Imaging fibre bundles for Fizeau-based optical coherence tomography

An OCT system incorporating a coherent fibre imaging bundle is described. Fibres are accessed sequentially by a beam focused onto the input face of the bundle, allowing 2D or 3D images to be acquired using point detection. A Fizeau interferometer configuration is used, in which light from the distal end of a fibre in the bundle (forming the reference arm) mixes with light reflected by the sample itself (forming the sample arm). The use of coherent imaging bundles for OCT beam delivery allows mechanical scanning parts to be removed from the sample arm, resulting in a passive probe. Such a configuration can form a compact, robust and "downlead insensitive" OCT system. In the common-path configuration used, an inherent path-length difference is present in the Fizeau sample interferometer, so an additional processing interferometer is required to ensure path-length matching. The depth scanning mechanism is confined within the processing interferometer, external to the sample probe.