Image-forming optical system and viewing optical system

• US 6,310,736 B1
• Filed: 06/14/1999
• Issued: 10/30/2001
• Est. Priority Date: 08/21/1998
• Status: Expired due to Term

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Togino, Takayoshi
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Cherry, Euncha
• Application Number:
  US09/332,155
• Time in Patent Office: 869 Days
• Field of Search: 359/833, 359/834, 359/836, 359/837, 359/726, 359/727, 359/728, 359/729, 359/730, 359/731, 359/732, 359/631, 359/633, 359/365, 359/366, 359/637, 345/7, 345/8
• US Class Current: 359/834
• CPC Class Codes: G02B 2027/0132 comprising binocular systems
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0172 characterised by optical features

Abstract

A viewing optical system and image-forming optical system in which an intermediate image is formed once and two decentered prisms, i.e. first and second prisms, are arranged to correct each other'"'"'s decentration aberrations, thereby attaining a wide viewing field angle and a short focal length. The second prism is placed closer to the object side than the first prism and has three optical surfaces, of which a first surface is an entrance surface also serving as a reflecting surface, a second surface is a reflecting surface, and a third surface is an exit surface. At least one of the first and second surfaces has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration. The first prism has a reflecting surface, an entrance surface, and an exit surface. The reflecting surface has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration. An intermediate image surface is formed between the first surface of the second prism and the exit surface of the first prism.

Claims

1. An image-forming optical system for forming an image of an object, said image-forming optical system comprising:

a first prism and a second prism, each of said first prism and second prism being formed from a medium having a refractive index (n) larger than 1 (n>

1), said second prism being placed closer to the object than said first prism;

said second prism having three optical surfaces that transmit or reflect a light beam, said three optical surfaces including;

a first surface through which a light beam from an object side of said second prism enters said second prism;

a second surface that reflects the light beam entering through said first surface in said second prism;

said first surface also reflecting the light beam reflected from said second surface in said second prism; and

a third surface through which the light beam reflected from said first surface exits from said second prism;

wherein at least one of said first surface and second surface has a curved surface configuration that gives a power to a light beam, said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration;

said first prism having at least;

a decentered reflecting surface having a curved surface configuration and internally reflecting a light beam in said medium, said reflecting surface having a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration;

an entrance surface through which a light beam enters said first prism; and

an exit surface through which the light beam exits from said first prism;

wherein an intermediate image surface is formed between the first surface of said second prism and the exit surface of said first prism.

2. An image-forming optical system according to claim 1, wherein both the first surface and second surface of said second prism have rotationally asymmetric surface configurations, respectively, which give a power to a light beam and correct aberrations due to decentration.

3. An image-forming optical system according to claim 1, wherein the rotationally asymmetric surface configuration of at least one of the first surface and second surface of said second prism is a plane-symmetry free-form surface having only one plane of symmetry.

4. An image-forming optical system according to claim 2, wherein the rotationally asymmetric surface configurations of both the first surface and second surface of said second prism are plane-symmetry free-form surfaces each having only one plane of symmetry.

5. An image-forming optical system according to claim 4, wherein the only one plane of symmetry of the plane-symmetry free-form surface that forms the first surface of said second prism and the only one plane of symmetry of the plane-symmetry free-form surface that forms the second surface of said second prism are formed in a same plane.

6. An image-forming optical system according to any one of claims 1 to 5, wherein the third surface of said second prism has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration.

7. An image-forming optical system according to claim 6, wherein the rotationally asymmetric surface configuration of the third surface of said second prism is a plane-symmetry free-form surface having only one plane of symmetry.

8. An image-forming optical system according to claim 7, wherein the only one plane of symmetry of the plane-symmetry free-form surface that forms the third surface of said second prism is coincident with a plane that connects segments of a folded optical path of an axial principal ray that is formed by reflections in said second prism.

9. An image-forming optical system according to any one of claims 1 to 5, wherein the rotationally asymmetric surface configuration of the reflecting surface in said first prism is a plane-symmetry free-form surface having only one plane of symmetry.

