Systems and processes for diamond certification

Abstract

A process for determining the type of diamond, wherein the diamond type is determined by: (i) measuring a fluorescence lifetime characteristic of a color center of a diamond of unknown type (110a); and (ii) determining the diamond type (120a) by comparing the fluorescence lifetime characteristic measured in step (i) with the fluorescence lifetime characteristic of a color center of a known diamond type, wherein the fluorescence lifetime characteristic of the color center is indicative of a physical property of the diamond, the physical property being indicative of the type of the diamond.

Description

Technical Field

[0001] The present invention relates to a process and system for determining the properties of a diamond. In particular, the present invention provides a process and system for authenticating and determining the type of a diamond. Background Art

[0002] As we all know, diamonds are generally considered a luxury and are often used in luxury goods, such as jewelry, and are generally considered to have very high value. Therefore, with the rise of new technologies regarding synthetic diamonds and their manufacturing, diamond certification has become increasingly important.

[0003] Natural diamonds are generally considered to be rare items and are reported to have formed between several million and 350 million years ago along with the Earth and are reported to have formed at depths of 150 to 250 kilometers below the Earth's surface.

[0004] It is well known that the clarity, cut, carat and color of a diamond all affect its value. Diamonds with higher value are generally those with little or no discernible color (usually a pale yellow) and higher clarity (i.e. fewer visible flaws or inclusions in the body of the diamond).

[0005] In recent years, synthetic or non-natural diamonds have been produced, which are formed or grown in a laboratory and are man-made, created in a controlled laboratory environment that is said to mirror the conditions required for diamonds to form in nature. There are two processes used to create synthetic diamonds, chemical vapor deposition (CVD diamond) and high pressure high treatment (HPHT diamond).

[0006] CVD (Chemical Vapor Deposition) diamonds are lab-grown diamonds that are created through a process called chemical vapor deposition. This method is usually used for large stones.

[0007] HPHT (High Pressure High Temperature) diamonds are lab-grown diamonds that are used with a process called High Pressure High Temperature Treatment. HPHT is used primarily on small diamond grains, rather than the larger stones that are usually used.

[0008] Lab-grown diamonds are considered real diamonds and are composed of a mineral that is made up of pure carbon crystallized in an isometric system and the difference is indistinguishable to the naked eye and nearly impossible to tell under magnification.

[0009] Such synthetically formed diamonds are considered "real" and grading agencies can issue one report for natural diamonds and a separate report for laboratory-grown diamonds. Both reports provide a full 4Cs assessment of cut, precision, color and carat. All diamonds go through the same rigorous grading process.

[0010] Non-natural (i.e., laboratory-grown) diamonds generally have a lower economic value and can be considered non-genuine or at least non-traditional.

[0011] As part of the value of natural diamonds, age (millions or billions of years) and the scarcity and uniqueness of each diamond drive the value of such diamonds. Further, the history of the diamond may also contribute to its value and, at least when the diamond is gifted or passed down through the generations in a family, contribute to sentimental value.

[0012] Not surprisingly, the advent of high-quality synthetically formed diamonds, such as CVP diamonds and HPHT diamonds, has had a significant impact on the diamond industry.

[0013] There have been instances where synthetic diamonds have been substituted for natural diamonds as part of fraudulent activity and the real owner was unaware of the deception.

[0014] There are many instances where high quality synthetic diamonds have been sold to customers as real diamonds, or where real diamonds with 20 complete documents have been replaced with synthetic diamonds between purchase and collection.

[0015] Traditionally, optical methods, such as Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, have been used to seek to effectively distinguish natural diamonds from synthetic diamonds.

[0016] However, due to the tremendous progress in synthetic diamonds using CVD and HPHT technologies in recent years, it has become increasingly difficult to identify different types of diamonds.

[0017] Furthermore, some low-grade natural diamonds can even be treated with HPHT to become high-grade diamonds, thus changing the value of the diamond, and 30 represents the diamond naturally existing at that grade.

[0018] As a result, diamond certification to determine the type of diamond (i.e. natural and unmodified diamonds) as opposed to synthetic or modified natural diamonds has become increasingly difficult, and existing processes for determining diamond type are becoming increasingly unreliable and uncertain and will inevitably become obsolete in the near future. Therefore, new methods are needed to identify natural, synthetic and treated diamonds.

