Abstract:
A gemstone micro-inscription system, comprising an energy source, a spatial light modulator, and a control, the control controlling a spatial light pattern modulation of the spatial light modulator, wherein the spatial light modulator exposes a photoresist on the gemstone, which selectively impedes an etching process to produce a pattern on the gemstone corresponding to the spatial light modulation pattern.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the field of systems and methods for inscribing indicia on a surface of gemstones. 
       BACKGROUND OF THE INVENTION 
       [0002]    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 μm, 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. 
         [0003]    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 μm, 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, 3,597,198, 3,622,739, 3,775,586 and 4,048,515, and foreign patents JP 00-48,489 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 U.S. Pat. No. 5,149,938. 
         [0004]    Gemstone News, Nov. 2, 1995, “Serial Numbers are Laser Inscribed”, and Jeweler&#39;s Keystone-Circular, June 1996, pp. 76 relate to gemstones inscribed with serial numbers or markings. 
         [0005]    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 saving 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. 
         [0006]    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. 3,440,338, 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”, March 1980, pp. 90 and 91; “Laser Application Notes”, 1(1) (February 1979); “New Hyperyag”, on Model DLPY 4-System 2000 Yag Laser; and “Diamonds”: N.A.G. Press LTD, Chapter Eleven, pp. 235, 239 242. 
         [0007]    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). 
         [0008]    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. 
         [0009]    U.S. Pat. Nos. 7,010,938; 6,684,663; 6;476;351; 6,211,484; 5,932,119; and U.S. application Ser. No. 10/764,937, each of which is expressly incorporated herein by reference, relate to an improved system providing a computerized system, mounted in a rigid frame, which provides electronic imagers for both control and image capture. 
         [0010]    See also, US 2003/0071021; US 2002/0030039; U.S. Pat. No. 6,552,300; U.S. Pat. No. 6,710,943; and U.S. Pat. No. 6,950,024, each of which is expressly incorporated herein by reference. 
         [0011]    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 
       [0012]    The present invention provides a system having an energy beam, which may be light source, a CW laser, pulse laser, ion milling device, electron beam, or the like, which is used to mark a gemstone with a micro-inscription pattern. The energy beam may directly produce an effect on the gemstone, or produce an effect in a coating on the stone, which is subsequently used as a basis to mark the stone. Alternately, the energy beam may result in a selective deposit on the stone. With respect to gemstone coatings, the energy beam may result in a maintenance or removal of the coating, depending on the nature of the beam and the nature of the coating material. 
         [0013]    Typically, the energy beam will be presented at a focus or spot, although a dispersed beam may also be presented, for example through a spatial light modulator, such as a TI digital light projector (DLP) device. 
         [0014]    A preferred energy beam is a diode excited solid state laser, e.g., 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 stage. A beam positioning system repositions the beam with respect to the stone, and controls the spot size through an automatically controllable beam expander. Alternately, a so-called cold laser may be employed, such as a UV excimer laser. 
         [0015]    If a latent marking is created in a photoresist, the photoresist is then developed, and the gemstone etched using a chemical or plasma etch process. For example, a diamond may be etched using an oxygen plasma. See U.S. Pat. No. 7,064,352, expressly incorporated herein by reference. See also, M. Karlsson and F. Nikolajeff, “Fabrication and evaluation of a diamond diffractive fan-out element for high power lasers,” Opt. Express 11, 191-198 (2003); M. Karlsson and F. Nikolajeff, “Diamond micro-optics: microlenses and antireflection structured surfaces for the infrared spectral region”; Opt. Express, 11, 502-507 (2003), R. E Stallcup II and J. M. Perez, “Scanning Tunneling Microscopy Studies of Temperature-Dependent Etching of Diamond (100) by Atomic Hydrogen,”  Phys. Rev. Lett.  86(15), 3368 (2001), expressly incorporated herein by reference. 
         [0016]    In the case of an energy beam which forms a spot, the energy beam is repositioned with respect to the gemstone to form the pattern or latent pattern. In the case of a spatial light modulator (SLM), depending on resolution, no repositioning may be required. Typically, an SLM is not useful for direct write systems, and therefore the SLM is used to expose a resist or otherwise form a latent image, which is then developed and processed. 
         [0017]    In any case, the pattern is controlled by an automated processor in two, or preferably three dimensions. While some energy beam systems do not require “focus”, that is, a concentration of the beam at a particular depth, in many cases this is advantageous. For example, if the energy beam is highly absorbed at the surface, damage beneath the surface due to concentrated energy is minimized. Likewise, some energy beams, such as electron and ion beams (e.g., charged particle beams), are readily controlled electrostatically or magnetically, and thus do not interact with lenses or mirrors, and thus may be collimated along much of their path. On the other hand, optical beams, such as lasers, are generally beam-expanded to allow interaction with reflective and refractive optics without damage. 
         [0018]    Therefore, in many cases, both the area (x, y) and depth (z) of an inscription surface are defined, and the energy beam modulated and positioned accordingly. 
         [0019]    A preferred method for determining the depth profile of a surface is by optically determining a depth of focus, or in some cases, by an imager acquiring a side profile view. 
         [0020]    In one embodiment, an X, Y. Z positioning stage achieves a positioning accuracy and resolution of about ±1 micron. In this system, the energy beam, an LED-excited pulse 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. 
         [0021]    According to a preferred embodiment, linear positioning actuators displace a laser beam for forming a marking on a gemstone. This positioning is preferably in three dimensions, and further is used in conjunction with a motorized beam expander to achieve automated control over laser spot size. The gemstone is fixed in position during marking, though the gemstone mount may be used for coarse positioning and control over rotational degrees of freedom. This system achieves positioning accuracy and resolution of about ±1 micron or better. 
         [0022]    On the other hand, a piezoelectric or electromagnetic actuator vibration-compensation system may be employed to reduce or eliminate the effects of vibration or residual vibration, and therefore eliminate one source of micro-inscription irregularities. Such a system may be employed in conjunction with a rigid system, inertially damped system, vibration damping system, or other type of vibration mitigation scheme. 
         [0023]    In a rigid frame embodiment, a frame having sufficient rigidity to ensure that the critical components mounted on the frame, i.e., those whose relative movement results in aberrations in the inscription, move together in a common mode. Therefore, simple and small passive vibration isolation mounts for the platform or chassis may be employed, rather than requiring active vibration suppression systems as in known systems. 
         [0024]    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 marking location of the energy beam. The correct positioning of the gemstone may thus be assured by correct alignment of the imagers on the workpiece. If two imagers are provided, one imager may be directed at the work surface along the axis of the energy beam (or slightly inclined so that it does not interfere with the energy beam path), and has a focal plane coinciding with the focal point of the energy beam (if the beam is focused). Optical feedback through the imagers may be used to set up parameters of the marking process, monitor the progress of the marking process, and review the results of the process. In an “autofocus” embodiment, the focus of the imager is used to establish the depth profile of the surface to be marked, and thus used to assure that the focus of the energy beam has a proper relationship with the gemstone during the process. 
         [0025]    Typical gemstone inscription devices permit or require skilled operator interventions in the process, and thus full automation is rarely employed. However, all aspects of the process, including, e.g., gemstone manipulation, gemstone analysis, marking definition, marking placement on the gemstone, preparation of the gemstone for marking, gemstone marking, marking analysis, repeat marking, removal of any coatings, and removal of the gemstone from the machine may all be automated. 
         [0026]    In a laser or pulse energy beam system, the control may, for example, 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. More typically, the marking is reviewed after an initial marking pattern is made, because during marking, it may be difficult to analyze the marking, since there may be debris and/or a film on the surface. This film, which will be discussed in more detail below, is typically provided to absorb the energy at the surface, and thus help ensure that the energy is not dissipated deeper in the stone, where it may cause thermal stresses and cracking, or at least will not be useful for forming the marking. For example, a black ink may be useful for coating diamonds prior to optical laser treatment, and especially those with a polished inscription surface. Such a coating may be unnecessary with a UV laser. The ink may be automatically applied to the gemstone, and automatically removed after marking. For example, it has been found convenient to use a black “Sharpie” marker to apply a pigment to a diamond surface, which can then be removed with an alcohol swab. 
         [0027]    In the case of a thermal marking applied by a laser, diamond substrates tend to graphitize, to form a blackened marking. If desired, this graphitic portion may be removed with an acid etch bath, which will generally leave the diamond unharmed. 
         [0028]    In a preferred system, one imager is directed to view a top portion of the workpiece, e.g., directed perpendicular to the table surface of a cut gemstone, allowing identification of a girdle profile, while the second imager is directed to views 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 and automatically analyze the marking process in real time. 
         [0029]    The optical 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 work-piece and formed markings. Preferably, images of the stones and/or marked stones are stored in a database. This database may be used to verify the authenticity of a gemstone, identify the stone, grade the stone, value the stone, or for other purposes. 
         [0030]    The database is generally indexed by an inscription serial number, and therefore the database record can be recalled by reading the inscription (manually or automatically). However, in some cases, the marking may be changed, obliterated, or corrupted, and therefore other index keys may be desirable. For example, a set of facet angles may be recorded as a vector. Likewise, characteristic inclusions or other flaws may be mapped and coded. While color, carat weight, and grade, for example, may also be used, there are typically not distinguishing for any one stone. 
         [0031]    The database may be useful for identifying or distinguishing “conflict diamonds” from diamonds derived from legitimate sources. For example, rough stones could be analyzed and marked at the mine. The analysis could include, for example, chemical/physical characteristics, morphology, and flaws of the stone. As the stone reaches the cutter, it is authenticated through the database record. After cutting, it is again analyzed, marked and a supplemental record stored in the database. In this case, the analysis seeks to ensure that the cut stone is consistent with the rough stone it purports to derive from, as well as to record the new characteristics of the stone, as cut. Likewise, the cut stone will be associated with the cutter, whose reputation will be judged by compliance with the laws and rules. It is preferable that the database record information relating to aspects of the marking itself that are difficult or impossible to replicate. For example, the relationship of the marking to facet edges or flaw may be difficult to reproduce (counterfeit), in conjunction with the other information about the stone. 
         [0032]    An encoded identifier may be provided on the gemstone which is purposeful organized, to provide, in readily ascertainable form, information and/or characteristics about the gemstone. For example, the first digits can encode the laboratory or entity which placed the marking on the stone. In addition, tracing information, such as the country or mine of origin, mining company, cutter, manufacturer, distributor, retailer, owner, grading laboratory, or the like may be encoded. The second set of digits can encode the type of stone material. The third set of digits can encode the cut of the stone, or if uncut. The forth set of digits can encode the qualitative aspects of the stone, such as color and clarity. The fifth set of digits can encode the setting type, if any. The sixth set of digits can be a serialized number. The seventh set of digits can encode the Kimberly process certificate number. The eighth set of digits can be parity and/or hash function to correct and/or detect errors or alterations in the preceding digits. The encoded identifier can also be referenced in an electronic database by the serial number. 
         [0033]    The database may be maintained as a private database, a public database, or as a database with both public and private fields. Thus, for example, the serial number of the stone may provide a database lookup index, which can be interpreted by an Internet search engine to reveal public information about that item. A user ID/password, or other authentication, may be used to additionally reveal private information. The electronic database information may replicate or supplement the information provided on the stone. It is also possible to make the stone self-authenticating, that is, to provide a cryptographic message, e.g., an public key-private key encrypted message which includes information defining difficult to reproduce characteristics, or a hash function of such characteristics. This thus permits a jeweler, appraiser, gemologist, insurer, or government agent, for example, to immediately verify that a stone properly derives from a “certificate holder”. That is, an entity with secret cryptographic information is the only entity which can create the marking, so a correspondence of the marking with the irreproducible characteristics of the physical stone verifies its trail. The cryptographic information may be stored on the stone as a 2D code, and indeed may be a multilevel code, with 2 bits (4 levels of intensity) per position. Likewise, a sub-stepping technology can modulate the position of a dot within a dot boundary as an additional or alternate coding scheme. Assuming a 10 micron dot pitch, 1 pit per position, 1.6 mm inscription length, and 80 microns inscription height, a raw coding of 8×160=1280 bits is possible. If a 3 micron dot is placed within a 6 micron coding space, and modulated in two of 9 positions (about six bits per space, assuming some modulations are dissallowed), the same inscription space could hold 13×266×6=20748 bits. Assuming error detection and correction, and inscription redundancy, this still permits substantial information to be encoded. Note that the later coding scheme would typically require a specific automated miscroscope reader to decode, while the former light permit a simplified microphotographic reader. 
         [0034]    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. 
         [0035]    Preferably, the inscription control reads a standard raster graphic file, for example, TIFF or BMP, or a standard vector graphic file, HP-GL, Postscript, PCL6, etc., and/or standard font files, such as True Type or Postscript fonts, as a source file. These allow modern computers with commercial image manipulation and/or page description software to create and modify the inscription as appropriate. Thus, it is preferred that the inscription control act as a computer printer device or receive as a marking control input a standard file format. 
         [0036]    The marking control typically acquires or derives a model of the surface to be marked, which is, for example, the girdle of the stone (polished or bruted), facet, or in the case of rough stones, a selected surface. It then preferably verifies that the proposed marking is appropriate for the surface, for example, that it does not extend beyond an edge. In cases where the surface is non-planar, the contour of the surface is determined, and this information used to map the inscription, which is typically two-dimensional, onto the three dimensional surface. Typically, this contour determination is performed prior to inscription, though it is also possible to determine marking surface depth as the inscription progresses. For example, a camera which as a focal plane coincident with the marking focal plane, may be used to “autofocus” the system, to ensure that the energy beam is adjusted for the proper depth. 
         [0037]    In one embodiment of the invention, excess or residual ink or pigment on the surface of the gemstone may be removed by defocusing the energy beam (raising the focus above the surface), to an energy intensity which is sufficient to vaporize the ink, but below an intensity which has an effect on the gemstone itself. For example, a lower laser power level may be employed than normally used for inscription. 
         [0038]    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 inscribed on every workpiece in a series. The gem rating or grading can be scanned as a bar code, printed on a sheet associated with that gemstone, such as a receipt or label. The serial number may be automatically determined, and for example, printed on a receipt or label, and employed as a unique identifier to be applied to the stone. The inscribed characters need not be limited to alphanumeric symbols, and in fact may be fonts in any language, line-drawing characters, custom characters or pictorial representations. 
         [0039]    It is also possible to determine or control a part of the inscription through the imaging system. For example, the optical system may be used to map the gemstone, and then an inscription, which may be a message, code, or simply dots or a line. For example, the energy beam may be employed to apply a cut line to a stone after gemological analysis. Thus, the marking control may include an express indication of the marking, or a logical directive as to characteristics or relationships of the marking, based on the stone to be marked. 
         [0040]    The workpiece may be associated with data, stored in a medium physically associated with the workpiece or in a remote medium accessible through use of an identification of the workpiece. For example, the associated memory is a nonvolatile memory, such as a battery-backed random access memory, an electrically erasable read only memory, a ferroelectric memory, or other storage media such as magnetic stripes, rotating magnetic media, optical memories, and printed matter. The latter medium is especially relevant to gemstones, which typically have associated certificates of authenticity, which identify the stone, and may include details of its characteristics, inscription, flaws, origin, value, owner, or other aspects. 
         [0041]    A vanity inscription may be provided on the workpiece as a custom or semicustom inscription, which may be provided as computer text, graphics or a computer-scanned image. The marking system may be employed to mark portions of a gemstone other than the girdle, for example the table. Therefore, in the case of such vanity inscriptions, the intent may be to provide a visible inscription, to enhance the sentimental value of the workpiece, rather than to provide an unobtrusive microscopic identification or authentication marking. 
