Zoom lens system and optical apparatus using the same

• US 6,639,721 B2
• Filed: 02/13/2002
• Issued: 10/28/2003
• Est. Priority Date: 02/19/2001
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Endo, Hiroshi
• Primary Examiner(s): Robinson, Mark A.
• Assistant Examiner(s): BOUTSIKARIS, LEONIDAS
• Application Number:
  US10/076,676
• Publication Number:
  US 20020163736A1
• Time in Patent Office: 622 Days
• Field of Search: 359/566, 359/676, 359/747, 359/686, 359/781, 396/72
• US Class Current: 359/566
• CPC Class Codes: G02B 15/144511 arranged -+-+
• CPC Class Codes: G02B 15/177 having a negative front lens or group of lenses
• 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 27/4211 correcting chromatic aberrations G02B27/0056, G02B27/4222, G02B27/4227 take precedence
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 27/4277 being separated by an air space
• CPC Class Codes: G02B 27/4288 having uniform diffraction efficiency over a large spectral bandwidth

Abstract

There are provided A zoom lens system comprising, in order from an object side, a first lens unit of negative refractive power, a second lens unit of positive refractive power, a third lens unit of negative refractive power, and a fourth lens unit of positive refractive power, wherein the zoom lens system zooming from a wide angle end to a telephoto end a separation between each lens units is varied so that conditional expressions D1W>D1T, D2W>D2T, and D3W>D3T are satisfied where DiW is a separation between an i-th lens unit and an (i+1)-th lens unit at a wide-angle end, DiT is a separation between an i-th lens unit and an (i+1)-th lens unit at a telephoto end, wherein a diffraction optical element is included in at least one of lens units.

Claims

1. A zoom lens system comprising, in order from an object side:

a first lens unit of negative refractive power,

a second lens unit of positive refractive power,

a third lens unit of negative refractive power, and

a fourth lens unit of positive refractive power,

wherein said zoom lens system zooming from a wide-angle end to a telephoto end while varying a separation between each lens units so that conditional expressions D1W>

D1T D2W<

D2T, and D3W>

D3T are satisfied where DiW is a separation between i-th and (i+1)-th lens units at a wide-anile end, DiT is a separation between the i-th and (i+1)-th lens units at a telephoto end, and

wherein a diffraction optical element is included in the fourth lens unit, and a conditional expression

2. A zoom lens system comprising, in order from an object side:

a first lens unit of negative refractive power,

a second lens unit of positive refractive power,

a third lens unit of negative refractive power, and

a fourth lens unit of positive refractive power,

wherein said zoom lens system zooming from a wide-angle end to a telephoto end while varying a separation between each lens units so that conditional expressions D1W>

D1T, D2W<

D2T, and D3W>

D3T are satisfied where DiW is a separation between i-th and (i+1)-th lens units at a wide-angle end, DiT is a separation between the i-th and (i+1)-th lens units at a telephoto end, and

wherein a diffraction optical element is included in the first lens unit, and a conditional expression

3. A zoom lens system comprising, in order from an object side:

a first lens unit of negative refractive power,

a second lens unit of positive refractive power,

a third lens unit of negative refractive power, and

a fourth lens unit of positive refractive power,

wherein said zoom lens system zooming from a wide-angle end to a telephoto end while varying a separation between each lens units so that conditional expressions D1W>

D1T, D2W<

D2T, and D3W>

D3T are satisfied where DiW is a separation between i-th and (i+1)-th lens units at a wide-angle end DiT is a separation between the i-th and (i+1)-th lens units at a telephoto end,

wherein a diffraction optical element is included in at least one of said lens units, and wherein conditional expressions 0.7<

|f1|/{square root over ((fw·

ft))}<

1.1, 0.6<

f2/{square root over ((fw·

ft))}<

1.4, 1.05<

|f3|/f2<

1.5, and 1.05<

f4/f2<

2.5 are satisfied where fw and ft are focal lengths of an entire lens system at the wide-angle and telephoto ends, respectively, and fi is a focal length of the i-th lens unit.

4. A zoom lens system comprising, in order from an object side:

a first lens unit of negative refractive power, wherein said first lens unit has such an aspheric surface that negative refractive power of the aspheric surface decreases from a center of the lens to a peripheral of the lens,

a second lens unit of positive refractive power,

a third lens unit of negative refractive power, and

a fourth lens unit of positive refractive power,

wherein said zoom lens system zooming from a wide-angle end to a telephoto end while varying a separation between each lens units so that conditional expressions D1W>

D1T, D2W<

D2T, and D3W>

D3T are satisfied where DiW is a separation between i-th and (i+1)-th lens units at a wide-angle end, DiT is a separation between the i-th and (i+1)-th lens units at a telephoto end,

wherein a diffraction optical element is included in at least one of said lens units.

