CN114113151A - Coupling magnetic imaging device and measuring method - Google Patents

Coupling magnetic imaging device and measuring method Download PDF

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Publication number
CN114113151A
CN114113151A CN202111311579.XA CN202111311579A CN114113151A CN 114113151 A CN114113151 A CN 114113151A CN 202111311579 A CN202111311579 A CN 202111311579A CN 114113151 A CN114113151 A CN 114113151A
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diamond
sample
microwave
magnetic field
imaging
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石发展
徐瑶
李万和
陈三友
王鹏飞
孙梓庭
蔡明诚
杜江峰
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University of Science and Technology of China USTC
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University of Science and Technology of China USTC
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    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N22/00Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables

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Abstract

The invention discloses a coupling magnetic imaging device and a measuring method, wherein the device comprises: the sample stage comprises a prism and a diamond, the diamond is fixed right above the prism, and the sample stage adopts a nitrogen vacancy defect in the diamond as a quantum magnetic sensor; the microwave device comprises a microwave signal generator and a radiation structure with symmetrical centers, wherein the microwave signal generator is used for transmitting microwave signals, and the radiation structure is used for receiving the microwave signals and is used as a microwave antenna to radiate a microwave magnetic field to the nitrogen vacancy defects of the diamond; the laser device is used for emitting laser with the central wavelength of 532nm, and the laser enters the prism at a certain angle; the external magnetic field device is positioned above the sample table, forms a certain angle with the vertical direction of the sample table, and is used for providing a stable magnetic field for the nitrogen vacancy defects of the diamond; wherein, the sample stage is coupled with the optical microscope in a plug-in mode.

Description

Coupling magnetic imaging device and measuring method
Technical Field
The invention relates to the field of life science measurement, in particular to the field of magnetic imaging detection, and particularly relates to a coupling magnetic imaging device and a measurement method.
Background
Optical, electrical, thermal, magnetic, etc. are important physical quantities involved in life science measurements, of which optical imaging is the most widely used. Optical imaging, particularly fluorescence imaging, can expand the field of biomedical research, but is difficult to quantify absolutely due to the instability of background and fluorescence signals in biological samples. Magnetic imaging or magnetic resonance imaging has the characteristics of high penetrability, low background influence, stability and the like, and has wide application in some important application scenes, such as the fields of medical magnetic resonance imaging, magnetoencephalography, particularly biomagnetic induction and the like which need to directly measure a magnetic field or a magnetic signal. If the magnetic imaging and other imaging technologies such as optical imaging are used together, the measurement information of the biological sample is increased, and the measurement accuracy of the biological sample can be improved.
When a magnetic imaging technology is used for measuring a biological sample, factors such as room temperature and atmospheric environment, better spatial resolution, biocompatibility and the like need to be considered. The existing magnetic imaging technology mainly comprises: superconducting quantum interferometer, magneto-optical Kerr microscope, atomic magnetic microscope, Lorentz electron microscope, and atomic gas magnetometer. Superconducting quantum interferometers can achieve high magnetometric sensitivity by increasing the size of the coil, but also increase the size of the sensor, limiting spatial resolution. And because the measurement environment of the superconducting quantum interferometer needs superconducting low temperature, the distance between the probe and the sample is difficult to be close, the spatial resolution of the sample is limited, and the measurement difficulty is increased. Although the magneto-optical kerr microscope can realize the nondestructive measurement of a sample and is compatible with an optical microscope, the magneto-optical kerr microscope cannot accurately measure the magnetic field intensity, and cannot measure dispersed magnetic particles because the measurement accuracy of a biological sample is influenced by the optical characteristics of the magneto-optical kerr microscope. Other magnetic imaging techniques are difficult to be compatible with optical imaging and require scanning during measurement, and are difficult to meet the requirements of room temperature atmosphere for biological sample detection. Therefore, it is necessary to design a magnetic imaging apparatus suitable for biological sample detection, which can be coupled with optical imaging, and increase the mode of magnetic field detection without affecting the original function of the optical microscope, so that both the optical imaging and the magnetic imaging have micron-scale spatial resolution.
Disclosure of Invention
It is therefore an object of the present invention to provide a coupled magnetic imaging apparatus and a measuring method, which are at least partially solved at least one of the above mentioned technical problems.
In order to achieve the above object, as an embodiment of an aspect of the present invention, there is provided a coupled magnetic imaging apparatus including: the sample table comprises a prism and a diamond, the diamond is fixed right above the prism, and the sample table adopts a nitrogen vacancy defect in the diamond as a quantum magnetic sensor; the microwave device comprises a microwave signal generator and a radiation structure with symmetrical centers, wherein the microwave signal generator is used for transmitting microwave signals, and the radiation structure is used for receiving the microwave signals and is used as a microwave antenna to radiate a microwave magnetic field to the diamond nitrogen vacancy defects; the laser device is used for emitting laser with the central wavelength of 532nm, and the laser enters the prism at a certain angle; the external magnetic field device is positioned above the sample table, forms a certain angle with the vertical direction of the sample table, and is used for providing a stable magnetic field for the nitrogen vacancy defects of the diamond; wherein, the sample stage is coupled with the optical microscope in a plug-in mode.
According to an embodiment of the invention, wherein the prism comprises a dove prism or a rectangular prism.
