An optical path control system and method for a SERF atomic magnetometer

Abstract

This invention relates to an optical path control system and method for a SERF atomic magnetometer. The system utilizes photoelectric detection data and visual image data generated by a photoelectric detection module and a visual detection module. A data fusion processing module calculates the optical path deviation and generates control commands, which are then transmitted to a motion controller. The motion controller controls a multi-degree-of-freedom adjustment structure to adjust the beam waist position, pitch angle, yaw angle, parallel offset, and polarization direction of the probe light, achieving intelligent adjustment of the SERF atomic magnetometer's optical path. Furthermore, the photoelectric detection module and the visual detection module simultaneously acquire spatial and intensity information of the probe light, enabling precise location of the deviation source and overcoming the limitation of pure photoelectric detection (a black box method) which cannot invert deviations.

Description

Technical Field

[0001] This invention relates to the field of quantum sensing and optical detection technology, and more specifically, to an optical path control system and method for a SERF atomic magnetometer. Background Technology

[0002] SERF atomic magnetometers are among the most sensitive magnetic sensing technologies currently available, with broad application prospects in fields such as biomagnetic imaging, geophysical exploration, and fundamental physics research. Precise control of its optical path system is a key prerequisite for ensuring the high performance of the SERF atomic magnetometer.

[0003] Currently, the optical path adjustment method of the SERF atomic magnetometer heavily relies on the experience and skills of the operator. Typically, a beam quality analyzer is used to observe the beam spot, and the position and angle of the input beam of the probe collimator are adjusted manually by a translation stage or a rotary stage. This method has the following inherent defects: (1) low efficiency, long initial alignment time, and high requirements for operators; (2) low degree of automation, making it difficult to integrate into automated measurement and control processes, which restricts the practical application and commercial development of the instrument. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to achieve automated and intelligent optical path control of the SERF atomic magnetometer.

[0005] This invention provides an optical path control system for a SERF atomic magnetometer, comprising: A laser source, used to generate laser light; An optical fiber collimator, placed in the optical path of a laser, is used to shape the laser beam to obtain the probe light; The control module includes a motion controller and a multi-degree-of-freedom electric adjustment mechanism connected to drive it. The fiber optic collimator is located at the execution end of the multi-degree-of-freedom electric adjustment mechanism. The multi-degree-of-freedom electric adjustment mechanism is used to adjust the spatial pose of the fiber optic collimator to adjust the beam waist position, pitch angle, yaw angle, parallel offset, and polarization direction of the probe light. The probe module includes a beam splitter prism and an atomic gas cell. The beam splitter prism is placed in the optical path of the probe light to split the probe light into transmitted light and reflected light. The reflected light enters the atomic gas cell for magnetic signal detection. The photoelectric detection module is located in the optical path of the transmitted light and is used to collect light intensity parameters and generate photoelectric detection data. The visual inspection module is used to acquire a first spot image on the optical path of the output probe light of the fiber collimator, and to acquire a second spot image on the optical path after the reflected light enters the atomic gas cell, thereby generating visual image data. The data fusion processing module is communicatively connected to the visual inspection module, the photoelectric inspection module, and the motion controller. It is used to receive visual image data and photoelectric inspection data, calculate optical path deviation, and generate control commands to be transmitted to the motion controller.

[0006] Compared with existing technologies, the system of this application has the following advantages: the photoelectric detection data and visual image data generated by the photoelectric detection module and the visual detection module are used to calculate the optical path deviation through the data fusion processing module and generate control commands which are transmitted to the motion controller. The motion controller controls the multi-degree-of-freedom adjustment structure to adjust the beam waist position, pitch angle, yaw angle, parallel offset and polarization direction of the probe light respectively, so as to realize the intelligent adjustment of the optical path of the SERF atomic magnetometer. In addition, the photoelectric detection module and the visual detection module simultaneously acquire the spatial information (spot position, attitude) and light intensity information of the probe light, which can accurately locate the source of deviation (such as angle tilt, parallel offset, polarization mismatch), overcoming the defect of pure photoelectric detection black box that cannot invert deviation.

