Doublet detection in gemstones
AssigneeDe Beers UK Ltd
InventorsPeter Lanigan, Colin McGuiness
Life of this patent
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Abstract
A method of characterising a composition of a gemstone comprises irradiating an upper portion and a lower portion of the gemstone with one or more pulses of ultraviolet radiation at a wavelength of substantially 225 nm or less; capturing luminescence emitted by the upper portion of the gemstone and luminescence emitted by the lower portion of the gemstone in one or more time windows having a predetermined relationship with the or each pulse; and comparing properties of the captured luminescence from the upper and lower portions. A composition of the gemstone is characterised, based upon the comparison.
Claims25
A method of characterising a composition of a gemstone, the method comprising:
- irradiating an upper portion and a lower portion of the gemstone with one or more pulses of ultraviolet radiation at a wavelength of substantially 225 nm or less;
- capturing luminescence emitted by the upper portion of the gemstone and luminescence emitted by the lower portion of the gemstone in one or more time windows having a predetermined relationship with the or each pulse;
- comparing properties of the captured luminescence from the upper and lower portions;
- and
- characterising a composition of the gemstone, based upon the comparison.
A method of comparing a colour of luminescence emitted by a crown and by a pavilion of a gemstone under ultraviolet excitation, said method comprising identifying said gemstone as a doublet where the luminescence colour of the crown and the pavilion do not match.
An apparatus for characterising a composition of a gemstone, the apparatus comprising:
- a source of ultraviolet radiation configured to irradiate an upper and a lower portion of the gemstone with one or more pulses of ultraviolet radiation at a wavelength of substantially 225 nm or less;
- an image capture device configured to capture luminescence emitted by the upper portion of the gemstone and luminescence emitted by the lower portion of the gemstone;
- a controller configured to synchronise the source and image capture device so as to capture luminescence emitted by the upper and lower portions of the gemstone in one or more time windows having a predetermined relationship with the one or more pulses;
- and
- a processor configured to determine properties of the captured luminescence from the upper and lower portions and to present said properties for comparison.
Dependencies are inferred from the claim text.