Gem sorting

Abstract

An apparatus and method for sorting gemstones from a batch of gemstones are disclosed. The apparatus comprises one or more measurement locations, each measurement location comprising at least one measurement device configured to measure one or more characteristics of a gemstone. A continuously movable surface supports the gemstone thereon and transports the gemstone to one or more measurement locations. The separating device separates the gemstones from each other as they are transported to the one or more measurement positions on the movable surface. The position trigger includes a sensor at a sensor position for identifying when a gemstone passes through the sensor position. The controller receives the signal from the position trigger, records the position of the movable surface upon receipt of the signal, and tracks subsequent positions of the gemstones by monitoring movement of the movable surface so that measurements of one or more characteristics of each gemstone can be associated with the position of the respective gemstone on the movable surface. Specific indicia in the luminescent properties of the gemstone can be used to identify the properties of the stone.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method and apparatus for sorting gemstones. In particular, but not exclusively, the present invention relates to a method and apparatus for sorting diamonds. BACKGROUND

[0002] Natural diamonds are stones from nature, consisting only of diamond formed over a long period of geological time. Synthetic diamonds are man-made stones manufactured by industrial processes such as HPHT (high pressure high temperature) and CVD (chemical vapour deposition).

[0003] Synthetic diamonds have a wide range of industrial applications, but currently only make up a small part of the gemstone industry and do not have the high value associated with natural diamonds of similar colour and quality. When in an unpolished state, synthetic diamonds can be relatively easily distinguished from natural diamonds, however, once polished and cut into gemstones, it can be more difficult to identify whether a stone is synthetic.

[0004] Advanced screening instruments, such as DiamondSure™ and DiamondView™, are available to detect whether a stone is natural or synthetic. Typically, such screening involves measuring the way light is absorbed by or emitted from a diamond. Prior to screening commencing, the stone to be detected is typically placed in a precise position on a measurement surface or holder with the "table down". In this context, the "table" is the largest central facet of the crown (the upper half of the stone when mounted).

[0005] In addition to screening larger individual stones, there is also a need to screen large quantities of smaller diamonds, including stones sometimes referred to as "micros". A micro is a trading term which does not have a defined size range but in practice can be taken to mean a stone of less than about 0.2 carats (20 points) and typically (but not necessarily) greater than about 0.01 or 0.02 carats. Due to their small size, micro diamonds are typically sold in packs or batches. As a pack can contain hundreds of stones, synthetic diamonds and non-diamond material can be mixed in with the natural stones.

[0006] Screening micro diamond stones can be very time consuming as each stone must be individually detected and therefore individually placed in the correct orientation. WO2012 / 146913 discloses an apparatus for orientating gemstones in which discrete gemstones are provided onto a travel path having a pair of opposing oscillating walls. As the gemstones travel along the path, the walls urge the gemstones into their most stable orientation (i.e. table down). Once in this orientation, individual stones can be picked up from the travel path and transported to a detection station by a vacuum bar.

[0007] Figure 1is a view of the apparatus 1 described in WO2012 / 146913 for orientating gemstones. Small diamond stones are poured into a hopper 2 and pass through a pair of rollers 6. The speed of the rollers 6 is configured to separate the stones so that they pass one at a time. The stones are then directed onto a rotating disc 10 as shown in Figure 2 The disc 10 rotates clockwise and provides a circular path of travel for the stones through a stirrer 13. The stirrer 13 comprises a pair of opposed parallel vertical walls 11 which form a semi-circular channel 12. The walls 11 are connected to an oscillator 15 which oscillates these walls at a sufficient amplitude and frequency that they collide with the stones on the path of travel. A pair of walls 14 oscillate along the radius of the rotating disc 10.

[0008] The level of impact of the walls 11 is chosen so that it is sufficient to knock the stones off their pavilion facets but not to knock the stones off their most stable table facets. Eventually the stones fall with their table facets facing downwards and are aligned when they reach a handling area 7. An orientation checking device 9 checks each stone to see if it is table facet down by recording a side profile image of the stone using a camera 16. If the stone is found to be correctly oriented, it is collected by a handler (which includes the swing arm 3 and vacuum bar 4) and is transported to a synthesis detection device 17. If the stone is found to be incorrectly oriented, it is transported back to the oscillating channel 12 to be re-oriented. The process continues until all of the stones in the small diamond are oriented, detected and distributed into the appropriate collection bin 5 via a chute 8.

