Title of Invention

A METHOD OF CONTROLLING THE FIRING OF NOZZLES IN A PRINTHED, A PRINTHED AND A PRINTER INCLUDING SAME

Abstract

The firing of nozzles on rows for respective ink channels in a multi-segment printhead, each segment being a printhead chip, is effected by loading print data to respective channel shift registers on respective segments, transferring all print data in parallel to nozzle enable bits provided one per nozzle and firing the nozzles in respective channels in time independent manner using separate timing generators in each channel. Nozzles are fired by a pulse train with a programmed profile. The pulse profile is determined by programmed bits loaded to a )'F timing generator. The programmed bits exist in tables loaded to the printhead, one for each channel. Ideally the printhead nozzle rows are in offset pairs for each channel and firing of the offset pairs is by out of phase pulse trains.

Full Text

FIELD OF THE INVENTION The Invention relales 1o a method of controlling the firing of nozzles in a prinihead having raws of nozzles defined on respective ink charaeSs, and to a prinlhead and printer including the printhead which operate according to the method. BACKGROUND OF THE INVENTION Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending applications filed by the applicant or assignee of the present invention on 24 May 2000: PCT/AUOO/00Slg, PCT/AUOO/00519, PCT/AU00iO0520, PCT/A1J0O/0D521, PCT/AlJOO/00523, PCT/AUOO/00524, PCT/AUOO/00525, PCT/AUOO/00526, PCT/AUOO/00527, PCT/AUO 0/00528, PCT/AU0O/0052g, PCT/AUOO/00530, PCT/AUOO/00531, PCT/AUOO;00532, PCT/AUO 0/00533, PCT/AUOO/00534, PCT/AU0O/0053S, PCT/AUOO/00536, PCT/AU00/00537, PCT/AUOO/00538, PCT/AUOO/OQ539, PCT/AUOO/00540, PCT/AUOO/00541, PCT/AUOO/00542, PCT/AU 00/005 43, PCT/AUOO/00544, PCT/AU0O/0O545, PCT/AU00/0O547, PCT/AU00/00546, PCT/AUO 0/0 05 54, PCT/AUOO/00556, PCT/AUOQ/00557, PCT/AUOQ/OOSSS, PCT/AU00/00S59, PCT/AUOO/OOS60, PCT/AUOO/00561, PCT/AUO 0/00 5 62, PCT/AUOO/00563, PCT/AU00/00S64. PCT/AUOO/00566, PCT/AUOO/00567,PCT/AUO0/OQ568, PCI/AU 00/00 569. PCT/AUlJO/00570, PCT;AUOO/00571, PCT/AUOO/00572, PCT/AUOO/00573, PCT/AUO 0/00 5 74, PCT/AU00/00575, PCT/AU 00/005 76, PCT/AUOO/00577, PCT/AUOO/0057S, PCT/AUOO/00579, PCT/AUQ0,"0Q58l, PCT/AU00/Qfl580, PCT/AUOO/00582, PCT/AUOO/00587, PCT/AU 00/00 5 8 S, PCT/AUOO/00589, PCT/AUOO/00583, PCT/AUOO/00593, PCT/AUOO/00590. PCT/AUOO/0059I, PCT/AU 00/005 9 2, PCT/AU 00/0 05 94, PCT/AUOO/00595, PCT/AUOO/00596, PCT/AU 00/005 97, PCT"AU00/0059S, PCT/AUOO/00516, PCT/AUO0/005I7 and PCT/AUOO/00511 The disclosures of these co-pending applications are incorporated herein by cross-reference. In addition, various methods, systems and apparatus relating lo the present invention are disclosed in the following co-pending PCT applications filed simultaneously by the applicant or assignee of the present invention: PCT/AUOO/00754, PCT/AUOO/00756 and PCT/AUOO/00757. The disclosures of these co-pending applications are incorporated herein by cross-reference. Of particular note are co-pending PCT application numbers patent applications PCT/AUOO/00591, PCT/AUOO/00578, PCT/AUOO/00579, PCT/AU00/00592 and PCT/AUO0/00590, which describe a microelectomechanical drop on demand printhead hereafter referred to as a Memjet printhead- The above Memjet prinlhead is a multi-segment printhead that is developed from printhead segments that are capable of producing, for example, 1600 dpi bi-level dots of liquid ink across the full width of a page. Dots are easily produced in isolation, allowing dispersed-doi dithering to be exploited lo its fiillest. Color planes might be printed in perfect registration, allowing ideal dot-on-dot printing. The prinlhead enables high-speed printing using microeleciromechanical ink dreip technologj"- In addition, co-pending PCT applications PCT/AUOO/00516, PCT/AUOO/00517, PCT/AU00/00511, and PCT/AUOO/00754, PCT/AUOO/00756 and PCT/AUOO/00757 describe a prim engine/controller suited lo driving the above referenced page wide printhead. A multi-segment pnnifieadofthe above kind may field 1280 nozzles. Firing all ihe nozzles together would consume too much power. It could give rise to problems in terms of ink refill and nozzle imetfetence. Firing logic controls the firing of iioi^zles. Normally the timing of firing of nozzles in a prinlhead is controlled ewemally. U is desirable to reduce the corapleMly thai arises in external printbead controllers as a consequence of this. Further, at the printhead, each of the colored inks used has different characteristics in terms of viscosity, heat profile etc. Firing pulses should therefore he generated independently for each color. SUMMARY OF THE INVENTION The invention resides in control of the firing of nozzles in a printhead, the nozzles being on rows for respective ink channels in the printhead. Print data is loaded to respective channel shift registers for respective channels. All the prim data is transferred to nozzle enable bits provided one per nozzle and the nozzles in respective channels are fired in lime independent raannei using separate timing geneiatois in each channel. Moving the timing mechanisms onto the printhead helps reduce complexity. In addition, as each color channel is given ils own timer, a given color"s firing pattern can be started at any lime, Ii need not be an exact number of dot-lines from anodier. It is possible to print dot on dot via appropriate staggering of the start liming in respective channels although ihis regime is noi adopted in ihe prefened embodiment described below. Normally the widths and profiles of firing pulses are generated externally to the printhead. In the preferred embodiment below the pulse widths of electrical