         [0042]    In many instances, it is desired that each inscribed workpiece be separately identifiable. This may be by way of a unique marking on the stone or a unique combination of marking and easily identified characteristics of the workpiece, such as weight, shape, type, etc. In one embodiment, the markings themselves form a code, such as an alphanumeric or bar code, which may be electronically or automatically read or ascertained from an examination of the workpiece. In order to facilitate automatic reading, a header sequence may be provided on the marking to facilitate self-clocking of the code. The clocking can be a time frequency, in the case of a scanning beam, or a spatial frequency, in the case of an area imager. Likewise, it is preferable that the code include error correction and detection information, and perhaps complete redundancy in the form of a replicate (or partially replicate) sequence elsewhere on the stone. 
         [0043]    An image of the marked workpiece may be formed or printed on a certificate which accompanies the workpiece, allowing verification that the workpiece corresponds to the certificate, by studying the image in comparison with the actual workpiece. The image advantageously includes all or a portion of the marking, as well as identifiable features of the workpiece, such as landmarks, edges, facets, etc. Thus, the image may be used as a “fingerprint” identification of the workpiece. The image on the certificate may be formed photographically or electronically. Thus, the image as stored need not be formed through the CCD images or the marking system and may be produced as a separate step. The certificate preferably has an electronically readable representation thereon, so that the certificate and the workpiece can be automatically compared. On the other hand, the certificate data is typically also stored in a database, so that an automated comparison may be based on the remote database information, rather than the local certificate information, which can then be used for manual confirmation and identification. 
         [0044]    Advantageously, an image of a completed marking or a bitmap of an inscription program is stored in a database, and therefore is available for comparison and later authentication of a workpiece, and to prevent inadvertent or undesired duplicate markings. In this case, the image is preferably created of the marking immediately after inscription, for example, within the marking machine. Since the stone is preferably cleaned prior to acquiring the image, the inscription apparatus preferably has an associated automated stone cleaning device, which for example, may include a low power energy irradiation to bleach or vaporize an energy absorptive ink, an alcohol wipe to dissolve the ink or pigment carrier, or another type of cleaning system. The image preferably includes both the inscription, as well as a portion of the stone around the inscription, which serve as landmarks for both finding the inscription and to provide authentication information. 
         [0045]    The storage may be electronic or photographic, and thus the database may reside on magnetic or magnetooptical media, microfilm, paper or film, holographic crystals, magnetic or optical tape, or other known media. Preferably, the database is networked, and in cases where remote authentication is required or encouraged, the database is accessible through the Internet. 
         [0046]    It is also advantageous in some cases to connect the inscription apparatus to the Internet, for diagnostic and maintenance purposes, remote control, and accounting. For example, the apparatus may include an inscription counter, wherein a usage of the machine may be audited remotely by accessing the counter. In some cases, it may be desired to permit a remote user to control the device, for example to provide inscription information or to confirm the desired placement of the inscription. Thus, both the imaging information and inscription information may be communicated remotely. According to another embodiment of the invention, the inscription apparatus requires a remote authorization for inscription. For example, where the device is provided to source authenticate diamonds to differentiate conflict diamonds from others, a remote authorization may be useful as part of a system of checks and balances. Likewise, the inscription device may require a cryptographic code, either for activation of the device, or for creation of the inscription, which may be provided remotely. Thus, one aspect of the invention provides a micro-inscription device which is connected to a communication network, and whose operation includes or requires communications over the network. 
         [0047]    In accordance with one aspect of the invention, a duplicate-prevention function is provided integral to the marking device which may not be overridden by a user, e.g., to prevent inadvertent or intentional misuse of the system. In this case, the laser system may include a lockout circuit which prevents activation of the laser control and positioning systems under unauthorized circumstances. Such a lockout may be provided in the power supply or other critical subsystem of the device. In some cases, it may be desired to create a duplicate inscription; for example, a stone may require re-inscription. In that case, an override may be provided for this lockout. For example, the override may be provided as a cryptographic message communicated through a network, which is authenticated by the apparatus. Such remote activation also permits enforcement of a per-use economic model for apparatus use, limiting use of the apparatus to authorized (and presumably compensated) uses. 
         [0048]    Based on the use of the marking system, a report may be generated by the computer/controller. Because the inscription is typically a raster ablated image, such report may advantageously include either the programmed inscription as a graphic printout or an image received from the optical feedback imaging system, e.g., the camera. 
         [0049]    According to one embodiment of the invention, one or more cameras in the apparatus are high resolution cameras, for example, 6-13 megapixels. These cameras permit detailed capture of the image, higher precision focus, better determination of a quality of a marking (for example to determine whether a repeat inscription is required), and a larger range of an inscription along the stone. While typically, a standard CMOS or CCD tri-color imager may be employed, in other cases, a monochrome and/or hyperspectral imager is appropriate. Advantageously, a high resolution camera has a “video” mode, for example 640×480 pixel resolution (30 frames per second, to facilitate real-time observation of movement and inscription, in addition to the higher resolution mode(s), to permit detailed capture for storage and/or analysis. 
         [0050]    As stated above, the report may also include or be associated with a certificate of authenticity, e.g., including a facsimile of the workpiece image including the marking. A known image authentication scheme is disclosed in U.S. Pat. No. 5,499,294, incorporated herein by reference. The certificate of authenticity may include a variety of security features, see e.g., U.S. Pat. No. 5,974,150, expressly incorporated herein by reference. Such levels of security enhance the trustworthiness of the certificate as self-evidence of the characteristics of the associated gemstone, though in many cases the certificate may be authenticated by reference to a remote authenticated database. 
         [0051]    The gemstone, which may be rough, cut or mounted in a setting, is held in place on a stage. The holder secures the stone in place, while presenting a line of sight path to the surface to be inscribed. Preferable, the holder is removable from the inscription device, while maintaining the stone in precise relation to the holder. The holder, in turn, may be precisely replaced within the inscription apparatus. Thus, the stone may be removed from the apparatus for inspection, and replaced with critical alignment, to allow further inscription. The holder, or its mount, allow coarse positioning of the gemstone within the machine, as well as various rotations to properly present the surface of the gemstone for marking. Preferably, the micro-inscription pattern is produced by repositioning the laser beam, though it is possible for both the laser and gemstone to be repositioned to form the marking. 
         [0052]    Alternately, after replacement in the inscribing apparatus, the stone is imaged through the electronic imaging system, and it is optically returned to its original position, based on prior images captured to determine a reference position of the stone. Of course, this may require control over stone position in up to six axes (x, y, z, yaw, pitch, roll), though if the stone is generally aligned mechanically, three axis positioning (x, y, rotation in x-y plane) may be sufficient. 
         [0053]    The energy beam, especially a collimated, focused beam, is positioned relative to the gemstone by one or more of a workpiece positioning stage, and a beam positioning system. A beam scanning system may also be provided, in which a beam is scanned in one or two dimensions over the surface of the stone. 
         [0054]    In one embodiment, the workpiece is mounted on a stage, which precisely holds the gemstone to avoid artifacts during marking. Thus, for compact designs, the holder may accommodate workpieces of less than about 30 mm in a largest dimension, although the stage is capable of accurate positioning over a larger distance. The inscription itself is typically less than about 2 mm in longest dimension. For example, about 1.6 mm. Typically, the optical imaging system has a range commensurate with the range of the inscription, especially where the resolution of the imaging system is limited, e.g., D1 video. On the other hand, using a higher resolution imager, the range of the imager may reasonably be larger than the inscription, for example, to include much or all of the stone. Advantageously, a single imager may be used to produce both real-time images of the positioning and inscription process at modest resolution, e.g., 640×480, and high resolution images for storage and/or analysis, e.g., ˜3000×˜2000. 
         [0055]    The stage of a one embodiment is generally translatable along three axes, X, Y, and Z in a Cartesian coordinate system, but may also include other axes e.g., rotational axes. Typically, the stone is mounted in the holder so that the inscription surface is accessible from a line-of-sight directly above, so that two axes of positioning (plus depth control, as necessary to ensure focus) are sufficient. Such a stage may also be used in conjunction with beam position control systems, though the need for high resolution control is diminished in that case. 
         [0056]    For example, a brilliant cut diamond is radially symmetric. Therefore, where an inscription or marking is desired around the diamond girdle, the diamond may be held in focus by adjusting a Z axial displacement and an inscription defined by translation along the X and Y axes during laser pulsing. If the desired inscription extends beyond the range of the device, the stone may be rotated to permit access to an adjacent range, which will typically be slightly overlapping, to allow stitching of the inscriptions to they appear continuous. 
         [0057]    Alternately, the diamond may be initially positioned appropriately along the X, Y and Z axes, and rotated about an axis and translated sequentially along a Y axis to define the inscription. In this case, the Z axis and possibly X axis may also be used to retain focus condition. Where X, Y, and Z axes are employed for automated control, a manual rotational control is preferably provided with detents at regular intervals. 
         [0058]    The positioning system, for moving the workpiece in relation to the energy beam may also include or be formed from beam steering systems, such as mirrors, electro-optical elements, holographic or diffractive elements, or other optical systems. However, a translatable stage is a preferred means for directing the focused laser energy onto a desired portion of the workpiece. 
         [0059]    As discussed above, the beam need not be a narrow collimated beam, but rather may be spatially modulated to allow parallel irradiation of a plurality of irradiation areas, e.g., pixels. Since direct modification of the gemstone structure requires high energy intensity, which is typically not achieved if the energy is spatially dispersed, this technique is preferably employed in an indirect inscription process. Thus, a spatial light modulator (SLM) illuminates a photosensitive layer on the stone. The irradiation alters the layer, to produce a latent image. The latent image is then developed. For example, the photosensitive layer is a photoresist, which polymerizes under light, and therefore the unexposed areas are more soluble in a solvent than the exposed portions, permitting formation of a pattern on the surface which masks regions of the surface. The exposed (unmasked) portions of the stone may then be selectively processed, for example by a chemical or plasma etch. It is also possible to use a photoactivated etchant, in which the stone is bathed in an etchant during illumination, and the illuminated regions are etched, while the dark regions remain untouched. 
         [0060]    According to a further embodiment, a layer of compatible material is formed on the surface of the gemstone, which is selectively etched or removed in accordance with an energy beam pattern. Thus layer remains on the stone, and thus forms a raised marking. Typically, a thin coating layer may be provided which has somewhat different chemical properties than the underlying material, and thus may be selected to be more readily etched than the gemstone, and therefore allows etch conditions which do not substantially risk harming the gemstone. After the marking is formed, it is also possible to “harden” the coating, or to overcoat it with a more durable material. 
         [0061]    For example, a diamond is coated with a layer of photoresist. (An underlayer, for example vacuum deposited gold, may be provided). The photoresist is exposed with the SLM to form a latent image. The latent image is developed, to leave a selective marking of the exposed photoresist on the surface of the diamond. According to one embodiment, an oxygen plasma is used to etch an inscription into the diamond. According to another embodiment, a diamond-like or other durable coating is formed over the developed layer, to fill the pattern. The exposed diamond seeds formation of the durable coating, thus selectively forming the coating at the exposed gemstone. The resist may then be stripped, leaving a raised durable coating. 
         [0062]    The SLM may be, for example, a Texas instruments Digital Mirror Device (“DMD”, also known as Digital Light Processor, “DLP”), for example a 4 k×4 k pixel device. Alternately, LCD, LCOS, or other SLM technologies may be employed. The DMD device is a preferred SLM, since it is a reflective mode device, and thus can use ultraviolet energy beam sources. It is noted that, to the extent photoresist technologies are employed, known semiconductor fabrication technologies may be used. However, typically, such semiconductor technologies are presently designed to achieve finer feature sizes than required or desired for a gemstone micro-inscription. See, Carolyn Fries, David Fries, Heather Broadbent, George Steimle, Eric Kaltenbacher, Jay Sasserath, “Direct Write Patterning Of Microchannels”, First International Conference on Microchannels and Minichannels, Apr. 24-25, 2003, Rochester, N.Y., USA; SF-100 (Intelligent Micro Patterning, L.L.C., St. Petersburg, Fla.). 
         [0063]    The workpiece generally sits in a holder which detachably mounts to the translatable stage. Thus, a workpiece may be suitably mounted in a holder outside the apparatus while another workpiece is being inscribed. These holders may also increase the versatility of the device by providing adaptation to workpieces or various sizes and shapes. For example, round, oval, heart, marquis and other cut gemstones may each be provided with separately optimized holders; further, diamonds of various size ranges may be accommodated by differing holders, as necessary. According to another embodiment, a mounted workpiece, e.g., a diamond in a setting, may be inscribed on portions which are not obscured. For example, in a pronged setting, a portion of the girdle may be exposed, and thus may be available for marking. In this case, a multi-articulated holder or set of holders may be provided to properly position the workpiece within the inscribing chamber of the device. Holders may be provided to accommodate mounted gems in rings, earrings, pendants, and possibly bracelets, brooches, and other common forms. 
         [0064]    The computerized control system provides a user interface making the various functionalities accessible to users, and may further limit use and operation to safe and/or desired activities. Therefore, the computerized control system may be programmed to limit activities which would damage the workpiece, circumvent security or authentication procedures, or otherwise be undesired. The computerized control system may therefore require user authentication, employ video pattern recognition of the workpiece, especially markings on the workpiece, and control operation of the laser system to avoid damage to the system components or the particular workpiece. The system may also acquire an image, fingerprint, retinal image or other secure identification of the operator. 
         [0065]    The interface may, for example, require biometric identification of a user, e.g., fingerprint, retinal scan, iris scan, etc. So-called two factor or three factor authentication schemes may also be employed. For example, a user password, dynamic code security token, and biometric identifier may all be used. The authentication may be local or involve a remote authentication system. The remote authentication system may be integrated with gemstone authentication, to provide full chain of custody logging for gemstones. 
         [0066]    The system may also include a diamond or gemstone analysis system for describing the quality and/or characteristics of the workpiece. This analysis may be employed by the system in order to optimize the marking process, generate data to be marked on the workpiece, and/or to store data identifying the workpiece in relation to the marking. This system may operate automatically or semiautomatically. It is noted that, where gemstone classification automation is employed, a failsafe classification scheme will generally be employed which provides a manual classification or preclassification first. Thus, the risk of mismarking or misclassification will be reduced by the redundancy. The characteristics of the workpiece may be used to control parameters of the marking process. These parameters can be, for example, the information contained in the marking, the marking parameters, or compensations of the marking to normalize the marking to the substrate, for example. 
         [0067]    Where a diamond having a polished girdle is to be marked, a single pass inscription is generally sufficient, and an automated optical feedback system may reliably control operation. However, the optical absorption of a smooth girdle on a diamond is low, so that a dye or ink coating is required to be placed on the surface, to ensure absorption of the laser energy. Where the girdle is rough, multiple passes of the inscription device may be necessary to generate a desired marking. The optical absorption of a rough girdle is generally high enough to dispense with the need for optically absorptive dyes or inks. 
         [0068]    While the execution of retries may be automated, user control may be desirable, and such control is possible through use of the video cameras which are directed at the workpiece, which display a real time image on a computer monitor. 
