Patent Publication Number: US-2007115249-A1

Title: Embedded location codes for e-brush position determination

Description:
The present invention generally relates to electrophoretic displays. The present invention specifically relates to location codes for writing an E-ink image onto electrophoretic display.  
      Electronic ink or E-ink as known in the art is formed from capsules that contain black negatively charged particles and white positively charged particles. In an electrophoretic display, the capsules are typically disposed between a pair of electrodes whereby an application of a voltage of a particular polarity can switch the system between black and white. Some known electrophoretic displays are optically addressable via an incorporation of a photoconductor layer between the electrodes. Upon illumination from a scanning laser beam, the photoconductor becomes a conductor and the E-ink can be switched between black and white via a voltage pulse. The combination of E-ink and photoconductor is known in the art as E-paint, and a hand held device known as an E-brush houses the illumination source.  
      In order to achieve a desired image in the E-ink, it is imperative that an E-brush has the capability of accurately determining its position relative to the E-ink. The present invention advances the art by providing an electronic ink stack employing a front electrode, a back electrode, an optical photoconductor layer, an electronic ink layer, and one or more location codes. The electronic ink layer is disposed between the front electrode and the back electrode. When employed, the photoconductor is also disposed between the front electrode and the back electrode. The location code(s) are embedded within the front electrode, the back electrode, and/or the photoconductor layer (if employed). 
    
    
      The foregoing forms as well as other forms, features and advantages of the present invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the present invention rather than limiting, the scope of the present invention being defined by the appended claims and equivalents thereof.  
       FIG. 1  illustrates one embodiment of an electronic paint system in accordance with the present invention;  
       FIG. 2  illustrates an exploded view of a first embodiment of an E-ink stack in accordance with the present invention;  
       FIG. 3  illustrates a side view of the E-ink stack illustrated in  FIG. 2 ;  
       FIG. 4  illustrates an exploded view of a first embodiment of an E-ink stack in accordance with the present invention;  
       FIG. 5  illustrates a side view of the E-ink stack illustrated in  FIG. 4 ;  
       FIG. 6  illustrates an exploded view of a first embodiment of an E-ink stack in accordance with the present invention;  
       FIG. 7  illustrates a side view of the E-ink stack illustrated in  FIG. 6 ;  
       FIG. 8  illustrates a flow chart representative of a method of providing various images in the E-ink stacks illustrated in  FIGS. 2-7 ;  
       FIG. 9  illustrates an exemplary graphical representation of one embodiment in accordance of the present invention of a voltage amplitude modulation for revealing and  
       FIG. 10  illustrates an exemplary graphical representation of one embodiment in accordance of the present invention of a voltage slope modulation for revealing. 
    