10. An image-forming optical system according to claim 9, wherein said first prism and said second prism each have at least one plane-symmetry free-form surface having only one plane of symmetry, and the only one plane of symmetry of the at least one plane-symmetry free-form surface in said first prism and that of the at least one plane-symmetry free-form surface in said second prism are placed in a same plane.

11. An image-forming optical system according to any one of claims 1 to 5, wherein said first prism has at least two reflecting surfaces each having a curved surface configuration that gives a power to a light beam.

12. An image-forming optical system according to claim 11, wherein said first prism is formed from three optical surfaces, which are an entrance surface serving as both a reflecting surface and a transmitting surface, a reflecting surface, and an exit surface.

13. An image-forming optical system according to claim 11, wherein said first prism is formed from three optical surfaces, which are an entrance surface, a reflecting surface, and an exit surface serving as both a reflecting surface and a transmitting surface.

14. An image-forming optical system according to claim 11, wherein said first prism is formed from four optical surfaces, which are two reflecting surfaces that give a power to a light beam, an entrance surface, and an exit surface.

15. An image-forming optical system according to claim 11, wherein the first surface and second surface of said second prism and the two surfaces having a reflecting action in said first prism are rotationally asymmetric surfaces that correct decentration aberrations and each have only one plane of symmetry.

16. An image-forming optical system according to claim 15, wherein the first surface and second surface of said second prism and the two surfaces having a reflecting action in said first prism are rotationally asymmetric surfaces that correct decentration aberrations and each have only one plane of symmetry, and the only one plane of symmetry of each of said rotationally asymmetric surfaces is coincident with each other in approximately a same plane.

17. An image-forming optical system according to claim 16, wherein all the optical surfaces constituting said first prism and second prism are rotationally asymmetric surfaces that correct decentration aberrations and each have only one plane of symmetry, and the only one plane of symmetry of each of said rotationally asymmetric surfaces is coincident with each other in approximately a same plane.

18. An image-forming optical system according to any one of claims 1 to 5, wherein said first prism and said second prism are arranged so that said intermediate image surface is formed between the second surface of said second prism and the entrance surface of said first prism.

19. An image-forming optical system according to any one of claims 1 to 5, wherein surface configurations of decentration aberration-correcting optical surfaces in said first prism and second prism are arranged so that an entrance pupil surface and image-formation surface of said image-forming optical system are approximately flat surfaces, and so that the intermediate image surface formed between said entrance pupil surface and said image-formation surface has a non-planar, curved configuration.

20. An image-forming optical system according to any one of claims 1 to 5, wherein said first prism and said second prism are arranged so that an entrance pupil of said image-forming optical system is formed on an object side of said second prism.

21. An image-forming optical system according to claim 20, wherein a stop is placed on said entrance pupil.

22. An image-forming optical system according to any one of claims 1 to 5, wherein said second prism has a fourth surface placed in an optical path between said first surface and said third surface where the light beam reflected from said first surface travels in said second prism until it exits from said third surface,

wherein said first surface allows the light beam from the object side to enter said second prism; said second surface reflects the light beam entering through said first surface in said second prism;

said first surface also reflects the light beam reflected from said second surface in said second prism;

said fourth surface reflects the light beam reflected from said first surface in said second prism; and

said third surface allows the light beam reflected from said fourth surface to exit from said second prism.

23. An image-forming optical system according to claim 22, wherein said fourth surface and second surface of said second prism are formed in a same surface, wherein a reflecting area of said same surface that forms said fourth surface is closer to said intermediate image surface than a reflecting area of said same surface that forms said second surface.

24. An image-forming optical system according to claim 22, wherein said fourth surface and said second surface have different curved surface configurations.

25. An image-forming optical system according to any one of claims 1 to 5, wherein said intermediate image surface is placed on the third surface of said second prism.

26. An image-forming optical system according to claim 25, wherein said intermediate image surface is placed on the third surface of said second prism, some area of said intermediate image surface lying inside said second prism, a remaining area of said intermediate image surface projecting outside said second prism.

