Detection of imitations in gemstones

Abstract

A method of characterizing a composition of a gemstone, the method comprising: illuminating an upper portion and a lower portion of the gemstone with one or more pulses of ultraviolet radiation having a wavelength substantially of 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 to the pulse or each pulse; and comparing properties of the luminescence captured from the upper portion and the lower portion. The composition of the gemstone is characterized based on the comparison.

Description

Technical Field

[0001] This invention relates to a method and apparatus for characterizing the composition of a gemstone based on a comparison of the cool light properties of the crown and pavilion. In particular, but not exclusively, this invention relates to the identification of colorless / near-colorless diamond simulants. Background Technology

[0002] A major problem in the gemstone (especially diamond) industry is the existence of undisclosed synthetics, including doublets and imitations. Imitations (doublets) are essentially synthetic stones grown onto or otherwise attached to natural cut stones. For example, such as... Figure 1a and Figure 1b As shown, the natural stone pavilion 10 (in this case, the chemical vapor deposition (CVD) crown 12) can be enhanced by adding synthetic stone to form a composite or imitation 14. Besides the combination of a natural pavilion and a synthetic crown, as... Figure 1b As shown, imitations can also be composed of a natural crown and a synthetic pavilion. Figure 1c The image further illustrates the various elements of a cut gemstone (table, crown, pavilion, culet).

[0003] Natural stone can be enhanced using synthetic layers or overgrowth techniques to alter its color (e.g., by adding a boron-doped synthetic layer to make colorless natural stone appear blue) or to cause a price surge (e.g., by increasing the weight of the natural stone to 0.5 or 1 carat). Imitations involving synthetic CVD overgrowth up to 740 micrometers thick have been reported.

[0004] The ability to identify diamonds (which are purely synthetic) has been primarily achieved through the development of deep UV imaging instruments such as DiamondView. TM and SYNTHdetect TM This can be addressed through knowledge of natural diamond markings. However, identifying imitations presents a greater challenge, as they may pass initial screening (e.g., by detecting natural markings) and therefore may never be used for reference testing by more advanced screening instruments such as DiamondView. In particular, while fancy colored (e.g., blue) stones or gemstones may be referenced by DiamondView for further testing due to their high value and rarity, this is unlikely to occur with colorless stones or gemstones that might undergo batch screening in SYNTHdetect.

[0005] Therefore, there is a need to develop an effective screening method for imitations (especially type IIa / IaAB diamonds). Preferably, this screening will detect synthetic materials present in the crown or pavilion of the stone or gemstone. Summary of the Invention

[0006] In one aspect of the invention, a method for characterizing the composition of a gemstone is provided. The method includes: irradiating an upper and lower portion of the gemstone with one or more pulses of ultraviolet radiation with a wavelength substantially 225 nm or less; capturing cold light emitted from the upper portion and cold light emitted from the lower portion of the gemstone within one or more time windows having a predetermined relationship with the pulse or each pulse; comparing the characteristics of the cold light captured from the upper and lower portions; and characterizing the composition of the gemstone based on the comparison results. The characteristics may include the color of the cold light.

[0007] One of the one or more time windows may start immediately after the pulse or after each pulse and turn off after about 50ms to 100ms, optionally after 80ms, such that the cold light includes phosphorescence.

[0008] One of the one or more time windows may begin 100 μs after the pulse or each pulse ends and turn off after less than 10 ms, or optionally after 5 ms, wherein the cold light includes phosphorescence.

[0009] One of one or more time windows may begin during the pulse or each pulse and end before the pulse or each pulse ends, wherein the cold light includes fluorescence.

[0010] The method may include generating color images of the cold light emitted from the upper part of the gemstone and color images of the cold light emitted from the lower part of the gemstone.

[0011] The method may optionally include displaying the color image to the user in a combined manner via a display screen.

[0012] The method may include generating pixel values ​​for cool light emitted from the upper part of the gemstone and pixel values ​​for cool light emitted from the lower part of the gemstone, and optionally generating a ratio of blue pixels to green pixels. The method may then include determining whether this ratio decreases within a predetermined time window.

[0013] The method may include determining whether the characteristics of the cold light captured from above substantially match the characteristics of the cold light captured from below.

