Patent Publication Number: US-2003222057-A1

Title: Laser perforator for music media

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     [0001] This applications claims priority of U.S. Provisional Patent Application No. 60/385335 filed on Jun. 3, 2002 by Eugene P. Gerety. 
    
    
     
       TECHNICAL FIELD OF THE INVENTION  
       [0002] The present invention relates to mechanical music devices, more particularly to music media (e.g., piano rolls) for mechanical music devices, and still more particularly to techniques for perforating music media for mechanical music devices.  
       BACKGROUND OF THE INVENTION  
       [0003] Mechanical music devices such as player pianos, roll-playing organs, fairground organs, band organs, orchestrions, nickelodeons, and a wide variety of other mechanical musical instruments have been available for over 100 years. Most of these instruments play music rolls or “book music” of one form or another. Music rolls are generally similar to the familiar piano roll used on player pianos. Book music is generally made of a thicker cardboard-like stock and kerfed (or hinged) to fold in fan-fold fashion, much like fan-fold printer paper. When played on a book-playing instrument, the book music is usually placed in a stack (the “book”) and the top “leaf” is fed into the instrument. As the instrument plays, book music is pulled from the stack and feeds out of the instrument where it folds up into another similar fan-fold stack (book).  
       [0004] Some music media, such as rolls for the Regina Sublima piano, are made up of a thicker, paper-like material similar to that used for making file folders.  
       [0005] All of these media will be referred to hereinafter as “paper-like music media”.  
       [0006] A variety of techniques have been employed for perforating paper-like music media, all involving one form or another of die-punch. Commercial perforators have a bank of punches arranged to coincide with desired punch positions on a paper-like music medium. As the medium is passed under the punches, selected ones of the punches are “fired” either mechanically or by solenoids to create perforations in the paper-like music medium. Typically the music medium is stepped forward in a “punch-step increment”, usually on the order of {fraction (1/30)} of an inch, although some punches use finer punch increments.  
       [0007] Other types of perforators have been built with fewer punches, wherein the punches are moved across the music medium to a desired position and then activated to produce a perforation. The music medium is “stepped” forward, at each step location pausing long enough for the movable punch head(s) to make all required perforations.  
       [0008] Except for manual perforation techniques, which do not lend themselves well to commercial roll production, most music media are perforated in essentially the same way.  
       [0009] There are a number of disadvantages of these prior-art perforation techniques, including, but not limited to the following  
       [0010] Relatively coarse punch-step increment, yielding coarse temporal resolution  
       [0011] The relatively coarse punch-step increment of typical perforators results in a relatively coarse temporal interpretation of the music being perforated, becoming more noticeable on fast passages, at slow media speeds, or for closely-spaced musical events.  
       [0012] Inability to use “standard” media widths  
       [0013] These mechanical punches all require media slit-to-width. Sometimes a perforator will integrate a slitter as a pre or post-process operation to permit the use of standard media widths, but considerable setup is required.  
       [0014] Lack of Flexibility  
       [0015] Once set up for a specific media format, considerable effort is required to “re-tool” for different formats. It is virtually impossible to rapidly switch from one media format to another, and format changes often require a “punch-bank” change. Such punch banks are extremely expensive.  
       [0016] Another problem with prior-art perforation techniques is related to realities of today&#39;s mechanical music marketplace, which differs greatly from the marketplace of 100 years ago.  
       [0017] In the heyday of mechanical music devices, there was considerable demand for music media of all types. Mechanical musical instruments were being widely produced by a number of manufacturers. There was considerable incentive to produce and stock large numbers of rolls (and other media forms) in a wide variety of titles for a wide variety of machines.  
       [0018] It is in this environment that many of the commercial music media perforation devices were designed. The commercial devices were designed to punch as rapidly as possible, often through as many as 16 thicknesses of medium (to produce 16 copies at a time). The music roll (book, etc.) market could easily support and justify substantial roll inventories.  
       [0019] Today, however, mechanical music devices are more of a nostalgic novelty. While many thousands of instruments still exist in working order, few manufacturers still produce them and there is no longer a huge mass-market for music media. While most commercial perforating devices were designed for high-speed, high-volume production, today&#39;s market for music media does match their capabilities well.  
       [0020] Some mechanical music devices (instruments) used relatively uncommon perforation formats. For example, the Angelus-Artrio reproducing piano (only a small number of which survive today), does not use the “standard” 11.25″ wide, 9 hole-to-the-inch format of most player pianos. This non-standard format has effectively “orphaned” these instruments, and has turned existing rolls into highly prized and sought-after items. New rolls for these instruments are often difficult or impossible to obtain.  
       [0021] While many instruments have been and continue to be restored to working order, it is difficult or impossible to restore old music media, which tend to become brittle and “crumble” when they age. Many rare titles that are no longer produced have been lost to this aging process. Unfortunately, market realities and the economics of prior-art perforating techniques tend to conspire against replacement of these old music media.  
       BRIEF DESCRIPTION (SUMMARY) OF THE INVENTION  
       [0022] It therefore is a general object of the present invention to provide an improved technique for perforating paper-like music media such as paper, cardboard, mylar sheet, and other substantially planar media capable of being perforated for use as music media.  
       [0023] It is a further object of the present invention to provide a perforator for music media without mechanical punches and/or dies.  
       [0024] It is a further object of the present invention to provide a perforator for music media capable of accepting standard media widths (e.g., standard bulk paper roll widths) while producing “product” (e.g., perforated music rolls) of width other than those standard media widths.  
       [0025] It is a further object of the present invention to provide a perforator for music media capable of perforating two or more different “products” (e.g., music rolls) simultaneously.  
       [0026] It is a further object of the present invention to provide a perforator for music media that can be switched rapidly between perforation formats with little or no mechanical setup.  
       [0027] These goals and others are achieve by employing a laser to perforate music media.  
       [0028] According to the invention, a laser perforator for music media comprises a laser providing a cutting beam, means for focusing/converging the cutting beam, means for passing a paper-like music medium under the cutting beam, and means for moving the cutting beam over the planar, paper-like medium to form perforations therein.  
       [0029] The laser perforator for music media uses a laser as a source of a cutting beam for perforating paper. The laser is collimated and/or focused down to a small spot, modulated and directed across the surface of a paper-like music medium for the purpose of forming perforations therein.  
       [0030] According to an aspect of the invention, the laser perforator can employ a commercial X-Y laser engraver as a cutting device for perforating the music media. A drive mechanism is provided for feeding the music medium into the engraver and into a cutting area of the laser engraver for perforation. The music medium can be fed either continuously, in stepped fashion, or in “panels”. The music medium can be perforated in either raster fashion, whereby large areas are traced by the laser engraver with the cutting beam being turned “on” over areas to be perforated (removed), or in vector fashion, whereby the cutting beam traces perforation outlines, thereby separating perforated “chad” from the music medium.  
       [0031] Further, according to the invention, the music medium can be slit to width by the laser cutting beam as it is perforated.  
       [0032] According to another aspect of the invention, a printhead can be provided for printing tempo markings, words, dynamic markings and/or other graphical items on the music medium. By coordinating the printing with the motion of the music medium through the laser perforator, the printing can be synchronized with perforations on the music medium (such as words on “word rolls” which appear as their corresponding notes are being played on a mechanical musical instrument such as a player piano).  
