Acousto-Optic Modulator Lunar Laser Ranging System
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Solution Overview
Problem
Existing common-path laser ranging systems face limitations in achieving high-repetition-frequency due to the constraints of rotating mirror technology, which hinders the quick switching required for kHz laser ranging.
Innovation Solution
A common-path high-repetition-frequency lunar laser ranging system is developed, utilizing a laser emitting optical path with a kHz laser, beam expanding lenses, and an echo receiving optical path with a beam splitter, focusing lens, rotating shutter, adjustable diaphragm, collimating lens, and optical filter, eliminating the need for a rotating mirror and enhancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a rotating mirror is used for receiving/transmitting path conversion, then the system structure is simple, but the switching speed is insufficient for kHz laser ranging
Solution Approach 1:
The patent replaces the mechanical rotating mirror system with an acousto-optic modulator (AOM) based optical switching system. The AOM uses acoustic waves to create periodic refractive index variations in the crystal, enabling rapid beam deflection without mechanical moving parts. This substitution achieves kHz switching speeds while eliminating the mechanical limitations of rotating mirrors.
Solution Approach 2:
The patent changes the operating parameters of the laser system from low repetition frequency to kHz repetition frequency, requiring corresponding changes in the path conversion mechanism. By adjusting the acoustic frequency and amplitude in the AOM, the system can dynamically control beam switching at kHz rates, matching the laser repetition frequency.
2Measurement precision
If the laser repetition frequency is increased to kHz, then the ranging accuracy is improved, but the rotating mirror cannot switch paths quickly enough
Solution Approach 1:
The patent replaces the mechanical rotating mirror system with an acousto-optic modulator (AOM) based optical switching system. The AOM uses acoustic waves to create periodic refractive index variations in the crystal, enabling rapid beam deflection without mechanical moving parts. This substitution achieves kHz switching speeds while eliminating the mechanical limitations of rotating mirrors.
Solution Approach 2:
The patent employs periodic acoustic waves in the AOM to create time-periodic refractive index gratings that deflect the laser beam. By synchronizing the acoustic drive frequency with the laser repetition frequency, the system achieves stable kHz-rate beam switching, enabling high-repetition-frequency lunar laser ranging with sufficient path conversion speed.
3Object-affected harmful factors
If a rotating mirror is used, then the device complexity is low, but the noise interference is high
Solution Approach 1:
The patent replaces the mechanical rotating mirror system with an acousto-optic modulator (AOM) based optical switching system. The AOM uses acoustic waves to create periodic refractive index variations in the crystal, enabling rapid beam deflection without mechanical moving parts. This substitution achieves kHz switching speeds while eliminating the mechanical limitations of rotating mirrors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This system improves the accuracy and frequency of lunar laser ranging by enabling efficient transmission and reception through shared telescope apertures, overcoming the speed limitations of rotating mirrors and reducing noise interference.
Implementation Method 1
the beam expanding negative lens and the beam expanding positive lens are arranged in a confocal manner
Implementation Method 2
the focusing lens and the collimating lens are a pair of confocal lenses
Implementation Method 3
transformed into an unfocused beam by the collimating lens
Implementation Method 4
an optical filter and a detector which are sequentially arranged along the optical path direction
Data Source
AI summary
The present disclosure discloses a common-path high-repetition-frequency lunar laser ranging system and method. In the system, a kHz laser, a beam expanding negative lens, a beam expanding positive lens and a laser docking mirror are sequentially arranged along the optical path direction; the laser beam emitted by the kHz laser enters a telescope through the laser docking mirror after passing through the beam expanding negative lens and the beam expanding positive lens, and then is emitted to a lunar retro-reflector; the beam expanding negative lens and the beam expanding positive lens are arranged in a confocal manner; a beam splitter, a focusing lens, a rotating shutter, an adjustable diaphragm, a collimating lens, an optical filter and a detector are sequentially arranged along the optical path direction; the adjustable diaphragm is installed at the common focus of the focusing lens and the collimating lens.