Patent Publication Number: US-2015086677-A1

Title: Method and apparatus for laser marking objects

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to laser systems and particularly a method and apparatus for laser marking objects at high speed. 
     It is known that food and medicinal products that are susceptible to spoilage or effectiveness often have a use by or expiration date that is printed on the items themselves or on the packaging of the items so a purchaser or potential user of the goods can make a judgment of whether the product is current or outdated. This is particularly important for some food products, which can become dangerous, with chicken eggs being a prime example because of the threat of  salmonella  poisoning. 
     It is for that reason that eggs are commonly packed in cartons that have expiration dates printed on the carton. A problem with this type of dating is that consumers often remove the eggs from a carton and put them in a special holders of their refrigerator and therefore lose the important expiration date information. Although it is not believed to be a widespread practice, there have been instances where establishments have removed eggs from one printed carton and placed in another having a later expiration date which can lead to usage beyond the date by which  salmonella  bacteria can develop into a dangerous condition. While there have been attempts to print expiration dates on the eggs themselves with ink jet printing or other type of marking, the permanency of such printed information is suspect and can often be removed. 
     A particularly desirable way in which to mark eggs is to use a laser to etch an expiration date and other information on the shell of the egg which results in a permanent marking that cannot be removed from the egg itself. Such marking is described in a patent application entitled METHOD AND APPARATUS FOR MARKING AN EGG WITH AN ADVERTISEMENT, A FRESHNESS DATE AND A TRACEABILITY CODE, having Ser. No. 11/333,580, filed Jan. 17, 2006, which is specifically incorporated by reference herein. 
     Because billions of eggs are produced annually in the United States alone, marking even a fraction of such numbers of eggs is a formidable undertaking. A large majority of eggs sold in the United States are produced in only a few hundred locations. At these locations, grader systems clean, candle, grade and pack eggs in large volumes. High volume grader systems generally have from two to six rows of eggs that are conveyed through the various stages of the grading system and can currently process up to 175,000 eggs an hour. 
     Since marking of eggs must be done during this grading process to be economical, it is necessary to mark the eggs very rapidly without slowing down the speed of operation of the grader system. Thus, the marking operation must necessarily occur within a very small time and physical size window. Because of time and physical size constraints, the amount and complexity of indicia that can be marked on the eggs is limited, and the laser marking apparatus must be sized to fit in the grader in a manner which does not interfere with the normal operation of the grader. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention comprise an apparatus for laser marking individual objects with indicia at a marking station wherein a predetermined window exists during which each object can be marked as the objects are conveyed along at least one path at a predetermined speed, the apparatus comprising, at least first and second lasers positioned adjacent one or more paths configured to direct a laser beam onto the objects to mark the same with indicia as the objects pass through the marking station, with each of the first and second lasers marking alternate following objects as they pass through the marking station. 
