KR19990035900A - Inspection of diamonds - Google Patents

Abstract

To check whether a synthesized diamond layer is deposited on the diamond 2, the diamond is irradiated with ultraviolet radiation 4 to form a pattern of reflected and refracted radiation, and the pattern of reflected and refracted radiation is diamond ( 2) observed on screen 5 behind.

Description

Inspection of diamonds

Synthetic diamond material may be deposited on uncut or partially processed natural diamond, which is later processed into round brilliant cuts and the like. Alternatively, a synthetic diamond material coating may be deposited onto the fully completed brilliant stone after processing the gem. Although the thickness of the synthetic diamond material layer can be very thin (in the range of 5 microns to 10 microns), the present invention can also be used to detect thicker layers.

The value of a diamond depends in part on its weight. Thus, the synthetic diamond material may be deposited onto the natural gem diamond before or after cutting the diamond to increase the weight of the finished product. However, the quality of a diamond depends on its authenticity and uniqueness and on what is entirely natural (ie quarryed). Thus, diamonds deposited by synthetic diamond materials that are not large have greater value than such diamonds.

Over the years, several methods of synthesizing diamonds have been developed. One of these is the chemical vapor deposition (CVD) technique, which is a low pressure technique for depositing synthetic diamond (hereinafter referred to as CVD diamond material) from a gas onto a substrate. Physical vapor deposition is also proposed, but CVD is a method where synthetic diamonds are more likely to be deposited onto diamonds. Diamond or pseudodiamond material artificially enlarged by CVD deposition is referred to herein as "CVD / natural diamond doublet".

CVD diamond material may be deposited on a non-diamond or diamond substrate. In the latter case, the CVD diamond material can duplicate the structure of the diamond substrate (called "homoepitaxial growth"). CVD / natural diamond doublets may have the same appearance, density and other physical properties as full natural stone, and may have problems identifying CVD / natural diamond doublets.

A method for checking whether a synthetic diamond layer is deposited on top of diamond is disclosed in British Patent Application No. 9401354.7. Multiple portions of the diamond are irradiated with radiation having a wavelength substantially in the range of 230 nm to 320 nm, and radiation from the diamond is observed.

British Patent Application No. 9401354.7 is based on the observation that if different regions of the diamond show a difference in the absorption of radiation at wavelengths between 230 nm and 320 nm, the diamond can be determined to have a synthetic diamond deposited. It is observed that if all regions of the diamond strongly absorb radiation of substantially 230 nm to 320 nm, the diamond can be almost classified as a fully natural diamond.

The intensity of the radiation coming from the area of the diamond can be confirmed by using an imaging device or by placing the diamond in an integrated sphere. Preferably, the image of the diamond is formed against a dark or light background.

It is an object of the present invention to provide a method of inspecting whether a synthetic diamond layer is deposited on a diamond, wherein a relatively simple imaging device is used and no expensive integral spheres are used.

The device is simple and inexpensive and preferably can be operated by an operator with relatively little training. The method and apparatus should be able to be reliably and consistently operated by a working jeweler who is not trained in jewelery analysis in the laboratory.

The present invention relates to a method and apparatus for checking whether a natural diamond has a synthetic diamond deposition layer thereon. This is especially important for testing whether a diamond is completely natural or if a portion of the diamond contains a chemical vapor deposition (CVD) diamond material and, if present, to detect its location.

The present invention will be described below by way of example with reference to the accompanying drawings.

1 is a schematic diagram of a device according to the invention.

2A-2F schematically show patterns of refractive and reflective beams made in accordance with the present invention when various diamonds are irradiated with ultraviolet or visible light.

The present invention relates to a method for inspecting whether a diamond has a layer of synthetic diamond deposited thereon,

Guiding an ultraviolet beam toward the face of the diamond to form a pattern of the beam of radiation by reflection and refraction of the irradiated radiation, and observing the pattern of the radiation beam having a wavelength substantially between 230 nm and 320 nm.

The present invention uses the same principle that a particular kind of diamond absorbs ultraviolet radiation of a particular wavelength, as in British Patent Application No. 9401354.7.

In US Pat. No. 3947120, et al, it is known that reflected and refracted radiation creates a pattern of spots characteristic of each gem when light is directed to the cut gem.

The inventors have discovered that different interactions of different types of diamond with ultraviolet radiation of the corresponding wavelength can affect the pattern of spots obtained and may help identify the synthetic diamond layer on the surface.

For simplicity, a substantial difference in the complexity and strength of the beams made in other parts of the diamond (also taking into account the shape of the diamond) indicates the presence of a synthetic layer on the diamond.

