Experimental and numerical studies of stitching interferometry for optical testing of large space telescopes

望远镜的波前误差通常是用光学干涉仪通过平面反射镜自准直来测量的。然而，对于大型（>1米）望远镜，很难制造尺寸与望远镜相当的精确平面镜，因此很难一次测量望远镜的全孔径。相反，小型移动的平面镜用于测量子光瞳，然后将它们缝合到整个孔径。在这项研究中，拼接测量的80厘米的望远镜与30厘米的平面镜与我们的软件进行。用一个高精度的平面镜重复测量，然后用另一个设计的大变形平面镜重复测量。验证了拼接干涉法的可行性。同时还发现，平面镜的误差对拼接结果有很大的影响。最后，在软件中实现了一种新的算法，发现它减轻了平面镜误差。

In general, the wave-front error of a telescope is measured by using an optical interferometer through autocollimation by reflecting flat mirrors. For a large (>1 m) telescope, however, it is difficult to manufacture accurate flat mirrors with sizes comparable to the telescope and thus to measure the full aperture of the telescope at one time. Instead, small mobile flat mirrors are used to measure the sub-pupils and then stitch them to the whole aperture. In this study, stitching measurements of a 80-cm telescope with a 30-cm flat mirror were conducted with our software. The mesurements were repeated with a high-precision flat mirror and then with another flat mirror which has a designed large deformation. As a result, the feasibility of the stitching interferometry is verified. It is also found that the error of the flat mirror gives a serious impact on the stitching result. Finally, a new algorithm is implemented in the software to find that it mitigates the flat mirror error.