     Various embodiments of the invention also comprise a method of laser marking individual objects while they travel along at least one path through a marking station at a preferably predetermined speed, comprising the steps of activating a first laser to begin marking a first object when it enters the marking station and continuing to mark the object through a first predetermined time window within the station, activating a second laser to begin marking a successive object when it enters the marking station and continuing to mark the successive object through a second predetermined time window within the station, the first and second predetermined time windows overlapping with one another so that both objects are being simultaneously marked for at least as portion of the length of the time windows. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is as plan view of an egg having graphical representations rendered thereon using a laser apparatus according to the present invention, which egg has a traceability code, an expiration date, a large pictorial representation of the word EGGFUSION with Logo features and as tine of text indicating as fresh new way to advertise; 
         FIG. 2  is a plan view of as grader having apparatus embodying the present invention shown in two locations along the grader system; 
         FIG. 3  is as plan view of the preferred embodiment of the laser marking apparatus embodying the present invention; 
         FIG. 4  is as side view of the apparatus shown in  FIG. 3 ; 
         FIG. 5  is an end view of the apparatus shown in  FIGS. 3 and 4 ; 
         FIG. 6  is as side view of components of the apparatus shown in  FIGS. 3-5 , and particularly illustrating the laser generator and components for directing the generator laser beam to a galvanometer for directing the beam upwardly to mark eggs; 
         FIG. 7  is a top view of a portion of the preferred embodiment of the laser marking apparatus embodying the present invention, similar to  FIG. 3 , but illustrating the protective plate having apertures in which laser transmitting Germanium lenses are installed to keep debris and matter from falling on galvanometer scanning heads; 
         FIG. 8  is a perspective view of an alternative embodiment of a portion of the apparatus shown in  FIGS. 3 and 4 , and particularly illustrating a protective plate interposed between the galvanometers and the eggs that are conveyed above the plate together with air knives for preventing material from dropping onto the galvanometers; 
         FIG. 9  is a side view illustrating the apparatus shown in  FIGS. 3-5  wherein a portion of the apparatus is shown in a retracted and tilted position; 
         FIG. 10  is a simplified view illustrating a portion of a grader system conveying three eggs, together with two galvanometers and particularly illustrating the arc of movement of the laser beams; 
         FIG. 11  is a graphic representation of as reclining Donald Duck that is made by a plurality of vectors; and 
         FIG. 12  is a similar view as  FIG. 11 , but with the number of vectors being reduced; 
         FIG. 13  is an enlargement of a portion of the representation shown in  FIG. 11 ; 
         FIG. 14  is an enlargement of a portion of the representation shown in  FIG. 12 ; and 
         FIG. 15  is an enlarged and simplified portion of the representation shown in  FIG. 14 . 
     
    
    
     PREFERRED EMBODIMENTS OF THE PRESENT INVENTION 
     Embodiments of the present invention are directed to apparatus as well as a method for laser marking objects as they pass through a marking station, with the marking being carried out by lasers that are designed and configured to render graphic representations as the objects pass through the marking station. While the objects may comprise many different sizes and forms, and ma be made of man different types of materials, the objects that are of particular importance and are the subject of the present invention are eggs produced by chickens. 
     Parenthetically, it should be understood that terms “marking” or “etching” as used herein is intended to mean that a laser is employed as a radiant energy source. The laser beam is applied to leave most of the area of the eggshell unaffected so as to provide contrast between the unaffected areas and the marking. The laser beam ablates and melts the outer surface material from the egg shell. A significant benefit of the use of laser marking is that brown eggs have etched indicia that is a contrasting white color, while white eggs have etched indicia that is a contrasting dark brown color. The structural integrity oh the egg shell is not affected because the etching by the beam only affects the outer approximately 50 to approximately 90 micrometers of the egg shell, which is approximately 5% to approximately 8% of the thickness of the egg shell. 
     Of the billions of eggs that are produced every year, the vast majority of them are produced in a rural facility, which often have hundreds of thousands of chickens which collectively produce more than a million eggs per day. These eggs are processed through grading systems that wash, grade, candle and pack the eggs at the facility and which are then shipped to various destinations. The grading operation is carried out by high speed graders, some of which can handle up to 175,000 eggs per hour. 
     For this type of production to be maintained, an egg marking apparatus and method must be highly efficient to mark such numbers of eggs as they are processed through the grader. This is particularly true if a significant amount of indicia such as graphic representations, is desired to be etched onto every egg. It may also be necessary to use multiple lasers if several lines of graphical representations are placed on each egg, and particularly if there are several rows of eggs. Not only that, if complex graphical representation is marked on an egg, such as an intricate or extensive logo or design, for example, it is necessary to process the graphical representations in a manner whereby the graphic representation can be rendered on the egg with visual fidelity to the representation within the constraints of the physical and time window that exists for each egg that passes through a marking station. 
     More particularly, and referring to  FIG. 1 , an egg  20  has an upper line  22  of graphic representation comprising text “A005 EXP 9/5”, which is a traceability code followed b an expiration date. A middle line  24  contains a larger graphic representation of the word EGGFUSION with logo features and a bottom line  26  of text indicates a fresh new way to advertise, Another larger graphic representation is shown in  FIGS. 11-14  which is a pictorial representation of the Disney® character Donald Duck that will be described in connection with vector technology. 
