Diffractive optical element and optical system having the same

• US 6,624,943 B2
• Filed: 07/05/2001
• Issued: 09/23/2003
• Est. Priority Date: 09/10/1997
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Nakai, Takehiko, Setani, Michitaka
• Primary Examiner(s): Juba, John
• Assistant Examiner(s): BOUTSIKARIS, LEONIDAS
• Application Number:
  US09/898,029
• Publication Number:
  US 20010036012A1
• Time in Patent Office: 810 Days
• Field of Search: 359/569, 359/570, 359/571, 359/573, 359/574, 359/575, 359/576, 359/587
• US Class Current: 359/569
• CPC Class Codes: G02B 27/4211 correcting chromatic aberrations G02B27/0056, G02B27/4222, G02B27/4227 take precedence
• CPC Class Codes: G02B 27/4216 correcting geometrical aberrations
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 5/1823 in an overlapping or superposed manner

Abstract

A diffractive optical element includes a plurality of laminated diffraction grating surfaces. Each of the diffraction grating surfaces is formed to have a sufficiently small grating thickness as compared with a grating pitch thereof.

Claims

1. A diffractive optical element comprising:

a plurality of diffraction grating surfaces, each of said plurality of diffraction grating surfaces being formed on a boundary surface between layers which differ from each other in dispersion,

wherein the length obtained by combining optical path length differences generated at said plurality of diffraction grating surfaces is the same as the wavelength of light diffracted by said plurality of diffraction grating surfaces, and

wherein, letting a grating height and a grating pitch of a diffraction grating surface be denoted by d (μ

m) and P (μ

m), respectively, the following condition is satisfied for each of said plurality of diffraction grating surfaces;

2. An optical system comprising:

a lens system; and

a diffractive optical element according to claim 1.

3. A diffractive optical element according to claim 2, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

4. A diffractive optical element according to claim 1, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

5. An optical system comprising:

a diffractive optical element according to claim 1, said diffractive optical element being configured to abate chromatic aberration in said optical system.

6. A diffractive optical element according to claim 1, wherein said plurality of diffraction grating surfaces are formed such that the diffraction efficiency is more than 90% over the whole visible spectrum.

7. A diffractive optical element comprising:

a plurality of diffraction grating surfaces, each of said plurality of diffraction grating surfaces being formed on a boundary surface between layers which differ from each other in dispersion,

wherein the length obtained by combining optical path length differences generated at said plurality of diffraction grating surfaces is the same as the wavelength of light diffracted by said plurality of diffraction grating surfaces, and

wherein, letting a grating height of a diffraction grating surface be denoted by d (μ

m), the following condition is satisfied for each of said plurality of diffraction grating surfaces;

8. An observation optical system comprising:

a lens system; and

a diffractive optical element according to claim 7, said diffractive optical element operating to have a corrective effect upon chromatic aberration generated in said lens system.

9. An observation optical system according to claim 8, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

10. An optical system comprising:

a lens system; and

a diffractive optical element according to claim 7.

11. An optical system according to claim 10, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

12. A diffractive optical element according to claim 7, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

13. An optical system comprising:

a diffractive optical element according to claim 7, said diffractive optical element being configured to abate chromatic aberration in said optical system.

14. A diffractive optical element according to claim 7, wherein said plurality of diffraction grating surfaces are formed such that the diffraction efficiency is more than 90% over the whole visible spectrum.

15. A diffractive optical element comprising:

a plurality of diffraction grating surfaces, each of said plurality of diffraction grating surfaces being formed on a boundary surface between layers which differ from each other in dispersion,

wherein the length obtained by combining optical path length differences generated at said plurality of diffraction grating surfaces is the same as the wavelength of light diffracted by said plurality of diffraction grating surfaces, and

wherein, letting a grating pitch and a grating height of a diffraction grating surface be denoted by P (μ

m) and d (μ

m), respectively, the following conditions are satisfied for each of said plurality of diffraction grating surfaces;

16. An optical system comprising:

a lens system; and

a diffractive optical element according to claim 15.

17. An optical system according to claim 16, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

18. A diffractive optical element according to claim 15, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

19. An optical system comprising:

a diffractive optical element according to claim 15, said diffractive optical element being configured to abate chromatic aberration in said optical system.

20. A diffractive optical element according to claim 15, wherein said plurality of diffraction grating surfaces include a first diffraction grating surface and a second diffraction grating surface having the same grating height.

21. A diffractive optical element according to claim 15, wherein said plurality of diffraction grating surfaces include a first diffraction grating surface and a second diffraction grating surface having different grating heights.

22. A diffractive optical element according to claim 15, wherein said diffractive optical element is disposed on a curved surface of a lens.

23. A diffractive optical element according to claim 15, wherein said diffractive optical element comprises a first layer, a second layer, a third layer, and a fourth layer,

wherein a first diffraction grating surface of said plurality of diffraction grating surfaces is formed between the first layer and the second layer,

wherein a second diffraction grating surface of said plurality of diffraction grating surfaces is formed between the third layer and the fourth layer,

wherein the first layer and the third layer are made of a material having a first dispersion, and

wherein the second layer and the fourth layer are made of a material having a second dispersion different from the first dispersion.

24. A diffractive optical element according to claim 23, further comprising a base plate,

wherein a lamination plate comprising the first through fourth layers in order is disposed on a surface of the base plate.

25. A diffractive optical element according to claim 23, wherein the first and second diffraction grating surfaces are blazed diffraction grating surfaces,

wherein the grating heights of the first and second diffraction grating surfaces are the same, and

wherein the first and second diffraction grating surfaces slant in the same direction.

26. A diffractive optical element according to claim 23, wherein for each of the first diffraction grating surface and the second diffraction grating surface, d=5.95 μ

m and P=59.5 μ

m.