[0009] While Figure 1 the apparatus of WO2015 / 024979 accelerates the process of orientation and detection, it still requires the disc 10 to be stopped from rotating whenever an oriented stone is ready to be picked up by the vacuum bar 4. Furthermore, conventional detection devices and methods generally fail to identify whether a stone is natural or synthetic at the end. If end identification is not available, the gemstone must be "sent out" for further detection. Further detection typically requires the use of more complex methods, such as photoluminescence or Raman spectroscopy and / or one or more different devices. For very small gemstones, further detection can not be economically feasible. WO2015 / 024979 describes a system which attempts to solve this problem by using Raman spectroscopy to distinguish between diamond and non-diamond materials on a rotating glass disc and subsequently performing a measurement of the intensity of ultraviolet transmission through the stones which contain diamond material. SUMMARY

[0010] According to one aspect of the application, there is provided an apparatus for sorting gemstones from a batch of gemstones. The apparatus comprises one or more measurement locations, each comprising at least one measurement device configured to measure one or more properties of a gemstone. A continuously moveable surface supports the gemstones thereon and transports the gemstones to the one or more measurement locations. Separation devices separate the gemstones from one another as they are transported on the moveable surface to the one or more measurement locations. A position trigger comprises a sensor at a sensor location for identifying when a gemstone passes the sensor location. A controller receives a signal from the position trigger, records the position of the moveable surface upon receipt of the signal, and tracks subsequent positions of the gemstone by monitoring movement of the moveable surface, so that a measured value of the one or more properties of each gemstone can be associated with the position of the respective gemstone on the moveable surface. Particular indicia in the luminescence properties of the gemstone can be used to identify the properties of the stone.

[0011] According to another aspect of the application, there is provided a method of sorting gemstones from a batch of gemstones. The method comprises the steps of: transporting the gemstones to one or more measurement locations on a continuously moveable surface; separating the gemstones from one another as they are transported on the moveable surface to the one or more measurement locations; identifying each instance when a gemstone passes a sensor location after the gemstones have been separated, associating the gemstone with the position of the moveable surface at that time, and tracking subsequent positions of the gemstone by monitoring movement of the moveable surface; measuring one or more properties of the gemstones at the one or more measurement locations; and associating each measured value of the one or more properties of each gemstone with the position of the respective gemstone on the moveable surface.

[0012] The one or more properties can comprise one or more particular indicia in the luminescence properties of the gemstone. These indicia can include the wavelength and decay time of the luminescence. Particular combinations of indicia can provide an indication as to whether the stone contains diamond material, and if so, whether it is natural or synthetic or requires further detection.

[0013] Further aspects and preferred features are set out in the dependent claims and the following description. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a perspective view of a known apparatus for orientating gemstones;

[0015] Figure 2 is Figure 1 is a plan view of the apparatus with some components removed for clarity;

[0016] Figure 3 is a perspective view of an apparatus for orientating gemstones according to the application;

[0017] Figure 4 isFigure 3 A front view of the device;

[0018] Figure 5 yes Figure 3 A top view of the device;

[0019] Figure 6 yes Figure 3 Another top view of the device showing the orientation device;

[0020] Figure 7 yes Figure 3 a top view of the apparatus showing the direction of travel of a batch of gemstones; and

[0021] Figure 8 is a flow chart illustrating a method of sorting gemstones from a batch of gemstones. DETAILED DESCRIPTION

[0022] Now refer to Figures 3 to 7 An apparatus 101 for sorting gemstones (e.g., diamonds) from a batch of gemstones is described. The gemstones to be sorted typically comprise polished stones (whether brilliant cut or fancy cut). Reference will be made to Figure 8 Describe a method of sorting gemstones from a batch.

[0023] Apparatus 101 includes one or more measurement locations 110a, 110b, each including at least one measuring device configured to measure one or more characteristics of a gemstone, and a movable surface 103 for supporting gemstones thereon and for transporting the gemstones to the one or more measurement locations 110a, 110b. Apparatus 101 also includes separation devices 107, 108 for separating the gemstones from one another as they are transported on movable surface 103 to the one or more measurement locations 110a, 110b. Once the gemstones are separated, each passes through a position trigger, such as a laser screen 109. The position of the gemstone on movable surface 103 then becomes known, and the subsequent position of the gemstone can be tracked by monitoring its movement. This enables the measurements at the one or more measurement locations 110a, 110b to be correlated with the known position of the gemstone on movable surface 103.

[0024] exist Figures 3 to 7 In the embodiment of the invention, the movable surface comprises a rotatable disk 103 having a generally flat upper surface on which gemstones can be transported. Disk 103 is rotated by a motor (not shown) at a rotational speed of between approximately 9 degrees per second and 13.5 degrees per second, depending on the size of the gemstone being transported. The rotational speed of disk 103 can be controlled via a controller (optionally including a screen 117).

[0025] existFigures 3 to 7 In the example shown, the surface of the rotatable disk 103 is manufactured to be flat, within a tolerance of 50 microns. The disk 103 is also hard black anodized to make it wear-resistant and to allow measurements to be taken at one or more measurement locations in a substantially dark environment, as will be discussed further below. To this end, the disk 103 is also provided with a cover 104 that defines a viewing port through which the gemstone being transported on the disk 103 can be observed.

[0026] like Figure 3 As best shown in FIG. 1 , the apparatus 101 includes a hopper 102 for receiving a batch of gemstones and delivering them onto the surface of a rotatable disk 103, near the center of the disk 103. The hopper 102 may be a reference Figure 1 and Figure 2 Hopper 102 includes two counter-rotating foam rollers (not shown) that control the flow of gemstones onto rotatable disk 103. The speed of the rollers can be controlled via controller 117 and can be varied depending on the size and shape of the gemstones being sorted. In this example, hopper 102 has a minimum capacity of approximately 500 carats and is typically suitable for gemstones ranging from approximately 0.3 to 30 points.

