ACHROMATIC DUAL-ZONE REFLECTING PHASE MASK FOR STELLAR CORONAGRAPHY

摘要

The dual-zone phase mask (DZPM) is a generalization of the Roddier and Roddier phase mask coro-nagraph for polychromatic observations. It consists of two concentric phase masks: a disk surrounded by a second annular phase mask. We consider here pure re ecting masks. The values of the mask thickness are optimized numerically to obtain an optimal nulling over a given large bandwidth. The DZPM presents the advantage of being insensitive to central obscuration of telescopes.