27. An image-forming optical system according to any one of claims 1 to 5, wherein when a decentration direction of said image-forming optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, the following condition is satisfied:

28. An image-forming optical system according to any one of claims 1 to 5, wherein when a decentration direction of said image-forming optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

29. An image-forming optical system according to any one of claims 1 to 5, wherein when a decentration direction of said image-forming optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an x-axis direction, at least one of the following conditions is satisfied:

30. An image-forming optical system according to any one of claims 1 to 5, wherein when a decentration direction of said image-forming optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

31. An image-forming optical system according to claim 12, wherein when a decentration direction of said image-forming optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

32. An image-forming optical system according to claim 13, wherein when a decentration direction of said image-forming optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

33. An image-forming optical system according to claim 14, wherein when a decentration direction of said image-forming optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

34. An image-forming optical system according to any one of claims 1 to 5, which has a focal length shorter than 12 millimeters.

35. A finder optical system comprising:

the image-forming optical system of any one of claims 1 to 5, said image-forming optical system being provided as a finder objective optical system;

an image-inverting optical system for erecting an object image formed by said finder objective optical system; and

an ocular optical system.

36. A camera apparatus comprising:

the finder optical system of claim 35; and

an objective optical system for photography provided in parallel to said finder optical system.

37. An image pickup optical system comprising:

the image-forming optical system of any one of claims 1 to 5; and

an image pickup device placed in an image plane formed by said image-forming optical system.

38. A camera apparatus comprising:

the image-forming optical system of any one of claims 1 to 5, said image-forming optical system being provided as an objective optical system for photography; and

a finder optical system placed in one of an optical path separate from an optical path of said objective optical system for photography and an optical path branched from the optical path of said objective optical system for photography.

39. An electronic camera apparatus comprising:

the image-forming optical system of any one of claims 1 to 5;

an image pickup device placed in an image plane formed by said image-forming optical system;

a recording medium for recording image information received by said image pickup device; and

an image display device that receives image information from one of said recording medium and said image pickup device to form an image for observation.

40. An endoscope system comprising:

an observation system having the image-forming optical system of any one of claims 1 to 5 and an image transmitting member for transmitting an image formed by said image-forming optical system along a longitudinal axis; and

an illumination system having an illuminating light source and an illuminating light transmitting member for transmitting illuminating light from said illuminating light source along the longitudinal axis.

41. A viewing optical system that forms an exit pupil for viewing an observation image, said viewing optical system comprising:

a first prism and a second prism, each of said first prism and second prism being formed from a medium having a refractive index (n) larger than 1 (n>

1);

said second prism being placed closer to said exit pupil than said first prism;

said first prism having at least;

a decentered reflecting surface having a curved surface configuration and internally reflecting a light beam in said medium, said reflecting surface having a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration;

an entrance surface through which a light beam from said observation image enters said first prism; and

an exit surface through which the light beam exits from said first prism;

said second prism having three optical surfaces that transmit or reflect a light beam, said three optical surfaces including;

a third surface through which the light beam exiting from said first prism enters said second prism;

a first surface that reflects the light beam entering through said third surface in said second prism;

a second surface that reflects the light beam reflected from said first surface in said second prism; and

said first surface also allowing the light beam reflected from said second surface to exit from said second prism;

wherein at least one of said first surface and said second surface has a curved surface configuration that gives a power to a light beam, said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration,

wherein an intermediate image surface is formed between the first surface of said second prism and the entrance surface of said first prism.

42. A viewing optical system according to claim 41, wherein both the first surface and second surface of said second prism have rotationally asymmetric surface configurations, respectively, which give a power to a light beam and correct aberrations due to decentration.

43. A viewing optical system according to claim 42, wherein the rotationally asymmetric surface configuration of at least one of the first surface and second surface of said second prism is a plane-symmetry free-form surface having only one plane of symmetry.

