United States Patent [191
`Winston et a].
`
`llllllllllllllIlllllllIlllllllllllllllllllllllllllllllllllllllHlllllllllll
`
`US005149938A
`[11] 7 Patent Number:
`[45] Date of Patent:
`
`5,149,938
`Sep. 22, 1992
`
`[54] METHODS FOR PRODUCING INDICIA ON
`DIAMONDS
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`[75] Inventors: Ronald H. Winston, scarsdale; Necip
`Alev, New York, both of N‘Y.
`
`[73] Assignee: Harry Winston, S.A., Geneva,
`Switzerland
`
`_
`[2]] Appl‘ No" 595’861
`_
`[22] Flled!
`
`Oct- 11, 1990
`
`[51] Int. Cl.5 ............................................ .. 323K 26/00
`[52] US. Cl. ........................ .. 219/121.69; 219/ 121.68;
`219/ 121,73
`[58] Field of Search .................... .. 2l9/l2l.68, 121.69,
`219/l2l.73, 121.75; 125/3001
`
`3,527,198 9/1970 Takaska .............................. .. 125/30
`4,401,876 8/1983 Cooper ......................... .. 2l9/l21.69
`Primary Examiner—C. L. Albritton
`Attorney’ Agent’ 0’ Firm_Darby & Darby
`[57]
`ABSTRACT
`
`A method of producing a marking on a diamond. For
`producing the marking, the region on the surface of the
`diamond which is to be marked is irradiated with an
`argon ?uorine excimer laser whose output beam is
`passed through a mask which de?nes the marking. The
`diamond selectively absorbs the excirner laser radiation
`and undergoes a partial allotropic transformation with
`out losing its diamond crystal lattice con?guration.
`
`21 Claims, 1 Drawing Sheet
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`77
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`US. Patent
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`Sep. 22, 1992
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`5,149,938
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`1
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`METHODS FOR PRODUCING INDICIA ON
`DIAMONDS
`
`5
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`5,149,938
`2
`lengths, such prior diamond marking processes gener
`ally involve the application of energy absorbing coat
`ings such as carbon black to the surface to be marked,
`further complicating the procedure.
`Moreover, since the indicia are formed by multiple
`spots, complex and expensive computer-driven X-Y
`tables are provided in the aforementioned prior art
`systems for accurately positioning the diamond with
`respect to the focussed spot of laser energy to be next
`applied. The need to create numerous spots to form a
`single mark further causes the prior art marking pro
`cesses to be relatively slow in operation.
`
`10
`
`BACKGROUND OF THE INVENTION
`a. Field of the Invention
`This invention relates to the creation of identi?cation
`marks of other visible or invisible (but detectable) indi
`cia on diamonds, for the purposes of quality control,
`consumer brand identi?cation, security or any other
`purpose requiring identi?cation of a stone.
`b. Description of the Pertinent Technical Art
`Luxury and consumer goods alike are most often
`provided with an identifying mark from which the
`source of the goods can be identi?ed. This is especially
`important in the case of a product whose quality and
`value can only be determined by specially skilled work
`ers. Such identifying marks must be on the goods in a
`permanent form. On the other hand, the indicia should
`not impair the value of the goods in any way.
`In the case of precious stones such as diamonds, there
`has long been a need for a reliable method by which the
`identity of a stone could be uniquely determined. Such
`a method would aid in locating and recovering speci?c
`pieces of lost or stolen jewelry. Furthermore, where
`diamonds are loaned on a temporary basis, as is not
`uncommon, permanent indicia on the stone would facil
`itate ensuring that the returned stone is identically the
`same as the loaned stone.
`In addition, such detection systems or indicia could
`serve to indicate the level of quality or craftsmanship of
`the faceting, cutting and polishing of the stone. In es
`sence, a permanent mark or detectible indicium on a
`diamond may serve as a hallmark or trademark in much
`the usual fashion, i.e., as an identi?cation of source.
