射电天文研究室知识库

针对1.2 m口径天文望远镜非球面主反射镜的镀膜问题,建立了大口径非球面镀膜的膜厚分布模型,使用数值分析的方法计算了非球面镀膜相对于球面镀膜的膜厚分布差异。针对非球面镀膜的膜厚均匀性问题,给出了非球面修正挡板的设计方法。为减少修正挡板的加工成本,提高修正挡板的结构刚度,研究了球面面型挡板用于非球面镀膜的可行性,提出了一种圆周分布式排列的挡板设计方法。结果表明:宽度较窄的分布式挡板能够在避免划伤镜面的前提下更贴近镜面,因而有更好的遮挡效果以达到膜厚均匀性的要求,并且有更低的加工成本、更高的结构刚度,以及能够根据实际情况便捷地进行挡板调整和改造。

The thickness distributionof the metal coatings,deposited by vacuum evaporation on the large aperture aspheric surface ( 1. 2 m paraboloidalprimary mirror of astronomical telescope) ,was mathematically modeled, theoretically analyzed and numerically simulated for design optimization of the correction mask. The simulated results show that the coating’s thickness distribution on the paraboloidal surface resembles that on the spherical surface, though their difference increased with an increase of the aperture radius. For example, the discrepancy was about 0. 2%, indicating the feasibility of spherical masks. A novel type of correction mask,consisting of three rotating narrow spherical lunes,was designed and tested. The results show that the newly-designed correction masks are capable of effectively improving the coatings’thickness uniformity without scratching the paraboloidal surface. Besides, the strengths of the new correction masks included lower fabrication cost,higher rigidity,easier adjustment and simpler modification.