We continue to develop MOI method to analyze the mutual optical intensity (MOI) propagation through non-ideal optics. Local stationary phase approximation is implemented to calculate the MOI propagating through a non-ideal mirror. The phase generated by the path length from the incident to exit plane is the key to solve the MOI propagation through the mirror. The effect of figure error can be expressed as phase shift. There are two methods to deal with the figure error, the analytical method and numerical one. The two methods are compared at different spatial frequency range of the figure error. An APS beamline is analyzed with the developed MOI model, in which a partially coherent beam with 10keV energy is focused to ~20nm by a non-ideal elliptical mirror. The MOI at the focal plane is acquired after propagation through the non-ideal mirror. The intensity profile, the wavefront and the global coherence degree can be get from the MOI. The results indicate that the figure error with low spatial frequency generates oscillations, redistributes coherence property and damages the wavefront on the image plane. However, the figure error does not change the global coherence degree. Comparison with other codes such as Hybrid and SRW was performed. The results show that MOI model and SRW have similar intensity profiles. The apparent oscillations from MOI model and SRW indicate high coherence. Limitation on the beam size by the BDA and mirror will increase the coherence, which can be quantitatively analyzed by global coherence degree from MOI.
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