[0027] exist Figures 3 to 7 In the embodiment and as Figure 5 As best shown in FIG. 1 , the apparatus 101 further comprises an orienting means for orienting the gemstones as they are transported on the central portion of the rotatable disc 103 so that the gemstones are oriented in their most stable configuration before being separated from one another. In this example, the orienting means comprises the device described above with reference to FIG. Figure 1 and Figure 2 An agitator 113 of the type described (although the agitator 113 lacks a vacuum wand). The agitator 113 comprises a pair of opposed parallel vertical walls 111 forming a generally semicircular channel 112. The gemstones are guided by the rotatable disc 103 into the semicircular channel 112.

[0028] The walls 111 are oscillated by an oscillator 115 so that a central portion 114 of the pair of walls 111 oscillates along a radius of the rotatable disk 103 (i.e., generally transverse to the direction of travel of the gemstone). It will be appreciated that relative lateral movement of the pair of walls 111 is minimal at the entrance and exit portions of the semicircular channel 112.

[0029] The walls 111 oscillate with sufficient amplitude and frequency to cause them to collide with the stones present on the surface of the rotatable disc 103, knocking the stones into their most stable configuration (i.e. their position of lowest potential energy). For the vast majority of cut stones, the most stable configuration will be table down. The level of impact of the walls 111 is chosen so that once a stone has fallen into its most stable plane, it will no longer be knocked over and will remain in its most stable configuration. In other words, the level of impact of the agitator 113 is carefully chosen so as to be sufficient to knock a stone off its pavilion, for example, but not sufficient to knock a stone off its table.

[0030] The length of the oscillating walls 111 is chosen so that all the stones will be oriented into their most stable configuration as they exit the agitator 113. Stones that have been oriented into their most stable configuration are easier to separate, measure and distribute as they are more predictable to handle.

[0031] The apparatus 101 of this embodiment comprises separation means 107, 108 for separating the stones from each other as they are transported on the rotatable disc 103 to one or more measurement locations 110a, 110b. In this embodiment, the separation means comprise a series of fixed cams 107 and movable cams 108. Figures 3 to 7 In the illustrated embodiment, the separation means comprise a series of fixed cams 107 and movable cams 108. As the disc 103 rotates, the stones come into contact with the cams 107. The fixed cams 107 are inclined relative to the direction of travel of the horizontal surface of the disc 103 so that the stones are pushed towards the outer regions of the disc 103 which move faster than the central regions of the disc 103. This therefore increases the spacing between the stones. The successive cam 107 surfaces can be inclined at successively smaller angles to the direction of travel of the horizontal surface of the rotatable disc 103 and / or the cams 107 can comprise curved surfaces in order to optimise the rate at which the stones move laterally across the moving surface. In this example, there are three fixed cams 107, but it will be appreciated that fewer or more cams 107 can be employed as desired.

[0032] As each cam 107 successively pushes the stones further away from the central regions of the rotatable disc 103, this naturally causes the stones to separate from each other as their average angular position relative to the disc 103 is maintained while their distance from the centre of the rotatable disc 103 increases.

[0033] Figures 3 to 7Embodiments include a moveable cam 108, which the stones come into contact with after they have passed the fixed cam 107. The angle of the moveable cam 108 can be adjusted depending on the size and shape of the stones to be sorted. The moveable cam 108 is used to provide the final separation between the stones. In this way, once the stones have passed the moveable cam 108, a stream of separated stones is provided on the surface of the rotatable disc 103. Although only one moveable cam 108 is provided in this example, it will be appreciated that further moveable cams can be provided as required. Additionally, the order of the fixed and moveable cams can be varied.

[0034] As Figure 5 shown, the apparatus 101 also includes a position trigger 109. This is located at a sensor position on the disc 103, through which the stones pass after they have been separated, so that they do not need to come into contact with any other items as they continue to travel on the disc 103. In this embodiment, the position trigger comprises a sensor 109, such as a laser curtain, at the sensor position. The controller 117 is configured to receive a signal from the sensor each time a stone passes the sensor. The passage of the stone through the sensor is correlated to the angular position of the disc 103 at that time, and the position of each stone can subsequently be tracked by knowing the angular position of the disc 103.

[0035] The apparatus 101 also includes one or more measurement positions 110a, 110b, each comprising at least one measurement device configured to measure one or more properties of the stones. In Figures 3 to 7 the embodiment shown, there are two measurement positions 110a, 110b, as will be described in more detail below. Each measurement position 110a, 110b comprises a measurement device or unit (not shown here). As the disc 103 rotates, the separated stones pass through the measurement positions 110a, 110b one at a time. Each measurement device measures the properties of an individual stone as it moves past, i.e. the rotatable disc 103 does not stop as the stones reach the measurement positions 110a, 110b, and all measurements are made while the stones are moving. This means that the disc 103 can be continuously rotated, and can rely on the correlation of stone position to angular position of the disc 103. The measured values of the properties of the stones are transmitted from the measurement devices to the controller 117. Further details of the measurements are detailed below.

