南方基地知识库

膜厚均匀性是制备高性能光学薄膜的一项重要指标。为进一步提高2.4 m主镜反射膜膜厚均匀性，针对大口径望远镜镀膜设计了膜厚均匀性优化方案。基于真空热蒸发遵循的余弦分布律，结合ZZ3200型真空镀膜机的几何结构和望远镜镀膜的实际需求，编写膜厚计算程序，模拟膜厚理论分布情况，给出膜厚优化设计方法和优化结果。方法一：在蒸发源内侧合适的位置加入修正挡板，结果表明，挡板的曲率半径安装误差在3 mm以内，膜厚均匀性峰谷（Peak to Valley, PV）值由不加挡板时的15%下降到4%,该方法具有一定的普适性，但是挡板安装位置要精确控制；方法二：结合反射主镜中间的圆孔结构，设计双圈蒸发源，结果表明，当内外圈蒸发源的中心距分别为10 cm和130 cm,且满足外圈蒸发源的数量为内圈的12倍时，膜厚均匀性峰谷值为1.85%。该方法是针对中心具有圆孔镜面设计的，适用于大多数反射式天文望远镜镀膜。 

Film thickness uniformity is an important indicator for the preparation of high-performance optical films. In order to further improve the uniformity of the film thickness of the 2. 4 m primary mirror reflective film, an optimization scheme for the film thickness uniformity of the large-aperture telescope coating is designed. Based on the cosine distribution law followed by vacuum thermal evaporation, combined with the geometry of ZZ3200 vacuum coater and the actual needs of telescope coating, a film thickness calculation program is written to simulate the theoretical distribution of film thickness. The film thickness optimization design method and optimization results are given. Method 1: Add a correction mask at a suitable position inside the evaporation source, the results show that the radius of curvature of the mask is installed within 3 mm, and the Peak to Valley value of film thickness inhomogeneity decreases from 15% to 4% without mask, this method has certain universality, but the installation position of the mask should be accurately controlled; Method 2: Combined with the circular hole structure in the middle of the reflection primary mirror, the double ring evaporation source is designed, and the results show that when the center distance between the inner and outer ring evaporation sources is 10 cm and 130 cm, respectively, and the number of evaporation sources in the outer ring is 12 times that of the inner ring, the PV value of film thickness uniformity is 1. 85%, which is designed for the mirror with a round hole in the center, and is suitable for most reflective astronomical telescope coatings.