Electric heating – Metal heating – By arc
Reexamination Certificate
1999-05-11
2001-04-03
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121690, C219S121830, C283S074000
Reexamination Certificate
active
06211484
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of inscribing indicia on a surface of gemstones, and more particularly to a system employing a Q-switched pulse laser for forming markings on a portion of a gemstone.
BACKGROUND OF THE INVENTION
A known system, as described in U.S. Pat. No. 4,392,476, incorporated herein by reference, for inscribing diamonds includes a Nd:YAG (1.06 &mgr;m, frequency doubled) Q-switched laser which marks diamonds by graphitizing the surface at a laser focal point. The beam position is computer controlled to create overlapping treated regions. The accuracy of known embodiments of this system are limited by vibration and laser steering system accuracy.
U.S. Pat. No. 4,467,172, incorporated herein by reference, describes a laser beam diamond inscribing system, which provides a Q-switched flashlamp pumped YAG laser (1.06 &mgr;m, frequency doubled) with the diamond mounted on a computer-controlled positioning table for inscribing alphanumeric characters. See also, U.S. Pat. Nos. 2,351,932, 3,407,364, 3,527,198, 3,622,739, 3,775,586 and 4,048,515, and foreign patents JP 0048,489 and JP 00-77,989.
U.S. Pat. Nos. 5,410,125 and 5,149,938 describe systems which produce a gemstone marking by employing an excimer laser (193 nm) with a masked marking image. Thus, repositioning to form complete characters or graphics is unnecessary. The diamond selectively absorbs the excimer laser radiation and undergoes a partial allotropic transformation without losing its diamond crystal lattice configuration. See also, U.S. Pat. Nos. 3,527,198 and 4,401,876. U.S. Pat. No. 5,410,125 is a continuation-in-part of Ser. No. 595,861, issued as Pat. No. 5,149,938.
Gemstone News, Nov. 2, 1995, “Serial Numbers are Laser Inscribed”, and Jeweler's Keystone-Circular, June 1996, pp. 76 relate to gemstones inscribed with serial numbers or markings.
U.S. Pat. No. 3,537,198 relates to a method of working diamonds using laser energy. U.S. Pat. No. 5,190,024, relates to a diamond sawing process. A laser can be used both to mark and saw the diamond in one operation. See also, U.S. Pat. Nos. 671,830, 671,831, 694,215, 732,118, 732,119, 3,527,198 and 4,392,476, as well as Foreign Reference GB 122,470.
U.S. Pat. No. 4,401,876 relates to a system for kerfing a gemstone such as a diamond, employing a high energy, high pulse rate, low order mode, laser beam. See also, U.S. Pat. Nos. 3,440,388, 3,527,198 and 3,700,850, as well as foreign references BE 877,326, DE 130,138, DE 133,023, GB 1,057,127, GB 1,059,249, GB 1,094,367, GB 1,254,120, GB 1,265,241, GB 1,292,981, GB 1,324,903, GB 1,326,775, GB 1,377,131, GB 1,405,487, GB 1,446,806, GB 2,052,369, Laser Institute of America, “Guide for Material Processing by Lasers” 1978; “Industrial Diamond Review”, Mar. 1980, pp. 90 and 91; “Laser Application Notes”, 1(1) (Feb. 1979); “New Hyperyag”, on Model DLPY 4-System 2000 Yag Laser; and “Diamonds”: N.A.G. Press LTD, Chapter Eleven, pp. 235, 239-242.
U.S. Pat. No. 4,799,786, incorporated herein by reference, relates to a method of diamond identification in which a sample to be identified is placed in a beam of monochromatic laser radiation of pre-determined wavelength. The scattered Raman radiation emitted from the sample is passed through a filter adapted to pass only scattered Raman radiation of frequency characteristic of a diamond. The filtered radiation is then detected by the human eye or a photocell device. See also, U.S. Pat. Nos. 4,397,556 and 4,693,377, and foreign patent GB 2,140,555, Melles Griot, Optics Guide 3, 1985, pp. 1, 333, 350, 351; and Solin et al., Physical Review B, 1(4):1687-1698 (Feb. 15, 1970).
