Patent Publication Number: US-6698866-B2

Title: Fluid ejection device using multiple grip pattern data

Description:
BACKGROUND OF THE INVENTION 
     Digital printing systems typically employ a dot placement pattern where circular dots are placed on a rectangular coordinated (Cartesian) grid. This pattern is convenient for the calculation of the placement of data and allows good generation of vertical and horizontal lines. However, the circular dots have to be relatively large to completely cover corresponding rectangular areas of the print media. A relatively large amount of overlapping of deposited ink occurs in areas directly between two adjacent dots, and a small amount of overlapping of deposited ink occurs at points on the grid that fall between diagonal dots. As such, rectangular systems using larger drops require more ink or toner to completely cover the print media and are not efficient for some printing applications. 
     One way to reduce the amount of ink overlap is to print on a hexagonal grid pattern. Hexagonal grid patterns inherently have an efficient geometry to allow circles to be closely packed when filling in an area on the print media, thus requiring less ink. 
     A system using a hexagonal grid will cover a higher percentage of the paper with a single drop, reducing the amount of ink required to cover a page. However, while hexagonal grid patterns produce high quality images, they are not optimal for other printing applications such as text and line graphics. 
     SUMMARY OF THE INVENTION 
     The present invention includes as one embodiment a method for printing ink on a print media with a fluid ejection device of an inkjet printing mechanism, comprising generating first grid pattern data and second grid pattern data different from the first grid pattern data, sending the first grid pattern data to a first printing mechanism of the fluid ejection device and sending the second grid pattern data to a second printing mechanism of the fluid ejection device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention can be further understood by reference to the following description and attached drawings that illustrate the preferred embodiments. Other features and advantages will be apparent from the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
     FIG. 1 is one embodiment showing an overall printing system incorporating the present invention. 
     FIG. 2 is one embodiment showing an exemplary printer that incorporates the present invention and is shown for purposes of illustration. 
     FIG. 3 is one embodiment showing for illustrative purposes only a perspective view of an exemplary print cartridge incorporating the present invention and usable with the printer of FIG.  2 . 
     FIG. 4A is a diagram illustrating one embodiment with a pattern of ink droplets printed using a rectangular grid pattern. 
     FIG. 4B is a diagram illustrating one embodiment with a pattern of ink droplets printed using a hexagonal grid pattern. 
     FIG. 5 is a high level block diagram illustrating another embodiment of the present invention. 
     FIG. 6 is a high level flow diagram illustrating a further embodiment of the present invention represented by FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following description of the invention, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration a specific example in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention as defined by the claims appended below. 
     I. General Overview of Components and Operation: 
     FIG. 1 is one embodiment showing an overall printing system incorporating the present invention. The printing system includes input print data  108  (contains information about the text and/or images to be printed), a printhead assembly  110 , an ink supply  112  (shown in dotted lines because it can be located either remotely from or integrated with the printhead assembly  110 ) and print media  114 . The printhead assembly  110 , may have a number of printing mechanisms, each of which would include a printhead body and a nozzle system. 
     In addition, the printing system of FIG. 1 includes a carriage motion control system  120 , a printhead control signal generator  122  and a signal processor  126 , which can be a digital signal processor. The printhead control signal generator  122  and signal processor  128  may be incorporated in a custom application specific integrated circuit (ASIC). During a printing operation, ink is provided from the ink supply  112  to an interior portion (such as an ink reservoir) of the printhead assembly  110 . The printhead assembly  110  receives commands derived from the input print data  108  to fire ink ejection elements of the printhead assembly  110  in order to release ink droplets for printing black and color ink as text, images, etc. on the print media  114 . Print quality of the desired placement scheme is dependent on, among other things, accurate placement of the ink droplets on the print media  114 . 
