TABLE OF CONTENTS Polarized light imaging offers images whose contrast is based on the scattering of light by the ultrastructure of a tissue, i.e., the nuclei, mitochondria, membranes (endoplasmic reticulum, other organelles), and fibers such as collagen or actinmyosin. Polarized light imaging is implemented in a complete form using 16 images involving four types of polarized light for both illumination and detection, which are summarized using the 16-element Mueller matrix to characterize each pixel of an image. Alternatively, a simplified form of imaging acquires only two images, using linearly polarized light, that are algebraically combined to create an image that is based only on photons scattered from the superficial tissue layers and rejects multiply scattered photons from deeper tissue layers. Hence, the simple polarization imaging is useful in surveying superficial tissues such as skin to find the margins of skin pathology.
What is polarized light? Why should one consider using polarized light to image tissues? In this introduction, the motivation for using polarized light in imaging is outlined and the nature of polarized light is described.
Optical scattering of polarized light offers a mechanism of image contrast. Previous experience with scattered light has considered the multiply scattered light from a bulk thickness of tissue, i.e., the light reflected from an in vivo tissue site. The randomization of photon trajectories, coherence, and polarization properties due to multiple scattering has yielded the impression that light scattering is a relatively uninteresting contrast mechanism.
