APPARATUS AND SYSTEM FOR WRITING DATA TO ELECTROMECHANICAL DISPLAY ELEMENTS

• US 20100026680A1
• Filed: 10/13/2009
• Published: 02/04/2010
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Chui, Clarence, Kothari, Manish
• Granted Patent: US 8,514,169 B2
• Time in Patent Office: Days
• US Class Current: 345/214
• CPC Class Codes: G09G 2300/06 Passive matrix structure, i.e. with direct application of both column and row voltages to the light emitting or modulating elements, other than LCD or OLED
• CPC Class Codes: G09G 2310/0245 Clearing or presetting the whole screen independently of waveforms, e.g. on power-on G09G2310/063 takes precedence
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

Charge balanced display data writing systems, apparatuses, and methods use write and hold cycles of opposite polarity during selected frame update periods. A release cycle may be provided to reduce the chance that a given display element will become stuck in an actuated state.

Claims

1. An apparatus for displaying images, comprising:

an electromechanical display element comprising at least a portion of an array of electromechanical display elements;

a column driver configured to assert a voltage on one or more columns of the array; and

a row driver configured to pulse one or more rows of the array with a voltage,

wherein the column driver and row driver are configured to apply a plurality of potential differences across the electromechanical display element during a display write process, the column driver and row driver being configured to write display data to the electromechanical display element with a first potential difference of a first polarity during a first portion of the display write process, re-write the display data to the electromechanical display element with a second potential difference having a polarity opposite the first polarity during a second portion of the display write process, apply a third potential difference having the first polarity to the electromechanical display element during a third portion of the display write process, and apply a fourth potential difference having the opposite polarity to the electromechanical display element during a fourth portion of the display write process,

wherein a state of the electromechanical display element does not change during the third and fourth portions of the display write process.

2. The apparatus of claim 1, wherein the column driver and row driver are configured to write a first frame of display data to the array of electromechanical display elements during the first portion of the display write process, and are configured to re-write the first frame of display data to the array of electromechanical display elements during the second portion of the display write process.

3. The apparatus of claim 2, wherein the column driver and row driver are configured to hold the first frame of display data during the third and fourth portions of the write process following said re-writing.

4. The apparatus of claim 3, wherein said column driver and row driver are configured to write a second frame of display data to the array by writing and re-writing to the electromechanical display elements in the array with opposite polarities and applying potential differences to the electromechanical display elements in the array with opposite polarities, wherein a state of the electromechanical display elements in the array does not change during the applying.

5. The apparatus of claim 1, wherein said first, second, third, and fourth portions of said 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 processor in communication with the column driver and row driver.

6. The apparatus of claim 1, wherein said first portion and said second portion together comprise less than ½

of a time period defined by the inverse of a rate at which frames of display data are received by a processor in communication with the column driver and row driver.

7. The apparatus of claim 1, wherein said first portion extends for a first time period and said second portion extends for a second time period, said first and second time periods being determined based at least in part on a polarity dependent dielectric charging rate of the electromechanical display element.

8. The apparatus of claim 1, wherein the apparatus is configured such that one or more of a time for writing using the first potential difference, a time for re-writing using the second potential difference, a time for applying the third potential difference, a time for applying the fourth potential difference, and a time for pulsing the rows is programmable.

9. An apparatus for actuating an electromechanical display element, said electromechanical display element comprising a portion of an array of electromechanical display elements, said apparatus comprising:

means for writing display data to said electromechanical display element with a potential difference of a first polarity during a first portion of a display write process;

means for re-writing said display data to said electromechanical display element with a potential difference having a polarity opposite said first polarity during a second portion of said display write process;

means for applying a first bias potential having said first polarity to said electromechanical display element during a third portion of said display write process; and

means for applying a second bias potential having said opposite polarity to said electromechanical display element during a fourth portion of said display write process,

wherein a state of said electromechanical display element does not change during said third and fourth portions.

10. The apparatus of claim 9, wherein one or more of the means for writing, means for re-writing, means for applying a first bias potential, and means for applying a second bias potential comprises a column driver circuit configured to assert a voltage on one or more columns of the array of electromechanical display elements.

11. The apparatus of claim 9, wherein one or more of the means for writing, means for re-writing, means for applying a first bias potential, and means for applying a second bias potential comprises a row driver circuit configured to pulse one or more rows of the array of electromechanical display elements with a voltage.

12. A system for writing frames of display data, comprising:

an array of electromechanical display elements; and

an array controller comprising a column driver and a row driver, the column driver configured to assert a potential on one or more columns of the array, the row driver configured to pulse one or more rows of the array with a potential,

wherein the array controller is configured to write display data to the electromechanical display elements, the writing requiring less than a defined frame update period, and wherein the array controller is further configured to apply a series of bias potentials of alternating polarity to the electromechanical display elements for the remainder of said frame update period, and

wherein a state of the electromechanical display elements does not change during the remainder.

13. The system of claim 12, wherein frames of display data are written to the electromechanical display elements at a rate of one frame per defined frame update period.

14. The system of claim 12, wherein said series comprises a bias potential of a first polarity applied during approximately half of the remainder, and a bias potential of a second opposite polarity applied during approximately half of the frame update period.

15. The system of claim 12, wherein the series of bias potentials comprises a polarity balanced sequence of bias voltages applied to substantially all columns of the array, and wherein the remainder is defined by a time remaining between completing a writing of display data for a first frame and beginning a writing of display data for a next subsequent frame.

16. The system of claim 12, wherein said column driver is configured to apply the same voltage to substantially all columns of the array during at least a portion of said frame update period.

17. The system of claim 12, wherein the series of bias potentials comprises approximately equal bias voltages of opposite polarities, and wherein the remainder is defined at least in part by the inverse of a rate at which frames of display data are received by the system.

18. The system of claim 17, wherein the remainder is substantially equal to 1/(2f), wherein f is a defined frequency of frame refresh cycles.

19. The system of claim 17, wherein the remainder varies based at least in part on a number of rows being written with display data that is different from display data written in a previous frame update period.

20. An apparatus for writing frames of display data to an array of electromechanical display elements at a rate of one frame per defined frame update period, said apparatus comprising:

means for writing display data to said electromechanical display elements, wherein said writing takes less than said frame update period; and

means for applying a series of bias potentials of alternating polarity to said electromechanical display elements for the remainder of said frame update period,

wherein a state of said electromechanical display elements does not change during said remainder.

21. The apparatus of claim 20, wherein at least one of the means for writing and the means for applying comprises an array controller configured to provide signals to the array.

22. A device for driving display elements, comprising:

a display comprising a plurality of pixels; and

a display controller configured to periodically release substantially all pixels of said display, the display controller being configured to periodically release each pixel at an infrequent rate such that there is no perceptible effect on visual appearance of the display to a normal observer.

23. The device of claim 22, wherein any given periodically released pixel is released at a rate slower than once per hour of display use.

24. The device of claim 22, wherein any given periodically released pixel is released at a rate slower than once per 100,000 displayed frames of image data.