表面轮廓仪传递函数对超光滑表面粗糙度测量的影响

Effects of transfer function of profilometer on roughness measurement of ultra-smooth surface

表面粗糙度是表征光学元件表面质量的一个重要指标 ,这使得人们不断致力于改进表面粗糙度的测量技术 ,以提高其测量精度。然而很多实验表明 ,在对超光滑表面粗糙度进行测量时 ,对于同一个表面 ,不同类型的表面轮廓仪通常会给出不同的结果 ,这使得测量结果之间的可比性成为问题。针对这种情况 ,本文运用线性系统理论方法 ,分析了表面轮廓仪的带宽对表面粗糙度测量的影响 ,并用离散傅里叶变换方法计算了表面粗糙度测量值随表面轮廓仪带宽的变化。结果表明 ,表面轮廓仪的带宽对表面粗糙度测量有着重要影响 ,轮廓仪的带宽越宽 ,则给出的测量值越大 ,也越接近真实值。因此对两种不同类型的轮廓仪测得的结果一般不能直接进行比较 ,除非两者具有相同的带宽。

Root_mean_square roughness is one of the most important figures that is used to characterize the ultra-smooth surfaces. Many experimental results show that different types of profilometers usually give different results, which make it difficult to compare them. In this paper, the effects of the transfer function of a profilometer on the roughness measurement of ultra_smooth surfaces are analyzed based on linear system theory and simulated with the discrete Fourier transformation method. The results show that because of the limited bandpass of the profilometer, the measured root_mean_square roughness is always less than the real roughness of the surfaces.