Fiber optic diffraction interferometry for optical testing

Abstract

Interferometry for optical testing has evolved according to the industrial demands such as semiconductor or large-scale optics and there are still some challenges that the interferometric metrology should solve. They are aspheric optics testing, highly accurate and environmentally robust measurement. This thesis is devoted to solve those problems and propose new interferometers with higher accuracy and vibration insensibility. In an effort to make more accurate interferometer, the oblique fiber optic diffraction interferometer was developed. And as a vibration insensitive interferometer, the fringe-stabilized fiber optic diffraction interferometer is presented. The main idea or key component of those interferometers is commonly a single-mode fiber. Optical fiber has various applications and full field optical testing interferometers found breakthroughs in single-mode fibers since they were known to generate near-perfect spherical waves. Wavefront sphericity from single-mode fibers, however, has not been thoroughly investigated enough to verify their uses in high precision metrology. This thesis deals with those issues in theoretical and experimental points of view, and some practical matters about the fabrication of the single-mode fiber source are included. In addition, nonparaxial Fresnel diffraction formula is derived, which predicts the diffraction field from single-mode fibers with unprecedented accuracy other than numerical solutions. The oblique fiber optic diffraction interferometer is presented as an application of the oblique fiber source and a large scale spherical mirror was successfully tested. Next, the fringe-stabilized fiber optic diffraction interferometer is proposed as a promising solution to the vibration insensitive on-machine measurement. Actual embodiment and some measurement results are presented.