[0014] The method may include: characterizing the gemstone as natural when the characteristics match, and characterizing the gemstone as partially natural and partially synthetic when the characteristics do not match.

[0015] The method may include: characterizing a gemstone as natural when its properties match and are consistent with those of a natural diamond.

[0016] In another aspect of the invention, a method is provided for comparing the colors of the cool light emitted by the crown and pavilion of a gemstone under ultraviolet excitation, the method comprising: identifying the gemstone as a counterfeit if the colors of the cool light emitted by the crown and pavilion do not match. Optionally, the gemstone is a diamond.

[0017] In another aspect of the invention, an apparatus for characterizing the composition of a gemstone is provided, the apparatus comprising: an ultraviolet radiation source configured to irradiate an upper and lower portion of the gemstone with one or more ultraviolet radiation pulses having a wavelength substantially 225 nm or less; an image capturing device configured to capture cold light emitted from the upper portion and the lower portion of the gemstone; a controller configured to synchronize the source and the image capturing device to capture the cold light emitted from the upper and lower portions of the gemstone within one or more time windows having a predetermined relationship with one or more pulses; and a processor configured to determine characteristics of the cold light captured from the upper and lower portions and to present the characteristics for comparison.

[0018] The ultraviolet source can directly irradiate a first surface of the gemstone. The device also includes a prism configured to direct ultraviolet radiation to a second surface of the gemstone facing away from the source. The prism may define a triangular portion that defines a frame for supporting the gemstone on the second surface.

[0019] The prism can be formed from a single piece of material, and optionally, the material includes high-grade UV-fused silica.

[0020] The stand can be configured to support multiple gemstones simultaneously.

[0021] The device may include a baffle configured to block the ultraviolet radiation source so that either the upper or lower part of the gemstone is irradiated at any given time.

[0022] The prism may include a cylindrical portion defining a concave upper surface, the cylindrical portion being adjacent to the frame.

[0023] The prism can be configured to guide ultraviolet radiation received at the concave upper surface through the pillar and triangular sections to the second surface of the gemstone.

[0024] The device may include a refocusing mechanism configured to focus the image capturing device on the upper or lower part of the gemstone.

[0025] The device may include a rotating mechanism configured to rotate the gemstone 180°. Attached Figure Description

[0026] Figure 1a Natural cut gemstones are shown;

[0027] Figure 1b Counterfeit products were shown;

[0028] Figure 1c It shows various aspects of cutting gemstones;

[0029] Figure 2 This is a flowchart of a method for characterizing the composition of gemstones;

[0030] Figure 3 This is a diagram of the short-time phosphorescence spectra of natural diamonds and CVD synthetic diamonds;

[0031] Figure 4a The image shows a cold light pattern obtained from a natural type Ia cut diamond;

[0032] Figure 4b The image shows a cool-light image of a cut diamond, including a natural diamond pavilion and a standard purity CVD crown.

[0033] Figure 5 Compare the blue / green pixel ratio of a natural Ia diamond to the blue / green pixel ratio of a stone or gemstone that includes both the CVD crown and the pavilion of a natural diamond.

[0034] Figure 6 Compare the blue / green pixel ratio of a natural Ia diamond with the blue / green pixel ratio of a stone or gemstone that includes both the CVD pavilion and the crown of a natural diamond.

[0035] Figure 7 It is used for execution Figure 2 A schematic diagram of an exemplary device for the method;

[0036] Figure 8a It is used for Figure 7 A three-dimensional diagram of the prism in the device; and

[0037] Figure 8b yes Figure 8a A plan view of the prism. Detailed Implementation

[0038] This article describes methods for characterizing the composition of gemstones with reference to Figures 1 through 8. For example... Figure 2 As shown, the method includes irradiating the upper and lower parts of a gemstone with one or more ultraviolet radiation pulses of wavelengths of about 225 nm or less; capturing cold light emitted from the upper part of the gemstone and cold light emitted from the lower part of the gemstone within one or more time windows having a predetermined relationship with the pulse or each pulse; comparing the characteristics of the cold light captured from the upper and lower parts; and characterizing the composition of the upper and lower parts of the gemstone based on the comparison results. An apparatus for performing the above method is also described.

