Image display apparatus

• US 20020034016A1
• Filed: 02/28/2000
• Published: 03/21/2002
• Est. Priority Date: 03/04/1999
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Inoguchi, Kazutaka, Yamazaki, Shoichi, Takagi, Akinari, Morishima, Hideki
• Granted Patent: US 6,480,337 B2
• Time in Patent Office: Days
• US Class Current: 359/630
• CPC Class Codes: G03B 21/10 Projectors with built-in or built-on screen

Abstract

An image display apparatus has a light source, a reflective display device, an illumination optical system for guiding light from the light source to the display device to illuminate the display device, and a display optical system for guiding the light reflected by the display device to the pupil of an observer to allow the observer to observe an image displayed on the display panel. The illumination optical system and the display optical system have an optical element shared in part or are arranged so as not to interfere with each other, thereby providing the image display apparatus of compact structure. Particularly, where the display optical system is a thin optical system having a plurality of decentered, reflecting, curved surfaces, the appropriate illumination optical system is arranged, thereby providing the thin image display apparatus using the reflective display device.

Claims

1. An image display apparatus comprising:

reflective display means;

an illumination optical system for making light from light source means obliquely incident to a display surface of the display means; and

a display optical system for guiding light from the display means to an observer to permit the observer to observe image information displayed on the display means,

wherein a principal ray emerging from a central part of the display means is emergent obliquely with respect to the display surface from the display means, the display optical system comprises a decentered, rotationally asymmetric, reflecting surface, the illumination optical system and the display optical system share at least one optical element, and at least one surface of the optical element(s) shared is a curved surface.

3. The image display apparatus according to claim 1 or 2, wherein said surface of the optical element is a rotationally asymmetric surface.

4. The image display apparatus according to claim 1 or 2, wherein said optical element comprises a surface acting as a transmitting surface in an optical path of said display optical system and acting as a reflecting surface in an optical path of said illumination optical system.

5. The image display apparatus according to claim 4, wherein said surface of said optical element acts as a surface having a positive power in both of said display optical system and said illumination optical system.

6. The image display apparatus according to claim 4, wherein said surface of said optical element is a curved surface.

7. The image display apparatus according to either one of claims 1 and 2, wherein said reflective display means is a ferroelectric liquid crystal display.

2. An image display apparatus comprising:

reflective display means;

an illumination optical system for guiding light from light source means to the display element; and

a display optical system for guiding the light reflected by the display element to the eye of an observer to allow the observer to observe an image,

wherein at least one surface of the display optical system is a decentered, rotationally asymmetric, reflecting surface, a principal ray of display light at a center of a field of view from the display element is emergent at a predetermined angle relative to a normal to a display surface of the display element, the illumination optical system and the display optical system share at least one optical element, and at least one surface of the optical element(s) is a curved surface.

8. An image display apparatus wherein light from light source means is guided via a first prism of a single medium having three or more optical surfaces comprising at least one decentered surface, to illuminate reflective display means obliquely, and light emerging obliquely from the display means is guided via part of the optical surfaces of the first prism and via a second prism of a single medium having three or more optical surfaces comprising at least one decentered surface to an observer, whereby the observer is allowed to observe image information displayed on the display means.

9. The image display apparatus according to claim 8, wherein said first prism comprises an entrance surface to which the light from said light source means is incident, a half mirror surface comprised of a rotationally asymmetric surface for reflecting part of light from the entrance surface, and an exit surface from which light reflected by the half mirror surface emerges toward said display means.

10. The image display apparatus according to claim 9, wherein the light from said display means is incident through the exit surface of said first prism, the light then travels through the half mirror surface and emerges from the first prism body, and thereafter the light is incident to said second prism.

11. The image display apparatus according to claim 10, wherein said second prism comprises an entrance surface to which the light from the half mirror surface of said first prism is incident, a totally reflecting surface for totally reflecting the light from the entrance surface, a reflecting surface comprised of a rotationally asymmetric surface for reflecting the light from the totally reflecting surface, and an exit surface having the same shape as the totally reflecting surface, from which the light from the reflecting surface emerges.

