Method, apparatus and circuitry for droplet ejection

1. Controller circuitry for a droplet deposition head that comprises an array of actuating elements and a corresponding array of nozzles, the controller circuitry configured to:

receive an input set of ejection data;

generate a series of sub-sets of ejection data based on the input set;

receive deposition media speed data, which indicates the current speed of relative movement of the droplet deposition head with respect to the deposition media; and

send said series of sub-sets of ejection data and respective ejection commands to actuating circuitry for the droplet deposition head, the ejection commands being sent at a time determined in accordance with the current speed of relative movement of the droplet deposition head with respect to the deposition media as indicated in said deposition media speed data, the time interval between sending successive sub-sets of ejection data varying generally inversely with the current speed of relative movement of the droplet deposition head;

wherein the actuating circuitry is configured so as to, for each set of ejection commands, apply drive waveforms to said actuating elements so as to repeatedly eject droplets from one or more of said nozzles, thus depositing successive rows of droplets, the one or more nozzles and the sizes of the droplets ejected therefrom being determined by the current sub-set of ejection data, wherein each of the one or more nozzles maintain the ejection of droplets with a substantially constant frequency of 1/T in accordance with successive sub-sets of ejection data.

2. The controller circuitry according to claim 1 , wherein each sub-set of ejection data implicitly acts as the respective actuation command.

3. The controller circuitry according to claim 1 , wherein each sub-set of ejection data is sent simultaneously with the corresponding actuation command.

4. The controller circuitry according to claim 1 , wherein said input set of ejection data represents a two-dimensional array of droplet ejection values; and

wherein consecutive sub-sets of ejection data in said series are determined based on successive slices of said two dimensional array.

5. The controller circuitry according to claim 1 , wherein each sub-set of ejection data defines, for each nozzle, a corresponding value for the size of droplets to be ejected by that nozzle, each droplet size value being between 0, corresponding to no ejection, and M, corresponding to a maximum droplet size.

6. The controller circuitry according to claim 5 , wherein each droplet size value can take any integer value between 0 and M.

7. The controller circuitry according to claim 5 , wherein each droplet size value can be either 0 or M.

8. The controller circuitry according to claim 1 , configured to generate substantially the whole of said series of sub-sets of ejection data prior to sending said series of sub-sets of ejection data to the actuating circuitry.

9. A method for depositing droplets using a droplet deposition head comprising an array of actuating elements and a corresponding array of nozzles, the method comprising:

receiving an input set of ejection data;

generating a series of sub-sets of ejection data based on the input set;

receiving deposition media speed data, which indicates the current speed of relative movement of the droplet deposition head with respect to deposition media; and

operating the droplet deposition head according to each sub-set of ejection data in turn, while moving the droplet deposition head relative to the deposition media, such operating comprising:

for each sub-set of ejection data, repeatedly ejecting droplets from one or more nozzles within said array so as to deposit successive rows of droplets, the one or more nozzles and the sizes of the droplets ejected therefrom being determined by the current sub-set of ejection data, each of the one or more nozzles ejecting droplets with a substantially constant frequency of 1/T; and

switching from ejecting droplets in accordance with one sub-set of ejection data to ejecting droplets in accordance with the consecutive sub-set of ejection data at a time determined in accordance with the current speed of relative movement of the droplet deposition head with respect to the deposition media as indicated by said media speed data, the time interval between starting ejecting droplets in accordance with successive sub-sets of ejection data varying inversely with the current speed of relative movement of the droplet deposition head, wherein each of the one or more nozzles maintain the ejection of droplets with a substantially constant frequency of 1/T in accordance with successive sub-sets of ejection data.

10. The method according to claim 9 , wherein said input set of ejection data represents a two-dimensional array of droplet ejection values; and

wherein consecutive sub-sets of ejection data in said series are determined based on successive slices of said two dimensional array.

11. The method according to claim 9 , wherein each sub-set of ejection data defines, for each nozzle, a corresponding value for the size of droplets to be ejected by that nozzle, each droplet size value being between 0, corresponding to no ejection, and M, corresponding to a maximum droplet size.

12. The method according to claim 11 , wherein each droplet size value can take any integer value between 0 and M.

13. The method according to claim 11 , wherein each droplet size value can be either 0 or M.

14. The method according to claim 9 , wherein the substantially the whole of said series of sub-sets of ejection data is generated prior to sending said series of sub-sets of ejection data to the actuating circuitry.

15. The method according to claim 9 , further comprising ceasing said repeated ejection of droplets determined by the current sub-set of ejection data once at least one of the one or more nozzles ejecting droplets has ejected Mx droplets, where Mx corresponds to a maximum number of droplets.

16. The method according to claim 9 , further comprising ceasing said repeated ejection of droplets determined by the current sub-set of ejection data in response to a “stop” command.

17. The method according to claim 9 , wherein, for each of the one or more nozzles that repeatedly ejects droplets in accordance with the current sub-set of ejection data, each such droplet ejected from the nozzle in question is of substantially the same size.

18. The method according to claim 9 , wherein, for each nozzle that ejects droplets in accordance with successive sub-sets of ejection data, the time interval between the final droplet resulting from the earlier set and the first droplet resulting from the later set is substantially equal to T.

19. The method according to claim 9 , wherein, in response to each sub-set of ejection data, the droplet deposition head operates in accordance with an actuation cycle, during which each of the one or more nozzles determined by the current sub-set of ejection data ejects a droplet.