Design And Application Study Of Transmissive Rapid Scanning Optical Delay Line

Optical coherence tomography (OCT) is a non-invasive, non-contact biomedical imaging technique, which can obtain in vivo cross-sectional images of tissue microstructure with high sensitivity and axial resolution. These years, it developed very fast in the field of biomedical imaging, especially in ophthalmic diagnoses. Rapid Scanning Optical Delay line (RSOD), which was first reported by Group Fujimoto of MIT in 1997, plays a great role in improving OCT's performance, such as the imaging speed, signal to noise ratio, resolution, etc. RSOD functions for phase modulation, axial scanning and dispersion compensation in OCT system. Because of its easy mobility, RSOD can be easily applied to the system.In this research, the RSOD's principle and structure have been realized. Compared with the noise characteristics of unbalanced detection OCT, the balanced detection OCT has more advantages. In order to achieve balance detection, we present a transmissive RSOD based on right-angle prism, which offsets the reflected beam. This transmissive RSOD, consisting of a reflective blazed grating, a Fourier lens, a fast-scanning galvo-mirror, a right-angle prism and a mirror, functions for phase modulation, axial scanning and dispersion compensation in OCT just as a reflective RSOD. We have designed and built the transmissive RSOD for balanced detection based OCT, developed the control software of this system. Comparison study indicates that improved quality of imaging is archived by the transmissive RSOD based OCT, in contrast to that by a conventional reflective RSOD based OCT.We realized the reason of mirror image in the Fourier domain OCT (FD-OCT) and various methods to resolve the complex-conjugate ambiguity, focused on the method which used dispersion encoding to eliminate the mirror image. The transmissive RSOD was introduced to the swept source OCT (SS-OCT), which produced dispersion encoding, to resolve the complex-conjugate ambiguity. Five chapters are included in this thesis:In the first chapter, the principle of OCT and various optical delay lines are introduced. The principle of RSOD, the significance of this topic, research content and creativityare mainly described.In the second chapter we discuss the advantages of balanced detection OCT.Compared with various transmissive RSODs, a new transmissive RSOD is reported.The principle of this transmissive RSOD is described. The designing parameters aredetermined and the adjust method of transmissive RSOD is introduced.In the third chapter, the transmissive RSOD applied to the balanced detection OCT.The basic function of RSOD and the performance of balanced detection OCT isexpressed by the experiment. Comparison study indicates that advantages arearchived by the transmissive RSOD based OCT, in contrast to that by a conventionalreflective RSOD based OCT.In the fourth chapter, we discuss the reason of mirror image in the SS-OCT, variousmethods to resolve the complex-conjugate ambiguity and currently developingsituation. A new method of eliminating the mirror image, which based on dispersionencoding produced by transmissive RSOD, is reported.In the fifth chapter, we summarize the results of this thesis and put forward furtherin-depth research.