Methods for driving electro-optic displays

• US 7,453,445 B2
• Filed: 07/31/2006
• Issued: 11/18/2008
• Est. Priority Date: 08/13/2004
• Status: Active Grant

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Amundson, Karl R.
• Primary Examiner(s): DHARIA, PRABODH M
• Application Number:
  US11/461,084
• Publication Number:
  US 20060262060A1
• Time in Patent Office: 841 Days
• Field of Search: 345/87, 345/107, 345/89, 345/214, 345/36, 345/48, 345/77, 345/84, 345/204, 345/210, 345/173, 345/178, 345/88, 356/479, 323/309, 715/716
• US Class Current: 345/173
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 3/18 using liquid crystals

Abstract

An electro-optic display is driven using a plurality of different drive schemes. The waveforms of the drive schemes are chosen such that the absolute value of the net impulse applied to a pixel for all homogeneous and heterogeneous irreducible loops divided by the number of transitions in the loop is less than about 20 percent of the characteristic impulse (i.e., the average of the absolute values of the impulses required to drive a pixel between its two extreme optical states).

Claims

1. A method of driving an electro-optic display using a plurality of different drive schemes, the waveforms of the drive schemes being chosen such that the absolute value of the net impulse applied to a pixel for all homogeneous and heterogeneous irreducible loops divided by the number of transitions in the loop is less than about 20 percent of the characteristic impulse,

wherein:

a homogeneous irreducible loop is a sequence of gray levels, starting at a first gray level, passing through zero or more gray levels, and ending at the first gray level, wherein all transitions are effected using the same drive scheme, and wherein the loop does not visit any gray level except the first gray level more than once;

a heterogeneous irreducible loop is a sequence of gray levels, starting at a first gray level, passing through one or more gray levels and ending at the first gray level, wherein the loop comprises transitions using at least two different drive schemes, the drive scheme used to effect the last transition in the loop is the same as the drive scheme used to effect the transition to the first gray level immediately prior to the start of the loop, and the loop comprises no shorter irreducible loops; and

the characteristic impulse is the average of the absolute values of the impulses required to drive a pixel between its two extreme optical states.

2. A method according to claim 1 wherein the net impulse applied to a pixel for all homogeneous and heterogeneous irreducible loops divided by the number of transitions in the loop is less than about 10 percent of the characteristic impulse.

3. A method according to claim 2 wherein the net impulse applied to a pixel for all homogeneous and heterogeneous irreducible loops divided by the number of transitions in the loop is less than about 5 percent of the characteristic impulse.

4. A method according to claim 3 wherein the net impulse applied to a pixel for all homogeneous and heterogeneous irreducible loops is essentially zero.

5. A method according to claim 1 wherein the drive schemes comprise a gray scale drive scheme and a monochrome drive scheme.

6. A method according to claim 1 wherein the drive schemes comprise two gray scale drive schemes and a monochrome drive scheme.

7. A method according to claim 6 wherein one of the two gray scale drive schemes uses local updating of the image and the other uses global updating.

8. A method according to claim 6 wherein one of the two gray scale drive schemes provides more accurate gray levels than the other but causes more flashing of the display.

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

10. A method according to claim 1 wherein the electro-optic display comprises a particle-based electrophoretic medium in which a plurality of charged particles move through a fluid under the influence of an electric field.

11. A method according to claim 10 wherein the charged particles and the fluid are encapsulated within a plurality of capsules or microcells.

12. A method according to claim 10 wherein the charged particles and the fluid are present as a plurality of discrete droplets within a continuous phase comprising a polymeric binder.

13. A method according to claim 10 wherein the fluid is gaseous.

14. An electro-optic display comprising a layer of electro-optic medium, least one electrode arranged to apply an electric field to the layer of electro-optic medium, and a controller arranged to control the electric field applied to the electro-optic medium by the at least one electrode, the controller being arranged to carry out a method according to claim 1.

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

16. A display according to claim 14 wherein the electro-optic display comprises a particle-based electrophoretic medium in which a plurality of charged particles move through a fluid under the influence of an electric field.

17. A display according to claim 16 wherein the charged particles and the fluid are encapsulated within a plurality of capsules or microcells.

18. A display according to claim 16 wherein the charged particles and the fluid are present as a plurality of discrete droplets within a continuous phase comprising a polymeric binder.

19. A display according to claim 16 wherein the fluid is gaseous.

20. An electronic book reader, portable computer, tablet computer, cellular telephone, smart card, sign, watch, shelf label or flash drive comprising a display according to claim 14.