IL294229B1 - Method and system for determining location of stresses in a diamond - Google Patents

Description

METHOD AND SYSTEM FOR DETERMINING LOCATION OF STRESSES IN A DIAMOND BACKGROUND Stress (or strain or tension – all synonyms) in diamonds is a phenomenon inherent in the growth of the different Carbon layers of the diamond, whether man made diamond or a natural one. Stress in diamonds can create many difficulties for the diamond manufacturers, among which but not solely are those involved in producing a finished diamond from a rough stone, including planning how to the rough stone is to be cut/sawn e.g. by a laser, into 2 or more pieces and providing polishing considerations. The Applicant and the inventors of the presently disclosed subject matter are not aware of any process or machine performing 3D mapping of diamonds and of stresses therein, and presentation of such stresses, if any, in a 3D model , and the presently disclosed subject matter is directed to such process and machine which are expected to make the manufacturing and processing of diamonds a more secure process allowing the manufacturer to plan his steps through all the manufacturing process. For the sake of good order it needs to be indicated that there exists a manual method, which uses a polariscope for viewing stresses in diamonds but such viewing is not mapping locations of the stresses, i.e. providing their map as a file with the applied resolution, and it does not allow to automatically determine the locations and presenting them in a 3D model of the diamond. BACKGROUND ART - WO2007/023444 - WO2008/1023 GENERAL DESCRIPTION The presently disclosed subject matter concerns a method and system for detecting stresses in a diamond and, more particularly, determining the location of at least one stress area, if any, in a diamond.

The method according to one aspect of the presently disclosed subject matter is to be performed on a diamond disposed in an immersion medium, and it includes providing illumination including a wavelength, at which the immersion medium can have a refractive index substantially matching that of the diamond; polarizing this illumination by a polarizer and illuminating therewith the diamond within the immersion medium; passing light which exits the diamond and the immersion medium through a polarization analyzer; detecting the light that has passed through the analyzer and determining location of at least one stress area within the diamond based on this detection. If an image, that is obtained based on the detected light, has substantially no dark areas, namely the polarized light did not change its polarization while propagating through the diamond and the immersion medium, it can be concluded that the diamond is free of stresses. Whilst if the image has dark areas (areas through which light did not pass or passed only partially), this can serve as an indication that the diamond might have at least one stressed area. Since the change of polarization can happen not only due to stresses within the diamond but also due to inclusions, the method of the presently disclosed subject matter can comprise an inclusion detection step performed in any known manner, before or after the above stress detection, to exclude the influence of inclusions on the polarized light during the stress detection, and a final decision on the location of the at least one stress in the diamond is made based on the results of the stress detection and inclusion detection. The polarizer and the analyzer can be aligned one to another such that they both are configured to pass light having the same polarization. In this case, when the polarized light propagates through a stressed area and inclusions within the diamond, if any, it will change its polarization and will be blocked by the analyzer, allowing only the light that has passed through the diamond in areas that are clean from stresses and inclusions to exit the diamond and the immersion medium with about the same polarization as it entered thereto. The detection of the light exiting the analyzer can be performed by a detection system including light collection optics, a camera, to which the light collection optics is configured to direct that light and a processor. The camera is being capable of detecting light having the wavelength mentioned above and produce signals responsive thereto, which signals are then processed by the processor to determine the location of at least one stress in the diamond.

The location of the stresses in the diamond is determined as described above relative to a predefined system of coordinates, and the method can further comprise 3D mapping of the exterior surface of the diamond, when free from the immersion medium, to produce its 3D model within the same or correlated system of coordinates, in which case the method can result in producing a 3D model of the diamond with the determined stresses shown therein. The above method can be carried out from at least two perspectives relative to the diamond. By one example, the method can be carried out in at least two rotational positions of the diamond about a vertical axis of rotation passing through the optical axis. The diamond can be held within the immersion medium by a holder so as to allow its rotation within the immersion medium, or it can be rotated together with the immersion medium, about the vertical axis of rotation to allow the diamond within the immersion medium to be illuminated from a plurality of different perspectives. In order to distinguish the stressed areas from the inclusions in this case, the inclusion detection can be performed at the same rotational positions of the diamond and with the same illumination as in the stress detection, though without using the polarizer and analyzer. It should be noted that the method can be carried out by other ways of tomography known in the art that do not require rotation of the diamond, e.g. using a confocal microscope. Another aspect of the presently disclosed subject matter also includes a system for determining location of at least one stress in a diamond as described above, comprising a detection area configured for mounting thereon the diamond within the immersion medium so that the system's optical axis passes through the detection area, an illumination source and the polarizer disposed on one side of the detection area, the polarization analyzer and the detection system disposed on the other side of the detection area, all being arranged along said optical axis. The polarizer and the polarization analyzer are rotatable around the optical and axis and also removable from the optical axis when it is desired to capture a non-polarized image. The system can further comprise means for rotating the diamond with or within the immersion medium. The system can further be configured to produce a 3D model of the diamond including the stresses, based on a 3D map of the exterior surface of the diamond produced externally and received by the system processor or produced by the system. In the latter case, the system can comprise a 3D mapping device via which the diamond can be conveyed prior to its insertion into the immersion medium, for producing a 3D map of its exterior surface. Such device can be any known diamond 3D mapping device. The 3D model can optionally include also the inclusions within the diamond along with the stressed areas. The stress detection of the present invention, as well as the inclusion detection, can be performed in a system, which is similar to that described in in WO 2008/102361, whose description from these publication is incorporated herein by reference, with added thereto the polarizer positioned between the illumination source and the immersion medium with the diamond, and the analyzer positioned between the immersion medium with the diamond and the detection system. In another aspect of the present invention is provided a method for generating a 3D model of a diamond comprising 3D mapping of the diamond configured for producing a 3D model of its external surface, determining location of stress areas in the diamond, if any, and generating a 3D model of the diamond with the representation of stress areas therein relative to the external surface of the diamond. In some embodiments the method further comprising determining location of inclusions in the diamond. In some other embodiments of the method, the determination of location of the stress areas comprises taking into account the location of inclusions. In yet some other embodiments of the method, the 3D model with the representation of stress areas further comprises representation of the inclusions. In yet some other embodiments of the method, the determination of location of stress areas and inclusions is performed when the diamond is disposed within an immersion medium having a refractive index substantially matching that of the diamond. In yet another embodiment the 3D mapping of the diamond configured for producing a 3D model of its external surface is performed when the diamond is free of the immersion medium. In another aspect of the present invention is provided a 3D model of a diamond that is obtainable by the above described methods.