27. A diffractive optical element according to claim 23, wherein for each of the first diffraction grating surface and the second diffraction grating surface, d=2 μ

m and P=40 μ

m.

28. A diffractive optical element according to claim 23, wherein for each of the first diffraction grating surface and the second diffraction grating surface, d=4 μ

m and P=80 μ

m.

29. A diffractive optical element according to claim 15, wherein said diffractive optical element comprises a first layer, a second layer, and a third layer,

wherein a first diffraction grating surface of said plurality of diffraction grating surfaces is formed between the first layer and the second layer,

wherein a second diffraction grating surface of said plurality of diffraction grating surfaces is formed between the second layer and the third layer,

wherein the first layer and the third layer are made of a material having a first dispersion,

wherein the second layer is made of a material having a second dispersion different from the first dispersion, and

wherein the first and second diffraction grating surfaces are blazed diffraction grating surfaces slanting in opposite directions and having the same grating height.

30. A diffractive optical element according to claim 15, wherein said plurality of diffraction grating surfaces are formed such that the diffraction efficiency is more than 90% over the whole visible spectrum.

31. A diffractive optical element comprising:

a plurality of diffraction grating surfaces, each of said plurality of diffraction grating surfaces being formed on a boundary surface between layers which differ from each other in dispersion, and a grating pitch of each of the diffractive grating surfaces being changed within the surface,

wherein the length obtained by combining optical path length differences generated at said plurality of diffraction grating surfaces is the same as the wavelength of light diffracted by said plurality of diffraction grating surfaces, and

wherein, letting a grating height and a minimum grating pitch of a the diffraction grating surface be denoted by d (μ

m) and P (μ

m), respectively, the following condition is satisfied for each of said plurality of diffraction grating surfaces;

32. An optical system comprising:

a lens system; and

a diffractive optical element according to claim 31.

33. A diffractive optical element according to claim 32, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

34. A photo-taking optical system comprising:

a lens system; and

a diffractive optical element according to claim 31, said diffractive optical element operating to have a corrective effect upon chromatic aberration generated in said lens system.

35. A photo-taking optical system according to claim 34, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

36. A diffractive optical element according to claim 31, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

37. An optical system comprising:

a diffractive optical element according to claim 31, said diffractive optical element being configured to abate chromatic aberration in said optical system.

38. A diffractive optical element according to claim 31, wherein said plurality of diffraction grating surfaces are formed such that the diffraction efficiency is more than 90% over the whole visible spectrum.

39. A diffraction optical element comprising:

a plurality of diffraction grating surfaces, each of said plurality of diffraction grating surfaces being formed on a boundary surface between layers which differ from each other in dispersion, and a grating pitch of each of the diffractive grating surfaces being changed within the surface,

wherein the length obtained by combining optical path length differences generated at said plurality of diffraction grating surfaces is the same as the wavelength of light diffracted by said plurality of diffraction grating surfaces, and

wherein, letting a grating height of a diffraction grating surface be denoted by d (μ

m) the following condition is satisfied for each of said plurality of diffraction grating surfaces;

40. An optical system comprising:

a lens system; and

a diffractive optical element according to claim 39.

41. An optical system according to claim 40, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces of whose grating slant directions are opposite to each other.

42. A photo-taking optical system comprising:

a lens system; and

a diffractive optical element according to claim 39, said diffractive optical element operating to have a corrective effect upon chromatic aberration generated in said lens system.

43. A photo-taking optical system according to claim 42, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

44. An observation optical system comprising:

a lens system; and

a diffractive optical element according to claim 39, said diffractive optical element operating to have a corrective effect upon chromatic aberration generated in said lens system.

45. An observation optical system according to claim 44, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

46. A diffractive optical element according to claim 39, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

47. An optical system comprising:

a diffractive optical element according to claim 39, said diffractive optical element being configured to abate chromatic aberration in said optical system.

48. A diffractive optical element according to claim 39, wherein said plurality of diffraction grating surfaces are formed such that the diffraction efficiency is more than 90% over the whole visible spectrum.

49. A diffractive optical element comprising:

a plurality of diffraction grating surfaces, each of said plurality of diffraction grating surfaces being formed on a boundary surface between layers which differ from each other in dispersion, and a grating pitch of each of the diffractive grating surfaces being changed within the surface,

wherein the length obtained by combining optical path length differences generated at said plurality of diffraction grating surfaces is the same as the wavelength of light diffracted by said plurality of diffraction grating surfaces, and

wherein, letting a grating height and a minimum grating pitch of a diffraction grating surface be denoted by d (μ

m) and P (μ

m), respectively, the following conditions are satisfied for each of said plurality of diffraction grating surfaces;

50. An optical system comprising:

a lens system; and

a diffractive optical element according to claim 49.

51. An optical system according to claim 50, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

52. A photo-taking optical system comprising:

a lens system; and

a diffractive optical element according to claim 49, said diffractive optical element operating to have a corrective effect upon chromatic aberration generated in said lens system.

53. A photo-taking optical system according to claim 52, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

54. An observation optical system comprising:

a lens system; and

a diffractive optical element according to claim 49, said diffractive optical element operating to have a corrective effect upon chromatic aberration generated in said lens system.

55. An observation optical system according to claim 54, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

56. A diffractive optical element according to claim 49, wherein said plurality of diffraction grating surfaces include two diffraction grating surfaces whose grating slant directions are opposite to each other.

57. An optical system comprising:

a diffractive optical element according to claim 49, said diffractive optical element being configured to abate chromatic aberration in said optical system.

58. A diffractive optical element according to claim 49, wherein said plurality of diffraction grating surfaces are formed such that the diffraction efficiency is more than 90% over the whole visible spectrum.