Spiderweb Masks for High-Contrast Imaging

Motivated by the desire to image exosolar planets, recent work by us and others has shown that high-contrast imaging can be achieved using specially shaped pupil masks. To date, the masks we have designed have been symmetric with respect to a Cartesian coordinate system but were not rotationally invariant, thus requiring that one take multiple images at different angles of rotation about the central point in order to obtain high contrast in all directions. In this paper we present a new class of masks that have rotational symmetry and provide high contrast in all directions with just one image. These masks provide the required 10^-10 level of contrast to within 4λ/D, and in some cases 3λ/D, of the central point, which is deemed necessary for exosolar planet finding/imaging. They are also well suited for use on ground-based telescopes, and perhaps the James Webb Space Telescope too, since they can accommodate central obstructions and associated support spiders.