Abstract:
In an internal drum scanner assembly having a curved platen for supporting media during exposure by a laser image scanner, media positioning apparatus comprising: a media feed device for feeding media onto the curved platen; and an assembly for pushing the media out of the feed device into the scanning region of the platen so that a borderless image can be produced on the media.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates in general to internal drum scanner assemblies and laser imaging systems incorporating such scanner assemblies. In particular, the present invention relates to a mechanism for aligning film into a scanning position in an internal drum type scanner assembly, suitable for use in a medical imaging system, where the entire film is accessible to a laser so that borderless images can be produced.  
         BACKGROUND OF THE INVENTION  
         [0002]    Laser imaging systems are commonly used to produce photographic images from digital image data generated by magnetic resonance (MR), computed tomography (CT) or other types of medical image scanners. Systems of this type typically include a continuous tone laser imager for exposing the image on photosensitive film, a film processor for developing the film, and control subsystems for coordinating the operation of the laser imager and the film processor.  
           [0003]    The digital image data is a sequence of digital image values representative of the scanned image. Image processing electronics within the control subsystem processes the image data values to generate a sequence of digital laser drive values (i.e., exposure values), which are input to a laser scanner. The laser scanner is responsive to the digital laser drive values for scanning across the photosensitive film in a raster pattern for exposing the image on the film.  
           [0004]    The continuous-tone images used in the medical imaging field have very stringent image-quality requirements. A laser imager printing onto transparency film exposes an image in a raster format, the line spacing of which must be controlled to better than one micrometer. In addition, the image must be uniformly exposed such that the observer cannot notice any artifacts. In the case of medical imaging, the observers are professional image analysts (e.g., radiologists).  
           [0005]    Film exposure systems are used to provide exposure of the image on photosensitive film. Known film exposure systems include a linear translation system and a laser or optical scanning system. The laser scanning system includes a laser scanner with unique optical configurations (i.e., lenses and mirrors) for exposure of the image onto the film. The linear translation system provides for movement of the laser scanning system in a direction perpendicular to the scanning direction, such that a full image may be scanned on a piece of photosensitive film.  
           [0006]    In an internal drum type laser scanner assembly, a piece of film is positioned onto a film platen, wherein the film platen has a partial cylindrical or partial drum shape. The photosensitive film is positioned against the film platen. The laser or optical scanning system is positioned at the center of curvature of the photosensitive film for scanning a scan line across the photosensitive film surface. A linear translation system moves the laser or optical scanning system lengthwise along a longitudinal axis as defined by the center of curvature of the film to expose an entire image onto the film.  
           [0007]    The film may be fed onto the film platen utilizing a film transport system which often incorporates a plurality of feed rollers. Once the piece of photosensitive film is fed onto the film platen, the film must be held tight against the curved surface of the film platen, and centered and aligned into a scanning position in order for an image to be correctly exposed onto the photosensitive film. Any skew of the film must also be removed. Often such methods and mechanisms for aligning and centering a piece of film on the internal surface of the film platen require multiple complex mechanical and electrical components and control systems.  
           [0008]    U.S. Pat. No. 5,956,071, issued Sep. 21, 1999, inventors Mattila et al., and U.S. Pat. No. 6,342,914, issued Jan. 29, 2002, inventors Johnson et al. disclose positioning a film into a scanning position on a curved film platen in an internal drum scanner assembly. After the leading edge of the film is properly positioned, the rear edge is held in the nip of feed rollers during film scanning by a laser. Thus, a narrow border of the film in the film nip cannot be imaged. It is thus desirable to provide an internal drum scanner that can produce a borderless film.  
         SUMMARY OF THE INVENTION  
         [0009]    According to the present invention, there is provided a solution to these problems.  
           [0010]    According to a feature of the present invention, there is provided in an internal drum scanner assembly having a curved platen for supporting media during exposure by a laser image scanner, media positioning apparatus comprising: a media feed device for feeding media onto said curved platen; and an assembly for pushing said media out of said feed device into the scanning region of said platen so that a borderless image can be produced on said media.  
         ADVANTAGEOUS EFFECT OF THE INVENTION  
         [0011]    The invention has the following advantages.  
           [0012]    1. An internal drum scanner assembly is provided that can produce a borderless film. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a front isometric view of an internal drum assembly including the present invention.  
         [0014]    [0014]FIG. 2 is a front isometric view of the present invention.  
         [0015]    [0015]FIGS. 3 a  and  3   b  are isometric views of the finger-carriage assembly of the invention of FIG. 1.  
         [0016]    [0016]FIG. 4 is an isometric view of the present invention excluding film guides and some rollers to show internal components.  
         [0017]    [0017]FIG. 5 is a cross-sectional elevational view of the present invention with film entering.  
         [0018]    [0018]FIGS. 6 a  and  6   b  are a cross-sectional elevational views of the present invention with film passing the film position sensor.  
