"In optical imaging, the high random scattering of light in biological tissue can degrade the contrast of an image which could be a drawback in detection of tumors. Polarization based imaging has shown its capability in overcoming such drawbacks over the recent years. It depends on discrimination of randomly polarized light from weakly polarized light yielding an enhanced image contrast. The purpose of this research study was to investigate, compare and assess the imaging potential of two widely used techniques in the field of polarimetric imaging namely, Linear Polarimeter method (uses linearly polarized light) and Rotating Retarder Polarimeter method (uses circularly polarized light) to interrogate targets embedded in turbid biological media. This novel study may contribute to early detection of diseases and pathologies in biological tissues. The polarization properties of the backscattered light from a turbid medium containing a target submerged in a scattering solution were studied. A preclinical optical phantom was designed and the experiments were done in two phases, each phase corresponding to a different polarimetric technique. Specifically, a polystyrene cylinder was used as the target and the turbid medium was simulated by adding skim milk in volume percentage increments in both the phases. The first phase of experiments involved the Rotating Retarder Polarimeter method and the Polarimetric Measurement Matrix Reduction techniques. The images obtained by this method were processed by iv means of a data reduction algorithm, based on Polarimetric Measurement matrix method to calculate the Degree of Linear Polarization (DOLP) image and total intensity (S0) image. The second phase of experiments involved the Linear Polarimeter method. The resulting co-polarized and cross-polarized images from this method were processed to obtain Degree of Polarization (Rpol) images. Both of these experiments were performed using a backscattered polarimetric imaging system. The images obtained by both the techniques were analyzed by computing signal to background ratio (SBR) values and number of pixels detected as edges for every concentration of skim milk solution added to the surrounding medium of the target. The obtained images were then compared to determine the image quality. Experimental results from both these techniques showed that the DOLP images obtained by the Rotating Retarder Polarimeter method provide better contrast in terms of signal to background ratio (SBR) values and number of pixels detected as edges compared to Degree of Polarization (Rpol) images obtained by the linear Polarimeter method. Overall, the contributions of this study suggest that the interrogation of targets in turbid media using circularly polarized light exhibits superior imaging characteristics with respect to linearly polarized light interrogation."--Abstract.

This research involved the development of a polarimetric imaging algorithm used for selective detection of back scattered photons transmitted through a medium. The novelty of the algorithm was the use of Stokes parameters and Mueller matrix methods to enhance turbid media imaging. This in turn may replace time-gated imaging, optical heterodyne, and second-harmonic generation techniques. The first part consisted of exploring polarimetric phenomenology of 1-D and 2-D signals in a variety of experimental scenarios. Corner cube reflectors and arrays, photodiode windows, and camera zoom lenses were used as targets. Their polarization signatures, mainly reflected signal, optical cross section, line spread function (LSF) and modulation transfer function (MTF), were studied by applying Mueller matrix formalism. The second part consisted of exploring the applicability of multi-fusional multispectral active imaging principles. This was aimed at enhancing image quality under different harsh imaging conditions using arithmetic manipulations of images at more than one wavelength. Aluminum strips, bar patterns, and computer chips were used as underwater targets and interrogated with more than one wavelength of laser. The images were analyzed using the Mueller matrix formalism. The resulting polarized images, and multi-wavelength subtraction images, were studied for contrast differences. As a result of the study, we noted a few improvements. There was a visible increase in signal level when applying the degree of linear polarization (DOLP) algorithm. Since significant results were established using polarimetric signals, the polarimetric algorithm was used to test the impact on the size of a target's cross section. Using the range equation, we were able to improve the back scattered cross section of a corner cube and a camera zoom lens. DOLP was also able to improve the contrast of images taken with the lens focused, blurry, and out of focus. Similar results were observed for the LSF and MTF. For underwater imaging, polarimetric intensities improved even though scattered intensities decreased with increasing water cloudiness. However, the increase was not uniform. When comparing images of two separate wavelengths, it was noted that the contrast of the DOLP images was not significantly better than the non-polarimetric images. The image of the first Stokes parameter of each wavelength managed to improve contrast two fold or better. The subtraction of back scattered images also improved contrast.

This book introduces the optical multi-band polarization imaging theory and the utilization of the multi-band polarimetric information for detecting the camouflage object and the optical hidden marker, and enhancing the visibility in bad weather and water. The book describes systematically and in detail the basic optical polarimetry theory; provides abundant multi-band polarimetric imaging experiment data; and indicates practical evaluation methods for designing the multi-band polarization imager, for analyzing and modeling the object’s multi-band polarization characteristics, and for enhancing the vision performance in scattering media. This book shows the latest research results of multi-band polarimetric vision, especially in camouflage object detection, optical hidden marker detection and multi-band polarimetric imagery fusion. From this book, readers can get a complete understanding about multi-band polarimetric imaging and its application in different vision tasks.

