WO2006117406A2

WO2006117406A2 - Identifying a gemstone

Info

Publication number: WO2006117406A2
Application number: PCT/EP2006/062104
Authority: WO
Inventors: Suranjith Gunasekara
Original assignee: Fabrique Holdings Co. Ltd.
Priority date: 2005-05-05
Filing date: 2006-05-05
Publication date: 2006-11-09
Also published as: WO2006117406A3; GB0509207D0

Abstract

Identification Apparatus (31, 32) for providing identification information relating to a gemstone (10), is arranged to obtain a measurement in absolute or relative terms of the length of each of plural sides of a table facet (14) of a gemstone, and automatically to use the plural measurements to provide a fingerprint for the gemstone. The fingerprint includes a measure of the length of a given side of the table facet as a proportion of the total of the lengths of all the sides of the table facet and a measure of the length of each side of the table facet.

Description

Identifying a Gemstone

Description

This invention relates to apparatus for providing identification information relating to a gemstone.

It is known to record information relating to diamonds and other gemstones. Such information can enable a gemstone to be distinguished from other gemstones. For instance, a gemstone can be weighed, and the weight of the gemstone can then enable it to be distinguished from gemstones having different weights. Weight is a crude measure since weight cannot easily be measured to such a resolution that it is possible to distinguish a gemstone from all other gemstones in a sample. Also, the weight of a gemstone can fairly easily be altered, for instance by polishing or by laser drilling.

Photography can allow gemstones to be distinguished between more easily and reliably. Photographs can record details of the cut, i.e. the three-dimensional shape, of the gemstone. Photographs can also reveal the locations and sizes of inclusions, which are imperfections within the gemstone, so gemstones can be identified with a high degree of certainty. GB-A-2 358 541 describes a system in which attributes of a diamond can be recorded. However, it is not currently possible automatically to search databases of photographs of gemstones to determine whether a particular gemstone is one which is included in a database, or indeed which of a number of gemstone entries in a database the particular gemstone relates to. It is likely that this will become possible in the future, although this may not be for some time and will be expensive, at least initially.

The inventors have thus perceived a need for the automatic identification of gemstones which can be performed reliably and without requiring complicated and expensive photograph analysis software.

According to the present invention, there is provided apparatus for providing identification information relating to a gemstone, the apparatus comprising: means for obtaining a measurement in absolute or relative terms of the length of each of plural sides of a table facet of a gemstone, and means arranged automatically for using the plural measurements to provide a fingerprint for the gemstone.

This allows a gemstone to be identified, at least coarsely, in a relatively straightforward manner and reliably. Significantly, it allows a computer-assisted search of gemstones to be carried out in a reliable and largely automated fashion.

Preferably the fingerprint includes a measure of the length of a given side of the table facet as a proportion of the total of the lengths of all the sides of the table facet.

In either case, the fingerprint may include a measure of the length of each side of the table facet.

Advantageously, the measurement obtaining means comprises means for measuring automatically the lengths of the sides of the table facet. More simple embodiments utilise manual or semi-automatic measurement.

One definition of fingerprint is "any distinctive pattern of characteristics or properties of an object which can serve to identify that object". Thus, the provision by apparatus according to the invention of a data set derived from measurements of the lengths of sides of a table facet of a gemstone constitutes the provision of a fingerprint, since it can serve to identify that gemstone.

The table facet is the largest facet on the top of the diamond. The table facet is octagonal for gemstones which have Round Brilliant, Oval or Pavilion cuts, and numerous other cuts. With certain cuts, the table facet may have three or four sides or edges. The invention is applicable to gemstones having any number of sides or edges. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a diamond with a Round Brilliant cut; Figure 2 is a schematic drawings of apparatus according to the invention; Figure 3 is a drawing showing a fingerprint obtained for a gemstone by the Figure 2 apparatus;

Figure 4 is a drawing showing part of a database of gemstones and their fingerprints; and

Figure 5 is a schematic drawing illustrating apparatus operable to search the Figure 4 database for an entry relating to a gemstone which has been fingerprinted.

