Balancing detector effects with aberrations in the design of wide-field 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 coma͒ are widely considered to be superior to nonaplanatic designs. However, there is little merit in an aplanatic design for wide-field applications because one needs to optimize some fieldweighted-average measure of resolution over the desired operational field of view ͑OFOV͒. 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 optical design process results in a different optimal ͑nonaplanatic͒ design for each OFOV that is even superior to an optimally despaced aplanatic design.

Front Matter: Volume 7071

“…When surface scatter effects and detector effects are included in a complete systems engineering analysis of image quality for such systems, there is often even less merit to an optical design that satisfies the Abbe sine condition. [10][11] Our complete systems engineering analysis of image quality indicated that our optimum non-aplanatic HH SXI design would result in an 80% increase in the number of spatial resolution elements in the solar disc over what could be achieved by the classical Wolter Type I baseline design. Figure 5 is an on-orbit image recorded with the GOES-13 SXI instrument utilizing a non-aplanatic HH grazing incidence X-ray telescope design optimized for an 18 arc min OFOV.…”

Integrating optical fabrication and metrology into the optical design process

“…A detailed analysis of detector effects was also included [52]. Figure 11 shows the comparison of the image quality predictions and experimental on-orbit data taken shortly after launch [51].…”