共查询到20条相似文献,搜索用时 15 毫秒
1.
Acoustic imaging of objects buried in soil 总被引:4,自引:0,他引:4
Frazier CH Cadalli N Munson DC O'Brien WD 《The Journal of the Acoustical Society of America》2000,108(1):147-156
In this study, we demonstrate an acoustic system for high-resolution imaging of objects buried in soil. Our goal is to image cultural artifacts in order to assess in a rapid manner the historical significance of a potential construction site. We describe the imaging system and present preliminary images produced from data collected from a soil phantom. A mathematical model and associated computer software are developed in order to simulate the signals acquired by the system. We have built the imaging system, which incorporates a single element source transducer and a receiver array. The source and receiver array are moved together along a linear path to collect data. Using this system, we have obtained B-mode images of several targets by using delay-and-sum beamforming, and we have also applied synthetic aperture theory to this problem. 相似文献
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This paper deals with the detection of a buried object beneath a rough surface in a two-dimensional configuration. A new method for detecting buried objects from wide-band, near-field, multi-static data is suggested. The so-called near-field configuration corresponds to a set of transmitters and receivers located along a line segment in the vicinity of the surface. The detection method proposed here is based on a correlation of the scattered fields from two sets of data associated with two transmitters. A theoretical study in the framework of a low-frequency approximation predicts an enhancement of the correlation peak resulting from cross-terms combining surface and target contributions, as confirmed by rigorous computations. The performance of the detector is tested with respect to both polarization and frequency through computation of the receiver operating characteristic curves. 相似文献
3.
S. P. Banerjee Zhijiang Chen I. Utkin R. Fedosejevs 《Applied Physics A: Materials Science & Processing》2013,111(3):791-798
Femtosecond laser micromachining together with Laser Induced Breakdown Spectroscopy (LIBS) allows us to drill precise hole in materials to internal buried layers as well as characterize the materials while drilling. We report detection of a metal layer buried deep inside silicon by creating an access hole through the semiconductor. We used 800 nm femtosecond laser pulses to carry out the drilling while monitoring the plasma emission with a spectrometer system. Higher drilling rates of 1 μm per shot were achieved using a Gaussian laser beam profile with peak fluences of 42 J/cm2. Lower drilling rates of 30 nm per pulse with better accuracy could be achieved using lower intensity flat top beam profiles at fluences of 1.4 J/cm2. 相似文献
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This paper describes two stereo imaging experimental set-ups useful in measuring the 3D geometry of objects: a parallel optical-axis model and a converging optical-axis model. Digital image correlation is used to find the disparities between corresponding points in a pair of images, for each of these models, with subpixel accuracy. To show the application of the developed algorithms and the stereo imaging experimental set-ups, four different body geometries are used. For some of the objects tested a higher measuring accuracy is obtainable from the converging optical-axis experimental set-up. 相似文献
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Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8 THz quantum cascade laser and an uncooled, 160 x 120 pixel microbolometer camera modified with Picarin optics. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was estimated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. Despite the appearance of fringe patterns produced by multiple diffraction effects, single-frame and extended video imaging of obscured objects show high-contrast differentiation between metallic and plastic materials, supporting the viability of this imaging approach for use in future security screening applications. 相似文献
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激光红外主被动复合导引系统 总被引:3,自引:0,他引:3
提出了采用激光主动三维成像技术配合被动红外成像技术共同工作的复合导引体制,用于提升地对地导弹的作战效能及对于隐身目标的识别能力。给出了各分系统的设计方案,并提出了合理的导引策略。该套系统能够兼顾红外大视场搜索及激光小视场三维成像,丰富的目标图像信息更加有利于对作战目标进行准确识别。整套复合光学导引系统结构简单、加工难度适中,在将整套导引系统口径控制在100 mm左右的情况下,同样能够实现4 km以上距离的导引。该项技术的提出对于我国复合导引技术的发展及我军导弹作战能力的提升有着重要意义。 相似文献
