Patent Publication Number: US-7722147-B2

Title: Printing system architecture

Description:
CROSS-REFERENCE TO CO-PENDING APPLICATIONS 
     The application is a co-pending application with U.S. patent application Ser. No. 10/966,023 filed Oct. 15, 2004. 
     BACKGROUND 
     This disclosure relates to printing systems. 
     When an image such as a picture or a page of text is to be printed, image data generally is translated by a computer system from one format into another format understandable by a printer and then relayed to a print buffer associated with the printer. The print buffer receives the translated image data and stores at least a portion of the image data for subsequent printing by the printer. 
     Many printers include multiple discrete print elements (e.g., an inkjet nozzle in an inkjet print module). The print elements can be deployed to print selected components of the image. For example, selected print elements can be deployed to print at selected locations on a workpiece. As another example, in color printing, selected print elements can be deployed to print selected colors. Control electronics can coordinate the printing of images by deploying the print elements to print image data from the print buffer. 
     The print elements in a printer can be arranged in groups called print modules. The print elements in a module can be grouped according to the deployment of the constituent elements. For example, print elements that print at a selected array of positions can be grouped in a print module. As another example, print elements that print the same color (at a selected array of positions) can be grouped into a print module. 
     SUMMARY 
     The following disclosure relates to systems and techniques for printing. In one implementation, described is a method for synchronously printing an image on a workpiece. The method involves receiving image data at a location that is remote from a print head, arranging the received image data according to physical parameters of the print head to be used to print the image data on the workpiece, and sensing the speed of the workpiece on a workpiece conveyor relative to the print head. The method also involves detecting the position of the workpiece on a workpiece conveyor, forming a packet of image data, and sending the packet of image data to the print head. The method includes using the receipt of the packet of image data as a trigger to cause the image data at the print head to be printed substantially immediately on the workpiece. 
     One aspect of the image data being printed substantially immediately on the workpiece may involve printing image data substantially at an instant at which the image data arrives at the print head. In another aspect of the image data being printed substantially immediately on the workpiece, the image data can be received at the print head and latched, and the latched image data can be printed on the workpiece when a subsequent image data packet arrives at the print head. The subsequent image data packet arriving at the print head can cause the latched image data to be printed on the workpiece. The subsequent image data packet arriving at the print head can be a next subsequent image data packet. Alternatively, a receipt of a subsequent image data packet other than the next subsequent image data packet can cause the latched data to be printed on the workpiece. 
     In another aspect of the method, the arranging, sensing, detecting, and forming may be order-independent, and two or more of the receiving, arranging, sensing, detecting, forming, sending, and using may be performed at least partially in parallel. The method may involve translating the image data into a format that is understandable by a printer. The packet of image data may be formed by a data pump. The packet of image data can be sent to the print head at a data rate sufficient to minimize gaps and white spaces when printing. Image data for the data pump can be received from a Peripheral Component Interconnect-type bus of a host computer. In one aspect, a number of print elements on the print head can be associated according to a physical column of associated print nozzles. The physical column of associated print nozzles is configured to function logically independently of other physical columns of associated print nozzles on the print head. 
     Another implementation describes a method that involves detecting a position of a workpiece relative to a print head with multiple print elements, dividing image data that represents an image into portions according to a configuration of print elements on the printing head, and communicating along an optical communication path the divided image data to the print elements. The method also involves synchronizing a timing of printing the image on the workpiece by the print elements with the detected position of the workpiece. 
     The synchronization may involve using the communication of the divided image data as a trigger to cause the printing of the image substantially immediately as the data arrives at the print elements. The method may also include allocating the divided image data to different memory locations. The allocation of the divided image data to different memory locations can involve allocating the divided image data to individual memory buffers and/or allocating the divided image data to an individual memory buffer dedicated to selected print elements. The timing of the printing can include timing the arrival of the divided image data at the print elements based on the position of the workpiece. The timing of the arrival of the divided image data can include introducing a delay into the optical communication path. The introduction of the delay into the optical communication path may involve programming a direct memory access device to delay the direct memory access, transmission, and printing of the first portion of the divided image data. 
     Also described is a print system with a collection of print elements arranged to span a print area, and a workpiece conveyor to move a workpiece through the print area. The print system has a detector to detect a position of the workpiece in the print area, and control electronics to instruct the collection of print elements to print an image on the workpiece substantially immediately when the collection of print elements receive the instruction through an optical communication path. 
     The control electronics may include a transceiver to send the instruction to the collection of print elements. The collection of print elements may be a collection of inkjet print elements. The system may have a data processing device to perform operations in accordance with logic with a set of machine-readable instructions. The operations can include a division of a collection of image data into portions according to the arrangement of print elements on a print head. The system may also include a collection of memory locations to store the divided portions of image data, and a timing element to time the printing of the image data portions according to the arrangement of print elements on a print head. 
     Another implementation described here involves a printing apparatus with a first set of electronics to send image data to a second set of electronics on a print head, in which each set of electronics includes multiple components to enable high-speed printing on a workpiece. The printing apparatus has an optical cable connection to connect the first and second sets of electronics. Each set of electronics includes an optical connection interface. The printing apparatus has a triggering device to cause the image data to be printed substantially immediately on the workpiece as the image data from the first set of electronics arrives at the second set of electronics. 
     In one aspect, a complexity of design of the first set of electronics can be greater than a complexity of design of the second set of electronics. The triggering device can be configured to enable synchronous printing of image data on the workpiece as the image data arrives at the second set of electronics. The second set of electronics can be physically separated or physically remote from the first set of electronics. 
     The described print systems and techniques can be implemented to realize one or more of the following advantages. The process of printing images on a workpiece is synchronized with the entry of a new workpiece in the print area of a printer. When a leading edge of a new workpiece is detected, image data is sent to the print head assembly at the precise time the print element association is to deposit ink on the workpiece to generate a high-quality image on the workpiece. Poor image quality on the workpiece can be avoided by substantially eliminating excessive pauses or gaps when receiving the image data for the print head assembly. Transmission of image data to the print head assembly can serve as a trigger that causes the image data to be printed substantially immediately as the data arrives at the print head assembly. 
     The printing system can be a scalable architecture that can print images at high image data rates. The printing system also can be implemented with lower cost hardware and design effort. The primary printing electronics can be implemented on a personal computer (PC) (e.g., a single-board computer card) and connected through a Peripheral Component Interconnect (PCI) on a host computer. The high-speed characteristics of PC memory (e.g., RAM) can be used to reduce the amount of memory needed for the print head assembly. Moreover, the disclosed architecture enables the print head assembly to be controlled by a relative small number of components, each being processed at relatively low speeds. 
     A data pump can send image data to a print head assembly at high data rates to enable just-in-time printing of images on the workpieces as the workpieces move along a workpiece conveyor. Because the amount of memory can be reduced on the print head assembly, the print head assembly may be implemented at a lower cost. The type of memory used on the print head assembly may also be implemented at a lower cost. In one implementation, memory for the print head assembly can be field programmable gate array (FPGA) integrated circuit (IC), which is programmed to control the print head electronics. As a result, the costs and engineering design efforts to implement the print head assembly may be reduced due to little or no buffering of high speed image data at the print head assembly. 
