In co-operation with the members of Hitachi Ltd., a spectrofluorometer with a Xenon lamp as the light source has beendevised and by this means a regression analysis concerning the relation between thescale values of visual impression and the three chromatic values (α, β and
Y) has been made on 53 samples of cloth whitened with various fluorescent agents .An equation for the whiteness derived from the anlysis is given as
W1=30.9α-17.9β+20.8
Y-1.3217
in which the coefficients are evaluated for calculated
W1 values to accord with those given by Judd formula for proximity factor
k=20 and for the equation to become applicable to non-fluorescent yellowish region. By developing the equation in lst order terms of
X,
Y and
Z in the neigh-bourhood of the ideal white, a whitereness sensitivity curve
-ω
1λ is obtained.
-ω
1λ is defiaed by
W1-1.0800=∫
λE-ω
λγ(λ)
dλ where
Eλ and γ(λ) are the energy of the light and the intensity ratio of the light from sample to the light from MgO respectively.
In non-fluorescent region, there are several whiteness sensitivity curves by known formulas for whiteness; they are however considerably different from one another. Such being the case, if in deriving the whiteness equation mentioned above the approximation is extended to include the term of α
2 with anegative coefficient, a better whiteness sensitivity curve could be worked out.
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