According to the embodiment of the invention, laser emitted by the laser device enters the prism, and total reflection is realized in the first surface of the diamond through the prism, wherein the first surface is a contact surface of the diamond and a sample to be measured. .
According to the embodiment of the invention, the radiation structure comprises a sample hole, a fixing hole, a microwave interface, a conductor copper layer and a copper wire, wherein the sample hole is positioned in the center of the radiation structure and used for placing a diamond; the conductor copper layers are positioned on two sides of the sample hole and are provided with parabolic and circular arc smooth connection structures, so that the trend of the copper wire is rotated by 90 degrees; the microwave interfaces are positioned at two ends of the radiation structure and are connected with the conductor copper layer; the copper wire is positioned above the diamond and is welded with the conductor copper layer across the sample hole; the fixing hole is used for fixing the radiation structure on the sample table.
According to the embodiment of the invention, the extending direction of the copper wire is parallel to the short side direction of the radiation structure, so that the included angle between the direction of the magnetic field generated by the copper wire on the diamond surface and the nitrogen vacancy defect of the diamond is consistent.
According to an embodiment of the present invention, the coupled magnetic imaging apparatus further comprises an imaging device, wherein the imaging device is located above the sample stage, and is configured to collect an imaging signal of the sample to be measured, and convert the imaging signal into binary data.
According to an embodiment of the present invention, further comprises data processing means for converting binary data into decimal data and processing the decimal data using a graphic processor.
There is also provided, as an embodiment of another aspect of the present invention, a measuring method applied to the above-described coupled magnetic imaging apparatus, including: connecting the coupling magnetic imaging device and the optical microscope, and adjusting the laser device so as to form a laser spot in the first surface of the diamond; adjusting the optical microscope in response to receiving the magnetic field from the external magnetic field device to form a fluorescence image with maximum intensity and uniform distribution in a field of view of the optical microscope; acquiring an imaging signal of a sample to be detected by adjusting measurement parameters of a microwave device and an imaging device, and converting the imaging signal into binary data; converting the binary data into decimal data; and processing the decimal data by adopting a graphic processor to obtain a magnetic image of the sample to be detected.
According to an embodiment of the present invention, wherein acquiring the imaging signal of the sample to be measured comprises: and changing the microwave frequency of the microwave emitted by the microwave device, and alternately scanning the left resonance peak and the right resonance peak of the diamond so as to simultaneously acquire the left resonance peak data and the right resonance peak data of the diamond.
According to an embodiment of the present invention, wherein the processing the decimal data using the graphic processor to obtain the magnetic image of the sample to be measured comprises: accumulating the multiple measurement data of each pixel point to obtain a continuous wave spectrum of each pixel point; determining an initial value of Lorentz fitting based on the continuous wave spectrum of each pixel point; the graph processor processes the decimal data in parallel to obtain a left resonance peak frequency diagram and a right resonance peak frequency diagram of the diamond, and a total magnetic field distribution image is obtained by combining the gyromagnetic ratio of the diamond; performing global multi-parameter polynomial fitting on the total magnetic field image based on the gradient threshold of the sample to be detected to obtain an external magnetic field distribution image; and obtaining a magnetic image of the sample to be detected based on the total magnetic field distribution image and the external magnetic field distribution image.
According to the coupled magnetic imaging device provided by the above example of the invention, the sample stage is coupled to the optical microscope in a plug-in mode, and the magnetic imaging measurement of the biological sample is realized by using the nitrogen vacancy defect of the diamond as the quantum magnetic sensor, so that the expansion cost and the expansion difficulty of the optical microscope can be reduced, and the compatibility of the magnetic imaging measurement platform is improved. In addition, the coupling magnetic imaging device can also improve the laser power by setting the radiation structure of the microwave device and the incidence relation between the laser emitted by the laser device and the prism. The coupling magnetic imaging device can realize magnetic imaging measurement compatible with optical imaging, avoids excessive damage of biological samples, and has micron-sized spatial resolution in both magnetic imaging and optical imaging. Therefore, the coupled magnetic imaging device provided by the invention can be applied to the fields of magnetic nanoparticle-mediated biosensing, biomagnetic induction, hyperthermia evaluation, magnetic resonance contrast agent analysis and the like.
According to the measuring method of the coupled magnetic imaging device provided by the above example of the invention, the laser angle emitted by the laser device is adjusted to form the excitation light path related to the total reflection of the inner surface of the prism, so that the high-power excitation of the diamond nitrogen vacancy defect is realized, and the laser power can be prevented from damaging the biological sample. The imaging signal of the sample to be detected is acquired by changing the parameter information of the microwave device, so that the magnetic imaging efficiency is improved, and the image contrast can be improved; processing the imaging signal by the graphics processor can also improve data processing efficiency. Therefore, the measuring method of the coupling magnetic imaging device provided by the invention has the characteristics of high magnetic imaging acquisition efficiency, high magnetic imaging processing efficiency and high imaging image contrast.