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig. 1A-1Bshow a top view of a schematic illustration of two embodiments of a system of the present invention. Fig. 2A-2C show exemplary images of a diamond captured in a system of the present invention. Figs. 2A-2Bshow images of a diamond captured in configurations of the system wherein the polarizer is offset by 0° and 20° respectively. Fig. 2Cshows an image that is a combination of the images of Fig. 2A-2B . Fig. 3A-3B show exemplary presentations of the stressed areas within the diamond of Figs. 2A-2C .

DETAILED DESCRIPTION OF EMBODIMENTS

Claims (14)

1.- 10 - CLAIMS: 1. A method for determining a location of at least one stress in a diamond, the method comprising: (a) illuminating the diamond with a polarized input illumination, (b) detecting a first output illumination indicative of the first polarized illumination after passing through the diamond and generating first image data, (c) illuminating the diamond with a non-polarized input illumination, (d) detecting a second output illumination indicative of the non-polarized input illumination after passing through the diamond and generating second image data, (e) processing the first and second image data to determine the location of the at least one stress in the diamond.

2. The method according to claim 1, wherein said steps (a)-(b) and (c)-(d) are performed with respect to two or more perspectives of the diamond.

3. The method according to claim 1 or 2, wherein the diamond is immersed within an immersion medium having a refractive index substantially matching that of the diamond in at least one wavelength of the polarized and non-polarized input illuminations.

4. The method according to any one of the preceding claims, wherein said polarized input illumination and said first output illumination are passed through a polarizer and an analyzer located respectively before and after the diamond, wherein the polarizer and analyzer have a 0 degree offset therebetween.

5. The method according to any one of the preceding claims, wherein said polarized input illumination and said fist output illumination are passed through a polarizer and an analyzer located respectively before and after the diamond, wherein the polarizer and analyzer have between 1 and 45 degree offset therebetween. - 11 -

6. The method according to any one of the preceding claims, comprising generating a 2D or 3D model of the diamond including the indication of the at least one stress therein.

7. The method according to any one of the preceding claims, wherein said second output illumination is indicative of inclusions within the diamond.

8. A system for determining a location of at least one stress in a diamond, the system comprising: - a first setup comprising: o a holder holding the diamond, o an illumination source configured to generate an illumination of at least one wavelength to illuminate the diamond, and o a detector configured to detect output illumination exiting from the illuminated diamond, - a second setup comprising: o the first setup, o a polarizer located between the illumination source and the diamond, the polarizer being configured to receive the illumination from the illumination source and generate a polarized illumination for illuminating the diamond, and o an analyzer located between the diamond and the detector, the analyzer being configured to transmit illumination having about the same polarization of the polarized illumination, and - a processor configured to activate the first setup to generate a first non-polarized image data of the diamond, and the second setup to generate a second polarized image data of the diamond, and process the first and second image data to determine the location of the least one stress in the diamond. - 12 -

9. The system according to claim 8, wherein said holder is rotatable about an axis enabling obtaining said first and second image data from two or more perspectives of the diamond.

10. The system according to claim 8 or 9, wherein said holder is configured to hold the diamond while immersed within an immersion medium having a refractive index substantially matching that of the diamond in the at least one wavelength.

11. The system according to any one of the claims 8 to 10, wherein for at least some of the second image data, said polarizer and analyzer have a 0 degree offset therebetween.

12. The system according to any one of the claims 8 to 11, wherein for at least some of the second image data, said polarizer and analyzer have between 1 and 45 degree offset therebetween.

13. The system according to any one of the claims 8 to 12, wherein said processor is configured for generating a 2D or 3D model of the diamond including the indication of the at least one stress therein.

14. The system according to any one of the claims 8 to 13, wherein said first image data is indicative of inclusions within the diamond.