Detection of moving point objects against a moving background

The temporal spectral characteristics of a dim moving point object and a moving background, as observed by a sensor array, are analyzed. This type of problem occurs in remote sensing, machine vision, and many other applications. The diffraction limitation of the sensor optics ensures that the temporal spectrum of the background moving with a finite velocity has a finite maximum bandwidth, regardless of background structure. Because the outputs of the sensor array are time sampled, its spectrum is infinitely replicated over an interval of temporal frequency equal to the reciprocal of the sampling time. If this interval is at least twice as large as the maximum background temporal frequency, there is a region with no background components in the middle of each interval. However, because the point object temporal spectrum in the sampled sensor array output is continuously distributed, this region will contain part of the point object signal. Thus, a criterion for the existence of an effective background suppression filter is that the point object fundamental frequency must be greater than the maximum background temporal frequency. When this criterion is satisfied, the amount of background leakage in the filter depends on the sharpness of its passband response and its stopband characteristics. In general, higher-order filters have sharper response and hence better performance. If the criterion is not met, all types of filter lose their effectiveness since the background signal will leak through the passband of the filter. The fundamental concepts developed here were examined for some typical parameter values. It is shown that for this system the point object can be effectively discriminated. In some cases the point object and background temporal spectral responses vary significantly with spatial position within the field of view. Because the filter's center frequency must match the point object temporal fundamental frequency, it is necessary to use an adaptive filter in these situations.     

Scanning moving surfaces of biological objects

We propose a simple device for scanning moving surfaces of biological objects. The device is based on the use of eddy-current sensors made in the form of an Archimedean spiral, and can be used to measure the movement parameters for different parts of the body in humans or animals. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 66–67, May, 1996.     

复杂背景下运动目标的提取

提出了在复杂背景以及摄像机运动的情况下运动目标提取的算法。采用了新的局部投影的方法,在图像中合理地划分了投影区域,在求投影偏移量时提出了峰值匹配的算法,合理地检测到了投影偏移量。求得各个局部运动矢量后,采用出现频率最高的局部运动矢量代表全局运动矢量,成功的补偿了背景的运动。实验结果表明该算法在图像背景复杂且由于摄像机运动使背号发生明显变化的情况下,可稳定准确地提取出运动目标,并能有效克服背景中存在的运动干扰。     

Feasibility study of synthetic aperture infrared laser radar techniques for imaging of static and moving objects

Techniques for two types of 10-mum band synthetic aperture infrared laser radar using a hypothetical reference point target (RPT) are presented. One is for imaging static objects with a single two-dimensional scanning aperture. Through the simple manipulation of a reference wave phase, a desired image can be obtained merely by the two-dimensional Fourier transformation of the correlator output between the intermediate frequency signals of the reference and object waves. The other, with a one-dimensional aperture array, is for moving objects that pass across the array direction without attitude change. We performed imaging by using a two-dimensional RPT correlation method. We demonstrate the capability of these methods for imaging and evaluate the necessary conditions for signal-to-noise ratio and random phase errors in signal reception through numerical simulations in terms of feasibility.     

Microwave tomography for compact-support dielectric objects

A technique for imaging compact-support dielectric objects from microwave backscattering data is proposed. It is based on a linear data model, which permits the evaluation of the object spectrum on a band-pass region, and the application of the Projected Landweber method for spectrum extrapolation. The performance of the resulting algorithm is then investigated as a function of the relaxation parameter and the possible preconditioning strategy. Several experimental results are shown both for noiseless and noisy cases. This algorithm is shown to be an additional possibility to be taken into consideration, alongside the classical linear algorithms and the fully nonlinear ones. The experimental results show that the solutions are far better than the ones obtained by linear methods, yet require far fewer computations than the nonlinear approaches. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 14–23, 1998     

一种快速移动对象轨道聚类算法

针对已有轨道聚类(TRACLUS)算法的线段聚类模块需要对划分后的每条线段进行邻域查询的问题,将取样技术引入轨道聚类,提出一种快速移动对象轨道聚类(FTCS)算法。FTCS算法根据基于极大连通子图的合并原理,对核心线段的Eps邻域以及与该Eps邻域相重叠的所有轨道聚类进行合并,避免了TRACLUS算法中核心线段Eps邻域内线段的不必要邻域查询操作。在真实和合成轨道数据集上的大量实验结果表明,FTCS算法显著降低了邻域查询操作次数,在保持TRACLUS算法轨道聚类质量的同时,成倍提高了轨道聚类的时间效率。     

Fourier-phase method for the location of moving objects

A novel method is presented that permits one to locate a moving object. According to this method, the change in location of a moving object can be detected from its Fourier spectrum. This method has the advantages of a high-precision locating mechanism and the capacity to permit one to ignore the change in the orientation and the size of the moving object. The principles are introduced, a computer simulation and experimental demonstration are given, and the practicality of this method is discussed.     

