三维激光扫描技术在犯罪现场重建中的应用

目的:研究利用三维激光扫描技术进行现场重建的技术方法。方法:首先,利用三维激光扫描仪对现场进行扫描,获取现场的点云数据;然后,依据点云数据进行现场建模和动画模拟。结果:精确地重建了犯罪现场的场景并获得具有交互性、沉浸感的动画模拟效果。结论:利用三维激光扫描技术可以精确、方便地进行现场重建。     

Dimensionality of color space in natural images

The color histogram (or color cloud) of a digital image displays the colors present in an image regardless of their spatial location and can be visualized in (R,G,B) coordinates. Therefore, it contains essential information about the structure of colors in natural scenes. The analysis and visual exploration of this structure is difficult. The color cloud being thick, its more dense points are hidden in the clutter. Thus, it is impossible to properly visualize the cloud density. This paper proposes a visualization method that also enables one to validate a general model for color clouds. It argues first by physical arguments that the color cloud must be essentially a two-dimensional (2D) manifold. A color cloud-filtering algorithm is proposed to reveal this 2D structure. A quantitative analysis shows that the reconstructed 2D manifold is strikingly close to the color cloud and only marginally depends on the filtering parameter. Thanks to this algorithm, it is finally possible to visualize the color cloud density as a gray-level function defined on the 2D manifold.     

Linear terrestrial laser scanning using array avalanche photodiodes as detectors for rapid three-dimensional imaging

As an active remote sensor technology, the terrestrial laser scanner is widely used for direct generation of a three-dimensional (3D) image of an object in the fields of geodesy, surveying, and photogrammetry. In this article, a new laser scanner using array avalanche photodiodes, as designed by the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, is introduced for rapid collection of 3D data. The system structure of the new laser scanner is first presented, and a mathematical model is further derived to transform the original data to the 3D coordinates of the object in a user-defined coordinate system. The performance of the new laser scanner is tested through a comprehensive experiment. The result shows that the new laser scanner can scan a scene with a field view of 30° × 30° in 0.2 s and that, with respect to the point clouds obtained on the wall and ground floor surfaces, the root mean square errors for fitting the two planes are 0.21 and 0.01 cm, respectively. The primary advantages of the developed laser scanner include: (i) with a line scanning mode, the new scanner achieves simultaneously the 3D coordinates of 24 points per single laser pulse, which enables it to scan faster than traditional scanners with a point scanning mode and (ii) the new scanner makes use of two galvanometric mirrors to deflect the laser beam in both the horizontal and the vertical directions. This capability makes the instrument smaller and lighter, which is more acceptable for users.     

Color reduction for complex document images

A new technique for color reduction of complex document images is presented in this article. It reduces significantly the number of colors of the document image (less than 15 colors in most of the cases) so as to have solid characters and uniform local backgrounds. Therefore, this technique can be used as a preprocessing step by text information extraction applications. Specifically, using the edge map of the document image, a representative set of samples is chosen that constructs a 3D color histogram. Based on these samples in the 3D color space, a relatively large number of colors (usually no more than 100 colors) are obtained by using a simple clustering procedure. The final colors are obtained by applying a mean‐shift based procedure. Also, an edge preserving smoothing filter is used as a preprocessing stage that enhances significantly the quality of the initial image. Experimental results prove the method's capability of producing correctly segmented complex color documents where the character elements can be easily extracted as connected components. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 14–26, 2009     

三维数字化爆破质量评价技术

爆破质量的全面定量检测和评价是推动精细化爆破的基础。三维激光扫描技术具有快速、准确和区域整体测绘的特点,为高效、定量检测和评价爆破质量提供了技术手段。采用三维激光扫描技术对爆后结构面和爆堆形态进行扫描,建立三维实景数字模型,然后在三维实景模型中进行几何测量和质量评价。研究内容包括爆破结构面、爆堆形态的现场三维激光扫描、三维实景数字化模型建立、爆破质量立体检测和爆破质量评价。研究表明,三维激光扫描技术具备精细化管理的全面质量检测和评价能力,为实现爆破数字化和智能化提供数据基础。     

