基于相位展开和一种新的迭代重建算法的流场莫尔层析术

使用莫尔层析方法测量温度场。设计了一种旋转莫尔偏折仪,该装置可以获取180°范围内的莫尔条纹图。采用傅里叶变换相位展开技术处理莫尔条纹,提取轴向任意截面的投影信息,使用一种新的莫尔层析迭代算法重建温度分布,该迭代算法与已有的代数重建算法不同,它由莫尔偏折基本公式和网格重建技术推导得出,直接使用光线偏折角进行迭代,可以直接实现对非完全投影数据的层析重建。实验中使用8个方向的莫尔条纹图对双峰结构温度场进行重建,得到了截面的温度分布,峰值的重建误差低于5%。测量结果证明这是一种准确、适用性广的层析重建方法。     

Moire/spl acute/ minimization condition in three-dimensional image displays

A moire/spl acute/ minimization condition is found analytically for the contact-type three-dimensional (3-D) imaging systems by approximating 3-D displays as four superposed sine gratings. Finding maximization conditions for two-dimensional (2-D) waves in this structure provides minimization of moire/spl acute/s. The global extremum was found at a certain angle which does not depend on the period. Experiments confirm the analytical findings. Practical advantage of using that angle is in its wide areas of applications: 3-D displays can be made to have almost invisible moire/spl acute/s with using this angle without regards to other specific parameters like pixel size and pitch of the screen.     

Using moire patterns to determine the distortion of graphic displays and graphic input devices

Before high-accuracy graphic displays can be successfully designed or implemented from existing displays, the display distortion need be known to a high degree of accuracy-typically of the order of 0.1 percent of the display area height or better. Present day methods of measuring distortion are clumsy and imprecise. Methods of measurement using moire fringes have been suggested before, but the treatment was intuitive and the interpretation quailtative. In this paper are derived quantitative relationships from which display distortion to the 0.1 percent accuracy mentioned can be obtained using moire fringes. Two distinct methods are described. Full experimental methods, limitations, accuracy of method, etc., are given. Actual case examples illustrate the method. Although the methods developed here were specifically for TV-mode displays, the methods are equally valid for any graphic display device such as cathode-ray tubes (storage or refresh), electromechanical X-Y plotters, flat-screen displays, etc., the only requirement being the ability to display or generate a parallel line pattern. The distortion of graphic input devices such as TV cameras, electronic X-Y input pads, etc., can also be obtained using these methods.     

基于莫尔条纹的三维物体的旋转不变识别

本文提出一种基于莫尔条纹的三维物体旋转不变识别方法。采用阴影莫尔法的装置和频域滤波的方法,可得到物体的莫尔条纹图。因为物体的莫尔条纹是物体的等高线,体现三维物体特征的高度函数以莫尔等高线的形式编码于强度图中,因此基于莫尔条纹的相关识别具有本征三维识别的特点。采用振幅调制和功率谱相减的联合变换相关,用实现旋转不变识别的综合鉴别函数(SDF)作为联合变换相关输入的参考图像,来获得具有识别目标的旋转不变性和高的相关识别率。计算机模拟试验结果证明了这种方法用于三维物体旋转不变性识别的有效性。     

A Pitch-variation Moire Fringes Method of Temporal Phase Unwrapping Profilometry

A method of pitch-variation moire fringes is proposed to realize the temporal phase unwrapping for three-dimensional profilometry. On the basis of the principle of moire pattern, we achieve variable spatial frequencies of fringes in a moire pattern by rotating two gratings. Furthermore a five-point fitting method is used to automatically compute the central position of side-lobe spectrum of the moire fringes. Finally, a generalized temporal phase unwrapping algorithm is introduced to process the three-dimensional reconstruction. The theoretical analysis and experimental results show the validity of the proposed method.     

Simultaneous Measurement of PWB and Chip Package Warpage Using Automatic Image Segmentation

The shadow moire and projection moire techniques are widely used methods for measuring printed wiring board (PWB) and PWB assembly (PWBA) warpage. Both methods have high resolution, high accuracy and are suitable for use in an online environment. When measuring the warpage of a bare PWB, maximum warpage across the PWB is calculated by subtracting the minimum out-of-plane displacement on the PWB from the maximum out-of-plane displacement on the PWB. However, when the PWB is populated with electronic components (chip packages); the difference between the maximum and minimum out-of-plane displacements on the PWBA is not the warpage of the PWB or the warpage of the chip packages. In order to use warpage measurement methods such as the shadow and projection moire techniques to accurately and separately determine the warpage of a PWB and chip packages in a PWBA, an automated chip package segmentation algorithm is developed and will be presented in this paper. The automated algorithm is based on active contour models (snakes) and can be used to detect chip package locations on an out-of-plane displacement image of a PWBA. This paper will discuss the characteristics of the automated algorithm, which is applicable to all warpage measurement methods, not just the out-of-plane moire methods. Warpage case studies of PWBs populated with plastic ball grid array chip packages measured using the projection moire technique will also be presented and will show that the developed algorithm along with a warpage measurement method is a powerful tool for measuring the warpage of populated PWBs.     

