Calibration device of bias magnetic field and measurement device and method of absolute magnetic field

Abstract

The invention provides a calibration device of a bias magnetic field and a measurement device and method of an absolute magnetic field, and the calibration device comprises a magnetometer which is used for implementing ODMR measurement and outputting magnetic field vector data; the rotating table is used for placing at least a probe part in the magnetometer, and after placing, the xyz coordinate axis of the diamond is aligned with the x'y'z 'rotating coordinate axis of the rotating table one by one; the control module is used for controlling the rotary table to rotate by 180 degrees around the x axis, the y axis and the z axis from the initial position; and the data processing module is used for calculating to obtain a bias magnetic field vector # imgabs5 # according to the magnetic field vector # imgabs0 # of the initial position output by the magnetometer, the magnetic field vectors # imgabs1 #, # imgabs2 # and # imgabs3 # after the initial position respectively rotates around the x axis, the y axis and the z axis by 180 degrees, and a formula # imgabs4 #, wherein the magnetic field vectors # imgabs0 #, the magnetic field vectors # imgabs1 #, # imgabs2 # and # imgabs3 # are obtained by rotating around the x axis, the y axis and the z axis by 180 degrees from the initial position by 180 degrees. The method can achieve the calibration of the bias magnetic field, is high in precision based on the precision measurement technology of the diamond NV color center, and can improve the measurement precision when being applied to the calculation of an absolute magnetic field.

Description

Technical Field

[0001] The present invention relates to the field of magnetic sensing measurement, and in particular to a device for calibrating a bias magnetic field, a device and a method for measuring an absolute magnetic field. Background Art

[0002] Nitrogen-vacancy (NV) color centers play a key role in diamond spin magnetic resonance technology and have become an important development direction in the field of spin magnetic resonance sensing. Its working principle is to use optical pumping to initialize the spin state of the NV color centers, and then precisely control them through a continuous microwave field, and optically reflect the changes of related physical quantities by detecting the fluorescence intensity changes of the spin state.

[0003] When a magnetic field acts along the axial direction of the color center, it will cause the Zeeman effect splitting of its energy levels. This splitting can be observed in the optically detected magnetic resonance (ODMR) scan spectrum. Generally, by applying a bias magnetic field, four pairs of different resonance peaks corresponding to the four axial directions of the NV color centers in the diamond ensemble respectively appear in the ODMR scan spectrum. By measuring the frequency differences corresponding to these four pairs of resonance peaks, the magnetic field components corresponding to the four axial directions of the NV can be calculated, and the current vector magnetic field information can be obtained through coordinate system conversion. However, the vector magnetic field information obtained at this time contains both the bias magnetic field and the external absolute magnetic field. Since the bias magnetic field is unknown, we cannot obtain the external absolute magnetic field and can only obtain the change amount of the magnetic field. And this change amount is the change relative to the sum of the initial magnetic field vectors, which is applicable to the measurement of a magnetic field with an unchanged direction, and the probe containing the diamond and the bias magnetic field needs to be kept stationary during the measurement. If the probe rotates slightly, the included angle between the absolute magnetic field to be measured and the bias magnetic field changes, causing the vector sum measured thereby to change with the change of the included angle, and there is an error brought by the probe rotation in the change amount calculated relative to the initial magnetic field vector. Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a device for calibrating a bias magnetic field, a device and a method for measuring an absolute magnetic field, which are used to solve the problems that when using NV color centers to detect a magnetic field in the prior art, the measured magnetic field vector contains a bias magnetic field and an external absolute magnetic field, the bias magnetic field cannot be calibrated, and thus the external absolute magnetic field cannot be obtained, only the change amount of the magnetic field can be measured, and the rotation of the probe will bring errors to the calculation of the change amount.

[0005] To achieve the above purpose and other related purposes, the first aspect of the present invention provides a device for calibrating a bias magnetic field, including: A magnetometer is used to perform ODMR measurements, output magnetic field vector data, and cause four pairs of resonance peaks to appear on the ODMR spectrum obtained from the ODMR measurements. The magnetometer includes at least a probe composed of a diamond containing NV color centers, a bias magnet, and a microwave antenna. A rotating stage is used to place at least the probe part in the magnetometer. After placement, the xyz coordinate axes established by the three crystal axes of the diamond are aligned one-to-one with the x'y'z' rotation coordinate axes of the rotating stage. A control module is used to control the rotating stage to rotate 180 degrees around the x, y, and z axes respectively from the initial position. The magnetometer is also used to perform ODMR measurements at the initial position and after each rotation of the rotating stage. A data processing module is used to calculate the bias magnetic field vector according to the magnetic field vector at the initial position output by the magnetometer and the magnetic field vectors after rotating 180 degrees around the x, y, and z axes respectively from the initial position 、 、 , and the formula . .

