Liquid crystal display with filtered black point

• US 20050248554A1
• Filed: 10/15/2004
• Published: 11/10/2005
• 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 7,532,192 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• 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 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.

Claims

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

(a) receiving said image with a controller integral with the display;

(b) modifying said image by

(i) reducing high frequency aspects of said image;

(ii) reducing the resolution of said image;

(iii) accounting for the effects of a diffusion later of said display;

(c) using data as a result of step (b) to select illumination levels for a spatial two-dimensional array of light emitting elements;

(d) using said image to modulate liquid crystal material within said display in such a manner that the luminance of said display is composed of greater than 60% transmission from a liquid crystal material times less than 40% luminance from said array of light emitting elements.

2. The method of claim 1 further 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 immediately following said first frame, wherein said second illumination level is greater than said second level;

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

3. The method of claim 1 wherein step (b)(i) is performed before step (b)(ii), step (b)(ii) is performed before step (b)(iii).

4. The method of claim 2 wherein step (b)(i) is performed before step (b)(ii), step (b)(ii) is performed before step (b)(iii).

5. The method of claim 1 wherein step (i) includes low pass filtering said image to provide a filtered image.

6. The method of claim 5 wherein step (ii) includes sub-sampling said filtered image.

7. The method of claim 6 wherein step (iii) includes convolving said sub-sampled image with a function representative of said diffusion layer;

8. The method of claim 7 wherein said function is a point spread function.

9. The method of claim 8 wherein the LCD image is a function of said image and the modified image as a result of said function.

10. The method of claim 1 wherein said plurality of light emitting elements has a lower density than pixel elements of said liquid crystal material.

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

(a) providing transmission from a liquid crystal material;

(b) providing illumination from a two-dimensional array of light emitting elements;

(c) wherein the luminance from said display is provided in such a manner that said luminance of said display is composed of greater than 60% transmission from said liquid crystal material times less than 40% luminance from said array of light emitting elements.