Methods for driving bistable electro-optic displays, and apparatus for use therein

• US 7,733,335 B2
• Filed: 02/27/2006
• Issued: 06/08/2010
• Est. Priority Date: 04/30/1999
• Status: Expired due to Fees

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Knaian, Ara N., Zehner, Robert W., Au, Joanna F., Gates, Holly G., Arango, Alexi C., Amundson, Karl R.
• Primary Examiner(s): Shalwala; Bipin
• Assistant Examiner(s): KOVALICK, VINCENT E
• Application Number:
  US11/307,886
• Publication Number:
  US 20060139310A1
• Time in Patent Office: 1,562 Days
• Field of Search: 345/36, 345/63, 345/107, 345/204, 345/214, 345/601, 358/519
• US Class Current: 345/204
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2310/02 Addressing, scanning or driving the display screen or processing steps related thereto
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/0286 Details of a shift registers arranged for use in a driving circuit
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2310/063 Waveforms for resetting the whole screen at once
• CPC Class Codes: G09G 2310/068 Application of pulses of alternating polarity prior to the drive pulse in electrophoretic displays
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/16 : Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 3/2011 : by amplitude modulation
• CPC Class Codes: G09G 3/2018 : by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/2081 : with combination of amplitude modulation and time modulation space and time error diffusion G09G3/2066
• CPC Class Codes: G09G 3/344 : based on particles moving in a fluid or in a gas, e.g. electrophoretic devices electrophoretic devices per se G02F1/167
• CPC Class Codes: G09G 5/10 : Intensity circuits
• CPC Class Codes: G09G 5/18 : Timing circuits for raster scan displays specially adapted for television H04N ; synchronisation between the display unit and other display units, videodisc player G09G5/12

Abstract

A bistable electro-optic display has a plurality of pixels, each of which is capable of displaying at least three gray levels. The display is driven by a method comprising: storing a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level; storing data representing at least an initial state of each pixel of the display; receiving an input signal representing a desired final state of at least one pixel of the display; and generating an output signal representing the impulse necessary to convert the initial state of said one pixel to the desired final state thereof, as determined from said look-up table. The invention also provides a method for reducing the remnant voltage of an electro-optic display.

Claims

1. A method of driving a bistable electro-optic display having a plurality of pixels, each of which is capable of displaying at least three gray levels, the method comprising:

storing a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level;

storing data representing at least an initial state of each pixel of the display;

receiving an input signal representing a desired final state of at least one pixel of the display;

receiving a humidity signal representing ambient humidity and

generating an output signal representing the impulse necessary to convert the initial state of said one pixel to the desired final state thereof, as determined from said look-up table, said output signal being generated dependent upon said humidity signal.

2. A method according to claim 1 wherein the display is an electrophoretic display.

3. A method according to claim 2 wherein the display is an encapsulated electrophoretic display.

4. A method according to claim 1 wherein the display is a microcell display comprising charged particles and a suspending fluid retained within a plurality of cavities formed in a carrier medium.

5. A method according to claim 1 wherein the display is a passive matrix display.

6. A method of driving a bistable electro-optic display, the display comprising a layer of a bistable electro-optic medium, first and second pixel electrodes disposed on one side of the layer of electro-optic medium and defining first and second pixels of the display, and a common electrode disposed on the opposed side of the layer of electro-optic medium, the method comprising:

(a) applying a first common electrode voltage to the common electrode, applying a first gamma voltage to the first pixel electrode, and applying the first common electrode voltage to the second pixel electrode, thereby applying an electric field in one direction to the first pixel of the display, and substantially no electric field to the second pixel; and

(b) applying a second common electrode voltage, different from the first common electrode voltage, to the common electrode, applying the second common electrode voltage to the first pixel electrode, and applying a second gamma voltage to the second pixel electrode, thereby applying substantially no electric field to the first pixel of the display, and an electric field in the opposed direction to the second pixel of the display.

