Sensor architectures and technologies for upper limb 3d surface reconstruction: A review

3D digital models of the upper limb anatomy represent the starting point for the design process of bespoke devices, such as orthoses and prostheses, which can be modeled on the actual patient’s anatomy by using CAD (Computer Aided Design) tools. The ongoing research on optical scanning methodologies has allowed the development of technologies that allow the surface reconstruction of the upper limb anatomy through procedures characterized by minimum discomfort for the patient. However, the 3D optical scanning of upper limbs is a complex task that requires solving problematic aspects, such as the difficulty of keeping the hand in a stable position and the presence of artefacts due to involuntary movements. Scientific literature, indeed, investigated different approaches in this regard by either integrating commercial devices, to create customized sensor architectures, or by developing innovative 3D acquisition techniques. The present work is aimed at presenting an overview of the state of the art of optical technologies and sensor architectures for the surface acquisition of upper limb anatomies. The review analyzes the working principles at the basis of existing devices and proposes a categorization of the approaches based on handling, pre/post-processing effort, and potentialities in real-time scanning. An in-depth analysis of strengths and weaknesses of the approaches proposed by the research community is also provided to give valuable support in selecting the most appropriate solution for the specific application to be addressed

Towards superfast 3D optical metrology with digital micromirror device (DMD) platforms

This paper summarizes our decade-long research efforts towards superfast 3D shape measurement leveraging the digital micromirror device (DMD) platforms. Specifically, we will present the following technologies: (1) high-resolution real-time 3D shape measurement technology that achieves 30 Hz simultaneous 3D shape acquisition, reconstruction and display with more than 300,000 points per frame; (2) Superfast 3D optical metrology technology that achieves 3D measurement at a rate of tens of kHz utilizing the binary defocusing method we invented; and (3) the improvement of the binary defocusing technology for superfast and high-accuracy 3D optical metrology using the DMD platforms. This paper will present both principles and experimental results. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

A Cost-Effective System for Aerial 3D Thermography of Buildings

Three-dimensional (3D) imaging and infrared (IR) thermography are powerful tools in many areas in engineering and sciences. Their joint use is of great interest in the buildings sector, allowing inspection and non-destructive testing of elements as well as an evaluation of the energy efficiency. When dealing with large and complex structures, as buildings (particularly historical) generally are, 3D thermography inspection is enhanced by Unmanned Aerial Vehicles (UAV-also known as drones). The aim of this paper is to propose a simple and cost-effective system for aerial 3D thermography of buildings. Special attention is thus payed to instrument and reconstruction software choice. After a very brief introduction to IR thermography for buildings and 3D thermography, the system is described. Some experimental results are given to validate the proposal

Automated Semantic Content Extraction from Images

In this study, an automatic semantic segmentation and object recognition methodology is implemented which bridges the semantic gap between low level features of image content and high level conceptual meaning. Semantically understanding an image is essential in modeling autonomous robots, targeting customers in marketing or reverse engineering of building information modeling in the construction industry. To achieve an understanding of a room from a single image we proposed a new object recognition framework which has four major components: segmentation, scene detection, conceptual cueing and object recognition. The new segmentation methodology developed in this research extends Felzenswalb\u27s cost function to include new surface index and depth features as well as color, texture and normal features to overcome issues of occlusion and shadowing commonly found in images. Adding depth allows capturing new features for object recognition stage to achieve high accuracy compared to the current state of the art. The goal was to develop an approach to capture and label perceptually important regions which often reflect global representation and understanding of the image. We developed a system by using contextual and common sense information for improving object recognition and scene detection, and fused the information from scene and objects to reduce the level of uncertainty. This study in addition to improving segmentation, scene detection and object recognition, can be used in applications that require physical parsing of the image into objects, surfaces and their relations. The applications include robotics, social networking, intelligence and anti-terrorism efforts, criminal investigations and security, marketing, and building information modeling in the construction industry. In this dissertation a structural framework (ontology) is developed that generates text descriptions based on understanding of objects, structures and the attributes of an image

Superfast three-dimensional (3D) shape measurement with binary defocusing techniques and its applications

