Small light weight head-mounted or face-mounted image display apparatus

• US 5,726,807 A
• Filed: 12/12/1995
• Issued: 03/10/1998
• Est. Priority Date: 12/13/1994
• Status: Expired due to Term

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Takahashi, Koichi, Togino, Takayoshi, Nakaoka, Masaya
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): MACK, RICKY LEVERN
• Application Number:
  US08/570,861
• Time in Patent Office: 819 Days
• Field of Search: 359/630, 359/631, 359/364, 359/365, 359/366, 359/633, 359/637
• US Class Current: 359/631
• CPC Class Codes: G02B 2027/011 comprising device for correcting geometrical aberrations, distortion
• CPC Class Codes: G02B 2027/0132 comprising binocular systems
• CPC Class Codes: G02B 2027/0136 with a single image source for both eyes
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0172 characterised by optical features

Abstract

An image display apparatus, e.g. a head-mounted image display apparatus, which is capable of satisfactorily correcting field curvature and other aberrations in an optical system simultaneously, and which enables even an image of high resolution to be sufficiently clearly observed, without forming an intermediate image. The apparatus has an image display device (6) for displaying an image, and an optical system for projecting an image formed by the image display device (6) without forming an intermediate image and for leading the projected image to an observer'"'"'s eyeball (1). The optical system includes at least one concave mirror (4) having a rotationally asymmetric reflecting surface which is concave toward the observer'"'"'s eyeball and decentered with respect to an optical axis, and at least one optical element (9) of positive refractive power which is disposed between the concave mirror (4) and the image display device (6).

Claims

1. An image display apparatus, comprising:

an image display device for displaying an image; and

an optical system for projecting an image formed by said image display device without forming an intermediate image and for leading the projected image to an observer'"'"'s eyeball,

said optical system including at least one concave mirror having a rotationally asymmetric reflecting surface which is concave toward the observer'"'"'s eyeball and decentered with respect to an optical axis, and at least one optical element of positive refractive power which is disposed between said concave mirror and said image display device,

wherein a focal length of said optical system and a focal length of said optical element of positive refractive power satisfy the following condition;

space="preserve" listing-type="equation">1<

f.sub.y <

f.sub.yO <

5 or 1<

f.sub.x /f.sub.xO <

5

where f_y and f_x are focal lengths in Y- and X-axis directions, respectively, of said optical element of positive refractive power, and f_yO and f_xO are focal lengths in the Y- and X-axis directions, respectively, of the entire optical system, wherein a direction of an optical axis incident on an observer'"'"'s pupil is defined as a Z-axis direction, a Y-axis is defined so that decentration of said concave mirror is made in a YZ-plane, and an X-axis is defined so as to intersect both the Y- and Z-axes at right angles.

2. An image display apparatus according to claim 1, wherein said optical element of positive refractive power has at least one surface which is decentered with respect to the optical axis.

3. An image display apparatus according to any one of claims 1 to 2, wherein a focal length of said optical system and a focal length of said optical element of positive refractive power satisfy the following condition:

space="preserve" listing-type="equation">1.1<

f.sub.y /f.sub.yO <

2.5 or 1.1<

f.sub.xO /f.sub.xO <

2.5

where f_y and f_x are focal lengths in Y- and X-axis directions, respectively, of said optical element of positive refractive power, and f_yO and f_xO are focal lengths in the Y- and X-axis directions, respectively, of the entire optical system, wherein a direction of an optical axis incident on an observer'"'"'s pupil is defined as a Z-axis direction, a Y-axis is defined so that decentration of said concave mirror is made in a YZ-plane, and an X-axis is defined so as to intersect both the Y- and Z-axes at right angles.

4. An image display apparatus according to claim 1, wherein said optical element of positive refractive power is a positive meniscus lens having a concave surface directed toward said image display device.

5. An image display apparatus according to claim 1, wherein said optical element of positive refractive power is a cemented positive lens.