     Two different laser marking apparatus, indicated generally at  30  and  32 , are shown in connection with a system that includes a grader  34  in  FIG. 2 . The grader  34  is positioned to receive eggs by a conveyor from buildings where hens are located and these eggs input to the grader  34  where they are candled, cleansed, graded and then transported by a conveying mechanism  36  where they are diverted at packing stations  38 ,  40 ,  42 ,  44  and  46 , where they are packed in cartons for shipping. The two apparatus  30 ,  32  illustrated in  FIG. 2  may represent alternate locations for a marking apparatus or they both may he provided to handle different rows of eggs of a multi row conveyor, for example. In this regard, each of the apparatus  30 ,  32  shown in  FIG. 2  are configured to mark two rows of eggs that are being moved through the grading system. 
     Since the movement of the eggs from the grader  34  is to the left, obviously the left marking apparatus  32  would not mark eggs that are diverted at packing stations  38 ,  40  and  42 . Each of the apparatus  30 ,  32  has the capability of handling two rows of eggs A and B as shown in  FIGS. 3 and 4 . 
     Each of the marking apparatus  30 ,  32  are shown in  FIGS. 3-10  and have four laser marking units, indicated generally at  50 , for marking eggs in row A and four laser marking units, indicated generally at  52 , for marking eggs in row B. The rows are shown by the lines marked A and B in  FIGS. 3 and 4 , with the eggs  20  shown in  FIG. 4 . The eggs  20  are carried by a conveyor indicated generally at  54  which has calipers  56  on opposite sides that hold the eggs as they are conveyed along a path of movement. The distance between successive eggs is defined as the pitch, which is preferably about 76 millimeters, but which can vary. In this regard, the pitch is determined by the grader manufacturer, to which laser marking apparatus is installed to mark the eggs. It is highly desirable not to slow the normal operation of the grader equipment, which conveys the eggs at a speed of up to about meters per second. 
     At that speed, there is a time window of about 69 milliseconds for each laser marking unit to mark each successive egg that passes through the marking station, which means that 14 eggs are marked per second. In this regard, a marking station is defined as the distance along the conveying lines A and B wherein one or more of the laser marking units  50  and  52  can mark eggs, it being understood that the laser beam that is emitted from the units can be moved within an arc  58  having a range of about 30 to about 35 degrees as is generally indicated in  FIG. 10 . Thus, the marking station extends generally between the width of the apparatus defined by outer surfaces  60  of a laser marking unit enclosure  62  as shown in  FIGS. 3-5 . 
     Turning now to the laser marking units  50 ,  52 , and referring to  FIG. 6 , a laser generator  64  is mounted to a vertical structural support  66  that in turn is connected to a horizontal support  68 . The laser generator  64  outputs a laser beam  70  that passes through a collimating and focusing lens  72 , is then reflected off of mirror  74  and passes through a hollow support pipe  76  supported by as bracket  78  to a galvanometer scanning head  80  that directs the beam  70  upwardly to mark the eggs  20  as they pass by. 
     The laser generator  64  is preferably a CO 2  laser having approximately a maximum of about 70 watts of power, but which can be adjusted downwardly if desired. The galvanometer scanning head is preferably a SCANcube® 7 scan head having a digital standard interface controlled by as RTC® PC interface board or an PC independent RTC® SCANalone board as sold by the SCANLAB America, Inc. of Naperville, Ill. The scan head has as 7 millimeter aperture, a beam displacement of 9.98 mm, a dynamic performance tracking error of 0.14 msec, an optical performance skew of less than 6 mrad, as step response time at 1% of full scale of 0.25 ms, as typical marking speed of 2.5 m/sec, a typical positioning speed of 12.0 m/s and as typical good writing quality speed for single stroke characters of 1 millimeter height of 900 cps. 