瞬态三维温度场的莫尔偏折层析

本文讨论了莫尔偏折法层析三维温度场的原理;提出了一种多通道(多方向)莫尔偏折的方法来获得多方向光线经过温度场后偏折的数据,然后利用计算机层析再现三维温度扬的方法;并分析了最佳通道采样角间隔的选取问题,得到了角间隔与角频率之间的关系。采用YAG脉冲激光光源,测量了非对称火焰的三维空间温度分布,并与干涉法测量的结果比较,得到一致的结果。     

Learning skeleton information for human action analysis using Kinect

Human action recognition plays an important role in modern intelligent systems, such as human–computer interaction (HCI), sport analysis, and somatosensory game. Compared with conventional 2-D based human action analysis, using Kinect sensor can obtain depth information of human action, which is significant for human action recognition. In this paper, we propose a joint angle sequence model for recognizing human actions, where depth images are acquired by using Kinect sensor. We design an improved DTW method to improve the matching accuracy. Comprehensive experiments show the effectiveness and robustness of our proposed method.     

单有向电磁矢量传感器的参数估计方法

传统的单电磁矢量传感器(UEMVS)由3个电偶极子和3个磁环构成且方向图是全向的。但是当多个单电磁矢量传感器依附在共形载体上构成共形电磁矢量传感器阵列时,为了降低共形电磁矢量传感器阵列的副瓣,通常每个传感器的方向图是有向的。基于有向方向图的单电磁矢量传感器也称为单有向电磁矢量传感器(UDEMVS)。该文针对UDEMVS的参数估计问题,提出两种参数估计方法,分别是基于免搜索的旋转不变信号参数估计和矢量叉积(ESPRIT-VCP)方法以及基于网格搜索的多重信号分类和最小瑞利商(MUSIC-MRQ)方法。ESPRIT-VCP方法是根据旋转不变性和矢量叉积,获得4维参数的闭式解,MUSIC-MRQ方法根据信号和噪声子空间正交性与最小瑞利商,利用网格搜索得到2维角度估计值,进而结合信号回波模型得到2维极化的估计值。所提两种方法只利用了UDEMVS的6通道数据就能有效得到目标的参数估计结果,有较低的计算复杂度。仿真结果从角度和极化的估计性能出发验证了所提方法的有效性。     

期望主瓣响应下任意阵方向图综合方法

为实现任意阵列天线的方向图综合,特别是考虑到不同空间指向对阵列方向图的影响,提出自适应原理与凸优化理论相结合的方向图综合法.该方法首先利用自适应原理综合法得到所需阵列方向图的旁瓣特性;而后,选择零度角的方向图主瓣作为期望主瓣;最后,在该期望主瓣响应下,将阵列方向图综合问题转化为二阶锥规划问题.采用凸优化循环迭代算法,完成对非凸优化问题的求解,从而保证方向图在满足期望主瓣响应的同时,使旁瓣特性与自适应方向图综合方法得到的结果最接近.理论分析与仿真结果表明,综合后阵列方向图在不同空间指向上具有与期望主瓣一致的主瓣特性,且其旁瓣也能够很好地保持对动态干扰的抑制特性.     

Computer-aided design of clustered-dot color screens based on ahuman visual system model

We address the problem of optimal periodic clustered-dot color-screen design. In traditional clustered-dot color screening, the screen for each colorant is rotated to a different angle relative to the others. If the angles are not carefully chosen, visible moire and rosette artifacts may appear These artifacts primarily result from the interaction of the periodic structures associated with the halftone screens of different colorants. Registration errors can also introduce unwanted artifacts in the screened images. Using lattice theory and a model for the perceived rendered halftone, we present a systematic method for designing moire- and rosette-free clustered-dot color screens for discrete-raster color systems. We also investigate strategies for choosing the periodicities so that the resulting screen is robust to registration errors     

Three-dimensional imaging methods based on multiview images

Three-dimensional imaging methods, based on parallaxes as their depth cues, can be classified into the stereoscopic providing binocular parallax only, and multiview providing both binocular and motion parallaxes. In these methods, the parallaxes are provided by creating a viewing zone with use of either a special optical eyeglasses or a special optical plate as their viewing zone-forming optics. For the stereoscopic image generations, either the eyeglasses or the optical plate can be employed, but for the multiview the optical plate or the eyeglasses with a tracking device. The stereoscopic image pair and the multiview images are presented either simultaneously or as a time sequence with use of projectors or display panels. For the case of multiview images, they can also be presented as two images at a time according to the viewer's movements. The presence of the viewing zone-forming optics often causes undesirable problems, such as appearance of moire/spl acute/ fringes, image quality deterioration, depth reversion, limiting viewing regions, low image brightness, image blurring, and inconveniences of wearing.     

