Performance predictions of a Schwarzschild imaging microscope for soft x-ray applications

The design of a Schwarzschild imaging microscope for soft x-ray applications has been reported by Hoover and Shealy. Based upon a geometrical ray-trace analysis of the residual design errors, diffraction-limited performance at a wavelength of 100 Angstrom was predicted over an object size (diameter) of 0.4 mm. We expand on the analysis of that design by determining the total image degradation due to diffraction, geometrical aberrations, and scattering effects due to residual optical fabrication errors. A linear systems treatment of surface scattering phenomena is used to model the image degradation effects of surface irregularities over the entire range of relevant spatial frequencies. This includes small angle scattering effects due to mid spatial frequency surface errors falling between the traditional ''figure'' and ''finish'' specifications. The implementation of this scattering theory as a general performance prediction code is validated by excellent agreement with limited test data for a different Schwarzschild microscope at a wavelength of 73 Angstrom. Finally, image quality predictions are presented parametrically to provide insight into the optical fabrication tolerances necessary to meet desired image quality requirements. (C) 1996 Society of Photo-Optical Instrumentation Engineers.