METHOD AND APPARATUS FOR DETERMINING AMBIENT LIGHT AND SURFACE REFLECTANCE

摘要

METHOD AND APPARATUS FOR DETERMINING AMBIENT LIGHT AND SURFACE REFLECTANCE An apparatus for dividing light reflected by an illuminated surface into constituent parts of illuminating light and surface spectral reflectance of the surface. The apparatus includes a receiving device for receiving signals representing measured spectral power distribution Im(.lambda.) of the light reflected by the illuminated surface. The apparatus generates a weighting coefficient .epsilon.i for each of M illuminant basis functions Ebi(.lambda.) for describing the illuminating light. Weighting coefficients .sigma.j for each of N reflectance basis functions Sbj(.lambda.) are generated to describe the reflectance of the surface. The apparatus compares an approximation Ia(.lambda.) of the measured spectral power distribution Im(.lambda.), Ia(.lambda.) being defined by the relation: where the set of product pairs Ebi(.lambda.)Sbj(.lambda.) is linearly independent. Different weighting coefficients are regenerated until said Ia(.lambda.) and said Im(.lambda.) are generally equal. Signals representing at least one of the constituent parts of illuminating light and said surface spectral reflectance are generated based on the weighting coefficients .epsilon.i and .sigma.j which make said Ia(.lambda.) generally equal to said Im(.lambda.). The apparatus has an output devise for outputting the signals.