Directional backlight, a multiple view display and a multi-direction display

• US 8,154,686 B2
• Filed: 01/21/2005
• Issued: 04/10/2012
• Est. Priority Date: 01/20/2004
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Mather, Jonathan, Barratt, Neil, Kean, Diana U., Walton, Emma J., Bourhill, Grant, Powell, Thomas Wynne
• Primary Examiner(s): Stahl, Mike
• Application Number:
  US11/814,383
• Publication Number:
  US 20090040426A1
• Time in Patent Office: 2,636 Days
• Field of Search: None
• US Class Current: 349/65
• CPC Class Codes: B60K 35/654 the user being the driver
• CPC Class Codes: B60K 35/656 the user being a passenger
• CPC Class Codes: G02B 6/0011 the light guides being planar or of plate-like form
• CPC Class Codes: G02F 1/1323 Arrangements for providing a switchable viewing angle
• CPC Class Codes: G02F 1/1335 Structural association of cells with optical devices, e.g. polarisers or reflectors
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: H04N 13/312 the parallax barriers being placed behind the display panel, e.g. between backlight and spatial light modulator [SLM]

Abstract

A directional backlight, a multiple view display and a multi-direction display A multiple view display (18) comprises a directional display device (19) for displaying a first image or sequence of images so as to be mainly visible from a first range of directions relative to the device and for simultaneously displaying a second image or sequence of images so as to be mainly visible from a second range of directions relative to the device different from the first range. The display (18) further comprises a directional backlight (20) for directing light through the display device (19) at least mainly in the first and second ranges. Since the directional backlight (20) directs light through the display device (19) at least mainly in the first and second ranges, the display provides users located in the first and second ranges with images of greater intensity than a conventional display. The backlight may be arranged to direct substantially no light in at least part of a third range of directions that lies between the first range of directions and the second range of directions. This provides a ‘black window’ between the first and second ranges in which the intensity of the display is lower than in other ranges. The intensity of the display in the black window is possibly zero, or close to zero, so that an observer located in this window will not perceive an image.

Claims

1. A directional backlight comprising a light source for emitting light that is at least partially collimated, and an optical arrangement for splitting the light from the light source and directing the light from the light source simultaneously in at least mainly a first range of directions and a second range of directions different from the first range of directions;

wherein the optical arrangement comprises a plurality of prisms, the prisms are arranged as an array of variable pitch, and the prisms have a prism angle greater than 70 degrees.

2. A backlight as claimed in claim 1 wherein the prisms have a prism angle of less than 110°

.

3. A backlight as claimed in claim 1 wherein the prisms have a prism angle of approximately 83°

.

4. A backlight as claimed in claim 1, in which the light source is arranged to supply at least partially collimated light.

5. A backlight as claimed in claim 4, in which the light source comprises a plurality of apertures aligned with imaging elements.

6. A backlight as claimed in claim 5, in which the apertures are separated by reflectors for reflecting light.

10. A backlight as claimed in claim 1 wherein the optical arrangement is arranged to direct light from the light source at least mainly in the first range of directions, the second range of directions, a third range of directions and a fourth range of directions, the third range of directions being different from the first range of directions and the second range of directions and the fourth range of directions being different from the first range of directions, the second range of directions and the third range of directions.

11. A display comprising:

a display device for displaying at least a first image or first sequence of images; and

a directional backlight as defined in claim 1 for directing light through the device at least mainly in a first range of directions relative to the device and a second range of directions relative to the device different from the first range of directions.

12. A display as claimed in claim 11 wherein the display device is a directional display device for displaying the first image or sequence of images so as to be mainly visible from the first range of directions relative to the device and for simultaneously displaying a second image or sequence of images so as to be mainly visible from the second range of directions relative to the device.

13. A display as claimed in claim 11, in which the first and second ranges are on opposite sides of the normal to a display surface of the device.

14. A display as claimed in claim 13, in which the first and second ranges are substantially symmetrical with respect to the normal.

15. A display as claimed in claim 12, in which the first image is substantially not visible from the second range.

16. A display as claimed in claim 12, in which the second image is substantially not visible from the first range.

17. A display as claimed in claim 11, in which the first and second ranges are separated by a third range of directions.

18. A display as claimed in claim 17, in which the backlight is arranged to direct substantially no light in at least part of the third range.

19. A display as claimed in claim 12 in which the second image or sequence of images is spatially multiplexed with the first image or sequence of images.

25. A display as claimed in claim 17 wherein the first image or sequence of images is spatially multiplexed with the second image or sequence of images.

26. A display as claimed in claim 11, in which the centres of the first and second ranges subtend an angle at the device of between 20°

and 140°

.

27. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of less than 130°

.

28. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of less than 120°

.

29. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of less than 110°

.

30. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of less than 100°

.

31. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of less than 90°

.

32. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of greater than 30°

.

33. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of greater than 40°

.

34. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of greater than 50°

.

35. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of greater than 60°

.

36. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of greater than 70°

.

37. A display as claimed in claim 26, in which the centres of the first and second ranges subtend an angle at the device of approximately 80°

.

38. A display as claimed in claim 11 and comprising a liquid crystal display device.

7. A directional backlight comprising a light source, and an optical arrangement for splitting the light from the light source and directing the light from the light source at least mainly in a first range of directions and a second range of directions, the first and second range of directions being on a same side of the optical arrangement, wherein light mainly directed in the second range of directions is non-parallel to and non-overlapping with light mainly directed in the first range of directions,

the first and second range of directions correspond to a first image and a second image, respectively, and the first and second images can be different from each other;

wherein the optical arrangement comprises a waveguide having a plurality of diffusive regions and an array of imaging elements disposed in the optical path of light from the waveguide.

8. A backlight as claimed in claim 7 wherein the light source extends substantially along one side face of the waveguide.

9. A backlight as claimed in claim 8 wherein the directional backlight comprises a second light source, the second light source extending substantially along another side face of the waveguide.

20. A multi-directional two-dimensional display comprising:

a display device for displaying a single image at a time, which image is visible throughout a range of directions including first and second ranges for first and second viewers, the first and second ranges being disposed on opposite sides of and spaced from the normal to a display surface of the device; and

a directional backlight for directing light through the device with higher intensity in the first and second ranges than in a third range including the normal;

wherein the directional backlight comprises a light source arranged to supply at least partially collimated light and a prism structure comprising truncated prisms composed of non-curved surfaces to allow the intensity in the third range to be non-zero.

21. A display as claimed in claim 20, in which the first and second ranges are substantially symmetrical with respect to the normal.

22. A display as claimed in claim 20, in which the backlight is switchable between a first mode, in which light is mainly directed in the first range, and a second mode, in which light is mainly directed in the second range.

23. A display as claimed in claim 22, comprising a controller for repeatedly switching the backlight between the first and second modes and for controlling the device to display a first image or sequence of images when the backlight is in the first mode and a second image or sequence of images when the backlight is in the second mode.

24. A display as claimed in claim 20, in which the backlight comprises first and second light sources disposed at opposite edges of a substantially rectangular generally planar light guide.