Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS20010013980 A1
Publication typeApplication
Application numberUS 09/810,245
Publication dateAug 16, 2001
Filing dateMar 19, 2001
Priority dateDec 22, 1998
Also published asCN1149419C, CN1261681A, CN1523392A, US6229655, US6456443, US6532114
Publication number09810245, 810245, US 2001/0013980 A1, US 2001/013980 A1, US 20010013980 A1, US 20010013980A1, US 2001013980 A1, US 2001013980A1, US-A1-20010013980, US-A1-2001013980, US2001/0013980A1, US2001/013980A1, US20010013980 A1, US20010013980A1, US2001013980 A1, US2001013980A1
InventorsTetsuo Kohno, Genta Yagyu
Original AssigneeTetsuo Kohno, Genta Yagyu
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Zoom lens system
US 20010013980 A1
Abstract
A zoom lens system has, from the object side, a first lens unit, a second lens unit and a third lens unit. The first lens unit has a negative optical power as a whole. The second and third lens units have a positive optical power as a whole. In the zoom lens system, zooming is achieved by varying the distance between the first and second lens units, and at least one of the lens elements is a plastic lens element.
Images(23)
Previous page
Next page
Claims(57)
What is claimed is:
1. A zoom lens system comprising, in order from an object side:
a first lens unit;
a second lens unit having a positive optical power; and
a third lens unit,
wherein zooming is achieved by moving at least two lens units so as to vary a distance between the first and second lens units and a distance between the second and third lens units, and wherein at least one of the lens elements included in the lens units is a plastic lens element that fulfills the following conditions:
−0.8<Cp(N′−N)/φW<0.8 −0.45<M3/M2<0.90 (where φT/φW>1.6)
where
Cp represents a curvature of the plastic lens element;
φW represents an optical power of the entire zoom lens system at a wide-angle end;
N′ represents a refractive index of an object-side medium of an aspherical surface for d line;
N represents a refractive index of an image-side medium of an aspherical surface for d line;
M3 represents an amount of movement of the third lens unit (where the direction pointing to the object side is negative with respect to the wide-angle end);
M2 represents an amount of movement of the second lens unit; and
φT represents an optical power of the entire zoom lens system at a telephoto end.
2. The zoom lens system of
claim 1
wherein said first lens unit has a negative optical power.
3. The zoom lens system of
claim 1
wherein said second lens unit includes a positive lens element and a negative lens element.
4. The zoom lens system of
claim 1
wherein said third lens unit has a positive optical power.
5. The zoom lens system of
claim 1
wherein said plastic lens element is contained in the first lens unit and fulfills the following conditions:
|φP/φ1|<1.20 0.20<|φ1/φW|<0.70
where
φP represents an optical power of the plastic lens element;
φ1 represents an optical power of the first lens unit; and
φT represents an optical power of the entire zoom lens system at a telephoto end.
6. The zoom lens system of
claim 5
wherein said first lens unit has a negative optical power.
7. The zoom lens system of
claim 6
wherein said first lens unit includes a positive lens element and a negative lens element.
8. The zoom lens system of
claim 5
wherein said third lens unit has a positive optical power.
9. The zoom lens system of
claim 1
, wherein said plastic lens element is included in the second lens unit and fulfills the following conditions:
P/φ2|<2.5 0.25<φ2/φW<0.75
where
φP represents an optical power of the plastic lens element; and
φ2 represents an optical power of the second lens unit.
10. The zoom lens system of
claim 9
wherein said first lens unit has a negative optical power.
11. The zoom lens system of
claim 9
wherein said second lens unit includes a positive lens element and a negative lens element.
12. The zoom lens system of
claim 9
wherein said third lens unit has a positive optical power.
13. The zoom lens system of
claim 1
wherein said plastic lens element is included in the third lens unit and fulfills the following conditions:
−0.30<M3/M2<0.90 |φP/φ3|<1.70 0.1<φ3/φW<0.60
where
φP represents an optical power of the plastic lens element; and
φ3 represents an optical power of the third lens unit.
14. The zoom lens system of
claim 13
wherein said first lens unit has a negative optical power.
15. The zoom lens system of
claim 13
wherein said third lens unit has a positive optical power.
16. The zoom lens system of
claim 1
, wherein at least one of the lens elements included in the first lens unit and at least one of the lens elements included in the second lens unit are plastic lens elements that fulfill the following conditions:
−1.4<φPi/φWhi<1.4 0.5<log(β2T/β2W)/log Z<2.2
where
φPi represents an optical power of an ith plastic lens element;
hi represents a height of incidence at which a paraxial ray enters an object-side surface of the ith plastic lens element at a telephoto end, assuming that initial values of a converted inclination α1 and a height h1, for paraxial tracing, are 0 and 1, respectively;
β2W represents a lateral magnification of the second lens unit at the wide-angle end;
β2T represents a lateral magnification of the second lens unit at the telephoto end;
Z represents a zoom ratio; and
log represents a natural logarithm.