[0006] Furthermore, the magnetometer also includes an illumination module, a detection module, an optical splitter, an optical fiber, and a microwave module. One end of the optical fiber is connected to the diamond, and the other end is connected to the optical splitter. The microwave module is connected to the microwave antenna and used to transmit microwaves to it. The excitation light generated by the illumination module enters the optical fiber through the optical splitter, excites the diamond to generate fluorescence, and the fluorescence entering the optical fiber is transmitted to the optical splitter and then to the detection module to be collected and detected.

[0007] Furthermore, the magnetometer also includes an illumination module, a detection module, an optical fiber, and a microwave module. One end of the optical fiber is connected to the diamond, and the other end is connected to the illumination module. The detection module is located on one side of the diamond. The microwave module is connected to the microwave antenna and used to transmit microwaves to it. The excitation light generated by the illumination module enters the optical fiber, excites the diamond to generate fluorescence, and is collected and detected by the detection module. The detection module and the probe are placed on the rotating stage together.

[0008] Furthermore, the magnetometer also includes an illumination module, a detection module, and a microwave module. The illumination module and the detection module are located on different sides of the diamond and are both placed on the rotating stage together with the probe. The microwave module is connected to the microwave antenna and used to transmit microwaves to it. The excitation light generated by the illumination module irradiates the diamond, excites the diamond to generate fluorescence, and is collected and detected by the detection module.

[0009] Further, the magnetometer further includes a frequency control module and a magnetic field calculation module. The frequency control module is connected to the microwave module and is configured to transmit a frequency signal thereto to control the microwave frequency transmitted by the microwave module to the microwave antenna. The magnetic field calculation module is connected to the detection module and is configured to obtain a resonance frequency based on the fluorescence electric signal output by the detection module and its corresponding microwave frequency, and calculate a magnetic field vector based on the resonance frequency.

[0010] Further, the magnetometer further includes a modulation and demodulation module and a magnetic field calculation module connected in sequence. The modulation and demodulation module is further connected to the microwave module and the detection module, and is configured to transmit a frequency signal and a modulation signal to the microwave module and demodulate the fluorescence electric signal output by the detection module, and transmit the demodulated data to the magnetic field calculation module. The magnetic field calculation module obtains a resonance frequency based on the demodulated data and its corresponding microwave frequency, and calculates a magnetic field vector based on the resonance frequency.

[0011] Further, the magnetometer further includes a modulation and demodulation module, a PID tracking module, and a magnetic field calculation module connected in sequence. The modulation and demodulation module is further connected to the microwave module and the detection module, and is configured to transmit a modulation signal to the microwave module and demodulate the fluorescence electric signal output by the detection module, and transmit the demodulated data to the PID tracking module. The PID tracking module is further connected to the microwave module and is configured to regulate the frequency of the modulated microwave transmitted by the microwave module to the microwave antenna through a PID algorithm to obtain a resonance frequency corresponding to the magnetic field to be measured, and transmit the resonance frequency to the magnetic field calculation module. The magnetic field calculation module calculates a magnetic field vector based on the resonance frequency.

[0012] To achieve the above and other related objectives, a second aspect of the present invention provides a measuring device for an absolute magnetic field, including: a calibration device for a bias magnetic field according to any one of the first aspects, wherein the magnetometer is further configured to perform ODMR measurement in a magnetic field to be measured, and its data processing module is further configured to calculate an absolute magnetic field vector of the magnetic field to be measured according to the total magnetic field vector of the magnetic field to be measured output by the magnetometer , and formula Calculate the absolute magnetic field vector of the magnetic field to be measured .

[0013] To achieve the above and other related objectives, a third aspect of the present invention provides a method for calibrating a bias magnetic field, including: Regulate the bias magnetic field applied to the diamond containing NV color centers so that four pairs of resonance peaks appear in the ODMR spectrum obtained by performing ODMR measurement on the diamond, and calculate the magnetic field vector at this initial position according to the resonance frequencies corresponding to the four pairs of resonance peaks ; An xyz coordinate system is established using the three crystal axes of a diamond. While keeping the excitation light, bias magnetic field, microwave radiation applied to the diamond unchanged, and the fluorescence detection method unchanged, the diamond is rotated 180 degrees around the x, y, and z axes of the coordinate system from its initial position respectively, and ODMR measurements are performed after each rotation to obtain the resonance frequency. The magnetic field vector is calculated based on the resonance frequency. , , ; The bias magnetic field vector is calculated by the formula .