[0039] WO2017 / 001835 details the use of specific cold light markers in diamonds detected within a specific time window following or during an ultraviolet (UV) excitation pulse. Cold light from the surface of the stone or gemstone is excited by a microsecond pulse with an energy of 225 nm or less. If the excitation pulse and the imaging device are synchronized, a specific delay can be applied to the imaging device, such that only the delayed cold light is captured, and any immediate cold light is “excluded.” This makes it possible to capture cold light that would otherwise be overwhelmed by immediate cold light.

[0040] Specifically, cold light, peaking at approximately 455 nanometers (nm), is a hallmark of most natural type Ia or IIa diamonds, exhibiting a window of light that turns on immediately after the excitation pulse ends and turns off after tens of milliseconds (ms) (e.g., approximately 80-100 ms). In WO2017 / 001835, this cold light is described as a blue fast phosphorescence marker. Other cold light markers within various time windows are also described.

[0041] In the SYNTHdetect environment, standard purity CVD can be defined as exhibiting a delayed cold light level other than blue (e.g., orange for NV or blue-green for boron), while the delayed cold light of high purity CVD will be inert.

[0042] When a standard-purity CVD material is applied to a natural diamond, the CVD layer will exhibit a cool glow within an 80ms time window; however, this cool glow will differ from the rapid blue phosphorescence exhibited by the natural stone. In one embodiment, a method for characterizing the gemstone's composition utilizes this difference. This method includes determining the presence of a CVD layer of standard (or higher) purity. This method covers cases where the CVD layer is present in the upper part (i.e., the crown) or lower part (i.e., the pavilion) of the stone or gemstone.

[0043] When a very high-purity CVD diamond material is applied over a natural diamond, a blue fast phosphorescence mark can be observed from the natural layer through the very high-purity CVD layer. In another embodiment, a method for characterizing the composition of a gemstone includes using other properties of the emitted cold light to determine the presence of a very high-purity CVD layer in the upper (i.e., crown) or lower (i.e., pavilion) part of the stone or gemstone.

[0044] Although this article refers to cool light emanating from the crown and / or pavilion of a stone or gemstone, this cool light can also be considered to emanate from the table and / or culet of the stone or gemstone, or simply from the upper and lower parts of the stone or gemstone.

[0045] A method for determining the presence of a CVD layer of standard purity in the crown or pavilion of a cut and polished gemstone (e.g., a diamond) will now be described. The method involves imaging the crown and pavilion of the stone or gemstone under deep UV excitation (i.e., UV in the range of 200 nm to 225 nm) and comparing the cool light emitted from the crown and pavilion within a predetermined time window. Specifically, the method enables determination within the same time window whether the color of the cool light emitted from the crown matches the color of the cool light emitted from the pavilion.

[0046] Figure 3 The difference in cold light emitted by natural diamonds and standard-purity CVD diamonds under deep UV excitation within the aforementioned 80 ms time window is shown. Short-time phosphorescence spectra of natural diamond (sample A) and CVD-synthetic diamond (sample B) are illustrated. Both samples A and B are standard round brilliant cut diamonds and less than 1 carat.

[0047] like Figure 3 As shown, spectrum A is the short-time phosphorescence spectrum of natural diamond sample A under deep UV excitation. Spectrum B is the short-time phosphorescence spectrum of synthetic CVD diamond sample B under deep UV excitation. Both samples exhibit short-time phosphorescence within less than 100 milliseconds after the electromagnetic radiation source is removed. Therefore, both samples A and B emit phosphorescence within the aforementioned 80 ms time window.

[0048] However, the spectral analysis showed that the short-duration or rapid blue phosphorescence produced by diamond sample A was blue, broad, and peaked at approximately 450 nm. In contrast, spectrum B showed that the synthetic CVD diamond sample B exhibited a weaker, short-duration or rapid green phosphorescence, which peaked at approximately 530 nm to approximately 550 nm.

[0049] Therefore, comparing the cool light (e.g., fast phosphorescence) emitted from the crown and pavilion of a cut stone or gemstone (assuming natural diamond) using the same excitation source within the same time window can indicate whether the entire stone or gemstone is actually formed of natural diamond material (in which case the cool light from the crown and pavilion will be identical (will “match”)) or whether the stone or gemstone comprises a crown or pavilion formed of CVD diamond layers (in which case the cool light from the crown and pavilion will be different from each other (will not “match”)). In this context, “match” includes values ​​of red, green, and blue within a predetermined range, or any ratio thereof.

