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SAR Tomography (TomoSAR) regards multi-baseline observation data as array observation data and realizes three-dimensional imaging by applying direction of arrival (DOA) estimation processing. To improve angular resolution of the TomoSAR with suppressing ambiguity, many repeat-pass data are required. However, it is often difficult to increase the number of data because of the cost. In this paper, we...
Sequent data acquisition and imaging in traditional active millimeter-wave imaging system in market results in serious time delay, cost, and system complexity. A point-by-point imaging approach is proposed in this paper to address the issue. Imaging starts shortly after data acquisition begins and virtually simultaneously with data acquisition. Partially known image and new data are used to image...
An active millimeter wave imaging system with sparse antenna array for security inspection is introduced in this review. Several key parts and related techniques of the imaging system are explained and numerical results are provided.
Terahertz (THz) radar has developed a lot in recent years. Its ability for near field security inspection becomes a popular research topic. However, the phase errors caused by THz radar's motion are difficult to compensate due to the submillimeter wavelength, which means a tiny motion error will bring a huge phase deviation. In this paper, we report a crossed array radar imaging method, which employs...
This paper presents our study on a sparse antenna array for 0.22 THz imaging. Based on the effective aperture concept for the design of sparse antenna array, two schemes for high performance THz imaging of a target at distance of 1 m have been achieved in simulation. Then, different schemes of larger array element spacing and mechanical scanning spacing have been investigated to build the relationship...
Fast cardiac imaging using diverging waves (DW) is receiving much attention. Coherent compounding is important to keep spatial resolution and CNR acceptable. Two approaches have been presented in literature to do so: i) the full aperture of the probe is used and the virtual focus is moved along an arc centered at the center of the probe (ARC); ii) a sub-aperture is used and the virtual focus is linearly...
As the medical ultrasound signals are not stationary, the radiation pattern of the corresponding input data does not have a specific shape. Thus, their reconstruction using adaptive beamformer (BF) become indispensable in order to improve the quality of the image. Generalized Side Lobe Canceller (GSC) is a robust realization against clutter and interference, resulting from an elegant representation...
As medical ultrasound (MU) signals are not stationary, the radiation pattern of the corresponding input data does not have a specific shape; thus, their reconstruction using Adaptive Beamformers (BF) becomes indispensable in order to improve the quality of the imaging system. Generalized Sidelobe Canceller (GSC) is a robust realization against clutter and interference, resulting from an elegant representation...
The aim of this study is to compare the performance of different multiple-input multiple-output (MIMO) array topologies, intended to be used in ultra-wideband (UWB) near-field imaging applications, by using an analysis method that does not include the effects of image reconstruction algorithm. For this purpose, maximum projection method, previously proposed for the analysis of UWB arrays under far-field...
PET scanner quality check control is performed on a daily basis. In Siemens scanners, for example, data are acquired from a uniform cylinder and the estimation of a crystal efficiencies (CE) normalization component is carried out. Besides producing a normalization array, the CE analysis provides information about whether or not additional calibration should be performed. In previous work we demonstrated...
The performance of the recently proposed axial-null illumination scheme for microwave imaging has been experimentally investigated in comparison with the conventional axial-peak illumination. The axial-null scheme is implemented as an array of four simultaneously transmitting X-band waveguides physically oriented to produce zero field along the array axis. Two independent direct inversion algorithms...
We apply the L1 norm approaches on sparsely acquired data of the array ground penetrating radar (GPR) system YAKUMO. Due to the limitation of the antenna size of YAKUMO system, the antenna offsets between each element are much larger than the wavelength. Such sparsely acquired data may introduce strong artifacts to the imaging results such as synthetic aperture radar (SAR) processing and the velocity...
In this paper, the computational spectral imaging system is reexamined, and the most time-consuming module, namely the two-step iterative shrinkage/thresholding (TwIST) reconstruction, is accelerated by GPU. The acceleration can be roughly divided into two level: 1) data parallelization and 2)operation parallelization. Data parallelization: by discovering that the observation data array in computational...
The advent of efficient short range radio communication coupled with advancement in miniaturization of computing devices has enabled the development of wireless multimedia sensor network (WMSN). Energy is one of the scarcest resources in such networks, especially it is scarce in transmitting multimedia data. This work presents an energy-saving image compression scheme. The nodes in WMSN are equipped...
This paper deals with a novel approach to determine the far field of a discrete source starting from the knowledge of far-field intensity data sets only. In particular, by taking advantage from a body of knowledge from antenna synthesis, as well as from the exploitation of suitable norms, we are able to formulate the problem as the superposition of (many) convex problems. Such a circumstance allows...
Camera arrays have been used to reconstruct occluded scene planes in the recent literature. In this paper we propose a new approach to solve this task. First, by finding the local minima of the absolute difference between every pair of the input images, the images captured with a camera array are aligned according to the target plane (the plane which is occluded and needs to be reconstructed). Then,...
In cone-beam computed tomography (CBCT) applications, one may be interested in detailed information only within a region of interest (ROI), while rough knowledge outside the ROI may be sufficient. Therefore, it is of practical value to develop algorithms that are capable of reconstructing an image with variable resolution: an image consisting of highresolution voxels within the ROI and low-resolution...
The Laue diffraction microscopy experiment uses the polychromatic Laue micro-diffraction technique to examine the structure of materials with sub-micron spatial resolution in all three dimensions. During this experiment, local crystallographic orientations, orientation gradients and strains are measured as properties which will be recorded in HDF5 image format. The recorded images will be processed...
A compressed sensing based approach is proposed in order to diagnose reflectarrays from far field measurements. The technique requires the preliminary measurement of the failure-free reflectarray. With this a priori knowledge, only the faulty elements have to be retrieved which leads to a significant reduction of required measurement data compared to conventional approaches. The proposed approach...
A method to reconstruct the excitation coefficients of wide-slot arrays from near-field data is presented. The plane wave spectrum (PWS) is used for reconstruction, and the shape of the field distribution on a wide slot is considered in the calculation of the PWS. The proposed algorithm is validated through the reconstruction of the excitation coefficients of a wide-slot array with element failures...
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