Side-viewing Endoscopic Fiber Probe For Optical Coherence Tomography

Optical Coherence Tomography(OCT)is a high resolution,high imaging speed and non-invasiveness optical imaging modality with a broad application prospects in medical research and clinical diagnosis.Combined with the traditional endoscope technology,the endoscopic OCT can realize high-resolution tomography imaging of living organisms.The endoscopic probe is the key device in the endoscopic OCT system.This dissertation introduces the principles,classification and characteristics of the OCT system.The theory and principle of the swept source OCT system is demonstrated,and the development process of the side-viewing endoscopic probes is introduced.A GRIN lens based side-viewing OCT endoscopic probe was designed and manufactured.The probe uses the air gap as the optical interval.By adjusting the length of the air gap,the optical performance of the probe can be flexibly tuned.To determine the optimal structure of the probe,the quantitative relationships between the optical performance parameters of the probe and its structural parameters are theoretically analyzed by using the beam transfer matrix theory.The fabricated probe has a maximum diameter of 1.4 mm,a rigid length of 11 mm,a working distance of 2.71 mm,and a focus spot diameter of 21.24 μm.A fiber ball lens based side-viewing OCT endoscopic needle probe was designed and manufactured.The probe uses an all-fiber design which has the characteristics of low power loss and low back-reflection.With the use of the fiber ball lens and packaging within a 26-gague hypodermic needle,the probe is protected from astigmatism caused by cylindrical surface of the optical fiber or the outer protective tube.By adjusting the length of the coreless fiber and the radius of the fiber ball lens independently,the optical performance of the probe can be optimized.The fabricated probe has a diameter of 0.45 mm and a working distance of 0.62 mm.The diameters of the focused spots in the two perpendicular directions are 18.72 μm and 19.03 μm,respectively.A fiber based swept source endoscopic OCT system was designed and built.The fabricated probes were connected to the system and its imaging performance were validated by the high-resolution OCT images of biological tissues.