Research on the High Tolerance Flexible Support Structure for the Primary Mirror in Cassegrain Optical Systems

Conventional mirror support structures often fail to meet optical system tolerances due to inadequate mitigation of the installation stresses caused by machining-induced surface irregularities and inclinations. This study proposes a novel single-point central support using an arc-shaped flexible hinge. Materials for the mirror and support structure are carefully selected based on their properties, and the optimal dimensions are determined through stiffness analysis. The new flexible support structure is detailed in this work. Simulations show that the mirror assembly achieves a first-order frequency of 296.66 Hz. Under separate triaxial gravitational and thermal loads at −40 °C and 50 °C, the mirror’s surface figure accuracy RMS remains better than λ/45 (λ = 632.8 nm). With a 0.008 mm forced displacement applied to the installation surface, the RMS change in the mirror’s surface figure is less than λ/200, meeting structural design specifications. In practical assembly tests, even when surface irregularities exceed tolerances by more than double, the RMS change in the mirror’s surface figure is only 7 nm. This design effectively ensures high-precision surface quality while significantly reducing assembly difficulty and installation surface precision requirements, achieving a large-tolerance assembly. It provides a valuable reference for mirror support design in imaging optical systems.