Dynamic dimming LED backlight for LCD array

• US 10,510,304 B2
• Filed: 08/10/2017
• Issued: 12/17/2019
• Est. Priority Date: 08/10/2016
• Status: Active Grant

• Current Assignee: Manufacturing Resources International, Inc.
• Original Assignee: Manufacturing Resources International, Inc.
• Inventors: Dunn, William, DeLaet, Rick
• Primary Examiner(s): Patel, Premal R
• Application Number:
  US15/673,580
• Publication Number:
  US 20180047345A1
• Time in Patent Office: 859 Days
• CPC Class Codes: G02F 1/13336 Combining plural substrates to produce large-area displays, e.g. tiled displays
• CPC Class Codes: G02F 1/133601 for spatial active dimming
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G09G 2300/026 Video wall, i.e. juxtaposition of a plurality of screens to create a display screen of bigger dimensions
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0686 with two or more screen areas displaying information with different brightness or colours
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127

Abstract

A LCD assembly having a dynamic dimming LCD backlight and a plurality of individual LCD displays positioned in front of the backlight, and a method for controlling a backlight of such an assembly. The backlight is divided into an array of individually controllable subsections, and adjacent edges of the LCD displays are used to define virtual boundary lines relative to the backlight subsections. Initial desired luminance values are determined for each subsection of the backlight based on incoming video data. A difference between desired luminance values for each pair of adjacent backlight subsections that border the virtual boundary lines is calculated and compared to a threshold value. Based on the comparisons, adjustments may be made to the desired luminance value of the backlight subsections.

Claims

1. A method for controlling a dynamic dimming liquid crystal display (LCD) backlight of a LCD assembly having a plurality of discrete LCDs positioned in front of the backlight, each LCD having a discrete display receiver board configured to deliver received video content to the LCD, the method comprising:

dividing the backlight into an array of individually controllable subsections;

using adjacent edges of the LCD displays as virtual boundary lines relative to the backlight subsections;

placing each display receiver board in electrical communication with one or more of the other receiver boards;

determining an initial desired luminance value for each subsection of the backlight based on incoming video data supplied to the LCDs;

(a) calculating the difference between desired luminance values for each pair of adjacent backlight subsections that border the virtual boundary lines;

(b) comparing the calculated difference in desired luminance values for each pair of adjacent backlight subsections to a predetermined threshold value; and

(c) when the calculated difference in desired luminance values between a pair of adjacent backlight subsections exceeds the threshold value, increasing the desired luminance value for the backlight subsection having a lower desired luminance value by adding a constant value to the existing desired luminance value of said subsection.

2. The method of claim 1, wherein the desired luminance value for the backlight subsection having a lower desired luminance value is also increased when the calculated difference in desired luminance values between a pair of adjacent backlight subsections is equal to the threshold value.

3. The method of claim 1, wherein all backlight subsections not having an increased desired luminance value are driven at the original desired luminance value.

4. The method of claim 1, wherein the threshold value is between 20% and 90% of the possible range of desired luminance values.

5. The method of claim 1, wherein the constant value is some fixed percentage of the threshold value.

6. The method of claim 1, wherein the constant value is selected from a lookup table, the constant values in the lookup table varying with the magnitude of the calculated difference in desired luminance values.

7. The method of claim 1, further comprising performing gamma correction.

8. The method of claim 1, further comprising rescaling LCD subpixel voltage.

9. The method of claim 8, wherein subpixel voltage rescaling is accomplished by dividing the voltage of a given subpixel by the ratio of the desired luminance value for said subpixel to the maximum possible luminance value for said subpixel.

10. The method of claim 8, further comprising creating a virtual backlight that allows bleed over behavior of adjacent backlight subsections to be mathematically modeled and accounted for during rescaling of subpixel voltages.

11. The method of claim 10, wherein:

the virtual backlight is created using virtual subsections that are based on the use of a stored matrix of data that represents the appearance of a single, fully illuminated backlight subsection as seen through a diffuser;

each virtual subsection is larger than the actual backlight subsection it represents, such that adjacent subsections may be overlapped; and

the principle of additive light may be used to blend the edges of the subsections.

12. The method of claim 1, further comprising repeating steps (a)-(c) on subsequent video frames after all of any backlight subsection desired luminance value increases are completed for a current video frame.

13. The method of claim 1, wherein the electrically communicating display receiver boards share desired luminance value information.

14. The method of claim 13, wherein the display receiver boards share desired luminance value information about backlight subsections that lie across virtual boundary lines.

15. The method of claim 1, wherein each display receiver board receives video content from an associated, discrete video player.

16. A method for controlling a dynamic dimming liquid crystal display (LCD) backlight of a LCD assembly, the backlight divided into an array of individually controllable subsections, and a plurality of discrete LCDs positioned in front of the backlight with adjacent edges of the LCDs defining virtual boundary lines relative to the backlight subsections, the method comprising:

providing each LCD with a discrete display receiver board and a discrete video player, the video player supplying the display receiver board with video content and the display receiver board supplying the video content to its associated LCD;

placing each display receiver board in electrical communication with one or more of the other receiver boards;

determining an initial desired luminance value for each subsection of the backlight based on incoming video data supplied to the LCDs, wherein the desired luminance value is between off and a maximum luminance value;

calculating the difference between desired luminance values for each pair of adjacent backlight subsections that border the virtual boundary lines;

comparing the calculated difference in desired luminance values for each pair of adjacent backlight subsections to a predetermined threshold value;

when the calculated difference in desired luminance values between a pair of adjacent backlight subsections exceeds the threshold value, increasing the desired luminance value for the backlight subsection having a lower desired luminance value by multiplying the calculated difference in desired luminance values by some predetermined fraction;

driving all backlight subsections not having an increased desired luminance value at the initially determined desired luminance value;

rescaling the voltage of any LCD subpixels that overlie a backlight subsection operating at less than the maximum luminance value; and

creating a virtual backlight that allows bleed over behavior of adjacent backlight subsections to be mathematically modeled and accounted for during rescaling of the LCD subpixel voltages;

wherein the communicating display receiver boards share desired luminance value information about backlight subsections that lie across virtual boundary lines.

17. The method of claim 16, wherein the desired luminance value for the backlight subsection having a lower desired luminance value is also increased when the calculated difference in desired luminance values between a pair of adjacent backlight subsections is equal to the threshold value.

18. The method of claim 16, wherein subpixel voltage rescaling is accomplished by dividing the voltage of a given subpixel by the ratio of the desired luminance value for said subpixel to the maximum possible luminance value for said subpixel.

19. The method of claim 16, wherein:

the virtual backlight is created using virtual subsections that are based on the use of a stored matrix of data that represents the appearance of a single, fully illuminated backlight subsection as seen through a diffuser;

each virtual subsection is larger than the actual backlight subsection it represents, such that adjacent subsections may be overlapped; and

the principle of additive light may be used to blend the edges of the subsections.

20. The method of claim 16, wherein the display receiver board of a given LCD only communicates with display receiver boards of other LCDs adjacent to the given LCD.