     In one implementation, the data rate of image data sent to the printhead assembly can be scaled by having multiple data pumps connected to a single host computer. In another implementation, the system may be scalable in having multiple computers to operate in parallel to deliver higher image data rates to the print head assembly. In this implementation, each computer may have at least one PC card of control electronics connected to the PCI slot of the computer. The system may also offer scalable transmission of high bandwidth, synchronous, just-in-time image data to the print head assembly in a number of configurations, including adding multiple FPGAs to the print assembly. Because the system can handle high bandwidths of image data, the system can provide just-in-time printing of high resolution images at high conveyor speeds, large-size images at high conveyor speeds, and/or multi-color and grayscale images at high conveyor speeds. 
     Image data that represents an image to be printed can be divided according to the deployment of associations of print elements in a printer. The divided image data can be stored at different memory locations, depending on the deployment of the print element associations. The different memory locations can be individual memory buffers. The memory buffers can be part of associated queues of like memory buffers. The data pump can receive the image data from the different memory locations. Each physical column of associated print modules can function logically independently from the others, so that printing on the workpiece can be continuous and substantially without printing gaps. The data pump can facilitate just-in-time, synchronous transmission of image data from the host PC without the need for buffering or additional robust or powerful logic at the print head assembly. Additional data pumps can be added to the host computer to scale to higher resolutions and/or to increase bandwidth requirements. Additional parallel host computers can be added to the system to further scale printing operations. 
     Because each of the physical columns of associated print modules function logically independently from the others, bit manipulation does not have to be performed in the hardware of the print head assembly to achieve real-time printing of images. The system can facilitate software bit manipulation, so bit manipulation can be performed at high data rates, and engineering and material costs can be reduced. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a block diagram of a printing system. 
         FIGS. 2 and 3  illustrate an arrangement of printer elements in the printing system of  FIG. 1 . 
         FIG. 4  schematically illustrates the deployment of print elements with relative shifts in lateral position. 
         FIG. 5  schematically illustrates the serial printing of an image on different workpieces. 
         FIG. 6  is a flowchart of a process for the serial printing of an image on different workpieces. 
         FIGS. 7 ,  8 , and  9  illustrate implementations of the division of image data according to the deployment of associated print elements. 
         FIG. 10  shows a schematic representation of an implementation of a printing system. 
         FIG. 11  is a flowchart of a process for synchronized printing on a workpiece. 
         FIG. 12  schematically illustrates a data pump. 
         FIG. 13  schematically illustrates a packet of image data generated by the data pump. 
         FIG. 14  shows exemplary specifications for the data pump. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  is a block diagram of a print system  100 . Print system  100  includes a workpiece conveyor  105  and a printer housing  110 . Workpiece conveyor  105  produces relative motion between a series of workpieces  115 ,  120 ,  125 ,  130 ,  135 ,  140 ,  145  and printer housing  110 . In particular, workpiece conveyor  105  conveys workpieces  115 ,  120 ,  125 ,  130 ,  135 ,  140 ,  145  in a direction D across a face  150  of printer housing  110 . Workpiece conveyor  105  can include a stepper or continuous motor that moves a roller, a belt, or other element that can retain workpieces  115 ,  120 ,  125 ,  130 ,  135 ,  140 ,  145  during conveyance. Workpieces  115 ,  120 ,  125 ,  130 ,  135 ,  140 ,  145  can be any of a number of different substrates upon which system  100  is to print. For example, workpieces  115 ,  120 ,  125 ,  130 ,  135 ,  140 ,  145  can be paper, cardboard, microelectronic devices, or foodstuffs. 
     Printer housing  110  houses a workpiece detector  155 . Workpiece detector  155  can detect the position of one or more workpieces  115 ,  120 ,  125 ,  130 ,  135 ,  140 ,  145 . For example, workpiece detector  155  can be a laser/photodetector assembly that detects the passage of edges of workpieces  115 ,  120 ,  125 ,  130 ,  135 ,  140 ,  145  across a certain point on face  150 . 
     Located remotely from the printer housing  110  are control electronics  160 . The control electronics  160  interface with the printer housing  110  by a cable  195  (e.g., an optical cable) and minimal electronics  190 . Control electronics  160  control the performance of print operations by system  100 . Control electronics  160  can include one or more data processing devices that perform operations in accordance with the logic of a set of machine-readable instructions. Control electronics  160  may be, for example, a personal computing system that runs image processing software and software for controlling printing at the printer housing  110 . 
     Located within the control electronics  160  is a print image buffer  165 . Print image buffer  165  is one or more data storage devices that store image data for printing by print elements. For example, print image buffer  165  can be a collection of random access memory (RAM) devices. Print image buffer  165  can be accessed by control electronics  160  to store and retrieve image data. 
     The control electronics  160  interface with the printer housing  110  via the cable  195  and minimal electronics  190 . The control electronics  160  can send data across the cable  195 , and the minimal electronics  190  can receive that data for printing at the printer housing  110 . The control electronics  160  may have special circuitry (e.g., a data pump, as described in more detail in reference to  FIG. 10 , that can receive and/or retrieve image data from print image buffers, store the image data, and enable print elements at a printing device to receive image data in time to deposit ink on the corresponding image locations on workpieces as they are moving along a conveyor) for generating data to send to the printer housing  110 . The minimal electronics  190  may be, for example, a field-programmable gate array that includes a microprocessor, transceiver, and minimal memory. The minimal electronics  190  may be connected to the printer housing  110  such that the minimal electronics  190  can be disconnected easily should the printer housing  110  and/or hardware in the printer housing  110  be changed. For example, if the printer housing  110  is replaced with a newer printer housing containing newer printing modules, the minimal electronics  190  can be disconnected from the older printer housing  110  and connected to the newer printer housing. 
     The printing of an image is divided between the control electronics  160  and the minimal electronics  190  such that the control electronics performs image processing and controls printing, whereas the minimal electronics  190  receives data received via the cable  195  and uses that data to cause firing of print elements at the printer housing  110 . Thus, for example, image data may be converted to jetmap image data, which may include dividing the image data into multiple image queues of image buffers as part of the process of converting to jetmap image data (as described in more detail later); delays may be inserted into image data (e.g., inserting delays corresponding to a deployment of print element associations); and image data may be sent (e.g., encoding data packets of image data and sending by a receiver) at an appropriate time by the control electronics  160 ; whereas, the minimal electronics  190  may merely receive the image data (e.g., decode image data packets sent across the cable  195 ) and relay the image data such that the image data is printed on a workpiece (e.g., cause firing of inkjet nozzles according to the image data). The control electronics  160  may synchronize printing of an image at the printer housing  110 . Following the previous example, the control electronics  160  may synchronize the printing of an image by receiving an indication of a leading edge of a workpiece and sending image data across the cable  195  to cause the printing of an image at the printer housing  110 . 
     The control electronics  160  can send image data to the printer housing  110  at high data rates to enable “just-in-time” printing of images on the workpieces as the workpieces move along the workpiece conveyor  105 . In one implementation of just-in-time printing, transmission of image data to the printer housing  110  can serve as a trigger that causes the image data in a packet to be printed “substantially immediately” as the data arrives at the printer housing  110 . In this implementation, the image data may not be stored on a storage component on the printer housing prior to printing the image data, but can be printed as the data arrives at the printer housing. Just-in-time printing may also refer to printing image data substantially at an instant at which the image data arrives at the printer housing. 
