Abstract:
The present invention is for an image processing apparatus (10) for sheet thermal print media. The image processing apparatus (10) comprises a vacuum imaging drum (300) for holding thermal print media (32) and dye donor sheet material (36) in registration on the vacuum imaging drum (300). A printhead (500) moves along a line parallel to the longitudinal axis (X) of the vacuum imaging drum (300) as the vacuum imaging drum (300) rotates. The printhead (500) receives information signals and produces radiation which is directed to the dye donor sheet material (36) which causes color to transfer from the dye donor sheet material (36) to the thermal print media (32). The vacuum imaging drum (300), having media contours (328) on the outer surface to facilitate holding media onto a vacuum imaging drum (300) revolving at high speeds.

Description:
FIELD OF THE INVENTION 
     This invention relates to an image processing apparatus in general, and more specifically to a vacuum imaging drum for such an apparatus capable of holding multiple sheets while revolving at high speeds. 
     BACKGROUND OF THE INVENTION 
     Pre-Press color proofing is a procedure that is used by the printing industry for creating representative images of printed material without the high cost and time that is required to actually produce printing plates and set up a high-speed, high volume printing press. These representative images may require correction and may be reproduced several times to satisfy customer requirements. 
     One such commercially available image processing apparatus, shown in commonly assigned U.S. Pat. No. 5,268,708, has half-tone color proofing capabilities. This image processing apparatus is arranged to form an intended image on a sheet of thermal print media in which dye from a sheet of dye donor material is transferred to thermal print media by applying thermal energy to the dye donor material. This image processing apparatus is comprised generally of a material supply assembly or carousel, lathe bed scanning subsystem (which includes a lathe bed scanning frame, translation drive, translation stage member, printhead, and vacuum imaging drum), and thermal print media and dye donor material exit transports. 
     The operation of the image processing apparatus comprises metering a length of the thermal print media, in roll form, from the material assembly or carousel. The thermal print media is measured and cut into sheets of a required length, transported to the vacuum imaging drum, registered, and wrapped around and secured onto the vacuum imaging drum. Next a length of dye donor material, in roll form, is metered out of the material supply assembly, measured, and cut into sheets of a required length. The dye donor material is transported to and wrapped around the vacuum imaging drum, such that it is superposed in registration with the thermal print media. 
     The thermal print media and the dye donor material are retained on the spinning vacuum imaging drum while it is rotated past the scanning subsystem to expose the thermal print media. The translation drive traverses the printhead and translation stage member axially along the vacuum imaging drum, in coordinated motion with the rotating vacuum imaging drum. These movements combine to produce the image on the thermal print media. 
     After the image has been written on the thermal print media, the dye donor material is removed from the vacuum imaging drum. This is done without disturbing the thermal print media beneath it. The dye donor material is then transported out of the image processing apparatus by the dye donor material exit transport. Additional sheets of dye donor material, each a different color, are sequentially superimposed with the thermal print media on the vacuum imaging drum and imaged onto the thermal print media as previously described, until the intended image is completed. The completed image on the thermal print media is unloaded from the vacuum imaging drum and transported to an external holding tray on the image processing apparatus by the exit transport. 
     The vacuum imaging drum is cylindrical in shape and includes a hollowed-out interior portion, and a plurality of holes extending through a surface of the drum for applying a vacuum from the interior of the vacuum imaging drum, for supporting and maintaining the position of the thermal print media and dye donor sheet material as the vacuum imaging drum rotates. The ends of the vacuum imaging drum are enclosed by cylindrical plates. The cylindrical end plates are each provided with a centrally disposed spindle which extends outwardly through support bearings and are supported by the lathe bed scanning frame. The drive end spindle extends through the support bearing and is stepped down to receive a DC drive motor armature which is held on by means of a nut. A DC motor stator is held stationary by the lathe bed scanning frame, encircling the armature to form a reversible, variable speed DC drive motor for the vacuum imaging drum. At the end of the spindle an encoder is mounted to provide timing signals to the image processing apparatus. The opposite spindle is provided with a central vacuum opening, which is in alignment with a vacuum fitting with an external flange that is rigidly mounted to the lathe bed scanning frame. The vacuum fitting has an extension which extends within but is closely spaced from the vacuum spindle, thus forming a small clearance. With this configuration, a slight vacuum leak is provided between the outer diameter of the vacuum fitting and the inner diameter of the opening of the vacuum spindle. This assures that no contact exists between the vacuum fitting and the vacuum imaging drum which might impart uneven movement or jitters to the vacuum imaging drum during its rotation. 
