In order to suppress the halo and any residual speckles over a region of interest, we find an anti-halo reconstructor which gives the required changes to a deformable mirror (DM) at the pupil plane. The reconstructor is built from a training set consisting of measurements of the complex halo influence functions for a spanning set of Fourier modes applied to the DM. The reconstructor is then found by multiplying the applied DM actuator values by the singular value decomposition (SVD) pseudo-inverse of the measured complex halo influence functions. Using a single fully illuminated 12×12 actuator DM at the pupil plane, halo suppression for complex pupils out to the control radius of 6 λ/D can be provided. In practice, a coronagraph is unlikely to achieve high performance without adaptive tuning. We use a coronagraphic focal plane interferometer [1], where the focal plane mask diverts the bright starlight for use as an interferometric reference beam to measure the residual complex halo. The result of the reconstructor acting on the complex halo measurements allowed us to implement a closed loop halo-suppression servo. We discuss the laboratory implementation and experience with this technique.

Date Published: 22 July 2010
PDF: 10 pages
Proc. SPIE 7736, Adaptive Optics Systems II, 77362S (22 July 2010); doi: 10.1117/12.857825

Published in SPIE Proceedings Vol. 7736:
Adaptive Optics Systems II
Brent L. Ellerbroek; Michael Hart; Norbert Hubin; Peter L. Wizinowich, Editor(s)