Advances in Axial Motion-like Artefact correction in Optical Coherence Tomography Imaging

Since its development back in the 1990s, Optical Coherence Tomography (OCT) has been an invaluable tool for biomedical imaging, more so in the area of ophthalmology, thanks to its ability to retrieve structural information from within a scattering sample in a non-destructive, non-invasive, and contactless way. Nonetheless, in order to fully comprehend the nature of a biological sample, it must be studied in its own environment, or in-vivo, and as most living things, they are susceptible to motion. This thesis focuses on different approaches and advances performed in motion detection and correction from three different points of views, starting from artefacts due to the motion of the device used for imaging, followed by the artefacts caused by the motion inherent to the sample, to finalise with a different type of artefact caused by the internal movement of the imaging system. Within these pages, different setups are presented, all working in the near infrared part of the optical spectrum. For the first point of view, motion caused by the displacement of the device, this thesis presents results obtained in an endoscopic set-up, in which the optical probe can be moved by the hand of the operator or using some mechanically actuated endoscope. In the case of the second point of view, the device employed consists on a free space Swept Source OCT (SS-OCT) in two different configurations, one described for skin applications, called configuration (s), and a second one described for ophthalmology applications, referred as configuration (e). These same configurations, except for the removal of a dichroic filter, are the ones explored in the third point of view, pairing the optics from the SS-OCT system with an extra swept source. The final study presented in this thesis led to another application, described in the same chapter, to characterise the sweeping direction of any swept source in an indirect way.