Alignment vertical beam system and calibration method thereof

Abstract

The invention discloses a system for aligning a vertical light beam, and the system comprises an input optical fiber, a light beam collimating mirror group, an incident light reflector, a reflex mirror group, and a vacuum cavity, which are sequentially arranged along a light path, and the incident light reflector is disposed on an incident light voice coil platform. The reflection light reflecting mirror and the attitude measurement sensor are arranged on the reflection light voice coil platform in the structural frame; the invention also discloses a calibration method. A pair of voice coil platforms and a reflecting mirror are adopted to control the directions of incident light and reflected light, light beam alignment and plumb control are achieved, and it is guaranteed that the aligned plumb light beam always passes through the atomic group trapping center position through a reflex mirror set; according to the invention, aiming at a complex light beam pointing control system comprising a reflex mirror group, light beam alignment and vertical reference establishment can be realized, and drift calibration in a long-term operation process of the system is realized by adopting a multi-alignment mode.

Description

Technical Field

[0001] This invention relates to the field of cold atom interferometry precision measurement, and more specifically to an alignment vertical beam system for a complex beam pointing control system including a folding mirror group, and its calibration method. Background Technology

[0002] Gravity acceleration measurement is of great significance in basic and cutting-edge scientific research such as resource exploration, space science, oceanography, geodesy, geophysics, and geodynamics. High-precision gravity acceleration measurement realizes the parameters of the Earth's gravity field, providing accurate initial alignment parameters for rocket launches, manned spaceflight, and lunar exploration projects, effectively serving space science. High-precision gravity acceleration measurement can effectively improve the accuracy of passive navigation information, suppress error divergence in inertial navigation, and significantly improve long-endurance stealthy autonomous navigation capabilities and positioning accuracy.

[0003] Cold atom interferometry has developed rapidly in the past 20 years and has been widely used in precision measurement physics and fundamental physics research, yielding fruitful results. The absolute gravity measurement method based on cold atom interferometry, because it uses cold atom clusters as its research object, has a very stable atomic energy level structure, thus possessing advantages such as high precision, good stabilization, and low drift. Furthermore, it is free from mechanical wear and has a long service life.

[0004] Maintaining the stability of the sensitive axis of an absolute gravimeter based on cold atom interferometry is a prerequisite for achieving effective gravity measurement. To address the miniaturization problem of absolute gravimeters in dynamic measurement environments, an alignment vertical beam system is adopted to stabilize the sensitive axis of the absolute gravimeter, replacing the traditional attitude stabilization platform solution. This effectively reduces the size of the absolute gravimeter while increasing its attitude response bandwidth and improving its adaptability to dynamic environments. Summary of the Invention

[0005] To address the need for stabilizing the sensitive axis of a miniaturized, high-bandwidth absolute gravimeter based on cold atom interferometry, one objective of this invention is to provide a novel alignment vertical beam system for a complex beam pointing control system that includes a folding mirror assembly. This system effectively reduces the size of the absolute gravimeter while increasing its attitude response bandwidth and improving its dynamic environmental adaptability.

[0006] The technical solution adopted by this invention to solve its technical problem is: a vertical beam alignment system, comprising an input optical fiber, a beam collimating mirror group, an incident light reflecting mirror, a folding mirror group, and a vacuum cavity arranged sequentially along the optical path within the system's structural frame. The incident light reflecting mirror is mounted on the incident light voice coil platform. The system also includes a reflecting light reflecting mirror mounted on the reflecting light voice coil platform within the structural frame, and an attitude measurement sensor for real-time measurement of the rotation of the system's structural frame. Except for the autocollimator, all physical structures of this system are installed within the structural frame and can rotate with the structural frame.

[0007] Furthermore, it also includes a polarization-maintaining circulator connected to the input optical fiber, and an input port optical fiber and a monitoring port optical fiber connected to the polarization-maintaining circulator, wherein the monitoring port optical fiber is connected to an optical power meter.