Drawings
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a system architecture diagram of a coupled magnetic imaging device according to an embodiment of the invention;
FIG. 2 is a schematic structural diagram of a coupled magnetic imaging apparatus according to an embodiment of the present invention;
FIG. 3A is a schematic diagram of a laser entrance dove prism of the coupled magnetic imaging device shown in FIG. 2;
FIG. 3B is a schematic diagram of a laser-incident rectangular prism of the coupled magnetic imaging device shown in FIG. 2;
FIG. 4 is a top view of the radiating structure of the coupled magnetic imaging device shown in FIG. 2;
FIG. 5 is a side view of the radiating structure of the coupled magnetic imaging device shown in FIG. 2;
FIG. 6 is a schematic diagram of the left and right formants of a sample to be measured using the coupled magnetic imaging apparatus shown in FIG. 2;
FIG. 7 is a flow chart illustrating a measurement method applied to the coupled magnetic imaging apparatus shown in FIG. 2;
FIG. 8 is a flow diagram of a method for processing decimal data using a graphics processor.
Reference numerals:
1-prism 2-diamond
3-radiation structure
301-copper wire 302-sample hole 303-conductor copper layer 304-microwave interface
305-fixing hole
4-external magnetic field device 5-laser 6-camera
7-Objective lens 8-sample to be measured
9-insertable sample holder 10-prism fixing frame
Detailed Description
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
It is to be understood that such description is merely illustrative and not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present application. Various structural schematics according to embodiments of the present invention are shown in the figures. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation.
According to an embodiment of an aspect of the present invention, there is provided a coupled magnetic imaging apparatus including: the sample table comprises a prism and a diamond, the diamond is fixed right above the prism, and the sample table adopts a nitrogen vacancy defect in the diamond as a quantum magnetic sensor; the microwave device comprises a microwave signal generator and a radiation structure with symmetrical centers, wherein the microwave signal generator is used for transmitting microwave signals, and the radiation structure is used for receiving the microwave signals and is used as a microwave antenna to radiate a microwave magnetic field to the diamond nitrogen vacancy defects; the laser device is used for emitting laser with the central wavelength of 532nm, and the laser enters the prism at a certain angle; the external magnetic field device is positioned above the sample table, forms a certain angle with the vertical direction of the sample table, and is used for providing a stable magnetic field for the nitrogen vacancy defects of the diamond; wherein, the sample stage is coupled with the optical microscope in a plug-in mode.
Fig. 1 is a system architecture diagram of a coupled magnetic imaging device according to an embodiment of the present invention, and fig. 2 is a structural diagram of a coupled magnetic imaging device according to an embodiment of the present invention.
As shown in fig. 1, the sample stage is coupled to the sample stage of the optical microscope in a plug-in mode, so that the sample stage can be coupled to the optical microscope conveniently and quickly, and can be adapted to various models of optical microscopes by being coupled to the optical microscope in the plug-in mode. The coupling magnetic imaging device can couple optical imaging and magnetic imaging, measure a biological sample, transmit measurement information to a data processing device for analysis, and finally obtain an optical imaging signal and/or a magnetic imaging signal. The coupling magnetic imaging device provided by the invention can conveniently and quickly complete the loading and unloading of the biological sample, and improve the imaging efficiency while realizing multi-mode associated imaging. The coupling magnetic imaging device added on the basis of the optical microscope not only can realize high magnetometric sensitivity, but also can reduce the improvement difficulty and the improvement cost of coupling optical imaging and magnetic imaging.
As shown in fig. 2, the coupled magnetic imaging apparatus includes: prism 1, diamond 2, radiation structure 3, copper wire 301, external magnetic field device 4, camera 6, objective 7, prism mount 10. The laser 5 is the laser emitted by the laser device, the copper wire 301 is positioned above the diamond 2, and the sample 8 to be measured is directly placed on the diamond 2.
The coupling magnetic imaging device utilizes the magnetism characteristic of a nitrogen-vacancy defect (NV color center) of the diamond 2 to detect a magnetic signal of the sample 8 to be detected through the NV color center of the diamond, so that micron-sized spatial resolution is realized. The NV colour centre is a quantum spin probe in diamond with fluorescent properties, and the fluorescence of the NV colour centre is spin state dependent. The microwave device comprises a microwave signal generator and a radiation structure 3 with symmetrical centers, the microwave signal generator can generate a microwave signal with a certain frequency, and the radiation structure 3 is used as a microwave antenna to radiate a microwave magnetic field to the NV color center of the diamond 2 after receiving the microwave signal. The laser device can emit laser 5 with the central wavelength of 532nm, the laser 5 enters the prism 1 at a certain angle and is used for exciting the NV color center of the diamond 2, at the moment, the electron spin of the NV color center of the diamond 2 is polarized to 0 state and emits fluorescence (637-800nm) from red light to infrared light, and the electron spin state of the NV color center of the diamond 2 can be read by observing the change of the fluorescence. The external magnetic field device 4 is positioned above the sample table, forms a certain angle with the vertical direction of the sample table, and is used for providing a stable magnetic field for the NV color center of the diamond 2. The vertical direction of outer magnetic field device and sample platform is 54.7, guarantees to be unanimous with the NV color center direction of diamond 2, can increase the effective range of microwave absorption, and then increase the imaging area. When the external magnetic field device provides a stable magnetic field for the NV color center of the diamond 2, the electron spin of the NV color center can generate energy level shift, the shift amount of the energy level shift is in direct proportion to the intensity of the external magnetic field, and external magnetic field intensity data is obtained through the microwave resonance frequency under the condition that the NV color center of the diamond is excited by continuous laser and the NV color center of the diamond is radiated by continuous microwave. In addition, the sample stage is directly installed on the optical microscope through a plug-in mode, and can be adapted to optical microscopes of various models, so that the compatibility of the magnetic imaging measurement platform is improved, the difficulty in expanding the structure of the optical microscope is reduced, and the cost for expanding the optical microscope is reduced.
