Abstract:
A printing system with a printer having a pair of printheads for printing on opposite sides of a receiver media. A host computer connected to the printer controls a page printing sequence in the printer and has a renderer for generating first page data to be printed. A language monitor determines that second page data is to be printed before the first page data, and so it delays sending a print command to the printer until the second page data is rendered. Then the language monitor sends a print command to the printer with the second page data before sending the first page data.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    U.S. patent application Ser. No. 13/______, entitled “Printer Driver Caching Method” filed concurrently herewith is assigned to the same assignee hereof, Eastman Kodak Company of Rochester, N.Y., and contains subject matter related, in certain respect, to the subject matter of the present application. The above-identified patent application is incorporated herein by reference in its entirety. 
         [0002]    Reference is made to commonly assigned, co-pending U.S. patent applications: Ser. No. 13/300,183 filed Nov. 18, 2011, entitled “System For Maintaining Proper Page Sequence While Reducing Printer Artifacts”; Ser. No. 13/300,251 filed Nov. 18, 2011, entitled “Printing Method For Maintaining Proper Page Sequence While Reducing Printer Artifacts”; Ser. No. 13/300,282 filed Nov. 18, 2011, entitled “Method For Maintaining Proper Page Sequence While Reducing Printer Artifacts”; Ser. No. 13/300,313 filed Nov. 18, 2011, entitled “Printing System For Maintaining Proper Page Sequence While Reducing Printer Artifacts”; the disclosures of which are incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The present invention is directed to duplex printing. In particular, the present invention is directed to methods and apparatuses for selectably controlling the order in which surfaces (the front and back sides of a duplex sheet) are sent to a multi-printhead duplex printer for printing thereby. 
       BACKGROUND OF THE INVENTION 
       [0004]    To overcome image quality issues in certain thermal duplex printers, the surface order delivery needs to vary in an irregular fashion, e.g., side A, side B, side B, side A. This irregular delivery sequence reduces the amount of contact between printed sheet surfaces and the drive roller. The drive roller typically comprises an aggressive texture for better feed control, however, it also compromises printable media surfaces and can deteriorate image quality. This method is inconsistent with the surface delivery mechanism from the Microsoft Windows driver, which always delivers rendered surfaces in a repeated and alternating “side A, side B” order (but which can start with either side). The central issue which needs to be resolved is how surfaces (the front and back sides of a duplex sheet) can be selectively delivered to a duplex printer that is capable of initially printing either side of a media sheet before printing the other side of the sheet. Certain software does not face this issue because both the front and back surfaces of a duplex sheet are individually available for selection prior to the delivery of the sheet print commands to the printer. Thus, there is a need in the art for a new printing architecture that implements a novel caching mechanism within the print driver. These changes are required to achieve the irregular surface delivery pattern that is required to obviate image quality issues. 
       SUMMARY OF THE INVENTION 
       [0005]    A preferred embodiment of the present invention comprises a printing system with a bidirectional printer having a pair of printheads for printing on opposite sides of a receiver media. A host computer connected to the printer controls a page printing sequence in the printer and has a renderer for generating first page surface data to be printed on one side of a receiver media in the printer. A language monitor determines that second page surface data is to be printed on the receiver media before the first page surface data, and so it delays sending a print command to the printer until the second page surface data is rendered. Then the language monitor sends a print command to the printer with the second page surface data before sending the first page surface data. The language monitor comprises programming for receiving information identifying a position of the receiver media in the printer and, in response to the information, determines that the second page surface data is to be printed on the receiver media before the first page surface data. The printing system comprises storage for temporarily storing the first page surface data while the second page surface data is rendered. These pages comprise a portion of a print job and the print job comprises a plurality of even numbered pages and a plurality of odd numbered pages. The language monitor is configured to print pairs of the even numbered pages consecutively during the print job and as well as pairs of the odd numbered pages. The print job is often a duplex print job. All of the even numbered pages are printed on one of the printheads and all of the odd numbered pages are printed on another one of the printheads. 