6. An image display apparatus according claim 1, wherein said concave mirror is a back-coated mirror.

7. An image display apparatus, comprising:

an image display device for displaying an image; and

an optical system for projecting an image formed by said image display device without forming an intermediate image and for leading the projected image to an observer'"'"'s eyeball,

said optical system including at least one concave mirror having a rotationally asymmetric reflecting surface which is concave toward the observer'"'"'s eyeball and decentered with respect to an optical axis, and at least one optical element of positive refractive power which is disposed between said concave mirror and said image display device,

said concave mirror is a backed-coated mirror, and

said image display apparatus satisfies the following condition;

space="preserve" listing-type="equation">R.sub.y1 /R.sub.y2 <

2

where R_y1 is a curvature radius of a transmitting surface of said back-coated mirror in a plane containing both said observer'"'"'s visual axis and a center of said image display device, and R_y2 is a curvature radius of a reflecting surface of said back-coated mirror in said plane.

8. An image display apparatus according to claim 7, which satisfies the following condition:

space="preserve" listing-type="equation">R.sub.y1 /R.sub.y2 <

1

where R_y1 is a curvature radius of a transmitting surface of said back-coated mirror in a plane containing both said observer'"'"'s visual axis and a center of said image display device, and R_y2 is a curvature radius of a reflecting surface of said back-coated mirror in said plane.

9. An image display apparatus according to claim 7, which satisfies the following condition:

space="preserve" listing-type="equation">R.sub.y1 /R.sub.y2 <

0.8

where R_y1 is a curvature radius of a transmitting surface of said back-coated mirror in a plane containing both said observer'"'"'s visual axis and a center of said image display device, and R_y2 is a curvature radius of a reflecting surface of said back-coated mirror in said plane.

10. An image display apparatus, comprising:

an image display device for displaying an image; and

an ocular optical system for projecting an image formed by said image display device and for leading the projected image to an observer'"'"'s eyeball,

said ocular optical system having at least a first surface and a second surface, said first surface is disposed closer to the observer'"'"'s eyeball than said second surface, a space between the first and second surfaces being filled with a medium having a refractive index n larger than 1 (n>

1), said first and second surfaces being decentered in the same direction with respect to an observer'"'"'s visual axis defined according to when the observer sees a center of the projected image, said second surface being a curved reflecting or semitransparent surface which is concave toward the observer'"'"'s eyeball, said first and second surfaces having different curvatures, and said first and second surfaces being arranged such that light rays emanating from said image display device are refracted by said first surface and then reflected by said second surface, and the reflected light rays are further refracted by said first surface, thereby allowing a first-order image of said image display device formed by said ocular optical system to enter the observer'"'"'s eyeball, and

said image display apparatus satisfies the following condition;

space="preserve" listing-type="equation">R.sub.y1 /R.sub.y2 <

2

where R_y1 is a curvature radius of the first surface of said ocular optical system in a plane containing both said observer'"'"'s visual axis and a center of said image display device, and R_y2 is a curvature radius of the second surface of said ocular optical system in said plane.

11. An image display apparatus according to claim 10, wherein light rays emanating from said image display device are projected directly into the observer'"'"'s eyeball.

12. An image display apparatus according to claim 10, wherein the first surface of said ocular optical system is a transmitting surface which is concave toward the observer'"'"'s eyeball.

13. An image display apparatus according to claim 10, which satisfies the following condition:

space="preserve" listing-type="equation">R.sub.y1 /R.sub.y2 <

1

where R_y1 is a curvature radius of the first surface of said ocular optical system in a plane containing both said observer'"'"'s visual axis and a center of said image display device, and R_y2 is a curvature radius of the second surface of said ocular optical system in said plane.

14. An image display apparatus according to claim 10, which satisfies the following condition:

space="preserve" listing-type="equation">R.sub.y1 /R.sub.y2 <

0.8

where R_y1 is a curvature radius of the first surface of said ocular optical system in a plane containing both said observer'"'"'s visual axis and a center of said image display device, and R_y2 is a curvature radius of the second surface of said ocular optical system in said plane.

