Giulio Sandini

Space-variant vision for an active camera mount

Robot systems that rely on vision as their main sensory capability need to be able to cope with changes in the visual environment and to manage a wide field of view. Moreover, in order not to loose real-time response capabilities, selective visual sensing is indeed highly desireable. The built-in selection in space and time provided by space variant sensors acts as a filter on the visual field having considerable implications for robotic applications. This paper focuses the attention on log-polar vision in the context of active control of visual sensors. The geometric distribution of sensing elements in the log-polar mapping provides visual task simplification and computational advantages. Correlation measurement techniques in the log- polar framework are formalized and two different uses are proposed. By performing global measurements on convergent log-polar images, a binocular mount can drive its cameras towards correct vergence configuration. It is also shown how image shifts can be detected by using 1D correlation measurements in the log-polar domain, and a possible use of this technique aimed at stabilizing gaze or tracking moving objects is presented. Both the reduced algorithm complexity, due to space variant topology, and the computational advantages, due to the limited number of pixels, make log-polar mapping a good candidate image geometry to obtain real-time responses in the context of reactive vision systems.