THREE DIMENSIONAL OPTICAL PROFILOMETRY USING A FOUR-CORE OPTICAL FIBER by KARAHAN BULUT

ACKNOWLEDGEMENTS My thesis advisor Dr. Naci Inci's unlimited tolerance and respectful interest has always been a strong intensive while doing this project. I would like to thank Dr. Canan Baysal who has always believed in my success at Sabanci University. Mehmet Bozkurt's discipline and eruditeness has always enlightened my academic career. Lastly, of course, my family and Güneş Avcı were always in my heart and will be. v ABSTRACT This study describes the use of a four-core optical fiber for the first time for measurements of three-dimensional rigid-body shapes. A fringe pattern, which was generated by the interference of four wavefronts emitted from the four-core optical fiber, was projected on an object's surface. The deformed fringe pattern containing the information of the object's height was captured by a digital CCD camera. The two-dimensional Fourier transformation was applied to the image, which was digitized by using a frame grabber. After filtering this data in its spatial frequency domain by applying a bandpass filter, the two-dimensional inverse Fourier transformation was applied. A phase-unwrapping algorithm was applied to convert this discontinuous phase data to a continuous one. Finally, the shape information of the object was determined. The two-dimensional Fourier transformation analysis used in this study permitted a better signal separation and a better noise reduction. Compared to other optical profilometry techniques, which are based on fiber optics, the use of a four-core optical fiber in this study ruled out the necessity for using a fiber coupler and the alignment of fiber ends. Thus, it increased the compactness and the stability of the fringe projection system.