Method and system for writing data to MEMS display elements
View Patent ↗Charge balanced display data writing methods use write and hold cycles of opposite polarity during selected frame update periods. The transitions between voltages of opposite polarity are sufficiently brief that the display elements do not change state. A release cycle may be provided to reduce the chance that a given display element will become stuck in an actuated state.
1. A method of actuating an electromechanical display element, the display element comprising a portion of an array of display elements, the method comprising:
writing display data to the display element with a potential difference of a first polarity during a first portion of a display write process;
applying a first bias potential to the display element during a second portion of the display write process, the first bias potential causing a first potential difference across the display element with the first polarity; and transitioning the potential applied to the display element from the first bias potential to apply a second bias potential polarity to the electromechanical display element during a third portion of the display write process, the second bias potential causing a second potential difference across the display element with a second polarity opposite the first polarity,
wherein a transition time between applying the first bias potential and applying the second bias potential is configured such that the display element does not change states as a result of transitioning the voltage from the first bias potential to the second bias potential; and
wherein a transition time between the bias potentials is less than or equal to “τ iMoD +“τ RC , wherein “τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
2. The method of claim 1 , further comprising writing display data to the electromechanical display element with a potential difference having a polarity opposite the first polarity during a fourth portion of the display write process.
3. The method of claim 2 , wherein during the first portion of the display write process, a first frame of display data is written to the array of electromechanical display elements, and wherein during the fourth portion of the display write process, the first frame of display data is re-written to the array of electromechanical display elements.
4. The method of claim 3 , wherein during the second and third portions of the display write process the first frame of display data is held following the re-writing.
5. The method of claim 4 , additionally comprising writing a second frame of display data using the writing, re-writing, applying a first bias potential and applying a second bias potential.
6. The method of claim 2 , wherein during the first portion of the display write process, a first row of display data is written to the array of electromechanical display elements, and wherein during the fourth portion of the display write process, the first row of display data is re-written to the array of electromechanical display elements.
7. The method of claim 6 , wherein during the second and third portions of the display write process, the first row of display data is held following the re-writing.
8. The method of claim 7 , additionally comprising writing a second row of display data using the writing, re-writing, applying a first bias potential and applying a second bias potential.
9. The method of claim 2 , wherein the first, second, third, and fourth portions of the display write process each comprise approximately one-fourth of a time period defined by the inverse of a rate at which frames of display data are received by a display system.
10. A method of actuating an electromechanical display element, the display element comprising a portion of an array of display elements, the method comprising:
writing display data to the display element with a potential difference of a first polarity during a first portion of a display write process;
applying a first bias potential having the first polarity to the display element during a second portion of the display write process; and
transitioning the potential applied to the display element from the first bias potential to apply a second bias potential having a polarity opposite the first polarity to the electromechanical display element during a third portion of the display write process, wherein a transition time between applying the first bias potential and applying the second bias potential is configured such that the display element does not change states as a result of transitioning the voltage from the first bias potential to the second bias potential, wherein the transition time is less than or equal to τ iMoD +τ RC , wherein τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
11. A method of maintaining a frame of display data on an array of electromechanical display elements, the method comprising alternately and sequentially transitioning a voltage applied to the electromechanical display elements between approximately equal bias potentials of opposite polarities so as to maintain a root mean square potential of the bias potentials within a hysteresis window of the electromechanical display elements wherein transitioning the voltage applied causes a potential difference across the display elements to vary between opposite polarities; and
wherein a transition time between the bias potentials is less than or equal to “τ iMoD +“τ RC , wherein “τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
12. A method of maintaining a frame of display data on an array of electromechanical display elements, the method comprising alternately and sequentially transitioning a voltage applied to the electromechanical display elements between approximately equal bias potentials of opposite polarities so as to maintain a root mean square potential of the bias potentials within a hysteresis window of the electromechanical display elements, wherein a transition time between the bias potentials is less than or equal to τ iMoD +τ RC , wherein τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
13. A method of writing frames of display data to an array of electromechanical display elements at a rate of one frame per defined frame update period, the method comprising:
writing display data to the electromechanical display elements, wherein the writing takes less than the frame update period; and
after the writing the display data, sequentially transitioning an applied voltage between bias potentials of alternating polarity to the electromechanical display elements for the remainder of the frame update period, wherein a root mean square potential of the applied voltage is within a hysteresis window of the electromechanical display elements, wherein transitioning the voltage applied causes a potential difference across the display elements to vary between opposite polarities; and
wherein a transition time between the bias potentials is less than or equal to “τ iMoD +“τ RC , wherein “τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
14. A method of writing frames of display data to an array of electromechanical display elements at a rate of one frame per defined frame update period, the method comprising:
writing display data to the electromechanical display elements, wherein the writing takes less than the frame update period; and
after the writing the display data, sequentially transitioning an applied voltage between bias potentials of alternating polarity to the electromechanical display elements for the remainder of the frame update period, wherein a root mean square potential of the applied voltage is within a hysteresis window of the electromechanical display elements, wherein a transition time between consecutive bias potentials is less than or equal to τ iMoD +τ RC , wherein τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
15. The method of claim 13 , wherein a bias potentially of a first polarity is applied during approximately half of the remainder of the frame update period, and a bias potentially of a second polarity is applied during approximately half of the remainder of the frame update period.
