title: Optical processing of color images with incoherent illumination: orientation-selective edge enhancement using a modified liquid-crystal display.
abstract: 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.
authors: Instituto de Física, Facultad de Ingeniería, UdelaR, J. Herrera y Reissig 565, 11300 Montevideo, Uruguay.
authors: Ariel
authors: A
authors: Fernández
authors: Julia R
authors: JR
authors: Alonso
authors: Jorge L
authors: JL
authors: Flores
authors: Gastón A
authors: GA
authors: Ayubi
authors: J Matías
authors: JM
authors: Di Martino
authors: José A
authors: JA
authors: Ferrari
mesh_terms: D003116:Color; D003196:Computer Graphics; D003626:Data Display; D004867:Equipment Design; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D050866:Liquid Crystals; D008422:Materials Testing; D015233:Models, Statistical; D055095:Optics and Photonics / Q000379:methods*; D014584:User-Computer Interface