[0008] The second objective of this invention is to provide a calibration method for aligning a vertical beam system, comprising the following steps:

[0009] S1, Beam pointing vertical calibration: Keep the autocollimator attitude unchanged, repeatedly adjust the structural frame to different attitudes, measure the incident light voice coil platform control value that makes the incident light vertical in each attitude and the attitude measurement value of the corresponding attitude measurement sensor, solve the installation error of the incident light voice coil platform and attitude measurement sensor, and obtain the control value of the incident light voice coil platform that keeps the incident light vertical in the system under the attitude measurement value of any attitude measurement sensor.

[0010] S2, Beam alignment calibration steps: Adjust the control value of the reflected light voice coil platform to maximize the output power of the optical power meter, obtain a series of control values ​​of the reflected light voice coil platform corresponding to the control values ​​of the incident light voice coil platform, compare them with the initial beam alignment results, obtain the control values ​​of the incident light voice coil platform and the corresponding reflected light voice coil platform when the beam is aligned after calibration, and calibrate the attitude control of the reflected light voice coil platform based on the return light power output by the reflected light in the optical fiber at the monitoring port.

[0011] Furthermore, in step S2, a polarization-maintaining circulator is used to inject and synchronously detect optical power, and the output optical power of the monitoring port fiber is observed to control and adjust the reflected optical voice coil platform under different incident optical voice coil platform control values.

[0012] Furthermore, by combining the relationship between the incident light voice coil platform control value and the reflected light voice coil platform control value, and the mapping relationship between the incident light voice coil platform control value and the attitude measurement value of the corresponding attitude measurement sensor, the installation error of the reflected light voice coil platform and the attitude measurement sensor can be calculated, and the reflected light voice coil platform control value that keeps the system beam aligned under the attitude measurement value of any attitude measurement sensor can be obtained.

[0013] The beneficial effects of this invention are:

[0014] This invention employs an aligned vertical beam system to stabilize the absolute sensitive axis, replacing the traditional attitude stabilization platform solution. This effectively reduces the size of the absolute gravimeter while increasing the attitude response bandwidth and improving dynamic environment adaptability.

[0015] This invention addresses the complex beam pointing control system that includes a folding mirror assembly, proposing a method for establishing a vertical reference and aligning the beam, thus providing a feasible technical path for the construction and implementation of a vertically aligned beam system.

[0016] This invention addresses the drift problem in vertical beam alignment systems during long-term operation by proposing a realignment method that combines beam backlight monitoring and modulation testing, effectively improving the effectiveness of vertical beam alignment systems during long-term operation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention;

[0018] Figure 2 This is a schematic diagram of the system structure for establishing a vertical reference in this invention;

[0019] Figure 3 This is a schematic diagram of the system structure for achieving beam alignment according to the present invention.

[0020] The labels in the attached figures are as follows: 1—Input optical fiber, 2—Beam collimating mirror group, 3—Incident light voice coil platform, 4—Incident light reflecting mirror, 5—Folding mirror group, 6—Vacuum cavity, 7—Reflected light voice coil platform, 8—Reflected light reflecting mirror, 9—Attitude measurement sensor, 10—Position of the trapped atomic cluster, 11—Polarization maintaining circulator, 12—Input port optical fiber, 13—Monitoring port optical fiber, 14—Optical power meter, 15—Autocollimator, 16—Structural frame. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings.

[0022] This invention includes a structure for aligning a vertical beam system, a method for establishing a vertical reference for aligning a vertical beam system, a beam alignment method for aligning a vertical beam system, and a calibration method for beam pointing vertically and beam alignment during long-term operation of the system.