[0019] Purpose of the Invention

[0020] It is an object of the present invention to provide a process and system for authenticating diamonds and diamond types which overcomes or at least partially ameliorates at least some of the disadvantages associated with the prior art. Summary of the invention

[0021] In a first aspect, the present invention provides a process for determining the type of a diamond, wherein the type of the diamond is determined by:

[0022] (i) measuring the fluorescence lifetime characteristics of the color centers of diamonds of unknown type, and

[0023] (ii) determining the type of diamond by comparing the fluorescence lifetime characteristics measured in step (i) with the fluorescence lifetime characteristics of color centers of known diamond types;

[0024] Among them, the fluorescence lifetime characteristics of the color center indicate the physical properties of the diamond, which in turn indicate the type of diamond.

[0025] Physical properties can include inclusions, defects, crystallinity inconsistencies, lattice distortions, internal stresses, impurities, and homogeneity.

[0026] The types of diamonds may be natural diamonds, chemical vapor deposition (CVD) synthetic diamonds, high pressure high temperature (HPHT) synthetic diamonds, and treated natural diamonds.

[0027] The process can provide a distinction between natural diamonds and synthetic diamonds. Synthetic diamonds can be CVD (chemical vapor deposition) diamonds.

[0028] The color center can be an NV center, a SiV center, or an NVN center.

[0029] In a second aspect, the present invention provides a process for identifying whether a diamond is a natural diamond or a CVD (chemical vapor deposition) diamond by measuring 30 the fluorescence lifetime of the color center of the diamond, wherein the fluorescence lifetime of the color center of the diamond is a physical property of the diamond.

[0030] Physical properties indicate the type of diamond.

[0031] Measurement of the fluorescence lifetime of the color centers of diamonds can be performed using a confocal laser scanning fluorescence microscope equipped with a time-correlated single photon counter module.

[0032] The confocal laser scanning fluorescence microscope may include a pulse laser excitation module, a diamond sample stage, an objective lens, a focus stabilizer, a laser scanning module, a time-correlated single photon counter module, and an emission filter.

[0033] Confocal laser scanning microscopes can be operated in laser scanning mode.

[0034] The pulse laser excitation module may be composed of a picosecond pulse green laser having a wavelength of, for example, 510 nm, 514 nm or 532 nm.

[0035] The pulse laser excitation module may be further provided with a linear polarizer and a half-wave plate for controlling the laser power and an acousto-optic modulator for the laser shutter.

[0036] The diamond sample stage may be composed of an XYZ 3-axis electric mechanical stage and an XYZ 3-axis piezoelectric stage for achieving sample scanning.

[0037] The objective lens may be oil-immersed and is used to illuminate the laser onto the diamond and collect the resulting fluorescence from the diamond.

[0038] The objective lens may have a numerical aperture equal to or greater than 1.3.

[0039] A focus stabilizer is preferably used to precisely control the distance between the diamond sample and the objective lens.

[0040] The laser scanning module preferably consists of a galvanoscopic arrangement.

[0041] A time-correlated single photon counter module is used to count the arrival time of fluorescence photons after the diamond is excited by a single-excitation focus stabilizer, which is used to precisely control the distance between the sample and the objective lens.

[0042] The color center can be an NV center, a SiV center, or an NVN center.

[0043] The type of diamond may be determined based on the fluorescence lifetime characteristics of the diamond measured in step (i) being consistent with a predetermined threshold of correlation with the fluorescence lifetime characteristics of known diamond types.

[0044] In a second aspect, the present invention provides a process operable using a computerized system for determining the type of a diamond, wherein the fluorescence lifetime characteristics of a color center of a diamond of unknown type are correlated with the fluorescence lifetime characteristics of a color center of a plurality of diamonds of each known type, the computerized system comprising a fluorescence lifetime data acquisition system, a processor module and an output module, which are operably connected to each other, the process comprising the steps of:

[0045] (i) acquiring, via a fluorescence lifetime data acquisition system, data indicative of fluorescence lifetime characteristics of a color center of a diamond of an unknown type;

[0046] (ii) in the processor module, comparing the data indicative of the fluorescence lifetime characteristics of the color center of the image of the unknown type of diamond with a plurality of data sets, each of which corresponds to the fluorescence lifetime characteristics of the color center of each of the plurality of diamonds of each known type, wherein the data sets of fluorescence lifetime characteristics of the color centers of the known types of diamonds are respectively obtained from the fluorescence lifetime acquisition system; and

[0047] (iii) providing, from an output module, an output signal in response to a predetermined threshold value of correlation between the data derived from step (i) and one of the plurality of data sets from step (ii), the output signal being indicative of the type of diamond, and wherein the fluorescence lifetime characteristic of the color centre of the diamond is indicative of a physical property of the diamond, the physical property being indicative of the type of diamond.