pulses by which to fire the nozzles is programmable. With the above in mind, the nozzles are fired by an electrical pulse. The profile of the pulse is pTOgtammed ID suit the ink at the nozzle, ideally the prinlhead includes ink nozzles in imiltipSe rows, successive rows of nozzles defining respective ink channels and an electrical pulse train fires the nozzles. Pulse profiles in the pulse train are programmed to suii the ink in respective channels. Ideally, programmed bits loaded to a timing generator adjust the pulse profile, ideally the programmed bits exist in tables loaded to the printhead, one for each channel, the tables being programmed via ihe printhead serial interface. The nozzle rows are preferably in offset pairs for each channel and firingof ihe offset pairs is effectedbyouiof phase pulse trains. With the above mulii-segment printhead (Memjel) technology (outlined in the referred-to documents) the microelectromechanical process is added to a CMOS process by which io construct the printheads. The consequent printhead is a new type. The matriage vjith CMOS lecSmology allows inciusion of logic io the printhead chip. Ii is an ideal place to locale timing circuitty for firing of nozzles. In a particular form the invemion resides in a method of controlling a printhead including nozzle rows, successive rows of nozzles defining respective ink channels wherein ihe nozzles in respective channels are similarly grouped and groups are fired successively. Ideally respective rows of nozzles are organized in repeated pods of nozzles along the length of each row of nozzles, the nozzles in a pod being fired one after the other along the row; successive pods of respective channels are linked as a chromapod wherein the one after the other firing of nozzles in each channel is in step along the row of nozzles in the respective pods; and blocks of chromapods are operated as a fitegtoup, the firegroups firing together. The nozzles within a single segment are grouped physically to reduce ink supply complexity and wiring complexity. They are also grouped logically to minimize power consumption and to enable a variety of printing speeds, thereby allowing speed/power consumption nade-offs to be made in different product configurations. Accordingly the present invention provides a meiliod of controlling the firing of nozzles in a printhead liaving rows of nozzles defined on respective ink channels, the method comprising the steps of; loading prim data to respective channel shift registers of die respective ink channels of the printhead; and transferring the loaded print daia to respective nozzle enable bits of the nozzles, one nozzle enable bit being provided per nozzle and temiining whether or not the respective nozzle will fire, characterized in that firing the nozzles of the respective ink channels in accordance vjith the nozzle enable biis in a time independent manner using separate timing generators in each ink channel. Accordingly the present invention also provides a printhead having rows of nozzles defined on respective ink channels, the printhead including; respective channel shift registers for the respective ink channels in which to receive print data; and one nozzle enable bit provided per nozzle for determining whether or not the respective ttozzle will fire, the nozzle enable bits being configured to receive the print data from the respective channel shift registers, the printhead characterized by including; separate timing generaiors in each ink channel configured to effect nozzle firing in the respective ink channels in a time independent manner in accordance with the nozzle enable bits. Accordingly the present invention also ptovides a priniey includiiig". a printhead having tows of nozzles defined on respective ink. channels; respective channel shift registers for ihe respective ink channels in which to receive prim data; and one nozzle enable bit provided per nozzle for determining whether or riol the respective nozzle will fire, Ihe nozzle enable bits being configured to receive the print data from the respective channel shift registers, the primer characterized by including: separate liming generators in each ink channel configured to effect nozzle firing in the respective ink channels in a time independent manner in accordance with the nozzle enable bits. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS fIG. I illustrates an arrangement of nozzles in a four-color printhead segment. FIG. 2isacloservi6wof die nozzle region of the printhead of FIG. 1. FIG, 3 illustrates a single pod and its firing order. FIG, 4 illustrates a single chromapod. FIG. 5 illustrates a single firegroup. FIG. 6 shows the relationships between segments, phasegroups, liregroups and chromapods. FIG. 7 illustrates the enabling pulses for nozzle firing. FIG. 8 shows the manner of overlap of segments in a multi-segment printhead. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS in FIG. I is seen the airangemeni of nozzles in a four color printhead segment 92. A single printhead segment in a multi-segment printhead is typically 21mm in length (93), The widih of the segment is typically SOjim for bond pads 94 and other logic, plus I I6tim (95) per color contained within ihe segrnetit (in high speed applications an extra color channel may be required for fixative). Table 1 lists the printhead segment widths for the most common printhead types, in FIG. 2 is seen a more detailed view of ihe nozzle region of the printhead of FIG. i. Witlun a single TOW of nozzles 98, the nozzles ate typically separated by 32|an (99), while the two rows 98,100 are offset by le^m (lOI). The distance fi-om one 1600 dpi dot to the next is actually I3.875jiiii, but the segment will be placed at 7.167 degrees relative to the paper such that the horizontal distance between printed dots is 15.875pm. This nozzle placement gives nse to interleaved nozzles for a single line of pixels - one row prints even dots and the other prints odd dots. Loolting at the nozzles in Figure 2, it is cleaT (hat if both rows 102,103 of cyan nozzles were to fire simultaneously, the ink fired would end up on different physical lines of the paper: the odd dots would end up on one lioe. and the evw dots would wd up on another. Likewise, the do.s printed by the magenia noazles 98.100 would end up on a comple.aly different set of two dot lines. 