Optics: measuring and testing – Inspection of flaws or impurities
Patent
1998-03-27
2000-01-11
Font, Frank G.
Optics: measuring and testing
Inspection of flaws or impurities
3562391, 3562397, G01N 2100
Patent
active
060142081
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND TO THE INVENTION
The present invention relates to a method of and apparatus for testing whether a natural diamond has had a layer of synthetic diamond deposited thereon. This is of particular importance in testing whether the diamond is wholly natural or whether any part of it comprises CVD diamond material and also in locating such material if present.
Synthetic diamond material may be deposited on an uncut or part processed natural diamond which is then worked, for example, into a round brilliant cut. Alternatively, the synthetic diamond material coating may be deposited onto a fully fashioned brilliant stone after working of the stone. The thickness of the synthetic diamond material layer may be very thin (it could be in the range from 5 microns to 10 microns) but the present invention may also be used to detect thicker layers.
The value of a diamond is in part dependent upon its weight. Accordingly, synthetic diamond material may be deposited onto natural gem diamonds, before or after cutting of the diamond, to increase the weight of the finished product.
However, the value of a diamond also resides in its qualities of authenticity and uniqueness and in the fact that it is an entirely natural (i.e. mined) product. Thus, a diamond that has not been enlarged by deposition of synthetic diamond material has a value over a diamond which has.
Over the years, a number of methods of synthesising diamond material have been developed. One of these methods is the chemical vapour deposition (CVD) technique, which is a low pressure technique involving deposition of synthetic diamond (referred to as CVD diamond material in this specification) onto a substrate from a gas. CVD is the most likely way in which synthetic diamond will be deposited on a diamond, although alternative techniques such as physical vapour deposition have been proposed. A diamond artificially enlarged by deposition of CVD or similar diamond material is referred to in this specification as a "CVD
atural diamond doublet".
CVD diamond material may be deposited on a non-diamond or diamond substrate. In the latter case, the CVD diamond material can replicate the structure of the diamond substrate (referred to as "homoepitaxial growth"). The CVD
atural diamond doublet produced can be identical in appearance, density and other common physical properties to an entirely natural stone and there may be a problem in identifying such a CVD
atural diamond doublet.
It is an object of the present invention to provide a method of and apparatus for testing whether a diamond has had a layer of synthetic diamond deposited thereon.
It is desired that the apparatus should be simple and may be put into operation by a person with relatively little training. The method and apparatus should be capable of being operated reliably and consistently by a practised jeweler who has no training in laboratory gemological analysis. The method and apparatus should be suitable for screening large numbers of stones, one at a time, and should be suitable for automation.
British patent application No 9404309.8 discloses a method of determining whether a diamond has had a layer of synthetic diamond deposited thereon in which the diamond is caused to luminesce with electrons or high energy ultraviolet radiation and the resulting pattern of luminescence is observed to detect zones of superficial synthetic diamond. Preferably, the whole diamond is irradiated and the pattern observed by eye through magnifying means or on a screen via a CCD camera.
The present invention provides a method of testing whether a diamond has had a layer of synthetic diamond deposited thereon, comprising observing a plurality of zones of the surface of the diamond, each zone being observed by irradiating the zone with high energy radiation to excite or stimulate emission of luminescence and assessing the intensity of the luminescence.
The present invention further provides an apparatus for testing whether a diamond has a layer of synthetic diamond deposited thereon, comprising a mounting means, a su
REFERENCES:
patent: 4284897 (1981-08-01), Sawamura et al.
patent: 4799786 (1989-01-01), Gerrard
patent: 5118181 (1992-06-01), Yifrach et al.
patent: 5406367 (1995-04-01), Sopori
patent: 5536943 (1996-07-01), Smith et al.
Cooper Martin
Martineau Philip Maurice
Smith James Gordon Charters
Smith Martin Phillip
Spear Paul Martyn
Font Frank G.
Gersan Establishment
Stafiro Michael P.
LandOfFree
Examining a diamond does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Examining a diamond, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Examining a diamond will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1466452