Imaging Through a Multiple Scattering Medium

Imaging Through a Multiple Scattering Medium
Author:
Publisher:
Total Pages:
Release: 1984
Genre:
ISBN:

The existing theory of imaging through an aerosol medium, based on the small-angle approximation to radiative transfer, is extended to the general case of multiple scattering with an arbitrary degree of anisotropy. By applying the discrete-ordinates, finite-element radiation transport code TWOTRAN, we compute the modulation transfer function for a medium characterized by optical depth, single scattering albedo, and a symmetry parameter. An extended version of this investigation will appear in a 1984 issue of Applied Optics.

Image Transfer Through a Scattering Medium

Image Transfer Through a Scattering Medium
Author: Eleonora P. Zege
Publisher: Springer
Total Pages: 349
Release: 1991-02-21
Genre: Technology & Engineering
ISBN: 9783540519782

The world around us appears as diverse and beautiful as it does owing to the fact that light is scattered. Scattering plays two roles in the intricate process of image formation. First, it is the means by which we perceive an object. An object which does not scatter light cannot be seen. However, scattering also distorts the image observed. Even in relatively pure air, visibility is limited to a range of a few tens of kilometers owing to aerosol and molecular light scattering. It is reduced to tens of meters in conditions of mist or fog. What occurs when we look at an object through a scattering medium? For example, when a point diffuse source is being observed, the radiation undergoes multiple scattering along the path to the photodetector. Therefore, the image produced by a source of this kind (i.e., the irradiance distribution in the image plane) appears as a more or less blurred speck. What we have said so far serves as an introduction to the concept of image transfer theory, or the point spread function ..

Image Transfer Through a Scattering Medium

Image Transfer Through a Scattering Medium
Author: Eleonora P. Zege
Publisher: Springer
Total Pages: 0
Release: 1991
Genre: Science
ISBN: 9783642752865

The world around us appears as diverse and beautiful as it does owing to the fact that light is scattered. Scattering plays two roles in the intricate process of image formation. First, it is the means by which we perceive an object. An object which does not scatter light cannot be seen. However, scattering also distorts the image observed. Even in relatively pure air, visibility is limited to a range of a few tens of kilometers owing to aerosol and molecular light scattering. It is reduced to tens of meters in conditions of mist or fog. What occurs when we look at an object through a scattering medium? For example, when a point diffuse source is being observed, the radiation undergoes multiple scattering along the path to the photodetector. Therefore, the image produced by a source of this kind (i.e., the irradiance distribution in the image plane) appears as a more or less blurred speck. What we have said so far serves as an introduction to the concept of image transfer theory, or the point spread function ..

Matricial Approaches for Spatio-temporal Control of Light in Multiple Scattering Media

Matricial Approaches for Spatio-temporal Control of Light in Multiple Scattering Media
Author: Mickaël Mounaix
Publisher:
Total Pages: 0
Release: 2017
Genre:
ISBN:

Optical imaging through highly disordered media such as biological tissue or white paint remains a challenge as spatial information gets mixed because of multiple scattering. Nonetheless, spatial light modulators (SLM) offer millions of degrees of freedom to control the spatial speckle pattern at the output of a disordered medium with wavefront shaping techniques. However, if the laser generates a broadband ultrashort pulse, the transmitted signal becomes temporally broadened as the medium responds disparately for the different spectral components of the pulse. We have developed methods to control the spatio-temporal profile of the pulse at the output of a thick scattering medium. By measuring either the Multispectral or the Time- Resolved Transmission Matrix, we can fully describe the propagation of the broadband pulse either in the spectral or temporal domain. With wavefront shaping techniques, one can control both spatial and spectral/temporal degrees of freedom with a single SLM via the spectral diversity of the scattering medium. We have demonstrated deterministic spatio-temporal focusing of an ultrashort pulse of light after the medium, with a temporal compression almost to its initial time-width in different space-time position, as well as different temporal profile such as double pulses. We exploit this spatio-temporal focusing beam to enhance a non-linear process that is two-photon excitation. It opens interesting perspectives in coherent control, light-matter interactions and multiphotonic imaging.

Microscopic Imaging Through Turbid Media

Microscopic Imaging Through Turbid Media
Author: Min Gu
Publisher: Springer
Total Pages: 192
Release: 2015-04-08
Genre: Science
ISBN: 3662463970

This book provides a systematic introduction to the principles of microscopic imaging through tissue-like turbid media in terms of Monte-Carlo simulation. It describes various gating mechanisms based on the physical differences between the un scattered and scattered photons and method for microscopic image reconstruction, using the concept of the effective point spread function. Imaging an object embedded in a turbid medium is a challenging problem in physics as well as in bio photonics. A turbid medium surrounding an object under inspection causes multiple scattering, which degrades the contrast, resolution and signal-to-noise ratio. Biological tissues are typically turbid media. Microscopic imaging through a tissue-like turbid medium can provide higher resolution than transillumination imaging in which no objective is used. This book serves as a valuable reference for engineers and scientists working on microscopy of tissue turbid media.

