High dynamic range display using LED backlighting, stacked optical films, and LCD drive signals based on a low resolution light field simulation

• US 8,482,698 B2
• Filed: 11/26/2012
• Issued: 07/09/2013
• Est. Priority Date: 06/25/2008
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Atkins, Robin
• Primary Examiner(s): Qi, Mike
• Application Number:
  US13/684,862
• Publication Number:
  US 20130120234A1
• Time in Patent Office: 225 Days
• Field of Search: 349/61, 349/62, 362/294, 345/690
• US Class Current: 349/61
• CPC Class Codes: G09G 2330/045 Protection against panel overheating
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 5/10 Intensity circuits

Abstract

An HDR display is a combination of technologies including, for example, a dual modulation architecture incorporating algorithms for artifact reduction, selection of individual components, and a design process for the display and/or pipeline for preserving the visual dynamic range from capture to display of an image or images. In one embodiment, the dual modulation architecture includes a backlight with an array of RGB LEDs and a combination of a heat sink and thermally conductive vias for maintaining a desired operating temperature.

Claims

1. A high dynamic range display, comprising:

an LCD panel;

a set of LEDs disposed behind a plane of the LCD panel and positioned to backlight the LCD panel with an approximation of an image;

a controller coupled to the set of LEDs configured to energize the set of LEDs so as to produce the image approximation, the controller energizing the set of LEDs with a Pulse-Width Modulation signal for each of individually controllable LEDs or groups of LEDs of the set of LEDs, the Pulse Width Modulation signal calculated based on an image signal comprising a desired image at a resolution lower than a resolution of the LCD panel;

a power supply coupled to the set of LEDs and configured to maintain a supply voltage to the coupled LEDs in a range that provides a minimum amount supply voltage sufficient to cover peak demands of the set of LEDs when energized without creating a potential difference between the supply voltage and power utilized by the display which is greater than a maximum power dissipation capability of the power supply;

a stack of optical films disposed between the set of LEDs and the LCD panel in an unconstrained manner so as to allow for heat related expansion, the stack of optical films comprising at least one diffuser that causes light from each of the individually controllable LEDs or groups of LEDs to spread into light from adjacent LEDs or groups of LEDs in an overlapping manner such that it causes the illumination on the LCD panel to vary smoothly, the light of the set of LEDs or groups of LEDs having a point spread function being mainly attributable to diffusion caused by the optical films stack;

the controller coupled to the LCD panel and configured to energize the LCD panel based on an image signal comprising the desired image and accounting for the illumination on the LCD panel via a calculated or simulated illumination of the LCD panel;

the LCD energization causing the LCD panel to further modulate the image approximation to produce the desired image;

wherein the calculated or simulated illumination of the LCD panel is at a resolution equal or less than the resolution of the LCD panel.

2. The high dynamic range display according to claim 1, wherein the controller is further configured to energize the set of LEDs to maintain a “

center-of-gravity”

of illumination around bright features of the desired image.

3. The high dynamic range display according to claim 1, wherein the stack of optical films comprises a bulk diffuser and a brightness enhancement film, wherein the bulk diffuser is upstream of the other films such that reflections are directed toward the bulk diffuser.

4. The high dynamic range display according to claim 1, wherein the set of LEDs comprising a backlight and the simulated illumination comprises components corresponding to illumination originating from edges of the backlight.

5. The high dynamic range display according to claim 1, wherein the set of LEDs comprising an array of LEDs spaced apart a distance d and a reflector surrounding the set of LEDs together comprising a backlight, wherein the LEDs closest to the surrounding reflector are spaced a distance d/2 from the surrounding reflector.

6. The high dynamic range display according to claim 5, wherein the array of LEDs comprises rows of LEDs wherein alternating rows of LEDs are offset by distance of approximately d/2.

7. The high dynamic range display according to claim 6, wherein the set of LEDs are fixed on a plurality of substrates fitted together to form the backlight.

8. A method, comprising the step of:

backlighting an LCD panel from a set of LEDs disposed behind a plane of the LCD panel;

wherein the set of LEDs are positioned to backlight the LCD panel with an approximation of an image;

the method further comprising the step of energizing the LEDs with data from a controller coupled to the set of LEDs and configured to energize the set of LEDs so as to produce the image approximation,

wherein the controller is further configured to energize the set of LEDs with a Pulse-Width Modulation signal for each of individually controllable LEDs or groups of LEDs of the set of LEDs, the Pulse Width Modulation signal calculated based on an image signal comprising a desired image at a resolution lower than a resolution of the LCD panel;

the method further comprising the step of providing power from a power supply coupled to the set of LEDs and configured to maintain a supply voltage to the coupled LEDs in a range that provides a minimum amount supply voltage sufficient to cover peak demands of the set of LEDs when energized without creating a potential difference between the supply voltage and power utilized by the display which is greater than a maximum power dissipation capability of the power supply;

wherein the set LEDs and LCD panel are arranged with a stack of optical films disposed between the set of LEDs and the LCD panel in an unconstrained manner so as to allow for heat related expansion, the stack of optical films comprising at least one diffuser that causes light from each of the individually controllable LEDs or groups of LEDs to spread into light from adjacent LEDs or groups of LEDs in an overlapping manner such that it causes the illumination on the LCD panel to vary smoothly, the light of the set of LEDs or groups of LEDs having a point spread function being mainly attributable to diffusion caused by the optical films stack;

wherein the controller coupled to the LCD panel and configured to energize the LCD panel based on an image signal comprising the desired image and accounting for the illumination on the LCD panel via a calculated or simulated illumination of the LCD panel the LCD energization causing the LCD panel to further modulate the image approximation to produce the desired image; and

wherein the calculated or simulated illumination of the LCD panel is at a resolution equal or less than the resolution of the LCD panel.

9. The method according to claim 8, further comprising the step of energizing the set of LEDs to maintain a “

center-of-gravity”

of illumination around bright features of the desired image.

10. The method according to claim 8, wherein the stack of optical films comprises a bulk diffuser and a brightness enhancement film, wherein the bulk diffuser is upstream of the other films such that reflections are directed toward the bulk diffuser.

11. The method according to claim 8, wherein the set of LEDs comprising a backlight and the simulated illumination comprises components corresponding to illumination originating from edges of the backlight.

12. The method according to claim 8, wherein the set of LEDs comprising an array of LEDs spaced apart a distance d and a reflector surrounding the set of LEDs together comprising a backlight, wherein the LEDs closest to the surrounding reflector are spaced a distance d/2 from the surrounding reflector.

13. The method according to claim 8, wherein the array of LEDs comprises rows of LEDs wherein alternating rows of LEDs are offset by distance of approximately d/2.

14. The method according to claim 8, wherein the set of LEDs are fixed on a plurality of substrates fitted together to form the backlight.

15. The method according to claim 8, wherein the step of energizing further comprising the step of processing the pulse-width modulation signal for the set of LEDs in a manner that reduces artifacts in the image displayed on the LCD panel.

16. The method according to claim 15, wherein the step of processing comprises producing the pulse-width modulation signal so as to maintain a “

center-of-gravity”

of illumination around bright features of the image being displayed.

17. The method according to claim 16, wherein the illumination maintains a “

center-of-gravity”

of the illumination around bright features displayed on the LCD panel.

18. The method according to claim 8, further comprising the step of maintaining an illumination from the LEDs around bright features of the image being displayed on the LCD panel.