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。     

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.     

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     

Additive noise effect in digital phase detection

The characteristic polynomials associated with the algorithms used in digital phase detection are used to investigate the effects of additive noise on phase measurements. First, it is shown that a loss factor eta can be associated with any algorithm. This parameter describes the influence of the algorithm on the global signal-to-noise ratio (SNR). Second, the variance of the phase error is shown to depend mainly on the global SNR. The amplitude of a modulation of this variance at twice the signal frequency depends on a single parameter beta. The material presented here extends previously published results, and as many as 19 algorithms are analyzed.     

Microwave imaging of moving objects

Microwave images for objects in motion can be obtained with quality as good as those obtained in the stationary case if the signal waveforms, data acquisition systems, and image reconstruction algorithms are cleverly designed. The principle of imaging for objects in motion is to eliminate the gross Doppler effect of the echo signals and only reserve the differential Doppler information to reconstruct the image. Accordingly, requirements for parameters of the signal waveform are established. Two steps are involved in the image reconstruction algorithm: range alignment and phase compensation. Focused images of complex-shaped targets with simulated motion have been obtained experimentally.     

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.     

Resolution-enhanced detection of moving objects embedded within scattering media using time-gated speckle methods

The holographic first-arriving-light method in combination with the speckle differencing method is used to provide resolution-enhanced detection of moving objects embedded in scattering media. Results show that the first-arriving-light technique provides significant resolution improvements over standard speckle differencing.     

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。     

Procedure for increasing the sensitivity of microminiature transducers of source information for systems controlling moving objects

Procedures are considered for creating small and microminiature transducers of source information having a digital output by utilizing modern methods of integrated technology, achievements in the areas of micromechanics, fiber-optic and laser engineering. One promising approach is based on using electromechanical systems of the compensation type operating in a self-oscillating regime. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 22–25, March, 1998.     

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.     

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.     

Discrete reconstruction of real phase objects: a comparison with computer-simulated phase objects

The Gerchberg-Saxton algorithm for iterative phase retrieval is applied in reconstructing an optical wave arriving from a coherently illuminated phase object. Computer simulations show that the algorithm converges to the correct solution when magnitude information for both image and Fourier domains is provided. Phase retrieval from measured intensities in an experimental optical system is compared with the simulations. Charge-coupled-device sensors, in which the output voltage is a nonlinear function of the light intensity, are used to perform measurements of the quasi magnitude information. Because of the accuracy of the measured data, phase retrieval for real simple objects is possible, and schlieren images can be generated on the computer screen.