Abstract:
A substrate structure encoded with information bearing indicia includes a substrate having a first surface and a second surface. Formed on the first surface is a first information bearing indicia defined by a fluorescent material. A second information bearing indicia is defined by a fluorescent material positioned adjacent to the second surface, the second indicia and the first indicia in an overlapping relationship. The substrate structure includes apparatus for preventing interference between the first indicia and the second indicia during a detection process. The interference preventing apparatus can include reflective or absorptive coatings formed on the first and second surfaces of the substrate, the first and second information bearing indicia positioned on the respective reflective coatings, a thin metal foil layer positioned between the first indicia and the second indicia, or a black background disposed between the first and second indicia.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to application Ser. No. 09/443,400, entitled TAPE INDICIA ON CLEAR FILM MEDIA, filed Nov. 19, 1999, and to application Ser. No. 09/328,543, filed Jun. 9, 1999, entitled SYSTEM AND METHOD FOR CONTROLLING AN IMAGE TRANSFER DEVICE, the entire contents of which applications are incorporated herein by this reference. 
     TECHNICAL FIELD OF THE INVENTION 
     This invention relates to print media, and more particularly to techniques for marking media with fluorescent indicia readable by an inkjet printer, copier, facsimile machine, large format printer or other printing mechanism. 
     BACKGROUND OF THE INVENTION 
     Fluorescing compounds are a class of dyes that are rapidly finding their way into ink formulation and many other commercial applications. One feature of these compounds in ink systems (or other systems) is their ability to convey information by fluorescing at the region of the electromagnetic spectrum between 200 and 1100 nanometers. The ink with a low concentration of dye, when printed, is invisible to normal vision. It is used to mark paper (and other media) with indicia containing information. Upon exposure to the radiation of a specific wavelength, the dye component of the ink fluoresces at some specific, higher wavelength. The emitting radiation can be interpreted by appropriate detection where the resulting signals reveal coded information. 
       FIG. 1  is a diagrammatic, not to scale view showing a fluorescing ink forming an indicia  12  on a sheet of paper or other print medium  10 . An illumination light source  14  directs the excitation radiation  16  onto the ink indicia  12 . The ink emits fluorescent radiation  18  in response to the excitation, which is detected by the detector  20 . 
     Exemplary inks are described in co-pending application entitled LIGHT SENSITIVE INVISIBLE INK COMPOSITIONS AND METHODS FOR USING THE SAME, application Ser. No. 09/181,581, filed Oct. 28, 1998, the entire contents of which are incorporated herein by this reference. Exemplary systems for reading fluorescing ink indicia are described in co-pending application Ser. No. 09/181,589, filed Oct. 28, 1998, entitled INTEGRATED PRINTING/SCANNING SYSTEM USING INVISIBLE INK FOR DOCUMENT TRACKING. 
     It can be desirable to mark both sides of a sheet media with indicia. For example, marking both sides of a single sheet of media is useful on special ink jet media to determine media type, side to print on, media size, media orientation in the printer and other information. Such a print media indicia marking technique is described in above-referenced co-pending application TAPE INDICIA ON CLEAR FILM MEDIA. This application describes machine readable indicia formed on a tape applied to the leading edge or other locations of a clear or transparent print medium. In one example, indicia are placed on both sides of the tape. 
     When both sides of a sheet of media or an indicia-bearing tape as described in the above-referenced co-pending application are printed with fluorescing inks, reading from one side of the sheet can interfere with reading from the other side of the sheet. This occurs when the fluorescent radiation leaks through the sheet or tape from ink printed on the back of the sheet or tape. This is illustrated in  FIG. 2 , which shows respective indicia  12 A and  12 B applied on opposite sides of the sheet  10 , emitting respective fluorescent radiation  18 A and  18 B which is detected by the detector  20 . Since different information can be coded on each side of the sheet  10 , the detector will receive scrambled information and thus there will be confusion during the decoding process. 
     The leakage of emitting fluorescing radiation through a print medium or indicia-bearing tape changes the signal to noise ratio, which in turn requires more ink or ink containing more dye. This increases the visibility of marks and the cost of ink. Using a more sensitive detector also increases the cost of the detection system. 
     It would be advantageous to prevent this kind of leakage. A further advantage would be to provide a coding system in which an indicia-bearing tape applied to a transparent medium such as an overhead transparency has indicia readable from each side without interference from the indicia on the other side. 
