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Ciencia y Tecnología del color. Seminario 2009 1
Gonio-Spectrophotometer for Low-Uncertainty Bidirectional Scatter Distribution Function
(BSDF) Measurements
A. M. Rabal, J. L. Fontecha, A. Ferrero, A. Pons, J. Campos y A. CorrónsIFA-CSIC
rabal@ifa.cetef.csic.es
Ciencia y Tecnología del color. Seminario 2009 2
BSDF. Theory Aims Instrument description Measurement procedure Future work
Outline
Ciencia y Tecnología del color. Seminario 2009 3
BSDF. Theory
ConicalDirectional Hemispherical
Nicodemus, 1977
isssiii
si ddBSDFsi
),;,(1),(
,,,,,,,,
ssii
ssii
EL
BSDF ie
ss
se
BSDF,,
,,cos
Ciencia y Tecnología del color. Seminario 2009 4
Aims
• Realization of diffuse reflectance and reflectance/radiance factors standards
• Uncertainty from the non-lambertianity in standards
• Relation between coloured-objects BSDF and the spatial distribution of the chromatic coordinates
Ciencia y Tecnología del color. Seminario 2009 5
Instrument description
Ciencia y Tecnología del color. Seminario 2009 6
Instrument description
Ciencia y Tecnología del color. Seminario 2009 7
Instrument description
Ciencia y Tecnología del color. Seminario 2009 8
Instrument description
Ciencia y Tecnología del color. Seminario 2009 9
,,,,
0,0,
0,0,
ii
iipLE Irradiance, E
Auxiliar System
ssiiiiiip
ssii
LLBSDF
,,,,
,,),,,,(
0,0,0,0,
Direct
Indirect
Measurement procedure
Ciencia y Tecnología del color. Seminario 2009 10
Spherical Coordinates BSDF
Degrees of freedom of experiment
Y
Source
Detector
Z
X
s
i
s
Z
X
Y
A
i
Germer, 1999
sisisisisiA sinsinsinsinsinsincoscoscoscosarccos
AiAisX sincos/coscoscosarctan
AisisY sin/sinsinsinarcsin
XYXAZ sin/sincosarctan
CoordinatesTransformation
Ciencia y Tecnología del color. Seminario 2009 11
Directional diffuse
Fitting to a BSDF ModelModel HTSG (He, Torrance, Sillion, Greenberg) (1991)
udddsp BRDFBRDFBRDFBRDF
Fitting experimental data to a model 0, , BRDFud
Ideal specular
Uniform diffuse
Ciencia y Tecnología del color. Seminario 2009 12
Assessment of the angles for the proper characterization of the BSDF
Determination of the characteristic parameters of the materials: 0, , BSDFud
Relation between BSDF and object appearance: knowledge of object RADIANCE for every direction within the observer frame
Future work
Ciencia y Tecnología del color. Seminario 2009 13
Gonio-Spectrophotometer for Low-Uncertainty Bidirectional Scatter Distribution Function
(BSDF) Measurements
A. M. Rabal, J. L. Fontecha, A. Ferrero, A. Pons, J. Campos y A. CorrónsIFA-CSIC
rabal@ifa.cetef.csic.es