A New Multiresolution Blob Detector Applied to Photogrammetry

Industrial applications of photogrammetry usually involve the detection of targets placed on the surfaces of objects. Typical targets present circular shapes, which under perspective distortion can be well approximated by an elliptical contour. In this paper we present a solution for the detection of circular targets, based on a new technique for radial symmetry detection. At a given scale, radial symmetry is defined as the product of a set of oriented features, so that only regions of space with contributions from all orientations will have strong responses. A multiresolution measure is obtained as the maximum over a set of scales. This operator detects both circular and elliptical regions and presents a sharper point spread function compared to other detectors.