U.S. Pat. No. 4,875,771, incorporated herein by reference, relates to a method for assessing diamond quality, by assessing diamonds with a laser Raman spectrometer. The system is initially calibrated by use of diamonds with known quality characteristics, the characteristics having been assessed, for example, by a conventional subjective procedure. Diamonds of unknown quality characteristics are then placed in the spectrometer and irradiated with laser radiation. The intensity of the scattered Raman signal from the diamond is monitored for one or more orientations of the diamond, the resultant signal being a characteristic of the diamond and believed to indicate a quality level of the diamond. See also, U.S. Pat. Nos. 3,414,354, 3,989,379, 4,259,011, 4,394,580, 4,397,556 and 4,620,284, and foreign patents FR 643,142, FR 2,496,888, JP 01-58,544, GB 1,384,813, GB 1,416,568, GB 2,010,474, GB 0,041,348 and GB 2,140,555, S. A. Solin and K. A. Ramdas, Raman Spectrum of Diamond, Physical Review vol. 1(4), pp. 1687-1698.
The aforementioned documents detail components, methods and systems which may be applied in the construction and operation of the present invention.
SUMMARY OF THE INVENTION
The present invention provides a system having a pulse laser, such as a Q-switched laser diode excited Nd:YLF laser, which produces a series of ablated or graphitized spots on the surface of a workpiece, such as a diamond gemstone. The workpiece is mounted on a translatable stage, for focusing and positioning of the beam.
The translatable stage is controlled by a computer to produce a complex marking pattern. This computer may also be used for process control and imaging, as well as other functions.
The process according to the present invention typically achieves a positioning accuracy of about ±1 micron. The laser and translatable mounting stage are compact and are preferably rigidly mounted on a common platform, allowing sufficient common mode vibration immunity so that only standard vibration damping need be employed rather than extraordinary damping. Therefore, simple and small passive vibration isolation mounts for the platform or chassis are employed, rather than requiring active vibration suppression systems as in known systems.
Optical feedback of the process is possible through one or more video cameras, e.g., 2 CCD imagers provided at right angles, which are provided with a field of view including the focal point of the laser. The correct positioning of the gemstone may thus be assured by correct alignment of the imagers on the workpiece. One imager is directed at the work surface along the axis of the laser, and has a focal plane including the focal point of the laser. Optical feedback through the imagers may also be used to monitor the progress of the marking process, and therefore may be used to adjust workpiece positioning as well as inscription speed, number, intensity and/or rate of pulses at a given location, as well as to verify progress of the marking process. One imager is directed to view a top portion of the workpiece, e.g., directed perpendicular to the table surface of a diamond, allowing identification of a girdle profile, while the second imager is directed to view a side portion of the workpiece, e.g., a profile, and also providing a direct view of the girdle of a gemstone. Thus, the second imager may be used to view the marking process in real time.
The optical feedback system also allows the operator to design an inscription, locate the inscription on the workpiece, verify the marking process and archive or store an image of the workpiece and formed markings.
The markings themselves may have an invariant inscription, a fully automated inscription, e.g., a serial number, a semiautomated inscription, e.g., having a fixed and variable portion, or a fully custom inscription, including graphics.
According to one embodiment, an inscription for a gemstone is defined in relation to a bar code which accompanies the packaging for the gemstone or a preprinted sheet. A bar code reader is provided for the operator to input the bar codes into a computer, without having to retype the data and with lower risk of error. Thus, an inscription may include a fixed portion, e.g., a logo or trademark, a semivariable portion, e.g., a gem rating or grading, and a hypervariable portion, e.g., a serial number. In this case, for example, a logo or trademark is preprogrammed, and i
Anner Oded
Gurvich Leonid
Kaplan George R.
Shachrai Avigdor
Evans Geoffrey S.
Lazare Kaplan International Inc.
Milde Hoffberg & Macklin, LLP
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