Electric heating – Metal heating – By arc
Reexamination Certificate
2002-01-15
2004-03-30
Alexander, M. (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06713715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject invention relates to a method and system for laser marking a gemstone. In particular, the present invention directs itself to the generation of a laser pulse having a pulse duration of 1 nanosecond or less. More particularly, this invention directs itself to the positioning and marking of a gemstone to be marked by the focused approximate 1 nanosecond laser pulse.
Further, a computer control system displaces the gemstone with respect to the focused laser pulse, the displacement corresponds to a predetermined path defining the contour of indicia to be marked. Still further, this invention directs itself to a gemstone laser marking system including a video camera and display for viewing and recording the laser marking process.
Further, this invention pertains to a method and system for laser-marking a gemstone where the image of any indicia formed therein may be viewed in a magnified state.
Still further, this invention is directed to a method of marking a gemstone by using a pulsed laser having a predetermined pulse duration. Additionally, this invention relates to an automated system for precisely marking a gemstone in a predetermined pattern.
2. Prior Art
Laser marking systems for inscribing indicia on gemstones are known in the art. Kaplan, et al, Ehrenwald, et al., and Winston, et al. all teach laser marking systems utilizing focused energy from a pulsed laser to ablate or vaporize material on one or more facets of a polished gemstone. Laser ablation of diamond is generally a two-step process in which the laser energy first converts a shallow layer at the surface of the irradiated region from diamond to graphite and then vaporizes a portion of the graphite layer. At the end of the laser marking operation, the surfaces underlying the vaporized regions are typically covered by a thin layer of graphite.
For the laser ablation or marking process, the laser energy must typically exceed a certain minimum threshold level for vaporization of any material to occur. When applied specifically to the marking of gemstones, deposition of excessive laser energy during the ablation process can chip or fracture the gem, thus equipment that reduces the laser energy required for marking, exhibits less risk of damaging the stone. Generally, the threshold energy for vaporization decreases with decreasing laser wavelength, in prior art gem marking systems utilize laser pulses in the green or ultraviolet wavelengths which reduce the laser energy required for the marking process. The duration of these pulses is typically 10 to 100 nanoseconds.
The threshold energy, however, for vaporization of most materials also decreases with decreasing laser pulse duration over a range extending from 10 picoseconds to 100 nanoseconds. Consequently, laser energy required for marking gemstones can be reduced by utilizing a laser with a pulse duration significantly shorter than that utilized in the prior art. Since the size, cost and support facilities associated with a laser source typically increase with its pulse energy capability, reduction of the pulse duration of the marking laser has the potential for reducing the overall size and cost of the marking system. Further, reducing the laser pulse duration to 1 nanosecond or less has the additional benefit of reducing the graphite residue remaining after marking diamond gemstones.
SUMMARY OF THE INVENTION
The present invention provides for a method and system for laser marking a gemstone. A pulsed laser generates a laser pulse with a pulse duration of less than 1 nanosecond. The laser pulse is directed towards a focusing lens which focuses the laser pulse onto a surface of a gemstone. A computer control system controls displacement of the gemstone with respect to the focused laser pulse in order to mark a predetermined pattern onto the surface of the gemstone.
Displacement of the gemstone with respect to the laser pulse is performed either by mounting the gemstone on a stage which is movable along three orthogonal axes, or directing the laser pulse through a set of movable optical elements. Additionally, a video camera and video display are provided for displaying and recording the laser marking process.
It is a principal objective of the subject laser marking system and method to provide a pulsed laser which generates a laser pulse having a duration of 1 nanosecond or less.
It is a further objective of the subject method and system for laser marking a gemstone to provide a focusing element for focusing the laser pulse onto the surface of a gemstone.
It is a further objective of the subject invention to provide a means for displacing the gemstone with respect to the focused laser pulse.
It is a further objective of the subject invention concept to provide a video camera and associated video display for displaying and recording the laser marking process.
It is an important objective of the present invention to provide a computer control system for controlling the displacement of the gemstone with respect to the focused laser pulse along a predetermined displacement path in three dimensions.
Another objective of the present invention is to provide a visual depiction of the pattern being marked on the gemstone in a magnified state.
REFERENCES:
patent: 4392476 (1983-07-01), Gresser et al.
patent: 4467172 (1984-08-01), Ehrenwald et al.
patent: 5410125 (1995-04-01), Winston et al.
patent: 5573684 (1996-11-01), Winston et al.
patent: 5886318 (1999-03-01), Vasiliev et al.
patent: 5932119 (1999-08-01), Kaplan et al.
patent: 6211484 (2001-04-01), Kaplan et al.
patent: 6483073 (2002-11-01), Benderly
Christensen C. Paul
Wright Sidney P.
Alexander M.
Johnson Jonathan
Potomac Photonics, Inc.
Rosenberg , Klein & Lee
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