16. An electromechanical display device, comprising: an array of electromechanical display elements; and a driver configured to: write display data to the display elements with a potential difference of a first polarity during a first portion of a display write process,
apply a first bias potential to the display element during a second portion of the display write process, the first bias potential causing a first potential difference across the display element with the first polarity, and
transition the potential applied to the display element from the first bias potential to apply a second bias potential to the electromechanical display element during a third portion of the display write process, the second bias potential causing a second potential difference across the display element with a second polarity opposite the first wherein a transition time between applying the first bias potential and applying the second bias potential is configured such that the display element does not change states as a result of transitioning the voltage from the first bias potential to the second bias potential; and
wherein a transition time between the bias potentials is less than or equal to “τ iMoD +“τ RC , wherein “τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC com rises a constant related to electrical characteristics of the electromechanical display element.
17. The device of claim 16 , wherein the driver is further configured to write display data to the electromechanical display elements with a potential difference having a polarity opposite the first polarity during a fourth portion of the display write process.
18. The device of claim 17 , wherein the driver is further configured to write a first row of display data to the array of electromechanical display elements during the first portion of the display write process, and to re-write the first row of display data to the array of electromechanical display elements during the fourth portion of the display write process.
19. The device of claim 18 , wherein the driver is further configured to hold the first row of display data following the re-writing during the second and third portions of the display write process.
20. The device of claim 19 , wherein the driver is further configured to write a second row of display data by writing the row of display data, re-writing the row of display data, applying a first bias potential, and applying a second bias potential.
21. An electromechanical display device, comprising:
an array of electromechanical display elements; and
a driver configured to:
write display data to the display elements with a potential difference of a first polarity during a first portion of a display write process,
apply a first bias potential having the first polarity to the display element during a second portion of the display write process, and
transition the potential applied to the display element from the first bias potential to apply a second bias potential having a polarity opposite the first polarity to the electromechanical display element during a third portion of the display write process,
wherein a transition time between applying the first bias potential and applying the second bias potential is configured such that the display element does not change states as a result of transitioning the voltage from the first bias potential to the second bias potential, wherein the transition time is less than or equal to τ iMoD +τ RC , wherein τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
22. An electromechanical display device, comprising: an array of electromechanical display elements; and a driver configured to alternately and sequentially transition a voltage applied to the electromechanical display elements between approximately equal bias potentials of opposite polarities so as to maintain a root means square value of the bias potentials within a hysteresis window of the electromechanical display elements, wherein transitioning the voltage applied causes a potential difference across the display elements to vary between opposite polarities; and
wherein a transition time between the bias potentials is less than or equal to “τ iMoD +“τ RC , wherein “τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
23. An electromechanical display device, comprising:
an array of electromechanical display elements; and
a driver configured to alternately and sequentially transition a voltage applied to the electromechanical display elements between approximately equal bias potentials of opposite polarities so as to maintain a root mean square value of the bias potentials within a hysteresis window of the electromechanical display elements, wherein a transition time between the bias potentials is less than or equal to τ iMoD +τ RC , wherein τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
24. An electromechanical display device, comprising: an array of electromechanical display elements; and a driver configured to: write frames of display data to the array at a rate of one frame per defined frame update period, wherein the writing takes less than the frame update period, and after the writing the display data, sequentially transition an applied voltage between bias potentials of alternating polarity to the electromechanical display elements for the remainder of the frame update period, wherein a root mean square potential of the applied voltage is within a hysteresis window of the electromechanical display elements, wherein transitioning the voltage applied causes a potential difference across the display elements to vary between opposite polarities; and
wherein a transition time between the bias potentials is less than or equal to “τ iMoD +“τ RC , wherein “τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
25. An electromechanical display device, comprising:
an array of electromechanical display elements; and
a driver configured to:
write frames of display data to the array at a rate of one frame per defined frame update period, wherein the writing takes less than the frame update period, and
after the writing the display data, sequentially transition an applied voltage between bias potentials of alternating polarity to the electromechanical display elements for the remainder of the frame update period, wherein a root mean square potential of the applied voltage is within a hysteresis window of the electromechanical display elements, wherein a transition time between consecutive bias potentials is less than or equal to τ iMoD +τ RC , wherein τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
26. The device of claim 24 , wherein a bias potentially of a first polarity is applied during approximately half of the remainder of the frame update period, and a bias potentially of a second polarity is applied during approximately half of the remainder of the frame update period.