According to an embodiment of the invention, the sample stage further comprises an insertable sample holder 9, a prism holder 10. The prism fixing frame 10 is positioned below the prism 1 and used for fixing the prism 1 on the sample table. An insertable sample holder 9 is fixed to the side of the prism 1 and holds the radiation structure 3 above the prism 1. By adjusting the position of the insertable sample holder 9, the position of the diamond 2 in the radiation structure 3 can be adjusted.
According to the embodiment of the invention, the microwave device further comprises an adjustable attenuator, a power amplifier and an isolator, wherein the microwave signal emitted by the microwave signal generator sequentially passes through the adjustable attenuator, the power amplifier and the isolator to output the modulated microwave signal.
According to an embodiment of the present invention, the laser apparatus further includes a high power laser, a half-wave plate, a beam splitter, a lens, and a mirror. After the high-power laser emits laser, the power density and the excitation area of the laser light source are adjusted through the half-wave plate, the beam splitter, the lens and the reflector.
According to an embodiment of the present invention, the external magnetic field means comprises a helmholtz coil or a single magnet or a pair of magnets symmetrical with respect to the diamond 2 to provide a stable external magnetic field to the diamond 2.
According to an embodiment of the present invention, the prism 1 in the sample stage may include a dove prism or a rectangular prism.
According to the embodiment of the invention, as shown in fig. 2, laser 5 emitted by a laser device is incident into a prism 1 and enters a diamond 2 through the prism 1, and total reflection is realized in a first surface of the diamond, wherein the first surface is a contact surface of the diamond 2 and a sample 8 to be measured. The first surface of the diamond 2 is a contact surface of the diamond 2 and a sample 8 to be tested, the laser 5 only generates reflected light and does not generate refracted light in the first surface of the diamond 2, and the high-power excitation of the NV color center of the diamond 2 is realized through the reflected light. By adjusting the coupling magnetic imaging device, laser is incident from the prism, the power loss of the laser generated by lens light irradiation can be avoided, and the energy loss of the coupling magnetic imaging device can be reduced.
FIG. 3A is a schematic diagram of a laser entrance dove prism of the coupled magnetic imaging device shown in FIG. 2;
FIG. 3B is a schematic diagram of a laser-incident rectangular prism of the coupled magnetic imaging device shown in FIG. 2.
According to an embodiment of the present invention, as shown in fig. 3A and 3B, laser light 5 emitted from a laser device is incident on a dove prism, and total reflection is achieved in the first surface of the diamond 2 by the dove prism, with an incident angle of 95.7 ° or less. Laser 5 emitted by the laser device is incident into the rectangular prism, total reflection is realized in the first surface of the diamond 2 through the rectangular prism, and the incident angle is greater than or equal to 90 degrees and less than or equal to 180 degrees. The incident angle formed by the laser 5 incident on the prism changes with the type of the prism, and it is necessary to ensure that the laser 5 is totally reflected in the first surface of the diamond after being incident on the prism.
FIG. 4 is a top view of the radiating structure of the coupled magnetic imaging device shown in FIG. 2.
As shown in fig. 3, the radiation structure 3 includes: copper wire 301, sample well 302, conductor copper layer 303, microwave interface 304, fixing well 305 and insertable sample holder 9.
A sample hole 302 is located in the center of the radiation structure 3 for placing the diamond 2. The radiation structure 3 is centrosymmetric with respect to the sample well 302. The insertable sample holder 9 is provided with a groove for placing the prism and an opening corresponding to the fixing hole 305 of the radiation structure 3. The radiation structure 3 is connected to the insertable sample holder 9 via a fixing hole 305 and is fixed above the prism 1. Adjusting the position of the insertable sample holder 9 can change the position of the diamond 2 in the sample hole 302 so that the diamond 2 is within the effective radiation range of the radiation structure 3.
The microwave interface 304 is located at both ends of the radiating structure 3 and is connected to the conductor copper layer 303. The microwave interface 304 may input a microwave signal generated by a microwave signal generator into the conductive copper layer 303. The conductor copper layers 303 are located on both sides of the sample well 302 and have a parabolic and circular arc smooth connection structure such that the orientation of the copper wire is rotated by 90 °. The parabolic and circular-arc smooth connection structure of the conductor copper layer 303 ensures that the propagation of the microwave in the conductor copper layer 303 is not hindered. Copper wire 301 is positioned over diamond 2 and is soldered to a conductive copper layer 303 across sample hole 302.
FIG. 5 is a side view of the radiating structure of the coupled magnetic imaging device shown in FIG. 2.
