- 标题
- 摘要
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- 实验方案
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[IEEE 2018 China International SAR Symposium (CISS) - Shanghai (2018.10.10-2018.10.12)] 2018 China International SAR Symposium (CISS) - Two Dimensional Image Formation of Interrupted FMCW SAR Through Spectral Analysis
摘要： Most of spaceborne Synthetic Aperture Radar (SAR) systems are based on pulsed mode of operation. Such systems are quite expensive and large sized. Frequency Modulated Continuous Wave (FMCW) based SAR is a light weight and less expensive solution, but the disadvantage is that it requires two antennas – one for transmit and other for receive. Interrupted-FMCW is a recently proposed idea for spaceborne SAR that uses a single antenna for transmission and reception. The main problem of this approach is discontinuity of data in azimuth. This paper proposes a two-dimensional image formation algorithm that uses spectral analysis methods for processing of interrupted-FMCW SAR data. The algorithm has been tested on simulated point target data as well as on a real FMCW data, and the results have been discussed.
关键词： spectral analysis,synthetic aperture radar,interrupted-FMCW,all-pole model,image formation
更新于2025-09-23 15:22:29
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A Beginners' Guide to Scanning Electron Microscopy || Imaging with the SEM
摘要： The scanning electron microscope is routinely used to characterize wide-ranging materials due to its ease of operation and relatively straightforward sample preparation as well as due to simple image interpretation. New users can readily obtain images after little practice. However, high-resolution microscopy and examination of “difficult” samples require experience and know-how of the principles of image formation in the SEM. This chapter describes the role of various operational parameters used during microscopy in more detail. The effect of these parameters on contrast, resolution, and depth of field depicted by images is discussed. Pros and cons of microscopy conditions that have a direct bearing on the quality of images, type of information obtained, and image interpretation are elaborated. Guidelines for operation and upkeep of the SEM instrument are also summarized in this chapter.
关键词： high-resolution microscopy,operational parameters,resolution,scanning electron microscope,SEM,image formation,contrast,microscopy conditions,image interpretation,depth of field
更新于2025-09-23 15:19:57
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Photometric Long-Range Positioning of LED Targets for Cooperative Navigation in UAVs
摘要： Autonomous ?ight with unmanned aerial vehicles (UAVs) nowadays depends on the availability and reliability of Global Navigation Satellites Systems (GNSS). In cluttered outdoor scenarios, such as narrow gorges, or near tall arti?cial structures, such as bridges or dams, reduced sky visibility and multipath effects compromise the quality and the trustworthiness of the GNSS position ?xes, making autonomous, or even manual, ?ight dif?cult and dangerous. To overcome this problem, cooperative navigation has been proposed: a second UAV ?ies away from any occluding objects and in line of sight from the ?rst and provides the latter with positioning information, removing the need for full and reliable GNSS coverage in the area of interest. In this work we use high-power light-emitting diodes (LEDs) to signalize the second drone and we present a computer vision pipeline that allows to track the second drone in real-time from a distance up to 100 m and to compute its relative position with decimeter accuracy. This is based on an extension to the classical iterative algorithm for the Perspective-n-Points problem in which the photometric error is minimized according to a image formation model. This extension allow to substantially increase the accuracy of point-feature measurements in image space (up to 0.05 pixels), which directly translates into higher positioning accuracy with respect to conventional methods.
关键词： image formation model,relative positioning,cooperative navigation,PnP,photometric error
更新于2025-09-11 14:15:04
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[IEEE ICASSP 2018 - 2018 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) - Calgary, AB (2018.4.15-2018.4.20)] 2018 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) - High-Speed Light Field Image Formation Analysis Using Wavefield Modeling with Flexible Sampling
摘要： Understanding the image formation inside plenoptic cameras is significant for the investigations of improving the low spatial resolution. Most researches explore the image formation from the perspective of geometric optics. However, as the hardware components in combination with low-aperture optical systems become smaller and smaller, geometric analysis will no longer be valid due to diffraction effects. In this paper, a wave-optic-based model is proposed that uses the Fresnel diffraction equation to propagate the whole object field into the plenoptic systems. The proposed model employs averaging of intensities on the sensor from uncorrelated coherent wave to avoid interference during propagations among the optical component planes. Besides, by utilizing the method of multiple partial propagations, the proposed model is much flexible at sampling on propagation planes. In order to verify the effectiveness of the proposed model, numerical simulations are conducted by comparing with existing wave optic model under different optical configurations of plenoptic cameras. Results demonstrate that the proposed model can describe the light field image formation properly. In addition, the time for image formation has been reduced by a factor of 19.22 using the proposed model.
关键词： Plenoptic cameras,multiple partial propagations,image formation,Fresnel diffraction equation,wave optics
更新于2025-09-09 09:28:46
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Monte Carlo Method in Scanning Electron Microscopy. 3. Modern Condition of the Problem
摘要： The applicability of the Monte Carlo method for modeling images obtained in a scanning electron microscope is assessed. It is shown that in the Monte Carlo method, it is impossible to take into account all the mechanisms of the interaction of electrons with matter that affect image formation. Modern random-number generators create an insufficient amount of random numbers necessary for modeling the scattering of electrons in matter. The time it takes to modeling images using contemporary personal computers is too long: it takes years of continuous computer operation. There is no evidence of correctness of the results of the Monte Carlo method when generating images. These factors prove the impossibility of using the Monte Carlo method to modeling the scattering of electrons in a solid, which is used in image formation in a scanning electron microscope.
关键词： modeling of electron trajectories,Monte Carlo method,scanning electron microscope,SEM,image formation,statistical modeling,virtual scanning electron microscope,random numbers
更新于2025-09-04 15:30:14