测量精度达3.2nm的在线表面粗糙度外差干涉仪信号处理系统

A Signal Processing System of the On Line Heterodyne Interferometer for Measuring Surface Roughness with Accuracy of 3.2nm

介绍了用于磨床加工的光外差表面粗糙度在线干涉测量仪整机的信号处理系统，着重讨论了其中的两项关键技术，即利用负反馈构成的宽动态范围测量信号的自动电压控制以及依据计大数和测小数相结合的高精度动态相位测量，系统的测量精度达２．６°（相当于３．２ｎｍ），允许测量中最大多普勒频移±１０ｋＨｚ（对应高度的变化率±８．７５×１０－３ｍ／ｓ），完全满足磨床加工中表面粗糙度在线测量的要求。现场测试证实了这一点，这对于精加工、超精加工表面粗糙度的在线质量控制、提高加工精度等非常重要。

A signal processing system of the on line heterodyne interferometer for measuring the surface roughness of the workpiece on the grinding machine is presented in the paper.The two key techniques,i.e.,automatic voltage control for the wide dynamic range measuring signal by use of negative feedback and the high precision dynamic phase measurement based on the combination of large numbers and small numbers,are discussed.The accuracy of the measuring system has be as high as 2.6° (equivalent to 3.2 nm).The permissible maximum frequency in measurement is ±20kHz (corresponding to the height variation ±8.75×10 -3 m/s).This fully meets the requirements in the on line measurement of the surface roughness in grinding machine processing.These have been demonstrated in the field.It is very important for the on line quality control and the improvement of the processing accuracy of the surface roughness in the fine processing and ultra fine processing.