17. The zoom lens system of
claim 16
wherein said first lens unit has a negative optical power.
18. The zoom lens system of
claim 16
wherein said third lens unit has a positive optical power.
19. The zoom lens system as claimed in
claim 1
, wherein at least one of the lens elements included in the first lens unit and at least one of the lens elements included in the third lens element are plastic lens elements that fulfill the following conditions:
−1.4<φPi/φWhi<1.4 −1.2<log(β3T/β3W)/log Z<0.5
where
φPi represents an optical power of an ith plastic lens element;
hi represents a height of incidence at which a paraxial ray enters an object-side surface of the ith plastic lens element at a telephoto end, assuming that initial values of a converted inclination α1 and a height h1, for paraxial tracing, are 0 and 1, respectively;
β3W represents a lateral magnification of the third lens unit at the wide-angle end;
β3T represents a lateral magnification of the third lens unit at the telephoto end;
Z represents a zoom ratio; and
log represents a natural logarithm.
20. The zoom lens system of
claim 19
wherein said first lens unit has a negative optical power.
21. The zoom lens system of
claim 19
wherein said second lens unit includes a positive lens element and a negative lens element.
22. The zoom lens system of
claim 19
wherein said third lens unit has a positive optical power.
23. The zoom lens system of
claim 1
, wherein at least one of the lens elements included in the second lens unit and at least one of the lens elements included in the third lens unit are plastic lens elements that fulfill the following conditions:
−1.4<φPi/φWhi<1.4 0.75<log(β3T/β3W)/log(β2T/β2W)<0.65
where
φPi represents an optical power of an ith plastic lens element;
hi represents a height of incidence at which a paraxial ray enters an object-side surface of the ith plastic lens element at a telephoto end, assuming that initial values of a converted inclination α1 and a height h1, for paraxial tracing, are 0 and 1, respectively;
β2W represents a lateral magnification of the second lens unit at the wide-angle end;
β2T represents a lateral magnification of the second lens unit at the telephoto end;
β3W represents a lateral magnification of the third lens unit at the wide-angle end;
β3T represents a lateral magnification of the third lens unit at the telephoto end; and
log represents a natural logarithm.
24. The zoom lens system of
claim 23
wherein said first lens unit has a negative optical power.
25. The zoom lens system of
claim 23
wherein said second lens unit includes a positive lens element and a negative lens element.
26. The zoom lens system of
claim 23
wherein said third lens unit has a positive optical power.
27. The zoom lens system comprising, in order from an object side:
a first lens unit;
a second lens unit having a positive optical power; and
a third lens unit,
wherein zooming is achieved by varying a distance between the first and second lens units and a distance between the second and third lens units, and wherein at least one of the lens elements included in the second lens unit is a plastic lens element that fulfills the following conditions:
P/φ2|<2.5 0.25<φ2/φW<0.75
where
φP represents an optical power of the plastic lens element;
φ2 represents an optical power of the second lens unit; and
φW represents an optical power of the entire zoom lens system at a wide-angle end.
28. A zoom lens system comprising, in order from an object side:
a first lens unit;
a second lens unit having a positive optical power; and
a third lens unit,
wherein zooming is achieved by moving at least two lens units so as to vary a distance between the first and second lens units and a distance between the second and third lens units, and wherein at least one of the lens elements included in the third lens unit is a plastic lens element that fulfill the following conditions:
−0.30<M3/M2<0.90 |φP/φ3|<1.70 0.1<φ3/φW<0.60
where
M3 represents an amount of movement of the third lens unit (the direction pointing to the object side is negative with respect to a wide-angle end);
M2 represents an amount of movement of the second lens unit;
φP represents an optical power of the plastic lens element;
φ3 represents an optical power of the third lens unit; and
φW represents an optical power of the entire zoom lens system at a wide-angle end.
29. A zoom lens system comprising, in order from an object side:
a first lens unit;
a second lens unit having a positive optical power; and
a third lens unit,
wherein zooming is achieved by moving at least two lens units so as to vary a distance between the first and second lens units and a distance between the second and third lens units, and wherein at least one of the lens elements included in the first lens unit and at least one of the lens elements included in the second lens unit are plastic lens element that fulfills the following conditions:
−1.4<φPi/φWhi<1.4 0.5<log(β2T/β2W)/log Z<2.2
where
φPi represents an optical power of an ith plastic lens element;
φW represents an optical power of the entire zoom lens system at a wide-angle end;
hi represents a height of incidence at which a paraxial ray enters an object-side surface of the ith plastic lens element at a telephoto end, assuming that initial values of a converted inclination α1 and a height h1, for paraxial tracing, are 0 and 1, respectively;
β2W represents a lateral magnification of the second lens unit at the wide-angle end;
β2T represents a lateral magnification of the second lens unit at the telephoto end;
Z represents a zoom ratio; and
log represents a natural logarithm.