High-speed and high-accuracy three-dimensional (3D) shape measurement has enormous potential to benefit numerous areas including advanced manufacturing, medical imaging, and diverse scientific research fields. For example, capturing the rapidly pulsing wings of a flying insect could enhance our understanding of flight and lead to better and safer aircraft designs. Even though there are numerous 3D shape measurement techniques in the literature, it remains extremely difficult to accurately capture rapidly changing events. Due to the potential for achieving high speed and high measurement accuracy, the digital fringe projection (DFP) techniques have been exhaustively studied and extensively applied to numerous disciplines. Real-time (30 Hz or better) 3D shape measurement techniques have been developed with DFP methods, yet the upper speed limit is typically 120 Hz, the refresh rate of a typical digital video projector. 120 Hz speed can accurately measure the slowly changing objects, such as human facial expressions, but it is far from sufficient to capture high-speed motions (e.g., live, beating hearts or flying insects). To overcome this speed limitation, the binary defocusing technique was recently proposed. Instead of using 8-bit sinusoidal patterns, the binary defocusing technique generates sinusoidal patterns by properly defocusing squared 1-bit binary patterns. Using this technique, kilo-Hertz (kHz) 3D shape measurement rate has been achieved. However, the binary defocusing technique suffers three major limitations: 1) low phase quality due to the influence of high-frequency harmonics; 2) smaller depth measurement range; and 3) low measurement accuracy due to the difficulty of applying existing calibration methods to the system with an out-of-focus projector. The goal of this dissertation research is to achieve superfast 3D shape measurement by overcoming the major limitations of the binary defocusing technique. Once a superfast 3D shape measurement platform is developed, numerous applications could be benefited. To this end, this dissertation research look into verifying its value by applying to the biomedical engineering field. Specifically, this dissertation research has made major contributions by conquering some major challenges associated with the binary defocusing technique. The first challenge this dissertation addresses is associated with the limited depth range and low phase quality of the binary defocusing method. The binary defocusing technique essentially generates quasi-sinusoidal fringe patterns by suppressing high-frequency harmonics through lens defocusing. However, the optical engines of the majority of digital video projectors are designed and optimized for applications with large depth of focus; for this reason, good quality sinusoids can only be generated by this technique within a very small depth region. This problem is exacerbated if the fringe stripes are wide. In that case, the high-frequency harmonics cannot be properly suppressed through defocusing, making it almost impossible to generate reasonable quality sinusoids. To alleviate this problem associated with high-frequency harmonics, an optimal pulse width modulation (OPWM) method, developed in power electronics, is proposed to improve the fringe pattern quality. Instead of projecting squared binary structures, the patterns are optimized, in one dimension perpendicular to the fringe stripes, by selectively eliminating the undesired harmonics which affect the phase quality the most. Both simulation and experimental data demonstrate that the OPWM method can substantially improve the squared binary defocusing technique when the fringe periods are between 30-300 pixels. With this technique, a multi-frequency phase-shifting algorithm is realized that enables the development of a 556-Hz 3D shape measurement system capable of capturing multiple rapidly moving objects. The OPWM technique is proved successful when the fringe stripe widths are within a certain range, yet it fails to achieve higher-quality fringe patterns when the desired fringe period goes beyond the optimal range. To further improve the binary defocusing technique, binary dithering techniques are proposed. Unlike the OPWM method, the dithering technique optimizes the patterns in both x and y dimensions, and thus can achieve higher-quality fringe patterns. This research demonstrates the superiority of this technique over all aforementioned binary defocusing techniques for high-quality 3D shape measurement even when the projector is nearly focused and the fringe stripes are wide. The second challenge this dissertation addresses is accurately calibrating the DFP system with an out-of-focus projector. The binary defocusing technique generates quasi-sinusoidal patterns through defocusing, and thus the projector cannot be perfectly in focus. In the meantime, state-of-the-art DFP system calibration assumes that the projector is always in focus. To address this problem, a novel calibration method is proposed that directly relates depth z with the phase pixel by pixel without the requirement of projector calibration. By this means, very high accuracy depth measurement is achieved: for a depth measurement range of 100 mm, the root-mean-squared (rms) error is approximately 70 &mu m. The third challenge this dissertation addresses is associated with the hardware limitation for the superfast 3D shape measurement technique. The high refresh rate of the digital micro-mirror device (DMD) has enabled superfast 3D shape measurement, yet a hardware limitation has been found once the speeds go beyond a certain range. This is because the DMD cannot completely turn on/off between frames, leading to coupling problems associated with the transient response of the DMD chip. The coupling effect causes substantial measurement error during high-speed measurement. Fortunately, since this type of error is systematic, this research finds that such error can be reduced to a negligible level by properly controlling the timing of the projector and the camera. The superfast 3D shape measurement platform developed in this research could benefit numerous applications. This research applies the developed platform to the measurement of the cardiac motion of live, beating rabbit hearts. The 3D geometric motion of the live, beating rabbit hearts can be successfully captured if the measurement speed is sufficiently fast (i.e. 200 Hz or higher for normal beating rabbit hearts). This research also finds that, due to the optical properties of live tissue, caution should be given in selecting the spectrum of light in order to properly measure the heart surface. In summary, the improved binary defocusing techniques are overwhelmingly advantageous compared to the conventional sinusoidal projection method or the squared binary defocusing technique. We believe that the superfast 3D shape measurement platform we have developed has the potential to broadly impact many more academic studies and industrial practices, especially those where understanding the high-speed 3D phenomena is critical