三维数字化爆破质量评价技术

爆破质量的全面定量检测和评价是推动精细化爆破的基础。三维激光扫描技术具有快速、准确和区域整体测绘的特点,为高效、定量检测和评价爆破质量提供了技术手段。采用三维激光扫描技术对爆后结构面和爆堆形态进行扫描,建立三维实景数字模型,然后在三维实景模型中进行几何测量和质量评价。研究内容包括爆破结构面、爆堆形态的现场三维激光扫描、三维实景数字化模型建立、爆破质量立体检测和爆破质量评价。研究表明,三维激光扫描技术具备精细化管理的全面质量检测和评价能力,为实现爆破数字化和智能化提供数据基础。     

基于3D点云平均曲率估算的损伤参数计算

针对高速滑动电接触滑轨表面的微小损伤,基于激光扫描3D点云平均曲率估算的原理,提出一种表面微小损伤特征参数的定量表征方法。对3D点云数据进行去噪、滤波平滑、数据精简、k-邻域搜索等处理后,进行局部二次曲面拟合,估算出点云的平均曲率,设定曲率阈值实现损伤区域特征点云提取,对损伤区域进行定位,进而计算被测滑轨表面的微小损伤的体积及质量损失。实验研究表明:被测滑轨表面损伤质量的测量精度可达mg级,验证了该方法的有效性。     

基于激光诱导表面周期结构的微纳防伪结构色

激光诱导表面周期结构由于其周期相关的光栅衍射特性在明场下显示出鲜艳的结构色,备受研究人员的广泛关注,而微纳结构在显微镜暗场显示的颜色通常容易被忽略.本文报道通过飞秒激光对氧化铟锡薄膜加工形成双周期光栅结构,利用其在明场和暗场的观察下具有不同的颜色特性实现图像加密应用.通过控制飞秒激光的偏振、脉冲能量和扫描速度在氧化铟锡...     

Alpha-Shapes分段改进算法在三维模拟树枝体积扫描测量中的应用

针对树木与树枝分叉部分体积计算困难,三维扫描建模易产生黏连现象等问题,提出一种Alpha-Shapes分段改进算法。通过三维激光扫描技术获取三维模拟树枝的点云数据,利用Alpha-Shapes算法计算出三维模拟树枝的点云边缘轮廓并进行三维重建,利用分段算法对三维重建数据进行体积分割计算,通过点云最高层补偿以此保证分段算法的准确度。最后用Alpha-Shapes算法计算各个分段体积并进行累加。实验使用标准塑料直管段、三通管段和四通管段对树干以及树枝的分叉情况进行模拟并通过扫描真实树枝进行验证,通过三维激光扫描技术获取点云数据,实验充分考虑树枝分叉情况、检测精度、黏连问题,结合不同模拟树枝分叉特点,对比选择最合适的半径α值与分段高度β值。实验表明该改进算法的体积计算误差值在4%-5%之间,较改进前降低5%。     

基于三维激光扫描及凸包算法的油罐底部排量快速测量

针对传统立式金属油罐底量计量方法测量准确度不高、重复性不好等问题,提出一种立式罐底部排量快速测量方法。该方法以三维激光扫描仪获取的罐体点云数据为研究对象,采用计算几何学的寻找凸包算法,形成三维凸包,并通过投影法计算立式罐底部排量。以立式罐为对象并与几何测量法进行对比,分析快速方法的重复性及准确性。快速方法与几何测量法的重复性误差分别为1.28%及11.81%,测量结果均值的相对偏差为7.43%。     

