Patent Publication Number: US-7223031-B2

Title: Print ribbon panel color identification

Description:
The present application is based on and claims the benefit of U.S. Provisional Patent Application Ser. No. 60/502,836, filed Sep. 12, 2003, the content of which is hereby incorporated by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   Identification card printers commonly utilize thermal printheads and thermal print ribbon to transfer dye from the ribbon to the card substrate to form an image thereon. The print ribbon includes different color frames or panels along its length. The frames or panels repeat in a sequence or group consisting of a yellow panel, followed by a magenta panel, which is followed by a cyan panel. In addition, black resin and overlay panels can be provided in the sequence of the color panels, if desired. 
   Ribbon sensors are used to detect the various panels of the print ribbon. Ribbon sensors typically include an emitter and a receiver that are positioned on opposite sides of the ribbon. The light received by the receiver is analyzed to determine the color of the panel being sensed by the sensor. 
   Prior art ribbon sensors typically utilize emitters that include a single yellow light emitting diode (LED) to detect the color panels. The yellow LED produces light having a wavelength of approximately 587 nanometers. The receiver, in the form of a photodetector, has a broad visible light wavelength response. When the yellow light passes through the color dye panels it is partially blocked depending on the light wavelength blocking characteristics of the dye of the panel. For example, the cyan panel blocks more of the yellow light than the magenta panel, which blocks more of the yellow light than the yellow panel. 
   The output signal from the receiver varies in accordance with the light received through the panels. Accordingly, the light received by the receiver through each panel results in a different output signal. This variance in the output signal is used to determine the color of the panel being sensed by the sensor. 
   Unfortunately, the differences in the output signals for the passage of yellow light through some types of cyan and magenta panels can be very small, making it difficult to distinguish those panels from each other. This problem is exacerbated by the slightly different wavelength blocking characteristics of panels of print ribbons from different vendors. 
   SUMMARY OF THE INVENTION 
   The present invention generally relates to a sensor of a printer for identifying color panels of a print ribbon. In accordance with one embodiment of the invention, the sensor includes first and second emitters and a receiver. The first emitter is configured to transmit a yellow light signal and the second emitter is configured to transmit a blue light signal. The receiver is configured to produce an output signal in response to the reception of the yellow and blue light signals through a panel of a print ribbon, wherein the output signal is indicative of a color of the panel. Additional aspects of the present invention are directed to a printer that includes the above-described sensor. 
   Another aspect of the present invention is directed to a method of identifying panel colors of a print ribbon. In the method, a ribbon sensor is provided that includes a first emitter configured to transmit a yellow light signal, a second emitter configured to transmit a blue light signal, and a receiver. Next, the yellow and blue light signals are transmitted with the first and second emitters. The transmissions of the first and second light signals through a panel of the ribbon are then detected with the receiver. Finally, an output signal is produced by the receiver that is indicative of a color of the panel in response to the detection of the first and second light signals. 
   Other features and benefits that characterize embodiments of the present invention will be apparent upon reading the following detailed description and review of the associated drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of an identification card printer in accordance with embodiments of the invention. 
       FIG. 2  is a top plan view of a print ribbon and ribbon sensor in accordance with embodiments of the invention. 
       FIG. 3  is a front plan view of a print ribbon and a ribbon sensor in accordance with embodiments of the invention. 
       FIG. 4  is a front plan view of a print ribbon and a ribbon sensor in accordance with embodiments of the invention. 
       FIG. 5  is a chart illustrating the behavior of an output signal from the ribbon sensor of the present invention in response to the reception of blue and yellow light signals through different colored ribbon panels while the intensity of the blue light signal is held constant and the intensity of the yellow light signal is varied. 
       FIG. 6  is a flowchart illustrating steps of a method of identifying ribbon panel colors in accordance with embodiments of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a schematic diagram of an exemplary identification card printer  100  with which embodiments of the present invention are useful. In general, printer  100  includes a card input  102 , a card transport  104 , a printhead  106 , and a card output  108 . Cards  110  are received by the card transport  104  at the card input  102 . The card transport  104  feeds cards  110  individually along a print path  112 . The print path  112  is preferably substantially flat between card input  102  and card output  108  to avoid substantially bending the rigid or semi-rigid card substrates  110 . 
   The card transport  104  includes card feed rollers  114  that are driven by a motor  116  through, for example, conventional gear and pulley arrangements. It should be understood that separate motors can be used in different stages of card delivery through the printer  100 . For example, one motor  116  can be used to drive the feeding of the card  110  through the input  102 , and another motor  116  can be used to drive the feeding of the card  110  thereafter through the printer  100 . The card feed rollers  114  drive the card  110  along the print path  112 . Card support plates or rails (not shown) can also be used to provide support to the card  110  during transport along the print path  112  by the card transport  104 . 
