Development of Novel Optical Design and Signal Processing Approaches in Optical Coherence Imaging

Abstract

Optical coherence tomography (OCT) is a non-invasive optical imaging modality which can provide high-resolution, cross-sectional images of retina and cornea. It has become a standard of care in ophthalmology for the diagnosis and monitoring of ocular diseases. However, current OCT systems face several major challenges, among which include: (1) difficult alignment and fixation in pediatric retinal imaging (2) limited cellular-level contrast for ophthalmic disease diagnosis and (3) expensive hardware and intensive computation requirements for real-time high-speed 3D imaging. This dissertation describes the development of several novel optical design and signal processing approaches in OCT and optical coherence imaging technologies to address these limitations. We first describe a long working distance swept-source OCT system to facilitate retinal imaging in young children (chapter 2). The system incorporates two custom lenses and a novel compact 2f retinal scanning configuration to achieve a working distance of 350mm with a 16o OCT field of view. The system achieves high quality retinal imaging of children as young as 21 months old without sedation in the clinic. We then present a spectroscopic OCT technology that utilizes time-frequency analysis to obtain quantitative diagnostic information of cellular responses in the anterior chamber of the eye, which can indicate many ocular diseases such as hyphema and anterior uveitis. We demonstrate that this technology can differentiate and quantify the composition of anterior chamber blood cells such as red blood cells and subtypes of WBCs, including granulocytes, lymphocytes and monocytes (chapter 3 and 4). Finally, we describe a coherence-based 3D imaging technique that uses a grating for fast beam steering, a swept-source laser with long coherence length, and time-frequency analysis for depth retrieval (chapter 5). We demonstrate that the system can achieve high-speed 3D imaging with sub-millimeter axial resolution and tens of centimeters axial imaging ranging.