         [0069]    An optically absorptive dye or ink may be manually applied to the workpiece, such as by a marking pen, or the application process may be automated by applying the dye to a workpiece surface to be marked, such as with a porous marking tip or pad. It is also possible to dip the entire stone into a dye bath prior to processing, and then stripping the dye in a cleaning bath when complete. Advantageously, these inks or optically absorptive dyes remain confined to the surface of the workpiece, and would not be expected to penetrate. In general, a dye is selected which may be easily removed after marking, by use of a solvent, such as alcohol. The dye may be removed manually or through an automated process, such as wiping with a solvent saturated pad. 
         [0070]    According to one embodiment, the spot selected to receive the inscription is selectively coated with an energy absorptive or fluorescent ink or dye. The workpiece is then mounted in a holder and inserted into the apparatus. The apparatus then executes an automated search and positioning function to bring the ink or dye region to the marking position. Thus, a technician can select a spot for inscription by placing an ink or dye spot on it, which is automatically recognized by the apparatus. The ink or dye also advantageously facilitates detection of surface contours. For example, an uncoated transparent stone may be difficult to distinguish the first air-stone interface from reflections, while in a coated stone such ambiguities are averted. 
         [0071]    It is also possible to provide a liquid transmissive medium through which the energy beam is transmitted, using immersion optics. 
         [0072]    In another embodiment, relief inscriptions are possible by modulating the laser pulses or selectively multiply ablating or graphitizing the workpiece at desired positions. Such relief markings are generally not necessary for simple alphanumeric or digital code inscription, but may be useful for logos, pictorial works, antialiasing of raster images, binary or Fresnel-type optics, diffraction optic effects, anti-piracy or anti-copying provisions, or in other circumstances. 
         [0073]    Diffractive optics are typically provided on a polished surface, and in order to be useful at visible wavelengths, the depth of a phase grating implementation must be critically controlled. This is more readily accomplished with a layer added to the surface, or an etching process into the surface, than a direct laser ablation, though in principle a direct write laser can have a controlled depth ablation or graphitization. In the case of an amplitude grating, this may be efficiently accomplished by, for example, selectively graphitizing diamond to produce alternating graphitized and non-graphitized regions, effecting a grating. In most cases, for aesthetic gemstones, amplitude grating structures would be disfavored due to their light loss. In the case of a diamond, a portion of the diamond may be graphitized, and then that portion removed in an acid etch bath, yielding a diffractive phase optic. In order to avoid accumulation of debris in the diffraction grating structures, they may be back-filled with a frit or the like, so that the resulting surface is smooth. The design equations for the grating may be optimized for the optical properties of the frit and gemstone. 
         [0074]    The diffractive or holographic pattern may be used, for example, to alter the return color patterns perceived by a viewer of the stone, separate from the intrinsic refractive properties of the stone material. This, in turn, can alter the design philosophy for stonecutters, who at present must produce a design which is refractively optimized for both light return and color properties. On the other hand, by applying diffractive optic principles to the facts of the stone, especially below the table, separate optimizations may be made. 
         [0075]    A computer model of the stone, including intrinsic material characteristics, gemological imperfections, and crystallography, along with a model of the cut gemstone, including facet angles and distances, may be formulated. This may be a custom model for each individual gemstone, or a generic model for a type of gem material and cut. Presumptions are then made regarding illumination conditions, and criteria for resulting stone optical performance applied, for example desired color appearance at a particular viewing angle or range of angles. The model, presumptions and performance criteria are then processed in an array processor, which may be a supercomputer (www.clearspeed.com/downloads/CSX600Processor.pdf, www.clearspeed.com/downloads/AdvanceAcceleratorBoard.pdf, www.clearspeed.com/downloads/Intel%20Math%20Kernel%20whitepaper.pdf, www.clearspeed.com/downloads/Architecture%20Whitepaper.pdf), grid or cluster processor array (www.tyan.com/products/html/clusterservers.html, (model B2881YDS4T or model B5160YDS4T), Cell processor (Sony, IBM, Toshiba) system (www-03.ibm.com/chips/news/2004/1129_cell1.html; http://www.blachford.info/computer/Cell/Cell0_v2.html), or graphic processor system (www.gpgpu.org, http://research.microsoft.com/˜gbell/CGB%20Files/Bell-Worley%20Graphics%20Supercomputer%201989%20c.pdf; www.osc.edu/press/releases/2002/nvidia.shtml; Gang Bao and David C. Dobson, “Modeling and Optimal Design of Diffractive Optical Structures”, citeseer.ist.psu.edu/6836.html, citeseer.ist.psu.edu/cache/papers/cs/7863/http:zSzzSzwww.math.tamu.eduzSz˜dobsonzSzpaper16.pdf/modeling-and-optimal-design.pdf. 
         [0076]    In systems provided with two video cameras, video profiling of the workpiece is possible, which may be used to determine an optimal position of the workpiece for marking without requiring focus checking at each location. The dual cameras also allow positioning and viewing on the same video screen, wherein the camera views are each provided as separate image windows. The cameras are useful for determining an appropriate marking location, ensuring laser beam focus, aligning the stone, and monitoring progress of the marking process. The system, in some cases, may employ no imagers (using other means to determine surface profile), one camera, or three or more cameras. 
         [0077]    The computerized control system allows versatility in the design, selection and implementation of graphic and font inscription. In a preferred embodiment, Borland fonts are employed. However, other fonts or combinations of fonts may also be employed, for example, Borland, postscript, TrueType, plotter, or other type fonts or typefaces may be employed. Further, the marking system may be set up to respond to Adobe Postscript, Microsoft Windows GDI, Macintosh QuickDraw, HP-GL, or other graphics standards. Likewise, image files, such as TIFF or BMP, may be employed to define the marking pattern. 
         [0078]    A preferred laser system is a self-standing diode laser pumped Q-switched Nd:YLF laser with an internal frequency doubler. Such a system avoids the requirements of a relatively large YAG laser with large power supply and strict environmental control, an external frequency doubler, a water cooling system, large size and weight, inherent instability, and long optical path. Of course, other lasers, having different lasing materials, output wavelengths, and the like, may be employed. 
         [0079]    In the preferred frequency-doubled infrared laser design, a green filter is provided on the output of the laser to selectively filter laser diode emissions, while allowing the green (530 540 nm) laser emissions to pass. Leakage of the laser diode illumination is undesirable because it saturates the image on the vertical (Z-axis) camera screen in the laser spot area, and prevents convenient viewing of the girdle and inscription. Likewise, its focus may be different in the optics, and may result in unnecessary heating of the gemstone. On the other hand, the infrared output from the LED sources and leakage from the laser fundamental wavelength may be useful for removing the dye or pigment from the surface of the gemstone, with low risk of harming the stone. 
         [0080]    The preferred translatable stage arrangement overcomes a typically limited range of optical movement of laser steering systems, requiring inscription operations in multiple segments, and provides good absolute positioning repeatability. However, according to some embodiments of the invention, other types of beam positioning apparatus may be employed, such as beam steering systems. 
         [0081]    A marking may be provided on the stone for a number of reasons. First, it may be desirable to identity a stone if it is lost or mixed with other stones. The marking may also be used to identify source or origin. In this case, the marking may be taken at face value, that is, a plain text identification may be employed which need not be investigated. 
         [0082]    In some instances, however, a risk of forgery or simulation requires further security measures, that is, the inscription must be authenticated. Therefore, it may be desired to ensure that the stone was marked by an indicated entity, or that the stone corresponds to the marking applied thereto. This requires one of at least two possible schemes. First, that a characteristic of the stone be unique and verse difficult to simulate be encoded within the inscription or associated with the identification of the stone implied by the inscription. For example, certain dimensions or ratios of the gemstone are the subject of somewhat random variations, and thus have a somewhat uncontrolled range of values. Natural flaws and other characteristics are also generally random in nature, and thus also difficult to simulate. It is therefore unlikely that one stone will correspond to another stone, and it is unlikely that another stone can be made to identically correspond to the determined dimensions and ratios through manipulations. 
         [0083]    According to one aspect of the invention, therefore, these difficult to reproduce characteristics are used as an integrity check for an encoded message or stone identification. These characteristics may be measured or recorded, and stored. Advantageously, these measurements and characteristics may be derived from an image of the stone captured in conjunction with the marking process, though the characteristics need not be derived or measured within the marking apparatus; the advantage here is that the marking apparatus is has an automated control which identifies the stone, has imaging devices to capture image(s) of the stone, and preferably has a remote communication facility. In fact, by storing such images and providing a pointer to the image, e.g., a serial number, the measurements or characteristics to be compared need not be determined in advance. Therefore, according to such a scheme, the stone need only include a pointer to a record of a database containing the data relating to the stone to be authenticated. This allows information relating to characteristics of the stone, which may be difficult to repeatably determine or somewhat subjective, to be preserved in conjunction with the stone or an identification of the stone. As stated above, an image of the stone on a certificate of authenticity may be used to verify that the stone is authentic, while providing a tangible record of the identification of the stone. 
         [0084]    Another scheme relies instead on the difficulty in identically copying an inscription, including subtle factors and interactions of the laser marking beam with the stone itself. Thus, the marking itself is self-authenticating. An attempt to copy the marking will likely fail because of the technological limitations on the laser marking techniques, and/or insufficient information to determine all of the encoding information. For example, on a bruted girdle, the interaction of the energy beam with the stone may be unpredictable, and lead to irregularities which are not defined by the marking instructions, not readily imposed by known processes. 
         [0085]    Thus, to authenticate a stone, either the markings alone or the markings in conjunction with the characteristics or physical properties of the stone are analyzed. In one scheme, the markings inscribed on the stone include information which correlates with characteristics of the stone which are hard to duplicate, and which recur with rarity, allowing self-authentication. In other schemes, the marking inscribed on the stone identifies a database record stored in a repository, thus requiring communication with the repository to obtain the authentication information. The hand cutting process for gemstones makes it is difficult or impossible to identically duplicate all measurable aspects of a stone, especially in conjunction with other physical characteristics, such as natural flaws. Such physical properties may include, for example, the girdle width at predetermined locations. The location may be identified, e.g., by an inscribed marking or by an offset from a marking which is not apparent from an examination of the stone alone. For any given gemstone, one or more such locations may be stored, thus increasing the difficulty in simulating the measurement. Further, such measurements are generally easy to obtain or determine from the imaging system of the inscribing system. 
         [0086]    Sophisticated techniques, such as Raman scattering, analysis, are known which may provide unique information about a particular natural crystal structure. While the preferred system does not employ Raman scattering analysis, such analysis may be used in conjunction with embodiments of the invention. Likewise, an optical refraction analysis may be employed to measure the interaction of the stone with a standardized light source. This may be recorded as an optical image, which then becomes a “signature” for the stone. This signature will depend on the dimensions and angles of the facets, and will be difficult to precisely repeat, especially if recorded in sufficient detail to reveal flaws or irregularities within the stone. This signature may reveal optical refraction and diffraction patterns, and to the extent that the diffraction pattern is imposed by a deterministic process, this allows another type of identification for the stone. 
         [0087]    According to a preferred embodiment, the authenticity of a stone may be determined by use of a jeweler&#39;s loupe or magnifying viewer, to compare the actual stone to an image of the stone, such as may be provided on or in conjunction with a certificate of authenticity. Because each stone has varying characteristics, including the marking, details of the cut, and the relationship of the marking to the landmarks of the stone, the image serves as a fingerprint, making each stone essentially unique. The certificate, in addition to the image of the stone, may also include other information, such as an encrypted code, as discussed below. Thus, both the stone and the accompanying certificate may include identifying information. 
         [0088]    Thus, the present invention also encompasses secure certificates, i.e., documents which are tamper and copy resistant, bearing an image of a marked stone, security features, and authentication features. Known secure documents and methods for making secure documents and/or markings are disclosed in U.S. Pat. Nos. 5,393,099; 5,380,047; 5,370,763; 5,367,319; 5,243,641; 5,193,853; 5,018,767; 4,514,085; 4,507,349; 4,247,318; 4,199,615; 4,059,471; 4,178,404; and 4,111,003, expressly incorporated herein by reference. U.S. Pat. No. 4,414,967, expressly incorporated herein by reference, discloses a latent image printing technique, which may be used to form an image of a workpiece. U.S. Pat. Nos. 5,464,690 and 4,913,858, expressly incorporated herein by reference, relate to certificate having holographic security devices. 
         [0089]    In another scheme, a stone may be authenticated without the certificate of authenticity, e.g., by a typical jeweler employing simple tools, such as a jeweler&#39;s loupe and telephone. Therefore, according to one embodiment or the invention, a jeweler uses a loupe to read an alphanumeric inscription, invisible to the naked eye, on a gemstone. The alphanumeric inscription, or a portion thereof, includes identifying information about the gemstone, e.g., a serial number, which is entered into an authentication system, e.g., by a telephone keypad. The characteristics of the stone, determined at or around the time of the marking process, are then retrieved from a database. In general, these stored characteristics may include grading, size, identification and possible location of flaws, and an image of the stone, including unique or quasi-unique features. Thus, for example, an image of the marking and stone or portions of the stone, e.g., surrounding landmarks of the stone may be stored. Some or all of these characteristics may then be provided to the jeweler, such as by voice synthesis, telefacsimile of the image, or otherwise. Where a certificate of authenticity is available, the certificate may be recreated and a facsimile transmitted to the jeweler, allowing verification of all information contained thereon. The jeweler then compares the retrieved metrics and indicia with those of the stone. If the stone corresponds to the stored information, the stone is likely genuine. If, on the other hand, the stone does not correspond to the stored information, it is possible that the stone is counterfeit, that is, a forgery attempt has been made to substitute a different stone with the same identifying number. 
         [0090]    Another authentication scheme employs a digital camera with a holder and macro lens attachment. For example, a 5-8 megapixel camera with a spring clip on a self-supporting arm for holding the gemstone in front of the lens, with a white LED illuminator is provided. A macro lens is provided, to achieve a 5:1-25:1 magnification. This, with a 1 cm imager size, 1.6 mm inscription, and 5× lens, the inscription will occupy about 80% of the image width. With a 2500 pixel width imager, this corresponds to 2000 pixels across for the image of the inscription. Assuming an inscription dot pitch of 5 microns, this results in &gt;6 pixels per dot, sufficient to provide high quality analysis. The image is captured, and typically converted to JPEG format. The image may then be analyzed within the camera itself, using custom firmware, or uploaded to a local computer or remote server for analysis. 
         [0091]    In another embodiment, the authentication system requests a series of measurements from the jeweler, which may be obtained by micrometer or reticle (or reticule) in a loupe, without providing the nominal values to the jeweler, so that no explanation is provided for a failure to authenticate, making forgery more difficult. Of course, the system may also employ more sophisticated equipment for measuring characteristics of the stone and for communications, including a fully automated analysis and communications system. 
         [0092]    In another embodiment, the gemstone is self authenticating. Thus, instead of comparison with metric data stored in a database system, the marking inscribed on the stone itself includes an encrypted message containing data relating to characteristics of the stone. A number of different types of messages may be employed. For example, a so-called public key/private key encryption protocol, such as available from PSA, Redwood Calif., may be used to label the workpiece with a “digital signature”. See, “A Method for Obtaining Digital Signatures and Public Key Cryptosystems” by R. L. Rivest, A. Shamir and L. Adelmann, Communications of ACM 21(2):120 126 (February 1978), expressly incorporated herein by reference. In this case, an encoding party codes the data using an appropriate algorithm, with a so-called private key. To decode the message, one must be in possession of a second code, called a public key because it may be distributed to the public and is associated with the encoding party. Upon use of this public key, the encrypted message is deciphered, and the identity of the encoding party verified. The data in the deciphered message includes a set of unique or quasi unique characteristics of the gemstone. Therefore, one need only compare the information from the decoded message with the stone to verify the origin of the gemstone and its authenticity. In this scheme, the encoding party need not be informed of the verification procedure. Known variations on this scheme allow private communications between parties or escrowed keys to ensure security of the data except under exceptional authentication procedures. 