         [0006]    Another preferred embodiment of the present invention comprises a printing system with a renderer configured for generating print image data for a first logical page of a duplex print job. A language monitor is configured for receiving information from a connected printer identifying a position of a receiver media in the printer with respect to one of two printheads in the printer. In response, it determines that a second logical page of the print job is to be printed next in the printer before printing the first logical page. It temporarily stores the first logical page of the print job while print image data for the second logical page is being generated. The language monitor also sends the second logical page of the print job to the printer before sending the first logical page. The language monitor queries the printer to identify the position of the receiver media. The first and second logical pages of the print job comprise a portion of the print job, and the print job comprises even numbered pages and odd numbered pages. Pairs of the even numbered pages are printed consecutively as well as the odd numbered pages. Each of the odd numbered pages is printed by only one of the printheads on an opposite side of the receiver media from an even numbered page. The system can temporarily store the first logical page of the print job on a hard disk of the system. 
         [0007]    Another preferred embodiment of the present invention comprises a printing system having a printer and a host computer connected to the printer. The host sends print commands and first page data to the printer. A renderer in the host generates the first page data and temporarily stores it in system storage. A language monitor is configured to selectively either send the print commands and the first page data to the printer or to retain the first page data in the system storage until the renderer completes generating second page data. A receiver media is positioned at either one of two printheads in the printer, wherein the host receives printer status data from the printer indicating the position of the receiver media. Based on this position, the language monitor is further configured to selectively either send the print commands and the first page data to the printer or to retain the first page data in system storage. The language monitor sends the second page data to the printer for printing on one side of the receiver media followed by sending the first page data to the printer for printing on an opposite side of the receiver media. The first page data is printed using only one of the printheads and the second page data is printed using only another one of the printheads. 
         [0008]    Another preferred embodiment of the present invention comprises a printing system having a renderer for generating image data for a logical first page of a print job and for generating a logical second page of the print job. Attached storage is used to store the image data for the logical first page of the print job and for the logical second page of the print job. The status data from the printer indicates a position of receiver media in the printer with respect to one of two printheads. A language monitor starts the print job in duplex format and is configured to send the logical second page of the print job before sending the logical first page of the print job. The image data for the logical first page and the logical second page are each accessible by the language monitor for being sent to the printer. The status data indicates which one of the two printheads is capable of printing on the receiver media without retracting the receiver media. The system comprises means for requesting the status data from the printer. 
         [0009]    These, and other, aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention and numerous specific details thereof, is given by way of illustration and not of limitation. For example, the summary descriptions above are not meant to describe individual separate embodiments whose elements are not interchangeable. In fact, many of the elements described as related to a particular embodiment can be used together with, and possibly interchanged with, elements of other described embodiments. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. The figures below are intended to be drawn neither to any precise scale with respect to relative size, angular relationship, or relative position nor to any combinational relationship with respect to interchangeability, substitution, or representation of an actual implementation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  illustrates a preferred embodiment of a print driver architecture for selective delivery of print surfaces to a printer. 
           [0011]      FIG. 2  illustrates a Windows driver that can be modified to operate in accordance with a preferred embodiment the present invention. 
           [0012]      FIGS. 3A-B  illustrate print command structures. 
           [0013]      FIG. 4  illustrates a user interface plug-in design. 
           [0014]      FIG. 5  illustrates a printing system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
       Printer Driver Architecture 
       [0016]    With reference to  FIGS. 1-2 , many Windows printer drivers are based on the Microsoft Universal Printer Driver architecture (Unidrv)  200 . The present implementation of these printer drivers includes a Rendering Plug-In  101 ,  201  which provides unique functionality such as, for example, color adjustment, scaling, and adding white borders to bordered prints. A User Interface Plug-In  203  provides the user the ability to select specific unique features such as launching a calibration utility, or a slider bar for selecting the color adjustments, such as illustrated in  FIG. 4 , for example. 