15. An image display apparatus according to claim 10, wherein the second surface of said ocular optical system has a rotationally asymmetric configuration.

16. An image display apparatus according to claim 10, wherein the second surface of said ocular optical system is an anamorphic aspherical surface.

17. An image display apparatus according to claim 10, wherein the second surface of said ocular optical system is tilted and, at the same time, decentered with respect to said visual axis.

18. An image display apparatus according to claim 10, wherein said ocular optical system has a right ocular optical system for leading light to an observer'"'"'s right eyeball, and a left ocular optical system for leading light to an observer'"'"'s left eyeball, so that an image formed on the image display surface of said image display device is led to both said right and left ocular optical systems.

29. An image display apparatus according to claim 10 or 25, further comprising means for positioning both said image display device and said ocular optical system with respect to an observer'"'"'s head.

30. An image display apparatus according to claim 10 or 25, further comprising means for supporting both said image display device and said ocular optical system with respect to an observer'"'"'s head, thereby allowing said image display apparatus to be fitted to the observer'"'"'s head.

31. An image display apparatus according to claim 10 or 25, further comprising means for supporting at least a pair of said image display apparatuses at a predetermined spacing.

32. An image display apparatus according to claim 10 or 25, wherein said image display device is disposed forwardly of an observer'"'"'s face, and said image display device is disposed so that an image display surface of said image display device faces in a forward direction from the observer'"'"'s face, and a reverse side of said image display device faces opposite to the observer'"'"'s face.

19. An image display apparatus comprising:

an image display device for displaying an image; and

an optical system for projecting an image formed by said image display device without forming an intermediate image and for leading the projected image to an observer'"'"'s eyeball,

said optical system including at least one concave mirror having a rotationally asymmetric reflecting surface which is concave toward the observer'"'"'s eyeball and decentered with respect to an optical axis, and at least one optical element of positive refractive power which is disposed between said concave mirror and said image display device,

wherein R_y2 a curvature radius of the reflecting surface of said concave mirror in a plane containing both said observer'"'"'s visual axis and a center of said image display device, R_x2 is a curvature radius of the reflecting surface of said concave mirror in a plane which perpendicularly intersects said plane containing both said observer'"'"'s visual axis and a center of said image display device and which contains said observer'"'"'s visual axis, and

R_x2 has a first value, R_y2 has a second value selected from one of sets A or B, where A is the set of all values greater said first value and B is the set of all values less than said first value.

20. An image display apparatus according to claim 19, wherein, the curvature radii R_x2 and R_y2 of the reflecting surface of said concave mirror satisfy the following condition:

space="preserve" listing-type="equation">R.sub.y2 /R.sub.x2 ≦

1.

21. An image display apparatus according to claim 19, wherein the curvature radii R_x2 and R_y2 of the reflecting surface of said concave mirror satisfy the following condition:

space="preserve" listing-type="equation">R.sub.y2 /R.sub.x2 <

0.8.

22.

24. An image display apparatus according to claim 21, wherein the curvature radii R_x2 and R_y2 of the second surface of said ocular optical system satisfy the following condition:

space="preserve" listing-type="equation">R.sub.y2 /R.sub.x2 <

0.8.

25.

22. An image display apparatus comprising:

an image display device for displaying an image; and

an ocular optical system for projecting an image formed by said image display device and for leading the projected image to an observer'"'"'s eyeball,

said ocular optical system having at least a first surface and a second surface, said first surface is disposed closer to the observer'"'"'s eyeball than said second surface, a space between the first and second surfaces being filled with a medium having a refractive index n larger than 1 (n>