[0050] When determining whether the cool light images of the crown and pavilion match, the color of the emitted cool light can be compared. Differences in the color of the cool light emitted from the crown and pavilion within the same time window can indicate that two or more parts of the stone or gemstone have different compositions.

[0051] Figure 4aThe image shows a cool-light image obtained from a natural type Ia cut diamond. Within the same time window, the imaged fluorescence emitted by the crown (tablet) and pavilion (culet) of the diamond matches in color. Similarly, within an 80ms time window, the imaged short-duration or rapid phosphorescence emitted by the crown and pavilion matches in color. Therefore, comparing the cool-light images of the upper part (crown / tablet) and the lower part (culet / pavilion) of the stone or gemstone allows for the identification of the stone or gemstone as a natural diamond.

[0052] Figure 4b The images show cold-light images obtained from cut diamonds, including the pavilion of a natural diamond and the crown of a standard-purity CVD diamond. The imaged fluorescence emitted from the crown (tablet) and pavilion (culet) of the stone or gemstone shows a color mismatch; that is, the colors of the fluorescence from the crown and pavilion are significantly different. Similarly, within an 80ms time window, the imaged short-duration or rapid phosphorescence emitted from the crown and pavilion shows a color mismatch. Therefore, comparing the cold-light images of the upper part (crown / tablet) and the lower part (culet / pavilion) of the stone or gemstone allows for the identification of the stone or gemstone as a potential imitation.

[0053] In cases involving imitations, including standard-purity CVD pavilions and natural diamond crowns / tables, a similar difference in the cool light color emitted by the crown and pavilion of the stone or gemstone can be detected. For higher-purity CVD pavilions, the phosphorescence of the crown and pavilion may match; however, the fluorescence emitted from the pavilion / culet may be distinctly red in color, thus the fluorescence of the crown and pavilion is mismatched and can be used to detect the presence of imitations.

[0054] The above-described method for determining the presence of a standard / higher purity CVD layer in the crown or pavilion of a cut stone or gemstone and a polished stone or gemstone can be used to identify loose stones or gemstones as imitations, including CVD crowns / natural pavilions, or natural crowns and CVD pavilions.

[0055] In contrast to standard purity CVD, when very high purity CVD diamond material is applied over a natural diamond, the blue fast phosphorescence emitted from the natural stone or gemstone can penetrate the high-purity CVD layer and is therefore visible from both the top and bottom of the stone or gemstone. This is because very high purity CVD is essentially inert to deep UV excitation and therefore does not emit any significant amount of cold light. Therefore, the light in the blue fast phosphorescence emitted by the natural diamond penetrates the CVD layer and is detected at both the top and bottom of the stone or gemstone within an 80ms time window.

[0056] Therefore, rapid blue phosphorescence labeling within an 80 ms time window is not very useful in determining the presence of very high-purity CVD. Similarly, when very high-purity CVD is present, fluorescence emitted from the coronal and pelvic regions may also match.

[0057] Another method will now be described for determining the presence of a very high-purity CVD layer in the crown or pavilion of a stone or gemstone. This method enables the observation of subtle differences in the cool light markings when comparing a natural Type Ia diamond with a natural Type Ia diamond covered with a high-purity CVD material (i.e., a natural Type Ia diamond whose pavilion / culet is covered by a CVD crown or table).

[0058] In this method, images of cool light emitted from the crown and pavilion (upper and lower parts) of a gemstone can be processed to determine the ratio of blue to green pixels. This ratio can be presented graphically, allowing observation of any changes in the ratio over time.

[0059] Figure 5 This is a comparison of the blue to green pixel ratio variation in the crown and pavilion of a natural Ia diamond with the blue to green pixel ratio of a second stone or gemstone (where a very high-purity CVD crown or table covers the pavilion of the natural Ia diamond). In this case, it is assumed that the second stone or gemstone is positioned such that the deep UV excitation source and image capture device (camera) face the table of the second stone or gemstone, i.e., the CVD crown is closest to the excitation source and camera.

