Scattering media diagnostics with the use of analysis of dynamic speckle: some manifestations of the scattered light pathlength distributions

2002 ◽  
Author(s):  
Maria M. Gonik ◽  
Liana V. Kuznetsova ◽  
Dmitry A. Zimnyakov
Keyword(s):  
Scattered Light ◽  
Scattering Media ◽  
Dynamic Speckle

scholarly journals Measurements of the nonlinear refractive index in scattering media using the Scattered Light Imaging Method - SLIM

2015 ◽  
Vol 23 (15) ◽  
pp. 19512 ◽  
Author(s):  
Kelly C. Jorge ◽  
Hans A. García ◽  
Anderson M. Amaral ◽  
Albert S. Reyna ◽  
Leonardo de S. Menezes ◽  
...  
Keyword(s):  
Refractive Index ◽  
Nonlinear Refractive Index ◽  
Scattered Light ◽  
Imaging Method ◽  
Scattering Media

scholarly journals Optimized Virtual Optical Waveguides Enhance Light Throughput in Scattering Media

2021 ◽  
Author(s):  
Adithya Pediredla ◽  
Matteo Giuseppe Scopelliti ◽  
Srinivasa Narasimhan ◽  
Maysam chamanzar ◽  
Ioannis Gkioulekas
Keyword(s):  
Optical Waveguide ◽  
Optical Waveguides ◽  
Scattered Light ◽  
Mean Free Path ◽  
Scattering Media ◽  
Optical Elements ◽  
Material Parameters ◽  
Throughput Enhancement ◽  
Light Confinement ◽  
Ultrasound Parameters

Abstract Ultrasonically sculpted gradient-index optical waveguides make it possible to non-invasively steer and confine light inside scattering media. This confinement capability has applications in tissue and brain imaging, where virtual optical waveguides can be used on their own or cascaded with physical optical elements. The level of light confinement strongly depends on ultrasound parameters such as modulation pattern, frequency, and amplitude, as well as the material parameters of the scattering medium such as the refractive index, scattering coefficient, and phase function. We provide a characterization of these dependencies for a radially symmetric virtual optical waveguide. To this end, we develop a physically-accurate simulator, and use it to quantify how different ultrasound and material parameters affect light confinement. We explain our observations through a qualitative analysis of the behavior of multiply scattered light. We use the results of this analysis to demonstrate that, by properly designing ultrasound parameters, we can achieve a fourfold improvement in light confinement compared to previous virtual optical waveguide designs. We additionally show that virtual optical waveguides can achieve up to 50% light throughput enhancement compared to an ideal external lens, in a medium that mimics the scattering properties of human bladder, and at an optical thickness of one transport mean free path. Lastly, we show experimental results that corroborate the simulation predictions. In particular, we demonstrate for the first time that virtual optical waveguides effectively recycle scattered light in turbid media, and can achieve a 15% light throughput enhancement at five transport mean free paths.

Subsurface Probing in Diffusely Scattering Media Using Spatially Offset Raman Spectroscopy

2005 ◽  
Vol 59 (4) ◽  
pp. 393-400 ◽  
Author(s):  
P. Matousek ◽  
I. P. Clark ◽  
E. R. C. Draper ◽  
M. D. Morris ◽  
A. E. Goodship ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Scattered Light ◽  
Disease Diagnosis ◽  
Scattering Media ◽  
Data Set ◽  
Trans Stilbene ◽  
Potential Applications ◽  
Subsurface Layers ◽  
Excitation Laser ◽  
The Individual

We describe a simple methodology for the effective retrieval of Raman spectra of subsurface layers in diffusely scattering media. The technique is based on the collection of Raman scattered light from surface regions that are laterally offset away from the excitation laser spot on the sample. The Raman spectra obtained in this way exhibit a variation in relative spectral intensities of the surface and subsurface layers of the sample being investigated. The data set is processed using a multivariate data analysis to yield pure Raman spectra of the individual sample layers, providing a method for the effective elimination of surface Raman scatter. The methodology is applicable to the retrieval of pure Raman spectra from depths well in excess of those accessible with conventional confocal microscopy. In this first feasibility study we have differentiated between surface and subsurface Raman signals within a diffusely scattering sample composed of two layers: trans-stilbene powder beneath a 1 mm thick over-layer of PMMA (poly(methyl methacrylate)) powder. The improvement in contrast of the subsurface trans-stilbene layer without numerical processing was 19 times. The potential applications include biomedical subsurface probing of specific tissues through different overlying tissues such as assessment of bone quality through skin, providing an effective noninvasive means of screening for bone degeneration, other skeletal disease diagnosis, and dermatology studies, as well as materials and catalyst research.

scholarly journals Experimental and numerical analysis of ballistic and scattered light using femtosecond optical Kerr gating: a way for the characterization of strongly scattering media

