光学外差法检测超光滑表面粗糙度

Measurement of the Roughness of Supersmooth Surface Using Optical Heterodyne Method

随着加工技术的发展，超光滑表面粗糙度的测量变得越来越重要．讨论了一种利用光学外差法检测超光滑表面粗糙度测量系统，采用Ｚｅｅｍａｎ效应激光管得到差频光束，提出了新的优化测量光路．该光路仅使用一个半波片改变一路光束的偏振态，不仅克服了以前广泛使用的类似测量系统中光路具有可逆性的缺陷，保证了系统的稳定性，且同时使接收端光束的偏振态方向一致，使干涉信号可见度最大，提高了系统的信噪比和测量精度．采用两光束同心聚焦扫描方法可实现表面粗糙度的绝对测量．光路结构简单，实用性强．通过样品测量研究了本系统的测量稳定性和测量精度．结果表明，系统对表面粗糙度测量精度均方根值小于１ｎｍ．

It investigated a measurement system of the roughness of supersmooth surface using optical heterodyne method and gave a novel architecture of optical path. The system used Zeeman laser as a light source. The architecture of this optical path only used a half wave plate to change the state of polarization (SOP) laser beam in one path. It not only overcame the fault of the previous system whose optical path was reversible and so to ensure the stability of system, but also got the maximum interfere visuality by the same state of polarization of laser beams at receivers. So the signal to noise ratio of the system was improved and the precision of measurement increased. Moreover, using two concentrical laser beams to scan the surface, it got the absolute root mean square values of supersoomth surface roughness. The stability and accuracy of this system were researched and the RMS value of a sample was given. The results show that RMS value is less than 1 nm.