11,6 physical distances between nozzles is therefore of critical imporcance ,n leims of ensuring that the combination of colored inks fired by the different noszSes ends up w the wnect to pasition on Ae page as the paper passes under the pnwhead. The distance between the hw rows of the same color is 32fim (104), or 2 dot rows. This means that odd and even dots of the same color are printed two dot rows apart. The distance between rows of one color and the next color is i le^m (105). Note that this gives 7.25 dot lines which is not an integral number of dot lines. The printing of one color compared to the next is therefore stagger^ in time to accommodate the time taken for the paper to move a complete dot. rf nozzles for one color"s dot line are fired at time T. then nozzles for the corresponding dots in the next color must be fired at time T + 7,25 dot-lines. The relationships between the various rows of nozzles can he generalized by defining two variables: Di = distance between two rows of the same color in dot-lines = 2 D; = distance between die same row of nozzles between two colors = 7.25 We can now say that if the first row of nozzles is row L, then raw I of color C is dot-line: L-(C-1)D> and row 2 of color C is dot-hne: L-(C-I)D2-D, The relationship is shown in Table 3 for an example 6-coIor primhead. Note that one of the 6 colors is fixative which must be applied first. Each of the colored inks used in a printhead has differeni characteristics in terms of viscosity, heat profile eic. Firing pulses are therefore generated indeperderaly for each coUw. This are explained further below. In addition, although coated paper may be used for pritiring, fixative is required for high speed printing applications on plain paper. When fixative is used it should be printed before any of the other inks are printed to thai dot position. The fixative represents an OR of the data for that dot position. Printing fixative first also preconditions the paper so thai the subsequent drops will spread to the right sue. A single segment contains a total of 12S0C nozzles, where C is the number of colors in the segment. ApWiifcK/einvolves the firing of up to all of diese nozzles, dependent on the information to be printed. A load cycle involves the loading up of the segment with the information to be printed during the subsequent print cycle. Each nozzle has an associated NozzfeEnable bit that determines whether or not die nozzle will fire during the print cycle, TheNo2zkEnab\ebits(or\eper nozzle) ate loaded via a set of shift cegisters. Logically there are C shift registers per segment (one per color), each 1280 deep. As bits are shifted into the shift register for a given color they are directed to the lower and upper nozzles on alternate pulses. Internally, each 1280-deep shifi register is comprised of two 640-deep shift registers: one for the upper nozzles, and one for the lower nozzles. Alternate bits are shifted into the alternate internal registers. As far as the external interface is concerned however, there is a single I-bit by 1280 deep shift register. Once all ihe shift Tegislers have been fiiUy loaded (U80 load pulses), all of the bits are transferred in parallel to the appropriate NozzleEnable bits. This equates to a single parallel transfer of 1280C bits. Once the pansfer has taken place, the print cycle can begin. The print cycle and the load cycle can occur simultaneously as long as the parallel load of all NozzleEnable bits occurs at the end of the print cycle. The load cycle is concerned with loading the segment"s shift registers with the next print cycle"s NozzleEnable bits. Each segment has C 1-bit inputs directly related to the C shift registers (where C is the number of colors in the segment). These inputs are named Dit. where n is 1 to C (for example, a 4 color segment would have 4 inputs labeled DI, D2, D3 and Of). A single pulse on the segment"s SCIk line transfers C bits into the appropriate shift registers. Alternate pulses transfer bits to the lower and upper nozzles respectively. A total of 1280 pulses are required for the complete transfer of data. Once all 1280C bits have been transferred, a single pulse on Ihe TEn line causes the parallel transfer of data from the shift registers to the appropriate NozzleEnable bits. The parallel transfer via a pulse on TEn must take place after the print cycle has fini5hed. Otherwise the NozeleEnable bits for the line being printed will be incorrect, U is imponant lo note that the t^dd and even dot outputs, although printed dtvring the same print cycle, do not appear on [he same physical output line. "Hie physical separation of odd and even nozzles within the prinlhead, as well as separation between nozzles of different colors ensures that they will produce dots on difTerent lines of the page. This relative difference must be accounted for when loading the data into the printhead. The actual difference in lines depends on the characteristics of the inkjel mechanism used in the pnnthead. The differences can be defined hy variables D| and D; where Di is the distance between nozzles of different colors, and D; is [he distance between nozzles of the same color. Table 4 shows the dots transferred to a C color segment on the first 4 pulses. And so on for all 1280 pulses. For more information about line differences due to physical placement of nozzles. Data can be clocked into a segment at a maximum rate of 80MHz, which will load the entire 12S0C bits of data in 15|is, A single Memjet prinlhead segment contains 1280 nozzles. To fire ihem all al once would consume loo much power and has the potential for problems in terms of ink refill and nozzle interference. This problem is made more apparent when we consider that a typical Memjet prinlhead is composed of multiple segments, each with ! 