无限共轭距物镜的数值孔径全自动测量方法与系统

提出了一种针对无限共轭距显微物镜的数值孔径测量方法,采用载玻片与空气界面处的全反射效应以及其在物镜的后焦面产生的全反射圆作为数值孔径参考基准,根据阿贝正弦定理推导出物镜的数值孔径。完成了基于该原理的实验测试系统的研发,包括光学系统、控制系统和完整的后焦面算法流程。其中的图像处理算法采用了二维傅立叶相关分析和灰度统计。对若干实际的油浸物镜的数值孔径进行了测量,结果表明本方法相对误差低于1%,远低于本文对比的其它方法。本方法对应的实验测量装置简单,可快速、全自动化地对实际的油浸物镜的数值孔径进行测量,且测量结果具有高精度和高重复性的优势,能直接用于无限共轭距油浸物镜的数值孔径测量,解决当前制约我国高端镜头检测方面的困难,具有很好的应用前景。

Approach and system for automatic numerical aperture measurement of infinite conjugate objective

Proposes an approach to measure the numerical aperture (NA) of the infinite conjugate objective. It utilizes the total internal reflection (TIR) phenomenon occurring on the air-coverslip interface to generate a reference on the back focal plane (BFP), and the NA is measured based on Abbe sine condition. According to the principle, a home-designed measurement system is developed, containing the optical system, the control system and the whole image-processing software to extract the NA value from experimentally acquired BFP images. The algorithm of the image-processing software utilizes the two-dimensional Fourier correlation analysis and grayscale statistics. The NA values of several objective lenses are measured experimentally. The results indicate that the relative error of the proposed method is no more than 1% , much lower than that of the other method compared in this work. The proposed method features on the simple measurement configuration and fast and automatic measurement of the NA of practical oil-immersion objective lenses. The results show high precision and good repeatability. The approach works for the NA measurement of the infinite conjugate oilimmersion objective lenses.