Signal processing in an optical laser triangulation system with the minimum set of components

A laser triangulation system is described which enables three-dimensional scanning of real objects to be carried out in order to obtain three-dimensional models of them, constructed from the minimum set of components without using specialized manipulators or a rigid laser-camera link. The results obtained with this system operating in real time are presented. The scanning errors are analyzed and algorithms which enable the accuracy of the system to be increased are considered. Translated from Izmeritel’naya Tekhnika, No. 10, pp. 35–39, October, 2008.     

基于三维激光扫描技术的复杂采空区群爆破治理

针对露天矿山采空区群严重制约着生产平台的问题,为了消除采空区群带来的安全隐患,首先采用时效性强的C-ALS三维激光扫描仪精准探测,构建了3个采空区真实三维模型,揭示了受限采空区群的空间赋存关系;其次以爆破全生命周期精准设计为出发点,通过采用数码电子雷管精准控制起爆网路,最后充分利用边坡自由面及加大局部采空区侧的炸药单耗,有效地减小了岩层间的夹制作用。在大宝山露天多金属矿山661平台成功实施了强制爆破崩落处理,通过无人机多角度航拍及爆堆现场检查,发现爆区塌陷现象明显,充填率达90%,较好地消除了采空区群的不利影响,可为类似采空区治理提供参考。     

3D scanning and geometry processing techniques for customised hand orthotics: an experimental assessment

In the field of rehabilitation, the 3D scanning of body parts can be considered a crucial starting point for subsequent 3D model design of customised devices, especially when additive manufacturing techniques are involved in their production. This study experimentally evaluates and identifies appropriate procedures to acquire and process 3D anatomic images of the hand, including fingers, for the design of customised orthoses. Hand scanning is a complex activity and requires solutions capable of solving problematic aspects, such as the difficulty in maintaining the hand in a steady position and the presence of motion artefacts due to involuntary movements. We addressed such issues by considering the use of two different kinds of optical scanning device. The acquisition process has been initially defined based on healthy subjects and then extended to patients affected by pathologies that compromise upper limb functionality. Quality anatomical models were produced thanks to the application of advanced geometry processing technologies for the automated alignment of multiple scans and the removal of artefacts due to involuntary movements. As a result, with distinctive pros and cons, both the proposed combinations of scanning procedures and dedicated geometry processing evidenced their suitability in producing complete and accurate enough 3D models to be exploited for the subsequent design and production of customised hand orthoses in a typical reverse engineering pipeline.     

Comparison of three-dimensional surface scanning techniques for capturing the external ear

Congenital facial anomalies, such as microtia (malformation of the external ear), lead to significant psychosocial effects starting from early childhood. Three-dimensional (3D) scanning and advanced manufacturing are being investigated as a cheaper and more personalised method of fabricating reconstructive treatments for patients compared to traditional approaches. To date, most case studies have used expensive 3D scanners, yet, there is potential for low-cost devices to provide comparable results. This study aimed to investigate these different approaches. Both ears of 16 adult participants were scanned with three devices: Artec Spider (Artec Group), Intel^® RealSense? (Intel), and the Apple iPhone^® 7 (Apple Inc.) combined with photogrammetry using 90, 60 and 30 photographs. The scanning time, processing time, accuracy, completeness, resolution and repeatability of each technique were assessed using the Artec Spider as a reference scanner. Our results show that the iPhone had the longest processing time however, this decreased nine-fold when reducing the number of photos from 90 to 30. There was no significant difference in the accuracy, completeness or repeatability of the iPhone scans with 90 photographs (1.4?±?0.6?mm, 79.9%, 1.0?±?0.1?mm), 60 photographs (1.2?±?0.2, 79.3%, 0.9?±?0.2?mm) or 30 photographs (1.2?±?0.3?mm, 74.3%, 1.0?±?0.2?mm). The Intel RealSesne performed significantly worse in each parameter (1.8?±?03?mm; 46.6%, 1.4?±?0.5). Additionally, the RealSense had significantly lower resolution with not enough detail captured for the application. These results demonstrate that the ear can be accurately 3D scanned using iPhone photographs. We would recommend capturing between 30 and 60 photographs of the ear to create a scan that is accurate but without the downfall of long processing time. Using these methods we aim to provide a more comfortable setting for the patient and a lower-cost and more personalised ear prosthesis.     

基于相位测量的摄像机标定方法

提出一种新的摄像机标定方法,该方法基于2D共面参照物摄像机标定方法和相移技术.首先由摄像机记录已知相位分布的平面,通过相移计算出相位分布.对任意标定平面,两个正交相位分布与平面坐标的对应关系已知,由此可以建立像素坐标与2D平面坐标的一一对应关系.将该已知相位分布的平面在空间中放置不同的位置,分别完成上述测量,即可根据2D共面参照物摄像机标定方法完成摄像机的高精度标定.该方法避开了复杂的标定特征点提取,大大增加了2D标定数据量,提高了标定精度.实验和计算机模拟表明,该方法简单、可靠和精度高.     