Referring firstly to Figure 1, a diamond 10 is shown in perspective line drawing form. The diamond 10 has a Round Brilliant cut. As such, it includes a girdle 11, which is the band that circumvents the diamond around its middle, a crown 12, which is the part above the girdle, and a pavilion 13, which is the part below the girdle. On top of the crown is a table facet 14, which is flat. The table facet 14 should be in a parallel plane to the girdle, although whether this is exactly so depends on the quality of the cut. The diamond 10 should have a longitudinal axis passing though a point 15 at the bottom of the pavilion 13 and the central point of the girdle 11 then through the central point of the table facet 14, although there may be some variation depending on the quality of the cut.

The table facet 14 is octagonal, and has first to eighth sides 16 to 22. If the cut of the diamond 10 were perfect, then each side 16-22 of the table facet 14 would have the same length. However, due to limitations in the accuracy of the cutting process, there necessarily is variation in the lengths of the sides 16-22 of the table facet 14. These variations will typically be so small that they would be imperceptible to the eye, even with magnification.

Referring now to Figure 2, the diamond 10 is shown mounted in a support 30. This may be a support like that shown in GB-A- 2 358 541, although it may take any suitable form. Associated with the support 30 is a measuring device 31, which is directed to the diamond 10 and is able to measure parameters thereof. The measuring device 31 is connected to a computer 32, which is connected to a keyboard 34 and to a display monitor 33.

The measuring device 31 may be an independent device which is able to make the relevant measurements without the involvement of the computer 32. Alternatively, the computer 32 may effect control over the measuring device 31 and/or perform calculations therefor.

The parameters of the diamond which are of particular importance are the measurements of the lengths of the sides 16-22 of the table facet 14. The measuring device 31 also is operable to measure the colour and the clarity of the diamond 10. Alternatively, the colour and clarity may be measured by one or more other measuring devices (not shown), or entered by a user via the keyboard 34. A further measuring device (not shown) is operable to measure the weight, in carats, of the diamond 10, or this information may be entered by a user via the keyboard.

The measuring device 31 is operable automatically to measure the lengths of all of the sides 16-22 of the table facet 14 in absolute or relative form. The measurement process may require input of an operator to initiate it, but the measurement process itself is automatic.

The measuring device 31 may take any suitable form.

In one embodiment, the measuring device 31 includes a microscope (not shown) through which an optical measurement instrument (not shown) is directed. Here, the support 30, and thus the diamond 10, is movable in x and y directions in a plane parallel to the plane of the table facet 14. The optical measurement instrument is operable to detect the edges which occur at the meetings of facets of the diamond 10. This is relatively easy to achieve. It may involve, for instance, detecting reflection of a low power highly focussed light source, such as a laser, as the support 30 and the diamond 10 are moved relative to the microscope. When the support 30 is moved, the reflection changes as the laser passes over an edge, allowing the location of the edge to be detected. The measuring device 31 is arranged to move the support 30 relative to the microscope until the locations of all of the corners of the table facet 14 have been determined. The locations are provided by the x and y coordinates of the support 30 at the transition between two edges which border the table facet 14. The locations of the corners then are used to calculate the lengths of the sides 16-22 of the table facet 14. This calculation involves triangulation of the x and y coordinates at the ends of a side 16-22, i.e. two adjacent corners. This is repeated for each side 16-22.

It is not important for the absolute lengths to be measured, as long as the lengths of the sides 16-22 of the table facet 14 relative to one another can be determined accurately. However, this type of measuring device 31 can allow absolute measurements to be made.

Apparatus for measuring dimensions of diamonds to within 20 micron accuracy is currently available from Sarin Technologies Limited of 4 Hahilazon St. Ramat-Gan, 52522, Israel under the product name DiaMension.