     In another implementation of just-in-time printing, data received at the printer housing is stored in one or more latches, and new or subsequent data that is being received at the printer housing can serve as a trigger to print the latched data. In this implementation, the data received at the printer housing is stored in a latch until the subsequent data arrives at the printer housing, and the subsequent data arriving at the printer housing can serve as a trigger to print the data that has been latched. The data, subsequent data, and latched data may be received and/or stored at the printer housing in the form of an image data packet. In one case, the subsequent data arriving at the printer housing is the next subsequent data. Alternatively, the subsequent data arriving at the printer housing is subsequent data other than the next subsequent data, such as subsequent data arriving after the next subsequent data. Because the image data is being printed at such a high-data rate, the data printed from latched data can also refer to data being printed “substantially immediately” as the data is arriving at the printer housing. 
     Because the printer housing  110  has minimal electronics  190  and a reduced amount of memory, the printer housing  110  may be implemented at a lower cost. The type of memory used on the printer housing  110  may also be implemented at a lower cost. In one implementation, the type of memory implemented on the printer housing  110  is part of a field-programmable gate array (FPGA) integrated circuit (IC) that may be part of the minimal electronics  190 . The costs and engineering design efforts to implement the printer housing  110  may also be reduced due to little or no buffering of high speed image data at the printer housing  110 . The system  100  may offer scalable transmission of high bandwidth, synchronous, just-in-time image data to the printer housing  110  in a number of configurations, including, for example, a configuration with multiple FPGAs at the printer housing  110 , each of which may implement the minimal electronics  190  and interface with one or more data pumps using one or more cables. 
       FIGS. 2 and 3  illustrate the arrangement of print modules and print elements on housing  110 . In particular,  FIG. 2  shows housing  110  from the side, whereas  FIG. 3  shows housing  110  from below. 
     Housing  110  includes a collection of print modules  205 ,  210 ,  215 ,  220 ,  225 ,  230 ,  305 ,  310 ,  315  on face  150 . Print modules  205 ,  210 ,  215 ,  220 ,  225 ,  230 ,  305 ,  310 ,  315  each include one or more print elements. For example, print modules  205 ,  210 ,  215 ,  220 ,  225 ,  230 ,  305 ,  310 ,  315  can each include a linear array of inkjet nozzles. 
     Print modules  205 ,  305  are arranged laterally along a column  320 . Print module  210  is arranged along a column  325 . Print modules  215 ,  310  are arranged laterally along a column  330 . Print module  220  is arranged along a column  335 . Print modules  225 ,  315  are arranged laterally along a column  340 . Print module  230  is arranged along a column  345 . This arrangement of print modules  205 ,  210 ,  215 ,  220 ,  225 ,  230 ,  305 ,  310 ,  315  along columns  325 ,  330 ,  335 ,  340 ,  345  spans an effective print area  235  on face  150 . Effective print area  235  has a longitudinal width W that spans from the print elements in print modules  205 ,  305  to the print elements in print module  230 . 
     Print modules  205 ,  210 ,  215 ,  220 ,  225 ,  230 ,  305 ,  310 ,  315  can be deployed in print element associations to print selected components of an image. For example, print modules  205 ,  210 ,  305  can be deployed in a first print element association to print a first color across the entire lateral expanse of a substrate moving across face  150 , print modules  215 ,  220 ,  310  can be deployed in a second print element association to print a second color across the entire lateral expanse, and print modules  225 ,  230 ,  315  can be deployed in a third print element association to print a third color across the entire lateral expanse. 
     As another example, the group of print modules  205 ,  210 ,  215 ,  220 ,  225 ,  230 ,  305 ,  310 ,  315  can be deployed in print element associations based on the columnar position of the constituent print elements in the modules. For example, a first print element association can include modules  205 ,  305  deployed so that their constituent print elements are arranged in a single column. A second print element association can include only print module  210 . Modules  215 ,  310  can form a third association. Associations four, five, and six include modules  220 ,  225  and  315 , and  230 , respectively. Forming associations of print elements in this columnar manner allows the printing of back-to-back dissimilar images with variable but small or nonexistent non-printed area between finished image areas, relative to longitudinal width W, without need for complex real-time adjustments in image data. 
     As another example, the group of print modules  205 ,  210 ,  215 ,  220 ,  225 ,  230 ,  305 ,  310 ,  315  can be deployed in print element associations based on the lateral position of the constituent print elements in the modules. For example, a first print element association can include modules  205 ,  210 ,  305  deployed so that their constituent print elements are shifted in lateral position relative to the print elements in modules  215 ,  220 ,  310  and to the print elements in modules  225 ,  230 ,  315 . A second print element association can include print modules  215 ,  220 ,  310  deployed so that their constituent print elements are shifted in lateral position relative to the print elements in modules  205 ,  210 ,  305  and to the print elements in modules  225 ,  230 ,  315 . Modules  225 ,  230 ,  315  can form a third association. The relative shifts in position can be smaller than the lateral spacing of the print elements in the modules to, in net effect, decrease the lateral spacing between print elements on housing  110  and thereby effectively increase the resolution at which an image can be printed. 
     As another example, groups of print modules can be deployed in print element associations based on the lateral expanses covered by the print modules. For example, a first print element association can include modules  205 ,  305 ,  215 ,  310 ,  225 ,  315  deployed to cover the laterally outer expanses of a workpiece. A second print element association can include print modules  210 ,  220 ,  230  deployed to cover the laterally central expanses of a workpiece. 
     As another example, groups of print elements can be deployed in print element associations based on a combination of these and other factors. For example, groups of print elements can be deployed in a print element association based on their printing the color cyan on an outer extent of a workpiece. As another example, groups of print modules can be deployed in a print element association based on their constituent print elements printing at certain lateral positions on the laterally outer expanses of a workpiece. 
     Each print element association can have a dedicated memory location in print image buffer  165  (shown in  FIG. 1 ) in that the association prints image data that once resided in the memory location. For example, when print image buffer  165  is a collection of queues of individual buffers, each print element association can have an individual, dedicated queue of buffers. 
       FIG. 4  schematically illustrates a deployment of print elements with relative shifts in lateral position. The illustrated portion of housing  110  includes print modules  205 ,  215 ,  225 . Print module  205  includes an array of print elements  405  laterally separated from one another by a distance L. Print module  215  includes an array of print elements  410  laterally separated from one another by a distance L. Print module  225  includes an array of print elements  415  laterally separated from one another by a distance L. 
     Print elements  405  are shifted relative to the lateral position of print elements  410  by a shift distance S. Print elements  405  are shifted relative to the lateral position of print elements  415  by shift distance S. Print elements  410  are shifted relative to the lateral position of print elements  415  by shift distance S. Shift distance S is smaller than distance L, and the net effect of the relative lateral shifts between print elements  405 , print elements  410 , and print elements  415  is to decrease the overall lateral spacing between print elements on face  150  of housing  110 . 
       FIG. 5  schematically illustrates the serial printing of an image  500  on two or more different workpieces using print system  100 . A series of workpieces  120 ,  125 ,  130 ,  135 ,  140  is conveyed across effective print area  235  on face  150  of printer housing  110  for printing. Image  500  can be serially printed in that image  500  can be printed sequentially on workpieces  120 ,  125 ,  130 ,  135 ,  140  (i.e., the same image is printed, in succession, on various workpieces). 
     Workpieces  120 ,  125 ,  130 ,  135 ,  140  each have a longitudinal width W 2 . Workpiece width W 2  is smaller than width W of effective print area  235 . A leading edge of workpiece  120  is separated from a trailing edge of workpiece  125  by separation distance SEP. A leading edge of workpiece  125  is separated from a trailing edge of workpiece  130  by separation distance SEP. A leading edge of workpiece  130  is separated from a trailing edge of workpiece  135  by separation distance SEP. A leading edge of workpiece  135  is separated from a trailing edge of workpiece  140  by separation distance SEP. The separation distance SEP may be smaller than width W of effective print area  235 . The separation distance SEP may be zero. As such, both workpiece  130  and workpiece  135  may be positioned in effective print area  235  simultaneously and be printed on at the same time. 