       Language Monitor Architecture 
       [0017]    In addition to the employing the Microsoft Universal Printer Driver architecture in modified printer driver embodiments described herein, a Microsoft Language Monitor  108 ,  208  has been implemented for each printer and is installed at the time of Printer Driver installation. The Language Monitor is responsible for (in most cases) building and sending USB command requests to, and for handling USB command responses from, the printer. Microsoft describes, in part, Language Monitors as follows 
         [0018]    “Language Monitors are user-mode DLLs that serve two purposes:
   They provide a full duplex communications path between the print spooler and bidirectional printers that are capable of providing software-accessible status information.   They add printer control information, such as commands defined by a printer job language, to the data stream.” (see http://msdn.microsoft.com/en-us/library/ff556450(VS.85).aspx)   
 
       Renderer Plug-In Modifications 
     Current Architecture 
       [0021]    Prior to sending each page of a document, a Page Info header structure is sent to the print spooler  204  indicating which page of the document is being sent as well as whether or not the page is simplex or duplex. This is a feature that was added to the print driver for the KODAK D4000 Duplex Photo Printer. This is later retrieved from the print spooler by the Language Monitor and is used to set up the printer appropriately. Interacting with software hooks provided by Microsoft to enable programmers to design custom plug-ins, the present Renderer Plug-In builds a print command and sends it to the print spooler. The Renderer Plug-In then applies the appropriate filters and image banding operations to the data created by the Renderer  202  and then spools out the rendered page (surface) data to the print spooler, three bytes (RGB) at a time, until the entire surface has been processed. The result of this process is that both the print command and a fully rendered, 8-bit RGB-interleaved page surface is transmitted to the print spooler as a rastered bit map. In parallel, the Language Monitor retrieves both the print command and associated image data and ultimately sends this to the bidirectional printer  206 . 
       Proposed Architecture 
       [0022]    Rather than writing the entire rendered surface to the print spooler, a temporary file name will be constructed, and the rendered page surface data  103  will be written  102  to a temporary file  109 ,  209 . The print command structure will be enhanced to include the name of the temporary file that was written. The result is that only the Page Info header and the enhanced command structure (see  FIG. 3 ,  351 , plus  352  and/or  353 ) will be sent from the renderer  202  through the spooler  204  and then read by the Language Monitor  208 . The Language Monitor will be able to retrieve the image data in the temporary file using the temporary file full path name. No image data will be present in the print spooler files. 
       Language Monitor Modifications 
     Current Architecture 
       [0023]    Now including reference to  FIG. 3 , the Language Monitor receives a Page Info header structure  301  from the spooler. On all Simplex pages and on Odd Duplex pages it constructs a Set Print Parameter Command and sends it to the Printer. Then, the Print Command and associated image data are retrieved from spooler and sent to the printer. The pages (surfaces) of the document are sent sequentially and the print spooler balances the process of rendering and printing. 
       Proposed Architecture 
       [0024]    When a Page Info header is received and ready to be processed  104 , and the printer is in a quiescent state, the printer will be queried as to the location of the paper position with respect to one of two thermal print heads in the printer  105 . At that point, the Language Monitor will possess the knowledge of which surface (side) of the following sheet is required to be sent first. The surface to be sent first corresponds to the print head at which the paper is positioned. This avoids unnecessary retraction and repositioning of the media sheet with respect to the print heads and also avoids compromising the media surface by additional rolling contact with the textured feed roller. 
         [0000]    a. Simplex Sheet 
         [0025]    If the Page Info header portion  351  indicates that the sheet is to be printed simplex, the Set Print Parameter Command will be built appropriately. This sets the parameter that signifies on which side the sheet should be printed. Since the back side of a simplex sheet is laminated automatically, only data for a single surface data needs to be sent. Then the Print Command and the enhanced print command structure will be read from the print spooler. The Language Monitor will read the surface data from the temporary cached file  109 ,  209  and transmit the Print Command followed by the surface data to the printer. Once the commands and image data have been successfully consumed by the printer, the 
         [0026]    Language Monitor will delete the temporary file for that surface. 
