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DIRECT ABSORPTANCE MEASUREMENT OF FLUORESCENT AND TURBID SAMPLES IN A 4 π GEOMETRY
Author(s) -
COSTA LORENZO F.,
GRUM FRÄNC,
WIGHTMAN THEODORE E.
Publication year - 1976
Publication title -
color research and application
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.393
H-Index - 62
eISSN - 1520-6378
pISSN - 0361-2317
DOI - 10.1111/j.1520-6378.1976.tb00042.x
Subject(s) - optics , absorptance , transmittance , absorption (acoustics) , integrator , integrating sphere , materials science , fluorescence , detector , radiance , attenuation coefficient , sample (material) , signal (programming language) , solid angle , physics , reflectivity , quantum mechanics , voltage , computer science , thermodynamics , programming language
The determination of optical absorption in turbid media requires optical integrators to collect all the light scattered by the sample. If under these measurement conditions the sample fluoresces, its emission is collected as scattered light by the integrator and produces a signal of the opposite sign to that of an absorption. The magnitude of this effect is a function of the luminescent quantum efficiency of the sample and the spectral response of the detector. The implications of the effects of fluorescence on the absorption measurements of turbid media are discussed, along with a method for direct measurement of absorptance in a 4 π geometry. In the presence of turbidity, the measurement of regular transmittance is not valid if obtained with very small angles of detection. It is perfectly valid, however, if a detection acceptance angle of 4 π steradians is used.