1. A system for detecting an eye, said system comprising: a video imaging camera oriented to generate images of a face of a subject; and a video processor for processing the images generated with the video imaging camera, said video processor comprising a salient feature detector for detecting potential eye candidates and filters for filtering the potential eye candidates based on appearance, spatial-geometrical constraint, and physiological skin property, said filters comprising a pattern recognition filter for filtering the potential eye candidates based on appearance, wherein the processor compares the potential eye candidates to one or more appearance-based models and classifies the potential eye candidates based on the comparison, said video processor further comprising weighting logic for weighting each potential candidate based on the appearance, spatial-geometrical constraint, and physiological skin property and generating a weighted value for each potential eye candidate, said video processor further comprising detecting logic for detecting an eye based on the weighted value of each eye candidate, wherein the filters comprise a spatial-geometrical constraint filter for weighting the potential eye candidates based on one or more spatial-geometrical constraints which compare horizontal eye candidates and compare vertical eye candidates.