Synthetic Aperture Imaging Algorithm Research Articles

High-Resolution Synthetic Aperture Imaging Algorithm for Terahertz

The reconstruction and recovery of targets in the terahertz band has always been a direction for the improvement of synthetic aperture radar imaging algorithms. In order to improve the imaging resolution of the target, the scattering principle of electromagnetic waves to the target is analyzed. Through model establishment and formula derivation, the propagation process between the electromagnetic wave and the target is obtained, and the simulation and experiment verify that the corresponding algorithm can greatly improve the accuracy of target recovery.

Enhancement synthetic aperture imaging algorithm with azimuth missing data

Enhancement synthetic aperture imaging algorithm with azimuth missing data

Highly Integrated Guidewire Ultrasound Imaging System-on-a-Chip.

In this article, we present a highly integrated guidewire ultrasound (US) imaging system-on-a-chip (GUISoC) for vascular imaging. The SoC consists of a 16-channel US transmitter (Tx) and receiver (Rx) electronics, on-chip power management IC (PMIC), and quadrature sampler. Using a synthetic aperture imaging algorithm, a Tx/Rx pair, connected to capacitive micromachined ultrasound transducers (CMUTs), can be activated at any time. The Tx generates acoustic waves by driving the CMUT, while the Rx picks up the echo signal and amplify it to be delivered through an interconnect that is driven by a buffer. On-chip logic controls the pulsers that generate the high-voltage (HV)-pulse for Tx. An on-chip PMIC provides 1.8-, 5-, 39-, and 44-V supplies and a clock signal from the two interconnects besides GND. A quadrature sampler down-converts the Rx echo signal to baseband, reducing its bandwidth requirement for the output interconnect. The system design, including transimpedance amplifier (TIA) optimization, based on the equivalent circuit of a specific CMUT is presented. The SoC was fabricated by a 0.18-μm HV CMOS process, occupying 1.5-mm2 active area and consuming 25.2 and 44 mW from 1.8 to 44 V supplies, respectively. The US Tx and Rx show bandwidths of 32-42 and 32.7-37.5 MHz, respectively. The input-referred noise of the system was measured as 9.66 nA in band with 2-m-long 52 American Wire Gauge (AWG) wire interconnects. The functionality of the GUISoC was verified in vitro by imaging wire targets.

Feature‐enhanced SAR imaging algorithm based on attributed scatttering centre models for man‐made radar targets

Traditional synthetic aperture (SAR) imaging methods assume that man-made targets are composed of point-based scattering centres. In this way, gaps of components may be resulted, because of neglecting their inherent scattering behaviours. In order to enhance the integrity of components in SAR, a feature-enhanced (FE) imaging method for SAR is proposed, taking into account the inherent behaviours of components of radar targets. Here, the radar echo is decomposed into attributed scattering centres (ASCs) instead of traditional point scattering centres. Based on the decomposed ASCs, different feature enhancement schemes are applied to different kinds of scattering centres according to their attributed parameters. As a result, a FE imaging image for SAR can be achieved by utilising the inherent feature of each decomposed ASCs.

基于相干系数的实时超声内镜合成孔径成像算法

基于相干系数的实时超声内镜合成孔径成像算法

基于前景移除的合成孔径成像算法

基于前景移除的合成孔径成像算法

内镜超声合成孔径成像算法的并行实现

内镜超声合成孔径成像算法的并行实现

High Performance Imaging through Occlusion via Energy Minimization-Based Optimal Camera Selection