       [0033] A variety of different techniques for directing a laser cutting beam can be employed by the laser perforator, such as a rotating polygonal mirror or one or more galvanometer driven mirrors. Commercial marking heads, which usually embody on of these techniques can also be employed to deflect and direct the cutting beam.  
       [0034] Since the useful cutting area provided by beam deflecting mechanisms is often considerably smaller than the width of a typical music medium “product” (e.g., piano roll), the inventive laser perforator can employ these mechanisms by providing a gantry mount whereby the entire cutting mechanism is attached to a movable mount whereby the cutting area can be moved across the music medium to permit perforation over the entire width thereof.  
       [0035] Other objects, features and advantages of the invention will become apparent in light of the following description thereof.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0036] Reference will be made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. The drawings are intended to be illustrative, not limiting. Although the invention will be described in the context of these preferred embodiments, it should be understood that it is not intended to limit the spirit and scope of the invention to these particular embodiments.  
     [0037] Often, similar elements throughout the drawings may be referred to by similar references numerals. For example, the element  199  in a figure (or embodiment) may be similar or analogous in many respects to an element  199 A in another figure (or embodiment). Such a relationship, if any, between similar elements in different figures or embodiments will become apparent throughout the specification, including, if applicable, in the claims and abstract. In some cases, similar or related elements may be referred to with similar numbers in a single drawing. For example, a plurality of elements  199  may be referred to as  199 A,  199 B,  199 B, etc.  
     [0038] The structure, operation, and advantages of the present preferred embodiment of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings, wherein:  
     [0039]FIGS. 1A and 1B are block diagrams of laser perforators for music media, according to the present invention.  
     [0040]FIG. 2 is a diagram of a media drive mechanism for the laser perforator of FIG. 1A, according to the invention.  
     [0041]FIGS. 3A, 3B and  3 C are diagrams of take-up assemblies for laser perforators, according to the invention.  
     [0042]FIG. 4A is a diagram showing raster-style perforation of a paper-like music medium, according to the invention.  
     [0043]FIG. 4B is a diagram showing vector-style perforation of a paper-like music medium, according to the invention.  
     [0044]FIG. 5 is a block diagram of a system for perforating/slitting a paper-like music medium, according to the invention.  
     [0045]FIGS. 6A, 6B and  6   c  are diagrams of different types of laser perforating apparatus for direct a laser cutting beam to perforate and/or slit a paper-like music medium, according to the invention.  
     [0046]FIGS. 7A and 7B are a side view and a top view, respectively, of a laser perforator head for perforating a paper-like music medium, according to the invention.  
     [0047]FIG. 8 is a block diagram of a system for perforating/slitting a paper-like music medium, according to the invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0048] The invention relates to a technique for perforating planar paper-like music media such as piano rolls, organ rolls, and other similar perforated music media. Such music media are not necessarily stored in roll form and can be quite thick (compared to conventional notions of “paper”). For example, many “keyed” fairground organs employ a thick card stock medium arranged in a fan-fold configuration. The medium itself need not be “paper” either. Other suitable materials may be substituted. For example, mylar sheet material or any other material capable of being perforated may be substituted. It is expressly intended that the laser perforator of the present invention be applied to any substantially planar medium capable of being perforated by a laser perforator to act as a music medium for mechanical, electrical and/or pneumatic musical instruments operated by punched media.  
     [0049]FIG. 1A is a block diagram of a laser perforator for music media  100 A wherein a paper medium  102  is fed through a cutting area  104  in a laser engraver  106  (such as a LaserPro Mercury 30 Watt laser engraver, manufactured by Great Computer Corp. of Taiwan, or similar). The paper medium  102  is driven by a paper drive mechanism  108  over a series of guide rollers  110  and onto a product takeup spool  112  and a scrap takeup spool  114 . The paper drive mechanism  108  can be a stepping drive that “steps” the paper medium  102  in small, predictable increments, or it can be a conventional motor drive mechanism. As the paper moves through the cutting area  104 , a laser cutting head  116  moving in an area  116 A over the cutting area  104  makes perforations in the paper medium  102 , and slits the paper medium  102  to a predetermined width, thereby dividing the paper medium into one or more music roll “product” portions  116  and one or more scrap portions  118 . A position encoder  120   a  measures the amount of paper medium  102  that has traveled through the cutting area  104 . Paper edge sensors  120   b  and  120   c  detect the edge position of the paper medium  102  as it enters and exits the cutting area  104 . In combination, the position encoder  120   a  and edge sensors  120   b  and  120   c  enable accurate determination of the exact amount of paper medium  102  that has been fed and its orientation (both lateral position and “azimuth” angle) in the cutting area  104 , permitting the pattern of perforations to be aligned and/or adjusted according to the known position and orientation of the paper medium  102 .  
     [0050] The music roll product portion  116  is fed onto the product takeup spool  112 , while the scrap portion  118  is fed onto the scrap takeup spool  114 . The product takeup spool  112  and the scrap takeup spool  114  are each driven by a tensioning drive arrangement such as a gearmotor with a slip clutch or a torque motor. As such, the product takeup spool  112  and the scrap takeup spool  114  serve not only to collect the music roll product  116  and scrap  118  portions of the paper medium  102 , but to maintain tension on the paper medium  102  in the cutting area  104 . Preferably, the tensioning forces applied by the product takeup spool  112  and the scrap takeup spool  114  are balanced such that substantially uniform tension is maintained across the entire width of the paper medium  102  in the cutting area  104 . A vacuum ventilation and chip removal duct  122  removes smoke and debris from the cutting area  104 .  
     [0051] Two primary modes of perforating are possible: vector and raster. In the raster mode of operation, the paper medium is moved either continuously or in stepped fashion by the paper drive mechanism  108  while the laser head  116  traces across the paper medium  102  perpendicular to the direction of motion of the paper medium  102 . The motion of the laser cutting head  116  traces a raster-line pattern over the surface of the paper. The laser&#39;s cutting beam is then modulated to produce the desired pattern of perforations in the paper medium  102 , by turning the cutting beam “on” (i.e., increasing the cutting beam&#39;s power level) as the beam passes over those areas of the paper medium  102  that are to be removed (perforated). Those of ordinary skill in the art will immediately understand that if the paper is moved in stepped fashion by a stepping paper drive  108 , the position encoder  120  is useful, but not essential since a sufficiently accurate stepping drive can accurately control the amount of motion of the paper medium  102  without feedback.  
     [0052] In the vector mode of operation, the paper medium  102  can be either moved continuously or “indexed” in “panels”. The laser head  116  traces outlines (in 2-D “X-Y” fashion) of the desired perforations on the paper medium  102 , with the laser&#39;s cutting beam turned on while tracing perforation outlines and turned off while moving between outlines. This effectively “cuts” or “punches” the outlined area from the paper medium  102 , causing the cutout pieces (“chips”) to release from the paper medium  102 . The vacuum ventilation and chip removal duct  122  carries the “chips” away.  