A Dual-Platform Laser Scanner for 3D Reconstruction of Dental Pieces

This paper presents a dual-platform scanner for dental reconstruction based on a three-dimensional (3D) laser-scanning method. The scanner combines translation and rotation platforms to perform a holistic scanning. A hybrid calibration method for laser scanning is proposed to improve convenience and precision. This method includes an integrative method for data collection and a hybrid algorithm for data processing. The integrative method conveniently collects a substantial number of calibrating points with a stepped gauge and a pattern for both the translation and rotation scans. The hybrid algorithm, which consists of a basic model and a compensation network, achieves strong stability with a small degree of errors. The experiments verified the hybrid calibration method and the scanner application for the measurement of dental pieces. Two typical dental pieces were measured, and the experimental results demonstrated the validity of the measurement that was performed using the dual-platform scanner. This method is effective for the 3D reconstruction of dental pieces, as well as that of objects with irregular shapes in engineering fields.     

卧式能源储罐容量计量中三维激光扫描方法的研究

提出了一种基于三维激光扫描原理的卧式罐容量全自动测量方法。讨论了一种卧式罐扫描点云数据分析算法,通过三角叠加原理计算出卧式罐等水平高度截面面积,在此基础上计算出不同液位高度对应的卧式罐容积值。设计了对比试验系统,以容量比较法为参考依据,三维激光扫描方法测得的容量值相对偏差明显小于几何测量法测量值,满足不确定度为0.4% (k=2)的计量要求,验证了这种方法的有效性,而且三维扫描方法可以有效提高卧式罐容量检定工作效率。     

广式古家具的逆向点云数据采集研究

目的研究广式古家具,对典型古家具样品进行三维扫描,掌握处理原始点云数据的技术要领和现场扫描古家具三维模型的实际操作方法,为广式古家具的Alias参数化模型建构与虚拟现实应用研究奠定原始数据基础。方法对广式古家具选择研究样品后进行设计调查,携带仪器设备对广式古家具进行现场扫描,获得其表面的点云数据,掌握点云数据处理与现场扫描的方法。结论广式古家具的逆向点云数据采集研究以未来信息化建设为视角,侧重于技术过程实践和参数化模型建构方法研究,为广式古家具的数字化传承技术作出了有益示范。     

传统壁画色彩数字化采集及管理小程序构建研究

目的 从设计学角度提出传统壁画色彩数字化采集、保护及传播的设计策略,通过“云图像色彩数据采集技术+数字交互小程序构建”来实现传统壁画色彩的数字化提取与传播,助推传统色彩文化的传承、保护、传播与创新。方法 以永乐宫壁画为研究对象,在案例研究、文献研究基础上,通过云图像聚类算法以物象为基础对壁画色彩进行数字化提取和汇总,结合数字平台的体验特征,搭建永乐宫壁画色彩小程序,为壁画色彩信息的保护和当代设计中的转化提供数据、路径支持。结论 通过设计学、图案学、数字技术将中国传统壁画中色彩信息进行数字化提取及交互式汇总传播,不仅能够更好地保护和弘扬中国传统色彩文化,同时为以国风为主题的各类设计提供精准的色彩数据支持。     

Two in One: Light as a Tool for 3D Printing and Erasing at the Microscale

The ability to selectively remove sections from 3D‐printed structures with high resolution remains a current challenge in 3D laser lithography. A novel photoresist is introduced to enable the additive fabrication of 3D microstructures at one wavelength and subsequent spatially controlled cleavage of the printed resist at another wavelength. The photoresist is composed of a difunctional acrylate cross‐linker containing a photolabile o‐nitrobenzyl ether moiety. 3D microstructures are written by photoinduced radical polymerization of acrylates using Ivocerin as photoinitiator upon exposure to 900 nm laser light. Subsequent scanning using a laser at 700 nm wavelength allows for the selective removal of the resist by photocleaving the o‐nitrobenzyl group. Both steps rely on two‐photon absorption. The fabricated and erased features are imaged using scanning electron microscopy (SEM) and laser scanning microscopy (LSM). In addition, a single wire bond is successfully eliminated from an array, proving the possibility of complete or partial removal of structures on demand.     

