I. Introduction
Face recognition might be one of the most well-known and attracting applications in computer vision. Because of the outstanding face recognition capability of human being and the numerous potential applications of face recognition technology, face recognition technology has been receiving more and more attentions. Over the past decades, researchers have focused on developing fully automatic facial recognition systems, which means, not only the recognition process but also face detection and feature extraction are all supposed to be handled by the computer automatically. As a result, a practical facial recognition system should at least include the three aforementioned parts.