[0060] In this specific example, for both stones or gemstones, the exposure time is 15 ms, and the capture delay increases from 100 μs to 5 ms in 50 μs increments.

[0061] As can be seen, in the case of natural diamonds, the crown T n Heting section / bottom tip C n The pixel ratios of blue and green in the phosphorescence are very similar (around 1.45) and remain fairly constant throughout the time window. In other words, the blue / green ratios of the crown and pavilion are essentially matched.

[0062] Conversely, in the case of a second stone or gemstone including a very high-purity CVD crown and a natural diamond pavilion, it can be seen that the crown T... d Heting section / bottom tip C d The blue to green ratio of phosphorescence in (natural diamonds) differs over the same exposure time. In other words, the blue / green ratios of the crown and pavilion do not match. Although the phosphorescence of the crown and culet initially shows essentially the same blue to green ratio, over time, the CVD crown T... d The phosphorescence changes from a blue / green ratio of just below 1.3 at the beginning of the time window to below 1.2 at the end. In other words, the phosphorescence becomes less blue and more green. The C-color emitted by the pavilion of a natural diamond... dThis "green transition" was not shown; instead, a blue / green ratio of approximately 1.4 was displayed at the end of the time window.

[0063] The "green transition" observed by the CVD crown under extended exposure times can occur as follows: Under deep UV excitation, with the table of the stone or gemstone closest to the UV source, the CVD crown acts as a UV filter, absorbing all energy up to 225 nm within the first few micrometers of material depth. Therefore, this energy will not reach the pavilion of the natural diamond beneath the CVD cover. Conversely, any wavelength above 225 nm will penetrate further into the stone or gemstone and thus reach the lower natural diamond pavilion. Only a small amount of energy above 225 nm will reach the natural pavilion, but this is sufficient to excite the blue fast phosphorescence marking within the underlying natural layer.

[0064] However, due to the greater penetration depth of excitation energies above 225 nm and the weak nature of the resulting phosphorescent emission, a higher level of emission absorption (self-absorption) will occur within the stone or gemstone. This contrasts with any emission generated by direct excitation at the surface of the CVD crown, where little or no absorption occurs. Therefore, all the cold light emanating from the CVD crown includes any phosphorescence emitted from the crown itself as well as phosphorescence emitted from the pavilion below.

[0065] Since very high-purity CVD is often essentially inert under deep UV excitation (i.e., producing little or no cold light), the phosphorescence captured within the aforementioned time window of 100 μs to 5000 μs may consist only of phosphorescence emitted from the natural pavilion. This weak phosphorescence may initially appear blue, but will become more green due to, for example, self-absorption as the time window extends.

[0066] Under deep UV excitation, the comparison of the blue / green pixel ratio of the cold light in the crown and pavilion of a stone or gemstone within a time window of 100μs to 5000μs after the excitation pulse ends can identify imitations with very high-purity CVD crowns.

[0067] The method described above for comparing the blue / green pixel ratio can also be used for imitations, including type Ia natural diamond crowns and very high purity CVD pavilions.

[0068] like Figure 6 As shown, in this case, the "green transition" exhibited by the very high-purity CVD replica is more subtle within a time window of 100 μs to 5000 μs. This is observed in the natural Ia crown T... dThe emitted phosphorescence has a blue / green pixel ratio of approximately 1.3 at the beginning of the time window and approximately 1.4 at the end of the time window. On the other hand, phosphorescence produced by very high-purity CVD pavilion C... d The emitted phosphorescence has a blue / green pixel ratio of approximately 1.3 at the beginning of the time window and approximately 1.275 at the end of the time window. Therefore, compared to... Figure 5 Compared to counterfeit products, the crown T d Heting Department C d The difference between the blue / green pixel ratio of phosphorescence is reduced.

[0069] This reduction in "green transition" may be related to Figure 6 Counterfeit products Figure 5 The imitations include those with less CVD material. Less CVD material allows a greater amount of excitation energy above 225nm to penetrate the CVD pavilion and enter the natural terrace.

[0070] The device used to perform the above methods will now be described. In one example (in...) Figure 7 (Schematably shown), device 100 includes a prism 110, a UV excitation source 120, a color image capture device 130, a processor 140, a baffle 150, and a controller 160. A beam splitter 125 allows UV light to pass through the baffle 150 from the excitation source 120 toward the prism 110, and transmits light returning from either side of the prism 110 to the image capture device 130. Figure 8a and Figure 8b Further explanations of the three-dimensional and two-dimensional views of prism 110 are provided in the document.

