Zoom lens

• US 6,215,600 B1
• Filed: 09/24/1998
• Issued: 04/10/2001
• Est. Priority Date: 09/30/1997
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Nishimura, Takeshi, Itoh, Yoshinori
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Lucas, Michael A.
• Application Number:
  US09/160,769
• Time in Patent Office: 929 Days
• Field of Search: 359/689, 359/686, 359/692
• US Class Current: 359/689
• CPC Class Codes: G02B 15/143105 arranged +-+

Abstract

A zoom lens which includes, in order from an object side, a first lens unit of positive refractive power, a second lens unit of positive refractive power and a third lens unit of negative refractive power, wherein the first, second and third lens units are moved such that, during zooming from a wide-angle end to a telephoto end, a separation between the first lens unit and the second lens unit increases and a separation between the second lens unit and the third lens unit decreases, and wherein the zoom lens has a diffractive optical element.

Claims

1. A zoom lens comprising, in order from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of refractive power and a third lens unit of negative refractive power, wherein said first, second and third lens units are moved such that, during zooming from a wide-angle end to a telephoto end, a separation between said first lens unit and said second lens unit increases and a separation between said second lens unit and said third lens unit decreases, and wherein said zoom lens has a diffractive surface, and wherein said first lens unit consists of a negative lens and a positive lens, and said positive lens and said negative lens are disposed in the order from the object side to the image side.

2. A zoom lens according to claim 1, wherein said diffractive surface is included in said third lens unit.

3. A zoom lens according to claim 1, wherein said diffractive surface is included in said second lens unit.

4. A zoom lens according to claim 1, wherein said third lens unit consists of a single lens.

5. A zoom lens according to claim 1, wherein said diffractive surface is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating is given by

6. A zoom lens according to claim 5, satisfying the following condition:

7. A zoom lens according to claim 5, where said diffractive surface is included in said third lens unit, and said zoom lens satisfies the following condition:

8. A zoom lens according to claim 1, wherein said third lens unit contributes to a greatest variation of magnification among said first to third lens units.

9. A zoom lens according to claim 1, further comprising a stop positioned on the object side of said second lens unit and arranged to move integrally with said second lens unit during zooming.

10. A zoom lens according to claim 1, wherein said second lens unit consists of a negative lens of meniscus form concave toward the object side and a positive lens, totaling two lenses.

11. A zoom lens according to claim 1, wherein there is a space between said negative lens and said positive lens.

12. A zoom lens according to claim 1, wherein said diffractive surface is included in each of said second lens unit and said third lens unit, and wherein said diffractive surface is composed of a diffraction grating of revolution symmetry with respect to an optical axis and, as a phase φ

n(H) of the diffraction grating in the n-th lens unit is given by

13. A zoom lens according to claim 1, wherein said first, second and third lens units each axially move toward the object side during zooming from the wide-angle end to the telephoto end.

14. A zoom lens according to claim 1, wherein said diffractive surface comprises a first diffraction grating, and a second diffraction grating formed on said first diffraction grating, wherein said first diffraction grating and said second diffraction grating are made of different materials from each other.

15. A zoom lens comprising a plurality of movable lens unit which consist of, in order from an object side to an image side, a first lens unit of positive refractive power, and a second lens unit of negative refractive power, wherein a separation between said first lens unit and said second lens unit is varied to effect zooming, and wherein said first lens unit includes at least three lenses and said first lens unit has a diffractive surface.

16. A zoom lens according to claim 15, wherein said second lens unit includes, in order from the object side, a positive lens and a negative lens.

17. A zoom lens according to claim 15, wherein said diffractive surface included in said first lens unit is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating is defined as

18. A zoom lens according to claim 15, wherein said second lens unit has a diffractive surface, and wherein said diffractive surface included in said second lens unit is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating included in said second lens unit is defined as

19. A zoom lens according to claim 15, satisfying the following conditions:

20. A zoom lens according to claim 15, wherein each of a positive lens disposed closest to the image side in said first lens unit and a negative lens disposed closest to the image side in said second lens unit is a diffractive surface.