280 nozzles. Nozzles are therefore grouped logically within a segment to enable a variety of printing speeds. These groupings allow speed/power consumption trade-offs to be made in different product configurations, in the lowest-speed printing mode, 10 nozzles of each color are fired from the segment at a time. The exact number of nozzles fired depends on how many colors are present in the printhead. For example, in a six color (e.g. CMYK-IR-F) printing environment, 60 nozzles are fired simultaneously. To fire all the nozzles in a segment, 128 different sets of nozzles must be fired. Di = number of lines between the nozzles of one cx)lor and the next (likely = 6-10) Di = number of lines between two raws of nozzles of the same color (likely ^ 2) In the Viighesl-speed priming mode, 80 noKzles of each color are fired from Ihe segment al a time. The ejtaci number of nozzles fired depends on how many colors are present in the printhead. For example, in a sis color (e.g. CMYK-IR-F) printing environment, 480 no2zles are fired simultaneously. To fire all the nozzles in a segment, 16 different sets of nozzles must he fired. The power consumption in the lowest-speed mode is one eighth that of the highest-speed mode. Note, hcfwever, thai the energy consumed to print a page is the same in both cases. Nozzles are grouped logically into pods, chromapods, phasegroups, firegroups, and finally the segment itself, A single pod consists of 8 contiguous nozzles from a single physical low. Each nozzle produces dots 22.5Mm in diameter spaced on a 15.87Stim grid to print at 1600 dpi. Figure 3 shows the arrangement of a single pod, with the nozzles numbered according to the order in which they should be fired. Although the nozzles are fired in this order, Ihe relationship of nozzles and physical placement of dots on the printed page is different. The nozzles within a pod are 2 dots apart, for the middle dot is primed by another row of nozzles, h single row therefore represents either the odd or even dots of a color. One pod of each color are logically grouped together into a chromapod. The number of pods in a chromapod will depend on the particular application. In a monochrome printing system (such as one that prints only black), there is otily a single color and hence a single pod. Photo printing application ptintheads require 3 colors (cyan, magenta, yellow), so prinihead segments used for these applications will have 3 pods per chromapod (one pod of each color), A desktop printer by contrast may contain 6 pods, one for each of cyan, magenta, yellow, black, infrared and fixative. A chromapod represents differem color components of the same horizontal set of 8 dots on different lines. The exact distance between different color pods depends on [he printhead operating parameters, and may vary from one printhead design to another. The distance must be taken into account when printing: ihe dots primed by the cyan nozzles for example, will be for different lines than those printed by the magenia, yellow or black nozzles. Figure 4 illustrates a single chromapod for a 4 color CMYK printing applicanon. 8 cliromapods are organized into a im^tt firegroHp. The firegioup is so named because groups of nozzles within a firegroup are fired simultaneously during a given firing phase (this is explained in more detail below). The formation of a firegroup from 8 chromapods is entirely for ttte purposes of multi-speed printing. During low-speed priming, only one of the eight Chromapods fires nozzles in a given firing pulse. During high¬speed priming, all eight Chromapods fire nozzles. Consequently the low-speed prim takes eight times as long as a high-speed print, since the high-speed print tires eight times as many nozzles at once, A firegroup therefore contains 64 nozzles for each color. The arrangement is shown in Figure 5, with chromapods numbered 0-7 and using a CMYK chromapod as ihe example. Note that the distance between adjacent chromapods is exaggerated for clarity. 10 firegroups are organized into a single phasegroup, with 2 phasegroups in each segment. The Even Phasegroup contains only the even nozzle rows, while the Odd Phasegroup contains the odd nozzle rows. Two enable lines, EvenEnable and OddEnable, independently control the firing of the two phasegroups as different firing phases. Since all firegroups widiin a single phasegroup share the same firing pulse, the firegroups fire simultaneously. The an-angenieni is shown in Figure 6. The distance between adjacent groupings is exaggerated for clarity. Table 5 is a summary of the nozzle groupings in a segment. The prim speed is programmed into the Memjet printhead by means of the serial interface. The interpretation of the print speed relies on an understanding of the printhead internals, which are therefore described here. Tlie nozzles to be fired in a given firing pulse are determined by: • 3 bits NozdeSelect (select 1 of 8 nozzles from a