According to the embodiment of the present invention, as shown in fig. 4 and 5, the extending direction of the copper wire 301 is parallel to the short side direction of the radiation structure 5, the copper wire 301 receives the microwave signal propagated by the conductor copper layer 303, and then generates the circular magnetic field centered on the copper wire 301. As shown in fig. 5, the plane of the magnetic field direction formed on the surface of the diamond 2 forms a fixed angle with the external magnetic field direction, and the formed angle is 54.7 °. Because the direction of the external magnetic field generated by the external magnetic field device is consistent with the NV color center direction of the diamond 2, the fixed included angle formed between the direction of the magnetic field formed on the surface of the diamond 2 and the NV color center direction of the diamond 2 is 54.7 degrees. According to the invention, by setting the extending direction of the copper wire 301, the copper wire 301 is parallel to the short side direction of the radiation structure 3, the included angle between the magnetic field direction formed by the copper wire 301 and the NV color center in the diamond 2 is ensured to be consistent, the radiation loss caused by the fact that the copper wire is perpendicular to the short side direction of the radiation structure 3 can be avoided, the radiation efficiency of the radiation structure 3 can be improved, and the fluorescence imaging area of the diamond 2 is increased.
In accordance with an embodiment of the present invention, as shown in FIG. 2, the coupled magnetic imaging device further comprises an imaging device positioned above the sample stage. The imaging device comprises a camera 6 and an objective 7, the objective 7 being an imaging objective of an optical microscope. The camera 6 is connected with the objective lens 7, collects the imaging signal of the sample 8 to be measured, converts the collected imaging signal into binary data and stores the binary data in the data processing device. The camera 6 includes a Charge Coupled Device (CCD) camera and a scientific Complementary Metal Oxide Semiconductor (sCMOS) camera. The CCD camera or the sCMOS camera is connected with the optical microscope, and can convert the acquired imaging signals of the NV color center of the diamond 2 into binary data and transmit the binary data to the data processing device for storage. The imaging signal of the NV colour centre of diamond 2 may be a fluorescence signal of the NV colour centre of diamond 2. Because the size of the binary data file is only 1/3 of a decimal text format (txt) file, the camera 6 converts the acquired imaging signal into the binary data, the storage speed and the reading speed of the data can be improved, and the hardware threshold of the data processing device is reduced, so that the cost of the coupling magnetic imaging device is reduced, and the wide utilization of the coupling magnetic imaging device is realized.
Fig. 6 is a schematic diagram of the left and right formants of a sample to be measured using the coupled magnetic imaging apparatus shown in fig. 2. In the figure, f1Is the left formant frequency, f2The right formant frequency.
In the presence of an external magnetic field, the electron spin can generate energy level shift due to the Zeeman effect, and the energy level shift is in direct proportion to the magnetic field intensity. The NV colour centre of the diamond is subjected to continuous laser excitation and continuous microwave scanning, and a decrease in the imaging signal can be detected when the microwave frequency resonates with the difference in energy level between the 0 state and the ± 1 state of the NV colour centre of the diamond. As shown in FIG. 6, the intensity of the fluorescent signal is f at the microwave frequency1And f2The obvious reduction occurs, and the strength of the external magnetic field can be obtained by determining the resonance frequency. The peak formed by the decrease in the intensity of the fluorescence signal becomes the left formant when the NV color center of the diamond resonates with the energy level difference between the 0 state and the-1 state, and the peak formed by the decrease in the intensity of the fluorescence signal becomes the right formant when the NV color center of the diamond resonates with the energy level difference between the 0 state and the +1 state.
Diamonds for magnetic imaging are NV ensemble samples, crystal lattice damage exists on the surface and inside of the diamonds due to the characteristics of a preparation process and a large number of NV color centers close to the surface, local stress can be generated on the crystal lattice damage parts, and even physical damage to the surface of the diamonds can be caused by multiple use, so that magnetic measurement is influenced. Currently, if only one side of the formants is measured, it can cause a glitch in the final magnetic image. The current method measures the continuous wave spectrum of the left formant and the continuous wave spectrum of the right formant successively, calculates the magnetic image respectively, then subtracts the difference, deducts the common stress signal, and retains the signal to be measured. However, this method can affect the effect of subtracting the stress signal due to the position drift of the sample during the measurement process. The microwave frequency output by the microwave device changes alternately between the frequency of the left resonance peak and the frequency of the right resonance peak, and the diamond 2 and the sample 8 to be detected are scanned in the microwave frequency changing alternately, so that the CCD camera or the sCMOS camera can acquire the left resonance peak data and the right resonance peak data of the diamond 2 at the same time. The left resonance peak data and the right resonance peak data of the diamond 2 are imaging signals acquired by the camera 6. Then, the CCD camera or the sCMOS camera converts the acquired imaging signal into binary data and stores the binary data in the data processing device. The camera 6 can reduce background stress signals by synchronously acquiring imaging signals, and ensure the reliability and accuracy of magnetic images.
According to an embodiment of the present invention, the data Processing apparatus converts an imaging signal of the stored binary data into decimal data, and processes the decimal data using a Graphics Processing Unit (GPU). The data processing device can convert the original binary data collected by the camera 6 through programming software to obtain decimal data, and the data processing device comprises a computer. The data processing device performs parallel Lorentz fitting processing on the imaging signals through the image processor by accumulating the imaging signals, and finally obtains a magnetic image of the sample to be detected by performing difference and global multi-parameter polynomial fitting. The data processing device can increase the data processing speed by two orders of magnitude through the graphic processor, and realize the rapid processing of light imaging and/or magnetic imaging.
