An active vision architecture based on iconic representations

Abstract

Active vision systems have the capability of continuously interacting with the environment. The rapidly changing environment of such systems means that it is attractive to replace static representations with visual routines that compute information on demand. Such routines place a premium on image data structures that are easily computed and used. The purpose of this paper is to propose a general active vision architecture based on efficiently computable iconic representations. This architecture employs two primary visual routines, one for identifying the visual image near the fovea (object identification), and another for locating a stored prototype on the retina (object location). This design allows complex visual behaviors to be obtained by composing these two routines with different parameters. The iconic representations are comprised of high-dimensional feature vectors obtained from the responses of an ensemble of Gaussian derivative spatial filters at a number of orientations and scales. These representations are stored in two separate memories. One memory is indexed by image coordinates while the other is indexed by object coordinates. Object location matches a localized set of model features with image features at all possible retinal locations. Object identification matches a foveal set of image features with all possible model features. We present experimental results for a near real-time implementation of these routines on a pipeline image processor and suggest relatively simple strategies for tackling the problems of occlusions and scale variations. We also discuss two additional visual routines, one for top-down foveal targeting using log-polar sensors and another for looming detection, which are facilitated by the proposed architecture.