pod) • 8 bits of ChromapodSelect (select 0-8 chromapods to fire) When one of the ChromapodSelect bits is set, only the specified chromapod"s nozzles will fire as determined by ChromapodSelect and NozzleSelecl. When all eight of the ChromapodSelect lines are set, all of the chromapods will fire their nozzles. When told to stari printing a line via a pulse on the NPSync line, the state machine inside the printhead simply runs through NozzleSelect from 0 to 7 for each valid set of ChromapodSelect values. To run through die valid set of ChromapodSelect values, ChromapodSelect is shifted a specified number of bits. When die ChromapodSelect matches the initial ChromapodSelect, the NozzleSelect value is incremented. This helps to spread the power and heal evenly across the printhead during the printing of The EvenEnable and OddEnable are sqiarale generaied signals for each color in order thai Ihe finng pulses can overlap. Thus ihe 128 phases of a low-speed print cycle consist of 64 Even phases and 64 Odd phases. Likewise, the 16phasesof a high-speed prim cycle consist of SBven phases and 8 Odd phases. There are consequently 2 separate liming generators for each color. Each timing generator uses iis own programmable 200-bii entry pulse profile. The 200 1-hii entries define a total of 2iis where each entry defines a lOns time inierval. Since the typical duration of a firing pulse is 1.3 - i.8 ps a 2ns duration is adequate. Two 200-bii tables are therefore required for each color present on the printhead. The tables are programmed via the printhead"s serial interface. It is quite reasonable for the odd and even pulse profiles to be the same, hut they will typically be offset from each other hy 1 [is to lake account of the fact that the pulses overlap. Figure 7 shows example EvenEnable and OddEnable lines for a single color during a typical print cycle where the pulse is very simple. The pulse profile for a given color depends on the viscosity of the ink (dependent on temperature and ink chasacteristics) and tiw amount of power available to rtie ptintbead. The viscosity curve of the ink can be obtained from the ink supply"s QA chip. The line times then for Ihe various print speeds are twice as fast as would first appear, since the two phases are overlapping. The print speeds are therefore as listed in Table 10. The firing of a nozzle also causes acoustic penurbations for a limited time within the ink reservoir of that nozzle. The perturbations can interfere with the firing of that nozzle for the next line. The shortest time between a single nozzles firing is 32f;s (the fastest print speed). As the ink channel is 300gni long and the velocity of sound in the ink is around ! 500m/s, the resonant frequency of the ink channel is 2.5MHz. The high¬speed mode allows 80 resonant cycles, which gives minimal acoustic interference, A segment produces several types of feedback, a1t of which can he used to adjust the liming of the firing pulses. Since multiple segments are collected together inio a printhead, it is effective to share the feedback line as a tri-state bus, with only one of the segments placing the feedback information on the feedback line, A pulse on the segment"s CCEn line ANDed with data on DJ selects if the particular segment will provide the feedback. The feedback sense line will come from that segment until the next CCEn pulse. The feedback is one of, • Tsense informs the controller how hot the printhead is. This allows the controller to adjust firing pulse profiles, since temperature affects the viscosity of the ink, ■ Vsense informs the controller how much voltage is available to the actuator. This allows the controller to compensate for a flat battery or high voltage source by adjusting the pulse width, ■ Rsense informs the controller of the resistivity (Ohms per square) of the actuator heater. This allows the controller to adjust the pulse widths to maintain a constant energy irrespective of the heater resistivity, • Wsense informs the controller of the width of the critical part of the heater, which may vary up to ± 5% due to lithographic and etching variations. This allows the controller to adjust the pulse width appropriately. The priming process has a strong tendency ID stay at the equilibrium temperature. To ensure thai the first section of the printed page has a consistent dot size, the equilibrium temperature must be met before printing any dots. This is accomplished via a preheat cycle. The preheat cycle involves a single load cycle lo all nozzles of a segment with Is (i.e. setting a)) nozzles to fire), and a number of shon firing pulses to each nozzle. The duration of the pulse must be insufficient to fire the drops, but enough to heat up the ink. Altogether about 200 pulses for each nozzle are required, cycling through in the same sequence as a standard print cycle. Feedback during the preheat mode is provided by Tsense, and continues until equilibrium temperature is reached (about 30° C above ambient). The duration of the preheat mode is around 50 milliseconds, and depends on Ihe ink composition. Preheat is performed before each print job. This does not affect performance as it is done while the data is being transferred to the printer. In order to reduce the chances of nozzles becoming clogged, a cleaning cycle can be undertaken before each print job. Each nozzle is fired a number of times into an absorbent sponge. The cleaning cycle involves a single load cycle to all noziles of a segment with Is (i.e. setting all nozzles to fire), and a number of firing pulses to each nozzle. The nozzles are cleaned via the same nozzle firing sequence as a standard print cycle. The number of times that each nozzle is fired