Polarized Light Examination and Photography of the Skin

TLDR

Skin reflects light in two components: surface glare that preserves the polarization plane and backscattered light that reveals pigmentation, erythema, and vascular structures. By illuminating skin with linearly polarized light and imaging through a linear polarizer, the two reflectance components are separated, and this method was applied to photographs of thirty patients. Parallel polarizer planes produce images with enhanced surface detail, while orthogonal planes suppress wrinkles and reveal vasculature and pigmented lesions, demonstrating a simple, clinically useful technique.

Abstract

Light reflected from skin has two components: regular reflectance, or "glare" arising from the surface, and light backscattered from within the tissue. The regular reflectance contains the visual cues related to surface texture, whereas the backscattered component contains the cues related to pigmentation, erythema, infiltrates, vessels, and other intracutaneous structures. Unlike the backscattered component, regular reflectance preserves the plane of polarization of polarized incident light. Thus, viewing skin through a linear polarizer, under linearly polarized illumination, separates the two components of tissue reflectance. Thirty patients were examined and photographed in this manner. When the planes of polarization are parallel, images with enhanced surface detail are obtained. When the planes are orthogonal, wrinkles and surface detail disappear, and an enhanced view of vasculature and pigmented lesions is obtained. Simple, clinically useful techniques are presented.