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3.5~20 μm, 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。

Spatial light modulator (SLM) is an alternative product as it can change the distribution of amplitude, phase and polarization state under the control of the electric signals. In recent years, SLM is used in aspheric testing in place of the computer generated holography (CGH) plate. However, SLM pixel pitch is around 3.5~20 μm, which is much larger than the CGH plate etching resolution and the phase modulation is discrete, error existing with ideal continuous phase modulation and causing detection accuracy reduction. So it is necessary to consider the influence of SLM pixel pitch on detection accuracy so as to choose SLM with proper pixel pitch. Wave-front reconstructed by SLM and spread to the measured surface process is simulated based on Fresnel diffraction theory and fast Fourier transform algorithm. And the relationship between the reference wave-front precision and SLM pixel pitch is analyzed. Several sets of wave-front are computed and the error distribution is analyzed. The conclusion is that the SLM generation compensation wave-front is related to the maximum frequency presented by SLM pixel pitch, and it is necessary to keep the maximum frequency presented by SLM pixel pitch above the compensation wave-front maximum frequency range.