   Printhead  106  is positioned adjacent print path  112  and includes a plurality of resistive heating print elements  118 . Although the printhead  106  is illustrated as being oriented such that the print elements  118  face upward, the printhead  106  can also be mounted in a more traditional manner in which the print elements  118  face downward. 
   In the exemplary identification card printer of  FIG. 1 , a supply of thermal print ribbon  120  extends between a supply spool  122  and a take-up spool  124 , and over the print elements  118 . The supply and take-up spools  122  and  124  are preferably positioned adjacent opposite sides of the printhead  106 . Print ribbon  120  can be contained in a removable ribbon cartridge. 
   During a printing operation, the card  110  is fed by the card transport  104  between the print ribbon  120  and a platen  132 . Pressure is applied to the print ribbon  120  and a print surface  134  of the card  110  by the platen  132  and the printhead  106 . The print elements  118  are selectively energized to heat portions of the print ribbon  120  in contact therewith to cause print material or dye from one or more panels of the print ribbon  120  to transfer to the surface  134  of card  110  to form the desired image thereon. The printed card  110  can then be discharged through the card output  108 . 
   Printer  100  includes a controller  140  that is configured to control the operations of the printer  100  including one or more motors  116  driving the card feed rollers  114  of the card transport  104 , one or more motors  142  controlling feeding of the print ribbon  120  between the supply and take-up spools  122  and  124 , the selective energization of the print elements  118  of the printhead  106 , and other components of printer  100 , in response to a print job provided by a card producing application  144 . 
   It should be understood that motors  116  and  142  provide a simplified illustration of the means by which the card transport  104  and supply and take-up rolls  122  and  124  are driven. Fewer or additional motors can be used as desired. Additionally, the motors  116  and  142  can operate to drive additional components than those depicted in  FIG. 1 . For example, the motor  142  can be configured to drive take-up roll  124  rather than supply roll  122 , or both. 
   The card producing application  144  can run on a computer  146 , or be contained in printer memory  148  for execution by controller  140 . The print job typically includes card processing instructions, such as print instructions, data writing instructions, data reading instructions, and other card processing instructions in accordance with normal methods. 
   Thermal print ribbon  120  includes multiple color frames or panels  150  along its length as shown in  FIG. 2 . The frames or panels typically repeat in a sequence or group consisting of a yellow panel, followed by a magenta panel, which is followed by a cyan panel. In addition, a black resin frame or panel can be provided in sequence of the color panels, if desired. 
   The printhead  106  selectively prints image lines to the surface  134  of card  110  from the panels of the ribbon  120  to form images thereon under the control of the controller  140 . Colored images are formed by transferring the dye from the different color panels to the surface  134  in an overlapping fashion. This process is made possible, in part, by ribbon sensor  152  of the present invention. 
   In general, ribbon sensor  152  is positioned adjacent print ribbon  120  and is configured to identify the different colored ribbon panels  150 . The controller  140  uses the information produced by the sensor  152  to align the desired colored dye panel with the print elements  118  of the printhead  106  to print a colored image. 
     FIG. 2  is a simplified top view of the sensor  152  adjacent ribbon  120  and  FIGS. 3 and 4  are simplified front views of sensor  152  adjacent print ribbon  120 , in accordance with embodiments of the invention. Sensor  152  generally includes dual emitters  154  and  156  and either one receiver  158  ( FIG. 3 ) configured to detect the light signals transmitted through the ribbon  120  by both emitters  154  and  156 , or dual receivers  158 A and  158 B ( FIG. 4 ) wherein receiver  158 A is configured to detect the light signal  160  from emitter  154  and receiver  158 B is configured to detect the light signal  162  from emitter  156 . 
   In accordance with one embodiment of the invention, the emitters  154  and  156  adjoin each other, as shown in  FIGS. 2 and 3 . The receivers are positioned on a side of the ribbon  120  that is opposite the side on which the emitters  154  and  156  are located in order to detect the light signals  160  and  162  transmitted by the emitters through the ribbon. For the single receiver configuration, the receiver  158  is preferably positioned immediately below the emitters  160  and  162 . For the dual receiver configuration, each receiver  158 A and  158 B is preferably positioned below the corresponding emitter  154  and  156 , respectively. 
   Emitters  154  and  156  are configured to transmit the light signals  160  and  162  having different wavelengths, or at least where each light signal has a primary energy level (i.e., peak intensity level) that is at a different wavelength than the other. The selection of the wavelengths of the light transmitted by the emitters is based upon the transmissivity of colored ribbon panels  150 , which are different for each color. The light transmitted by emitters  154  and  156  pass through print ribbon  120  and are received by receiver  158 , which produces an output signal  164  in response thereto. The object is to make use of the different transmissivities such that a difference in the light that is received by the one or more receivers  158  can be detected and thereby used to identify the colored panels  150 . 