In another embodiment, a scale is etched onto an ocular forming part of a microscope (not shown). The ocular is also known as the eyepiece, and typically is a combination of lenses at the viewing end of the microscope. The scale takes the form of a fine grid. The grid is detectable by an optical measuring device. In this embodiment, the positions of the corners of the table facet 14 relative to intersections on the grid are identified automatically. The measuring device 31 then is able to use this information along with information identifying in which block on the grid the corner is present to calculate the locations of the corners of the table facet 14. The measuring device 31 then calculates the distances between adjacent corners, to determine the length of the side 16-22 that joins those two corners. This is repeated for each side 16-22.

The calculations of the locations of the corners is dependent on, among other things, the distance between the relevant part of the measuring device 31 and the table facet 14, so it may not be possible with this embodiment to obtain absolute measurements of the lengths of the sides. However, very accurate relative measurements can be obtained, particularly if it is ensured that the axis of the measurement device 31 is aligned with the geometric centre of the table facet 14.

The lengths of the sides are expressed as a sequence in a clockwise direction. The starting side for the sequence is not important. The lengths of the sides may instead be expressed as a sequence in an anti-clockwise direction.

If the table facet 14 is not exactly perpendicular to the relevant component of the measuring device 31, then the accuracy of the measurements of the lengths of the sides 16-22 of the table facet 14 may be compromised. Accordingly, the measuring device 31 includes either means for ensuring that the table facet 14 is correctly aligned, and thus will refrain from operating until there is alignment, or else is arranged to detect the angle and direction from the perpendicular that the table facet 14 is arranged at. In this latter case, the measuring device 31 or the computer 32 is arranged to use the detected deviation from perpendicular and the apparent lengths of the sides 16-22 to calculate the actual lengths of the sides 16-22 of the table facet 14.

In the above embodiments, the measurements are made fully automatically. Alternatively, the measurements could be made semi-automatically or fully manually, as follows.

In a further embodiment, the measuring device 31 includes a microscope (not shown). The measuring device 31 may include for example be the Ml 13 or the M213 microscope produced by ISOMA SA, 7, Chemin des Pinsons, CH-2500 Bienne 7, Switzerland. These microscopes include a support, constituting the support 30, which is movable in x and y directions in a plane perpendicular to the microscope. By suitable placement of the diamond 10, the support is movable in small increments in x and y directions in a plane parallel to the table facet 14. Under control of an operator, the support 30 is moved until a corner of the table facet 14 is centrally aligned with the microscope. The x and y coordinates of the support 30 the diamond 10 then are noted, either manually or automatically. The support 30 then is moved manually until the next corner of the table facet 14 is aligned with the microscope, when the x and y coordinates of the support again are noted. This is repeated until the locations of all of the corners of the table facet 14 have been determined. The locations of the corners then are used by the measuring device 31 or by the computer 32 to calculate the lengths of the sides 16-22 of the table facet 14. This calculation involves triangulation of the x and y coordinates at the ends of a side 16-22, i.e. two adjacent corners. This is repeated for each side 16- 22.

In another embodiment, a scale is etched onto an ocular forming part of a microscope (not shown). The scale takes the form of a fine grid. In this embodiment, the positions of the corners of the table facet 14 relative to intersections on the grid are identified manually. The ocular then is moved manually until it is aligned with one corner of the table facet 14. The position of the ocular at that position is noted, either manually or automatically. The position is reported to the computer 32, if the computer does not already have this information. The ocular then is moved until it is aligned with the next corner on the table facet 14, and the location is noted. This is repeated for each corner. The measuring device 31 or the computer 32 then is able to use the ocular location information to calculate the locations of the corners of the table facet 14. The measuring device 31 or the computer 32 then calculates the distances between adjacent corners, to determine the length of the side 16-22 that joins those two corners. This is repeated for each side 16-22.

