Full-field refractive index measurement of a liquid using highly sensitive total-internal-reflection phase-shifting interferometry

• Main Author: 詹前偉
• Other Authors: 林俊佑
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/69jp2a

碩士 === 國立彰化師範大學 === 機電工程學系 === 102 === In this thesis, we propose a highly sensitive total-internal-reflection (TIR) phase-shifting interferometry for measuring the full-field refractive index of a liquid. A linearly-polarized expanding beam after passing through a Soleil-Babinet compensator and a spatial filter penetrates into a high-sensitivity TIR apparatus. The apparatus comprises a phase level shifter (being formed by combining a half-wave plate and two quarter-wave plates that exhibit specific optic-axis azimuths), an isosceles right-angle prism whose base is directly contacted with a tested substance, and an analyzer. The interference intensity of the TIR beam output from the apparatus is captured by a CCD camera. Using the four-step phase-shifting method by controlling the Soleil-Babinet compensator, the full-field phase difference used to determine the full-field the refractive index of the tested substance is obtained. Because the full-field phase difference exhibited by the full-field refractive index is associated with the azimuth angle of the analyzer transmission axis, the highly phase sensitive measurement can be achieved by regulating the transmission axis. The resolution of 2.18×10-5 RIU was achievable. In addition to high, tunable sensitivity and excellent resolution, the proposed approach also provides the advantage of high stability due to its common-path configuration.