21. A zoom lens according to claim 15, wherein said diffractive surface comprises a first diffraction grating, and a second diffraction grating formed on said first diffraction grating, wherein said first diffraction grating and said second diffraction grating are made of different materials from each other.

22. A zoom lens according to claim 15, wherein each of said first lens unit and said second lens unit has a diffractive surface.

23. A zoom lens comprising a plurality of movable lens unit which consists of, in order from an object side to an image side, a first lens unit of positive refractive power and second lens unit of negative refractive power, wherein a separation between said first lens unit and said second lens unit is varied to effect zooming, and wherein said first lens unit has a positive lens disposed closest to the object side and a negative lens disposed closer to the image side than said positive lens, and said zoom lens has a diffractive surface.

24. A zoom lens according to claim 23, satisfying the following conditions:

25. A zoom lens according to claim 23, wherein said second lens unit comprises, in order from the object side, a positive lens and a negative lens.

26. A zoom lens according to claim 23, wherein said diffractive surface is included in said first lens unit, and wherein said diffractive surface included in said first lens unit is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating is defined as

27. A zoom lens according to claim 23, wherein said diffractive surface is included in said second lens unit, and wherein said diffractive surface included in said second lens unit is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating is defined as

28. A zoom lens according to claim 23, satisfying the following conditions:

29. A zoom lens according to claim 23, wherein each of a positive lens disposed closest to the image side in said first lens unit and a negative lens disposed closest to the image side in said second lens unit is a diffractive surface.

30. A zoom lens according to claim 23, wherein said diffractive surface comprises a first diffraction grating, and a second diffraction grating formed on said first diffraction grating, wherein said first diffraction grating and said second diffraction grating are made of different materials from each other.

31. A zoom lens comprising a plurality of movable lens unit which consists of, in order from an object side to an image side, a first lens unit of positive refractive power and a second lens unit of negative refractive power, wherein a separation between said first lens unit and said second lens unit is varied to effect zooming, and wherein said first lens unit has two positive lenses and two negative lenses and said first lens unit has a diffractive surface.

32. A zoom lens according to claim 31, wherein said first lens unit comprises, in order from the object side, a positive lens, a negative lens and a positive lens.

33. A zoom lens according to claim 31, wherein said second lens unit comprises, in order from the object side, a positive lens and a negative lens.

34. A zoom lens according to claim 31, wherein said diffractive surface included in said first lens unit is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating is defined as

35. A zoom lens according to claim 31, wherein said second lens unit has a diffractive surface, and wherein said diffractive surface included in said second lens unit is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating included in said second lens unit is defined as

36. A zoom lens according to claim 31, satisfying the following conditions:

37. A zoom lens according to claim 31, wherein each of a positive lens disposed closest to the image side in said first lens unit and a negative lens disposed closest to the image side in said second lens unit is a diffractive surface.

38. A zoom lens according to claim 31, wherein said diffractive surface comprises a first diffraction grating, and a second diffraction grating formed on said first diffraction grating, wherein said first diffraction grating and said second diffraction grating are made of different materials from each other.

39. A zoom lens comprising a plurality of lens unit which consist of, in order from an object side to an image side, a first lens unit of positive refractive power and a second lens unit of negative refractive power, wherein a separation between said first lens unit and said second lens unit is varied to effect zooming, and wherein said first lens unit has one positive lens and two negative lenses, and said first lens unit has a diffractive surface.

40. A zoom lens according to claim 39, wherein said first lens unit comprises, in order from the object side, a positive lens, a negative lens, a negative lens and a positive lens.

41. A zoom lens according to claim 39, wherein second lens unit comprises, in order from the object side, a positive lens and a negative lens.

42. A zoom lens according to claim 39, wherein said diffractive surface included in said first lens unit is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating is defined as

43. A zoom lens according to claim 39, wherein said second lens unit has a diffractive surface, and wherein said diffractive surface element included in said second lens unit is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating included in said second lens unit is defined as

44. A zoom lens according to claim 39, satisfying the following conditions:

45. A zoom lens according to claim 39, wherein each of a positive lens disposed closest to the image side in said first lens unit and a negative lens disposed closest to the image side in said second lens unit is a diffractive surface.