[0007] In one possible implementation, the multi-degree-of-freedom electric adjustment mechanism includes a base stacked in series from bottom to top, and a three-dimensional electric translation stage, an electric rotary stage, a two-dimensional electric swing stage, and a two-dimensional electric translation stage that are communicatively connected to a motion controller. A spatial rectangular coordinate system is established with the length direction of the base as the Z-axis, the width direction as the X-axis, and the thickness direction as the Y-axis; The base of the three-dimensional electric translation stage is fixed on the base, and the moving platform of the three-dimensional electric translation stage is fixed to the base of the electric rotary stage, which is used to drive the electric rotary stage to move along the X-axis, Y-axis and Z-axis to adjust the beam waist position of the probe light. The moving platform of the electric rotary table is fixed to the base of the two-dimensional electric swing table, and is used to drive the two-dimensional electric swing table to rotate around the Z-axis to adjust the polarization direction of the probe light. The moving platform of the two-dimensional electric swing stage is fixed to the base of the two-dimensional electric translation stage, and is used to drive the two-dimensional electric translation stage to swing around the X-axis to adjust the pitch angle and swing around the Y-axis to adjust the yaw angle. The fiber collimator is mounted on the moving platform of the two-dimensional electric translation stage and is used to drive the fiber collimator to move along the X-axis and Y-axis to adjust the parallel offset of the probe light. The displacement resolution of the two-dimensional electric translation stage along the X and Y axes is higher than that of the three-axis electric translation stage along the X and Y axes.

[0008] Compared with existing technologies, the multi-degree-of-freedom pose adjustment of the fiber optic collimator is achieved by using a three-dimensional electric translation stage, an electric rotary stage, a two-dimensional electric swing stage, and a two-dimensional electric translation stage stacked in series. Furthermore, the displacement resolution of the two-dimensional electric translation stage along the X and Y axes is higher than that of the three-axis electric translation stage. This allows the three-dimensional electric translation stage to handle the large-stroke coarse adjustment of the fiber optic collimator, while the two-dimensional electric translation stage handles the small-stroke fine adjustment, thus achieving both fast search and high-precision alignment.

[0009] In one possible implementation, the visual detection module includes a first camera, a second camera, and an image processing unit. The first camera is positioned on the optical path of the output probe light of the fiber optic collimator to acquire a first spot image. The second camera is positioned on the optical path after the reflected light enters the atomic gas cell to acquire a second spot image. The first camera and the second camera are respectively communicatively connected to the image processing unit.

[0010] Compared with existing technologies, the first camera monitors the quality and direction of the collimator output beam, and the second camera monitors the position of the light spot entering the air chamber, realizing dual visual feedback at both the front and rear ends; the pointing angle deviation can be determined by the first light spot image, and the parallel offset can be determined by the second light spot image, which facilitates step-by-step correction.

[0011] In one possible implementation, the beam splitting prism includes a polarizer, a polarizing beam splitter, and a quarter-wave plate. The polarizer and the polarizing beam splitter are arranged sequentially along the incident light path of the probe light, and the quarter-wave plate is arranged on the light path of the reflected light emitted from the polarizing beam splitter.

[0012] Compared with existing technologies, the polarizer and polarizing beam splitter achieve polarization beam splitting, and the quarter-wave plate converts the reflected light into circularly polarized light to meet the atomic polarization requirements; the change in light intensity in the transmitted light path can directly reflect the polarization alignment state, providing a pure feedback signal for photoelectric detection.

[0013] A method for optical path control of a SERF atomic magnetometer, applied to any of the optical path control systems described above, includes the following steps: S1, the optical path control system is activated, and the first camera acquires the first spot image of the probe light; the image processing unit extracts the center coordinates of the spot and compares them with the center coordinates of the target surface of the first camera. If the deviation between the center coordinates of the spot and the center coordinates of the target surface exceeds the preset deviation threshold, then proceed to S2; otherwise, proceed to S3. S2, drive the three-dimensional electric translation stage to move the fiber collimator along the Z-axis by a preset distance. The first camera acquires the first spot image before and after the movement. The center coordinates of the spot in the two first spot images are extracted using the sub-pixel positioning method. After calculating the offset of the spot center on the x-axis and y-axis, the pitch angle and yaw angle of the probe light are calculated according to the mapping relationship. It is determined whether the pitch angle and yaw angle are both less than the preset threshold. If so, go to S3. Otherwise, the motion controller drives the two-dimensional electric swing stage to rotate in the opposite direction around the X-axis by the same pitch angle and around the Y-axis by the same yaw angle, and then returns to S2. S3 drives the electric rotary table to rotate the fiber optic collimator continuously around the Z-axis, synchronously acquiring the light intensity signal output by the photoelectric detection module; it then takes the rotation angle corresponding to the maximum value of the light intensity signal and locks it. S4, with the geometric center of the atomic gas chamber as the reference center, based on the X-axis offset and Y-axis offset of the spot center of the second spot image acquired by the second camera relative to the reference center; the motion controller drives the two-dimensional electric translation stage to move in the opposite direction on the X-axis by the X-axis offset distance, and in the opposite direction on the Y-axis by the Y-axis offset distance.