[0023] like Figure 1As shown, the present invention discloses a vertical beam alignment system, comprising an input optical fiber 1, a beam collimating lens group 2, an incident light reflecting mirror 4 on an incident light voice coil platform 3, a folding mirror group 5, a vacuum cavity 6, a reflecting light reflecting mirror 8 on a reflecting light voice coil platform 7, an attitude measurement sensor 9, and a system structural frame 16. In this embodiment, all physical structures 1-9 are mounted within the structural frame 16 and can rotate with the structural frame 16. The folding mirror group 5 ensures that the laser beam, after being angled by the incident light voice coil platform 3, always converges through the atomic cluster trapping center position 10. The incident light voice coil platform 3 and the reflecting light voice coil platform 7 are the driving mechanisms for the incident light reflecting mirror 4 and the reflecting light reflecting mirror 8, respectively, and control the alignment of the incident and reflected light and the vertical beam in real time based on the attitude measurement values ​​from the attitude measurement sensor 9.

[0024] The laser beam is injected into the optical components through the laser input fiber 1, and is expanded and collimated by the beam collimating lens group 2. The expanded and collimated beam passes through the incident light reflector 4 and the folding mirror group 5 to form incident light aligned with the vertical beam system. The incident light passes through the reflecting light reflector 8 to form reflected light aligned with the vertical beam system. The folding mirror group 5 ensures that the laser beam, after its angle is adjusted by the incident light voice coil platform 3, always converges through the atomic cluster trapping center position 10. The attitude measurement sensor 9 is used to measure the real-time rotation of the system's structural frame. The generated attitude information, combined with the system calibration results, is used to adjust the rotation of the incident light voice coil platform 3 and the reflecting light voice coil platform 7, driving the incident light reflector 4 and the reflecting light reflector 8 to change their attitude in real time, ensuring that the incident light and reflected light aligned with the vertical beam system remain vertical and coincident.

[0025] like Figure 2 As shown, the vertical beam system of this invention establishes a vertical reference system, comprising an input optical fiber 1, a beam collimating mirror group 2, an incident light reflecting mirror 4 on the incident light voice coil platform 3, a folding mirror group 5, a vacuum cavity 6, an attitude measurement sensor 9, an autocollimator 15, and a system structural frame 16. All physical structures 1-6 of the system are installed within the structural frame 16 and can rotate with the structural frame 16. The process of establishing a vertical reference requires the temporary removal of the reflected light voice coil platform 7 and the reflected light reflecting mirror 8 from Example 1. The autocollimator 15, as a reference observation device, must remain vertical throughout the measurement process. The autocollimator 15 can operate in autocollimation mode to observe the liquid surface for initial alignment and correction of its own attitude.

[0026] The laser beam is injected into the optical components through the laser input fiber 1, and beam expansion and collimation are completed by the beam collimating lens group 2. The expanded and collimated beam passes through the incident light reflecting mirror 4 and the folding mirror group 5 to form the incident light aligned with the vertical beam system. The structural frame 16 is adjusted to a certain posture and fixed. By adjusting the translation of the structural frame 16, the incident light of the system can accurately enter the field of view of the autocollimator 15. The incident light of the system is observed through the autocollimator 15. By adjusting the incident light voice coil platform 3, the imaging position of the incident light in the autocollimator 15 is moved so that the imaging position of the incident light in the autocollimator 15 is located at the center of the image of the autocollimator 15. At this time, the incident light of the system is parallel to the optical axis of the autocollimator 15. Since the vertical adjustment of the self-collimator 15 has been achieved, this scheme realizes the vertical calibration of the incident light of the system in a certain posture.

[0027] By repeatedly adjusting the structural frame 16 to different postures, the control value of the incident light voice coil platform 3 that keeps the incident light vertical and the posture measurement value of the corresponding posture measurement sensor 9 are measured under each posture. The installation error of the incident light voice coil platform 3 and the posture measurement sensor 9 can be calculated, and the control value of the incident light voice coil platform 3 that keeps the incident light vertical under any posture measurement value of the posture measurement sensor 9 can be obtained.