         [0019]    [0019]FIG. 7 is a cross-sectional front view of the present invention with the trailing edge of the film at the last roller set.  
         [0020]    [0020]FIGS. 8 a  and  8   b  are cross-sectional elevational views of the present invention with the fingers pushing the film into the imaging region of the cylinder.  
         [0021]    [0021]FIG. 9 is a cross-sectional elevational view of the present invention demonstrating the finger motor over travel.  
         [0022]    [0022]FIGS. 10 a  and  10   b  are isometric views of the present invention showing the operation for one size film.  
         [0023]    [0023]FIGS. 11 a  and  11   b  are isometric views of the present invention showing the operation for another size film.  
         [0024]    [0024]FIG. 12 is a rear isometric view of an internal drum assembly. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    [0025]FIG. 12 is a rear isometric view of internal drum assembly including a film platen  20  and platen registration bar assembly  10 , a bar  2  attached to a pair of large gears  4  and five independently spring-loaded sliders  1 . A geared motor  3  actuated by control system  100  locates the bar by rotating the large gears, synchronized with a pair of gears  6  attached to a rod  5 . Assembly  10  is able to deskew films ranging in lengths from 18 cm. to 43 cm. and in widths of both 25 cm. and 36 cm.  
         [0026]    Assembly  10  is mounted for movement on a horizontally oriented concave curved film platen  20  having first and second horizontal edge regions  22 ,  24  and third and fourth curved side regions  26 ,  28  connected between said first and second edge regions  22 ,  24 . The concave, curved film platen has a curved surface  30  defining a film path from first edge region  22  to second edge region  24 . Platen  20  is preferably cast aluminum and has arcuate slots  32  in which said sliders  1  are slidably mounted. When a film is fully positioned on platen  20  bar  2  and sliders  1  establish the location of the leading edge of the film.  
         [0027]    Referring now to FIG. 1, there is shown the internal drum assembly of FIG. 12 form the front and including an embodiment of the present invention. As shown, a film  40  has been positioned on curved platen  20  by film (media) feed device  42  which includes feed roller set  44  and independently spring loaded fingers  46 . As will be described in greater detail below, fingers  46  have been rotated into the film path and moved vertically through segmented roller set  44  to push film  40  into the scanning region of platen  20 . Scanning is represented by laser beam  48  which is rotated about axis  50  and translated the length of film  40  to expose film  40  in a raster pattern of a digital image.  
         [0028]    [0028]FIG. 2 is an isometric view of film feed device  42  including a platen finger assembly. Film feed device  42  includes leading edge guide  50 , film guide  52 , segmented drive roller  54 , drive roller  56 , rollers  58 ,  60 , film position sensor  61 , segmented roller set  44  including rollers  64 ,  66 , roller drive stepper motor  68 , linear stepper motor  70  coupled to bracket  72 . Using a leading edge guide  50  in combination with a solid drive roller  56  acting as an entrance guide reduces the probability of film scratching. A segmented drive roller  54  prevents the trailing portion of the film from slapping the leading edge guide  52  after leaving the vertical transport. The film enters a roller set  58 ,  60  which is necessary to maintain the roller set pitch required to transport smaller film sizes, and is then constrained by another film guide  52 . The two film guides  50 ,  52  constrain the film path to properly actuate the film position sensor  62  and ensure proper feeding into the segmented roller set  64 ,  66 . The stepper motor  63  driving the rollers stops shortly after the trailing edge of film  40  passes the sensor  61 . A linear stepper motor pulls a bracket  72  downward. The bracket  72  interlocks with the finger carriages  74 . Drawer slides  76 , constrain the bracket&#39;s motion vertically.  
         [0029]    An important advantage of this invention is the ability to produce a borderless image in a small diameter scanning cylinder by using five independently spring loaded fingers to push the film out of the roller set and into the scanning region of the platen.  
         [0030]    [0030]FIGS. 3 a  and  3   b  show a platen finger assembly including a finger  46  rotatably mounted on pin  80  of carriage  74 . Carriage  74  slides on shafts  82 , torsion spring  84  loading the finger  46  against the carriage  74 . This spring  84  spring-loads the finger  46  into the film path. The finger  46  rotates about a pin  80 . The cam surface  85  on the finger serves to rotate the finger  46  out of the film path at the home position. Two shafts  82  constrain each carriage  74  to translate linearly in the vertical direction (parallel to the film path). An extension spring  86  provides the independent spring-loading aspect of the mechanism. This spring  86  acts as a tolerance accumulator, allowing all the intended fingers  46  (number depends on film width) to apply pressure to the film.  
         [0031]    [0031]FIG. 4 shows the platen finger assembly without the film guides and some of the rollers. The bottom segmented idler roller  64  has a larger diameter to allow the fingers  46  to pass through the segmented regions as shown. The fingers  46  rotate out of the film path when the flag  90  interrupts the finger home sensor  62 .  
