Facial Expression Recognition

Facial expressions are visible signs of a person’s affective state, cognitive activity and personality. Humans can perform expression recognition with a remarkable robustness without conscious effort even under a variety of adverse conditions such as partially occluded faces, different appearances and poor illumination. Over the last two decades, the advances in imaging technology and ever increasing computing power have opened up a possibility of automatic facial expression recognition and this has led to significant research efforts from the computer vision and pattern recognition communities. One reason for this growing interest is due to a wide spectrum of possible applications in diverse areas, such as more engaging human-computer interaction (HCI) systems, video conferencing, augmented reality. Additionally from the biometric perspective, automatic recognition of facial expressions has been investigated in the context of monitoring patients in the intensive care and neonatal units for signs of pain and anxiety, behavioural research, identifying level of concentration, and improving face recognition. Automatic facial expression recognition is a difficult task due to its inherent subjective nature, which is additionally hampered by usual difficulties encountered in pattern recognition and computer vision research. The vast majority of the current state-of-the-art facial expression recognition systems are based on 2-D facial images or videos, which offer good performance only for the data captured under controlled conditions. As a result, there is currently a shift towards the use of 3-D facial data to yield better recognition performance. However, it requires more expensive data acquisition systems and sophisticated processing algorithms. The aim of this chapter is to provide an overview of the existing methodologies and recent advances in the facial expression recognition, as well as present a systematic description of the authors’ work on the use of 3-D facial data for automatic recognition of facial expressions, starting from data acquisition and database creation to data processing algorithms and performance evaluation.