44. A viewing optical system according to claim 42, wherein the rotationally asymmetric surface configurations of both the first surface and second surface of said second prism are plane-symmetry free-form surfaces each having only one plane of symmetry.

45. A viewing optical system according to claim 44, wherein the only one plane of symmetry of the plane-symmetry free-form surface that forms the first surface of said second prism and the only one plane of symmetry of the plane-symmetry free-form surface that forms the second surface of said second prism are formed in a same plane.

46. A viewing optical system according to any one of claims 41 to 45, wherein the third surface of said second prism has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration.

47. A viewing optical system according to claim 46, wherein the rotationally asymmetric surface configuration of the third surface of said second prism is a plane-symmetry free-form surface having only one plane of, symmetry.

48. A viewing optical system according to claim 47, wherein the only one plane of symmetry of the plane-symmetry free-form surface that forms the third surface of said second prism is coincident with a plane that connects segments of a folded optical path of an axial principal ray that is formed by reflections in said second prism.

49. A viewing optical system according to any one of claims 41 to 45, wherein the rotationally asymmetric surface configuration of the reflecting surface in said first prism is a plane-symmetry free-form surface having only one plane of symmetry.

50. A viewing optical system according to claim 49, wherein said first prism and said second prism each have at least one plane-symmetry free-form surface having only one plane of symmetry, and the only one plane of symmetry of the at least one plane-symmetry free-form surface in said first prism and that of the at least one plane-symmetry free-form surface in said second prism are placed in a same plane.

51. A viewing optical system according to any one of claims 41 to 45, wherein said first prism has at least two reflecting surfaces each having a curved surface configuration that gives a power to a light beam.

52. A viewing optical system according to claim 51, wherein said first prism is formed from three optical surfaces, which are an exit surface serving as both a reflecting surface and a transmitting surface, a reflecting surface, and an entrance surface.

53. A viewing optical system according to claim 51, wherein said first prism is formed from three optical surfaces, which are an exit surface, a reflecting surface, and an entrance surface serving as both a reflecting surface and a transmitting surface.

54. A viewing optical system according to claim 51, wherein said first prism is formed from four optical surfaces, which are two reflecting surfaces that give a power to a light beam, an entrance surface, and an exit surface.

55. A viewing optical system according to claim 51, wherein the first surface and second surface of said second prism and the two surfaces having a reflecting action in said first prism are rotationally asymmetric surfaces that correct decentration aberrations and each have only one plane of symmetry.

56. A viewing optical system according to claim 55, wherein the first surface and second surface of said second prism and the two surfaces having a reflecting action in said first prism are rotationally asymmetric surfaces that correct decentration aberrations and each have only one plane of symmetry, and the only one plane of symmetry of each of said rotationally asymmetric surfaces is coincident with each other in approximately a same plane.

57. A viewing optical system according to claim 56, wherein all the optical surfaces constituting said first prism and second prism are rotationally asymmetric surfaces that correct decentration aberrations and each have only one plane of symmetry, and the only one plane of symmetry of each of said rotationally asymmetric surfaces is coincident with each other in approximately a same plane.

58. A viewing optical system according to any one of claims 41 to 45, wherein said first prism and said second prism are arranged so that said intermediate image surface is formed between the second surface of said second prism and the exit surface of said first prism.

59. A viewing optical system according to any one of claims 41 to 45, wherein surface configurations of decentration aberration-correcting optical surfaces in said first prism and second prism are arranged so that an exit pupil surface and an observation image surface of said viewing optical system are approximately flat surfaces, and so that the intermediate image surface formed between said exit pupil surface and said observation image surface has a non-planar, curved configuration.

60. A viewing optical system according to any one of claims 41 to 45, wherein a cover member is provided between the first surface of said second prism and the exit pupil to cover said first surface.

61. A viewing optical system according to claim 60, wherein said cover member is a plane-parallel plate that gives no power to a light beam.

62. A viewing optical system according to claim 60, wherein said cover member is a positive lens that converges a light beam.