5. A zoom lens system comprising, in order from an object side:

a first lens unit of negative refractive power,

a second lens unit of positive refractive power,

a third lens unit of negative refractive power, and

a fourth lens unit of positive refractive power,

wherein said zoom lens system zooming from a wide-angle end to a telephoto end while varying a separation between each lens units so that conditional expressions D1W>

D1T, D2W<

D2T, and D3W>

D3T are satisfied where DiW is a separation between i-th and (i+1)-th lens units at a wide-angle end, DiT is a separation between the i-th and (i+1)-th lens units at a telephoto end,

wherein a diffraction optical element is included in at least one of said lens units, and

wherein a conditional expression −

30<

θ

<

30 is satisfied where θ

is an angle between a ray incident to and emitted from said diffraction optical element and a plane normal of said diffraction optical element.

6. A zoom lens system according to claim 5, wherein a conditional expression 1.6<

SKw/fw<

2.8 is satisfied where fw is a focal length of an entire lens system at the wide-angle end, and SKw is a back focal distance at the wide-angle end.

7. A zoom lens system according to claim 5, wherein the second and fourth lens units move together as one member during zooming.

8. A zoom lens system according to claim 5, wherein said first lens unit moves while drawing a convex locus at a side of an image surface during zooming.

9. A zoom lens system according to claim 5, further comprising a stop adjacent to said third lens unit at the object side or an image side.

10. A zoom lens system according to claim 5, wherein a conditional expression −

15<

θ

<

15 is satisfied where θ

is an angle between a ray incident to and emitted from said diffraction optical element and a plane normal of said diffraction optical element.

11. A zoom lens system according to claim 5, wherein the diffraction optical element has a layered structure.

12. A zoom lens system comprising, in order from an object side:

a first lens unit of negative refractive power,

a second lens unit of positive refractive power,

a third lens unit of negative refractive power, and

a fourth lens unit of positive refractive power, wherein said fourth lens unit has such an aspheric surface that positive refractive power of the aspheric surface decreases from a center of the lens to a peripheral of the lens,

wherein said zoom lens system zooming from a wide-angle end to a telephoto end while varying a separation between each lens units so that conditional expressions D1W>

D1T, D2W<

D2T, and D3W>

D3T are satisfied where DiW is a separation between i-th and (i+1)-th lens units at a wide-angle end, DiT is a separation between the i-th and (i+1)-th lens units at a telephoto end,

wherein a diffraction optical element is included in at least one of said lens units.

13. A zoom lens system comprising, in order from an object side:

a first lens unit of negative refractive power,

a second lens unit of positive refractive power,

a third lens unit of negative refractive power, and

a fourth lens unit of positive refractive power,

wherein said zoom lens system zooming from a wide-angle end to a telephoto end while varying a separation between each lens units so that conditional expressions D1W>

D1T, D2W<

D2T, and D3W>

D3T are satisfied where DiW is a separation between i-th and (i+1)-th lens units at a wide-angle end, DiT is a separation between the i-th and (i+1)-th lens units at a telephoto end,

wherein a diffraction optical element is included in at least one of said lens units, and

wherein a conditional expression |dQ(h)/dh|<

30 is satisfied where Ci is a phase coefficient, h is a height from a center of an optical axis, λ

_o is a reference wave length, and Q(h)=(C1·

h²+C2·

h⁴+C3·

h⁶+ . . . )/λ

_o.

14. An optical apparatus comprising a zoom lens system comprising, in order from an object side,

a first lens unit of negative refractive power,

a second lens unit of positive refractive power,

a third lens unit of negative refractive power, and

a fourth lens unit of positive refractive power,

wherein said zoom lens system zooming from a wide angle end to a telephoto end a separation between each lens units is varied so that conditional expressions D1W>

D1T, D2W<

D2T, and D3W>

D3T are satisfied where DiW is a separation between an i-th lens unit and an (i+1)-th lens unit at a wide-angle end, DiT is a separation between an i-th lens unit and an (i+1)-th lens unit at a telephoto end,

wherein a diffraction optical element is included in at least one of lens units, and

wherein a conditional expression −

30<

θ

<

30 is satisfied where θ

is an angle between a ray incident to and emitted from said diffraction optical element and a plane normal of said diffraction optical element.