CN-122015783-A - Remote high-precision laser positioning system and method based on tunnel environment

CN122015783ACN 122015783 ACN122015783 ACN 122015783ACN-122015783-A

Abstract

The invention discloses a remote high-precision laser positioning system and method based on tunnel environment, wherein the system comprises a laser emitting unit for emitting a Gaussian beam of a fundamental mode, a beam expanding and collimating unit arranged at the downstream of a light path of the laser emitting unit for expanding and collimating the beam and compressing the far-field divergence angle of an output beam, and a self-adaptive optical control unit comprising a wavefront correction device and a control processor. The beam expansion collimation unit is provided with a thermal stability structure, the optical material combination adopted by the lens is configured to enable the thermal expansion coefficient of the lens material and the influence of the refractive index temperature coefficient on the focal length to be mutually compensated based on a thermal drift model, the control processor runs a random parallel gradient descent algorithm, and the wave front phase of the output light beam is adjusted in real time by applying random disturbance voltage to the wave front correction device and performing iterative optimization by taking the Style ratio of far-field light spots as an evaluation function. The invention can improve the precision of long-distance laser positioning in the complex tunnel environment.

Inventors

Chen Kuiyou
ZHOU TINGYING
ZHI HUALONG
DENG JIANFENG
OU JIANLIANG
Xiao Xiangnan
LIU WEIXIN
ZHANG CAN
Lian Jiaqi
CHEN YANGYANG

Assignees

中建五局土木工程有限公司

Dates

Publication Date: 20260512
Application Date: 20251229

Claims (10)

1. A long-range high accuracy laser positioning system based on tunnel environment, includes the laser emission unit that is used for the emission basic mode gaussian beam, its characterized in that still includes: A beam expansion and collimation unit arranged at the downstream of the light path of the laser emission unit and used for carrying out beam expansion and collimation treatment on the Gaussian beam of the fundamental mode and compressing the far field divergence angle of the output beam, and The self-adaptive optical control unit comprises a wavefront correction device and a control processor; The beam expansion collimation unit is provided with a thermal stability structure, and the optical material combination adopted by the lens is configured to enable the thermal expansion coefficient of the lens material and the influence of the refractive index temperature coefficient on the focal length to be mutually compensated based on a thermal drift model so as to inhibit light beam divergence caused by environmental temperature change; The adaptive optics control unit is configured to perform dynamic compensation by the control processor running a random parallel gradient descent algorithm to adjust the wavefront phase of the output beam in real time by applying a random disturbance voltage to the wavefront correction device and performing iterative optimization with the stoneley ratio of the far field spot as an evaluation function to compensate for dynamic aberrations caused by environmental turbulence or vibration.
2. The system of claim 1, wherein the beam expansion and collimation unit adopts a kepler telescope structure and comprises a focal length of Is of the eyepiece and focal length of Is provided; the system beam expansion ratio M is defined as: The system beam expansion ratio M is configured to satisfy an initial divergence angle of the laser emitting unit output After beam expansion, the far field divergence angle of the output beam Less than 0.1mrad.
3. The system of claim 1, wherein the lens curvature and thickness parameters in the expanded beam collimation unit are optimized based on a zernike polynomial-built wavefront aberration model, the optimized objective function being a root mean square value that minimizes the wavefront error to eliminate static aberrations introduced by lens fabrication and assembly.
4. The system of claim 1, wherein the thermal stability configuration has a coefficient of thermal expansion α and a refractive index temperature coefficient β of the lens material such that an amount of focal length shift due to a change in lens geometry caused by a change in temperature is opposite and equal in magnitude to an amount of focal length shift due to a change in refractive index, maintaining stability of the system output divergence angle at the change in temperature.
5. The system of claim 1, wherein the wavefront correction device is a deformable mirror, and the control processor is configured to perform a random parallel gradient descent algorithm as follows: Generating a set of random disturbance voltage vectors and applying to the deformable mirror; Collecting performance index value after disturbance application And (3) with Wherein the performance index A stehl ratio that is the far field spot; calculating the gradient of the change of the performance index, and updating the control voltage vector according to the descending or ascending direction of the gradient: Wherein, the For the updated control voltage vector at the next time of the n +1 th iteration, A set of control voltages applied to the respective actuators of the wavefront correction device for a current time instant of an nth iteration, As the gain factor of the gain factor, As the amount of change in the performance index, For the random disturbance vector applied by human, k is the number of control channels, and a random disturbance vector with the dimension of k is generated in iteration 。
6. The system of claim 1, wherein the expanded beam collimation unit is configured to adjust the beam waist radius by So that the Rayleigh distance of the light beam Increase in propagation distance Meter, beam diameter Kept below 1 cm.
7. The system of claim 1, wherein the system further comprises: The far-field light spot detection unit is arranged at the far-field end of the beam propagation path or coupled into the light path through the beam splitting device and is used for acquiring far-field light spot images of laser beams in real time; The far-field light spot detection unit is in communication connection with the control processor, the collected light spot image is transmitted to the control processor, and the control processor calculates the ratio of the peak light intensity of the actual light spot to the peak light intensity of the ideal diffraction limit system so as to obtain the Style ratio.
8. The system of claim 1, wherein the laser emitting unit is configured to emit laser light in a near infrared band, and a laser center wavelength of the near infrared band ranges from 1500 nm to 160 nm.
9. The system of claim 1, wherein the control processor is further configured to perform system initialization prior to laser firing: Receiving an input laser wavelength Initial beam waist radius Target throw distance ; Calculating the meeting target projection distance according to the Gaussian beam transmission model Rayleigh range required for spot width requirement ; According to the Rayleigh distance Calculating the minimum beam expansion ratio required by the beam expansion collimation unit And adjusts or verifies the combination parameters of the objective lens and the eyepiece based on the minimum beam expansion ratio.
10. A method of remote high precision laser positioning based on a tunnel environment, characterized in that the method is based on the system according to claim 1, comprising the steps of: transmitting a Gaussian beam of a fundamental mode, and performing beam expansion and collimation treatment on the beam by using a beam expansion collimation unit so as to compress a far-field divergence angle of an output beam; The beam expansion collimating unit is configured with a lens of a specific optical material combination, and the beam divergence caused by the change of the ambient temperature is restrained by the mutual offset effect of the thermal expansion coefficient of the lens material and the focal distance influence of the refractive index temperature coefficient; And executing the real-time dynamic compensation based on the adaptive optics, namely running a random parallel gradient descent algorithm, applying random disturbance voltage to a wavefront correction device in a light path, performing iterative optimization by taking the Style ratio of far-field light spots as an evaluation function, and adjusting the wavefront phase of an output light beam in real time to compensate dynamic aberration caused by environmental turbulence or vibration.

