Research on simultaneous measurement of the phase and group indices and the thickness of transparent plates and the scattering medium by the low coherence interferometry

提出了一种实用的低相干干涉仪系统，该系统可以同时测量透明平板和生物组织等散射介质的位相、群折射率和厚度。主要研究成果如下：1.研究成果。我们提出并演示了一种新的技术，用于同时测量被测物体的相折射率、群折射率和厚度。该技术基于低相干度干涉技术和精密平移平台相结合。在物体扫描法的实验中，对近1 mm厚的透明平板的测量精度达到了0.2%或更低。为了实现稳定、紧凑的测量系统，在50×60 cm？2.2的光学工作台上，低相干干涉仪由微型光学元件组成。在该方法的基础上，成功地在3分钟内实现了考虑样品色散的np和t的自动测量，以及利用专用样品保持器测量np、ng和t的方法。由于补偿了干涉仪中样品和参照臂之间的色散不平衡，并采用了交替扫描的方法，即使在样品薄到20um的情况下，测量精度也达到了1%。此外，我们的测量系统还适用于精确测量生物组织等散射介质的折射率。当工作台分辨率为1um时，当样品厚度t大于100um时，测量精度可保证在1%以下。成功地实现了人指甲、牙齿、鸡组织和多层甲壳动物的n和t的同时测量。

The research has been made to demonstrated the practical low coherence interferometer system which can provide simultaneous measurement of the phase and group indices and the thickness of transparent plates and the scattering medium such as biological tissues. Major research results are described in the following.1. We proposed and demonstrated a novel technique for simultaneous 'measurement of the phase and group indices and the thickness of a measured object. The technique is based on the low coherence interferometry combined with precise translation stages. In the experiment using the object scanning method, the measurement accuracy of 0.2% or less was attained for nearly 1-mm thick transparent plates. To realize a stable and compact measurement system, the low coherence interferometer consisted of micro-optic components on a optical bench of 50 x 60cm^2.2. On the basis of our proposed method, the automatic measurement of n_p and t taking the chromatic dispersion of the sample into account and the measurement n_p, n_g and t using the specific sample holder were successfully achieved within three minutes.3. The measurement accuracy of <1% was achieved even when the sample is as thin as 20mum, because of compensation for the unbalance of the chromatic dispersion between the sample and reference arms in the interferometer and using the alternative scanning method.4. Moreover, our measurement system is applicable for accurate measurement of refractive index of the scattering medium such as biological tissues. When the stage resolution is 1mum, the measurement accuracy of 1% or less is guaranteed for the sample thickness t more than 100mum. Simultaneous measurement of n and t were successfully achieved for a human nail, tooth, chicken tissue and a crustacean which has multiple layers.