Full-range optical imaging of planar collagen fiber orientation using polarized light microscopy

A novel method for automated assessment of directions of collagen fibers in soft tissues is presented. It is based on multiple rotated images obtained via polarized light microscope with perpendicular and inclined polarizers and thus it breaks the limitation of 90{\deg} periodicity of polarized light intensity and evaluates the fiber orientation over the whole 180{\deg} range accurately and quickly. After having verified the method, we used histological specimens of porcine Achilles tendon and aorta to validate the proposed algorithm and to lower the number of rotated images needed for evaluation. Our algorithm is capable to analyze 5.10^5 pixels in one micrograph in a few seconds and is thus a powerful and cheap tool for histological image analysis of such samples promising a broad application.