     The opposite end of the vacuum fitting is connected to a high-volume vacuum blower which is capable of producing 50-60 inches of water at an air flow volume of 60-70 cfm. The vacuum required varies during loading, scanning, and unloading of the thermal print media and the dye donor materials. With no media loaded on the vacuum imaging drum the internal vacuum level of the vacuum imaging drum is approximately 10-15 inches of water. With just the thermal print media loaded on the vacuum imaging drum the internal vacuum level of the vacuum imaging drum is approximately 20-25 inches of water. This level is required such that when a dye donor sheet material is removed, the thermal print media does not move, otherwise color to color registration will not be maintained. With both the thermal print media and dye donor sheet material completely loaded on the vacuum imaging drum the internal vacuum level of the vacuum imaging drum is approximately 50-60 inches of water. 
     The outer surface of the vacuum imaging drum is provided with an axially extending flat, which extends approximately 8 degrees around the vacuum imaging drum circumference. The vacuum imaging drum is also provided with a circumferential recess which extends circumferentially from one side of the axially extending flat circumferentially around the vacuum imaging drum to the other side of the axially extending flat, and from approximately one inch from one edge of the vacuum imaging drum to approximately one inch from the other edge of the vacuum imaging drum. The thermal print media when mounted on the vacuum imaging drum is seated in the circumferential recess and therefor the circumferential recess has a depth substantially equal to the thermal print media thickness seated there within which is approximately 0.004 inches in thickness. 
     The purpose of the circumferential recess on the vacuum imaging drum surface is to eliminate any creases in the dye donor material, as it is drawn down over the thermal print media during the loading. This assures that no folds or creases will be generated in the dye donor materials which could extend into the image area and seriously adversely affect the image. The circumferential recess also substantially eliminates the entrapment of air along the edge of the thermal print media, where it is difficult for the vacuum holes in the vacuum imaging drum surface to assure the removal of the entrapped air. Any residual air between the thermal print media and the dye donor material, can also adversely affect the intended image. 
     The purpose of the vacuum imaging drum axially extending flat is two fold, it assures that the leading and trailing ends of the dye donor material are protected from the effects of air drag during high speed rotation of the vacuum imaging drum during the imaging process. Without the axially extending flat, the air drag will tend to lift the leading or trailing edges of the dye donor material. The vacuum imaging drum axially extending flat also ensures that the leading and trailing ends of the dye donor sheet material are recessed from the vacuum imaging drum periphery. This reduces the chance of the dye donor material contacting other parts of the image processing apparatus, such as the printhead, causing a jam, possible loss of the intended image, or catastrophic damage to the image processing apparatus. 
     The vacuum imaging drum axially extending flat also acts to impart a bending force to the ends of the dye donor materials when they are held onto the vacuum imaging drum surface by vacuum from within the interior of the vacuum imaging drum. Consequently when the vacuum is turned off to that portion of the vacuum imaging drum, the end of the dye donor material will tend to lift from the surface of the vacuum imaging drum. 
     Although the present image processing apparatus is satisfactory, it is not without drawbacks. Throughput, the number of intended images per hour, is limited by the vacuum imaging drum rotational speed. With some constraints imposed by the technology itself, the faster the vacuum imaging drum rotates without the centrifugal forces or increased air turbulence separating the thermal print media and the dye donor sheet material from the vacuum imaging drum, the faster the intended image can be exposed onto the thermal print media, thus increasing the throughput of the image processing apparatus. However, with the existing image processing apparatus, the physical characteristics of the thermal print media, the interface of the axially extending flat, circumferential recess, and the dye donor material, limit the rotational speeds that are possible. At high rotational speeds, in excess of 1000 RPM, the centrifugal forces and air turbulence lift or separate the dye donor materials from the vacuum imaging drum surface at the corners of the sheet of dye donor material. 
     One approach to solving the above problem is adding external clamping components to hold the thermal print media and the dye donor sheet material to the vacuum imaging drum. This, however, adds increased cost and introduces mechanical complexity to the vacuum imaging drum design. This solution may also cause the vacuum imaging drum to go out of round as much as 80 microns, which would not allow the image processing apparatus to meet quality specifications. (The image processing apparatus tolerance requirement for focus is approximately 10 microns.) Clamping the thermal print media and the dye donor material would also introduce a clearance problem since the working distance of the printhead to the surface of the thermal print media loaded on the vacuum imaging drum is approximately 0.030 inches. 
