Signal processing for high-precision wavefront control in Adaptive Optics

Lisa Poyneer, LLNL

I present new methods for high-precision wavefront control
that will be used in the Gemini Planet Imager project.
All are built on a foundation of signal processing,
in particular the use of the Fourier transform.
The method of Fourier Transform Reconstruction (FTR)
uses the DFT and filtering to reconstruct the wavefront phase.
The Fourier framework is particularly useful because each
mode can be controlled independently; each mode also corresponds to
a specific location in the PSF. This enables optimization of the PSF
based on measurements of the temporal statistics of the atmosphere.
Optimized-gain Fourier Control blends FTR with the technique
of modal gain optimization, determining the best gain for the
integral controller of each Fourier mode.
Predictive Fourier Control exploits the uncorrelated nature of the
Fourier modes under frozen flow to produce a computationally
efficient, adaptive predictive controller based on Kalman filtering.