Liquid crystal display with filtered black point

• US 7,532,192 B2
• Filed: 10/15/2004
• Issued: 05/12/2009
• 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): Nguyen; Chanh
• Assistant Examiner(s): Snyder; Adam J
• Application Number:
  US10/966,973
• Publication Number:
  US 20050248554A1
• Time in Patent Office: 1,670 Days
• Field of Search: 345/698, 345 87-107, 349/114, 362/355
• 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 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 that displays an image having a luminance that is separated into a transmission component driving liquid crystal material and an illumination component driving a backlight, where the transmission component comprises at least 60% of the image luminance and the illumination component comprises less than 30% of the image luminance.

Claims

1. A method for displaying an image on a liquid crystal display having an LED array, an LCD array, and a diffusion layer over said LED array said LED array having a lower resolution than said LCD array, said method 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 by subsampling said image at the resolution of said LED array and after said high frequency aspects of said image have been reduced; and

(iii) convolving the subsampled said image with a point spread function of said LED array and said diffusion layer of said display;

(c) selecting illumination levels for each of a respective plurality of regions of a spatial two-dimensional array of light emitting elements, illumination levels of each region of said plurality of regions selected independently of each other, and selected based on an amount by which said image is modified in step (b) measured over a plurality of pixels corresponding to the respective said region for which said illumination level is being selected;

(d) using said image to modulate liquid crystal material within said display.

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. The method of claim 1 further comprising:

(a) providing a transmission component of a luminance signal, received from said image, to a liquid crystal material of said liquid crystal display;

(b) providing a backlight illumination component of said luminance signal, received from said image, to a two-dimensional array of light emitting elements illuminating said liquid crystal material;

(c) wherein said transmission component comprises at least 60% of said luminance signal and said illumination component comprises less than 40% of said luminance signal.