depends upon the ink composition and the time diat the printer has been idle. As with preheat, the cleaning cycle has no effect on printer performance. The printhead segment is programmed via an I^C serial interface. This includes setting the following parameters: 2 sets of200-bilpulseprofiles for each color • Print speed • Feedback data type (temperature, resistivity etc.) In addition, the combined printhead"s eliaractenzation vector is read back via the serial interface. The characterization vector includes dead nozzle infontiation as well as relative segment alignment data. Each printhead segment can be queried via its low speed serial bus to return a characterization vector of the segment. The chatacisriiatioii vectors trora multiple priatlieads can be combisied W construct a nozzle defect list for the entire printhead and allows the print engine to compensate for defective nozzles during the print. As long as the number of defective nozzles is low, the compensation can produce results indistinguishable from those of a printhead with no defective nozzles. Each segment has 384 bits for characterization vector, comprised of • 64 bits of flags and printhead segment infonnation, including serial number and number of colon represented in the segmetit • 16 bits of alignment data relative to previoiis segmait (0 = fiist segmem) ■ a variable lengthed defective nozzle list using up the remaining bits TTie defective nozzle list is variable lengthed, with each set of defective nozzles having the following structure: 5 bits count (0 = end-of-list) • 3 bits of color • count ^ \ 1 bits, one entry per defective nozzle In general terms a printhead segment has connections as defined in Table 11. Note that some of the connections are replicated when multiple colors present. A mulii-segmeni printhead is ideally composed of a number of identical prinihead segmenis. These are typically llmin segments that are manufactured together, or placed together after manufacture, to produce a prinihead of the desired leiigth. The segmei^ts may be set with overlap, as desired, to ailow for smooth transitions bet^^"ee^ segments. Each 21mm inch segments prints 1600 dpi bi-level dots over a different part of the page 10 produce the final image. AlOiough each segment produces 1280 doK of the final image, each dot is represented by a combination of colored inks. For example, 15 segments can be combined side-by-side to produce a 12-inch printhead. Each segment can be considered to have a lead-in area, a central area, and a lead-out area. The lead-out of one segment conesponds to the lead-in of the next. In FIG, Sis seen the three areas of a segment by showing two overlapping segments 106,107. Note ihat the lead-out area 108 of segment S (110) corresponds to the lead-in ar^a I09of segment S+l (107). The central area of a segment is that area that has no overlap at all (110 of 106 and II1 of 107). Although the figure shows the segments vertically staggered, the segmenis are staggered at a slight angle so that they are aligned in the vertical dimension. A number of considerations must be made when wiring up a printhead. As the width of die prinihead increases, the number of segmenis increases, and the number of connections also increases. Each segment has ilsownDnconneciionsfCof ihem), aswellasSClkiind othei connections for loadmg anii piiraing. When the number of segments 1? is small it is reasonable to load ail the segments simultaneously by using a common SCIk line and placing C bits of data on each of the Dn inputs for the segments. In a 4-segment 4 color printer, the toial number of bits to transfer to the printhead in a single SCIk pulse is 16. However for a six channel enabled (C=6) 12-inch printer, S=l 5, and it is unlikely to be reasonable to have 90 data lines running from the print data generator to the printhead. histead, it is convenient to group a number of segmenis together for loading purposes. Each group of segments is small enough to be loaded simultaneously, and share an SClk. For example, a 12-inch prmtbead can have 1 scgmem giotips, each segmeni group cojilainrag 8 segments. 4E Dn lines can be shared for both groups, with 2 SClk lines, one per segment group. Even though there is no segment for the 2nd set of 8 segments, it is still convenient to group the segments. Some bits will therefore be unused in the last group. As the number of segment groups increases, the time taken to load the printhead increases. When there is only one group, 1280 load pulses are required (each pulse transfers C data bits). When there are G groups, 1280G load pulses are required. The bandwidth of the connection between the data generator and the printhead must be able to cope and be within the allowable timing paiameieTS for the pariiculav appiscation. If G is the number of segment groups, and L is the largest number of segments in a group, the printhead requires LC ColorData lines and G SClk lines. Regardless of G, only a single TEn line is required - it can be shared across all segments. Since L segments in each segment group are loaded wiih a single SClk pulse, any printing process must produce rhe data in the correei sequence for the prinlhead. As an example, when G=2 and L=4, the First SClkl pulse will transfer ihe Dn bits for the next Prim Cycle"s dot 0, 1280, 2560 and 3840, The tirst SCIk2 pulse will iransfer the Dn bits for the next Print Cycle"s dot 5120, 6400, 7680, and 8960. The second SClkl pulse will transfer the Dn bits for the next Print Cycle"s dot 1, 12S1, 2561, and 3841. The second SCIk2 pulse will ffansfer the Dn bits for the next Print Cycle"s dot 5121,6401, 7681 and 8961, Afier 1280G SCIk pulses (1280 to each of SClkl and SCIk2), the entire line has been loaded into the ptinlhead. and the common TEn pulse can be given !