     Another way to prevent the increased air turbulence and centrifugal force from separating the dye donor sheet material from the rotating vacuum imaging drum would be to add more vacuum holes or enlarge the diameter of the vacuum holes. This, however, would require an increase in the vacuum level in the interior of the vacuum imaging drum. A higher vacuum will increase in the cost of the blower that produces the vacuum, require complex vacuum coupling, adding additional cost, and higher customer operating costs with increased electrical consumption. In addition, there is a limit to how high the vacuum level can be without distorting the media, hence decreasing the image quality of the intended image. 
     Another problem with present vacuum imaging drum designs is that the corners of the dye donor material may cause a flute or ridge-like ripple to be formed in the dye donor material as the leading and trailing edge is drawn down at the axially extending flat. This fluting, where it extends over the thermal print media, will adversely affect the quality of the image. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a dramatic increase in through put of an image processing apparatus by increasing the rotational speed of the vacuum imaging drum. 
     It is another object of the present invention to provide an imaging apparatus capable of supporting dye donor material and thermal print media at multiple positions on donor support rings, to allow use of different lengths of the thermal print media and dye donor materials on the same drum. 
     It is the object of the present invention to eliminate fluting at the corners of the dye donor material. 
     The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, a vacuum imaging drum, mounted for rotation about an axis, holds a sheet of thermal print media in registration with a sheet of dye donor material. A circumferential recess on a surface of the drum is approximately equal in length, width, and height to the thermal print media, so that the thermal print media fits into the recess. A first donor support ring and a second donor support ring on the surface of the drum, form a first edge and a second edge of the recess. An axially extending flat on the surface of the drum is adjacent a leading edge and a trailing edge of the thermal print media. A first media contour is located in the first donor support ring and a second media contour is located in the second donor support ring, both at opposite ends of the axially extending flat. The first media contour and the second contour bend corners of the dye donor material, to prevent fluting. In one embodiment, media contours are concave which insures full support and contact of the corner area of the dye donor material with the surface of the vacuum imaging drum. 
     Other embodiments of the invention include a single sheet vacuum imaging drum, multiple donor support ring position for use of different lengths of thermal print media dye donor material, and a vacuum imaging drum with no axially extending flat. 
     It is an advantage of the present invention that it can also be used on a vacuum imaging drum without an axially extending flat. 
     It is an advantage of the present invention that it can be used on a single sheet vacuum imaging drum. 
     It is an advantage of the present invention that can be implemented with only minor changes to prior art vacuum imaging drums and with no changes to the rest of the image processing apparatus. 
     It is an advantage of the present invention that there is no significant change in the mass of the vacuum imaging drum or its mechanical characteristics, minimizing the problem of distorting the vacuum imaging drum at high rotational speeds. 
     It is an advantage of the present invention that a change in bower design is not required. 
     By adding the media contours to the donor support rings at the ends of the axially extending flat, the dye donor material will be in full contact with the surface of the vacuum imaging drum and the rotational speed of the vacuum imaging drum can be increased to as high as 3000 rpm substantially increasing the through put of the image processing apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view in vertical cross-section of an image processing apparatus of the present invention; 
     FIG. 2 is a perspective view of a lathe bed scanning subsystem of the present invention; 
     FIG. 3 is a top view in horizontal cross-section, partially in phantom, of a lead screw of the present invention; 
     FIG. 4 is a exploded, perspective view of a vacuum imaging drum of the present invention; 
     FIG. 5 is a plane view of a surface of a surface of the vacuum imaging drum of the present invention; 
     FIGS. 6a-6c plane view of the vacuum imaging drum showing the sequence of placement for the thermal print media and dye donor sheet material; 
     FIG. 7 is a plane view of the vacuum imaging drum showing donor support rings with a plurality of media contours to accommodate different lengths of the dye donor sheet material and the thermal print media on the same drum; 
     FIG. 8 is a exploded, perspective view of an alternate embodiment of a vacuum imaging drum without an axially extending flat; 
     FIG. 9 is a exploded, perspective view of yet another embodiment of a vacuum imaging drum with a single sheet of thermal print media and an axially extending flat; 
     FIG. 10 is a exploded, perspective view of a vacuum imaging drum for a single sheet of thermal print media without axially extending flat utilizing area and the present invention; 
