基于全息补偿检验非球面的原理,提出并设计了一种二元纯相位型双计算全息图。该全息图由主全息和对准全息两部分组成,用于检测非球面的主全息位于基底的中心,而对准全息位于其边缘,用来精确定位主全息,从而消除离焦、偏心及倾斜所引入的误差。两部分全息同心是实现对主全息准确定位的前提,为此,提出了"一次曝光,两次刻蚀"的制作方法,即一次性将两部分图形在同一块掩膜版上制作出,曝光一次后,基底经两次刻蚀制作出具有两种不同相位深度的双计算全息图。最后给出了一个检测Φ140、F2抛物面镜的双计算全息设计实例,并将其检测结果与自准直检测结果比较,二者吻合良好,验证了该设计方法的正确性及制作工艺的可行性。

Based on the principle of testing aspherical surfaces with Computer-generated Holograms (CGH), a binary phase twin CGH is proposed and designed. It consists of two segments, namely main CGH and alignment CGH. Main CGH, fabricated on the inner part of a substrate, is used for testing an aspherical surface. The outer segment is alignment CGH, used for aligning the main CGH accurately by eliminating errors such as defocus, decentration and tilt on the premise that they are concentric with each other. A fabricating method which is able to manufacture twin CGHs with two different phase depth is introduced. Both holograms are fabricated on one mask simultaneously. After being exposed, the substrate is etched twice. Finally, a design example of twin CGH for testing a paraboloidal mirror (Φ140、F2) is presented. The validity of design method and the feasibility of fabrication process are demonstrated by comparing the test result with that of the autocollimation test.