Micro-Display Engine

• US 20070081256A1
• Filed: 10/03/2006
• Published: 04/12/2007
• Est. Priority Date: 02/18/2004
• Status: Active Grant

• Current Assignee: TDG Acquisition Company, LLC
• Original Assignee: Icuiti Corporation
• Inventors: Travers, Paul
• Granted Patent: US 7,397,607 B2
• Time in Patent Office: Days
• US Class Current: 359/630
• CPC Class Codes: G02B 2027/011 comprising device for correcting geometrical aberrations, distortion
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/144 using partially transparent surfaces without spectral selectivity G02B27/147 takes precedence
• CPC Class Codes: G02B 27/16 used as aids for focusing
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00

Abstract

Virtual displays with micro-display engines are arranged in compact, lightweight configurations that generate clear virtual images for an observer. The displays are particularly suitable for portable devices, such as head-mounted displays adapted to non-immersive or immersive applications. The non-immersive applications feature reflective optics moved out of the direct line of sight of the observer and provide for differentially modifying the amount or form of ambient light admitted from the forward environment with respect to image light magnified within the display. Micro-display engines suitable for both non-immersive and immersive display applications and having LCD image sources displace polarization components of the LCD image sources along the optical paths of the engines for simplifying engine design. A compound imaging system for micro-display engines features the use of reflectors in sequence to expand upon the imaging possibilities of the new micro-display engines. Polarization management also provides for differentially regulating the transmission of ambient light with respect to image light and for participating in the image formation function of the image source.

Claims

1. A micro-display engine comprising:

an image source and a reflective focusing optic aligned along a common optical axis;

a viewing aperture aligned with a viewing axis that is inclined to the common optical axis;

a polarization-sensitive beamsplitter located at an intersection of the viewing axis and the common optical axis;

a phase adjuster located along the common optical axis between the polarization-sensitive beamsplitter and the reflective focusing optic; and

the polarization-sensitive beamsplitter being arranged for transmitting image light generated by the image source along the common optical axis toward the reflective focusing optic;

the phase adjuster being arranged for rotating polarization of the image light transmitted through the polarization-sensitive beamsplitter en route to and from the reflective focusing optic; and

the polarization-sensitive beamsplitter being arranged for reflecting the polarization-rotated image light along the viewing axis toward the viewing aperture.

2. The engine of claim 1 in which the common optical axis extends in a substantially horizontal direction within a transverse plane that intersects an observer'"'"'s eyes and that includes the viewing axis.

3. The engine of claim 2 in which the beamsplitter includes an interface at which incident light is transmitted and reflected, and the beamsplitter interface extends substantially normal to the transverse plane.

4. The engine of claim 2 in which the image source includes an output plane that extends substantially normal to the transverse plane.

5. The engine of claim 1 in which the image source includes a controllable polarization rotator that is responsive to the application of a control signal for varying local polarization characteristics in an output plane and a polarizer that cooperates with the polarization rotator for producing a polarized image.

6. The engine of claim 5 in which the polarizer is spaced from the output plane.

7. The engine of claim 6 in which polarizer is incorporated into the polarization-sensitive beamsplitter.

8. The engine of claim 6 in which the reflective focusing optic forms a magnified virtual image of the output plane visible along the viewing axis.

9. The engine of claim 1 in which the image source includes a controllable polarization rotator that is responsive to the application of a control signal for varying local polarization characteristics in an output plane and first and second polarizers straddling the polarization rotator for producing a polarized image.

10. The engine of claim 9 in which the reflective focusing optic forms a magnified virtual image of the output plane visible along the viewing axis, and the second polarizer is spaced from the output plane outside the depth of field of the reflective focusing optic.

11. A micro-display engine comprising:

an image source including a controllable polarization rotator that is responsive to the application of a control signal for varying local polarization characteristics in an object plane for encoding an image and a polarizer that cooperates with the polarization rotator for converting the encoded image into a visible image;

an at least partially reflective focusing optic that forms a magnified virtual image of the object plane; and

the polarizer being spaced from the object plane along an image path of the reflective focusing optic for filtering light emitted from the object plane to produce the visible image substantially clear of imageable artifacts of the polarizer.

