High-Resolution Adaptive Optics
E.W. Justh and P.S. Krishnaprasad (University of Maryland)
Mikhail Vorontsov, Leonid Beresnev, Gary Carhart (Army Research Laboratory,
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.
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.
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.
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
Page maintained by Eric Justh. Send comments to
Last Updated: May 29, 2003.