PhD Candidate, CREOL
Non-imaging characterization by statistical analysis of scattered light under random illumination
Computational optical imaging and sensing are rather new multidisciplinary fields in which one try to take advantage of the available computation power, both in hardware and software, in conjunction with optical instruments to enhance certain attributes of the optical characterization processes. Following this philosophy, we proposed a computational method for characterising objects’ length scales. For instance, when we talk about a cell culture, length scales define averaged size of the alive cells. These length scales and their dynamic over the time encode specific biological processes. However, since these activities are slow and happen statistically, to follow them, one has to investigate them over an extended time that results in overall high level of light exposure energy. Unfortunately, the high exposed energy is shown to have collateral damages, e.g. changing the natural activity of the cell during the measurement that can result in the erroneous measurement. For example, it is shown that the visible light illumination to embryos in a specific level, even for less than 30 minutes, can stop their development. Here we are after addressing this issue through developing a sensing method in which one can measure the length scale (spatial information) over the time (dynamic information) without imaging the target. Our method is based on illuminating the target with randomly structured light, with parametric statistical properties, and then measuring the scattered light power only using a single pixel power meter. To avoid the requirement of the high illumination level, we don’t use either indigenous or exogenous tags. Having scattered light power for different illumination statistical parameters, we show that one can infer spatial properties through statistical analysis of the measured power. The time resolution of the method is 3 orders of magnitude faster than usual biological activities time scales (hundreds of milliseconds). Moreover, since we don’t use any tag and we rely on only measured power, the whole process can be done in an extremely low light condition, i.e. 3 orders of magnitude less than usual white light microscope illumination level. These properties, in conjunction with simplicity and versatility of the method, makes it an excellent candidate for the time-lapse biological study.
Abstract: The state of polarization of an optical field provides detailed information concerning both the radiation emission processes and the intricate interaction between light and matter. We report here a novel approach for characterizing the polarization properties of electromagnetic fields for which the electric field vector at a point may fluctuate in three dimensions. Using probes which couple all three components of the field, we were able to extract the polarized and unpolarized components of such fields. Our results constitute the proof of concept for what could be called three-dimensional optical polarimetry.
Pub.: 31 Dec '05, Pinned: 08 Jun '17
Abstract: We propose and demonstrate the feasibility of a new microscopic technique, which is based on variable coherence illumination. By manipulating the spatial coherence properties of an incident evanescent field, subwavelength resolution is achieved over a large field of view from far-field intensity measurements.
Pub.: 31 Dec '05, Pinned: 08 Jun '17
Abstract: We introduce the general concept of stochastic scattering polarimetry and demonstrate that the anisotropic polarizability of a scattering object can be obtained by analyzing the statistical moments of polarimetrically measured intensity distributions. This general procedure is valid even in situations where the state of polarization of the incident field is not known. The efficiency of recovering different scattering polarizabilities is demonstrated numerically for several particular cases pertaining to both far- and near-field optics.
Pub.: 21 Mar '08, Pinned: 08 Jun '17