Flush line generation in printing systems that utilize control marks

Systems and methods are provided for generating flush lines that do not interfere with control marks for post-processing equipment. The system includes a print controller able to receive a print job and to insert printable control marks into the print job to direct the actions of post-processing equipment. The system also includes an ink flushing controller that can detect horizontal locations of the control marks along the width of the print job. Responsive to detecting the locations of the control marks, the ink flushing controller can generate flush lines for the print job that have altered optical densities at the horizontal locations.

FIELD OF THE INVENTION

The invention relates to the field of printing systems, and in particular, to generating flush lines for printing systems.

BACKGROUND

Businesses or other entities having a need for volume printing typically purchase a production printer. A production printer is a high-speed printer used for volume printing (e.g., one hundred pages per minute or more). Production printers are typically continuous-form printers that print on webs of print media which are stored on large rolls.

A production printer typically includes a localized print controller that controls the overall operation of the printing system, and a marking engine (sometimes referred to as an “imaging engine” or as a “print engine”). The marking engine includes one or more printhead assemblies, with each assembly including a printhead controller and a printhead (or array of printheads). An individual printhead includes multiple tiny nozzles (e.g., 360 nozzles per printhead depending on resolution) that are operable to discharge ink as controlled by the printhead controller. A printhead array is formed from multiple printheads that are spaced in series across the width of the print media.

When in operation, the web of print media is quickly passed underneath the printhead arrays while the nozzles of the printheads discharge ink at intervals to form pixels on the web. In order to ensure that ink does not dry onto the printheads during printing (which would adversely affect print quality), flush lines are printed at page boundaries on the web. These flush lines are used to flush ink from each of the nozzles (i.e., across the entire width of the web) on a regular basis to ensure that the ink does not become overly viscous.

Additionally, many printing systems utilize one or more control marks to guide the actions of post-processing equipment at the print shop. For example, a printing system may add control marks onto a web to indicate where to cut the web to form pages, how to stack groups of pages, and how to perform other post-printing activities.

Unfortunately, the sensors that trigger actions at post-processing equipment may use simple heuristics, such as optical density, to detect control marks on the page. This means that flush lines can be mistakenly interpreted as control marks by post-processing equipment, which can result in the print job being cut, stacked, hole-punched, etc. at the wrong location.

SUMMARY

Embodiments described herein provide systems that detect the horizontal location of control marks that have been inserted into a print job by a print controller. The systems reduce the optical density/reflectance of flush lines that are in substantially the same horizontal location along the width of the print job as the control marks. This keeps sensors for post-processing equipment from mistakenly identifying portions of the flush line as control marks.

One embodiment is a system that generates flush lines that do not interfere with control marks for post-processing equipment. The system includes a print controller able to receive a print job and to insert printable control marks into the print job to direct the actions of post-processing equipment. The system also includes an ink flushing controller that can detect horizontal locations of the control marks along the width of the print job. Responsive to detecting the locations of the control marks, the ink flushing controller can generate flush lines for the print job that have altered optical densities at the horizontal locations.

Another embodiment is a method. The method includes receiving a print job, and inserting printable control marks into the print job to direct the actions of post-processing equipment. The method also includes detecting horizontal locations of the control marks along the width of the print job. Responsive to detecting the locations of the control marks, the method also includes generating flush lines for the print job that have altered optical densities at the horizontal locations.

Another embodiment is a non-transitory computer readable medium embodying programmed instructions which, when executed by a processor, are operable for performing a method. The method includes receiving a print job, and inserting printable control marks into the print job to direct the actions of post-processing equipment. The method also includes detecting horizontal locations of the control marks along the width of the print job. Responsive to detecting the locations of the control marks, the method also includes generating flush lines for the print job that have altered optical densities at the horizontal locations.

Other exemplary embodiments (e.g., methods and computer-readable media relating to the foregoing embodiments) may be described below.