7. A method according to claim 6 wherein the display is provided with means for generating a plurality of different gamma voltages, the first common electrode voltage is set to the largest of the gamma voltages and the second common electrode voltage is set to the smallest of the gamma voltages.

8. A method according to claim 7 wherein the gamma voltages are arranged on a linear ramp between the first and second common electrode voltages.

9. A method according to claim 6 wherein steps (a) and (b) are repeated a plurality of times during one rewriting of the display.

10. A method according to claim 9 wherein steps (a) and (b) are applied alternately during successive periods of the rewriting.

11. A method according to claim 6 wherein the display is an electrophoretic display.

12. A method according to claim 11 wherein the display is an encapsulated electrophoretic display.

13. A method according to claim 6 wherein the display is a microcell display comprising charged particles and a suspending fluid retained within a plurality of cavities formed in a carrier medium.

14. A method according to claim 6 wherein the display is a passive matrix display.

15. A device controller for controlling a bistable electro-optic display having a plurality of pixels, each of which is capable of displaying at least three gray levels, said controller comprising:

storage means arranged to store both a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level, and data representing at least an initial state of each pixel of the display;

first input means for receiving a first input signal representing a desired final state of at least one pixel of the display;

second input means for receiving a second input signal representing ambient humidity;

calculation means for determining, from the first and second input signals, the stored data representing the initial state of said pixel, and the look-up table, the impulse required to change the initial state of said one pixel to the desired final state; and

output means for generating an output signal representative of said impulse.

16. A bistable electro-optic display having a plurality of pixels, each of which is capable of displaying at least three gray levels, and a device controller according to claim 15 arranged to control the electro-optic display.

17. An electro-optic display according to claim 16 which is an electrophoretic display.

18. An electro-optic display according to claim 17 which is an encapsulated electrophoretic display.

19. An electro-optic display according to claim 16 which is a microcell display comprising charged particles and a suspending fluid retained within a plurality of cavities formed in a carrier medium.

20. An electro-optic display according to claim 16 which is a passive matrix display.

21. A bistable electro-optic display comprising a layer of a bistable electro-optic medium, first and second pixel electrodes disposed on one side of the layer of electro-optic medium and defining first and second pixels of the display, a common electrode disposed on the opposed side of the layer of electro-optic medium, and a display controller for controlling the voltages applied to the first and second pixel electrodes and the common electrode, the controller being arranged to:

(a) apply a first common electrode voltage to the common electrode, apply a first gamma voltage to the first pixel electrode, and apply the first common electrode voltage to the second pixel electrode, thereby applying an electric field in one direction to the first pixel of the display, and substantially no electric field to the second pixel; and

(b) apply a second common electrode voltage, different from the first common electrode voltage, to the common electrode, apply the second common electrode voltage to the first pixel electrode, and apply a second gamma voltage to the second pixel electrode, thereby applying substantially no electric field to the first pixel of the display, and an electric field in the opposed direction to the second pixel of the display.

22. A display according to claim 21 provided with means for generating a plurality of different gamma voltages, and wherein the display controller is arranged to set the first common electrode voltage equal to the largest of the gamma voltages and the second common electrode voltage equal to the smallest of the gamma voltages.

23. A display according to claim 22 wherein the gamma voltages are arranged on a linear ramp.

24. A display according to claim 21 wherein the controller is arranged to repeat (a) and (b) a plurality of times during one rewriting of the display.

25. A display according to claim 24 wherein the controller is arranged to apply (a) and (b) are applied alternately during successive periods of the rewriting.

26. A display according to claim 21 wherein the electro-optic medium is an electrophoretic medium.

27. A display according to claim 26 wherein the electro-optic medium is an encapsulated electrophoretic medium.

28. A display according to claim 21 wherein the electro-optic medium is a microcell medium comprising charged particles and a suspending fluid retained within a plurality of cavities formed in a carrier medium.

29. A display according to claim 21 which is a passive matrix display.