Sodium guide star uplink laser light field pre-correction system

Abstract

The invention discloses a sodium guide star uplink laser light field pre-correction system. The system comprises a sodium guided star laser, a beam expanding lens, an inclined reflector, an inclined controller, a spectroscope, a sodium guide star transmitting telescope and an inclined detection camera; the system further comprises a light field detection system and a light field pre-correction system; the light field detection system comprises a light field detector and a light field controller; the light field pre-correction system comprises a first deformable mirror, a Fourier transform lens, a light splitting mechanism and a second deformable mirror; and the Fourier transform lens is located in a Fraunhofer diffraction region of the first deformable mirror. By the adoption of the scheme, real-time compensation can be conducted on amplitude and phase disturbance generated by atmospheric turbulence at the same time, light spots obtained after pre-correction are closer to the diffraction limit, and the number of returned light of the sodium guide star is more stable, so that performance of a rear-end self-adaptive optical system can be effectively improved, and development of the self-adaptive optical system and the theory is promoted.

Description

technical field [0001] The invention relates to the field of adaptive optical devices, in particular to a sodium guide star uplink laser light field pre-correction system. Background technique [0002] The Adaptive Optics (AO) system compensates the wavefront distortion caused by atmospheric turbulence in real time, restores the distorted wavefront to a plane wavefront, and obtains imaging close to the diffraction limit, thus becoming an indispensable part of large-aperture ground-based telescopes. The adaptive optics system compensates atmospheric turbulence in real time, first of all, it needs to use the guide star to detect the distortion caused by the turbulence in real time. Usually, the natural guide star that meets the brightness requirement and is in the halo area of ​​the observation target is usually less than 1% ( near-infrared band), which limits the application range of adaptive optics systems. [0003] The emergence of artificial guide stars has greatly improv...

AI Technical Summary

Problems solved by technology

The adaptive optics system compensates atmospheric turbulence in real time, first of all, it needs to use the guide star to detect the distortion caused by the turbulence in real time. Usually, the natural guide star that meets the brightness requirement and is in the halo area of ​​the observation target is usually less than 1% ( near-infrared band), which limits the application range of adaptive optics systems

Among them, the static aberration of the emission optical path and the dynamic aberration of atmospheric turbulence will cause the wavefront distortion of the uplink sodium laser. After passing through the transmission distance of 90km, due to the effect of Fresnel diffraction, the sodium laser reaching the sodium layer will produce light field fluctuations, resulting in Sodium guide star spot expansion and return light brightness fluctuations, resulting in increased wavefront detection errors

[0006] In order to overcome the degradation of the shape of the sodium guide star caused by the dynamic aberration of the atmosphere and the static aberration of the transmitting system, pre-calibration of the uplink sodium laser has become an effective method. The impact of the value fluctuation on the results, such as the patent number 201511030788.1 applied by Wei Kai, Huang Jian and others in 2015, the patent name is an invention patent of a common-aperture emission and correction telescope combining Rayleigh beacons and sodium beacons. This patent mainly corrects the phase fluctuation of the sodium laser, ignoring the influence of the amplitude fluctuation; and the patent number 2018101025269 submitted by Wei Kai, Huang Jian and others in 2018, the patent name is a sodium beacon emission with complex amplitude modulation The invention patent of the telescope, which also pre-corrects the phase fluctuations caused by the uplink path turbulence on the sodium laser, without considering the influence of amplitude fluctuations

[0007] Since the atmospheric seeing at Chinese astronomical observatories is worse than that of foreign observatories, and the influence of turbulence is stronger, after the sodium laser emits from the ground and travels for a certain distance, Fresnel diffraction converts phase fluctuations into amplitude fluctuations, resulting in amplitude fluctuations. The uplink light field has a great influence, which is an urgent problem to be solved, and if the amplitude detector and the corresponding controller are simply added, the system complexity and cost will inevitably be increased.

[0008] At the same time, the first two patents use Hartmann detectors to detect phase fluctuations, and cannot detect amplitude fluctuations at the same time

In order to detect amplitude fluctuations, additional detectors are required, which increases the complexity and cost of the system

Images