     [0053] If the paper medium  102  is moved continuously (or stepped continuously), then the motion of the laser head  116  is adjusted such that the perforation outlines traced by the laser head  116  track the motion of the paper medium  102 . If a stepping paper drive mechanism  108  is employed, then the step rate can be controlled and used to synchronize the motion of the laser head  116  with the motion of the paper. If a conventional motor drive (e.g., a gearmotor) is used for the paper drive mechanism  108 , then the position encoder  120  provides the paper motion information necessary to synchronize the motion of the laser cutting head  116  to the motion of the paper medium  102 .  
     [0054] If the paper is not moved continuously (or stepped continuously) in the vector mode of operation, then it can “indexed” through the cutting area  104  in a series of “panels”. An amount of paper medium  102  (a “panel”) is moved into the cutting area  104  and the paper drive mechanism  108  is stopped, halting the motion of the paper medium  102 . The laser head  116  traces outlines of the desired perforations, which releases “chips” from the paper medium  102  as described above. After all of the desired perforations are cut in on “panel” of the paper medium, a new “panel” is indexed into the cutting area  104  and cutting begins again in the new panel. If a conventional motor drive (e.g., gearmotor) is used in indexing the paper medium  102 , then the position encoder  120  can be used to determine the exact amount of paper medium  102  indexed into the cutting area  104 . This measurement is then used to synchronize the outlines traced by the laser head  114  to the amount of paper medium  102  passed through the cutting area.  
     [0055] Those of ordinary skill in the art will immediately recognize that other hybrid forms of motion and cutting are possible. For example, an “indexed raster” cutting mode is possible wherein the paper medium  102  is indexed in “panels”, and the laser cutting head  116  traces a raster pattern over each panel, with the laser head  116  stepping parallel to the direction of paper travel between perpendicular passes across the paper medium  102  to form the raster pattern.  
     [0056] Combination modes are also possible, with raster cutting used to perform some operations and vector cutting used to perform others. For example, raster cutting might be used to either cut or mark (“scorch”) text annotation into the paper medium  102 , while vector cutting might be used for note perforations (i.e., piano roll note perforations).  
     [0057]FIG. 1B is a block diagram of another embodiment of a laser perforator for music media  100 B, adapted for perforating thick, fanfold card media  102 B. The perforator  100 B is similar to the perforator  100 A of FIG. 1A in most regards, except that the medium  102 B is fed through the cutting area  104  in the opposite direction and that hold-down shoes  122  are used to keep the medium  102 B flat in the cutting area.  
     [0058] Those of ordinary skill in the art will understand that the basic techniques shown in FIGS. 1A and 1B can be used as-is can be adapted with different media drive mechanisms to perforate many different kinds of planar paper-like media, including various types of cardboard and plastic media (e.g., mylar).  
     [0059] The paper edge-sensors  120   a  and  120   b  can be optical, ultrasonic or other suitable means of detecting the lateral position of the paper edge. Those of ordinary skill in the art will immediately understand that there are numerous devices commercially available for detecting paper edge position. Exemplary of such edge detectors are a line of ultrasonic array edge detectors available from Accuweb, Inc. of Madison, Wis. Those of ordinary skill in the art will also immediately understand that the edge detectors can be used “passively” in a monitoring capacity to report the actual position of the paper edge, “actively” in a control mechanism to actively control the position of the paper edge, or both.  
     [0060]FIG. 2 is a diagram of a paper drive mechanism  200  illustrating a technique for feeding a paper medium  102  off of a heavy roll  202  without unduly stressing the paper medium  102 . A pair of parallel horizontal rollers  204 , preferably rubber-covered rollers, are spaced apart from one another, forming a “cradle” in which the heavy roll  204  sits. The heavy roll  204  rests on the two rollers and is supported by them. The rollers  204  are each provided with a drive sprocket  206 . A motor driven sprocket  208  is disposed near the drive sprockets  206  and a toothed belt  210  passes around the motor driven sprocket  208  and the two drive sprockets such that when the motor-driven sprocket  208  is turned, the toothed belt causes both drive sprockets  206  to turn in the same direction, which causes the rollers  204  to turn. By virtue of friction between the heavy roll  204  and the two rollers  206 , the heavy roll  204  is caused to turn by the motion of the two rollers. The paper medium  102  is tensioned by take-up spools (see  112 ,  114 ) such that as the heavy roll  202  turns, the paper medium  102  is fed off of the heavy roll through the cutting area  104  and taken up by the takeup spools.  
     [0061] Those of ordinary skill in the art will immediately recognize that similar alternative drive arrangements are possible. For example, gears could be substituted for the sprockets ( 206 , 208 ) and toothed belt  210 . By way of further example, it is possible to drive only one of the two rollers  204  (the one nearest an exit point of the paper medium  102  from the heavy roll  202 ) allowing the other roller to “freewheel”.  
     [0062]FIG. 3A is a diagram of a take-up assembly  300   a  for a laser perforator, wherein a paper-like music medium  302  has been perforated by a laser head, forming holes  303  therein. The paper has also been separated into a product portion  316  and a scrap portion  318  by a slit  305  cut into the paper-like medium  302 .  
     [0063] A product take-up assembly comprises a product takeup motor  312   a,  a product takeup shaft  312   b  driven by the product takeup motor  312   a,  a product takeup spool  312   c,  and a continuous-duty slip clutch  312   d.  The product take-up spool  312   c  has flanges  312   d  and  312   e,  and pivots freely on the product takeup shaft  312   b.  The slip-clutch  312   d  is attached to the product takeup shaft  312   b  and drives the product takeup spool  312   c  such that torque applied to the product takeup spool  312   c  by the product takeup shaft  312   b  is limited to a maximum value set by the slip clutch  312   d.    
     [0064] A similar scrap take-up assembly comprises a scrap takeup motor  314   a,  a scrap takeup shaft  314   b  driven by the scrap takeup motor  314   a,  a scrap takeup spool  314   c,  and a continuous-duty slip clutch  314   d.  The scrap take-up spool  314   c  has flanges  314   d  and  314   e,  and pivots freely on the scrap takeup shaft  314   b.  The slip-clutch  314   d  is attached to the scrap takeup shaft  314   b  and drives the scrap takeup spool  314   c  such that torque applied to the scrap takeup spool  314   c  by the scrap takeup shaft  314   b  is limited to a maximum value set by the slip clutch  314   d.    
     [0065] As the paper-like medium  302  is fed, perforated and slit (e.g., by a mechanism such as that described hereinabove with respect to FIG. 1A), the product portion  316  thereof is collected on the product takeup spool  312   c  and the scrap portion  316  thereof (assuming that there is a scrap portion) is collected by the scrap takeup spool  314   c.  The torques applied to the product takeup spool  312   c  and the scrap takeup spool  314   c  tension the product portion  316  and scrap portion  318 , respectively.  
     [0066] Preferably, the slip clutches  312   d  and  314   d  are adjusted such that the tension on the product portion  316  and scrap portion  318  are substantially equal, thereby substantially uniformly tensioning the paper-like medium  302  to minimize the likelihood of “puckering” of the paper-like medium  302 .  
