CMOS FOVEATED IMAGE SENSOR - SIGNAL SCALING AND SMALL GEOMETRY-EFFECTS

A new foveated (log-polar) image sensor using standard CMOS technology has been designed and fabricated. The pixel distribution follows the log polar transform having more resolution in the center than in the p eriphery. For the fovea or central part, a different but also polar di stribution has been adopted to fit the inner pixels. The particular pr oblem of foveated image sensors is the signal scaling; pixels at diffe rent positions are different sizes and therefore different signal resp onses to the same illumination level. The difference among pixel respo nses is not only due to the differences among sensitive areas, but als o to the differences among transistor channel sizes that, for submicro n technologies, become a nonlinear problem. Some solutions for the sig nal scaling, small geometry effects (especially narrow-channel effects ), and foveated structure, have been analyzed and successfully adopted for the presented sensor. The election of the CMOS process, instead o f the CCD, is also discussed and analyzed.