Seeing an object in a cluttered scene with severe occlusion is a significantly challenging task for many computer vision applications. Although camera array synthetic aperture imaging has proven to be an effective way for occluded object imaging, its imaging quality is often significantly decreased by the shadows of the foreground occluder. To overcome this problem, some recent research has been presented to label the foreground occluder via object segmentation or 3D reconstruction. However, these methods usually fail in the case of complicated occluder or severe occlusion. In this paper, we present a novel optimal camera selection algorithm to handle the problem above. Firstly, in contrast to the traditional synthetic aperture photography methods, we formulate the occluded object imaging as a problem of visible light ray selection from the optimal camera view. To the best of our knowledge, this is the first time to “mosaic” a high quality occluded object image via selecting multi-view optimal visible light rays from a camera array or a single moving camera. Secondly, a greedy optimization framework is presented to propagate the visibility information among various depth focus planes. Thirdly, a multiple label energy minimization formulation is designed in each plane to select the optimal camera view. The energy is estimated in the 3D synthetic aperture image volume and integrates the multiple view intensity consistency, previous visibility property and camera view smoothness, which is minimized via graph cuts. Finally, we compare this approach with the traditional synthetic aperture imaging algorithms on UCSD light field datasets and our own datasets captured in indoor and outdoor environment, and extensive experimental results demonstrate the effectiveness and superiority of our approach.

An iterative synthetic aperture imaging algorithm with correction of diffraction effects

In this paper we present an iterative version of the synthetic aperture imaging algorithm extended synthetic aperture technique (ESAFT) proposed recently. The algorithm is based on a linear model that accounts for the distortions effects of an imaging system used for acquisition of ultrasonic data. Improved resolution (both lateral and temporal) in the reconstructed image is obtained as a result of minimizing the reconstruction mean square error. In this work, the minimization is extended to parameters that characterize expected amplitudes of each image element in the area of interest. An iterative optimization scheme is proposed, which in each step performs minimization of the reconstruction error based on the parameter matrix found in the previous step. Comparing to ESAFT, the proposed approach yields a significant improvement in resolution and a high degree of robustness with regard to initial choice of the parameter matrix. Performance of the proposed algorithm is evaluated using both real and simulated ultrasonic data.

Efficient three-dimensional imaging from a small cylindrical aperture.

Small-diameter cylindrical imaging platforms, such as those being considered in the development of in vivo ultrasonic microprobes, pose unique image formation challenges. The curved apertures they provide are incompatible with many of the commonly used frequency-domain synthetic aperture imaging algorithms. At the same time, their frequently small diameters place limits on the available aperture and the angular resolution that may be achieved. We obtain a three-dimensional, frequency-domain imaging algorithm for this geometry by making suitable approximations to the point spread function for wave propagation in cylindrical coordinates and obtaining its Fourier transform by analogy with the equivalent problem in Cartesian coordinates. For the most effective use of aperture, we propose using a focused transducer to place a virtual source a short distance from the probe. The focus is treated as a diverging source by the imaging algorithm, which then forms images on deeper cylindrical shells. This approach retains the simplicity and potential angular resolution of a single element, yet permits full use of the available probe aperture and a higher energy output. Computer simulations and experimental results using wire targets show that this imaging technique attains the resolution limit dictated by the operating wavelength and the transducer characteristics.

Unified framework for modern synthetic aperture imaging algorithms

Imaging using synthetic aperture techniques is a mature technique with a host of different reconstruction algorithms available. Often the same basic algorithm has a different name depending on where the particular algorithm is used, since it may have originated from the medical, nondestructive testing, geological, or remote sensing fields. All this adds to confusion for the nonspecialist. This article gives a short historical precise of active synthetic aperture imaging as it applies to airborne, spaceborne, and underwater remote sensing systems using either radar or sonar, then defines some generic imaging geometry and places all the usable synthetic aperture reconstruction algorithms in a unified framework. This is done by the introduction of mapping operators, which simplify the mapping or reformatting of data from one sampling grid to another. Using these operators, readers can see how strip-map synthetic aperture systems (both radar- and sonar-based) differ from spotlight synthetic aperture systems, how the various algorithms fit together, and how the chirp-scaling algorithm is likely to be the reconstruction algorithm of choice for most future strip-map systems, and just why that should be so. Multilook processing and methods to deal with undersampled apertures using postdetection digital spotlighting are put into the same unified framework, as both of these techniques are frequent adjuncts to synthetic aperture imaging. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 343–358, 1997