Liquid crystal display with illumination control

• US 8,395,577 B2
• Filed: 10/15/2004
• Issued: 03/12/2013
• 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: Feng, Xiao-fan, Daly, Scott J.
• Primary Examiner(s): Snyder, Adam J
• Application Number:
  US10/966,980
• Publication Number:
  US 20050248555A1
• Time in Patent Office: 3,070 Days
• Field of Search: 345/46, 345/691, 345 87-107, 349/61
• US Class Current: 345/102
• 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 2320/062 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 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• 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. The disclosed display illuminates a pixel of the display at respective non-zero illumination levels during each of a first frame and a second frame and decreases the illumination level of the pixel during the interval between the first frame and the second frame.

Claims

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

(a) illuminating a first LCD pixel, with a light-emitting element, at a first non-zero illumination level during an initial frame, where said liquid crystal display prevents said light-emitting element from having a non-zero luminance below a minimum threshold value;

(b) illuminating said first LCD pixel at a second non-zero illumination level during a next subsequent frame;

(c) wherein said first pixel is selectively decreased in illumination a plurality of times to respective black point illumination levels during the interval of said initial frame; and

(d) wherein said respective black point illumination levels have associated respective widths each automatically selected to cooperatively achieve a non-zero illumination level in said first LCD pixel below said threshold value.

2. The method of claim 1 including the step of providing said first LCD pixel with an electrical signal representative of image data from said next subsequent frame while said first pixel is decreased in illumination after illuminating said pixel to said first non-zero illumination level and before illuminating said pixel to said second non-zero illumination level.

3. The method of claim 1 wherein at least one of said another illumination levels is substantially zero and where said first and second non-zero illumination levels are substantially of the same value.

4. The method of claim 1 wherein said first LCD pixel is illuminated at said second non-zero illumination level, while said LCD pixel is provided with said electrical signal representative of image data from said next subsequent frame, after a delay, measured from the time at which said first LCD pixel is decreased in illumination to said another illumination level, said delay being greater than 1/10 of a frame interval.

5. The method of claim 1 wherein said another illumination level is selected based upon the change of said first pixel between two frames.

6. The method of claim 5 wherein said selection is further based upon a set of two thresholds.

7. A method for displaying an image on a liquid crystal display, said method comprising:

(a) providing an electrical signal to a first LCD pixel, and representative of image data for said first LCD pixel, at a frame rate over a plurality of sequential frames, where said liquid crystal display prevents light illuminating said first LCD pixel from having a non-zero luminance below a minimum threshold value;

(b) repeatedly illuminating said first LCD pixel at non-zero illumination levels over first intervals respectively occurring at said frame rate but at an offset phase from said input electrical signal; and

(c) wherein said first pixel is decreased in illumination a plurality of times to respective black point illumination levels during an interval equal to one of said plurality of sequential frames, wherein said respective black point illumination levels have associated respective widths each automatically selected to cooperatively achieve a non-zero an illumination level of said first LCD pixel and in said first frame below said threshold value.

8. The method of claim 7 wherein said first LCD pixel is illuminated at respective said non-zero illumination levels, while said LCD pixel is provided with said electrical signal representative of image data for said first LCD pixel, and after a delay measured from the time at which said first LCD pixel is decreased in illumination to said another illumination level.

9. The method of claim 8 wherein said delay is greater than 1/10 of a frame.

10. The method of claim 7 wherein said decreased illumination level is selected based upon the change of said first pixel between two frames.

11. The method of claim 10 wherein said selection is further based upon a set of two thresholds.

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

(a) illuminating a first LCD pixel, with a light-emitting element, at non-zero illumination levels over respective intervals each occurring during one of a plurality of different frames, where said liquid crystal display prevents said light-emitting element from having a non-zero luminance below a minimum threshold value;

(b) wherein said first pixel is decreased in illumination a plurality of times to respective black point illumination levels during an interval equal to one of said plurality of sequential frames, wherein said respective black point illumination levels have associated respective width each automatically selected to cooperatively achieve a non-zero illumination level in said first LCD pixel below said threshold value;

(c) sequentially providing said first LCD pixel with respective electrical impulses each representative of image data specific to said first LCD pixel during one of said plurality of different frames, where said value is automatically selected based only on a comparison between sequential ones of said electrical impulses to said first LCD pixel.

13. The method of claim 12 wherein said sequential electrical impulses and said respective intervals occur at the same frequency but are offset in phase.

14. The method of claim 13 wherein said frequency is the frame rate of the image displayed on said liquid crystal display.

15. The method of claim 13 wherein said offset in phase is greater than 1/10 of a frame.