[0014] To achieve the above and other related objectives, a fourth aspect of the present invention provides a method for measuring an absolute magnetic field, including: calculating by a calibration method for a bias magnetic field described in any one of the third aspects, obtaining the total magnetic field vector in the environment to be measured by ODMR measurement, and then calculating the absolute magnetic field vector of the environment to be measured according to .

[0015] As described above, a calibration device for a bias magnetic field, a measurement device and method for an absolute magnetic field of the present invention have the following beneficial effects: By keeping the conditions such as the bias magnetic field relatively unchanged with respect to the diamond, the diamond is rotated 180 degrees around the x, y, and z axes from the initial position respectively, and ODMR measurements are performed at the initial position and after each rotation to calculate the magnetic field vectors at the initial position and after rotation. Then, using the formula to calculate the bias magnetic field vector , the calibration of the bias magnetic field can be achieved, and it is calculated based on the magnetic field measured by the diamond NV color center with micro / nanoscale spatial resolution and ultra-high sensitivity in the picotesla range. It has high precision. When applied to the calculation of the external absolute magnetic field, the measurement precision can also be improved. Moreover, the calculated absolute magnetic field can accurately describe the magnitude of the magnetic field and has high stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Shows a schematic structural diagram of the calibration device for the bias magnetic field of the present invention; Figure 2 Shows a schematic diagram of the coordinate system established by the three crystal axes of the diamond of the present invention; Figure 3 Shows an exemplary structural diagram of the turntable of the present invention; Figure 4 Shows a first schematic diagram of a part of the magnetometer placed on the turntable of the present invention; Figure 5Shown is a schematic diagram of a second embodiment of a magnetometer of the present invention placed on a rotating table; Figure 6 FIG. 1 is a schematic diagram showing a third partial method of placing the magnetometer of the present invention on a rotating table.

[0017] Component number explanation: 1—magnetometer; 11—probe; 111—diamond; 112—bias magnet; 113—microwave antenna; 114—housing; 115—second mounting hole; 12—illumination module; 121—excitation light source; 13—detection module; 131—filter; 132—photodetector; 14—light separator; 15—optical fiber; 16—microwave module; 161—microwave source; 162—microwave amplifier; 163—microwave circulator; 17—magnetic field calculation module; 18—modulation and demodulation module; 19—PID tracking module; 10—frequency control module; 2—rotating stage; 21—first mounting hole; 22—outer frame; 23—middle frame; 24—inner stage; 3—control module; 4—data processing module. DETAILED DESCRIPTION

[0018] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0019] It should be noted that the illustrations provided in the following embodiments are merely schematic illustrations of the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0020] Example 1: Figure 1 As shown, the present invention provides a calibration device for a bias magnetic field, comprising: A magnetometer 1 is configured to perform ODMR measurements and output magnetic field vector data, and to cause four pairs of resonance peaks to appear on the ODMR spectrum obtained by the ODMR measurements. The magnetometer comprises at least a probe 11 comprising a diamond 111 containing NV color centers, a bias magnet 112, and a microwave antenna 113. The rotating table 2 is used to place at least the probe part of the magnetometer 1, and after being placed, the xyz coordinate axes established by the three crystal axes of diamond are aligned one by one with the x'y'z' rotation coordinate axes of the rotating table 2; The control module 3 is used to control the rotating table 2 to rotate 180 degrees around the x, y, and z axes respectively from the initial position; the magnetometer is also used to perform ODMR measurements at the initial position and after each rotation of the rotating table. The data processing module 4 is used to calculate the bias magnetic field vector based on the magnetic field vectors output by the magnetometer 1 and the magnetic field vectors after rotating 180 degrees around the x, y, and z axes respectively from the initial position , and the formula .

[0021] In this embodiment, the magnetic field calculated by the ODMR measurement method includes bias magnetic field and external absolute magnetic field vector information: , The initial total magnetic field measured in the initial state is: , The external magnetic field is: ; After rotating 180 degrees around the x-axis from the initial position, the bias magnetic field rotates simultaneously with the diamond, and the bias magnetic field vector information remains unchanged. At this time, the total magnetic field is: , The external absolute magnetic field is: ; Similarly, after rotating 180 degrees around the y-axis from the initial position, the total magnetic field is: , The external absolute magnetic field is: ; Similarly, after rotating 180 degrees around the z-axis from the initial position, the total magnetic field is: , The external absolute magnetic field is: ; Adding the four measurement values gives: , Therefore, the bias magnetic field vector can be obtained as: .

