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从正投影光流场计算刚体运动参数和结构 总被引:1,自引:0,他引:1
从光流场恢复刚体三维运动和结构是计算机视觉中一个基本问题。本文研究从正投影光流场恢复刚体三维运动和结构问题,建立了光流运动方程,提出一种判别多个光流点是否共面或是否属于同一刚体的有效方法。证明了平移运动刚体有两个自由度,旋转运动刚体有一个自由度,一般运动刚体有三个自由度,至少需要四个光流点才能获得一般运动刚体的流参数(含一比例因子)。 相似文献
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Byung Jun Kang Kang Ryoung Park 《International journal of imaging systems and technology》2009,19(4):323-331
Iris recognition is a form of biometric technology that authenticates individuals by using the unique iris patterns between the pupil and the sclera. To solve security problems in mobile environments, mobile iris recognition devices have been commercialized recently. A motion‐and‐optical blurred image can be sometimes captured because users capture the iris images of a testee by holding the recognition devices. Motion‐and‐optical blurred images reduce iris recognition accuracy. Previous researches of restoring iris image only dealt with optical or motion blurred image. To overcome these problems, we propose a new method of restoring motion‐and‐optical blurred iris images at the same time. This article presents three contributions over previous research. (1) A new focus assessment method is proposed to measure accurate focus scores regardless of motion blurring. (2) Previous research restored coexisting motion‐and‐optical blurred images in terms of visibility, but in this article, we restored them in terms of recognition. (3) We used a modified CLS (Constrained Least Square) filter to prevent the zero‐crossing of the PSF (Point Spread Function) of motion blurring with a uniform shape. So, the iris recognition accuracy was better than when using a conventional CLS filter. Experimental results showed that the EER was 0.796% when using the proposed method and it was 1.431% when not using the proposed method. Consequently, the EER was reduced as much as 0.635% (1.431–0.796%) when using the proposed method. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 323–331, 2009 相似文献
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Yang CH Tsai YC 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2005,52(8):1372-1377
This paper describes a laser optical technique that allows the detection of in-plane motion of Lamb waves. This interference-based laser optical technique includes a tiny square indentation with a width of about 30 micron on the sample surface and a relatively simple optical arrangement. The current technique is applied for the detection of in-plane motions of Lamb waves propagating in a 70-micron thick brass plate. Measurement of So mode dominated by in-plane motion in the low fd (frequency times thickness) regime is successfully demonstrated with the current technique. With the indentation replaced by a microreflector in a microelectromechanical (MEMS) structure, this technique is applicable for the detection of in-plane motion in MEMS structures. 相似文献
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Y. Q. Shi S. Lin Ya-Qin Zhang 《International journal of imaging systems and technology》1998,9(4):230-237
In this article, we propose an efficient compression algorithm for very low-bit-rate video applications. The algorithm is based on (a) an optical-flow motion estimation to achieve more accurate motion prediction fields; (b) discrete cosine transformation (DCT) coding of the motion vectors from the optical-flow estimation to reduce the motion overheads; and (c) an adaptive threshold technique to match optical flow motion prediction and minimize the residual errors. Unlike the classic block-matching based DCT video coding schemes in MPEG-1/2 and H.261/3, the proposed algorithm uses optical flow for motion compensation and the DCT is applied to the optical flow field instead of predictive errors. Thresholding techniques are used to treat different regions to complement optical flow technique and to efficiently code residual data. While maintaining a comparable peak signal-to-noise ratio (PSNR) and computational complexity with that of ITU-T H.263/TMN5, the reconstructed video frames of the proposed coder are free of annoying blocking artifacts, and hence visually much more pleasant. The computer simulation are conducted to show the feasibility and effectiveness of the algorithm. Results at 11 kbps are presented which can be used for videophone applications in the existing public switched telephone network (PSTN). © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 230–237, 1998 相似文献
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Kelly DP Ward JE Hennelly BM Gopinathan U O'Neill FT Sheridan JT 《Journal of the Optical Society of America. A, Optics, image science, and vision》2006,23(11):2861-2870
