Fast optimal design of a flexure for lightweight, horizontally supported mirror

Abstract

Due to optical performance requirements, the primary mirror assembly must have the ability to be unaffected by environmental influences. These environmental influences include gravity, assembly error, and thermal change, by which external loads are imposed on the mirror. The external loads degrade the mirror surface accuracy and cause misalignment between mirrors. We describe a method to determine the allowable external loads. The performance of a flexure is evaluated by the transmitted loads to the mirror. The force acting on the mirror was analyzed under various conditions and the influence functions were obtained using inertia relief. With the knowledge of influence functions, the relationship between external loads and mirror surface distortion was built. According to the error budget of the primary mirror, the permissible loads required of the flexure were directly established. The optimization was achieved through optimizing the compliance of the flexure without mirror. With our method, the mirror design and flexure design are decoupled, and time and resources required for optimization are reduced. A parallel flexure is demonstrated for a 2-m lightweight, horizontally supported mirror.