Real-Time Face-Priority Auto Focus for Digital and Cell-Phone Cameras

Auto-focus (AF) has been a key feature in consumer level digital and cell-phone cameras allowing users to focus automatically on a particular plane in a scene in order to get a sharp image. Face priority AF has become of interest lately due to the fact that most pictures captured by consumers are of human faces. In face-priority AF the focusing decision is made based on a detected face area in the image, thus capturing a sharp picture of the face. While many face detection algorithms exist in the literature, very few of them are actually suitable for real-time software deployment on resource limited digital or cell-phone camera processors. In this paper, a fast face-detection algorithm is introduced by combining a skin color model cluster with a computationally efficient shape processing scheme. Comparison results with a standard algorithm in terms of robustness, speed and accuracy are provided. This face detection algorithm is incorporated into our previously developed rule-based AF method to achieve real-time face-priority AF on an actual digital camera platform(1).