CN108717168B - Scalar magnetic field gradient measuring device and method based on light field amplitude modulation - Google Patents
Scalar magnetic field gradient measuring device and method based on light field amplitude modulation Download PDFInfo
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- CN108717168B CN108717168B CN201810417773.8A CN201810417773A CN108717168B CN 108717168 B CN108717168 B CN 108717168B CN 201810417773 A CN201810417773 A CN 201810417773A CN 108717168 B CN108717168 B CN 108717168B
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Abstract
A scalar magnetic field gradient measuring device and method based on light field amplitude modulation enable a processor to enable a laser to output laser through a laser control circuit, the frequency of the laser and atomic transition resonance and amplitude of the laser are changed periodically, the laser emitted by the laser is respectively emitted into a first atomic gas chamber and a second atomic gas chamber through an optical fiber beam splitter, the laser is respectively received by a first detector and a second detector after reacting with atoms, and a voltage signal output by the detectors is sent to the processor. The laser polarizes atoms, the polarization axis precesses around an external magnetic field at the Larmor frequency, the processor changes the modulation frequency of the laser amplitude, when the frequency value is the same as the atom Larmor precession frequency, the laser spectrum emitted from the atom gas chamber has a maximum value, and the magnetic field value is obtained through the Larmor frequency calculation. And measuring the magnetic field at the positions of the first atomic gas cell and the second atomic gas cell, and calculating the difference to obtain the magnetic field gradient value. The magnetic sensitive part of the invention adopts an all-optical structure, thus improving the measurement precision of the magnetic field gradient.
Description
Technical Field
The invention relates to a scalar magnetic field gradient measurement device and method based on light field amplitude modulation, and belongs to the field of magnetic field precision measurement.
Background
The magnetic field is widely present in the space, the magnetic field measurement can be used in the fields of geological exploration, underground pipeline detection, nondestructive testing, geomagnetic navigation, medical diagnosis and the like, the magnetic field comprises information such as magnetic field amplitude, direction, magnetic field gradient and the like, and the precision of the underground pipeline detection, the geomagnetic navigation and the biological magnetic field measurement can be improved by the accurate measurement of the magnetic field gradient.
The traditional scalar magnetic field gradient measurement adopts two independent magnetometer probes, the volume of the traditional magnetometer probe is large, and the length of a baseline of the magnetic gradient measurement is limited. In addition, the conventional magnetometer probe contains electronic components such as a laser, a photoelectric detector and the like, and the inherent magnetism of the electronic components and the magnetic field interference generated by the current in the corresponding circuit can influence the magnetic field gradient measurement precision. The magnetic field gradient measurement method adopts a light field amplitude modulation scheme to measure the magnetic field, can transmit laser by using optical fibers, realizes full-optionalization of a magnetic sensitive part, eliminates magnetic field interference caused by electronic components, and can provide a high-precision and high-stability magnetic field gradient measurement means for scientific research and engineering application.
Disclosure of Invention
The technical problem of the invention is solved: the device and the method for measuring the scalar magnetic field gradient based on the light field amplitude modulation can realize the all-optical design of a magnetic sensitive part and improve the measurement precision of the magnetic field gradient.
The technical scheme adopted by the invention is as follows: a scalar magnetic field gradient measurement apparatus based on light field amplitude modulation, comprising: the device comprises a laser, an optical fiber beam splitter, a first atomic gas chamber, a second atomic gas chamber, a laser control circuit, a first detector, a second detector and a processor; the processor enables the laser to output laser through the laser control circuit, the laser frequency and atomic transition resonance are realized, the laser amplitude is changed periodically, the laser emitted by the laser is respectively emitted into the first atomic gas chamber and the second atomic gas chamber through the optical fiber beam splitter, the laser is respectively received by the first detector and the second detector after reacting with atoms, and a voltage signal output by the detectors is sent to the processor; the processor changes the modulation frequency of the laser amplitude, when the frequency value is the same as the atom Larmor precession frequency, the laser spectrum emitted from the atom gas chamber has a maximum value, and a magnetic field value is obtained through Larmor frequency calculation; and calculating to obtain a magnetic field gradient value by measuring the magnetic fields at the positions of the first atomic gas chamber and the second atomic gas chamber.
