Refractive index measurement system based on total internal reflection maximum phase difference

• Main Authors: Tzu-Yang Weng, 翁子揚
• Other Authors: Ju-Yi Lee
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/hv837m

碩士 === 國立中央大學 === 光機電工程研究所 === 107 === This study developed a refractive index measurement system to improve the problems encountered in the measurement of refractive index of liquids and solids currently. The developed system architecture introduces different phase delays based on the reflected light of the vertical and horizontal polarization states when total reflection occurs. By calculating the maximum value of the phase difference between the vertical and horizontal delay phases, and finding the phase difference maximum value and the relationship between the refractive indices and the refractive index is derived. The system uses the focusing method to incident laser beam into the prism, and the incident angle of the laser beam is a range. Compared with the conventional single-incident angle total reflection measurement system, the system does not need to adjust the incident angle very precisely. And the optical path adjustment is relatively simple and fast. In the measurement experiment, the medium to be tested is represented by three types of ambient air, tap water and glass of different refractive indices. When the sample is ambient air and tap water, the interface between the sample and the prism is tightly coupled, through the measurement area of the xyz axis can easily move the focused spot between the prism and the sample, and make the totally reflective happended. When the sample is glass, it is necessary to add an index matching oil which is consistent with the refractive index of the prism between the prism and the sample, and to move the spot to the surface of the sample through the xyz axis movement of the measurement area. The purpose of this system is to analyze the phase delay of the vertical and horizontal polarization through two light intensities with a polarization direction of ±45 degrees. Since the light source is in focus, the measurement point focused on the surface of the object to be tested and the received light intensity of the linear CCD camera, the position is the object image relationship. When measuring, must make sure the surface of the sample is clean. Otherwise, the scratches, dust or impurities on III the surface of the sample will be measured on the linear CCD camera. The measurement performance of the system was verified by measurement experiments of ambient air, tap water and glass samples with different refractive indices. The system resolution was 0.0079.