Dynamic 3D shape of the plantar surface of the foot using coded structured light:a technical report

The foot provides a crucial contribution to the balance and stability of the musculoskeletal system, and accurate foot measurements are important in applications such as designing custom insoles/footwear. With better understanding of the dynamic behavior of the foot, dynamic foot reconstruction techniques are surfacing as useful ways to properly measure the shape of the foot. This paper presents a novel design and implementation of a structured-light prototype system providing dense three dimensional (3D) measurements of the foot in motion. The input to the system is a video sequence of a foot during a single step; the output is a 3D reconstruction of the plantar surface of the foot for each frame of the input. Methods Engineering and clinical tests were carried out to test the accuracy and repeatability of the system. Accuracy experiments involved imaging a planar surface from different orientations and elevations and measuring the fitting errors of the data to a plane. Repeatability experiments were done using reconstructions from 27 different subjects, where for each one both right and left feet were reconstructed in static and dynamic conditions over two different days. Results The static accuracy of the system was found to be 0.3 mm with planar test objects. In tests with real feet, the system proved repeatable, with reconstruction differences between trials one week apart averaging 2.4 mm (static case) and 2.8 mm (dynamic case). Conclusion The results obtained in the experiments show positive accuracy and repeatability results when compared to current literature. The design also shows to be superior to the systems available in the literature in several factors. Further studies need to be done to quantify the reliability of the system in clinical environment

A VARIANT OF POINT-TO-PLANE REGISTRATION INCLUDING CYCLE MINIMIZATION

3D models are very important in many industrial and scientific applications. Most part of commercial sensors obtain only a partial acquisition of the object, so that a set of views are required to build a complete model of the object. Although the motion between these views is usually unknown, it can be computed by means of registration algorithms. A survey of most important techniques is presented in this paper, in which they have been classified into coarse and fine registration and compared in terms of the number of views aligned at every step, the accuracy and the robustness against outliers. The second part of the article presents an improvement of point-to-plane registration, which includes the determination of cycles in a sequence of views with the aim of minimizing the propagation error or drift.