`Such a mark may be employed in dispelling the com
`mon misunderstanding that diamonds are essentially
`fungible, for any given weight, color and clarity. In
`fact, the quality of the gemstone may be markedly af
`fected by the skill and care of the stoneworker in the
`selection, sawing, girdling, cutting and polishing pro
`cesses.
`There have been devised a number of processes for
`marking diamonds, such as are disclosed in US. Pat.
`Nos. 4,467,172 and 4,392,476, which entire disclosures
`are incorporated herein by reference. In each of these
`patents, lasers are disclosed for creating focussed spots
`of laser energy on or in the diamond to be marked,
`wherein the desired indicia are formed by creating se
`ries or patterns of dots with such focussed spots of
`energy.
`The aforementioned laser marking systems employ
`YAG or NdzYAG lasers operating at 1.06 microns
`wavelength, alone or in conjunction with frequency
`doublers. Thus the disclosed laser radiation incident on
`the diamond is at either 1.06 or 0.532 micron wave
`length. As recognized in US. Pat. No. 4,467,172, laser
`energy at 0.532 microns wavelength can penetrate the
`surface of a diamond and can heat and vaporize portions
`of material below, as well as at, the diamond surface.
`This penetration of energy is undesirable and poses
`undue risks of fracturing the stone as a result of internal
`heating of the crystal structure. The prior art systems
`thus include complex arrangements to precisely control
`the amount of laser energy delivered so as to prevent
`damage to the diamonds being thus marked.
`.
`In addition, because diamond is substantially trans
`parent or transmissive at the aforementioned wave
`
`SUMMARY OF THE INVENTION
`Accordingly, it is an object of the invention to pro
`vide an improved method for producing an identifying
`mark on a diamond. It is a more speci?c object of the
`invention to provide such a method which permits rela
`tively rapid marking of diamonds without the need for
`expensive computer-driven X-Y tables.
`"
`It is a further object of the invention to provide a
`method of marking a diamond which entails a signi?
`cantly reduced risk of damaging the stone.
`Another object is to apply photolithograhic tech
`niques to a diamond marking process so as to obtain
`markings of varying gray shades, rather than black-and
`white only.
`Another object of the invention is to provide a simple
`process for providing a “branded” diamond whose
`source, and thus quality of workmanship, could be rela
`tively easily determined upon inspection.
`Yet another object is to provide on diamonds identi~
`fying marks of superior line de?nition than is presently
`possible with current processes.
`It is still another object of the invention to provide
`more complex arrangements for providing visible or
`invisible indicia on a diamond for security purposes.
`One method according to the invention involves
`marking a diamond with a pulsed excimer laser.
`Excimer lasers are pulsed gas-discharge lasers. In
`these lasers, a gas mixture (for example, argon and ?uo
`rine) is energetically charged and, upon suf?cient
`charging, is caused to produce an intense emission of
`pulsed laser energy. Excimer lasers are conventionally
`used to produce a pulse or a plurality of pulses at wave
`lengths ranging from approximately 193 nano-meters
`(rim), or 0.193 microns, to about 351 nm, depending on
`the particular rare-gas-halide excimer produced.
`Argon ?uorine excirners produce laser energy at 193
`nm. For radiation at this wavelength, the depth of pene
`tration into pure diamond is very minimal. While
`diamond is highly energy transmissive across a broad
`wavelength spectrum, pure diamond has particularly
`low transmissivity, low re?ectivity and high absorption
`at about 193 nm, which corresponds to nearly the cutoff
`frequency of the crystal. For this reason, the excimer
`laser energy is taken up in a particularly thin surface
`layer which is rapidly brought to a high temperature. A
`thin layer of material in the range of from several ang
`stroms to several microns is in this way vaporized from
`the surface by each pulse, or alternatively may be par
`tially graphitized by each pulse of the excimer laser.
`vaporization of material serves to protect the stone
`from overheating because of the high energy of subli
`mation for diamond carbon.