Imaging Methods of Multiple Scattering in Isotropic Point-like Discrete Random Media

Imaging Methods of Multiple Scattering in Isotropic Point-like Discrete Random Media
Author: Ray-Hon Sun
Publisher:
Total Pages:
Release: 2013
Genre:
ISBN:

During the last decades growing attention has been paid to the effect of propagation of waves in different types of randomly inhomogeneous media. This increasing interest is due, among other factors, to the novel methods that are being proposed for imaging small objects in cluttered environments and the need to have good solvers to correctly model fluctuations effects in these media. This is a major challenge in many research areas such as medical imaging, remote sensing, nondestructive testing and wireless communications, etc. In these applications, distinctly different mathematical models are used for imaging in continuous and discrete random media. The discrete random media are used to describe multiple scattering in continuous random media but it is unlikely that discrete inclusions are always adequate to represent inhomogeneities that have no clear boundaries between their different components. In imaging problems the emitted waves may be scattered multiple times by one or many inhomogeneities of the medium. Hence, the recorded waves include information about the medium through which they have propagated. The framework originally developed by Foldy, Lax, Twersky, and Keller together with the Lippmann-Schwinger equation is employed for the multiply scattered waves, in the frequency domain, in the case of an ensemble of randomly distributed point-like scatterers. The Foldy-Lax-Lippmann-Schwinger formalism is an exact method when scatterers are far from each other, and the scattering properties from a single isolated scatterer are known and easy to compute from the solution of a linear system. Thus, a very complicated scattering with multiples of all orders can be described in terms of a succession of interactions among multiply scattered waves in the cluttered media. Resonance is one of the most striking phenomena in multiple scattering. In a two-body system experiment, I show that resonances lead to sharp peaks in the spectrum as a function of energy when the scattering amplitudes of scatterers are not weak. The effects of resonances provide useful information about the image distortion arising from the underlying interactions of multiply scattered waves at resonance frequencies. I approach the problem of image distortion in randomly distributed point media by either removing the frequencies above the cutoff ratio or pruning the signals whose strength exceeds the threshold of permitted strength. The former is called the spectral cutoff method and the latter is the prune-and-average method. It should be emphasized that the scattering matrix of the Foldy-Lax-Lippmann-Schwinger formalism is a non-Hermitian Euclidean random matrix. Our heuristic formulation for the eigenvalue distribution of the scattering matrix can be expected to provide useful information about the choice of the cutoff parameter of the spectral-cutoff method. I apply the Foldy-Lax-Lippmann-Schwinger formulation to the correlation-based imaging in discrete random media. This approach seems relevant to seismology, nondestructive testing, structural health monitoring, and wireless sensor networks. I then use numerical simulation for different configurations to explore the limitations of this methodology.

Waves and Imaging through Complex Media

Waves and Imaging through Complex Media
Author: P. Sebbah
Publisher: Springer Science & Business Media
Total Pages: 452
Release: 2012-12-06
Genre: Science
ISBN: 9401009759

Recent advances in wave propagation in random media are certainly consequences of new approaches to fundamental issues, as well as of a strong interest in potential applications. A collective effort has been made to present in this book the state of the art in fundamental concepts, as well as in biomedical imaging techniques. As an example, the recent introduction of wave chaos, and more specifically random matrix theory - an old tool from nuclear physics - to the study of multiple scattering, has pointed the way to a deeper understanding of wave coherence in complex media. At the same time, efficient new approaches for retrieving information from random media promise to allow wave imaging of small tumors in opaque tissues. Review chapters are written by experts in the field, with the aim of making the book accessible to the widest possible scientific audience: graduate students and research scientists in theoretical and applied physics, optics, acoustics, and biomedical physics.

Optical Imaging Through Turbid Media with a Degenerate Four-wave Mixing Correlation Time Gate

Optical Imaging Through Turbid Media with a Degenerate Four-wave Mixing Correlation Time Gate
Author:
Publisher:
Total Pages:
Release: 1998
Genre:
ISBN:

Optical imaging through turbid media is demonstrated using a degenerate four-wave mixing correlation time gate. An apparatus and method for detecting ballistic and/or snake light while rejecting unwanted diffusive light for imaging structures within highly scattering media are described. Degenerate four-wave mixing (DFWM) of a doubled YAG laser in rhodamine 590 is used to provide an ultrafast correlation time gate to discriminate against light that has undergone multiple scattering and therefore has lost memory of the structures within the scattering medium. Images have been obtained of a test cross-hair pattern through highly turbid suspensions of whole milk in water that are opaque to the naked eye, which demonstrates the utility of DFWM for imaging through turbid media. Use of DFWM as an ultrafast time gate for the detection of ballistic and/or snake light in optical mammography is discussed.