63. A viewing optical system according to any one of claims 41 to 45, wherein said second prism has a fourth surface placed in an optical path between said third surface and said first surface where the light beam entering said second prism through said third surface travels until it is reflected by said first surface,

wherein said third surface allows the light beam exiting from said first prism to enter said second prism; said fourth surface reflects the light beam entering through said third surface in said second prism;

said first surface reflects the light beam reflected from said fourth surface in said second prism;

said second surface reflects the light beam reflected from said first surface in said second prism; and

said first surface allows the light beam reflected from said second surface to exit from said second prism.

64. A viewing optical system according to claim 63, wherein said fourth surface and second surface of said second prism are formed in a same surface, wherein a reflecting area of said same surface that forms said fourth surface is closer to said intermediate image surface than a reflecting area of said same surface that forms said second surface.

65. A viewing optical system according to claim 63, wherein said fourth surface and said second surface have different curved surface configurations.

66. A viewing optical system according to any one of claims 41 to 45, wherein said intermediate image surface is placed on the third surface of said second prism.

67. A viewing optical system according to claim 66, wherein said intermediate image surface is placed on the third surface of said second prism, some area of said intermediate image surface lying inside said second prism, a remaining area of said intermediate image surface projecting outside said second prism.

68. A viewing optical system according to any one of claims 41 to 45, wherein when a decentration direction of said viewing optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, the following condition is satisfied:

69. A viewing optical system according to any one of claims 41 to 45, wherein when a decentration direction of said viewing optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

70. A viewing optical system according to any one of claims 41 to 45, wherein when a decentration direction of said viewing optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

71. A viewing optical system according to any one of claims 41 to 45, wherein when a decentration direction of said viewing optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

72. A viewing optical system according to claim 52, wherein when a decentration direction of said viewing optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

73. A viewing optical system according to claim 53, wherein when a decentration direction of said viewing optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

74. A viewing optical system according to claim 54, wherein when a decentration direction of said viewing optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, at least one of the following conditions is satisfied:

75. A viewing optical system according to any one of claims 41 to 45, which has a focal length shorter than 12 millimeters.

76. A finder optical system comprising:

the viewing optical system of any one of claims 41 to 45, said viewing optical system being provided as a finder ocular optical system; and

an objective optical system placed in front of said finder ocular optical system to form an observation image to be viewed through said finder ocular optical system.

77. A camera apparatus comprising:

the finder optical system of claim 76; and

an optical system for photography provided in parallel to said finder optical system.

78. An electronic finder optical system comprising:

an electronic image display device for forming an observation image on a display surface thereof; and

the viewing optical system of any one of claims 41 to 45 for viewing the image on the display surface of said image display device.

79. An electronic camera apparatus comprising:

an image-forming optical system;

an image pickup device placed in an image plane formed by said image-forming optical system;

a recording medium for recording image information received by said image pickup device;

an image display device that receives image information from one of said recording medium and said image pickup device to form an image for observation on a display surface thereof; and

the viewing optical system of any one of claims 41 to 45 for viewing the image on the display surface of said image display device.

80. An endoscope system comprising:

an observation system having an image-forming optical system and an image transmitting member for transmitting an image formed by said image-forming optical system along a longitudinal axis;

an illumination system having an illuminating light source and an illuminating light transmitting member for transmitting illuminating light from said illuminating light source along the longitudinal axis; and

the viewing optical system of any one of claims 41 to 45, said viewing optical system being used to view the image transmitted by the image transmitting member of said observation system.

81. A head-mounted image display apparatus comprising:

an apparatus body unit having an image display device for forming an observation image on an image display area thereof, and the viewing optical system of any one of claims 41 to 45 which is provided as an ocular optical system for viewing said observation image; and

a support member arranged to be mounted on a head of an observer to retain said apparatus body unit in front of a face of the observer.

82. A head-mounted image display apparatus according to claim 81, wherein a combination of said image display device and said ocular optical system is provided for each of left and right eyes of the observer to enable the observer to see with his or her two eyes.