Including detector effects in the design of grazing incidence x-ray telescopes

Abstract

Most imaging systems today include a mosaic detector array in the focal plane. Optical designers of astronomical telescopes typically produce a design that yields a superb on-axis aerial image in the focal plane, and detector effects are included only in the analysis of the final system performance. Aplanatic optical designs (corrected for spherical aberration and coma) are widely considered to be superior to non-aplanatic designs. However, there is little merit in an aplanatic design for wide field applications because one needs to optimize some field weighted average measure of resolution over the desired operational field of-view (OFOV). Furthermore, when used with a mosaic detector array in the focal plane, detector effects eliminate the advantage of the aplanatic design even at small field angles. For wide fields of view, the focal plane is frequently despaced to balance field curvature with defocus thus obtaining better overall performance. We will demonstrate that including detector effects in the design process results in a different optimal (non-aplanatic) design for each OFOV that is even superior to an optimally despaced aplanatic design.