基于计算全息的大口径离轴非球面子镜的折衍混合补偿检测方法

Large Aperture Off-Axis Aspherical Segment Test Using Refraction and Diffraction Mixed Compensation Based on Computer Generated Hologram

提出一种基于计算全息元件(CGH)的折衍混合补偿检测光路,通过CGH和消球差透镜组合实现离轴子镜的缩焦零位检测。该方法使得检测光路长度减少至CGH直接检测的1/4至1/8,同时提高了小焦比子镜的调节灵敏度,将大离轴量子镜的干涉图长宽畸变比率由12.5优化至1.25。保持光路各器件位置不动,通过更换相应的计算全息片,还可实现不同离轴量子镜的批量高效检测。应用该方法完成直径为330 mm的离轴试验镜的加工与检测,测试结果面形均方根(RMS)值为0.0290λ(λ为波长)。通过标准球面镜对消球差透镜进行标定,RMS值降至0.0267λ。

In this paper,a refraction and diffraction mixed compensation test optical path based on computer-generated hologram(CGH)has been proposed,and the combination of the CGH and aplanatic lens is realized to measure the off-axis segment in null test with focal reducing.The total length has been reduced to 1/4 to 1/8 of that of the conventional method.And the adjustment sensitivity of the small focus ratio segment has been improved.The distortion ratio of the interferogram of the large off-axis segment has been optimized from 12.5 to 1.25.The segments with different off-axis distances can be measured rapidly with high precision by replacing different computer-generated holograms and keeping every elements in place.The method is used to complete the processing and testing of aΦ330 mm off-axis trial mirror,and the root mean square(RMS)value of the test surface figure is 0.0290λ(λis wavelength).The RMS value of the test surface figure is reduced to 0.0267λ,by calibrating the aplanatic lens using a standard spherical mirror.