[0022] Thus, this embodiment can achieve the calibration of the bias magnetic field, and it is calculated using the magnetic field measured by the diamond NV color center with micro / nanoscale spatial resolution and ultra-high sensitivity in the picotesla range. It has high precision, and when applied to the calculation of the external absolute magnetic field, it can also improve the measurement precision.

[0023] For the coordinate system established based on the diamond crystal axis, it can be as Figure 2As shown, since diamond is generally produced by chemical vapor deposition, during cutting, it will be cut along a growth base plane. For example, for a diamond cut along the (100) crystal plane, the crystal axis direction

[100] can be determined according to its cutting surface, and then the other two crystal axis directions

[010] and

[001] can be determined by methods such as calibrating the NV axis direction or X-ray diffraction experiments. For diamonds cut along other crystal planes, such as the (111) crystal plane, it is necessary to calculate the angle between the crystal axis direction and the cutting surface or use methods such as X-ray diffraction experiments to determine the crystal axis direction, and then label its coordinate system. As Figure 2 shown, with the

[100] crystal direction as the x-axis, the

[010] crystal direction as the y-axis, and the

[001] crystal direction as the z-axis, an xyz coordinate system is established. The diamond particles usually used are of nanometer or micrometer size, and even bulk diamonds are in the micrometer size range. After determining the crystal axis direction, the diamond can be regarded as a point and a coordinate system can be established for it. The error and spatial resolution obtained in this way are also in the micrometer range, which can meet the requirements of measurement accuracy. When placing the diamond on the rotating table, align the xyz coordinate axes with the rotating coordinate axes x′y′z′ of the rotating table, as Figure 4 shown, in this embodiment, a housing 114 is provided outside the probe 11. By fixing the probe in the housing and making the xyz coordinate axes of the diamond align with the rotating coordinate axes x′y′z′ of the rotating table after installing the housing on the rotating table, the implementation method can be to determine the xyz axes of the housing according to the installation position of the diamond in the housing, and then design the installation structure of the housing and the rotating table after aligning the xyz axes of the housing with the rotating axes x′y′z′ of the rotating table. Exemplarily, as Figure 3 shown, corresponding first mounting holes 21 and second mounting holes 115 are provided on the rotating table 2 and the housing 114 respectively. After being fixed through the mounting holes, the two coordinate axes are aligned one by one.

[0024] The rotating table 2 can rotate around three axes. A structure such as Figure 1 shown can be selected. The outer frame 22 rotates around the z′ axis, and the middle frame 23 and the inner table 24 rotate around the y′ and x′ axes respectively. The probe 11 is placed on the inner table 24. When the outer axis rotates, the inner part rotates accordingly. Other structural forms of rotating tables can also be used as long as the three-dimensional rotation axes can be aligned with the coordinate axes of the diamond, and the rotating table is made of non-magnetic material. During rotation, after rotating 180 degrees around one coordinate axis, it can be rotated 180 degrees in the reverse direction to the initial position and then rotated 180 degrees around the next coordinate axis; it can also be rotated 180 degrees around one coordinate axis and then rotated from this position until it rotates to the same position as the position rotated 180 degrees around the next coordinate axis from the initial state.

[0025] The magnetometer 1 further includes an illumination module 12, a detection module 13, an optical splitter 14, an optical fiber 15, and a microwave module 16; one end of the optical fiber 15 is connected to the diamond 111, and the other end is connected to the optical splitter 14; the microwave module 16 is used to transmit microwaves to the microwave antenna 113; the excitation light generated by the illumination module 12 enters the optical fiber 15 through the optical splitter 14, excites the diamond 111 to generate fluorescence, the fluorescence entering the optical fiber 15 is transmitted to the optical splitter 14, and then transmitted to the detection module 13 to be collected and detected. In this embodiment, the optical fiber 15 is used to realize the transmission of the excitation light and the fluorescence, and the optical splitter 14 is used to realize the separation of the two kinds of light. The optical splitter 14 can be, for example, Figure 1 the optical circulator or dichroic film or other optical elements with this function in [[ID=?]] Figure 1

[0026] The illumination module 12 may exemplarily include, for example, Figure 5 the excitation light source 121 shown as in [[ID=?]] Figure 5 Figure 5 The excitation light source 121 can adopt a light source in the form of a laser or an LED. The illumination module 12 may further include components for processing the light generated by the light source, such as components for filtering, collimating, polarizing, light quantity adjusting, etc. The excitation light source 121 in this embodiment adopts a laser source. The detection module 13 may exemplarily include, for example,

[0027] the filter film 131 and the photodetector 132 shown as in Figure 5 to convert the received fluorescence into an electrical signal. A light collection structure may also be provided between the diamond 111 and the filter film 131, such as a hollow cavity for condensing light, with a reflective film provided on the wall to enhance the light collection efficiency, or a condensing lens, etc., while being able to enhance the integration.

