Open-loop correction of horizontal turbulence: system design and result

Area of Science:

• Optical Engineering
• Astronomy
• Adaptive Optics

Background:

• Conventional adaptive optics (AO) systems rely on closed-loop configurations due to the limitations of traditional deformable mirrors, such as hysteresis and nonlinearity.
• Open-loop control in AO is crucial for advanced concepts but has been challenging to implement with existing technologies.

Purpose of the Study:

• To design and demonstrate a novel open-loop adaptive optics system utilizing a liquid-crystal-on-silicon (LCoS) wavefront corrector.
• To evaluate the performance, simplicity, speed, and light efficiency of the proposed open-loop AO system compared to conventional closed-loop systems.

Main Methods:

• Development of an open-loop AO system incorporating an LCoS wavefront corrector.
• Experimental validation using a 250 mm telescope to correct 500 m horizontal atmospheric turbulence in a laboratory setting.
• Performance evaluation including correction frequency, precision in closed-loop configuration, and achieved resolution in open-loop mode.

Main Results:

• The system achieved a correction frequency of 60 Hz.
• Closed-loop evaluation showed a correction precision of 0.2 lambda (at lambda=0.633 microm) peak-to-valley.
• Open-loop correction yielded dynamic image resolution comparable to closed-loop correction, achieving 0.68 arc sec resolution, close to the diffraction limit of 0.65 arc sec.

Conclusions:

• The developed open-loop adaptive optics system with an LCoS wavefront corrector is a viable and advantageous alternative to traditional closed-loop systems.
• This system demonstrates simplicity, speed, and improved light efficiency, enabling advanced AO applications.
• The experimental results confirm the effectiveness of open-loop control for high-resolution imaging in AO systems.