Three-Dimensional Foot Scanning System with a Rotational Laser-Based Measuring Head

Abstract

Knowledge of the exact three-dimensional (3D) shape of the feet is extremely important for the footwear industry, since the correct fit between the shoe and the foot is an important comfort factor. Badly fitting shoes are the major cause of pain, foot related diseases and injuries [1] to [4]. 3D feet measurement therefore provides state of the art data for: (i) producing an adaptive design of a standard shoe; (ii) personalizing the shoe to individual foot dimensions; (iii) creating a better fitting for standard mass produced shoes and (iv) determining the best-fitting shoe for customers in a shop selling standard shoes. Traditionally, foot measuring techniques used callipers and measuring tapes. Simple mechanical devices were developed later, such as the Brannock device [5] and [6] or the Ritz stick length measuring device [7], which only measures a few of the most important foot dimensions, such as foot length, arch length and foot width. The next step in the foot measurement evolution are two-dimensional foot scanners, which measure the shape and dimensions of the footwear using a photo capturing in a flat plane [8]. The major drawback of these systems is the lack of foot height measurement. So-called two-and-half-dimension scanners, which measure foot contours from the top and side view [9] to [11] enable extraction of foot's length, width and height in any cross-section. But the girths of the crosssections, their curvature and local foot deformation are still not known.The complete 3D scanning systems are the logical progression to the mentioned limitations of the earlier systems. These systems are mainly based on the laser triangulation principle. One of the first such systems was the measuring system made by the VORUM research corporation [12]. It has four laserline projectors and eight cameras, which measure the lateral cross-section of the foot, defined by the projected light plane. The entire 3D foot shape is further scanned by moving the complete projectorscameras assembly along the longitudinal foot axis (from the toes to the heel). Since the complexity of this system is relatively high due to the many cameras and lasers, which should be actuated during the measurement procedure, the price of the system is rather high. Similar system, but low cost, was later developed by Kouchi and Mochimaru [13]. Such systems are therefore mainly used in research and medical applications [14] to [17].There are many attempts to overcome the economical drawback of above solution, which is still a gold standard in terms of measurement precision. One direction of development was to eliminate the scanning procedure. A representative of this technique is described in [18] where the foot is measured by four stationary measuring modules based on laser multiple line triangulation. The methods based on the fringe projection technique are also presented in [19] to [21]. The major improvement regarding the scanning techniques is the shorter measuring time, which in principle enables the study of the foot shape during walking [1...

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