Measuring whiteness

Ref: SHLS20022

Whiteness is a perceptual quale of a reflecting object, important in many applications (textile industry, dentistry etc.). Current approaches to measuring whiteness are based on comparing the light reflected by the object with the light from an ideal diffuser. However, in this case the measurement depends on both the object and incident light. But as we know from our experience, the object whiteness is rather constant under illumination variations.
The main objective of the project is to develop and test a new index of whiteness, which would be a characteristic of the reflective properties of the object, rather than its lighting. As a departing point, the measure put forward by Logvinenko (JoV, 2009) will be taken. It can be computed from the spectral reflectance function of the object.
In order to see how this measure correlate with whiteness, the latter will be measured (in psychophysical experiments) by using the hue scaling technique in the form that was previously used in my lab (Logvinenko & Beattie, JoV, 2011). The index will be elaborated so as to predict the whiteness as measured in these experiments.
An important part of the project is to ascertain how robust the new whiteness index will be to the illumination variations. The main part of research will be conducted under daylight. Then these experiments will be repeated under different illuminations. Although the dependence on illumination is not expected to be considerable, some computer modelling will be performed to improve the index so that it takes into account the lighting variations.
The results can be used in any activity where there is need to know how white the white is.