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空间光调制器(SLM)可以在电驱动等信号控制下,实时调节振幅、相位、偏振态等信息,近年来已被尝试用于代替计算全息(CGH)板实现非球面检测。SLM像素尺寸在3.5~20μm,远大于CGH板刻蚀分辨率,使得SLM的相位调制量在像素尺度离散化,与理想的连续相位存在误差,带来检测精度的降低。因此,有必要评估SLM像素尺寸对检测精度的影响,从而选择合适像素尺寸的SLM。基于菲涅耳衍射原理以及快速傅里叶变换算法,仿真波面经SLM调制并传播到待测表面的过程,并探究待测面处生成波面精度与SLM像素尺寸大小之间的关系。对多组波面进行仿真并分析波面误差分布发现,SLM生成补偿波面误差与SLM像素尺寸所能表示的最大频率相关,检测时需保证SLM像素尺寸所能表示的最大频率大于补偿波面频率最大值。
The spatial light modulator (SLM) can adjust the amplitude, phase, polarization state and other information in real time under the control of electrical driving signals. In recent years, the SLM has been tried to realize the aspheric surface detection instead of the CGH. SLM pixel size of 3.5 ~ 20μm, much larger than the CGH board etching resolution, making the phase modulation SLM discretization pixel size, and the ideal continuous phase error, resulting in lower detection accuracy. Therefore, it is necessary to evaluate the influence of the SLM pixel size on the detection accuracy so as to select the SLM of a suitable pixel size. Based on the Fresnel diffraction principle and the Fast Fourier Transform algorithm, the process of wavefront modulation by SLM and propagation to the surface to be measured is simulated, and the relationship between the wavefront precision generated at the test surface and the size of the SLM pixel is explored. Simulation of multiple sets of wavefronts and analysis of the wavefront error distribution found that the SLM-generated compensation wavefront error is related to the maximum frequency that the SLM pixel size can represent. The maximum frequency that the SLM pixel size can represent is greater than the maximum of the compensation wavefronts.