Recent trends in metal ion based hydrogel biomaterials for tissue engineering and other biomedical applications

Recently,the metal ion cross-linked hydrogels have gained enormous interest because of its excellent properties like self-healing,fast recovery,biocompatibility and high mechanical properties combined with multi-stimuli responsiveness.In this review article,we have summarized the recent trends in the development of metal ion cross-linked hydrogels for tissue engineering and biomedical applications.A number of metal ions and their contribution in the synthesis of various cross-linked hydrogels are discussed with respect to their crosslinking mechanisms,compositions,physio-chemical and biological properties.A special emphasis has been given to ferric(Fe³⁺)ion cross-linked hydrogels and their different combinations owing to their numerous researches reported in the recent past with exceptional properties.The application of these metal ion based hydrogels in biomedical applications including tissue engineering,sensing,wound healing,drug delivery and as tissue adhesive and tissue sealants are reviewed with specific examples.Importantly,the application of these metal ion cross-linked hydrogels as inks in 3 D printing is explained in a separate section.Finally,the possible toxic effects of the different metal ions and their effects have been scrutinized.Future directions and comprehensive applications of the hydrogels are highlighted.     

基于CT图像与反求技术的缺损器官三维CAD建模

为克服传统人体骨骼缺损修复存在的缺陷，提出了基于CT图像与反求技术的缺损器官三维数字化建模方法。通过CT扫描获得缺损器官的二维图像，利用图像处理技术及反求技术实现了缺损器官数字化三雏模型的重建。三维重建的缺损器官修复体表面形态与原实物（或器官对侧健康组织）高度相似，个体匹配性好，精度高，能够更好的满足患者对缺损器官恢复后的审美要求和舒适协调性要求。     

Research on adaptive scanning and quantisation for 3D DCT video coding

Abstract

Nowadays, a well-established video coding method is based on the block-matching algorithm that is in the core of all MPEG and H.26x standards. However, this method involves motion estimation and compensation; thus the computational complexity is high. However, the video coding based on three-dimensional discrete cosine transform (3D DCT) is a potential method, and the scanning order and quantisation of 3D DCT coefficients play a crucial role in coding effect. So, the statistical performances of 3D DCT are studied in this paper, and then adaptive scanning order and quantisation of 3D coefficients are proposed. The theoretical analysis and experiment results show significant improvement in performance over previously reported methods.     

An automatic alignment system for measuring optical path of transmissometer based on light beam scanning

This paper proposes a novel alignment system based on the measurement of optical path using a light beam scanning mode in a transmissometer. The system controls both the probe beam and the receiving field of view while scanning in two vertical directions. The system then calculates the azimuth angle of the transmitter and the receiver to determine the precise alignment of the optical path. Experiments show that this method can determine the alignment angles in less than 10 min with errors smaller than 66 μrad in the azimuth. This system also features high collimation precision, process automation and simple installation.     

基于Web3D的灯饰协同设计定制系统

论文分析了目前传统的灯饰设计所存在的不足,提出了客户与设计师协同设计的可行方案,详细介绍了基于Web3D的灯饰协同设计关键技术,包括灯饰模型交互设计和同步互斥技术,开发出了一个以客户为主,以设计师为辅并基于Web3D技术的网上协同设计系统,并通过实验验证了系统的可行性。     

一种基于传像束的新型微三维形貌测量系统

文章根据结构光的测量原理提出了一种基于传像束的微三维形貌检测系统。充分利用传像束自由度大、能弯曲、易实现长度超过1m的光路等优点，在投射结构光条纹及摄取变形条纹图像时用它来代替传统的光学系统，从而使该系统比一般的微三维形貌测量系统多了内腔测量和远距离测量的功能。文中给出了实验结果，该系统的可行性得到了验证。     

基于互补式多波段带通滤光片的3D投影显示系统

本文提出一个基于互补式多波段带通滤光片的3D投影显示系统,该系统可以使观看者通过特制眼镜获得3D视觉体验。不同于时分复用和空分复用的3D显示系统,该系统借助成对的互补式滤光片实现谱分复用。通过设计可以实现两块滤光片的三对互补通带恰好分别覆盖RGB三色光谱范围,且每对互补通带相互交错几乎不重叠。在本文中,将两台普通的2D投影仪改造成3D投影系统,并测量了该系统的光谱、亮度、串扰等参数,其平均串扰3%,满足3D显示串扰小于10%的基本要求。     

FDM型3D打印机的高精度进料系统研究

为了提高打印成型件的精度和质量,对FDM型3D打印机进料系统及其具体实现方法进行了改进.系统采用功率管IRF530N、加热管和PWM组成加热模块,采用铂热电阻Pt100、差动放大电路和PID算法组成温度测控模块.既简化了标度变化的计算量,又降低了电阻值温漂对测量结果的影响.针对基于步进电机结构的送料控制模块,给出了减少步进电机失步的措施.系统实现了180~250℃,±1℃精度的恒温控制,为FDM型3D打印机系统的恒温和高精度进料提供了保障,并且在简单调整后,还可对湿度、压力、位移和角度等物理量进行控制.     