`It is known by those skilled in the art that diamonds
`are rarely “pure” crystals. Instead, impurities in the
`
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`3
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`3
`form of nitrogen atoms substituted into the crystal
`structure exist in almost every stone. The cutoff fre
`quency of a given diamond increases with increasing
`presence of nitrogen impurities, and may range as high
`as 300 nm. Therefore, while the preferred embodiment
`is described in terms of use of an ArF excimer laser,
`other lasers may be suitably employed, wherein laser
`energy having wavelengths ranging from under 200 nm
`to about 300 nm can be provided. These include, in the
`ultraviolet range, krypton ?uorine excimers (248 nm),
`xenon chlorine excimers (308 nm), and xenon ?uorine
`excimers (351 nm). The most effective laser wavelength
`for a given stone will always depend on the purity of
`that diamond.
`
`15
`
`20
`
`Thus, it will be understood the “about 193 nm” as
`used herein is meant to embrace a range suf?cient to
`include the cutoff frequency of any given stone, i.e.,
`from about 190 nm to about 350 nm.
`It is especially advantageous to irradiate the diamond
`through a mask which contains a form of the mark or
`indicium as a cutout or other area of high transmissivity.
`Such masks can be mounted on or in front of the
`diamond. The spacing of the mask from the diamond
`surface is not critical because of the parallel radiation
`beam produced by an excimer laser, unless reduction
`optics are also employed, in which case the position of
`the mask is necessarily important. Masks may also be
`fabricated with areas having different transmissivities to
`laser energy at the desired wavelength, yielding marks
`with areas of differentiated contrast selected from a
`generated gray scale.
`It is still more advantageous to image the mask on a
`surface of the diamond through optical means which
`passes ultraviolet radiation, e.g., sapphire or fused
`' quartz or fused silica. If the image to be produced is ?rst
`reduced, a high energy density is obtained on the sur
`face of the diamond and therefore a lesser number of
`40
`pulses or a reduced output capacity of the laser is re
`quired.
`An arrangement similar to the foregoing brie?y de
`scribed embodiment, but instead for producing an indi
`cium or trademark on glass spectacle lenses, is disclosed
`in U.S. Pat. No. 4,912,298, entitled “Method For Pro
`ducing A Marking On A Spectacle Lens,” the entire
`disclosure of which is hereby incorporated by refer
`
`35
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`45
`
`ence.
`
`‘
`
`A method according to another embodiment of the
`invention involves the use of an excimer laser to infuse
`various detectible substances into the surface of a
`diamond. Where a diamond is to be marked with indicia
`which are invisible to the naked eye, i.e., primarily for
`security purposes, it is obviously more difficult to subse
`quently locate the mark for identity veri?cation. Ex
`cimer laser energy can be used to “force” or infuse
`certain materials, such as ?uorescent dyes and other
`inorganic compounds which ?uoresce in the ultraviolet
`range, into the surface of the diamond crystal structure.
`A mark created on a diamond which has first been
`coated with such a dye or material will ?uoresce under
`appropriate lighting conditions, thus making it easier to
`locate the mark which would otherwise ordinarily be
`invisible to the naked eye.
`
`Alternatively, other detectable materials such as con
`ductive or magnetic substances may also be so depos
`ited on or into the diamond, for subsequent detection.
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`5,149,938
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`4
`BRIEF DESCRIPTION or THE DRAWINGS
`
`, The invention will now be described with reference
`to the accompanying drawings wherein:
`FIG. 1 is a partially schematic perspective view of an
`arrangement for creating indicia on a diamond with an
`excimer laser;
`FIG. 2 is a plan view of a mask provided with a
`trade-mark; and
`FIG. 3 is a side view of a diamond bearing an identi
`fying mark.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS OF THE INVENTION
`FIG. 1 generally illustrates an arrangement 10 for
`providing indicia on a diamond 15. A conventional
`argon ?uorine excimer laser 11 provides pulsed laser
`energy for use in the methods of the invention. Such
`excimer lasers are commonly available from a number
`of commercial sources. One such supplier is Lambda
`Physik Inc., a West German company having offices in
`Acton, Mass, which sells such lasers under the designa
`tions “LPX 100" and “LPX 200” Series. Another such
`supplier is Questek, Inc. of Chatsworth, Calif. which
`markets an excimer laser under the designation “Model
`2720.”