         [0000]    b. Duplex Sheet 
         [0027]    If the Page Info header portion  351  indicates that the sheet is to be printed duplex, the Set Print Parameter Command will be built appropriately (based upon the heuristic that determines which thermal head will be used and which media side must be printed upon next). There are now two possible scenarios: 
         [0028]    Scenario 1: The next surface required is the next logical page of the document. The next logical page of the document is the next lowest page number (after the current page number) of the document in its completed printed form, which logical page number sequence might not reflect the print sequence in which the pages were printed. In this case, the print command and the enhanced print command structure will be read from the spooler. The Language Monitor will read the surface data from the temporary cached file and transmit the Set Print Parameter Command followed by the Print Command followed by the surface data to the printer  106 . Once the commands and image data have been successfully consumed by the Printer, the Language Monitor will delete the temporary file for the surface. Then this process repeats with the second surface of the Duplex sheet. 
         [0029]    Scenario 2: The next surface required is the page after the next logical page of the document. We refer to the next logical page as the “first page” and the page after that as the “second page.” In this case, the print command and the enhanced print command structure will be read from the spooler. Then, the Language Monitor caches this enhanced print command information (as a function separate from the page surface image data) and waits until the next page (second page) print command is available to be read from the Spooler, i.e. after the Renderer finishes generating the second page image surface. Thus, image data for two surfaces are cached and the Language Monitor selects which is sent first to the printer. Then, the Set Print Parameter Command will be transmitted to the printer. The Language Monitor will read the second surface image data (second page) from the temporary file and then send the print command followed by the second surface image data to the printer  107 . Then, the Language Monitor reads the temporary cached information (first page) and sends the print command followed by this first surface image data to the printer. 
         [0030]    After the commands and image data have been successfully consumed by the printer, the Language Monitor will delete the temporary files for both surfaces of the duplex sheet. 
       Error Detection and Recovery 
       [0031]    With this caching scheme, there are five new error conditions that need to be accounted for:
   1. Rendering Plug-In, the temporary filename cannot be constructed.   2. Rendering Plug-In, the temporary file cannot be written. In either of these cases, the print spooler needs to be informed that the Rendering failed. The user will observe this as a failure to print their jobs.   3. Language Monitor, in the case of duplex where the second surface of the sheet is required to be printed first, but is never received. After the first surface is received, a timer will be initiated that will be cleared when the second surface arrives. If the timer expires prior to receiving the second surface, and new error will be generated and sent to the print spooler.   4. Language Monitor, temporary files cannot be read. If the files cannot be opened or if their image data is corrupted or incomplete, a new error will be generated and sent to the print spooler.   5. User cancellation of jobs. In the current architecture, the print spooler removes all of the rendered surfaces that are no longer required. That is because the rendered data co-exists with the page meta data within the print spooler. In the proposed architecture, this is not the case. To eliminate these older cached temporary files, the Language Monitor will examine the time stamps of the active jobs and delete any outdated previously rendered files from the temporary directory.   
 
         [0037]      FIG. 5  illustrates an example printing system for practicing embodiments of the present invention. In this example embodiment, the printing system includes a host computer  10  which typically comprises input devices keyboard  46  and mouse  44  communicatively connected to the computer&#39;s desktop interface device  28 . The interfaces illustrated in  FIG. 5  can include USB interfaces and other wired connections, as well as wireless connections via Wi-Fi or cellular. The term “host computer” or “host PC” is intended to include any data processing device, such as a server, desktop computer, PC, a laptop computer, a mainframe computer, a router, a personal digital assistant, a Blackberry PDA, or any other computing device. The phrase “communicatively connected” is intended to include any type of connection or transmission media, whether wired, wireless, or both, between devices, computers, or programs in which data may be communicated. 
