Optical system and display

1. An optical system for varying the shape of a surface in which an image is perceived, the optical system comprising first and second spaced-apart partial reflectors, at least one of which is selectively switchable between a non-flat first shape and at least one second shape different from the first shape, and providing a doubly reflected light path, where light incident on the first reflector is first at least partially transmitted through the first reflector towards the second reflector, then at least partially reflected from the second reflector back towards the first reflector, then again at least partially reflected from the first reflector towards the second reflector, and finally at least partially transmitted through the second reflector.

2. A system as claimed in claim 1 , in which the optical system is arranged substantially to prevent emission from the second reflector of light not reflected during reflection by the first and second reflectors, wherein light incident on the second partial reflector for the first time does not leave the optical system.

3. A system as claimed in claim 1 , in which the second shape is flat.

4. A system as claimed in claim 1 , in which the second shape is non-flat.

5. A system as claimed in claim 1 , in which the at least one of the first and second reflectors which is selectively switchable comprises one of the first and second reflectors and the other of the first and second reflectors is of fixed shape.

6. A system as claimed in claim 5 , in which the fixed shape is flat.

7. A system as claimed in claim 5 , in which the fixed shape is non-flat.

8. A system as claimed in claim 1 , in which the other of the first and second reflectors is selectively switchable between a non-flat third shape and a fourth shape different from the third shape.

9. A system as claimed in claim 8 , in which the fourth shape is flat.

10. A system as claimed in claim 8 , in which the fourth shape is non-flat.

11. A system as claimed in claim 8 , in which the third shape is a mirror image of the first shape.

12. A system as claimed in claim 8 , in which the fourth shape is a mirror image of the second shape.

13. A system as claimed in claim 1 in which the first and/or third shape is continuously curved in at least one direction for producing a concave or convex image.

14. A system as claimed in claim 1 , in which the first and/or third shape comprises a plurality of flat segments, adjacent ones of which abut each other along an edge and subtend an angle greater than 0° and less than 180°.

15. A system as claimed in claim 1 , in which the first and/or third shape has a serpentine cross-section.

16. A system as claimed in claim 1 , in which the first and/or third shape is planar but tilted in at least one direction.

17. A system as claimed in claim 1 , in which the first and/or third shape has flat and non-flat regions.

18. A system as claimed in claim 1 , in which the first and/or third shape comprises a plurality of flat and/or non-flat regions which are non-coplanar.

19. A system as claimed in claim 1 , in which the first and third shapes are of an at least similar shape and everywhere parallel to each other.

20. A system as claimed in claim 1 , in which the optical system is arranged to change the polarisation of light during passage along the light path.

21. A system as claimed in claim 20 , in which the optical system is arranged to change the polarisation of light during passage along the light path between incidence on the second reflector and reflection from the first reflector.

22. A system as claimed in claim 1 , including a lens arrangement for at least partially correcting for image distortion.

23. A system as claimed in claim 1 , comprising at least one quarter wave plate.

24. A system as claimed in claim 23 , in which the quarter wave plate or a second of the quarter wave plates is disposed between the first and second reflectors.

25. A system as claimed in claim 23 , in which the quarter wave plate or a first of the quarter wave plates is disposed on a side of the first reflector opposite the second reflector.

26. A system as claimed in claim 1 , in which the first reflector comprises a first partial mirror.

27. A system as claimed in claim 26 , in which the first partial mirror comprises a patterned mirror associated with an array of converging lenses.

28. A system as claimed in claim 26 , in which the quarter wave plate or the second of the quarter wave plates and the patterned mirror form an integrated cell.

29. A system as claimed in claim 28 , in which the quarter wave plate or the second of the quarter wave plates is patterned and has retarding portions disposed on reflector regions of the patterned mirror and non-retarding portions disposed on transparent regions of the patterned mirror.

30. A system as claimed in claim 1 , in which the first reflector comprises a first reflective polariser.

31. A system as claimed in claim 1 , in which the second reflector comprises a second reflective polariser.

32. A system as claimed in claim 31 , in which the second reflective polariser comprises a cholesteric reflector.

33. A system as claimed in claims 31 , in which the second reflective polariser is non-flat and in which the system comprises a first prism film arranged to redirect light from the first partial reflector to be incident substantially normally on the second reflective polariser.

34. A system as claimed in claim 33 , comprising a second prism film arranged to redirect light from the second reflective polariser to the direction of light incident on the first prism film.

35. A system as claimed in claim 1 , in which the second reflector comprises a second partial mirror.

36. A system as claimed in claim 1 , comprising a Faraday rotator.

37. A system as claimed in claim 36 , in which the Faraday rotator is arranged to provide 45° of polarisation rotation.

38. A system as claimed in claim 1 , comprising an input linear polariser.

39. A system as claimed in claim 1 , comprising an output linear polariser.

40. A display comprising: a display device for modulating light with an image or sequence of images at an image display surface of the device; and an optical system as claimed in claim 1 , the first reflector being disposed between the device and the second reflector.

41. A display as claimed in claim 40 , in which the device comprises one of a liquid crystal device, a projection display device, an organic light emitting diode device, a plasma light emitting device and a cathode ray tube.

42. A display as claimed in claim 40 , comprising at least one of an instrument display, an advertising display, an immersive display, an amusement display and a television display.

43. A display as claimed in claim 40 , comprising an image processor for remapping image pixels to correct at least partially for image distortion by the or each non-flat one of the first and second reflectors.

44. A display as claimed in claim 40 , comprising an image processor for remapping colour channels of image pixels to correct at least partially for light exiting the optical system along an unintended light path.

45. A display as claimed in claim 40 , comprising an image processor for manipulating grey levels of image pixels to increase at least partially the apparent brightness of at least part of the image.

46. A display as claimed in claim 40 , in which the optical system comprises a removable attachment attached to the device.

47. A display as claimed in claim 40 , including a touch panel.