[0014] Compared with existing technologies, the method of this application has the following advantages: by moving a preset distance to measure the offset of the dual light spots, the pitch and yaw angles are accurately calculated using the arctangent formula, and the two-dimensional oscillating stage is driven by the reverse angle to achieve iterative convergence and realize the accurate correction of the pointing angle of the probe light; the electric rotary stage rotation scanning combined with light intensity feedback automatically locks the angle corresponding to the maximum light intensity, avoiding the inefficiency and error of manually rotating the polarization element; after the pointing angle correction is completed, the two-dimensional translation stage is moved to align the light spot with the center of the atomic gas cell, solving the problem that traditional methods cannot separate angular deviation and translation deviation. The method of this application is fully automated from deviation detection to correction execution, without manual intervention, and significantly shortens the optical path preparation time.

[0015] In one possible implementation, the sub-pixel positioning algorithm is any one of the gray-scale centroid method, Gaussian fitting method, and ellipse fitting method.

[0016] Compared with existing technologies, using grayscale centroid method, Gaussian fitting method or ellipse fitting method can improve the spot center positioning accuracy to the sub-pixel level (below 0.1 pixels), thereby ensuring the accuracy of ΔX and ΔY calculations and indirectly improving the angle inversion accuracy.

[0017] In one possible implementation, the mapping relationship in step S2 includes: ; ; In the formula, Indicates pitch angle, Indicates the yaw angle. Indicates the preset distance.

[0018] In one possible implementation, step S3 specifically includes: The electric rotary table is driven by a first angular velocity to drive the fiber collimator to rotate continuously around the Z-axis 360°. The correspondence between the light intensity signal and the rotation angle is recorded in real time to determine the first angle corresponding to the maximum light intensity. Then, the optical fiber collimator is rotated back and forth within the range of ±5° of the first angle by a second angular velocity. The second angle corresponding to the maximum light intensity is determined as the rotation angle and locked. The second angular velocity is less than the first angular velocity.

[0019] Compared with existing technologies, the method first uses a first angular velocity to coarsely scan 360° to find the angle corresponding to the maximum light intensity, and then uses a smaller second angular velocity to finely scan within ±5°. The coarse scan quickly locates the approximate area, and the fine scan avoids misjudgment of local extreme values. The overall scanning time is short and the alignment accuracy is high.

[0020] In one possible implementation, after step S4 is completed, a verification step is also included: the second spot image is acquired again to verify whether the deviation between the center of the spot and the geometric center of the atomic gas chamber is less than a preset acceptance threshold. If not, step S4 is repeated.

[0021] Compared with existing technologies, after S4 is completed, a second spot image is acquired again to verify the alignment quality. If it does not meet the requirements, the compensation is repeated to form a final closed loop, ensuring long-term stability and reliability and avoiding performance degradation caused by a single improper adjustment.

[0022] In one possible implementation, the preset distance ranges from 1 mm to 10 mm; The preset threshold in step S2 ranges from 0.01° to 0.1°. In step S1, the preset deviation threshold is 5% to 10% of the spot diameter. Attached Figure Description

[0023] Figure 1 This is a system block diagram of Embodiment 1 of this application; Figure 2 This is a schematic diagram of the structure of the multi-degree-of-freedom electric adjustment mechanism in Embodiment 1 of this application; Figure 3 This describes the process of adjusting the polarization angle of the probe beam in Embodiment 2 of this application; Figure 4 This is an image showing the deviation between the center of the second spot and the reference center in Embodiment 2 of this application.