     In one embodiment of the invention, during operation, the carriage motion control system  120  electronically receives the input print data  108  and sends carriage location and position timing signals to the printhead control signal generator  122 . The printhead control signal generator  122  processes these signals to control the correct placement of the ink to be printed. If the input print data  108  contains information for printing text, images, single bit black and white line art, etc. with black ink only (black ink data), the printhead control signal generator  122  generates first grid pattern data of a first placement scheme and sends it to at least one black printing mechanism  124  (multiple black printing mechanisms can be used), such as a black ink printhead or cartridge, of the printhead assembly  110 . This allows black ink representing the black ink data to be printed on the print media  114  based on the first grid pattern data. 
     Alternatively or additionally, if the input print data  108  contains information for printing color text, color photographs, etc. with predominantly color ink and possibly some black ink (color ink data), the signal processor  128  of the printhead control signal generator  122  interpolates the color ink data and extracts position information for generating second grid pattern data of a second placement scheme, different from the first placement scheme. The second grid pattern data is then sent to at least one color printing mechanism  126  (multiple color printing mechanisms can be used), such as a color ink printhead or cartridge. This allows color text, color photographs, etc., representing the color ink data to be printed on the print media  114 . 
     The grid placement schemes use dot matrix manipulation to form both images and alphanumeric characters to be printed. These schemes are created by predefined algorithms that may be implemented with the printer driver. Colors and tone of a printed image are modulated by the presence or absence of drops of ink deposited on the print medium at each target picture element or dot (referred to as a “pixel”) of a superimposed grid overlay of the image to be printed of a particular grid placement scheme. 
     Also, it should be noted that both the first and second grid pattern data are typically sent simultaneously to the printhead assembly  110 . Also, additional black and color printing mechanisms can be used with corresponding grid pattern data different than the first and second grid patterns. As such, the printhead assembly  110  uses multiple grid pattern data during a single printing operation. 
     In one embodiment, a rectangular grid placement scheme is used for firing black ink on the print media  114  and a hexagonal grid placement scheme is used for firing color ink on the print media  114 . Color ink data includes color ink and also may contain black ink on the printed output. For example, print data of a color photographic image would likely contain both color ink and black ink, but would be categorized as color ink data. In contrast, print data for black text would contain black ink without color ink and be categorized as black ink data. As such, black ink could exist in color ink data (images and color text for color graphic presentations, color newsletters, color business charts, color photographs, etc.), but color ink typically would not exist in black ink data (black text for monochrome documents and single bit black and white line art printouts). 
     In another embodiment, a signal processor  128 , such as a digital signal processor, is optionally used to receive the color ink data from the printhead control signal generator  122  for analyzing and interpolating the color ink data to extract the position information for generating the second grid pattern. The signal processor  128  is used to digitally interpolate and subdivide or time slice the position and timing signals of the color ink data for generating a hexagonal grid pattern as the second grid pattern. This could also be performed by custom logic included in a main control application specific integrated circuit. It should be noted that the black and color printing mechanisms are shown with dotted lines because they can be separate print cartridges. 
     Each black and color printing mechanism  124 ,  128  receives data formatted according to a different preprogrammed grid placement scheme as part of the firing signals for producing systematic ink drop placement on the print media  114 . A general grid placement scheme can be developed for a type of inkjet printhead assembly during design of the assembly. The grid placement schemes used in the embodiments of the inkjet printhead assemblies of the present invention may include a rectangular grid and a hexagonal grid. Other geometrical grids can be used, such as circular grids, triangular grids, octagonal grids, etc. 
     The grid placement scheme can be implemented by a printer driver implemented as software operating on a computer system that is connected to the inkjet printer or as firmware incorporated into the printer in a controller device. Also, the grid placement scheme can be encoded on a memory device incorporated into the inkjet printhead assembly itself. Information can be written and stored at the time the printhead assembly is manufactured or during printer operation. The grid placement scheme can typically be accessed and applied by the printer driver. 