         [0093]    Typical encryption and document encoding schemes which may be incorporated, in whole or in part, in the system and method according to the invention, to produce secure certificates and/or markings, are disclosed in U.S. Pat. No. 5,426,700 (and Ser No. 07/979,081), U.S. Pat. Nos. 5,422,954; 5,420,924; 5,388,158; 5,384,846; 5,375,170; 5,337,362; 5,263,085; 5,191,613; 5,166,978; 5,163,091; 5,142,577; 5,113,445; 5,073,935; 4,981,370; 4,853,961; 4,893,338; 4,995,081; 4,879,747; 4,868,877; 4,853,961; 4,816,655; 4,812,965; 4,637,051; 4,507,744; and 4,405,829, expressly incorporated herein by reference. See also, W. Diffie and M. E. Hellman, “New directions in cryptography,”, IEEE Trans. Information Theory, Vol. IT-22, pp. 644 654, November 1976, R. C. Merkle and M. E. Hellman, “Hiding information and signatures in trapdoor knapsacks”, IEEE: Trans. Information Theory, Vol. IT-24, pp. 525 530, September 1978; Fiat and Shamir, “Dow to prove yourself practical solutions to identification and signature problems”, Proc. Crypto 86, pp. 186 194 (August 1986); “DSS: specifications of a digital signature algorithm”, National Institute of Standards and Technology, Draft, August 1991; and H. Fell and W. Diffie, “Analysis of a public key approach based on polynomial substitution”, Proc. Crypto. (1985), pp. 340 349, expressly incorporated herein by reference. 
         [0094]    Another encoding scheme uses a AES-type encryption system, which does not allow decoding of the message by the public (in the absence of the key), but only by authorized persons in possession of the codes. The therefore requires involvement of the encoding party, who decodes the message and assists in stone authentication. 
         [0095]    Through use of proxy key cryptography (for conveyance of the key) and secure (trusted) decryption modules, it may be possible to deliver the secret key without unnecessarily exposing it. 
         [0096]    In order to provide enduring authentication, it may be desired that multiple codes, containing different information in different schemes, be encoded on the gemstone, so that if the security of one code is breached or threatened to be breached, another, generally more complex code, is available for use in authentication. For example, a primary code may be provided as an alphanumeric string of 14 digits. In addition, a linear bar code may be inscribed with 128-2048 symbols. A further 2-D array of points may be inscribed, e.g., as a pattern superimposed on the alphanumeric string by slight modifications of the placement of ablation centers, double ablations, laser power modulation, and other subtle schemes which have potential to encode up to about 1 k-16 k symbols, or higher, using multivalued modulation. Each of these increasingly complex codes is, in turn, more difficult to read and decipher. 
         [0097]    The ablation pattern of the marking is subject to random perturbations due to both system limitations and surface variations of the stone. Thus, even with a self authenticating code, it is generally desired to store image information relating to the stone in a database after the marking process is completed. This database may then be used for further verification or authentication by image comparison or feature extraction. 
         [0098]    Thus, a number of authentication schemes may be simultaneously available. Preferably, different information is encoded by each method, with the more rudimentary information encoded in the less complex encoding schemes. Complex information may include spectrophotometric data, image information, and geometric dimensional topology. Thus, based on the presumption that deciphering of more complex codes will generally be required at later time periods, equipment for verifying the information may be made available only as necessary. 
         [0099]    Known techniques for using ID numbers and/or encryption techniques to preventing counterfeiting of secure certificates or markings are disclosed in U.S. Pat. Nos. 5,367,148; 5,283,422; 4,494,381; 4,814,589, 4,630,201 and 4,463,250, expressly incorporated herein by reference. 
         [0100]    It is also noted that information may also be stored holographically in crystalline matter. Therefore, in accordance with the present invention, authentication holographic data may be stored within a crystal. The techniques for forming and reading such holographically encoded messages are known, and the use of such encoded messages to authenticate gemstones is a part of the present invention. Thus, the information may be stored as a hologram within the crystalline structure of the stone, or as a relief or phase hologram on a certificate. Therefore, a hologram may be formed directly from the gemstone, preferably optically enlarged. Since the laser markings comprise ablation spots, these will be apparent in the hologram. Further, since the marking process includes a laser, this same laser may advantageously be used to expose the hologram, using a modified optical system. For example, a pair of chromate holograms may be individually formed for each gemstone, one placed on the certificate and the other stored with the originator of the marking. The certificate may also include known security features. 
         [0101]    As discussed above, the hologram need not store information, but may be designed to produce a desired optical effect, similar to the above-described surface diffraction structure, but effective on a volume basis. For natural gemstones, the change in refractive index as a result of irradiation will generally be small, therefore the hologram will require a relatively large effective volume to have a pronounced effect. 
         [0102]    Where an original hologram of the workpiece is available, authentication may be automated by optically correlating the hologram and the workpiece. This method will be very sensitive to subtle changes in the workpiece, and thus particularly tamper resistant. Preferably, the optical correlation pattern of the hologram and the workpiece is stored after generation or developing the final hologram, in order to compensate for any changes during processing. This optical correlation pattern may be stored photographically or digitally. 
         [0103]    Therefore, it is a characteristic of this aspect of the invention that, in order to identify a gemstone, the information stored thereon identifies a database record relating to the stone, and including information relating thereto, or the stored information itself relates to characteristics of the stone. 
         [0104]    In one aspect of the invention, the imaging system has components ordinarily disposed to view both a portion of the girdle of the stone and a profile thereof. Therefore, it is generally desirable to derive the required information relating to the stone from the imaging system while the gemstone is mounted in the apparatus. Where the marking itself includes encoded characteristics, these may be applied by the apparatus by imaging the stone through the imaging system, and applying an inscription based on the imaging system output, e.g., by using feedback positioning. An image of the inscribed stone may also be obtained and stored. As stated above, the inscription may be explicitly encoded with readily apparent information, such as an inscribed alphanumeric code, or may include covert information, such as ablation spot placement with respect to stone landmarks, beam modulation, spacing between distant ablation spots, and pseudorandom ablation markings. The markings may also include indicia made at critical portions to allow repeatable measurements, such as edge margins of the girdle. 
         [0105]    According to one method of the invention, a gemstone to be marked is imaged, with the image analyzed and extracted information compared to information in a database. Preferably, the database is a central database, remote from the marking apparatus, and the stored information is in digital form. The image is compared to data relating to at least a subset of images of comparable gemstones. An encoded marking is then proposed for a location on the girdle of the stone which, is either absolutely unique, or unique when taken with at least one readily defined characteristic of the stone. The database system is employed to prevent identical markings on comparable gemstones, and thus fails to approve (authorize) a proposed marking if it is too similar to any other stone in the database. Thus, according to this aspect of the invention, each stone has a unique coding, and only rarely will a stone be found which is capable of receiving an identical marking to a previously inscribed stone while meeting the same coding criteria. In a simple embodiment, the database assigns a unique serial number to each stone and prevents use of duplicate serial numbers. On the other hand, in a more complex scheme, serial numbers need not be unique if other characteristics of the stone may be used to distinguish candidates. 
         [0106]    The coding may also provide a hash function of a set of signature characteristics of the gemstone, for example SHA-256, SHA-384, SHA-512, and HMAC. A serial number may also be included in the hash, for self-authentication. 
         [0107]    According to another aspect of the invention, the inherent limitations on the accuracy and repeatability of the marking process are employed to provide a unique encoding of a gemstone. Thus, the surface imperfections of the girdle and the ablation process itself interact to prevent a theoretically ideal marking, i.e., one with a perfectly cylindrical, conical or spherical ablation of the gemstone material at precisely the designated spot. Because these effects may be due to vibration, power line fluctuations, laser instability and the like, they will tend to be random over a number of marking operations. These effects will also result from characteristics of the stone. Thus, an attempt to recreate a marking to a high level of detail, even with advanced equipment, will invariably be met with difficulty. Thus, by storing high resolution images of the actual marking, possibly including off axis images or defocused images to gain ablation depth information, authentication of the markings is facilitated. 
         [0108]    Of course, it is advantageous not only to have information theoretically available for authentication, if this information is not accessible, nor usable without special equipment or training, then it will be of limited value. Thus, it is preferred to have an authentication scheme which is available for use with limited user training, readily available and/or inexpensive equipment, rapid and definitive results, and including an off-line operation option. Since the marking is microscopic, some optical apparatus will probably be required as a minimum. Further, since human vision may be impaired, and the results of viewing possibly subjective, an automated device, generally electronic, is preferred. 
         [0109]    Assuming a security marking which comprises 6 micron spots formed on 3 micron centers (to permit overlapping inscriptions), with up to 4 superposed spots at any location (i.e., 2 bits), and 1 micron positioning accuracy (95%) and 1 micron positioning resolution, and further that the security encoded portion of the inscription is at maximum 500 microns across, and also assuming that the optical detection of the pattern should have a resolution of at least 5 times greater than the minimum feature to be analyzed, this leads to a conclusion that the pixel size of an electronic imager after magnification should be 0.2 micron (1 micron precision/5 pixels). Assuming also that we wish to view the entire inscription in a single frame, this leads to a linear dimension of 2,500 pixels, available in a 5-8 megapixel imager. However, a 0.2 micron resolution nears the optical limit, and in any case would require oil immersion optics. 
         [0110]    The limit of optical resolution of a lens may be determined by the formula: 
         [0000]      1.22×λ/(numerical aperture of the lens+numerical aperture of condenser). 
         [0111]    Assuming 420 nm (UV) illumination from a GaN UV LED, and a lens numerical aperture of 1.3, and a diamond condenser numerical aperture of 2.42, the resolution limit is 0.14 microns, leaving opportunity for compromise in one or more parameters. 
         [0112]    It is also possible to use an interferometric/holographic method to measure the distance between spots or structures. For example, the security marking may be illuminated with laser irradiation, or in some cases, monochromatic irradiation. The reflection pattern from a laser on the security pattern will be distinctive for each stone, varying slightly in dependence on the actual spot placement. This method requires high repeatability of the laser, and high resolution representations of the reflection pattern. 
         [0113]    The security inscription comprises two parts, separately recorded. A first part comprises a test pattern, having sufficient complexity to exercise the limits of the inscription device. This pattern may be random, pseudorandom, or identical for each inscription. For example, it may comprise a set of lines of 6 micron spots spaced 10 microns on centers. The array may extend about 50-100 microns high and 500 microns across. Adjacent to this marking is a binary code which represents a hash or description of differences between the actual inscription, as formed on the stone, from the nominal inscription, represented at 0.2 micron resolution. 
         [0114]    Instead of truly random deviations from a nominal spot placement, intentional or “pseudorandom” irregularities (seemingly random, but carrying information in a data pattern) may be imposed on the marking, in order to encode additional information on top of an a marking pattern. Such irregularities in the marking process may include beam modulation, double ablations, fine changes in ablation position, varying degrees of overlap of ablation locations, varying laser focus during pulses. Without knowledge of the encoding pattern, the positional irregularities will appear as random jitter and the intensity irregularities will appear random. Because a pseudorandom pattern is superimposed on a random noise pattern, it may be desirable to differentially encode the pseudorandom noise with respect to an actual encoding position or intensity of previously formed markings, with forward and/or backward error correcting codes. Thus, by using feedback of the actual marking pattern rather than the theoretical pattern, the amplitude of the pseudorandom signal may be reduced closer to the actual noise amplitude while allowing reliable information retrieval. By reducing the pseudorandom signal levels and modulating the pseudorandom signal on the actual noise, it becomes more difficult to duplicate the markings, and more difficult to detect the code without a priori knowledge of the encoding scheme. 
         [0115]    While alphanumeric codes and other readily visible codes may be read by common jewelers, subtle encoding methods may require specialized equipment for reading. Therefore, another aspect of the invention provides an automated system for reading codes inscribed on a gemstone. Such a system operates as an electronic imager microscope with image analysis capability. The image analysis capability will generally be tuned or adapted for the types of coding employed, reducing the analysis to relevant details. Therefore, where a pseudorandom code appears in the ablation pattern, the individual ablation locations and their interrelations are analyzed. Likewise, where ablation depth or amplitude is relevant, confocal microscopy may be employed. 
         [0116]    In another embodiment, the pattern is filled with a fluorescent dye, such as fluorescein, and illuminated with a UV source, such as a UV LED. The fluorescence pattern is then detected with an electronic imager microscope. 
         [0117]    In like manner, a certificate of authenticity may be provided with authentication and security coding, to prevent forgery or counterfeiting. In addition to the techniques discussed above, a number of other known techniques are available for the tamper and copy protection of documents. In this case, the certificate adds an additional level to the security of the marking process. Therefore, while the workpiece preferably includes a secure marking which does not require a certificate of authenticity for authentication, the addition of the certificate eases the authentication process while making forgery more difficult. 
         [0118]    A typical electronic reading device for a gemstone inscription will include a CCD imaging device with a high magnification lens, e.g., about 200 times magnification, and an illumination device. Apparent resolution of the CCD may be increased by multiframe averaging with slight shifts of the gemstone with respect to the CCD optical system. For example, a piezoelectric positioning device may be useful for slight repositioning. A computer system with a USB port and/or network interface may be used to obtain the data and analyze it. In general, known image processing schemes may be used to extract the encoded information. 
         [0119]    In addition to being analyzed for information content, i.e., the markings, the workpiece image may also be compared with an image stored in a database. Therefore, based on a presumptive identification of a gemstone, an image record in a database is retrieved. The image of the presumptive gemstone is then compared with the stored image, and any differences then analyzed for significance. These differences may be analyzed manually or automatically. Where a serial number or other code appears, this is used to retrieve a database record corresponding to the stone which was properly inscribed with the serial number or code. Where the code corresponds to characteristics of the stone and markings, more than one record may be retrieved for possible matching with the unauthenticated stone. In this case, the information in the database records should unambiguously authenticate or fail to authenticate the stone. 
         [0120]    According to another aspect of the invention, the laser energy microinscribing system includes a semiconductor excited Q-switched solid state laser energy source, a cut gemstone mounting system, having an aperture, an optical system for focusing laser energy from the laser energy source, through said aperture onto a cut gemstone, a displaceable stage for moving said gemstone mounting system with respect to said optical system so that said focused laser energy is presented to desired positions on said gemstone, having a control input, an imaging system for viewing the gemstone from one or a plurality of vantage points, and/or a rigid frame supporting said laser, said optical system and said stage in fixed relation, to resist differential movements of said laser, said optical system and said stage and increase immunity to vibrational misalignments. By employing a laser system with low cooling and power requirements, the device may be made self contained and compact. By minimizing the size of the apparatus, and enclosing the device in a rigid frame or chassis, vibration immunity is improved. Thus, as compared to systems employing flashlamp excited lasers, substantial vibration isolation apparatus is eliminated. 
         [0121]    According to another aspect of the invention, prior to any marking operation, the proposed marking and/or the presumed resulting image are compared to database records to determine if the proposed marking and/or resulting marked gemstone are too close to any previously marked gemstone to be easily distinguished. If so, the marking or proposed marking may be altered. In addition, as an automatic nature of the machine, this comparison may prevent use of an authorized machine to counterfeit a previously marked gemstone, and will insure the integrity of the database. 