DETAILED DESCRIPTION

FIG. 1is a block diagram of a printing system100of a print shop in an exemplary embodiment. Printing system100receives print jobs from a customer (e.g., via a client, print server, etc.) that include print data for printing. Each print job is processed by printing system100to generate a printed output, and this printed output is manipulated by post-processing equipment to generate a final, deliverable product. For example, the post-processing equipment may include cutters, stackers, hole-punchers, binders, perforators, and other post-printing devices.

Printing system100includes print controller110, ink flushing controller120, and marking engine130. Print controller110may perform operations such as translating Page Description Language (PDL) print jobs into a rasterized format, processing job tickets for the print job, and other functions. Print controller110also generates control marks that are inserted/overlaid onto print jobs from customers. The control marks, when printed onto the job, provide instructions that direct the operations of post-processing equipment in the print shop. For example, a control mark may direct a cutter to cut at a given vertical location, may instruct a stacker to start a new stack of pages at a boundary between print jobs, may instruct a hole-puncher where to punch holes, etc. Control mark140is an example of such a control mark. Control marks are often located at the margins of a given page (e.g., the top, bottom, or sides), or in other locations that will not draw the attention of a customer away from the content of the print job itself (e.g., billing statements, chapters of a book, etc.). While control mark140is illustrated as a black square, any shape, design, or color may be used to implement control marks. In one embodiment, control marks of different shapes provide different instructions to post-processing equipment.

The control marks inserted by print controller110are located at specific horizontal locations along the width of the print job/page/web. When the print job is printed out onto the web, the web is driven toward downstream post-processing equipment. Sensors for each piece of post-processing equipment have been placed at specific horizontal locations along the width of the web, and have been calibrated to search for control marks at these specific horizontal locations. The sensors used by each piece of post-processing equipment may vary, but many sensors utilized will trigger their associated post-processing equipment whenever a sufficiently dark mark (i.e., a mark with a large enough optical density/reflectance) is detected. As used herein, the term “optical density” refers to optical density and/or optical reflectance, and refers to these measurements taken in any suitable spectrum including (but not limited to) the visible and infrared spectrums.

Because printing system100is an ink-based printing system, printing system100utilizes ink flushing controller120to generate flush lines at regular intervals throughout the print job. Like the control marks, the flush lines do not exist in the print job at the time the print job is received. The flush lines prevent ink from drying out (or becoming more viscous) at the nozzles of marking engine130and thereby adversely impacting print quality. In most systems, flush lines are printed on every page of a print job, along the entire width of the print job (i.e., along the width of the web/page).

Because flush lines are often uniform across the entire width of the page, and because flush lines are often very dark, sensors for post-processing equipment can misinterpret flush lines as control marks. This means that the print job may be cut, stacked, hole-punched, etc. at the wrong location. Such a result may necessitate re-printing the print job, at great cost to the print shop operator.

Ink flushing controller120has been enhanced to vary the optical density of the flush lines that it generates, based on the existence of detected control marks for the print job. For example, ink flushing controller120can reduce the intensity of a generated flush line at a given horizontal location, if a control mark is known to occupy the same horizontal position.

Ink flushing controller120may be implemented, for example, as custom circuitry, as a special or general purpose processor executing programmed instructions stored in an associated program memory, or some combination thereof. While ink flushing controller120is illustrated as an independent element inFIG. 1, in some embodiments ink flushing controller may be integrated into print controller110, or marking engine130.

Once flush lines and control marks have been added to the print job, the print job is provided to marking engine130, which marks a web of print media to generate a printed output. InFIG. 1, the printed output includes flush line150and control mark140. Here, flush line150has been generated so that it is less optically dense at the location along the width of the page at which control mark140is located.

Illustrative details of the operation of printing system100will be discussed with regard toFIG. 2. Assume, for this embodiment, that printing system100has initialized and that print controller110has been programmed with information describing available pieces of post-processing equipment, as well as the location at which to place control marks for each piece of post-processing equipment.

FIG. 2is a flowchart illustrating a method200for operating a printing system to generate flush lines in an exemplary embodiment. The steps of method200are described with reference to printing system100ofFIG. 1, but those skilled in the art will appreciate that method200may be performed in other systems. The steps of the flowcharts described herein are not all inclusive and may include other steps not shown. The steps described herein may also be performed in an alternative order.