The specific process of calculating the magnetic field gradient value is as follows: the magnetic fields at the positions of the first atomic gas chamber and the second atomic gas chamber are subjected to differential calculation, and then are divided by the baseline value L to obtain a magnetic field gradient value; the baseline value is the distance between the center of the first atomic gas cell and the center of the second atomic gas cell.
A scalar magnetic field gradient measurement method based on light field amplitude modulation comprises the following steps:
the method comprises the following steps: adjusting the laser control circuit to enable the laser to output laser with constant power and frequency resonant with atomic intrinsic transition;
step two: determining the Larmor precession frequency w of atoms in a first atom gas cell1；
Step three: determining the Larmor precession frequency w of atoms in a second atom gas cell2；
Step four: calculating the difference value delta w of the atom Larmor precession frequency in the first atom air chamber and the second atom air chamber as w1-w2；
Step five: and calculating to obtain a magnetic field gradient value.
Determining Larmor precession frequency w of atoms in the first atom gas chamber1The specific process comprises the following steps:
11) measuring laser emitted from the first atomic gas chamber by using a first detector, converting light intensity into a voltage value, and sending the voltage value to a processor;
12) the processor changes the modulation frequency of the laser amplitude;
13) determining the modulation frequency corresponding to the maximum value of the laser spectrum emitted from the first atomic gas chamber, namely w1。
Step three, determining Larmor precession frequency w of atoms in the second atom gas chamber2The specific process comprises the following steps:
21) measuring laser emitted from the second atomic gas chamber by using a second detector, converting the light intensity into a voltage value, and sending the voltage value to a processor;
22) the processor changes the modulation frequency of the laser amplitude;
23) Determining the modulation frequency corresponding to the maximum value of the laser spectrum emitted from the second atomic gas chamber, namely w2。
The step five magnetic field gradient value delta B ═ delta w/(r × L) ═ w1-w2) And (r × L), wherein r is the gyromagnetic ratio of atoms, and L is a baseline value.
Compared with the prior art, the method has the advantages that:
(1) the invention adopts the same laser to provide excitation light sources for the two probes, can eliminate common-mode noise through differential calculation, and improves the measurement precision of the magnetic gradiometer.
(2) The traditional magnetometer probe contains electronic components such as a laser, a photoelectric detector and the like, and the invention adopts a light field amplitude modulation scheme to realize magnetic field measurement, thereby avoiding the inherent magnetism of the electronic components and the magnetic field interference generated by the current in the corresponding circuit when the electronic components work.
(3) The magnetometer probe used in the traditional scalar magnetic field gradient measurement has a large volume, and the baseline value of the magnetic gradient measurement is limited. The magnetic sensitive part of the invention is designed in full optics, structures such as an exciting coil and the like are not needed, the probe has small volume, the adjustable range of the baseline value of magnetic gradient measurement is increased, and the use requirement under the condition of small space can be met.
Drawings
FIG. 1 is a block diagram of a scalar magnetic field gradient measurement device based on light field amplitude modulation according to the present invention;
FIG. 2 is a flow chart of a scalar magnetic field gradient measurement method based on light field amplitude modulation according to the present invention.
Detailed Description
As shown in fig. 1, the present invention provides a scalar magnetic field gradient measurement apparatus based on optical field amplitude modulation, including: the device comprises a laser, an optical fiber beam splitter, a first atom air chamber, a second atom air chamber, a laser control circuit, a first detector, a second detector and a processor.
The processor makes the laser output laser with frequency and atomic transition resonance and amplitude period variation through the laser control circuit, and the laser emitted by the laser is respectively incident to the first source through the optical fiber beam splitterA sub-cell and a second atomic cell. In a specific embodiment, the first atomic gas cell and the second atomic gas cell are filled with gas87Rb atom, VCSEL laser output by optical fiber as light source with laser wavelength of 795nm, and87the D1 line resonance of Rb atoms was set at a frequency range of 35kHz to 500kHz with amplitude modulation to cause the laser output power to vary periodically between a maximum value of 120uW and a minimum value of 0 uW. The fiber splitter used was a fiber coupler model PN780R5a1 from Thorlabs with a splitting ratio of 50: 50.
