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      Alternative Interpretation of Speckle Autocorrelation Imaging Through Scattering Media

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          Abstract

          High-resolution optical imaging through or within thick scattering media is a long sought after yet unreached goal. In the past decade, the thriving technique developments in wavefront measurement and manipulation do not significantly push the boundary forward. The optical diffusion limit is still a ceiling. In this work, we propose that a scattering medium can be conceptualized as an assembly of randomly packed pinhole cameras and the corresponding speckle pattern as a superposition of randomly shifted pinhole images. The concept is demonstrated through both simulation and experiments, confirming the new perspective to interpret the mechanism of information transmission through scattering media under incoherent illumination. We also analyze the efficiency of single-pinhole and dual-pinhole channels. While in infancy, the proposed method reveals a new perspective to understand imaging and information transmission through scattering media.

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          Most cited references43

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          Ultrastructural Characterization of the Lower Motor System in a Mouse Model of Krabbe Disease

          Krabbe disease (KD) is a neurodegenerative disorder caused by the lack of β- galactosylceramidase enzymatic activity and by widespread accumulation of the cytotoxic galactosyl-sphingosine in neuronal, myelinating and endothelial cells. Despite the wide use of Twitcher mice as experimental model for KD, the ultrastructure of this model is partial and mainly addressing peripheral nerves. More details are requested to elucidate the basis of the motor defects, which are the first to appear during KD onset. Here we use transmission electron microscopy (TEM) to focus on the alterations produced by KD in the lower motor system at postnatal day 15 (P15), a nearly asymptomatic stage, and in the juvenile P30 mouse. We find mild effects on motorneuron soma, severe ones on sciatic nerves and very severe effects on nerve terminals and neuromuscular junctions at P30, with peripheral damage being already detectable at P15. Finally, we find that the gastrocnemius muscle undergoes atrophy and structural changes that are independent of denervation at P15. Our data further characterize the ultrastructural analysis of the KD mouse model, and support recent theories of a dying-back mechanism for neuronal degeneration, which is independent of demyelination.
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            Photoacoustic tomography: in vivo imaging from organelles to organs.

            Photoacoustic tomography (PAT) can create multiscale multicontrast images of living biological structures ranging from organelles to organs. This emerging technology overcomes the high degree of scattering of optical photons in biological tissue by making use of the photoacoustic effect. Light absorption by molecules creates a thermally induced pressure jump that launches ultrasonic waves, which are received by acoustic detectors to form images. Different implementations of PAT allow the spatial resolution to be scaled with the desired imaging depth in tissue while a high depth-to-resolution ratio is maintained. As a rule of thumb, the achievable spatial resolution is on the order of 1/200 of the desired imaging depth, which can reach up to 7 centimeters. PAT provides anatomical, functional, metabolic, molecular, and genetic contrasts of vasculature, hemodynamics, oxygen metabolism, biomarkers, and gene expression. We review the state of the art of PAT for both biological and clinical studies and discuss future prospects.
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              Phase retrieval algorithms: a comparison

              J Fienup (1982)
              Iterative algorithms for phase retrieval from intensity data are compared to gradient search methods. Both the problem of phase retrieval from two intensity measurements (in electron microscopy or wave front sensing) and the problem of phase retrieval from a single intensity measurement plus a non-negativity constraint (in astronomy) are considered, with emphasis on the latter. It is shown that both the error-reduction algorithm for the problem of a single intensity measurement and the Gerchberg-Saxton algorithm for the problem of two intensity measurements converge. The error-reduction algorithm is also shown to be closely related to the steepest-descent method. Other algorithms, including the input-output algorithm and the conjugate-gradient method, are shown to converge in practice much faster than the error-reduction algorithm. Examples are shown.
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                Author and article information

                Journal
                Photonic Sensors
                Photonic Sens
                Springer Science and Business Media LLC
                1674-9251
                2190-7439
                September 2022
                March 17 2022
                September 2022
                : 12
                : 3
                Article
                10.1007/s13320-022-0654-9
                83a4ed06-d199-479d-b02b-9587a1a1d57f
                © 2022

                https://creativecommons.org/licenses/by/4.0

                https://creativecommons.org/licenses/by/4.0

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