[OPTICAL REVIEW Vol. 13, No. 3 (2006) 149-157]
© 2006 The Optical Society of Japan

Analytical Designing of Two-Aspherical-Mirror Anastigmats Permitting Practical Misalignments in a Soft-X-Ray Optics

Mitsunori TOYODA and Masaki YAMAMOTO

Research Center for Soft X-Ray Microscopy, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan

(Received July 6, 2005; Accepted March 4, 2006)

A new analytical method of designing two-aspherical-mirror anastigmats was developed and applied to searching solution groups of soft X-ray microscopes of a large misalignment tolerance. The two-mirror anastigmat configurations were expressed by a practical variable related to pupil obstruction limiting the system throughput. Axial coma and other aberrations caused by a slight decenter of the system were then formulated to represent sensitivity to misalignment. These formulations enabled a global survey of solution groups as demonstrated by a designing example of soft X-ray microscopes with a magnification m=-1/50, which resulted in four solutions more insensitive to misalignment than a standard Schwarzschild optics in the soft X-ray region. Some solutions were also found to have much larger fields of view suitable for high resolution imaging as confirmed by computer ray tracing.

Key words: anastigmat, aspherical mirror, misalignment, soft X-ray, microscope