     As shown in  FIGS. 3-5 , each of the laser marking units  50 ,  52  is mounted in the cabinet  62 , with the laser generators  64  associated with units  50  being staggered relative to those associated with units  52  so more efficiently use space and keep all of the units in as small of a footprint as possible. The power supplies for the laser generators  64  are stored in a lower enclosure  82 . A frame structure  84  has adjustable feet  86  for leveling and adjusting the elevation of the apparatus on the floor of an installation, and the frame structure has horizontal rail members  88  which carry the enclosure  62  and enable it to be moved from an operating position shown in  FIGS. 3-5  to a retracted position as shown in  FIG. 9 . 
     The retracting capability enables the laser control units to be separated from the grader conveyor line  36  and serviced, without stopping the grader if necessary. Because of clearances, before it is retracted, it may be necessary to lower the galvanometer scanning heads  80  and tins is accomplished by having pivot connections  90  on each side of the rear corner of the enclosure  62 , and a tilt frame actuator assembly  92  on the front that can tilt the entire enclosure  62  which lowers the galvanometer scanning heads  80  so that the cabinet can be moved away from the conveyor  36 . 
     Another enclosure  94  is mounted on the frame structure  84  which includes control and operating equipment, including program logic controllers, computers that also include RTC® PC interface hoards for controlling the galvanometer scanning heads  80 , modems for communicating with lap top computers as well as off site networking equipment that upload and download data relating to the operation of the equipment. The data files that define the graphic representations including those that provide vector coordinate information are generally downloaded from off-site networking, and the production information is uploaded for billing and other purposes. The computers are also interconnected with the computer system associated with the grader  34  that provides washer environmental information such as wash water temperature, rinse water temperature and wash water pH values. There are sensors that sense operating temperatures of the laser generators and of the galvanometer scanning heads  80 , as well as current sensors for power supplies. Position sensors are also provided so that the operating status of all important moving components are monitored. The temperature and humidity within each of the enclosures is monitored. 
     An operator keyboard  96  and LCD display  98  are provided to enable onsite trouble shooting or maintenance work. However, during normal operation, and because of the extent of the monitoring and reporting that is done, the need for an on-site attendant is minimized for many types of maintenance work. If a problem arises, there are typically employees at the production facility that oversee the grader  34  operation among other activities that can use the keyboard  96  and display  98  while communicating with offsite personnel knowledgeable about the marking apparatus and rectify most problems. A laser marking unit power switch  100  is provided, as is an emergency stop switch  102 . Because of the heat that is generated b the equipment, coupled with relatively high ambient temperature and humidity in such production facilities, air conditioning units  104  are provided for each enclosure. A main power disconnect panel  106  is located on the end of the apparatus. 
     Because the galvanometer scanning heads  80  are located below the eggs  20 , there is a likelihood that some eggs will be cracked and leaking or will otherwise be wet so that material will drop toward the galvanometer scanning heads  80  and impair their operation. To guard against such occurrences, as protective plate structure  110  shown in  FIG. 7  is provided. It has left and right mounting legs  112  that are mounted to the frame members  88 , and which carry horizontal support pipes  114 , to which as plate  116  is attached. The plate has circular apertures  118  that are located above the galvanometer scanning heads  80  that have germanium protective lenses  119  covering the apertures so that matter from the eggs cannot pass through the apertures and fall onto the galvanometer scanning heads  80 . The Germanium lenses are stronger than glass and have the property of passing a laser beam without distortion. Alternatively, zinc selenide lenses can be used inasmuch as this composition also passes laser light. Because the Germanium lenses are relatively expensive, the size of he apertures  118  is preferably only large enough so that the normal arc or range of movement of the laser beam can be made. To further prevent matter from entering the galvanometer scanning heads  80 , a protective lens  120  is provided over the output of each head, as is indicated in  FIG. 10 . 
