Cool Stars 14 - Submitted Abstract # 40
This version created on 05 October 2006

Closed-loop wavefront correction for high-contrast imaging:  the
"Peak-a-boo" algorithm


Amir Give'on, California Institute of technology
Jeremy Kasdin, Princeton University
Robert Vanderbei, Princeton University
Stuart Shaklan, JPL

High contrast imaging from space must overcome photon noise of the
diffracted star light and scattered light from optical components
defects.  The very high contrast required (up to 10^{-10} for
terrestrial planets) puts severe requirements on the wavefront control
system, as the achievable contrast is limited by the quality of the
wavefront.  The ``Peak-a-boo'' correction algorithm, presented here,
is a closed loop correction method for the Lyot coronagraph and the
shaped pupil coronagraph that minimizes the energy in a pre-defined
region in the image where terrestrial planets would be found.  The
reconstruction part uses three intensity measurements in the image
plane with a pinhole added to the shaped pupil for diversity.  This
method has been shown in simulations to converge to the nominal
contrast in 2-3 iterations.  In addition, the ``peak-a-boo'' has shown
to be effective in broadband light conditions.

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