   In accordance with one embodiment of the invention, the light signal  160  transmitted by the emitter  154  has a wavelength of greater than 500 nanometers (nm). Preferably, emitter  154  includes a yellow LED that is configured to transmit the light signal  160  as a yellow light signal having a wavelength of approximately 587 nm. The light signal  162  produced by emitter  156  preferably has a wavelength of less than 500 nm. In accordance with one embodiment of the invention, the emitter  156  includes a blue LED that is configured to transmit the light signal  162  as a blue light signal having a wavelength of approximately 468 nm. 
   The use of both the yellow and blue light signals allows the ribbon sensor  152  of the present invention to provide a relatively wide distribution of output signals  164  that are indicative of the yellow, magenta and cyan ribbon panels  150  as compared to ribbon sensors of the prior art that utilize only yellow light signals. This improvement allows for more accurate ribbon panel color identification. 
   The one or more receivers  158  can include photodetectors, such as a Sharp photodarlington detector, or other suitable detector. Each are configured to produce the output signal  164  in response to the detection of the light signals  160  and  162  transmitted through the ribbon  120  by emitters  154  and  156 . The output signal  164 , or a combination of the output signals  164 A and  164 B ( FIG. 4 ), is indicative of the intensity of the light that is transmitted through the subject panel  150 . 
   In accordance with one embodiment of the invention, the output signal  164  is analyzed by signal analyzer circuitry  170  to detect the color of the subject panel  150  by measuring a voltage across a resistance through which the output signal  164  is conducted. The resultant voltage signal has a magnitude that varies in response to the intensity of the light transmitted through the ribbon  120  that is received by the receiver  158  and the color of the subject ribbon panel  150 , as shown in  FIG. 5 . The signal analyzer utilizes voltage threshold detectors, comparators, etc. to determine where the output signal  158  lies within a predetermined voltage range, which then identifies the color of the subject panel  150 , in accordance with known methods. 
   As discussed above, the light signals  160  and  162  are selected to have different transmissivities through each of the ribbon panels such that the intensity of light received by the receiver  158  will be indicative of the color of the subject panel  150 . The yellow light signal emitted by the emitter  154  has the greatest transmissivity (i.e., substantially unblocked) through the yellow panel  150 A. The yellow light signal  160  has significantly lower transmissivities (i.e., substantially blocked) through the magenta panel  150 B and the cyan panel  150 C. On the other hand, the blue light signal  162  produced by emitter  156  has the greatest transmissivity through the cyan panel  150 C, a lower transmissivity through the yellow panel  150 A, and is mostly blocked by the magenta panel  150 B. 
   The differences in the transmissivity of the combined yellow and blue light signals  160  and  162  through the colored ribbon panels  150  allows for easy identification of the color of the panel  150  being analyzed. This is illustrated in the bar chart of  FIG. 5 , which shows voltages of the output signal from the receiver  158  (measured across a resistance) that are produced in response to the reception of the light signals  160  and  162  through yellow, magenta, and cyan colored panels  150 A– 150 C. The intensity of the blue light signal  162  was held constant while the intensity of the yellow light signal  160  was adjusted from a dim setting to a bright setting. As shown in  FIG. 5 , the output signal  164  has three distinct modes  170 A– 170 C that correspond to the reception by the receiver of the yellow and blue light signals  160  and  162  through the yellow, magenta, and cyan panels  150 A– 150 C that become more distinguishable (i.e., spread apart) as the intensity of yellow light signal  160  is increased. More particularly, the readings of the yellow panels  150 A become more displaced from the readings of the magenta panels  150 B as the intensity of the yellow light signal  160  is increased and while the intensity of the blue light signal  162  remains constant. 
   The large differences between the three modes  170 A– 170 C of the output signal  164  for the colored ribbon panels allow for more accurate ribbon panel color identification. The large spread also results in reduced sensitivity to color panel variations found between ribbon panels of different manufactures. 
   Another aspect of the present invention is directed to a method of identifying color panels of a print ribbon utilizing the ribbon sensor  152  described above.  FIG. 6  is a flowchart illustrating steps of the method, in accordance with embodiments of the invention. At step  180 , a ribbon sensor, such as ribbon sensor  152  described above, is provided. The ribbon sensor includes a first emitter  154  configured to transmit a yellow light signal  160 , a second emitter  156  configured to transmit a blue light signal  162 , and a receiver  158 . Next, at step  182 , the yellow and blue light signals  160  and  162  are transmitted with the first and second emitters  154  and  156 . The transmissions of the first and second light signals  160  and  162  through a panel  150  of the ribbon  120  are detected with the receiver  158 , at step  184 . Finally, at step  186 , an output signal  164  is produced by the receiver  158  that is indicative of a color of the panel  150  in response to the detection of the first and second light signals  160  and  162 . Additional embodiments of the method of the present invention include providing the sensor  152  with selected features discussed above. 
   Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.