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      Improvements and validation of spatiotemporal speckle correlation model for rolling shutter speckle imaging

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      , , , *
      Biomedical Optics Express
      Optica Publishing Group

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          Abstract

          Rolling shutter speckle imaging (RSSI) is a single-shot imaging technique that directly measures the temporal dynamics of the scattering media using a low-cost rolling shutter image sensor and vertically elongated speckles. In this paper, we derive and validate a complete spatiotemporal intensity correlation (STIC) model for RSSI, which describes the row-by-row correlation of the dynamic speckles measured with a rolling shutter in the presence of static scattering. Our new model accounts for the finite exposure time of the detector, which can be longer than the sampling interval in RSSI. We derive a comprehensive model that works for all correlation times of rolling shutter measurements. As a result, we can correctly utilize all data points in RSSI, which improves the measurement accuracy and ranges of speckle decorrelation time and dynamic scattering fraction, as demonstrated by phantom experiments. With simulations and experiments, we provide an understanding of the design parameters of RSSI and the measurement range of the speckle dynamics.

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          Most cited references27

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          Laser speckle contrast imaging in biomedical optics.

          First introduced in the 1980s, laser speckle contrast imaging is a powerful tool for full-field imaging of blood flow. Recently laser speckle contrast imaging has gained increased attention, in part due to its rapid adoption for blood flow studies in the brain. We review the underlying physics of speckle contrast imaging and discuss recent developments to improve the quantitative accuracy of blood flow measures. We also review applications of laser speckle contrast imaging in neuroscience, dermatology and ophthalmology.
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            Laser speckle contrast imaging: theoretical and practical limitations.

            When laser light illuminates a diffuse object, it produces a random interference effect known as a speckle pattern. If there is movement in the object, the speckles fluctuate in intensity. These fluctuations can provide information about the movement. A simple way of accessing this information is to image the speckle pattern with an exposure time longer than the shortest speckle fluctuation time scale-the fluctuations cause a blurring of the speckle, leading to a reduction in the local speckle contrast. Thus, velocity distributions are coded as speckle contrast variations. The same information can be obtained by using the Doppler effect, but producing a two-dimensional Doppler map requires either scanning of the laser beam or imaging with a high-speed camera: laser speckle contrast imaging (LSCI) avoids the need to scan and can be performed with a normal CCD- or CMOS-camera. LSCI is used primarily to map flow systems, especially blood flow. The development of LSCI is reviewed and its limitations and problems are investigated.
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              Optical properties of human skin.

              A survey of the literature is presented that provides an analysis of the optical properties of human skin, with particular regard to their applications in medicine. Included is a description of the primary interactions of light with skin and how these are commonly estimated using radiative transfer theory (RTT). This is followed by analysis of measured RTT coefficients available in the literature. Orders of magnitude differences are found within published absorption and reduced-scattering coefficients. Causes for these discrepancies are discussed in detail, including contrasts between data acquired in vitro and in vivo. An analysis of the phase functions applied in skin optics, along with the remaining optical coefficients (anisotropy factors and refractive indices) is also included. The survey concludes that further work in the field is necessary to establish a definitive range of realistic coefficients for clinically normal skin.
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                Author and article information

                Journal
                Biomed Opt Express
                Biomed Opt Express
                BOE
                Biomedical Optics Express
                Optica Publishing Group
                2156-7085
                30 January 2024
                01 February 2024
                : 15
                : 2
                : 1253-1267
                Affiliations
                [1]School of Electrical and Electronic Engineering, Yonsei University , 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
                Author notes
                Author information
                https://orcid.org/0000-0001-8427-3791
                https://orcid.org/0000-0002-7238-2314
                https://orcid.org/0000-0001-5173-1565
                Article
                514497
                10.1364/BOE.514497
                10890878
                38404314
                5e69a33c-f79e-4921-b66c-1c5914b71355
                © 2024 Optica Publishing Group

                https://doi.org/10.1364/OA_License_v2#VOR-OA

                © 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

                History
                : 29 November 2023
                : 19 January 2024
                : 19 January 2024
                Funding
                Funded by: National Research Foundation of Korea 10.13039/501100003725
                Award ID: 2021R1C1C101290013
                Award ID: 2022R1A4A200074812
                Funded by: Commercializations Promotion Agency for R and D Outcomes 10.13039/501100023443
                Award ID: 1711198540
                Categories
                Article

                Vision sciences
                Vision sciences

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