Digital speckle photography can be used in the analysis of surface motion in combination with an optical linear canonical transform (LCT). Previously [D. P. Kelly et al. Appl. Opt.44, 2720 (2005)] it has been shown that optical fractional Fourier transforms (OFRTs) can be used to vary the range and sensitivity of speckle-based metrology systems, allowing the measurement of both the magnitude and direction of tilting (rotation) and translation motion simultaneously, provided that the motion is captured in two separate OFRT domains. This requires two bulk optical systems. We extend the OFRT analysis to more general LCT systems with a single limiting aperture. The effect of a limiting aperture in LCT systems is examined in more detail by deriving a generalized Yamaguchi correlation factor. We demonstrate the benefits of using an LCT approach to metrology design. Using this technique, we show that by varying the curvature of the illuminating field, we can effectively change the output domain. From a practical perspective this means that estimation of the motion of a target can be achieved by using one bulk optical system and different illuminating conditions. Experimental results are provided to support our theoretical analysis. 相似文献
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北冈明佳运动错视作品的表现形式 总被引:1,自引:1,他引:0
日本著名错视大师北冈明佳创作的运动错视作品通过不同色彩和明度的运用,精心地排列和布局,创造出强烈的视幻之美。运动错觉是北冈明佳作品的一大特色,他将各种运动错觉展现在静态图片上,呈现出独特的视错觉效果,其运动错视包括旋转错视、波动错视、移动错视和发射错视4种表现形式。 相似文献
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Nano-stages are used in many ultra-precision systems, such as scanning probe microscope (SPM), optical fiber aligners, ultra-precision cutting, measuring and optical systems. Generally, ultra-precision machining and measuring are achieved using a nano-scale motion stage actuated using Piezo-electric actuators (PZT), and the importance of and demands for the motion stage increase with the need to improve system performance and accuracy. However, it is difficult to find solutions because the performance and characteristics of nano-scale motion stages are determined by various factors, such as the hinge structure, actuator, and method of system control. This paper focuses on improving of leafspring and planar joint hinges, and suggests a composite joint hinge stage. 相似文献
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The goal of motion segmentation is to segregate a visual scene into independently moving objects. It is an indispensable pre-processing step for various tasks in computer vision and has evolved as an active and flourishing research area in the last few decades. In the sequences captured using a monocular camera, motion segmentation is typically performed by analyzing apparent motion of pixels in the image plane, i.e. the optical flow. Optical flow is generally contemplated as an appropriate representation of image motion. Numerous techniques for reliable flow estimation and subsequent advancements in their framework have been proposed in the last couple of decades and are outlined briefly in this work. The paper attempts to give a summary of diverse optical flow-based approaches used for robust segmentation of static or dynamic scenes containing rigidly moving objects and discusses in brief the shortcomings associated with them. 相似文献
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In an absolute gravity meter, a laser interferometer measures the position of a test mass that is falling ina vacuum. The calculated value of gravity is the average acceleration of the mass during a set ofdrops. Since systematic accelerations of the optical system will bias the measured value of gravity,various interferometer geometries have been implemented in the past to isolate the optical system fromground motion. We have developed and tested a low-finesse fiber-optic extrinsic Fabry-Perotinterferometer that is fixed to the mass of a critically damped seismometer in which the effects ofsystematic ground motion and acoustic vibrations are reduced. 相似文献
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The probe-to-sample separation in near-field scanning optical microscopes can be regulated by a noncontact shear-force sensing technique. The technique requires the measurement of a minute dither motion applied to the probe. We have characterized an optical detection method for measuring this motion to determine the optimum detection configuration in terms of sensitivity and stability. A scalar diffraction model of the detection method is developed for calculating sensitivity, and experimental results are found to be in good agreement with the theoretical predictions. We find that maximum sensitivity and stability cannot be achieved simultaneously, and it may be desirable in practice to trade sensitivity for enhanced stability. 相似文献
