Investigation of a fibre-optic Fizeau interferometer configuration and coherent fibre-optic imaging bundles for optical coherence tomography

摘要

Currently several medical imaging techniques are in operation in clinicalenvironments that help the doctors to diagnose diseases before proceeding totreatment. This research investigated and implemented configurations for a medicalimaging technique called Optical Coherence Tomography (OCT).The Michelson interferometer has been the principal configuration for OCT systems.For endoscopic OCT applications though such a configuration is susceptible topolarisation induced signal fading due to environmental changes within the samplearm, like fibre bending and temperature fluctuations. The development and testing ofa Fizeau interferometer based OCT system demonstrate the elimination of thispolarisation induced signal fading as the sample and reference arm of theinterferometer experience the same environmental changes. The Fizeau interferometeris formed between the end of the fibre and the sample itself. A secondary processinginterferometer is used in this configuration, to compensate the path difference inherentto the Fizeau configuration. Longitudinal resolution is about 19 m in air, and lateralresolution about 23 m. A signal-to-noise ratio of about 80 dB was achieved with thissystem and several sets of image data were collected from laboratory and biologicalsamples.An OCT system based on a Fizeau interferometer incorporating a coherent fibreimaging bundle was also investigated. Fibres in the bundle are accessed sequentiallyby a beam focused onto the input face of the bundle, allowing 2D information to beacquired using point detection. Incorporating a fibre optic imaging bundle in Fizeaubased interferometer OCT allows mechanical scanning parts to be removed from thesample arm, resulting in a passive probe. Such a configuration can form a compact,robust and “downlead insensitive” OCT system and is a strong candidate for in vivoapplications. The performance of leached and wound coherent fibre optic bundles wasaccessed and an analysis is presented. The longitudinal resolution of the systemdeveloped was about 10 m in air, and lateral resolution about 9 m. This thesisdemonstrates several sets of image data that were collected from various samplesusing a Fizeau interferometer based OCT incorporating coherent imaging bundles. 2Dimage data captured by such a configuration are presented and reported for the firsttime in this thesis.