[0036] The apparatus 101 also includes a plurality of dispensing positions, in Figure 3 , Figure 4 and Figure 5In the example shown, the allocation locations comprise collection bins 105. There are five collection bins 105 in this example, although it will be appreciated that the number of bins 105 can be reduced or increased as required. Associated with each collection bin 105 is an allocation mechanism 106, such as a push rod or a spike foam wheel, which is operated via a solenoid 116 and is configured to push a gemstone off the outer surface of the rotatable disc 103 and cause the gemstone to be allocated to the relevant collection bin 105. The five collection bins 105 can be designated as follows Figure 3 , Figure 4 and Figure 5 as shown in

[0037] 1. Non-Diamond (for gemstones composed of simulants, such as cubic zirconia)

[0038] 2. Synthetic (for synthetic diamonds, such as diamonds grown by CVD or HPHT)

[0039] 3. Natural (for natural diamonds)

[0040] 4. Submission (for gemstones for which the properties have not yet been finally determined)

[0041] 5. Clear (for use when the gemstone apparatus needs to be quickly emptied).

[0042] It will be appreciated that the order of the collection bins 105 described above is provided by way of example only, and that other names and orders can be envisaged.

[0043] Since the time at which a particular gemstone passes a sensor location and the rotational speed of the disc 103 are known, the controller 117 can accurately predict when a particular gemstone will pass one or more measurement locations 110a, 110b. Accordingly, the measured values of one or more properties of a particular gemstone received by the controller 117 can be associated by the controller 117 with the location of the particular gemstone on the rotatable disc 103. From the received measured values, the controller 117 can determine, for example, whether the particular gemstone is a natural diamond, a synthetic diamond or a non-diamond. When the particular gemstone reaches a location adjacent to the appropriate collection bin 105, the controller 117 activates the appropriate allocation mechanism 106 to allocate the gemstone into the correct bin 105.

[0044] The use of the gemstone apparatus 100 in use will now be described. Figures 3 to 7Device 101. A batch of gemstones is deposited into a hopper 102 and individually conveyed onto the surface of the inner area of ​​a rotating disk 103 via a foam roller within hopper 102. As disk 103 rotates, the gemstones are drawn into a semicircular channel 112 of an agitator 113, where they are oriented with the tabletop facing downward. Upon exiting agitator 113, the gemstones are brought by rotating disk 103 into contact with a series of fixed cam surfaces 107 and movable cam surfaces 108, deflecting them toward the outer area of ​​rotatable disk 103, separating from one another in the process. The separated stream of gemstones is then conveyed by rotatable disk 103 to a sensor location, where the individual gemstones pass one at a time through a sensor (laser curtain) 109.

[0045] The separated gemstones are then transported by the rotatable disk 103 through two successive measurement locations 110a, 110b, so that at each location 110a, 110b, a separate and distinct measurement value is obtained for each gemstone. These measurements are transmitted to the controller 117 and associated with the gemstone to which they relate. The controller 117 tracks the exact location of each measured gemstone and activates the appropriate dispensing mechanism 106 to dispense the measured gemstone into the appropriate collection bin 105. The appropriate bin 105 is determined by the controller 117 based on the measured characteristics of the gemstone.

[0046] Therefore, if Figure 7 As shown, the gemstones deposited by the hopper 102 onto the inner area of ​​the rotating disk 103 generally follow a path of travel as indicated by arrow A and ultimately reach the outermost area of ​​the disk 103 where they are distributed to the collection bin 105. It will be appreciated that as the batch of gemstones is gradually deposited onto the rotatable disk 103, the orientation, separation, measurement, and distribution of the gemstones from the batch can be performed simultaneously. In other words, the first gemstone from the batch to be deposited onto the disk 103 can be distributed while subsequent gemstones from the same batch are being oriented, separated, or measured. In this way, the entire batch of gemstones can be sorted without stopping the rotation of the disk 103, thereby Figures 3 to 7 The apparatus 101 is capable of sorting a batch of gemstones into appropriate collection bins 105 at a rate of approximately at least 3,600 gemstones per hour.

[0047] It should be noted that in the event that the controller 117 determines that a gemstone was not measured correctly or at all, the gemstone may not be dispensed into the bin 105, but may instead remain on the surface of the rotating disk 103. The gemstone may then be "recirculated" by being deflected back to an appropriate interior area of ​​the disk 103 so that it can again pass the sensor and measurement locations 110a, 110b.

[0048] As mentioned above, Figures 3 to 7The apparatus 101 comprises two measurement locations 110a, 110b, each comprising at least one measurement device configured to measure one or more properties of a gemstone. The separated gemstones are transported through the measurement locations 110a, 110b on the moving surface of the rotatable disc 103 one at a time. As mentioned above, the measurements at the measurement locations 110a, 110b are performed in a substantially dark environment.

[0049] As the gemstones on the disc 103 are not in contact with any other part of the apparatus after passing through the sensor location, the controller 117 knows the position of each gemstone accurately, and so the controller 117 can accurately determine when a particular gemstone reaches each of the two measurement locations 110a, 110b. Therefore, the measurements made at each measurement location 110a, 110b can be associated with the particular gemstone to which they relate by the controller 117. Furthermore, as the measurements made do not require physical contact with the gemstone, the controller 117 can also accurately determine when a particular gemstone reaches each collection bin 105.