     It would also be an advantage to provide a means of placing indicia which can be read from a simple, inexpensive detector. 
     SUMMARY OF THE INVENTION 
     A substrate structure encoded with information bearing indicia is described, and includes a substrate having a first surface and a second surface. Formed on the first surface is a first information bearing indicia defined by a fluorescent material. A second information bearing indicia is defined by a fluorescent material positioned adjacent to the second surface, the second indicia and the first indicia in an overlapping relationship. In accordance with an aspect of the invention, the substrate structure further includes means for preventing interference between the first indicia and the second indicia during a detection process. 
     In a first embodiment, the interference preventing means includes reflective or absorptive coatings formed on the first and/or second surfaces of the substrate, the first and second information bearing indicia positioned on the respective reflective coatings, the coatings reflecting and/or absorbing the excitation energy as well as the fluorescing energy. 
     In another embodiment, the interference preventing means includes a thin metal foil layer positioned between the first indicia and the second indicia. 
     In a further exemplary embodiment, the interference preventing means includes a black background disposed between the first and second indicia. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       These and other features and advantages of the present invention will become more apparent from the following detailed description of an exemplary embodiment thereof, as illustrated in the accompanying drawings, in which: 
         FIG. 1  is a diagrammatic view showing a fluorescing ink forming an indicia on a print medium or indicia tape, with an illumination light source directing excitation radiation onto the ink indicia, and a detector for detecting radiation fluorescing from the ink. 
         FIG. 2  shows respective indicia applied on opposite sides of a print medium or indicia tape, emitting respective fluorescent radiation which are detected by the detector. 
         FIG. 3  is a diagrammatic side view of a print medium with indicia on both sides thereof, and employing a first embodiment of a radiation blocking technique in accordance with the invention. 
         FIG. 4  is a diagrammatic side view of a print medium, wherein reflective (or absorptive) radiation blocking agents have been added to the paper during manufacturing. 
         FIG. 5  is a diagrammatic side view of a print medium in accordance with another embodiment of the invention, wherein a thin layer of a metal foil is sandwiched between two layers of paper or film, and respective indicia are formed on the paper or film layers. 
         FIG. 6  is a diagrammatic side view illustrating another embodiment of the invention, wherein a sheet of a print medium is laminated on both sides with black ink, paint or carbon to provide a black background to prevent leakage of radiation. 
         FIG. 7  illustrates an embodiment wherein a thin layer of a black background material is sandwiched between two layers of paper, and indicia are placed on the top layer and bottom layer. 
         FIG. 8  is a top view illustrating a sheet of transparent film print medium having applied to a leading edge a strip of indicia-bearing tape. 
         FIG. 9  is a simplified block diagram of a printer system with a sensor capable of reading the indicia and with indicia interpreting logic capable of interpreting the indicia and controlling printer operations. 
         FIG. 10  is a schematic frontal view of a printer employing roll media, which printer is adapted to employ the invention hereof. 
         FIG. 11  is a perspective view of a roll of transparent film media for use with the printer of  FIG. 10 , which bears an indicia-bearing opaque tape in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Several exemplary techniques in accordance with the invention are described to prevent leakage of fluorescing signals of fluorescing dyes through a print or tape medium.  FIGS. 3–7  illustrate techniques for preventing leakage through indicia-bearing tape materials, such as, for example, paper, polyester, polyethylene, polystyrene, which are then applied to a print medium, as illustrated in the referenced application, entitled TAPE INDICIA ON CLEAR FILM MEDIA. A first technique is to coat one or both sides of the tape with reflective or absorptive material(s). A second technique is to sandwich some reflective (or absorptive) material(s) between two layers of the tape to form a composite tape structure. A third exemplary technique is to place a black background under the indicia or between the first and second indicia. These exemplary techniques are now described in further detail. 
     One way to prevent radiation leakage is to coat one (or both) sides of the tape with some coating mixture that contains reflective or absorptive material(s), e.g., a white ink or coating mixture containing reflective material such as, Titanium (IV) Oxide (TiO2), Zinc Oxide (ZnO), Zirconium (IV) Oxide (ZrO2), aluminum oxide (AlO3), aluminum oxide hydroxide (AlO(OH)), aluminum trihydroxide (Al(OH)3), etc. Because of the reflective and/or absorptive nature of these materials, the fluorescing radiation is blocked and prevented from leakage. A typical coating mixture could be any combination of pigments (Alumina, Silica, etc.) and binders (polyvinyl alcohols, polyvinyl acetates, etc.), cellulosics materials (hydroxypropyl methyl cellulose, hydroxyethyl cellulose, etc.). 
