Abstract
Abnormal interference colour produced by crystals with birefringence dispersion was discussed from the colorimetric point of view. The tristimulus values of the colour were calculated on the basis of the previous data on apophyllite which has various types of birefringence dispersion. From the view point of chromaticity, abnormal interference colour was classified into three types: chromo-cyclic, centro-cyclic and non-cyclic types.
In chromo-cyclic colour, the figure of the chromatic locus depends much upon the curvature of the birefringence dispersion curve.
Variation of luminance factor with thickness is also discussed.
A chromaticity diagram for the maximum purity in the chromo-cyclic colour is presented.
