基于条纹投影的三维形貌与形变测量技术研究进展

基于条纹投影的三维形貌测量技术，已经在提升测量精度、提高测量速度、扩大测量景深、增加测量场景适应性等方面被进行了大量研究。但由于条纹投影技术本身的原理限制，仅利用传统条纹投影方法难于实现准确的对应点匹配。而依赖于对应点追踪的形变测量和应变分析可以进一步分析物体的运动状态、材料特性以及结构力学参数，在运动仿生学、材料力学、结构力学等诸多领域中起着不可或缺的作用。本文回顾了近年来新发展出的一系列基于条纹投影的三维形貌与形变测量技术，论述了学者们如何在条纹投影系统上一步步实现从简单刚体位移的测量到复杂、精细结构的形变测量和应变分析。分析了此类技术在测量完整度、分辨率以及计算效率上相比于已有形变测量技术的优势，给出了此技术所面临的挑战和潜在发展动向。     

基于条纹投影的高速三维形貌测量技术发展综述

在虚拟现实和增强现实、智能制造检测、材料性能测试等需要对动态场景进行三维建模、对动态过程进行深入分析的领域中，高速三维面形测量技术具有重要的科学研究意义和广泛的应用价值。随着高速动态场景测量需求的日趋增长和测量硬件设备的迅速发展，相应领域的研究热点逐渐从简单静态场景的三维测量转移到复杂动态场景的测量中。以测量任务需求为主线，综述基于条纹投影的高速三维测量技术在硬件和算法上的研究进展，随后分类比较已有技术各自的优缺点，给出不同测量任务下的方法选择建议，最后总结基于条纹投影的高速三维形貌测量技术所面临的挑战和潜在发展动向。     

基于光栅投影的叶片轮廓测量技术研究现状

本文首先概述了利用光栅投影对叶片三维轮廓进行测量的必要性。然后从四个关键技术角度即光栅投影技术、标定技术、解相位技术和点云拼接技术对国内外研究现状进行梳理。在此基础上整理出国内外已经开发出的叶片三维测量软件并加以对比。最后根据光栅投影的叶片轮廓测量技术现状和尚存问题指出未来发展趋势。     

多阶段深度学习单帧条纹投影三维测量方法

深度学习的应用简化了数字条纹投影三维测量的过程,在传统数字条纹投影三维测量技术条纹投影、相位计算、相位展开、相位深度映射的流程中,研究者们已经成功证明了前三个环节以及整个流程结合深度神经网络的可行性。基于深度学习,PDNet (Phase to Depth Network)神经网络模型被提出,用于绝对相位到深度的映射。结合多阶段深度学习单帧条纹投影三维测量方法,通过分阶段学习方式依次获得物体的绝对相位与深度信息。实验结果表明,PDNet能较准确地测量出物体的深度信息,深度学习应用于相位深度映射步骤具有可行性。并且,相较于直接从条纹图像到三维形貌的单阶段深度学习单帧条纹投影三维测量方法,多阶段深度学习单帧条纹投影三维测量方法可以明显提升测量精度,仅需单帧条纹图像输入即可获得毫米级测量精度,且能适应具有复杂形貌物体的三维测量。     

条纹投影与相位偏折测量技术研究进展

条纹投影和相位偏折测量术可用于精确地测量待测物面形,在全场光学三维轮廓测量领域具有较好的发展前景。首先,介绍了条纹投影和相位偏折测量技术的基本原理,重点是这两种技术中的相位提取技术、摄像机定标技术等关键技术。其次,对条纹投影和相位偏折测量术这两种测量方法的异同点做了对比。最后,介绍了条纹投影和相位偏折测量技术在提升测量精度和速度方面的发展。为了提升测量精度,主要有校正条纹Gamma效应、提升相位提取精度、摄像机标定精度和相位-高度/梯度标定精度等途径;为了提升测量速度,主要有提升相位提取速度、相位解包裹速度等方法。     

基于窗口匹配的对称条纹投影测量方法

条纹投影三维测量技术因高精度、高鲁棒性、低成本等优点而被众多学者广泛研究和应用。然而，传统的方法大多需要投影多张条纹才能获取物体的三维形貌。因此提出一种快速条纹投影三维测量方法。设计一个对称相位用于相位解包，可以有效减少投影条纹的数量；将投影仪看作逆相机，把系统构建为一个立体视觉系统，利用立体视觉的极线约束对对称相位设计一种窗口匹配方式，增强相位解包的鲁棒性。相比传统的倍频法、多频外差法等，所提方法的条纹数量可以减少50%，同时保证高的精度和鲁棒性。     

