Optimal Dark Hole Generation via Two Deformable Mirrors with Stroke Minimization

The past decade has seen a significant growth in research targeted at space based observatories for imaging exo-solar planets. The challenge is in designing an imaging system for high-contrast. Even with a perfect coronagraph that modifies the point spread function to achieve high-contrast, wavefront sensing and control is needed to correct the errors in the optics and generate a "dark hole". The high-contrast imaging laboratory at Princeton University is equipped with two Boston Micromachines Kilo-DMs. We review here an algorithm designed to achieve high-contrast on both sides of the image plane while minimizing the stroke necessary from each deformable mirror (DM). This algorithm uses the first DM to correct for amplitude aberrations and the second DM to create a flat wavefront in the pupil plane. We then show the first results obtained at Princeton with this correction algorithm, and we demonstrate a symmetric dark hole in monochromatic light

Speckle noise reduction techniques for high-dynamic range imaging

High-dynamic range imaging from space in the visible, aiming in particular at the detection of terrestrial exoplanets, necessitates not only the use of a coronagraph, but also of adaptive optics to correct optical defects in real time. Indeed, these defects scatter light and give birth to speckles in the image plane. Speckles can be cancelled by driving a deformable mirror to measure and compensate wavefront aberrations. In a first approach, targeted speckle nulling, speckles are cancelled iteratively by starting with the brightest ones. This first method has demonstrated a contrast better than 1e9 in laboratory. In a second approach, zonal speckle nulling, the total energy of speckles is minimized in a given zone of the image plane. This second method has the advantage to tackle simultaneously all speckles from the targeted zone, but it still needs better experimental demonstration.Comment: 7 pages, 3 figures, in Optical techniques for direct imaging of exoplanets (a special issue of Comptes Rendus de Physique

High dynamic range imaging in space: overview and wavefront control

NASA is endeavoring to launch missions capable of detecting Earth-like planets around neighboring stars. In visible wavelengths, this requires better than one 10 to the minus ten suppression of scattered light as close as 50 milli-arcsec to the stellar image. This extraordinary requirement is within reach but it requires broad-band wave front control to sub-Angstrom levels. We describe several high dynamic range imaging solutions, describe the various factors that contribute to the scattered light level and introduce a novel closed-loop broad-band correction system, suitable for the Shaped Pupil Coronagraph and the Lyot Coronagraph

The application of algebraic systems to finite automata : technical report

http://deepblue.lib.umich.edu/bitstream/2027.42/5077/5/bac2694.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/5077/4/bac2694.0001.001.tx

Normal monoids and factor monoids of commutative monoids

http://deepblue.lib.umich.edu/bitstream/2027.42/5079/5/bac2693.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/5079/4/bac2693.0001.001.tx

Outline for an algebraic study of event automata : technical report

http://deepblue.lib.umich.edu/bitstream/2027.42/5080/5/bac2719.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/5080/4/bac2719.0001.001.tx

A homomorphic theory of context-free languages and its generalizations : technical report

http://deepblue.lib.umich.edu/bitstream/2027.42/5078/5/ajc8116.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/5078/4/ajc8116.0001.001.tx