Lateral Scanning System And External Trigger Method For Optical Coherence Tomography

Optical Coherence Tomography (OCT) is one of the newly developed techniques for bio-tomography. In an OCT system the depth information of samples is obtained by longitudinal scanning, which is controlled by an optical delay line (ODL) in the reference arm. To get 2-D images of the sample, it is necessary to deflect the sample arm beam to different points of the sample. So it is very important to design a lateral scanning system for the OCT system.Optical delay lines are often used in OCT systems to perform longitudinal scanning, however, the scanning velocity of a typical optical delay line cannot be a constant. Meanwhile, the sampling rate of the A/D convertor is a constant, which should be set before the scanning. The mismatch between the rates of the A/D convertor and the longitudinal scanning will result in distortion in the longitudinal information of the sample.To build a lateral scanning system for the OCT system, a new f-theta linear lens has been designed based on a Superluminescent diode source, whose center wavelength is 1282.7nm. Several methods to generate the synchronous signals to drive the lateral scanning system and the ODL to work synchronously have also been studied.Secondly based on the existing conditions of the lab, we selected the components for the lateral scanning system and picked an appropriate synchronous method to drive the lateral and longitudinal scanning. The lateral scanning system of the OCT has been successfully built, and the lateral resolution of the scanning system and the scanning rate of the system are measured and tested by both experiments and calculations.Finally, an external trigger A/D convert method for the OCT system has been proposed for the first time and realized in this paper. With the external trigger A/D convert method, the distortion which is generated by the mismatch of the longitudinalscanning and A/D convertor decreases effectively.This paper is divided into seven chapters of the following major elements:Chapter 1: Introduction. The outline of optical coherence tomography technology, and the purpose of this research project.Chapter 2: The time-domain OCT principle and system. The principles of OCT and several major subsystems of OCT.Chapter 3: The research for OCT lateral scanning systems. Detail descriptions of the lateral scanning systems of OCT. According to the OCT system of the lab, the design of the new linear scanning lens for the OCT system. And the study of the methods and systems for generating the synchronous driving signals.Chapter 4: The lateral scanning system construction. In this chapter the Selection of the components and synchronous driving signal generating system methods for the lateral scanning system, and the construction of the lateral scanning system, are interpreted in detailChapter 5: The OCT system construction and the experiments for testing the lateral scanning system.Chapter 6: External triggered A/D convert method for OCT. The new system for OCT has been constructed and tested by experiments.Chapter 7: Summary and Outlook. In this chapter we summarize the content of the work and achievements, and set out the future direction for further research.