     [0067] While FIG. 3A shows a takeup assembly adapated to a perforated medium slit into a single product portion  316  and a single scrap portion  318 , the technique is readily adapted to multiple scrap and/or product portions.  
     [0068]FIG. 3B shows a takeup assembly  300   b  adapted to a perforator setup that divides the paper-like medium into a single product portion  316  and two scrap portions  318   a  and  318   b  by slits  305   a  and  305   b  formed in the paper-like medium  302  by the perforator. Similar to the takeup assembly  300   a  of FIG. 3A, the takeup assembly  300   b  of FIG.  3 B has a product takeup assembly and a scrap takeup assembly. In this case, however, the scrap takeup assembly collects the two scrap portions  318   a  and  318   b  onto separate scrap spools.  
     [0069] As before, the product take-up assembly comprises a product takeup motor  312   a,  a product takeup shaft  312   b  driven by the product takeup motor  312   a,  a product takeup spool  312   c,  and a continuous-duty slip clutch  312   d.  The product take-up spool  312   c  has flanges  312   d  and  312   e,  and pivots freely on the product takeup shaft  312   b.  The slip-clutch  312   d  is attached to the product takeup shaft  312   b  and drives the product takeup spool  312   c  such that torque applied to the product takeup spool  312   c  by the product takeup shaft  312   b  is limited to a maximum value set by the slip clutch  312   d.    
     [0070] Similar to the scrap take-up assembly of FIG. 3A, the scrap takeup assembly comprises a scrap takeup motor  314   a  and a scrap takeup shaft  314   b  driven by the scrap takeup motor  314   a.  In this case, however, the scrap takeup assembly further comprises first and second scrap takeup spools  314   c  and  314   g,  and first and second continuous-duty slip clutches  314   d  and  314   h.  The first scrap take-up spool  314   c  has flanges  314   d  and  314   e,  and pivots freely on the scrap takeup shaft  314   b.  The second scrap take-up spool  314   g  has flanges  314   i  and  314   j,  and pivots freely on the scrap takeup shaft  314   b.  The first slip-clutch  314   d  is attached to the scrap takeup shaft  314   b  and drives the first scrap takeup spool  314   c  such that torque applied to the first scrap takeup spool  314   c  by the scrap takeup shaft  314   b  is limited to a first maximum value set by the first slip clutch  314   d.  Similarly, the second slip-clutch  314   d  is attached to the scrap takeup shaft  314   b  and drives the second scrap takeup spool  314   c  such that torque applied to the second scrap takeup spool  314   c  by the scrap takeup shaft  314   b  is limited to a maximum value set by the second slip clutch  314   d.    
     [0071] As the paper-like medium  302  is fed, perforated and slit (e.g., by a mechanism such as that described hereinabove with respect to FIG. 1A), the product portion  316  thereof is collected on the product takeup spool  312   c  and the scrap portions  316   a  and  316   b  thereof are collected by the first and second scrap takeup spools  314   c  and  314   g,  respectively. The torques applied to the product takeup spool  312   c  and to the first and second scrap takeup spools  314   d  and  314   g  tension the product portion  316  and scrap portions  318   a  and  318   b,  respectively.  
     [0072] As before, the slip clutches  312   d,    314   d  and  314   h  are preferably adjusted such that the tension on the product portion  316  and scrap portions  318   a  and  318   b  are substantially equal, thereby substantially uniformly tensioning the paper-like medium  302  to minimize the likelihood of “puckering” of the paper-like medium  302 .  
     [0073] As described hereinabove with respect to FIG. 1A, the laser perforator of the present invention is capable of producing “one or more” product portions (ref.  116 , FIG. 1A) from a paper (or paper-like) medium. For example, a 24″ wide bulk dry-waxed 40# paper medium can be slit to produce two 11.25″ piano rolls (totaling 22.5″ in width) and one or two scrap portions (making up the remainder of the 24″ width of the bulk medium.  
     [0074]FIG. 3C shows a takeup assembly  300   b  adapted to a perforator setup that divides the paper-like medium into two product portions  316   a  and  316   b  and two scrap portions  318   a  and  318   b  by means of slits  305   a,    305   b  and  305   c  formed in the paper-like medium  302  by the perforator. Similar to the takeup assemblies  300   a  and  300   b  of FIGS. 3A and 3B, respectively, the takeup assembly  300   b  of FIG. 3B has a product takeup assembly and a scrap takeup assembly. In this case, however, the product takeup assembly collects the two product portions  316   a  and  316   b  onto separate takeup spools.  
     [0075] The product take-up assembly comprises a product takeup motor  312   a,  a product takeup shaft  312   b  driven by the product takeup motor  312   a,  a product takeup spool  312   c,  and a continuous-duty slip clutch  312   d.  The product take-up spool  312   c  has flanges  312   d  and  312   e,  and pivots freely on the product takeup shaft  312   b.  The slip-clutch  312   d  is attached to the product takeup shaft  312   b  and drives the product takeup spool  312   c  such that torque applied to the product takeup spool  312   c  by the product takeup shaft  312   b  is limited to a maximum value set by the slip clutch  312   d.    
     [0076] Similar to the scrap take-up assembly of FIG. 3B, the product takeup assembly comprises a product takeup motor  312   a  and a product takeup shaft  312   b  driven by the product takeup motor  312   a.  In this case, however, the product takeup assembly further comprises first and second product takeup spools  312   c  and  312   g,  and first and second continuous-duty slip clutches  312   d  and  312   h.  The first product take-up spool  312   c  has flanges  312   d  and  312   e,  and pivots freely on the product takeup shaft  312   b.  The second product take-up spool  312   g  has flanges  312   i  and  312   j,  and pivots freely on the product takeup shaft  312   b.  The first slip-clutch  312   d  is attached to the product takeup shaft  312   b  and drives the first product takeup spool  312   c  such that torque applied to the first product takeup spool  312   c  by the product takeup shaft  312   b  is limited to a first maximum value set by the first slip clutch  312   d.  Similarly, the second slip-clutch  314   d  is attached to the product takeup shaft  312   b  and drives the second product takeup spool  312   c  such that torque applied to the second product takeup spool  312   c  by the product takeup shaft  312   b  is limited to a maximum value set by the second slip clutch  312   d.    
     [0077] Similar to the scrap take-up assembly of FIG. 3B, the scrap takeup assembly comprises a scrap takeup motor  314   a  and a scrap takeup shaft  314   b  driven by the scrap takeup motor  314   a.  The scrap takeup assembly further comprises first and second scrap takeup spools  314   c  and  314   g,  and first and second continuous-duty slip clutches  314   d  and  314   h.  The first scrap take-up spool  314   c  has flanges  314   d  and  314   e,  and pivots freely on the scrap takeup shaft  314   b.  The second scrap take-up spool  314   g  has flanges  314   i  and  314   j,  and pivots freely on the scrap takeup shaft  314   b.  The first slip-clutch  314   d  is attached to the scrap takeup shaft  314   b  and drives the first scrap takeup spool  314   c  such that torque applied to the first scrap takeup spool  314   c  by the scrap takeup shaft  314   b  is limited to a first maximum value set by the second slip clutch  314   d.  Similarly, the second slip-clutch  314   d  is attached to the scrap takeup shaft  314   b  and drives the second scrap takeup spool  314   c  such that torque applied to the second scrap takeup spool  314   c  by the scrap takeup shaft  314   b  is limited to a maximum value set by the second slip clutch  314   d.    
