结合CGH与辅助透镜的长焦距非球面反射镜检测（特邀）

目前，一些大口径光学望远镜主镜的曲率半径已经达到了几十米量级，若单纯利用计算全息实现对镜面进行面形检测，则检测光路长度不低于其曲率半径长度。受场地大小及环境气流扰动等因素的限制，该条件下难以实现对镜面的高精度测量。为了解决大口径长焦距光学镜面的高精度面形检测问题，提出了一种混合补偿干涉检测方法。该混合补偿方法结合了计算全息图和辅助透镜，在有效地缩短检测光路长度的前提下，可以实现对非球面镜面的零位补偿干涉测量。在光路设计中，需要有效地实现混合补偿光路光学设计参数优化以及对CGH衍射级次的分离；同时，检测光路长度应小于非球面反射镜曲率半径大小，以实现缩短检测光路长度的目的。通过对EELT主镜镜面进行仿真检测，结果表明:该方法检测光路长度可缩短至镜面曲率半径长度的1/8以内，设计检测精度优于RMS λ/100 （λ=632.8 nm）。上述仿真结果证明了该方法可以在缩短检测光路长度的情况下实现对待测非球面反射镜的高精度面形检测。

Long focal length aspherical mirror testing with CGH and auxiliary lenses (invited)

At present, the radius of curvature of the primary mirror in some large-aperture optical telescopes has reached the order of tens of meters. If the surface of the mirror is tested simply by CGH, the length of the testing optical path is not lower than the length of its radius of curvature. Due to factors such as site size and ambient airflow disturbance, it is difficult to achieve high-precision measurement of the mirror surface under these conditions. In order to solve the problem of high-precision surface testing of large-aperture long focal length optical mirror, a hybrid compensation method is proposed. This hybrid compensation method combines CGH and auxiliary lenses to effectively shorten the length of the testing optical path, and can realize null testing of aspherical mirrors. In the optical path design, it is necessary to effectively optimize the optical design parameters of the hybrid compensation optical path and the separation of the CGH diffraction order. At the same time, the optical path length should be less than the radius of curvature of the aspherical mirror to achieve the purpose of shortening the length of the testing optical path. By testing the EELT main mirror, the simulation test shows that the testing path length of the method can be shortened to less than 1/8 of the length of the radius of curvature of the surface. Designing testing accuracy is better than that of RMS λ/100 (λ=632.8 nm). The above simulation results show that this method can not only realize the shortening the length of the testing optical path, but also achieve the high-precision surface testing of the aspherical mirror.