Display having particular polarisation modifying layer

• US 7,400,377 B2
• Filed: 12/07/2005
• Issued: 07/15/2008
• Est. Priority Date: 12/14/2004
• 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: Evans, Allan, Tillin, Martin D., Walton, Emma J.
• Primary Examiner(s): QI, ZHI QIANG
• Application Number:
  US11/299,068
• Publication Number:
  US 20060126156A1
• Time in Patent Office: 951 Days
• Field of Search: 349/194, 349/9, 349/141, 349/61, 359/320
• US Class Current: 349/194
• CPC Class Codes: G02F 1/1323 Arrangements for providing a switchable viewing angle
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133631 with a spatial distribution of the retardation value
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 1/13471 in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells G02F1/13475 takes precedence
• CPC Class Codes: H04N 13/359 Switching between monoscopic and stereoscopic modes

Abstract

A display is provided for providing a restricted viewing mode, for example a private viewing mode where the display may be viewed from a limited region of space by a single viewer and not by other people outside the viewing region. The display comprises a source of polarised light and an output polariser. Between these are provided a controllable pixellated spatial polarisation modulating layer, for example of the liquid crystal type. Also, a polarisation modifying layer is provided between the polarisers and is spaced from the modulating layer. The modifying later comprises a plurality of sets of regions with the regions of each set having the same polarisation modifying effect and the regions of different sets having different polarisation modifying effects. The light path between the modulating layer and the modifying layer is polariser-free. A controller supplies modified image data to compensate for the effect of each region through which light from one or more associated pixels passes to the viewing region so that a viewer in the viewing region sees the displayed image. Outside the viewing region, light passes through regions for which the pixels receive uncompensated data so that the image is obscured or corrupted and is not visible. The modifying layer may be disablable in order to provide a public viewing mode for viewers throughout a wide viewing region.

Claims

1. A display comprising:

a polarisation modulating layer having a plurality of controllable pixels;

a first polariser disposed at a side of a display surface of the polarisation modulating layer;

a source of light disposed at a side of a back of the polarisation modulating layer; and

a polarisation modifying layer disposed between the source and the first polariser and spaced from the polarisation modulating layer,

wherein;

the polarisation modifying layer has at least a first region and a second region,

the polarisation modulating layer includes a single pixel or a plurality of pixels and has a first pixel associated with the first region and a second pixel associated with the second region,

in each of a first set including the first pixel and the first region and a second set including the second pixel and the second region, each region of the polarisation modulating layer has a same polarisation modifying effect, and

between different sets, such as a set including the first pixel and the second region or a set including the second pixel and the first region, each region of the polarisation modulating layer has a different polarisation modifying effect.

2. A display as claimed in claim 1, further comprising a second polariser between the polarisation modulating layer and the source of light.

3. A display as claimed in claim 1, wherein the polarisation modulating layer comprises a liquid crystal layer.

4. A display as claimed in claim 1, wherein the first region of the polarisation modifying layer has substantially no polarisation modifying effect.

5. A display as claimed in claim 4, wherein the first region of the polarisation modifying layer comprises a Freedericksz cell with an alignment direction oriented substantially parallel to a transmission axis of the first polariser.

6. A display as claimed in claim 1, wherein the second region of the polarisation modifying layer is arranged to change a polarisation of light passing therethrough by 90°

.

7. A display as claimed in claim 6, wherein the second region of the polarisation modifying layer comprises a retarder.

8. A display as claimed in claim 6, wherein the second region of the polarisation modifying layer comprises a polarisation rotator.

9. A display as claimed in claim 8, wherein the polarisation rotator is a twisted nematic liquid crystal polarisation rotator.

10. A display as claimed in claim 6, wherein the second region of the polarisation modifying layer comprises a Freedericksz cell with an alignment direction oriented at substantially 45°

to a transmission axis of the first polariser.

11. A display as claimed in claim 1, further comprising a controller arranged to supply, to each pixel, image data modified so as to compensate for the polarisation modifying effect of the polarisation modifying layer.

12. A display as claimed in claim 11, wherein the controller is arranged to supply, to each pixel, the image data representing a difference between a pixel polarisation change for selecting a desired pixel grey level and a polarisation change produced by the polarisation modifying layer.

13. A display as claimed in claim 1, wherein the display provides a private viewing mode in which visibility of a displayed image is restricted to a limited region of space sufficient only for a viewer to view the image.

14. A display as claimed in claim 13, wherein the polarisation modifying layer is disablable to provide a public viewing mode in which the displayed image is visible throughout an extended region of space larger than the limited region.

15. A display as claimed in claim 14, wherein, in the public viewing mode, the regions of all of the sets are arranged to have substantially a same polarisation modifying effect.

16. A display as claimed in claim 15, wherein, in the public viewing mode, the regions of all of the sets are arranged to have substantially no polarisation modifying effect.

17. A display as claimed in claim 1, wherein the polarisation modifying layer comprises a liquid crystal layer.

18. A display as claimed in claim 17, wherein the polarisation modifying layer comprises a patterned electrode defining the regions.

19. A display as claimed in claim 18, wherein the polarisation modifying layer comprises a Freedericksz cell, a twisted nematic layer, or a twisted vertically aligned nematic layer.

20. A display as claimed in claim 1, wherein the polarisation modulating layer is arranged to output light of substantially linear polarisation for all pixel grey levels.

21. A display as claimed in claim 20, wherein the polarisation modifying layer comprises a half wave plate having optic axes which are differently oriented in the regions of the different sets.

22. A display as claimed in claim 21, wherein the polarisation modifying layer is disposed between the modulating layer and the half wave plate.

23. A display as claimed in claim 20, wherein the polarisation modulating layer is of an in-plane switching liquid crystal type.

24. A display as claimed in claim 20, wherein the polarisation modulating layer is a liquid crystal switchable between a substantially vertical alignment and a substantially horizontal alignment.

25. A display as claimed in claim 24, wherein the regions of the different sets provide different retardations.

26. A display as claimed in claim 1, wherein the pixel of the polarisation modulating layer is disposed as a composite colour group which is repeated in a row direction of the display.

27. A display as claimed in claim 26, wherein each of the regions is aligned in a viewing direction using a set of a composite colour group (R, G, B) with at least one pixel at each end of a set of the composite colour group being arranged to display a fixed brightness.

28. A display as claimed in claim 27, wherein the fixed brightness is substantially equal to 50% of a maximum brightness.

29. A display as claimed in claim 27, wherein the at least one pixel comprises a blue pixel (B).

30. A display as claimed in claim 27, wherein the at least one pixel comprises red and blue pixels (R, B).

31. A display as claimed in claim 27, wherein the at least one pixel comprises a composite colour group (R, G, B).

32. A display as claimed in claim 1, wherein the display provides an optical decoding mode for viewing encoded image data.

33. A display as claimed in claim 32, wherein the polarisation modifying layer is disablable to provide a plane viewing mode for viewing non-encoded image data.

34. A display as claimed in claim 1, wherein:

the polarisation modifying layer further comprises a third region, and

the polarisation modulating layer includes a single pixel or a plurality of pixels and has a third pixel associated with the third region, and

the display comprises a third set including the third pixel and the third region.