[0050] In this embodiment, the first measurement location 110a comprises a luminescence measurement unit. The luminescence measurement unit comprises a source of electromagnetic radiation of a wavelength of substantially 225 nanometres (nm) or less (i.e. ultraviolet or UV light) for exciting the gemstone, and a light detection device or camera for capturing any visible light emitted by the gemstone when excited by the electromagnetic radiation.

[0051] The controller 117 synchronises the operation of the UV light and the camera, taking into account any offset values applicable to the camera. The light used in this embodiment is a microsecond Xenon flash lamp, such as a Perkin Elmer FX-4402, filtered to provide the above-mentioned diamond bandgap excitation at wavelengths less than 225 nm. The camera in this example uses a complementary metal-oxide-semiconductor (CMOS) sensor, such as a Sony IMX174. As the controller 117 knows the position of a particular gemstone on the rotatable disc 103, the excitation pulse and camera operation can be triggered to coincide with the particular gemstone reaching the excitation and detection region of the luminescence measurement unit 110a.

[0052] The camera can be configured with a delay by the controller system 117 so that it is able to capture visible light only during a time window that begins after the excitation pulse produced by the lamp has ended. Thus, the camera can capture phosphorescence as well as fluorescence. Since in most cases the time scale of fluorescence decay is shorter than the time scale of the excitation source used here, it will be appreciated that fluorescence is a type of luminescence that is characterized by being produced only during the ultraviolet excitation of the gemstone. Thus, once the excitation is terminated, any fluorescence produced during the excitation will decay very rapidly. Phosphorescence, on the other hand, is a type of luminescence that persists upon removal of the excitation but then decays on a longer time scale. The phosphorescence can persist for a period of time after the excitation is terminated or it can decay within milliseconds of the end of the excitation pulse. The process of delaying the capture of visible light until the excitation pulse has ended and any fluorescence has decayed ensures that fluorescence is "filtered out" and does not obscure any phosphorescence that is emitted after the end of the excitation pulse. The end of the time window used to capture the visible light emitted by the gemstone can also be carefully chosen to select the decay time of the fluorescence and / or phosphorescence that is captured. In this way, the apparatus can capture visible light emissions that might otherwise be missed.

[0053] A method of determining whether a gemstone is natural or synthetic by observing certain specific signatures in the luminescence properties of the gemstone will now be described. The method can comprise irradiating the gemstone with a plurality of excitation pulses of electromagnetic radiation, and during and / or after each excitation pulse, detecting light emitted by the diamond in at least one time window having a predetermined temporal relationship to the excitation pulse, so as to obtain luminescence data. The or each time window is selected to include luminescence having a decay time characteristic of one or more signatures. The luminescence data associated with all of the pulses can be combined and then analysed to determine the presence or absence of the one or more signatures. The pulses and detections all occur while the stone is passing through the measurement location 110a.

[0054] One of the signatures can be a blue fast phosphorescence signature comprising luminescence with a wavelength band peaking at about 450 nm and a decay time of less than about 80 milliseconds (ms). Detection of this can involve detecting for a luminescence band at about 450 nm peaking, in a time window that begins at or after the end of the excitation pulse and ends about 80 milliseconds after the end of the associated excitation pulse. The presence of the blue fast phosphorescence signature can be a signature of the diamond being a natural Type Ila or Type la diamond.

[0055] One of the indicia can be a turquoise slow phosphorescence indicium comprising luminescence having a wavelength peaking at about 480 nm and a decay time greater than 80 milliseconds. Detection of this can involve detection for a band of luminescence centered at about 480 nm in a time window beginning about 80 milliseconds after the end of the associated excitation pulse. The time window can end at about 500 ms after the end of the associated excitation pulse (especially in the case of multiple excitation pulses. The presence of the turquoise slow phosphorescence indicium can be an indicium that the diamond is a Type I lb diamond.

[0056] One of the indicia can be a green slow phosphorescence indicium comprising luminescence having a wavelength between about 530 nm and about 550 nm and a decay time greater than 80 milliseconds. Detection of this indicium can involve detection for a band of luminescence between about 530 nm and about 550 nm in a time window beginning about 80 milliseconds after the end of the associated excitation pulse. Again, the time window can end at about 500 ms after the end of the associated excitation pulse. The presence of the green slow phosphorescence indicium can be an indicium that the diamond should be submitted for further detection.

[0057] One of the indicia can be a "missing" indicium, where little or no luminescence is detected after the end of the excitation pulse. The presence of this indicium indicates that the diamond should be submitted for further detection.

[0058] One of the indicia can be an orange long-lived fluorescence indicium comprising luminescence having a wavelength between about 535 nm and about 600 nm and a decay time less than 1 millisecond. The presence of the orange long-lived fluorescence indicium can indicate that the diamond should be submitted for further detection.

[0059] One of the indicia can be a red phosphorescence indicium comprising luminescence having a wavelength between about 575 nm and about 690 nm and a decay time greater than 1 millisecond. The presence of the red phosphorescence indicium can indicate that the diamond should be submitted for further detection.