[0028] It further includes a magnetic field calculation module 17, which is used to obtain the resonance frequency according to the fluorescence electrical signal output by the detection module 13 and its corresponding microwave frequency, and calculate the magnetic field vector according to the resonance frequency. The magnetic field calculation module 17 transmits the calculated magnetic field vector to the data processing module 4.

[0029] It should be noted that there seem to be some missing references in the original text for the tags Figure 1 , Figure 5 , Figure 5 etc. which are marked as "?". This might need to be clarified in the original source to provide a more accurate translation.The method for calculating the magnetic field vector based on ODMR measurement is well-known in the art, and a brief introduction is given here in combination with coordinates. First, optically detected magnetic resonance (ODMR) refers to a resonance phenomenon in which the resonance of the optical frequency of atoms and molecules occurs simultaneously with the magnetic resonance of radio frequency or microwave frequency. In the ODMR measurement described in this embodiment, the diamond NV color center is used as the implementation object. When irradiating it with excitation light, radiating microwaves, and detecting the generated fluorescence signal, if resonance occurs, the fluorescence decreases, and the microwave frequency radiated during resonance is the resonance frequency. To obtain the resonance frequency, the microwave sweep method is used to implement ODMR measurement in this embodiment. By scanning the microwave frequency, an ODMR spectrum line of the fluorescence electrical signal changing with the microwave frequency can be obtained. To control the scanning of the microwave frequency, a frequency control module 10 is also provided, which is connected to the microwave module and used to transmit frequency signals to it to control the frequency of the microwave transmitted by the microwave module to the microwave antenna. This frequency control module is connected to the microwave source 161 and transmits frequency signals to the microwave source, such as hardware signals of high and low levels or software signals of program instructions, to control the microwave frequency transmitted to the microwave antenna. After obtaining the resonance frequency on the ODMR spectrum line, the magnetic field vector can be calculated from the resonance frequency. In the probe, the direction of the bias magnetic field applied by the bias magnet is such that four pairs of resonance peaks appear on the ODMR spectrum line obtained by the magnetometer implementing ODMR measurement, which is convenient for calculating the magnetic field vector using the four pairs of resonance peaks. For example, Figure 2 For the established coordinate system, the axial directions of the diamond NV color center are [1 1 1], [1 -1 -1], [-1 1 -1], [-1 -1 1] in sequence, the external magnetic field is B=(Bx, By, Bz), and the magnetic fields projected onto the four NV axes are obtained from the following matrix (according to the vector projection formula): , The magnitudes of the magnetic fields on the four NV axes will affect the resonance frequency values on the ODMR scan spectrum, and the corresponding relationship is , is the difference between two resonance frequencies in the same axial direction, from which we can obtain: , According to the above formula, the magnetic field vector B=(Bx, By, Bz) is calculated, where the sign of each is initially determined according to the position of the bias magnetic field relative to the NV axial direction (for the weak magnetic field being measured, the bias magnetic field is relatively large), and then it is verified and adjusted based on the principle that the sum of the magnetic field components on the four axes is 0.

[0030] Embodiment 2: As shown in Figure 5 , the difference between this embodiment and Embodiment 1 is that it does not include the optical separator 14, and the detection module 13 is placed on one side of the diamond to collect and detect the generated fluorescence. In this embodiment, when there is a housing 114 provided on the outside of the probe, as shown in Figure 5As shown, the detection module is placed inside the housing, or a detection port is opened on the housing 114. The detection module 13 is installed in the detection port, and the detection surface faces the diamond. Thus, when the probe is placed on the rotating table, the detection module is also placed on the rotating table.

[0031] In this embodiment, the magnetometer 1 further includes a modulation and demodulation module 18, which is connected to the microwave module 16, the detection module 13, and the magnetic field calculation module 17. It is used to transmit frequency signals and modulation signals to the microwave module 16, demodulate the fluorescence electrical signal output by the detection module 13, and transmit the demodulated data to the magnetic field calculation module 17. The magnetic field calculation module 17 obtains the resonance frequency according to the demodulated data and its corresponding microwave frequency, and calculates the magnetic field vector according to the resonance frequency. The microwave module 16 modulates the corresponding frequency according to the frequency signal and the modulation signal and then transmits it to the microwave antenna. In the magnetic field calculation module 17, the demodulation curve of the demodulated data changing with the microwave can be obtained from the demodulated data and its corresponding microwave frequency. The resonance frequency is obtained from the zero-crossing point on the curve, and then the magnetic field vector is calculated by the foregoing method. In this embodiment, the modulation and demodulation module 18 controls the microwave frequency transmitted by the microwave module to the microwave antenna by transmitting frequency signals to the microwave module. The modulation and demodulation module 18 can adopt an algorithm program module that realizes the above functions. The modulation method is, for example, frequency modulation or amplitude modulation, and the modulation signal can be a sine signal or a square wave signal, including parameters such as modulation frequency or amplitude, and modulation depth.