激光测量点云的数据处理方法研究

激光测量技术具有高分辨率、快速、非接触和数字化的特点,其应用日益广泛。基于激光测量的散乱点云,研究测量点云的数据处理方法。在分析通常的数据处理流程与方法的基础上,重点研究了如何应用数据的虚拟切割技术和测量点云的虚拟投影技术。点云虚拟切割技术主要包括径向/轴向切割技术、柱面切割技术与指定切割半径处的轴向截面切割技术。点云虚拟投影技术主要包括规则特征投影技术和轴向旋转投影技术。基于点云的虚拟投影,阐述了零件的参数提取策略。通过基于激光测量的零件数字化检测的实践表明所提出的点云数据处理方法与策略是行之有效的。     

光刻机投影物镜像差的现场测量技术

为了在光刻机工作过程中保证投影物镜的成像质量．人们开发了一系列投影物镜像差的现场测量技术。对目前国际上常用的几种高精度投影物镜像差现场测量技术进行了分析和比较。     

投影光学迅速发展

投影光学既属于经典光学的范畴也可被看作一门新兴学科。经典光学包括:望远光学、显微光学、摄影光学和投影光学。在这四大经典光学中,投影光学最为薄弱。最原始的投影技术被应用于投影绘画,以后发展成幻灯放映技术、电影放映技术和投影测量技术。多年来投影光学进步缓慢,并且局限于光源、照明系统以及投放镜头的研究三个方面,这是由于投影     

光栅投影三维轮廓测量及关键技术分析

说明了光栅投影三维测量技术的原理；就国内外的研究和应用状况，对三维测量中的关键技术，如相位测量，解相位，数据配位和拼接，系统结构的调整和标定等进行了分析综述。     

Combining a morphological interpolation approach with a surface reconstruction method for the 3-D representation of tomographic data

In this paper, a new interpolation scheme, based on Mathematical Morphology and a modified Marching Cubes (MC) Algorithm to reconstruct 3-D anatomical structures is presented. The proposed interpolation technique is implemented using morphological operations and incorporates a distance function to improve the computational effectiveness of the technique. The morphological interpolation technique is compared to an existing shape based interpolation method and its advantages include superiority capability on handling various cases such as the branching and holes problem (appearance and disappearance of information) and more accurate volume estimation. Furthermore, the morphological technique is companied with a 3-D reconstruction algorithm capable of representing any anatomical structure from real 3-D medical data. Introducing a novel general rule, the algorithm triangulates all standard cube configurations introduced from the standard MC algorithm, without producing topologically incoherent surfaces or holes. Finally, the technique is implemented in JAVA and its output is in VRML 1.0 format; therefore it can be executed over the internet and implemented for telemedicine applications.     

Theoretical Proof of Unconditional Stability of the 3-D ADI-FDTD Method

In order to eliminate Courant-Friedrich-Levy(CFL) condition restraint and improvecomputational efficiency,a new finite-difference time-domain(FDTD)method based on the alternating-direction implicit(ADI) technique is introduced recently.In this paper,a theoretical proof of the stabilityof the three-dimensional(3-D)ADI-FDTD method is presented.It is shown that the 3-D ADI-FDTDmethod is unconditionally stable and free from the CFL condition restraint.     

A computational framework for approximating boundary surfaces in 3-D biomedical images.

We propose a new method for detecting and approximating the boundary surfaces in three-dimensional (3-D) biomedical images. Using this method, each boundary surface in the original 3-D image is normalized as a zero-value isosurface of a new 3-D image transformed from the original 3-D image. A novel computational framework is proposed to perform such an image transformation. According to this framework, we first detect boundary surfaces from the original 3-D image and compute discrete samplings of the boundary surfaces. Based on these discrete samplings, a new 3-D image is constructed for each boundary surface such that the boundary surface can be well approximated by a zero-value isosurface in the new 3-D image. In this way, the complex problem of reconstructing boundary surfaces in the original 3-D image is converted into a task to extract a zero-value isosurface from the new 3-D image. The proposed technique is not only capable of adequately reconstructing complex boundary surfaces in 3-D biomedical images, but it also overcomes vital limitations encountered by the isosurface-extracting method when the method is used to reconstruct boundary surfaces from 3-D images. The performances and advantages of the proposed computational framework are illustrated by many examples from different 3-D biomedical images.     

