| 摘要 |
<p>1480936 Identification of polished gemstones YEDA RESEARCH & DEVELOPMENTS CO Ltd 22 Oct 1974 [23 Oct 1973] 45556/74 Heading G2J A pattern of reflected light from a gemstone is recorded on a plane recording medium. As shown in Fig. 1 light from a source 11 is passed by a shutter 12 and then collimated. The collimated light is focused through a pinhole 16 and reconverted to parallel light by lens 17. Reflected light from the gemstone 19 is refocused by the lens 17 to be recorded as a pattern of spots on recording medium 22. In the preferred arrangement the "table" of a brilliant cut gem is aligned to be perpendicular to the light 21, i.e. the principal reflection is refocused on the pinhole 16. The other reflections are derived from other facets and from imperfections, both imperfections in polished facets and internal inhomogenieties in the crystal. Other alignments are possible Fig. 2 (not shown) if the arrangement of Fig. 1 is vertical with the light source lowermost the gemstone may be placed with its "table" on a glass plate. In other embodiments Figs. 5 and 6, Fig. 5 (not shown) the light path is folded using beam-splitters to obtain more compact and convenient arrangement. The gem or the resulting record may be "rotated" about the optic axis of the system to provide a series of concentric circles suitable for automatic evaluation.</p> |
