基于相关和最小二乘原理的光栅栅距动态测量

Dynamic measurement method of grating pitch based on correlation and least square principle

栅距是光栅位移精密测量的基准,测出栅距值是进一步提高位移测量精度的关键。根据光栅莫尔条纹的动态特性,提出在光栅传感器运动过程中将栅距量转换为时间量测量的新方法。首先基于相关原理测量莫尔条纹信号经过两个距离固定的光电转换器的时间延迟来获得传感器的运行速度,时延估计采用了小波自适应算法;其次基于最小二乘原理确定莫尔条纹信号的相邻两个最小值来获得光栅栅距所对应的时间;最后由运行速度与栅距所对应时间的乘积确定栅距值。实验结果表明对于20μm栅距的光栅传感器测量误差小于0.08μm,验证了方法的可行性。

Grating pitch is the benchmark of accurate grating displacement measurement;measuring the pitch value is the key of further improving displacement measurement accuracy. According to the dynamic characteristics of grating Moir6 fringe, a new grating pitch measurement method is proposed ,which converts the pitch measurement to time meas- urement in the motion process of grating sensor. Firstly, based on the correlation principle the time delay within which the Moir6 fringe signal passes through two fixed distance photoelectric converters is measured, and then the sensor mov- ing speed can be obtained;the time delay is estimated with the wavelet adaptive algorithm. Secondly, the time corre- sponding to the grating pitch can be obtained according to the two adjacent minimum values of the Moir6 fringe signal that are determined based on the least squares principle. Finally, the pitch value is determined according to the product of the moving speed and the corresponding time of the pitch. The experimental results show that the measuring error is less than 0. 08 μm for the grating sensor with the pitch of 20μm,which verifies the feasibility of the method.