基于框架理论的最小阵元数稀疏阵综合算法研究

随着越来越高的角度分辨率要求与进一步降低的天线成本,大规模阵列越来越普及。在重量、体积和成本有限时,要获得大孔径天线得到较高的角度分辨率,且尽量减少天线阵元数目,可采用最小阵元稀疏阵设计方法。本文基于框架理论,提出了一种新的最小阵元数的稀疏阵综合方法。该方法将稀疏阵设计问题转化为压缩感知问题模型,然后利用次优反馈的零空间追踪硬阈值算法求解。该方法可同时综合阵元位置与阵元权重来匹配给定的阵列方向图,并可有效降低阵元数。仿真实验证明了算法的正确性和有效性     

Pre-Processing of Integral Images for 3-D Displays

This paper seeks to explore a method to accurately correct geometric distortions caused during the capture of three-dimensional (3-D) integral images. Such distortions are rotational and scaling errors which, if not corrected, will cause banding and moire effects on the replayed image. The method for calculating the angle of deviation in the 3-D Integral Images is based on Hough Transform. It allows detection of the angle necessary for correction of the rotational error. Experiments have been conducted on a number of 3-D integral image samples and it has been found that the proposed method produces results with accuracy of 0.05 deg     

3D shape from focus using LULU operators and discrete pulse transform in the presence of noise

3D shape recovery is an interesting and challenging area of research. Recovering the depth information of an object from a sequence of 2D images with varying focus is known as shape from focus. Focus value of an image carries information about the object and shape from focus is a method which depends on different focused value images. It reconstructs the shape/surface/depth of an object based on the different focused values of the object. These different focused valued images should be captured from the same angle. Calculating the shape of the object from different images with different focused values can be done by applying sharpness detection methods to maximize and detect the focused values. In this paper, we propose new 3D shape recovery techniques based on LULU operators and discrete pulse transform. LULU operators are nonlinear rank selector operators that are efficient with low complexity. They hold consistent separation, total variation and shape preservation properties. Discrete pulse transform is a transform that decomposes image into pulses. Therefore selection of right pulses, give sharpest focus values. The proposed techniques provide better result than traditional techniques in a noisy environment.     

基于光逻辑的莫尔偏折学

光逻辑莫尔是基于光学逻辑运算的原理而提出的获取特定莫尔条纹的新方法.本文将其能消除载频和窄化条纹的特性应用于偏折学,并给出了实际结果.     

基于人工神经网络的时间调制阵列谐波波束形成

针对时间调制阵列(time-modulated array, TMA)提出了一种基于人工神经网络(artificial neural network, ANN)的谐波波束形成技术.该技术通过一个由编码器和解码器串联组成的ANN实现时序信息的优化,其中,编码器以目标角度的方向图约束值作为输入,通过在线训练输出对应的激励值;而解码器经过预训练可以实时输出辐射方向图.然后利用训练完成优化后的激励可以获得不同阵元的开关导通持续时间和起始时刻. 8元/16元不同指向TMA谐波波束形成算例仿真结果表明,所提方法可以有效抑制副瓣电平(sidelobe level, SLL),快速精确控制方向图,在目标角度实现高方向性波束形成,同时该方法具有耗时短、鲁棒性好和易调节的特点,有望应用于快速目标搜索和跟踪.     

分布式阵列方向图设计与栅瓣抑制方法研究

针对分布式阵列栅瓣抑制问题,提出了基于非周期阵列和随机阵列的分布式阵列方向图设计方法。首先,利用 Minimax 优化方法对子阵的边界进行优化并获取子阵最优位置参数, 实现分布式子阵随机优化布阵,从而消除阵列的周期性并最大限度地抑制栅瓣;其次,采用角度旋转的方式来消除分布式子阵之间的周期性,使得在方向图优化设计时能够避免栅瓣的累积叠加, 达到抑制栅瓣的目的。仿真分析结果表明,所述方法能够有效抑制分布式阵列的栅瓣,获得无栅瓣影响的分布式阵列方向图。     

无钥匙位相型双图像莫尔编码技术

根据光的衍射原理和莫尔图像编码原理,实现了无钥匙位相型双图像莫尔编码技术。用该技术制作的位相板可以在不同的衍射级上分别再现出2个被编码的图像和3个模板的图像,它们在空间上是按一定的顺序排列的。这一特性用其他技术难以模仿。该技术可应用于防伪领域,使产品的防伪力度大大提高。     

基于ESPRIT算法的L型阵列MIMO雷达降维DOA估计

该文针对L型阵列MIMO雷达的2维角度估计问题,基于ESPRIT算法提出两种降维DOA估计方法。首先通过降维矩阵的设计及回波数据的降维变换,将高维回波数据转换至低维信号空间;然后分别基于特征分解和传播算子获得信号子空间的估计,最后利用ESPRIT算法实现2维空间角参量的联合估计及参数的自动配对。算法不牺牲阵列孔径,最大程度地降低了回波数据的维数,具有更低的运算复杂度。仿真结果验证了该文理论分析的正确性和算法的有效性。