[0048] In a third aspect, the present invention provides a process operable using a computerised system for determining the type of diamond using a pre-trained neural network for determining the type of diamond, the computerised system comprising a fluorescence lifetime data acquisition system, a pre-trained neural network and an output module, operatively connected to each other via a communication link, the process comprising the steps of:

[0049] (i) acquiring data by a fluorescence lifetime data acquisition system, the data indicating fluorescence lifetime characteristics of a color center of a diamond of an unknown type;

[0050] (ii) determining the type of the unknown type of diamond in a pre-trained neural network from the data indicating the fluorescence lifetime characteristics of the color center of the unknown type of diamond acquired in step (i);

[0051] wherein the pre-trained neural network has been pre-trained using a plurality of data sets, each of the data sets corresponding to a fluorescence lifetime characteristic of a color center of a plurality of diamonds of each known type; and

[0052] (iii) From the output module, the type of the diamond is provided.

[0053] In a fourth aspect, the present invention provides a computerized system for determining the type of a diamond, wherein the fluorescence lifetime characteristics of a color center of a diamond of unknown type are correlated with the fluorescence lifetime characteristics of a color center of a plurality of diamonds of each known type, the computerized system comprising:

[0054] a fluorescence lifetime data acquisition system for acquiring data indicative of fluorescence lifetime characteristics of a color center of a diamond of an unknown type;

[0055] a processor module for comparing said data indicative of the fluorescence lifetime characteristics of the color centres of the image of the unknown type of diamond with a plurality of data sets, each of the data sets corresponding to the fluorescence lifetime characteristics of the color centres of a plurality of diamonds of each known type; and

[0056] an output module for providing an output signal indicative of a type of diamond of the unknown type based on a predetermined threshold of correlation between the data indicative of the fluorescence lifetime characteristic of a color center of the diamond of the unknown type and one of a plurality of data sets corresponding to the fluorescence lifetime characteristic of the color center of a plurality of diamonds of each known type. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order that a more accurate understanding of the above invention may be obtained, the invention briefly described above will be described in more detail with reference to specific embodiments shown in the accompanying drawings. The drawings presented herein may not be drawn to scale, and any reference to dimensions in the drawings or the following description is for the disclosed embodiments.

[0058] Figure 1a A schematic representation of an example of the process of the present invention is shown;

[0059] Figure 1b A schematic representation of an example of a system of the present invention is shown;

[0060] Figure 1c is a diagrammatic representation of a model of nitrogen vacancies in a diamond lattice as illustrated in the present invention;

[0061] Figure 2 A graphical representation of the fluorescence spectrum of a single NV center in diamond excited at 514 nm is shown;

[0062] Figure 3 is a diagrammatic representation of fluorescence and the fluorescence light cycle;

[0063] Figure 4 A graphical representation of the excitation of an NV center of bulk diamond is shown;

[0064] Figure 5 Schematic representation showing the synchronization of the Zeiss LSM880 and the PicoQuant TCSPC used in the experimental procedure of the present invention;

[0065] Figure 6 is a schematic illustration of the determination of fluorescence lifetime measurements of color centers in diamond used in accordance with the present invention;

[0066] Figure 7 A magnified photographic representation of a fluorescence lifetime image of a CVD diamond is shown;

[0067] Figure 8 shows a decay curve of fluorescence from a color center in a diamond used in accordance with the present invention; and

[0068] Fig. 9 A flow chart describing the overall process of an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0069] The present inventors have identified the shortcomings of the prior art and have provided a system and process that overcomes the problems of the prior art.

[0070] For the purposes of this invention, the term "type" of diamond is defined and understood to mean natural diamond, chemical vapor deposition (CVD) synthetic diamond, high pressure high temperature (HPHT) synthetic diamond and treated natural diamond, which are all different types of diamond. 1. Background of the invention

[0072] In order to identify whether a diamond is a natural diamond, such as a CVD diamond or an HPHT diamond, or a natural diamond that may have been treated to have altered properties, physical properties within the material can be used to make this determination of diamond type.

[0073] Diamonds contain impurities and by understanding the physical properties of the impurities according to the present invention, the way in which diamonds form can be shaped and this phenomenon and its determination and use has been provided by the present invention in order to determine the type of diamond.

[0074] Thus, the present invention provides a process and system for determining the type of a diamond.

