New technique for the determination of spectral reflectance of individual and bulk particulate suspended matter in natural water samples

Rodolfo H. Iturriaga; Juli Berwald; Gregory J. Sonek

doi:10.1117/12.266483

6 February 1997 New technique for the determination of spectral reflectance of individual and bulk particulate suspended matter in natural water samples

Rodolfo H. Iturriaga, Juli Berwald, Gregory J. Sonek

Author Affiliations +

Proceedings Volume 2963, Ocean Optics XIII; (1997) https://doi.org/10.1117/12.266483
Event: Ocean Optics XIII, 1996, Halifax, Nova Scotia, Canada

Abstract

The behavior of real scattering surfaces is often specified by measuring the bidirectional reflectance factor (BRF), defined as the ratio of the flux scattered into a given direction by a surface under given conditions of illumination to the flux scattered in the same direction by a Lambertian scatterer under identical conditions.THe utility of this factor is that measurements on surfaces can be related to known standards, which have a BRF greater than 99 percent for a broad range of wavelengths. In addition to the incidence angle and spectral features of the incident flux, the reflectance properties of a surface are affected by the intrinsic composition and roughness properties of the surface. Therefore, the spectral reflectance of different targets will generally yield spectral reflectance curves of different shapes, forming the basis for identification of materials. For example, optical principles developed for the determination of reflectance properties of marine particles facilitate the determination of the BRF of oceanic samples. We have recently developed and implemented a system for determining the BRF composed of a Zeiss photomicroscope equipped with a reflective system. In this system, excitation is provided over a large field of view while reflection collection is acquired over a slightly smaller solid angle. Multi-wavelength measurements allow the determination of the effect of the excitation wavelength on both the reflectance and fluorescence properties of the sample, whereas monochromatic measurements exclude fluorescence effects. This new technique provides the advantages of determination of the BRF for different types of individual and bulk particulates transferred onto an optical embedding medium or collected on an Anopore filter. Abundance and other optical properties of dominant particle types can also be determined by individual particle analysis on the same sample.

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Rodolfo H. Iturriaga, Juli Berwald, and Gregory J. Sonek "New technique for the determination of spectral reflectance of individual and bulk particulate suspended matter in natural water samples", Proc. SPIE 2963, Ocean Optics XIII, (6 February 1997); https://doi.org/10.1117/12.266483

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