大型光学红外望远镜拼接非球面子镜反衍补偿检测光路设计

Optical testing path design for LOT aspheric segmented mirrors with reflective-diffractive compensation

为了实现大口径、长焦距、批量化离轴镜面的高精度面形检验,本文提出了一种零位反衍补偿检测方案,采用计算全息和球面反射镜共同对离轴镜面法向像差进行补偿,检测光路波像差残差接近于零。检测方案为非轴对称离轴结构,设计了相应的全息对准光路,以保证检测光路装调切实可行。不同离轴量子镜检测光路参数完全一致,仅需更换相应位置计算全息片、调整待测镜空间姿态,即可实现不同类型镜面的快速批量化检验。误差分析结果表明,由补偿元件制造误差、光路失调、干涉仪面形测量重复性以及干涉仪标准球面波偏差引起的待测镜面形误差小于λ/40(RMS值,λ=632.8 nm)。

In order to achieve high precision surface testing for the large diameter and long focal length off-axis segmented mirrors,we designed a reflective diffractive compensation null testing system.Using a computer-generated hologram and a spherical mirror to compensate for normal aberration of the off-axis mirror.The design results show that the residual wavefront error of the optical path is close to zero.For a testing system,CGH alignment optical paths corresponding to the non-axisymmetric off-axis structure are designed to ensure the feasibility of the assembly.Parameters of the optical path testing for different off-axis distance mirrors are the same.Rapid high-precision null testing of different types of segmented mirrors can be achieved simply by replacing the CGH at corresponding position and adjusting the spatial positions of the mirror to be measured.Error analysis shows that the RMS error of the mirror surface to be measured is better thanλ/40(λ=632.8 nm),which is caused by the manufacturing error of the compensating elements,misalignment of the optical path,repeatability of the interferometer surface measurement and standard spherical wavefront deviation of the interferometer.