低相干光干涉高精度透镜中心厚度的测量方法

Measurement Method of Lens Central Thickness with High Precision Based on Low Coherence Interferometry

阐述了一种基于低相干光干涉技术的透镜中心厚度的测量方法,并设计了腔式测量结构对未知折射率的材料进行中心厚度测量。测量系统为包括低相干测量和激光测距的全光纤结构。低相干测量结构参考臂和激光测距结构参考臂的共光路设计降低了环境因素的影响,提高了测量稳定性,并利用七步相移法实现对干涉信号的定位和提取。另外,利用低相干测量方法中的平衡差分结构去除了干涉信号中的直流项,同时提高了弱信号的定位精度。实验结果表明,该腔式测量结构对殷瓦合金标准块的测量精度优于0.5μm,该系统能够实现对透镜中心厚度的高精度测量,满足高精密光学系统的测量要求。

A lens central thickness measurement method based on low coherence interferometry technique is presented, The cavity measurement structure is designed to measure the central thickness of the material with unknown refractive index. The measurement system is an all-fiber structure including low coherence measurement and laser ranging. The design of common optical path of low coherence measurement structure reference arm and laser ranging structure reference arm reduces the influence of environmental disturbances and obtains a higher measurement stability. The interference signal can be located and extracted by seven-step phase shifting method. By using the balanced differential structure of low coherence measurement method, the direct current item in the interference signal is removed and the positioning accuracy of the weak signal is improved. The experimental results show that the measurement accuracy for Invar standard block from the cavity measurement structure is below 0. 5 μm. The system can realize high precision measurement of lens central thickness, and satisfy measurement request of high precision optical system.