Liquid crystal display with area adaptive backlight

• US 8,941,580 B2
• Filed: 11/30/2006
• Issued: 01/27/2015
• Est. Priority Date: 11/30/2006
• 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: Li, Feng, Feng, Xiao-Fan
• Primary Examiner(s): Sitta, Grant
• Application Number:
  US11/607,553
• Publication Number:
  US 20080129677A1
• Time in Patent Office: 2,980 Days
• Field of Search: 345/87, 345/204, 345/102, 345/690
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• 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 2320/0252 Improving the response speed
• 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 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A backlight display has improved display characteristics. An image is displayed on the display which includes a liquid crystal material with a light valve. The display receives an image signal and modifies the light for a backlight array and a liquid crystal layer.

Claims

1. A method for displaying an image on a liquid crystal display including a light valve and a backlight array of individually controllable lighting elements, where said display has a leakage value representing the intensity of light that passes through closed liquid crystal elements of said display, said method comprising:

(a) receiving an image;

(b) modifying said image to provide data to said light valve;

(c) modifying said image to provide data to said backlight array;

(d) wherein said data provided to said backlight array is based upon maintaining the following constraints;

(i) the lighting element value is greater than a corresponding pixel value;

(ii) the lighting element is decreased in value when less than the leakage value of the display; and

(e) wherein said data to said backlight array is determined by a sequence of iteratively calculated values based on a crosstalk constraint, and such that;

(i) the difference between each successive pair of iterated values is calculated; and

(ii) iteration ends when the calculated said difference between a successive pair of iterated values is less than a threshold.

2. The method of claim 1 wherein said constraints impose that the light valve has a transmission no greater than unity.

3. The method of claim 1 wherein said leakage value is determined based upon the image data and the contrast ratio of the display.

4. The method of claim 1 wherein said lighting elements are decreased based upon a power savings criteria.

5. A method for displaying an image on a liquid crystal display including a light valve and a backlight array of individually controllable lighting elements comprising:

(a) receiving an image;

(b) modifying said image to provide data to said light valve;

(c) modifying said image to provide data to said backlight array;

(d) wherein said data provided to said backlight array is based upon maintaining the following constraint;

(i) the lighting element value is based upon the substantial maximum of the image data for the corresponding portion of the image;

(e) wherein said data provided to said light value corresponding to said lighting element is suitable to provide the desired illumination for said image; and

(f) wherein said data to said backlight array is determined by a sequence of iteratively calculated values based on a crosstalk constraint, and such that;

(i) the difference between each successive pair of iterated values is calculated; and

(ii) iteration ends when the calculated said difference between a successive pair of iterated values is less than a threshold.

6. The method of claim 5 where said display has a leakage value representing the intensity of light that passes through closed liquid crystal elements of said display, and wherein said data provided to said backlight is based upon maintaining the following constraints:

(i) the lighting element value is greater than the corresponding pixel value;

(ii) the lighting element is decreased in value when less than the leakage value of the display.

7. The method of claim 5 wherein said lighting element is further based upon a low pass filtered image data for the corresponding portion of the image.

8. The method of claim 7 wherein said lighting element is based upon a selection between said lower pass filtered image data and said substantial maximum.

9. A method for displaying an image on a liquid crystal display including a light valve and a backlight array of individually controllable lighting elements comprising:

(a) receiving an image;

(b) modifying said image to provide data to said light valve;

(c) modifying said image to provide data to said backlight array;

(d) wherein said data provided to said backlight array is determined by a sequence of iteratively calculated values based on a crosstalk constraint, and such that;

(i) the difference between each successive pair of iterated values is calculated; and

(ii) iteration ends when the calculated said difference between a successive pair of iterated values is less than a threshold.

10. The method of claim 9 where said display has a leakage value representing the intensity of light that passes through closed liquid crystal elements of said display, and wherein said data provided to said backlight array is based upon maintaining the following constraints:

(i) the lighting element value is greater than the corresponding pixel value;

(ii) the lighting element is decreased in value when less than the leakage value of the display.

11. A method for displaying an image on a liquid crystal display including a light valve and a backlight array of individually controllable lighting elements comprising:

(a) receiving an image;

(b) modifying said image to provide data to said light valve;

(c) modifying said image to provide data to said backlight array;

(d) wherein said data provided to said backlight array is based upon a temporal filter and determined by a sequence of iteratively calculated values based on a crosstalk constraint, and such that;

(i) the difference between each successive pair of iterated values is calculated; and

(ii) iteration ends when the calculated said difference between a successive pair of iterated values is less than a threshold.

12. The method of claim 11 wherein said temporal filter is low-pass.

13. The method of claim 11 wherein said data provided to said backlight array is based upon maintaining the following constraints:

(i) the lighting element value is greater than the corresponding pixel value;

(ii) the lighting element is decreased in value when less than the leakage value of the display;

(iii) the lighting elements are decreased in value while the corresponding light value is increased in transmission.

14. A method for displaying an image on a liquid crystal display including a light valve and a backlight array of individually controllable lighting elements comprising:

(a) receiving an image;

(b) modifying said image to provide data to said light valve;

(c) modifying said image to provide data to said backlight array;

(d) wherein said data provided to said backlight array is determined by a sequence of iteratively calculated values based on a crosstalk constraint, and such that;

(i) the difference between each successive pair of iterated values is calculated; and

(ii) iteration ends when the calculated said difference between a successive pair of iterated values is less than a threshold, said calculated pair of iterated values based upon a data structure denser than the individual backlight array elements.

15. The method of claim 14 wherein said data structure has twice the density of said backlight array elements.

16. The method of claim 14 where said display has a leakage value representing the intensity of light that passes through closed liquid crystal elements of said display, and wherein said data provided to said backlight array is based upon maintaining the following constraints:

(i) the lighting element value is greater than the corresponding pixel value;

(ii) the lighting element is decreased in value when less than the leakage value of the display.