LIQUID CRYSTAL DISPLAY WITH MODULATED BLACK POINT

• US 20090184918A1
• Filed: 03/27/2009
• Published: 07/23/2009
• Est. Priority Date: 05/04/2004
• Status: Active Grant

• 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
• Granted Patent: US 8,217,890 B2
• Time in Patent Office: Days
• 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.

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;

¹

¹The purpose of non-zero is because a transition from zero to zero is a “

dark”

insertion, albeit not a very interesting one.

(b) illuminating said first pixel at a second non-zero illumination level during a second frame,² wherein said second frame is the next frame immediately following said first frame,³ wherein said second illumination level is greater than said second level;

⁴

²A second frame to do the comparison with.

³Sets the temporal relationship between the first frame and the second frame. This avoids the interpretation of a first and second frame temporally far apart, where the pixel just happens to go “

black”

because of the video in the intermediate time period.

⁴ This claim requires an increasing value of illumination where the pixel is then dropped to a lower level, which is “

black”

point insertion. There may be cases where the pixel is under-driven to force it to a low value in some display implementations, and thus this avoids that interpretation.

(c) wherein said first pixel is decreased in illumination to a level less than said first illumination level⁵ prior to illuminating said first pixel at said second illumination level during said second frame.⁶

⁵ In some circumstances this will be a valid constraint, and that is all that is necessary for infringement. Other claims remove this limitation.

⁶ Defines when the drop in level takes place, namely after the first image and before the second image. It is not defined by “

frames”

since the action may occur during a frame depending upon your definition of a 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 3 wherein at least 20% are said decreased.

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

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

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

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

10. 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.

11. The method of claim 5 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.

12. The method of claim 6 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.

13. The method of claim 7 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.

14. The method of claim 8 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.

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

16. 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.

17. The method of claim 5 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.

18. The method of claim 6 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.

19. The method of claim 7 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.

20. The method of claim 8 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.