[0028] Using the autocollimator 15 as the plumb line reference, the vertical calibration of the incident light under different attitudes is realized. The attitude measurement value of the attitude measurement sensor 9 and the corresponding control value of the incident light voice coil platform 3 are used to calculate the installation error between the incident light voice coil platform 3 and the attitude measurement sensor 9, and obtain the control value of the incident light voice coil platform 3 that keeps the incident light vertical under any attitude measurement value of the attitude measurement sensor 9.

[0029] like Figure 3 As shown, the system structure of the vertical beam system of the present invention for beam alignment includes an input optical fiber 1, a beam collimating mirror group 2, an incident light reflecting mirror 4 on the incident light voice coil platform 3, a folding mirror group 5, a vacuum cavity 6, a reflecting light reflecting mirror 8 on the reflecting light voice coil platform 7, an attitude measurement sensor 9, a system structure frame 16, a polarization maintaining circulator 11, a polarization maintaining circulator input port optical fiber 12, a polarization maintaining circulator monitoring port optical fiber 13, and an optical power meter 14.

[0030] The laser beam is input to the polarization-maintaining circulator 11 through the input port fiber 12, and then injected into the optical component through the input fiber 1 connected to the output port of the polarization-maintaining circulator. The beam is expanded and collimated by the beam collimating lens group 2. The expanded and collimated beam passes through the incident light reflecting mirror 4 and the folding mirror group 5 to form incident light aligned with the vertical beam system. The incident light is reflected by the reflecting light reflecting mirror 8. The reflected light is returned to the input fiber 1 along the original incident light path by adjusting the voice coil platform 7. The returned reflected light partially enters the monitoring port fiber 13 of the polarization-maintaining circulator 11. The optical power meter 14 is used to monitor the return power of the reflected light entering the monitoring port fiber 13 of the polarization-maintaining circulator.

[0031] The control value of the incident light voice coil platform 3 is set to the control value of the incident light voice coil platform 3 that makes the incident light vertical in various postures during the establishment of the incident light vertical reference. The control value of the reflected light voice coil platform 7 is adjusted to maximize the output power of the optical power meter 14. A series of control values ​​of the reflected light voice coil platform 7 corresponding to the control values ​​of the incident light voice coil platform 3 that make the incident light vertical in various postures during the establishment of the incident light vertical reference are obtained. Through the mapping relationship between the control value of the incident light voice coil platform 3 and the attitude measurement value of the corresponding attitude measurement sensor 9, the installation error of the reflected light voice coil platform 7 and the attitude measurement sensor 9 can be calculated, and the control value of the reflected light voice coil platform 7 that keeps the system beam aligned under any attitude measurement value of the attitude measurement sensor 9 can be obtained.

[0032] This invention discloses a calibration method for aligning a vertical beam system. This method combines beam backlight monitoring and modulation testing to calibrate the beam direction to the vertical and the beam alignment during long-term operation of the system.

[0033] The calibration during long-term operation consists of two steps: beam alignment calibration and beam pointing vertical calibration. Beam alignment calibration is performed first, followed by beam pointing vertical calibration after beam alignment is achieved. Both calibration steps employ a combination of beam backlight monitoring and modulation testing.

[0034] S1, Beam alignment and calibration steps.

[0035] The beam alignment calibration is a calibration method for controlling the attitude of the reflected light voice coil platform 7 based on the return power of the reflected light output at the monitoring port fiber optic 13. This involves adjusting the control values ​​of the reflected light voice coil platform 7 according to the beam alignment operation under selected multiple sets of incident light voice coil platform 3 attitudes, maximizing the output power of the optical power meter 14, obtaining a series of control values ​​of the reflected light voice coil platform 8 corresponding to the incident light voice coil platform 3 control values, comparing these with the initial beam alignment results, and obtaining the calibrated control values ​​of the incident light voice coil platform 3 and the corresponding reflected light voice coil platform 7 during beam alignment. The attitude control of the reflected light voice coil platform 7 is calibrated based on the return power of the reflected light output at the monitoring port fiber optic 13.

