Stochastic temporal dithering for color display devices

• US 9,811,923 B2
• Filed: 09/24/2015
• Issued: 11/07/2017
• Est. Priority Date: 09/24/2015
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Inventors: Wang, Shen-Ge, Ma, Jian Jim, Cai, Songhe, Mienko, Marek, Wen, Bing
• Primary Examiner(s): Caschera, Antonio A
• Application Number:
  US14/864,528
• Publication Number:
  US 20170091960A1
• Time in Patent Office: 775 Days
• CPC Class Codes: G06T 1/20 Processor architectures; Processor configuration, e.g. pipelining
• CPC Class Codes: G06T 11/001 Texturing; Colouring; Generation of texture or colour inpainting G06T5/77
• CPC Class Codes: G06T 2200/28 involving image processing hardware
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/2055 the pattern being varied in time
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

Systems, methods and apparatus, including computer programs encoded on computer storage media, for displaying high bit-depth images using spatial vector screening and/or temporal dithering on display devices including display elements that have multiple primary colors. The systems, methods and apparatus described herein are configured to assign one of the primary colors to a display element of the display device that corresponds to the image pixel based on a rank order and a partition index of an associated screen element of a stochastic screen associated with the display device or a portion thereof.

Claims

1. An apparatus comprising:

a display device including a plurality of display elements, each display element capable of displaying N primary colors in a color space associated with the display device, wherein N is a positive number greater than 2; and

a computing device capable of communicating with the display device, the computing device capable of processing image data that includes a plurality of input colors for display by the display device, the image data including a plurality of image pixels with each image pixel associated with an input image pixel color, wherein the computing device is further capable of;

for a given image pixel;

identifying, from a color palette including colors capable of being displayed by temporal dithering of the N primary colors in K number of temporal sub-frames, L number of colors that can be combined by spatio-temporal dithering to produce a color that is perceptually similar to the input image pixel color, wherein K is a positive number greater than or equal to 2, and L is a positive number greater than 2;

associating a stochastic screen with the display device or a portion thereof, the stochastic screen including a plurality of screen elements belonging to one of M number of partitions and each of the plurality of screen elements associated with a corresponding display element of the display device, wherein M is a positive number greater than or equal to 2; and

for each of the K number of temporal sub-frames,

assigning one of the L number of colors to a display element of the display device that corresponds to the image pixel, and

displaying an image produced by a respective one of the K number of temporal sub-frames,

wherein the assignment of one of the L number of colors to the display element in each of the K number of temporal sub-frames is based on a rank order and a partition index of a screen element of the stochastic screen that is associated with the display element,

wherein the stochastic screen is configured such that visual appearance of the image produced by each of the K number of temporal sub-frames is similar to an image produced by combining the K number of temporal sub-frames.

2. The apparatus of claim 1, wherein the stochastic screen includes at least 256 screen elements.

3. The apparatus of claim 1, wherein the stochastic screen includes a plurality of partitions P(i) and the screen element belongs to one of the plurality of partitions P(i).

4. The apparatus of claim 3, wherein the M number of the plurality of partitions is equal to the K number of temporal sub-frames.

5. The apparatus of claim 3, wherein the M number of the plurality of partitions is greater than the K number of temporal sub-frames.

6. The apparatus of claim 3, wherein the plurality of partitions are equal in size.

7. The apparatus of claim 3, wherein the plurality of partitions are mutually exclusive.

8. The apparatus of claim 3, wherein each of the plurality of partitions include an equal number of screen elements.

9. The apparatus of claim 3, wherein a difference in the rank order of two successive screen elements in one of the plurality of partitions is equal to a total number of the plurality of partitions.

10. The apparatus of claim 3, wherein the stochastic screen is determined by a merit function Q_sum given by an equation:

Q_sum=Q<sub>Σ

P(i)</sub>+w*Σ

_i=1^MQ_P(i), wherein w is a weighting factor for balancing dithered image quality for each of the plurality of partitions P(i), M is the number of partitions, Q_P(i) is a merit function that determines a stochastic screen which when applied to display elements in the partition P(i) generates an image to be displayed in the i^th temporal sub-frame and Q<sub>Σ

(i)</sub> is a merit function that determines a stochastic screen that generates the entire temporally dithered image.

11. The apparatus of claim 1, wherein the stochastic screen is configured to reduce a contrast difference between consecutive temporal sub-frames.