     System  100  has partially printed image  500  on both workpiece  130  and workpiece  135 . Such serial printing of image  500  on two or more different workpieces using a single effective print area speeds the throughput of workpieces in system  100 . 
       FIG. 6  includes flowcharts of processes  650 ,  655 ,  660  for the serial printing of an image on two or more different workpieces using a single effective print area. Processes  650 ,  655 ,  660  can be performed in whole or in part by a data processing apparatus and/or circuitry configured to exchange data with a buffer and control printing by print elements. In system  100 , processes  650 ,  655 ,  660  can be performed by control electronics  160  using input received from workpiece conveyor  105  and workpiece detector  155 . Within the control electronics  160 , different processes may be performed by different parts of the system  100 . For example, the process  650  may be performed by software operating in the control electronics  160  and the processes  655  and  660  may be performed by a data pump. The processes of  650 ,  655 , and  660  are separate to indicate that they can be performed concurrently and/or independently of each other. 
     The system performing the process  650  receives image data at  605 . The image data can be a stand-alone collection of data regarding an individual image. For example, the image data can be a graphic image format (gif) file, a joint photographic experts group jpeg) file, PostScript, Printer Command Language (PCL), or other image data collection. 
     The system can then translate and divide the received image data according to a deployment of associated print elements at  610 . The image data can be translated before it is divided, divided before it is translated, or translated and divided as part of the same process. The translation of image data can include, for example, a conversion of image data into a format understandable by a printing device, such as bitmap raster data, and a further conversion of the bitmap raster data into jetmap data. Converting bitmap raster image data into jetmap data involves taking an input bitmap, which is arranged in an order corresponding to a geographic order used by the bitmap image format, and rearranging the bitmap raster image data to correspond to physical locations of the print elements. It may also involve dividing the image data as part of the process of converting the bitmap raster image data to jetmap data (i.e., the jetmap data is divided into image buffers corresponding print element associations). As an example, the process at  610  may include converting jpeg formatted image data to bitmap formatted image data, and then converting the bitmap formatted image data into jetmap image data as image buffers corresponding to print element associations. In an alternative implementation, image data may be converted directly to jetmap data without first converting to an intermediary format. 
     The division of image data according to the deployment of associated print elements can include the identification of portions of the image data that are to be printed by an association of print elements based on the deployment of the association. 
       FIG. 7  illustrates one implementation of the division of image data representing an image  700  according to a deployment of print element associations. Image  700  includes a cyan line  705 , a magenta line  710 , and a yellow line  715 . Cyan line  705  is printable by an association of print elements deployed to print cyan. Magenta line  710  is printable by an association of print elements deployed to print magenta. Yellow line  715  is printable by an association of print elements deployed to print yellow. 
     When the image data representing image  700  is divided (indicated by arrows  720 ), three individual collections of data representing images  725 ,  730 ,  735  are formed. Image  725  includes cyan line  705  and is thus printable by an association of print elements deployed to print cyan. Image  730  includes yellow line  715  and is thus printable by an association of print elements deployed to print yellow. Image  735  includes magenta line  710  and is thus printable by an association of print elements deployed to print magenta. Thus, the image data representing images  725 ,  730 ,  735  are the result of a division of data representing image  700  according to the deployment of associations of print elements to print different colors. 
       FIG. 8  illustrates another implementation of the division of image data (namely, image data representing a portion of an image  800 ) according to a deployment of print element associations. In particular, a division according to a deployment of print elements with relative shifts in lateral position is illustrated. The shifts in the lateral position of print elements can correspond to the lateral shifts S between print elements  405 , print elements  410 , and print elements  415  in the implementation of housing  110  shown in  FIG. 4 . 
     Image portion  800  includes collections of pixel rows  805 ,  810 ,  815 . Pixel rows  805 ,  810 ,  815  each include a longitudinal row of pixels. Pixel rows  805  are laterally shifted relative to the position of pixel rows  810  by a shift distance S. Pixel rows  805  are laterally shifted relative to the position of pixel rows  815  by shift distance S. Pixel rows  810  are laterally shifted relative to the position of pixel rows  815  by shift distance S. Shift distance S (and hence the lateral resolution of the printed imaged) is determined by the overall lateral spacing between print elements. 
     When a workpiece is moved longitudinally across an array of print elements, each pixel row  805 ,  810 ,  815  can be printed by an individual print element. For example, when image portion  800  is printed using the implementation of housing  110  shown in  FIG. 4 , a single print element  405  can print a single pixel row  805 , a single print element  410  can print a single pixel row  810 , and a single print element  415  can print a single pixel row  815 . 
     When the image data representing image portion  800  is divided (indicated by arrows  820 ), three individual collections of data representing image portions  825 ,  830 ,  835  are formed. Image portion  825  includes pixel rows  805  and is thus printable by a first array of print elements separated by a lateral distance L. Image portion  830  includes pixel rows  810  and is thus printable by a second array of print elements separated by a lateral distance L. Image portion  835  includes pixel rows  815  and is thus printable by a third array of print elements separated by a lateral distance L. The print elements in these arrays are shifted in lateral position relative to one another. Thus, the image data representing image portions  825 ,  830 ,  835  are the result of a division of data representing image portion  800  according to the deployment of associations of print elements to print at different lateral positions. 
       FIG. 9  illustrates another implementation of a division of image data representing an image  900  according to a deployment of print element associations. Image  900  includes a single line  905  that spans the entire lateral expanse of image  900 . 
     When the image data representing image  900  is divided (indicated by arrows  910 ), two individual collections of data representing images  915 ,  920  are formed. Image  915  includes two outer line portions  925  and is thus printable by an association of print elements deployed toward the outside of a workpiece. For example, outer line portions  925  may be printable by an association that includes print modules  205 ,  305 , by an association that includes print modules  215 ,  310 , or by an association that includes print modules  225 ,  315  ( FIG. 3 ). 
     Image  920  includes a central line portion  930  and is thus printable by an association of print elements deployed toward the center of a workpiece. For example, central line portion  930  may be printable by an association that includes print module  210 , by an association that includes print module  220 , or by an association that includes print module  230  ( FIG. 3 ). Thus, the image data representing images  915 ,  920  are the result of a division of data representing image  900  according to the deployment of associations of print elements to print different lateral expanses. 
     Returning to  FIG. 6 , the system performing process  650  allocates the image data portions that result from a division to respective image queues at  615 . In other words, the allocation results in each buffer of image data being allocated to a respective queue. In general, each buffer of image data corresponds to an association of print elements at a printing device. Similarly, a set of buffers corresponds to a set of image data to be printed by the print element associations. The buffers of image data, which were generated at  610 , are queued in queues, with each queue corresponding to a print element association. For example, if there are eight image queues, each image queue corresponding to a print element association, then a set of buffers of image data that correspond to the first print element association may be allocated to the first image queue, a set of buffers of image data that correspond to the second print element association may be allocated to the second image queue, and so on. The memory locations where the image queues and the buffers are located can be dedicated to the storage of image data for printing by a specific print element association. For example, the memory locations may be blocked off from memory management by an operating system and the memory locations may be accessible by a data pump using direct memory access. The queues for the buffers of image data may be first in first out queues (i.e., FIFO queues). 