Description

Remote high-precision laser positioning system and method based on tunnel environment Technical Field The invention belongs to the technical field of tunnel construction equipment and lasers, and particularly relates to a long-distance high-precision laser positioning system and method based on tunnel environment. Background In the technical field of tunnel construction, accurate control of a tunneling axis and positioning and installation of construction equipment are highly dependent on a high-precision optical datum line. The establishment of a long-distance high-stability laser datum line is a precondition for realizing the automation and the intellectualization of tunnel construction. The invention discloses a laser collimation guiding device and system for tunnel construction, wherein the device comprises a base, a calibration plate, a calibration support, a height adjusting structure, a rotating structure and a horizontal displacement structure, wherein the base is provided with a laser emitter on one surface, the other surface of the calibration plate is used for receiving laser signals from the initial end of a tunnel or laser signals from laser emitters of other calibration plates, the calibration support is connected with the calibration plate through a cross rod, the cross rod is a rotating shaft of the calibration plate, the height adjusting structure is arranged on the calibration support and used for adjusting the height of the calibration plate, the rotating structure is connected with the calibration support and used for adjusting the angle of the calibration plate, the horizontal displacement structure is connected with the calibration support and used for adjusting the horizontal displacement of the calibration plate. The coordinate positioning is carried out through the calibration plate, so that the laser beams emitted by the laser transmitters are connected end to end, the definition of the long-distance transmission of the laser beams is guaranteed, and the problem that the accuracy of the tunnel construction process in a distance is low when the total station is used for measuring under dim light is solved. The scheme still has obvious technical bottlenecks when facing high-precision construction requirements, and is mainly characterized in the following aspects: The prior art focuses mainly on the displacement and angular adjustment of the mechanical structure without optimizing the physical transmission characteristics of the laser beam itself. Due to the physical diffraction effect of light, a common laser beam inevitably diverges in long distance (e.g., 50 meters and more) transmission. At a distance of 50 meters, the light spot width of a conventional laser line projector often exceeds 1 cm required by engineering, so that the light spot on a calibration plate is fuzzy, the center is difficult to identify, and the positioning accuracy of a reference line is seriously affected. The tunnel internal working condition is extremely complicated, and a large amount of dust scattering, airflow disturbance caused by temperature and humidity change and vibration generated by large-scale mechanical operation exist. The mechanical adjusting structure in the prior art can only perform static geometric alignment, and cannot cope with beam jitter and wave front distortion caused by air turbulence in real time, so that far-field light spots drift and form degradation occur on the calibration plate. The dust interference is mainly characterized in that laser energy attenuation, signal-to-noise ratio reduction and far-field light spot contrast reduction are caused, the transmission direction of a light beam is changed, wave front distortion of a non-fixed mode is caused, and the scattering effect is particularly strong on dust particles with the size similar to the wavelength of laser. The change of the tunnel environment temperature can cause the optical device to expand and contract with heat, and the refractive index and the curvature radius of the lens are changed. The prior art does not relate to the design of thermal stability of an optical system, and under long-time operation, the thermal drift of optical parameters can further aggravate the divergence and pointing errors of light beams, so that the construction requirements of all-weather high-precision automation are difficult to meet. Disclosure of Invention The invention provides a long-distance high-precision laser positioning system and method based on a tunnel environment, and aims to solve the problem of insufficient positioning precision in the field of long-distance laser positioning in the tunnel environment. In order to solve the technical problems, in one aspect, the present invention provides a remote high-precision laser positioning system based on a tunnel environment, which includes a laser emitting unit for emitting a gaussian beam of a fundamental mode, and: The beam expansion and collimation unit is arranged at the dow