Patent Publication Number: US-2006012665-A1

Title: Print media and photo printer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit under b  35  U.S.C. § 119(a) of Korean Patent Application No. 10-2004-0054702, filed on Jul. 14, 2004, in the Korean Intellectual Property Office, the entire disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a print media and a photo printer. More particularly, the present invention relates to a print media that has marks formed on one side, and a photo printer that includes means for measuring the distance the print media travels by detecting the marks on the print media.  
      2. Description of the Related Art  
      Thermal photo printers can be classified into two types of printer. One type uses paper that responds to heat to show a predetermined color on the paper. The other type uses an ink ribbon which responds to heat and transfers the ink (which is a predetermined color) to a typical sheet of paper. Photo printers using an ink ribbon need to have a driver for driving the ink ribbon, leading to complex structures and high costs. Further, since the ink ribbon is consumable, it must be replaced with a new one periodically, thereby causing high printing costs per sheet.  
      Referring to  FIG. 1 , a print media  10 , which responds to heat to show a predetermined color, includes a base sheet  11  having a first surface  10   a  and a second surface  10   b  on which ink layers of predetermined colors are formed. The ink layers have different colors. For example, layers of yellow Y and magenta M are sequentially stacked on the first surface  10   a,  and a layer of cyan C is formed on the second surface  10   b.  It is preferable that the base sheet  11  is made of transparent material. A reflective or transparent layer  13  may be formed on the layer of cyan C. An example of the print media  10  is disclosed in U.S. patent Publication No. 2003-0125206, which is hereby incorporated by reference in its entirety.  
      A photo printer using the print media  10  employs a thermal printhead (TPH) having heating elements arranged perpendicular to a path of the print media  10  in a horizontal resolution.  
       FIG. 2  is a diagram illustrating a conventional photo printer. Referring to  FIG. 2 , the conventional photo printer includes a feed roller  2  for feeding the print media  10 , a platen roller  3  for supporting one surface of the print media  10 , and a TPH  4  for forming an image on the print media  10  supported by the platen roller  3 . An encoder disk wheel  7  is installed on one side of the feed roller  2 . An encoder sensor (not shown) detects slits  7   a  formed on the encoder disk wheel  7  to measure the travel distance, that is, the distance that the print media  10  travels.  
      Since the encoder disk wheel  7  indirectly measures the travel distance of the print media  10 , it is difficult to exactly measure the travel distance due to slippage of the print media  10 . Further, the encoder disk wheel, which is relatively large, hinders the manufacturing of a more compact photo printer.  
      Accordingly, there is a need for a thermal printer with an improved apparatus for measuring the travel distance of a print media.  
     SUMMARY OF THE INVENTION  
      An aspect of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide a print media and a photo printer which can directly measure a travel distance of the print media.  
      According to an aspect of the present invention, a print media for a photo printer comprises a printing area and a mark area formed at one side of the printing area. The mark area has first marks at regular intervals in a printing direction.  
      A printing start mark representing a printing start position may be formed in the mark area.  
      At least one second mark having a length different in the printing direction from that of the first marks may be formed in the mark area.  
      The second mark may be longer than that of the first marks in the printing direction, and the printing start position may correspond to a first mark formed after the second mark.  
      A tear line may be formed between the printing area and the mark area.  
      The first marks may be formed at a resolution of 100 to 300 dpi in the printing direction.  
      The print media may further comprise first and second tab areas formed on both end portions of the printing area, respectively.  
      Tear lines may be formed between the printing area and the first tab area and between the printing area and the second tab area, respectively.  
      According to another aspect of the present invention, a print media comprises a transparent base sheet, a mark area having first marks formed at regular intervals in a printing direction at one side of the transparent base sheet, and a printing area having layers stacked on both surfaces of the transparent base sheet (at locations other than the mark area). The layers can respond to heat and display predetermined colors.  