After the laser and the atoms act, the laser and the atoms are respectively received by the first detector and the second detector, and voltage signals output by the detectors are sent to the processor. The laser polarizes atoms, the polarization axis precesses around an external magnetic field at the Larmor frequency, the processor changes the modulation frequency of the laser amplitude, when the frequency value is the same as the atom Larmor precession frequency, the laser spectrum emitted from the atom gas chamber has a maximum value, and the magnetic field value is obtained through the Larmor frequency calculation. The magnetic field gradient value can be obtained by measuring the magnetic fields at the first atomic gas cell and the second atomic gas cell, performing differential calculation, and dividing the difference by a baseline value (the distance between the center of the first atomic gas cell and the center of the second atomic gas cell) L. In a specific embodiment, the value range of L is 10 cm-1 m.
As shown in fig. 2, based on the above device, the present invention further provides a scalar magnetic field gradient measurement method based on optical field amplitude modulation, which includes the following steps:
the method comprises the following steps: adjusting the laser control circuit to enable the laser to output laser with constant power and frequency resonant with atomic intrinsic transition;
step two: determining the Larmor precession frequency w of atoms in a first atom gas cell1
(1) Measuring laser emitted from the first atomic gas chamber by using a first detector, converting light intensity into a voltage value, and sending the voltage value to a processor;
(2) the processor changes the modulation frequency of the laser amplitude;
(3) determining the modulation frequency corresponding to the maximum value of the laser spectrum emitted from the first atomic gas chamber, namely w1；
Step (ii) ofThirdly, the method comprises the following steps: determining the Larmor precession frequency w of atoms in a second atom gas cell2
(1) Measuring laser emitted from the second atomic gas chamber by using a second detector, converting the light intensity into a voltage value, and sending the voltage value to a processor;
(2) the processor changes the modulation frequency of the laser amplitude;
(3) determining the modulation frequency corresponding to the maximum value of the laser spectrum emitted from the second atomic gas chamber, namely w2；
Step four: calculating the difference value delta w of the atom Larmor precession frequency in the first atom air chamber and the second atom air chamber as w1-w2；
Step five: calculating to obtain the magnetic field gradient value delta B ═ delta w/(r multiplied by L) ═ w1-w2) And (r × L), wherein r is the gyromagnetic ratio of atoms, and L is a baseline value.
The above-described embodiments are merely preferred embodiments of the present invention, and general changes and substitutions by those skilled in the art within the technical scope of the present invention are included in the protection scope of the present invention.
The present invention has not been described in detail as is known to those skilled in the art.
Claims (5)
1. A scalar magnetic field gradient measurement apparatus based on light field amplitude modulation, characterized by comprising: the device comprises a laser, an optical fiber beam splitter, a first atomic gas chamber, a second atomic gas chamber, a laser control circuit, a first detector, a second detector and a processor; the processor enables the laser to output laser through the laser control circuit, the laser frequency and atomic transition resonance are realized, the laser amplitude is changed periodically, the laser emitted by the laser is respectively emitted into the first atomic gas chamber and the second atomic gas chamber through the optical fiber beam splitter, the laser is respectively received by the first detector and the second detector after reacting with atoms, and a voltage signal output by the detectors is sent to the processor; the processor changes the modulation frequency of the laser amplitude, when the frequency value is the same as the atom Larmor precession frequency, the laser spectrum emitted from the atom gas chamber has a maximum value, and a magnetic field value is obtained through Larmor frequency calculation; calculating to obtain a magnetic field gradient value by measuring magnetic fields at the positions of the first atomic gas chamber and the second atomic gas chamber;
the first atomic gas cell and the second atomic gas cell are filled with gas87Rb atom, VCSEL laser output by optical fiber as light source with laser wavelength of 795nm, and87d1 line resonance of Rb atoms, setting the frequency range of amplitude modulation to be 35 kHz-500 kHz, and enabling the output light power of the laser to periodically change between a maximum value of 120uW and a minimum value of 0 uW; the optical fiber beam splitter adopts a PN780R5A1 type optical fiber coupler of Thorlabs company, and the splitting ratio is 50: 50.
