将变焦透镜组的方法用于解决光纤低相干测厚系统中光束损失问题，介绍了一套基于光纤低相干干涉技术的测厚装置。根据光纤耦合条件与光纤出射光束能量分布规律，给出了关于光束耦合效率受光束横向尺寸与反射面曲率半径影响的分析；理论分析了变焦透镜组引入侧厚系统后耦合效率的提升效果。实验证明，引入变焦透镜后信号损失情况明显得到改善，该系统的相对测量误差小于0.05%。

A thickness measurement device based on low-coherent fiber-optic interferometry is proposed to solve coupling loss in thickness measurement system by using zoom lenses. According to optical fiber coupling condition and beam energy distribution，the light beam coupling efficiency influenced by the transverse size of the light beam and the curvature radius of surface is analyzed. Enhancing effect of coupling efficiency is theoretically analyzed when zoom lenses are applied to thickness measurement device. The experimental results show that the signal intensity is obviously improved via the introduction of zoom lenses and the relative measurement error of device is less than 0.05%.