      According to still another aspect of the present invention, a photo printer comprises a thermal printhead applying heat to a print media to display predetermined colors, a feed roller feeding the print media, a feed roller motor driving the feed roller, a mark detecting unit detecting marks that are formed at predetermined intervals in a printing direction at one side of the print media, and a control unit controlling the feed roller motor using signals detected by the mark detecting unit to feed the print media.  
      The mark detecting unit may be a reflective optical sensor.  
      The print media may include a transparent base sheet, a mark area having the marks formed on the transparent base sheet, and a printing area having layers that are formed on surfaces of the transparent base sheet (at locations other than the mark area). The layers respond to heat applied by the thermal printhead to display the predetermined colors. The mark detecting unit may be a transparent optical sensor composed of a light emitting unit and a light receiving unit formed over and under the mark area, respectively.  
      The photo printer may further comprise a puncher forming a tear line between the mark area, where the marks are formed, and the printing area, where printing is done, when the print media is discharged.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects, features, and advantages of certain embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:  
       FIG. 1  is a sectional view of a conventional print media;  
       FIG. 2  is a diagram of a conventional photo printer;  
       FIG. 3  is a diagram of a photo printer according to an embodiment of the present invention;  
       FIG. 4  is a plan view of a print media according to an embodiment of the present invention;  
       FIG. 5  is a diagram illustrating waveforms of detected pulse signals for explaining a method of dividing and using the signals;  
       FIG. 6  is a schematic plan view illustrating some elements of the photo printer shown in  FIG. 3 ;  
       FIG. 7  is a schematic side view of the elements shown in  FIG. 6 ;  
       FIG. 8  is a block diagram of a printing control system of a photo printer according to an embodiment of the present invention;  
       FIG. 9  is a plan view of a print media according to another embodiment of the present invention;  
       FIG. 10  is a sectional view of a print media according to still another embodiment of the present invention; and  
       FIG. 11  is a block diagram of a printing control system of a photo printer according to another embodiment of the present invention. 
    
    
      Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features, and structures.  
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
      The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.  
       FIG. 3  is a diagram of a photo printer according to an embodiment of the present invention. As shown in  FIG. 3 , a photo printer includes at least three paths through which a print media  10  is conveyed. The print media  10  is conveyed through the first path to the second path. In the second path, the print media  10  is moved backward in the direction indicated by the arrow B and is moved forward in the direction indicated by the arrow F to print on the print media  10 . After printing, the print media  10  goes through the third path. To elaborate, if only the first surface of the print media  10  has been printed on, the print media  10  is returned to the second path from the third path so that the second surface may be printed on. If both the first and second surfaces of the print media  10  have been printed on, the print media  10  is discharged through the third path.  
      A guide  65  is interposed between the first path and the third path. The guide  65  guides the print media  10  from the first path to the second path, and guides the print media  10  from the second path to the third path. Further, the guide  65  only allows the print media  10  on the second path to be conveyed to the third path. That is, it prevents the print media  10  from being conveyed from the second path to the first path.  
      An image forming process is performed using an image forming unit  50  in the second path. Before the image forming process is performed on the first and second surface of the print media  10 , the positions of a thermal printhead (TPH)  51  and a platen roller  55  of the image forming unit  50  should be determined. For example, if the image forming process is being performed on the first surface of the print media  10 , the TPH  51  should be placed at the position C. On the other hand, if the image forming process is being performed on the second surface of the print media  10 , the TPH  51  should be placed at the position D. It is preferable that the position change of the TPH  51  be accomplished by rotating the platen roller  55  and the TPH  51  about an axis of the platen roller  55 . The position change of the TPH  51  is made when there is no interference between the TPH  51  and the print media  10 , such as before the print media  10  is supplied from the first path to the second path or before the print media  10  that has been conveyed to the third path after printing on the first surface is returned to the second path.  