1), said first and second surfaces being decentered with respect to an observer'"'"'s visual axis, said second surface being a curved reflecting or semitransparent surface which is concave toward the observer'"'"'s eyeball, said first and second surfaces having different curvatures, and said first and second surfaces being arranged such that light rays emanating from said image display device are refracted by said first surface andthen reflected by said second surface, and the reflected light rays are further refracted by said first surface, thereby allowing a first-order image of said image display device formed by said ocular optical system to enter the observer'"'"'s eyeball,

wherein R_y2 is a curvature radius of the second surface of said ocular optical system in a plane containing both said observer'"'"'s visual axis and a center of said image display device, and R_x2 is a curvature radius of the second surface of said ocular optical system in a plane which perpendicularly intersects said plane containing both said observer'"'"'s visual axis and a center of said image display device and which contains said observer'"'"'s visual axis, and, and

R_x2 has a first value, R_y2 has a second value selected from one of sets A or B, where A is the set of all values greater said first value and B is the set of all values less than said first value.

23. An image display apparatus according to claim 22, wherein the curvature radii R_x2 and R_y2 of the second surface of said ocular optical system satisfy the following condition:

space="preserve" listing-type="equation">R.sub.y2 /R.sub.x2 ≦

1.

25. An image display apparatus comprising:

an image display device for displaying an image; and

an ocular optical system for projecting an image formed by said image display device and for leading the projected image to an observer'"'"'s eyeball,

said ocular optical system having at least a first surface and a second surface, said first surface is disposed closer to the observer'"'"'s eyeball than said second surface, a space between the first and second surfaces being filled with a medium having a refractive index n larger than 1 (n>

1), said first and second surfaces being decentered with respect to an observer'"'"'s visual axis, said second surface being a curved reflecting or semitransparent surface which is concave toward the observer'"'"'s eyeball, said first and second surfaces having different curvatures, and said first and second surfaces being arranged such that light rays emanating from said image display device are refracted by said first surface and then reflected by said second surface, and the reflected light rays are further refracted by said first surface, thereby allowing a first-order image of said image display device formed by said ocular optical system to enter the observer'"'"'s eyeball,

said ocular optical system further having an optical element of positive refractive power, said optical element being provided between said observer'"'"'s eyeball and said first and second surfaces, and

said image display device satisfies the following condition;

space="preserve" listing-type="equation">5°

<

θ

.sub.2 <

25°

where θ

₂ is an angle at which an optical axis extending from said image display device is reflected by the second surface of said ocular optical system to said observer'"'"'s eyeball.

26. An image display apparatus according to claim 25, wherein said optical element of positive refractive power is a lens of positive refractive power.

27. An image display apparatus according to claim 25, wherein said optical element of positive refractive power is decentered with respect to said observer'"'"'s visual axis.

28. An image display apparatus according to claim 25, wherein said optical element of positive refractive power is a cemented lens.

33. An image display apparatus according to claim 25, which satisfies the following condition:

space="preserve" listing-type="equation">7°

<

θ

.sub.2 <

15°

where θ

₂ is an angle at which an optical axis extending from said image display device is reflected by the second surface of said ocular optical system to said observer'"'"'s eyeball.

34. An image display apparatus according to claim 25, which satisfies the following condition:

space="preserve" listing-type="equation">0.6<

(θ

.sub.1 /θ

.sub.3)×

n<

1.6

where θ

₃ is an angle formed between a line normal to the first surface of said ocular optical system and an optical axis extending from said image display device after it has been incident on said first surface, θ

₁ is an angle formed between a line normal to said first surface and the optical axis from said image display device when it exits from said first surface after being reflected by the second surface of said ocular optical system, and n is a refractive index of a medium lying between the first and second surfaces.

35. An image display apparatus according to claim 25, which satisfies the following condition:

space="preserve" listing-type="equation">0.8<

(θ

.sub.1 /θ

.sub.3)×

n<

1.6

where θ

₃ is an angle formed between a line normal to the first surface of said ocular optical system and an optical axis extending from said image display device after it has been incident on said first surface, θ

₁ is an angle formed between a line normal to said first surface and the optical axis from said image display device when it exits from said first surface after being reflected by the second surface of said ocular optical system, and n is a refractive index of a medium lying between the first and second surfaces.