Optical 3D Measurement Research Articles

Metrological changes in surface morphology of high-strength steels in manufacturing processes

In this paper the surfaces of high-strength steels were analyzed using an optical 3D measurement system to investigate into the surface morphology and parameters of surface topography. Analyzed surfaces were generated by the most commonly used in the production facilities of manufacturing processes. The study was conducted for 400 HB plates. It was established that the behavioral changes in the manufacturing process influence the surface characteristics to a great extent. Comprehensive parametric analysis was conducted for dry production conditions. It has been observed that there exists a close correlation between mesh grit size and parameters of surface roughness Ssk and Sku in abrasive blasting processes. Furthermore the results show that the surface morphology in turning process depends to a large extent on the direction of feed motion. The study was performed within a production facility during the machining of components subject to wear.

On the accuracy potential of focused plenoptic camera range determination in long distance operation

Plenoptic cameras have found increasing interest in optical 3D measurement techniques in recent years. While their basic principle is 100years old, the development in digital photography, micro-lens fabrication technology and computer hardware has boosted the development and lead to several commercially available ready-to-use cameras. Beyond their popular option of a posteriori image focusing or total focus image generation, their basic ability of generating 3D information from single camera imagery depicts a very beneficial option for certain applications.The paper will first present some fundamentals on the design and history of plenoptic cameras and will describe depth determination from plenoptic camera image data. It will then present an analysis of the depth determination accuracy potential of plenoptic cameras. While most research on plenoptic camera accuracy so far has focused on close range applications, we will focus on mid and long ranges of up to 100m. This range is especially relevant, if plenoptic cameras are discussed as potential mono-sensorial range imaging devices in (semi-)autonomous cars or in mobile robotics.The results show the expected deterioration of depth measurement accuracy with depth. At depths of 30–100m, which may be considered typical in autonomous driving, depth errors in the order of 3% (with peaks up to 10–13m) were obtained from processing small point clusters on an imaged target. Outliers much higher than these values were observed in single point analysis, stressing the necessity of spatial or spatio-temporal filtering of the plenoptic camera depth measurements. Despite these obviously large errors, a plenoptic camera may nevertheless be considered a valid option for the application fields of real-time robotics like autonomous driving or unmanned aerial and underwater vehicles, where the accuracy requirements decrease with distance.

Shot noise limit of the optical 3D measurement methods for smooth surfaces

The measurement uncertainty of optical 3D measurement methods for smooth surfaces caused by shot noise is investigated. The shot noise is a fundamental property of the quantum nature of light. If all noise sources are eliminated, the shot noise represents the ultimate limit of the measurement uncertainty. The measurement uncertainty is calculated for several simple model methods. The analysis shows that the measurement uncertainty depends on the wavelength of used light, the number of photons used for the measurement, and on a factor that is connected with the geometric arrangement of the measurement setup.

Precision hole making on laminate composite: a tool wear analysis and comparison between drilling and punching

Hole precision is highly critical for accurate and strong fastener assembly. This factor is considerably important for structural materials, such as composite materials. Drilling is the most commonly used process for producing holes on composites. However, drilling causes excessive tool wear, which may affect the quality of holes and result in damage, such as delamination. The main objective of this study is to compare the drilling and punching processes in terms of tool wear by using the focus variation technique. The scanned images of both the puncher and drill bits are obtained by using a 3D optical surface measurement device called Alicona IFM. Tool wear patterns from both drilling and punching are analysed and compared, and the effects of the processes on the quality of the produced holes are observed.

Integrating Optical 3D Measurement Techniques in Pipe Bending: A Model-based Approach Minimizing Waste by Deriving Real Functional Design Behaviour

Due to springback, deviations compared to the designed ideal modal occur during pipe bending processes. With quality control gauges no quantitative statements can be made regarding the process stability. The components are either good or bad and no production trends can be determined. This leads to high scrap rates and in addition, the real performance of the produced components may differ from the target behaviour of the initially designed CAD model. As addressed within this contribution, with integrating optical 3D measuring systems into the bending process, the actual state can be detected continuously. This enables to give feedback to the bending device for automatically readjust of bending parameters and thus prevent producing defective components. Moreover, the digitalisation of the actual contour allows a parametric correction of the designed CAD model, whereby the functional behaviour can be closer to reality within simulation models.

Definition of anatomical zero positions for assessing shoulder pose with 3D motion capture during bilateral abduction of the arms.

