Abstract:
A method of digital printing in which, upon sensing a defect area in a page image in the marking process or on the printed media, the page image is reconfigured to rotate, translate, change print jobs, or reduce the number of pages printed concurrently to avoid the defect area and continue the printing process without interruption utilizing the available non-defect area.

Description:
BACKGROUND 
       [0001]    The present disclosure relates to digital printing of images such as by electrostatic or ink jet marking on print media either in roll or sheet form. Such print engines have found widespread usage and popularity in view of their relatively high productivity for small and medium size print jobs and particularly for print jobs where time is of the essence and a high rate of productivity is required. 
         [0002]    However, where defects arise in the printing process, the run time of the printing system must be interrupted in order to repair or replace machine components responsible for the defect, thereby resulting in reduced productivity. For example, clogged or inoperative ink jets may cause streaks or voids in the image marking, or a gouge or defect in a photoreceptor in an electrostatic print engine may produce periodically recurring blotches in a limited area of the image being marked on the print media, with the balance of the marking remaining of acceptable quality. 
         [0003]    It has thus been desired to provide a way or means of avoiding a defective area of the image in the marking process yet be able to continue the printing operation thereby avoiding a shutdown of the printing process and the resulting loss of productivity. 
       SUMMARY 
       [0004]    The present disclosure provides a technique for continuing printing from digital images either electrostatically or by direct marking such as with the use of ink jets in the event a predictable defect, such as a continuous or periodically recurring defect, is detected in the marking process and particularly where the cause of the defect is isolated to a localized area of the marking process. The present disclosure describes a way and means for relocating or shifting the image within the marking process or on the print media to enable continuation of the printing process without interruption or the necessity of shutting down the print engine for maintenance or repair. 
         [0005]    The print engine controller&#39;s model is altered so as to reroute and/or reschedule pages and/or jobs such that the subsequently printed pages have acceptable quality despite the marking system&#39;s reduced capability due to the defect. The disclosure has particular applicability to wide format printing such as 2-up continuous feed processes and provides for continuing concurrent printing of more than one print job to minimize productivity losses. In particular, the technique or method of the present disclosure permits translational shifting of images and rotation of images to avoid localized defects in the marking process yet enable continued printing of images in the non-defect area without repairing the printing process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a pictorial representation of a digital image marking engine employing print media in roll form; 
           [0007]      FIG. 2  is a view similar to  FIG. 1  of a marking engine employing sheet feed print media; 
           [0008]      FIG. 3A  is a pictorial representation of wide page image or landscape format media printing showing a defect area; 
           [0009]      FIG. 3B  is a view similar to  FIG. 3A  with the page image rotated for narrow edge or portrait format feed printing to avoid the defect area; 
           [0010]      FIG. 4A  is a pictorial representation of 2-up side-by-side page image printing with a defect area; 
           [0011]      FIG. 4B  is a view similar to  FIG. 4A , showing the page images translated to avoid the defect area; 
           [0012]      FIG. 5A  is a pictorial representation of 2-up side-by-side page image printing with another defect area; 
           [0013]      FIG. 5B  is a view similar to  FIG. 5A , showing a single page image rotated to utilize wide page image feed to avoid the defect area; and, 
           [0014]      FIGS. 6A and 6B  comprise a block flow diagram of the process of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Referring to  FIG. 1 , a marking engine is indicated generally at  10  and includes paper media  12  in roll form feeding through rollers  14 ,  18  to print heads  16   a ,  16   b ,  16   c ,  16   d  which may be of the ink jet variety and which are controlled by an image path controller  28  inputting signals to print controllers  22  for each of the print heads  16   a - 16   d . The media, after marking by the print heads, is passed by a sensor  32  for detection of defects in the printed image. The inked image may then be reheated by mid-heaters  33  in preparation for final passage through a final gloss and spread roller unit  34 . The printed media is then transported for further handling in finishing stations (not shown). 
