3D scanning

The 3D scanner domain normally relies on the presence of many tools and technologies. They are mainly divided between contact and non-contact ones, but at present a new trend is coming up, starting from the articulated arms family, where the traditional mechanical joints, allowing flexible measures on complex objects, have been replaced by handy scanner with laser trackers, or with markers. These new systems have the advantage to get the entire object shape without changing the object position itself, but moving the scanning device without the involvement of long software alignments and post treatment operations. Anyway, the use of laser trackers obliges the operator to maintain the scanner head always visible, while the marker usage is quite critical because the measure precision depends strongly on the marker position. Starting from these considerations, the research project presented in this paper has been focused on the design and development of a flexible 3D scanner, without trackers and markers, that merge low-cost optical technologies together with low-cost inertial sensors. Thanks to this synergy, the developed 3D scanner is able to measure the three-dimensional shape of the object recording its movement and transferring it to a control unit for obtaining a point cloud. The paper presents the main concepts of the 3D scanner design and is concluded by an experimental phase made with the use of a benchmark. © 2013 Elsevier Inc.

Keywords: 3D scanners , Inertial sensors , Reverse engineering

The object of this paper is testing the performance of a new device for 3D oral scanning: a two channel PTOF (pulsed time-of-flight) laser scanner, designed for dental and industrial applications in the measurement range of zero to a few centimetres. The application on short distances (0-10 cm) has entailed the improvement of performance parameters such as single shot precision, average precision and walk error up to mm-level and to μm-level respectively. The single-shot precision (σ-value) has resulted to range from 43 to 63 ps (9-10 mm), having considered the measurement range (6.5-10 mm) corresponding to 1-2 V signal; this result agrees well with estimates made from simulations. The average precision has resulted to be dependent on the number of measurements and can reach a value equal to ±25 μm, whenever the measurements frequency is sufficiently high. For example, if the required scanning speed is 1000 points/s and the required average precision is ±25 μm, then a pulses frequency of 30-50 MHz is needed, considering signal amplitude varying between 1-2 V. On the whole, the performance of this new device, based on PTOF has proven to be adequate to its employment in the field of restorative dentistry. © 2013 Elsevier Ltd.

Keywords: CAD/CAM , Intraoral scanner , Laser range-finding techniques , Pulsed time of flight , Restorative dentistry

Intra-oral scanning technology is a very fast-growing field in dentistry since it responds to the need of an accurate three-dimensional mapping of the mouth, as required in a large number of procedures such as restorative dentistry and orthodontics. Nowadays, more than 10 intra-oral scanning devices for restorative dentistry have been developed all over the world even if only some of those devices are currently available on the market. All the existing intraoral scanners try to face with problems and disadvantages of traditional impression fabrication process and are based on different non-contact optical technologies and principles. The aim of this publication is to provide an extensive review of existing intraoral scanners for restorative dentistry evaluating their working principles, features and performances. © 2013 Elsevier Ltd.

Keywords: Confocal microscopy , Digital dental impressions , Intraoral scanner , Optical coherence tomography , Triangulation

In a previous paper these authors presented a new mesh- growing approach based on the Gabriel 2 - Simplex (G2S) criterion. If compared with the Cocone family and the Ball Pivoting methods, G2S demonstrated to be competitive in terms of tessellation rate, quality of the generated triangles and defectiveness produced when the surface to be reconstructed was locally flat. Nonetheless, its major limitation was that, in the presence of a mesh which was locally non - flat or which was not sufficiently sampled, the method was less robust and holes and non-manifold vertices were generated. In order to overcome these limitations, in this paper, the performance of the G2S mesh-growing method is fully improved in terms of robustness. The performances of the new version of the G2S approach (in the following Robust G2S) has been compared with that of the old one, and that of the Cocone family and the Ball Pivoting methods in the tessellation of some benchmark point clouds and artificially noised test cases. The results obtained show that the use of the Robust G2S is advantageous, as opposed to the other methods here considered, even in the case of noised point clouds. Unlike the other methods, the one which is proposed preserves manifoldness and geometric details of the point cloud to be meshed. © 2013 CAD Solutions, LLC.

