No abstract

No abstract

No abstract

No abstract

A free space optical (FSO) network consists of many reconfigurable, directional, high data-rate links. Its performance can be optimized by using topology control algorithms, which involve: (1) potential neighbor information collection, (2) an optimization algorithm with given constraints, and (3) a precise pointing procedure. In general, if a sensor at each node can observe a large field of view (FOV), then more potential link targets can be detected. With more possible link choices, the optimization algorithm will have greater degrees of freedom in determining the optimum topology. The intuitive way to acquire a wide spatial acquisition range is to use a camera with a wide FOV. However, for such a wide angle lens/mirror, there are inevitable large aberrations, which cause errors in a pointing procedure based on image analysis. To mitigate these aberrations, a possible solution is to build a correction procedure from the wide FOV lens imaging model to a pinhole imaging model. In this context, a mapping model is proposed, based on analyses of several wide angle lens sets using CodeV. The proposed model also compensates for the effect of deviations between the center lines of the lens and a CCD imaging array. To obtain the optimum parameters of the model, an off-line calibration procedure based on geometrical constraints is introduced. A sensor system consisting of a widely available fisheye converter (Nikon FC-E8) and a high-resolution CCD camera (1392x1040 pixels) has been built for evaluating the model's performance, as part of our pointing, acquisition and tracking (PAT) system.