二元伪随机光栅与台阶校准检测系统传递函数的影响分析

采用高质量的标准位相结构是实现光学干涉检测系统的系统传递函数精确校准及保证光学元件波前/表面中高频段信息准确检测的前提。通过对二元伪随机光栅结构和台阶位相结构两类典型表面进行模拟,分析了空间周期误差及跃变边缘陡度等制造误差对于检测系统传递函数校准的影响,并分析了检测系统CCD对二元伪随机光栅欠采样和过采样时功率谱密度(PSD)的变化。结果表明：存在同等制造误差时,二元伪随机光栅结构比台阶位相结构对检测系统传递函数中高频能够实现更高精度的校准；当对二元伪随机光栅存在欠采样或过采样时,均会造成PSD随频率的下降,可通过对理想二元伪随机光栅的高度分布进行相应的采样修正消除因采样对传递函数校准的影响。

Effect of binary pseudo-random grating and step on system transfer function calibration of interferometric measurement system

Using standard phase structures with high quality is the precondition for accurate calibration of system transfer function(STF) of the interferometric measurement system, which guarantees the accurate measurement of the optical wavefront or surface informations in the mid and high spatial frequency bands. Two types of typical standard phase structures are simulated and analyzed, one is the binary pseudo-random(BPR) grating, and the other is the step. According to the comparison of the effect of the fabrication imperfections on the measurement of system transfer function between the BPR grating and the step, more reliable calibration of the STF in mid and high spatial frequency bands can be obtained using BPR grating as the standard, when the error parameters are the same. The changes of the corresponding PSD are also analyzed, when the BPR grating is oversampled or undersampled by CCD, the PSD will decline with the frequency, and the effect of sampling on the STF calibration can be removed by modifying the height distribution of the theoretical BPR grating.