Challenges in coronagraph optical design

Abstract

The point spread function (PSF) for astronomical telescopes and instruments depends not only on geometric aberrations and scalar wave diffraction, but also on the apodization and wavefront errors introduced by coatings on reflecting and transmitting surfaces within the optical system. Geometrical ray tracing provides incomplete image simulations for exoplanet coronagraphs with the goal of resolving planets with a brightness less than 10^-9 of their star located within 3 Airy disk radii. The Polaris-M polarization analysis program calculates uncorrected coating polarization aberrations couple around 10^-5 light into crossed polarized diffraction patterns about twice Airy disk size. These wavefronts not corrected by the deformable optics systems. Polarization aberrations expansions have shown how image defects scale with mirror coatings, fold mirror angles, and numerical aperture.