光栅点衍射干涉法检测Φ400mm瞬态波前

Evaluation of Φ400 mm instantaneous wavefront using grating point diffraction interferometry

提出了一种基于光栅点衍射干涉原理的Φ400mm瞬态波前检测方法。该方法使用位相光栅在参考光与测试光中引入横向错位,即在干涉图中引入线性载频,然后利用傅里叶变换相位解调法提取待测波前。基于标量衍射理论以及傅里叶光学理论建立了瞬态波前检测方案的理论模型,推导了线性载频公式,研究了影响载频大小的因素;基于基尔霍夫公式分析了针孔衍射导致的孔径角变化与能量衰减效应,给出了位相光栅的刻蚀深度公式。实验搭建了Φ400mm瞬态波前检测装置,采集了对比度良好的高线性载频干涉图。采用傅里叶变换相位解调法恢复波面,所得波面RMS值为0.105λ。与采用SID-4波前探测器测得的波面RMS值(0.101λ)基本一致,满足了Φ400mm瞬态波前测量的要求。

A method to measure Ф400 mm instantaneous wavefront based on grating point diffraction interferometry was proposed. The method introduced the lateral displacement into the test wavefront and reference wavefront by applying a phase grating, which means that a linear carrier was introduced in an interferogram. Then, the test wavefront was retrieved by Fourier Transform（FT）. On the basis of scalar diffraction theory and Fourier optics theory, a theoretical model of instantaneous wavefront was established and the formula of linear carrier was derived. Furthermore, the effects of energy reducing and aperture angle changing due to pinhole diffraction were studied by using Kirchhoff formula, then the formula of grating etched depth was derived. An experimental installation of Ф400 mm instantaneous wavefront testing was set up and the interferogram with high modulation and a linear carrier was acquired. The FT method was applied to the restoration of the interferogram. The results indicate that the root mean square value of tested wavefront is 0. 105λ, which is in accord with that of 0. 101λ, acquired by a SID-4 wavefront sensor. It concludes that the measurement of Ф400 mm instantaneous wavefront has been realized by this method.