There is also provided, as an embodiment of another aspect of the present invention, a measuring method applied to the above-described coupled magnetic imaging apparatus, including: connecting the coupling magnetic imaging device and the optical microscope, and adjusting the laser device so as to form a laser spot in the first surface of the diamond; adjusting the optical microscope in response to receiving the magnetic field from the external magnetic field device to form a fluorescence image with maximum intensity and uniform distribution in a field of view of the optical microscope; acquiring an imaging signal of a sample to be detected by adjusting measurement parameters of a microwave device and an imaging device, and converting the imaging signal into binary data; converting the binary data into decimal data, and accumulating the decimal data to obtain a continuous wave spectrum of each pixel point; determining an initial value of Lorentz fitting based on the continuous wave spectrum of each pixel point; and processing the decimal data by adopting a graphic processor based on the initial value of Lorentz fitting to obtain a magnetic image of the sample to be detected.
FIG. 7 is a flow chart of a measurement method applied to the coupled magnetic imaging apparatus shown in FIG. 2.
As shown in fig. 7, the coupled magnetic imaging device and the optical microscope are connected, and the laser device is adjusted to form a laser spot in the first surface of the diamond in operation S701.
According to an embodiment of the invention, the coupled magnetic imaging device is connected to an optical microscope, and a sample to be measured is loaded into the sample stage. And adjusting the angle of a laser incidence prism emitted by the laser device to enable the laser to be totally reflected in the first surface of the diamond and form a laser spot.
As shown in fig. 7, in operation S702, in response to receiving a magnetic field from an external magnetic field device, an optical microscope is adjusted to form a fluorescence image with a maximum intensity and uniform distribution in a field of view of the optical microscope.
According to an embodiment of the invention, the optical microscope is switched to the NV fluorescence channel. And adjusting the intensity of the output magnetic field of the external magnetic field device to stabilize the intensity of the external magnetic field. And the magnetic field intensity output by the external magnetic field device is less than or equal to 500Gs, and for the sample to be detected with magnetism, the magnetic field intensity output by the external magnetic field device is determined according to the magnetization curve of the sample to be detected. And then adjusting the angle between the external magnetic field adjusting device and the vertical direction of the sample table to be along the direction of the NV color center of the diamond. The magnetic field strength of the external magnetic field device is gradually increased. And adjusting a reflector in the light path to adjust the laser spot to the center of the visual field so as to form a fluorescence image with maximum intensity and uniform distribution in the visual field of the optical microscope.
According to the inventionAccording to the embodiment, the intensity of the output magnetic field of the external magnetic field device is adjusted to enable the intensity of the external magnetic field to be stabilized near 100Gs, then the angle between the external magnetic field device and the vertical direction of the sample table is adjusted to be near 54.7 degrees, and the angle between the external magnetic field device and the vertical direction of the sample table is enabled to be along the direction of the NV color center of the diamond. Gradually increasing the magnetic field intensity of the external magnetic field device to 400Gs, and adjusting the reflector to form a laser spot of 50-1000 μm on the diamond, wherein the power density of the laser is generally 200W/cm2
As shown in fig. 7, in operation S703, an imaging signal of a sample to be measured is acquired by adjusting measurement parameters of the microwave device and the imaging device, and the imaging signal is converted into binary data.
According to the embodiment of the invention, a LabVIEW program of the platform is started, the whole microwave frequency range, interval and power of the microwave device, the exposure time of a camera of the imaging device and the collection cycle number are adjusted, the camera and the microwave device are controlled to collect imaging signals, and the collected imaging signals are converted into binary data to be stored in the data processing device. By starting a LabVIEW program of the platform, the measurement parameters of the coupling magnetic imaging device are adjusted, so that the camera collects imaging signals, the collected imaging signals can be prevented from being stacked in a buffer (buffer) of the camera, the imaging signals are prevented from being influenced by a data processing device, the storage and reading of data are accelerated, and the data processing speed is increased.
As shown in fig. 7, in operation S704, binary data is converted into decimal data, and the decimal data is accumulated to obtain a continuous spectrum of each pixel.
According to an embodiment of the invention, the coupled magnetic imaging device converts the binary data into decimal data by means of a data processing device. Specifically, the data processing device may include a computer that reads in binary data by programming software, reads basic information of the imaging signal, and rearranges the data to obtain decimal two-dimensional fluorescence data. And accumulating the multiple measurement data of the same pixel point to obtain the continuous wave spectrum of each pixel point.
As shown in fig. 7, in operation S705, an initial value of the lorentzian fitting is determined based on the continuous spectrum of each pixel point.
According to an embodiment of the invention, the Lorentzian fitted curve satisfies the formula:
Figure BDA0003342127820000111
wherein x is the microwave frequency output by the microwave device, f (x) is the fluorescence accumulation function related to the microwave frequency, and a, b, c and d are constants.
According to the continuous wave spectrum of each pixel point, determining initial values of constants a, b, c and d of Lorentz fitting, wherein the specific values satisfy the following conditions:
a=-(max(f)-min(f))*(max(x)-min(x))/10
b=xmin={xmin,f(xmin)}
c=(max(x)-min(x))/10
d=max(f)
wherein max () is a function to take the maximum value, min () is a function to take the minimum value, xminIs the minimum value of the microwave frequency, where f (x)min)=min(f)。
As shown in fig. 7, in operation S706, the decimal data is processed using a graphic processor based on the initial value of the lorentz fitting to obtain a magnetic image of the sample to be measured.