12. The apparatus of claim 1, wherein the stochastic screen is configured to distribute a color difference between images produced by each of the temporal sub-frames to spatial high frequency regions.

13. The apparatus of claim 1, further comprising a non-transitory memory device that is capable of communicating with the computing device, the non-transitory memory device configured to store the look-up table.

14. The apparatus of claim 1, wherein the display device is a reflective display device.

15. The apparatus of claim 1, wherein at least some of the plurality of display elements include a movable mirror.

16. The apparatus of claim 15, wherein each of the N primary colors corresponds to a distinct position of the movable mirror.

17. The apparatus of claim 1, further comprising a driver circuit capable of sending at least one signal to the display device.

18. The apparatus of claim 17, further comprising a controller capable of sending at least a portion of the image data to the driver circuit.

19. The apparatus of claim 1, further comprising an image source module capable of sending the image data to the processor.

20. The apparatus of claim 19, wherein the image source module includes at least one of a receiver, transceiver, and transmitter.

21. The apparatus of claim 1, further comprising an input device capable of receiving input data and to communicate the input data to the processor.

22. A computer-implemented method to display image data on a display device including a plurality of display elements, each display element capable of displaying N primary colors in a color space associated with the display device, wherein N is a positive number greater than 2, the image data including a plurality of input colors for display by the display device, the image data including a plurality of image pixels with each image pixel associated with an input image pixel color, the method comprising:

under control of a hardware computing device associated with the display device;

for a given image pixel;

identifying, from a color palette including colors capable of being displayed by temporal dithering of the N primary colors in K number of temporal sub-frames, L number of colors that can be combined by spatio-temporal dithering to produce a color that is perceptually similar to the input image pixel color, wherein K is a positive number greater than or equal to 2, and L is a positive number greater than 2;

associating a stochastic screen with the display device or a portion thereof, the stochastic screen including a plurality of screen elements belonging to one of M number of partitions and each of the plurality of screen elements associated with a corresponding display element of the display device, wherein M is a positive number greater than or equal to 2; and

for each of the K number of temporal sub-frames,

assigning one of the L number of colors to a display element of the display device that corresponds to the image pixel, and

displaying an image produced by a respective one of the K number of temporal sub-frames,

wherein the assignment of one of the L number of colors to the display element in each of the K number of temporal sub-frames is based on a rank order and a partition index of a screen element of the stochastic screen that is associated with the display element,

wherein the stochastic screen is configured such that visual appearance of the image produced by each of the K number of temporal sub-frames is similar to an image produced by combining the K number of temporal sub-frames.

23. The method of claim 22, wherein the stochastic screen includes a plurality of partitions P(i) and the screen element belongs to one of the plurality of partitions P(i).

24. A non-transitory computer storage medium comprising instructions that when executed by a hardware computing device associated with a display device processor cause the hardware computing device processor to perform a method for displaying image data on the display device including a plurality of display elements, each display element capable of displaying N primary colors in a color space associated with the display device, wherein N is a positive number greater than 2, the image data including a plurality of input colors for display by the display device, the image data including a plurality of image pixels with each image pixel associated with an input image pixel color, the method comprising:

for a given image pixel;

identifying, from a color palette including colors capable of being displayed by temporal dithering of the N primary colors in K number of temporal sub-frames, L number of colors that can be combined by spatio-temporal dithering to produce a color that is perceptually similar to the input image pixel color, wherein K is a positive number greater than or equal to 2, and L is a positive number greater than 2;

associating a stochastic screen with the display device or a portion thereof, the stochastic screen including a plurality of screen elements belonging to one of M number of partitions and each of the plurality of screen elements associated with a corresponding display element of the display device, wherein M is a positive number greater than or equal to 2; and

for each of the K number of temporal sub-frames,

assigning one of the L number of colors to a display element of the display device that corresponds to the image pixel, and

displaying an image produced by a respective one of the K number of temporal sub-frames,

wherein the assignment of one of the L number of colors to the display element in each of the K number of temporal sub-frames is based on a rank order and a partition index of a screen element of the stochastic screen that is associated with the display element,

wherein the stochastic screen is configured such that visual appearance of the image produced by each of the K number of temporal sub-frames is similar to an image produced by combining the K number of temporal sub-frames.

25. The non-transitory computer storage medium of claim 24, wherein the stochastic screen includes a plurality of partitions P(i) and the screen element belongs to one of the plurality of partitions P(i).