13. The image display apparatus according to claim 12, which satisfies the following condition:

(Dy/Ly)·

Wy°

<

Pθ

<

40°

where Pθ

represents a prism vertex angle of said prism.

15. The image display apparatus according to claim 14, wherein said display optical system comprises an optical element making use of a plurality of reflecting surfaces and each of said reflecting surfaces forming the optical element is comprised of a surface decentered from a principal ray at a center of a field of view.

16. The image display apparatus according to claim 15, wherein at least one optical surface forming said optical element is a rotationally asymmetric surface.

17. The image display apparatus according to claim 16, wherein one of said rotationally asymmetric surfaces comprises a surface acting as a totally reflecting surface and also as a transmitting surface.

18. The image display apparatus according to claim 14, wherein said optical member is comprised of a prism in which an entrance surface, a reflecting surface, and an exit surface are formed integrally, and the light from said light source means is guided into the entrance surface, is reflected by the reflecting surface, and is guided out of the exit surface toward said display means.

19. The image display apparatus according to claim 18, wherein at least a partial area makes use of total reflection, out of reflection on the reflecting surface of said optical member.

20. The image display apparatus according to claim 19, wherein said optical member comprises at least one curved surface.

21. The image display apparatus according to claim 20, wherein said illumination optical system comprises at least one rotationally asymmetric surface.

22. The image display apparatus according to claim 14, wherein said display means is a ferroelectric liquid crystal display.

23. The image display apparatus according to claim 14, wherein said light source means comprises a light source for emitting light of three colors of R, G, and B and the light source means emits the light in synchronism with image display on said display means.

24. The image display apparatus according to claim 23, wherein said light source comprises LEDs for emitting the light of the three colors of R, G, and B.

26. The image display apparatus according to claim 25, wherein said display optical system comprises an optical element making use of a plurality of reflecting surfaces and each of said reflecting surfaces forming the optical element is comprised of a surface decentered from a principal ray at a center of a field of view.

27. The image display apparatus according to claim 26, wherein at least one surface forming said optical element is comprised of a rotationally asymmetric surface.

28. The image display apparatus according to claim 27, wherein one of said rotationally asymmetric surfaces comprises a surface acting as a totally reflecting surface and also as a transmitting surface.

29. The image display apparatus according to claim 25, wherein said optical member is comprised of a prism in which an entrance surface, a reflecting surface, and an exit surface are formed integrally, and the light from said light source means is guided into the entrance surface, is reflected by the reflecting surface, and is guided out of the exit surface toward said display means.

30. The image display apparatus according to claim 29, wherein at least a partial area makes use of total reflection, out of reflection on the reflecting surface of said optical member.

31. The image display apparatus according to claim 30, wherein said optical member comprises at least one curved surface.

32. The image display apparatus according to claim 31, wherein said illumination optical system comprises at least one rotationally asymmetric surface.

33. The image display apparatus according to claim 25, wherein said display means is a ferroelectric liquid crystal panel.

34. The image display apparatus according to claim 25, wherein said light source means comprises a light source for emitting light of three colors of R, G, and B and the light source means emits the light in synchronism with image display on said display means.

35. The image display apparatus according to claim 34, wherein said light source comprises LEDs for emitting the light of the three colors of R, G, and B.

37. The image display apparatus according to claim 36, wherein said display optical system comprises a plurality of reflecting surfaces and each of said plurality of reflecting surfaces is comprised of a surface decentered from a principal ray at a center of a field of view.

38. The image display apparatus according to claim 37, wherein said display optical system comprises an optical surface acting as a totally reflecting surface and also as a transmitting surface.

39. The image display apparatus according to claim 38, wherein a reflection film is formed in part of said surface functioning as a totally reflecting surface and also as a transmitting surface.

40. The image display apparatus according to either one of claims 37 to 39, wherein a surface forming said display optical system is comprised of a rotationally asymmetric surface.