[0032] Embodiment 3: Different from Embodiment 2, in this embodiment, optical fiber is not used to transmit the excitation light, but as Figure 6 shown, the illumination module is arranged on one side of the diamond and on a different side from the detection module, and is placed on the rotating table together with the probe. The illumination module 12, the probe 11, and the detection module 13 are integrated in the housing 114. This way improves the integration and portability of the magnetometer on the one hand, and on the other hand, the optical path is all located on the rotating table, avoiding the influence on the optical path transmission during rotation and further improving the accuracy.

[0033] In this embodiment, a PID tracking module 19 is further provided, which is connected to the microwave module 16, the modulation and demodulation module 18, and the magnetic field calculation module 17. It is used to regulate the frequency of the modulated microwave transmitted by the microwave module 16 to the microwave antenna 113 through the PID algorithm, so as to obtain the resonance frequency corresponding to the magnetic field to be measured, and transmit the resonance frequency to the magnetic field calculation module. The magnetic field calculation module 17 calculates the magnetic field vector according to the resonance frequency. Thus, another way to obtain the resonance frequency is provided, which is applicable to the situation where ODMR measurements need to be carried out multiple times and the magnetic field vectors need to be calculated multiple times. First, the ODMR measurement is carried out by the microwave frequency sweeping method, and the resonance frequency is obtained from the ODMR spectrum line. Then, the ODMR measurement is carried out by the PID tracking method. Specifically, the resonance frequency obtained for the first time is used as the initial microwave frequency for PID regulation, and the frequency of the modulated microwave transmitted by the microwave module 16 to the microwave antenna 113 is adjusted through the PID algorithm until the obtained demodulation data is equal to the target value. The microwave frequency corresponding to this demodulation data is used as the resonance frequency corresponding to the current magnetic field and transmitted to the magnetic field calculation module 17 for magnetic field vector calculation. In this way, the PID tracking module 19 controls the microwave module 16 to perform the first microwave frequency sweep, specifically by transmitting a frequency signal to the microwave source 161.

[0034] Since in the demodulation curve drawn by the demodulation data, the resonance frequency is located at the zero crossing point, in the PID tracking, the target value is set to zero or a near-zero value.

[0035] For the initial frequency of each PID regulation, at the initial stage of measurement, it is the resonance frequency determined by using the microwave frequency scanning method to carry out the ODMR measurement, and subsequently it is the resonance frequency obtained by the previous PID tracking method to carry out the ODMR measurement.

[0036] The parameter values in the PID algorithm are determined through experimental analysis, specifically according to the relationship between the demodulation data near the zero crossing point and the corresponding frequency change. This is a common algorithm in this field and will not be elaborated here.

[0037] Embodiment 4: This embodiment provides a device for measuring the absolute magnetic field, including: the calibration device for the bias magnetic field in Embodiment 1 or Embodiment 2 or Embodiment 3. The magnetometer is also used to carry out ODMR measurement in the environment to be measured, and its data processing module is also used to calculate the total magnetic field vector of the environment to be measured output by the magnetometer , and the formula to calculate the absolute magnetic field vector of the environment to be measured .

[0038] Since the bias magnetic field can be set as a quantitative value, after calibrating the bias magnetic field vector in one measurement, when measuring the magnetic field in the environment each time subsequently, first measure the total magnetic field in the environment , and then directly use the formula The absolute magnetic field vector to be measured can be obtained through calculation. , and this method is convenient and fast. The total magnetic field here can also be that at the initial position . Since during calibration , at least the probe part of the magnetometer is placed on the rotating table. If after calibration , when measuring other magnetic fields, it can be placed in the environment to be measured together with the rotating table, or the part placed on the rotating table can be removed and placed in the environment to be measured together with other parts of the magnetometer. At this time, it is still necessary to keep the excitation light, bias magnetic field, microwave radiation applied to the diamond unchanged and the fluorescence detection method unchanged.

[0039] For the magnetic field in the environment to be measured that changes continuously and needs to be measured multiple times, it is still possible to choose to implement ODMR measurement using the frequency scanning method or choose to implement ODMR measurement using the PID frequency tracking method.

