BACKGROUND

[0001] An inkjet printhead includes hundreds or thousands of actuators that dispense ink and other fluids, for example as drops or streams. It may be desirable in some inkjet printing applications to monitor the performance of individual actuators, for example to detect defective actuators. Actuator performance may be compromised, for example, by a clogged nozzle, a damaged resistor (in a thermal inkjet printhead), or a malfunctioning drive transistor.

DRAWINGS

[0002] Fig. 1 illustrates one example of an inkjet type fluid dispensing system.

[0003] Fig. 2 illustrates one example of a printhead controller for a dispensing system such as the system shown in Fig. 1.

[0004] Figs. 3 and 4 illustrate example activation sequences for actuators in a printhead in a dispensing system such as the system shown in Fig. 1.

[0005] Figs. 5 and 6 illustrate an example series of activation sequences for actuators in a printhead in a dispensing system such as the system shown in Fig. 1 . [0006] Figs. 7 and 8 illustrate another example series of activation sequences for actuators in a printhead in a dispensing system such as the system shown in Fig. 1 .

[0007] Fig. 9 illustrates one example of a process to activate fluidic actuators on an inkjet printhead.

[0008] The same part numbers refer to the same or similar parts throughout the figures. The figures are not necessarily to scale.

DESCRIPTION

[0009] The performance of an actuator in an inkjet printhead may be assessed by periodically measuring a characteristic of the actuation. For example, in “drive bubble detection” (DBD) for a thermal inkjet printhead, the performance of an actuator may be assessed by measuring the electrical impedance of a bubble that forms in the actuation chamber when the actuator is activated to dispense a drop of ink from the chamber. If a DBD activation follows too soon after a previous activation or another activation follows too soon after a DBD activation, then the DBD measurement may not be an accurate indication of actuator performance. [0010] A new activation sequence has been developed for inkjet actuators to help reduce the risk of compromising DBD for actuator assessment. In one example, an activation sequence for a group of actuators on a printhead includes all of the actuators in the group with the first actuator in the sequence repeated as the last actuator in the sequence and none of the other actuators is repeated in the sequence. For example, the last, repeat activation in the sequence may be used for DBD to help provide sufficient time since the prior activation (the first in the sequence) for an accurate assessment. In addition, the activation sequence following a DBD activation may shifted from the preceding sequence by one or more actuators to help provide sufficient time after a DBD activation for an accurate assessment. To assess all of the actuators in the group, for example, a series of activation sequences may be generated in which each successive sequence in the series is shifted from the preceding sequence by one or more actuators such that the first actuator in a successive sequence is the same as the second (or later) actuator in the preceding sequence (and with the first actuator in each sequence repeated as the last actuator for DBD assessment, as noted above). If the number of sequences in the series matches the number of actuators in the group, then each actuator in the group will be activated twice (first and last) in one sequence in the series.

[0011] Examples are not limited to drive bubble detection (DBD), but may be implemented with other actuator assessment techniques, for other types of actuator activation, and/or for other types of printheads. The examples shown in the figures and described herein illustrate but do not limit the scope of the patent, which is defined in the Claims following this Description.

[0012] As used in this document: “and/or” means one or more of the connected things; a “primitive” means a group of actuators; a “printhead” means an inkjet type dispenser to dispense ink or other fluids for 2D and 3D printing and/or for uses other than printing; and a “processor readable medium” means any non-transitory tangible medium that can embody, contain, store, or maintain programming for use by a computer processor and may include, for example, circuits, integrated circuits,

ASICs (application specific integrated circuits), hard drives, random access memory (RAM), read-only memory (ROM), and memory cards and sticks and other portable storage devices. [0013] Fig. 1 illustrates one example of a fluid dispensing system 10 that includes a printhead 12, a printhead controller 14, a source 16 of activation data, and an actuator health controller 18. Printhead 12 includes actuators 20, a fluid supply channel 22 to supply fluid to actuators 20, and actuation sensors 24 to sense a characteristic of respective actuators 20 during activation, for example to assess the performance or “health” of the actuators. In this example, actuators 20 are organized logically and/or physically into N number of groups, called primitives, P1- PN, each primitive P1-PN includes eight actuators 20 addressed 0-7, and the actuators 20 in each primitive P1-PN are physically adjacent to one another in a column along fluid supply channel 22. Also in this example, primitives P1-PN are organized into groups PG1 and PG2 along each side of channel 22. In one example, each primitive group PG1 , PG2 includes 132 primitives (i.e. , PN=P132) such that channel 22 supplies fluid to 2,112 actuators 20.

