A Unified View of Coronagraph Image Masks

The last few years have seen a variety of new image mask designs for diffraction-limited coronagraphy. Could there still be useful designs as yet undiscovered? To begin to answer this question, I survey and unify the Fraunhofer theory of coronagraph image masks in the context of a one-dimensional classical coronagraph. I display a complete solution to the problem of removing on-axis light assuming an unapodized entrance aperture and I introduce the attenuation function, a measure of a generic coronagraph’s off-axis performance. With these tools, I demonstrate that the masks proposed so far form a nearly complete library of image masks that are useful for detecting faint extrasolar planets. Subject headings: astrobiology — circumstellar matter — instrumentation: adaptive optics — planetary systems