12. The engine of claim 11 further comprising a beamsplitter that directs image light emitted from the object plane a first direction toward the at least partially reflective focusing optic and that directs the reflected image light in a second direction for viewing.

13. The engine of claim 12 in which the beamsplitter is a polarizing beamsplitter and the polarizer is incorporated into the beamsplitter.

14. The engine of claim 13 further comprising a phase adjuster located between the beamsplitter and the reflective focusing optic.

15. The engine of claim 14 in which the phase adjuster is arranged for rotating polarization of the image light en route to and from the reflective focusing optic in the first direction so that the polarization rotated image light propagates from the beamsplitter in the second direction.

16. The engine of claim 12 further comprising a housing including a viewing aperture and an ambient-light-admitting aperture aligned in the second direction.

17. The engine of claim 16 further comprising an ambient-light-admitting adjuster that regulates the amount of ambient light transmitted between the ambient-light-admitting aperture and the viewing aperture along the second direction.

18. The engine of claim 17 in which the polarizer is a first of two polarizers, a first of the polarizers being incorporated into the beamsplitter for forming the polarized visible image and a second of the polarizers being located at the ambient-light-admitting adjuster for varying the amount of ambient light reaching the viewing aperture.

19. The engine of claim 18 in which the ambient-light-admitting adjuster varies a relative angular orientation of the first and second polarizers.

20. A virtual imaging display comprising:

an image source including a polarization-rotator that is responsive to the application of a control signal for varying local polarization characteristics of an optical output and a polarizer that cooperates with the polarization-rotator for producing a polarized image;

a magnifier that forms an enlarged image of the optical output of the polarization-rotator; and

the polarizer being spaced from a conjugate focus of the magnifier for filtering the optical output and producing the polarized image.

21. The display of claim 20 in which the polarization rotator has an output plane that is located at a conjugate focus of the magnifier.

22. The display of claim 21 in which the output plane of the polarization rotator is an object plane of the magnifier and the polarized image is a virtual image of the object plane.

23. The display of claim 20 further comprising a beamsplitter that directs the optical output of the polarization rotator to the magnifier and that directs a magnified image of the optical output of the polarization rotator to an observer.

24. The display of claim 23 in which the magnifier is a reflective focusing optic.

25. The display of claim 23 in which the magnifier forms an enlarged virtual image of the optical output of the polarization-rotator.

26. The display of claim 23 in which the beamsplitter is polarization sensitive and also functions as the polarizer.

27. The display of claim 26 further comprising a phase adjuster located between the beamsplitter and the magnifier.

28. The display of claim 27 in which the phase adjuster is arranged for rotating polarization of the optical output of the polarization rotator en route to and from the magnifier in a first direction so that the polarization rotated optical output propagates from the beamsplitter toward the observer in a second direction.

29. An imaging system comprising:

a polarization rotator comprising a plurality of controllable pixels that differentially rotate local polarization of image light appearing as different polarizations in an output plane;

a focusing optic focused on the output plane; and

a polarizer that is located beyond the depth of field of the focusing optic and that filters the different polarizations of the image light for producing an image.

30. The imaging system of claim 29 in which the focusing optic is arranged for producing a virtual image of the output plane.

31. The imaging system of claim 29 in which the focusing optic is a magnifier.

32. The imaging system of claim 29 in which the focusing optic is a reflective focusing optic.

33. The imaging system of claim 32 in which the reflective focusing optic produces an enlarged virtual image of the output plane.

34. The imaging system of claim 29 in which the polarizer is formed as a part of an at least partially reflective optic that directs image light from the output plane to the focusing optic.

35. The imaging system of claim 34 in which the partially reflective optic is a polarizing beamsplitter.

36. The imaging system of claim 34 in which the polarizing beamsplitter provides for directing an image of the output plane from the focusing optic to an observer.

37. An image source of a micro-display engine comprising:

a polarization rotator comprising a plurality of controllable pixels that differentially rotate local polarization of image light encoding an image in an output plane as different polarizations lacking contrast between the different polarizations;

a polarizer that is spaced apart from the output plane along a viewing pathway of the output plane and that filters the different polarizations of the image light for providing a view of the output plane that includes contrast between the different polarizations; and

the polarizer being spaced apart from the output plane by an amount that precludes the appearance of the encoded image as a real image on the polarizer.