     Since the embodiments of the present invention supports both rectangular and hexagonal grid printing, text and line art can be rendered with a rectangular grid pattern, while images can be rendered with a hexagonal grid pattern. Text and line art, which typically have significant areas of vertical and horizontal lines but low ink density (i.e. lots of unprinted white space) are efficiently printed with a rectangular grid pattern. Images, such as photographic images, however, which have high ink density are printed with a hex grid pattern so as to conserve consumables, such as ink/toner. In addition, the multiple grid pattern system decreases the adverse visual effects of defective nozzles so as to maintain a higher quality throughout the print swath. 
     II. Exemplary Printing System: 
     FIG. 2 is one embodiment of an exemplary inkjet printing mechanism or arrangement, an “off-axis” high-speed printer, that incorporates an embodiment of the invention, which is shown for illustrative purposes only. The inkjet printing arrangement or printer  200  of FIG. 2 may be used for printing for business reports, correspondence, desktop publishing, and the like, in an industrial, office, home or other environment. A variety of inkjet printing mechanisms are commercially available. For instance, some of the printing mechanisms that may embody the present invention include plotters, portable printing units, copiers, cameras, video printers, point of sale (POS) horizontal printers and facsimile machines, to name a few, as well as various combination devices, such as a combination facsimile/printer and a combination scanner/copier/printer or “All in One” device. For convenience the concepts of the present invention are illustrated in the environment of an inkjet printer  200 . 
     While it is apparent that the printer components may vary from model to model, the typical inkjet printer  200  includes the printhead assembly  110  of FIG.  1  and further includes a tray  222  for holding print media. When printing operation is initiated, print media, such as paper, is fed into printer  200  from tray  222  using sheet feeder  226 . The sheet is then brought around in a U turn and then travels in an opposite direction toward output tray  228 . Other paper paths, such as a straight through paper path, can also be used. 
     The sheet is stopped in a print zone  230 , and a scanning carriage  234 , supporting one or more printhead assemblies  236 , is scanned across the sheet for printing a swath of ink thereon. After a single scan or multiple scans, the sheet is then incrementally shifted using, for example, a stepper motor and feed rollers to a next position within the print zone  230 . Carriage  234  again scans across the sheet for printing a next swath of ink. The process repeats until the entire image sheet has been printed, at which point the sheet is ejected into the output tray  228 . 
     The print assemblies  236  can be removeably mounted or permanently mounted to the scanning carriage  234 . Also, the printhead assemblies  236  can have self-contained ink reservoirs. Alternatively, each print cartridge  236  can be fluidically coupled, via flexible conduits  240 , to one of a plurality of fixed or removable ink containers  242  acting as the ink supply. Further, the printer  200  can include a carriage position locator (not shown), such as an encoder. The encoder is typically a single electrical-optical component consisting of an electrical emitter (LED), a photo detector (photodiode) with some form of a mask which sets an encoder pitch or resolution that resides on the carriage. The encoder is mechanically positioned relative to a fixed encoder strip (linear in nature) such that as the carriage traverses reversibly along a carriage rod, it can detect position data printed on the encoder strip. 
     There are other types of encoders, such as an electro-magnetic encoders. With these encoders, the carriage is an electro-mechanical assembly consisting in part of the carriage, carriage electronics, timing belt attachment, print head latching mechanism, electrical print head interconnection and electrical interconnect to the main controller. The printheads are electro-mechanically attached to the carriage. Signals detected by the encoder are sent to the main controller where they are utilized to determine and control the location of the carriage. 
     Signal output is also routed to a printhead firing control component which may be a separate component located on either the carriage or the main logic controller or may be integrated into the print head assembly. Print data is generated on a host and transmitted to the printer in any of a number of data formats. Data received at the main controller is decoded and turned into printhead assembly firing commands. Firing commands are synchronized to encoder pulses by a firing control component of the printhead. This data is used to initiate the flow of power to individual firing resistors within a printhead. 