     An exemplary embodiment is illustrated in  FIG. 3 , wherein an indicia-bearing tape structure  50  includes a tape  50  has an upper surface  52 A and a lower surface  52 B. In an exemplary embodiment, the tape has a width of 0.5 cm to about 0.9 cm, although this dimension can vary depending on the application. A first reflective (or absorptive) layer  54  is placed on surface  52 A. A second reflective (or absorptive) layer  56  is placed on surface  52 B. The layers  54  and  56  can comprise white ink (or coating mixture) that contains any or any combination of the above referenced reflective or absorptive material. The reflective (or absorptive) layers are formed with sufficient thickness to either scatter radiation back toward the detector or absorb the radiation. The indicia  58  and  60  are placed on layers  54  and  56  respectively. 
     In an exemplary embodiment, the tape structure  50  is applied to a leading edge of a sheet of print medium, such as a transparent polyester sheet, and the indicia provide data regarding characteristics of the print medium. For example, the tape structure can be applied to the sheet by an adhesive layer. The reflective (or absorptive) coating layers block the leakage of fluorescing radiation through the tape when indicia are radiated by a light source as shown in  FIG. 1 . 
     The reflective (or absorptive) radiation blocking agents of the embodiment of  FIG. 3  could alternatively be added to the tape during manufacturing, instead of or in addition to layers formed on the sheet. Such an embodiment is shown in  FIG. 4 , illustrating a tape structure  70  wherein the blocking agents  74  are added to the tape  72 , and then the indicia  76  and  78  are placed on the top and the bottom of the tape  70 . 
     Another embodiment for preventing radiation leakage through an indicia-bearing tape is illustrated in  FIG. 5 . Here, the structure  80  includes a thin (sufficient to provide a resistance of 1 ohm per square or sufficiently thick to scatter radiation) layer  82  of a metal (foil) such as aluminum sandwiched between two layers  84 A and  84 B of paper. Respective indicia  86  and  88  are formed on the paper layers. When used in an indicia detecting system as shown in  FIG. 1 , the aluminum layer  82  reflects the leaked fluorescing radiation back to the direction of the detector. It should be noted that the aluminum layer also reflects some of the emitted radiation toward the direction of indicia, thus increasing the fluorescing signals. 
     Another technique is to use a black background to prevent leakage of radiation. The tape structure  90  illustrated in  FIG. 6  includes tape  90  laminated on both sides with black ink (or paint or carbon)  94  and  96 . The thickness of the black background is sufficient enough to prevent radiation leakage. The indicia  98  and  100  are then placed on the surface of the respective black backgrounds  94  and  96 . In this technique, the black background absorbs unreflected radiation, and prevents scrambling of fluorescing radiation from two opposite sides of the paper. Alternatively, a tape structure  110  shown in  FIG. 7  includes a thin (sufficiently thick enough to prevent leakage) layer  112  of black background between two layers  114  and  116  of tape material. The indicia  118  and  120  are then placed on the top layer  114  and bottom layer  116 . 
     In an exemplary embodiment, the tape structure is prefabricated in a roll of tape material, from which are cut or slit respective tape strips in a desired width. The tape strips are then applied to respective sheets of the print media, e.g. along the leading edge. This is shown in  FIG. 8 , wherein a sheet  130  of a print medium such as a clear polyester used for overhead projection has applied along its leading edge  132  a strip  134  of a tape structure as illustrated in any of  FIGS. 3–7 , with indicia formed on each side of the tape. A layer of adhesive can be used to adhere the strip to the print media. Since the strip is of narrow width, the indicia on the respective sides will overlap in a direction normal to the sheet in a typical application. In such an exemplary application, the indicia on each side can extend the full length of the strip to avoid the need to register the position of the indicia relative to the sensor. 
     The indicia is applied to the tape structure by ink jet printing, or by other printing processes such as flexographic, letterpress, rotogravure, etc. 
     In an alternate embodiment, the tape structure is not employed, and the indicia are applied to at least one surface of the print medium. The reflective or absorptive material can be applied directly to a portion of the print medium, and the indicia printed onto the reflective or absorptive material, in a manner similar to that shown in  FIG. 3 , but with the print medium replacing the tape. Other alternative arrangements are contemplated, wherein the print medium replaces the tape material described in respective  FIGS. 4–7 . 