BackgroundSurgical interventions at the shoulder may alter function of the shoulder complex. Clinically, the outcome can be assessed by universal goniometry. Marker-based motion capture may not resemble these results due to differing angle definitions.MethodsThe clinical inspection of bilateral arm abduction for assessing shoulder dysfunction is performed with a marker based 3D optical measurement method. An anatomical zero position of shoulder pose is proposed to determine absolute angles according to the Neutral-0-Method as used in orthopedic context. Static shoulder positions are documented simultaneously by 3D marker tracking and universal goniometry in 8 young and healthy volunteers. Repetitive bilateral arm abduction movements of at least 150° range of motion are monitored. Similarly a subject with gleno-humeral osteoarthritis is monitored for demonstrating the feasibility of the method and to illustrate possible shoulder dysfunction effects.ResultsWith mean differences of less than 2°, the proposed anatomical zero position results in good agreement between shoulder elevation/depression angles determined by 3D marker tracking and by universal goniometry in static positions. Lesser agreement is found for shoulder pro-/retraction with systematic deviations of up to 6°. In the bilateral arm abduction movements the volunteers perform a common and specific pattern in clavicula-thoracic and gleno-humeral motion with maximum shoulder angles of 32° elevation, 5° depression and 45° protraction, respectively, whereas retraction is hardly reached. Further, they all show relevant out of (frontal) plane motion with anteversion angles of 30° in overhead position (maximum abduction). With increasing arm anteversion the shoulder is increasingly retroverted, with a maximum of 20° retroversion. The subject with gleno-humeral osteoarthritis shows overall less shoulder abduction range of motion but with increased out-of-plane movement during abduction.ConclusionsThe proposed anatomical zero definition for shoulder pose fills the missing link for determining absolute joint angles for shoulder elevation/depression and pro-/retraction. For elevation-/depression the accuracy suits clinical expectations very well with mean differences less than 2° and limits of agreement of 8.6° whereas for pro-/retraction the accuracy in individual cases may be inferior with limits of agreement of up to 24.6°. This has critically to be kept in mind when applying this concept to shoulder intervention studies.

Documentation, Multi-scale and Multi-dimensional Representation of Cultural Heritage for the Policies of Redevelopment, Development and Regeneration

Abstract. The paper describes reading criteria for the documentation for important buildings in Milan, Italy, as a case study of the research on the integration of new technologies to obtain 3D multi-scale representation architectures. In addition, affords an overview of the actual optical 3D measurements sensors and techniques used for surveying, mapping, digital documentation and 3D modeling applications in the Cultural Heritage field. Today new opportunities for an integrated management of data are given by multiresolution models, that can be employed for different scale of representation. The goal of multi-scale representations is to provide several representations where each representation is adapted to a different information density with several degrees of detail. The Digital Representation Platform, along with the 3D City Model, are meant to be particularly useful to heritage managers who are developing recording, documentation, and information management strategies appropriate to territories, sites and monuments. Digital Representation Platform and 3D City Model are central activities in a the decision-making process for heritage conservation management and several urban related problems. This research investigates the integration of the different level-of-detail of a 3D City Model into one consistent 4D data model with the creation of level-of-detail using algorithms from a GIS perspective. In particular, such project is based on open source smart systems, and conceptualizes a personalized and contextualized exploration of the Cultural Heritage through an experiential analysis of the territory.

Label-free characterization of white blood cells by measuring 3D refractive index maps.

The characterization of white blood cells (WBCs) is crucial for blood analyses and disease diagnoses. However, current standard techniques rely on cell labeling, a process which imposes significant limitations. Here we present three-dimensional (3D) optical measurements and the label-free characterization of mouse WBCs using optical diffraction tomography. 3D refractive index (RI) tomograms of individual WBCs are constructed from multiple two-dimensional quantitative phase images of samples illuminated at various angles of incidence. Measurements of the 3D RI tomogram of WBCs enable the separation of heterogeneous populations of WBCs using quantitative morphological and biochemical information. Time-lapse tomographic measurements also provide the 3D trajectory of micrometer-sized beads ingested by WBCs. These results demonstrate that optical diffraction tomography can be a useful and versatile tool for the study of WBCs.

