ABSTRACT
The resolution of the Wölter mirror, which is utilized as an objective in soft-x-ray microscopes, is limited by fabrication errors. We studied the relation between fabrication errors and imaging performance of the Wölter mirror to determine how this performance could be improved. Figure errors, which are characterized by low spatial frequency, were analyzed by ray tracing, and surface roughness, characterized by high spatial frequency, was analyzed by modified ray tracing. Modified ray tracing was based on ray tracing but took scattering into account. The results of these analyses were compared with experimental data. As a result, we obtained a simple and practical fabricating tolerance criterion that may be employed to obtain higher Wölter mirror resolution. Additionally, we discuss problems in current Wölter mirror fabrication techniques and the changes that might be made in both the design and the fabrication process to improve imaging performance.