[0075] The type of diamond can be determined, such as natural diamond, chemical vapor deposition (CVD) synthetic diamond, high pressure high temperature (HPHT) synthetic diamond, and treated natural diamond.

[0076] In particular, the present invention can be used to determine whether a diamond is a naturally occurring diamond, or whether the diamond is a synthetic diamond or a treated diamond.

[0077] The type of diamond is determined by:

[0078] (i) measuring the fluorescence lifetime characteristics of color centers of diamonds of unknown type; and

[0079] (ii) determining the type of diamond by comparing the fluorescence lifetime characteristics measured in step (i) with the fluorescence lifetime characteristics of color centers of known diamond types;

[0080] The fluorescence lifetime characteristics of the color center indicate a physical property of the diamond which indicates the type of diamond.

[0081] Therefore, the type of diamond may be determined based on the agreement of a predetermined threshold of the correlation between the fluorescence lifetime characteristics of the diamond measured in step (i) and the fluorescence lifetime characteristics of known diamond types.

[0082] Such thresholds may be determined by mathematical analysis or by a processor or automated computer operable process.

[0083] Alternatively, a pre-trained artificial intelligence system may be used using a pre-trained neural network. In this case, the pre-trained neural network is trained using a plurality of data sets, each of which corresponds to a fluorescence lifetime characteristic of a color center of a plurality of diamonds of each known type; and when data indicating a fluorescence lifetime characteristic of a color center of a diamond of an unknown type is received, the type of the diamond is provided via the output module.

[0084] Reference Figure 1a , there is a flow chart of a process 100a according to the present invention. As will be appreciated, the process may be implemented in a computerized system, and further in embodiments, the process may utilize a pre-trained neural network.

[0085] In process 100a, the following steps applicable to determining the type of diamond are determined by:

[0086] Step 1 (110a) - measuring the fluorescence lifetime characteristics of the color center of the unknown type of diamond;

[0087] Step 2 (120a) - comparing the fluorescence lifetime characteristics measured in step (i) with the fluorescence lifetime characteristics of color centers of known diamond types; and

[0088] Step 3 (130a) determines the diamond type of the unknown diamond type based on a correlation threshold consistent with the fluorescence lifetime characteristics of the color centers of the known diamond types.

[0089] Reference Figure 1b , showing an example of a computerized system 100b according to the present invention.

[0090] The system 100b is used to determine the type of diamond, wherein the fluorescence lifetime characteristics of the color center of a diamond of unknown type are correlated with the fluorescence lifetime characteristics of the color center of a plurality of diamonds of each known type.

[0091] The system 100b includes a fluorescence lifetime data acquisition system 110b for acquiring data indicative of fluorescence lifetime characteristics of a color center of an unknown type of diamond.

[0092] The system 100b further comprises a processor module 120b in communication 112b with the fluorescence lifetime acquisition system 110b and for comparing said data indicative of the fluorescence lifetime characteristics of the color centres of the image of the unknown type of diamond with a plurality of data sets, each of the data sets corresponding to the fluorescence lifetime characteristics of the color centres of a plurality of diamonds of each known type.

[0093] The system 100b further comprises an output module 140b in communication 124b with the processor module 120b and for providing an output signal indicative of a type of diamond of the unknown type based on a predetermined threshold of correlation between the data indicative of the fluorescence lifetime characteristic of a color centre of diamond of the unknown type and one of a plurality of data sets corresponding to the fluorescence lifetime characteristic of a color centre of a plurality of diamonds of each known type.

[0094] 2. Diamond’s Nitrogen Vacancy (NV) Center

[0095] Diamond color centers have received much attention in quantum technology, especially nitrogen-vacancy (NV) centers.

[0096] A diamond NV center is a point defect in the diamond lattice. As shown in FIG1 , a diamond NV center consists of a carbon atom in a tetrahedral structure replaced by a nitrogen atom 110 , and the adjacent lattice site is vacant, referred to as a vacancy 120 .

[0097] Diamond NV centers emit fluorescence when excited by light of a suitable wavelength (eg, 450 nm to 650 nm).

[0098] Reference Figure 2 , shows a graphical representation of the fluorescence spectrum of a single NV center in diamond, where the NV center of the diamond is excited by laser light with a wavelength of 514nm.

