Liquid crystal display with black point modulation

• US 8,217,890 B2
• Filed: 03/27/2009
• Issued: 07/10/2012
• Est. Priority Date: 05/04/2004
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Daly, Scott J, Feng, Xiao-fan
• Primary Examiner(s): Snyder, Adam J
• Application Number:
  US12/413,259
• Publication Number:
  US 20090184918A1
• Time in Patent Office: 1,201 Days
• Field of Search: 345/102
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2330/10 Dealing with defective pixels
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A backlit display with improved dynamic range. A first pixel is illuminated at a first non-zero illumination level during a first frame and a second non-zero illumination level during a second frame, immediately following the first frame. The second illumination level is greater than the first level. The first pixel is decreased in illumination to a level less than the first illumination level prior to illuminating the first pixel at the second illumination level during the second frame.

Claims

1. A method for displaying an image on a liquid crystal display comprising:

(a) illuminating a first pixel at a first non-zero illumination level during a first frame;

(b) illuminating said first pixel at a second non-zero illumination level during a second frame, wherein said second frame is the next frame immediately following said first frame, wherein said second illumination level is greater than said first level;

(c) selectively decreasing said first pixel in illumination to a third non-zero illumination level less than said first illumination level prior to illuminating said first pixel at said second illumination level during said second frame;

(d) wherein the magnitude and duration of said second non-zero illumination level are each automatically calculated as a function of selection of said step of selectively decreasing said first pixel to said third non-zero illumination level and a target image brightness for said next frame.

2. The method of claim 1 wherein said liquid crystal display includes a plurality of addressable light emitting elements.

3. The method of claim 2 wherein said liquid crystal display includes a total number of addressable light emitting elements.

4. The method of claim 3 wherein at least 10% of said total light emitting elements are each decreased in illumination to a level less than a corresponding initial illumination level in said first frame prior to illuminating said corresponding pixel at a final illumination level during said second frame, wherein said final illumination level is greater than the corresponding said initial illumination level.

5. The method of claim 4 wherein said decreased illumination of each corresponding ones of said 10% of said total light emitting elements is less than 10% of the maximum brightness of said corresponding pixel.

6. The method of claim 4 wherein said decreased illumination of each corresponding ones of said 10% of said total light emitting elements is less than 5% of the maximum brightness of said corresponding pixel.

7. The method of claim 3 wherein at least 20% are said decreased.

8. The method of claim 7 wherein said decreased illumination of each corresponding ones of said 20% of said total light emitting elements is less than 10% of the maximum brightness of said corresponding pixel.

9. The method of claim 7 wherein said decreased illumination of each corresponding ones of said 20% of said total light emitting elements is less than 5% of the maximum brightness of said corresponding pixel.

10. The method of claim 3 wherein at least 50% are said decreased.

11. The method of claim 10 wherein said decreased illumination of each corresponding ones of said 50% of said total light emitting elements is less than 10% of the maximum brightness of said corresponding pixel.

12. The method of claim 10 wherein said decreased illumination of each corresponding ones of said 50% of said total light emitting elements is less than 5% of the maximum brightness of said corresponding pixel.

13. The method of claim 3 wherein at least 75% are said decreased.

14. The method of claim 13 wherein said decreased illumination of each corresponding ones of said 75% of said total light emitting elements is less than 10% of the maximum brightness of said corresponding pixel.

15. The method of claim 13 wherein said decreased illumination of each corresponding ones of said 75% of said total light emitting elements is less than 5% of the maximum brightness of said corresponding pixel.

16. The method of claim 3 wherein at least 90% are said decreased.

17. The method of claim 16 wherein said decreased illumination of each corresponding ones of said 90% of said total light emitting elements is less than 10% of the maximum brightness of said corresponding pixel.

18. The method of claim 16 wherein said decreased illumination of each corresponding ones of said 90% of said total light emitting elements is less than 5% of the maximum brightness of said corresponding pixel.

19. The method of claim 1 wherein said decreased illumination level is less than 10% of the maximum brightness of said first pixel.

20. The method of claim 1 wherein said decreased illumination level is less than 5% of the maximum brightness of said first pixel.