[0024] Explanation of reference numerals in the attached figures: 1. Laser source; 2. Fiber optic collimator; 3. Motion controller; 4. Multi-degree-of-freedom electric adjustment mechanism; 4.1. Three-dimensional electric translation stage; 4.2. Electric rotary stage; 4.3. Two-dimensional electric swing stage; 4.4. Two-dimensional electric translation stage; 4.5. Base; 5. Probe module; 6. Beam splitting prism; 7. Atomic gas chamber; 8. Photoelectric detection module; 9. Visual inspection module; 9.1. First camera; 9.2. Second camera; 9.3. Image processing unit; 10. Data fusion processing module; 10.1. Embedded control unit; 10.2. Industrial computer. Detailed Implementation

[0025] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0026] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0027] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0028] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] Example 1: See Figure 1 As shown in the figure, this application discloses an optical path control system for a SERF atomic magnetometer, including a laser source 1, an optical fiber collimator 2, a control module, a probe module 5, a photoelectric detection module 8, a visual detection module 9, and a data fusion processing module 10; The fiber collimator 2 is located in the optical path of the laser. The laser emitted by the laser source 1 is shaped by the fiber collimator 2 to form a collimated probe light. The fiber collimator 2 is installed on the control module, and its output end face faces the probe module 5.

[0030] The control module includes a motion controller 3 and a multi-degree-of-freedom electric adjustment mechanism 4 connected to drive it. The fiber optic collimator 2 is located at the execution end of the multi-degree-of-freedom electric adjustment mechanism 4. The multi-degree-of-freedom electric adjustment mechanism 4 is used to adjust the spatial pose of the fiber optic collimator 2 to adjust the beam waist position, pitch angle, yaw angle, parallel offset, and polarization direction of the probe light; specifically: The multi-degree-of-freedom electric adjustment mechanism 4 includes a base stacked in series from bottom to top, and a three-dimensional electric translation stage 4.1, an electric rotary stage 4.2, a two-dimensional electric swing stage 4.3, and a two-dimensional electric translation stage 4.4 that are communicatively connected to the motion controller (3). A spatial rectangular coordinate system is established with the length direction of the base 4.5 as the Z-axis, the width direction as the X-axis, and the thickness direction as the Y-axis; like Figure 2 As shown, the base of the three-dimensional electric translation stage 4.1 is fixed on the base 4.5. The moving platform of the three-dimensional electric translation stage 4.1 moves along the X-axis, Y-axis, and Z-axis. The moving platform of the three-dimensional electric translation stage 4.1 is fixed to the base of the electric rotary stage 4.2 and is used to drive the electric rotary stage 4.2 to move along the X-axis, Y-axis, and Z-axis to adjust the beam waist position of the probe light. In this embodiment, the three-axis electric translation stage is composed of three single-axis electric translation stages stacked in series in the order of X-axis → Y-axis → Z-axis or other orders. Each single-axis translation stage includes a base, a drive motor, a ball screw, a ball nut, a linear guide rail, and a slider. The output shaft of the drive motor is connected to the ball screw through a coupling. A ball nut is fitted on the ball screw, and the ball nut is fixedly connected to the slider. The slider can slide along the linear guide rail. When the motion controller 3 receives the command, the drive motor rotates, driving the ball screw to rotate. The ball screw converts the rotational motion into linear motion through the balls, pushing the slider to move along the linear guide rail. Each axis moves independently, and when the three axes are linked, point control at any position in space can be achieved; the travel range of the X, Y, and Z axes is ±20mm to ±100mm, the displacement resolution is 1μm, and the repeatability is ±1μm to ±5μm.

[0031] The moving platform of the electric rotary table 4.2 is fixed to the base of the two-dimensional electric swing table 4.3, and is used to drive the two-dimensional electric swing table 4.3 to rotate around the Z-axis to adjust the polarization direction of the probe light. The electric rotary table 4.2 in this embodiment is an electric actuator capable of driving a load to perform circular rotation or reciprocating swing motion around a rotation axis (Z-axis). The electric rotary table 4.2 includes a base, a rotating platform, a drive motor, and a transmission mechanism. The transmission mechanism uses a worm gear pair with crossed roller bearings, utilizing the large transmission ratio of the worm gear to obtain a large driving torque and has a self-locking function. A high-resolution angle encoder is installed on the electric rotary platform for real-time measurement and feedback of the rotation angle. After the motion controller 3 issues an angle command, the drive motor rotates, driving the rotary platform to rotate around the Z-axis via worm gear deceleration or direct drive. The angle encoder provides real-time feedback of the angle position, forming a closed-loop control. The electric rotary table 4.2 can typically rotate continuously for 360°. In addition, since the fiber collimator 2 rotates together with the electric rotary stage 4.2, the polarization direction of its output beam changes accordingly; by collecting the transmitted light intensity through the photoelectric detection module 8, the polarization angle corresponding to the maximum light intensity can be found in a closed loop.

