Figure 7.
Schematic diagram of working of UV–Vis spectrophotometer.
12
Colorimetry
UV–Vis reflectance spectrophotometer, showing provision of specular component
inclusion and exclusion by keeping specular port off and on (close or open).
Since the colour of the illuminant is white, specular reflections add white, with
the effect of de-saturating the colour. Textiles or any non-metallic glossy surfaces
look more saturated in directional than in diffuse illumination, while matte surfaces
scatter the light diffusely — matte surfaces usually look less saturated than glossy
surfaces.
Most of the textile surfaces are between glossy and matte and hence in reflec-
tance spectrophotometer, diffuse illumination is provided by integrating spheres
with provision of gloss traps /lid at regular reflection points to include or exclude
specular/regular reflectance in instrumental set up. REflactance spectrophotometer
Instruments with 45/0 and 0/45 geometry are less critical and give better results and
accuracy. ASTM recommends [1–4] use the geometry that minimises surface effects
(usually the one that gives lowest Y and highest excitation purity) for partly glossy
samples. 45/0 geometry gives rise to polarisation problems [9].
Figure 8.
Schematic diagram of optical system of UV–Vis reflectance spectrophotometer.
Figure 9.
Schematic diagram of working of integrating shere type optical system in UV–Vis reflectance spectrophotometer.
13
Basic Principles of Colour Measurement and Colour Matching of Textiles and Apparels
DOI: http://dx.doi.org/10.5772/intechopen.101442
2.6.1 Calibration and certification of the instrument ‘s accuracy
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