Polarimetric methods for the image enhancement in biological applications

Abstract

This paper summarizes the research work undertaken by the author at the Optics Group of the Universitat Autònoma de Barcelona (UAB) for the completion of the Doctoral Thesis "Polarimetric methods for image enhancement in biological applications" supervised by Dr. Ángel Lizana Tutusaus and Prof. Juan Campos Coloma. It is studied, for the first time, the experimental implementation of a series of polarimetric methods to improve the analysis and visualization of biological tissues, both animal and plant tissues. The Thesis analyses the relationship between the two main groups of polarimetric techniques, Polarization Gating and Mueller matrix-based techniques, and a new method to obtain Polarization Gates based on measurements from a single Mueller matrix is proposed. Since the analysis of light depolarization in biomedical studies is restricted to the use of global observables, we studied the interest of applying to the study of biological tissues the Indices of Polarimetric Purity, a group of specialized observables that describe the depolarization properties of samples in more detail. These are applied in the inspection of animal tissues, improving tissue visualization, revealing certain structures hidden in standard depolarization channels, and also enhancing efficiency in classifying different types of tissue. The Thesis also studies the use of polarimetry in plant tissues, an area where Mueller matrix-based techniques are scarcely used. For this reason, our studies with plant samples focus on the potential of Mueller polarimetry, resulting in complementary, or even yielding to superior information, to other non-polarimetric optical techniques.