基于激光干涉的电容位移传感器非线性误差标定方法

Nonlinear Error Calibration Method for Capacitive Displacement Sensor Based on Laser Interferometry

针对微推力测量中电容位移传感器需要频繁标定非线性误差的问题,提出了一种基于激光干涉的现场标定方法。标定原理为:在直线位移台上同时调节可动角隅棱镜与测量目标的位置,进而改变干涉光路光程差及电容位移传感器极板间距,以激光干涉测量结果为基准,采用线性拟合方法,对传感器非线性误差进行标定。搭建了基于常用光学元件的干涉光路,对应用于微推力测量中不同量程的传感器进行标定。在分析干涉光强变化特点的基础上,确定了干涉条纹数计算方法,得到干涉光路的位移测量精度为66.5nm。实验验证了该校准装置的实用性和准确性,最后对标定结果、传感器输出非线性误差以及影响激光干涉测量精度的主要因素进行了分析,得到激光干涉测量总误差为67.2nm。

In order to solve the problem of frequent calibration of nonlinear error for capacitive displacement sensors in micro-thrust measurement, an in-situ calibration method based on laser interferometry is studied. The calibration principle is that the optical path difference and capacitive displacement sensor .plate spacing are changed simultaneously by adjustment and measurement of the positions of movable corner prism and object through the linear displacement, and the nonlinear error of sensor is calibrated by the linear fitting method based on the measuring results of laser interference. The interferometric optical path based on common optical elements is built and sensors with different measuring ranges are calibrated in micro-thrust measurement. Based on the analysis of characteristics of the interference intensity, the calculation method of interference fringe number is determined. The measuring accuracy of interference light path displacement is 66. 5 nm. The practicability and accuracy of the calibration device are verified by experiment. Finally, the results of calibration, the nonlinear sensor output relative error and the main factors affecting the laser interference measurement accuracy are analyzed. The total error is 67.2 nm.