         [0038]    Output from host computer  10  is typically presented on a video display  52 , which may be communicatively connected to the computer  10  via the display interface device  24 . Internally, the computer  10  contains components such as CPU  14  and computer-accessible memories, such as read-only memory  16 , random access memory  22 , and a hard disk drive  20 , which may retain some or all of the image data, page surface data, cached page data, commands, print documents, character data, and programming referred to herein, including a language monitor, print spooler, plug-ins, renderers, and other rendering engines. The phrase “computer-accessible memory” is intended to include any computer-accessible data storage device, whether volatile or nonvolatile, electronic, magnetic, optical, or otherwise, including but not limited to, floppy disks, hard disks, Compact Discs, DVDs, flash memories, such as USB compliant flash drives, for example, and ROMs, and RAMs. The CPU  14  communicates with other devices over a data bus  12 . The CPU  14  executes software stored on, for example, hard disk drive  20  as described above. In addition to fixed media such as a hard disk drive  20 , the host computer  10  may also contain computer-accessible memory drives for reading and writing data, such as page print image data, from and to removable computer-accessible memories. This may include a CD-RW drive  30  for reading and writing various CD media  42  as well as a DVD drive  32  for reading and writing to various DVD media  40 . The printer  50 , such as described herein, is a dye diffusion thermal transfer printer bidirectionally connected to a printer interface device  26  for communicating with processor  14  over data bus  12 . However, the printer  50  should not be considered as limited only to this type. Printer  50  can record images on a tangible surface using a variety of known technologies including, but not limited to, conventional four color offset separation printing, other contact printing such as silk screening can be performed, or dry electrophotography, other thermal printing technology, drop on demand ink jet technology, and continuous inkjet technology, or any combination of the above is represented as printer  50 . The connection between the thermal printer  50  and the printer interface device  26  serves as a two way communication channel between the printer and the host computer. The printer  50  includes a supply of receiver media, typically in rolled form, and preferably includes an exit tray for holding a plurality of printed receiver media sheets. Printer  50  typically incorporates memory sufficient to store print data for a plurality of pages of a print job. Additional information can be stored for each type and size of media, including a finish of media, for example. The printer preferably includes selectable printing options such as duplex and simplex printing. These selectable options can be controlled by user input to the computer system via the mouse  44  or keyboard  46  illustrated, and as confirmed by a convenient graphical user interface on video display  52 . A digital scanner  6  or other image capture device such as a digitizing tablet or a camera can be communicatively connected to the computer  10  through, for example, the USB interface device  34  to transfer image from the scanner  6  to the computer&#39;s hard disk drive or other connected memory devices. Finally, the computer  10  can be communicatively connected to an external network  60  via a network connection device  18 , thus allowing the computer to access digital objects and media assets from other computers, devices, or data-storage systems communicatively connected to the network. 
         [0039]    A collection of print documents, and/or media assets can reside exclusively on the hard disk drive  20 , compact disc  42 , DVD  40 , or on remote data storage devices, such as a networked hard drive accessible via the network  60 , or on other local memory devices such as a thumb drive. A collection of digital objects and documents can also be distributed across any or all of these storage locations. A collection of digital objects and documents may be represented by a database that uniquely identifies individual digital objects (e.g., such as a print job) and their corresponding location(s). 
         [0040]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
       PARTS LIST 
       [0000]    
       
           6  Scanner 
           10  Host 
           12  Bus 
           14  CPU 
           16  Memory 
           18  Connection Device 
           20  HDD 
           22  RAM 
           24  Interface 
           26  Interface 
           28  Interface 
           30  CD Drive 
           32  DVD Drive 
           34  Interface 
           40  DVD 
           42  CD 
           44  Mouse 
           46  Keyboard 
           50  Printer 
           52  Display 
           60  Network 
           101  Renderer Plug-In 
           102  Step 
           103  Step 
           104  Step 
           105  Step 
           106  Step 
           107  Step 
           108  Language Monitor 
           109  Temporary Cached File 
           200  Universal Printer Driver architecture 
           201  Renderer Plug-In 
           202  Renderer 
           203  User Interface Plug-In 
           204  Print Spooler 
           206  Printer 
           208  Language Monitor 
           209  Temporary Cached File 
           301  Page Header 
           351  Command Set Header 
           352  Page Header 
           353  Page Header