`The argon ?uorine excimer laser 11 produces a laser
`output 12 at 193 nm wavelength having a ?at-top beam
`pro?le (in horizontal cross-section) which propagates in
`a parallel beam path, when such laser 11 is provided
`with appropriate conventional resonator optics as is
`known. The output beam 12 is directed to pass through
`a mask 23 in order to produce a beam con?gured to
`produce a speci?c mark, as opposed to the conventional
`excimer beam of generally rectangular cross section. A
`portion of the laser radiation is stopped by the mask 23
`and only in those regions which correspond to the form
`of the desired mark is the radiation of the laser allowed
`to pass through the mask.
`After passing through the mask 23, more details of
`which will be described later, the beam is directed to
`reduction optics 24, which may be a 10:1 reduction lens
`suitable for use with laser energy at 193 nm, such as a
`lens fabricated of fused silica or sapphire. Surface lenses
`of any other desired demagni?cation value, such as
`30:1, may be used as appropriate.
`The reduction lens 24 serves to focus the beam to a
`size which is small enough so that the mark produced
`on the edge or girdle 17 of the diamond does not signi?
`cantly impair the value of the stone. The mark pro
`duced according to the invention is preferably so small
`that it is essentially invisible to the naked eye. The fo
`cussed beam impinges upon the surface of the diamond
`15 and effects a small removal in the form of the desired
`mark. The low wavelength of the laser output energy
`enables marks of exceedingly high line resolution to be
`created in the described manner. Moreover, the resolu
`tion is so ?ne that a mark may even be created on the
`culet of the stone. In practical terms, surface details of
`one micron resolution can be achieved.
`Because diamond is essentially opaque to laser radia
`tion at about 193 nm wavelength, the laser energy is
`absorbed only at the outermost surface portion of the
`stone. The rapid absorption of energy causes the entire
`image to be formed with only one or a relatively few
`energy pulses, such as several or several tens of pulses.
`The required output energy (or ?uence) of the excimer
`laser beam may range from a few to several tens or
`more milliJoules per square centimeter, with the precise
`energy output necessary for a given application depend
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`4
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`5
`ing on the size of the mark to be produced, the degree
`of optical reduction of the beam, and the desired depth
`of the mark to be created (i.e., the amount of material to
`be vaporized).
`The diamond may be held in a single ?xed position
`during the entire marking process and accordingly
`there is no need in this embodiment of the invention for
`a complex and expensive computer-controlled X-Y
`table or any other expensive or complex positioning
`means such as those described in US. Pat. Nos.
`4,392,476 and 4,467,172. These prior art systems must
`scan the surface to be marked with individual pulses,
`each creating only a minute portion of the image at any
`given moment.
`As already stated, a small amount of material may be
`removed by vaporization from the surface of the
`diamond. In addition, remaining portions of the
`diamond material may also be heated sufficiently to
`“graphitize” or undergo an allotropic transformation
`from one form of elemental carbon, i.e., diamond, to
`another, e.g., graphite. It is known that at suf?ciently
`high temperatures, e.g., about 900° C., diamond will
`transform into graphite and the entire diamond crystal
`lattice will decompose. Before such decomposition oc
`curs, however, it appears that the material may trans
`form or partially transform into graphite while retaining
`the strength and durability of the diamond crystal lat
`tice con?guration.
`It is believed that the diamond may undergo such a
`conversion within the crystal structure or at its surface,
`as it has been found that darkened or “graphitized"
`regions cannot be removed with conventional acid
`washes which would normally remove graphite from
`the surface of a diamond. Thus, a completely permanent
`mark is formed. In effect, diamond is treated as a photo
`sensitive material according to the principles of the
`invention.