     FIG. 3 shows one embodiment for illustrative purposes only, of a perspective view of an exemplary printhead assembly  300  (an example of the printhead assembly  110  of FIG.  1 ). A detailed description of an embodiment of the present invention follows with reference to a typical printhead assembly used with a typical printer, such as printer  200  of FIG.  2 . However, other printhead and printer configurations may be employed depending upon the particular implementation. 
     Referring to FIGS. 1 and 2 along with FIG. 3, the printhead assembly  300  is comprised of a nozzle member  302  through which drops of at least one ink are ejected onto the print media, a printhead body  304  and a printhead memory device  306 . The printhead assembly  110  includes a flexible circuit  320 , which can be a flexible material commonly referred to as a Tape Automated Bonding (TAB) circuit bonded to the printhead assembly  110 . The flexible circuit  320  also includes an interconnect area  324  with interconnect contact pads that align with and electrically contact electrodes (not shown) on carriage  234  of FIG.  2 . 
     In one embodiment, the nozzle member  302  contains printhead drive circuitry (not shown). The printhead drive circuitry comprises a distributive processor (not shown) coupled to the nozzle member  302 . The distributive processor may include digital and/or analog circuitry and communicates via electrical signals with a controller (not shown), nozzle member  302  and various analog devices, such as temperature sensors, which can be located on the nozzle member  302 . The distributive processor processes the signals for precisely controlling firing, timing, thermal and energy aspects of the printhead assembly  110  and nozzle member  302 . The nozzle member  302  typically contains plural orifices or nozzles  310 , which can be created by, for example, laser ablation, for creating ink drop generation on a print media. 
     III. Details of the Operation: 
     FIG. 4A is a diagram illustrating one embodiment with a pattern of ink droplets using a rectangular grid pattern. The input data is formatted by predefined algorithms to conform to predetermined dot grid patterns. These grid patterns may be understood as invisible overlays (created by predefined algorithms) that define the positions on the print medium onto which ink droplets may be deposited. The formatting of the input data according to these grid patterns may be implemented with the printer driver. The input data, when printed according to these dot grid patterns, form both the images and alphanumeric characters to be printed. 
     The rectangular grid pattern  400  is typically used for generating text and line art typically printed with black ink. The rectangles typically are squares  402 . This rectangular grid  400  could model a six hundred by six hundred (600×600) dot per inch (dpi) printing mode where a carriage scan pitch  406  or center-to-center spacing of printed ink drops  402  along an x axis equals paper motion pitch  408  or center-to-center spacing of ink drops  402  along a y axis. In order for a substantially circular ink drop to fully cover a square  402 , the ink drop will also cover overlapping portions of adjacent squares. In the case of a printing mode with equal print density (i.e. dots per inch) in both the x and y directions (such as 600×600 dpi), the portion of a square  410  covered by neighboring ink drops  402  is about 57% of the area of the square  410 , as illustrated by overlapped regions  412 . 
     FIG. 4B is a diagram illustrating one embodiment with a pattern of ink droplets using a hexagonal grid pattern. FIG. 4B shows a hexagonal grid pattern  420  of ink droplets  402  that may be used for generating images and graphics typically printed with but not limited to color ink, wherein the ink drops  402  are placed on hexagonal grid pattern  420  to increase coverage efficiency. A carriage scan pitch  430  of the ink drops  402  along an x axis is related to paper motion pitch  432  of the ink drop  402  along a y axis. In one hexagonal grid pattern embodiment, x=cube root of y. With the hexagonal grid  420 , the portion in a given hexagon  640  covered by neighboring ink drops  402  is only about a 21% are  414 , which is less than that for the square grid case discussed above with reference to FIG.  4 A. In other words, in the y axis, the dot pitch is unchanged. 
