A Novel Omnidirectional Stereo Vision System with a Single Camera

The omnidirectional vision system has been given increasing attentions in recent years in many engineering research areas such as computer vision and mobile robot since it has wide field of view (FOV). A general method for 360o omnidirectional image acquisition is the catadioptric approach using a coaxially aligned convex mirror and a conventional camera. The catadioptric approach with the convex mirror is simple and fast compared to the mosaic approach using multiple cameras or a rotating camera. There are several types of commercially available convex mirrors such as conical, spherical, parabolic, or hyperbolic mirrors (Baker & Nayar, 1999)(Nayar, 1977).. In order to extract 3D information from the camera vision, the stereo image with disparity should be taken. One obvious method for the stereo image acquisition is using two cameras with different view angles. However, two-camera stereo introduces difficulties in the image processing caused by the non-identical intrinsic camera parameters such as focal length, gain, and spectral responses etc (Gluckman & Nayar, 2001). Accordingly, there have been much work on single-camera stereo system to overcome the problems of the two-camera stereo. One straightforward method for the single camera stereo is sequential image acquisition with respect to camera movement. A typical application of the method is in the mobile robot area, where the camera system on a mobile robot takes a sequence of images, and extracts 3D information from the set of images. Due to the uncertainties in the sequential camera position, however, it is difficult to get the accurate 3D information in that method. Moreover, the information is basically not real-time due to the time-lag of the sequential images. In order to overcome the problems according to the sequential camera motion, additional optical devices are introduced to the single camera stereo system such as two planar mirrors which have different view angles (Gluckman & Nayar, 2001) or a biprim which gives two virtual images for an object (Lee & Kweon, 2000). On the other hand, the stereo methods have also been developed in the omnidirectional vision area. An exemplar omnidirectional stereo vision is the direct application of twocamera stereo with two convex mirrors in (Gluckman et al., 1998)(Pajdlar et al., 2002). Since