30. A zoom lens system comprising, in order from an object side:
a first lens unit;
a second lens unit having a positive optical power; and
a third lens unit,
wherein zooming is achieved by moving at least two lens units so as to vary a distance between the first and second lens units and a distance between the second and third lens units, and wherein at least one of the lens elements included in the first lens unit and at least one of the lens elements included in the third lens unit are plastic lens element that fulfill the following conditions:
−1.4<φPi/φWhi<1.4 −1.2<log(β3T/β3W)/log Z<0.5
where
φPi represents an optical power of an ith plastic lens element;
φW represents an optical power of the entire zoom lens system at a wide-angle end;
hi represents a height of incidence at which a paraxial ray enters an object-side surface of the ith plastic lens element at a telephoto end, assuming that initial values of a converted inclination α1 and a height h1, for paraxial tracing, are 0 and 1, respectively;
β3W represents a lateral magnification of the third lens unit at the wide-angle end;
β3T represents a lateral magnification of the third lens unit at the telephoto end;
Z represents a zoom ratio; and
log represents a natural logarithm.
31. A zoom lens system comprising, in order from an object side:
a first lens unit;
a second lens unit having a positive optical power; and
a third lens unit having a positive optical power,
wherein zooming is achieved by moving at least two lens units so as to vary a distance between the first and second lens units and a distance between the second and third lens units, and wherein at least one of the lens elements included in the second lens unit and at least one of the lens elements included in the third lens unit are plastic lens elements that fulfill the following conditions:
−1.4<φPi/φWhi<1.4 −0.75<log(β3T/β3W)/log(β2T/β2W)<0.65
where
φPi represents an optical power of an ith plastic lens element;
φW represents an optical power of the entire zoom lens system at a wide-angle end;
hi represents a height of incidence at which a paraxial ray enters an object-side surface of the ith plastic lens element at a telephoto end, assuming that initial values of a converted inclination α1 and a height h1, for paraxial tracing, are 0 and 1, respectively;
β2W represents a lateral magnification of the second lens unit at the wide-angle end;
β2T represents a lateral magnification of the second lens unit at the telephoto end;
β3W represents a lateral magnification of the third lens unit at the wide-angle end;
β3T represents a lateral magnification of the third lens unit at the telephoto end; and
log represents a natural logarithm.
32. A digital camera comprising a zoom lens system, a low pass filter and an image sensor, wherein said zoom lens system includes, in order from the object side thereof:
a first lens unit;
a second lens unit having a positive optical power; and
a third lens unit,
wherein zooming is achieved by moving at least two lens units so as to vary a distance between the first and second lens units and a distance between the second and third lens units, and wherein at least one of the lens elements included in the lens units is a plastic lens element that fulfills the following conditions:
−0.8<Cp(N′−N)/φW<0.8 −0.45<M3/M2<0.90(where φT/φW>1.6)
where
Cp represents a curvature of the plastic lens element;
φW represents an optical power of the entire zoom lens system at a wide-angle end;
N′ represents a refractive index of an object-side medium of an aspherical surface for d line;
N represents a refractive index of an image-side medium of an aspherical surface for d line;
M3 represents an amount of movement of the third lens unit (where the direction pointing to the object side is negative with respect to the wide-angle end);
M2 represents an amount of movement of the second lens unit; and
φT represents an optical power of the entire zoom lens system at a telephoto end.
33. The digital camera of
claim 32
, wherein said first lens unit has a negative optical power.
34. The digital camera of
claim 32
, wherein said second lens unit includes a positive lens element and a negative lens element.
35. The digital camera of
claim 32
, wherein said third lens unit has a positive optical power.
36. The digital camera of
claim 32
, wherein said plastic lens element is contained in the first lens unit and fulfills the following conditions:
P/φ1|<1.20 0.20<|φ1/φW|<0.70
where
φP represents an optical power of the plastic lens element;
φ1 represents an optical power of the first lens unit; and
φT represents an optical power of the entire zoom lens system at a telephoto end.
37. The digital camera of
claim 36
, wherein said first lens unit has a negative optical power.
38. The digital camera of
claim 37
, wherein said first lens unit includes a positive lens element and a negative lens element.
39. The digital camera of
claim 36
, wherein said third lens unit has a positive optical power.
40. The digital camera of
claim 32
, wherein said plastic lens element is included in the second lens unit and fulfills the following conditions:
P/φ2|<2.5 0.25<φ2/φW<0.75
where
φP represents an optical power of the plastic lens element; and
φ2 represents an optical power of the second lens unit.
41. The digital camera of
claim 40
, wherein said first lens unit has a negative optical power.