[0036] In the beam alignment method, a polarization-maintaining circulator 11 is used to inject and synchronously detect optical power, and the optical power is output through the observation and monitoring port fiber 13 to achieve control and adjustment of the reflected light voice coil platform under different incident light voice coil platform control values.

[0037] S2, Beam pointing vertical calibration step.

[0038] To maintain the orientation of the structural frame 16, gravity measurement is performed using an absolute gravimeter based on the aligned vertical beam system, under the control values ​​of the aligned incident light voice coil platform 3 and the corresponding reflected light voice coil platform 7. The gravity values ​​measured under different control values ​​are used as the ordinate, and the control values ​​of the reflected light voice coil platform 7 are used as the abscissa for a second-order fitting. The corresponding extreme values ​​are the calibrated beam plumb direction.

[0039] The method of this invention combines beam return monitoring and modulation testing to calibrate the vertical direction of the beam and the beam alignment during long-term system operation. Under the selected attitudes of multiple incident light voice coil platforms, the attitude control calibration of the reflected light voice coil platform is achieved based on the return power of the reflected light output from the optical fiber at the monitoring port of the polarization-maintaining circulator, while keeping the attitude of the system structural frame unchanged. Under the aligned incident light voice coil platform and the corresponding control value of the reflected light voice coil platform, modulation testing is carried out to calibrate the vertical direction of the beam and the beam alignment.

[0040] Those skilled in the art will readily understand that the above description is merely a preferred use case of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for aligning a vertical beam, characterized in that: The system includes an input optical fiber (1), a beam collimating lens group (2), an incident light reflector (4), a folding mirror group (5), and a vacuum cavity (6) arranged sequentially along the optical path within the structural frame (16). The incident light reflector (4) is mounted on the incident light voice coil platform (3). The system also includes a reflecting light reflector (8) mounted on the reflecting light voice coil platform (7) within the structural frame (16), and an attitude measurement sensor (9) for real-time measurement of the rotation of the structural frame (16).

2. The calibration method for aligning a vertical beam system as described in claim 1, characterized in that, Includes the following steps: S1, Beam pointing vertical calibration: Keep the autocollimator (15) in the same position, repeatedly adjust the structural frame (16), measure the control value of the incident light voice coil platform (3) that makes the incident light vertical under each position and the corresponding measurement value of the attitude measurement sensor (9), calculate the installation error of the incident light voice coil platform (3) and the attitude measurement sensor (9), and obtain the control value of the incident light voice coil platform (3) under the attitude measurement value of any attitude measurement sensor (9); S2, Beam alignment calibration: Adjust the control value of the reflected light voice coil platform (7) to maximize the output power of the optical power meter (14), obtain a series of control values ​​of the reflected light voice coil platform (8) corresponding to the control values ​​of the incident light voice coil platform (3), compare them with the initial beam alignment results, obtain the control values ​​of the incident light voice coil platform (3) and the corresponding reflected light voice coil platform (7) when the beam is aligned after calibration, and realize the calibration of the attitude control of the reflected light voice coil platform (7) based on the return light power output by the reflected light in the monitoring port optical fiber (13).

3. The calibration method for aligning a vertical beam system according to claim 2, characterized in that, In step S2, a polarization-maintaining circulator (11) is used to inject and synchronously detect optical power, and the output optical power of the monitoring port fiber (13) is observed to control and adjust the reflected optical voice coil platform (7) under different control values ​​of the incident optical voice coil platform (3).

4. A calibration method for aligning a vertical beam system according to claim 2 or 3, characterized in that, By combining the relationship between the control value of the incident light voice coil platform (3) and the control value of the reflected light voice coil platform (7), and the mapping relationship between the control value of the incident light voice coil platform (3) and the attitude measurement value of the corresponding attitude measurement sensor (9), the installation error between the reflected light voice coil platform (7) and the attitude measurement sensor (9) is calculated, and the control value of the reflected light voice coil platform (7) that keeps the system beam aligned is obtained under the attitude measurement value of any attitude measurement sensor (9).

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