[0014] Other configurations for a printhead 12 are possible. For example, actuators 20 may be organized logically into primitives in which some or all of the actuators in a primitive are not physically adjacent to one another, more or fewer than eight actuators 20 may be included in a primitive, and/or actuators 20 may not be grouped logically or physically (in which case there are no primitives). For another example, primitives P1-PN may be organized into more or fewer primitive groups and/or arranged differently from that shown in Fig. 1 , or there may be no primitive groups.

[0015] Printhead actuators 20 in Fig. 1 may dispense fluid by ejecting fluid through an opening and/or by pumping fluid through a conduit. In a thermal inkjet printer, for example, actuators 20 may be implemented with resistive heating elements that function as drop ejectors at activation chambers with dispensing nozzles and as microfluidic pumps at activation chambers without dispensing nozzles.

[0016] Printhead controller 14 represents the processing and memory resources, programming, and the electronic circuitry and components needed to control the operative components of printhead 12, and may include distinct control elements for individual printhead components, including actuators 20. In particular, printhead controller 14 is programmed to generate actuator activation sequence data, as indicated by activation sequence programming 26 in Fig. 1. Some or all of the elements of printhead controller 14 may be integrated into a higher level dispensing device controller, a printer controller for example. Although printhead controller 14 is shown separate from printhead 12 in Fig. 1 , some or all of the elements of printhead controller 14 may reside on printhead 12.

[0017] Activation data source 16 represents any source of data for printhead controller 14 to activate actuators 20. In a system 10 for an inkjet printer, for example, the source 16 of activation data for printhead controller 14 may be an imaging pipeline that includes a printer driver (on a device connected to the printer, for example) and/or the printer controller.

[0018] Actuator health controller 18 represents the processing and memory resources, programming, and the electronic circuitry and components needed to control actuator health sensing for printhead 12. For example, health controller 18 may be programmed to periodically activate one or more actuation sensors 24 to measure impedance and/or another characteristic of an actuator 20 and to signal printhead controller 14 that a sensor 24 is to be activated. Printhead controller 14 may generate the desired activation sequence for actuators 20 in response to the signal from health controller 18. Health controller 18 may be programmed to receive measurements from sensors 24, and assess the health of actuators 20 and, if desired, initiate an appropriate response. Some or all of the elements of health controller 18 may be integrated into printhead controller 14 or a higher level, dispensing device controller such as a printer controller. Although health controller 18 is shown separately from printhead 12 in Fig. 1 , some or all of the elements of health controller 18 may reside on printhead 12.

[0019] Fig. 2 illustrates one example of a printhead controller 14 in a system 10 shown in Fig. 1. Referring to Fig. 2, printhead controller 14 includes a processor readable medium 28 with activation sequence programming 26 and a processor 30 to read and execute programming 26.

[0020] Figs. 3 and 4 illustrate example activation sequences 32, 34 for a primitive P1-PN in a printhead 12 shown in Fig. 1. Sequences 32, 34 may be generated, for example, by processor 30 executing programming 26 on a printhead controller 14 shown in Figs. 1 and 2. In sequence 32 shown in Fig. 3, each actuator in the primitive is activated only once, in the order 0 36 1 4 72 5. The activation order in sequence 32 is just one example. Other suitable activation orders are possible. In sequence 34 shown in Fig. 4, the first actuator in the sequence (address 0) is also the last actuator in the sequence. Accordingly, the actuator at address 0 is activated twice in sequence 34 (first and last) and each of the other actuators in the primitive (addresses 3 6 1 4 72 5) is activated only once. The added/repeat activation of actuator 0 at the end of sequence 34 in Fig. 4 may be used, for example, to assess the health of actuator 0 while helping to provide sufficient time since the prior activation at the beginning of the sequence for an accurate health assessment.