According to the embodiment of the invention, the data processing device determines the initial value of Lorentz fitting through programming software, and the graphics processor performs parallel Lorentz fitting on a plurality of pixel points according to the initial value of Lorentz fitting to obtain the frequency of each pixel point. And rearranging the frequency of each pixel point to obtain a frequency graph of the left formant and a frequency graph of the right formant. And the data processing device performs difference processing on the frequency diagram of the left resonance peak and the frequency diagram of the right resonance peak, obtains a total magnetic field distribution image by combining the gyromagnetic ratio of the diamond, performs global multi-parameter polynomial fitting on the obtained total magnetic field distribution image, subtracts a static magnetic field signal provided by an external magnetic field, and finally obtains a magnetic image of the sample to be detected.
According to an embodiment of the present invention, acquiring an imaging signal of a sample to be measured includes: and changing the microwave frequency of the microwave device for transmitting the microwaves, and alternately scanning the left resonance peak and the right resonance peak of the diamond so as to simultaneously acquire the left resonance peak data and the right resonance peak data of the diamond. Changing the microwave frequency once at intervals of 0.01s-0.5s to ensure that the microwave frequency is changed alternately between the resonance frequencies of the left resonance peak and the right resonance peak of the diamond, repeating the alternate scanning for 10-300 times, and acquiring the imaging signal of the sample to be detected. The time interval of the resonance frequency may coincide with the exposure time of the camera according to the actual application. The microwave frequency is scanned alternately between the left resonance peak and the right resonance peak by improving the data acquisition sequence, so that the left resonance peak data and the right resonance peak data are acquired simultaneously, and the acquisition method is called as a left-right peak synchronization technology. The invention can reduce the influence of thermal drift and low-frequency noise on magnetism measurement through the left-right seam synchronization technology, and can also reduce background stress signals and ensure the reliability and accuracy of magnetic images.
FIG. 8 is a flow diagram of a method for processing decimal data using a graphics processor.
According to an embodiment of the present invention, as shown in fig. 8, in operation S801, a graphic processor processes decimal data in parallel to obtain a left formant frequency map and a right formant frequency map of a diamond, and a total magnetic field distribution image is obtained in combination with a gyromagnetic ratio of the diamond.
According to the embodiment of the invention, the decimal data processing comprises the steps of carrying out Lorentz fitting on each pixel point according to the continuous wave spectrum of each pixel point and the initial value of the Lorentz fitting of each pixel point to obtain the left resonant peak frequency and the right resonant peak frequency of each pixel point after the Lorentz fitting. Since the graphics processor is a parallel lorentz fit, a left and right formant frequency map of the entire imaging signal can be obtained. And (4) performing difference processing on the left resonance peak frequency diagram and the right resonance peak frequency diagram by combining the gyromagnetic ratio of the diamond to obtain a total magnetic field distribution image. The total magnetic field distribution image comprises a magnetic image of the sample to be measured and a static magnetic field provided by the external magnetic field device. Lorentz fitting data are paralleled through the graphic processor, the fitting speed can be improved by two orders of magnitude, and the process of processing the fitting image is accelerated. And (3) carrying out difference processing on the left formant frequency graph and the right formant frequency graph according to a formula:
B=(f2-f1)/2πγ0
wherein f is1Is the left formant frequency, f2Is the right formant frequency, gamma0Is the gyromagnetic ratio of diamond, and B is the total magnetic field strength.
As shown in fig. 8, in operation S802, global multi-parameter polynomial fitting is performed on the total magnetic field distribution image based on the gradient threshold of the sample to be measured, so as to obtain an external magnetic field distribution image.
According to the embodiment of the invention, the signal of the sample to be detected has the property of local distribution, and the magnetic field gradient of the sample to be detected is far larger than that provided by the external magnetic field device. And selecting a gradient threshold value according to the characteristics of the sample to be detected, enabling the imaging signal of the sample to be detected to be larger than the threshold value, covering the imaging signal of the sample to be detected by using a mask, and only the imaging signal provided by the external magnetic field device is left in the processed total magnetic field distribution image. The gradient threshold is chosen to range from 0.2MHz per pixel to 1MHz per pixel. And (3) carrying out global multi-parameter polynomial fitting on the total magnetic field distribution image, actually carrying out global multi-parameter polynomial fitting on the residual external magnetic field imaging signals in the total magnetic field distribution image, and obtaining the external magnetic field distribution image.
As shown in fig. 8, in operation S803, a magnetic image of the sample to be measured is obtained based on the total magnetic field distribution image and the external magnetic field distribution image.
According to the total magnetic field distribution image and the external magnetic field distribution image obtained in operation S802, the data processing device subtracts the external magnetic field distribution image from the total magnetic field distribution image to obtain a magnetic image of the sample to be measured.