         [0016]    Referring to  FIG. 2 , another type of print engine is indicated generally at  40  which includes a plurality of side-by-side sheet stackers  42   a ,  42   b  and  44 A,  44 B which contain respectively cut sheet media denoted respectively  46   a ,  46   b  and  48   a ,  48   b . The stackers or trays include feeders/separators respectively  50   a ,  50   b  and  52   a ,  52   b  which are operative for feeding individual sheets from adjacent trays concurrently along path  54  in the direction denoted by the black arrows to the positions indicated at  56   a ,  56   b  for guidance by edge registration system  58   a ,  58   b  and lateral side registration edges  60   a ,  60   b . The sheets are advanced through roller  62  to an imaging system indicated generally at  64  which may comprise a photoreceptor drum or belt for marking or printing. After marking, the sheets are moved by feed rollers  66   a ,  66   b  respectively from their position indicated at  68   a ,  68   b  to a lateral merging system indicated generally at  40  through a lateral side shifting system  72   a ,  72   b  to a stacking system indicated generally at  74 . As is common in the industry, but not shown in  FIG. 2 , various feeding trays, stacking trays, and media handling hardware are available beneath the shown cross section to provide for the selection and transport of media cut to various dimensions. 
         [0017]    Referring to  FIGS. 3A and 3B , the width of the printing process is represented by the horizontal line denoted by the reference characters A-B. In  FIG. 3A , a page image is arranged to be printed in wide or landscape format on media extending substantially the full width of the available printing process on a wide sheet format denoted by reference numeral  80  in solid outline. An area of defect in the process is denoted by reference numeral  82  and is located on the page image  80  in the region between the vertically oriented dashed line and the left hand margin of the sheet  80 , leaving the portion of the page between the dashed line  84  and the right hand edge of the page image  80  unaffected by the defect and usable for continued printing or marking. 
         [0018]    Referring to  FIG. 3B , the page image has been rotated 90° to orient the narrow edge of the page in the feed or process direction, indicated by the black arrow such, that the width of the page is located in the non-defect region to the right of the defect area  84 , thereby enabling continued printing of the new page image  86  in the portrait format on the media. 
         [0019]    Referring to  FIGS. 4A and 4B , a printing process for printing 2-up images as denoted by reference numerals  88 ,  90  is shown where a defect area  92  is located between the dashed line  94  and the left-hand margin of the page  88 . In response to this defect location, the system has shifted the printing of the page images  88 ,  90  to the right. The right-hand margin of the image  90  remains within the boundaries of the process width A-B, whereas the image  88  has been shifted in a rightward direction by the width of the process defect  92  consequently reducing the space between the images  88 ,  90  yet allowing continued printing of the 2-up printing process. 
         [0020]    Referring to  FIGS. 5A and 5B , a 2-up page printing is illustrated in  FIG. 5A  wherein pages  96 ,  98  are being printed side-by-side in the process direction indicated by the black arrow with the available process printing width indicated by the horizontal line A-B. In the process of  FIG. 5A , an image defect area  100  is present between the dashed line  102  and the left margin on the page  96 . Referring to  FIG. 5B , a page image  104  is being printed in landscape format in the region to the right of the defect area  100  of the process width A-B which is free of defect thereby enabling continued printing or marking of a single page serially without interruption of the printing process. Thus, by rotating a page image 90° the non-defect area of the printing process is continued to be utilized albeit with a single page without the necessity of stopping printing in order to repair or replace machine components responsible for the defect in the process. If appropriate, page image  104  may be chosen from a different print job. 
         [0021]    Referring to  FIGS. 6A and 6B , a flow diagram of the process of the present disclosure is shown beginning at step  106  and proceeds concurrently therefrom to construct an initial software model of the machine at step  108  and to receive a user submitted print job to the digital front end (DFE) of the print engine at step  110 . The system proceeds from step  110  to attach the print job to a job queue or at a user specified location at step  112 ; and, steps  110 ,  112  may be repeated asynchronously. 