     However, in the x axis, the dot pitch is adjusted to match a suitable ratio for a rectangular-hex grid. Ink deposited on top of ink has much less visual effect than ink deposited on an unprinted portion of the print media  114 . As such, the larger the percentage of the paper covered by only one drop in the pattern, namely drop  440 , the higher the coverage efficiency of the system. In this embodiment, the area with the least amount of drop-to-drop overlap is covered. Consequently, the hexagonal grid pattern  620  reduces the volume of ink required to entirely cover the print media  114 , and therefore the amount of ink per unit area of print medium requires for coverage. 
     In one embodiment, both the rectangular and hexagonal grid patterns are used at the same time when printing an image (rectangular grid is used for black ink data and hexagonal grid for color ink data). Specifically, since text and single bit line art are predominantly printed with black ink, a rectangular grid pattern is used for black ink data to minimize manufacturing and design changes. However, for color ink data, which can include color photographs, color presentations, etc., the hexagonal grid is typically used to produce more efficient and continuous print coverage. 
     IV. Working Example: 
     FIG. 5 is a high level block diagram illustrating one embodiment that includes a working example of the present invention. In this working example, the printer  200  of FIG. 2 includes an application specific integrated circuit (ASIC)  500 , which can be a digital or analog device, a position module  504  and printhead drive circuitry  506  for controlling operations of the printhead  110  of FIG.  1  and producing printed output with multiple grid patterns in a single printing system. It should be noted that the ASIC  500 , position module  504  and printhead drive circuitry  506  can be incorporated as a single unit or each may reside in any suitable location within the printing system. For example, in one embodiment, the ASIC  500  and position module  504  reside on an inside location of the printer  200 , remote from the printhead  110 , while the printhead drive circuitry  506  is located directly on the printhead  110 . 
     Input print data  108  is generated for each print job and received by the ASIC  500 . Position and timing signals  508  of the carriage  234  are generated based on a location device  510  and sent to the ASIC  500  for processing. The ASIC  500  decodes the print data  108  and synchronizes the decoded information with the position and timing signals  508 . This information is forwarded, via the position module  504 , to the printhead drive circuitry  506 . The position module  504  may be a closed loop encoder system that uses an optical encoder module coordinated with positioning strips that are read by optional encoders to precisely locate the carriage and accurately print the input data  108 . Alternatively, the position module  504  can be an open loop servo system that uses a crystal oscillator and a stepper motor to precisely locate the carriage and accurately print the input data  108 . 
     The position module  504  generates black print data  520  (black text, black images, etc.) and color print data  524  (color text, color images, etc., with or without black print data). In the case where the position module  504  is an optical encoder module, encoders are used to gather position data of the carriage  234  in any suitable manner, but typically from either a single optical encoder strip or a multiple optical encoder strip that is located on a scan axis of the carriage  234 . A single optical encoder strip  525  (shown in dotted lines as an optional element that is used with a system with optical encoders) would contain encoder markings for both black and color ink data  527 ,  529  and optically detected by an encoder calibrated with the carriage  234 . Multiple optical encoder strips that can be used include a dual strip (one black strip for black text and one color strip for color text and images) or a triple optical encoder strip (one strip for black text, one strip for black images, and one strip for color text and images) can be used. 
     In the embodiment that uses a single optical encoder strip, black ink data is generated from black linear encoder markings  527  of the strip  525 . For color ink data, the encoder strip  525  comprises color linear encoder markings  529 , which is one a different pitch than the black linear markings  527  for producing different grid pattern data. For example, for a system that uses a rectangular grid for black ink data and a hexagonal grid for color ink data, the color markings have a carriage scan pitch equal to the cube root of the paper motion pitch, and the black markings have a carriage scan pitch equal to the paper motion pitch. This is because every other row of dots in the hexagonal grid is offset by one-half the dots in the x-axis in comparison to the rectangular grid and as discussed above with reference to FIG. 4, in the hexagonal grid pattern, x=cube root of y. 
