نتایج جستجو برای: aperture

تعداد نتایج: 28240  

Journal: :Applied optics 2004
Arnaud Dubois

We show by analytical and numerical calculations that the phase change on reflection that occurs in interference microscopy is almost independent of the numerical aperture of the objective. The shift of the microscope interferogram response due to the phase change on reflection, however, increases with the numerical aperture. Measurements of the interferogram shift are made with a Linnik interf...

1995
Amr M. Shaarawi Ioannis M. Besieris Richard W. Ziolkowski Sherif M. Sedky

It is demonstrated that an approximation to the focus-wave-mode field can be generated from a dynamic Gaussian aperture. A source of this type is characterized by the time variation of its effective radius. The performance of such an aperture is studied in detail; it is demonstrated that the dynamic aperture shows a great enhancement over the corresponding static one. The types of source invest...

2017
Michael K O'Connor Thuy D Tran Tiffinee N Swanson Lacey R Ellingson Katie N Hunt Dana H Whaley

BACKGROUND Breast lesions closer than 2 cm to the chest wall are difficult to position in the field of view of dedicated breast PET (db-PET) systems. This inability to detect such lesions is a significant limitation of these systems. The primary objective of this study was to determine if modifications to the design of the imaging table and detector used for a db-PET system would enable improve...

2001
LARS M. H. ULANDER

Synthetic aperture radar (SAR) is a general method for generating high-resolution radar maps from low-resolution aperture data which is based on using the relative motion between the radar antenna and the imaged scene. Originally conceived in the early 1950s [1], it is extensively used to image objects on the surface of the Earth and the planets [2]. A synthetic aperture is formed using electro...

2012
Jian Dong Qingxia Li

During the past few decades, there has been growing interest in the use of microwave and millimeter wave radiometers for remote sensing of the Earth. Due to the need of large antennas and scanning mechanism, the conventional real aperture radiometer becomes infeasible for high spatial resolution application. Interferometric aperture synthesis was suggested as an alternative to real aperture rad...

Journal: :رادار 0
حامد گروسی بیژن ذاکری سید مهدی حسینی اندارگلی

study on polsar target detection essentially requires the cattering information and polarimetric statistical data. theoretical analysis shows that some terms of the second order scattering matrices such as coherence and covariance matrix clearly show the differences between nonsymmetrical man-made objects and natural clatters which being reflection symmetric. using the model derived from these ...

Journal: :SIAM J. Scientific Computing 2008
Aaron Luttman Johnathan M. Bardsley

In this erratum, we correct the previous explanation of the data-collection procedure as outlined in [SIAM J. Sci. Comput., 29 (2007), pp. 1550–1566]. DOI. 10.1137/070700036 In [1], the authors incorrectly described the data-collection procedure for capturing the botanical fluorescence data. • In the abstract, the sentence “In order to visualize a particular leaf’s stomatal aperture, an experim...

Journal: :EURASIP J. Adv. Sig. Proc. 2006
Marco Martorella John Homer James Palmer Victor Chen Fabrizio Berizzi Brad Littleton Ian Dennis Longstaff

1The school of ITEF, The University of Queensland, Brisbane 4072, Australia 2Department of Information Engineering, University of Pisa, Via G. Caruso 16, 56122 Pisa, Italy 3 School of Information Technology & Electrical Engineering, University of Queensland, Brisbane 4072, Australia 4Radar Modelling & Analysis Group, Electronic Warfare & Radar Division, Defence Science & Technology Organisation...

2011
D. J. Rabideau Shakti Davis Daniel Bliss Keith Forsythe Paul Monticciolo Pamela Evans Shawn Kraut Larry Horowitz Joshua Kantor

In a multiple-input, multiple-output (MIMO) radar system, two or more transmitters emit independent waveforms, with the resulting reflections received by an array of receivers. Recently, MIMO radar has become a subject of great interest. In part, this interest is due to the potential for MIMO techniques to reduce radar weight and cost, while maintaining performance (as compared with conventiona...

1998
Richard Bamler Philipp Hartl

Synthetic aperture radar (SAR) is a coherent active microwave imaging method. In remote sensing it is used for mapping the scattering properties of the Earth’s surface in the respective wavelength domain. Many physical and geometric parameters of the imaged scene contribute to the grey value of a SAR image pixel. Scene inversion suffers from this high ambiguity and requires SAR data taken at di...

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