Specifically, the present invention strongly absorbs ultraviolet light with wavelengths shorter than approximately 230 nm in synthetic diamond layers, especially class II diamonds, while most of the natural diamonds are classified as 1aA or 1aAB and strongly absorb ultraviolet light with wavelengths shorter than approximately 320 nm. It is based on the observation that it is a kind. Natural diamond is generally expected to produce reflective or refracted beams that are weak or unobservable to radiation of wavelengths shorter than 320 nm.

Synthetic diamond layers are generally expected to produce complex refractive and reflective beams. Any diamond foreseeing the presence of a synthetic layer can be examined in more detail.

Preferably, the entire present face of the diamond is investigated. This allows a complete pattern of the beam to be formed and observed.

In principle, one observation of the reflected and refracted beam of radiation will be sufficient to confirm the presence of the synthetic diamond material layer. If, for example, the diamond's plane of symmetry is exposed to radiation and an asymmetric pattern of the beam is obtained, the presence of the synthetic diamond layer can be predicted.

However, it is desirable to direct the beam of radiation to the diamond continuously in several directions and to compare the resulting patterns. The interpretation of the results will be explained in more detail below.

Only a few faces (maybe two faces) may be sufficient to detect the difference in the pattern of the reflected or refracted beam. However, preferably several aspects will be examined continuously.

The diamond can be irradiated with the appropriate radiation (discussed below) at a suitable source. The irradiated radiation can be focused if necessary.

The beam of radiation to be irradiated may be of smaller dimensions than the face of the current diamond but is preferably larger.

In the present invention, the pattern of the reflected reflected and refracted beam does not correspond to the image of the diamond. What is observed is the pattern produced when the reflected and refracted beam is caught on an imaginary plane away from the diamond. Screens or scanning means may be placed on this virtual surface. The scanning means can measure the intensity of the light at points on the virtual plane to record the pattern of the reflected and refracted beams.

Preferably, the pattern of reflected and refracted beams places the screen at a predetermined distance from the diamond so that the reflected and refracted beam of radiation impinges on the screen and senses the pattern of the screen. Preferably, an image of the pattern on the screen is formed.

The screen can be moved relative to the diamond and can be adjusted in the angular direction.

The screen is preferably placed in the direction of irradiation of the diamond so that the reflected and refracted beams scattered backwards are observed. In this case, it is preferable that the radiation passes through the diamond through the gap in the screen.

The screen may be equipped with an ultraviolet photosensitive fluorescent screen to reveal the pattern of the beam being made. In this case, the screen can be observed through viewing means having a filter for blocking harmful radiation.

Alternatively, a camera can be used to view the screen.

The observed radiation may comprise narrow bands of wavelengths substantially lying within the aforementioned ranges, and may be several such narrow bands or a relatively wide band thereof. Optionally, it falls within the range of 230 nm to 300 nm, preferably below 290 nm. The radiation observed may include radiation of wavelengths deviating from 230 nm to 320 nm, but such radiation is preferably of low enough intensity to avoid confusion with observation of the relevant wavelength.

The radiation can be generated by a suitable laser, for example a krypton fluoride excimer laser.

To observe radiation at wavelengths of substantially 230 nm to 320 nm, diamond can be irradiated with this radiation (made by a wider band source with a laser or filter). Alternatively, the diamond may be irradiated with radiation having a wider range of wavelengths, and a wavelength selecting means such as a filter may be provided between the diamond and the screen, or imaging means may be provided for passing radiation of substantially 230 nm to 320 nm wavelengths. have. If the diamond has been irradiated at a wavelength of substantially 230 nm to 320 nm, a wavelength selection means may be provided to exclude radiation produced by the fluorescence excited by the projected ultraviolet radiation. Typically, however, the intensity of the fluorescence is not strong enough to require filtering.

If the radiation to be irradiated is a projection on the diamond region, it will generally be strongly absorbed or partially transmitted. The radiation transmitted by the area of diamond will be refracted within the diamond and some of the transmitted radiation can be observed to leave the surface of the diamond. Thus, reflected and refracted radiation will be produced when the diamond face is irradiated.

The intensity of the beam refracted from any given plane depends in part on the transmittance of that surface and in part on the angle at which radiation is projected onto the surface. The intensity of the refracted radiation beam will depend, in part, on the transmittance and thickness of the diamond material of the part being observed.

Natural diamond typically has a high absorption at that wavelength such that the projected radiation is almost completely absorbed.

CVD or other synthetic diamond material layers, in particular type II diamond, are at least partially transparent.

Thus, if the face of the diamond is normally irradiated and hardly a refracted beam is made other than the reflection perpendicular to the face, the face can be determined to be a natural diamond.