     At  620 , the system performing process  650  determines whether the system should update the locations indicating where the print image buffers (i.e., buffers of image data) are located. For example, the system might update locations at one or more data pumps. In that example, the data pumps can store a location indicating where print buffers are located at each of the image queues so the data pumps are able to access each of the memory devices where the buffers are located and retrieve image data. If, at  620 , the system determines that the locations should be updated, the locations are updated with references to the buffers at  625 . Otherwise, image-data is received at  605  and the process continues. Also, the process continues at  605  if updated locations are not needed at  620 . In some implementations, the process of  650  may stop, for example, if there are no more images to receive (e.g., no more images to print), or if the image queues are full. 
     A determination is made as to whether printing should start or continue at  627 . If not, the process continues at  627 . If so, at  630 , image data may be retrieved from buffers in the image queues. For example, a data pump may retrieve buffers of image data. In that example, the data pump is able to identify the proper buffers because the locations of the buffers may be updated at the data pump at  625 . A sufficient amount of image data for one impression of an association of print elements may be retrieved. Thus, image data may be retrieved from each of the image queues. In alternative implementations, portions of image data representing a portion of a single impression may be retrieved. Similarly, portions of image data representing several impressions may be retrieved. In those implementations, a queue, such as a FIFO queue, may store image data (e.g., sets of buffers of image data). 
     At  635 , positional delays are added to selected portions of image data. The delays are upfront delays that align image data with the associations of print elements to which respective portions of image data correspond. Thus, the extent of the up front delay can be determined based on the deployment of the print element association to which image data corresponds. For example, a minimal positional delay or no delay at all may be inserted into image data that corresponds to a print element association near the entry of workpieces across an effective print area, whereas a larger positional delay may be inserted into image data that corresponds to a print element association near the exit of workpieces across an effective print area. Because the positional delays correspond to the position of print element associations (or rather, the separation distance between print element associations), the positional delays may differ depending on a type of print head assembly that contains the print element associations. In any case, the positional delays may be a fixed delay(s) for a particular print head assembly and the delays may be measured in an amount corresponding to an amount of print lines. 
     Inserting an upfront delay into image data can be performed in a number of different ways. For example, an appropriate amount of null “placeholder” data can be inserted before and after the image data portions that result from a division of image data. As another example, the upfront delay can be introduced into a data communication path between a memory location and print elements. For example, a data pump may be aligned such that the data pump can insert different upfront delays for different portions of image data at different memory locations. Image data with delays may be sent to a printing device at  637 . In alternative implementations, image data with delays may be added to a queue (e.g., a first in first out queue) prior to sending the data to a printing device. The process at  655  may continue at the process of  627  after image data is sent at  637 . In some implementations, the process at  655  may stop after image data is sent at  637  for various reasons. For example, if all image data packets have been sent by a data pump, the data pump may determine at  627  that the system should no longer be printing (i.e., determine not to start or continue printing). In some implementations, empty data image packets may be sent, effectively causing no ink to be deposited on a workpiece. 
     The system can identify the entry of a leading edge of a workpiece to an effective print area of a print system at  640 . The entry of the leading edge can be identified using a workpiece detector (such as workpiece detector  155  ( FIG. 1 )). The further progress of the workpiece across the effective print area can be followed by sensing the speed of the workpiece, e.g., by measuring the speed of a workpiece conveyor (such as workpiece conveyor  105  ( FIG. 1 )) using a rolling encoder. 
     When the workpiece is appropriately positioned, the print system performing process  660  can commence printing of the workpiece at  645 . The printing of the workpiece can include relaying image data that has been divided according to the deployment of the print element association. The image data can be relayed from a memory location to the appropriate print element association. The relaying can be driven by a central data processing device, such as a central data processing device in control electronics  160 . The relaying can be done on a firing-by-firing basis. In the processes shown in the flowcharts of  FIG. 6 , a signal may be sent to the system performing the process of  655  (e.g., a data pump) to start printing, causing a relaying of image data to a printing device. 
     As the workpiece moves across the effective print area, different print elements can be triggered by the same trigger signal to fire at the same instant. Alternatively, different print elements can be staggered to fire at different instants. Regardless of when the actual firing of individual elements occurs, the elements in the effective print area are printing on the initial workpiece at the same time. 
     In a print system where the effective print area has a longitudinal width that is greater than the separation distance to the next workpiece, one or more workpieces may be positioned beneath the effective print area at the same time. As such, more than one workpiece may be available for serial printing. One example of this situation is illustrated in  FIG. 5 , where the separation distance SEP between workpieces is smaller than width W of effective print area  235 , and, both workpiece  130  and workpiece  135  are positioned beneath effective print area  235  and available to be printed in series. 
     In such a print system, the system performing process  660  can also identify the entry of the leading edge of a next workpiece at  640 . The entry of the leading edge can be identified using a workpiece detector (such as workpiece detector  155  ( FIG. 1 )). The progress of both an initial workpiece and the next workpiece across the effective print area can be followed by sensing the speed of the workpieces, e.g., by measuring the speed of a workpiece conveyor (such as workpiece conveyor  105  ( FIG. 1 )). 
     Printing on both workpieces can continue as the initial workpiece and the next workpiece continue to progress across the effective print area. When the effective print area has a longitudinal width that is greater than the sum of the width of a next workpiece and twice the separation distance between workpieces, an initial workpiece, the next workpiece, and yet another workpiece may be positioned beneath the effective print area at the same time. As such, three workpieces may be available for printing in series. In this case, the system performing process  660  can identify the leading edge of another “next workpiece” at  640  before stopping printing on an initial workpiece. Otherwise, the system can stop printing on the initial workpiece before identifying the leading edge of another “next workpiece” at  640 . 
     In some implementations, image data may be divided based on associations of print modules. In some implementations, print element associations may be split across a single print module. For example, if each print module in a print system includes two rows of print elements, image data may be divided by the rows of print elements. Thus, a space between workpieces may be reduced to zero. 
     In some implementations, the system(s) performing processes shown in  FIG. 6  can calculate the positional delay required between print element associations (rather than having a fixed delay). The memory locations can be dedicated to specific print element associations. For example, individual buffers can store image data for printing by individual print element associations. The system performing processes shown in  FIG. 6  can control a data pump or other hardware device to extract data from memory locations at the appropriate point in time to properly place image data on a workpiece on which the image data is to be printed. 
     Although the processes of  FIG. 6  are shown as being composed of a certain number and type of processes, additional and/or different processes can be used instead. For example, in the process of  655 , rather than continually determining whether to continue or start printing at  627 , the system performing the process of  655  may start printing when started and stop printing when the system decides to stop printing, only to start printing when called on again. Similarly, the processes need not be performed in the order depicted, or by the components that were discussed to have performed certain processes. 
       FIG. 10  shows a schematic representation of an implementation of a print system  1000 . System  1000  includes workpiece conveyor  1005 , a printer housing  1010 , a workpiece detector  1055 , and control electronics  1060 . 
     Workpiece conveyor  1005  conveys workpieces  1020 ,  1025 ,  1030 ,  1035  in a direction D across an effective print area  1040  of printer housing  1010 . Workpiece conveyor  1005  includes an encoder  1007  that senses the speed of workpieces  1020 ,  1025 ,  1030 ,  1035 . Encoder  1007  also generates a signal that encodes the sensed speed and relays the signal to control electronics  1060 . Workpiece detector  1055  is an optical sensor that detects the position of one or more workpieces  1020 ,  1025 ,  1030 ,  1035 , and generates trigger signals (such as trigger signals  1056  and  1057 ) based upon that detection. 
