High-Resolution Adaptive Optics

E.W. Justh and P.S. Krishnaprasad (University of Maryland)
Mikhail Vorontsov, Leonid Beresnev, Gary Carhart (Army Research Laboratory, Adelphi, MD)

Project Background and Goals

In collaborative work with the Intelligent Optics Laboratory at the Army Research Lab in Adelphi, MD, we have investigated some of the control issues associated with high-resolution actuation and sensing of optical fields. Specifically, we have focused on the problem of sensing and controlling wave-front phase, using advanced phase-contrast techniques based on optically (or electronically) controlled spatial light modulators (SLMs), and parallel, distributed feedback architectures. Due to the underlying physics, nonlinearity plays an essential role in the dynamical behavior of the feedback systems.

Methodology/Procedure

The approach involves mitigating the nonlinear effects as much as possible through design, and then using analysis to assess the effects that remain. Models of the relevant optical physics are used which have sufficient fidelity, and yet are simple enough to yield qualitative insights.

Project Results

A class of feedback systems for high-resolution optical wave-front control (or adaptive optic wave-front distortion suppression) is modeled and analyzed. Under certain conditions, the nonlinear dynamical system models obtained are shown to be gradient systems, with energy functions that also serve as Lyapunov functions.

Significance

From an optics point of view, the significance of this work is that it shows there is a practical approach for achieving high-resolution wave-front control. A standard problem in adaptive optics is phase distortion suppression to compensate for the effects atmospheric turbulence. Wave-front phase aberrations degrade signal quality, whether the application is laser communication, astronomy, or terrestrial imaging. Conventional approaches rely on extensive calculations to reconstruct the input beam phase based on, for example, measurements of its spatial derivatives.

To realize the potential of the upcoming generation of fast, high-resolution wave-front shaping devices for real-time suppression of strong atmospheric turbulence, a control scheme with much less centralized processing is required: the scheme we developed is amenable to parallel, distributed processing. We are working on extending our results to more general optical field control problems


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Last Updated: May 29, 2003.