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

• US 7,733,311 B2
• Filed: 06/21/2006
• 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: Zion, Benjamin, Knaian, Ara N., Zehner, Robert W., Amundson, Karl R.
• Primary Examiner(s): Shalwala; Bipin
• Assistant Examiner(s): Kovalick; Vince E
• Application Number:
  US11/425,408
• Publication Number:
  US 20060232531A1
• Time in Patent Office: 1,448 Days
• Field of Search: 345/87, 345/89, 345/90, 345/95, 345/210, 349/33
• US Class Current: 345/87
• CPC Class Codes: G09G 2300/08 Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
• 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 2310/04 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 2310/065 Waveforms comprising zero voltage phase or pause
• CPC Class Codes: G09G 2310/068 Application of pulses of alternating polarity prior to the drive pulse in electrophoretic displays
• 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 2320/04 Maintaining the quality of display appearance
• 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 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 3/344 : 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 3/38 : using electrochromic devices

Abstract

A gray scale bistable electro-optic display is driven by storing a look-up table containing data representing the impulses necessary for transitions, storing data representing at least an initial state of each pixel of the display, storing data representing temporal and gray level prior states of each pixel, 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 for a transition, as determined from the look-up table, dependent upon the temporal and gray level prior states. Other similar methods for driving such displays are also disclosed.

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;

storing data representing at least one temporal prior state of each pixel of the display at a predetermined time prior to the initial state;

storing data representing at least one gray level prior state of each pixel prior to a change in gray scale level to produce the initial state;

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 the look-up table, the output signal being generated dependent upon said at least one temporal prior state, said at least one gray level prior state and said initial state of said one pixel.

2. A method according to claim 1 further comprising receiving a temperature signal representing the temperature of at least one pixel of the display and generating said output signal dependent upon said temperature signal.

3. A method according to claim 1 further comprising generating a lifetime signal representing the operating time of said pixel and generating said output signal dependent upon said lifetime signal.

4. A method according to claim 1 wherein at least one entry in the look-up table comprises a pointer to an entry in a second table specifying one of a plurality of types of waveform to be used for the relevant transition, and at least one parameter specifying how the waveform is to be varied for the relevant transition.

5. A method according to claim 1 wherein the display comprises a rotating bichromal member or electrochromic electro-optic medium.

6. A method according to claim 1 wherein the display comprises a electrophoretic medium comprising a fluid and a plurality of charged particles arranged to move through the fluid on application of an electric field.

7. A methods according to claim 6 wherein the fluid and the charged particles are retained within a plurality of capsules, are present in discrete droplets within a continuous phase of a polymeric material, or are present within a plurality of cavities formed within a carrier medium.

8. A controller according to claim 7 wherein the input means is arranged to receive a lifetime signal representing the operating time temperature of the pixel, and the calculation means is arranged to determine the impulse dependent upon the lifetime signal.

9. A device controller comprising:

storage means arranged to store a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level, data representing at least an initial state of each pixel of the display, data representing at least one temporal prior state of each pixel of the display at a predetermined time prior to the initial state, and data representing at least one gray level prior state of each pixel prior to a change in gray scale level to produce the initial state;

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

calculation means for determining, from the input signal, the stored data representing the initial state, the at least one temporal prior state and the at least one gray level prior 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.

10. A controller according to claim 9 wherein the input means is arranged to receive a temperature signal representing the temperature of at least one pixel of the display, and the calculation means is arranged to determine the impulse dependent upon the temperature signal.

11. 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;

storing compensation voltage data representing a compensation voltage for each pixel of the display, the compensation voltage for any pixel being calculated dependent upon at least one impulse previously applied to that pixel;

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

generating an output signal representing a pixel voltage to be applied to said one pixel, said pixel voltage being the sum of a drive voltage determined from the initial and final states of the pixel and the look-up table, and a compensation voltage determined from the compensation voltage data for the pixel.

12. A method according to claim 11 wherein the compensation voltage for each pixel is calculated dependent upon at least one of a temporal prior state of the pixel and a gray level prior state of the pixel.

13. A method according to claim 12 wherein the compensation voltage is applied in the form of an exponentially decaying voltage applied at the end of at least one drive pulse.

14. A method according to claim 11 wherein the display comprises a rotating bichromal member or electrochromic electro-optic medium.

15. A method according to claim 11 wherein the display comprises a electrophoretic medium comprising a fluid and a plurality of charged particles arranged to move through the fluid on application of an electric field.

16. A methods according to claim 15 wherein the fluid and the charged particles are retained within a plurality of capsules, are present in discrete droplets within a continuous phase of a polymeric material, or are present within a plurality of cavities formed within a carrier medium.

17. A device 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, data representing at least an initial state of each pixel of the display; and

compensation voltage data for each pixel of the display;

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

calculation means for determining, from the input signal, the stored data representing the initial state of said pixel, and the look-up table, a drive voltage required to change the initial state of said one pixel to the desired final state, the calculation means also determining, from the compensation voltage data for said pixel, a compensation voltage for said pixel, and summing the drive voltage and the compensation voltage to determine a pixel voltage; and

output means for generating an output signal representative of said pixel voltage.

18. A device controller according to claim 17 wherein the calculation means is arranged to determine the compensation voltage dependent upon at least one of a temporal prior state of the pixel and a gray level prior state of the pixel.

19. A device controller according to claim 17 wherein the output means is arranged to apply the compensation voltage in the form of an exponentially decaying voltage applied at the end of at least one drive pulse.

20. A method for updating a bistable electro-optic display having a plurality of pixels arranged in a plurality of rows and columns such that each pixel is uniquely defined by the intersection of a specified row and a specified column, and drive means for applying electric fields independently to each of the pixels to vary the display state of the pixel, each pixel having at least three different display states, the method comprising:

storing region data representing a defined region comprising a part but less than all of said display;

determining for each pixel whether the pixel is within or outside the defined region;

applying a first drive scheme to pixels within the defined region and a second drive scheme, different from the first drive scheme, to pixels outside the defined region.

21. A method according to claim 20 wherein the defined region comprises a text box used for entry of text on to the display.

22. A method according to claim 20 wherein the display comprises a rotating bichromal member or electrochromic electro-optic medium.

23. A method according to claim 20 wherein the display comprises a electrophoretic medium comprising a fluid and a plurality of charged particles arranged to move through the fluid on application of an electric field.

24. A methods according to claim 23 wherein the fluid and the charged particles are retained within a plurality of capsules, are present in discrete droplets within a continuous phase of a polymeric material, or are present within a plurality of cavities formed within a carrier medium.

25. 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 applying to each pixel of the display an output signal effective to change the pixel from an initial state to a final state, wherein, for at least one transition for which the initial and final states of the pixel are different, the output signal consists of a pulse having a voltage level of 0 preceded and followed by at least two pulses having voltage levels of the same one of V and −

V.

26. A method according to claim 25 wherein the display comprises a rotating bichromal member or electrochromic electro-optic medium.

27. A method according to claim 25 wherein the display comprises a electrophoretic medium comprising a fluid and a plurality of charged particles arranged to move through the fluid on application of an electric field.

28. A methods according to claim 27 wherein the fluid and the charged particles are retained within a plurality of capsules, are present in discrete droplets within a continuous phase of a polymeric material, or are present within a plurality of cavities formed within a carrier medium.