[0099] Fluorescence spectroscopy relates the emitted fluorescence (in arbitrary units) to its wavelength. Figure 2 As can be seen in the figure, there are two peaks 210 and 220 at wavelengths of about 575nm and 635nm. Peak 210 indicates that the peak 0 The peak 220 indicates the fluorescence emitted from the NV - Fluorescence emitted from the center.

[0100] 3. Fluorescence lifetime and photocycle used in the present invention

[0101] The fluorescence lifetime time is a measure of the time a fluorophore stays in an excited state before returning to the ground state by emitting a photon.

[0102] Reference Figure 3 , showing fluorescence and the fluorescence photocycle.

[0103] Fluorescence light recycling is the process by which fluorescent materials emit visible light for a period of time after being excited by an energy source. Figure 3 As shown in , the light cycle begins by applying a light source 310 to a phosphor particle. This allows the phosphor particle 330 to absorb light that matches its absorption spectrum, thereby being excited from its ground state to its electronic excited state.

[0104] The excited fluorescent particle, also called a fluorophore, will remain in its electronic excited state for a certain period of time 350. After this period 350, the excited fluorescent particle 340 decays back to the electronic ground state by releasing the energy 360 of the absorbed light, typically in the form of phonons and photons.

[0105] The certain period of time 350 after the excited fluorescent particle 340 decays back to the ground state is called the fluorescence lifetime. The photons emitted during the decay are optically visible and together they form the emitted fluorescent light.

[0106] In order to measure the fluorescence emitted by an object, in particular by a bulk diamond with NV defects, the fluorescence emitted by Figure 4 The experimental setup shown in .

[0107] Figure 4 The excitation and fluorescence emission process for the excitation of NV centres in bulk diamond material is illustrated.

[0108] In the excitation process, an excitation laser 420 is applied to the system, reflected from the filter 450, and reaches the bulk diamond 410 through the objective lens 430. The laser 420 acts as an energy excitation to the NV center 415 within the bulk diamond 410.

[0109] The filter 450 allows only the transmission of the fluorescent signal, so any incident light other than the fluorescent light will be reflected from the filter 450 .

[0110] Under the excitation of laser 420, NV center 415 emits fluorescence when decaying from the excited state back to the ground state. The emitted fluorescence is then collected by the same objective lens 430.

[0111] Filter 450 allows transmission of the fluorescence signal so that any fluorescence emitted by the NV centre 415 can reach and be measured by the optical sensor 470, which in this embodiment is a CCD sensor.

[0112] The optical sensor 470 detects the intensity and wavelength of the collected fluorescent signal, thereby providing a Figure 2 The graphs shown in the fluorescence spectra.

[0113] 4. The present invention

[0114] For natural diamonds, since their formation process is on the scale of millions of years, they usually have relatively low internal strain and stress.

[0115] In contrast, for CVD (chemical vapor deposition) diamonds, such diamonds typically have greater internal strain and stress than natural diamonds.

[0116] Additionally, because synthetic diamonds take a shorter time to form than natural diamonds, they typically exhibit more uniform physical properties than natural diamonds.

[0117] Further, different types of diamonds have physical properties including inclusions, defects, inconsistencies in crystallinity, lattice deformations, impurities and homogeneity.

[0118] The present inventors have identified that all of these conditions can affect the fluorescence lifetime of a diamond and have therefore come up with an invention for determining the type of diamond, in particular whether the diamond is a natural diamond or a CVD diamond.

[0119] Thus, the present inventors have provided a process and system for determining the type of diamond, which is based on fluorescence lifetime.

[0120] 5. Experimental Procedure of the Present Invention

[0121] Reference Figure 5 and Figure 6 To verify and confirm the usefulness of the present invention for determining and assessing diamond types, the fluorescence properties of NV centers were studied using an upgraded system of a Zeiss LSM 880 confocal microscope with an Elyra system for super-resolution imaging and a PicoQuant TSCPC for lifetime measurements.

[0122] Figure 5 is a flow chart showing the experimental procedure for the measurement of fluorescence lifetime. This can be achieved by counting time-correlated single photons.

[0123] like Figure 5 As shown in , the sample to be measured is excited by a pulsed diode laser with a high repetition rate via a PicoQuant module 510. The photons emitted by the sample are detected with a dual detector 520 and the time relative to the excitation pulse is measured.

[0124] The excited sample then undergoes fluorescence emission, where photons are emitted until the sample fully returns to the electronic ground state. Over time, most of the excited particles return to the ground state, so the number of photons emitted also decays over time. Time-correlated single photon counting (TCSPC) 530 is used as a 'stopwatch' to measure the decay time.