[0021] When an actuator assessment is desired, to assess the first actuator in a sequence for example, a second/repeat activation for the first actuator is added to the end of the regular sequence to form a new sequence in which, as shown in the example of Fig. 4, the last actuator in the sequence is the same as the first actuator in the sequence. When it is desired to assess each actuator in the regular sequence, and thus each actuator on each primitive P1-PN in a primitive group PG1 , PG2, a series of activation sequences may be generated in which each successive sequence in the series is shifted from the preceding activation sequence in the series by one actuator such that the first actuator in a successive activation sequence is the same as the second actuator in the preceding activation sequence. [0022] One example series of activation sequences is shown in a matrix 36 in Fig. 5 for a primitive P1-PN with eight actuators 20 addressed 0-7. Activation matrix 36 is implemented in a series 38 of activation sequences 34 shown in the timing diagram of Fig. 6. Referring to Figs. 5 and 6, matrix 36 includes a series 38 of eight activation cycles 40 to cycle through corresponding eight activation sequences 34 each with a last/repeat assessment actuation for each of the eight actuators 20. Activation sequence 34 for each successive cycle 40 is shifted from the preceding sequence in the series by one actuator such that the first actuator in a successive activation sequence is the same as the second actuator in the preceding activation sequence. Thus, in this example, the activation sequence for cycle 40-1 begins and ends with actuator 0; the activation for sequence for cycle 40-2 begins and ends with actuator 3; the activation for sequence for cycle 40-3 begins and ends with actuator 6; the activation for sequence for cycle 40-4 begins and ends with actuator 1 ; the activation for sequence for cycle 40-5 begins and ends with actuator 4; the activation for sequence for cycle 40-6 begins and ends with actuator 7; the activation for sequence for cycle 40-7 begins and ends with actuator 2; and the activation for sequence for cycle 40-8 begins and ends with actuator 5, to complete the series 38.

[0023] Sequence 34 in the starting activation cycle 40-1 is just one example. Other suitable starting activation sequences are possible. For example, it may be desirable in some implementation to repeat more than one actuator in a sequence. Also, while a one-actuator shift between preceding and successive cycles is shown, other suitable shifts are possible. For example, it may be desirable in some implementations to shift by more than one actuator between preceding and successive cycles, such as when more than one actuator is repeated in an activation sequence.

[0024] Another example series of activation sequences is shown in a matrix 42 in Fig. 7. Activation matrix 42 is implemented in a series 44 of activation sequences 46 shown in the timing diagram of Fig. 8. Referring to Figs. 7 and 8, matrix 42 includes a series 44 of four activation cycles 48 to cycle through corresponding four activation sequences 46 each with multiple last/repeat activations. In this example, there are two last/repeat activations in each of the sequences in series 44. Accordingly, the activation sequence for each successive sequence is shifted from the preceding sequence by two actuators such that the first actuator in a successive activation sequence 48-2, 48-3, and 48-4 is the same as the third actuator in the preceding activation sequence 48-1 , 48-2, and 48-3, respectively.

[0025] Thus, in the example shown in Figs. 7 and 8, the activation sequence for cycle 48-1 begins and ends with actuators 0 3, the activation sequence for cycle 48- 2 begins and ends with actuators 6 1 , the activation sequence for cycle 48-3 begins and ends with actuator 4 7, and the activation sequence for cycle 48-4 begins and ends with actuators 2 5.

[0026] To maintain a consistent period after repeat activations, the number of actuators shifted in a successive sequence may be set to match the number of actuators repeated in the preceding sequence. In the example shown in Figs. 5 and 6, a single actuator is repeated in each preceding cycle 40-1 through 40-7 and, therefore, the sequence in each successive cycle 40-2 through 40-8 is shifted by one actuator. In the example shown in Figs. 7 and 8, two actuators are repeated in each preceding cycle 48-1 through 48-3 and, therefore, the sequence in each successive cycle 48-2 through 48-4 is shifted by two actuators. [0027] In some inkjet dispensing operations, corresponding actuators in each primitive in the primitive group are activated together, in sequence, for printing and servicing, and/or for other types of dispensing operations. For example, and using the activation sequence 32 shown in Fig. 3, all of the actuators with address 0 on primitives P1-PN in a group CG1 in Fig. 1 are activated together, followed by the actuators with address 3, and so on until all the actuators in the primitive group have been activated. When an actuator assessment is desired, to assess the first actuator in a sequence 32 for example, a second/repeat activation for the first actuator may be added to the end of the regular sequence to form a new sequence 34 in which, as noted above, the last actuator in the sequence is the same as the first actuator in the sequence. When it is desired to assess each actuator in the regular sequence 32 (and thus each actuator on each primitive in the primitive group), a series of activation sequences is generated in which each successive sequence in the series is shifted from the preceding activation sequence in the series by one (or more) actuators such that the first actuator in a successive activation sequence is the same as the second (or another subsequent) actuator in the preceding activation sequence, for example as shown in Figs. 5 and 6.