Experimental investigation on the deformation of CFRP cylinders using piezo-actuators

In this paper, the deformation of cylindrical composite structures employing piezoelectric actuators is investigated. It specifically addresses radial deformations of a composite cylinder generated by macro fibre composites (MFC). The purpose is to experimentally characterise the shape as well as the magnitude of the composite cylinder’s deformation using an optical full-field 3D measurement system. Besides cylinder expansion and contraction under operating conditions, shell bending appeared to contribute significantly to the overall deformation behaviour. With the data provided the development of an adaptive primary aircraft structure is conceivable.

Influence of argon pollution on the weld surface morphology

In this paper the surfaces of butt welded joints in steel tubes were analyzed using an optical 3D measurement system to determine the morphology and topographic parameters. It was established that pollution of the argon shield gas with oxygen did not influence the width of the heat-affected zone. However, the composition of the shield gas significantly influenced the surface asymmetry, Ssk, and its inclination Sku. The measurement of these parameters enabled the selection of a higher quality surface, which was visually proven by the reduction in discoloration of the surface of the weld joint. High quality surfaces eliminate a potential habitat for bacteria and a future source of corrosion as well as providing less resistance to fluid flow.

에어컨 실내기 사출 조립품의 열 변형 3D측정과 유한요소해석

Thermal deformation, such as bending and twisting, occurs among the polymer parts of air-conditioner indoor units because of repetitive temperature change during heating operation. In this study, a numerical method employing finite-element analysis to efficiently simulate the thermal deformation of an assembly is proposed. Firstly, the displacement of an actual assembly produced by thermal deformation was measured using a 3D optical measurement system. The measurement results indicated a general downward sag of the assembly, and the maximum displacement value was approximately 1 mm. The temperature distribution was measured using a thermographic camera, and the results were used as initial-temperature boundary conditions to perform temperature-displacement analysis. The simulation results agreed well with the measured data. To reduce the thermal deformation, the stiffness increased 100%. As the results, the maximum displacement decreased by approximately 5.4% and the twisting deformation of the holder improved significantly.

Influence of the explosive treatment on the mechanical properties and microstructure of copper

The manuscript discusses mechanical properties and microstructure of copper before and after the explosive treatment. The aim of this research was to characterize and evaluate the influence of explosive treatment which is present during the manufacturing procedure of a new type of unidirectional cellular structure. For this purpose testing of tensile copper specimens before and after explosive treatment has been performed, accounting also for strain rate sensitivity. The experimental measurements have been supported by the 3D optical deformation measurement system and infrared thermography. The effect of the explosive treatment on coppers’ microstructure has been analysed using the electron microscopy. The study shows that the explosive treatment significantly influences the global response of copper throughout the complete loading range. All specimens exhibit a positive strain rate sensitivity. The uniform distribution of principle strain in untreated specimens is replaced by strain localization which appears just after the start of the loading resulting in much lower failure strain. The observations of microstructure before and after explosive treatment revealed that explosive loading resulted in intensive fragmentation of grains that are enriched with sub-grain layered structure. Such grain size refinement is the main contributor to strengthening of the explosive treated copper.

Monitoring phase transitions of crystals in-line

An online control in production of crystalline substances with respect to their morphology or a solvent mediated phase transfer is of key importance in many industries. Here two rather new PAT tools are tested. Monitoring of solvent mediated phase transition by ultrasound (single frequency) and 3D optical reflectance measurement (ORM) (advanced particle analyzing system (APAS)) is evaluated based on case studies with sulfathiazole, magnesium sulfate and di-sodium tetraborate. The achieved results by the in-line PAT tools are proven by optical microscopy. The different solvates and polymorphic forms could be detected by the use of ultrasound (single frequency) and 3D ORM (APAS) techniques, however, the application of these techniques does not work in all cases, but always at least one is working. There are limitations with respect to the nature of the examined substances.

The Method of Design Sine Grating Based on Optimal PWM

In the structured light 3d optical measurement field, the sinusoidal grating design is one of the research focus. The traditional focus methods of generating sine pattern can’t be widely accepted because of many well known defects. While the another traditional binary pattern generated from Ronchi grating which need defocusing processing, its application has also been a certain limit because of its projected pattern contrast ratio is not high.In this paper, we have proposed a designing sine grating method with the spatial modulation theory based on Optimal PWM in electronic engineering. Compared with Ronchi grating, this method of generating pattern have better fringe contrast, and more simple defocusing requirements, so this method have good practical economic value.

