3,930 research outputs found
Pre-Processing of Point-Data from Contact and Optical 3D Digitization Sensors
Contemporary 3D digitization systems employed by reverse engineering (RE) feature ever-growing scanning speeds with the ability to generate large quantity of points in a unit of time. Although advantageous for the quality and efficiency of RE modelling, the huge number of point datas can turn into a serious practical problem, later on, when the CAD model is generated. In addition, 3D digitization processes are very often plagued by measuring errors, which can be attributed to the very nature of measuring systems, various characteristics of the digitized objects and subjective errors by the operator, which also contribute to problems in the CAD model generation process. This paper presents an integral system for the pre-processing of point data, i.e., filtering, smoothing and reduction, based on a cross-sectional RE approach. In the course of the proposed system development, major emphasis was placed on the module for point data reduction, which was designed according to a novel approach with integrated deviation analysis and fuzzy logic reasoning. The developed system was verified through its application on three case studies, on point data from objects of versatile geometries obtained by contact and laser 3D digitization systems. The obtained results demonstrate the effectiveness of the system
Analysis of Modern Optical Inspection Systems for Parts Manufactured by Selective Laser Melting
[EN] Metal additive manufacturing (AM) allows obtaining functional parts with the possibility of optimizing them topologically without affecting system performance. This is of great interest for sectors such as aerospace, automotive, and medicalâsurgical. However, from a metrological point of view, the high requirements applied in these sectors constitute a challenge for inspecting these types of parts. Non-contact inspection has gained great relevance due to the rapid verification of AM parts. Optical measurement systems (OMSs) are being increasingly adopted for geometric dimensioning and tolerancing (GD&T) verification within the context of Industry 4.0. In this paper, the suitability (advantages and limitations) of five different OMSs (based on laser triangulation, conoscopic holography, and structured light techniques) for GD&T verification of parts manufactured by selective laser melting (SLM) is analyzed. For this purpose, a specific testing part was designed and SLM-manufactured in 17-4PH stainless steel. Once the part was measured by contact (obtaining the reference GD&T values), it was optically measured. The scanning results allow comparing the OMSs in terms of their inspection speed as well as dimensional and geometrical accuracy. As a result, two portable systems (handheld laser triangulation and structured blue-light scanners) were identified as the most accurate optical techniques for scanning SLM parts.S
Fibre imaging bundles for full-field optical coherence tomography
An imaging fibre bundle is incorporated into a full-field imaging OCT system,
with the aim of eliminating the mechanical scanning currently required at the
probe tip in endoscopic systems. Each fibre within the imaging bundle addresses
a Fizeau interferometer formed between the bundle end and the sample, a
configuration which ensures down lead insensitivity of the probe fibres,
preventing variations in sensitivity due to polarization changes in the many
thousand constituent fibres. The technique allows acquisition of information
across a planar region with single-shot measurement, in the form of a 2D image
detected using a digital CCD camera. Depth scanning components are now confined
within a processing interferometer external to the completely passive endoscope
probe. The technique has been evaluated in our laboratory for test samples, and
images acquired using the bundle-based system are presented. Data are displayed
either as en-face scans, parallel to the sample surface, or as slices through
the depth of the sample, with a spatial resolution of about 30 ĂÂŻĂ ĂÂm. The minimum
detectable reflectivity at present is estimated to be about 10-3, which is
satisfactory for many inorganic samples. Methods of improving the signal-to-
noise ratio for imaging of lower reflectivity samples are discuss
A review of advances in pixel detectors for experiments with high rate and radiation
The Large Hadron Collider (LHC) experiments ATLAS and CMS have established
hybrid pixel detectors as the instrument of choice for particle tracking and
vertexing in high rate and radiation environments, as they operate close to the
LHC interaction points. With the High Luminosity-LHC upgrade now in sight, for
which the tracking detectors will be completely replaced, new generations of
pixel detectors are being devised. They have to address enormous challenges in
terms of data throughput and radiation levels, ionizing and non-ionizing, that
harm the sensing and readout parts of pixel detectors alike. Advances in
microelectronics and microprocessing technologies now enable large scale
detector designs with unprecedented performance in measurement precision (space
and time), radiation hard sensors and readout chips, hybridization techniques,
lightweight supports, and fully monolithic approaches to meet these challenges.
This paper reviews the world-wide effort on these developments.Comment: 84 pages with 46 figures. Review article.For submission to Rep. Prog.
