The classical Wolter type I grazing-incidence x-ray telescope consists of a paraboloidal primary mirror and a confocal hyperboloidal secondary mirror. This design exhibits stigmatic imaging on-axis but suffers from coma, astigmatism, field curvature, and higher-order aberrations such as oblique spherical aberration. Wolter–Schwarzschild designs have been developed that strictly satisfy the Abbe sine condition and thus exhibit no spherical aberration or coma. However, for wide-field applications such as the solar x-ray imager (SXI), there is little merit in a design with stigmatic imaging on-axis. Instead, one needs to optimize some <i>area-weighted-average</i> measure of resolution over the desired operational field of view. This has traditionally been accomplished by mere despacing of the focal plane of the classical Wolter type I telescope. Here we present and evaluate in detail a family of hyperboloid–hyperboloid grazing-incidence x-ray telescope designs whose wide-field performance is much improved over that of an optimally despaced Wolter type I and even somewhat improved over that of an optimally despaced Wolter–Schwarzschild design.
© 2001 Optical Society of America
(220.1000) Optical design and fabrication : Aberration compensation
(220.2740) Optical design and fabrication : Geometric optical design
(340.7440) X-ray optics : X-ray imaging
(340.7470) X-ray optics : X-ray mirrors
James E. Harvey, Andrey Krywonos, Patrick L. Thompson, and Timo T. Saha, "Grazing-incidence hyperboloid-hyperboloid designs for wide-field x-ray imaging applications," Appl. Opt. 40, 136-144 (2001)