Calibration and Performance Evaluation of Omnidirectional Sensor with Compound Spherical Mirrors

We have proposed a correspondenceless stereo system that consists of a single camera with multiple omnidirectional mirrors, which can detect approaching close objects without finding correspondences along epipolar lines. The system offers omnidirectional observation, portability, and real-time detection of near objects. The detection method requires for creating a model of the shape and location of the mirrors. However, it is difficult to make the model accurately because small positioning errors for mirrors enlarge erroneous detection of near objects. This paper describes a method for calibrating a multiple omnidirectional mirror sensor through observing a point light source at an infinite range. It also evaluates detectable distances at every pixel by analyzing in simulated experiments. As a result, it is proved that the detectable distance is enhanced by using a combination of various mirrors and that it is in proportion to the resolution of the image and the size of mirrors.