Calibration of the LISST-VSF to derive the volume scattering functions in clear waters

Hu, Lianbo; Zhang, Xiaodong; Xiong, Yuanheng; He, Ming-Xia

doi:10.1364/oe.27.0a1188

Cited by 16 publications

(11 citation statements)

References 51 publications

(76 reference statements)

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“…The LISST VSF meter is a submersible multi-angle polarized light scattering meter and consists of 32 ring detectors and a rotating eye ball. The ring detectors are used to sense light scattered by bubbles in the near-forward angles (0.094-15 0 , with very high resolution) and a rotating eye ball to measure the scattering intensity at other (larger) angles (with 1 0 resolution) [40]. The instrument uses the ring detector with a single 515 nm TE-cooled diode laser with a longer path length.…”

Section: B Experimental Resultsmentioning

confidence: 99%

Inversion of Volume Scattering Function for Estimation of Bubble Size Distribution in Ocean Waters

2021

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Angular distribution of the intensity of light scattered by a spherical air bubble in the oceanic medium is distinctive near the critical scattering angle region, when light interacts with a bubble with a refractive index less than its surrounding medium. This study is aimed at presenting theoretical and experimental results for the volume scattering function (VSF) of the bubbles generated under oceanic and laboratory conditions. The effect of bubbles on the VSFs was investigated using Mie calculations for the bubble sizes ranging from 5 to 200 µm and their size distribution slopes ranging from 3.6 to 4.6. Findings revealed that the critical angle scattering patterns (50 0 -80 0 ) produced by bubbles become well-pronounced, enhanced and dependent on the minimum and maximum bubble sizes and their size distribution slopes (rmin, rmax and α). A relationship of the volume scattering phase function (̃( , )) between an inverse power-law and a normally-distributed bubble population was established based on experimental data. Both experimental results and Mie simulations showed that the angular position of the first critical dark fringe (θ1) shifts in the direction of the critical angle as the minimum and mean values of the bubble size increase in accordance with the power law and normally-distributed bubble populations. The new inversion method predicted the light scattering patterns produced by bubbles near the critical angle region in close agreement with results from Mie theory simulations. The inversion method for estimating the bubble size distribution based on the measured VSF data have significant implications for underwater optical communication, imaging and ocean colour remote sensing studies.

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Section: B Experimental Resultsmentioning

confidence: 99%

Inversion of Volume Scattering Function for Estimation of Bubble Size Distribution in Ocean Waters

2021

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“…By contrast, the large beads exhibited ripples in the angular scattering that made the calibration result highly sensitive to the angular acceptance of the detector. Following the suggestion of Hu et al [29], we used small-sized beads with a nominal diameter of 0.203 µm for calibration and other large-sized beads for validation. Its attenuation coefficient c is equal to the scattering coefficient b and thus:…”

Section: Amplitude Calibrationmentioning

confidence: 99%

Measurements of Aquatic Particle Volume Scattering Function up to 178.5° in the East China Sea

Tao

Guo

et al. 2022

Applied Sciences

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Particulate volume scattering function (VSF), especially at angles larger than 170°, is of particular importance for interpreting ocean optical remote sensing signals and underwater imagery. In this study, a laboratory-based VSF instrument (VSFlab) adopting the periscopic optical system was developed to obtain VSF measurements from 1°–178.5°. In the VSFlab, a new prism design that simply combines a single prism and a neutral density filter was proposed to more efficiently reduce the stray light in the backward direction, while a detailed calibration procedure was given. A full validation based on standard beads of various sizes and a comparison with the results from LISST-VSF and POLVSM indicated that the VSFlab can provide reliable results from 1° to 178.5°. VSFlab measurements in the East China Sea (ECS) exhibited a moderate increase (not more than 5 times) in VSF from 170° to 178.5° rather than a sharp increase of more than one order of magnitude presented in other instrument results measured in other coastal regions. The estimates of the particulate backscattering coefficient using single angle scattering measurements near 120° or 140° and suitable χp were justified. Two types of the VSFs with different size distribution and shape parameters in the ECS can be distinguished based on the variability of χp after 155°. The measured VSF could provide a basis for the parameterization of VSF in the radiative transfer model and the variability of χp in the backward direction had the potential to be used to characterize the particles in the coastal region of the ECS.

