A camera that combines lenses and mirrors to capture a wide field of view through a central projection (i.e. a single viewpoint). Most common examples use paraboloidal or hyperboloidal mirrors. In the former case a telecentric lens is needed to focalize parallel rays reflected by the mirror and there are no constraints for mirror to camera relative positioning: the internal focus of the parabola acts as the unique viewpoint in the latter case it is possible to use a normal lens, but mirror to camera positioning is critical for achieving a single viewpoint it is essential that the principal point of the lens coincides with the external focus of the hyperboloid to let the internal one be the unique viewpoint for the observed scene
Published in Chapter:
Hybrid Dual Camera Vision Systems
Stefano Cagnoni (Università degli Studi di Perugia, Italy), Monica Mordonini (Università degli Studi di Perugia, Italy), Luca Mussi (Università degli Studi di Perugia, Italy), and Giovanni Adorni (Università degli Studi di Genova, Italy)
Copyright: © 2009
|Pages: 5
DOI: 10.4018/978-1-59904-849-9.ch125
Abstract
Many of the known visual systems in nature are characterized by a wide field of view allowing animals to keep the whole surrounding environment under control. In this sense, dragonflies are one of the best examples: their compound eyes are made up of thousands of separate light-sensing organs arranged to give nearly a 360° field of vision. However, animals with eyes on the sides of their head have high periscopy but low binocularity, that is their views overlap very little. Differently, raptors’ eyes have a central part that permits them to see far away details with an impressive resolution and their views overlap by about ninety degrees. Those characteristics allow for a globally wide field of view and for accurate stereoscopic vision at the same time, which in turn allows for determination of distance, leading to the ability to develop a sharp, three-dimensional image of a large portion of their view. In mobile robotics applications, autonomous robots are required to react to visual stimuli that may come from any direction at any moment of their activity. In surveillance applications, the opportunity to obtain a field of view as wide as possible is also a critical requirement. For these reasons, a growing interest in omnidirectional vision systems (Benosman 2001), which is still a particularly intriguing research field, has emerged. On the other hand, requirements to be able to carry out object/pattern recognition and classification tasks are opposite, high resolution and accuracy and low distortion being possibly the most important ones. Finally, three-dimensional information extraction can be usually achieved by vision systems that combine the use of at least two sensors at the same time. This article presents the class of hybrid dual camera vision systems. This kind of sensors, inspired by existing visual systems in nature, combines an omnidirectional sensor with a perspective moving camera. In this way it is possible to observe the whole surrounding scene at low resolution, while, at the same time, the perspective camera can be directed to focus on objects of interest with higher resolution.