An enhanced optical design for wide-field imaging X-ray astronomy telescopes

Wolter-1 (W1) and Wolter-Schwarzschild (WS) optical designs are widely used for narrow-field X-ray observations, providing high angular resolution along the axial direction. However, surface figure errors in mirror fabrication limit the theoretical on-axis resolution. Additionally, these designs suffer from inherent optical aberrations, resulting in a broader point spread function (PSF) at wider field angles, making them inefficient for wide-field applications, such as X-ray survey missions or solar X-ray imaging telescopes. To address these limitations, we introduced the Field-angle Optimized (FO) design, which is coma-free, similar to WS, but optimized to deliver a sharp PSF at any specified field angle. The FO design minimizes PSF size across all field angles, providing better overall imaging performance when averaged across the entire field of view compared to W1 and WS. The improvement in the performance of the FO design remains consistent across various telescope parameters, such as focal length, diameter, and mirror length, making it adaptable to different telescope configurations. The FO design provides significant improvements in wide-field X-ray imaging, enabling more efficient astronomical surveys and solar observations.