[0071] In this example, prism 110 is formed from a single sheet of advanced UV fused silica (UVFS). Prism 110 includes an L-shaped base or frame 112 and a triangular portion 114 (shown in...). Figure 7 (below the dashed line A) and column portion 116 (shown in) Figure 7 Above the dashed line A). The upper surface of the column portion 116 defines a recess 118. The sides of the prism 110 that form the apex of the triangular portion 114 can form an angle of approximately 90°. The recess 118 of the column portion 116 can have a radius of approximately 31 mm. However, it will be understood that these dimensions may vary depending on the specific application.

[0072] The L-shaped frame 112 serves as a platform on which one or more loose gemstones to be imaged can be placed table-down. The triangular portion 114 directs deep UV excitation from the UV source 120 to the base (i.e., the crown) of the stone or gemstone. The triangular portion 114 also directs the cool light emitted by the stone or gemstone to the image capturing device 130. The columnar portion 116 and its recess 118 serve as negative lenses to focus the base of the stone or gemstone onto the image capturing device 130.

[0073] Essentially, UV radiation at 230 nm (i.e., above the diamond bandgap excitation) is emitted by UV source 120 to excite the surface of a stone or gemstone positioned on holder 112. The UV source can emit radiation in microsecond pulses. This excitation causes the stone or gemstone to emit cold light according to its composition. Image capturing device 130 is configured to capture this cold light. In one example, a liquid lens or corrective optics is used to focus the image capturing device.

[0074] In this example, controller 160 synchronizes UV source 120 and image capturing device 130 such that image capturing device 130 begins capturing emitted cold light at the end of the UV excitation pulse and stops capturing emitted cold light after 80 ms (however, it will be understood that 80 ms is provided by way of example, and the window may be longer or shorter, such as a window as short as about 50 ms or as long as about 100 ms). Thus, in this embodiment, cold light in the form of phosphorescence is captured within the aforementioned 80 ms time window. Optionally or additionally, controller 160 may be configured to synchronize image capturing device 130 with UV source 120 to capture cold light within the aforementioned 100 μs to 5000 μs time window. Optionally or additionally, controller 160 may enable the capture of cold light in other time windows having a predetermined relationship with the excitation pulse. For example, image capturing device may be configured to capture cold light emitted from the crown and / or pavilion of the stone or gemstone (i.e., capture fluorescence) during a time window that closes before the end of the excitation pulse.

[0075] Return to reference Figure 7 A baffle 150 is mounted in front of the field aperture (iris) of the image capturing device 130. The baffle 150 shields the UV source 120 so that the pillar portion 116 or the frame 112 of the prism 110 is illuminated at any given time, but not both simultaneously. In other words, the baffle 150 ensures that only the pavilion or only the crown of the stone or gemstone is illuminated by the UV source 120. This arrangement eliminates crosstalk caused by light leakage between the top and bottom of the stone or gemstone. It will be understood that the UV radiation from the UV source 120 directly illuminates the pavilion of the stone or gemstone, i.e., it does not pass through the prism 110.

[0076] Therefore, depending on the configuration of the baffle 150, the field of view of the image capturing device 130 includes an image of the crown of the stone or gemstone, or an image of the pavilion of the stone or gemstone. In this example, the image of the pavilion of the stone or gemstone is an affine transformation image. Both the images of the pavilion and the crown are in focus.

[0077] The aforementioned device 100 enables the image capturing device 130 to sequentially capture one or more images of the cold light emitted from the crown and pavilion of one or more cut gemstones located on the holder 112 of the prism 110. The captured images are then transmitted from the image capturing device 130 to the processor 140.

[0078] In an embodiment, processor 140 may perform image processing on one or more cold light images. For example, processor 140 may perform an inverse transform on an affine transformation image of the pavilion of a stone or gemstone. The processor may pair the inversely transformed pavilion image with a corresponding crown image of the same gemstone captured in the same time window. In the case of simultaneously imaging multiple stones or gemstones, the paired images may include multiple crowns and multiple pavilions.

