Liquid crystal display backlight with level change

• US 7,714,830 B2
• Filed: 10/30/2004
• Issued: 05/11/2010
• Est. Priority Date: 11/09/2001
• 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.
• Primary Examiner(s): Awad; Amr
• Assistant Examiner(s): Sherman; Stephen G
• Application Number:
  US10/976,715
• Publication Number:
  US 20050088401A1
• Time in Patent Office: 2,019 Days
• Field of Search: 345/102, 345/87, 345/204, 345/82, 345/690, 345/76, 349/61, 349/62
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2320/0238 Improving the black level
• 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 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/066 for control of contrast
• 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 display is backlit by a source having spatially modulated luminance to attenuate illumination of dark areas of images and increase the dynamic range of the display.

Claims

1. A method of illuminating a backlit display, said method comprising the steps of:

(a) spatially varying the luminance of a light source by

(i) illuminating a plurality of displayed pixels in response to a plurality of pixel values dependent on the content of an image to be displayed on said display,

(ii) modifying the illumination from said display based upon a filter that is determined at least in part by a non-uniform illumination profile of said light source, and;

(iii) varying the transmittance of respective light valves arrayed over a viewing region of said display in a non-binary manner, wherein said light source is spatially displaced at a location at least partially directly beneath said plurality of pixels, wherein said light source provides different respective non-zero luminance intensities to first and second said light valves, relative to each other, using a non-linear transformation of said plurality of pixel values;

(b) modifying the light to be output from said display by rescaling said light to be said output from said display in such a manner to alter the tone-scale of said light to be said output from said display from a state that would have substantially non-uniform tone-scale to a state that has substantially uniform tone-scale resulting from the luminance of said light source.

2. The method of claim 1 wherein a relationship of said pixel values and said luminance of said light source is a nonlinear relationship.

3. The method of claim 1 further comprising the step of filtering pixel value for a plurality of pixels.

4. The method of claim 3 further comprising the step of sampling said filtered intensity value for a spatial location of said light source.

5. The method of claim 4 further comprising the step of rescaling a sample of said filtered intensity value to reflect a nonlinear relationship between said intensity of said light source and said intensity of said displayed pixel.

6. The method of claim 1 further comprising:

(a) operating said light source at substantially a maximum luminance if a luminance of at least one displayed pixel exceeds a threshold luminance; and

(b) otherwise, attenuating said luminance of said light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels.

7. The method of claim 6 wherein the step of attenuating a luminance of a light source according to a relationship of said luminance of said light source and a luminance of a plurality of pixels comprises the step of attenuating said luminance of said light source based upon of said luminance of said light source and a mean luminance of said plurality of pixels.

8. The method of claim 1 wherein said spatially varying the luminance is based upon low pass filtered pixel values.

9. The method of claim 1 further comprising variably reducing luminance of a portion of said light source based upon a dark local spatial area of said pixel data.

10. The method of claim 1 further comprising non-linear modification of said pixel values in a manner that simulates a CRT display.