Ink jet printing

1. A method of driving an inkjet module having a plurality of ink jets, the method comprising:

applying a voltage waveform to the inkjet module in a jetting cycle, the voltage waveform comprising a first pulse that occurs at a first time during the jetting cycle and a second pulse that occurs at a second, different time during the jetting cycle, wherein within the jetting cycle the method comprises:

using a first signal to activate a selected ink jet among the plurality of ink jets so that the selected ink jet: (1) accepts the first pulse of the voltage waveform at the first time; and (2) ejects a fluid droplet in response to accepting the first pulse; and

using a second signal to activate all of the ink jets in the inkjet module to: (1) accept the second pulse of the voltage waveform at the second, different time; and (2) cause motion of a fluid meniscus without ejecting a droplet,

wherein:

for the selected ink jet, the jetting cycle includes only one first pulse; and

for all of the ink jets in the ink jet module, the jetting cycle includes only one second pulse.

2. The method of claim 1 wherein each ink jet comprises a piezoelectric transducer.

3. The method of claim 1 further comprising applying additional voltage waveforms to the inkjet module, wherein the voltage waveforms are applied with a frequency of about 2 kHz or more.

4. The method of claim 1 wherein the first pulse has a first period and the second pulse has a second period less than the first period.

5. The method of claim 1 wherein the first pulse has a first amplitude and the second pulse has a second amplitude less than the first amplitude.

6. The method of claim 1 , wherein activating all of the ink jets comprises applying signal to all of the ink jets.

7. The method of claim 1 , wherein the first pulse comprises a bipolar pulse.

8. The method of claim 1 , wherein the second pulse comprises a unipolar pulse.

9. The method of claim 1 , wherein the second pulse has a voltage of 100 V or less.

10. The method of claim 1 , wherein the first pulse has a period between 1 microsecond and 100 microseconds.

11. The method of claim 1 , wherein the second pulse has a period of 20 microseconds or less.

12. The method of claim 1 , wherein the jetting cycle has a cycle period between 20 microseconds and 500 microseconds.

13. The method of claim 2 wherein activating the selected ink jet causes the voltage waveform to be applied to the piezoelectric transducer for that ink jet.

14. The method of claim 7 , wherein the first pulse comprises a first trapezoidal portion of negative voltage and a second portion having positive voltage.

15. The method of claim 14 , wherein the first trapezoidal portion has a minimum voltage held for a first period, the second portion has a maximum voltage held for a second period and then the maximum voltage is reduced to an intermediate voltage that is held for a third period before the pulse ends.

16. The method of claim 15 , wherein the minimum voltage is -5 V or less.

17. The method of claim 15 , wherein the maximum voltage is 5 V or more.

18. A method of driving an inkjet module having a plurality of ink jets, the method comprising:

a) applying a voltage waveform to the inkjet module in a cycle, the voltage waveform comprising a first pulse that occurs at a first time during the cycle and a second pulse that occurs at a second, different time during the cycle, wherein within the cycle the method comprises:

i) using a first signal to activate a selected ink jet among the plurality of ink jets so that the selected ink jet: (1) accepts the first pulse of the voltage waveform at the first time; and (2) ejects a fluid droplet in response to accepting the first pulse; and

ii) using a second signal to activate all of the ink jets in the inkjet module to: (1) accept the second pulse of the voltage waveform at the second, different time; and (2) cause motion of a fluid meniscus without ejecting a droplet; and

b) repeating a), and wherein

for the selected ink jet, the cycle includes only one first pulse; and

for all of the ink jets in the ink jet module, the cycle includes only one second pulse.

19. The method of claim 18 , wherein the first pulse of the voltage waveform comprises multiple voltage oscillations.

20. The method of claim 18 , wherein each of the ink jets comprises a piezoelectric transducer.