     Printer housing  1010  includes a collection of print modules arranged laterally along a series of columns  1011 ,  1012 ,  1013 ,  1014 ,  1015 ,  1016 ,  1017 ,  1018 . This arrangement of print modules spans an effective print area  1040 . Each group of print modules deployed along each of columns  1011 ,  1012 ,  1013 ,  1014 ,  1015 ,  1016 ,  1017 ,  1018  constitutes a print element association. As examples, print modules  1091 ,  1093 ,  1095  constitute a print element association along column  1018 , and print modules  1092 ,  1094  constitute a print element association along column  1017 . 
     Control electronics  1060  controls the performance of print operations by system  1000 . Control electronics  1060  includes a collection of print image buffers  1065 . Control electronics  1060  can access the print image buffers in collection  1065  to store and retrieve image data. In the configuration shown in  FIG. 10 , there are eight print image buffers in collection  1065 , and each print image buffer is dedicated to a print element association arranged along one of columns  1011 ,  1012 ,  1013 ,  1014 ,  1015 ,  1016 ,  1017 ,  1018 . For example, print image buffers  1066 ,  1067 ,  1068 ,  1069  may correspond to the print element associations arranged along columns  1015 ,  1016 ,  1017 ,  1018 , respectively. In particular, each print element association prints image data only from the associated print image buffer. 
     Control electronics  1060  also includes a data pump  1070 . A “data pump” refers to a functional component, e.g., implemented in hardware, software, programmable logic or a combination thereof, that processes data and transmits it to one or more printing devices for printing. In one implementation, the data pump can refer to a direct memory access (DMA) device. The data pump  1070  is positioned along the data communication path between the print element associations and their dedicated print image buffers in collection  1065 . The data pump  1070  can receive and store image data from each print image buffer in collection  1065 . The data pump  1070  is programmable by control electronics  1060  to delay the communication of information from the print image buffers in collection  1065  to the print element associations. 
     In operation, control electronics  1060  can divide image data according to the deployment of print element associations in effective print area  1040 . Control electronics  1060  can also allocate the divided image data to an appropriate print image buffer in collection  1065 . 
     As workpiece  1035  is conveyed by workpiece conveyor  1005  to enter effective print area  1040 , workpiece detector  1055  detects the leading edge of workpiece  1035  and generates trigger signal  1056 . Based on receipt of trigger signal  1056 , control electronics  1060  can program data pumps  1070  with positional delays  1071 ,  1072 ,  1073 ,  1074 ,  1075 ,  1076 ,  1077 ,  1078 . Delay  1071  delays the communication of image data from a first print image buffer in collection  1065  to the print element association arranged along column  1011 . Delay  1072  delays the communication of image data from a second print image buffer in collection  1065  to the print element association arranged along column  1012 . Delays  1073 ,  1074 ,  1075 ,  1076 ,  1077 ,  1078  delay the communication of image data from respective print image buffers in collection  1065  to the print element associations arranged along columns  1013 ,  1014 ,  1015 ,  1016 ,  1017 ,  1018 . 
     As workpiece  1035  is conveyed by workpiece conveyor  1005  across effective print area  1040 , the print element associations arranged along columns  1011 ,  1012 ,  1013 ,  1014 ,  1015 ,  1016 ,  1017 ,  1018  successively print. In particular, as workpiece  1035  is advanced one scan line across effective print area  1040 , the data pump  1070  dumps image data to the appropriate receiver electronics at the print element associations arranged along columns  1011 ,  1012 ,  1013 ,  1014 ,  1015 ,  1016 ,  1017 ,  1018  (i.e., the data pump  1070  causes the image data to be transmitted to the printing device). The dumped image data identifies print elements that are to fire for the instantaneous position of workpiece  1035  in effective print area  1040  (the identification of print elements may be implicit; e.g., an ordering of image data in a data packet in a format corresponding to an order of print elements and/or print element associations at a printing device). Data for successive firings can be loaded from print image buffers in collection  1065  to the data pump  1070  during firings. 
     While workpiece  1035  is still being printed, workpiece  1030  can be conveyed by workpiece conveyor  1005  to enter effective print area  1040 . Workpiece detector  1055  detects the leading edge of workpiece  1030  and generates trigger signal  1057 . Based on receipt of trigger signal  1057 , control electronics  1060  may cause the data pump  1070  to insert delays  1079 ,  1080 ,  1081 ,  1082 ,  1083 ,  1084 ,  1085 ,  1086 . Delay  1079  delays the communication of image data from a first print image buffer in collection  1065  to the print element association arranged along column  1011 . Delay  1080  delays the communication of image data from a second print image buffer in collection  1065  to the print element association arranged along column  1012 . Delays  1081 ,  1082 ,  1083 ,  1084 ,  1085 ,  1086  delay the communication of image data from respective print image buffers in collection  1065  to the print element associations arranged along columns  1013 ,  1014 ,  1015 ,  1016 ,  1017 ,  1018 . Alternatively, delays may already be inserted into image data and the trigger signal may cause the sending of image data by the data pump  1070 . 
     As workpiece  1030  is conveyed by workpiece conveyor  1005  into effective print area  1040 , the print element associations arranged along columns  1011 ,  1012 ,  1013 ,  1014 ,  1015 ,  1016 ,  1017 ,  1018  print upon workpieces  1030 ,  1025 . In particular, as workpieces  1035 ,  1030  are advanced one scan line, the data pump  1070  dumps image data to the appropriate receiver electronics for the print element and workpieces  1035 ,  1030  are printed at the same time. 
     Image data for each workpiece may differ. For example, if two workpieces were to have two different images printed upon them, different image data representing different images would be used to print on each workpiece. In that example, two sets of image data may be gathered at a data pump. A first set of image data may correspond to a first image (e.g., a print line of an image of a frog) and a second set of image data may correspond to a second image (e.g., three print lines of an image of an apple). Gathering the image data may include taking image data from image queues and/or generating a data packet that comprises the first and second sets of image data. The gathered image data may be provided to the print element associations by sending a data packet to the printing device that includes the print element associations (e.g., a data packet include the print line of the image of the frog and the three print lines of the image of the apple). When the two workpieces are printed at substantially the same time, a first portion of the print buffers (e.g., print buffer  1066 ) may store the first set of image data corresponding to the first image (e.g., the print line of the image of the frog) and a second portion of the print buffers (e.g., print buffers  1067 ,  1068 ,  1069 ) may store the second set of image data corresponding to the second image (e.g., the three print lines of the image of the apple). A first set of print elements corresponding to the first set of print buffers (e.g., the print elements in the association of print elements along column  1015 ) can print the first image (e.g., the print line of the image of the frog) and a second set of print elements corresponding to the second set of buffers (e.g., the print elements in the associations of print elements along columns  1016 ,  1017 ,  1018 ) can print the second image (e.g., the three print lines of the image of the apple). As such, different print elements print two images at substantially a same time (e.g., print elements along the columns  1015 ,  1016 ,  1017 ,  1018  may fire at substantially a same time). 
     Or, the image data for each workspace may represent the same image. For example, the same image may be continually printed on multiple workpieces. In that example, if two workpieces are printed at substantially a same time, different portions of the same image may reside in different sets of print buffers such that different print elements print different portions of the same image. 
     Although not shown, in addition to using different sets of print elements to print different portions of image data on different workpieces, a same workpiece may be printed on with different sets of image data. 
