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.

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 ..

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 ..

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.

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.

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.