         [0032]    The platen finger assembly operates using one rotational stepper  68  to turn the rollers, one linear stepper  70  to actuate the fingers, and two sensors  61 ,  62  (one  61  for film detection and one  62  for finger position). The sequence of operations begins with input from software indicating a film is approaching the platen as a result of a signal from sensor  61 . The rotational stepper motor  68  turns the rollers with a tangential velocity of, for example 20 inches per second. FIG. 5 shows a cross-sectional view of the platen finger assembly with a film  40  approaching the film position sensor  61 . The entrance guide roller  56  ensures a scratch free handoff between the vertical assembly and the platen  20 . The linear stepper motor  70  holds the fingers  46  in the home position, indicated by the flag  71  attached to the bracket  72  blocking the optical sensor  62 . As mention earlier, carriages  74  interlock with the bracket  72  and transport the fingers  46 , which are spring loaded with torsion springs  74 . The fingers  46  are in the home position, which is outside of the film path, behind the film guide.  
         [0033]    The film  40  is actuating the film position sensor  62  in FIG. 6 a . The exit guide roller  54  prevents the tail edge of the film from slapping against a sheet metal edge or bend, which helps eliminate scratches on the film surface. The rollers continue to turn as software waits for the film  40  to clear the film position sensor  61 , see FIG. 6 b . Control system  100  continues to turn the rollers until the trailing edge reaches the last roller set  64 ,  66  based on timing, see FIG. 7. The sequence of operations and timing used to determine trailing edge placement in the roller set  64 ,  66  is independent of film size, since the film position sensor  61  checks for the trailing edge of the film  40 .  
         [0034]    The rollers  64 ,  66  stop turning and the linear stepper motor  70  moves the finger-carriages  74  downward, such that the fingers  46  rotate into the film path and the bottom surface of fingers  46  is perpendicular to the film  40  as depicted in FIG. 8 a . The linear stepper motor  70  continues to pull the fingers  46  downward, which travel linearly without further rotation, and the fingers  46  register with the platen  40  surface as shown in FIG. 8 b  pushing film  40  out of the nip of rollers  64 ,  66  so that film  40  can be exposed to a borderless image.  
         [0035]    The linear stepper motor  70  has a small over travel, which allows each finger  46  to individually register to the platen  40  surface (via the spring loaded constraint with the bracket  74 ). The gap  110  in FIG. 9 occurs as the bracket  74  continues to travel downward after the finger registers with the platen surface. This additional travel made by the bracket  74  is possible with the use of the use of the extension springs  86 .  
         [0036]    The platen finger assembly contains five fingers  46  in an attempt to apply a distributed force to the trailing edge of the film  40 . Experimental results indicated that a solid finger across the entire trailing edge of the film is optimal and support is required near the corners. This design ensures that there are at least three fingers  46  on each film size, one in the middle and near each corner. All five fingers  46  engage the film for film widths of 36 cm for example. FIG. 10 shows the operation for 25 cm film for example, and FIG. 11 for 36 cm wide film, for example.  
         [0037]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.  
       Parts List  
       [0038]    [0038] 1  spring-loaded sliders  
         [0039]    [0039] 2  bar  
         [0040]    [0040] 3  geared motor  
         [0041]    [0041] 4  pair of large gears  
         [0042]    [0042] 5  rod  
         [0043]    [0043] 6  pair of gears  
         [0044]    [0044] 10  platen registration bar assembly  
         [0045]    [0045] 20  curved film platen  
         [0046]    [0046] 22 , 24  first and second edge regions  
         [0047]    [0047] 26 , 28  third and fourth edge regions  
         [0048]    [0048] 30  curved surface  
         [0049]    [0049] 32  arcuate slots  
         [0050]    [0050] 40  film (media)  
         [0051]    [0051] 42  film (media) feed device  
         [0052]    [0052] 44  feed roller set  
         [0053]    [0053] 46  fingers  
         [0054]    [0054] 48  laser beam  
         [0055]    [0055] 50  leading edge guide  
         [0056]    [0056] 52  film guide  
         [0057]    [0057] 54  segmented drive roller  
         [0058]    [0058] 56  drive roller  
         [0059]    [0059] 58 , 60  rollers  
         [0060]    [0060] 61  film position sensor  
         [0061]    [0061] 62  finger position sensor  
         [0062]    [0062] 64 , 66  rollers  
         [0063]    [0063] 68  roller drive stepper motor  
         [0064]    [0064] 70  linear stepper motor  
         [0065]    [0065] 72  bracket  
         [0066]    [0066] 74  finger carriage  
         [0067]    [0067] 76  drawer slides  
         [0068]    [0068] 80  pin  
         [0069]    [0069] 82  shaft  
         [0070]    [0070] 85  cam surface  
         [0071]    [0071] 86  extension spring  
         [0072]    [0072] 90  flag  
         [0073]    [0073] 100  control system  
         [0074]    [0074] 110  gap