[0032] The moving platform of the two-dimensional electric swing stage 4.3 is fixed to the base of the two-dimensional electric translation stage 4.4, and is used to drive the two-dimensional electric translation stage 4.4 to swing around the X-axis to adjust the pitch angle and around the Y-axis to adjust the yaw angle. In this embodiment, the two-dimensional electric swing stage 4.3 is an electric actuator used to drive a load to swing at a small angle around two orthogonal axes (X-axis and Y-axis). It is composed of two single-axis swing stages orthogonally connected in series, or uses an integrated two-axis linkage structure. Each single-axis swing stage includes a base, a swing platform, a drive motor, a worm gear transmission mechanism, and a guide mechanism. The worm gear mechanism converts the rotational motion of the motor into the pitch or yaw swing of the swing stage, and the arc-shaped guide rail ensures the smoothness and rigidity of the swing process. After the motion controller 3 issues an angle command, the drive motor drives the worm to rotate. The worm gear is fixedly connected to the swing platform, and when the worm rotates, it drives the swing platform to swing at a small angle around the swing axis. The two-dimensional electric swing stage 4.3 can independently realize swinging around the X-axis (adjusting the pitch angle) and swinging around the Y-axis (adjusting the yaw angle). Due to the limitations of the oscillating physical structure, the oscillation range is typically ±5° to ±45°.

[0033] The fiber optic collimator 2 is mounted on the moving platform of the two-dimensional electric translation stage 4.4, and is used to drive the fiber optic collimator 2 to move along the X-axis and Y-axis to adjust the parallel offset of the probe light. In this embodiment, the two-dimensional electric translation stage 4.4 is composed of an X-axis translation stage and a Y-axis translation stage arranged in an orthogonal stack, and can be designed as an integral structure to improve orthogonality. Compared with a three-axis electric translation stage, the two-dimensional electric translation stage 4.4 has a smaller stroke and higher precision. Its basic components include a base, an X-axis linear motion module, and a Y-axis linear motion module. Each linear motion module includes a drive motor (stepper motor or linear motor), a ball screw or linear motor drive mechanism, a high-precision linear guide (cross roller guide or linear slider guide), and a grating ruler that can be added as a closed-loop feedback element. A light-transmitting hole is usually provided in the center to facilitate the passage of light. The displacement resolution of the two-dimensional electric translation stage 4.4 along the X-axis and Y-axis is higher than that of the three-axis electric translation stage. Each translation stage has a travel range of ±2mm to ±200mm, a displacement resolution of 0.1μm to 1μm, and a repeatability of ±0.2μm to ±2μm.

[0034] In addition, in this embodiment, the three-dimensional electric translation stage 4.1, the electric rotary stage 4.2, the two-dimensional electric swing stage 4.3, and the two-dimensional electric translation stage 4.4 are all equipped with high-precision position sensors, which feed back position / angle information to the motion controller 3 in real time.

[0035] The probe module 5 includes a beam splitter prism 6 and an atomic gas cell 7, as well as a probe clamp and a probe base (not shown in the figure). The beam splitter prism 6 and the atomic gas cell 7 are both fixedly mounted on the probe base. The beam splitter prism 6 is located on the optical path of the probe light output from the fiber collimator 2. The beam splitter prism 6 includes a polarizer, a polarizing beam splitter prism, and a quarter-wave plate. The polarizer and the polarizing beam splitter prism are arranged sequentially along the incident optical path of the probe light. The quarter-wave plate is located on the optical path of the reflected light emitted from the polarizing beam splitter prism. After the probe light output from the fiber collimator 2 is incident on the beam splitter prism 6, it is split into two paths: transmitted light and reflected light. The reflected light enters the atomic gas cell 7 and is used to interact with atoms to detect magnetic signals. The transmitted light is used to detect the polarization alignment status and power stability of the probe light in real time.

[0036] The photoelectric detection module 8 is located on the optical path of the transmitted light and is used to receive the transmitted light and collect light intensity parameters in real time, generate photoelectric detection data and send it to the data fusion processing module 10.

[0037] The visual detection module 9 is used to acquire a first spot image on the optical path of the probe light output from the fiber optic collimator 2, and to acquire a second spot image on the optical path after the reflected light enters the atomic gas cell 7, thereby generating visual image data. The visual detection module 9 includes a first camera 9.1, a second camera 9.2, and an image processing unit 9.3. The first camera 9.1 is set on the optical path of the probe light output from the fiber optic collimator 2 and is used to acquire the first spot image. The second camera 9.2 is set on the optical path after the reflected light enters the atomic gas cell 7 and is used to acquire the second spot image. The first camera 9.1 and the second camera 9.2 are respectively communicatively connected to the image processing unit 9.3.