According to the invention, the NV color center in the diamond is used as a quantum magnetic sensor, a set of coupling magnetic imaging device which is suitable for a biological sample and coupled with an optical microscope is built, the coupling magnetic imaging device can be compatible with optical imaging and magnetic imaging, large-area, rapid and clear magnetic imaging of the biological sample is realized, and both the magnetic imaging and the optical imaging can reach micron-scale spatial resolution. Meanwhile, the sample stage, the laser device, the microwave device and the external magnetic field device are provided on the basis of the optical microscope, and the sample stage is coupled to the optical microscope in a plug-in mode, so that multi-mode associated imaging can be realized, the operability of biological sample loading and unloading and the operability of multi-mode associated imaging can be improved, and the imaging efficiency can be improved. According to the invention, the total internal reflection excitation light path can be realized by adjusting the laser device, and the transition damage to the biological sample can be avoided; data processing efficiency can also be improved by employing a graphics processor.
The invention adopts the measurement method of the coupling magnetic imaging device, does not influence the properties of the biological sample, and can carry out magnetic quantitative analysis on the imaging result. Through improving the collection order, can realize synchronous data acquisition, and then improve magnetic imaging efficiency and image contrast to with gathering data storage in binary format can also accelerate the storage and the reading rate of data at data processing apparatus, avoid gathering the influence that the piling up of data at the camera buffer caused.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A coupled magnetic imaging apparatus, comprising:
the sample table comprises a prism and a diamond, the diamond is fixed right above the prism, and the sample table adopts a nitrogen vacancy defect in the diamond as a quantum magnetic sensor;
the microwave device comprises a microwave signal generator and a radiation structure with symmetrical centers, wherein the microwave signal generator is used for transmitting microwave signals, and the radiation structure is used for receiving the microwave signals and is used as a microwave antenna to radiate a microwave magnetic field to the nitrogen vacancy defects of the diamond;
the laser device is used for emitting laser with the central wavelength of 532nm, and the laser enters the prism at a certain angle;
the external magnetic field device is positioned above the sample table, forms a certain angle with the vertical direction of the sample table, and is used for providing a stable magnetic field for the nitrogen vacancy defects of the diamond;
wherein the sample stage is coupled to the optical microscope in a plug-in mode.
2. The coupled magnetic imaging device of claim 1, wherein the prism comprises a dove prism or a rectangular prism.
3. The coupled magnetic imaging device according to claim 1, wherein the laser emitted from the laser device is incident on the prism, and total reflection is achieved in a first surface of the diamond through the prism, wherein the first surface is a contact surface of the diamond and a sample to be measured.
4. The coupled magnetic imaging device of claim 1, wherein the radiating structure comprises a sample well, a fixing well, a microwave interface, a conductor copper layer, and a copper wire,
the sample hole is positioned in the center of the radiation structure and used for placing the diamond;
the conductor copper layers are positioned on two sides of the sample hole and are provided with parabolic and circular arc smooth connection structures, so that the trend of the copper wire is rotated by 90 degrees;
the microwave interfaces are positioned at two ends of the radiation structure and are connected with the conductor copper layer;
the copper wire is positioned above the diamond and is welded with the conductor copper layer across the sample hole;
the fixing hole is used for fixing the radiation structure on the sample table.
5. The coupled magnetic imaging device of claim 4, wherein the extending direction of the copper wire is parallel to the short side direction of the radiation structure, so that the direction of the magnetic field generated by the copper wire on the diamond surface is consistent with the included angle of the nitrogen vacancy defects of the diamond.
6. The coupled magnetic imaging device of claim 1, further comprising an imaging device, wherein the imaging device is located above the sample stage and is configured to acquire imaging signals of a sample to be measured and convert the imaging signals into binary data.
7. The coupled magnetic imaging device of claim 6, further comprising a data processing device for converting the binary data to decimal data and processing the decimal data with a graphics processor.
8. A measurement method applied to the coupled magnetic imaging apparatus as claimed in any one of claims 1 to 7, comprising:
connecting the coupled magnetic imaging device and the optical microscope, and adjusting the laser device so as to form a laser spot in the first surface of the diamond;
adjusting the optical microscope in response to receiving a magnetic field from an external magnetic field device to form a fluorescence image with a maximum intensity and uniform distribution in a field of view of the optical microscope;
acquiring an imaging signal of a sample to be detected by adjusting measurement parameters of the microwave device and the imaging device, and converting the imaging signal into binary data;
converting the binary data into decimal data, and accumulating the decimal data to obtain a continuous wave spectrum of each pixel point;
determining an initial value of Lorentz fitting based on the continuous wave spectrum of each pixel point;
and processing the decimal data by adopting a graphic processor based on the initial value of the Lorentz fitting to obtain a magnetic image of the sample to be detected.
9. The measurement method of claim 8, wherein the acquiring imaging signals of a sample to be measured comprises:
and changing the microwave frequency of the microwave emitted by the microwave device, and alternately scanning the left resonance peak and the right resonance peak of the diamond so as to simultaneously acquire the left resonance peak data and the right resonance peak data of the diamond.
10. The measurement method of claim 8, wherein the processing the decimal data with a graphics processor to obtain a magnetic image of the sample under test comprises:
the graphics processor processes the decimal data in parallel to obtain a left resonance peak frequency diagram and a right resonance peak frequency diagram of the diamond, and a total magnetic field distribution image is obtained by combining the gyromagnetic ratio of the diamond;
performing global multi-parameter polynomial fitting on the total magnetic field image based on the gradient threshold of the sample to be detected to obtain an external magnetic field distribution image;
and obtaining the magnetic image of the sample to be detected based on the total magnetic field distribution image and the external magnetic field distribution image.
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