In step202, print controller110receives a print job for processing. The print job comprises one or more logical pages of print data for printing by printing system100. Print controller110may receive the print job via a network interface, a serial communication interface, etc.

In step204, print controller110inserts printable control marks into the print job to direct the actions of post-processing equipment. In one embodiment, print controller110performs this step by reviewing a job ticket for the print job to determine how the print job should be manipulated by post-processing equipment. Print controller110then correlates the parameters from the job ticket with known pieces of post-processing equipment in the print shop. Based on known horizontal locations of sensors for the post-processing equipment along the width of the page, print controller110generates control marks to direct the post-processing equipment to perform the operations requested by the job ticket. Print controller110may further rasterize the print job from a Page Description Language (PDL) format into a bitmap version.

In step206, ink flushing controller120detects the horizontal locations of control marks that have been inserted into the print job. In embodiments where the print job is in a PDL format when analyzed by ink flushing controller120, the control marks may be indicated with specific tags, data structures, or other information that indicates the marks are used to direct post-processing equipment. In embodiments where ink flushing controller120analyzes a rasterized version of the print job for control marks, the control marks may be identified based upon their shapes, sizes, colors, or other characteristics.

Having detected the locations of the various control marks along the width of the print job, ink flushing controller120generates flush lines for the print job. The flush lines have varying optical density (e.g., darkness) along the width of the print job, and the varying optical density is based on the locations of the detected control marks along the width of the print job. Specifically, the optical densities of the flush lines have been altered where they occupy the same horizontal position as a control mark. For example, a flush line may be made lighter when it is in the same location along the width of the page as a control mark. This reduces the chances of a sensor for post-processing equipment falsely identifying the flush line as another control mark.

In a further embodiment, ink flushing controller120determines the optical density of each control mark, and may specifically alter the flush line at the horizontal location of detected marks to be below the determined optical density. For example, if the control mark is 50% grey, the portion of the flush line at the same location may be reduced to 40% grey, or some other value. In another embodiment, ink flushing controller120determines the sensitivity of down-stream sensors for detected control marks. For example, ink flushing controller120may determine a threshold of optical density that will cause the sensor to trigger. Ink flushing controller120may then adjust the optical density of the flush line from a default value to less than the triggering threshold to ensure that the sensor does not trigger by mistake when the flush line passes by. Altering the optical density may include, for example, removing all or a portion of the flush line at the same horizontal position as the control mark.

FIGS. 3-6are block diagrams illustrating exemplary flush lines on a printed page in various exemplary embodiments.

According toFIG. 3, a printed page (currently integrated into a web of print media) includes printed content310, which corresponds to print data requested for printing by a customer (e.g., billing statements, chapters of a book, etc.). The printed page further includes control mark320, and flush line330. Ink flushing generator120has detected a horizontal location (X) of control mark320along a width of the page. Control mark320is placed at horizontal location X because a downstream sensor322for post-processing equipment is oriented to detect marks on the web at horizontal location X. Thus, when the page (currently integrated into a web of print media) passes underneath sensor322, sensor322will detect control mark320and trigger the post-processing equipment. In order to prevent false positives from sensor322, ink flushing generator120removes a portion340of flush line330where flush line330would overlap the horizontal location of control mark320. In this manner, sensor322will not misinterpret flush line330as another control mark.

FIG. 4illustrates a similar scenario to that described forFIG. 3. However, inFIG. 4, the portion of flush line430at the horizontal location of control mark320is reduced in intensity (not removed entirely). Furthermore, the overall height of a portion440of flush line430is increased, so that the same amount of ink is flushed, but over a longer span. Thus, flush line430flushes the desired amount of ink and also does not interfere with control mark320.

