Zoom lens with diffractive optical elements

• US 5,978,153 A
• Filed: 10/26/1998
• Issued: 11/02/1999
• Est. Priority Date: 10/31/1997
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Nishio, Akihiro
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Spector, David N.
• Application Number:
  US09/178,690
• Time in Patent Office: 372 Days
• Field of Search: 359/690, 359/576, 359/570, 359/676, 359/683, 359/687, 359/688, 359/708
• US Class Current: 359/690
• CPC Class Codes: G02B 15/144113 arranged +-++
• CPC Class Codes: G02B 15/145113 arranged +-++-
• CPC Class Codes: G02B 15/145121 arranged +-+-+
• CPC Class Codes: G02B 15/145129 arranged +-+++
• CPC Class Codes: G02B 15/173 arranged +-+
• CPC Class Codes: G02B 27/0037 with diffracting elements G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876
• CPC Class Codes: G02B 27/0056 by using a diffractive optical element
• CPC Class Codes: G02B 27/4277 being separated by an air space

Abstract

A zoom lens includes, in order from an object side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, and a subsequent lens unit of positive refractive power as a whole, wherein during zooming from a wide-angle end to a telephoto end, at least the first lens unit is moved along an optical axis such that a separation between the first lens unit and the second lens unit increases, and wherein at least one diffractive optical element is provided in the first lens unit.

Claims

1. A zoom lens comprising, in order from an object side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, and a subsequent lens unit of positive refractive power as a whole, wherein during zooming from a wide-angle end to a telephoto end, at least said first lens unit is moved along an optical axis such that a separation between said first lens unit and said second lens unit increases, and wherein at least one diffractive optical element is provided in said first lens unit.

2. A zoom lens according to claim 1, wherein at least one diffractive optical element is provided in said second lens unit.

3. A zoom lens according to claim 1, wherein said first lens unit and said second lens unit each have at least one positive lens and at least one negative lens.

4. A zoom lens according to claim 1, wherein a diffractive optical surface of said diffractive optical element is formed as a diffraction grating of a laminated structure.

11. A zoom lens according to claim 1, wherein, when a diffractive optical surface of said diffractive optical element has a phase φ

(H) at a distance H from the optical axis as expressed by

space="preserve" listing-type="equation">φ

(H)=(2 π

·

m/λ

)·

(C2·

H.sup.2 +C4·

H.sup.4 +C6·

H.sup.6 + . . . +C(2i)·

H.sup.(2i))

where λ

is a reference wavelength,

m is a diffraction order, and

C(2i) is a phase coefficient of a term in the 2i-th degree,

said zoom lens satisfies the following condition;

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

10.sup.-9 <

|C2/F1|<

5×

10.sup.-6

where F1 is a focal length of said first lens unit.

12. A zoom lens according to claim 1, wherein said subsequent lens unit comprises a third lens unit of positive refractive power, a fourth lens unit of positive refractive power, and a fifth lens unit of negative refractive power.

13. A zoom lens according to claim 1, wherein said subsequent lens unit comprises a third lens unit of positive refractive power, a fourth lens unit of positive refractive power, and a fifth lens unit of positive refractive power.

14. A zoom lens according to claim 1, wherein said subsequent lens unit comprises a third lens unit of positive refractive power, and a fourth lens unit of positive refractive power.

15. A zoom lens according to claim 1, wherein said subsequent lens unit comprises a third lens unit of positive refractive power, a fourth lens unit of negative refractive power, and a fifth lens unit of positive refractive power.

16. An optical apparatus comprising a zoom lens according to one of claims 1 to 15.

5. A zoom lens comprising, in order from an object side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, and a subsequent lens unit of positive refractive power as a whole, wherein during zooming from a wide-angle end to a telephoto end, at least one of said first lens unit and said second lens unit is moved along an optical axis such that a separation between said first lens unit and said second lens unit increases, and wherein at least one diffractive optical element is provided in said first lens unit, said zoom lens satisfying the following condition:

space="preserve" listing-type="equation">0.3<

|F2/Fw|<

0.75

where F2 is a focal length of said second lens unit, and Fw is a focal length in the wide-angle end of said zoom lens.

6. A zoom lens according to claim 5, wherein at least one diffractive optical element is provided in said second lens unit.

7. A zoom lens according to claim 5, wherein said first lens unit and said second lens unit each have at least one positive lens and at least one negative lens.

8. A zoom lens according to claim 5, wherein a diffractive optical surface of said diffractive optical element is formed as a diffraction grating of a laminated structure.

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

space="preserve" listing-type="equation">0.35<

|F2/Fw|<

0.65

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

space="preserve" listing-type="equation">0.2<

|F2/F1|<

0.7

where F1 is a focal length of said first lens unit.