`It has been observed that graphitization begins to
`occur at energy levels of about 20 milliJoules per square
`centimeter, measured at the mask and before any reduc
`tion optics. For a plot of surface damage versus beam
`energy density, it is known that this curve for diamond
`is theoretically a step function. Below a lower threshold
`value no damage occurs, while above an upper thresh
`old no further damage is done, regardless of energy
`applied. In practice, it has been observed that there is a
`very narrow transition zone around 20 milliJoules per
`square centimeter per pulse (at the mask) in which sur
`face damage, e.g., graphitization, can be selectively
`controlled by carefully and minutely adjusting the ex
`cimer laser energy output. By so controlling the laser,
`marks having different degrees of opacity, i.e., a “gray
`scale,” can be produced.
`Further advantageous is the fact that the laser energy
`at about 193 nm wavelength does not penetrate into the
`crystal structure. Internal heating of the crystal is thus
`avoided, such heating being a signi?cant cause of
`diamond fracture in prior art diamond marking schemes
`employing laser energy. At least one prior art method
`included an additional step of applying a coating of an
`energy absorbing material such as carbon black to the
`surface of a diamond before carrying out any laser
`marking. The success of this prior technique depended
`at least in part on the uniformity and density of the
`energy absorbing coating on the diamond surface, and
`this dependency is entirely eliminated by the present
`invention.
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`6
`Permanent marks on the surface of a diamond have
`been created according to the foregoing described em
`bodiment of the invention. Marks in the form of the
`letter “Q” having dimensions 300 microns wide by 400
`microns high were formed by application of from 1 to
`10 pulses of an ArF excimer laser.
`FIG. 2 illustrates a mask 33 used to form a particular
`image on a diamond according to the invention. The
`mask is constructed of any suitable material 31 suffi
`ciently strong to withstand the excimer laser energy
`without itself vaporizing, such as paper. The mask 33
`includes cut-out areas 32 in the pattern of the desired
`mark.
`In an alternative embodiment, the mask comprises a
`plate of fused quartz, fused silica or sapphire, coated
`with a suitably opaque and heat-resistant material, such
`as a photoresist. The mask may be prepared so as to
`have areas which are not coated with the opaque mate
`rial or which are only diffusely so coated. By control
`ling the density of the coating on the mask as selected
`areas thereof, a mask having areas of different transmis
`sivities is provided. Such a mask may advantageously be
`used to produce a mark having predetermined areas of
`differentiated contrast, i.e., different qray shades, as
`explained hereinabove.
`FIG. 3 shows a diamond 40 having been marked at a
`particular circumferential location 43 on the girdle 42.
`The girdle 42 customarily includes numerous small
`facets such as the facet 44 shown in the enlarged view
`50 of the gindle 42, any of which is suitable for dis
`creetly placed markings. It will be understood that the
`methods of the present invention are equally well ap
`plied to polished and unpolished, i.e., rough ?nished,
`diamond surfaces alike. While markings may be created
`anywhere on a diamond, it is aesthetically preferable to
`create such markings only on minor facets of the stone.
`The present method may even be advantageously used
`to place a mark on the culet 48 of the stone 40.
`As shown in FIG. 3, the laser-created indicia include
`a letter “H” 46 and a smaller representation of a
`diamond 47. As described above, these marks 46, 47
`may either be of equal or differing depths and/ or con
`trasts, even when produced at the same time by the
`same excimer laser pulses.
`In an alternative embodiment of the invention, the
`same apparatus and process steps as just described are
`repeated, but the diamond is ?rst coated at the location
`to be marked with a substance having special properties,
`such as ?uorescence or phosphorescence. When a mark,
`especially a mark which is so small that it is invisible to
`the naked eye, is created on a diamond, it may often be
`difficult to subsequently ?nd the mark in the ?rst place.
`This would undermine the value of the mark as a means
`for additional security in instances where the diamond
`must be relatively quickly identi?ed. A fluorescing
`mark could more easily be located and inspected, given
`the appropriate lighting conditions, e. g., ultraviolet, and
`is thus a desirable feature of a method for marking
`diamonds.