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In this paper, a novel method is proposed for spatio-temporal segmentation of moving objects using edge features in infrared videos. We define motion saliency of edge (MSoE) to generate the MSoE-map. The seeds of moving objects are extracted from the MSoE-map by using Otsu's method and subsequently compensated by historical data. An improved layer-based region growing method is applied to the seeds to achieve spatial segmentation of moving objects. The region growing method has an adjustable growing threshold. So, one of the focuses of our work is how to determine the best growing threshold. A Markov Random Field (MRF) based criterion with maximum a posterior (MAP) estimation principle is proposed for performance evaluation of moving object segmentation without ground truth (GT) in infrared videos. This criterion can be considered as an object function of threshold determination during global searching. The global optimum is accomplished by using simulated annealing (SA) algorithm to obtain the best growing threshold. The final segmentation mask of moving objects is grown from the seeds with the best growing threshold. Experimental results are provided to illustrate that the proposed method has better performance for moving object segmentation with fewer effects of object-background misclassification in infrared videos. 相似文献
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On the detection of objects buried at a shallow depth using seismic wave reflections 总被引:1,自引:0,他引:1
Papandreou B Brennan MJ Rustighi E 《The Journal of the Acoustical Society of America》2011,129(3):1366-1374
This paper concerns the detection of shallow (of the order 1 m) buried objects using seismic excitation. Time-extended signals are used to generate a compressional wave using a shaker attached to the ground. The wave propagates through the ground, reflects off a buried object and is captured by an array of geophones on the surface. The envelopes of the cross-correlation functions between the measured ground velocities and the excitation signal are calculated and summed to generate a cross-sectional image of the ground. The wide cross-correlation peaks caused by high ground attenuation are partially compensated for by using the generalized cross-correlation function called the phase transform. Simple simulations are conducted to demonstrate the method, and some field experiments have been carried out aimed at the detection of a buried concrete pipe. In the experiments the pipe could be detected using the method proposed, with experimental and simulated data producing good agreement. 相似文献
10.
We present a major improvement to the Fourier-transform infrared (FTIR) imaging technique brought about by replacement of the commonly used step-scan spectrometer with a rapid-scanning spectrometer. This advancement dramatically decreases the time required for data collection without decreasing the data quality. With this new instrumental setup, an imaging data set consisting of 64x64 spectra with a 4-cm (-1) spectral resolution over a 1360-cm (-1) spectral range can be collected in 34 s. As a practical example, we demonstrate what we believe to be the first application of FTIR imaging to the screening of adsorbates on the elements of a combinatorial library containing different supported catalyst materials in the same reactant feed. 相似文献
11.
《Infrared Physics & Technology》2002,43(3-5):171-174
Due to the drastic increase in the field of product imitation and the request for plagiarism protection, there is a high interest in new protection methods providing new security features. Invisible laser markings within or below paint layers embrace these requirements, as they can be detected and decoded using an IR-reflection technique in conjunction with a focal plane array camera. 相似文献
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Attenborough K Qin Q Jefferis J Heald G 《The Journal of the Acoustical Society of America》2007,122(6):3230-3241