      If the print media  10  having a printed first surface is fed back to the second path, an image forming process is performed on the second surface of the print media  10  by the TPH  51  whose position has been changed to position D. During the process, the print media is gradually moved by a conveying unit  40 . After the second surface is completely printed, the print media  10  is discharged through a print media discharging unit  60 . The conveying unit  40  includes a feed roller  41  for feeding the print media  10  and an idle roller  42  for pushing the print media located between the feed roller  41  and the idle roller  42  toward the feed roller  41 .  
      Reference numeral  70  denotes a print media storing unit, and reference numeral  72  denotes a pickup roller for the print media supply.  
      The print media discharging unit  60  includes a discharging roller  61  and an idle roller  62 . The discharging roller  61  and the pickup roller  72  may be disposed so that one roller performs the functions of both rollers  61  and  72 .  
       FIG. 4  is a plan view of a print media according to an embodiment of the present invention. Referring to  FIG. 4 , a print media  110  includes a printing area  101 , a top tab area  102  and a bottom tab area  103 , which extend from both end portions of the printing area  101 , respectively, and a mark area  104 , which has marks  104   a  formed lengthwise at one side of the print media  110  at predetermined regular intervals. When a photo-image is printed on the print media  110 , the printed image may be slightly larger than the printing area  101  as shown by box  105  in  FIG. 4 . After the image is printed, the top tab area  102 , the bottom tab area  103 , and the mark area  104  are cut off along tear lines  106   a,    106   b,  and  106   c  to obtain a borderless photo-image.  
      The print media  110  is available in various standard sizes, for example, 4″×6″, 3″×5″, postcard size, and A6. If the print media  110  is smaller than a printed image, the whole image cannot be printed. Conversely, if the print media  110  is larger than the printed image, a borderless output cannot be obtained.  
      The marks  104   a  may be formed at a resolution of 100 to 300 dpi. If the marks  104   a  are formed at a resolution of 300 dpi, the marks  104   a  can be used at a resolution of 1200 dpi by dividing a pulse signal, which is generated when the marks  104   a  are detected by a sensor, into two parts and dividing a space between adjacent pulse signals into two parts (refer to  FIG. 5 ).  
       FIG. 6  is a schematic plan view illustrating some elements of the photo printer shown in  FIG. 3 .  FIG. 7  is a schematic sectional view illustrating the elements shown in  FIG. 6 . Referring to  FIGS. 6 and 7 , the print media  110  which is gripped between the platen roller  55  and the TPH  51  is moved by the feed roller  41 .  
      The print media  110  is moved by the feed roller  41  in a feedback direction indicated by the arrow B and in a printing direction indicated by the arrow F. A reflective optical sensor  53  is installed above the mark area  104 . A light emitting unit of the optical sensor  53  emits light at a predetermined speed, and a light receiving unit of the optical sensor  53  generates pulse signals to detect the marks. A control unit  80  counts the pulse signals to measure the travel distance of the print media  110  that is moved by the feed roller  41 , and controls the travel distance of the print media  110  moved by the feed roller  41  by driving a feed roller motor  47 . If the number of counted pulse signals from the optical sensor  53  reaches a predetermined number, the control unit  80  outputs a signal for firing heating elements  52  of the TPH  51 .  
      The photo printer includes a rotating unit  57  for rotating the TPH  51  and the platen roller  55  to print on the second surface after the first surface of the print media  110  is printed and a lifting unit  59  for lifting or lowering the TPH  51  a predetermined height above the printing path. When the print media  110  is fed back, the lifting unit  59  lifts the TPH  51  from the platen roller  55  a predetermined distance, for example, 1 to 2 mm, so that the print media  110  can easily pass between the TPH  51  and the platen roller  55 .  
      Since the marks  104   a  formed on the print media  110  are detected using the optical sensor  53  when the print media  110  travels, an actual travel distance of the print media  110  can be measured.  
       FIG. 8  is a block diagram of a printing control system of a photo printer according to an embodiment of the present invention. Referring to  FIG. 8 , the printing control system includes a control unit  200 , a mark detecting unit  210 , a TPH driver  220 , a TPH  230 , a feed roller driver  240 , and a feed roller motor  250 .  