Phy
CMOS-3D smart imager architectures for feature detection
This paper reports a multi-layered smart image sensor architecture for feature extraction based on detection of interest points. The architecture is conceived for 3-D integrated circuit technologies consisting of two layers (tiers) plus memory. The top tier includes sensing and processing circuitry aimed to perform Gaussian filtering and generate Gaussian pyramids in fully concurrent way. The circuitry in this tier operates in mixed-signal domain. It embeds in-pixel correlated double sampling, a switched-capacitor network for Gaussian pyramid generation, analog memories and a comparator for in-pixel analog-to-digital conversion. This tier can be further split into two for improved resolution; one containing the sensors and another containing a capacitor per sensor plus the mixed-signal processing circuitry. Regarding the bottom tier, it embeds digital circuitry entitled for the calculation of Harris, Hessian, and difference-of-Gaussian detectors. The overall system can hence be configured by the user to detect interest points by using the algorithm out of these three better suited to practical applications. The paper describes the different kind of algorithms featured and the circuitry employed at top and bottom tiers. The Gaussian pyramid is implemented with a switched-capacitor network in less than 50 ÎŒs, outperforming more conventional solutions.Xunta de Galicia 10PXIB206037PRMinisterio de Ciencia e InnovaciĂłn TEC2009-12686, IPT-2011-1625-430000Office of Naval Research N00014111031
Implementation of 3D Optical Scanning Technology for Automotive Applications
Reverse engineering (RE) is a powerful tool for generating a CAD model from the 3D scan data of a physical part that lacks documentation or has changed from the original CAD design of the part. The process of digitizing a part and creating a CAD model from 3D scan data is less time consuming and provides greater accuracy than manually measuring the part and designing the part from scratch in CAD. 3D optical scanning technology is one of the measurement methods which have evolved over the last few years and it is used in a wide range of areas from industrial applications to art and cultural heritage. It is also used extensively in the automotive industry for applications such as part inspections, scanning of tools without CAD definition, scanning the casting for definition of the stock (i.e. the amount of material to be removed from the surface of the castings) model for CAM programs and reverse engineering. In this study two scanning experiments of automotive applications are illustrated. The first one examines the processes from scanning to re-manufacturing the damaged sheet metal cutting die, using a 3D scanning technique and the second study compares the scanned point clouds data to 3D CAD data for inspection purposes. Furthermore, the deviations of the part holes are determined by using different lenses and scanning parameters
State-of-The-Art and Applications of 3D Imaging Sensors in Industry, Cultural Heritage, Medicine, and Criminal Investigation
3D imaging sensors for the acquisition of three dimensional (3D) shapes have created, in recent years, a considerable degree of interest for a number of applications. The miniaturization and integration of the optical and electronic components used to build them have played a crucial role in the achievement of compactness, robustness and flexibility of the sensors. Today, several 3D sensors are available on the market, even in combination with other sensors in a âsensor fusionâ approach. An importance equal to that of physical miniaturization has the portability of the measurements, via suitable interfaces, into software environments designed for their elaboration, e.g., CAD-CAM systems, virtual renders, and rapid prototyping tools. In this paper, following an overview of the state-of-art of 3D imaging sensors, a number of significant examples of their use are presented, with particular reference to industry, heritage, medicine, and criminal investigation applications
Practical and Rich User Digitization
A long-standing vision in computer science has been to evolve computing
devices into proactive assistants that enhance our productivity, health and
wellness, and many other facets of our lives. User digitization is crucial in
achieving this vision as it allows computers to intimately understand their
users, capturing activity, pose, routine, and behavior. Today's consumer
devices - like smartphones and smartwatches provide a glimpse of this
potential, offering coarse digital representations of users with metrics such
as step count, heart rate, and a handful of human activities like running and
biking. Even these very low-dimensional representations are already bringing
value to millions of people's lives, but there is significant potential for
improvement. On the other end, professional, high-fidelity comprehensive user
digitization systems exist. For example, motion capture suits and multi-camera
rigs that digitize our full body and appearance, and scanning machines such as
MRI capture our detailed anatomy. However, these carry significant user
practicality burdens, such as financial, privacy, ergonomic, aesthetic, and
instrumentation considerations, that preclude consumer use. In general, the
higher the fidelity of capture, the lower the user's practicality. Most
conventional approaches strike a balance between user practicality and
digitization fidelity.
My research aims to break this trend, developing sensing systems that
increase user digitization fidelity to create new and powerful computing
experiences while retaining or even improving user practicality and
accessibility, allowing such technologies to have a societal impact. Armed with
such knowledge, our future devices could offer longitudinal health tracking,
more productive work environments, full body avatars in extended reality, and
embodied telepresence experiences, to name just a few domains.Comment: PhD thesi
Infrastructure for Detector Research and Development towards the International Linear Collider
The EUDET-project was launched to create an infrastructure for developing and
testing new and advanced detector technologies to be used at a future linear
collider. The aim was to make possible experimentation and analysis of data for
institutes, which otherwise could not be realized due to lack of resources. The
infrastructure comprised an analysis and software network, and instrumentation
infrastructures for tracking detectors as well as for calorimetry.Comment: 54 pages, 48 picture
Comparative analysis of 3d digitization systems in the field of dental prosthetics
Amongst the modern engineering technologies which have found broad application in the field of dentistry, one of the most widely used is the 3D digitization. This paper deals with the application of 3D digitization systems in the field of dental prosthetics, and attempt to contribute in this field through comparative analysis of this kind of systems. Special attention is focused on extra oral 3D digitization systems and among them on non specialized dental 3D digitization systems. Beside the general overview and analysis of nine different systems, this paper presents experimental results of comparative accuracy analysis of two high-end 3D digitization systems - Atos II Triple Scan and Zeiss Metrotom 1500. Investigation was based on CAD inspection technique and included 3D and 2D cross sectional analysis. Results related to 3D analysis show that the majority of deviations are in positive direction, concentrated around 0,025 mm. Results of 2D analysis implicate the conclusion that the accuracy of the analysed systems is dependent on surface shape as well as on the model position during the process of 3D digitization
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