Keywords: Reverse engineering , Surface reconstruction , Triangular meshes

Coded Structured Light techniques represent one of the most attractive research areas within the field of optical metrology. The coding procedures are typically based on projecting either a single pattern or a temporal sequence of patterns to provide 3D surface data. In this context, multi-slit or stripe colored patterns may be used with the aim of reducing the number of projected images. However, color imaging sensors require the use of calibration procedures to address crosstalk effects between different channels and to reduce the chromatic aberrations. In this paper, a Coded Structured Light system has been developed by integrating a color stripe projector and a monochrome camera. A discrete coding method, which combines spatial and temporal information, is generated by sequentially projecting and acquiring a small set of fringe patterns. The method allows the concurrent measurement of geometrical and chromatic data by exploiting the benefits of using a monochrome camera. The proposed methodology has been validated by measuring nominal primitive geometries and free-form shapes. The experimental results have been compared with those obtained by using a time-multiplexing gray code strategy. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Keywords: 3D shape acquisition , Coded Structured Light , De Bruijn pattern , Texture reconstruction

In the field of dental health care, plaster models combined with 2D radiographs are widely used in clinical practice for orthodontic diagnoses. However, complex malocclusions can be better analyzed by exploiting 3D digital dental models, which allow virtual simulations and treatment planning processes. In this paper, dental data captured by independent imaging sensors are fused to create multi-body orthodontic models composed of teeth, oral soft tissues and alveolar bone structures. The methodology is based on integrating Cone-Beam Computed Tomography (CBCT) and surface structured light scanning. The optical scanner is used to reconstruct tooth crowns and soft tissues (visible surfaces) through the digitalization of both patients' mouth impressions and plaster casts. These data are also used to guide the segmentation of internal dental tissues by processing CBCT data sets. The 3D individual dental tissues obtained by the optical scanner and the CBCT sensor are fused within multi-body orthodontic models without human supervisions to identify target anatomical structures. The final multi-body models represent valuable virtual platforms to clinical diagnostic and treatment planning. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Keywords: Dental CBCT images , Optical scanning , Orthodontic model , Sensor fusion , Tooth segmentation

Recent developments in digital imaging techniques have allowed a wide spread of three-dimensional methodologies based on capturing anatomical tissues by different approaches, such as cone-beam computed tomography, three-dimensional photography and surface scanning. In oral rehabilitation, an objective method to predict surgical and orthodontic outcomes should be based on anatomical data belonging to soft facial tissue, facial skeleton and dentition (maxillofacial triad). However, none of the available imaging techniques can accurately capture the complete triad. This article presents a multi-modal framework, which allows image fusion of different digital techniques to create a three-dimensional virtual maxillofacial model, which integrates photorealistic face, facial skeleton and dentition. The methodology is based on combining structured light surface scanning and cone-beam computed tomography data processing. The fusion procedure provides multi-modal representations by aligning different tissues on the basis of common anatomical constraints. © IMechE 2012.

Keywords: Computer assisted , Cone-beam computed tomography scanning , Maxillofacial modelling , Multi-modal image fusion , Optical scanning , Three-dimensional medical imaging

Three-dimensional shapes can be digitised by using active imaging techniques, which reconstruct entire objects by capturing multiple range maps from different viewpoints. Multiple-view reconstructions require the computation of translation and rotation parameters to transform each range map with reference to a global coordinate frame. In this paper, an automatic method has been developed to efficiently align 3D range maps acquired by an active stereo vision system. The methodology is based on referring range maps to a global frame of fiducial markers captured by the stereo system. The procedure includes a refinement of the marker frame in order to globally minimise the misalignment errors. The methodology optimises the overall accuracy of 3D reconstructions regardless of the scanning strategies, even processing large data sets. The proposed approach has been experienced and validated by measuring both nominal shapes and industrial models. © 2012 Elsevier Ltd. All rights reserved.