[0079] The processed image can then be displayed to the user via a color display screen (not shown herein) for comparison and / or further analysis. Simultaneous display of cool-light color images of the crown and pavilion, captured at the same location on the stone or gemstone using the same apparatus, allows the user to directly compare the two images side-by-side.

[0080] Optionally or additionally, the processor 140 may perform image analysis on the captured cold light images to determine whether the cold light colors of the crown and pavilion images match. The processor 140 may provide the user with auditory or visual indications regarding the color matching based on the image analysis.

[0081] Optionally or additionally, the processor 140 may perform image analysis on the captured cold light image to generate a blue / green pixel ratio for the cold light images of the crown and pavilion. In an embodiment, the ratio may optionally be presented to the user graphically via a display screen. In an embodiment, the processor 140 may provide the user with auditory or visual indications regarding whether the pixel ratio deviates or the degree of deviation based on the image analysis.

[0082] Optionally, device 100 can be configured to generate multiple excitation pulses and capture multiple cold light images within each time window. These images can be combined to produce a composite cold light image. Device 100 can be configured to capture cold light markers from different time windows. Exemplary cold light markers and associated time windows are described in WO2017 / 001835.

[0083] In an alternative embodiment of device 100 (not shown herein), the baffle may be omitted, and the pavilion and crown may optionally be irradiated sequentially by two or more UV sources.

[0084] The device 100, with or without a baffle as described above, can be incorporated into conventional deep UV imaging instruments such as SynthDetect.

[0085] It will be understood that the prism described above can have alternative configurations. For example, as discussed below, the column portion can be omitted.

[0086] Alternative devices (not shown herein) used to determine the presence of a CVD layer of standard purity in the crown or pavilion of a cut and polished stone or gemstone may include a catadioptric system instead of the step prism described above. In this case, it will be necessary to “flip” the stone or gemstone to capture cool-light images of the crown and pavilion separately (i.e., rotate the stone or gemstone 180°). A refocusing mechanism will also be needed to refocus the image capturing device during capture. The “flip” and / or refocusing can be performed manually or automatically via a rotating mechanism. Refocusing can be achieved by mounting the stone or gemstone on a platform that can be raised and lowered relative to the image capturing device.

[0087] As an alternative, a simple prism can be used (i.e., without pillar 116 and recess 118). Figure 7 The remaining components shown can remain in place, but since the light emitted by the stone or gemstone has different optical path lengths, it is necessary to refocus the image capturing device between capturing images of the crown and pavilion.

[0088] Alternatively (not shown in this document), the sample can be illuminated from the pavilion and imaged with cold light from the crown (and vice versa), and can be imaged with two light sources and two imaging devices, thus eliminating the need for movable baffles and UV-grade quartz prisms.

[0089] It will be understood that the methods described in this article are not mutually exclusive, but can be combined and executed.

[0090] As used herein, "natural" is defined as a stone that comes from nature and is composed solely of diamonds or other gemstones formed through geological processes. As defined herein, the term "natural" indicates that the stone or material is not synthetic.

[0091] As used herein, synthetic is defined as artificial stone or material consisting solely of diamonds or other gemstones produced through artificial or industrial processes such as chemical vapor deposition (CVD) or high pressure high temperature (HPHT) processes.

[0092] As used in this article, a standard diamond classification system is used to define the type, which classifies diamonds based on their physical and chemical properties (e.g., Type Ia, Type IIb, etc.).

[0093] As used herein, fluorescence is a type of cold light characterized as being produced only when excited by ultraviolet light. Phosphorescence is a type of cold light that is retained but decays once the excitation is removed.

[0094] The images described in this article are actual color images of visible cold light, not spectral images or images showing decay time.

Claims

1. A method for characterizing the composition of a gemstone, the method comprising: Irradiate the upper and lower parts of the gemstone with one or more ultraviolet radiation pulses with a wavelength of 225 nm or less; Within one or more time windows that have a predetermined relationship with the pulse or each pulse, capture the cold light emitted from the upper part of the gemstone and the cold light emitted from the lower part of the gemstone; Pixel values ​​for cold light emitted from the upper part of the gemstone and pixel values ​​for cold light emitted from the lower part of the gemstone are generated. The ratio of blue pixels to green pixels; Compare the characteristics of the cold light captured from the upper and lower parts; as well as The composition of the gemstones was characterized based on the comparison results.