41. The image display apparatus according to claim 36 or 37, wherein said reflective display means is a ferroelectric liquid crystal panel.

42. The image display apparatus according to claim 41, wherein polarizing plates whose axes of polarization are approximately perpendicular to each other are placed between said light source means and said display means and between said display means and said display optical system.

43. The image display apparatus according to claim 36, wherein a reference axis ray traveling from said light source means to said display means intersects with a reference axis ray traveling from the display means to said display optical system only on the display means.

12. An image display apparatus comprising:

reflective display means;

an illumination optical system for making light from light source means incident to a display surface of the display means; and

a display optical system for guiding light from the display means to the pupil of an observer to allow the observer to observe image information displayed on the display means,

wherein the illumination optical system guides the light from the light source means via a prism of a triangular prism shape making use of a totally reflecting surface to the display means, the display optical system guides the light from the display means through the totally reflecting surface of the prism to the observer, and an angle θ

between the totally reflecting surface and the display surface of the display means is set so as to satisfy the following condition;

(Dy/Ly)·

Wy°

<

θ

<

40°

where Dy represents a diameter of the exit pupil formed by the display optical system in the y-direction, Ly represents an effective image display size of the display means in the y-direction, and Wy represents a field of view in the y-direction.

14. An image display apparatus comprising:

light source means;

reflective display means;

an illumination optical system for guiding light from the light source means to the display means;

a display optical system for guiding the light reflected by the display means to the pupil of an observer and making the observer recognize a virtual image formed thereby as an enlarged image of an image displayed on the display means; and

an optical member comprising surface acting to totally reflect light when guiding the light from the light source means to the display means and acting to transmit light when guiding the light reflected by the display means to the pupil,

wherein an angle θ

between the surface and an image display surface of the display means is set to satisfy θ

<

45°

.

25. An image display apparatus comprising:

reflective display means;

an illumination optical system for making light from light source means incident to a display surface of the display means; and

a display optical system for guiding light from the display means to the pupil of an observer to allow the observer to observe image information displayed on the display means,

wherein the illumination optical system guides the light from the light source means via an optical member making use of a totally reflecting surface to the display means and the display optical system guides the light from the display means through the totally reflecting surface of the optical member to the observer.

36. An image display apparatus comprising:

reflective display means;

an illumination optical system for making light from light source means incident to a display surface of the display means; and

a display optical system for guiding light from the display means to the pupil of an observer to allow the observer to observe image information displayed on the display means,

wherein the display optical system is arranged so as not to interfere with an illumination optical path running from the light source means to the display means and the illumination optical system is arranged so as not to interfere with a display optical path running from the display means to the display optical system.

44. An image display apparatus comprising:

reflective display means;

an illumination optical system for making light from light source means incident to the display means; and

a display optical system for guiding light from the display means to an observation position of an observer, the display optical system comprising a plurality of decentered, reflecting surfaces each having an optical power,

wherein a principal ray at a center of a field of view, passing a center of an exit pupil of the display optical system, is emergent at a predetermined angle relative to a normal to an image display surface of the display means.

45. The image display apparatus according to claim 44, wherein said display optical system comprises an optical element in which an entrance surface, a plurality of decentered, curved, reflecting surfaces, and an exit surface are made in surfaces of a material.

46. The image display apparatus according to claim 44, wherein the decentered, reflecting surfaces each with the optical power forming said display optical system are rotationally asymmetric surfaces.

47. The image display apparatus according to claim 44, wherein said illumination optical system comprises an optical element having a positive power and being independent of the display optical system.

48. The image display apparatus according to claim 44, wherein said illumination means turns on light of the three primary colors of R, G, and B in time series in synchronism with image display on said display means, thereby implementing color display.

49. The image display apparatus according to claim 44, wherein said dis play means is a ferroelectric liquid crystal panel.

50. The image display apparatus according to claim 44, wherein said illumination optical system comprises a first polarizing plate for forming illumination light linearly polarized in a predetermined direction and said display optical system comprises a second polarizing plate whose axis of polarization is approximately perpendicular to that of the first polarizing plate.