     FIG. 11 is a perspective view partially in section of a vacuum imaging drum according to the present invention showing a media contour; 
     FIG. 12 is a plan view, partially in phantom, of a section of the vacuum imaging drum shown in FIG. 11; 
     FIG. 13 is a section view along line 13,14--13,14 of FIG. 12 with the media contour configured to accommodate a flute formed on a dye donor sheet; 
     FIG. 14 is a sectional view of an alternate embodiment along line 13,14--13,14 of FIG. 12 with the media contour to reverse a flute formed in a dye donor sheet; and 
     FIG. 15 shows a perspective view partially in section of a vacuum imaging drum according to the present invention showing a corner of a dye donor sheet being formed by the media contour. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, there is illustrated an image processing apparatus 10 according to the present invention having an image processor housing 12 which provides a protective cover. A movable, hinged image processor door 14 is attached to the front portion of the image processor housing 12 permitting access to the two sheet material trays, lower sheet material tray 50a and upper sheet material tray 50b, that are positioned in the interior portion of the image processor housing 12 for supporting thermal print media 32, thereon. Only one of the sheet material trays 50 will dispense the thermal print media 32 out of its sheet material tray 50 to create an intended image thereon; the alternate sheet material tray either holds an alternative type of thermal print media 32 or functions as a back up sheet material tray. In this regard, the lower sheet material tray 50a includes a lower media lift cam 52a for lifting the lower sheet material tray 50a and ultimately the thermal print media 32, upwardly toward a rotatable, lower media roller 54a and toward a second rotatable, upper media roller 54b which, when both are rotated, permits the thermal print media 32 to be pulled upwardly towards a media guide 56. The upper sheet material tray 50b includes a upper media lift cam 52b for lifting the upper sheet material tray 50b and ultimately the thermal print media 32 towards the upper media roller 54b which directs it towards the media guide 56. 
     The movable media guide 56 directs the thermal print media 32 under a pair of media guide rollers 58 which engages the thermal print media 32 for assisting the upper media roller 54b in directing it onto the media staging tray 60. The media guide 56 is attached and hinged to the lathe bed scanning frame 202 at one end, and is uninhibited at its other end for permitting multiple positioning of the media guide 56. The media guide 56 then rotates its uninhibited end downwardly, as illustrated in the position shown, and the direction of rotation of the upper media roller 54b is reversed for moving the thermal print medium receiver sheet material 32 resting on the media staging tray 60 under the pair of media guide rollers 58, upwardly through an entrance passageway 204 and around a rotatable vacuum imaging drum 300. 
     A roll of dye donor material 34 is connected to the media carousel 100 in a lower portion of the image processor housing 12. Four rolls are used, but only one is shown for clarity. Each roll includes a dye donor material 34 of a different color, typically black, yellow, magenta and cyan. These dye donor materials 34 are ultimately cut into dye donor sheet materials 36 and passed to the vacuum imaging drum 300 for forming the medium from which dyes imbedded therein are passed to the thermal print media 32 resting thereon, which process is described in detail herein below. In this regard, a media drive mechanism 110 is attached to each roll of dye donor material 34, and includes three media drive rollers 112 through which the dye donor material 34 of interest is metered upwardly into a media knife assembly 120. After the dye donor material 34 reaches a predetermined position, the media drive rollers 112 cease driving the dye donor material 34 and the two media knife blades 122 positioned at the bottom portion of the media knife assembly 120 cut the dye donor material 34 into dye donor sheet materials 36. The lower media roller 54b and the upper media roller 54b along with the media guide 56 then pass the dye donor sheet material 36 onto the media staging tray 60 and ultimately to the vacuum imaging drum 300 and in registration with the thermal print media 32 using the same process as described above for passing the thermal print media 32 onto the vacuum imaging drum 300. The dye donor sheet material 36 now rests atop the thermal print media 32 with a narrow gap between the two created by microbeads imbedded in the surface of the thermal print media 32. 
     A laser assembly 400 includes a quantity of laser diodes 402 in its interior, the lasers 402 are connected via fiber optic cables 404 to a distribution block 406 and ultimately to the printhead 500. The printhead 500 directs thermal energy received from the laser diodes 402 causing the dye donor sheet material 36 to pass the desired color across the gap to the thermal print media 32. The printhead 500 is attached to a lead screw 250 via the lead screw drive nut 254 and drive coupling 256 (not shown in FIG. 1) for permitting movement axially along the longitudinal axis of the vacuum imaging drum 300 for transferring the data to create the intended image onto the thermal print media 32. 