[0038] The data fusion processing module 10 is communicatively connected to the vision detection module 9, the photoelectric detection module 8, and the motion controller 3, respectively. It receives visual image data and photoelectric detection data, determines optical path deviation, and generates control commands that are transmitted to the motion controller 3. In this embodiment, the data fusion processing module 10 includes an embedded control unit 10.1 and an industrial computer 10.2. The industrial computer is communicatively connected to the vision detection module 9, the photoelectric detection module 8, and the motion controller 3, respectively. It receives visual image data and photoelectric detection data, executes a fusion algorithm to determine the type and magnitude of optical path deviation, generates control commands, and sends them to the motion controller 3. The embedded control unit is responsible for low-level real-time control and data preprocessing.

[0039] Example 2: like Figure 3-4 The method for controlling the optical path of a SERF atomic magnetometer, as shown, is applied to the optical path control system described in Example 1 and includes the following steps: S1, the optical path control system is activated, and the first camera acquires the first spot image of the probe light; the image processing unit extracts the center coordinates of the spot and compares them with the center coordinates of the target surface of the first camera. If the deviation between the center coordinates of the spot and the center coordinates of the target surface exceeds the preset deviation threshold, then proceed to S2; otherwise, proceed to S3. The preset deviation threshold is 5% to 10% of the spot diameter.

[0040] S2, as Figure 3 As shown, the three-dimensional electric translation stage is driven to move the fiber collimator a preset distance along the Z-axis. The first camera captures images of the first light spot before and after movement. The center coordinates of the light spot in the two images are extracted using a sub-pixel localization method. The offsets of the light spot center along the x and y axes are then calculated. Then, the elevation angle of the probe light is calculated based on the mapping relationship. and yaw angle ,judge and If all values ​​are less than the preset threshold, proceed to step S3; otherwise, the motion controller drives the two-dimensional electric swing table to rotate counterclockwise around the X-axis by the same pitch angle. The angle that is the same as the yaw angle when rotating counterclockwise around the Y-axis is... And return S2; where: The sub-pixel positioning algorithm is any one of the gray-scale centroid method, Gaussian fitting method, and ellipse fitting method. To avoid the offset being insignificant due to too small a movement, or the light spot moving out of the camera's field of view due to too large a movement, a preset distance is used. The value ranges from 1mm to 10mm; To meet the stringent requirements of the SERF magnetometer for beam parallelism without excessively long adjustment time, the preset threshold value ranges from 0.01° to 0.1°. The mapping relationships used include: ; .

[0041] S3 drives the electric rotary table to rotate the fiber optic collimator continuously around the Z-axis, synchronously acquiring the light intensity signal output by the photoelectric detection module; it then takes the rotation angle corresponding to the maximum value of the light intensity signal and locks it. S4, such as Figure 4 As shown, with the geometric center of the atomic gas chamber as the reference center, the offset between the center of the spot and the reference center of the second spot image acquired by the second camera is calculated. , , , This indicates the coordinates of the center of the light spot in the second light spot image. The coordinates of the reference center are indicated; the motion controller drives the two-dimensional electric translation stage to move in the opposite direction along the X-axis by the distance of the X-axis offset. The distance of the Y-axis offset in the opposite direction is... .

[0042] To ensure the reliability of the adjustment, the second spot image is acquired again after step S4 to verify whether the deviation between the spot center and the geometric center of the atomic gas cell is less than the preset acceptance threshold. If not, step S4 is repeated. This avoids performance degradation due to a single incomplete adjustment and ensures long-term stability and reliability.

