| 摘要 |
The colour of a precious stone is determined by aligning the table of the precious stone normal to the axis of the light which is projected from a source. The optical axis is directed colinearly with an axis of symmetry of the precious stone which is normal to the table. The light of a given single wavelength is projected onto the precious stone, and a proportion of the incident light which is transmitted by the precious stone is measured. This measurement is repeated for different wavelengths of the light over the range of visible wavelengths, in order to obtain a transmission spectrum. The tristimulus value components are calculated from this. The figure shows the tristimulus value components of a set of 7 diamonds which are visually classified in a sequence of rising yellow tinge and are denoted by 1A to 7A, as well as another set of 5 visually classified diamonds which are denoted by 1B to 5B. <IMAGE> |
