Display device with directional control of the output, and a backlight for such a display device and a light direction method

• US 10,397,557 B2
• Filed: 03/16/2016
• Issued: 08/27/2019
• Est. Priority Date: 03/26/2015
• Status: Active Grant

• Current Assignee: Leia Inc.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Vdovin, Olexandr Valentynovych, Van Putten, Eibert Gerjan, Kroon, Bart, Johnson, Mark Thomas
• Primary Examiner(s): Garlen, Alexander K
• Application Number:
  US15/559,093
• Publication Number:
  US 20180249149A1
• Time in Patent Office: 1,259 Days
• CPC Class Codes: G02B 30/24 involving temporal multiplexing, e.g. using sequentially activated left and right shutters
• CPC Class Codes: G02B 6/0023 provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
• CPC Class Codes: G02B 6/0025 Diffusing sheet or layer; Prismatic sheet or layer
• CPC Class Codes: G02B 6/003 Lens or lenticular sheet or layer
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0033 Means for improving the coupling-out of light from the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0091 of the light source relative to the light guide G02B6/0021 takes precedence
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G09G 2358/00 Arrangements for display data security
• CPC Class Codes: G09G 3/003 to produce spatial visual effects
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: H04N 13/32 using arrays of controllable light sources; using moving apertures or moving light sources
• CPC Class Codes: H04N 13/398 Synchronisation thereof; Control thereof
• CPC Class Codes: H04N 2013/405 the images being stereoscopic or three dimensional
• CPC Class Codes: H04N 2213/001 Constructional or mechanical details

Abstract

A display backlight comprises an edge-lit lightguide having an array of light out-coupling structures to enable light to escape from the lightguide at the location of the light out-coupling structures. A light source arrangement is used for providing light into the lightguide at one or both of the opposite side edges. The light source arrangement is controllable to provide a selected one of at least first and second light outputs into the lightguide, the two light outputs having a different angle to the general plane of the lightguide and resulting in light which escapes from the lightguide with a different range of exit angles. In this way, a directional backlight output is enabled, based on the way light is coupled into a lightguide. This provides a simple structure only requiring control of the light provided to the lightguide. The backlight may for example enable an auto stereoscopic display to be formed without the need for a lenticular array.

Claims

1. A device, comprising:

a lightguide having a top face and a bottom face, and opposite first and second side edges extending between the top face and the bottom face,

wherein the top face is parallel to the bottom face, and

wherein light is output from the top face;

a light source arranged to provide the light into the lightguide at one or both of the opposite side edges; and

an array of light out-coupling structures formed at the top face or the bottom face of the lightguide to redirect the light so that the light escapes from the lightguide at the location of the light out-coupling structures,

wherein the light source is controllable to provide a selected one of at least a first light output and second light output into the lightguide,

wherein the first light output and the second light output are each at least partially collimated,

wherein an angular direction of elevation is defined with respect to a plane of the top face and across a direction from the first side edge of the lightguide to the second side edge of the lightguide,

wherein the light source is arranged to provide the first light output and the second light output into the lightguide with different angular directions of elevation than each other, and

wherein the first light output entering into the lightguide results in the light exiting the top face of the lightguide at a first range of angles, and the second light output entering the lightguide results in the light exiting the top face of the lightguide at a second range of angles, wherein the first range of angles is different than the second range of angles.

2. The device of claim 1, wherein the first light output and the second light output are each collimated in a plane extending between the side edges of the lightguide.

3. The device of claim 1, wherein the light out-coupling structures comprise prismatic strips which extend parallel to the side edges of the lightguide.

4. The device of claim 1,

wherein the light source comprises at least a first light source and a second light source,

wherein the first light source is mounted at first source angle with respect to the plane of the top face of the lightguide and the second light source is mounted at second source angle respect to the top face of the lightguide,

wherein the first source angle is different than the second source angle.

5. The device of claim 1,

wherein the light source comprises at least a first light source and a second light source,

wherein each light source has an associated beam shaping element,

wherein each beam shaping element is arranged to set a corresponding light output angle into the lightguide,

wherein the light output angle is defined with respect to the plane of the top face of the lightguide.

6. The device of claim 5, wherein each of the beam shaping elements comprise:

static prismatic structures designed for a specific light output angle with respect to the plane of the top face of the lightguide.

7. The device of claim 1,

wherein the light source comprises at least first a first light source and a second light source,

wherein each light source comprises a light emitter array and an output lens.

8. The device of claim 1, further comprising a light redirection structure over the top face of the lightguide providing a redirection of the light output from the top face of the lightguide.

9. The device of claim 1, wherein the light output angles from the top face vary as a function of position over the top face such that light reaches a common view point from all positions of the top face.

10. The device of claim 1, further comprising a display panel having an array of display pixels,

wherein the display panel is illuminated by the light exiting from the waveguide.

11. The device of claim 10, further comprising a controller,

wherein the controller is arranged to operate the display in a first mode and a second mode:

wherein the first light output is provided into the lightguide and the display panel is controlled to display a first image in the first mode;

wherein the second light output is provided into the lightguide and the display panel is controlled to display a second image in the second mode, and

wherein the controller is arranged to implement the first and second modes time-sequentially.

14. The device of claim 1, wherein the cross section of the lightguide, in the plane of the top face, is a rectangle.

15. The device of claim 3, wherein the prismatic strips extend parallel to the side edges.

16. The device of claim 5, wherein each of the beam shaping elements comprise:

dynamic beam shaping elements arranged to provide a specific light output angle with respect to the plane of the top face of the lightguide.

12. A method, comprising:

providing light from a light source into a lightguide which has top face and a bottom face, and opposite first and second side edges extending between the top face and the bottom face, wherein the top face is parallel to the bottom face, wherein the light is provided to at least one opposite side edge, and wherein the light source provides the light into the lightguide via at least a first light output and a second light output;

using an array of light out-coupling structures formed at the top face or bottom face of the lightguide to redirect the light so that the light escapes from the lightguide from the top face at locations of the light out-coupling structures;

controlling an angular direction of elevation of the light entering the lightguide,

wherein the angular direction of elevation is defined with respect to a plane of the top face of the lightguide across a direction from the first side edge of the lightguide to the second side edge of the lightguide,

wherein the light source is arranged to provide the first light output and the second light output into the lightguide with different angular directions of elevation than each other, and

wherein the first light output entering the lightguide results in the light exiting the top face of the lightguide at a first range of angles, and the second light output entering the lightguide results in the light exiting the top face of the lightguide at a second range of angles, wherein the first range of angles is different than the second range of angles.

13. The method of claim 12, further comprising:

providing the light from the lightguide to a display panel; and

controlling the image displayed by the display panel,

wherein the display device is operated in a first mode and a second mode;

wherein the first light output enters the lightguide and the display panel is controlled to display a first image in the first mode;

wherein the second light output enters the lightguide and the display panel is controlled to display a second image in the second mode, and

wherein the first and second modes are provided time-sequentially.