Effect of matte coating on 3D optical measurement accuracy

The aim of this study is to gain basic information about matte coating thickness in the area of 3D optical digitization. Thickness measurement was performed for two matting materials; chalk spray and titanium coating. A 3D optical scanner ATOS III, Triple Scan was used for data capturing and evaluation. The scanner technology is based on active fringe projection and triangulation. Fifteen measurements for chalk material and fifteen for titanium coating were carried out. The measurement conditions included the effects of lighting, operation, imperfections of coating materials deposition, etc. The results show significant differences between chalk and titanium matting materials.

Introductory review on ‘Flying Triangulation’: a motion-robust optical 3D measurement principle

‘Flying Triangulation’ (FlyTri) is a recently developed principle which allows for a motion-robust optical 3D measurement of rough surfaces. It combines a simple sensor with sophisticated algorithms: a single-shot sensor acquires 2D camera images. From each camera image, a 3D profile is generated. The series of 3D profiles generated are aligned to one another by algorithms, without relying on any external tracking device. It delivers real-time feedback of the measurement process which enables an all-around measurement of objects. The principle has great potential for small-space acquisition environments, such as the measurement of the interior of a car, and motion-sensitive measurement tasks, such as the intraoral measurement of teeth. This article gives an overview of the basic ideas and applications of FlyTri. The main challenges and their solutions are discussed. Measurement examples are also given to demonstrate the potential of the measurement principle.

Effect of Particle Shape on Inline Particle Size Measurement Techniques

AbstractThe influence of the particle shape on the results of different measuring techniques was investigated. Considered were single‐frequency ultrasound technique, 3D optical reflectance measurement (advanced particle analyzing system with multi capture signal technology), and focused‐beam reflectance measurement probes as techniques which are usable inline and in suspension density ranges usually present in industrial crystallization processes. Advantages and shortcomings of these techniques are compared and discussed.

3D optical displacement measurements on dynamically loaded adhesively bonded T-peel specimens

Adhesively bonded T-Peel specimens are loaded in a rotary impact device to investigate the behaviour of adhesive joints under high-strain rates. To gain a better understanding of that kind of tests and their results, the deformation of the samples as well as the movement of specimen support during the test is analyzed. A three-dimensional optical measurement system is used in combination with two synchronized high-speed cameras to obtain the deformations. The paper explains the experimental challenges and discusses the results of the analyses with respect to a planned usage of the experimental results in a finite element crash simulation. As main results of the investigations it can be summarized that the compliant clamping leads to an inadvertent out-of-plane-movement of the load introduction point. Based on finite element calculations it can be concluded that the measured out-of-plane-movement possesses a negligible influence on the obtained force signal, which is of primary interest in a T-Peel test.

Compressive Behavior of AA6061 at Room Temperature and Validation of the FE Model Based on Optical 3D Measurement Technique

Recently, manufacturing process simulation using finite element (FE) model become important. Therefore, validation of the finite element model is crucial. This study will present validation of 2D finite element simulation of cold heading at room temperature. Validation of the simulation model is carried out by comparing the resulted bulge profile of the cold upsetting specimen to the profile of the specimen, which is obtained from an optical 3D surface measurement technique namely Infinite Focus Alicona system. Based on the result, both profiles show a very good agreement.

Application of optical 3D measurement on thin film buckling to estimate interfacial toughness

The shape-from-focus (SFF) method has been widely studied as a passive depth recovery and 3D reconstruction method for digital images. An important step in SFF is the calculation of the focus level for different points in an image by using a focus measure. In this work, an image entropy-based focus measure is introduced into the SFF method to measure the 3D buckling morphology of an aluminum film on a polymethylmethacrylate (PMMA) substrate at a micro scale. Spontaneous film wrinkles and telephone-cord wrinkles are investigated after the deposition of a 300nm thick aluminum film onto the PMMA substrate. Spontaneous buckling is driven by the highly compressive stress generated in the Al film during the deposition process. The interfacial toughness between metal films and substrates is an important parameter for the reliability of the film/substrate system. The height profiles of different sections across the telephone-cord wrinkle can be considered a straight-sided model with uniform width and height or a pinned circular model that has a delamination region characterized by a sequence of connected sectors. Furthermore, the telephone-cord geometry of the thin film can be used to calculate interfacial toughness. The instability of the finite element model is introduced to fit the buckling morphology obtained by SFF. The interfacial toughness is determined to be 0.203J/m2 at a 70.4° phase angle from the straight-sided model and 0.105J/m2 at 76.9° from the pinned circular model.