     An exemplary technique of reading indicia employs special fluorescent indicia placed on media with a special coding configuration, and a printer system with a sensor capable of reading the indicia and with indicia interpreting logic capable of interpreting the indicia and controlling printer operations. An exemplary printing system  250  is shown in simplified block diagram form in  FIG. 9 . Here, the system includes a controller  252 , sensor system  254 , carriage drive system  256 , media advance system  258  and inkjet printheads  260 . The controller in this exemplary embodiment is a microprocessor or ASIC, programmed to perform the functions to control elements shown in  FIG. 9 , in a manner known in the art. The controller  252  further is programmed to perform an indicia interpreting function  252 A, in response to the sensor signals received from the sensor system  254 , to read the data encoded by the indicia, and to adjust or set operating parameters of the printing system in response to the data for the particular medium  150 . Thus, the controller  252  operates the media advance system to advance the medium  150  from an input location past the sensor  254 . The sensor  254  is controlled to illuminate the medium with radiation of the appropriate wavelength range to excite the fluorescent ink forming the indicia, and to read the indicia in response to the excitation. The controller interprets this indicia using logic function  252 A, and then can perform the printing on the medium, taking into account the information read from the indicia. 
     The above-referenced application entitled SYSTEM AND METHOD FOR CONTROLLING AN IMAGE TRANSFER DEVICE describes an image transfer device which can also use a print media in accordance with this invention. 
     While the invention has been described above in the context of an inkjet printer or image transfer device which utilizes media in sheet form, the invention can be applied to other types of printers, e.g. printers that employ roll media or folded media.  FIGS. 10 and 11  illustrate an ink-jet plotter/printer which can use encoded transparent media as described above, but in roll form. 
     Referring to  FIG. 10 , printer  300  includes an inkjet printhead  302  which translates along a pair of slider bars  304  and  306  across the width of medium  308 . In the known manner, a controller  310 , by control signals causes printhead  302  to traverse along slider bars  304  and  306  and to eject ink droplets onto medium  308  which passes therebeneath. Media  308  passes over a roll  311  which positions media  308  accurately beneath printhead  302  for printing. Media  308  also passes over a cutter bar  312  which, in cooperation with a cutter  314  (similar to a pizza cutter), enables a transverse cut to be made across medium  308 . 
     Cutter  314  is mounted on a carrier  316  which is also mounted for sliding movement along slider bars  304  and  306 . When printhead  302  is moved into contact with carrier  316 , a coupling mechanism  318  enables carrier  316  to move along with printhead  302  and to cut off a section of medium  308 . 
     Referring to  FIG. 11 , a roll  320  of transparent medium  308  is shown, before mounting in printer  300 . In an exemplary embodiment, the leading edge of medium  308  includes an indicia-bearing tape  340 , which can take the form of any of the indicia-bearing tapes described above with respect to  FIGS. 3–7 . The indicia can identify, for example, the media type and size, and length. Alternatively, or additionally, the tape  340  can be disposed along a longitudinal edge of the medium  308 , as also shown in  FIG. 11 . In this longitudinal orientation, the indicia can identify, in addition to the media type and size, the remaining length of medium on the roll. Thus, at spaced intervals along the length, the indicia can identify a remaining length. With this arrangement, the remaining length information is readable by the printer controller, even after the roll has been partially used, removed from the printer, and later reinstalled in the printer for subsequent use. The tape can be placed along both longitudinal edges of the medium  308  to provide mechanical stability on the roll. 
     Sensor  324  is positioned to read the coded indicia formed on tape  340  as it passes thereover. Data read from the coded indicia is fed to controller  310 , which stores the data in a memory  328 . Controller  310  then utilizes the data derived from the indicia to set parameters for control of printer  300 , e.g. in accordance with the media type identified by the coded indicia. 
     Controller  310  further causes roller  311  to move the medium  308  a short distance so that the tape  340  passes the cutter bar  312 . Printhead  302  is then moved to engage carrier  316 . Thereafter, printhead  302  drags carrier  316  and cutter  314  across the medium  308 , cutting off the portion of medium  308  carrying the tape  340 . Normal printing/plotting then occurs. Alternatively, the tape can remain on the medium during printing, in an area which does not receive ink droplets. 
     It is understood that the above-described embodiments are merely illustrative of the possible specific embodiments which may represent principles of the present invention. Other arrangements may readily be devised in accordance with these principles by those skilled in the art without departing from the scope and spirit of the invention.