METHOD FOR REDUCING IMAGE ARTIFACTS ON ELECTRONIC PAPER DISPLAYS

• US 20080309953A1
• Filed: 06/15/2007
• Published: 12/18/2008
• Est. Priority Date: 06/15/2007
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Feng, Guotong
• Granted Patent: US 8,130,192 B2
• Time in Patent Office: Days
• US Class Current: 358/1.9
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 3/2062 using error diffusion in time
• CPC Class Codes: G09G 3/3433 using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices using liquid crystal devices G09G3/36; using electrochromic devices G09G3/38
• 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 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

A method and apparatus for reducing image artifacts on displays (e.g., electronic paper, etc.) are described. In one embodiment, the method comprises generating pixels of an image for a bistable display using halftoning based on data of one or more previously displayed images.

Claims

1. A method comprising:

generating pixels of an image for a bistable display using halftoning based on data of one or more previously displayed images.

2. The method defined in claim 1 wherein generating pixels of the image comprises converting image data to a dithered output image and using the dithered output image as part of a halftoning process applied to an immediately preceding displayed image.

3. The method defined in claim 2 wherein the halftoning process comprises error diffusion.

4. The method defined in claim 3 wherein the error diffusion incorporates display quantization errors.

5. The method defined in claim 4 wherein the error diffusion modifies input image data using an output from an error diffusion filter that is responsive to an input error for each pixel that is based on a display quantization error associated with said each pixel.

6. The method defined in claim 5 wherein the input error is based on a gray level quantization error.

7. The method defined in claim 5 wherein the display quantization error is generated using a lookup table (LUT) of display quantization errors.

8. The method defined in claim 7 further comprising generating the display quantization error using the LUT having inputs of a pixel value of a previously displayed image and a dithered output image.

9. The method defined in claim 3 further comprising wherein the image sequence correlated error diffusion applies filters for gray level quantization error and display quantization error separately.

10. The method defined in claim 9 further comprising generating the display quantization error using the LUT having inputs of a pixel value of a previously displayed image and a dithered output image.

11. The method defined in claim 1 wherein a predicted display error for each gray level transition is included into a feedback loop of an error diffusion filter.

12. The method defined in claim 1 wherein the image comprises a grayscale image.

13. The method defined in claim 1 wherein the bistable display comprises an electrophoretic display.

14. An article of manufacture having one or more computer-readable storage media storing instructions thereon which, when executed by a system, cause the system to perform a method comprising:

generating pixels of an image for a bistable display using halftoning based on data of one or more previously displayed images.

15. The article of manufacture defined in claim 14 wherein generating pixels of the image comprises converting image data to a dithered output image and using the dithered output image as part of a halftoning process applied to an immediately preceding displayed image.

16. The article of manufacture defined in claim 15 wherein the halftoning process comprises error diffusion that incorporates display quantization errors.

17. The article of manufacture defined in claim 16 wherein the error diffusion modifies input image data based on an output of an error diffusion filter generated responsive to an input error for each pixel that is based on a display quantization error associated with said each pixel.

18. The article of manufacture defined in claim 16 wherein the display quantization errors are generated using a lookup table (LUT) of display quantization errors.

19. An apparatus comprising:

a memory to store image data

a halftoning unit coupled to the memory to receive the image data and to generate pixels of an image for a bistable display using halftoning based on data of one or more previously displayed images.

20. The apparatus defined in claim 19 wherein the halftoning unit converts the image data to a dithered output image and using the dithered output image as part of a halftoning process applied to an immediately preceding displayed image.

21. The apparatus defined in claim 20 wherein the halftoning process comprises an error diffusion module.

22. The apparatus defined in claim 21 wherein the error diffusion module incorporates display quantization errors.

23. The apparatus defined in claim 22 wherein the error diffusion module comprises:

an error diffusion filter to generate an output for each pixel in response to an error value that is based on a display quantization error associated with said each pixel; and

an substractor to subtract the first output from input image data.

24. The apparatus defined in claim 23 wherein the error value for each pixel is based on a gray level quantization error.

25. The apparatus defined in claim 23 further comprising a lookup table (LUT) of display quantization errors coupled to the error diffusion filter to output a display quantization error for said each pixel in response to a pixel value from a previously displayed image and a corresponding pixel value of a currently displayed image.

26. The apparatus defined in claim 19 wherein the halftoning unit comprises a halftoning filter to generate a first output in response to a gray level quantization error, and further comprising:

an error diffusion filter to generate a second output for each pixel in response to an error value that is based on a display quantization error associated with said each pixel;

an adder to add the first and second outputs to create a third output; and

an substractor to subtract the third output from input image data.

27. The apparatus defined in claim 26 further comprising a LUT to generate the second output in response to inputs of a pixel value of a previously displayed image and a dithered output image.

28. The apparatus defined in claim 19 wherein a predicted display error for each gray level transition is included into a feedback loop of an error diffusion filter.

29. The apparatus defined in claim 19 wherein the image comprises a grayscale image.

30. The apparatus defined in claim 19 wherein the bistable display comprises an electrophoretic display.