[0028] In a printing application for a fluid dispensing system 10 in Fig. 1 , for example, printhead controller 14 may (and usually does) receive data in blocks from an imaging pipeline or other data source 16 for an entire primitive group PG1 , PG2. Each block of printing data from source 16 may not be addressed to the primitives P1-PN in the group and/or sequenced to actuators 0-7. Printhead controller 14, therefore, addresses and sequences the imaging data to generate activation data transmitted to printhead 12. In addition, each block of printing data from source 16 may (and usually does) include data for more than one primitive activation cycle. For example, for primitives P1-PN each with eight actuators 20, as shown in Fig. 1 , printhead controller 14 may receive a block of data for eight activation cycles - imaging data to activate each of the eight actuators 20 on all of the primitives P1-PN in a primitive group PG1 .

[0029] Printhead controller 14 executing programming 26 addresses and sequences each block of imaging data, for example according to an activation matrix 36, 42 shown in Figs. 5 and 7. While it is expected that activation sequences 34, 46 in Figs. 4-8 usually will be used for DBD and other actuator health assessments, activation sequences 34, 46 may be used for other dispensing operations in which it is desirable to repeat the first actuator(s) in the sequence at the end of the sequence.

[0030] Fig. 9 illustrates one example of a process 100 to activate fluidic actuators in a primitive on an inkjet printhead. Part numbers in the description of process 100 refer to the examples shown in Figs. 1-5. Referring to Fig. 9, process 100 includes generating a first activation sequence 32 for the actuators 20 in a primitive P1-PN (block 102), activating the actuators 20 according to the first activation sequence 32 while printing an image (block 104), and receiving a signal to activate an actuator 20 in the primitive P1-PN for drive bubble detection (DBD) (block 106). Process 100 also includes, in response to receiving the DBD signal, generating a second activation sequence 34 by adding the first actuator from the beginning of the first sequence 32 to the end of the first sequence 32 so that the first and last actuators in the second sequence 34 are the same as the first actuator in the first sequence 32 (block 108), and activating the actuators according to the second sequence 34 while still printing the image (block 110).

[0031] In one implementation, to perform DBD on each actuator in a printhead primitive P1-PN or group of primitives PG1 , PG2 for example, a series of first sequences is generated at block 102 and a corresponding series of second activation sequences is generated at block 108. Thus, in this implementation (1) generating the first activation sequence at block 102 in Fig. 9 includes generating a first series of first activation sequences in which each successive first activation sequence in the first series is shifted from the preceding first activation sequence in the first series by one or more actuators, such that the first actuator in a successive first activation sequence is different from the first actuator in the preceding first activation sequence (with the last actuator in each sequence the same as the first actuator in the sequence), and (2) generating the second activation sequence at block 108 in Fig. 9 includes generating a second series of second activation sequences by adding the first actuator in each of the first activation sequences to the end of the respective first activation sequence so that the first and last actuators in each of the second activation sequences are the same as the first actuator in each of the corresponding first activation sequences. [0032] While process 100 uses DBD sequencing while printing an image, the same processing actions could be used for DBD sequencing while servicing a printhead 12 and/or while performing other dispensing operations with a printhead 12.

[0033] The examples shown in the figures and described above illustrate but do not limit the patent, which is defined in the following Claims.

[0034] "A" and "an" used in the claims means one or more. For example, “a first actuator” means one or more first actuators and subsequent reference to “the first actuator” means the one or more first actuators.