`When the excimer laser energy impinges the coated
`surface of the stone, a signi?cant number of molecules
`of the coating remain at the area of the mark and are
`adhered to or infused into the surface of the diamond,
`without having been vaporized. The precise machanism
`of this action is not understood at this time. Nonethe
`less, when materials such as zinc sul?de or diethyl zinc
`in combination with gaseous sulfur compounds are em
`ployed or deposited as coating the marks so produced
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`7
`according to the invention, they can be located only
`under lighting conditions (ultraviolet) which cause the
`mark to fluoresce in a preselected, extremely narrow
`frequency band, thus aiding in the prevention of unau
`thorized detection.
`In addition, such deposition and/or alloy combining
`of metals or volatile metal compounds with diamond
`carbon, such as arsine, phosphine, iron or iron carbonyl,
`and nickel or nickel carbonyl, at the surface of the
`diamond can produce magnetically detectable indicia,
`i.e., diffused or decomposed metal and/or metal car
`bides catalyzed by the laser on the indicia. Such deposi
`tion of other substances such as titanium carbide or
`molybdenum carbide could produce other electrically
`detectable indicia. Similarly, diborane or any other
`gaseous or solid compound elements, could cause pro
`fusion of substances to create electron junctions to
`cause a change in electrical properties, i.e., in a manner
`similar to doping of silicon to produce npn and/or pnp
`semiconductors.
`Thus a range of optical, magnetic or electrical prop
`erties could be engendered.
`It may be advantageous in some circumstances to
`create a series of precisely spaced circumferential marks
`according to this alternative embodiment, wherein an
`electronically readable, unique “signature” may be de
`?ned for a stone. For example, the stone could be ro
`tated at a predetermined speed and the magnetic marks
`electronically detected by a ?xed counter or similar
`device. The counter output would provide a distinctive
`signal pattern which could be maintained as a secret by
`the owner of the diamond. Given the existence of suffi
`ciently accurate measuring systems, it would be particu
`larly dif?cult for a would-be thief to "forge" the correct
`pattern of marks on a different stone.
`Such advantageous marking of diamonds is entirely
`novel and the range of uses for such marks is not com
`pletely exhausted by this brief description.
`It is also known that diamond may be “created" by
`thin-?lm chemical-vapor-deposition (CVD) techniques.
`It may be advantageous in certain cases to sandwich an
`identi?cation mark between the natural stone and a
`super?cial CVD layer of diamond for added security.
`It will be understood that the foregoing description is
`that of the preferred embodiments of the invention and
`45
`that various changes and modi?cations may be made
`thereto without departing from the spirit and scope of
`the invention as de?ned in the appended claims. For
`example, the mask 23 in FIG. 1 is shown as being posi
`tion between the laser 11 and the reduction lens 24, yet
`the mask 23 could also be located between the lens 24
`and the diamond 15 to be marked, although the illus
`trated position is preferred. When the reduction lens 24
`is not used, the position of the mask 23 may range from
`just at the output of the laser 11 to adjacent the stone 15,
`without any signi?cant effect on operation.
`As noted above, some diamonds may be more advan
`tageously marked according to the invention by using
`KrF, XeCl or XeF lasers. Alternatively, any laser
`source capable of delivering suf?cient energy at the
`appropriate wavelength would suf?ce.
`It is further envisioned that the principles of the in
`vention may be readily useful and advantageous to
`those in the extrusion arts. More speci?cally, extremely
`?ne complex patterns may be used as masks in the pro
`duction of diamond plate extrusion dies such as for use
`in extruding metal wire, glass ?ber or synthetic ?bers.
`By repetitively pulsing the excimer laser, thin diamond
`
`5,149,938
`8
`plates may be essentially “drilled" with the resulting
`hole in the form of the mask, after reduction.