     For writing, the vacuum imaging drum 300 rotates at a constant velocity, and the printhead 500 begins at one end of the thermal print media 32 and traverse the entire length of the thermal print media 32 for completing the transfer process for the particular dye donor sheet material 36 resting on the thermal print media 32. After the printhead 500 has completed the transfer process, for the particular dye donor sheet material 36 resting on the thermal print media 32 the dye donor sheet material 36 is then removed from the vacuum imaging drum 300 and transferred out the image processor housing 12 via a skive or ejection chute 16. The dye donor sheet material 36 eventually comes to rest in a waste bin 18 for removal by the user. The above described process is then repeated for the other three rolls 30 of dye donor materials 34. 
     After the color from all four sheets of the dye donor sheet materials 36 have been transferred and the dye donor sheet materials 36 have been removed from the vacuum imaging drum 300, the thermal print media 32 is removed from the vacuum imaging drum 300 and transported via a transport mechanism 80 to a color binding assembly 180. The entrance door 182 of the color binding assembly 180 is opened for permitting the thermal print media 32 to enter the color binding assembly 180, and shuts once the thermal print media 32 comes to rest in the color binding assembly 180. The color binding assembly 180 processes the thermal print media 32 for further binding the transferred colors on the thermal print media 32 and for sealing the microbeads thereon. After the color binding process has been completed, the media exit door 184 is opened and the thermal print media 32 with the intended image thereon passes out of the color binding assembly 180 and the image processor housing 12 and comes to rest against a media stop 20. 
     Referring to FIG. 2, there is illustrated a perspective view of the lathe bed scanning subsystem 200 of the image processing apparatus 10, including the vacuum imaging drum 300, printhead 500 and lead screw 250 assembled in the lathe bed scanning frame 202. The vacuum imaging drum 300 is mounted for rotation about an axis X in the lathe bed scanning frame 202. The printhead 500 is movable with respect to the vacuum imaging drum 300, and is arranged to direct a beam of light to the dye donor sheet material 36. The beam of light from the printhead 500 for each laser diode 402 (not shown in FIG. 2) is modulated individually by modulated electronic signals from the image processing apparatus 10, which are representative of the shape and color of the original image, so that the color on the dye donor sheet material 36 is heated to cause volatilization only in those areas in which its presence is required on the thermal print media 32 to reconstruct the shape and color of the original image. 
     The printhead 500 is mounted on a movable translation stage member 220 which, in turn, is supported for low friction slidable movement on translation bearing rods 206 and 208. The translation bearing rods 206 and 208 are sufficiently rigid so that they do not sag or distort between their mounting points and are arranged as parallel as possible with the axis X of the vacuum imaging drum 300 with the axis of the printhead 500 perpendicular to the axis X of the vacuum imaging drum 300 axis. The front translation bearing rod 208 locates the translation stage member 220 in the vertical and the horizontal directions with respect to axis X of the vacuum imaging drum 300. The rear translation bearing rod 206 locates the translation stage member 220 only with respect to rotation of the translation stage member 220 about the front translation bearing rod 208 so that there is no over-constraint condition of the translation stage member 220 which might cause it to bind, chatter, or otherwise impart undesirable vibration or jitters to the printhead 500 during the generation of an intended image. 
     Referring to FIGS. 2 and 3, a lead screw 250 is shown which includes an elongated, threaded shaft 252 which is attached to the linear drive motor 258 on its drive end and to the lathe bed scanning frame 202 by means of a radial bearing 272. A lead screw drive nut 254 includes grooves in its hollowed-out center portion 70 for mating with the threads of the threaded shaft 252 for permitting the lead screw drive nut 254 to move axially along the threaded shaft 252 as the threaded shaft 252 is rotated by the linear drive motor 258. The lead screw drive nut 254 is integrally attached to the to the printhead 500 through the lead screw coupling 256 (not shown) and the translation stage member 220 at its periphery so that as the threaded shaft 252 is rotated by the linear drive motor 258 the lead screw drive nut 254 moves axially along the threaded shaft 252 which in turn moves the translation stage member 220 and ultimately the printhead 500 axially along the vacuum imaging drum 300. 