46. A zoom lens according to claim 39, wherein said diffractive surface comprises a first diffraction grating, and a second diffraction grating formed on said first diffraction grating, wherein said first diffraction grating and said second diffraction grating are made of different materials from each other.

47. A zoom lens comprising a plurality of lens unit which consist of, in order from an object side to an image side, a first lens unit of positive refractive power and a second lens unit of negative refractive power, wherein a separation between said first lens unit and said second lens unit is varied to effect zooming, and wherein a stop is disposed within said first lens unit and, when said first lens unit is divided into a front lens sub-unit closer to the object side than the stop and a rear lens sub-unit disposed closer to the image side than the stop, said rear lens sub-unit has a diffractive surface.

48. A zoom lens according to claim 47, satisfying the following condition:

49. A zoom lens according to claim 47, wherein second lens unit comprises, in order from the object side, a positive lens and a negative lens.

50. A zoom lens according to claim 47, wherein said diffractive surface included in said rear lens sub-unit is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating is defined as

51. A zoom lens according to claim 47, wherein said second lens unit has a diffractive surface, and wherein said diffractive surface included in said second lens unit is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating included in said second lens unit is defined as

52. A zoom lens according to claim 47, satisfying the following conditions:

53. A zoom lens according to claim 47, wherein each of a positive lens disposed lens disposed closest to the image side in said first lens unit and a negative lens disposed closest to the image side in said second lens unit is a diffractive surface.

54. A zoom lens according to claim 47, wherein said diffractive surface comprises a first diffraction grating, and a second diffraction grating formed on said first diffraction grating, wherein said first diffraction grating and said second diffraction grating are made of different materials from each other.

55. A zoom lens comprising, in order from an object side, a first lens unit of positive refractive power, a second lens unit of positive refractive power and a third lens unit of negative refractive power, wherein said first, second and third lens units are moved such that, during zooming from a wide-angle end to a telephoto end, a separation between said first lens unit and said second lens unit increases and a separation between said second lens unit and said third lens unit decreases, wherein said zoom lens has a diffractive surface and wherein said first lens unit is consists of a positive lens and a negative lens, and there is a space between said positive and negative lenses.

56. A zoom lens according to claim 55, wherein said diffractive surface is included in said third lens unit.

57. A zoom lens according to claim 55, wherein said diffractive surface is included in said second lens unit.

58. A zoom lens according to claim 55, wherein said third lens unit consists of a single lens.

59. A zoom lens according to claim 55, wherein said diffractive surface is composed of a diffraction grating of revolution symmetry with respect to an optical axis, and, as a phase φ

(h) of said diffraction grating is given by

60. A zoom lens according to claim 59, satisfying the following condition:

61. A zoom lens according to claim 59, where said diffractive surface is included in said third lens unit, and said zoom lens satisfies the following condition:

62. A zoom lens according to claim 55, wherein said third lens unit contributes to a greatest variation of magnification among said first to third lens units.

63. A zoom lens according to claim 55, further comprising a stop positioned on the object side of said second lens unit and arranged to move integrally with said second lens unit during zooming.

64. A zoom lens according to claim 55, wherein said second lens unit consists of negative lens of meniscus form concave toward the object side and a positive lens, totaling two lenses.

65. A zoom lens according to claim 55, wherein said diffractive surface is included in each of said second lens unit and said third lens unit, and wherein said diffractive surface is composed of a diffraction grating of revolution symmetry with respect to an optical axis and, as a phase φ

n(h) of the diffraction grating in the n-th lens unit given by

66. A zoom lens according to claim 55, wherein said first, second and third lens units axially move toward the object side during zooming from the wide-angle end to the telephoto end.

67. A zoom lens according to claim 55, wherein said diffractive surface comprises a first diffraction grating, and a second diffraction grating formed on said first diffracting grating, wherein said first diffraction grating and said second diffraction grating are made of different materials from each other.