[0060] One of the indicia can be a weak green fluorescence indicium having a wavelength of about 510 nm. Detection of the weak green fluorescence indicium can involve detection in a time window synchronized with the excitation pulse, as the fluorescence is only produced during excitation of the gemstone and decays very rapidly once excitation is terminated. As before, the ends of the time window will be carefully chosen to coincide with the ends of the pulse, so that any phosphorescence emitted after the gemstone excitation has terminated (which might otherwise obscure detection of the weak fluorescence) will be "filtered out". The presence of the weak green fluorescence indicium can indicate that the diamond should be submitted for further detection.

[0061] From the foregoing, it can be appreciated that the measurement of fluorescence and / or phosphorescence and the presence of certain signatures can allow the controller to identify a particular gemstone as being of the natural type IIa, Ia or IIb diamond. However, for example, the presence of a green slow phosphorescence signature or a "missing" signature does not allow the gemstone to be identified and, in the absence of further information, any gemstone which produces a green slow phosphorescence signature or a "missing" signature upon ultraviolet excitation can need to be "referred" for further detection using alternative equipment.

[0062] Advantageously, Figures 3 to 7 The apparatus of Figure 1 comprises a second measurement location 110b configured to measure one or more properties of the gemstone. In this embodiment, the second measurement location 110b comprises a photoluminescence (PL) measurement unit.

[0063] The gemstone is subjected to laser excitation at about 450 nm by the PL measurement unit on the surface of the rotatable disc 103, with the laser having a 3 mm diameter beam and being at an angle of 41 ° to the vertical. Detection of the PL is performed using a micro-spectrometer over a 3 mm diameter measurement area, using a single lens system at 0° to the vertical. The controller 117 knows precisely the position of the gemstone on the rotatable disc 103 and so is used to trigger the PL measurement when the gemstone enters the PL measurement unit. The excitation laser, spectrometer and collection optics are optimised to acquire high quality (high signal to noise ratio) PL spectra from a moving gemstone in the time frame of about 150 milliseconds (the gemstone needs about 150 milliseconds to pass through the 3 mm diameter PL measurement area).

[0064] Once the PL spectrum is obtained, it is conveyed to the controller 117 and analysed. Based on the presence of the Raman line and / or the detection of a nickel (Ni) related PL feature, a determination is made about the gemstone being detected and the gemstone is identified. The determination can be made based on the results received from the first measurement location and the second measurement location 110a, 110b for the gemstone being detected and so can not be made until the gemstone has passed through both measurement locations 110a, 110b.

[0065] The presence of a sharp single Raman line in the spectrum centred at about 1332 cm -1 The presence of a sharp single Raman line in the spectrum centred at about 1332 cm -1 The presence of a sharp single Raman line in the spectrum centred at about 1332 cm-1 The absence of a Raman line would indicate that the gem being tested is not a diamond. The detection algorithm used by the controller 117 completes the determination before the next gem in the separate gem stream enters the PL measurement area.

[0066] Thus, a gem that displays green slow phosphorescence during detection at the first measurement location 110a (i.e. the luminescence measurement unit) can be identified as a natural or synthetic diamond in subsequent detection at the second measurement location 110b (i.e. the PL measurement unit). Without this capability, as described above, green phosphorescent natural diamonds can be incorrectly classified as synthetic diamonds, or can be “referred” for further detection by another device, which would result in a higher “referral” rate.

[0067] Thus, Figures 3 to 7 The apparatus 101 can utilize the combination of different indicia detected at the two measurement locations 110a, 110b to identify the gem, thereby significantly reducing the number of gems in the batch that need to be further detected by an alternative apparatus in order to be identified. Any gem that is not reliably identified after passing through the two measurement locations 110a, 110b will typically be allocated to a collection bin 105 designated as “referral”. These gems can then be further detected.

[0068] Table 1 shows how the combination of different indicia detected at the two measurement locations 110a, 110b of the apparatus 101 shown in Figures 3 to 7 Table 1 can be used to identify individual gems. The stones can then be allocated to the appropriate collection bin 105.

[0069] Starting from the left, the contents of the first column (Raman) of Table 1 indicate whether there is (“1332”) or is not (“non-1332”) a sharp, single Raman line centered at about 1332 cm -1 in the PL spectrum. As described above, in this example, the PL spectrum is taken at the second measurement location 110b.

[0070] The contents of the second and third columns of Table 1 (Phosphor 1, Phosphor 2) indicate the presence or absence of certain phosphorescence markers discussed above. As noted above, in this example, phosphorescence is measured at the first measurement location 110a. The entries in the second column of "blue" and "non-blue" ("Phosphor 1") indicate the presence and absence, respectively, of a blue fast phosphorescence marker, which includes luminescence in a wavelength band peaking at about 450 nm and having a decay time of less than about 80 ms after the end of the associated excitation pulse. The third column ("Phosphor 2") indicates the presence and color of a slow phosphorescence having a decay time greater than about 80 ms. The entry "turquoise" in the third column indicates that the slow phosphorescence marker includes luminescence in a wavelength band peaking at about 450 nm and having a decay time greater than about 80 ms after the end of the associated excitation pulse, as described above. The entry "non-turquoise" in the third column indicates the absence of the turquoise slow phosphorescence marker. It will be appreciated that detection of these two markers includes detecting phosphorescence in two separate time windows (i.e., < 80 ms after the end of the excitation pulse and > 80 ms after the end of the excitation pulse).

