Image display apparatus and head mount display

• US 20060268421A1
• Filed: 05/25/2006
• Published: 11/30/2006
• Est. Priority Date: 05/30/2005
• Status: Active Grant

• Current Assignee: Konica Minolta Holdings Incorporated (Konica Minolta Inc.)
• Original Assignee: Konica Minolta Holdings Incorporated (Konica Minolta Inc.)
• Inventors: Endo, Takeshi, Tanijiri, Yasushi, Shimizu, Yoshie, Noda, Tetsuya
• Granted Patent: US 7,405,881 B2
• Time in Patent Office: Days
• US Class Current: 359/630
• CPC Class Codes: G02B 2027/0112 comprising device for genereting colour display
• CPC Class Codes: G02B 2027/0174 holographic
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0103 comprising holographic elements
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G03H 2001/2231 Reflection reconstruction

Abstract

The light directed from a light source to a concave mirror and the light directed from a display device to an eyepiece optical system are intersected by each other in a layout. This allows the light source, the concave mirror, and the display device to be arranged in compactness adjacent to the eyepiece optical system without increasing the optical power of an illumination optical system. As the result, the apparatus can easily be minimized in the thickness or the overall size. A hologram optical element is provided where the relationship between the wavelength range Δλ1 at half of the diffraction efficiency of each of the three primary colors of the light in the hologram optical element and the wavelength range Δλ2 at half of the intensity of each of the three primary colors of the light emitted from the light source is defined by Δλ1<Δλ2. Accordingly, a component at desired wavelengths of each of the R, G, and B colors of the light emitted from the light source can be diffracted by the action of the hologram optical element and then directed to the pupil of the viewer. This allows the image to be increased in the color reproduction area and improved in the quality regardless of the display device actuated in a time-division mode.

Claims

1. An image display apparatus comprising:

an illumination optical system;

a reflective type display device for displaying an image by modulating illumination light from the illumination optical system; and

an eyepiece optical system for directing image light from the reflective type display device to a pupil of a viewer,

the illumination optical system comprising;

a light source for emitting light; and

an optical-path bending member for bending an optical path leading from the light source to the reflective type display device,

wherein the optical-path bending member is so arranged that a ray of light traveling from the light source to the optical-path bending member and a ray of light traveling further on a same optical path as said ray of light from the reflective type display device to the eyepiece optical system cross each other in a medium located outside the eyepiece optical system and having a substantially uniform index of refraction.

2. An image display apparatus according to claim 1, wherein

the medium arranged substantially uniform in the index of refraction is air.

3. An image display apparatus according to claim 1, wherein

the medium arranged substantially uniform in the index of refraction is an illumination prism whose index of refraction n is defined by 1.4<

n<

2.0.

4. An image display apparatus according to claim 3, wherein

the illumination prism has two sides thereof arranged across which the light directed from the reflective type display device to the eyepiece optical system runs in a sequence, and

the two sides are arranged planer and not parallel to each other.

5. An image display apparatus according to claim 3, wherein

the illumination prism has two sides thereof arranged across which the light directed from the reflective type display device to the eyepiece optical system runs in a sequence, and

at least one of the two sides is arranged arcuate as having an optical power.

6. An image display apparatus according to claim 1, wherein

the optical-path bending member is located at the side opposite to the light source about the optical path which extends from the reflective type display device to the eyepiece optical system.

7. An image display apparatus according to claim 1, wherein

the optical-path bending member is arranged to bend the optical path, which extends from the light source to the reflective type display device, on the plane arranged parallel to the short side of the reflective type display device and vertical to the screen of the reflective type display device.

8. An image display apparatus according to claim 1, wherein

the optical-path bending member is a reflective mirror.

9. An image display apparatus according to claim 8, wherein

the reflective mirror is of a concave mirror type for reflecting and converging the incoming light.

10. An image display apparatus according to claim 9, wherein

the concave mirror is a cylindrical concave mirror for reflecting and converging the incoming light on the plane arranged parallel to the short side of the reflective type display device and vertical to the screen of the reflective type display device.

11. An image display apparatus according to claim 1, wherein

the illumination optical system includes a first polarizer for passing a desired polarized component of the light of which the optical path is bent by the optical-path bending member and directing the same to the reflective type display device, and

the eyepiece optical system includes:

an eyepiece prism for reflecting and advancing the incoming light in the its interior; and

a second polarizer for passing, of light incident from the reflective type display device, another polarized component of the light which is orthogonal to the desired polarized component and directing the same to the eyepiece prism.

12. An image display apparatus according to claim 11, wherein

the first polarizer is provided at the surface with an anti-reflection coating.

13. An image display apparatus according to claim 11, wherein

the illumination optical system includes a third polarizer for passing, of the light emitted from the light source, a polarized component of the light which is identical to the desired polarized component passed through the first polarizer and directing the same to the optical-path bending member.

