Abstract:
A user interface for a printing apparatus, the printing apparatus including a plurality of print heads and an apparatus control system, each of the plurality of print heads being movable in a first direction, includes a display including a window. The display is configured to be connected to the apparatus control system and arranged to visualize an aligning of the plurality of print heads in the window. The window includes, for each pair of neighboring print heads in the first direction of the plurality of print heads, a user operable digital object. A color of the user operable digital object is changeable by means of a color function on the window for selecting a color for the user operable digital object. Upon a change of the color of the user operable digital object by means of the color function, a change in a distance in the first direction between the corresponding pair of neighboring print heads is determined, the change in distance being proportional to the change of the color of the user operable digital object.

Description:
BACKGROUND OF THE PRESENT INVENTION 
     1. Field of the Invention 
     The present invention relates to a user interface for a printing apparatus comprising a plurality of print heads and an apparatus control system, each print head being movable in a first direction. The user interface includes a display device connected to the apparatus control system and is arranged to visualize an aligning of the plurality of print heads in at least one window thereof. 
     2. Description of Background Art 
     By the term “printing apparatus,” an apparatus is meant that has a print function, for example a printer, a copier, a multi-functional, a roll-to-roll printer, a roll-to-sheet printer, a cut sheet printer, a flatbed printer, and a relief printer. By the term “color,” an arbitrary color is meant, including white, grey and black. 
     By the term “print head movable in the first direction” is meant that the print head is physically or virtually movable in the first direction. When the print head is physically moving in the first direction, the print head itself is actually moved in the first direction. When the print head is virtually moving in the first direction, the print head itself is not moved in the first direction, but nozzles at at least one end of the print head in the first direction are activated or deactivated. 
     From a known printing apparatus, like described in U.S. Pat. No. 8,292,398, aligning of a plurality of print heads is known. In the known printing apparatus, aligning is performed by determining the position of each of the print heads and indicating that a print head should be moved in the first direction over a distance. The distance can be input by a user at the user interface. However, if at least one print head has to be moved, the user has to consider mutual influences caused by the movements with respect to the final positions of the print heads. Most of the time, the movement of the print heads is a virtual movement, accomplished by using less or more nozzles in an overlapping area of the print heads. 
     SUMMARY OF THE PRESENT INVENTION 
     An object of the present invention is to provide a method for aligning a plurality of print heads, which is intuitive and less cumbersome. 
     The object is achieved in a user interface of the above-mentioned kind, wherein the at least one window comprises, for each pair of neighboring print heads in the first direction of the plurality of print heads, a user operable digital object, wherein a color of the user operable digital object is changeable by means of a color function on the at least one window for selecting a color for the user operable digital object, and wherein, upon a change of the color of the user operable digital object by means of the color function, a change in a distance in the first direction between the corresponding pair of neighboring print heads is determined, the change in distance being proportional to the change of the color of the user operable digital object. 
     More specific optional features of the invention are indicated in the dependent claims. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  is a block diagram of a printing apparatus having a user interface according to the present invention; 
         FIG. 2  is a schematic diagram of the plurality of print heads in the printing apparatus according to the present invention; and 
         FIG. 3  is a more detailed example of a display window showing the user operable digital objects for aligning the print heads according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described with reference to the accompanying drawings. 
     As an illustrative example,  FIG. 1  shows schematically a printing apparatus  10  having a control system  12  that is connected to a user interface  14 . 
     The user interface  14  has a control panel  16  with a display  18 , e.g. in the form of a touch-sensitive screen. In this example, the touch sensitive screen includes a window  20  and a command window  22 . The command window  22  may be used for entering operating commands such as “cancel,” “back,” “apply” and “test print,” as is generally known in the art and will not be described in detail here. The window  20  is shown in detail in  FIG. 3 . 