(is imponam lo \w«e thai the odd asid even coloi oviipuis, although primed during *e same prim cycle, do not appear on the same physical output line. The physical separation of odd and even nozzles within the prinihead, as well as separation between nozzles of different colors ensures that they will produce dots on different lines of ihe page. This relative difference must be accounted for when loading the data into the prinihead. Considering only a single segment group. Table 13 shows the dots n-ansferred to segment M of a prinihead during the first 4 pulses ofthe shared SClk. And so on fo( all 128Q SClk pulses to the parricular segment group. With regards to printing, IOC nozzles are printed from each segment in the lowest speed printing mode, and gOC nozzles from each segment in the highest speed printing mode. While il is certainly possible to wire up segraems in any way, this specificauon only corisiders the situation where all segments fire sitnultaneously. This is because the low-speed printing mode allows low-power printing for small printheads (e.g. 2-inch and 4-inch), and the controller chip design assumes there is sufficient power available for the large print sizes (such as 8-18 inches). It is a simple matter to alter the connections in the primhead to allow grouping of firing should a particular application require it. When all segments are fired at the same lime IOCS nozzles are fired in the low-speed printing mode and 80CS nozzles are fired in the high-speed printing mode. Since all segments print simultaneously, the printing logic is the same as defined aboveand the line limes are the same as defined by Table 10, A segment produces an analog line of feedback, as defined above. The feedback is used to adjust the profile of the firing pulses. Since multiple segments are collected together into a prinihead, it is effective to share the feedback lines as a m-staie bus, with only one of the segments placing the feedback information on the feedback lines at a time. Since the selection of which segment will place the feedback information on the shared sense line relies on Dl, the groupings of segments for loading data can be effectively used for selecting the segment for feedback. Just as there are G SClk lines (a single line is shared between segments ofthe same S = segmert mmte Di ^ njmber of lines between the nozzles ot one color aid the next (likely = 7-10) Dj = number of lines between two rows of nozzles of the same color (likely - 2) segmeni gioup), there aie G CCEn lines shared in the same way. When the ct>rreci CCEn line is pulsed, the segment of that group whose Dl bit is set will start to place data on the shared feedback lines. The segment previously active in terms of feedback must also be disabled by having a 0 on its Dl bit, and this segment may be in a different segment group. Therefore when there is more than one segment group, changing the feedback segment requires two steps: disabling the old segment, and enabling the new segment. It is assumed below that a printhead has been constructed from a number of segments as described above. It is assumed that for data loading purposes, the segments have been grouped into G segment groups, with L segments in the largest segment group. It is assumed there are Ccolors in the printhead. It is assumed that the firing mechanism for the printhead Is that all segments fire simultaneously, and only one segment at a time places feedback information on a common tri-state bus. Assummg all these things. Table 14 lists the external coimections that are available from a printhead: Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. Persons skilled in the art may realise variations from the specific embodiments that will nonetheless fall within the scope of the invention. WE CLAIM : 1. A method of controlling the firing of nozzles in a printhead having rows of nozzles defined on respective ink channels, the method comprising the steps of: loading print data to respective channel shift registers of the respective ink channels of the printhead; and transferring the loaded print data lo respective nozzle enable bits of the nozzles, one nozzle enable bit being provided per nozzle and determining whether or not the respective nozzle will fire, characterized in that firing the nozzles of the respeciive ink channels in accordance with the nozzle enable bits in a time independent mannei using separate timing generators in each ink channel. 2. A method as claimed in claim I, wherein a channel"s firing can be started at a set time allowing printing at a chosen delay fot off-doi-line and doi-on-dot priming. 3. A method as claimed in claim I, wherein the nozzles are fired by an electrical pulse. 4. A method as claimed in claim 3, wherein the profile of the pulse is adjusted to suit the ink at the nozzle by programmed bits loaded to a liming generator, the programmed bits being loaded to the prinlhead from tables, one for each channel, via a prinlhead serial interface. 5. A method as claimed in any one of claims 3 or 4. wherein the printhead nozzle rows are in offset pairs for each channel andfiriugof the offset pairs is effected by ovil of phase pulse trains. 