The lengths of the sides 16-22 of the table facet 14 are fed from the measuring device 31 to the computer 32 once the measurement process is complete. Of course, if the computer 32 made the calculations, then it already has this information at the end of the measurement process. The computer is also provided with clarity, cut and weight measurements, if these are obtained.

To provide a fingerprint for the diamond 10, the computer 32 firstly sums the measured lengths of the sides 16-22 of the table facet 14, to provide a table facet circumference measurement. The computer 32 then divides the measured lengths of each side 16-22 of the table facet 14 in turn by the table facet circumference measurement, to provide a measure of the length of each side 16-22 expressed as a proportion of the sum of the lengths of all the sides. This information is provided as a data set and forms the whole of or part of the fingerprint for the diamond 10. The fingerprint is shown in Figure 3.

Referring to Figure 3, a fingerprint 40 is shown in template form. The template includes n side length fields 41a to 41 n. In this example twelve fields are shown. Since the diamond 10 has an octagonal table facet 14, only the first eight fields are filled with side length data, with the other four fields being empty. The fingerprint 40 also includes a colour field 42, a clarity field 43 and a weight field 44. The fingerprint 40 preferably also includes one or more photographs of the diamond 10, for instance photographs taken along the longitudinal axis of the diamond through the table facet 14. The fingerprint 40 may also include any other information potentially of interest.

The clarity field 43 includes an indication of the clarity, according to the following key:

which interfere with transparency.

Currently, clarity gradings may need to be made by a gemmologist, although this is expected to be automatable in the future.

The colour field 42 includes an indication of colour according to conventional nomenclature. Accordingly, the field includes a letter between D and Z. D, E and F denotes a colourless diamond. G, H, I and J denote nearly colourless diamonds. Letters higher than K denote more coloured diamonds. Colour can be measured automatically, for instance using the DC3000 Colorimeter produced by Sarin Technologies Limited, or may be measured by a gemmologist

The result is a fingerprint 40 which includes a measure of the length of each side 16-22 of the table facet 14 of the diamond 10 expressed as a fraction of the sum of the lengths, and includes some other identifying information. The fingerprint 40 in this example includes lengths expressed to six significant figures. The measurements will normally be expressed to as many significant figures as is possible having regard to the accuracy and resolution of the measuring device 31.

The computer 32 then stores the fingerprint 40 in memory, along with a unique identifier for the diamond 10 and any other relevant information, such as the origin and value of the diamond. The computer 32 is then operable to include the fingerprint 40 and the additional information in a database, which is shown at 50 in Figure 4.

Referring to Figure 4, the database 50 includes fingerprints and other information relating to many diamonds. The database 50 may be located locally to the computer 32. For maximum utility, though, the database 50 is located at some location where it is accessible by many users. Connection between the computer 32 and the database 50 may be made through the Internet.

A part of the contents of the database 50 is shown in Figure 5. Here, the database 50 is shown including first to fourth records 51a, 51b, 51c and 5 Id. Each record 51a to 5 Id includes a gem identifier number, an owner identifier number, and a fingerprint, like the fingerprint 40.

The identification of a gemstone will now be described with reference to Figures 4 and 5. The first stage is to obtain the fingerprint of the gemstone. To do this, the measuring device 31 is used, perhaps under control or with the assistance of the computer 32 as necessary. The fingerprint thus obtained is then fed to the database 50 as part of a query command.

On receiving a query command including a fingerprint, the database 50 conducts a search for records 51a to 51 d within it that have the same fingerprint. Since the fingerprint may not have the same side as the first side measurement, the database 50 offsets the received fingerprint a number of times and searches for matches with each offset. For instance, a fingerprint having eight side measurements is compared to records with no offset. Then the fingerprint is compared with an offset of one side. Here, the first side of the received fingerprint is compared to the second side of the fingerprints in the database 50, the second side of the received fingerprint is compared to the third side of fingerprints in the database, etc. The amount of offset is then incremented again, and another search carried out. This process is continued until the amount of offset is equal to the number of side measurements in the received fingerprint.

