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

研究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板和散射介质（如生物组织）的相位、群折射率和厚度。主要研究成果如下：1.我们提出并证明了一种新的技术，用于同时测量相位和群指数和被测物体的厚度。该技术是基于低相干干涉与精确的平移阶段相结合。在实验中使用的对象扫描方法，测量精度为0.2%或更低，达到了近1毫米厚的透明板。为了实现稳定和紧凑的测量系统，低相干干涉仪由50 x 60 cm ^2.2的光具座上的微光学元件组成。在此基础上，成功地实现了考虑样品色散的n_p和t的自动测量以及使用特定样品保持器的n_p、n_g和t的测量，测量时间仅为3 min.由于补偿了干涉仪中样品臂和参考臂之间的色散不平衡，并采用了交替扫描的方法，即使样品薄至20 μ m，测量精度也能达到<1%.此外，我们的测量系统是适用于散射介质，如生物组织的折射率的精确测量。当载物台分辨率为1 μ m时，对于厚度t大于100 μ m的样品，保证了1%或更小的测量精度。同时测量n和t成功地实现了人的指甲，牙齿，鸡组织和甲壳类动物，具有多层。

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.