2. The method according to claim 1, wherein, The characteristics include cool light color.

3. The method according to claim 1, wherein, One of the one or more time windows begins immediately after the pulse or each pulse ends and turns off after 50ms to 100ms, such that the cold light includes phosphorescence.

4. The method according to claim 1, wherein, One of the one or more time windows begins immediately after the pulse or each pulse ends and ends after 80ms, such that the cold light includes phosphorescence.

5. The method according to any one of claims 1-4, wherein, One of the one or more time windows begins 100µs after the pulse or each pulse ends and turns off after less than 10ms, wherein the cold light includes phosphorescence.

6. The method according to any one of claims 1-4, wherein, One of the one or more time windows begins 100µs after the end of the pulse or each pulse and ends 5ms later, wherein the cold light includes phosphorescence.

7. The method according to any one of claims 1-4, wherein, One of the one or more time windows begins during the pulse or each pulse and turns off before the pulse or each pulse ends, wherein the cold light includes fluorescence.

8. The method according to any one of claims 1-4, comprising generating a color image of cold light emitted from the upper part of the gemstone and cold light emitted from the lower part of the gemstone.

9. The method of claim 8, further comprising displaying the color image to a user in a combined manner via a display screen.

10. The method according to any one of claims 1-4, comprising determining whether the ratio decreases within a predetermined time window.

11. The method according to any one of claims 1-4, comprising determining whether the characteristics of the cold light captured from the upper portion match the characteristics of the cold light captured from the lower portion.

12. The method of claim 11, comprising: When the properties match, the gemstone is characterized as natural; when the properties do not match, the gemstone is characterized as partially natural and partially synthetic.

13. The method of claim 11, comprising: When the characteristics match and are consistent with those of natural diamonds, the gemstone is characterized as natural.

14. The method according to any one of claims 1 to 4, wherein, The gemstone is a diamond.

15. An apparatus for characterizing the composition of a gemstone, the apparatus comprising: An ultraviolet radiation source is configured to irradiate the upper and lower parts of the gemstone with one or more ultraviolet radiation pulses with a wavelength of 225 nm or less. An image capturing device is configured to capture cold light emitted from the upper part of the gemstone and cold light emitted from the lower part of the gemstone; The controller is configured to synchronize the ultraviolet radiation source and the image capturing device to capture cold light emitted from the upper and lower parts of the gemstone within one or more time windows that have a predetermined relationship with one or more pulses. as well as The processor is configured as follows: Pixel values ​​for cold light emitted from the upper part of the gemstone and pixel values ​​for cold light emitted from the lower part of the gemstone are generated. The ratio of blue pixels to green pixels; The characteristics of the cold light captured from the upper and lower parts are determined, and the characteristics are presented for comparison.

16. The device according to claim 15, wherein, The ultraviolet radiation source directly irradiates a first surface of the gemstone, and the device further includes a prism configured to direct the ultraviolet radiation to a second surface of the gemstone opposite to the ultraviolet radiation source.

17. The device according to claim 16, wherein, The prism defines a triangular portion, which defines a frame for supporting the gemstone on the second surface.

18. The device according to claim 17, wherein, The prism is formed from a single piece of material.

19. The device according to claim 18, wherein, The material includes high-grade UV-fused silica.

20. The device according to claim 17, 18 or 19, wherein, The frame is configured to support multiple gemstones simultaneously.

21. The device according to any one of claims 17 to 19, comprising a baffle configured to shield the ultraviolet radiation source such that either the upper portion or the lower portion of the gemstone is irradiated at any given time.

22. The device according to any one of claims 17 to 19, wherein, The prism includes a column portion defining a concave upper surface, the column portion being adjacent to the frame.

23. The device according to claim 22, wherein, The prism is configured to guide ultraviolet radiation received at the concave upper surface through the columnar portion and the triangular portion to the second surface of the gemstone.

24. The device according to any one of claims 15 to 19, comprising a refocusing mechanism configured to focus the image capturing device on the upper or lower part of the gemstone.

25. The device of claim 24, further comprising a rotating mechanism configured to rotate the gemstone 180°.

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