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Related papers: Backward Propagation

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We present Wideband Back-Projection Diffusion, an end-to-end probabilistic framework for approximating the posterior distribution induced by the inverse scattering map from wideband scattering data. This framework produces highly accurate…

Machine Learning · Computer Science 2025-05-20 Borong Zhang , Martín Guerra , Qin Li , Leonardo Zepeda-Núñez

We consider wave propagation problems in which there is a preferred direction of propagation. To account for propagation in preferred directions, the wave equation is decomposed into a set of coupled equations for waves that propagate in…

Geophysics · Physics 2020-06-09 Kees Wapenaar

We consider the inverse scattering problem for inhomogeneous media of compact support governed by the fractional s-Helmholtz equation, with $0<s<1$, in dimensions $d=1,2,3$. In particular, we study the determination of the support of the…

Analysis of PDEs · Mathematics 2026-04-30 Dana Zilberberg

Conventional methods of wavefront reconstruction from the raw data of the Shack-Hartmann sensor use the focal spot shifts and discard the high-frequency information about the wavefront. Phase-retrieval-based methods treat the Hartmann…

We have investigated the transmission and reflection properties of structures incorporating left-handed materials with graded index of refraction. We present an exact analytical solution to Helmholtz' equation for a graded index profile…

Optics · Physics 2012-03-22 Mariana Dalarsson , Philippe Tassin

An approach to diffraction tomography is investigated for two-dimensional image reconstruction of objects surrounded by an arbitrarily-shaped curve of sources and receivers. Based on the integral theorem of Helmholtz and Kirchhoff, the…

Mathematical Physics · Physics 2014-11-20 G. T. Clement

Nonlinearity parameter tomography leads to the problem of identifying a coefficient in a nonlinear wave equation (such as the Westervelt equation) modeling ultrasound propagation. In this paper we transfer this into frequency domain, where…

Numerical Analysis · Mathematics 2023-03-31 Barbara Kaltenbacher , William Rundell

Scattering hinders the passage of light through random media and consequently limits the usefulness of optical techniques for sensing and imaging. Thus, methods for increasing the transmission of light through such random media are of…

Optics · Physics 2014-06-23 Curtis Jin , Raj Rao Nadakuditi , Eric Michielssen , Stephen Rand

We present a method for the propagation of partially coherent radiation using coherent mode decomposition and wavefront propagation. The radiation field is decomposed into a sum of independent coherent modes. Each mode is then propagated…

Optics · Physics 2015-05-30 Andrej Singer , Ivan A. Vartanyants

Tomography is the three-dimensional reconstruction of an object from images taken at different angles. The term classical tomography is used, when the imaging beam travels in straight lines through the object. This assumption is valid for…

Quantitative Methods · Quantitative Biology 2016-10-10 Paul Müller , Mirjam Schürmann , Jochen Guck

Helmholtz stereopsis is one the versatile techniques for 3D geometry reconstruction from 2D images of objects with unknown and arbitrary reflectance surfaces. HS eliminates the need for surface reflectance, a challenging parameter to…

Image and Video Processing · Electrical Eng. & Systems 2024-07-29 Razieh Azizi , Hamidreza Amindavar , Hassan Aghaeinia

A particular mix of integral equations and discretization techniques is suggested for the solution of a planar Helmholtz transmission problem with relevance to the study of surface plasmon waves. The transmission problem describes the…

Computational Physics · Physics 2018-08-01 Johan Helsing , Anders Karlsson

Solving the wave equation is one of the most (if not the most) fundamental problems we face as we try to illuminate the Earth using recorded seismic data. The Helmholtz equation provides wavefield solutions that are dimensionally reduced,…

Geophysics · Physics 2021-06-04 Tariq Alkhalifah , Chao Song , Umair bin Waheed , Qi Hao

This contribution deals with image restoration in optical systems with coherent illumination, which is an important topic in astronomy, coherent microscopy and radar imaging. Such optical systems suffer from wavefront distortions, which are…

Instrumentation and Methods for Astrophysics · Physics 2017-04-04 Claudius Zelenka , Reinhard Koch

The fundamental problem of optical wave propagation is the determination of the field at an observation point, given a disturbance specified over some finite aperture. In both vacuum and inhomogeneous media, the solution of this problem is…

Analysis of PDEs · Mathematics 2007-05-23 Peng Li

This paper introduces an extension of the backpropagation algorithm that enables us to have layers with constrained weights in a deep network. In particular, we make use of the Riemannian geometry and optimization techniques on matrix…

Computer Vision and Pattern Recognition · Computer Science 2016-11-21 Mehrtash Harandi , Basura Fernando

Plane Wave imaging enables many applications that require high frame rates, including localisation microscopy, shear wave elastography, and ultra-sensitive Doppler. To alleviate the degradation of image quality with respect to conventional…

Signal Processing · Electrical Eng. & Systems 2021-12-24 Nishith Chennakeshava , Ben Luijten , Massimo Mischi , Yonina C. Eldar , Ruud J. G. van Sloun

We analyze multi-bounce propagation of light in an unknown hidden volume and demonstrate that the reflected light contains sufficient information to recover the 3D structure of the hidden scene. We formulate the forward and inverse theory…

In the scalar light model given by Helmholtz' equation in R^{1+d} , we consider the transformation of an initial scene (a hologram) in {0}xR^d by an arbitrary affine transformation (which can be viewed as a propagation into a tilted…

Signal Processing · Electrical Eng. & Systems 2025-06-11 Patrick Gioia , San Vu Ngoc

We present the discovery of a novel and intriguing global geometric structure of the (interior) transmission eigenfunctions associated with the Helmholtz system. It is shown in generic scenarios that there always exists a sequence of…

Analysis of PDEs · Mathematics 2020-12-16 Yat Tin Chow , Youjun Deng , Youzi He , Hongyu Liu , Xianchao Wang
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