The resolution of the Wolter mirror, which is utilized as an objective
in soft-x-ray microscopes, is limited by fabrication errors. We studi
ed the relation between fabrication errors and imaging performance of
the Wolter 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. Th
e results of these analyses were compared with experimental data. As a
result, we obtained a simple and practical fabricating tolerance crit
erion that may be employed to obtain higher Wolter mirror resolution.
Additionally, we discuss problems in current Wolter mirror fabrication
techniques and the changes that might be made in both the design and
the fabrication process to improve imaging performance. (C) 1998 Optic
al Society of America.