Using reflectance models for color scanner calibration

We examine the use of linear spectral reflectance models for calibrating a color scanner to generate device-independent CIE XYZ values from scanner vectors. Polynomial regression approaches to color scanner calibration use parameterized functions to approximate the calibration mapping over a set of training colors. These approaches can perform poorly if the parameterized functions do not accurately model the structure of the desired calibration mapping. Several studies have shown that linear reflectance models accurately characterize a wide range of materials. By viewing color scanner calibration as reflectance estimation, we can incorporate linear reflectance models into the calibration process. We show that in most cases linear models do not constrain the calibration problem sufficiently to allow exact recovery of X, Y, Z from a scanner vector obtained with three filters. By examining a series of methods that exploit information about reflectance functions, however, we show that reflectance information can be used to improve the accuracy of calibration over that of standard methods applied to the same set of inputs.     

逆向工程中三维离散点云的平滑整定新算法

 目前逆向工程中关于三维数据的平滑整定一般都是建立在三维数据之间的拓扑关系上的.提出一种平滑整定新算法,该算法是针对散乱、无序的,没有任何拓扑关系的三维离散点云数据.根据概率统计学中的频数法从大量的离散三维数据点云中找到噪声点,然后基于三维数据点云所建立的K-D树空间数据结构,找到噪声点周围的k个最近点,根据噪声点周边k个最近点的信息对噪声点处的真实信息进行恢复.基于激光三维平面扫描机器人系统证明该算法对离散三维数据点云的平滑整定的效果是令人满意的,在逆向工程中对数据预处理是切实可行的.     

Remote sensing of three-dimensional cirrus clouds from satellites: application to continuous-wave laser atmospheric transmission and backscattering

A satellite remote sensing methodology has been developed to retrieve 3D ice water content (IWC) and mean effective ice crystal size of cirrus clouds from satellite data on the basis of a combination of the conventional retrieval of cloud optical depth and particle size in a horizontal plane and a parameterization of the vertical cloud profile involving temperature from sounding and/or analysis. The inferred 3D cloud fields of IWC and mean effective ice crystal size associated with two impressive cirrus clouds that occurred in the vicinity of northern Oklahoma on 18 April 1997 and 9 March 2000, obtained from the Department of Energy's Atmospheric Radiation Measurement Program, have been validated against the ice crystal size distributions that were collected independently from collocated and coincident aircraft optical probe measurements. The 3D cloud results determined from satellite data have been applied to the simulation of cw laser energy propagation, and we show the significance of 3D cloud geometry and inhomogeneity and spherical atmosphere on the transmitted and backscattered laser powers. Finally, we demonstrate that the 3D cloud fields derived from satellite remote sensing can be used for the 3D laser transmission and backscattering model for tactical application.     

激光扫描仪在容积测量中的应用

介绍了三维激光扫描仪的原理,典型行业的应用,并将三维激光扫描技术引入油罐的容积测量,给出了不确定度分析,同传统测量比较,表明此测量方法高效、准确。     

Spectral bar coding of polystyrene microbeads using multicolored quantum dots

This paper focuses on encoding polystyrene microbeads, 10-100 microm in diameter, with a luminescent spectral bar code composed of mixtures of quantum dots (QDs) emitting at different wavelengths (colors). The QDs are encapsulated in the bead interior during the bead synthesis using a suspension polymerization, and the bar code is constructed by varying both the number of colors included in the bead and, for each color, the number of QDs of that color. Confocal laser scanning microscopy images of the beads demonstrate that the multicolored QDs are pushed together into inclusions within the bead interior. The encoded bead emission spectrum indicates that the peak position of the included colors does not shift relative to the corresponding peaks of the spectra recorded for the nonaggregated QDs at identical loading concentrations. Due to the spatial proximity of the QDs in the inclusions, electronic energy transfer from the lower wavelength emitting QDs to the higher emitting QDs changes the relative intensities of the colors compared to the values in the nonaggregated spectra. We show that this energy transfer does not obscure the spectral uniqueness of the different codes. Ratiometric encoding, in which the bar code is read as relative color intensity, is shown to remove the dependence of the code on the bead size.