Stereo matching cost computation based on nonsubsampled contourlet transform

A new matching cost computation method based on nonsubsampled contourlet transform (NSCT) for stereo image matching is proposed in this paper. Firstly, stereo image is decomposed into high frequency sub-band images at different scales and along different directions by NSCT. Secondly, by utilizing coefficients in high frequency domain and grayscales in RGB color space, the computation model of weighted matching cost between two pixels is designed based on the gestalt laws. Lastly, two types of experiments are carried out with standard stereopairs in the Middlebury benchmark. One of the experiments is to confirm optimum values of NSCT scale and direction parameters, and the other is to compare proposed matching cost with nine known matching costs. Experimental results show that the optimum values of scale and direction parameters are respectively 2 and 3, and the matching accuracy of the proposed matching cost is twice higher than that of traditional NCC cost.     

Reconfigurable hardware implementation of a phase-correlation stereoalgorithm

This paper describes the implementation of a stereo-vision system using Field Programmable Gate Arrays (FPGAs). Reconfigurable hardware, including FPGAs, is an attractive platform for implementing vision algorithms due to its ability to exploit parallelism often found in these algorithms, and due to the speed with which applications can be developed as compared to hardware. The system outputs 8-bit, subpixel disparity estimates for 256× 360 pixel images at 30,fps. A local-weighted phase correlation algorithm for stereo disparity [Fleet, D. J.: {Int. Conf. Syst. Man Cybernetics 1:48–54 (1994)] is implemented. Despite the complexity of performing correlations on multiscale, multiorientation phase data, the system runs as much as 300 times faster in hardware than its software implementation. This paper describes the hardware platform used, the algorithm, and the issues encountered during its hardware implementation. Of particular interest is the implementation of multiscale, steerable filters, which are widely used in computer vision algorithms. Several trade-offs (reducing the number of filter orientations from three to two, using fixed-point computation, changing the location of one localized low-pass filter, and using L1 instead of L2 norms) were required to both fit the design into the available hardware and to achieve video-rate processing. Finally, results from the system are given both for synthetic data sets as well as several standard stereo-pair test images.     

Quadtree-based genetic algorithm and its applications to computer vision

Many computer vision problems can be formulated as optimization problems. Presented in this paper is a new framework based on the quadtree-based genetic algorithm that can be applied to solve many of these problems. The proposed algorithm incorporates the quadtree structure into the conventional genetic algorithm. The solutions of image-related problems are encoded through encoding the corresponding quadtrees, and therefore, the 2D locality within a solution can be preserved. Examples addressed using the proposed framework include image segmentation, stereo vision, and motion estimation. In all cases, encouraging results are obtained.     

丽音（NICAM）双伴音／立体声电视广播技术

本文首先介绍了电视双伴音/立体声广播的几种常用方式,然后着重分析丽音(NICAM)双伴音/立体声广播系统的基本原理,并给出其接收系统的集成电路。     

Stereo and motion correspondences using nonlinear optimization method

This paper presents a new approach for using stereo and motion correspondences to solve the problem of tracking multiple independently moving features. In this approach, quantitative relational structure (QRS) is proposed as a framework for the integration of stereo–motion correspondences. The similarity function, tightly coupled to stereo and motion cues, is constructed on QRS, and then energy function E² consisting of the similarity function is defined. The tracking problem can be converted into the maximization problem of the energy function E². The stereo and motion correspondences that maximize E² are recovered by applying an extended graduated assignment algorithm. The relaxation labeling method is also presented for the comparison with the proposed method. Experimental results are presented to illustrate the performance of the proposed method.     

微波热处理对无托槽隐形正畸矫治器的力学性能影响

为探究微波热处理对无托槽隐形正畸矫治器的力学性能影响,对立体光固化(SLA)打印的标准试样件在不同功率的微波热处理后进行拉伸、弯曲力学性能测试,并通过3D偏差验证矫治器压膜工序前添加微波热处理工艺的有效性。结果表明,微波功率为400 W时,拉伸强度为50.6 MPa,提升了19.06%,断裂伸长率达到13.24%,弯曲强度为66.8 MPa,弯曲模量为2042 MPa;经过微波热处理的牙模压膜后在0.1 mm公差范围内的变形率降低了14.33%。微波热处理能够优化树脂制件的力学性能,并有效提高矫治器的制造精度。     

3D soft-tissue tracking using spatial-color joint probability distribution and thin-plate spline model

Visual tracking techniques based on stereo endoscope are developed to measure tissue motion in robot-assisted minimally invasive surgery. However, accurate 3D tracking of tissue surfaces remains challenging due to complicated deformation, poor imaging conditions, specular reflections and other dynamic effects during surgery. This study employs a robust and efficient 3D tracking scheme with two independent recursive processes, namely kernel-based inter-frame motion estimation and model-based intra-frame 3D matching. In the first process, target region is represented in joint spatial-color space for robust estimation. By defining a probabilistic similarity measure, a mean-shift-based iterative algorithm is derived for location of the target region in a new image. In the second process, the thin-plate spline model is used to fit the 3D shape of tissue surfaces around the target region. An iterative algorithm based on an efficient second-order minimization technique is derived to compute optimal model parameters. The two processes can be computed in parallel. Their outputs are combined to recover 3D information about the target region. The performance of the proposed method is validated using phantom heart videos and in vivo videos acquired by the daVinci^®${\mathrm{daVinci}}^{\circledR }$ surgical robotic platform and a synthesized data set with known ground truth.     

Evaluation of stereo correspondence algorithms and their implementation on FPGA

The accuracy of stereo vision has been considerably improved in the last decade, but real-time stereo matching is still a challenge for embedded systems where the limited resources do not permit fast operation of sophisticated approaches. This work presents an evaluation of area-based algorithms used for calculating distance in stereoscopic vision systems, their hardware architectures for implementation on FPGA and the cost of their accuracies in terms of FPGA hardware resources. The results show the trade-off between the quality of such maps and the hardware resources which each solution demands, so they serve as a guide for implementing stereo correspondence algorithms in real-time processing systems.     

板料应变视觉测量系统研究

介绍了板料应变视觉测量系统结构和基本原理。该系统运用立体视觉技术对板料成形物理模拟中的圆形坐标网格系统进行测量，获得变形板料的应变分布。实验结果表明，该系统可以较为迅速地完成各种成形工艺的板料件应变参数的测量与分析，并取得比较理想的精度。