[0043] The optical path adjustment sequence of this application method is as follows: First, the propagation direction of the probe light output from the fiber collimator needs to be accurately incident on the reflecting surface of the beam splitter prism; when the probe light has an angle with the Z-axis, the fiber collimator is moved along the Z-axis. This will cause a lateral shift in the center of the light spot on a plane perpendicular to the Z-axis. This application calculates the included angle precisely by measuring the displacement and moving distance, and then combines this with a two-dimensional electric oscillating stage to provide high-resolution angle compensation capabilities, making the propagation direction of the probe light parallel to the ideal Z-axis. Next, the polarization direction may not yet be aligned with the transmission axis of the polarizer, so step S3 uses the light intensity parameters collected by the photoelectric detection module for feedback adjustment, so that the polarization direction of the probe light is completely coincident with the transmission axis of the polarizer, and the transmitted light intensity reaches the theoretical maximum value. Then, step S2 has corrected the pointing angle of the beam, but the beam axis may still have an overall translation (i.e., parallel offset) relative to the geometric center of the atomic gas cell. Therefore, step S4 uses the image feedback from the second camera to perform fine-tuning compensation through a two-dimensional electric translation stage.

[0044] Preferably, in step S3, the electric rotary table is first driven by a first angular velocity to drive the fiber collimator to rotate continuously around the Z-axis by 360°, and the correspondence between the light intensity signal and the rotation angle is recorded in real time to determine the first angle corresponding to the maximum light intensity; then, the optical fiber collimator is rotated back and forth within the range of ±5° of the first angle by a second angular velocity to determine the second angle corresponding to the maximum light intensity as the rotation angle and lock it, wherein the second angular velocity is less than the first angular velocity.

[0045] In the description of the embodiments of this application, it should be noted that the terms "inner" and "outer" and other terms indicating direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application.

[0046] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0047] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An optical path control system for a SERF atomic magnetometer, characterized in that, include: A laser source (1) is used to generate laser light; An optical fiber collimator (2) is placed in the optical path of the laser to shape the laser light to obtain the probe light. The control module includes a motion controller (3) and a multi-degree-of-freedom electric adjustment mechanism (4) connected to drive it. The fiber collimator (2) is located at the execution end of the multi-degree-of-freedom electric adjustment mechanism (4). The multi-degree-of-freedom electric adjustment mechanism (4) is used to adjust the spatial pose of the fiber collimator (2) to adjust the beam waist position, pitch angle, yaw angle, parallel offset and polarization direction of the probe light. The probe module (5) includes a beam splitting prism (6) and an atomic gas cell (7). The beam splitting prism (6) is located on the optical path of the probe light and is used to split the probe light into transmitted light and reflected light. The reflected light enters the atomic gas cell (7) for magnetic signal detection. The photoelectric detection module (8) is located on the optical path of the transmitted light and is used to collect light intensity parameters and generate photoelectric detection data. The visual detection module (9) is used to collect a first spot image on the optical path of the output probe light of the fiber collimator (2), and to collect a second spot image on the optical path after the reflected light enters the atomic gas cell (7) to generate visual image data. The data fusion processing module (10) is connected to the visual detection module (9), the photoelectric detection module (8) and the motion controller (3) respectively. It is used to receive visual image data and photoelectric detection data, calculate optical path deviation and generate control commands to transmit to the motion controller (3).

2. The optical path control system of the SERF atomic magnetometer according to claim 1, characterized in that, The multi-degree-of-freedom electric adjustment mechanism (4) includes a base stacked in series from bottom to top, and a three-dimensional electric translation stage (4.1), an electric rotary stage (4.2), a two-dimensional electric swing stage (4.3), and a two-dimensional electric translation stage (4.4) that are communicatively connected to the motion controller (3). A spatial rectangular coordinate system is established with the length direction of the base as the Z-axis, the width direction as the X-axis, and the thickness direction as the Y-axis; The base of the three-dimensional electric translation stage (4.1) is fixed on the base, and the moving platform of the three-dimensional electric translation stage (4.1) is fixed to the base of the electric rotary stage (4.2) for driving the electric rotary stage (4.2) to move along the X-axis, Y-axis and Z-axis to adjust the beam waist position of the probe light. The moving platform of the electric rotary stage (4.2) is fixed to the base of the two-dimensional electric swing stage (4.3) and is used to drive the two-dimensional electric swing stage (4.3) to rotate around the Z-axis to adjust the polarization direction of the probe light. The moving platform of the two-dimensional electric swing stage (4.3) is fixed to the base of the two-dimensional electric translation stage (4.4) and is used to drive the two-dimensional electric translation stage (4.4) to swing around the X-axis to adjust the pitch angle and swing around the Y-axis to adjust the yaw angle. The fiber collimator (2) is set on the moving platform of the two-dimensional electric translation stage (4.4) to drive the fiber collimator (2) to move along the X-axis and Y-axis to adjust the parallel offset of the probe light. The displacement resolution of the two-dimensional electric translation stage (4.4) along the X and Y axes is higher than that of the three-axis electric translation stage along the X and Y axes.

