Patent Publication Number: US-7581799-B2

Title: Apparatus and method for printing according to the type of print media using a printer having wide printhead

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2004-0051980, filed on Jul. 5, 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 printing method for obtaining an optimal vertical resolution according to the type of print media used when a printing process is performed on a print media using a printer having a wide printhead covering a width of the print media. 
     2. Description of the Related Art 
     In general, a printhead that discharges ink droplets of a predetermined color on a print medium is disposed at a bottom of an ink cartridge of an inkjet printer. For performing a printing process on a print medium, the medium is fed in a sub-scan direction sequentially while the ink cartridge is moved in a main scan direction. The ink cartridge should be moved slowly in the main scan direction for performing the printing of high resolution. 
     U.S. Pat. No. 5,469,199 discloses a wide printhead, nozzles of which are disposed longer than a width of a print medium. When a high resolution image is printed using the wide printhead, the printing speed in the main scan direction can be improved, and since the ink is dropped from the printhead in a suspended state, a precise printing operation can be performed. 
     There are various types of print media that can be used in the inkjet printer having the wide printhead, for example, plain paper, paper exclusively for inkjet printer, photo paper, and transparencies. The each type of the media has an appropriate resolution thereof, for example, the appropriate resolution for the paper exclusively for inkjet printers is 600 dpi, and the appropriate resolution for photo paper is 1200 dpi. For transparencies, it is important to control ink dropping speed in order to prevent the ink from spreading. 
     Particularly, since the printer having the wide printhead is mainly used in a printing operation for high quality, if a user uses the plain paper together with the specialized media such as the paper exclusively for inkjet, the photo paper, and the transparent paper, the user may deal with the specialized paper as though it is plain paper without recognizing the resolution appropriate for the specialized paper and the printing quality may be degraded. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus and method for printing according to the type of print media when a printer having a wide printhead is used. 
     According to an aspect of the present invention, there is provided a printing method for printing according to a type of print media used with an inkjet printer, which includes a wide printhead having a width longer than a width of the print media and is disposed perpendicular to the media conveying direction, the method comprising the steps of picking up the print medium and feeding the medium under the wide printhead; determining the type of the medium being fed; and printing on the medium in a predetermined resolution and at a predetermined ink dropping speed according to the type of the medium. 
     The determining of the type of the medium may be performed by inputting the type of the medium that will be fed using a control panel or a host computer that provides printing data by a user. 
     The determining of the type of the medium may comprise the steps of detecting a characteristic value of the fed medium; and determining the type of the medium by comparing a characteristic value of the medium to values stored in a look-up table. 
     The characteristic value may be an optical output value that is measured by an optical sensor by irradiating light onto the fed medium and receiving the light reflected from the medium. 
     When printing on the medium, a vertical resolution may be formed by controlling a feeding speed of the medium using a feeding roller driver, and a horizontal resolution and an ink dropping speed may be controlled by using a printhead driver that controls the nozzles of the printhead. 
     An exemplary embodiment of the invention comprises a printer controller for controlling the printing of an image on a medium, a sensor for detecting a characteristic of a print medium on which an image is to be printed; a look-up table for storing characteristics of different types of print media, a feeding roller driver for controlling the vertical resolution of the image to be printed on the print medium, and a printhead driver for controlling the horizontal resolution of the image to be printed on the print medium. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a schematic plan view showing an inkjet printer having a wide printhead, which is applied in a method for printing according to the type of print media according to an embodiment of the present invention; 
         FIG. 2  is a block diagram illustrating a structure of a print control system adopted in the printing method according to an embodiment of the present invention; and 
         FIG. 3  is a flow chart illustrating the printing method according to an embodiment of the present invention. 
     
    
    