     [0078] As the paper-like medium  302  is fed, perforated and slit (e.g., by a mechanism such as that described hereinabove with respect to FIG. 1A), the product portions  316   a  and  316   b  thereof are collected on the first and second product takeup spools  312   c  and  312   g,  respectively, and the scrap portions  316   a  and  316   b  thereof are collected by the first and second scrap takeup spools  314   c  and  314   g,  respectively. The torques applied to the first and second product takeup spools  312   c  and  312   g  and to the first and second scrap takeup spools  314   d  and  314   g  tension the product portions  316   a  and  316   b  and scrap portions  318   a  and  318   b,  respectively.  
     [0079] As before, the slip clutches  312   d,    312   h,    314   d  and  314   h  are preferably adjusted such that the tension on the product portions  316   a  and  316   b  and scrap portions  318   a  and  318   b  are substantially equal, thereby substantially uniformly tensioning the paper-like medium  302  to minimize the likelihood of “puckering” of the paper-like medium  302 .  
     [0080] The tensioning takeup techniques described hereinabove with respect to FIGS. 3A, 3B and  3 C rely on slip clutches to maintain tension. As the punched medium (product) and scrap accumulate on the spools, the tension applied to the medium will decrease in proportion to increasing spool diameter. Assuming that all of the empty spools start out at the same diameter, they will increase in diameter at substantially the same rate as the medium accumulates on them, so the tensions will decrease in proportion, thereby maintaining even tension across the entire medium.  
     [0081] Those of ordinary skill in the art will immediately understand that more elaborate schemes can be employed to maintain constant tension. For example, separate torque motors can be used to drive each spool and constant tension can be maintained by adjusting the torque dynamically to compensate for increasing spool diameter, either in closed-loop fashion by direct measurement of tension or in open-loop fashion by calculating the spool diameters based upon paper travel. This more elaborate technique of using torque motors has the advantage that it readily accommodates spools of differing diameters, dynamically adjusting applied torque to maintain substantially constant tension across the medium. For either open-loop or closed-loop control of tension, appropriate initial tension settings can readily be determined (and automatically calculated) from the overall width of the medium and the widths of each of the product and scrap portions.  
     [0082] Those of ordinary skill in the art will also recognize that it is possible to use a single shaft for both product and scrap spools, provided that slits between product portions are cut with sufficient width to clear spool flanges between spools. Preferably, each spool would have its own separate tensioning device (e.g., slip clutch or torque motor).  
     [0083] Generally speaking, the drive systems for paper-like media described hereinabove rely on a positive feed mechanism that feeds paper into the cutting area from the supply side and uses the takeup spools as tensioning devices to keep the medium substantially flat in the cutting area. These drive systems have the advantage of keeping media tension low by way of comparison to techniques that “pull” the medium off of a heavy roll. With higher tension, there is increased risk of tearing or stretching of the medium.  
     [0084] Those of ordinary skill in the art will immediately understand that many other alternative media feed mechanisms are possible. For example, a much simpler scheme is possible whereby a driven takeup spool pulls the paper-like medium through the cutting area, relying upon drags either inherent in or engineered into the paper path to maintain tension on the paper. It is also possible to use guides and supports to keep the medium flat in the cutting area.  
     [0085] Those of ordinary skill in the art will further recognize that it is possible to operate the laser perforator of the present invention without slitting the medium into separate portions, thereby requiring a single takeup spool. In this case if slitting is required, it can be done later in a separate process.  
     [0086] As described hereinabove, there are two primary modes of perforating/slitting: raster and vector. These two techniques are shown and described with respect to FIGS. 4A and 4B.  
     [0087]FIG. 4A is a diagram of a portion  400  of a paper-like music medium being perforated in raster fashion. Holes  410  are intended to be perforated by the laser perforator of the present invention. A raster path  420  comprising “beam off” portions  420 A, shown by dashed line segments and “beam on” portions  420 B, shown by solid line segments describe the path of the laser cutting head back and forth over the portion  400  of the medium. The raster path  420  is deliberately abbreviated for clarity and to reduce illustrative clutter. The laser beam is turned “on” (raised to a power level sufficient to perforate the medium) in the “beam on” portions  420 A of the raster path  420  and turned off (reduced to a power level low enough that there will be no appreciable effect on the medium) such that the “beam on” portions  420 A of the raster path coincide with the locations of holes  410  (and the interiors thereof) so that the medium is perforated in the desired pattern of the holes  410 .  
     [0088] The raster path  420  is shown as a “serpentine” path, i.e., the laser head traces back and forth across the medium, cutting in both directions. Those of ordinary skill in the art will understand that single-direction raster perforation is also possible.  
     [0089]FIG. 4B is a diagram of a portion  400  of a paper-like music medium being perforated in vector fashion. In this case, however, the holes  410  (see FIG. 4A) are cut by tracing their outlines with the laser cutting head in a “beam on” condition and moving the laser cutting head between holes in a “beam off” condition. Dashed lines  430 A indicate “beam off” motion of the cutting head between holes and over areas not to be cut, and solid lines  430 B indicate “beam on” tracing of the hole outlines by the cutting head.  
     [0090] In the case of raster perforation, the interior of the holes is substantially burned away producing primarily smoke and vapors, but in the case of vector perforation, the hole interiors remain intact and fall away as “chips” or “chad”. Smoke, vapors and chips are all carried away by the ventilation and chip removal system (see  122 , FIGS. 1A, 1B).  
     [0091]FIG. 5 is a block diagram of a system  500  for perforating a paper-like music medium  502  using a laser engraver  506  (compare  106 , FIGS. 1A, 1B) with an X-Y cutting head  516 . A paper drive mechanism  508  feeds the paper-like music medium  502  into the engraver  506  where it passes under the cutting head  516  to be perforated and/or slit as described hereinabove. A motion pickoff  520   a,  preferably a rubber “tire”, controls a paper position monitor  520   d,  preferably a rotary encoder, to indicate the amount of paper that has passed into the laser engraver  506 . Paper edge position sensors  520   b  and  520   c  report the edge position of the paper-like medium as it enters and exits the cutting area. A printhead  524   a  is positioned to print on the paper-like medium  502  and is driven by a printhead controller  524   b  to print markings such as words, tempo markings, dynamic markings and/or graphics on the paper-like music medium  502 . A product takeup drive  512   a  drives one or more product takeup spools  512   b  and a scrap takeup drive  514   a  drives one or more scrap takeup spools  514   b.  The product takeup spool(s)  512   b  and scrap takeup spool(s)  514   b  collect product and scrap portions, respectively, of the paper-like music medium after perforation and slitting. A ventilation and chip (chad) removal system  522   a  removes smoke, fumes and chips (e.g., paper chad) from the engraver by means of a ventilation duct  522   b  and a chip removal duct  522   c.  The chip removal duct  522   c  is further connected to a chip receiver mounted near the paper-like medium to receive chips and carry them into the chip removal duct.  