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J. V. Condell B. W. Scotney P. J. Morrow 《International journal of imaging systems and technology》2006,16(2):35-50
Confident adaptive algorithms are described, evaluated, and compared with other algorithms that implement the estimation of motion. A Galerkin finite element adaptive approach is described for computing optical flow, which uses an adaptive triangular mesh in which the resolution increases where motion is found to occur. The mesh facilitates a reduction in computational effort by enabling processing to focus on particular objects of interest in a scene. Compared with other state‐of‐the‐art methods in the literature our adaptive methods show only motion where main movement is known to occur, indicating a methodological improvement. The mesh refinement, based on detected motion, gives an alternative to methods reported in the literature, where the adaptation is usually based on a gradient intensity measure. A confidence is calculated for the detected motion and if this measure passes the threshold then the motion is used in the adaptive mesh refinement process. The idea of using the reliability hypothesis test is straightforward. The incorporation of the confidence serves the purpose of increasing the optical flow determination reliability. Generally, the confident flow seems most consistent, accurate and efficient, and focuses on the main moving objects within the image. © 2006 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 16, 35–50, 2006 相似文献
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提出一种异形热态锻件几何尺寸测量方法。基于线激光器、CCD和伺服系统构建线激光扫描测量系统,通过提取图像上被锻件表面轮廓调制的激光条纹二维信息,经过坐标变换及点云三维重构得到锻件三维尺寸信息。针对被测异形锻件形貌特征,建立基于摄像机运动的扫描测量模型,并提出一种基于棋盘参考平面的摄像机光心轨迹求解方法。根据平面上特征点在CCD图像不同帧中的坐标拟合摄像机的运动轨迹,结合扫描测量模型实现对异形锻件完整轮廓尺寸的测量。通过实验对封头进行扫描测量,得到球冠部分截面测量直径误差小于4 mm,满足热态锻件测量要求,验证了该方法的可行性。 相似文献
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Development of efficient and sensitive motion transducers for arrays of nanoelectromechanical systems (NEMS) is important for fundamental research as well as for technological applications. Here, we report a single-wire nanomechanical transducer interface, which relies upon near-field optomechanical interactions. This multiplexed transducer interface comes in the form of a single-mode fiber taper on a fiber-optic cable. When the fiber taper is positioned sufficiently close to the NEMS array such that it can attain evanescent optical coupling with the array, individual NEMS resonances can be actuated using optical dipole forces. In addition, sensitive detection of nanomechanical motion can be realized when the evanescent waves confined around the taper are scattered by the motion. We have measured resonances from an array of 63 NEMS resonators with a displacement sensitivity of 2-8 pm·Hz(-1/2) at a detection power of ~100 μW (incident on the entire array). 相似文献
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We address the problem of body pose tracking in a scenario of multiple camera setup with the aim of recovering body motion robustly and accurately. The tracking is performed on three-dimensional (3D) space using 3D data, including colored volume and 3D optical flow, which are reconstructed at each time step. We introduce strategies to compute multiple camera-based 3D optical flow and have attained efficient and robust 3D motion estimation. Body pose estimation starts with a prediction using 3D optical flow and then is changed to a lower-dimensional global optimization problem. Our method utilizes a voxel subject-specific body model, exploits multiple 3D image cues, and incorporates physical constraints into a stochastic particle-based search initialized from the deterministic prediction and stochastic sampling. It leads to a robust 3D pose tracker. Experiments on publicly available sequences show the robustness and accuracy of our approach. 相似文献
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Klapp I Yitzhaky Y 《Journal of the Optical Society of America. A, Optics, image science, and vision》2006,23(8):1856-1864
When motion blur is considered, the optics point spread function (PSF) is conventionally assumed to be fixed, and therefore cascading of the motion optical transfer function (OTF) with the optics OTF is allowed. However, in angular motion conditions, the image is distorted by space-variant effects of wavefront aberrations, defocus, and motion blur. The proposed model considers these effects and formulates a combined space-variant PSF obtained from the angle-dependent optics PSF and the motion PSF that acts as a weighting function. Results of comparison of the new angular-motion-dependent PSF and the traditional PSF show significant differences. To simplify the proposed model, an efficient approximation is suggested and evaluated. 相似文献