Shape reconstruction using coded structured light is considered one of the most reliable techniques to recover object surfaces. Having a calibrated projector–camera pair, a light pattern is projected ...onto the scene and imaged by the camera. Correspondences between projected and recovered patterns are found and used to extract 3D surface information. This paper presents an up-to-date review and a new classification of the existing techniques. Some of these techniques have been implemented and compared, obtaining both qualitative and quantitative results. The advantages and drawbacks of the different patterns and their potentials are discussed.
Coded structured light is considered one of the most reliable techniques for recovering the surface of objects. This technique is based on projecting a light pattern and viewing the illuminated scene ...from one or more points of view. Since the pattern is coded, correspondences between image points and points of the projected pattern can be easily found. The decoded points can be triangulated and 3D information is obtained. We present an overview of the existing techniques, as well as a new and definitive classification of patterns for structured light sensors. We have implemented a set of representative techniques in this field and present some comparative results. The advantages and constraints of the different patterns are also discussed.
Optical 3D measuring systems serve as indispensable tools for the measurement and quality control of complex objects feeding process chains in industrial information integration. However, the ...accuracy of 3D measurements is influenced by a multitude of parameters, and the associated measurement uncertainties and influential factors remain insufficiently researched. This study investigates the effects of measurement object properties and software on measurement outcomes. Specifically, we examine seven geometries (diameter, distance, roundness, concentricity, flatness, parallelism and verticality) and four influencing factors (surface roughness, coating, polygonization, and interpolation). Our analysis employs variance analysis and compares the results with those obtained through linear regression using machine learning. In conclusion, the analysis of measurement uncertainty for optical 3D measurement systems in the assessment of seven distinct geometric characteristics provides a framework for determination of process chain suitability of the optical 3D measuring system.
Abstract
Laser micro drilling stands as a precise manufacturing method that employs a focused laser beam to craft accurate, small holes within a diverse array of materials. Its applications span ...across vital industries like aerospace, medical, and electronics, playing a pivotal role in creating components like fuel injectors, medical implants, and microelectronics. Within this context, a notable challenge emerges in obtaining a refined surface finish during laser micro drilling. This study delves into the impact of a laser loop, a crucial parameter, on the surface quality of TC4, also known as Ti6Al4V—an aerospace staple. Employing a Conventional Fiber Laser with a peak output of 30 W, the experiment meticulously directs the laser beam onto the TC4 surface via a microscope objective lens. The drilling process unfolds in controlled conditions, mitigating external variables such as temperature and humidity. Assessment of drilled hole surfaces transpires through both light and 3D microscopes. Interestingly, holes subjected to higher laser power and increased laser loop rates demonstrate enhanced surface smoothness. In essence, this inquiry demonstrates the substantial influence of laser loop on TC4’s surface finish during laser micro drilling. Elevating the laser loop factor leads to heightened surface refinement and diminished roughness in drilled holes. It was found that the diameter entry of the micro-holes was increased by 61% - 89.35% and the diameter exit of the micro-holes also increased by 55.55% - 62.79%. The outcomes of this investigation offer valuable insights for refining the laser micro drilling process to achieve premium surface quality on TC4 and comparable materials. As such, these findings extend guidance for optimal laser loop settings in the realm of laser micro drilling across various materials, benefiting future manufacturing endeavors.
The propeller is the important component of the power system in ships, the blades of which are spatial curved structures with continually changing sections. Wire arc additive manufacture (WAAM) is a ...novel technology and an effective method for manufacturing propellers. Currently, the planar slicing methods cannot form the high-accuracy propellers with complex spatial curves, a new cylindrical surface slicing method, based on the principles of conformal slicing, is applied to WAAM, the section for slicing being a cylindrical surface coaxial with the hub. Both cylindrical circumferential filling and cylindrical axial filling are used for filling the blades. In the manufacturing process, the hub is firstly formed by plane slicing and offset filling, then the blade is formed piece by piece by cylindrical slice and cylindrical axial filling and cylindrical circumferential filling alternately. A non-contact 3D measuring is conducted with a surface structure light 3D scanner after the completion of printing, and a 3D comparison is made with Geomagic qualify software. The dimensional error of the product is within ± 1.6 mm. The mechanical properties of WAAM propeller components are higher than the casting ones with the same composition.