     [0092] A system controller  530  comprising a peripheral interface  530   a  and a computer  530   b  receives output from the paper position monitor  520   d  and edge sensors  520   b  and  520   c  and controls the laser engraver, the paper drive mechanism  508 , the product takeup drive  512   a  and the scrap takeup drive  514   a  as necessary to cause appropriate motion of the paper-like medium  502  (e.g., continuous, stepped or “panelized” motion) to coordinate the cutting head&#39;s motions with the motion of the paper-like music medium  502  for proper perforation.  
     [0093] In addition, the system controller  530  can control and monitor the status of the ventilation and chip removal system  522  ( 522   a,b,c,d ) and the printhead  524   a  (via the printhead controller  524   b ). For example, the system controller can activate the ventilation and chip removal system  522  when perforating, monitor its status to ensure that it is functioning properly, and shut it down after perforation is completed. In the event of a ventilation failure, the system controller  530  can abort the perforation process and shut down the perforation system  500  in an orderly fashion to minimize risk of fire.  
     [0094] The system controller  530  can also control the printhead  524   a  via the printhead controller  524   b  to coordinate printing with the motion of the paper-like music medium  502 . This facilitates such features as printing a graphical leader on a piano roll, printing a roll index or printing words on a music roll in synchronization with note perforations thereon.  
     [0095] The peripheral interface  530   a  provides electrical connectivity between the computer  530   b  and the various component parts of the system  500  (i.e., laser engraver  506 , paper position monitor  520   b,  paper drive  508 , etc..), and can be integrated into the computer  530   b,  or one or more portions thereof can be implemented as one or more separate interfaces. The computer  530   b  is preferably a personal computer or computer workstation, but can also be implemented as a dedicated controller.  
     [0096] The various components of the system  500  need not be physically separate from the peripheral interface  530   a.  For example, electronic circuitry for driving a paper drive motor could be integrated into the system controller  530 . By way of further example, the printhead controller  524   b  could be integrated into the system controller  530 . While physical contact or close proximity to the paper-like medium is required of certain components (e.g., laser cutting head  506 , printhead  524   a,  pickoff  520   a,  etc.), much of the supporting electronics and other mechanism can be integrated into other portions of the system  500 . That is, the functional blocks shown in FIG. 5 should not be interpreted as implying either physical separateness or specific organization of the components and functions represented.  
     [0097] Although the embodiments described hereinabove are described with respect to a laser engraver with an X-Y cutting head. Other opto-mechanical configurations for directing a laser cutting beam can be employed, such as a rotating polygonal mirror or galvanometer-driven mirrors. Such configurations are described hereinbelow with respect to FIGS. 6A, 6B, and  6 C.  
     [0098]FIG. 6A is a diagram of a laser perforating apparatus  600   a  using a polygonal mirror  644  to direct a cutting beam  642   c.  In the Figure, a laser  640  provides a source of high-energy, collimated light in the form of a laser beam  642   a.  A collimating/focusing optical element  652   a  reduces/focuses the beam  642   a  into a collimated beam  642   b,  which is in turn reflected off of a rotating polygonal mirror  644  to produce the swept cutting beam  642   c.  As the polygonal mirror  644  rotates, it causes the cutting beam  642   c  to sweep across a substantially planar paper-like music medium  602 . The polygonal mirror  644  is driven by a mirror drive system  646 . The mirror drive  646  system drives the mirror in a fashion such that its angular position is known at any time while the cutting beam  642   c  is sweeping across the music medium  602 . A field-flattening optical element  652   b  compensates for varying path length via the rotating mirror  644  to the music medium  602 , keeping the cutting beam  642   c  in focus across a substantial portion of its sweep. The cutting beam  642   c  repeated traces a line across the music medium  602 . The music medium  602  is fed past the cutting beam  642   c  by a drive mechanism  608  so that the music medium advances slightly between passes of the cutting beam  642   c,  thereby permitting large areas of the music medium to be “painted” by the cutting beam  642   c  in a raster pattern. From a desired pattern of perforations/slits, a raster pattern generator monitors the position of the swept beam (via the mirror drive/position monitor  646 ) and the position of the music medium (via a position monitoring mechanism  620 ) and produces a desired on-off sequence for the laser  640 . This sequence is provided to a beam modulation function  648 , which causes the laser beam  642   a  (and  642   b,    642   c  as a result) to be modulated in synchronism with the motion of the music medium  602  and cutting beam  642   c  to perforate the music medium and/or form a slit  605 , producing one or more product portions  616  and/or scrap portions  618 . The beam modulation function  648  can further modulate the laser  640  to compensate for sweep speed variations, increasing beam power where the cutting beam  642   c  sweeps faster and decreasing power where it sweeps slower. If a compensating shape is not used for facets of the polygonal mirror  644 , the cutting beam  642   c  can be expected to sweep faster towards the end of its swept path.  
     [0099] Although the music medium  602  is shown as being substantially flat as it passes over the beam  642   c,  it can also travel a curved path or be formed into a partial cylindrical shape (e.g., to produce a constant beam length, eliminating the need for focal length compensation.) The functions of the optical elements  652   a,    652   b  can be combined or eliminated, as appropriate, and placed either before or after the rotating polygonal mirror  644 .  
     [0100] Those of ordinary skill in the art will immediately understand that the position of the rotating mirror  644  can be determined in many different ways, such as, encoding its position with an optical encoder, or controlling its speed accurately and producing a “beginning of sweep” pulse, then determining position as a function of time passed since the last pulse. A variety of techniques can be used to infer position of the music medium as well, such as direct encoding, stepping or synchronous drive. If the drive system is sufficiently steady (i.e., medium speed is substantially constant), then the amount of medium passed under the cutting beam  642   c  can be assumed to be the product of the speed of travel of the medium and elapsed time. Position monitoring and motion control techniques such as these are well known to those of ordinary skill in the art and will not be further elaborated upon herein.  
     [0101]FIG. 6B is a diagram of laser perforating apparatus  600   b,  similar to the laser perforating apparatus  600   a  of FIG. 6A, except that a galvanometer  645   a  and mirror  645   b  are substituted for the rotating polygonal mirror ( 644 , FIG. 6A). The galvanometer  645   a  has an output shaft to which a mirror  645   b  is attached, such that as the galvanometer  645   a  turns its output shaft, the mirror is turned. The collimated beam  642   b  is reflected off of the mirror  645   b  to produce a swept beam  642   c  directed generally towards the music medium  602 . The turning motion of the mirror  645   b  is arranged such that the swept beam  645   c  traces a path across the music medium  602 . Unlike the rotating mirror  644  of FIG. 6A, the galvanometer  645   a  is driven such that it causes the mirror  645   b  to oscillate back and forth, in turn causing the swept beam  642   c  to oscillate back and forth across the music medium  602 , thereby tracing a “serpentine” raster pattern across the music medium. As before, the pattern generator  650  and beam modulator  648  are employed to synchronize modulation of the laser  640  with the motion of the mirror  645   b  and the music medium  602 , to produce the desired pattern of perforations and/or slits ( 605 ) on the music medium  602 , thereby dividing it into one or more perforated product portions  616  and/or one or more scrap portions  618 .  