If the face is typically irradiated and a weak reflection and refraction beam is observed, it indicates the presence of a thin synthetic diamond layer.

If the face of the diamond is irradiated far away from the relatively normal angle (called "oblique irradiation"), and a relatively weak and simple pattern of the reflected beam is made, the face to be irradiated can be determined to contain natural diamond. . However, if the pattern is relatively strong and complex reflective and refractive beams are observed, then the presence of synthetic diamond material is predicted.

Because it can be reflective and refractive beams due to rare natural diamonds, what is expected of synthetic diamond materials should be further examined.

If the diamond is irradiated on a nearly symmetrical surface and a very asymmetrical pattern is created (for example, one bright and one dark), it can be concluded that the diamond face is a different configuration.

Due to the complex pattern of light paths in the brilliant cut diamond, the two parts of the CVD / natural diamond doublet may not be immediately apparent. It may be necessary to make observations while manipulating CVD / natural diamond doublets to more clearly see the two parts of the diamond.

When the diamond is irradiated with the first mentioned radiation, to aid in the interpretation of the reflected and refracted beam pattern, the diamond may be irradiated with almost transmitted radiation, for example visible light, in all kinds of diamonds to form a reference pattern. will be. This pattern will then be compared using the first mentioned radiation, preferably with diamonds of the same configuration.

The reference pattern is expected to exhibit a relatively strong and complex pattern that is reflected and refracted for all kinds of diamonds.

The present invention provides a means for irradiating diamond with ultraviolet radiation, and

A screen on which the screen is mounted at a predetermined distance from the diamond so that the screen catches a pattern of beams of reflected and refracted radiation produced when the diamond is irradiated, and

Provided is a method for inspecting having a synthetic diamond layer deposited over diamond having means for allowing a pattern of radiation beams of wavelengths substantially in the range of 230 nm to 320 nm on the observed screen.

The device according to the invention can be automated to interpret and analyze the resulting image or reading. However, this is not desirable as a simple system in which an operator can easily and easily interpret an image.

In an apparatus such as 1 schematically shown in FIG. 1, the diamond 2 is irradiated by a laser 3 by radiation of a wavelength substantially in the range of 230 nm-320 nm. The laser beam 4 is directed through the gap 6 and the screen 5 provided in the middle of the screen 5. If a beam of radiation 4 is projected onto the diamond 2, a pattern of reflected and refracted radiation beams will be made. In the embodiment of FIG. 1 a pattern made in the direction of scattering backwards is studied. The screen 5 is movable and adjustable in the angular direction. The pattern is studied by placing the screen 5 away from the diamond 2 so that all beams of reflected and refracted radiation are substantially captured by the screen. Typically, for a 100 mm x 100 mm screen, the distance between the diamond and the screen is about 60 mm.

Observation means 7 are provided for observing the pattern of the reflected and refracted beams formed on the screen 5.

The screen 5 is an ultraviolet fluorescent screen, which creates spots of visible light upon the leakage of ultraviolet radiation of 230-320 nm wavelength thereon. Observation means 7 comprise suitable optics for filtering ultraviolet wavelength radiation which may be dangerous to the eye.

The entire device 1 except for the observation means 7 can be housed in a light-tight box in order to retain external ultraviolet radiation and eliminate external radiation that can disrupt the pattern on the screen. The observing means 7 is mounted at a suitable position in the wall of the light-tight box so that the observer can observe the pattern on the screen 5.

To provide a reference pattern, a laser 8 has been provided that produces light of visible wavelengths. A beam splitter 9 can be provided in the path of the beam 4 so that visible radiation from the laser 8 can be directed down the path of the radiation 4 irradiated from the laser 3. Preferably, the lasers 3 and 8 are used alternately so that different patterns of different types of radiation can be compared.

2a to 2f, the results of the diamond irradiation according to the present invention are shown.

Three cases were studied.

a. Diamond, a CVD / natural diamond doublet with synthetic parts on the diamond's culet.

b. CVD / natural diamond doublet in which synthetic diamond is formed on a table of diamonds.

c. Perfect natural diamond.

In each case, the diamond was cut into diamonds with brilliant cuts, which are frequently encountered cuts. However, the technique is more complex and care must be taken in the interpretation of the return pattern, but it can be applied to all diamond cuts including fancy cuts.

Diamonds are examined using three steps.

1. Irradiating the table in the vertical direction using ultraviolet radiation having a wavelength substantially in the range of 230 nm-320 nm.

2. conventionally illuminating the table using visible radiation, and

3. Irradiating the curet using substantial ultraviolet radiation at a wavelength substantially falling within the range of 230-320 nm.

The three types of diamonds mentioned above can be distinguished using different patterns of radiation that they reflect and refractate.

