Nephelometer for the Measurement of Volume Scattering Function in Situ*†

Tyler, John E.; Richardson, W. H.

doi:10.1364/josa.48.000354

Cited by 31 publications

(12 citation statements)

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“…A typical measurement principle for VSF determination, which dates back to 1950s-1980s [5][6][7][8][9][10], is that either an optical sensor or a light projector turns around the center of the scattering volume. This principle has been used and advanced by several investigators.…”

Section: Introductionmentioning

confidence: 99%

A new approach to measure the volume scattering function

et al. 2013

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We present a novel optical approach to measure the volume scattering function (VSF) by image detection. The instrument design, based upon a combination of two reflectors, uses a unique measurement principle and allows the rapid simultaneous determination of scattering at a wide range of angles. The advantages of the newly developed scattering meter are that: 1) it can determine the scattering function from 8° to 172° at 1° intervals without changing the sensitivity of the detector, without moving any optical parts, and can do so within a few seconds, 2) the unique optical design facilitates determination of the spectral VSF over the full visible spectrum, i.e. it can obtain the VSF at a specific wavelength with an optional wavelength-resolution. Measurements under controlled conditions for the assessment of the instrument agreed well with theoretically predicted scattering functions. Measurements with cultured phytoplankton of different species revealed a significant variety of the VSF together with spectral variation. The observed results will stimulate and improve radiative transfer and/or two-flow models of light in the ocean, which is an important role for ocean color remote sensing algorithm development, particularly for coastal regions.

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Section: Introductionmentioning

confidence: 99%

A new approach to measure the volume scattering function

et al. 2013

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“…Additionally, the shape of the volume scattering function requires a large dynamic range of the detector, spanning multiple orders of magnitude. First measurements of the VSF in situ were made over 25 years ago, by, among others, Tyler and Richardson [5], Petzold [7], and Kullenberg [6]; however, operation of these instruments was difficult and the angular resolution was not satisfactory to solve the radiative transfer equation. Another problem inherent to all VSF meters is the necessity to have a small sampling volume in order to have high resolution.…”

Section: Chapter III Current Instrumentsmentioning

confidence: 99%

“…In the 1950s and 1960s, new instruments and measurements of scattering in water were done by several groups, among them Tyler and Richardson [5] and Kullenberg [6].…”

Section: Introductionmentioning

confidence: 99%

Instrumentation to measure the backscattering coefficient b_b for arbitrary phase functions

2011

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The backscattering coefficient b b is one of the inherent optical properties of natural waters which means that it is independent of the ambient light field in the water.As such, it plays a central role in many problems of optical oceanography and is used in the characterization of natural waters. Essentially, any measurement that involves sending a beam of light into water must account for all inherent backscattering. Some of the applications that rely on the precise knowledge of the backscattering coefficient include studies of suspended particle distributions, optical bathymetry, and remote sensing. Many sources contribute to the backscattering, among them any suspended particles, air bubbles, and the water molecules themselves. Due to the importance of precise measurements and the ease with which water samples can be contaminated, an instrument to determine directly and quickly the backscattering coefficient in situ is highly desirable.We present such an instrument in both theory and experiment. We explain the theory behind our instrument and based on measurements made in the laboratory we demonstrate that our prototype shows the predicted behavior. We present data for increased extinction in the water, and show how measuring the extinction and taking it into account improves the quality of our measurements. We present calibration data obtained from three different particle sizes representing differently shaped volume scattering functions. Based on these measurements we demonstrate that our prototype has the necessary resolution to measure the backscattering coefficient b b iv over the whole range found in natural waters. We discuss potential improvements that should be made for a commercial version of the instrument.

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“…Also, in the construction of an instrument for determining the forward scattering coefficient by this method, it will be nccessary to restrict the detection beam so as to achieve a constant scattering volume along the path r. In the diagrammatic geometry of Figure 1 the scattering volume would be large at 90" and small at 20", for example. Errors from this source can be minimized by cylindrically restricting the beam of detection in the manner described by Tyler ( 1958).…”

Section: S=xzmentioning

confidence: 99%

Instrument for Measuring the Forward Scattering Coefficient of Sea Water1

Tyler

Howerton

1962

Limnology & Oceanography

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The theory dcvclopcd by Beuttel and Brewer for an instrument to measure the total scattering coefficient is re-examined to detcrminc its usefulness in sea water. It is found that, with a properly dcsigncd instrument, one can WC this principle to measure the forward scattering coefficient with an accuracy better than 10% if the total attenuation coefficient of the water dots not exceed 2.1/m. The errors that could be introduced by the size and shape of the source or of the beam of clctcction arc cxamincd and discussed.Beuttel and Brewer ( 1949) devised a remarkably simple and ingenious device for measuring the total scattering coefficient of the atmosphere. The principle of this device is shown in Figure 1 where A is a small cosine emitter of radiance WO. If a multiplier phototube looks across this source from 0 along a line of sight OM, which is parallel to the surface of the source and a distance h above it, then for the condition in which A is the only source of light, and the absorption coefficient is substantially zero, Beuttel and Brewer demonstrated that the total scattering coefficient, s, could be obtained by means of equation 1, 2,rNhS=xz (1) where N is the measured radiance of the scattered flux in the path OM. The assumption that the absorption coefficient is zero> is not, of course, a valid assumption for a medium such as ocean water. For a medium in which both the scattering and the absorption are significant, the measured radiance of the path of sight in the Beuttel and Brewer instrument is given by equation 2, N = 2rrNoA e-a" 5 n/2

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Nephelometer for the Measurement of Volume Scattering Function in Situ*†

Cited by 31 publications

References 1 publication

A new approach to measure the volume scattering function

A new approach to measure the volume scattering function

Instrumentation to measure the backscattering coefficient b_b for arbitrary phase functions

Instrument for Measuring the Forward Scattering Coefficient of Sea Water1

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