         [0122]    According to another aspect of the invention, a pattern marking is emplaced on a portion of the gemstone, such as a girdle. Because it is difficult to recreate a particular girdle pattern exactly, the pattern will allow, for example with a loupe, quantification or girdle characteristics, including width, contour and size. Thus, the pattern assists in providing a metric for gemstone authentication. 
         [0123]    The database may be stored locally to the marking apparatus but preferably a central database is maintained, receiving identification and/or image information from many remote marking locations, and allowing central control and retrieval of records. This also facilitates a separation of function to maintain the integrity of the system and long term authentication procedures. 
       OBJECTS OF THE INVENTION 
       [0124]    It is therefore an object of the invention to provide an energy micro-marking system, comprising an energy source; a workpiece mounting system, having an aperture; a system for directing energy from the energy source, through said aperture onto a workpiece; means for directing said energy onto a desired portion of the workpiece, having a control input; an imaging system for viewing the workpiece from one or more vantage points; an input for receiving marking instructions; a processor for controlling said directing means based on said marking instructions and information received from said imaging system, to generate a marking in accordance with said instructions; and optionally a storage system for electronically storing information relating to images of markings on a plurality of workpieces. 
         [0125]    It is also an object of the invention to provide a method of microinscribing a workpiece with energy from an energy source, directed onto a desired portion of the work-piece, comprising the steps of mounting a work-piece in a mounting system; directing the energy onto the desired portion of the workpiece; electronically imaging the workpiece from one or more vantage points; receiving marking instructions from an input; controlling the directing of the energy based on the marking instructions and the electronic imaging, to generate a marking in accordance with said instructions; and optionally storing electronic information relating to images of markings on a plurality of workpieces. 
         [0126]    It is a still further object of the invention to provide a laser energy microinscribing system, comprising a semiconductor excited Q-switched solid state laser energy source; a cut gemstone mounting system, having an aperture; an optical system for focusing laser energy from the laser energy source, through said aperture onto a cut gemstone; a displaceable stage for moving said gemstone mounting system with respect to said optical system so that said focused laser energy is presented to desired positions on said gemstone having a control input; an imaging system for viewing the gemstone from one or more vantage points; and a rigid frame supporting said laser, said optical system and said stage in fixed relation, to resist differential movements of said laser, said optical system and said stage and increase immunity to vibrational misalignments. 
         [0127]    A further object of the invention provides a system for marking a gemstone with an energy beam, comprising an energy beam source adapted to produce a spatially dispersed energy beam; and a spatial modulator adapted to independently modulate a plurality of spatially dispersed portions of the spatially dispersed energy beam; a control, adapted to control the spatial modulator to independently modulate the plurality of spatially dispersed portions; wherein the plurality of spatially dispersed portions are directed toward a gemstone, to at least one of: interact with a material on the surface of the gemstone, interact with a material for deposition on the gemstone, and interact with the gemstone substrate. The corresponding method comprises producing a spatially dispersed energy beam; independently modulating a plurality of spatially dispersed portions of the spatially dispersed energy beam; directing the independently modulated plurality of spatially dispersed portions of the spatially dispersed energy beam toward a gemstone, to at least one of: interact with a material on the surface of the gemstone, interact with a material for deposition on the gemstone, and interact with the gemstone substrate. The energy beam source may comprise a laser, an ion beam, an electron beam, and/or a light beam (coherent and/or incoherent). The control may receive an input from at least one imager. The control may alter a modulation pattern in dependence on an input received from at least one imaging device. The control may receive real time input from at least one imaging device to provide closed loop feedback for control of the spatial modulator. The plurality of dispersed portions may produce a persistent diffractive and/or holographic pattern at visible wavelengths on or in the gemstone. The control may produce a pattern on the gemstone which is dependent on a configuration of the gemstone and/or a desired optical interaction with the gemstone. The system may further comprise an array processor for modeling an optical interaction with the gemstone. The system may further comprise, for example, a photoresist deposition device, an unexposed photoresist removal device, and an etching device to differentially etch the gemstone in a pattern based on the independently modulated plurality of spatially dispersed portions of the energy beam. The independently modulated plurality of spatially dispersed portions may be focused in an area smaller than an area of the spatially dispersed energy beam, wherein an energy density of the spatially dispersed energy beam is lower at the spatial modulator than at the focus. The method may further comprise the steps of receives an input from at least one imager, and altering a modulation pattern of the spatially dispersed portions of the spatially dispersed energy beam in dependence on the input. The method may further comprise the steps of coating the gemstone with a photoresist, exposing the photoresist-coated gemstone to the modulated spatially dispersed portions of the spatially dispersed energy beam to selectively interact with regions thereof, and differentially etching the gemstone through the exposed photoresist to produce a persistent pattern thereon. The method may further comprise the step of automatically identifying a first marking position and a second marking position, and then automatically positioning the gemstone to the first marking position and then to the second marking position. The method may further comprise the steps of imaging the gemstone to determine a set of persistent characteristics thereof, storing at least one image representing at least one persistent characteristic of the gemstone, and controlling said directing step in dependence on at least a portion of the set of persistent characteristics determined by the imaging step. The method may further comprise the steps of receiving a graphic image, and directing the independently modulated plurality of spatially dispersed portions of the spatially dispersed energy beam to produce a pattern on the gemstone corresponding to the received graphic image. The spatial modulator may be a binary modulator, a higher level digital modulator, having, for example, at least three modulation states, or me an analog modulator, for modulating each respective portion of the spatially dispersed energy beam. 
         [0128]    It is a further object to provide a method for marking a gemstone with an energy beam, comprising independently modulating a plurality of spatially dispersed portions of an energy beam; directing the independently modulated plurality of spatially dispersed portions of the energy beam toward a gemstone, to produce a latent image on a surface of the gemstone; and 
         [0129]    developing the latent image to produce a persistent modification at a surface of the gemstone, the persistent modification having sufficient depth to produce an interference pattern with visible light. The persistent modification may be a diffraction pattern, a hologram, a graphic image, a human readable semantic message, a machine readable message, or the like. The message may be cryptographic and/or steganographic. 
         [0130]    These and other objects will become apparent. For a fuller understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0131]    The invention will now be described with respect to the drawings of the Figures, in which: 
           [0132]      FIG. 1  is a diagram of the laser optical path of the system according to the present invention; 
           [0133]      FIG. 2  is a diagram of the too illumination and imaging systems according to the present invention; 
           [0134]      FIG. 3  is a diagram of a side illumination and imaging systems according to the present invention; 
           [0135]      FIG. 4  is a diagram of a bottom illumination system according to the present invention; 
           [0136]      FIG. 5  is a block diagram of the stage positioning system and control according to the present invention; 
           [0137]      FIG. 6  is a diagram of a prior art beam steering system; 
           [0138]      FIGS. 7A ,  7 B,  7 C,  7 D, and  7 E are various views of a workpiece mounting system according to the present invention; 
           [0139]      FIG. 8  is a flow chart depicting operation of a system according to a first embodiment of the present invention; 
           [0140]      FIG. 9  is a block diagram of an apparatus according to the first embodiment of the present invention; 
           [0141]      FIG. 10  is a block diagram of an apparatus according to a second embodiment of the present invention; 
           [0142]      FIG. 11  is a flow chart depicting an automatic marking generating routine according to the present invention; 
           [0143]      FIG. 12  is a flow chart depicting an authentication sequence according to the present invention; 
           [0144]      FIGS. 13A ,  13 B,  13 C and  13 D show details of a marked diamond, a two dimensional marking pattern, a modulated dot placement encoding scheme and a detail or the marked diamond, according to the present invention; 
           [0145]      FIG. 14  is a semischematic view of the mounting frame, showing vibration dampers the corners thereof; 
           [0146]      FIG. 15  is an exploded, perspective view of the scanner system according to the present invention, showing the four units of the system; 
           [0147]      FIG. 16  is an exploded view of the X-axis unit; 
           [0148]      FIG. 17  illustrates the fully assembled X-axis unit; 
           [0149]      FIG. 18  is an exploded view of the Y-axis unit in its position above the XY-bracket of the assembled X-axis unit; 
           [0150]      FIG. 19  illustrates the fully assembled X-axis and Y-axis units; 
           [0151]      FIG. 20  is an exploded view of the Z-axis unit in relation to the fully assembled X-axis and Y-axis units; 
           [0152]      FIG. 21  illustrates an optional camera unit in its relation to the fully assembled Y-axis and Z-axis units; 
           [0153]      FIG. 22  schematically illustrates the optical path of the system, including the optical components; and 
           [0154]      FIG. 23  illustrates the manner in which the scanner system according to the invention is used to cover larger volumes. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0155]    The detailed preferred embodiments of the invention will now be described with respect to the drawings. Like features of the drawings are indicated with the same reference numerals. 
         [0156]    The system according to the present invention may be used to micro-inscribe alpha/numeric characters on the girdle of diamonds  13 . The gemstone may also be another type of gemstone, for example, colored precious or semiprecious gemstones. It is based on a pulse laser  1 , and preferably a Q-switched laser diode pumped solid state laser, to provide minimum volume and installation requirements, and optimum compatibility with any office environment. 
         [0157]    A preferred laser based inscribing system according to the present invention thus contains the following primary elements: 
         [0158]    In a vibration isolated frame  140  with shock absorbers  141 , at the positions of support: 
         [0159]    (1) Laser diode pumped laser  1  and programmable power supply  14 , with a Beam Expander  5 . (2) Optical assembly containing guiding  8  and focusing optics  10 , miniature CCD cameras  25 ,  32  and illumination system. (3) XYZ motion stages  50  (with Z elevator stage) including encoders  145 , limits and DC brushless motors or linear magnetic drive. (4) Diamond holder  144  and accessories (5) Enclosure  142  with safety interlock  143  to prevent operation with open cabinet and to prevent stray or scattered laser energy from posing a safety hazard. (6) Computer system  52  for control: (a) PC (Pentium 100 Mhz), PCI bus, 1024 by 768 VGA monitor (b) Frame grabber  56  (Matrox, videographic card). (c) 3-axis motion controller card  60 . (d) Cables, Power Supplies. (e) System operation software, (Windows XP). (f) Application Software Apparatus. 
         [0160]    As an alternate, or in addition to, the XYZ motion stages  50 , the system described in WO02/103433, expressly incorporated herein by reference, may be employed. This system provides a compact, linear XYZ-scanner system, including an X-axis unit mounted on a chassis member and including an X-axis motor fixedly attached to the chassis and adapted to drive a slide linearly guided by first guide means; an X-mirror mount moving together with the X-axis unit; a Y-axis unit mounted on a first bracket that moves together with the X-axis unit and including Y-axis motor means fixedly attached to the first bracket and adapted to drive a slide linearly guided by second guide means; a Y-mirror mount moving together with the Y-axis unit; a Z-axis unit mounted on a second bracket that moves together with the Y-axis unit and including a Z-axis motor fixedly attached to the second bracket and adapted to drive a side linearly guided by third guide, and a lens mount carrying a focusing lens and moving together with the Z-axis unit; wherein a light bean emitted by a light source and impinging on the X-mirror is reflected in an XY-plane onto the Y-mirror and thence, in an YZ-plane into the focusing lens, and wherein, by selectively actuating the motor means, the focal point of the light beam focused by the focusing lens can be moved to any point within a three-dimensional coordinate system. 
         [0161]    As seen in  FIG. 15 , there are three units of the laser beam positioning system according to this embodiment: the X-axis unit  100 , the Y-axis unit  200  and the Z-axis unit  300 . The fourth unit shown is a camera unit  400 , which is optional. 
         [0162]      FIG. 16  illustrates X-axis unit  100 , showing a chassis member  102 , to the bottom of which is fixedly attached stator  104  of a linear motor  106 . Such motors are commercially available and can be, e.g., of the electromagnetic, piezo-ceramic, or even the lead-screw type. To runner  108  of motor  106  is connected a vertical, rib-like member  113 , downwardly projecting from the XY-bracket  114 , i. e., the bracket that moves along the X-axis and carries the Y-axis unit  200  ( FIG. 4 ). Bracket  114  has a horizontal member  116  and a vertical member  118 . To horizontal member  116  is fixedly attached a slide  110 , riding on a guide rail  112  mounted on the bottom surface of chassis member  102 . Horizontal member  116  carries a post  120 , to which is attached a block  122  mounting X-mirror  124 . Block  122  is rendered elastically deformable by the provision of two slots  126 ,  126 ′, whereby, with the aid of adjusting screws (not shown), mirror  124  can be tilted about two mutually perpendicular axes. 
         [0163]    Also seen in  FIG. 16  is a linear encoder read head  128 , fixedly attached to chassis member  102  and cooperating with an encoder scale strip (not shown) attached to rib-like member  113 . Further seen are two mechanical stops  130 ,  132  limiting the X-motion of slide  110  and fixedly attached to chassis member  102 . Bore  134  in the rear wall of chassis member  102  serves as the entrance opening for a laser beam, as seen in  FIG. 16 , and holes  136  serve for the attachment of camera unit  400 . 
         [0164]      FIG. 17  shows the fully assembled X-axis unit. 
         [0165]      FIG. 18  is an exploded view of the Y-axis unit  200  in its position above XY-bracket  114  of the assembled X-axis unit. It will be appreciated that, both functionally and structurally, Y-axis unit  200  is largely an analogue of X-axis unit  100 . Linear motor  204 , including its stator  206  and runner  208 , is mounted on horizontal member  116  of Y-bracket  114 , as is guide rail  212  on which rides slide  210 . To the latter is fixedly attached YZ-bracket  214 , the horizontal member  216  of which carries post  220 , complete with Y-mirror  224  and mirror mount  226 . 
         [0166]    Vertical member  218  of Y-bracket  214  serves for the attachment of Z-axis unit  300 , as shown in  FIG. 18 . Also seen is linear encoder read head  228 , which, in assembly, is attached to vertical XY-bracket member  118 . It will be understood that, due to the nature of the exploded view, encoder  228  appears to be below YZ-bracket  214 , while in assembly it is obviously located above bracket  214 , as seen in the illustration of the fully assembled X-axis and Y-axis units  100  and  200  of  FIG. 19 . 
         [0167]      FIG. 20  is an exploded view of Z-axis unit  300 , shown in its relation to the fully assembled X-axis and Y-axis units  100  and  200 . Linear motor  304  is mounted on Y-bracket member  218  ( FIGS. 18 and 19 ), as is guide rail  312 . For purely technical reasons, the Z-bracket is designed in two parts: the vertical, channel-shaped member  318 , and the plate-shaped horizontal member  316 . In assembly, both parts  316  and  318  are joined by screws. Member  318  is connected to motor runner  308  with one of its flanges, and to slide  310  with its web. Also shown is focusing lens  338 , the focal length of which is not limited by considerations of distortion-free imaging. 
         [0168]    The kinematic hierarchy of the system is as follows: linear motor  104  moves all three units; linear motor  204  moves the Y-axis and Z-axis units  200  and  300 , and linear motor  304  moves only the Z-axis unit  300 . 
         [0169]      FIG. 21  illustrates an optional camera unit  400  and its position relative to units  100 ,  200  and  300 , shown fully assembled. Unit  400 , which is attachable to chassis member  102  at its upper left-hand corner, comprises a camera system  440 , advantageously of the CCD type, a spacer  442  which accommodates the imaging optics and a mirror housing  444 , in which a beam splitter  446  and a dichroic mirror  448  are mounted. Also seen are an LED light source  450 , used to illuminate the scanned object, and a laser beam LB, which enters the system through bore  134  ( FIG. 15 ). Further shown is an additional, annular light source  352 , which can be slipped over focusing lens  338  and is intended to provide diffuse light. 