[0040] The absolute magnetic field measurement device of this embodiment, on the one hand, is based on the precise magnetic measurement technology of diamond NV color centers to achieve the measurement of the absolute magnetic field, with high precision; on the other hand, it is applicable to the measurement of the absolute magnetic field with changing directions, and the probe containing the diamond and the bias magnet can rotate freely in the magnetic field to be measured. For the same magnetic field, the scalar of the measured absolute magnetic field will not change due to the rotation of the probe. Compared with the existing measurement of the magnetic field change amount, it reduces the introduction of errors, is more conducive to accurately describing the magnetic field magnitude, has high stability and reliability, and can be used in various complex electromagnetic environments.

[0041] Embodiment 5: This embodiment provides a method for calibrating a bias magnetic field, including: Regulate the bias magnetic field applied to the diamond containing NV color centers so that four pairs of resonance peaks appear in the ODMR spectrum obtained by performing ODMR measurement on the diamond, and calculate the magnetic field vector at this initial position according to the resonance frequencies corresponding to the four pairs of resonance peaks ; Using the xyz coordinate system established by the three crystal axes of the diamond, while keeping the excitation light, bias magnetic field, microwave radiation applied to the diamond unchanged and the fluorescence detection method unchanged, rotate the diamond by 180 degrees around the x, y, and z axes of the coordinate system respectively from the initial position, and perform ODMR measurement after each rotation to obtain the resonance frequencies, and calculate the magnetic field vectors , , ; Calculate the bias magnetic field vector from the formula .

[0042] The principle of obtaining the calculation formula of the bias magnetic field vector by rotating the diamond in this embodiment can be referred to the explanation in Embodiment 1, which will not be elaborated here.

[0043] During rotation, to keep the excitation light, bias magnetic field, microwave radiation applied to the diamond unchanged and the fluorescence detection method unchanged, the calibration devices in Embodiments 1 to 3 can be used for implementation. In the case of using optical fibers, due to the flexibility of the optical fibers, the optical fibers can be set long enough so that the influence on the irradiation of the excitation light and the collection of fluorescence can be ignored; other devices that can achieve this method can also be used.

[0044] The calibration method of this embodiment is simple and easy to operate, and the calculation of the magnetic field is based on the micro / nanoscale spatial resolution and ultra-high sensitivity of the order of picotesla of the diamond NV color center, with high accuracy.

[0045] Embodiment 6: This embodiment provides a method for measuring an absolute magnetic field, including: calculating from the calibration method of the bias magnetic field in Embodiment 5 , measuring the total magnetic field vector in the environment to be measured by ODMR , and then according to calculating to obtain the absolute magnetic field vector of the environment to be measured .

[0046] After calibrating the bias magnetic field vector in this embodiment, in the subsequent measurement, under the condition that the bias magnetic field remains unchanged, there is no need to calibrate again. First, measure the total magnetic field in the environment , and then directly use the formula , and the absolute magnetic field vector to be measured can be calculated . The measurement method of this embodiment can be implemented by the measurement device in Embodiment 4, which will not be elaborated here, and other devices that can implement the corresponding method can also be used.

[0047] The above embodiments only illustratively explain the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A calibration device for a bias magnetic field, characterized in that The device includes: A magnetometer for performing ODMR measurement, outputting magnetic field vector data, and causing four pairs of resonance peaks to appear on the ODMR spectrum obtained from the ODMR measurement; the magnetometer includes at least a probe composed of diamond containing NV centers, a bias magnet, and a microwave antenna; A rotating stage for placing at least the probe part in the magnetometer, and after placement, aligning the xyz coordinate axes established by the three crystal axes of the diamond with the x'y'z' rotation coordinate axes of the rotating stage one by one; A control module for controlling the rotating stage to rotate 180 degrees around the x, y, and z axes respectively from the initial position; the magnetometer is also used to perform ODMR measurement at the initial position and after each rotation of the rotating stage; A data processing module, which is used to calculate the bias magnetic field vector according to the magnetic field vectors at the initial position output by the magnetometer and the magnetic field vectors after rotating 180 degrees around the x, y, and z axes respectively from the initial position , , , and the formula , to calculate the bias magnetic field vector .

2. The calibration device for the bias magnetic field according to claim 1, characterized in that: The magnetometer further includes an illumination module, a detection module, an optical separator, an optical fiber, and a microwave module. One end of the optical fiber is connected to the diamond, and the other end is connected to the optical separator. The microwave module is connected to the microwave antenna for transmitting microwaves thereto. The excitation light generated by the illumination module enters the optical fiber through the optical separator, excites the diamond to generate fluorescence, and the fluorescence entering the optical fiber is transmitted to the optical separator and then to the detection module to be collected and detected.