     Throughout the drawings, it should be understood that like reference numerals refer to like features, structures, and elements. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Exemplary embodiments of the present invention will now be described more fully with reference to the accompanying drawings. 
       FIG. 1  is a schematic plan view showing a structure of an inkjet printer having a wide printhead, which is used in a method for printing based on the type of print media according to an embodiment of the present invention. 
     Referring to  FIG. 1 , in the inkjet printer, a wide printhead  20 , a feeding roller  30 , and an optical sensor  40  are sequentially disposed in a paper conveying direction, that is, the direction represented by arrow X. The speed at which the thermal paper  10  enters under the wide printhead  20  is controlled by an operation of the feeding roller  30 . 
     A plurality of nozzle plates  21 , through which yellow (Y), magenta (M), cyan (C), and black (K) color inks are respectively discharged, are disposed at a bottom of the wide printhead  20 . The four nozzle plates  21  of each of four colors are overlapped with each other perpendicularly to the paper conveying direction (sub-scan direction) represented by the arrow X. In a case where the effective lengths of the nozzle plates  21  are 2.1 inches respectively and the length (d 1 ) in which they are overlapped is 0.1 inch, an effective length (d 2 ) of the printhead  20  is 8.1 inches in a main scan direction. Therefore, the print medium, typically, paper,  10  having an effective printing width of 8.1 inches or less, for example, A4 sized paper can be printed on using the inkjet printer. 
     On the each nozzle plate  21 , nozzles  22 , through which inks are dropped, are disposed in two rows in zigzag or offset formations. The nozzles  22  may be disposed in a row, two rows or more. 
     A predetermined distance (d 3 ) is formed between the nozzle plates  21  of the respective colors, and wires (not shown) for applying signals to the nozzles  22  are disposed on the distance (d 3 ). 
     An encoder disk wheel  32  is installed on an outer circumference of the feeding roller  30 . Slits  32   a  are formed on an edge of the encoder disc wheel  32  at predetermined locations, and rotary encoder sensors  34  including a light emitting portion  34   a  and a light receiving portion  34   b  are mounted on both sides of the slit  32   a . The light emitting unit  34   a  of the rotary encoder sensor  34  emits light at predetermined intervals, and the light receiving unit  34   b  generates pulse signals whenever it receives light emitted by the light emitting unit  34   a  through the slit  32   a . A print controller  50  counts the pulse signals to measure a conveyed distance that the medium  10  is transported by the feeding roller  30 , and drives a driving motor  36  to control the distance the medium  10  is transported by the feeding roller  30 . Reference numeral  52  denotes a look-up table (LUT). 
     The optical sensor  40  is disposed in front of the feeding roller  30 . The paper is transported in the direction shown by the arrow X, during which light is emitted onto the paper  10  as it is transported under the sensor  40 , which receives the light reflected from the paper  10 . The Optical sensor  40  transmits the received optical output to the print controller  50 . The print controller  50  determines the type of paper  10  by comparing the transmitted optical output to optical output values of respective paper types stored in the LUT  52 . 
       FIG. 2  is a block diagram illustrating a structure of a print control system that implements the printing method of an embodiment of the present invention. 
     Referring to  FIG. 2 , the print control system comprises a host computer  60  and a printer apparatus  61 . The printer apparatus  61  comprises a system controller  62 , a control panel  63 , a sensor  64 , an LUT  65 , a print controller  66 , a printhead driver  67 , and a feeding roller driver  68 . 
     The host computer  60  transmits print data that is generated by a printer driver (not shown) thereof to the printer apparatus  61 . 
     In the printer apparatus  61 , the system controller  62  controls the overall operation of the printer apparatus  61 , and preferably includes a central processing unit (CPU) of a microprocessor form, a read only memory (ROM) for storing fixed data such as a control program, and a read access memory (RAM) for storing operating data of the system controller  62 . The system controller  62  determines the type of the paper that is fed into the printer by comparing a characteristic value of the paper, for example, the optical output value, to the optical output values stored in the LUT  65  for different types of print media. 
     The control panel  63  includes a key matrix (not shown) and a display unit (not shown). The key matrix generates data according to the keys pushed by the user for designating a print mode and operating the designated mode, and outputs the generated data to the system controller  62 . The display unit displays the operation status of the printer apparatus  61  when the system controller  62  performs the print modes. 
     The print controller  66  generates control data corresponding to the type of print media determined by the system controller  62 , and controls the printhead driver  67  and the feeding roller driver  68  according to the control data to form an image on the paper  10  in a predetermined resolution. 
     The printing method according to an embodiment of the present invention will now be described with reference to  FIG. 3 . 
       FIG. 3  is a flow chart illustrating the printing method according to an embodiment of the present invention. 
     When a command for printing is input into the print controller  66  from the host computer  60  connected to the inkjet printer  61 , a sheet of paper  10  is picked up by a pickup roller (not shown) and fed under the wide printhead  20  (S 101 ). 
     In addition, it is determined whether the user has input the type of paper (S 102 ). If it is determined that the user inputs the paper type using the control panel  63  or the host computer  60  that provides the print data in step S 102 , step S 104  is performed. 
     Alternatively, if it is determined that the user has not input the type of paper in S 102 , the type of paper is measured by a media sensor installed in the printer  61 , for example, the optical sensor  64 . The optical sensor  64  emits light onto the paper  10 , measures the light reflected from the paper  10 , and outputs the optical output value to the print controller  66 . The print controller  66  determines the type of paper  10  by comparing the input optical output to the optical output values of respective paper types previously stored in the LUT  65  (S 103 ). 
     In addition, the print controller  66  extracts an appropriate resolution and ink dropping speed according to the type of paper from the LUT  65  (S 104 ). 
     Then the print controller  66  controls the feeding roller driver  68  according to the resolution and the ink dropping speed to form a vertical resolution in a sub-scan direction, and controls the printhead driver  67  that controls the nozzles  22  of the printhead  20  to form a horizontal resolution in a main scan direction, and controls the ink dropping speed to perform the printing operation (S 105 ). 
     According to the printing method according to the media types using the printer having the wide printhead of the present invention, an optimal printing quality according to the type of print media can be obtained even when the user does not set the resolution. 
     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.