Imaging Through Scattering

In this thesis we demonstrate novel methods to overcome optical scattering in order to resolve information about hidden scenes, in particular for biomedical applications. Imaging through scattering media has long been a challenge, as scattering corrupts scenes in a non-invertible way. The use of near-visible optical spectrum for biomedical purposes has many advantages, such as optical contrast, optical resolution and nonionizing radiation. Particularly, it has important applications in biomedical imaging, such as sub-dermal imaging for diagnostics, screening and monitoring conditions. We demonstrate methods to overcome and use scattering in order to recover scene parameters. In particular we demonstrate a method for locating and classifying fluorescent markers hidden behind turbid layers using ultrafast time-resolved measurements with a sparse-based optimization framework. This novel method has applications in remote sensing and in-vivo fluorescence lifetime imaging. Another method is demonstrated to resolve blood flow speed within skin tissue. This method is based on a computational photography technique and coherent illumination. This method can be applied in diagnosis and monitoring of burns, wounds, prostheses and cosmetics. A particularly important application of this technology is analysis of diabetic ulcers, which is the main cause for non-traumatic amputations in India. The suggested prototype is suitable for assisting clinicians in assessing the wound healing process. The methods developed in this thesis using ultrafast time-resolved measurements, sparsity-based optimization and computational photography can spur research and applications in biomedical imaging, skin conditions diagnosis and more general modalities of imaging through scattering media. Thesis Supervisor: Ramesh Raskar Title: Associate Professor