3. The calibration device for the bias magnetic field according to claim 1, wherein: The magnetometer further includes an illumination module, a detection module, an optical fiber, and a microwave module. One end of the optical fiber is connected to the diamond, and the other end is connected to the illumination module. The detection module is located on one side of the diamond. The microwave module is connected to the microwave antenna for transmitting microwaves thereto. The excitation light generated by the illumination module enters the optical fiber, excites the diamond to generate fluorescence, and is collected and detected by the detection module. The detection module and the probe are placed on the rotating stage together.

4. The calibration device for the bias magnetic field according to claim 1, characterized in that: The magnetometer further includes an illumination module, a detection module, and a microwave module; the illumination module and the detection module are located on different sides of the diamond and are both placed on the rotating stage together with the probe. The microwave module is connected to the microwave antenna for transmitting microwaves thereto. The excitation light generated by the illumination module irradiates the diamond, excites the diamond to generate fluorescence, and is collected and detected by the detection module.

5. The calibration device for the bias magnetic field according to any one of claims 2-4, characterized in that: The magnetometer further includes a frequency control module and a magnetic field calculation module. The frequency control module is connected to the microwave module for transmitting a frequency signal thereto to control the frequency of the microwave transmitted by the microwave module to the microwave antenna. The magnetic field calculation module is connected to the detection module for obtaining the resonance frequency according to the fluorescence electrical signal output by the detection module and its corresponding microwave frequency, and calculating the magnetic field vector according to the resonance frequency.

6. The calibration device for the bias magnetic field according to any one of claims 2-4, characterized in that: The magnetometer further includes a modulation and demodulation module and a magnetic field calculation module connected in sequence. The modulation and demodulation module is also connected to the microwave module and the detection module for transmitting a frequency signal, a modulation signal to the microwave module and demodulating the fluorescence electrical signal output by the detection module, and transmitting the demodulated data to the magnetic field calculation module. The magnetic field calculation module obtains the resonance frequency according to the demodulated data and its corresponding microwave frequency, and calculates the magnetic field vector according to the resonance frequency.

7. The calibration device for the bias magnetic field according to any one of claims 2-4, characterized in that: The magnetometer further includes a modulation and demodulation module, a PID tracking module, and a magnetic field calculation module that are connected in sequence. The modulation and demodulation module is also connected to a microwave module and a detection module, and is used to transmit a modulation signal to the microwave module, demodulate the fluorescence electrical signal output by the detection module, and transmit the demodulated data to the PID tracking module. The PID tracking module is also connected to the microwave module and is used to regulate the frequency of the modulated microwave transmitted by the microwave module to the microwave antenna through a PID algorithm to obtain a resonance frequency corresponding to the magnetic field to be measured, and transmit the resonance frequency to the magnetic field calculation module. The magnetic field calculation module calculates the magnetic field vector based on the resonance frequency.

8. A measuring device for absolute magnetic field, characterized in that, The measurement device includes: a calibration device for the bias magnetic field as described in any one of claims 1-7. The magnetometer is further configured to perform ODMR measurement in the environment to be measured, and its data processing module is further configured to calculate the absolute magnetic field vector of the environment to be measured based on the total magnetic field vector of the environment to be measured output by the magnetometer , and the formula to calculate the absolute magnetic field vector of the environment to be measured .

9. A calibration method for a bias magnetic field, characterized in that, The method includes: Adjust the bias magnetic field applied to the diamond containing NV centers so that four pairs of resonance peaks appear in the ODMR spectrum obtained by performing ODMR measurement on the diamond, and calculate the magnetic field vector at this initial position according to the resonance frequencies corresponding to the four pairs of resonance peaks ; An xyz coordinate system is established using the three crystal axes of a diamond. While keeping the excitation light, bias magnetic field, microwave radiation applied to the diamond unchanged and the fluorescence detection method unchanged, the diamond is rotated 180 degrees around the x, y, and z axes of the coordinate system respectively from its initial position, and ODMR measurements are performed after each rotation to obtain the resonance frequencies, and the magnetic field vectors are calculated based on the resonance frequencies , , ; The bias magnetic field vector is calculated from the formula to obtain .

10. A method for measuring an absolute magnetic field, characterized in that, The method includes: calculating from a calibration method of a bias magnetic field as described in claim 9 , measuring the total magnetic field vector in the environment to be measured by ODMR , and then calculating the absolute magnetic field vector in the environment to be measured according to . .

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