[0125] By counting many events, a histogram of the photon distribution over time is built, which is also called a decay curve. The fluorescence lifetime is then the time constant of the decay curve after curve fitting.

[0126] NV centers were studied using a Zeiss LSM 880 confocal microscope 540 upgrade system.

[0127] Figure 6Further illustration shows the Figure 5 Schematic illustration of the procedure used in the determination of fluorescence lifetime measurements of color centers in diamond.

[0128] The measurement conditions are as follows:

[0129] - Sample light box CVD diamond and natural diamond

[0130] -Excitation wavelength: 510nm

[0131] - Repetition rate: 5MHz (the signal in each channel is completely attenuated in each repetition cycle)

[0132] -Objective: Oil immersion NA 1.3, 40X

[0133] The filters being used include T635LPXR, FF01-582 / 75-25 and H690 / 70. The experiment started with a 514nm continuous wavelength laser, where the primary beam splitter T80 / R20 was used to locate the diamond NV center. Then, at 78.8×78.8μm 2 A pre-scan of NV centres in bulk diamond was performed by focusing 5 μm into the sample in an area of ​​1000 nm and at a resolution of 512 × 512 pixels.

[0134] When an excitation laser pulse 615 is applied to the diamond 610, a green fluorescence (from the NV center of the diamond 610) is emitted. 0 state), red fluorescence (from NV - The emitted light (together with the background) is then split into two channels: green fluorescence and red fluorescence by a beam splitter 630, which in this embodiment is a T635LPXR.

[0135] From NV 0 The green fluorescence signal from the center will be detected by the SPAD 2 detector 640; - The red fluorescence signal at the center is detected by the SPAD 1 detector 650. The collected backscattered laser light is then further filtered by the H690 / 70 and FF01-582 / 75-25 filters of each corresponding detector 640 and 650, respectively. Graph 660 shows the light transmittance through the three optical filters T635LPXR, FF01-582 / 75-25, and H690 / 70. The beam splitter 630 (T635LPXR in this embodiment) only allows the transmission of light with a wavelength between 625nm and 750nm, thereby effectively separating the green fluorescence signal from the red fluorescence signal.

[0136] Optical filter FF01-582 / 75-25 allows transmission of green light signals, while optical filter H690 / 70 only allows red light signals to pass, thereby blocking any backscattered laser light received at SPAD 1 and SPAD 2 detectors 640 and 650.

[0137] By evaluating the signals received by the SPAD 1 detector 640 and the SPAD 2 detector 650 respectively, Figure 5 The experimental procedures shown in the 0 Center and NV - The decay time of the fluorescence emitted from the center.

[0138] The NV-defect 710 can be successfully excited via the sideband using a 510 nm argon laser, e.g. Figure 7 Afterwards, a pulse wavelength of 510 nm was applied to excite the NV-centers via strong photon sidebands at a pulse rate of 10 MHz for 5 min.

[0139] Then, TCSPC was applied to record the temporal decay and determine the NV based on optical excitation in short light pulses. - The fluorescence lifetime of the center, such as Figure 8 as shown in .

[0140] Figure 8 is a decay curve of fluorescence from a color center in a diamond that relates the intensity of fluorescence to time. The sample used in this graph is a CVD diamond (type II, with dense pink).

[0141] This is a profiling method based on the repeated, precisely timed registration of single photons of the fluorescence signal. It measures the time between sample excitation by a pulsed laser and the arrival of the emitted photons at a detector.

[0142] The time between the start of the laser pulse and the detector receiving the arrival signal of the emitted photon is measured, and this is repeated many times to collect the statistical characteristics of the fluorophore emission. The delay time is then sorted into a histogram of the time after which the emission occurs and the excitation.

[0143] 6. Data validating the experimental procedure of the present invention

[0144] Table 1 below shows the fluorescence lifetime measurement results of CVD diamonds and natural diamonds.

[0145]

[0146] Table 1

[0147] For the natural diamond measured in the table, it has a longer fluorescence lifetime of about 11 ns (nanoseconds) due to the lower strain of <10 nm relative to CVD diamond.

[0148] Regarding homogeneity differences, since natural diamonds are more heterogeneous (i.e., less uniform), they have greater lifetime variation, and in CVD diamonds, the reverse is true.

[0149] Reference Fig. 9 , a flow chart is shown which describes the overall process 900 of an embodiment of the present invention as a process for determining whether a diamond is a natural diamond or a synthetic diamond.