The surface velocity of sand inside a large PVC container, induced by the sound pressure from either a large loudspeaker radiating into an inverted cone and pipe or a Bruel and Kjaer point source loudspeaker mounted with its axis vertical, has been measured using accelerometers. Results of white noise and stepped frequency excitation are presented. Without any buried object the mass loading of an accelerometer creates resonances in the spectral ratio of sand surface velocity to incident acoustic pressure, i.e., the acoustic-to-seismic (A/S) admittance spectra. The A/S responses above a buried compliant object are larger and distinctive. The linear A/S admittance spectra in the presence of a buried electronic components box have been studied as a function of burial depth and sand state. The nonlinear responses above the buried box have been studied as a function of depth, sand state, and amplitude. Predictions of a modified one-dimensional lumped parameter model have been found to be consistent with the observed nonlinear responses. Also the modified model has been used to explain features of the A/S responses observed when using an accelerometer without any buried object. 相似文献
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We have proposed a method to recognize partially occluded three-dimensional (3D) objects by using 3D volumetric reconstruction integral imaging (II). An II system captures multiple perspectives of occluded objects by using a microlens array. The reconstruction of the occluded 3D scene and target recognition are done digitally to reduce the effects of the occlusion. To verify system performance, we have implemented an optimum filter for object recognition. Both two-dimensional (2D) images and 3D II volumetric reconstructed images are considered. The correlation results of occluded 3D images for volumetric reconstruction show substantial improvements compared with those for conventional 2D imaging of occluded images. 相似文献
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采用连续波红外激光对可见光面阵CCD成像系统进行了干扰实验,观察到饱和串扰、全屏饱和等干扰现象,并测到串扰阈值小于2.0×102 W/cm2,全屏饱和阈值为1.2×104 W/cm2。通过分析CCD输出电压、视频信号,提出基于有效干扰面积的干扰效果评估方法,并利用该方法对干扰面积与激光功率密度、辐照时间之间的关系进行了半定量分析。结果显示:激光功率密度对干扰效果的影响较大,而辐照时间在0.5~2.0 s之间时,辐照时间对CCD干扰效果的影响不明显。 相似文献
17.
采用连续波红外激光对可见光面阵CCD成像系统进行了干扰实验,观察到饱和串扰、全屏饱和等干扰现象,并测到串扰阈值小于2.0×102W/cm2,全屏饱和阈值为1.2×104W/cm2。通过分析CCD输出电压、视频信号,提出基于有效干扰面积的干扰效果评估方法,并利用该方法对干扰面积与激光功率密度、辐照时间之间的关系进行了半定量分析。结果显示:激光功率密度对干扰效果的影响较大,而辐照时间在0.5~2.0 s之间时,辐照时间对CCD干扰效果的影响不明显。 相似文献
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Infrared thermography determines the surface temperature of an object or human body. It is a promising imaging technology for medical and biological observations due to its contactless and completely non- invasive properties. However, traditional two-dimensional (2D) infrared thermography cannot retain the spatial information, and thus provides only qualitative diagnosis information. A novel real-time three- dimensional (3D) infrared imaging system which takes full advantages of high-speed, high-quality, high- sensitivity, and low-cost in 3D thermograph is presented. We demonstrate the real-time 3D thermal imaging at the speed of 24 frmnes per second (fps), with resolution of 640 ×480 points. Experimental results demonstrate quantitatively measurement of temperature distribution of 3D surfaces in real-time is realized with this system. 相似文献
19.
J.C. Dainty 《Optics Communications》1973,7(2):129-134
In this paper we suggest that a recent method of stellar interferometry developed by Labeyrie and his colleagues may be used to obtain diffraction-limited resolution from telescopes whose aberrations are poor by conventional standards. 相似文献
20.
B.B. Lahiri M.P. Divya S. Bagavathiappan Sabu Thomas John Philip 《Infrared Physics & Technology》2012,55(6):485-490
Detection of viable bacteria is of prime importance in all fields of microbiology and biotechnology. Conventional methods of enumerating bacteria are often time consuming and labor-intensive. All living organisms generate heat due to metabolic activities and hence, measurement of heat energy is a viable tool for detection and quantification of bacteria. In this article, we employ a non-contact and real time method – infrared thermography (IRT) for measurement of temperature variations in four clinically significant gram negative pathogenic bacteria, viz. Vibrio cholerae, Vibrio mimicus, Proteus mirabilis and Pseudomonas aeruginosa. We observe that, the energy content, defined as the ratio of heat generated by bacterial metabolic activities to the heat lost from the liquid medium to the surrounding, vary linearly with the bacterial concentration in all the four pathogenic bacteria. The amount of energy content observed in different species is attributed to their metabolisms and morphologies that affect the convection velocity and hence heat transport in the medium. 相似文献