Keywords: 3D optical scanning , Global refinement , Marker detection , Multi-view measurements , Stereo-vision

Wheel alignment, consisting of properly checking the wheel characteristic angles against vehicle manufacturers' specifications, is a crucial task in the automotive field since it prevents irregular tyre wear andaffects vehicle handling and safety. In recent years, systems based on Machine Vision have been widely studied in order to automatically detect wheels' characteristic angles. In order to overcome the limitations of existing methodologies, due to measurement equipment being mounted onto the wheels, the present work deals with design and assessment of a 3D machine vision-based system for the contactless reconstruction of vehicle wheel geometry, with particular reference to characteristic planes. Such planes, properly referred to as a global coordinate system, are used for determining wheel angles. The effectiveness of the proposed method was tested against a set of measurements carried out using a commercial 3D scanner; the absolute average error in measuring toe and camber angles with the machine vision system resulted in full compatibility with the expected accuracy of wheel alignment systems. © 2013 Furferi et al.

Keywords: Machine vision , Stereovision , Wheel alignment

Contouring of surfaces covers both metrology measurements and determination of displacements. There are a variety of scientific methods and corresponding devices used in contouring problems. Optical methods of contouring (OMC) have been proven to compete with the high precision and accuracy of Coordinate Measurement Machines (CMM). A general model of moiré contouring was recently developed by C.A. Sciammarella and his collaborators. The model integrates concepts of projective geometry and differential geometry of surfaces and utilizes symmetric projectors to reproduce the condition of projection from infinity. For specimens with dimensions ranging from few mm to more than 1 m, the measuring system and software provided standard deviations of the measured values that can reach 1/500 of the theoretical sensitivity defined by the pitch of the utilized grating. This paper will discuss the most recent trends in the optical contouring of surfaces focusing in particular on how to extend the general model of moiré contouring to the measurement of the three-dimensional displacement field of objects of arbitrary shape. © The Society for Experimental Mechanics, Inc. 2013.

In this article, we present an approach that uses both two force sensitive handles (FSH) and a flexible capacitive touch sensor (FCTS) to drive a haptic-based immersive system. The immersive system has been developed as part of a multimodal interface for product design. The haptic interface consists of a strip that can be used by product designers to evaluate the quality of a 3D virtual shape by using touch, vision and hearing and, also, to interactively change the shape of the virtual object. Specifically, the user interacts with the FSH to move the virtual object and to appropriately position the haptic interface for retrieving the six degrees of freedom required for both manipulation and modification modalities. The FCTS allows the system to track the movement and position of the user's fingers on the strip, which is used for rendering visual and sound feedback. Two evaluation experiments are described, which involve both the evaluation and the modification of a 3D shape. Results show that the use of the haptic strip for the evaluation of aesthetic shapes is effective and supports product designers in the appreciation of the aesthetic qualities of the shape. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Keywords: Conformable sensor , Flexible sensor , Haptic interface , Haptic strip , Tactile data processing

The paper describes the results of an on-going research activity whose aim is to allow companies, operating in the consumer goods market, to design the multisensory experience of their products. In case of the household appliances market, which is the research context of this study, the user experience derives from the interaction with specific product features such as the door, buttons, and drawers. Designing a good multisensory experience is complex since it means taking into account a combination of visual, hearing and haptic feedbacks a user perceives when interacting with the product. Virtual Reality offers the technologies to design and test that experience thought virtual prototypes, even if to date there is a lack of methodological approaches to practically guide and support this design activity. Relying on the results of previous authors' researches, the paper describes further methodological advances focused on making usable the proposed approach in the current design practice. The case study chosen to demonstrate the effectiveness of the method is a dishwasher door and the paper describes how to re-engineer the haptic feedback of a commercial model in order to make it more perceptually appealing at the moment of purchase. © 2013 CAD Solutions, LLC.