FIG. 5illustrates a further scenario, wherein a multicolor CMYK (Cyan, Magenta, Yellow, Black) flush line520is altered based on a detected control mark. According toFIG. 5, control mark510utilizes black ink. Therefore, black ink will already be flushed from the print nozzles at the horizontal location for control mark510, regardless of whether a flush line is used in that horizontal location Ink flushing controller120detects this, and removes black ink from portion530of flush line520. This reduces the optical density of the flush line, while still allowing most of the nozzles of the printhead to completely flush. WhileFIG. 5discusses black ink specifically, in further embodiments ink flushing controller120may be operable to detect the color of control mark510, and to selectively remove inks from portion530of flush line520based on the color of control mark510.

In a further embodiment, ink flushing controller120may determine a frequency at which a control mark repeats, and may adjust the intensity of the flush line at the same horizontal location as the control mark, based on the frequency of the control mark. For example, if a control mark repeats once every two pages and utilizes substantially the same amount of ink as a single flush line, the flush line may be printed at half of its default intensity where it is in the same horizontal location as the control mark. In this way, the same amount of ink is flushed in that horizontal location as in other locations.

In a further embodiment, ink flushing controller120is operable to reduce the intensity of the flush line where the flush line occupies the same horizontal location as a control mark. Ink flushing controller120further applies the ink that would have been applied to the flush line to the exact same physical position as the control mark (i.e., directly on top of the control mark). In this scenario, particularly when the control mark is black, the ink that is flushed into the control mark is substantially undetectable.

Examples

In the following examples, additional processes, systems, and methods are described in the context of a continuous-forms ink printing system that utilizes post-processing equipment.

FIG. 6illustrates a portion of a continuous-forms print media that is being driven toward post-processing equipment. InFIG. 6, all control marks are placed in a specific region630at the bottom of the page, and each type of control mark has a different horizontal position on the page. In this example, a cutter mark610has been added to each page, and cutter mark610indicates the location for a post-processing cutter to separate one page from another. Here, the pages are to be cut into letter-sized sheets of paper. Region612of the flush line for the page has been altered to substantially remove the flush line where it overlaps with the horizontal position of cutter mark610.

The page also includes stacker mark620, which occurs only once every five pages, and indicates a job boundary where a new stack should be formed by a post-processing stacker. To ensure that flushing still adequately occurs for this horizontal portion of the job, an ink flushing controller generates region622of the flush line at 80% of the default flush line intensity. Thus, every five pages, the ink from the flush lines from those pages, combined with the ink from the stacker mark, is roughly the same amount of ink that is flushed from other horizontal location on the job.

Embodiments disclosed herein can take the form of software, hardware, firmware, or various combinations thereof. In one particular embodiment, software is used to direct a processing system of printing system100to perform the various operations disclosed herein.FIG. 7illustrates a processing system700operable to execute a computer readable medium embodying programmed instructions to perform desired functions in an exemplary embodiment. Processing system700is operable to perform the above operations by executing programmed instructions tangibly embodied on computer readable storage medium712. In this regard, embodiments of the invention can take the form of a computer program accessible via computer-readable medium712providing program code for use by a computer or any other instruction execution system. For the purposes of this description, computer readable storage medium712can be anything that can contain or store the program for use by the computer.

Computer readable storage medium712can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor device. Examples of computer readable storage medium712include a solid state memory, a magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and an optical disk. Current examples of optical disks include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W), and DVD.

Processing system700, being suitable for storing and/or executing the program code, includes at least one processor702coupled to program and data memory704through a system bus750. Program and data memory704can include local memory employed during actual execution of the program code, bulk storage, and cache memories that provide temporary storage of at least some program code and/or data in order to reduce the number of times the code and/or data are retrieved from bulk storage during execution.

Input/output or I/O devices706(including but not limited to keyboards, displays, pointing devices, etc.) can be coupled either directly or through intervening I/O controllers. Network adapter interfaces708may also be integrated with the system to enable processing system700to become coupled to other data processing systems or storage devices through intervening private or public networks. Modems, cable modems, IBM Channel attachments, SCSI, Fibre Channel, and Ethernet cards are just a few of the currently available types of network or host interface adapters. Presentation device interface710may be integrated with the system to interface to one or more presentation devices, such as printing systems and displays for presentation of presentation data generated by processor702.