KEYWORDS: Receivers, Refraction, Stereoscopy, 3D image processing, Dielectrics, Finite-difference time-domain method, 3D image reconstruction, Optical engineering, 3D modeling, 3D acquisition
This paper describes the use of microwaves to accurately image objects behind dielectric walls. The data are first simulated by using a finite-difference time-domain code. A large model of a room with walls and objects inside is used as a test case. Since the model and associated volume are big compared to wavelengths, the code is run on a parallel supercomputer. A fixed 2-D receiver array captures all the return data simultaneously. A time-domain backprojection algorithm with a correction for the time delay and refraction caused by the front wall then reconstructs high-fidelity 3-D images. A rigorous refraction correction using Snell's law and a simpler but faster linear correction are compared in both 2-D and 3-D. It is shown that imaging in 3-D and viewing an image in the plane parallel to the receiver array is necessary to identify objects by shape. It is also shown that a simple linear correction for the wall is sufficient.
Relativistic electron motion is considered in the axi-symmetric system, and a formalism which can be solved semi-analytically in any magnetic field profile is developed. As a special case, the analyses are applied to nonadiabatic magnetic compression of axis-rotating electron beams. The results, which have a direct application to the cusptron or the peniotron microwave tubes, are compared with the predictions obtained by assuming an adiabatic behavior of electron. Beam parameters such as off-centering, Larmor radius, and velocity are examined for optimum beam-wave interaction.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.