Keywords: Haptic interaction , Reverse engineering , User experience design , Virtual prototyping

This paper describes the development of an innovative hardware and software tool useful to sketch planar shapes in computer aided industrial design and computer aided design systems. The proposed system is based upon a tracked touch screen hand-held by the designer. The whole system is composed by a portable hand-held small touch screen (tablet size), a fixed LCD display and an optical tracking equipment. The touch screen is added by a simple camera for mixed reality optional functionality and its 6° of freedom movements are tracked. A custom software has been implemented for optimal exploitation and 3D sketching. The system acts as a free sketching device, a 3D mouse, as a realtime virtual and physical sketching plane or an external shape remodelling tool. The results obtained confirm the benefits of the virtual tablet in design, modelling and reverse engineering of industrial products. Copyright © 2013 Inderscience Enterprises Ltd.

Keywords: Computer aided sketching , Pose estimation , Reverse engineering , Sensor fusion , Touch screen tablet

In this paper we report the application of CAD/CAM based technologies for the innovative development of customized surgical devices to assist the mandibular rehabilitation in both primary surgery (resection and reconstruction) and secondary surgery (only reconstruction). Design and manufacturing of such customized surgical device are conducted according to the virtual pre-operative planning of the surgeon and with the aim to transferring this planning into the operating theatre. In the case of primary surgery, a cutting guide is developed to assist the resection step while a bone plate is developed to assist the reconstruction step. Instead, in the case of secondary surgery, in addition to the bone plate to support the reconstruction, also a repositioning guide is designed to bring back to the original position the resected stumps according to the original shape of the mandible. Finally, the components of the surgical devices are manufactured by DMLS in alloys suitable for biomedical applications. © 2012 Springer-Verlag France.

Keywords: 3D Reconstruction , Computed tomography , Computer aided design , Direct metal laser sintering , Rapid prototyping

In this work a novel design and manufacturing procedure have been experimented in order to improve the production of implant-supported nasal prosthesis. The complete workflow was divided into three main steps: data capture, prosthesis design and prosthesis manufacturing. First, the data capturing of the patient's face was obtained by means of 3D laser scanning. Then, design and manufacturing phases were carried out through CAD-CAM procedures and Rapid Prototyping technologies to obtain the mold for the silicone processing and the substructure for the retention of the prosthesis. Moreover, to design the customized prosthesis based on real anatomic shapes, a novel "Ear&Nose Digital Library" was developed in the framework of a multidisciplinary project with the involvement of students from medicine and engineering faculties. Advantages in terms of improvement of retention and cost reduction are presented. © 2012 Springer-Verlag.

Keywords: Facial rehabilitation , Prosthesis design , Rapid Prototyping , Reverse Engineering

The contribution regards the surveying of two statues of famous contemporary sculptors that have been placed in the central zone of Cosenza, which has been transformed in an open air museum. To realize a 3-D representation of the museum, different methodologies have been used, based on classical surveying (total stations and GNSS), image data and range data. The increasing performances of the new models of Time Of Flight (T.O.F.) laser scanners allow to build accurate models also for medium-size objects; on the other hand, the recent techniques of 3D modeling enable the processing of large amount of data and the effective removal of noises. Thus, if an extreme accuracy is not required, one can think to use the T.O.F. laser scanner, also for the surveying of statues. For the acquisition of the surfaces of the statues, two different types of laser scanning have been used: the Leica Scan StationC10, based on Time Of Flight, and the Minolta VIVID 300 triangulation scanner. In the paper, the comparison between the results obtained by using the different techniques is described.