     The process of printing images on a workpiece is synchronized with the entry of a new workpiece in the print area. When a leading edge of a new workpiece is detected, and the control electronics is notified of the new workpiece, data pump  1070  dumps image data to the print head assembly at the precise time the print element association is to deposit ink on the workpiece to generate a high-quality image on the workpiece. Poor image quality on the workpiece is avoided due to no undue pauses or gaps when receiving the image data for the print head assembly. 
     In one implementation, the printing system  1000  can be a scalable architecture that can print images at high image data rates. The control electronics  1060  can be implemented on a personal computer (PC) card that is connected into a Peripheral Component Interconnect (e.g., a PCI-type interconnection system) in the personal computer. The high-speed characteristics of PC memory (e.g., RAM) can be used to reduce an amount of memory for the print head assembly. 
     The data pump  1070  can send image data to the print head assembly at high data rates to enable just-in-time printing of images on the workpieces as the workpieces move along the conveyor. Because the amount of memory can be reduced on the print head assembly, the print head assembly may be implemented at a lower cost. The type of memory used on the print head assembly may also be implemented at a lower cost. In one implementation, the type of memory implemented on the print head assembly is a floating-point gate array (FPGA) integrated circuit (IC). The costs and engineering design efforts to implement the print head assembly may also be reduced due to little or no buffering of high speed image data at the print head assembly. 
     In one implementation, the data rate of image data sent to the print head assembly can be scaled. For example, a personal computer may have multiple PC cards of control electronics  1060  for the print head assembly by having each PC card of control elections  1060  connected into a PCI slot of the computer. For instance, two-sided newspaper printing may require 2 Gb/s of image data to be sent to the print head assembly to enable just-in-time printing of an image on a workpiece. If the data pump  1070  for each of the control electronics  1060  is able to send around 1 Gb/s of image data to the print head assembly then 2 data pumps can be connected in parallel in corresponding PCI slots to deliver the 2 Gb/s for just-in-time printing of the two-sided newspaper image. In this example, each PC card of control electronics  1060  may have an optical connection to the print head assembly. In one implementation, the top and bottom sides of the workpiece can receive 1 color printed on each side. 
     In another implementation, the system  1000  may be scalable in having multiple computers to operate in parallel to deliver higher image data rates to the print head assembly. In this implementation, each computer may have at least one PC card of control electronics  1060  connected to the PCI slot of the computer. In one example, four parallel computers, each containing two PCB cards of control electronics  1060 , can offer 8 Gbps aggregate bandwidth, which can be enough to print four colors on each of the two sides of a newspaper in real time. The system  1000  may offer scalable transmission of high bandwidth, synchronous, just-in-time image data to the print head assembly in a number of configurations, including adding multiple FPGAs to the print assembly. Because the system  1000  can handle high bandwidths of image data, the system  1000  can provide just-in-time printing of high resolution images at high conveyor speeds, large-size images (e.g., wide and/or long images) at high conveyor speeds, and/or multi-color and grayscale images at high conveyor speeds. 
       FIG. 11  shows is a flowchart of a process for synchronized printing on a workpiece using the system  1000  of  FIG. 10 . The system  1000  receives the image data at  605 . The image data may be received into a personal computer having a PC card with a data pump  1070  in the control electronics  1060  of the PC card. 
     The system  1000  can translate and divide the received image data according to the deployment of the associated print elements on the print assembly at  610 . The image data can be translated before it is divided or can be divided before being translated. The system  1000  can allocate the image data portions that result from a division to different memory locations, such as individual print buffers at  615 . A workpiece may be conveyed into the print area at  1105 . A workpiece is not limited to be conveyed into the print area only at  1105 , but may occur at other times, such as before  615  or  610 . 
     The process of printing the received image on the workpiece is synchronized with the system  1000  detecting that the workpiece has entered the print area at  1170 . The detection for this process utilizes the encoder  1007  to sense the speed of the workpiece across the conveyor at  1110 . The encoder  1007  encodes a signal with information for the sensed speed and relays the encoded signal to control electronics  1060 . The optical sensor  1055  detects the position of the workpiece and generates a signal to send to the data pump  1070  in the control electronics  1060  to facilitate synchronous printing on the workpiece. 
     The data pump  1070  fetches image data according to the deployment of printing element associations at  1120 . The image data fetched by the data pump  1070  may be from the print image buffers  1065  of the PC. The data pump  1070  is not limited to fetching image data from the computer&#39;s different memory locations through the PCI slot at  1120 , but rather may fetch image data at a time between  1125  and  1130 . 
     At  1125 , the data pump  1070  receives delay information for the associated columns  1011 ,  1012 ,  1013 ,  1014 ,  1015 ,  1016 ,  1017 , and  1018 . The delay information that is delivered to the data pump through the PCI slot may be delay values that are pre-programmed or fixed and are generated by an application software. The delay values may represent the physical distance between the associated columns  1011 ,  1012 ,  1013 ,  1014 ,  1015 ,  1016 ,  1017 , and  1018  of print elements on the print head assembly. For example, if a print head assembly has four columns of associated columns with an inch of distance between each column, the first four delay values can represent an inch worth of scan line information. So, the physical design of the associated print element columns can determine the delay values. The data pump  1070  is not limited to receive delay information at  1125 , but may receive delay information at a time prior to  1125 . 
     The data pump arranges each column of data in time according to each column&#39;s delay value. The delay values are used by multiple state machines in the data pump to correctly arrange the image data into logical scan lines. The data pump serializes the data from each column into a data packet at  1130  and sends the serialized data to the print head assembly across a communication channel at  1135 . In one implementation, the communication channel uses an optical fiber connection. The optical fiber may transmit image data at a rate of 1.25 Gb/s. In another implementation, the communication channel may utilize a copper cable connection. 
     Transmission of each scan line data packet at  1137  can serve as a trigger that causes the image data in the packet to be printed substantially immediately as the data arrives at the print head assembly. The electronics on the print head assembly receives the data packet sent over the communication channel and deserializes the data packet at  1140 . The deserialized image data is allocated to the associated print elements on the print head assembly at  1145 , and the image is printed on the workpiece at  1150 . In one implementation, data received at the print head assembly is stored in one or more latches, and new (additional) data that is being received at the print head can serve as a trigger to print the latched data. 
       FIG. 12  schematically illustrates a data pump  1200 . The data pump  1200  represents a hardware architecture for assembling the scan line data packets to send to the print head assembly. The data pump  1200  includes circuitry and components on a PC board that plugs into the PCI or PCI-X (Peripheral Component Interconnect Extended) or equivalent slot of the host computer. The data pump  1200  includes a parallel array of separate state machines  1222 ,  1226 ,  1230 ,  1234 ,  1238 ,  1242 ,  1250 ,  1254 , one for each logical image queue. Each image queue can correspond to a separate physical column of associated print elements. 
     Each state machine can have a corresponding delay input that is configured to correctly arrange the image data into logical scan lines. Each state machine  1222 ,  1226 ,  1230 ,  1234 ,  1238 ,  1242 ,  1250 ,  1254  fetches image data from the host computer&#39;s PCI bus. The outputs of the read state machines are fed into a serializer  1266  that feeds the communication interface  1276  in the correct data order such that the appropriate image data is sent to the print head assembly at the correct timing. The serializer  1266  creates a packet of image data to travel to the print head assembly. Transmission of each scan line data packet can serve as a trigger that causes the image data in the packet to be printed substantially immediately as the data arrives at the print head assembly. In one implementation, the data received at the print head assembly is stored in a latch until new data arrives at the print head assembly. In this implementation, the new data arriving at the print head assembly can serve as a trigger to print the data that has been latched. 