14. An image display apparatus according to claim 13, wherein

the third polarizer is located at the light source side about the optical path which extends from the reflective type display device to the eyepiece optical system.

15. An image display apparatus according to claim 13, wherein

both the first and third polarizers are arranged to pass a P polarized component of the light.

16. An image display apparatus according to claim 11, wherein

the illumination optical system includes a diffuser plate for diffusing the light of which the optical path is bent by the optical-path bending member.

17. An image display apparatus according to claim 16, wherein

the diffuser plate and the first polarizer are located in this order from the optical-path bending member side across the optical path between the optical-path bending member and the reflective type display device.

18. An image display apparatus according to claim 16, wherein

the diffuser plate is a volume phase type hologram optical element.

19. An image display apparatus according to claim 3, wherein

the illumination optical system includes a first polarizer for passing a desired polarized component of the light of which the optical path is bent by the optical-path bending member and directing the same to the reflective type display device, and

the first polarizer is bonded to the illumination prism between the illumination prism and the optical-path bending member.

20. An image display apparatus according to claim 19, wherein

the illumination optical system includes a diffuser plate for diffusing the light of which the optical path is bent by the optical-path bending member, and

the diffuser plate is supported by the illumination prism across the first polarizer.

21. An image display apparatus according to claim 20, wherein

the optical-path bending member is supported by the illumination prism across the diffuser plate and the first polarizer.

22. An image display apparatus according to claim 19, wherein

the illumination prism has a side thereof arranged of a planer or cylindrical shape to which the first diffuser is bonded.

23. An image display apparatus according to claim 19, wherein

the eyepiece optical system includes:

an eyepiece prism for reflecting and advancing the incoming light in the its interior; and

a second polarizer for passing, of the light exiting from the reflective type display device, another polarized component of the light which is orthogonal to the desired polarized component and directing the same to the eyepiece prism, the second polarizer located between the illumination prism and the eyepiece prism.

24. An image display apparatus according to claim 23, wherein

the second polarizer is bonded the illumination prism.

25. An image display apparatus according to claim 24, wherein

the eyepiece prism is supported by the illumination prism across the second polarizer.

26. An image display apparatus according to claim 24, wherein

the illumination prism has a side thereof arranged of a planer or cylindrical shape to which the second polarizer is bonded.

27. An image display apparatus according to claim 1, wherein

providing a reference axis extending between the center of the screen of the reflective type display device and the center of the pupil across the optical path which extends from the reflective type display device across the eyepiece optical system to the pupil,

the reflective type display device is arranged with its display screen tilting towards the reference axis between the reflective type display device and the eyepiece optical system.

28. An image display apparatus according to claim 27, wherein

when the angle of incidence is θ

at which the light of which the optical path is bent by the optical-path bending member enters the reflective type display device, it is defined by 10°

<

θ

<

60°

.

29. An image display apparatus according to claim 1, wherein

the light source includes at least one set of point light sources which emit different wavelengths of the light respectively, and

the point light sources are aligned along the direction parallel to the long side of the reflective type display device.

30. An image display apparatus according to claim 29, wherein

the light source includes an even number of sets of the point light sources, and

any two adjacent sets of the point light sources are opposite to each other in the order of the point light sources along the direction parallel to the long side of the reflective type display device.

31. An image display apparatus according to claim 1, wherein

the reflective type display device is a reflective type ferroelectric liquid crystal display device.

32. An image display apparatus according to claim 31, wherein

the eyepiece optical system includes a reflective type hologram optical element for enlarging the image receive from the reflective type display device and directing the same as a virtual image to the eyes of the viewer.

33. A head-mount display comprising:

an image display apparatus; and

a supporting member for supporting the image display apparatus at the front of a viewer,

the image display apparatus comprising;

an illumination optical system;

a reflective type display device for displaying an image by modulating illumination light from the illumination optical system; and

an eyepiece optical system for directing image light from the reflective type display device to a pupil of a viewer,

the illumination optical system comprising;

a light source for emitting light; and

an optical-path bending member for bending an optical path leading from the light source to the reflective type display device,

wherein the optical-path bending member is so arranged that a ray of light traveling from the light source to the optical-path bending member and a ray of light traveling further on a same optical path as said ray of light from the reflective type display device to the eyepiece optical system cross each other in a medium located outside the eyepiece optical system and having a substantially uniform index of refraction.

34. An image display apparatus comprising:

a light source for emitting a light at different wavelengths corresponding to the three primary colors;

a display device for displaying an image through modulating the light emitted from the light source at each pixel; and

an eyepiece optical system for directing the image received from the display device to the pupil of a viewer, wherein

each pixel in the display device is driven in a time-division mode in response to each of the three primary colors of the light emitted in a time-division sequence from the light source, and

the eyepiece optical system includes a hologram optical element for diffracting the light at difference wavelengths corresponding to the three primary colors emitted from the light source, and

when the wavelength range at half of the diffraction efficiency of each of the three primary colors of the light in the hologram optical element and the wavelength range at half of the intensity of each of the three primary colors of the light emitted from the light source are Δ

λ

1 and Δ

λ

2 respectively, a relation of Δ

λ

1<

Δ

λ

2 is established for each of the three primary color.