2A-2F, high intensity spots are shown as black dots, medium intensity spots are short solid lines, and low intensity spots are indicated by broken lines.

In Figures 2A-2C, although practically separate, Step 1 and Step 2 are shown on a single screen for comparison.

2a shows the results of steps 1 and 2 in diamond (a).

In step 1 the pattern on the screen is observed to comprise a single high intensity spot 10 created by the normal reflection of the irradiated radiation.

In step 2, a complex and powerful pattern of spot 11 is observed.

2b shows the results of steps 1 and 2 for diamond (b). In step 1, a pattern of relatively low intensity reflected and refracted beam 12 is observed. In step 2, a pattern of reflected and refracted beams of relatively high intensity is made. The pattern is different because the refractive index at the observed ultraviolet wavelength is different from the refractive index of visible radiation.

In figure 2c the results of steps 1 and 2 are shown with respect to diamond (c). In step 1, a single relatively high intensity spot 14 is made only by radiation that is reflected vertically. In step 2, a relatively strong and complex pattern of reflective and refracting beams 15 is made. The pattern observed in FIG. 2C is similar to that shown in FIG. 2A.

2d shows the result of step 3 for diamond (a). A relatively complex pattern of strongly reflected and refracted beam 17 is created with strong beam 16 because of the radiation reflected vertically in the curet (assuming a curette facet).

2e shows the result of step 3 for diamond (b). A relatively weak and simple reflective beam 18 is produced due to the reflection of the cut face around the curet.

2f shows the result of step 3 for diamond (c). A simple pattern of relatively weak reflecting beam 19 is made.

In the device shown in FIG. 1, the ultraviolet laser comprises a 248 nm krypton fluorine excimer laser from Potomac lasers. The laser 8 may comprise a 635 nm diode or 633 nm HeNe laser from Vector Technology / Melles Griot. The beam splitter 9 is manufactured by Spindler and Hoyer and the ultraviolet photosensitive fluorescent screen is supplied by Levy-Hill Ltd. If a camera is used to view the screen 5, it may be a CCD camera that can be combined with a computer to analyze the spot pattern that is made.

Claims (15)

A method of checking whether a layer of synthetic diamond is deposited on a diamond, Directing an ultraviolet radiation beam towards the face of the diamond to form a pattern of the radiation beam according to the refraction and reflection of the irradiated radiation, and Observing a pattern of a substantially radiation beam of wavelength substantially in the range of 230 nm to 320 nm. 2. The method of claim 1, further comprising: directing a beam of ultraviolet radiation to the second face of the diamond, observing a pattern of the beam of radiation having a wavelength substantially in the range of 230-320 nm made by the second face; Comparing the pattern of the beam of the diamond face to the pattern of the beam of the diamond second face. A method according to claim 1 or 2, characterized in that a plurality of faces of the diamond to be irradiated are irradiated continuously. The method of claim 1, wherein the pattern of reflected and refracted beams is arranged at a distance from the diamond so that the beam of reflected and refracted radiation hits the screen and senses the pattern of the beam on the screen. Characterized in that the method. The method of claim 4, wherein an image of the screen is formed. 6. A method according to claim 4 or 5, wherein the screen lies on the direction in which the diamond is irradiated so that reflected and refracted beams scattered backwards are observed. 7. A method according to claim 4, 5 or 6, wherein the screen comprises an ultraviolet photosensitive fluorescent screen. The method of any one of the preceding claims, further comprising irradiating the face of the diamond with radiation transmitted from almost all kinds of diamonds to form a reference image. A device for checking whether a layer of synthetic diamond is deposited on a diamond, Means for irradiating the diamond with ultraviolet radiation; A screen mounted at a distance from the diamond to pattern a beam of radiation that is reflected and refracted when the diamond is irradiated, and And means for observing a pattern on the screen of the radiation beam within a substantial range of wavelengths wherein the pattern of the radiation beam is substantially 230 nm to 320 nm. 10. The device of claim 9, wherein the screen comprises an ultraviolet fluorescent screen. The apparatus according to claim 9 or 10, wherein the irradiation means comprises a laser. 12. The apparatus according to any one of claims 9 to 11, further comprising means for irradiating diamond with radiation transmitted through almost all midstream diamonds. 13. The apparatus according to any one of claims 9 to 12, wherein the screen lies on the direction of the irradiated side of the diamond to catch the reflected and refracted beams scattered back from the diamond. A method for inspecting whether a synthetic diamond layer is deposited on a diamond, the method being substantially described herein in connection with the accompanying drawings. An apparatus for inspecting whether a synthetic diamond layer is deposited on a diamond, wherein the apparatus is substantially described in connection with the accompanying drawings.