Glossary term: 反射镜
Description: 反射镜是一种从其表面反射光线的光学设备。凸面镜能使光束发散，而凹面镜则能使光束会聚。凹面镜可以经过塑形，从而使平行光束聚焦到一点。大多数现代望远镜都使用大型凹面镜作为主要集光区。
天文望远镜中使用的大多数反射镜的主体都是由玻璃制成的。镜体有时使用的其他材料包括陶瓷和金属。镜体需要经过研磨（或塑形）并抛光，如果材料本身不具有反射性，则会在表面涂上一层薄薄的金属涂层。铝是最常见的涂层材料，而金或银也是可选择的涂层材料。
对于直径超过6米的望远镜来说，铸造并支撑如此巨大的玻璃反射镜非常困难。因此，如今世界上最大的一些望远镜使用了许多较小的反射镜，这些反射镜排列在一起，就像一面巨大的反射镜一样聚焦光线。
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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
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