         [0170]      FIG. 22  is a schematic representation of the light path of the scanning system according to the invention, including the optional camera system  400 . A laser beam LB from a laser source outside the system impinges on dichroic mirror  448 , is reflected at  90  in the X-direction, impinges on X-mirror  124  and is reflected at  90  in the XY-plane, hitting Y-mirror  224 , whence it is reflected upwards in the YZ-plane into focusing lens  338 , to be focused onto the object scanned. Clearly, by selectively actuating any or all of the linear motors, the object-side focal point of lens  338  can be moved to any point of a three-dimensional coordinate system. 
         [0171]    Illumination required for the imaging process is supplied by LED  450 , the light of which (dashed line) impinges on beam splitter  446 , which reflects it right into the optical axis via dichroic mirror  448 . Mirror  448  reflects light of the wavelength of laser beam LB, but passes ordinary light. This light, reflected from the scanned object, is collected and collimated by focusing lens  338  and returned along the optical path, passing dichroic mirror  448  and beam splitter  446 , and reaching the objective of the CCD camera system. The camera unit, added to the scanner system, provides an integrated scanner/camera system. 
         [0172]    XYZ-motion control is provided by a per se known motion controller system and based on the position information provided by linear encoders  128 ,  228 ,  328 . 
         [0173]    Also required are a CPU, a frame grabber and a monitor (not shown in  FIGS. 15-23 ). 
         [0174]    The compactness of the scanner according to the invention is the result of the interlinking, indeed, the extensive mechanical integration. of units  100 ,  200  and  300 , producing a “closepacking” effect. Due to this effect, a scanner of this type, covering a three-dimensional coordinate system of, e.g., 100×100×100 mm, weighs less than 15 kg and has physical dimensions of less than 200×200×250 mm. A scanner covering a 3-D-coordinate system of 50×50×50 mm, weighs less than 6 kg and measures 140×150×170 mm. 
         [0175]    This scanner is suitable for a variety of purposes, using a laser beam or an ordinary light beam, to scan a three-dimensional surface with high precision. In a different configuration (including the camera unit), it can be used for viewing an object illuminated either by an external source or by an internal source via the optical system of the scanner; for 3-D measurement, tracing, viewing (as through a microscope), or for pick-and-place applications. 
         [0176]    The present scanner is designed to achieve, over a 3-D coordinate system of 50×50×50 mm, an accuracy of a ±1.0 micron or better, and a repeatability of 0.1 microns. This accuracy may be achieved through optical feedback or native optic or mechanical tolerances. 
         [0177]      FIG. 23  shows an extended range system, showing the four principal units of the system, the X-axis unit  100 , the Y-axis unit  200 , the Z-axis unit  300 , and the camera unit  400 . Further seen is an X-, or Y, or XYZ-motion work table  500 , on which the workpiece (not shown) is positioned. 
         [0178]    The camera system  440  is an integral part of the scanner and views the workpiece at any given moment with an accuracy determined by the optical design and camera design. This accuracy employs an optical design appropriate to assure the required accuracy, which is in excess of normal commercial standards. The workpiece is positioned on a motion system  500  which may be a XY-or XYZ-motion system. Because the workpiece positioning system is redundant, repeatability and resolution for these systems (0.01-0.1 mm and even up to 0.5 mm) is sufficient. When one 50×50 mm segment is completed by the scanner, the motion system  500  will advance somewhat less than 50 mm, in order to bring the next segment into position. The connection between each segment to the next, maintaining the high accuracy and repeatability required by the user, is kept by image processing and optical feedback techniques. 
         [0179]    The system is programmed to identify the workpiece and its positioning, or the prior inscription marking. When the motion positions the next segment under the scanner, the scanner moves to the area where that element is expected to be (known to within 0.01-0.5 mm). 
         [0180]    As shown in  FIG. 1 , a Nd:YLF 2.sup.nd harmonic laser  1  (QD321) is provided, which emits a beam  2  having about 515 nm wavelength. A 1047 nm filter  3  is provided to attenuate any residual fundamental laser output energy, to produce a filtered laser beam  4 . The filtered beam is then expanded in a ten-times beam expander  5  to reduce energy density. In the path of the expanded beam  6 , a 780 nm filter  7  is provided to eliminate energy from the diode pumps. A dichroic mirror  8  reflects the expanded, filtered beam  9  toward a ten-times microscope objective  10 . The microscope objective  10  focuses the beam onto the workpiece  11 , which is for example a girdle  12  of a cut diamond  13 . 
         [0181]      FIG. 2  shows the top illumination and imaging systems. An LED  20  or array of LEDs having emission at about 650 nm projects through a collimating lens  21  to produce a collimated illumination beam  22 . The collimated illumination beam  22  projects on a beam splitter  23 , which reflects the collimated illumination beam  22  toward a reflecting mirror  24 . The reflected collimated illumination beam  25  passes through the dichroic mirror  8 , parallel to the filtered beam  9 , and through the microscope objective  10  onto the workpiece  11 . The workpiece  11  reflects a portion of the illumination beam back through the microscope objective  10  and through the dichroic mirror  8 , onto the reflecting mirror  24 , tracing an opposite path from the collimated illumination bear  25 . A portion of the reflected illumination beam  27 , however, passes through the beam splitter  23 , toward a top CCD camera  28 . Thus, the top CCD camera  28  views the workpiece  11  with the 650 nm illumination. When displayed on a 14 inch video monitor  159 , the resulting magnification or the image  29  is about 200 times. 
         [0182]    The side illumination and imaging systems, shown in  FIG. 3  is somewhat simpler than the top illumination and imaging systems shown in  FIG. 2 . A set of spaced 650 nm LEDs  30  produce illumination  31  at angles generally converging from the top toward the workpiece  11 . A side CCD camera  32 , views the workpiece  11  through a doublet lens  33  and window  34 , at right angles to the top CCD camera  28 . The resulting image  35  of the side CCD camera  32  on a 14 inch video monitor is also about 200 times magnification. Where the workpiece  11  is a cut diamond  13  having a girdle  12 , the side image  35  includes the profile of the girdle  12 ′. 
         [0183]    The bottom illumination system, shown in  FIG. 4  includes a set of spaced miniature are lamps  40  below the workpiece  11 , producing illumination along paths  41  which are upwardly converging. 
         [0184]    The stage positioning and control system is shown in  FIG. 5 . The workpiece is mounted on a three axis stage  50 , with encoder feedback in a workpiece mount assembly  144 . The drivers  51  for the three axis stage are provided within the laser system enclosure  142 , separate from the computer control  52 . The computer control  52  communicates through a positioning control system  53  (Galil), which is an ISA bus card. A breakout box  54  is provided within the laser system enclosure  142 , which is connected by a set of cables  55  to the positioning control system  53 . The controller performs all I/O operations such as laser on/off, limit switches, etc., as well as performing the motion itself. 
         [0185]    As shown in  FIG. 6  (prior art), a known system described in U.S. Pat. No. 4,392,476 includes an X scanner  61  and a Z scanner  63 , which steer the laser beam onto the diamond  13 . This known system has limited repeatability. Further, the system is relatively large, and subject to vibrational influences. 
         [0186]      FIGS. 7A   7 E show the diamond holder in top, side, side detail, mounted stone holder (e.g., ring, earring, pendant, etc.), and unmounted stone holder, respectively. A slide  116  allows precise positioning with respect to a slot, within the cabinet. The slide  116  is positioned by a set of hardened steel balls and spring loaded balls which positions the holder  116  as it is inserted into the slot. A set of manual adjustments allow control over coarse  106  and fine  104  rotation, with a lock/release chuck  107  provided. The workpiece  11  is set in a pot  108  mounted in a chuck  109 , with two round rods positioning the workpiece, held in place by a finger  110 . 
         [0187]    As shown in  FIG. 7D , a mounted workpiece holder allows a mounted workpiece  111  to be held precisely. A spring loaded trigger  112  is provided to allow mounting and unmounting of the mounted workpiece. 
         [0188]    The system includes a static laser beam, e.g., a laser beam generation apparatus which does not move. The XYZ positioning system  50  moves the workpiece  11  and generates the inscription with repeatability and resolution of about 1.0 microns. The beam size at the focal point is greater than about 1 micron, so that the positioning system  50  accuracy is not the limiting factor in the placement of the marking. 
         [0189]    With the axis of symmetry of the workpiece  11 , which is for example diamond  13 , horizontally disposed, the diamond girdle  12  is viewed horizontally (profile mode) and vertically (inscription mode) by two CCD cameras  28 ,  32 . The vertical axis also corresponds to the axis of laser  1 . A third camera may also be provided, for example having an optical path facing generally upward toward the laser. Of course, an imaging device facing the laser beam is provided in a manner to prevent damage during operation. Due to the focus of the laser  1 , as well as filtering optics  8 ,  23 ,  34  there is low risk of damage to the CCDs  28 ,  32  due to laser energy. The user can choose to view one or more cameras. There multiple images are present, they may be tiled at reduced size on the computer monitor screen  159 . Using, a mouse  161  as a pointing device, the girdle  12  is centered and focused by viewing the screen  159 , using particularly a profile view. The diamond  13  can be manually rotated in its mounting  144  to bring the correct part of the girdle  12  to the center of a display window on the screen  159 . The images are provided with a magnification of about 200 times, although other magnifications or variable magnifications are possible. Magnification is defined herein as the ratio of the inscription size as measured on screen  159  and that of the actual inscription size. In general, a 14 or 15 inch diagonal video monitor is employed, with a resolution of 1024 by 768 pixels. 
         [0190]    The user-entered portion of the content of the inscription is typed on a keyboard  148  or entered by a bar-code reader  149  into the computer. Of course, the data entry may also be by voice through a microphone  150  for speech recognition, magnetic strip through reader  151 , or through point-and-click operations using a computer mouse  161 . The entered inscription and logo are shown on the video screen  159  superimposed on an area corresponding to the girdle  12  of the diamond  13 . Using the mouse  161  and keyboard  160 , the user can change all inscription characteristics in order to fit it correctly in the girdle  12 . While the preferred user interface is a graphic user interface with pointing device (mouse  161 ), keyboard  160  and display screen  159 , where the user&#39;s hands may be occupied, a voice-command recognition system may be used, e.g., through microphone  150 , with verification of all input information and commencement of operational sequence by a specific sequence of actions by the user in fail-safe manner, so that, e.g., stray noises do not cause catastrophic interference. 
         [0191]    The user may also entry the type of gemstone, or this may be determined automatically, for example by refractive index, dichroism, color, LIBS, or other technique. This allows, for example, alteration of energy beam parameters in dependence on the material to be processed. 
         [0192]    In the horizontal camera  32  screen the user can measure the girdle  12  profile, using a mouse input device  161  to mark the critical dimensions. This data is then used to keep the focal point of the laser output on the surface of the girdle  12  at all times. The profile data and girdle  12  outline may be automatically extracted from the images, or a manual entry step employed to outline the profile and/or girdle boundaries. In general, the inscription positioning on the girdle will be manually assisted, although full automation, especially for low value small stones, known as mellee, may be employed. When these procedures are complete a controller code file, also known as a G-code file, is generated containing all inscription data. This file is transferred to the positioning stage controller  51  for performance of the actual inscription. 
         [0193]    The profile data from the electronic imagers may also be automatically analyzed to extract the profile of the stone for focal control, and/or the outline of the girdle or a facet, for inscription range control. For example, the imager output(s) are input to an image analysis program, which performs edge detection. The edges are vectorized, and then processed for consistency with a model, for example, the girdle viewed in the side should be a line or gentle arc, and inscriptions across corners require manual confirmation. The outline of the girdle of facet is extracted from the top view, as a coarse edge, which may be straight, curved, and/or segmented with corners. At low magnification, the girdle is a thin band having a height of 50-200 microns, while facets are polygonal. The inscription is then placed on the girdle or facet, and if there is ambiguity as to which surface is intended, manual conformation is requested. 
         [0194]    The auto-tracing function can recognize the diamond profile in side view (assuming the profile is in view, otherwise the stone is jogged to bring it to view. In the normal range of stone sizes, this is the case in 99% of the cases) and move the profile automatically to the focal plane (horizontally line on screen). In a few percent of the cases some manual intervention may be required (the software allows for manual override on the automatic tracing). 
         [0195]    An alternate embodiment provides direct control over the positioning stage, rather than autonomous control. This, in turn, facilitates intelligent feedback during inscription, for example based on the cameras directed at the inscription area. 
         [0196]    The inscription code file may optionally be automatically generated and authorized based on an algorithm to prevent unauthorized or fraudulent inscriptions, as depicted in  FIG. 11 . The authorization process according to one embodiment of the invention includes the steps of obtaining or retrieving an image of the workpiece  171 , analyzing the image to determine characteristics of the workpiece  172 , transmission of the characteristics in conjunction with data relating to the stone to an authenticator, through, for example, a telecommunications link  152 , which may be at a different location, determining whether the characteristics and proposed marking are unique  173 , which may be performed remotely, or locally, and if the characteristics and marking are not unique, proposing a change in the marking  174  and then re-verifying the modified proposed marking with the authenticator. After a marking is approved, the marking is encrypted  175 , and the encrypted code transmitted to the marking control  176 . Thus, only if the authenticator approves a marking does the system commence marking. 
         [0197]    The characteristics of the workpiece may be determined by eye  146 , and may also be determined by a sensor  117  or appropriate type. For example, dimensions, weight, optical transmission characteristics, facet angles and the like may be measured. During the initial marking process, the characteristics are determined, and are preferably stored in conjunction with the marking information in a database  136 . For example, this database may store images, compressed images or aspects of images derived from the CCD imagers  28 ,  32 . Preferably, after the marking has occurred, the top CCD imager  28  is used to capture an image of the marking, which is then stored. According to one embodiment of the invention, information stored in the database or marked on the stone may be encrypted using a secure encryption method by means or an encryption processor  157 , reducing the risk of fraud. Further, the marking may be, in part, self authenticating by including identification of characteristics of the marked workpiece. Of course, the encryption processor may be the same as the control system  155 , and need not be a separate physical device. 
         [0198]    The controller executes all I/O operations such as laser on/off, laser power out of range, limit switches, mouse, etc., as well as performing the motion itself. Thus, the control system may easily be upgraded as desired separately from the marking system hardware. 
         [0199]    The operator can observe the diamond before, during and after the inscription marking process. In case the inscription is not complete, the operator can choose to repeat all or selected parts of this inscription in a second or subsequent marking operation. 
         [0200]      FIG. 8  shows a flow diagram of the operation of the control system for the laser inscription process. A software module in the control system generates interrupts which sense laser system conditions, and may also initiate action automatically based on those conditions  121 . The inputs to the laser system sensing module  121  include emergency stop  122 , laser ready  123 , mechanical limit reached  124 , and door open  125 . Of course, other conditions may be sensed and controlled by this sensing module  121 . 