     As best illustrated in FIG. 3, an annular-shaped axial load magnet 260a is integrally attached to the driven end of the threaded shaft 252, and is in a spaced apart relationship with another annular-shaped axial load magnet 260b attached to the lathe bed scanning frame 202. The axial load magnets 260a and 260b are preferably made of rare-earth materials such as neodymium-iron-boron. A generally circular-shaped boss 262 part of the threaded shaft 252 rests in the hollowed-out portion of the annular-shaped axial load magnet 260a, and includes a generally V-shaped surface at the end for receiving a ball bearing 264. A circular-shaped insert 266 is placed in the hollowed-out portion of the other annular-shaped axial load magnet 260b, and includes an accurate-shaped surface on one end for receiving the ball bearing 264, and a flat surface at its other end for receiving an end cap 268 placed over the annular-shaped axial load magnet 260b and attached to the lathe bed scanning frame 202 for protectively covering the annular-shaped axial load magnet 260b and providing an axial stop for the lead screw 250. The circular shaped insert 266 is preferably made of material such as Rulon J or Delrin AF, both well known in the art. 
     The lead screw 250 operates as follows. The linear drive motor 258 is energized and imparts rotation to the lead screw 250, as indicated by the arrows, causing the lead screw drive nut 254 to move axially along the threaded shaft 252. The annular-shaped axial load magnets 260a and 260b are magnetically attracted to each other which prevents axial movement of the lead screw 250. The ball bearing 264, however, permits rotation of the lead screw 250 while maintaining the positional relationship of the annular-shaped axial load magnets 260, i.e., slightly spaced apart, which prevents mechanical friction between them while obviously permitting the threaded shaft 252 to rotate. 
     The printhead 500 travels in a path along the vacuum imaging drum 300, while being moved at a speed synchronous with the vacuum imaging drum 300 rotation and proportional to the width of the writing swath 450, not shown. The pattern that the printhead 500 transfers to the thermal print media 32 along the vacuum imaging drum 300, is a helix. 
     Referring to FIG. 4, there is illustrated an exploded view of the vacuum imaging drum 300. The vacuum imaging drum 300 has a cylindrical shaped vacuum drum housing 302 that has a hollowed-out interior portion 304, and further includes a plurality of vacuum grooves 332 and vacuum holes 306 which extend through the vacuum drum housing 302 for permitting a vacuum to be applied from the hollowed-out interior portion 304 of the vacuum imaging drum 300 for supporting and maintaining position of the thermal print media 32, and the dye donor sheet material 36, as the vacuum imaging drum 300 rotates. 
     The ends of the vacuum imaging drum 300 are closed by the vacuum end plate 308, and the drive end plate 310. The drive end plate 310, is provided with a centrally disposed drive spindle 312 which extends outwardly therefrom through a support bearing 314, the vacuum end plate 308 is provided with a centrally disposed vacuum spindle 318 which extends outwardly therefrom through another support bearing 314. 
     The drive spindle 312 extends through the support bearing 314 and is stepped down to receive a DC drive motor armature 316 (not shown), which is held on by means of a drive nut 340 (not shown). A DC motor stator 342 is stationary held by the late bed scanning frame member 202, encircling the DC drive motor armature 316 to form a reversible, variable DC drive motor for the vacuum imaging drum 300. At the end of the drive spindle 312 a drum encoder 344 is mounted to provide the timing signals to the image processing apparatus 10. 
     The vacuum spindle 318 is provided with a central vacuum opening 320 which is in alignment with a vacuum fitting 222 with an external flange that is rigidly mounted to the lathe bed scanning frame 202. The vacuum fitting 222 has an extension which extends within but is closely spaced from the vacuum spindle 318, thus forming a small clearance. With this configuration, a slight vacuum leak is provided between the outer diameter of the vacuum fitting 222 and the inner diameter of the central vacuum opening 320 of the vacuum spindle 318. This assures that no contact exists between the vacuum fitting 222 and the vacuum imaging drum 300 which might impart uneven movement or jitters to the vacuum imaging drum 300 during its rotation. 
