Ford Helen D, Francis Daniel, Hallam Jonathan M, Tatam Ralph P
Appl Opt. 2019 Aug 20;58(24):6474-6485. doi: 10.1364/AO.58.006474.
Confocal scanning combined with low-coherence interferometry is used to provide remote refractive index and thickness measurements of transparent materials. The influence of lens aberrations in the confocal measurement is assessed through ray-trace modeling of the axial point-spread functions generated using optical configurations comprised of paired aspherics and paired achromats. Off-axis parabolic mirrors are suggested as an alternative to lenses and are shown to exhibit much more symmetric profiles provided the system numerical aperture is not too high. The modeled results compare favorably with experimental data generated using an optical instrument comprised of a broadband source and line-scan spectrometer. Refractive index and thickness measurements are made with each configuration with most mirror pairings offering better than twice the repeatability and accuracy of either lens pairing.
共焦扫描与低相干干涉测量相结合，用于对透明材料进行远程折射率和厚度测量。通过对由成对非球面镜和成对消色差透镜组成的光学配置所产生的轴向点扩散函数进行光线追迹建模，评估共焦测量中透镜像差的影响。建议使用离轴抛物面镜替代透镜，并表明只要系统数值孔径不太高，其表现出的轮廓要对称得多。建模结果与使用由宽带光源和线扫描光谱仪组成的光学仪器生成的实验数据相比具有优势。对每种配置进行折射率和厚度测量，大多数镜组的重复性和精度都优于任何一种透镜组的两倍。
