Open AccessOptical processing of color images with incoherent illumination: orientation-selective edge enhancement using a modified liquid-crystal display
Author(s) -
Ariel Fernández,
Julia R. Alonso,
Jorge L. Flores,
Gastón A. Ayubi,
J. Matías Di Martino,
José A. Ferrari
Publication year - 2011
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.19.021091
Subject(s) - polarizer , optics , liquid crystal display , replica , liquid crystal , image processing , edge enhancement , polarization (electrochemistry) , materials science , computer vision , artificial intelligence , computer science , physics , birefringence , image (mathematics) , art , chemistry , visual arts
We present a novel optical method for edge enhancement in color images based on the polarization properties of liquid-crystal displays (LCD). In principle, a LCD generates simultaneously two color-complementary, orthogonally polarized replicas of the digital image used as input. The currently viewed image in standard LCD monitors and cell phone's screens -which we will refer as the "positive image or true-color image"- is the one obtained by placing an analyzer in front of the LCD, in cross configuration to the back polarizer of the display. The orthogonally polarized replica of this image -the "negative image or complementary-color image"- is absorbed by the front polarizer. In order to generate the positive and negative replica with a slight displacement between them, we used a LCD monitor whose analyzer (originally a linear polarizer) was replaced by a calcite crystal acting as beam displacer. When both images are superimposed laterally displaced across the image plane, one obtains an image with enhanced first-order derivatives along a specific direction. The proposed technique works under incoherent illumination and does not require precise alignment, and thus, it could be potentially useful for processing large color images in real-time applications. Validation experiments are presented.