[0150] Color Center(910)

[0151] According to the present invention, the fluorescence lifetime of the NV centre or other colour centre of the diamond is used to determine the type of the diamond.

[0152] Inspire(920)

[0153] The unknown type of diamond is excited under a confocal microscope, usually by a laser of a predetermined and appropriate wavelength. The excited diamond produces fluorescence under the laser, and the fluorescence lifetime is measured and recorded by TCSPC.

[0154] Emitted fluorescence properties (930)

[0155] The emitted fluorescence characteristics 930 including the lifetime distribution and the shape of the spectrum may also be examined and analyzed in the present invention.

[0156] Effects of physical properties (940)

[0157] The fluorescence lifetime of an NV center or other color center is affected by the physical properties 940 of the diamond, such as inclusions, defects, crystallinity inconsistencies, lattice deformations, internal stresses, internal stresses, impurities, and homogeneity.

[0158] These physical properties vary between types of diamonds, such as natural diamonds, synthetic CVD or HPHT diamonds, treated diamonds, treated CVD or HPHT diamonds.

[0159] Determination of diamond type (950)

[0160] Therefore, the decay curve of the fluorescence intensity over time has characteristics indicative of the diamond type, thereby allowing the diamond type 950 to be assessed according to the present invention.

[0161] The present invention provides a process system and method for determining or evaluating the type of diamond based on the decay of fluorescence lifetime after excitation due to the physical characteristics of the diamond.

[0162] This is achieved by analyzing the fluorescence lifetime based on emission from color centers within the body of the diamond, whereby the inventors have discovered that the decay curve of natural diamonds is different from the decay curve of synthetically formed diamonds, and therefore the present invention provides a non-invasive assessment process based on the decay of the fluorescence lifetime following excitation of the color centers of the diamond, which can be used to determine whether the diamond is a naturally occurring diamond, or whether such a diamond may indeed be synthetically formed in a laboratory, such as a CVD diamond.

[0163] Synthetic diamonds provided under current manufacturing conditions may be difficult to distinguish from natural diamonds due to enhanced and improved manufacturing techniques, and therefore, the optical properties of such synthetic diamonds cannot generally be determined because they are different from the optical properties of naturally occurring diamonds.

[0164] Thus, the present invention provides a process by which natural diamonds and synthetic diamonds can be determined to be different from one another, which is useful for a variety of reasons, including misconduct, theft, diamond substitution, synthetic diamonds being passed off as natural diamonds, and the valuation of diamonds to determine whether a diamond is naturally or synthetically formed.

[0165] As will be appreciated, the process according to the present invention may be implemented in various forms and embodiments and systems embodying the process while utilizing the present invention to determine the fluorescence lifetime and thereby distinguish whether a diamond is a naturally occurring diamond or a laboratory synthesized or industrially grown diamond.

Claims

1. A method for determining the type of diamond, in, The type of diamond is determined by the following steps: (i) measuring the fluorescence lifetime characteristics of color centers of diamonds of unknown type; and (ii) determining the type of diamond by comparing the fluorescence lifetime characteristic measured in step (i) with the fluorescence lifetime characteristics of color centers of known diamond types; wherein the fluorescence lifetime characteristics of the color center indicate a physical property of the diamond, the physical property indicates the type of diamond, and wherein the diamond of unknown type and the diamond of known diamond type are excited by picosecond pulsed green laser with a wavelength of 510nm, 514nm or 532nm, and The measurement of the fluorescence lifetime of the color center of the unknown type of diamond and the fluorescence lifetime characteristics of the color center of the known type of diamond is achieved by a confocal laser scanning fluorescence microscope equipped with a time-correlated single photon counter module.

2. The method according to claim 1, in, The physical properties include inclusions, defects, inconsistencies in crystallinity, lattice distortion, internal stress, internal stress, impurities, and homogeneity.

3. The method according to claim 1 or claim 2, in, The types of diamonds described are natural diamonds, chemical vapor deposition (CVD) synthetic diamonds, high pressure high temperature (HPHT) synthetic diamonds, and treated natural diamonds.

4. The method according to claim 1 or claim 2, in, The method provides for the differentiation of natural diamonds from synthetic diamonds.

5. The method according to claim 4, in, The synthetic diamond is a CVD (chemical vapor deposition) diamond.

6. The method according to claim 1, in, The color center is an NV center, a SiV center or a NVN center.

7. The method according to claim 1, in, The physical properties are indicative of the type of diamond.

8. The method according to claim 1, in, The confocal laser scanning fluorescence microscope comprises: Pulse laser excitation module; Diamond sample stage; Objective lens; Focus stabilizer; Laser scanning module; A time-correlated single photon counter module; and Emission filter.