         [0201]    A main interface screen  126  is provided allowing the operator to access and control the main functionality of the laser inscription system. This interface screen  12  initially controls laser warm up and positioning at a home position  127 . Alter a gemstone is inserted into the laser inscription system, it is jogged into alignment  218  with reference to the top and side views, displayed on the video monitor. Next, the inscription is entered or edited by an input device such as a keyboard  148  or bar code reader  149 , and the inscription positioned with respect to the workpiece in the top view  192 . If the workpiece has a rough surface, such as a bruted girdle of a diamond, the inscription positioning is verified in the side view  130 . The host computer  52  sends commands to the laser inscription controller  60  defining the inscription pattern, by defining XYZ positioning of the workpiece  131  and a pattern of laser modulation  132 , in order to define the inscription pattern, e.g., the font or logo structure. After all or a segment of the inscription is made, the inscription is verified to ensure complete inscription, and all or a portion of the inscription may be repeated as necessary  133 . The inscription is then complete, and a new inscription process may be commenced  134 . 
         [0202]    In addition, a maintenance mode of operation is available, which allows adjustment of system parameters  135 , motion system diagnostics  136 , and a summary report of inscription data  137 . 
         [0203]    Inscription Specification 
         [0204]    The length of inscription depends on size, number of characters and spacing. Below is a table representing appropriate dimensions, which are software defined. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Height 
                   
                   
               
               
                   
                 (microns) 
                 Width (microns) 
                 Spacing (microns) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Large characters (max) 
                 80 
                 60 
                 30 
               
               
                 Medium characters 
                 60 
                 45 
                 25 
               
               
                 Small characters 
                 40 
                 30 
                 20 
               
               
                 Ex. Small 
                 20 
                 15-20 
                 10 
               
               
                 characters (min.) 
               
               
                   
               
             
          
         
       
     
         [0205]    In appropriate circumstances, multiple line inscriptions may be provided, with possibly different marking parameters, and logos may be larger than a line of text. 
         [0206]    The maximum single inscription length is determined by the field of view set by the optical design. With the preferred camera, optics and viewing requirements, the field of view is about 1.6 mm. This field of view can support an inscription with &gt;20 letters at 60 micron size (for example) or more if the letters are smaller. The field of view can be enlarged at the expense of a smaller magnification on screen (current magnification is about 200). Inscribed messages longer than 1.6 mm and even around the stone are possible. One way to achieve this is to divide the inscription into segments; inscribe a segment, rotate the stone, inscribe the next segment and so on, which may be automatically or operator controlled. 
         [0207]    The user selects a font from a list of fonts provided. Letter shape is proportional, as defined by the specific font used. Letter size and spacing between letters can be continually controlled by the user. The user can get minimum size limits to letter size. The system will not let the user exceed the set limits. The machine and software will prevent characters in the inscription from overlapping. 
         [0208]    The machine preferably has a default setting whereby a “most frequently used font” or the previously used font size is automatically used. This default setting is adjustable by the user. All fonts, business characters and logos are together adjustable in size. 
         [0209]    Character size is displayed on the screen prior to and after scribing. 
         [0210]    Total length of inscription=number of characters×(width+spacing)+logo length. 
         [0211]    The machine can make an inscription to a maximum length of approximately 1.6-2.0 mm on a single scribe. At an average of 80 microns per character (including spacing), this gives 20-25 character spaces (logo+14 characters). Longer inscriptions can be done by consecutive inscriptions without dismounting stones. In this case there is no limit on the number of characters. Each logo+14 characters is automatically accounted for as a single scribe, in an accounting system, supporting a royalty-based accounting scheme. Inscribing more characters would normally present no problem. It is noted that the characters may be alphanumeric, line-drawing, multi-lingual fonts, custom bitmaps, or other pictorial representations, and may be fully programmable. 
         [0212]    Depth of inscription &lt;8 microns on a single scribe, &lt;12 microns on multiple (two) scribes. It is generally not recommended nor required to perform more than two scribes on the same character to obtain a distinctly complete and clear character. A trained operator is generally able to highlight only those areas which may not have been inscribed on the first run for a rescribe. 
         [0213]    Line width &lt; is 8 microns on polished girdle, and &lt;10 microns on bruted girdle. It is possible to vary the line thickness from about 2 to 8 microns by modulating the laser power or optically altering the spot size (diameter of the focused beam), using a beam expander, though for lines thicker than about 12 microns, it is advantageous to produce overlapping rows of spots, rather than larger spots. The user selects (from a menu on screen) any line thickness in the range 2-8 microns. Lines in the 2-3 micron range provide fine detail. Lines in the 7-8 micron range provide a thick line. When operating at constant laser parameters, the line width in bruted girdles is always larger by 20-30% than line width in polished girdles. 
         [0214]    With a preferred motorized beam expander, a theoretic dynamic range of 4 is achieved for the line width. This means that in principle the ratio of maximum width to minimum width is  4 . This number might vary according to laser-stone interaction and other factors. 
         [0215]    Net inscription (laser time) is typically less than 25 seconds for polished and bruted diamonds for a single scribe containing a logo (equivalent to no more than 3 letters in complexity) plus 14 regular characters. Reinscription may increase the inscription time by about 10 seconds. 
         [0216]    The inscription time depends on number of characters, size of characters and complexity of logo. Under normal conditions, where the logo is equivalent to 6 characters and there are, for example, 12 additional (single-line) characters and the character size is 50 microns, the inscription will take about 1 second per character. The result is less than 20 seconds. 
         [0217]    On polished girdles, inscriptions are generally satisfactory after a first pass. If the inscription is not adequate, partial or complete reinscription may be performed. Bruted girdles are more likely to require multiple passes, depending on surface quality to achieve a desired marking. For time efficiency, multiple runs are executed only on those characters requiring additional runs. These characters can be marked with the mouse. Of course, the reruns may be automatically performed based on a predetermined criteria or based on optical feedback from the video cameras. 
         [0218]    On loose round brilliant stones, mounting and dismounting the stone should take another 20-30 seconds. The rest of the operations (locating optimal place for inscription, painting, etc.) should take a properly trained operator 30-40 seconds. 
         [0219]    Therefore, properly trained, dedicated laser machine operators shall be able to mount and dismount a loose round brilliant stone, locate its optimal place of inscription, and perform a single scribe at a rate of approximately 30 stones per hour on a routine basis in the normal course of business. 
         [0220]    The software of the control system also allows any number of inscribed symbols. It is also easy to rotate the stone and position a section of the inscription so that it is or seems to be continuous with the first one. Any symbol size may be produced, within the limits of the line width and surface to be inscribed. For example, with a red beam, the lower limit of symbol size is around 30 microns. With a green beam the lower limit of symbol size is about 15-20 microns. 
         [0221]    The Line width (green beam) is less than about 9 microns on a polished girdle and less than about 12 microns on a bruted girdle. More typically, the spot diameter on a polished girdle is between 2-8 microns, and may be adjusted by modulating laser power. Bruted girdle spot size is somewhat larger, and lower laser power spots may be more variable. The system employs a green laser to provide a finer inscription line width than is possible with a standard-type red laser. Start up time for the system is about 15 minutes, mostly accounted for by laser stabilization time, after which the instrument is fully operational, an advantage over other laser types. In a preferred marking method, the irradiated areas overlap, to provide an appearance of continuity of marking. 
         [0222]    The laser output is provided as a Q-switched laser, which may be provided in a range of about 1200 to 200 nm, with a frequency doubler or harmonic generator as necessary to provide an output wavelength of less than about 600 nm. A preferred laser  1  is a Q-switched solid state neodymium laser e g., a laser diode pumped Nd:YLF laser, operating at 1.06 μm, with a frequency doubler to provide an output of 530 nm. 
         [0223]    Mounting and dismounting the stone is performed using a modular holder  144  with a quick connect socket, and therefore may be accomplished in about 20 30 seconds. The rest of the operations, e.g., locating optimal place for inscription, painting, etc., depend on the manual skill of the operator, and may take about 30 40 seconds. Consequently, 40 stones per hour throughput is possible using the apparatus according to the present invention. 
         [0224]    DC brushless motors are employed in the translatable stage system  50 . These are driven by a standard-type motor driver system. The X, Y stage employs linear encoders for feedback of stage position, while the Z stage employs a rotary encoder for a helical positioning mechanism. 
         [0225]    Font and Symbol Capabilities 
         [0226]    An assortment of characters may be provided with each system, such as an ASCII font set containing 26 letters and 10 numerals, business characters as follows: (™), ( SM ), ® and a logo. These font sets are, e.g., available from Borland. Additional fonts, e.g., Japanese and/or Hebrew, and logos may, of course, be employed, e.g., added to the system using removable magnetic media, smart cards, or by digital telecommunication. The font may also include custom or editable characters, allowing full freedom to define a raster bitmap represented by a character identification code. Thus, any figure which can be rendered in lines or a bitmap may be included as a marking. The logos are provided from a pick list, by numeric identifier, or by bar code selection from a coded sheet. A thumbnail list may also be provided for visual selection. 
         [0227]    Inscription data can be entered in three ways: Manually-alphanumeric symbols entered from the keyboard  148  and logo selected from the logo library. Semi-automatic—part of the alphanumeric symbols from bar-code  149  or from a keyboard  148  and part of the symbols selected automatically by a serialization counter. Fully automatic—a complete inscription is generated by the device, after inputting an identification from bar code or similar system. 
         [0228]    Using a graphic video overlay, the inscription position and dimensions can be easily adjusted. 
         [0229]    The system controller also provides over/under power protection. In case laser power exceeds set limits the system will stop working and issue a warning, thus ensuring that no damage is caused to the diamond or a workpiece. 
         [0230]    Vibration dampers  141  are provided at the base of the laser system frame  140 . Thus, due to the compact size of the system and relatively small components, the frame  140  may have sufficient rigidity to provide isolation from vibrational effects. Operation is therefore possible in any normal office environment at normal room temperature, without extraordinary measures, such as strict environmental control, or active vibration damping. 
         [0231]    The computer  52  is a “PC” type, and is gene rally provided as a separate enclosure from the laser inscribing system enclosure  142 . Generally, two cables  55  connect the computer controller  55  to the laser system enclosure  142 , a motion controller and laser control cable and a frame grabber cable. The user may therefore position the screen  159  and keyboard  160  with mouse  161  at the most convenient position. 
         [0232]    Inscription Observation 
         [0233]    The system preferably includes a high resolution miniature CCD camera (with a resolution of 760×500) and video screen with illumination and filter systems for efficient viewing of entire inscription process as follows: 
         [0234]    A. The complete inscription with logo is projected on the girdle and the user has the ability to change the length of inscription, height of characters or move and align the entire inscription. The inscription is observable on the screen before, during and after scribing. 
         [0235]    B. Projection of surrounding area is performed by user via manual control of stones with the mouse. 
         [0236]    C. The operator observes the inscription before scribing; observes the scribing process itself, and then observes the result and decides if the inscription is complete or not. 
         [0237]    D. The operator has complete control of positioning, changing and observing inscription before laser operation. Cursors on the screen help in centering the inscription. 
         [0238]    E. The system has a side camera for girdle profile mapping. The operator marks as many points as are needed on the profile and the system will then automatically change focal location with changes in girdle height. In some cases, a surface which is excessively coarse or wavy will defeat auto inscription depth focusing, requiring manual assistance. 
         [0239]    F. The user has complete control over character sizing. Once the cursors are placed on the girdle (according to girdle dimensions) the computer displays the default character size, which is, for example, the most recently-used character size or a predetermined value. 
         [0240]    G. Motorized Z-axis for the focusing lens enables the operator to focus onto the girdle of the stones by means of the mouse with direct position input to CNC. 
         [0241]    The system includes two high resolution miniature CCD cameras with illumination and filter systems for efficient viewing of entire inscription process on a video screen as follows: 
         [0242]    The complete inscription with logo is projected on an image from a vertically oriented camera  28  of the girdle  12  providing the user with the ability to interactively change length of inscription, height of characters remove and align the whole inscription. The girdle  12  area may be outlined by the user with a mouse  161  or automatically determined by image analysis in the computer system  52 . 
         [0243]    The operator can thus observe the inscription before marking; observe the marking process itself, and then observe the result and decide if the inscription is complete or not. A protective enclosure  112  prevents scattered radiation from reaching operator eyes. Filters or the like may also be provided to prevent damage to the video cameras from reflected laser energy. 
         [0244]    The operator is provided with complete control of positioning, and inscription allocating approval of the inscription before laser operation. Cursors on the screen help in centering the inscription. The system also has a side camera  32  for girdle  12  profile mapping and table viewing. 
         [0245]    The operator marks as many points that are needed on the profile allowing the system to then automatically adjust (Z-axis focal location) to the girdle profile during marking. A manual override is also provided where the automated inscription depth control is riot desired. 
         [0246]    The side camera  32  allows precise determination of the position of the girdle  12  or the gemstone  11 , so that the laser  1  may be focused onto the gemstone  11  surface with high precision. In order to effectively ablate a small surface portion of the gemstone  11 , without damaging deeper portions, or producing significant undesired thermal stress effects around the inscription, the laser  1  is provided with a very narrow depth of field, e.g., about 30 μm. In addition, the small depth of field is required in order to obtain maximum power density from a relatively low power laser  1 . Thus, by attempting to focus using a top view only, without a profile view, to achieve focus by maximizing contrast and edge sharpness, user discretion is required and accuracy is limited. In contrast, by providing a side view, the profile of the stone is aligned with a predetermined focal plane, assuring accuracy of about ±7 μm. In practice, at 200 times magnification, the ±7 μm corresponds to ±2 pixels of the video imaging camera. Thus, after determining the exact focal plane of the laser  1  empirically, this plane may be provided as a reference in the control system, and the workpiece moved manually or automatically with relative ease to the desired location(s). The reference may appear, for example as a line on a computer monitor displaying a Z-axis video image of the workpiece. The operator jogs the Z-axis control until the profile of the workpiece  11  in the image is tangent to the reference line. 
         [0247]    Vibration and/or impact during e.g., shipping, may alter the focal plane of the laser with respect to the workpiece mount  144 . In this case, a simple “trial and error” or empirical study is conducted to redetermine the exact focal plane, which is then used to provide the correct reference in the control. This calibration study may be conducted, for example, on a relatively inexpensive diamond or other material test piece, in which successive ablations are conducted under differing conditions, e.g., differing Z-axis positions at successive positions in the X-Y plane. After the series of ablations, the test piece is examined to determine the optimal conditions of orientation, e.g., smallest spot size. The conditions of the optimal orientation are then used to determine the focal plane and hence the calibrated reference plane. 
         [0248]    The user has complete control over character sizing. Once the cursors are placed on the girdle (according to girdle dimensions) the computer will display a first choice which the user can change. 
         [0249]    A motorized Z-axis is provided for focusing the laser onto the workpiece surface. This Z-axis is computer controlled, and enables the operator to focus onto the girdle  12  of the diamond  13  by means of the computer keyboard controls, with direct position input to computerized numeric control (CNC). The girdle profile is determined by reference to an orthogonal view to the girdle surface, and therefore the Z-axis may be controlled for each coordinate. A system may also be provided which uses hand operated micrometer screws for focusing, for example where long inscriptions on fancy shaped stones necessitates the use of segmented inscriptions. 
         [0250]    The parameters of the inscription process, including laser power, Q-switch frequency and inscription speed may be controlled for optimization of the laser-material interaction when switching between substrates and differing surface qualities. Thus, the present invention allows the implementation of varying ablation sequences based on the desired inscription and the characteristics of the workpiece. Often, the characteristics of the workpiece are known and input into the control system, i.e., by a bar code magnetic strip, manual keying, database retrieval, or other method. However, the system according to the present invention may, also include a system for itself determining a characteristic or set of characteristics of the workpiece and implement an inscription process based on the input or determined characteristics and the desired resulting inscription. Likewise, where an inscription is preexisting, the system according to the present invention may analyze the existing inscription and produce a modified inscription. Thus, where features according to the present inscription method are desired, they may be superimposed on or added to existing inscriptions. Further, an old inscription may be analyzed and stored according to the present methods without any modifications thereto, e.g., for security and authentication purposes. 