Heritage documentation techniques and methods

This methodology notebooks "Heritage documentation techniques and methods", contains • 3D modelling, digital photography and information dissemination • Creation of 3D models by using scanners • Low-cost desktop scanner • Photography notes: Exposure • Photography notes: Focal length, lenses and cross-polarization • White adjustment and colour calibration • Image-Based Modelling Systems • Focus stacking technique • Rollout photography and DStretch filter • Information dissemination • 3D diagram blocks • Simple animations of 3D modelsEsta serie de cuadernos tiene como objetivo difundir un conjunto de técnicas usadas principalmente para la construcción y documentación de modelos tridimensionales (3D) y fotografía de alta resolución de objetos arqueológicos. Estas técnicas posibilitan construir modelos con calidad métrica contrastada, color calibrado y alta resolución que se difunden por internet usando diversas plataformas.This series of notebooks aims to describe a set of techniques used mainly to construct and document the three-dimensional (3D) models and high-resolution photographs of archaeological objects. These techniques can be used to build models with a contrasting metric quality, calibrated colour and high resolution, to be disseminated on the Internet using various platforms and web services.Parte de la realización de estos cuadernos ha sido financiada a través del proyecto GR18028 (Grupo de investigación RNM026) el cual ha sido cofinanciado por los Fondos Europeos de Desarrollo Regional (FEDER) y el Gobierno de Extremadura

ipProjector: Designs and Techniques for Geometry-Based Interactive Applications Using a Portable Projector

We propose an interactive projection system for a virtual studio setup using a single self-contained and portable projection device. The system is named ipProjector, which stands for Interactive Portable Projector. Projection allows special effects of a virtual studio to be seen by live audiences in real time. The portable device supports 360-degree shooting and projecting angles and is easy to be integrated with an existing studio setup. We focus on two fundamental requirements of the system and their implementations. First, nonintrusive projection is performed to ensure that the special effect projections and the environment analysis (for locating the target actors or objects) can be performed simultaneously in real time. Our approach uses Digital Light Processing technology, color wheel analysis, and nearest-neighbor search algorithm. Second, a paired projector-camera system is geometrically calibrated with two alternative setups. The first uses a motion sensor for real-time geometric calibration, and the second uses a beam splitter for scene-independent geometric calibration. Based on a small-scale laboratory setting, experiments were conducted to evaluate the geometric accuracy of the proposed approaches, and an application was built to demonstrate the proposed ipProjector concept. Techniques of special effect rendering are not concerned in this paper

自己投影法に基づく高速三次元形状検査の研究

広島大学(Hiroshima University)博士(工学)Doctor of Engineeringdoctora