Optical detection of rapidly moving objects in space

We compare the sensitivity of photon-counting and charged-coupled-device (CCD) imagers for rapidly moving objects. Our test case involves the detection of small objects in space, seen against a diffuse zodiacal light background, as observed from a space platform. We contrast photon-counting detectors, with excellent time resolution and negligible readout noise, against CCDs with a significantly larger quantum efficiency. For fast moving objects and small fields of view, the photon-counting detectors are able to detect significantly smaller targets, with the added benefit of providing angle-angle-time metric information in addition to high-time-resolution light curves. For larger fields of view and slower moving objects, the CCDs are more sensitive. These results may motivate the further development of microchannel-plate photon-counting systems and amplified CCDs for detecting and tracking space objects.     

一种结合Grabcut的Vibe目标检测算法

针对传统背景建模方法不能非常有效地提取出完整运动目标这一问题,提出了一种新颖的结合Grabcut和Vibe算法的运动目标检测方法.首先利用改进的Vibe目标检测算法初步寻找出当前帧中的所有可能目标前景区域;然后对这些前景区域进行进一步的选择从而滤去无效前景,合并有效区域;最后对每个前景区域再利用Grabcut算法来分割出更加完整的目标前景.实验结果表明,与传统的背景建模方法相比,本算法在有效时间内可以更加完整地分割出运动目标前景,对与背景颜色类似的目标前景也有很好的检测效果.     

Strain measurement of moving periodic objects with optical sensors

Measuring the strain of an object provides information about axial loads which it is exposed to. In some applications, this information is wanted not from still-standing, but from linearly moving objects. Measuring the strain of V-belts, e.g., permits investigating the operational behavior of combustion engine belt drives. For this purpose, new noncontact measurement methods using optical sensors are being developed. The sensors detect periodic patterns on the moving object. The strain is determined from a frequency analysis of the sensor signal.     

Laser photoacoustic imaging of inhomogeneous objects

The process of photoacoustic response formation in inhomogeneous objects is analyzed. In a quasi-static case, the photoacoustic image is formed predominantly due to inhomogeneities in the thermoelastic coupling coefficient. Expressions describing thermoelastic strains in an inhomogeneous object with allowance for the inhomogeneous thermoelastic coupling coefficient in the general form are obtained within the framework of a three-dimensional model using the perturbation theory. A comparative analysis is performed for the process of photoacoustic image formation in various regimes of piezoelectric sensor operation. The results are used to explain the behavior of a photoacoustic signal at the ends of vertical cracks.     

一种新的运动目标检测与跟踪算法

常用的运动目标检测算法无法解决在摄像机运动-目标运动情况下的运动目标检测，为此提出了背景匹配法。通过相关匹配算法使背景对齐，结合帧间差分技术有效地将运动目标提取出来；然后利用卡尔曼预测器对运动目标在图像中的位置进行预测，结合增量式带死区的PID控制算法，控制摄像机对准目标。实验结果表明，匹配块的选择加快了处理速度和提高了算法的稳定性，卡尔曼预测器使得跟踪更为平稳可靠。本方法具有简单、通用、抗噪等特点。     

Real-time detection of multiple moving objects in complex image sequences

In this article, a real-time multistage method for detecting multiple objects moving in real scenes is presented. At the first level, a rough focus-of-attention mechanism is used to individuate areas of the input image that show remarkable differences with a real-time updated background image. Binary statistical morphology (BMS) operators are applied to individuate image pixels, which can be associated with real objects moving into the scene. High stability to noise is obtained by tuning the smoothing effects of the BSM operators according to the noise level present in the original image sequence. Then, at the second level, a composition of BSM is applied to eliminate isolated points and to favor dense agglomerate of changed pixels, i.e., blobs. The last level attempts to describe changes in terms of motion of blobs by allowing blobs to merge, split, appear, and vanish. A blob-matching procedure is used for tracking blobs over consecutive frames. Experimental results on real scenes, which demonstrate the advantages of the proposed method with respect to existing change detection methods, are given. © 1999 John Wiley & Sons, Inc. Int J Imaging Syst Technol 10, 305–317, 1999     

一种视频图像序列中运动对象的分割与跟踪算法

本文提出了一种视频图像序列中运动对象的分割与跟踪算法。该算法通过Canny算子检测出差帧图像的边缘信息,并结合当前帧与背景帧的边缘图像,提取出运动对象。在后续帧中通过建立前帧感兴趣运动对象与当前帧中各运动对象的帧间向量来跟踪当前帧中感兴趣的视频对象。实验结果表明,该算法可行,而且由于该算法简单、计算复杂度小,能很好地满足实时监控系统中对感兴趣运动对象的提取与跟踪。