An adaptive 3-D discrete cosine transform coder for medical imagecompression

A new three-dimensional (3-D) discrete cosine transform (DCT) coder for medical images is presented. In the proposed method, a segmentation technique based on the local energy magnitude is used to segment subblocks of the image into different energy levels. Then, those subblocks with the same energy level are gathered to form a 3-D cuboid. Finally, 3-D DCT is employed to compress the 3-D cuboid individually. Simulation results show that the reconstructed images achieve a bit rate lower than 0.25 bit per pixel even when the compression ratios are higher than 35. As compared with the results by JPEG and other strategies, it is found that the proposed method achieves better qualities of decoded images     

Magnetic resonance diffractive imaging

Magnetic resonance (MR) diffractive imaging is proposed as a new approach to MR angiography. The expression of the nuclear MR signal is similar to the equation for the Fresnel diffraction of a three-dimensional (3-D) object in light or sound waves. The proposed technique offers the possibility of fast angiographic imaging and the on-line reconstruction of 3-D volumetric images using the holographic technique. Static imaging experiments using an ultra-low-field MRI system are performed to verify the feasibility of the technique. It is shown that the images focused on an arbitrary plane can be reconstructed from data scanned in two dimensions, even though blurred image data is superimposed on the image. Moreover, the 3-D image can be observed in a coherent optical imaging system. This study demonstrates the possibility of the proposed method as a fast imaging technique for MR angiography.     

Lock-in thermal laser stimulation for non-destructive failure localization in 3-D devices

We report a new non-destructive method to localize interconnection failures in 3-D devices. The scanning optical microscopy (SOM) technique is based on lock-in thermal laser stimulation (LI-TLS) and uses thermal waves to non-destructively map the current path in a 3-D device. We validate the method with test structures and show how the magnitude and phase of a propagating thermal wave may provide valuable 3-dimensional information on the failure location. We apply the technique on a short failed chain structure in a four level chip stack with an intensity modulated laser as a thermal wave injector and the structure under test as a detector. We confirm our results by physical failure analysis through a selective cross sectioning process.     

基于压缩感知的地基MIMO SAR近场层析成像研究

合成孔径雷达(Synthetic Aperture Radar,SAR)层析技术是一种通过多航迹观测,获取目标高程信息,重建目标三维结构的重要手段。目前,层析SAR成像多应用于星载与机载平台,均以远场假设为基础,即认为雷达与目标间的距离远大于目标几何尺寸,此时多航迹观测雷达对目标的视角变化很小,目标的散射特征变化很小。但是在近场构型下,多航迹观测雷达对目标的视角变化大,目标的散射特征变化大,现有基于远场假设的层析处理方法不再适用。为解决这一问题,本文研究了基于压缩感知的地基多输入多输出(Multiple Input Multiple Output, MIMO)SAR近场层析成像方法,主要包含了以下方法创新:(1)基于孤立强点定标完成通道间幅相误差补偿,提高成像质量;(2)基于散射体结构信息与闪烁强点剔除实现高精度多图配准;(3)利用解斜思想与三维空间几何关系估计高程信息。最后,本研究实现了基于Ku频段MIMO SAR的建筑物三维结构反演。      

Opti-Acoustic Stereo Imaging: On System Calibration and 3-D Target Reconstruction

Utilization of an acoustic camera for range measurements is a key advantage for 3-D shape recovery of underwater targets by opti-acoustic stereo imaging, where the associated epipolar geometry of optical and acoustic image correspondences can be described in terms of conic sections. In this paper, we propose methods for system calibration and 3-D scene reconstruction by maximum likelihood estimation from noisy image measurements. The recursive 3-D reconstruction method utilized as initial condition a closed-form solution that integrates the advantages of two other closed-form solutions, referred to as the range and azimuth solutions. Synthetic data tests are given to provide insight into the merits of the new target imaging and 3-D reconstruction paradigm, while experiments with real data confirm the findings based on computer simulations, and demonstrate the merits of this novel 3-D reconstruction paradigm.      

An iterative measured equation technique for electromagneticproblems

An iterative measured equation technique (IMET) is presented for a numerical solution of electromagnetic problems. This technique is an extension and improvement of the method of measured equation of invariance (MEI). In this technique, an iterative scheme is designed in such away that a new set of metrons used to generate the measured equations is formed in each iteration based on the solution of the previous iteration. The new metrons are more meaningful in that they converge to the physical quantity of interest such as the surface current density for electrodynamic problems and the surface charge density for electrostatic problems. The IMET offers several advantages over the MEI method because it requires only two mesh layers, resulting in a significant reduction in the memory requirement and computing time. More importantly, it provides a means for a systematic improvement of the accuracy of solution. The IMET is applied successfully to two-dimensional (2-D) electrodynamic and three-dimensional (3-D) electrostatic problems. Numerical results show that the technique is highly accurate and the iterative process converges very quickly, usually within two iterations