Imaging is almost synonymous with optics. Imaging is the process of using light to form a tangible or visible representation, an imitation (imitari) of a material property. There are many situations, however, where one can only aspire to 'sense making' rather than forming an image per se. In other words, objects cannot be directly resolved by conventional intensity-based imaging, a situation commonly referred to as 'unresolved imaging'. However, there is still information retained in other properties of light, which can be exposed by other means. In this thesis I will discuss two typical situations: subwavelength and multiple scattering, which are very different in terms of the spatial extent of light-matter interaction. In the subwavelength regime, information can be encoded through both inelastic and elastic interaction processes. When the latter is the preferred approach, observables such as optical phase are determined by the properties of evanescent waves while the measurements are usually conducted in the far-field. I will describe a novel energetic interpretation of the light-matter interaction in this regime, which provides an accurate estimation of the interaction volume of a single scattering event and of the small phase delay it introduces. I will also show how this minute phase occurring in subwavelength scattering can be quantitatively measured with optimal sensitivity by a polarization-encoded common path system and how it enables subwavelength sizing in a label-free fashion. At the other extreme, evaluating the information transfer in multiple scattering regimes is usually constrained by the computational complexity of the problem. I will describe two forward modeling approaches that alleviate these limitations in non-line-of-sight sensing geometries and in coherent illumination methods for imaging through obscurants. These simplifying descriptions also reveal the fundamental limits for information transfer in these two scenarios.
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Doctor of Philosophy (Ph.D.)
College of Optics and Photonics
Optics and Photonics
Optics and Photonics
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Shen, Zhean, "On the Information Content in Unresolved Imaging" (2021). Electronic Theses and Dissertations, 2020-. 1346.