wide-field dynamic magnetic imaging apparatus according to any one of claims 1 to 8, wherein, The method comprises: outputting an initial uniform pulsed laser by a laser modulation assembly to excite the diamond containing NV centers to emit fluorescence, the fluorescence including magnetic field information of the sample to be measured; modulating the initial uniform pulsed laser by a stripe light modulation assembly to output a stripe pulsed laser, so that the fluorescence emitted by the diamond is stripe fluorescence; or modulating the fluorescence emitted by the diamond into stripe fluorescence; generating a uniform microwave field and a uniform bias magnetic field at the position of the diamond by a microwave magnetic field assembly to regulate the spin energy level and quantum state evolution process of the diamond; spatially imaging the stripe fluorescence by a fluorescence detection assembly to obtain the magnetic field information of the sample to be measured, and further obtain an initial magnetic image of the sample to be measured; performing Fourier transform and inverse Fourier transform processing on the initial magnetic image by a data processing assembly to obtain a first magnetic image; wherein the initial magnetic image includes a two-dimensional real space image obtained by superimposing a plurality of sub-two-dimensional real space images obtained at a plurality of time instants, and the first magnetic image includes a plurality of sub-two-dimensional real space images corresponding to the plurality of time instants respectively.

10. The wide-field dynamic magnetic imaging method of claim 9, wherein, The Fourier transform and inverse Fourier transform processing of the initial magnetic image by the data processing assembly to obtain a first magnetic image comprises: performing Fourier transform processing on the initial magnetic image to obtain a frequency domain signal, the frequency domain signal being represented in the form of a two-dimensional k-space image; acquiring image frequency domain signals at different time instants according to the two-dimensional k-space image; performing inverse Fourier transform on the image frequency domain signals to acquire a first magnetic image.

Images