METHODS FOR DRIVING ELECTRO-OPTIC DISPLAYS

• US 20140292830A1
• Filed: 02/28/2014
• Published: 10/02/2014
• Est. Priority Date: 03/01/2013
• Status: Active Grant

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Harrington, Demetrious Mark, Crounse, Kenneth R., Amundson, Karl Raymond, Aprea, Matthew J., Sjodin, Theodore A., Bouchard, Alain, Telfer, Stephen J., Ben-Dov, Yuval, Lattes, Ana L.
• Granted Patent: US 9,495,918 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02B 26/005 based on electrowetting
• CPC Class Codes: G02F 1/163 Operation of electrochromic cells, e.g. electrodeposition cells; Circuit arrangements therefor
• CPC Class Codes: G02F 1/1681 having two or more microcells partitioned by walls, e.g. of microcup type
• CPC Class Codes: G09G 2230/00 Details of flat display driving waveforms
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2310/062 Waveforms for resetting a plurality of scan lines at a time
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• 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 2380/14 Electronic books and readers
• CPC Class Codes: G09G 3/2007 Display of intermediate tones
• CPC Class Codes: G09G 3/2044 using dithering
• CPC Class Codes: G09G 3/2048 with addition of random noise to an image signal or to a gradation threshold
• CPC Class Codes: G09G 3/2051 with use of a spatial dither pattern
• 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

Methods for driving electro-optic displays, especially bistable displays, include (a) using two-part waveforms, the first part of which is dependent only upon the initial state of the relevant pixel; (b) measuring the response of each individual pixel and storing for each pixel data indicating which of a set of standard drive schemes are to be used for that pixel; (c) for at least one transition in a drive scheme, applying multiple different waveforms to pixels on a random basis; and (d) when updating a limited area of the display, driving “extra” pixels in an edge elimination region to avoid edge effects.

Claims

1. A method of driving an electro-optic display comprising a plurality of pixels, the method comprising:

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

receiving data representing a final state of the at least one pixel; and

applying to the at least one pixel a waveform arranged to change the optical state of the at least one pixel from the initial state to the final state, the waveform being in two parts, a first part which depends upon the initial state of the pixel but not upon the final state thereof, and a second part which depends upon both the initial and final states of the pixel.

2. A method according to claim 1 wherein each pixel of the display is capable of displaying two extreme optical states and at least one gray optical state intermediate the two extreme optical states, and wherein the first part of the waveform drives the at least one pixel to a gray optical state.

3. A method according to claim 1 wherein a two part waveform is applied to all the pixels of the display, and at the end of the first part of each waveform all pixels are at the same gray optical state.

4. A method according to claim 1 wherein the first part of the waveform comprises at least about 50 percent of the total duration of the waveform.

5. A method according to claim 4 wherein the first part of the waveform comprises at least about 66 percent of the total duration of the waveform.

6. A display controller adapted to carry out the method of claim 1.

7. A method of driving an electro-optic display having a plurality of pixels, the method comprising:

in a first phase, applying at least one standard waveform to each pixel;

measuring the optical state of each pixel following application of the standard waveform;

determining, for each pixel, one of a selection of standard drive schemes to be applied to the pixel; and

storing, for each pixel, at least one selection datum indicating the selected standard drive scheme;

in a second phase, storing data representing at least an initial state of each pixel of the display, and the standard drive schemes;

receiving input signals representing final gray level of a plurality of pixels of the display;

determining from the stored data representing the initial state, the input signals, the selection data for the relevant pixels and the standard drive schemes, the impulses necessary to drive said plurality of pixels to said final gray levels; and

generating a plurality of output signals representing pixel voltages to be applied to said plurality of pixels.

8. A method according to claim 7 wherein the first phase comprises driving each pixel of the display to each of the gray levels which the drive schemes can display;

forming images of each pixel in each of the gray levels, and sampling the images at the positions corresponding to the display pixels.

9. A method according to claim 7 wherein one or more of the standard drive schemes contains at least one variable parameter, and the parameters to be used for any specific pixel are chosen on the basis of data accumulated in the first phase of the process.

10. A method according to claim 7 wherein, for at least one pixel, there is used for a transition a waveform present in a standard scheme but intended, in that standard drive scheme, for use in a transition other than the one for which it is used.

11. A method according to claim 7 wherein the electro-optic display comprises a rotating bichromal member, electrochromic or electro-wetting material.

12. A method according to claim 7 wherein the electro-optic display comprises an electrophoretic material comprising a plurality of electrically charged particles disposed in a fluid and capable of moving through the fluid under the influence of an electric field.

13. A method according to claim 12 wherein the electrically charged particles and the fluid are confined within a plurality of capsules or microcells.

14. A method according to claim 12 wherein the electrically charged particles and the fluid are present as a plurality of discrete droplets surrounded by a continuous phase comprising a polymeric material.

15. A method according to claim 12 wherein the fluid is gaseous.

16. A display controller adapted to carry out the method of claim 7, the controller having provision for storing, for each pixel of the display, at least one selection datum indicating which of a selection of standard drive schemes is to be applied to each specific pixel, and for taking this selection datum into account in determining the waveform to be applied to each pixel during updating of the display.

17. A method of driving an electro-optic display having a plurality of pixels using a drive scheme which defines the waveform to be applied to each pixel for each transition from an initial gray level to final gray level, and wherein, for at least one transition in the drive scheme, multiple waveforms are provided in the drive scheme, and these multiple waveforms are applied to pixels undergoing the relevant transition on a random basis, so that different pixels undergoing the same transition experience different waveforms.

18. A method according to claim 17 further comprising the step of changing, at intervals, which of the multiple waveform is used for which said at least one transition at a particular pixel.

19. A method according to claim 17 further comprising tracking the DC imbalance at each pixel and making the selection from among the multiple waveforms to reduce the accumulated DC imbalance.

20. A method according to claim 17 wherein multiple waveforms are provided for each transition in the drive scheme, and any specific pixel uses the same waveform for each transition.

21. A method according to claim 17 wherein the selection from among the multiple waveforms is made so that a fixed image is always or intermittently visible in the background of the display.

22. A method of driving an electro-optic display having a plurality of pixels, the method comprising applying at local drive scheme to change the optical state of at least one limited area of the display and driving pixels in an edge elimination region, at least one pixel wide and substantially surrounding the at least one limited area, from their original gray level to an intermediate gray level, and then back to their original gray level.

23. A method according to claim 22 wherein the edge elimination region comprises pixels which share only a common corner with the at least one limited area.

24. A method according to claim 22 wherein the edge elimination region comprises pixels within the at least one limited area.

25. A method according to claim 22 wherein the edge elimination region is more than one pixel wide, and the pixels in the edge elimination region are driven to differing intermediate gray levels depending upon the distance of the pixels from the boundary of the at least one limited area.

26. A display controller adapted to carry out the method of claim 22, the display controller being capable of driving an electro-optic display having a plurality of pixels and comprising edge detection means for detecting the edges of limited areas of the display undergoing a transition, and for determining an edge elimination region at least one pixel wide and substantially surrounding the at least one limited area, the display controller being arranged to drive the pixels in the edge elimination region from their original gray level to an intermediate gray level, and then back to their original gray level.