New Depth From Focus Filters in Active Monocular Vision Systems for Indoor 3-D Tracking

In this paper, new methodologies for the estimation of the depth of a target with unknown dimensions, based on depth from focus strategies, are proposed. The measurements are extracted from images acquired with a single camera, resorting to the minimization of a new functional, deeply rooted on the optical characteristics of the lens system. The analysis and synthesis of two complementary filters and a linear parametrically varying observer are discussed in detail. These estimators use information present on the boundary of the target, which is assumed to be on a plane parallel to the camera sensor, and whose dimensions are considered to remain constant over time. This paper complements a single pan and tilt camera-based indoor positioning and tracking system. To assess the performance of the proposed solutions, a series of indoor experimental tests for a range of operation of up to ten meters, which included tracking and localizing a small unmanned aerial vehicle with unknown dimensions, was carried out. Depth estimates with accuracies on the order of a few centimeters were obtained.