Gersan Establishment

Spandrel Establishment

Anstalt Gersan

Martin P Smith

Christopher M Welbourn

Martin Cooper

Robin W Smith

James Gordon Smith

Andrew D Stewart

Paul Martyn Spear

Philip Maurice Martineau

Daniel J Brink

Marie-Line Rooney

Ricardo Simon Sussmann

Colin D Saunders

In order to test whether a diamond has had a layer a synthetic diamond deposited thereon, the diamond is radiated with ultraviolet radiation so as to form a pattern of beams of refracted and reflected radiation, the pattern of refracted and reflected radiation being observed on a screen behind the diamond.

Examining a diamond

In order to examine a gemstone, the stone is irradiated and observed though a filter (5) at a first wavelength which is characteristic of a first class of gemstones. The filter can be rocked from a setting normal to the optical axis to transmit radiation of at least one reference wavelength. The intensities of radiation transmitted at first and reference wavelengths are observed and compared, to classify the gemstone as belonging to the first class or not. In order to detect whether the gemstone is a diamond or diamond simulant, the first wavelength comprises raman emission characteristic of diamond. In order to detect whether the gemstone is definitely natural or not definitely natural, the gemstone is classified as definitely natural if there is a maximum of absorption of radiation at 415.5 nm.

Method and apparatus for examining an object

Method and an apparatus for testing whether a diamond has a layer of

This invention relates to a method and apparatus for classifying or sorting objects by projecting and irradiating an object through an irradiation zone and then examining the radiation emitted by the object to determine its class, the irradiating zone having a length in a vertical plane greater than its width where its length to width ratio is greater than 5:1.

Classifying or sorting

Detecting diamonds in a rock sample

Method and apparatus for detecting diamonds in a plurality of objects

Optical inspection method and apparatus

In order to sort diamond-bearing ore particles conveyed on a wide belt, exciting radiation strikes the belt along an extended line. Diamonds are detected by passing the emitted radiation through a narrow band pass filter and sensing the Raman radiation with a photo-multiplier tube. Only axial-parallel rays passing through the filter reach the photo-multiplier tube. An array of side-by-side converging lenses can be used, the lenses being of rectangular shape as seen looking along the optical axis with their long axes at right angles to the line of radiation. The ore particles are in the plane of the foci of the lenses, so that radiation emitted by each particle is passed in parallel rays through the filter. In order to stop rays having an angle of incidence greater than the maximum permitted, to avoid identifying non-diamond material as diamond, a further converging lens is used to focus the rays at the plane of a telecentric stop. The stop stops rays having too great an angle of incidence. The position of the diamond can be detected for instance by a CCD array or by a time domain technique. The apparatus can be monitored by giving a signal when the radiation from tracer stones and holes on either side of the belt, differs from predetermined values.

Sensing a narrow frequency band and gemstones

Sensing a narrow frequency band of radiation and gemstones

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.

Sensing the shape of an object

Objects are dropped in succession through a viewing zone, where they are viewed in bright field illumination by three viewers along mutually orthogonal axes, using radiation of different wave-lengths (or viewing in rapid succession). The viewers sense the presented area. The presented areas are compared in a microprocessor in order to obtain a rough determination of the shape of the object. The presented areas can, for example, be summated to obtain a rough determination of the size of the object.

Method of classifying objects according to shape

Growing community of inventors

Wargrave, United Kingdom

Martin P Smith