35. An image display apparatus according to claim 34, wherein

a relation of Δ

λ

1<

20 nm is established for each of the three primary color.

36. An image display apparatus according to claim 34, wherein

a relation of Δ

λ

1≦

10 nm is established for each of the three primary color.

37. An image display apparatus according to claim 34, wherein

the hologram optical element is fabricated by exposing a hologram photo-sensitive material coated on a substrate to light, and

the hologram photo-sensitive material is a single-layer color photo-polymer which is sensitive to all the three primary colors of the light.

38. An image display apparatus according to claim 34, wherein

a relation of Δ

λ

1>

3 nm is established for each of the three primary color.

39. An image display apparatus according to claim 34, wherein

a relation of 1/10<

Δ

λ

1/Δ

λ

2<

1 is established for each of the three primary color.

40. An image display apparatus according to claim 34, wherein

the peak wavelength at the diffraction efficiency of each of the three primary colors in the hologram optical element stays in the wavelength range at half of the intensity of the light emitted from the light source.

41. An image display apparatus according to claim 40, wherein

when the peak wavelength at the diffraction efficiency of each of the three primary colors of the light in the hologram optical element and the peak wavelength at the intensity of each of the three primary colors of the light emitted from the light source are λ

1 and λ

2 respectively, λ

1 is in a range of λ

2±

20 nm.

42. An image display apparatus according to claim 34, wherein

the display device is a ferroelectric liquid crystal display device.

43. An image display apparatus according to claim 42, wherein

the ferroelectric liquid crystal device is of a reflective type.

44. An image display apparatus according to claim 43, further comprising:

an optical-path bending member for bending the optical path which extends from the light source to the reflective type display device, wherein

the optical-path bending member is arranged so that the light directed from the light source to the optical-path bending member and the light directed from the reflective type display device to the eyepiece optical system are intersected by each other, and

when the angle of incidence is θ

at which the light received from the light source through the optical-path bending member enters the reflective type display device, a relation of 10°

<

θ

<

60°

is established.

45. An image display apparatus according to claim 42, wherein

the ferroelectric liquid crystal display device is of a transmissive type.

46. An image display apparatus according to claim 45, wherein

the hologram optical element is fabricated by exposing a hologram photo-sensitive material coated on a substrate to light, and

the hologram photo-sensitive material is a three-layer color photo-polymer of which the three layers are sensitive to the three primary colors of the light respectively.

47. An image display apparatus according to claim 34, wherein

the hologram optical element has a positive optical power at axially asymmetry.

48. An image display apparatus according to claim 34, wherein

the diffraction efficiency for each of the three primary colors of the light in the hologram optical element is determined in response to the intensity of each of the three primary colors of the light emitted from the light source.

49. An image display apparatus according to claim 34, wherein

the displacement of the peak position of the intensity in the optical pupil formed by the eyepiece optical system is not greater than 1 mm between any two of the three primary colors.

50. An image display apparatus according to claim 34, wherein

the hologram optical element is a combiner for directing both the light of the image received from the display device and the ambient light at the same time to the pupil of the viewer.

51. An image display apparatus according to claim 34, wherein

the eyepiece optical system includes a first transparent substrate for fully reflecting the light of the image received from the display device and passing the same across the hologram optical element to the pupil of the viewer while passing the ambient light directly to the pupil of the viewer.

52. An image display apparatus according to claim 51, wherein

the eyepiece optical system includes a second transparent substrate for canceling the refraction of the ambient light at the first transparent substrate.

53. A head-mount display comprising:

an image display apparatus; and

a supporting member for supporting the image display apparatus at the front of a viewer, wherein

the image display apparatus includes;

a light source for emitting a light at different wavelengths corresponding to the three primary colors;

a display device for displaying an image through modulating the light emitted from the light source at each pixel; and

an eyepiece optical system for directing the image received from the display device to the pupil of a viewer,

each pixel in the display device is driven in a time-division mode in response to each of the three primary colors of the light emitted in a time-division sequence from the light source,

the eyepiece optical system includes a hologram optical element for diffracting the light at difference wavelengths corresponding to the three primary colors emitted from the light source, and

when the wavelength range at half of the diffraction efficiency of each of the three primary colors of the light in the hologram optical element and the wavelength range at half of the intensity of each of the three primary colors of the light emitted from the light source are Δ

λ

1 and Δ

λ

2 respectively, a relation of Δ

λ

1<

Δ

λ

2 is established for each of the three primary color.