         [0022]    The system proceeds from step  108  to run diagnostic images on the in-process stations and the media at step  114  and proceeds to sense and analyze the location of defects in the process at step  116 . The system then proceeds to update the software model of the machine at step  118  and coding predictable defects as lost print capability. Defects are predictable if they are either continuous or periodic with respect to one or more marking elements in the print process. For the purpose of the present invention, defects can be either voids (i.e. the lost ability to produce pixel markings on demand) or extraneous marks (i.e. the production of marks regardless of demand). The steps  114 - 118  are repeated opportunely. 
         [0023]    The system then proceeds to step  120  and tries to schedule a given job X with default routing. 
         [0024]    From step  112 , the system proceeds to concurrently perform a coarse raster image process mirror queue of the job queue from front to back at step  122  and also constructs an assembly tree of each job in the job queue at step  124  and then proceeds to step  120 . 
         [0025]    From step  122 , the system proceeds to ask whether the coarse rip of the front job X is complete at step  126 ; and, if the determination at step  126  is answered in the affirmative, the system proceeds from there to step  120 . However, if the query at step  126  is answered in the negative, the system returns to step  122 . 
         [0026]    The system proceeds from step  120  to step  128  and asks whether the scheduling is successful. The job can only be successfully scheduled if all job requirements are within the capabilities of the machine as encoded in the model of the machine. A job will not be successfully scheduled if the job requires printed marks in a location where the printing process produces a void defect, or the job requires an unmarked region where the printing process produces extraneous mark defects. For example, if the coarse RIP of a job specifies that magenta pixels are required in a page region where the machine indicates that the marking process is producing a predictable magenta void, the job requirements are not compatible with the machine capabilities, and the job cannot be successfully scheduled. However, if the coarse RIP of a job indicates there is no demand for magenta in page region that is producing a magenta void, the job requirements and the machine capabilities are compatible in this regard, and such a magenta void does not preclude scheduling of the job. With respect to extraneous mark defects, a job will not be scheduled if the coarse RIP indicates a demand for a mark free region for a given color separation where the machine specifies that the process has lost the capability of producing a mark free region for that color. In the event that defective prints are acceptable as a final product for specific jobs, an operator would have the option to manually flag such jobs as being compatible with lost print capability associated with predictable void defects or extraneous mark defects, and such lost capability would not preclude scheduling of the flagged jobs. If the determination at step  128  is affirmative, the system proceeds to step  130  and adds job X to mark the job queue and proceeds concurrently to step  132  to create a final raster image process and to step  136  to remove job X from the print queue and coarse RIP queue. From step  132  the system proceeds to step  134  and print jobs X. From step  136  the system returns to step  126 . 
         [0027]    If the determination at step  128  is negative, the system proceeds to step  138  and attempts to schedule job X with a translated page and from there to step  140  and enquires as to whether the scheduling is successful. If the determination at step  140  is affirmative, the system proceeds to step  130 ; however, if the determination at step  140  is negative, the system proceeds to step  148 , attempts to schedule job X with a rotated page, where the rotated page can also be translated from a default location as necessary. The system then proceeds to step  150  and enquires as to whether the scheduling is successful. If the determination at step  150  is affirmative, the system proceeds to step  130 ; however, if the determination at step  150  is negative, the system proceeds to step  152  and enquires whether there are job X pages to be printed side-by-side. If the determination at step  152  is answered in the affirmative, the system proceeds to step  154  and reduces the number of side-by-side pages in job X by one and then proceeds to step  120 . The resulting side-by-side or one-at-a-time printed pages may be rotated or translated from a default location and orientation to optimize productivity of the remaining capability of the machine. However, if the determination at step  152  is negative, the system alerts the operator and stores job X for manual or automatic re-entry into the job queue at step  156  and then proceeds to step  158  and removes job X from the print and coarse rip queues and then returns to step  126 . 
         [0028]    The present disclosure thus provides for determining if defects exist in the marking process in digital printing and performs either translation and/or rotation of the pages, if possible, to proceed with printing or marking without interruption in the non-defect area of the printing width, thereby enabling optimization of productivity in a modified printing scheme, albeit with reduced capability until it is convenient to stop the process in order to repair or replace machine components responsible for the defect. 
         [0029]    It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.