`This would permit creation of fabrics having new and
`as yet unappreciated qualities. For example, ?bers hav
`ing uniquely high nap could be produced and then
`woven into new materials having applications such as
`?lters, substrates or insulators. Almost any cross-section
`could be obtained for an extruded material, at extremely
`high resolution of surface features.
`Moreover, the die could be “drilled” in the direction
`of greatest strength of the diamond. Particularly strong
`and durable dies are thus obtainable according to the
`basic principles of the present invention.
`What is claimed is:
`1. A method of producing a marking on a diamond,
`the method comprising the steps:
`positioning a mask between an output of an excimer
`laser and a portion of a surface of the diamond to be
`marked; and
`directly irradiating the portion of the surface of the
`diamond with the excimer laser through the mask
`so as to permit the radiation of the excimer laser
`itself to create the mark in a pattern de?ned by the
`mask.
`-
`2. The method of claim 1, wherein the excimer laser
`irradiates the diamond with at least one energy pulse at
`a wavelength of about 193 nm.
`3. The method of claim 1, wherein said step of irradi
`ating includes passing the excimer laser radiation
`through cut-out areas in the mask.
`4. The method of claim 1, wherein said step of irradi
`ating includes passing the excimer laser radiation
`through areas of different transmissivities in the mask.
`5. The method of claim 1, said mask being spaced
`away from the surface of the diamond.
`6. The method of claim 1, said mask being directly on
`or adjacent the surface of the diamond.
`7. The method of claim 1, said mask being imaged
`onto the surface of the diamond at a reduced size
`through means for optically reducing the mask pattern.
`8. The method of claim 3, said mask being made of
`paper.
`9. The method of claim 4, said mask being made of
`one of the group of materials which are substantially
`transmissive at the wavelength of the excimer wave
`length radiation, the group including fused quartz, silica
`and sapphire.
`10. The method of claim 1, wherein the energy of the
`excimer laser is adjusted to remove only a thin layer
`from the surface of the diamond.
`11. The method of claim 10, wherein said layer re
`moved from said surface has a thickness ranging from
`approximately several angstroms to several microns.
`12. The method of claim 1, wherein the entire mark is
`created while holding the diamond in a single ?xed
`position.
`13. The method of claim 1, including the step, before
`irradiating the diamond, of applying a coating of mate
`rial to the surface to be marked, which material is de
`tectable only under predetermined lighting conditions.
`14. The method of claim 13, wherein the material is a
`?uorescent material.
`15. The method of claim 13, wherein the material is a
`phosphorescent material.
`-
`16. The method of claim 1, including the step, before
`irradiating the diamond, of applying a coating of detect
`able material to the surface to be. marked, wherein the
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`detectable material is optically or electrically or mag
`netically detectable.
`17. The method of claim 16 wherein the detectable
`material is molybdenum carbide, nickel carbide, tita
`nium carbide of iron carbide.
`18. The method of claim 16, comprising the further
`step of similarly directly irradiating at least a second
`portion of the diamond to form at least a second mark.
`19. The method of claim 1, wherein the energy of the
`excimer laser is adjusted to partially transform the
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`diamond from one form of elemental carbon to another
`form of elemental carbon.
`20. The method of claim 1, wherein the energy of the
`excimer laser is adjusted to partially graphitize the
`diamond at the portion being marked.
`21. The method of claim 21, wherein the darkness of
`the mark so produced varies with the degree of graphi
`tization caused by the excimer laser radiation.
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`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`CERTIFICATE OF CORRECTION
`
`PATENT NO. I
`5 , 149,938
`DATED
`: September 22, 1992
`
`INVENTOMS) Z RONALD H. WINSTON et al.
`
`It is uni?ed that not appears in the above-identified patent and that said Letters Patent is hereby
`corrected as shown below:
`
`In claim 21, line I, delete "claim 21" and insert therefor ——claim 20—-.
`
`Signed and Sealed this
`
`Eighth Day of March, 1994
`
`Attesting O?icer
`
`Commissioner of Parents and Trademarks
`
`BRUCE LEHMAN
`
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