     In the implementation shown in  FIG. 12 , an eight-column architecture for the data pump is used in which each of the physical columns of associated print elements function logically independently from the others, so that printing on the workpiece can be substantially continuous and without printing gaps. The schematic shows how the eight different delay values  1220 ,  1224 ,  1228 ,  1232 ,  1236 ,  1240 ,  1248 , and  1252  serve as input delay values for the eight different state machines  1222 ,  1226 ,  1230 ,  1234 ,  1238 ,  1242 ,  1250 ,  1254  that read image data from the eight different buffers ( 1065  in  FIG. 10 ) in the PC&#39;s memory space. The state machines are responsible for gathering image data from the PC out of a buffer  1065  that is specific to each state machine. The state machines gather image data that is temporally spaced in time, so that corresponding print columns  1011 ,  1012 ,  1013 ,  1014 ,  1015 ,  1016 ,  1017 ,  1018  each can print an image (or part of an image) on the workpiece at the correct time. 
     The delay values  1220 ,  1224 ,  1228 ,  1232 ,  1236 ,  1240 ,  1248 , and  1252  for the input of each corresponding state machine  1222 ,  1226 ,  1230 ,  1234 ,  1238 ,  1242 ,  1250 ,  1254  are preprogrammed by application software. In this implementation, the delay values are fixed values that represent the physical distance between the columns of associated print elements on the print head assembly. 
     In one implementation, the state machine  1222  for column  1  fetches and processes the image data from the PCI bus after being delayed by delay value D 1   1220 . As the output from state machine  1222  for column  1  is sent into the serializer  1266 , delay D 1  is completed and state machine  1226  for column  2  fetches and processes the image data from the PCI bus after being delayed by delay value D 2   1224 . The process continues until all of the state machines send image data to the serializer  1266 . When the scan line data packet from the data pump is sent to the print head assembly, the process begins again, and the state machine  1222  for column  1  fetches and processes new image data from the PCI bus after being delayed by delay value D 1   1220 . The state machines&#39; fetching of data from the computer&#39;s PCI bus may be done ahead of time into a FIFO memory or an equivalent memory to minimize the effects of computer bus latency on the printing. 
     The data pump  1200  can facilitate just-in-time, synchronous transmission of image data from the host PC without the need for buffering or synchronizing logic at the print head assembly. Additional data pumps can be added to the host computer to scale to higher resolutions and/or to increase bandwidth requirements. Because each of the physical columns of associated print elements function logically independently from each other, bit manipulation does not have to be performed in the hardware of the print head assembly to achieve real-time printing of images with varying amounts of non-printed area between each image. The system can facilitate software bit manipulation, so bit manipulation can be performed at high data rates, and engineering and material costs can be reduced. 
       FIG. 13  schematically illustrates a packet of image data generated by the data pump. The scan line data packet  1305  includes information to be used by the print head assembly. The packet  1305  has a start of frame (SOF)  1310  and setup data  1313  for the print head assembly. The setup data  1313  may specify an operating mode on the print head assembly (e.g., forward direction or reversion direction). The image data  1314 - 1328  for each column include a number of bytes that depends on the number of elements in the print column. For example, the image data for column  1  can have a number of bytes that depends on the number of print elements in column  1 . PH  1  represents print element  1  for column  1 , PH  2  represents print element  2  for column  1 , and PH  5  represents print element  5  for column  1 . CRC  1330  is the cyclic redundancy check, a 32-bit number that is generated from the data being sent so that the receiving electronics can verify that the entire data packet was sent correctly. The last word is the End of Frame  1332  to complete the data packet. 
     The packet  1305  is sent from the serializer  1266  to the communication interface  1276  on the data pump  1200  that converts the electronic signals to light signals to send to the optical fiber connection. On the other end of the optical fiber connection, the image data can be received by receiving hardware on the print head assembly. The receiving hardware can include an optical transceiver and logic to receive the light signal and convert the light signal into electronic signals. The receiving hardware also may include a deserializer to deserialize the data, and a decoder to decode the fiber transmission protocol. The image data can then be sent to the corresponding print element electronics to turn on or turn off the individual ink nozzles. 
       FIG. 14  shows exemplary specifications for the data pump. The data pump can have more than one type of hardware interface with the communication channel to the print assembly. One type of hardware interface can use PCI-X and optical fiber  1405  (for industrial or high-bandwidth applications) to send print data and control information to the print head assembly at data rates  1430  over 1 Gb/s. Another type of hardware interface is a PCI copper-cable interface  1410  having an image bandwidth capability  1430  of around 96 Mbit/s. The bus type  1415  for the optical fiber data pump is PCI-X and the bus type for the copper cable data pump is PCI. 
     The data pump can carry synchronous image data to the print head assembly, as well as lower-speed control data and tending or monitoring data. The control communication channels may be transparent to the high speed image data, and may be protocol-independent. The data pump&#39;s external interface  1420  for the optical fiber and the copper cable can differ, with the optical fiber having a duplex optical fiber, and the copper cable having a 50-conductor Flat Flexible Cable (FFC). The optical fiber and the copper cable versions can have the same hardware control inputs  1425 . 
     Both the optical fiber version and the copper-cable version can operate the printing system in various printing modes  1445 : triggered, free-running, forward scanning, and reverse scanning. Triggered mode can be used in printing images onto discrete, individual workpieces using a hardware trigger signal to initiate each image print. Free-running mode can provide printing of a continuous run of images, with programmable white spaces between each printed image. Forward and reverse scanning modes can provide printing in the forward or reverse directions. In one implementation, a single image may be printed for the forward or reverse scanning mode. In another implementation, multiple images may be printed while the system is in the forward or reverse scanning mode. The printing modes may also be mixed, so a reverse trigger mode or a reverse free-running mode may be utilized. 
     In the example configurations specified in  FIG. 14 , the data pump can service a print head assembly with one to eight logically independent columns of printing elements, with up to 5120 nozzles per column. This configuration can allow the use of large print head assemblies of 720 dpi (dots per inch) to be constructed with approximately 32 to 64 jet modules with 304 print elements each that can be fed by a single optical fiber. The size of the print head assembly may be determined as a function of the nozzle count multiplied by the maximum firing frequency of the nozzles, as well as the 1.25 Gb/s data rate. In one aspect, the frequency of the printing jets may operate in a range of around 40 kHz. In one implementation, several data pumps may be plugged into one PC motherboard and operated in parallel to provide higher bandwidths for larger print head assemblies. In another implementation, several PCs with data pumps may be operated in parallel to utilize large print head assemblies at low cost. 
     Each column of print elements can be independently provided with image data over the optical fiber or copper cable to allow continuous image printing, with little or no white space between images, and without a hardware bitmap-to-jetmap converter. Instead, the bitmap-to-jetmap conversion can be performed in real time by software running on the PC. 
     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. For example, the sequences in  FIG. 11  may be described in an order other than shown (e.g., the optical sensor may detect the position of the workpiece (block  1115 ) before the encoder senses the speed of the workpiece (block  1110 )). The number of state machines and delay components may vary from the amount shown in  FIG. 12 . In another example, the exemplary data rates of the PC bus ( 1415 ) may vary from those shown in  FIG. 14 . 
     Accordingly, other implementations are within the scope of the following claims.