Assessment of anisotropy has many applications in tissue engineering and early detection of disease such as cancer or stroke. One of the emerging optical technologies for quantifying anisotropy in biological tissues is polarized light imaging. In this technique, the full Mueller matrix of the tissue is measured and then decomposed to yield optical retardance, which is proportional to the tissue anisotropy. The theory of polarized light imaging, its biomedical application and instrumentation are the subject of this thesis. To retrieve more information from the Mueller matrix, a quantitative analysis of generic turbid media's Mueller matrices beyond their decompositions was proposed. Two new metrics based on Mueller matrix were established in this thesis: 1) Tissue depolarization, calculated from the Mueller matrix, can be used to estimate its optical properties, and 2) Symmetry of the off-diagonal elements of a turbid medium's Mueller matrix can be used to detect the axial heterogeneity of anisotropy. Polarized light imaging, followed by Mueller matrix decomposition, was then successfully applied to locate the structural disorders induced by bladder outlet obstruction disease, in ex vivo functioning rat bladders. Motivated by the result of this study and to enable in vivo polarized light measurements of the bladder, a novel thin fiber based polarimetric probe which can measure the full Mueller matrix of the turbid media was suggested. Finally, to enhance the speed of the ex vivo examinations of biological tissues and avoid artifacts, a new rapid benchtop polarized light imaging system based on photoelastic modulators (PEM) and a charge-coupled device (CCD) was proposed and implemented. The demonstrated scheme does not involve using mechanically moving components and thus reduces systematic errors. This imaging system proved to be the fastest high resolution polarimetric characterization tool for imaging turbid media to date.

The Handbook of Photonics for Biomedical Science analyzes achievements, new trends, and perspectives of photonics in its application to biomedicine. With contributions from world-renowned experts in the field, the handbook describes advanced biophotonics methods and techniques intensively developed in recent years.Addressing the latest problems in

In the year 2012, there were approximately 226,160 cases of lung cancer and 160,340 deaths out of it as per the National Cancer Institute. There are mainly two types of lung cancer, small cell lung cancer and non-small cell lung cancer, of which 87% are diagnosed as non-small cell. A physical algorithm and a systematic study relating the morphological, chemical and metabolic properties of lung cancer to the physical and optical parameters of the polarimetric detection process are missing. Therefore, one of the purposes of the study is to explore the polarimetric phenomenology of near infrared light interaction with healthy and lung cancer monoline cells by using efficient polarimetric backscattering detection techniques. Preliminary results indicate that enhanced discrimination between healthy and different types of lung cancer cells can be achieved based on their backscattered intensities, Mueller matrix, diattenuation and depolarization properties. Also, various optical parameters like linear depolarization ratio and degree of linear polarization play an important role in discriminating healthy and different lung cancer cells. Specifically, the sizes of the nuclei of the cancer cells and the nucleus-to-cytoplasmic ratios appear to have potential impact on the detected polarimetric signatures leading to enhanced discrimination of lung cancer cells. The second work in this thesis has been done with the support of the Air Force Research Laboratory (AFRL). Polarimetric signals have always played an important role in the identification, discrimination and analysis of a material's optical properties. This work presents a novel remote sensing approach based on polarimetric fractal detection principles. Backscattered polarimetric signals contribution from different materials used in space applications have already been detected using a laboratory LADAR testbed and this thesis presents implememtation of the LADAR testbed and analysis techniques of these backscattered signals based on fractal analysis. Fractal dimension has been chosen as a measure for the discrimination purposes of these materials. The outcome of this thesis indicates that polarimetric fractal principles may enhance the capabilities of the LADAR for characterization and discrimination of different materials.

"The main purpose of this study is to explore the potential of optically active molecules in conjunction with single pixel detectors and polarimetric techniques for early detection of tissue pathologies. Optical polarimetry can provide invaluable biological information based on molecular composition of the medium, structure, geometry, and metabolism. The preclinical phantom used was a rectangular plexiglass container and the experiments were carried out under backscattering detection geometry. A NIRVANA (Newfocus Inc., Model 2007, Santa Clara, CA, USA) auto balance detector was employed throughout the study. Initial readings were taken with water, and then aqueous solution of optically active molecules was added into it. The readings were obtained for the two states of polarization of light, parallel and perpendicular polarization. The signal-to-noise ratio and detective quantum efficiency (DQE) were calculated. The outcome of this study indicated an increase of the backscattered detected signal, signal-to-noise ratio, and the DQE of the imaging system, with increase in the concentration of optically active contrast agents. The results obtained were validated by performing linear regression analysis and paired t-test. The statistical analysis indicated increase in backscattered detected signal, signal to noise ratio, DQE and significant difference between the two states of polarization. This increase in the backscattered signal due to difference in the refractive index between the background and the object, leads to an increased contrast image that would assist in the early detection of tumor, other tissue pathologies, and biological structures."--Abstract.