利用全反射及移相干涉術量測物質的折射率分佈

Abstract

在此利用p-偏光在待測物與玻璃界面上的TIR效應，由於在角度接近臨界角時，入射角對相移的影響很大，藉由該效應所引起的相位變化，我們可以進一步利用干涉的方式，推得透明生物組織在二維空間中的折射率分佈。本研究中提出一量測系統，用來量測透明生物組織的結構，在本系統中，將僅有p-偏光分量的平行光入射至一Twyan-Green干涉儀中，入射光被干涉儀中的beam splitter(BS)分為參考光以及測試光兩部份：參考光經過一由PZT推動的反射鏡反射之後，循原路再次回到BS，得到一個參考相位，測試光經由放置在精密旋轉台上的面鏡引導，入射至一直角稜鏡使其在底部界面滿足全反射條件，全反射後的測試光由稜鏡另一側穿出，並垂直入射到面鏡上，最後經由面鏡垂直反射使得測試光循原光路回到BS，後與參考光形成干涉條紋，並以CCD擷取，擷取的資料利用電腦軟體IntelliWaveTM分析該資料，並進一步的計算得知相位分佈。經由將放置待測物前後的相位分佈相減，可得因為待測物所引入的額外相位差，將此相位差經由計算之後即可推得折射率的分佈，能將透明物質分佈情形，利用此法將其解析出來，最終目標是將折射率分佈在1.4~1.6附近，浸泡於水中的透明物質，能夠以此法簡單而又快速地量測。本法與傳統方法相比較，對待測物不具破壞性，並具有操作簡單、精確、迅速以及方便等優點。

We make use of the TIR effect of p-polarization on the interface between test materials and prism whose base is contacted with the test material. Due to this effect, the incident angle greatly affects the phase shift as the incident angle approaches the critical angle. We can measure the phase shift accurately with phase-shifting technology. Then the two dimensional refractive index distribution of the test material can be derived with the measurement of the phase shift. We propose a optical configuration to distinguish the structure of transparent biological tissue. A collimated light of p-polarization is incident into a Twyman-Green interferometer and is divided into reference light and test light by a BS. Reference light is directly reflected by a Mirror mounted on a PZT and propagates back to the BS. This gives a reference phase. Two mirrors mounted on a rotation stage lead the test light to the prism. Test light is then incident on the prism surface and propagates toward the base surface of the prism. At the base surface of the prism, there is a boundary between the prism and the test material with refractive index distribution to measure. Test light is totally reflected under the condition of total internal reflection. The totally reflected test light passes through the prism and it is normally incident on a mirror. Then the test light propagate back along the original path. Finally, the reference and the test light combine together and a CCD camera can take its associated interferograms. The captured interograms are sent into IntelliWaveTM for future Analyzing and we can calculate the phase distribution. Subtracting the phase distribution without test materials from the one with test materials, we can obtain the extra phase introduced by the existence of the test material. We can calculate the refractive index distribution from the extra phase information. And then we can distinguish the structure of the transparent biological tissue. Our goal is to swiftly and easily distinguish the transparent tissue immersed in the water whose refractive index ranging from 1.4 to 1.6 by the optical configuration. Comparing to the tranditional method, proposed method has the advantages of non-destructive、easily to operate、accurate、swift and convenient.