Alternatively, the database may be arranged so as to have the longest side of a fingerprint always as the first side measurement, so that offsetting and repeated searching is not necessary. In this case, suitable provision may be used to handle fingerprints in which two or more sides have the same longest length.

If the database 50 includes a record 51 having the same fingerprint as the received fingerprint, then it is assumed that the gemstone has been fingerprinted previously and is included in the database. The record having the same fingerprint then is returned from the database to the computer 32, so that the gem identifier and the owner identifier information is known by the operator of the computer 32 and can be used appropriately. The other information present in the fingerprint 40, such as any photographs, can be used to confirm the identity of the gemstone 10.

Depending on the accuracy afforded by the measuring device 31 used at a particular fingerprinting station, it is possible that there will be a small error in length measurements included in fingerprints in the database. As such, the database 50 may be arranged so as to search for close matches as well as identical fingerprints. Since the identity of the gemstone 10 can be confirmed using other information in the fingerprint 40, the database 50 may be arranged to search for fingerprints having length measurements which are similar, thereby providing a 'shortlist' of candidate gemstones. The actual gemstone can then be identified manually using the other information included with the fingerprint 40.

Furthermore, the database 50 may be arranged so as to search for records which have a certain number, for example four, of sequential matching length measurements. This would also allow gemstones which had been modified slightly, for example by having a face adjoining the table facet 14 ground down slightly, to be identified since the length measurements relating to the unmodified sides would be unchanged. In this instance though the circumference of the table facet 14 would have been modified slightly, so it may be possible to identify such gemstones from their fingerprint only if a slightly reduced resolution is used by the database 50 in the search.

Depending on the resolutions afforded by the measuring device 31 used at a particular fingerprinting station, it is possible that some records in the database 50 will be at a higher resolution to other records. In this event, the database 50 is arranged to conduct comparisons with records at a resolution which is the lower of the resolution of the received fingerprint and the resolution of the database record 51.

The information in the fields 42, 43 and 44 of the records 51 can be used to distinguish between two gemstones which otherwise have the same or closely similar fingerprints. There are many applications for this invention. For instance, a dealer could fingerprint a gemstone before sale. If the purchaser then later wanted to return the gemstone for some reason, the dealer would be able to identify whether it was the same gemstone by determining its fingerprint and comparing it to the fingerprint made before the sale. Previously, it has not been possible for dealers to identify diamonds other than perhaps through the use of photographs and physical inspection, or unreliable measures such as clarity, cut and colour.

The trade in stolen gemstones is a significant international problem. Using the invention, it is possible for gemstones to be fingerprinted and their details stored in a central database. If the database is provided with information identifying trades of the gemstones, then the database 50 can be used to identify the current owner of a given gemstone. If thefts are recorded on the database, then a gemstone which is stolen can be identified as such from its fingerprint. It would be necessary for the gemstone to be re-cut before it would stop it being possible for it to be identified from its fingerprint.

The scope of the invention is not limited by the above-described embodiments, which are merely illustrative, but is limited only by the appended claims.

Claims

1. Apparatus (31, 32) for providing identification information relating to a gemstone (10), the apparatus comprising: means (31) for obtaining a measurement in absolute or relative terms of the length of each of plural sides of a table facet (14) of a gemstone, and means (32) arranged automatically for using the plural measurements to provide a fingerprint for the gemstone.

2. Apparatus as claimed in claim 1, in which the fingerprint includes a measure of the length of a given side of the table facet as a proportion of the total of the lengths of all the sides of the table facet.

3. Apparatus as claimed in either preceding claim, in which the fingerprint includes a measure of the length of each side of the table facet.

4. Apparatus as claimed in any preceding claim, in which the measurement obtaining means comprises means for measuring automatically the lengths of the sides of the table facet.