27. An electromechanical display device, comprising:
means for writing display data to the display element with a potential difference of a first polarity during a first portion of a display write process;
means for applying a first bias potential to the display element during a second portion of the display write process, the first bias potential causing a first potential difference across the display element with the first polarity; and
means for transitioning the potential applied to the display element from the first bias potential to apply a second bias to the electromechanical display element during a third portion of the display write process, the second bias potential causing a second potential difference across the display element with a second polarity opposite the first polarity,
wherein a transition time between applying the first bias potential and applying the second bias potential is configured such that the display element does not change states as a result of transitioning the voltage from the first bias potential to the second bias potential; and
wherein a transition time between the bias potentials is less than or equal to “τ iMoD +“τ RC , wherein “τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
28. The device of claim 27 , further comprising means for writing display data to the electromechanical display elements with a potential difference having a polarity opposite the first polarity during a fourth portion of the display write process.
29. An electromechanical display device, comprising:
means for writing display data to the display element with a potential difference of a first polarity during a first portion of a display write process;
means for applying a first bias potential having the first polarity to the display element during a second portion of the display write process; and
means for transitioning the potential applied to the display element from the first bias potential to apply a second bias potential having a polarity opposite the first polarity to the electromechanical display element during a third portion of the display write process,
wherein a transition time between applying the first bias potential and applying the second bias potential is configured such that the display element does not change states as a result of transitioning the voltage from the first bias potential to the second bias potential, wherein the transition time is less than or equal to τ iMoD +τ RC , wherein τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
30. An electromechanical display device, comprising: an array of electromechanical display elements; and means for alternately and sequentially transitioning a voltage applied to the electromechanical display elements between approximately equal bias potentials of opposite polarities so as to maintain a root mean square potential of the bias potentials within a hysteresis window of the electromechanical display elements, wherein transitioning the voltage applied causes a potential difference across the display elements to vary between opposite polarities; and
wherein a transition time between the bias potentials is less than or equal to “τ iMoD +“τ RC , wherein “τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
31. An electromechanical display device, comprising:
an array of electromechanical display elements; and
means for alternately and sequentially transitioning a voltage applied to the electromechanical display elements between approximately equal bias potentials of opposite polarities so as to maintain a root mean square potential of the bias potentials within a hysteresis window of the electromechanical display elements, wherein a transition time between the bias potentials is less than or equal to τ iMoD +τ RC , wherein τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
32. An electromechanical display device, comprising: an array of electromechanical display elements; and means for writing frames of display data to the array at a rate of one frame per defined frame update period, wherein the writing takes less than the frame update period, and means for sequentially transitioning an applied voltage between bias potentials of alternating polarity to the electromechanical display elements for the remainder of the frame update period, wherein a root mean square potential of the applied voltage is within a hysteresis window of the electromechanical display elements, wherein transitioning the voltage applied causes a potential difference across the display elements to vary between opposite polarities; and
wherein a transition time between the bias potentials is less than or equal to “τ iMoD +“τ RC , wherein “τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.
33. An electromechanical display device, comprising:
an array of electromechanical display elements; and
means for writing frames of display data to the array at a rate of one frame per defined frame update period, wherein the writing takes less than the frame update period, and
means for sequentially transitioning an applied voltage between bias potentials of alternating polarity to the electromechanical display elements for the remainder of the frame update period, wherein a root mean square potential of the applied voltage is within a hysteresis window of the electromechanical display elements, wherein a transition time between consecutive bias potentials is less than or equal to τ iMoD +τ RC , wherein τ iMoD comprises a constant of the electromechanical display element determined with reference to physical characteristics of the electromechanical display element, and wherein τ RC comprises a constant related to electrical characteristics of the electromechanical display element.