     An alternative embodiment is shown in  FIG. 8 , which has rectangular apertures  118 ′ in the plate  116  with this embodiment having an air nozzle or knife  122  provided adjacent each aperture  118  that is connected to an air supply  124  through a series of hoses such as the hose  126  which directs a current of air over the apertures which blows dripping matter away so that it does not penetrate the apertures  118 . Operation of the air knives  122  may be controlled by solenoid valves  128  in the hoses  126 . A compressed air supply of at least 40 PSI at 50 CFM preferably powers the eight air knives  122  shown. Since the plate structure  110  is mounted to the stationary frame  84 , the hoses  126  and other air supplying components should be separated from the laser marking units and the enclosure  62  because the latter can be retracted from the conveyor  36  as previously described, and the plate structure does not move. 
     With regard to laser marking eggs, a more powerful laser does not necessarily enable the speed to be increased. It takes time to transfer energy to get the right effect. For example, baking a potato generally takes about 45 minutes, and using a more powerful oven may explode the potato. There is also a power transfer function to an egg shell that produces the right effect on the egg. The laser generator is sometimes adjusted downwardly, so the maximum ob 70 watts is not used. Wet eggs and soft eggs may require power nearer the upper value. Experience has shown that time is more valuable than power in marking eggs. It is for that reason that it is preferred to maximize the writing time of the particular graphic being written to the full 138 millisecond window (or 69 milliseconds for some of the lasers). The preferred optics produced by the lens  72  is 100 millimeters which produces width of the beam or spot size of about 0.3 millimeters. These optical characteristics also provide good depth of focus effect, which means that the eggs need not be the same size. Stated in other words, a 10 millimeter change caused in different size eggs does not matter because the focal point of the beam accommodates for such differences. 
     During operation, there are four laser marking units  50  or  52  marking eggs in each row, and the four units mark the upper, middle and bottom lines as shown in the egg  20  in  FIG. 1 . When the conveyor  54  moves at the speed of 1.1 meter per second, there is only about 69 milliseconds in which to mark each egg  20 . As is evident from  FIG. 1 , the amount and size of a graphic representation that is being marked in the upper and bottom lines  22  and  26  is less than that in the middle line  24 , which may be quite complex such as shown in  FIGS. 11-15 . The present apparatus uses two of laser marking units for marking the lines  22  and  26 , and the two remaining lasers for marking the middle line on alternating eggs. This effectively doubles the time window from about 69 milliseconds to about 138 milliseconds with each of the two units marking every other egg. Using such an alternating procedure, more complex and extensive marking can be carried out in the middle line  24 . Whereas the laser marking units  50  that mark the top and bottom lines  22  and  26  are operated during the 69 millisecond window to mark every egg as it comes along, the two laser marking units  50  that mark line  24  will each operate in 138 millisecond time windows which will overlapping with one another so that both laser marking units  50  will be simultaneously marking eggs for most of said 138 millisecond time window. 
     When an involved graphic representation is to be marked on an egg, it is accomplished by mapping a plurality of vectors on a physical grid that has a maximum size of about 20 millimeters by 40 millimeters. Referring to the graphic representation shown in  FIG. 11 , it is comprised of 572 vectors, such as vector  130  which has a start point  132  and an end point  134 . Each of the start and end points have an X and a Y coordinate and each vector is a straight line. 
     The start and stop coordinates for every vector have to be programmed. This is generally done with an automatic conversion tool from web images that are used in various steps to produce a vector representation of the image. CorelDRAW® can be used, for example, which will produce as vector graphic representation from a bit graphic representation. However, the effectiveness of such tools may be sufficiently lacking that it is necessary to manually render certain types of graphics to obtain the right style of the graphic. The graphics can be provided in a PostScript format, i.e., “pps” or “ps”. Also there is a vector based plot file format called as “.plt” that can be used. 
     Generally, as the graphic representation moves through the time and spatial window, all of the lines on the left third are preferably completed as the middle third is being rendered, and similarly the middle third is rendered before the right third is rendered This generally requires very long vectors to be segmented. The graphic is generally drawn from left to right, but the rendering is not strictly required. However, it is not be possible to render a vector beginning at the left edge of the graphic if most rendering is being performed at the right third of it. To achieve the above, the order of every vector must be programmed and becomes part of the electronic file of a graphic representation. The programming is done so that all of the vectors are specified consistent with these requirements. 