     The markings  527 ,  529  are read by at least one encoder, but typically dual encoders, one for each marking, which produces position and timing pulses that are used by the printhead assembly firing process. When a single encoder strip with dual markings is used, the printhead assembly or assemblies in the printer are synchronized to the single encoder for the single strip. Fire pulses are generated by the printhead drive circuitry  506  based on position and timing signals received by the position module  504  and the strip markings. As discussed above, these position and timing signals can be subdivided by any suitable device to produce multiple grid patterns. 
     During a printing operation, for black text and black images, the black print data  520  is sent to a black data print controller  526  and includes position and timing signals for the black ink to be printed. The black data print controller  526  interprets these signals and translates them into firing signals for the black printing mechanism  528 . In one embodiment, the firing signals contain Cartesian coordinate grid information, such as rectangular grid pattern data for firing specific black ink on the print media  114 . 
     In a system that does not use the encoder strip  525  with dual markings  527 ,  529 , for color ink, the color print data  524  is sent to a grid preprocessor  530  that analyzes and processes the position and timing signals from the location device  510  for generating grid pattern data different from the black print data  520 . The preprocessor  530  subdivides or time slices the position and timing signals as interpolated signals. The interpolation can be formulated for any predefined time division associated with a particular grid pattern. For example, a hexagonal grid pattern can be created by subdividing the position and timing signals of the Cartesian based rectangular grid pattern with a one-half time division. A one-half time division interpolation is used because every other row of dots in the hexagonal grid is offset by one-half the dots in the x-axis in comparison to a Cartesian rectangular grid. The hexagonal grid pattern data is used for firing color ink on the print media  114  and sends this to a color print controller  532 . The color print controller  532  interprets these signals and translates them into firing signals for the color printing mechanism  534 . 
     In this embodiment, the encoder strip is used as the location device  510  to generate the position and timing signals  508 . The ASIC  500  can be used to subdivide the position and timing signals  508  into multiple time divisions with time slicing techniques, for example with a digital signal processor (DSP) or custom hardware logic programmed for this task, for creating different grid patterns, other than the black print data. 
     In particular, referring to FIGS. 1-2 along with FIG. 5, the printhead drive circuitry  506  sends the position and timing signals  508  to the scanning carriage  234  via the carriage motion controller  120 . The scanning carriage  234  analyzes the data so that it can be positioned for black print data or color print data. The printhead drive circuitry  506  also calculates the position of each ink droplet through a drop position controller for black and for color. 
     FIG. 6 is a high level flow diagram illustrating one embodiment of the present invention that is represented by of FIG.  5 . Referring to FIGS. 1-5 along with FIG. 6, in operation, first, print data  108  is generated by a host computer (step  610 ). Second, the print data  108  is transmitted to the printer  200  (step  612 ). Third, the location of the carriage is read to generate position and timing signals  508  of carriage  234 . The position and timing signals  508  are sent to the ASIC  500  (step  614 ). Fourth, the ASIC  500  decodes the print data  108  and translates it into firing commands. The firing commands and the position and timing signals  508  are then synchronized (step  616 ). Fifth, the ASIC  500  uses the synchronized data to concurrently create printhead fire data on multiple coordinate systems. This fire data is transmitted to the printhead drive circuitry (step  618 ). 
     Sixth, the position and timing signals  508  are subdivided into multiple time divisions for use with multiple grids, respectively (step  620 ). Namely, for the multiple grid pattern system that includes rectangular grid data for black print data  520  and hexagonal grid data for color print data  524 , the position and timing signals  508  are subdivided, for black print data  520 , into first time divisions for rectangular grid pattern data. For the color print data  524 , the position and timing signals  508  are subdivided into second time divisions that are smaller that the first time divisions for hexagonal grid pattern data. Next, the printhead drive circuitry  506  synchronizes the fire data with the position and timing signals  508  (step  622 ). Last, the printhead  110  prints the print data  108  using an appropriate grid on the print media  114  (step  624 ). 
     The foregoing has described the principles, preferred embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed. The above-described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.