[0071] The contents of the fourth column of Table 1 (Fluorescence) indicate whether the weak green fluorescence marker having a wavelength of about 510 nm discussed above is present (weak green) or absent (non-weak green). Detection of the weak green fluorescence marker can include detection in a time window synchronized with the excitation pulse (i.e., detection of the marker during excitation of the stone). As noted above, in this example, fluorescence is measured at the first measurement location 110a.

[0072] The contents of the fifth column of Table 1 (PL) indicate whether a particular Ni-related PL feature (having a 787 nm feature in the absence of a stronger 793 nm feature) is present in the PL spectrum. As noted above, in this example, the PL spectrum is acquired at the second measurement location 110b.

[0073] A dash in any column means that any result is possible, and this measurement should be ignored. For example, as shown in the first row of Table 1, the presence of a sharp, single Raman line centered at about 1332 cm -1 in the PL spectrum (non-1332) can identify the stone to be tested as a simulant (i.e., a non-diamond, such as cubic zirconia, for example) regardless of the presence or absence of other markers.

[0074] Table 1

[0075]

[0076] As can be seen from Table 1, most of the gemstones will be identified as natural diamond, a simulant (i.e. not diamond) or an HPHT synthetic. Only in a few cases will the gemstone be sent for further testing. For example, as shown in row 6 of Table 1, in the case where the Raman line at about 1332 cm -1 in the PL spectrum and the turquoise slow phosphor signature are both present, but the blue fast phosphor signature is not present, and the weak green fluorescence signature and the Ni-related PL feature at 787 nm in the PL spectrum are both not present, the gemstone under test will be assigned to the "send-out" collection bin.

[0077] Reference Figure 8 A method of sorting gemstones from a batch of gemstones comprises the steps of:

[0078] Step 1 : transporting the gemstones to one or more measurement locations on a continuously moveable surface;

[0079] Step 2: separating the gemstones from each other as they are transported on the moveable surface to the one or more measurement locations;

[0080] Step 3: after the gemstones have been separated, identifying each instance of a gemstone passing a sensor location, correlating the gemstone with the position of the moveable surface at that time, and tracking the subsequent position of the gemstone by monitoring the movement of the moveable surface;

[0081] Step 4: measuring one or more properties of the gemstones at the one or more measurement locations; and

[0082] Step 5: correlating each measurement of the one or more properties of each gemstone with the position of the respective gemstone on the moveable surface.

[0083] Those skilled in the art will appreciate that various modifications can be made to the above described embodiments without departing from the scope of the present invention. For example, although the above described embodiments include two measurement locations 110a, 110b, other embodiments can include more than two measurement locations, each of which measures one or more properties of the gemstones. Alternatively, the measurement of more than one property of the gemstones can be made at a single measurement location.

[0084] Furthermore, although Table 1 above shows the detection of the phosphor signatures in two separate time windows, further time windows can be utilised to detect one or more further phosphor signatures, as described above.

[0085] Furthermore, it will be appreciated that the above identified signatures can be used as an indication of the type of gemstone even if the measurements are taken using different instruments.

Claims

1. An apparatus for sorting gemstones from a batch of gemstones, the apparatus comprising: one or more measurement locations, each of the measurement locations comprising at least one measurement device configured to measure one or more characteristics of the gemstone; a continuously movable surface for supporting a gemstone thereon and transporting the gemstone to the one or more measurement locations; a separating device for separating the gemstones from one another as they are transported on the movable surface to the one or more measurement locations; a position trigger comprising a sensor at a sensor location for identifying when a gemstone passes the sensor location; as well as a controller for receiving a signal from the position trigger, recording the position of the movable surface upon receipt of the signal, and tracking subsequent positions of the gemstones by monitoring movement of the movable surface so that measurements of one or more characteristics of each gemstone can be associated with the position of the corresponding gemstone on the movable surface.

2. Apparatus according to claim 1 further comprising orienting means for orienting the gemstones as they are conveyed to the separation means such that the gemstones are oriented in their most stable configuration before being separated from one another.

3. The device according to claim 1 or 2, wherein: Each measuring device is configured to measure the one or more characteristics of the gemstone as it moves past a measurement location on the movable surface.

4. The apparatus according to any one of the preceding claims, wherein The separating device comprises a series of cam surfaces located above and in close proximity to the movable surface, each of the cam surfaces being inclined relative to the direction of travel of the movable surface so that the gemstone is successively pushed away from its initial path of travel by successive cams in the series.

5. Apparatus according to any one of the preceding claims, wherein The movable surface comprises a rotatable disc.

6. Apparatus according to any one of the preceding claims, wherein The removable surface has a dark finish.

7. Apparatus according to any preceding claim, further comprising a plurality of dispensing locations, each location comprising a collection bin and an associated dispensing mechanism.

8. The apparatus according to claim 7, wherein The associated dispensing mechanism includes one of a push rod and a spiked foam wheel.