         [0251]    Software 
         [0252]    The computer controller preferably operates in a Windows XP (or predecessors) environment, although Macintosh, UNIX derivatives, X-terminal or other operating system which supports the various system components may be employed. The optical feedback system and preview of inscription functions advantageously employ a graphic user interface, having a pointing device (e.g., mouse). 
         [0253]    The application software can generate various reports according to specifications and format created by the user. 
         [0254]    All machine features, including stone positioning and rotation, are generally controlled by the software, with the exception of laser pulse power and pulse frequency, which may be set from power supply panel. Of course, the laser control system may be completely automated with a computer control, allowing software control over pulse power, Q-switch frequency, and inscription speed. 
         [0255]    User control and input for interaction with the software, which is preferably a graphic user interface system, is generally performed via mouse  161  and keyboard  160 . Data entry or workpiece information may employ other input devices, such as a microphone, optical or bar code scanner, gemstone characteristic sensor, magnetic disk or stripe, or other known input devices. 
         [0256]    The software can generate various reports according to specifications and formats as desired, based on an individual inscription procedure or a number of inscriptions. The software may also be used to generate a certificate of authenticity with anti-forgery and anti-tamper features, with an image of the workpiece. 
         [0257]    Images obtained through the CCD images can be stored, for example, on magnetic disks or optical media, and may be stored locally or remotely. Such storage may be useful in order to identify and inventory workpieces, or to ensure system operation. 
         [0258]    The computer may also be provided with standard computer networking and communications systems. For example, an Ethernet communication link, IEEE 802.3 may be used to communicate over a local area network. Communications with a central database may occur over telephone lines using a standard analog modem, e.g., v.34, ISDN, Frame Relay, the Internet (using TCP/IP), or through other types of private networks. Data is preferably encrypted, especially when in transit over insecure public channels. The network provides the ability to store images and data outside of the device, to download logos, inscription information, authorization data, and the like. This interface may also support remote diagnostics and administration, accounting and maintenance. 
         [0259]    Logo and graphic editors are also provided for the creation of logos and graphics. A font editor is provided to edit character raster images of fonts. Because the raster image corresponding to each code is programmable or modifiable, complex symbols may be inscribed with the same ease as letters and numbers, once the symbol is defined as a font character. According to one aspect of the invention, a graphic pictorial image is engraved onto the stone, thereby making the stone an artwork. The pictorial image may be identical or different for each stone, and mats also include encoded information. A logo may differ from a character by being larger, with potentially a higher dot density. Thus, characters are generally defined as raster bitmaps, while logos may be further optimized or the laser controlled to obtain a desired appearance. 
         [0260]    Imported fonts, such as True Type fonts, are typically double line, meaning that each expanse of a letter in the font is defined as at least two rows of dots wide. Such fonts may be processed to single line style after importing, to provide a narrower font better suited for the limited resolution of the laser inscription process. 
         [0261]    The native logo editor may include a variety of graphics functions, such as cut, copy, paste, smooth, insert and erase points, line, arc, etc. In addition, a standard graphic editor may be provided, whose output may then be translated into native format. 
         [0262]    Images can be created by a logo editor which is part of the control computer, or uploaded to the machine in a JPEG, TIF, bitmap, etc. format, and converted to a usable file, for example having a desired degree of spot overlap, and stored in a bitmap or compressed bitmap file format up to the system&#39;s memory capacity (memory upgrades are possible). Network interfaces are also possible to facilitate data exchange and interaction with remote systems. 
         [0263]    The control system preferably incorporates a self-diagnostic and autocalibation functionality, to avoid a lengthy calibration process which may be required to manually calibrate the X and Y axes. 
         [0264]    The computer interface preferably includes diagnostic and error messages which are human readable. Likewise, an on-line instruction manual is preferably provided. 
         [0265]    Stone Mount 
         [0266]    The mount includes a fixed base, held in Fixed position with respect to the frame  140 , with a removable holder  118 , as shown in  FIGS. 7A   7 E. The holder  118  can be easily removed or taken out from the fixed base without changing the diamond&#39;s orientation. A holder  118  is selected based on the diamond size to be processed in the machine, with various holders available for differing sized stones. The diamond can be easily placed in or removed from the holder and can be externally adjusted to bring the correct part of the girdle to face the camera. 
         [0267]    The diamond holder is based on a standard holder known in the diamond industry. The diamond center sits in a concave depression suited to the diamond size. A spring loaded metal strip  110  pushes against the table to hold the diamond securely into the pot  108 , while making sure that the table is parallel to the holder  118  axis. If the girdle plane is not parallel to the table or the girdle surface is not parallel to the diamond axis of symmetry, the holder provides two adjustments knobs  105 ,  117  to correct for those cases so that, when viewed through the video camera  28  on a video screen  159  the girdle  12  is horizontal and the entire relevant surface is in focus. In addition, there are adjustments for rough  106  and precise  104  rotation of the diamond  13  in the holder  118 . Rotation about the center axis of the diamond  13  is therefore achieved manually, although an automated or mechanized rotation is also possible. The rough adjustment  106  has  16  rotational steps, while the fine adjustment  104  is continuous. 
         [0268]    All of the above adjustments of the diamond in the holder  118  can be performed outside of the inscribing apparatus and the diamond  13  can therefore be pre-aligned before insertion into the machine. The holder  118  is designed in a manner enabling access to all the adjustment knobs with one hand, while the holder  118  is inserted into the machine. Correction through visual on screen feedback  159  can be easily achieved. 
         [0269]    The preferred mount is capable of holding stones with a total depth of 2.5 to 20.0 mm and a diameter or length of 3.5 to 30.0 mm. 
         [0270]    The user is provided with a range of controllable-intensity illumination aids. The laser axis, for example, is illuminated with a red LED  20 , which is useful for viewing polished girdles  12  in the vertical (Z-axis) camera  28 . In order to provide high contrast between the workpiece  11  profile and the background, three groups of LEDs  30  are provided around the microscope objective  10 , illuminating the workpiece  11  from three sides. Each side-illumination group  30  may have, e.g., three LEDs. Further, two miniature are lamps  40  are provided to illuminate the workpiece  11  from the bottom. This lower illumination is useful, e.g., for observing bruted girdles  12  of diamonds  13  in the vertical (Z-axis) camera  28 . 
         [0271]    The complete holder  118  is very easily inserted into the machine. In the machine there is a fixed base with a slot. The slide  116  of the holder  118  slides in the slot, in the manner of a credit card or cassette tape, and comes to a precise halt. Spring based ball-tipped plungers facilitate the sliding action and prevent the holder from making any movement when the machine is operating, by engaging countersunk recesses  103 . The holder  118  can be taken out and inserted back again with the diamond  13  coming to the same place as before. 
         [0272]    The general structure of the holder  118  is shown in  FIGS. 7A   7 E. The operator can hold the unit with one hand, normally the left hand, and insert the holder into slot. With the same hand the operator can make all the adjustments while monitoring the video screen and operating the mouse or keyboard with his right hand. The holder  18  position in the slot is very well-defined and the holder can be taken out and reinserted with the diamond  13  and holder  118  regaining the same position. When taken out, the holder  118  has an “out” position where it is still supported by the slide  116  and the stone is  40  mm out of the machine. In this position, the stone can be inked, inspected, cleaned, etc., without need for the user to support the unit with one hand. 
         [0273]    The stone  11  is positioned by the holder  118  and mount so that the center taxis is horizontal and is perpendicular to the laser beam. The holder  118  is made of steel. The contact points are the concave cup  108  which supports the center of the diamond, and a strip  110  which presses on the table toward the cup  108  in a manner that assures parallelism of the table to the symmetry axis of the holder  118 , and assures correct positioning with respect to the laser beam. In a preferred arrangement, three sizes of holders  118  are provided to cover a range of diamond  13  sizes. The holder  118  can support any stone which has a center and a table. In addition, holders  118  may also be designed to accommodate special fancy shapes. 
         [0274]    In general, it is desired to make the set-up and inscribing times approximately equal, so that the machine is always busy inscribing. Thus, further improvements in set-up time will not improve throughput. Therefore, a set of stone holders is provided. The user is provided with enough holders ready for inscribing, and that means the machine is inscribing almost continuously. The procedure is as follows: 
         [0275]    Stones are prealigned on holders. The operator, on completing the inscription, removes the holder with an inscribed stone and inserts a prepared holder with a stone to be inscribed. Minor adjustments may be required of the diamond or the holder, which may be accomplished under guidance of the video imaging system. In addition, the operator must also input or define the inscription. The inscription process is then commenced During the inscription, the operator can remove the stone from the previously used holder, allowing reuse. Generally, a large number of holders will not be required to ensure that the inscribing system is always busy, i.e., there is always a holder ready when the inscribing operation is complete. Where single operator productivity is maximum, a second operator may assist in mounting stones in holders and/or defining the inscription process. 
         [0276]    Mounted stones are held by a holder  119  which has a design which depends on the fact that some of the girdle  12  must be exposed for the inscription process to take place. Thus, the holder  119  is provided with three fine “claws”  120  which can be opened and closed by pressing a “trigger”  112 . The claws  120  are spring loaded in the closed position. The claws  120  grasp around the girdle  12  (between prongs of the setting) and press the table against a that surface  138  upon release of the trigger  112 . The flat surface  138  is perpendicular to the gemstone central axis. The holder  119  design thus assures that the gemstone  11  is centered and held firmly, and allows the stone to be rotated to a desired location for an inscription. 
         [0277]    Since a mounted stone is held in an opposite manner from an unmounted stone, the inscription direction is preferably reversed. This reversal is accomplished, for example, within the control software. In this case, the inscription may be inverted, with the inscription process commencing from the “beginning”, or the inscription made in reverse order. In order to facilitate the following of the inscription process by the human operator, the inscription preferably proceeds from the “beginning”, and the reversal is selected as a screen “button” of the graphic user interface system. In addition, the processed video image of the stone may also be selectively inverted, so that the apparent orientation of the stone in a processed image during mounted and unmounted inscription operations is the same. 
         [0278]    The operator will always “OK” the process before laser operation. He will either see the complete inscription on the text screen, or on the video directly on the girdle. 
         [0279]    When the inscription is completed the operator can judge (even before cleaning) whether the inscription is successful. Additionally, an internal cleaning mechanism may be provided to clean the inscribed surface automatically, allowing immediate viewing of the cleaned inscription within the machine, through the electronic imagers. This cleaning mechanism may take the form of an alcohol or other solvent saturated swab or pad which wipes the inscribed portion. It is noted that the solvent should either not be flammable, or vapors maintained at low levels. Further, after viewing, and before reinscription on a polished surface, a re-inking of the surface may be necessary, which may also be automated. Further, after cleaning, an image of the stone and/or inscription may be captured and maintained in a database, for example in a TIFF, JPEG, or other standard image file format. 
         [0280]    The automatic cleaning feature is achieved moving the stone to the cleaning unit via a specific motion program, and then returning it to former position for viewing. An alcohol reservoir is provided to which alcohol can be readily added by the user. Cleaning pads are also replaceable by the operator. The cleaning process adds approximately 5 seconds to the diamond marking cycle time. 
         [0281]    The stone holder and mounting system is designed to allow the stone to be removed from the machine for cleaning and to determine inscription sufficiency, while permitting precise return to the marking position if further inscription is necessary. Thus, even after cleaning, so long as the stone remains seated in the holder, will return to exactly the same position. The operator can choose to repeat the whole inscription or parts thereof any number of times he wishes to. Verification of the inscription is performed prior to removal of the diamond from the holder, so that the process may be repeated if necessary. The inscription is clearly visible on the video screen even before cleaning the ink/graphite from the stone. Even with the preferred 200 times magnification, an inscription will have to be extremely long in order not to be wholly visible on the screen. 
         [0282]    Authentication 
         [0283]    Where a workpiece bears a marking, it may be desired to determine whether the marking is authentic, for example according to the flow chart depicted in  FIG. 12 . The workpiece is viewed under magnification to read markings present thereon  181 . The authentication process provides at least two options. First, the markings may be encrypted, and are thus processed with a key  183 , e.g., a public key. Where the actual characteristics of the stone form the encrypted message, the decrypted message is compared to the actual characteristics of the workpiece  184 . Thus, the authenticity may be determined. Alternately, the markings may include a code which identifies the workpiece, allowing retrieval of information relating to the workpiece from a database. The database thus stores the characterizing information. 
         [0284]    In a second embodiment, also shown in  FIG. 12 , the authentication process involves a remote system. Therefore, the markings are transmitted to a central system  182 . The characteristics of the workpiece are read or extracted  185  and also transmitted to the central system  186 . The central system then authenticates the marking and the characteristics  187 , for example against a stored database of characteristics of marked workpieces. The authentication result is then transmitted to the remote site  189 . 
         [0285]    Encryption 
         [0286]    A diamond  200 , as shown in  FIG. 13A , with further detail, enlarged in  FIG. 13D , is provided with a number of identification and security features. The diamond  200 , for example, is a color F stone weighing 0.78 Carats, grade VS2 with two identified flaws  207 . The diamond  200  has a set of markings inscribed on the girdle  201 . The markings include an “LKI” logo  202 , formed as characters, a trademark registration symbol  203 , a serial number in Arabic numerals  204 , a one dimensional bar code  205 , a two dimensional code  206 , a set of visible dimensional references  209 , and single ablation spots  208 ,  210  having defined locations. For most purposes, the logo identifies the series of marking, while the serial number is used to identify the diamond  200 . In order to encode further information, a visible bar code  205  allows, for example, binary information to be encoded and retrieved from the diamond  200 . The two dimensional code generally requires a machine for reading, and allows high density data encoding. The visible dimensional references  209  allow use of a reticle to measure distances, providing additional characteristics of the diamond  200  which may be used to uniquely define the diamond  200 . The single ablation spots  208 ,  210  are less visible, and may thus require a key for searching. In other words, authentication of these spots may require transmission of their location, with confirmation by inspection of the diamond  200 . The marking  210 , for example, has a defined physical relation to one or both flaws  207 , making copying very difficult. 
         [0287]      FIG. 13B  shows, in more detail, a typical two dimensional code, with simple binary modulation. Thus, the presence  213  or absence  214  of an ablation at a coordinate  211 ,  212  location defines the data pattern. On the other hand,  FIG. 13C  shows a more complex code. In this case, ablations are spaced discontinuously or partially overlapping, so that an outline or partial outline of each spot  223  may be identified. Due to stochastic processes, the actual placement of the center  224  of an ablation, or its outline may vary. However, the modulation pattern imposed may be greater in amplitude than the noise, or a differential encoding technique employed so that the noise is compensated. Thus, an array of spots  223  on generally coordinate  221 ,  222  positions, with the exact positions  225  modulated according to a pattern  225 . In this case, without knowledge of the modulation scheme, it would be difficult to read the code, thus making it difficult to copy the code. Further, to the extent that the noise amplitude is near the apparent signal amplitude, a copying system may require very high precision. 
         [0288]    There has thus been shown and described novel receptacles and novel aspects of laser work piece marking systems and related databases, which fulfill all the objects and advantages sought therefor. Many changes, modifications, variations, combinations, subcombinations and other uses and applications of the subject invention will, however, become apparent to those skilled in the art after considering this specification and the accompanying drawings which disclose the preferred embodiments thereof. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is to be limited only by the claims which follow.