Optical imaging in presence of scattering

This project represents a step towards the overarching aim of imaging scattering specimens. In such samples, the contrast and sharpness of optical images is se-verely reduced since a large fraction of the light is scattered and manifests itself as a uniform background. In optical projection tomography it has been demon-strated previously that the scattered background can be separated from the im-age-forming light by capturing only the first arriving photons with ingenious ultra-fast gated optical set-ups [1-3]. The goal of this project is to investigate if the same can be achieved for optical microscopy using a gated camera and a low-cost laser. In addition, this project aims to be to quantitatively stating how much the image quality can be improved using a time gated optical set-up and to enhance a 3D reconstruction of a biological tissue. In order to accomplish the objectives, several programs and/or experiments which facilitates the everyday work in the lab were developed: like a way to or-chestrate a camera, a laser, and an oscilloscope; testing two super-resolution techniques; and finding way to record data from an oscilloscope. In short, the aforementioned set-ups are based on the same fact: if light is passed through a sample and only the first portion of the photons coming out of it are integrated to form an image, the negative effects of light scattering are reduced. To simplify the notation, I shall only refer to this idea as ‘time -gated’. This idea will be explained in detail, after the concepts of light microscopy and scattering are first introduced in this thesis. After it, the equipment that was used in order to develop the time-gated set-up will be elucidated. These two elements makes up the introduction, the first of the five blocks onto which the text is structured. The introductory block contains all the information that was available beforehand, and after reading it, the reader should be able understand the expectations and motivations of the time-gated system before it was tested. Then, all the experiments and programs that were performed/developed are ex-plained in the second thematic block, followed by the third one, where the main conclusions and outlook are stated. The rest of the blocks are self-explanatory and are included for quick reference. As can be seen, the manuscript is structured so that particular information can be found, without having to read the whole text. It is not necessary to be an expert on imaging to completely understand the dis-cussion, as all the needed clarifications will be included in the introduction and throughout the document. Note that supplementary movies are included to help convey the more complex topics; the reader can watch then by clicking on the corresponding link. To make navigation more comfortable several links are included to go directly to some sec-tions/figures within the document. All the fonts have been automatically checked using Microsoft Word 2013 to make sure that this document is accessible and can be easily be read by people with sight disabilities. In addition, the hidden characters are optimized so that the document can be read by an automatically reading software. Ingeniería Biomédica