    
      An electronic paint system  20  as illustrated in  FIG. 1  employs a conventional monitor  30 , a conventional computer  40 , a conventional electronic brush  50 , and a conventional controller  60  as will be appreciated by those having ordinary skill in the art. Electronic paint system  20  further employs a new and unique electronic ink stack  70  having embedded location codes exemplarily represented by the dashed circles shown in  FIG. 1 . The embedded location codes enable a user of system  20  to accurately produce an E-ink image on electronic ink stack  70  as will be further explained in connection with a subsequent description of  FIG. 8  herein.  
      Each embodiment of electronic ink stack  70  in accordance with the present invention employs a front electrode, a back electrode and an electronic ink layer.  
      Each electrode is preferably fabricated from a reflective conductive material (e.g., aluminum, platinum, and chrome), or a transparent conductive material (e.g., indium tin oxide). The electronic ink layer is preferably one of several commercially available electrophoretic inks having thin electrophoretic film with millions of tiny microcapsules in which positively charged white particles and negatively charged black particles are suspended in a clear fluid.  
      Each embodiment of electronic ink stack  70  in accordance with the present invention can further employ a photoconductor layer (e.g.,) list examples of suitable material).  
      Location codes for electronic ink stack  70  are embedded within the front electrode, the back electrode, and/or the photoconductor layer (if employed.). In practice, the actual form, shape and dimensions of the location codes are dependent upon the intended commercial application of an embodiment of electronic ink stack  70 . Thus, the inventors of the present invention do not impose any restrictions as to the form, shape and dimensions of the embedded location codes, and do not assert any “best form”, any “best shape” or any “best” dimensions of the embedded location codes. Furthermore, the inventors of the present invention do not imposes any restrictions as to the coding scheme implemented by the location codes.  
       FIGS. 2-7  illustrate three exemplary embodiments of electronic ink stack  70 , which are not drawn to scale, but drawn to facilitate an understanding of the various principles of underlying the embedded location codes.  
      Referring to  FIGS. 2 and 3 , a first exemplary embodiment of electronic ink stack  70  employs a bottom electrode  71 , a photoconductor layer  72 , an electrophoretic ink layer  73 , and a front electrode  74 . Electronic ink stack  70  further employs embedded location codes in the form of insulation pads  75  disposed within photoconductor layer  72 . Insulation pads  75  function as local resistors. Accordingly, an application of a voltage V as illustrated in  FIG. 3  between electrodes  71  and  74  by controller  60  ( FIG. 1 ) establishes a voltage drop across photoconductor layer  72  and electrophoretic ink layer  73  in areas of photoconductor layer  72  between insulation pads  75 . Conversely, an application of the voltage V between electrodes  71  and  74  establishes a voltage drop across photoconductor layer  72 , insulation pad  75 , and electrophoretic ink layer  73  in areas of photoconductor layer  72  having insulation pads  75 .  
      Referring to  FIGS. 4 and 5 , a second exemplary embodiment of electronic ink stack  70  employs bottom electrode  71 , a photoconductor layer  76 , electrophoretic ink layer  73 , and a front electrode  74 . Electronic ink stack  70  further employs embedded location codes in the form of indentations  77  within photoconductor layer  76 .  
      Indentations  77  function to reduce the resistive strength of photoconductor layer  76  in areas of photoconductor layer  76  having indentations  77 . Accordingly, an application of a voltage V as illustrated in  FIG. 3  between electrodes  71  and  74  by controller  60  ( FIG. 1 ) establishes a voltage drop across photoconductor layer  76  and electrophoretic ink layer  73  whereby the resistance to the voltage drop is greatest in areas of photoconductor layer  76  between indentations  77 .  
      Referring to  FIGS. 6 and 7 , a third exemplary embodiment of electronic ink stack  70  employs bottom electrode  78 , a photoconductor layer  72 , electrophoretic ink layer  73 , and a front electrode  74 . Electronic ink stack  70  further employs embedded location codes in the form of holes  79  extending through back electrode  78 . Accordingly, an application of a voltage V as illustrated in  FIG. 6  between electrodes  78  and  74  by controller  60  ( FIG. 1 ) establishes a voltage drop across photoconductor layer  72  and electrophoretic ink layer  73  whereby the resistance to the voltage drop is greatest in areas of photoconductor layer  72  and electrophoretic ink layer  73  where electrodes  78  and  74  overlap.  
       FIG. 8  illustrates a flowchart  80  representative of a method of producing various images in the exemplary embodiments of electronic ink stack  70  illustrated in  FIGS. 2-7 .  
      Referring to  FIG. 8 , a blank image in the form a black blank image  90  or a white blank image  91  is produced during a stage S 82  of flowchart  80 . In one embodiment of stage S 82 , as illustrated in  FIGS. 9 , the voltage V applied to the electrodes during stage S 82  is in the form of erasing voltage pulse having a magnitude V E + for switching the electronic ink layer to an entirely black state to produce black blank image  90 , or to an entirely white to produce white blank image  91 .  
      In another embodiment, as illustrated in  FIG. 10 , the voltage V applied to the electrodes during stage S 82  is in the form of an erasing voltage pulse having a magnitude V O + for switching the electrophoretic ink layer to entirely black or entirely white.  
      Referring again to  FIG. 8 , a coded image in the form a black coded image  92  or a white coded image  93  is produced during a stage S 84  of flowchart  80 . In one embodiment of stage S 84 , as illustrated in  FIG. 9 , the voltage V applied to the electrodes during stage S 84  is in the form of coding voltage pulse having a magnitude V C1 − for switching areas of the electronic-eink layer corresponding to the embedded location codes, employing layer. The transition from the erasing voltage pulse V E + pulse to the coding voltage pulse V C1 − is appropriately sloped in  FIG. 9  in as would be appreciated by one having ordinary skill in the art  FIG. 9  to to thereby prevent all areas of the electronic ink layer from switching from black to white, or vice-versa.  
      In another embodiment of stage S 84 , as illustrated in  FIG. 10 , the voltage V applied to the electrodes during stage S 84  is in the form of a coding voltage pulse having a magnitude V C2O − for switching areas of the electronic ink layer corresponding to the embedded location codes. The transition from the erasing voltage V E + pulse to the coding voltage pulse V C1 − pulse is appropriately sloped in  FIG. 10  to prevent all areas of the electronic ink layer from switching from black to white, or vice-versa. Furthermore, the slope of the  FIG. 10  transition, which is greater than the slope of the  FIG. 9  transition, achieves the switching areas of the electronic ink layer not corresponding to the embedded location codes although the absolute magnitude of the applied voltage V remain unchanged, location.  
      Referring again to  FIG. 8 , a pictorial image, such as, for example, a pictorial image  94  is produced during a stage S 86  of flowchart  80 . In embodiments of stage. S 86 , as illustrated in  FIGS. 9 and 10 , the voltage V applied to the electrodes during stage S 86  is in the form of a writing voltage pulse having a magnitude voltage V W  that . Electronic brush  50  ( FIG. 1 ) is utilized during stage S 86  to create the appropriate grey levels within the pictorial image. To this end, electronic brush  50  is moved over the electronic ink stack whereby, after detection of location code, electronic brush  50  is operated to apply laser pulse(s) for creating the appropriate grey level(s) associated with the detected location codes. As known in the art, the creation of the appropriate grey level(s) is dependent upon the light intensity and/or pulse period of the laser pulse(s). As would be appreciated by those having ordinary skill in the art, t  
      While the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.