     [0102] Those of ordinary skill in the art will immediately appreciate that one advantage of the galvanometer  645   a  and mirror  645   b  over the rotating mirror assembly  644  is that the galvanometer can be “commanded” by the galvanometer drive  647  to any angular position, thereby permitting the swept beam  642   c  to be “commanded” to any point along its path across the music medium  602 . In the apparatus  600   a  shown in FIG. 6A, the swept beam was limited to continuous motion (not necessarily constant speed) across the music medium  602 . In the apparatus  600   b  of FIG. 6B, however, the swept beam  645   c  can be slowed down, sped up, or even stopped as it travels its path across the music medium  602 . The permits the beam to be slowed down to “dwell” over areas to be perforated or slit and moved rapidly between perforations/slits. By permitting slower motion of the beam in areas to be cut through, it is possible to use a lower power laser for some applications.  
     [0103] With the addition of a second galvanometer and mirror, it is possible to permit two-axis (two-dimensional) deflection of the swept beam over an area of the music medium. This is shown and described with respect to FIG. 6C.  
     [0104]FIG. 6C is a diagram of laser perforating apparatus  600   c  for a paper-like music medium  602  similar to laser perforating apparatus  600   a  and  600   b  shown and described hereinabove with respect to FIGS. 6A and 6B, except that a two-axis beam deflection arrangement comprising a first galvanometer  645   a,  a first mirror  645   b,  a second galvanometer  645   c  and a second mirror  645   d  are provided. In this case, the galvanometer drive  647  controls position of the first and second galvanometers  645   a  and  645   c  independently, thereby controlling the positions of the first and second mirrors  645   b  and  645   d  to deflect the cutting beam  642   c  in two axes. Unlike the single-axis rotating mirror  644  of FIG. 6A and the single galvanometer and mirror ( 645   a,    645   b ) of FIG.  6 B, the deflection arrangement of FIG. 6C permits the cutting beam  642   c  to be deflected to trace out complex shapes (such as perforation outlines) over a two-dimensional area of the paper-like music medium  602 . This permits vector-mode cutting as described hereinabove with respect to FIG. 4B.  
     [0105] The pattern generator  650  and beam modulator  648  are employed to synchronize modulation of the laser  640  with the motion of the mirror  645   b  and the music medium  602 , to produce the desired pattern of perforations and/or slits  605 , such as hole outlines, on the music medium  602 , thereby dividing it into one or more perforated product portions  616  and/or one or more scrap portions  618 .  
     [0106] The apparatus  600   c  of FIG. 6 c  has a potential advantage over a laser perforator built around a commercial X-Y laser engraver in that the galvanometers/mirrors have very low mass compared to the optical head, arms, etc., of a typical X-Y engraver such as those manufactured by Great Computer Corporation, Universal Laser Systems, Epilog, and others. This means that the beam can be “moved” from point to point on the music medium more rapidly than would be possible with laser engraver. This permits the cutting beam to be directed very rapidly between perforations, greatly speeding yup perforation. Further, the vector cutting approach has the advantage that it only cuts outlines of perforations and other shapes, rather than having to burn away the entire interior of those shapes and trace over large areas of imperforate medium. This can potentially greatly speed up overall perforator operation, and by permitting the cutting beam to dwell only outlines to be cut, may permit a lower power laser to be used.  
     [0107] It will be readily appreciated by those of ordinary skill in the art that converging and field-flattening optics of the type described hereinabove with respect to FIGS. 6A, 6B, and  6 C can be expensive and difficult to align, especially when both a small spot size and a large cutting area (or length—FIGS. 6A, 6B) are desired. It is generally much simpler and much less expensive to provide converging/field-flattening optics to maintain a small spot size over a smaller cutting area (or length).  
     [0108] X-Y “Marking” heads capable of producing a small spot size (highly focused laser beam of a few thousandths of an inch in diameter) over a relatively small area (a few square inches) are commercially available from a number of sources, including Synrad, Inc. of Mukilteo, Wash. Such heads are often used for marking parts, or for producing repeating patterns on a variety of media. These heads generally employ galvanometer driven mirrors or similar techniques for beam deflection, and provide for control of beam power. Laser spot size, however, is dependent upon the size of the cutting area desired. The smallest spot sizes can be maintained only over relatively small areas. For example, Synrad specifies that using its FH series marking head, a spot size of 0.007″ can be employed over a working area of about 2.5 inches square (6.25 square inches).  
     [0109]FIGS. 7A and 7B are a side view and a top view, respectively, of a laser perforator head  700  for perforating a paper-like music medium  702 , employing such a marking head  760 . A laser  740  provides a source of a cutting beam  742  to be deflected by the marking head  760 . The marking head is positioned an appropriate focal distance away from the music medium  702  such that the cutting beam  742  can be deflected over a cutting area  743 . The laser  740  and cutting head  760  are mounted to a support bracket  762 , which is in turn slide-mounted to a pair of guide rails  764 . The slide-mounted bracket  762  and rails  764  in effect form a “gantry” by which the laser  740  and marking head  760  can be moved back and forth along the rails  764  such that the cutting area  743  can be repositioned to cover any desired position across the with of the music medium  702 . A gantry drive motor  770  drives a first sprocket  772   a.  A gantry drive belt  774  passes around the first sprocket  772   a  and a second sprocket  772   b,  and attaches to the support bracket  762  such that the gantry drive motor  772  moves the laser  740  and marking head  760  along the rails  764  over the music medium  702 . By coordinating the cutting action of the marking head  760  with motion of the marking head, perforations and/or one or more slits  705  can be made in the music medium  702  anywhere across the entire width of the music medium  702 , thereby dividing into one or more product portions  716  and/or one or more scrap portions  718   
     [0110]FIG. 8 is a block diagram of a system  800  for perforating a paper-like music medium  802  using a marking head  860  and laser  840  (compare  740 ,  760 , FIGS. 7A, 7B). The system  800  is similar in many respects to the system  500  shown and described hereinabove with respect to FIG. 5. A paper drive mechanism  808  feeds the paper-like music medium  802  under the marking head  860  to be perforated and/or slit as described hereinabove. A motion pickoff  820   a,  preferably a rubber “tire”, operates a paper position monitor  820   b,  preferably a rotary encoder, to indicate the amount of paper that has passed under the marking head  860 . A printhead  824   a  is positioned to print on the paper-like medium  802  and is driven by a printhead controller  824   b  to print markings such as words, tempo markings, dynamic markings and/or graphics on the paper-like music medium  802 . A product takeup drive  812   a  drives one or more product takeup spools  812   b  and a scrap takeup drive  814   a  drives one or more scrap takeup spools  814   b.  The product takeup spool(s)  812   b  and scrap takeup spool(s)  814   b  collect product and scrap portions, respectively, of the paper-like music medium after perforation and slitting. A ventilation and chip (chad) removal system  822   a  removes smoke, fumes and chips (e.g., paper chad) from the engraver by means of a ventilation duct  822   b  and a chip removal duct  822   c.  The chip removal duct  822   c  is further connected to a chip receiver  822   d  mounted near the paper-like medium to receive chips and carry them into the chip removal duct.  
