광섬유 간섭계를 이용한 센서 및 광결맞음 단층영상기에 관한 연구

Abstract

ABSTRACT

A Study on Sensor and Optical Coherence Tomography System Using Fiber Optic Interferometer

Seung Seok Lee Advisor : Prof. Eun Seo Choi, Ph.D. Department of Physics Graduate School of Chosun University

In this paper, we studied a sensor system based on fiber optic interferometry and Optical Coherence Tomography system that can measure non-destructive tomographic images using an optical fiber optic interferometer. We have developed a phase shifting interferometer that can adjust the phase of the interferometer and could improve the performance of the tomographic imaging system. The vibration, the temperature, and the number of cells were measured by using a fiber optic interferometer-based sensor system. Using a fiber-optic probe in the form of a coil, the external oscillation frequency could be measured with high accuracy at the error less than 1%. Based on the fiber optic interferometer, cell counts were performed and 524 beads per second could be counted, which confirmed the capability of cell counts performed in flow cytometry. Using the interferometer, the temperature change by the external heat source could be measured in real time by the non–contact method. It was possible to measure the temperature on a silicon wafer at a temperature resolution of 11 K. By adding an scanner to high speed interferometer, the temperature distribution on the surface could be mapped in real time. The optical coherence tomography (OCT) system was developed by using a fiber based interferometer and the pattern fabricated by direct imaging method using ultraviolet light showed the depth variation in the tomographic image according to the exposure power. It is expected to be useful in inspecting patterns in real time. Using a common path interferometer that does not use a partial reflector, it was possible to perform measurement of width and depth of the processed pattern with a high accuracy. The average error rate of 10% was achieved by using proposed method compared with an electron scanning microscope. A fiber-based phase shifting interferometer has been developed using a Doppler effect via external vibration or all optical method using an optical fiber doped with ytterbium. By controlling the applied current or the pump current of PZT, precise control of phase shift was done properly. The complex conjugate signal and the DC signal generated in the Fourier transform of the interference signal in OCT can be effectively removed by using this characteristic