title: Incoherent optical processor for nondirectional edge enhancement of color images.
abstract: We present an optical method for nondirectional edge extraction/enhancement in color images. The method is based on the capability of twisted-nematic LCDs to traduce the image information in changes of the state of polarization of light, which allows us to generate simultaneously two replicas of the digital image displayed on the LCD: a true-color ("positive") image and a complementary-color ("negative") one. In our setup the imaging system consists of a lens plus a pupil mask formed with concentric apertures and orthogonal polarizers. This layout allows us to simultaneously image a well-focused positive replica (due to the circular aperture) superimposed to a slightly defocused negative one (due to the annular aperture). It is not difficult to demonstrate that this generates a nondirectional (Laplacian) edge enhancement. Unlike Fourier, our proposal works with incoherent illumination and does not require precise alignment, and thus, it could be a useful tool for edge extraction/enhancement in large images in real-time applications. Validation experiments are presented.
authors.affiliation: Electronic Engineering Department, University of Guadalajara, Avenida Revolución #1500, CP. 44840 Guadalajara, Jalisco, Mexico. luis.flores@cucei.udg.mx
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Flores
authors.forename: Gastón A
authors.initials: GA
authors.lastname: Ayubi
authors.forename: Julia R
authors.initials: JR
authors.lastname: Alonso
authors.forename: Ariel
authors.initials: A
authors.lastname: Fernández
authors.forename: J Matías
authors.initials: JM
authors.lastname: Di Martino
authors.forename: José A
authors.initials: JA
authors.lastname: Ferrari