     The opposite end of the vacuum fitting 222 is connected to a high-volume vacuum blower 224 which is capable of producing 50-60 inches of water at an air flow volume of 60-70 cfm. And provides the vacuum to the vacuum imaging drum 300 supporting the various internal vacuum levels of the vacuum imaging drum 300 required during the loading, scanning and unloading of the thermal print media 32 and the dye donor material 36 to create the intended image. With no media loaded on the vacuum imaging drum 300 the internal vacuum level of the vacuum imaging drum 300 is approximately 10-15 inches of water. With just the thermal print media 32 loaded on the vacuum imaging drum 300 the internal vacuum level of the vacuum imaging drum 300 is approximately 20-25 inches of water this level is required such that when a dye donor sheet material 36 is removed. The thermal print media 32 does not move otherwise color to color registration will be able to be maintained. With both the thermal print media 32 and dye donor sheet material 36 completely loaded on the vacuum imaging drum 300 the internal vacuum level of the vacuum imaging drum 300 is approximately 50-60 inches of water in this configuration. 
     The outer surface of the vacuum imaging drum 300 is provided with an axially extending flat 322 (as shown FIG. 5), which extends approximately 8 degrees of the vacuum imaging drum 300 circumference. The vacuum imaging drum 300 is also provided with donor support rings 324 which form a circumferential recess 326 which extends circumferentially from one side of the axially extending flat 322 circumferentially around the vacuum imaging drum 300 to the other side of the axially extending flat 322, and from approximately one inch from one end of the vacuum imaging drum 300 to approximately one inch from the other end of the vacuum imaging drum 300. 
     The thermal print media 32 when mounted on the vacuum imaging drum is seated within the circumferential recess 326, as shown in FIGS. 6a-6c. The donor support rings 324 have a thickness substantially equal to the thickness of thermal print media 32, approximately 0.004 inches. In one embodiment, donor support rings are movable axially to accommodate different sizes of thermal print media. The purpose of the circumferential recess 326 on the vacuum imaging drum 300 surface is to eliminate any creases in the dye donor material 36, as it is drawn down over the thermal print media 32 during the loading of the dye donor material 36. This ensures that no folds or creases will be generated in the dye donor sheet material 36 which could extend into the image area and seriously adversely affect the intended image. The circumferential recess 326 also substantially eliminates the entrapment of air along the edge of the thermal print media 32, where it is difficult for the vacuum holes 306 in the vacuum imaging drum 300 surface to assure the removal of the entrapped air. Any residual air between the thermal print media 32 and the dye donor sheet material 36, can also adversely affect the intended image. 
     Formed in the donor support rings 324 at the ends of the axially extending flat 322 are media contours 328. The axially extending flat 322 and the media contours 328 are somewhat the same, they assure that the leading and trailing ends of the dye donor material 36 are protected from the effect of increased air turbulence during the relatively high speed rotation that the vacuum imaging drum 300 undergoes during the image scanning process. Thus increased air turbulence will have less tendency to lift or separate the leading or trailing edges of the dye donor sheet material 36 off from the vacuum imaging drum 300, also the axially extending flat 322 and the media contours 328 ensure that the leading and trailing ends of the dye donor sheet material 36 are recessed from the vacuum imaging drum 300 periphery. This reduces the chance that the dye donor sheet material 36 can come in contact with other parts of the image processing apparatus 10, such as the printhead 500, this could cause a media jam within the image processing apparatus, resulting in the possible loss of the intended image or at worse catastrophic damage to the image processing apparatus 10 possibly damaging the printhead 500. 
     The media contours 328 support the corners of the dye donor material 36 as the dye donor material 36 is drawn down on the vacuum imaging drum, preventing flutes or air under the corners of the dye donor material 36 and insuring full contact with the vacuum imaging drum 300 surface. In the absence of media contour 328, a flute would be formed due to the interface of dye donor material 36, thermal print media 32, axially extending flat 322, and circumferential recess 326 which would cause both the thermal print media 32 and dye donor sheet material 36 to lift or separate off from the vacuum imaging drum 300. 
     Referring to FIG. 7, there is illustrated a plane view of the surface of the vacuum imaging drum 300 showing the media contours 328 used in multiple positions on the donor support rings 324 to provide the use of different lengths of the thermal print media 32 and dye donor sheet material 36 on the same drum 300. 
     Referring to FIG. 8, there is illustrated an exploded, perspective view of the vacuum imaging drum 300 utilizing the media contours 328 of the present invention with no axially extending flat 322. 
     Referring to FIG. 9, there is illustrated an exploded, perspective view of the vacuum imaging drum 300 utilizing the media contours 328 of the present invention arranged to hold a single sheet of thermal print media 32 with no donor support rings 324. The media contours 328 are formed in the surface of the vacuum imaging drum 300. The media contours 328 are at the opposed ends of axially extending flat 322. 
