XV Wei，ZHANG Li-min，LIU Chang-hua

（Changchun Institute of Optics，Fine Mechanics and Physics，the Chinese Academy of Sciences，

Changchun 130033，China）

Abstract：Aiming at the support structure of M3 was needed to respond to the effect of gravity and deformation due to temperature changing，a support method was researched based on the kinematic method；an analysis that used finite element method to optimize the

support position by using the optimizing module of ANSYS was made which regarded the RMS value as a target；the deformation of mirror was analyzed and the curve of RMS value changed by different directions of gravity was obtained；the deformation of mirror before and after support were tested by using ZYGO，a result was obtained that the test value of RMS under the effect of gravity was 0.021 λ which was only 0.002 λ ，s bigger than that without support. The results indicate that，this support method can reduce the concentrated

stress due to uncoordinated deformation when the effect of gravity or the temperature change，by making the flexible three-point bottom support and the side support in center to be decoupled，and so to get a fine RMS value. The support method is reliable，the optimized position of support points is feasible.

Key words：kinematic method；the support of M3；optimized analysis