Research on simultaneous measurement of refractive index and thickness of bilogical tissue by low coherence interferometry

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The research has been made to demonstrated a novel low coherence interferometer which can provide simultaneous measurement of the refractive index and thickness of biological tissue. Major research results are described in the following.1. We proposed and demonstrated a novel technique for simultaneous measurement of refractive index n and thickness t of a measured object. The technique is based on the low coherence interferometry combined with precise translation stages. It is applicable for accurate measurement of refractive index of biological tissue. The measurement accuracy of <0.1% is expected for a thickness of more than 1mm. In the experiment using the object scanning method, the accuracy of 0.2% or less was attained for nearly 1-mm thick transparent plates.2. On the basis of our proposed method, refractive index and thickness measurement were successfully achieved for a human nail, tooth, chicken tissue and a crustacean which has multiple layrs.3. We suggest that this method is applicable for birefringence measurement without any polarization control. The ordinary and extraordinary indices, n_o and n_e of a X-cut LiNbO_3 plate were measured.4. Moreover, we propose and demonstrate a novel technique for simultaneous measurement of plase and group lidices n_p and n_g of a transparent plate, as well as the thickness t, using the low coherence interferometer where a single superluminescent diode is used as the light source.5. To realize a stable and compact measurement system, the low coherence interferometer consisted of micro-optic components on a breadboard of 50 x 50cm^2.