6. A method as claimed in claim I, wherein nozzles in respeciive channels are similarly grouped and the nozzles wiihin groups are fired successively, 7. A method as claimed in claim 6, wherein: respeciive rows of nozzles are organized in repeated pods of nozzles along the length of each row of nozzles, the nozzles in a pod being fired one after the other aSong the row; successive pods of respective channels are linked as a chromapod, the one after the other firing of the nozzles in each channel being in siep along the K)W of nozzles in the respective pods; and blocks of chromapods are operated as a firegroup, the firegroups firing together. S. A method asclaimediuclaim 7, wherein the firing of the nozzles is controlled by seattig the firing pattern of the chromapods within their firegroups, 9. A method as claimed in claim 7, wherein the prinlhead nozzle rows are in offset pairs for each channel and blocks of firegroups form phasegroups, there being two phasegroups driving each segmeni of a segmented printhead, one phasegroup for each of the two offset nozzle rows. 10. A prinihead. having rows of nozzles defined on respective ink channels, ihe printhead comprising : respective channel shift registers for the respective ink channels in which to receive print data; and one nozzle enable bit provided per nozzle for determining whether or not the respective nozzle will fire, the nozzle enable bits being configured to receive the prinl data from the respective channel shift registers, characterized in that separate timing generators in each ink channel configured to effect nozzle firing in the respective ink channels in a time independent manner in accordance with the nozzle enable bits. 11. A printhead as claimed in claim 10, wherein Ihe nozzles are fired by an electrical pulse train. 12. A printhead as claimed in claim 11, wherein the profile of each pulse is determined by programmed bits loaded to a liming generator, 13. A printhead as claimed in claim 12. wherein the programmed bits exist in tables loaded to the prinihead, one for each channel. 14. A prinihead as claimed in claim 13, wherein the tables are programmed via a serial interface to the printhead. 15. A prinihead as claimed in any one of claims 10 to 14, wherein the printhead nozzle rows are in offset pairs for each channel and firing of the offset pairs is by out of phase pulse trains. 16. A prinihead as claimed inany one of claims 10 to 14, comprises an interface lo the print head by which the liming parameters can be specified externally operated via a slow serial interface. 17. A printhead as claimed in claim 10, wherein the nozzles in respective channels are similarly grouped and groups are fired successively. iS. A printhead as claimed in claim 17, wherein: respective rows of nozzles are organized in repeated pods of nozzles along [he length of each row of nozzles, the nozzles in a pod being fired one after the other along ihe row; successive pods of respective channels are linked as a chromapod, the one after the other firing of the nozzles in each channel being in step along the row of nozzles in the respective pods; and firing of the nozzles is controlled by selling the firing paiiem of the cliromapods. 19, A printhead as claimed in claim 18, wherein each channel is formed by two offset rows of nozzles and chromapods are organized in blocks as firegroups whose chromapods fire simultaneously to form two phasegroups each, driving ail of the nozzles of one of the offset rows of a segment of a segmented printhead. 20, A printer comprising : a printhead having rows of nozzles defined on respeclive ink channels; respective channel shift registers for the respective ink channels in which to receive print data; and one nozzle enable bit provided per nozzle for determining whether or not the respective nozzle will fire, the nozzle enable bits being configured to receive the print daia ftora the Tespective channel shift registers, characterized in that: separate timing generators in each ink channel configured to effect nozzle firing in the respective ink channels in a time independent manner in accordance with the nozzle enable bits, 21, A printey as claimed in claim 20, wherein ihe nozzles are fited b^ aneieclrital pulse Hain, the profile of the pulses being determined by programmed bits loaded to a tirning generator, 22, A printer a5 claimed in ciaitn 21, wherein the programmed bits exist in tables loaded lo the printhead, one for each channel via an inicrface to the printhead, 23, A printer as claimed in claim 20, wherein; respeclive rows of nozzles are organized in repeated pods of nozzles along the length of each row of nozzles, die nozzles in a pod being fired one after the other along the row; successive pods of respective channels are linked as a chromapod, the one after the other firing of the nozzles in each cViaimel being in step along the row of nozzles in the respective pods; and firing of the nozzles is controlled by setting Che firing pattern of the chrotnapods, 24, A method of controlling the firing of nozzles in a prinlhead, substantially as hereinabove described and illustraled with reference lo the accompanying drawings, 25, A piiYithead, subsiantiaUy as hereinabove described and illustrated with reference to the accoitipanying drawings. 26, A printer, substantially as hereinabove described and illustraled with reference lo the accompanying drawings.

Documents:

in-pct-2002-2058-che abstract-duplicate.pdf

in-pct-2002-2058-che abstract.jpg

in-pct-2002-2058-che abstract.pdf

in-pct-2002-2058-che claims-duplicate.pdf

in-pct-2002-2058-che claims.pdf

in-pct-2002-2058-che correspondence-others.pdf

in-pct-2002-2058-che correspondence-po.pdf

in-pct-2002-2058-che description(complete)-duplicate.pdf

in-pct-2002-2058-che description(complete).pdf

in-pct-2002-2058-che drawings-duplicate.pdf

in-pct-2002-2058-che drawings.pdf

in-pct-2002-2058-che form-1.pdf

in-pct-2002-2058-che form-19.pdf

in-pct-2002-2058-che form-26.pdf

in-pct-2002-2058-che form-3.pdf

in-pct-2002-2058-che form-4.pdf

in-pct-2002-2058-che form-5.pdf

in-pct-2002-2058-che others.pdf

in-pct-2002-2058-che pct.pdf