基于双视角的真实感三维人脸重建系统

人脸建模是计算机图形学及三维重建领域的一个研究热点,论文根据结构光测量及编码原理,利用两组CCD及结构光投影仪实现了人脸双视角测量,保证了数据测量的范围和完整性;针对测量得到的几何及纹理数据,开发了可视化数据软件处理平台,能够完成两部分数据的精简、分割、拼接及网格化等处理过程,并通过纹理映射实现具有真实感的人脸模型三维重建;最终,将上述硬件测量方案及软件处理平台结合,形成了一套完整的三维人脸重建系统,并通过试验验证了系统的可行性。     

基于环形激光的深孔内膛形貌检测系统研究

提出了一种基于环形激光的深孔内膛检测系统,该系统主要由环形激光发生器、反射锥镜、CCD相机以及驱动装置等组成。通过对环形激光器投射在被测身管内膛上的环形光斑进行成像和分析计算,可对身管内膛的一个截面形廓进行检测,并在驱动装置的驱动下,实现对深孔内膛形貌的三维检测。     

A method to design biomimetic scaffolds for bone tissue engineering based on Voronoi lattices

In regenerative medicine, 3D scaffolds are used to sustain the regeneration of tissues in removed or damaged parts of the human body. As such practices are being widely experimented in clinical applications, the design, the materials and the manufacturing process to obtain efficient 3D biocompatible lattices are being significantly investigated. Nevertheless, most of the proposed designs are based on regular 3D shapes obtained from the repetition of unit cells disposed in a three-dimensional array. This approach does not exploit the whole potential of computer-aided design tools coupled with manufacturing capabilities for freeform shapes. In this paper, we propose a method to model biomimetic lattices controlling the porosity and the pores size of scaffolds to be integrated with the anatomical shape of the defect. The method has been implemented in bone tissue case study and implements a generative design approach based on Voronoi diagrams.     

A new solution for 3D crack extension based on linear elastic stress fields

A solution to the 3D stress field based on the maximum tangential stress (MTS) criterion is presented in this paper. The solution allows for the estimation of the critical crack plane, the direction of growth in terms of both twist and tilt angles and the equivalent crack driving force for a given mixed-mode loading condition. It also shows the graphical relationship between the three different stress intensities for a given driving force. Initial results have shown good correlation with experimental data obtained from literature.     

A review on powder-based additive manufacturing for tissue engineering: selective laser sintering and inkjet 3D printing

Abstract

Since most starting materials for tissue engineering are in powder form, using powder-based additive manufacturing methods is attractive and practical. The principal point of employing additive manufacturing (AM) systems is to fabricate parts with arbitrary geometrical complexity with relatively minimal tooling cost and time. Selective laser sintering (SLS) and inkjet 3D printing (3DP) are two powerful and versatile AM techniques which are applicable to powder-based material systems. Hence, the latest state of knowledge available on the use of AM powder-based techniques in tissue engineering and their effect on mechanical and biological properties of fabricated tissues and scaffolds must be updated. Determining the effective setup of parameters, developing improved biocompatible/bioactive materials, and improving the mechanical/biological properties of laser sintered and 3D printed tissues are the three main concerns which have been investigated in this article.     

A review on powder-based additive manufacturing for tissue engineering: selective laser sintering and inkjet 3D printing

Since most starting materials for tissue engineering are in powder form, using powder-based additive manufacturing methods is attractive and practical. The principal point of employing additive manufacturing (AM) systems is to fabricate parts with arbitrary geometrical complexity with relatively minimal tooling cost and time. Selective laser sintering (SLS) and inkjet 3D printing (3DP) are two powerful and versatile AM techniques which are applicable to powder-based material systems. Hence, the latest state of knowledge available on the use of AM powder-based techniques in tissue engineering and their effect on mechanical and biological properties of fabricated tissues and scaffolds must be updated. Determining the effective setup of parameters, developing improved biocompatible/bioactive materials, and improving the mechanical/biological properties of laser sintered and 3D printed tissues are the three main concerns which have been investigated in this article.