3. The optical path control system of the SERF atomic magnetometer according to claim 2, characterized in that, The visual detection module (9) includes a first camera (9.1), a second camera (9.2), and an image processing unit (9.3). The first camera (9.1) is set in the optical path of the output probe light of the fiber collimator (2) and is used to acquire a first spot image. The second camera (9.2) is set in the optical path after the reflected light enters the atomic gas cell (7) and is used to acquire a second spot image. The first camera (9.1) and the second camera (9.2) are respectively connected to the image processing unit (9.3).

4. The optical path control system of the SERF atomic magnetometer according to claim 3, characterized in that, The beam splitting prism (6) includes a polarizer, a polarizing beam splitter, and a quarter-wave plate. The polarizer and the polarizing beam splitter are arranged sequentially along the incident light path of the probe light, and the quarter-wave plate is arranged on the light path of the reflected light emitted from the polarizing beam splitter.

5. A method for optical path control of a SERF atomic magnetometer, applied to the optical path control system according to any one of claims 1-4, characterized in that, Includes the following steps: S1, the optical path control system is activated, and the first camera acquires the first spot image of the probe light; the image processing unit extracts the center coordinates of the spot and compares them with the center coordinates of the target surface of the first camera. If the deviation between the center coordinates of the spot and the center coordinates of the target surface exceeds the preset deviation threshold, then proceed to S2; otherwise, proceed to S3. S2, drive the three-dimensional electric translation stage to move the fiber collimator along the Z-axis by a preset distance. The first camera acquires the first spot image before and after the movement. The center coordinates of the spot in the two first spot images are extracted using the sub-pixel positioning method. After calculating the offset of the spot center on the X-axis and Y-axis, the pitch angle and yaw angle of the probe light are calculated according to the mapping relationship. It is determined whether the pitch angle and yaw angle are both less than the preset threshold. If so, go to S3. Otherwise, the motion controller drives the two-dimensional electric swing stage to rotate in the opposite direction around the X-axis by the same pitch angle and around the Y-axis by the same yaw angle, and then returns to S2. S3 drives the electric rotary table to rotate the fiber optic collimator continuously around the Z-axis, synchronously acquiring the light intensity signal output by the photoelectric detection module; it then takes the rotation angle corresponding to the maximum value of the light intensity signal and locks it. S4, with the geometric center of the atomic gas chamber as the reference center, based on the X-axis offset and Y-axis offset of the spot center of the second spot image acquired by the second camera relative to the reference center; the motion controller drives the two-dimensional electric translation stage to move in the opposite direction on the X-axis by the X-axis offset distance, and in the opposite direction on the Y-axis by the Y-axis offset distance.

6. The method for controlling the optical path of the SERF atomic magnetometer according to claim 5, characterized in that, The subpixel positioning algorithm can be any one of the following: grayscale centroid method, Gaussian fitting method, or ellipse fitting method.

7. The method for controlling the optical path of the SERF atomic magnetometer according to claim 5, characterized in that, The mapping relationships in step S2 include: ； ； In the formula, Indicates pitch angle, Indicates the yaw angle. Indicates the preset distance.

8. The method for controlling the optical path of the SERF atomic magnetometer according to claim 5, characterized in that, Step S3 specifically includes: The electric rotary table is driven by a first angular velocity to drive the fiber collimator to rotate continuously around the Z-axis 360°. The correspondence between the light intensity signal and the rotation angle is recorded in real time to determine the first angle corresponding to the maximum light intensity. Then, the optical fiber collimator is rotated back and forth within the range of ±5° of the first angle by a second angular velocity. The second angle corresponding to the maximum light intensity is determined as the rotation angle and locked. The second angular velocity is less than the first angular velocity.

9. The method for controlling the optical path of the SERF atomic magnetometer according to claim 8, characterized in that, After step S4 is completed, a verification step is also included: the second spot image is acquired again to verify whether the deviation between the spot center and the geometric center of the atomic gas chamber is less than the preset acceptance threshold. If not, step S4 is repeated.

10. The optical path control method for the SERF atomic magnetometer according to claim 5, characterized in that, The preset distance ranges from 1mm to 10mm; The preset threshold in step S2 ranges from 0.01° to 0.1°. In step S1, the preset deviation threshold is 5% to 10% of the spot diameter.

Images