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“…A polarizing beam splitter was placed in front of two PMT detectors to separate the scattered light into vertical and horizontal components (Slade et al, 2013). In this configuration, four different combinations of linear polarization between the incident and the scattered light are measured by two PMT detectors at scattering angles between 15 °and 155 °and used to compute the three Mueller matrix components, P 11 , P 12 , and P 22 (Sequoia Scientific Inc, 2016;Hu et al, 2019b). The following three equations describe how the measurements are converted to P 11 , P 12 , and P 22 at different scattering angles θ:…”

Section: Lisst-vsf Data Processingmentioning

confidence: 99%

“…Therefore, only the "roving eyeball" unit measured P 11 , P 12 , and P 22 , which are reported in this study. Before and after each cruise, the LISST-VSF "eyeball" unit was calibrated using polystyrene beads of standard sizes to obtain κ(θ) following the method described in Hu et al (2019b). The calibration coefficient differed between the two cruises because the LISST-VSF was serviced after the NPO-18 and the voltage of PMT detectors changed.…”

Section: Lisst-vsf Data Processingmentioning

confidence: 99%

“…Some of the instruments used in these studies also measured the linear polarization components (Sullivan and Twardowski, 2009;Babin et al, 2012;Chami et al, 2014). Recently, a commercial instrument LISST-VSF (Laser In Situ Scattering and Transmissometer -Volume Scattering Function) developed by Sequoia Scientific Inc. has been used to measure P 11 from 0.1 °to 155 °as well as P 12 and P 22 from 15 °to 155 °in the aquatic environment (Koestner et al, 2018;Hu et al, 2019b;Koestner et al, 2020;Sandven et al, 2020). The Mueller matrix elements are determined by the particle size distribution (PSD), refractive index, shape, and internal structure of the particles.…”

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confidence: 99%

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Contribution of Submicron Particles to the Unpolarized and Linearly Polarized Angular Scattering

Zhang

Xiong

2022

Front. Remote Sens.

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The scattering by suspended particles is being measured with increasing frequency in the global oceans. Yet, little is known of size fractioned contribution, particularly from submicron particles and to the polarized scattering. In this study, three Mueller scattering matrix elements, P11, P12, and P22, for the bulk particles and for size fractions <0.2 μm and <0.7/0.8 μm were measured using a commercial instrument LISST-VSF in the North Pacific Ocean in 2018 (NPO-18) and in the North Atlantic Ocean in 2021 (NAO-21). We found that P11 and P12 by particles <0.2 μm each had median value that was very similar between the two sites, even though the variability was greater in the NAO-21 than in the NPO-18. Relatively, particles <0.2 µm accounted for the same fraction of total particle scattering in P11 and P12, approximately 20% at near surface water and 40–60% at deeper depths. In contrast, P11 and P12 by particles <0.7/0.8 μm differed between the two sites, which we found was because particles of sizes 0.25–1.0 µm had greater concentration in the NAO-21 than in the NPO-18. P22 normalized to P11 indicated that the sphericity of particles was the same between submicron and bulk particles in the NPO-18 site, but bulk particles deviated more from sphericity than submicron particles in the NAO-21 site where the experiment took place during a phytoplankton spring bloom. Simulations were conducted using three particle models including homogenous spheres, mix of homogenous/coated spheres, and homogenous asymmetric hexahedra to account for the effects of particle shapes or internal structures on the polarized scattering. Using the size distribution that was measured, each of the models can reproduce some of the scattering features measured in this study, but neither of them can reproduce all. Our results suggest that accurate simulation of the polarized scattering by oceanic particles needs to account for both their nonsphericity and heterogeneity, in addition to the concentration and size distribution of the particles.

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Calibration of the LISST-VSF to derive the volume scattering functions in clear waters

Cited by 16 publications

References 51 publications

Inversion of Volume Scattering Function for Estimation of Bubble Size Distribution in Ocean Waters

Inversion of Volume Scattering Function for Estimation of Bubble Size Distribution in Ocean Waters

Measurements of Aquatic Particle Volume Scattering Function up to 178.5° in the East China Sea

Contribution of Submicron Particles to the Unpolarized and Linearly Polarized Angular Scattering

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