38. The imaging system of claim 37 in which the pixels are separately controllable for rotating plane polarized light by different amounts to encode the image in the output plane.

39. The imaging system of claim 38 in which the linearly polarized light from one of the pixels is overlapped by the linearly polarized light from a plurality of adjacent pixels on the polarizer.

40. The imaging system of claim 39 in which the overlapping linearly polarized light on the polarizer appears as elliptical or randomly polarized light.

41. The imaging system of claim 37 further comprising a focusing optic that is focused on the output plane, and the polarizer being located beyond the depth of field of the focusing optic.

42. The imaging system of claim 41 in which the focusing optic is a magnifier.

43. The imaging system of claim 42 in which the focusing optic is a reflective focusing optic for enlarging the image encoded in the output plane as a virtual image in plane polarized light.

44. A micro-display engine comprising:

an image source for producing a real image;

a beamsplitter optically connected to the image source;

a pair of reflective optics optically connected in sequence by the beamsplitter for producing an enlargement of the real image as a virtual image that is visible through the beamsplitter.

45. The engine of claim 44 in which a first optical pathway connects the image source to a first of the pair of reflective optics by one of transmission through and reflection from the beamsplitter.

46. The engine of claim 45 in which a second optical pathway connects the first reflective optic to a second of the pair of reflective optics by the other of transmission through and reflection from the beamsplitter.

47. The engine of claim 46 in which a third optical pathway provides for connecting the second reflective optic with a viewing aperture by the one of transmission through and reflection from the beamsplitter.

48. The engine of claim 47 in which the beamsplitter is a polarizing beamsplitter.

49. The engine of claim 48 in which a first phase adjuster is located along a common portion of the first and second optical pathways between the beamsplitter and the first reflective optic.

50. The engine of claim 49 in which a second phase adjuster is located along a common portion of the second and third optical pathways between the beamsplitter and the second reflective optic.

51. The engine of claim 48 in the image source forms the real image with image light, and the image light propagating along the first optical pathway is polarized before encountering the beamsplitter to avoid directing the image light toward the viewing aperture before encountering the pair of reflective optics.

52. The engine of claim 44 in which one of the reflective optics has a nominally planer reflective surface and the other of the reflective optics has a non-planar reflective surface.

53. The engine of claim 44 in which both of the reflective optics have non-planer reflective surfaces for contributing to the magnification of the virtual image.

54. The engine of claim 53 in which at least one of the reflective optics has an aspheric reflective surface for contributing to a focusing function for enhancing a view of the virtual image.

55. A compound imaging system of a micro-display engine comprising:

a beamsplitter for transmitting and reflecting light in different directions;

first and second reflective optics for imaging light emitted from an image source through a viewing aperture;

a first of optical pathway from the image source to the first reflective optic by one of transmission through and reflection from the beamsplitter;

a second optical pathway connecting the first reflective optic to the second reflective optic by the other of transmission through and reflection from the beamsplitter; and

a third optical pathway for connecting the second reflective optic to the viewing aperture by the one of transmission through and reflection from the beamsplitter.

56. The imaging system of claim 55 in which the beamsplitter is polarization sensitive.

57. The imaging system of claim 56 in which the beamsplitter transmits and reflects the light emitted by the image source in accordance with a polarization state of the light.

58. The imaging system of claim 57 in which the polarizer is a polarizing beamsplitter.

59. The imaging system of claim 58 further comprising a phase adjustment system for sequentially varying the polarization state of the light between encounters with the beamsplitter along the first, second, and third optical pathways.

60. The imaging system of claim 55 in which one of the reflective optics has a nominally planer reflective surface and the other of the reflective optics has a non-planar reflective surface.

61. The imaging system of claim 55 in which both of the reflective optics have non-planer reflective surfaces for contributing to the magnification of the virtual image.

62. The imaging system of claim 61 in which at least one of the reflective optics has an aspheric reflective surface for contributing to a focusing function for enhancing a view of the virtual image.