     Based on the fact that the eggs are moving at a predetermined speed and galvanometer parameters are known rid or set, such as turning on and turning of delay times, repositioning times, positioning speed, and the fact that only 70 milliseconds are available the marking or writing speed is determined to render the image of the graphic based on those calculations and determine whether the representation can be effectively rendered. Since all of the vectors are known, together with the above parameters, it can be calculated at what speed the galvanometer scanning head  80  must write to complete the representation. Through experience, it has been found that approximately 200 vectors can be rendered in the 138 millisecond time window with acceptable quality. Because the physical size of the window on the egg is 20 millimeters by 40 millimeters, vectors can be removed without significantly detrimentally affecting the visual fidelity of the representation that is being rendered. The marking speed is preferably within the range of 400-800 bits per millisecond with an acceptable result being achieved at 800, a good result at 600 and a great result at 400. These units represent the coordinate space of 16 by 16 (0-65535 bits) that cover the 20 by 40 millimeter physical size of the window, the galvanometer scanning heads  80  can scan the entire field of 65535 bits in 65 milliseconds at as marking speed of 1000. Based on the optics described above, a marking speed of 1000 also translates to as distance of approximately 100 millimeters per millisecond. The quality of the mark can be affected by the quality of egg, so that a mark rendered on good eggs by the system at a particular set of parameters may be good, while those on poor eggs may not be. 
     Returning to  FIG. 11 , if all of the 572 vectors cannot be etched in the allotted time, the representation must be simplified by steps that include vector thinning and raster scanning to try to simplify the representation while maintaining realistic visual fidelity of the representation. 
     Vector thinning involves a process for simplifying the representation by reducing the number of vectors using an algorithm that is based on the Douglas Ramer Peucker algorithm for line simplification and generalization, which is used in digital cartography. The method for removing intermediate points, i.e., vectors, consists of joining the two ends of the line with a straight line, called the base line. The perpendicular distances of all intermediate points from this base line are then calculated. If all these distances are less than some predefined tolerance, representing half the width of the graphic line at source scale, these points may be discarded and the original line can be represented by the base line. If any of the intermediate points fait outside the tolerance band, the line is split into two parts at the furthest point and the process is repeatedly applied to the two resulting parts. 
     Raster scanning involves rasterizing all of the vectors onto a fixed grid that enables the determination of the existence of coincident points, which is a process for removing redundant coordinates. When points of two vectors are coincident with one another, one is preferably eliminated. The grid is defined and vectors are drawn on the grid from longest to smallest If a new vector is drawn without changing any of the grid, that means it is on top of another, and the point or points of coincidence are removed by turning off the laser at those points. This is done by digital differential analysis. This raster thinning eliminates vector elements that provide no additional graphics artifacts. It is not technically a graphics grid, but is an internal memory grid. When vectors are rasterized from longest to smallest and when get to small vectors, if not shading new grid squares, then nothing is being added to the final rendering and the are eliminated. 
     The process uses a digital differential analysis process that is similar to that described in a publication entitled Digital Differential Analyzer for Lines by Jon Kirwan, published at http://users:easystreet.com/jkirwan/dda.html, copyright November 1999, where there are a series of coordinates that make up a string of lines. This publication is specifically incorporated by reference herein. If redundant grid locations are already filled in, that portion of the vector is eliminated. The grid is preferably comprised of as 16×16 bit matrix that is mapped to a 15×15 bit physical grid that lays out on a 20×40 millimeter space on an egg. The physical grid therefore contains about 65536 blocks. The grid shown in the upper right-hand corner of  FIG. 15  representatively illustrates the size of blocks of the grid. 
     Very short vectors and point or near-point artifacts can be also removed because they are not visible when rendered. Such a process together with other processes was used to reduce the number of vectors shown in  FIG. 11  from 572 vectors to 227 vectors shown in  FIG. 12 . 
