The principle of common-path heterodyne interferometer and its applications

• Main Authors: Chiu, Ming-Horng, 邱銘宏
• Other Authors: Su Der-Chin
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/81376109498665226297

博士 === 國立交通大學 === 光電工程研究所 === 86 === The principles, applications, and merits of the common-path heterodyneinterferometer are described in this dissertation. To investigate thisinterferometer, a new type of heterodyne light source is designed firstly. Then,two new techniques for measuring several physical quantities are proposed. According to the physical quantities to be measured, and the characteristics of the test medium, this interferometer can be arranged intohree different types : transmission type, total- internal-reflection type, and reflection type. As for the transmission type, two lasers with different wavelengths andthe heterodyne interferometry are used to determine the phase retardation of a wave plate, and to locate its fast axis or slow axis, simultaneously. As for the total-internal-reflection (TIR) type, the total-internal-reflection heterodyne interferometry is presented to measure the quantities,such as, refractive index of liquid or gas, the absolute value of small angle, and vacuum pressure. This new method is based on the total-internal-reflectioneffect and the heterodyne interferometry to measure the phase difference between s- polarization and p-polarization due to TIR effect. The quantity to be measured will be derived by submitting the corresponding phase difference to Fresnel*s equations. As for the reflection type, the phase difference versus incident anglemethod for measuring the complex refractive index of a medium is proposed. In this new method, the complex refractive index can be derived by introducing the corresponding phase differences between s- and p-polarizations of two different incident angles into Fresnel*s equation. And the comparisons between these methods and other traditional methods are described. Because of its common-path optical configuration and heterodyne interferometric phase evaluation, it has both the merits of conventionalcommon-path interferometer and the heterodyne interferometric technique. Hence it is suitable for applying this interferometer to industry.