Simulations and analysis of small strain measurement using total-internal reflection heterodyne interferometry

• Main Author: 周泰龍
• Other Authors: 林俊佑
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/04327457776013703252

碩士 === 國立彰化師範大學 === 機電工程學系 === 97 === In this thesis, an optical method for measuring small strain by using total-internal reflection heterodyne interferometer is presented. As a heterodyne light beam is incident on a holographic grating, the +1 order diffraction beam generates and then enters a total-internal reflection (TIR) apparatus, thereby resulting in multiple total-internal reflections. The output beam of the TIR apparatus travels passes through an analyzer for interference. When a strain applied to the holographic grating, the diffractive angle of the +1 diffraction is changed, hence causing the abrupt variation of the phase difference between the p- and s-polarization of the beam emerging from the TIR apparatus. The variation of the phase difference can be accurately determined with heterodyne interferometric technique. Substituting the variation of the phase difference into the special equation derived by Fresnel’s equations, strain can be estimated. As a heterodyne light beam is incident into a parallelogram prism by -5 degrees ; 10μm holographic period grating; 30 numbers of total-internal reflections; The sensitivity of 1.5000 Nt/deg can be achieved. The resolution of the system is 0.015 Nt. Due to its common-path configuration, this method should have some merits of high sensitivity , high resolution, and high stability.