2. A scalar magnetic field gradient measurement apparatus based on light field amplitude modulation according to claim 1, characterized in that: the specific process of calculating the magnetic field gradient value is as follows: the magnetic fields at the positions of the first atomic gas chamber and the second atomic gas chamber are subjected to differential calculation, and then are divided by the baseline value L to obtain a magnetic field gradient value; the baseline value is the distance between the center of the first atomic gas cell and the center of the second atomic gas cell.
3. A scalar magnetic field gradient measurement method based on light field amplitude modulation is characterized by comprising the following steps:
the method comprises the following steps: adjusting the laser control circuit to enable the laser to output laser with constant power and frequency resonant with atomic intrinsic transition;
step two: determining the Larmor precession frequency w of atoms in a first atom gas cell1；
Step three: determining the Larmor precession frequency w of atoms in a second atom gas cell2；
Step four: calculating the difference value delta w of the atom Larmor precession frequency in the first atom air chamber and the second atom air chamber as w1-w2；
Step five: calculating to obtain a magnetic field gradient value;
determining Larmor precession frequency w of atoms in the first atom gas chamber1The specific process comprises the following steps:
11) measuring laser emitted from the first atomic gas chamber by using a first detector, converting light intensity into a voltage value, and sending the voltage value to a processor;
12) the processor changes the modulation frequency of the laser amplitude;
13) determining the modulation frequency corresponding to the maximum value of the laser spectrum emitted from the first atomic gas chamber, namely w1。
4. A scalar magnetic field gradient measurement method based on light field amplitude modulation according to claim 3, characterized in that: step three, determining Larmor precession frequency w of atoms in the second atom gas chamber2The specific process comprises the following steps:
21) measuring laser emitted from the second atomic gas chamber by using a second detector, converting the light intensity into a voltage value, and sending the voltage value to a processor;
22) the processor changes the modulation frequency of the laser amplitude;
23) determining the modulation frequency corresponding to the maximum value of the laser spectrum emitted from the second atomic gas chamber, namely w2。
5. A scalar magnetic field gradient measurement method based on light field amplitude modulation according to claim 3, characterized in that: the step five magnetic field gradient value delta B ═ delta w/(r × L) ═ w1-w2) And (r × L), wherein r is the gyromagnetic ratio of atoms, and L is a baseline value.
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| CN109521376B (en) * | 2018-11-09 | 2023-12-15 | 中国计量科学研究院 | Atomic magnetometer based on miniature atomic air chamber |
| CN111220934A (en) * | 2020-01-14 | 2020-06-02 | 杭州昕磁科技有限公司 | Gradient detection system based on pulse pumping magnetometer |
| CN112014777B (en) * | 2020-09-09 | 2021-10-15 | 中国海洋大学 | Space magnetic gradient tensor measurement system based on optical fiber magnetic field sensor and working method thereof |
| CN112540328B (en) * | 2020-12-30 | 2022-03-25 | 之江实验室 | Probe structure based on double-air-chamber optical pumping alkali metal atomic gradient magnetometer |
| CN113447862A (en) * | 2021-06-30 | 2021-09-28 | 北京量子信息科学研究院 | Magnetic field gradient measuring device |
| CN113447861A (en) * | 2021-06-30 | 2021-09-28 | 北京量子信息科学研究院 | Magnetic field measuring device |
| CN113679389B (en) * | 2021-07-21 | 2022-09-16 | 北京大学 | Biological magnetic signal detection device and detection method based on optical pump atomic magnetic gradiometer |
| CN113671424B (en) * | 2021-07-23 | 2023-11-03 | 南方科技大学 | Magnetic field gradient measurement method and atomic magnetic gradiometer system |
| CN113721171B (en) * | 2021-07-27 | 2024-06-04 | 北京量子信息科学研究院 | Magnetic gradient system and detection method thereof |
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