2012 ◽  
Vol 20 (9) ◽  
pp. 9604 ◽  
Author(s):  
François-Xavier d’Abzac ◽  
Myriam Kervella ◽  
Laurent Hespel ◽  
Thibault Dartigalongue
Keyword(s):  
Numerical Analysis ◽  
Scattered Light ◽  
Scattering Media

scholarly journals Light Scattering in a Turbulent Cloud: Simulations to Explore Cloud-Chamber Experiments

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 837
Author(s):  
Corey D. Packard ◽  
Michael L. Larsen ◽  
Subin Thomas ◽  
Will H. Cantrell ◽  
Raymond A. Shaw
Keyword(s):  
Standard Deviation ◽  
Radiative Transfer ◽  
Turbulent Mixing ◽  
Light Propagation ◽  
Scattered Light ◽  
Cloud Droplet ◽  
Separation Distance ◽  
Cloud Chamber ◽  
Scattering Media ◽  
Exponential Behavior

Radiative transfer through clouds can be impacted by variations in particle number size distribution, but also in particle spatial distribution. Due to turbulent mixing and inertial effects, spatial correlations often exist, even on scales reaching the cloud droplet separation distance. The resulting clusters and voids within the droplet field can lead to deviations from exponential extinction. Prior work has numerically investigated these departures from exponential attenuation in absorptive and scattering media; this work takes a step towards determining the feasibility of detecting departures from exponential behavior due to spatial correlation in turbulent clouds generated in a laboratory setting. Large Eddy Simulation (LES) is used to mimic turbulent mixing clouds generated in a laboratory convection cloud chamber. Light propagation through the resulting polydisperse and spatially correlated particle fields is explored via Monte Carlo ray tracing simulations. The key finding is that both mean radiative flux and standard deviation about the mean differ when correlations exist, suggesting that an experiment using a laboratory convection cloud chamber could be designed to investigate non-exponential behavior. Total forward flux is largely unchanged (due to scattering being highly forward-dominant for the size parameters considered), allowing it to be used for conditional sampling based on optical thickness. Direct and diffuse forward flux means are modified by approximately one standard deviation. Standard deviations of diffuse forward and backward fluxes are strongly enhanced, suggesting that fluctuations in the scattered light are a more sensitive metric to consider. The results also suggest the possibility that measurements of radiative transfer could be used to infer the strength and scales of correlations in a turbulent cloud, indicating entrainment and mixing effects.

scholarly journals Time-reversed optical focusing through scattering media by digital full phase and amplitude recovery using a single phase-only SLM

2015 ◽  
Vol 08 (02) ◽  
pp. 1550007 ◽  
Author(s):  
Qiang Yang ◽  
Xinzhu Sang ◽  
Daxiong Xu
Keyword(s):  
Single Phase ◽  
Scattered Light ◽  
Incident Light ◽  
Scattering Media ◽  
Ballistic Regime ◽  
Light Modulator ◽  
Speckle Field ◽  
Biomedical Optical Imaging ◽  
Wavefront Shaping ◽  
Optical Focusing

Focusing light though scattering media beyond the ballistic regime is a challenging task in biomedical optical imaging. This challenge can be overcome by wavefront shaping technique, in which a time-reversed (TR) wavefront of scattered light is generated to suppress the scattering. In previous TR optical focusing experiments, a phase-only spatial light modulator (SLM) has been typically used to control the wavefront of incident light. Unfortunately, although the phase information is reconstructed by the phase-only SLM, the amplitude information is lost, resulting in decreased peak-to-background ratio (PBR) of optical focusing in the TR wavefront reconstruction. A new method of TR optical focusing through scattering media is proposed here, which numerically reconstructs the full phase and amplitude of a simulated scattered light field by using a single phase-only SLM. Simulation results and the proposed optical setup show that the time-reversal of a fully developed speckle field can be digitally implemented with both phase and amplitude recovery, affording a way to improve the performance of light focusing through scattering media.

scholarly journals Wavefront Shaping Concepts for Application in Optical Coherence Tomography—A Review

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7044
Author(s):  
Jonas Kanngiesser ◽  
Bernhard Roth
Keyword(s):  
Optical Coherence Tomography ◽  
Scattered Light ◽  
Three Dimensional ◽  
Medical Diagnostics ◽  
Optical Coherence ◽  
Scattering Media ◽  
Destructive Testing ◽  
Non Invasive ◽  
Wavefront Shaping ◽  
Micrometer Scale

Optical coherence tomography (OCT) enables three-dimensional imaging with resolution on the micrometer scale. The technique relies on the time-of-flight gated detection of light scattered from a sample and has received enormous interest in applications as versatile as non-destructive testing, metrology and non-invasive medical diagnostics. However, in strongly scattering media such as biological tissue, the penetration depth and imaging resolution are limited. Combining OCT imaging with wavefront shaping approaches significantly leverages the capabilities of the technique by controlling the scattered light field through manipulation of the field incident on the sample. This article reviews the main concepts developed so far in the field and discusses the latest results achieved with a focus on signal enhancement and imaging.

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