9. The apparatus according to claims 2 to 8, wherein The orienting device comprises a pair of opposed parallel vertical walls forming a generally semicircular channel, the pair of walls being oscillated by an oscillator so that a central portion of the pair of walls oscillates in a direction generally transverse to the direction of travel of the gemstone.

10. Apparatus according to any preceding claim, comprising two measuring locations.

11. The apparatus according to claim 10, wherein The first measurement location comprises a first measurement device configured to measure luminescence emitted by the gemstone after being excited by an ultraviolet source.

12. The apparatus according to claim 11, wherein The first measurement device is configured to measure luminescence in a plurality of different time windows following an excitation pulse from the ultraviolet source.

13. The apparatus according to claim 12, wherein The different time windows include one or more of the following: a window synchronized with the start and end of the pulse to measure fluorescence; a window that begins at the end of the pulse and ends approximately 80 ms later to measure fast phosphorescence; as well as A window for measuring slow phosphorescence begins approximately 80 ms after the end of a pulse and ends before the following pulse.

14. The apparatus of claim 11, 12 or 13, wherein: The first measuring device is configured to measure a wavelength of the luminescence.

15. The apparatus according to any one of claims 11 to 14, wherein The second measurement location comprises a measurement device configured to measure photoluminescence emitted by the gemstone following laser excitation.

16. Apparatus according to claims 5 to 15, further comprising a hopper configured to receive a supply of gemstones and deliver the supply of gemstones onto the surface of the rotatable disc.

17. The apparatus according to claims 5 to 16, wherein Gemstones are transported onto the inner region of the rotatable disc and are subsequently distributed to collection bins located near the outermost region of the rotatable disc according to their measured properties.

18. A method for sorting gemstones from a batch of gemstones, the method comprising the steps of: transporting the gemstone to one or more measuring locations on a continuously movable surface; separating the gemstones from one another as they are transported on a movable surface to one or more measurement locations; After the gemstone is separated, identifying each time the gemstone passes a sensor location, associating the gemstone with the position of the movable surface at that time, and tracking the subsequent position of the gemstone by monitoring movement of the movable surface; measuring one or more properties of the gemstone at the one or more measurement locations; as well as Each measurement of the one or more properties of each gemstone is associated with the position of the corresponding gemstone on the movable surface.

19. The method according to claim 18, wherein The one or more properties include one or more specific signatures of the luminescence and / or photoluminescence properties of the gemstone.

20. The method according to claim 19, wherein One of the one or more specific labels is a blue fast phosphorescent label that includes luminescence in a wavelength band with a peak at about 450 nm and a decay time of less than about 80 ms, and wherein detecting the blue fast phosphorescent label includes detecting the luminescence band with a peak at about 450 nm in a time window that begins at or after the end of the excitation pulse and ends about 80 milliseconds after the end of the associated excitation pulse.

21. The method according to claim 19 or 20, wherein One of the one or more labels is a turquoise slow phosphorescent label comprising luminescence having a peak wavelength at approximately 480 nm and a decay time greater than 80 milliseconds, and wherein detection of the turquoise slow phosphorescent label comprises detecting a band of luminescence centered approximately around 480 nm in a time window beginning approximately 80 milliseconds after the end of an associated excitation pulse, wherein the time window optionally ends approximately 500 ms after the end of the associated excitation pulse.

22. The method according to any one of claims 19 to 21, wherein One of the one or more labels is a weak green fluorescent label having a wavelength of about 510 nm, and wherein detecting the weak green fluorescent label can include detecting in a time window synchronized with the excitation pulse.

23. The method according to any one of claims 19 to 22, wherein One of the one or more markers is a light emitting element present in the photoluminescence spectrum of the gemstone at approximately 1332 cm -1 A single Raman line centered at .

24. The method according to claim 23, comprising: If 1332cm does not exist -1 Raman lines, then the stone is identified as a simulant.

25. A method according to any one of claims 19 to 24, comprising identifying a stone as a natural diamond if: 1332cm -1 Raman lines, and The presence of a blue fast phosphorescent marker; or The absence of a blue fast phosphorescent label and the presence of a turquoise slow phosphorescent label and the absence of a weak green fluorescent label and the presence of a photoluminescent label at approximately 787 nm in the absence of a stronger line at 793 nm; or There is no blue fast phosphorescent label, and no turquoise slow phosphorescent label, and there is a photoluminescent label at approximately 787 nm.

26. A method according to any one of claims 19 to 25, comprising: If there is 1332cm -1 The presence of Raman lines, the absence of a blue fast phosphorescent marker, the presence of a turquoise slow phosphorescent marker, and the presence of weak green fluorescence identify the stone as an HPHT synthetic.

27. A method according to any one of claims 19 to 26, comprising submitting the stone for further testing if: 1332cm -1 Raman lines, and There is no blue fast phosphorescent label, and there is a turquoise slow phosphorescent label, and there is no weak green fluorescent label, and there is no photoluminescent label at about 787 nm; or There are no blue fast phosphorescent labels, and no turquoise slow phosphorescent labels, and no photoluminescent labels at about 787 nm.

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