The pursuit of increasing the efficiency of internal combustion engines is an ongoing engineering task that requires numerous research efforts. New concepts of injection or combustion systems require ...preliminary investigation work using research engines. These engines, usually single-cylinder, make it possible to isolate a single variable in a complex combustion mixture preparation process, thus enabling analysis of the changes being made. However, these engines are relatively expensive and their designs are offered by a limited number of manufacturers. The authors of this paper have successfully undertaken the engineering task of modifying an existing research engine cylinder head in such a way as to implement an electronically controlled variable valve timing system of the intake system. The process of reverse engineering, together with design assumptions that finally contributed to the construction of the assumed solution has been described in this paper.
In the context of optimizing dental care for patients who are elderly, the purpose of this in vitro study was to evaluate the surface gloss (with a micro-area gloss meter) of, surface roughness (with ...a compact surface roughness measuring instrument) of, and color change (with a dental colorimeter) in two commercially available injectable resin-based composites (Estelite Universal Flow (EUF) and Beautifil Flow Plus F00 (BFP)) as well as two glass-ionomer cements (GC Fuji II LC CAPSULE (FLC) and GC Fuji IX GP EXTRA CAPSULE (FGP)), before and after dental prophylaxis. After 24 h, the surfaces of each specimen were polished at 2500 rpm with a prophy brush (Mersage Brush, Shofu) and one-step prophylaxis paste (Prophy Paste Pro, Directa): under 100 or 300 gf load, and for 10 or 30 s, 4× cycles of cleaning. After mechanical cleaning, conditions were found for a significant reduction in the gloss level (EUF, BFP, or FLC;
< 0.05) and a significant increase in surface roughness (BFP; 300 gf load, 10 s × four cycles of cleaning). Overall, the longer time or higher prophylaxis load tended to decrease the surface gloss. However, the observed change in surface roughness varied between the restorative materials. There was no color change post-prophylaxis.
Background
Measuring wound dimensions is important for monitoring and predicting the healing process. In our paper we propose and validate a handheld measuring system with dedicated software for ...measuring wound dimensions.
Methods
The measuring system comprises a commercial DSLR camera and a light pattern projection system. It is based on triangulation and structured illumination principles which enable handheld measuring. An edge of the wound is detected from the colour information of the measurement. Across the area of the wound, virtual healthy skin is approximated which enables the calculation of the wound volume and area, in addition to the wound circumference, which is calculated from the detected edge.
Results
In vitro verification using virtual standards showed that the accuracy of the analysis software is over 95% and 93% for measuring the area and volume respectively. A significant part of the error can be attributed to the inability of approximation to replicate entirely missing features. The accuracy of measuring the volume reduced to about 89% when a 3D measuring step was included in the analysis. When measuring in vivo wounds, the unrepeatability of the system was under 8% for measuring the area, which is a bit lower than comparable systems, and 5% for measuring the volume, which is about 4 times lower.
Conclusion
Based on these results and the ease of use, we conclude that the system is suitable to be used in daily clinical practice for measuring wound dimensions.
80/20 natural rubber (NR)/butadiene rubber (BR) blends in which the carbon black (CB) was replaced partially by multi-walled carbon nanotubes (MWCNTs) according to the ratios m (CNTs): m (decreasing ...amount of CB)=1: X (X was varied from 1 to 6), was prepared by blending of internal mixer and the two-roll mill at the mill opening of 0.5mm for 10 times. SEM and TEM were used to investigate the filler networks and the good dispersion of fillers. The compounds containing 5phr CNTs/27.5phr CB exhibited the best abrasion resistance which was increased by 12.69% compared that without CNTs. 3D morphology images of wear surfaces and tensile fracture surfaces being similar to the layered map of the geography, which match the abrasion resistance and tensile properties, were observed by 3D measuring laser microscope. The uncured blend with 5phr CNTs/35phr CB showed the shortest cure time, the highest modulus and level of crosslink density. Significant improvement in mechanical properties were achieved by incorporating 5phr CNTs and 35phr CB, and the tear strength, 100% and 300% modulus of the vulcanizate were enhanced by 36.36%, 61.29% and 31.63% compared with the composite with 0phr CNTs/40phr CB, respectively. Additionally, compared with the composite without CNTs, the thermal conductivity of the composites with 5phr CNTs/35phr CB is increased by an average of 6.15% at three different temperatures. These considerable reinforcements resulted from the synergistic effect of CNTs and CB.
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