     The processes are illustrated in  FIGS. 11-14 , wherein a portion  136  of the representation of  FIG. 11  is shown in  FIG. 13  that compares with as similar portion  138  of the simplified representation of  FIG. 14 . The lines of portion  138  from  FIG. 14  are slightly different and simplified relative to the portions  136  shown in  FIG. 13 , and an enlargement of the box  140  of  FIG. 14  is shown in  FIG. 15 . 
     An example of the vector thinning simplification is shown by comparing connected vectors  142 ,  144 ,  146   148 ,  150 ,  152  and  154  in  FIG. 13 , with as simplified version comprised of vectors  156 ,  158 ,  160  and  162  shown in  FIG. 14 . While these two versions look relatively dissimilar in the enlarged  FIGS. 13 and 14 , they are quite similar in effect when viewed in the boxes  136  and  138  of  FIGS. 11 and 12 . 
     An example of the raster scanning is represented by the enlargement of box  140  from  FIG. 14 , which is shown in  FIG. 15 . The rasterization of vectors  164 ,  166  and  168  show that they overlap one another in the area that is crosshatched. Therefore, addresses that represent duplicates are used to turn off the laser marking units at appropriate time so that the location is only marked once. 
     Given that a laser etched line has to discrete width, another technique that can he used is that if two lines that are crossing or are very close together, there can be over-burn because of the width aspect of the line. Therefore, vector boundaries can be compared with other vector boundaries and thinning appropriately done. Given that it takes time to turn the laser on and off, there is a point of diminishing returns with the complexity of a vector thinning process. 
     The galvanometer scanning heads  80  are controlled by the RTC® PC interface boards which are programmed using a 16-bit coordinate system. To compensate for marking a moving product, that graphics are staged to the far right, i.e., when the left end of the representation of  FIG. 11 , to “anticipate” etching a moving egg. 
     This cannot be done with the 16-bit coordinate system, so it is mapped into a 15 bit physical window, which essentially halves the size of the coordinate space. A correction matrix ignores coordinates that are outside of the 15 bit space. So the graphic is positioned in virtual space so that when the egg comes into the frame, the galvanometer scanning heads  80  is moved over to the edge and starts rendering the image immediately. 
     This technique is necessary because the entire graphic must be sent to the galvanometer system in a coordinate system. Without the virtual mapping, it would he necessary for the entire graphic to be within the physical window before rendered could begin, which would dramatically reduce the time in which rendering could occur. This technique enables the system to render the graphic during the entire window, i.e., the entire time in which rendering can be done. 
     If this were completely in the real or principal coordinate system, the system cannot start rendering until the whole graphic is within the spatial window. The graphic is staged as far to the right as possible with respect to the coordinate system. So when the galvanometer scanning head  80  is to start rendering, it will move to the right and move with the egg so that when the egg comes into the real coordinate system, the galvanometer scanning head  80  can be controlled to go to a physical coordinate, i.e. an edge in the physical space so that it can start rendering the graphic when it appears in the 15 bit coordinate space. 
     It may be highly desirable for embodiments of the present invention to mark multiple objects with different graphical representations. In the event that eggs are being marked, it may be desired to have a carton of a dozen eggs marked with 12 different graphical representations, i.e., advertisements for 12 different products or messages. In such event, the complexity of the graphical representations may at significantly. For a complex representation, the marking speed may have to be increased to a relative maximum to complete the entire representation. The faster marking speed will reduce the print contrast, and conversely a slower marking speed will increase the print contrast. It is desirable to have the greatest possible print contrast and therefore it is desirable to mark each graphical representation using the entire 69 or 138 millisecond time window. Since, each graphical representation is contained in a separate file, the optimum marking speed for each representation is made to be part of the file, and the operating parameters of the apparatus are thereby tuned or configured for utilizing the entire time window during marking. In the example of having 12 different representations or a dozen eggs in a carton, the apparatus would likely have its operating characteristics change during the marking of each successive egg having a different representation. Such configuration flexibility optimizes the effectiveness and quality of the marking operation. 
     While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can he made without departing from the spirit and scope of the invention, which should be determined from the appended claims. 
     Various features of the invention are set forth in the appended claims.