相位凝固技术中干涉信号调制解调误差分析

Error analysis of interference signal modulation and demodulation in phase freezing technique

为了进一步减小基于相位凝固技术的激光反馈干涉系统测量运动物体微位移时的测量误差,采用MATLAB数值仿真及曲线拟合的方法,对移相间隔和外腔反射面振动幅度引起的系统误差进行了理论分析。在系统实验中依据相位凝固原理对物体运动产生的干涉信号进行采样,获取多组光功率曲线,在光功率曲线上实时判向并标记特征点。根据特征点重构被测物体的微位移曲线,对重构得到的微位移台阶曲线进行多项式拟合以提高测量精度。结果表明,在固定移相间隔为π/5、激光器波长为1550nm的情况下,测量分辨率优于λ/20(77.5nm),实际测量的绝对误差最大值为47.98nm,峰峰值误差平均值小于1nm。相位凝固技术调制解调干涉信号为微位移的方向辨识和高精度测量提供了新的解决方案。

In order to reduce measurement errors with a laser feedback interference system measuring micro displacements of moving objects based on phase freezing technique,system errors induced by intervals of phase shift and vibrating amplitudes of reflecting surface were analyzed theoretically by means of MATLAB numerical simulation,interpolation and curve fit. In system experiments,interference signals produced by moving objects were collected and sampled by phase freezing principle so as to obtain multiple curves of optical power. Feature points were marked on the optical power curves to judge moving direction and reconstruct micro-displacement curves. Polynomial fitting based on the reconstructed micro displacement curves improved system measurement precision. Experimental results show that measurement resolution is superior to λ /20（77. 5nm） when fixed interval of phase shift is π /5 and wavelength of laser is1550 nm. The maximum absolute error of actual measurement of micro-displacements is 47. 98 nm and the average value of peak-peak errors is less than 1nm. Phase freezing technique provides a new solution for laser feedback interferometer system to identify directions and realize high precision measurement of micro-displacements.