Abstract: To make an elongate cut (1) in a diamond (2) using a laser radiation, a cylindrical optical system (5, 6) is used which converges the radiation at a greater angle of convergence in the plane of the cut (1) than in the transverse plane. In this way, the focal spot energy density is increased and cutting at depth is made more effective.

Abstract: In order to make a laser cut in a diamond (1), the diamond (1) is reciprocated transversely, the radiation is focussed onto the bottom of the cut (6) by a stationary focussing lens (4 ), and the radiation is passed to the focussing lens (4) by a mirror (3) which is reciprocated in the same direction as the diamond (1), thereby rocking the axis (5) of the beam below the lens (4). This increases the energy entering the cut and reduces the focal spot area projected on the cut wall, thus increasing the energy density of radiation on the inclined cut walls.

Abstract: In order to determine the external profile of a diamond, particularly a large diamond which has re-entrant features, an elongate and thin beam is projected onto the diamond while the diamond is rotated about an axis normal to the beam; an imaging system is used to image from one side the line along which the beam strikes the diamond, this image being formed on a diffraction grating which is tilted in accordance with the Scheimpflug condition and in order to employ the first order beam of the diffraction grating. The image on the diffraction grating is viewed with a second imaging system. Furthermore, there may be a substantial improvement in light capture. The arrangement is applicable to systems other than those for determining profile.

Abstract: A feeder has a rotary bowl with a highly resilient foam plastic insert providing a V-shaped annular trough to which objects are fed, a rotary feeder head whose axis is inclined to the axis of the bowl, and a nozzle wheel carried by the feeder head with a number of suction nozzles arranged so that the nozzles pick up successive objects from the bowl. As the nozzle wheel rotates, ports on the nozzle wheel register with stationary ports to which compressed air is supplied, and cause the suction to be released and a blast of compressed air to be blown through an annular array of discharge openings.