Keywords: 3D modelling , Augmented reality , City model , Cultural heritage , Laser scanning , Multiresolution , Representation

Minimisation techniques are commonly adopted methodologies for retrieving a 3D surface starting from its shaded representation (image), i.e., for solving the widely known shape from shading (SFS) problem. Unfortunately, depending on the imaged object to be reconstructed, retrieved surfaces often results to be completely different from the expected ones. In recent years, a number of interactive methods have been explored with the aim of improving surface reconstruction; however, since most of these methods require user interaction performed on a tentative reconstructed surface which often is significantly different from the desired one, it is advisable to increase the quality of the surface, to be further processed, as much as possible. Inspired by such techniques, the present work describes a new method for interactive retrieving of shaded object surface. The proposed approach is meant to recover the expected surface by using easy-to-set boundary conditions, so that the human-computer interaction primarily takes place prior to the surface retrieval. The method, tested on a set of case studies, proves to be effective in achieving sufficiently accurate reconstruction of scenes with both front and side illumination. © 2013 Inderscience Enterprises Ltd.

Keywords: Boundary conditions , Computational vision , Human-computer interaction , Minimisation techniques , SFS , Shape from shading

Industrial esthetic designers typically produce hand-drawn sketches in the form of orthographic projections. A subsequent translation from 2D-drawings to 3D-models is usually necessary. This involves a considerably time consuming process, so that some automation is advisable. Common approaches to this "reconstruction problem" start directly from "exact" 2D vector representations or try to vectorize 2D raster images prior to the reconstruction phase. These approaches, however, typically fail to deal with free form geometries like the ones commonly found in esthetic industrial design. This work presents a new methodology suitable for free form geometries, comprising the generation and processing of a 3D voxel image obtained from a hand drawing, the creation of a set of 3D curves fitting the voxel image and the automatic generation of surface patches on the resulting curve network. Several case studies are also presented in order to emphasize and discuss strengths and weaknesses of the proposed method. © 2013 Elsevier B.V. All rights reserved.

Keywords: 3D geometry fitting , 3D reconstruction , Industrial design , Orthographic views , Voxel imaging

3D optical scanning systems are used more and more for quality control purposes. The effective utilization of such systems needs an efficient virtual planning of the product acquisition viewpoints. Literature shows how 3D CAD product models can be used as reference in order to manage the verification process and as a basis for the computation of the optimal viewpoints. However, in the mechanical field, a variety of inspection tasks is experienced by engineers involved in the quality control process: GD&T verification, production phases control such as sheet metal cutting, evaluation of aesthetic appearance of parts, global shape deformation measurement and specific point deviations assessment. This leads to the necessity of flexible view planning approaches which adapt to the specificity of the required inspection task. The present work targets the development of a comprehensive view planning approach in which several algorithmic options are triggered by the product features to be inspected. Algorithms have been implemented in a prototypal software system which has been experimented as an off-line application to provide inputs to a multi-axis degree of freedom robot arm mounting an optical 3D scanner. Two test cases from die casting and automotive fields are presented. They show the computation of acquisition poses in a suitable sequence and efficiency in the obtained results. © 2012 Springer-Verlag.

Keywords: 3D scanning , GD&T , Inspection , Quality control , View planning

Literature shows how 3D CAD product models can be used as reference in order to manage the verification process by 3D optical scanning systems and the computation of the optimal viewpoints. However, in the mechanical field, a variety of inspection tasks is experienced by engineers involved in the quality control process: GD&T verification, production phases control such as sheet metal cutting, evaluation of aesthetic appearance of parts, global shape deformation measurement and specific point deviations assessment. This leads to the necessity of flexible view planning approaches which adapt to the specificity of the required inspection task. The present work targets the development of a comprehensive view planning approach in which several algorithmic options are triggered by the product features to be inspected. Algorithms have been implemented in a prototypal software system which has been experimented as an off-line application to provide inputs to a multiaxis Degree of Freedom (DoF) robot arm mounting an optical 3D scanner. Two test cases from die casting and automotive fields are presented. They show the computation of acquisition poses in a suitable sequence and efficiency in the obtained results. © 2013 CAD Solutions, LLC.

Keywords: 3D scanning , GD&T , Inspection , Quality control , View planning