       FIG. 2  is a schematic diagram of the plurality of print heads  231 - 235  mounted on a carriage  220  in the printing apparatus  10  such as shown in  FIG. 1 . Each of the print heads  231 - 235  comprises a plurality of nozzles  250  for ejecting marking material on media  210 . The media  210  is transported in a transport direction C under the carriage  220 . A movement of the carriage  220  in one of the directions of the direction B relative to the media  210  may also be envisioned. The print heads  231 - 235  are staggered and aligned in a direction A. An overlap in the direction A between a first print head  231  and a second print head  232  is visualized by a first distance d 1 . An overlap in the direction A between the second print head  232  and a third print head  233  is visualized by a second distance d 2 . An overlap in the direction A between the third print head  233  and a fourth print head  234  is visualized by a third distance d 3 . An overlap in the direction A between the fourth print head  234  and a fifth print head  235  is visualized by a fifth distance d 5 . Since the print heads  231 - 235  are not correctly aligned, a light line  242  and/or a dark line  244  with respect to the color of a printed image  240  may appear on the media  240 . The white line  242  is caused by too large a distance d 2  in the direction A between the second print head  232  and the third print head  233 . The dark line  244  is caused by too small a distance d 4  in the direction A between the fourth print head  234  and the fifth print head  235 . In practice, a print head comprises a large plurality of nozzles and the overlap or the lack of overlap measured in nozzle distances will be a plurality of nozzle distances. 
     A user who has printed the image by means of the printing apparatus  10  may detect the lighter and/or darker areas on the print and realize that the print heads are not correctly aligned. The user may know where each of the plurality of print heads  231 - 235  is positioned in the printing apparatus and may derive which of the distances d 1 -d 4  have to be changed. Therefore the user navigates via the user interface to the window  20  shown in  FIG. 1 . 
       FIG. 3  is a more detailed example of the window  20  showing user operable digital objects  321 - 324  for aligning the print heads  231 - 235  shown in  FIG. 2  according to the present invention. The print heads  231 - 235  are schematically shown on the window  20  by print head representations  311 - 315 , respectively. Each pair of print heads neighboring in the first direction A corresponds to a user operable digital object according to the present invention. A print head representation  311 - 315  will be hereinafter mentioned as a print head  311 - 315 . 
     A first pair of neighboring print heads  311 ,  312  corresponds to a first user operable digital object  321 . A second pair of neighboring print heads  312 ,  313  corresponds to a second user operable digital object  322 . A third pair of print heads  313 ,  314  corresponds to a third user operable digital object  323 . A fourth pair of print heads  314 ,  315  corresponds to a fifth user operable digital object  324 . Each of the user operable digital objects  321 - 324  is provided with a color bar  361 - 364 , a plus button  331 - 334 , a minus button  341 - 344 , a slider S 1 -S 4 , and an indicator  351 - 354 , respectively. 
     Each of the color bars  361 - 364  is colored gradually from white to black. Another color may be envisioned to gradually color the color bars  361 - 364  from the light version of the color to the dark version of the color. By means of the plus buttons  331 - 334  and the minus buttons  341 - 344  a color can be selected from the area of the color bar  361 - 364 , respectively. The sliders S 1 -S 4  can also be used for the selection of the color of the color bars  361 - 364 , respectively. Near the slider S 1 -S 4 , an indicator  351 - 354  is displayed, respectively, to indicate the selected color. The indicator  351 - 354  may be provided with a numerical value, for example a first indicator  351  is provided with the numerical value+3. The numerical value may indicate the number of nozzles that the overlap of a corresponding pair of print heads deviates from a standard overlap. This deviation may be corrected by changing a selected color of a color bar according to the present invention. The deviation may be positive, if the overlap is larger than the standard overlap, or negative, if the overlap is smaller than the standard overlap. The deviation is equal to zero if the overlap is equal to the standard overlap of the print heads of the pair. If the standard overlap is zero nozzles, the numerical value directly shows the number of nozzles present in the overlap or a distance between the two neighboring print heads expressed in a number of nozzles. The window  20  also comprises a common plus button  335  and a common minus button  345 . The common plus button  335  may be used to simultaneously change the selected colors of the color bars  361 - 364  to a darker color. The common minus button  345  may be used to simultaneously change the selected colors of the color bars  361 - 364  to a lighter color. 
     The inventor has realized that the use of the color bars intuitively hints the user how to change the colors of the color bars, since they correspond to the print artefacts of the light line  242  and the dark line  244  in  FIG. 2 . This is advantageous, since the user will make fewer mistakes and does not have to bother about the direction in which each print head should be moved. 
     It is noted that the present invention should not be deranged with an automatic print head alignment. An automatic print head alignment does not solve all problems with print artefacts in a printed image on the media. 
     The manual print head alignment according to the present invention is in principal media dependent. The user could automatically align the print heads for new media. However, the user may not want to align for every print job, but may want to select color values in the window in the user interface according to the present invention which on average result in an acceptable print quality of the printed images. 
