DISPLAY DEVICE WITH DIRECTIONAL CONTROL OF THE OUTPUT, AND A BACKLIGHT FOR SUCH A DISPLAY DEVICE AND A LIGHT DIRECTION METHOD

• US 20180249149A1
• Filed: 03/16/2016
• Published: 08/30/2018
• 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
• Granted Patent: US 10,397,557 B2
• Time in Patent Office: 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 display backlight, comprising:

a lightguide having top face and bottom face, and a pair of opposite side edges,

wherein the top face is parallel to the bottom face,

wherein the light output is from the top face;

a light source arranged to provide 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 to redirect 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 entering into the lightguide,

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

wherein the light source is arranged to enter the first light output and the second light output into the lightguide with a different angular direction of elevation,

wherein the angular direction of elevation is with respect to the plane of the top face and across the edge-to-edge direction,

wherein the first light output and the second light output entering into the lightguide result in different light output angles from the top face.

2. A backlight as claimed in claim 1, wherein the shape of the lightguide is a rectangle.

3. A backlight as claimed in claim 1, wherein the first light output and the second light output result in light which escapes from the lightguide with a different range of exit angles in a plane perpendicular to the plane of the top face.

4. A backlight as claimed in claim 3, wherein the first light output and the second light outputs are collimated in a plane extending between the side edges.

5. A backlight as claimed in claim 1, wherein the light out-coupling structures comprise prismatic strips which extend parallel to the side edges.

6. A backlight as claimed in 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 and the second light source is mounted at second source angle respect to the top face,

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

7. A backlight as claimed in claim 1,

wherein the light source comprises at least 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 light output angle into the lightguide,

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

8. A backlight as claimed in claim 7, wherein each of the beam shaping elements comprise:

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

9. A backlight as claimed in claim 1,

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

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

10. A backlight as claimed in claim 1, further comprising a light redirection over the top face of the lightguide.

11. A backlight as claimed in 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.

12. An autostereoscopic display device:

a backlight as claimed in claim 1; and

a display panel having an array of display pixels,

wherein the display panel illuminated by the backlight.

13. An autostereoscopic display device as claimed in claim 12, 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,

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

16. A backlight as claimed in claim 1, wherein the cross section of the lightguide, in the plane of the top face, is a rectangle.

17. A backlight as claimed in claim 5, wherein the prismatic strips extend parallel to the side edges.

18. A backlight as claimed in claim 7, wherein each of the beam shaping elements comprise:

dynamic beam shaping elements designed for a specific light output angle to the plane of the top face.

19. A privacy display comprising:

a backlight as claimed in claim 1; and

a display panel having an array of display pixels,

wherein the display panel illuminated by the backlight.

14. A method of controlling the direction of a light output from a backlight, comprising:

providing light into a lightguide which has top face and a bottom face, and a pair of opposite side edges, wherein the top face is parallel to the bottom face,

wherein the light is provided to at least one opposite side edge;

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

wherein the method comprises controlling the angular direction of elevation of the light entering the lightguide,

wherein the angular direction of elevation with respect to the plane of the top face across the edge-to-edge direction,

wherein each of at least a first light output and a second light output has a different angular direction,

wherein each of the at least first light output and the second light output entering the lightguide results in different light output angles from the top face.

15. A method of controlling an autostereoscopic display device, comprising:

controlling the direction of light output from a backlight using the method as claimed in claim 14;

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

controlling the image displayed by the display panel,

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

wherein the first light output enters 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,

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