Abstract: A system is described for obtaining images of a gemstone, and performing quantitative analysis on the images to obtain measures of properties of the gemstone. The system comprises a support structure for supporting the gemstone at an observation position. An illumination structure is arranged to illuminate the gemstone. The illumination structure comprises a plurality of radially dispersed directional light sources directed towards the observation position, the support structure and illumination system being rotatable relative to one another around a rotation axis so that the gemstone can be illuminated by one or more of the directional light sources at each of a plurality of rotational positions, the axis of rotation being normal to a selected facet of the gemstone. An imaging device is directed towards the gemstone for obtaining images of the gemstone at each of the rotational positions, the imaging device having an imaging axis parallel to or coincident with the axis of rotation.

Abstract: A method and apparatus for generating a 3D model of and/or detecting inclusions in a polished gemstone such as diamond is described. The gemstone (103) is rotated in a series of discrete increments. At each rotational position of the gemstone, the gemstone (103) is illuminated with collimated light (111,112) and a silhouette image recorded. At each rotational position, the gemstone (103) is also (before further rotation) illuminated with diffuse light (109), and a diffuse image recorded. The images are analysed to obtain a 3D model of the surface of the gemstone. Features may then be identified in the diffuse images and tracked between subsequent diffuse images. The tracked features may be located relative to the 3D model of the gemstone, taking into account reflection and refraction of light rays by the gemstone. Some or all of the located features may then be identified as inclusions.