     For a printing apparatus which prints on—and cuts off—a roll of receiving material, there may be differences between the front edge, the middle and/or the back edge of a cut sheet. From a user&#39;s perspective, it is important that over the whole length of the sheet from front edge to back edge, an acceptable print quality is demonstrated. The middle of the cut sheet may even be the most important part. 
     The manual alignment according to the present invention is a kind of compromise in order to try to have an overlap of a predetermined number of nozzles, e.g. 2 nozzles, between two neighboring print heads. At some places on the print, dark lines may be visible. At other places on the print, white lines may be visible. Dependent on the image to be printed, an overlap of 0 or 1 nozzle may be preferred, or an overlap of 3 or 4 nozzles may be preferred, etc. In another case, you may want to have a different overlap for the print heads on one side in the direction A than for the print heads on the opposite side of the direction A. With the present invention, the user is capable of manually optimizing the printing of the image by means of the user interface according to the present invention before he starts the printing of a substantial number of prints of images. 
     When the user looks at the printed image  240  in  FIG. 2 , he detects a white line  242  corresponding to the pair of print heads  232 ,  233  in  FIG. 2 , or mutatis mutandis corresponding to the pair of print heads  312 ,  313  in  FIG. 3 , or in other words to the user operable digital object  322 . Since the user wants to have a darker line than the white line  242 , the user may touch the plus button to select a darker color from the color bar  362 . The numerical value near the indicator  352  will increase. 
     When an apply button is pressed in the command window  22  shown in  FIG. 1 , the user interface screen will send signals to the control system  12  shown in  FIG. 1  in order to move the print heads  232 ,  233  closer to each other in the direction A. By doing so, a larger overlap between the print heads  232 ,  233  will be realized and the white line  242  will disappear in subsequent prints of the image  240 . 
     When the user looks at the printed image  240  in  FIG. 2 , he detects a dark line  244  corresponding to the pair of print heads  234 ,  235  in  FIG. 2 , or mutatis mutandis corresponding to the pair of print heads  314 ,  315  in  FIG. 3 , or in other words corresponding to the user operable digital object  324 . Since the user wants to have a lighter line than the dark line  244 , the user may touch the minus button to select a lighter color from the color bar  364 . The numerical value near the indicator  354  will decrease. 
     When an apply button is pressed in the command window  22  shown in  FIG. 1 , the user interface screen will send signals to the control system  12  shown in  FIG. 1  in order to move the print heads  234 ,  235  more remote from each other in the direction A. By doing so, a smaller overlap between the print heads  232 ,  233  will be realized and the dark line  244  will disappear in subsequent prints of the image  240 . 
     Changes of the colors of the color bars  361 - 364  may be executed after each other before pressing the apply button in the command window  22  shown in  FIG. 1 . 
     When at least one color of color bar  361 - 364  is changed, at least one print head will be moved in the direction A. Methods may be envisioned to efficiently move the at least one print head in one or more movements. One method is envisioned to select the movements in such an order that the total sum of the magnitudes of the movements of the plurality of print heads is minimized. Another method is envisioned to spread the movements over the print heads. This is advantageous, since the number of nozzles which have to be additionally activated is small. 
     In  FIG. 2  and  FIG. 3 , five print heads are displayed. However, any other number of print heads larger than 1 may be envisioned. In  FIG. 2 , for each print head, four nozzles are displayed, but the dashed lines between the nozzles indicate that a plurality of nozzles other than four nozzles may be envisioned. In  FIG. 2 , an overlap or lack of overlap of one or two nozzle distances is indicated. However, an overlap or a lack of overlap may be a plurality of nozzle distances larger than two. 
     Other digital components may be envisioned than the plus buttons  331 - 335  and minus buttons  341 - 345  for selecting a color from a color bar  361 - 364 . 
     The color bar  361 - 364  itself may also be touched to select the desired color. This is possible since the color bar contains many colors in a range from white to black. 
     A “test print” button may be activated in the command window  22  in  FIG. 1 . A test pattern is printed on receiving material by the printing apparatus using nozzles of each print head  231 - 235 . The nozzles eject marking material on the receiving material. The test pattern may be looked at by the user for print quality artefacts like the dark and white lines. Then, he may decide to use the manual alignment possibility according to the present invention. 
     Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
     The present invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.