     Referring to FIG. 10, there is illustrated an exploded, perspective view of the vacuum imaging drum 300 utilizing the media contours 328 of the present invention arranged to hold a single sheet of thermal print media 32 without donor support rings 324. In this embodiment, an axially extending flat 322 is not used. The media contours 328 are formed in the surface of the vacuum imaging drum 300. 
     FIG. 11 shows a perspective view partially in section of a vacuum imaging drum showing the media contour 328 formed in donor support ring 324. The media contour 328 is at one end of axially extending flat 322. A similar media contour is found at the opposite end of the axially extending flat. FIG. 12 shows media contour 328 in phantom as a gradually extending slope in an axial direction starting circumferential recess 326, extending upward to the surface of donor support ring 324. FIG. 13 shows an end view of media contour 328 having a profile which is approximately concave at the edges. This configuration allows the naturally forming flute in a corner of the dye donor material to be pressed flat against the shape of the shoulder on the media contour 328. FIG. 14 shows an alternate embodiment wherein the edges of the media contour 328 are predominately concave. This configuration forces a reverse of the flute formed in the corners of the dye donor material. 
     FIG. 15 shows a perspective view of a section of the vacuum imaging drum showing the arrangement of the thermal print media 32 overlaid with the dye donor material 36. As the leading edge of dye donor material 36 is drawn down on axial extending flat 322, a flute would tend to form at a corner of dye donor material 36. Media contour 328 prevents the flute from forming. 
     The invention has been described with reference to the preferred embodiment thereof. However, it will be appreciated and understood that variations and modifications can be effected within the spirit and scope of the invention as described herein above and as defined in the appended claims. by a person of ordinary skill in the art without departing from the scope of the invention. For example, the invention is applicable to any drum. Also, the dye donor may have dye, pigments, or other material which is transferred to the thermal print media. Thermal print media includes paper, films, plates, and other material capable of accepting or producing an image. 
     Parts List 
     10. Image processing apparatus 
     12. Image processor housing 
     14. Image processor door 
     16. Donor ejection chute 
     18. Donor waste bin 
     20. Media stop 
     32. Thermal print media 
     34. Dye donor roll material 
     36. Dye donor sheet material 
     50. Sheet material trays 
     50a. Lower sheet material tray 
     50b. Upper sheet material tray 
     52. Media lift cams 
     52a. Lower media lift cam 
     52b. Upper media lift cam 
     54. Media rollers 
     54a. Lower media roller 
     54b. Upper media roller 
     56. Media guide 
     58. Media guide rollers 
     60. Media staging tray 
     80. Transport mechanism 
     100. Media carousel 
     110. Media drive mechanism 
     112. Media drive rollers 
     120. Media knife assembly 
     122. Media knife blades 
     180. Color binding assembly 
     182. Media entrance door 
     184. Media exit door 
     200. Lathe bed scanning subsystem 
     202. Lathe bed scanning frame 
     204. Entrance passageway 
     206. Rear translation bearing rod 
     208. Front translation bearing rod 
     220. Translation stage member 
     222. Vacuum fitting 
     224. Vacuum blower 
     250. Lead screw 
     252. Threaded shaft 
     254. Lead screw drive nut 
     256. Drive coupling 
     258. Linear drive motor 
     260. Axial load magnets 
     260a. Axial load magnet 
     260b. Axial load magnet 
     262. Circular-shaped boss 
     264. Ball bearing 
     266. Circular-shaped insert 
     268. End cap 
     270. Hollowed-out center portion 
     300. Vacuum imaging drum 
     302. Vacuum drum housing 
     304. Hollowed out interior portion 
     306. Vacuum hole 
     308. Vacuum end plate 
     310. Drive end plate 
     312. Drive spindle 
     314. Support bearing 
     316. DC drive motor armature 
     318. Vacuum spindle 
     320. Central vacuum opening 
     322. Axially extending flat 
     324. Donor support ring 
     326. Circumferential recess 
     328. Media contours 
     332. Vacuum grooves 
     344. Drum encoder 
     400. Laser assembly 
     402. Lasers diode 
     404. Fiber optic cables 
     406. Distribution block 
     450. Writing swath 
     454. Optical centerline 
     500. Printhead