9. The method according to claim 8, in, The pulse laser excitation module is further provided with a linear polarizer and a half-wave plate for controlling the laser power and an acousto-optic modulator for the laser shutter.

10. The method according to claim 8, in, The diamond sample stage is composed of an XYZ 3-axis piezoelectric stage and an XYZ 3-axis electric mechanical stage for realizing sample scanning.

11. The method according to claim 8, in, The objective lens is an oil immersion type for irradiating the laser onto the diamond and collecting the resulting fluorescence from the diamond.

12. The method according to claim 11, in, The objective lens has a numerical aperture equal to or greater than 1.

3.

13. The method according to claim 8, in, The focus stabilizer is used to precisely control the distance between the diamond sample and the objective lens.

14. The method according to claim 8, in, The laser scanning module is composed of an electron microscope arrangement.

15. The method according to claim 8, in, The time-dependent single photon counter module is used to calculate the arrival time of the fluorescent photons after the diamond is excited by the single excitation focus stabilizer, and the single excitation focus stabilizer is used to accurately control the distance between the sample and the objective lens.

16. The method according to claim 1, in, The color center is an NV center, a SiV center or a NVN center.

17. The method according to claim 1, in, The type of diamond is determined based on the fluorescence lifetime characteristic of the diamond measured in step (i) being consistent with a predetermined threshold of correlation between the fluorescence lifetime characteristic of a known diamond type.

18. The method according to claim 1, in, The method can be operated using a computerized system, the computerized system comprising a fluorescence lifetime data acquisition system, a processor module, and an output module operatively connected to each other, wherein the type of the unknown type is determined by: (i) in a processor module, comparing data indicative of a fluorescence lifetime characteristic of a color center of the image of the diamond of unknown type with a plurality of data sets, each of the plurality of data sets corresponding to fluorescence lifetime characteristics of a color center of a plurality of diamonds of known types, wherein each of the data sets of fluorescence lifetime characteristics of color centers of diamonds of known types is obtained from a fluorescence lifetime acquisition system; and (ii) providing, from an output module, an output signal in response to a predetermined threshold of correlation between the data indicative of a fluorescence lifetime characteristic of a color center of the unknown type of diamond and one of the plurality of data sets, the output signal being indicative of the type of the diamond, and wherein the fluorescence lifetime characteristic of the color center of the diamond is indicative of a physical property of the diamond, the physical property being indicative of the type of diamond.

19. The method according to claim 1, in, The method can be operated using a computerized system comprising a pre-trained neural network and an output module operably connected to each other via a communication link, wherein the type of the unknown type is determined by: (i) determining, in a pre-trained neural network, a diamond type of the unknown type of diamond from data indicating fluorescence lifetime characteristics of color centers of the unknown type of diamond, wherein the pre-trained neural network has been pre-trained using a plurality of data sets, each of the plurality of data sets corresponding to fluorescence lifetime characteristics of color centers of a plurality of diamonds of known types; and (ii) From the output module, provide the type of the diamond.

20. A computerized system for determining the type of diamond, in, The computerized system relates a fluorescence lifetime characteristic of a color center of a diamond of unknown type to fluorescence lifetime characteristics of color centers of a plurality of diamonds of known types, the computerized system comprising: a fluorescence lifetime data acquisition system for acquiring data indicating fluorescence lifetime characteristics of a color center of a diamond of an unknown type; a processor module for comparing the data indicative of the fluorescence lifetime characteristics of the color centre of the image of the diamond of unknown type with a plurality of data sets, each of the plurality of data sets corresponding to the fluorescence lifetime characteristics of the color centre of a plurality of diamonds of known type; and an output module for providing an output signal indicating the type of the unknown type of diamond based on a predetermined threshold of correlation between the data indicating the fluorescence lifetime characteristics of the color center of the unknown type of diamond and one of the plurality of data sets corresponding to the fluorescence lifetime characteristics of the color centers of a plurality of diamonds of known types, Wherein, the system further comprises: a picosecond pulsed green laser with a wavelength of 510 nm, 514 nm or 532 nm for exciting the unknown type of diamond, and A confocal laser scanning fluorescence microscope, equipped with a time-correlated single photon counter module, was used to measure the fluorescence lifetime of the color centers of the unknown type of diamond.

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