      The mark detecting unit  210  detects marks formed at one side of a print media and outputs detecting signals to the control unit  200 .  
      The control unit  200  drives the feed roller driver  240  and controls the feed roller motor  250  in response to the detecting signals output from the mark detecting unit  210 . Further, if the number of accumulated detecting signals reaches a predetermined number, the control unit  200  drives the TPH driver  220  and transmits a driving signal to the TPH  230  so that the TPH  230  can apply heat to the print media. That is, the control unit  200  counts the number of pulses output from the mark detecting unit  210 , and synchronizes and controls the TPH  230  and the feed roller motor  250 .  
       FIG. 9  is a plan view of a print media  120  according to another embodiment of the present invention. The elements which are the same as in the previously described embodiment are given the same reference numerals, and a detailed explanation of those elements is not repeated for clarity and conciseness.  
      Referring to  FIG. 9 , two marks  104   c  longer than the marks  104   a  are formed in the top tab area  102  that extends from the printing area  101 . In  FIG. 9 , the time when a first mark  104   b  after the two marks  104   c  is detected by the optical sensor  53  can be set to the printing start position. Consequently, the print media  120  can easily detect the printing start position, and accordingly, the printing start positions on the first and second surfaces can be aligned. The other effects and functions of the print media  120  are the same as those of the print media  110  according to the previous embodiment illustrated in  FIG. 4 , and therefore, a detailed explanation is not repeated.  
       FIG. 10  is a sectional view of a print media according to still another embodiment of the present invention. The elements which are the same as in the previously described embodiment are given the same reference numerals, and a detailed explanation of those elements is not repeated for clarity and conciseness.  
      Referring to  FIG. 10 , a print media  130  includes a transparent base sheet  131 , a mark area  104  having marks  104   a,    104   b,  and  104   c  formed at one side of the transparent base sheet  131 , and a printing area  101  having layers M, Y, and C stacked on both surfaces of the transparent base sheet  131 . The layers M, Y, and C respond to heat and display magenta M, yellow Y, and cyan C colors. The marks  104   a,    104   b,  and  104   c  may perform the same functions as described in the previous embodiments illustrated in  FIGS. 4 and 9 .  
       FIG. 11  is a block diagram of a printing control system of a photo printer according to another embodiment of the present invention. The elements which are the same as in the previously described embodiment are given the same reference numerals, and a detailed explanation of those elements is not repeated for clarity and conciseness.  
      Referring to  FIG. 11 , the printing control system of the photo printer includes a control unit  200 , a mark detecting unit  210 , a TPH driver  220 , a TPH  230 , a feed roller driver  240 , a feed roller motor  250 , a punching driver  260 , and a puncher  270 .  
      When printing is completed and a print media is discharged, the control unit  200  drives the punching driver  260  so that the puncher  270  can periodically punch a printing area adjacent to a mark area of the print media discharged to the puncher  270  to form tear lines of the print media, for example, the tear line  106   c  shown in  FIG. 4 . Accordingly, even though the tear line  106   c  is not formed previously, such as on the print media  110 ,  120 , and  130  of the previous embodiments, the tear line  106   c  can be formed later using the puncher  270 .  
      Furthermore, if marks are formed on a transparent base sheet  131  as shown in the print media  130  of  FIG. 10 , it is preferable that the mark detecting unit  210  be a transparent optical sensor including a light emitting unit and a light receiving unit that are formed over and under the mark area  104  to face each other.  
      Although the mark area is formed at one side in the embodiments described above, the present invention is not limited to that configuration. For example, another mark area may be formed on an opposite side of the print media.  
      As described above, since the photo printer can measure the actual travel distance of the print media by detecting marks formed at one side of the print media, print timing can be exactly synchronized with the feeding of the print media. Moreover, since the printing start positions on the first and second surfaces can be aligned during printing, superior image quality can be achieved.  
      While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.