Bending Mode Correction on a 1.23m SiC Microscopy Scale System

Considering high stiffness of the large SiC mirror, the orthogonal bending mode which is calculated from the mirror influence matrix is used to optimize active force and improve correction capability. First, a finite element model of a 1.23m SiC mirror and support system is employed to verify the algorithm's validity. Then, a 1.23m SiC mirror active support system is set up to correct surface using bending mode, and a further optimize of the algorithm is made based on this microscopy scale system. Finally, surface is corrected from 0.248 lambda, RMS to 0.056 lambda, RMS (lambda=632.5nm). Result of the analysis and experiment shows that using bending mode can efficiently reduce active force range and improve correction capability. It is significant for active correction of high stiffness large SiC mirror.