     [0111] A system controller  830  comprising a peripheral interface  830   a  and a computer  830   b  receives output from the paper position monitor  820   b  and controls the laser  840  and marking head (via a head control function  866 , typically built into the marking head and/or its associated equipment), the paper drive mechanism  808 , the product takeup drive  812   a,  the scrap takeup drive  814   a  and a gantry drive mechanism  870  (compare  770 ,  772   a,b,    774 , FIGS. 7A, 7B) as necessary to cause appropriate motion of the paper-like medium  802  (e.g., continuous, stepped or “panelized” motion) and to coordinate motion of the marking head  860  and modulation of the laser  840  with the motion of the paper-like music medium  802  for proper perforation and/or slitting. As the paper-like medium  802  and marking head  860  are moved relative to one another, deflection of the cutting beam is adjusted to track and compensate for the motion. This motion correction is accomplished and coordinated by the system controller  830  by means of positional feedback from the paper drive and the head control  866 .  
     [0112] A ventilation housing  822   e  surrounds a cutting area  804  where the paper-like music medium  802  is perforated/slit. Considerable smoke and/or fumes can be generated in this area, and the ventilation housing  822   e  contains these fumes and permits their proper removal by the ventilation and chip removal system  822   a.  Preferably, the ventilation housing  822   e  is mode of a material that blocks light from the laser  840  (e.g., acrylic for CO2 lasers), providing protection for bystanders against injury.  
     [0113] As in the system of FIG. 5, the system controller  830  can control and monitor the status of the ventilation and chip removal system  822  ( 522   a,b,c,d ) and the printhead  824   a  (via the printhead controller  824   b ). For example, the system controller can activate the ventilation and chip removal system  822  when perforating, monitor its status to ensure that it is functioning properly, and shut it down after perforation is completed. In the event of a ventilation failure, the system controller  830  can abort the perforation process and shut down the perforation system  800  in an orderly fashion to minimize risk of fire.  
     [0114] The system controller  830  can also control the printhead  824   a  via the printhead controller  824   b  to coordinate printing with the motion of the paper-like music medium  802 . This facilitates such features as printing a graphical leader on a piano roll, printing a roll index or printing words on a music roll in synchronization with note perforations thereon.  
     [0115] The peripheral interface  830   a  provides electrical connectivity between the computer  830   b  and the various component parts of the system  500  (i.e., head control  866 , head drive  870 , paper position monitor  520   b,  paper drive  508 , etc..), and can be integrated into the computer  830   b,  or one or more portions thereof can be implemented as one or more separate interfaces. The computer  830   b  is preferably a personal computer or computer workstation, but can also be implemented as a dedicated controller.  
     [0116] The various components of the system  800  need not be physically separate from the peripheral interface  830   a.  For example, electronic circuitry for driving a paper drive motor could be integrated into the system controller  830 . By way of further example, the printhead controller  824   b  could be integrated into the system controller  830 . While physical contact or close proximity to the paper-like medium is required of certain components (e.g., marking head  860 , printhead  824   a,  pickoff  820   a,  etc.), much of the supporting electronics and other mechanism can be integrated into other portions of the system  800 . That is, the functional blocks shown in FIG. 8 should not be interpreted as implying either physical separateness or specific organization of the components and functions represented.  
     [0117] As described hereinabove, a typical commercial marking head (such as the Synrad FH series) cannot provide both a small spot size and a large “marking” (cutting) area. In order to overcome this limitation for the purpose of perforating/slitting music media wider than the longest dimension of the marking head&#39;s marking area, the marking head can be gantry mounted as shown and described hereinabove with respect to FIGS. 7A, 7B and  8 , and moved across the music medium to cover the entire width thereof. As the gantry-mounted marking head and paper-like music medium are moved, the system controller (see  830 , FIG. 8) compensates for that motion by adjusting cutting coordinates sent to the marking head, effectively creating a moving coordinate system.  
     [0118] One method of moving the gantry mechanism to cause the marking head&#39;s cutting area to sweep over the entire surface of the music medium is to move the gantry back and forth above the music medium, creating a serpentine sweep of the marking head over the music medium. Preferably, the “sweeps” of the cutting area overlap. As the sweep process progresses, new areas of the music medium become available for cutting and “old” areas become unavailable for cutting. With overlap of the sweep passes, some areas of the medium will pass under the marking head more than once. Preferably, faced with a choice of which items (perforations or slits) to cut first, the system controller prioritizes commands to the cutting head so that areas of the music medium which will become unavailable for cutting soonest are processed (perforated or slit) first.  
     [0119] Those of ordinary skill in the art will also realize that other sweep schemes are possible. For example, both music medium and marking head can be moved in discrete steps, stopping periodically to cut an area of the music medium, effectively cutting the music medium in a series of “tiles”.  
     [0120] The present inventive technique has a number of advantages over prior art techniques for perforating music media. Prior-art perforators, usually mechanical step-advance die-punching machines, have a “punch step” increment, i.e., a minimum distance between punches. As described hereinabove, a typical punch-step increment for American 88-note piano rolls is on the order of {fraction (1/30)} of an inch. The laser perforator of the present invention has an effective punch step increment as small as the laser engraver, marking head, or other laser cutting apparatus can resolve—typically less than 0.001 inch. At a tempo of 50 (music medium speed across a “tracker bar” or its equivalent of 5 feet/minute or 1 inch per second), this means that the temporal resolution of a typical prior-art perforation technique is not better than 33 milliseconds, while the temporal resolution of the present invention is typically 1 millisecond or less. The 33 millisecond resolution corresponds to 30 events per second—within the range of human temporal perception under certain conditions—while the 1 millisecond resolution is well below the threshold of perception. Even with the speed of the medium doubled to tempo 100 (2 inches per second—generally considered a fairly fast speed for roll playing instruments) the temporal resolution for the prior-art technique is only improved to 17 milliseconds; still relatively coarse by some standards.  
     [0121] Various aspects of the present inventive technique for laser perforation of music media enable capabilities previous impossible using prior-art techniques. Some examples are:  
     [0122] switching between different perforation formats for media of the same width (e.g., between 11.25 inch “A” roll format at 6 holes per inch and 11.25 inch 88-note format at 9 holes per inch) requires no change of setup.  
     [0123] switching between product formats of differing widths (but using the same basic medium, e.g., paper) requires only adjustment of receiving product and/or scrap spool widths  
     [0124] no die changes are ever required  
     [0125] media can be perforated face-up, face-down, head-first or tail-first without change of physical setup (assuming spool directions are reversible).  
     [0126] media are slit to width while perforating, permitting the use of standard bulk media (e.g., 12 inch wide dry waxed kraft paper, slit to 11.25″ width while perforating)  
     [0127] two or more products can be perforated at once  
     [0128] products of differing format, width, and/or hole spacing can be perforated simultaneously  
     [0129] Although the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character—it being understood that only preferred embodiments have been shown and described, and that all changes and modifications that come within the spirit of the invention are desired to be protected. Undoubtedly, many other “variations” on the “themes” set forth hereinabove will occur to one having ordinary skill in the art to which the present invention most nearly pertains, and such variations are intended to be within the scope of the invention, as disclosed herein.