42. The digital camera of
claim 40
, wherein said second lens unit includes a positive lens element and a negative lens element.
43. The digital camera of
claim 40
, wherein said third lens unit has a positive optical power.
44. The zoom lens system of
claim 32
wherein said plastic lens is included in the third lens unit and fulfills the following conditions:
−0.30<M3/M2<0.90 |φP/φ3|<1.70 0.1<3/φW<0.60
where
φP represents an optical power of the plastic lens element; and
φ3 represents an optical power of the third lens unit.
45. The digital camera of
claim 44
, wherein said first lens unit has a negative optical power.
46. The digital camera of
claim 44
, wherein said third lens unit has a positive optical power.
47. The digital camera of
claim 32
, wherein at least one of the lens elements included in the first lens unit and at least one of the lens elements included in the second lens unit are plastic lens elements that fulfill the following conditions:
−1.4<φPi/φWhi<1.4 0.5<log(β2T/β2W)/log Z<2.2
where
φPi represents an optical power of an ith plastic lens element;
hi represents a height of incidence at which a paraxial ray enters an object-side surface of the ith plastic lens element at a telephoto end, assuming that initial values of a converted inclination α1 and a height h1, for paraxial tracing, are 0 and 1, respectively;
β2W represents a lateral magnification of the second lens unit at the wide-angle end;
β2T represents a lateral magnification of the second lens unit at the telephoto end;
Z represents a zoom ratio; and
log represents a natural logarithm.
48. The digital camera of
claim 47
, wherein said first lens unit has a negative optical power.
49. The digital camera of
claim 47
, wherein said third lens unit has a positive optical power.
50. The digital camera of
claim 32
, wherein at least one of the lens elements included in the first lens unit and at least one of the lens elements included in the third lens element are plastic lens elements that fulfill the following conditions:
−1.4<φPi/φWhi<1.4 −1.2<log(β3T/β3W)/log Z<0.5
where
φPi represents an optical power of an ith plastic lens element;
hi represents a height of incidence at which a paraxial ray enters an object-side surface of the ith plastic lens element at a telephoto end, assuming that initial values of a converted inclination α1 and a height h1, for paraxial tracing, are 0 and 1, respectively;
β3W represents a lateral magnification of the third lens unit at the wide-angle end;
β3T represents a lateral magnification of the third lens unit at the telephoto end;
Z represents a zoom ratio; and
log represents a natural logarithm.
51. The digital camera of
claim 50
, wherein said first lens unit has a negative optical power.
52. The digital camera of
claim 50
, wherein said second lens unit includes a positive lens element and a negative lens element.
53. The digital camera of
claim 50
, wherein said third lens unit has a positive optical power.
54. The digital camera of
claim 32
, wherein at least one of the lens elements included in the second lens unit and at least one of the lens elements included in the third lens unit are plastic lens elements that fulfill the following conditions:
−1.4<φPi/φWhi<1.4 −0.75<log(β3T/β3W)/log(β2T/β2W)<0.65
where
φPi represents an optical power of an ith plastic lens element;
hi represents a height of incidence at which a paraxial ray enters an object-side surface of the ith plastic lens element at a telephoto end, assuming that initial values of a converted inclination α1 and a height h1, for paraxial tracing, are 0 and 1, respectively;
β2W represents a lateral magnification of the second lens unit at the wide-angle end;
β2T represents a lateral magnification of the second lens unit at the telephoto end;
β3W represents a lateral magnification of the third lens unit at the wide-angle end;
β3T represents a lateral magnification of the third lens unit at the telephoto end; and
log represents a natural logarithm.
55. The digital camera of
claim 54
, wherein said first lens unit has a negative optical power.
56. The digital camera of
claim 54
, wherein said second lens unit includes a positive lens element and a negative lens element.
57. The digital camera of
claim 54
, wherein said third lens unit has a positive optical power.
Description
  • [0001]
    This disclosure is based on applications No. H10-363664 filed in Japan on Dec. 22, 1998 and No. H1 1-005056 filed in Japan on Jan. 12, 1999, the entire contents of which are hereby incorporated by reference.
  • BACKGROUND OF THE INVENTION
  • [0002]
    1. Field of the Invention
  • [0003]
    The present invention relates to a zoom lens system, and more particularly to a compact and inexpensive zoom lens system particularly suited for use in digital still cameras.
  • [0004]
    2. Description of the Prior Art
  • [0005]
    In recent years, as personal computers become more prevalent, digital still cameras that allow easy storage of image data on a recording medium such as a floppy disk have been coming into wider use. This trend has created an increasing demand for more inexpensive digital still cameras. This in turn has created an increasing demand for further cost reduction in imaging optical systems. On the other hand, photoelectric conversion devices have come to have an increasingly large number of pixels year by year, which accordingly demands imaging optical systems that offer higher and higher performance. To comply with such requirements, it is necessary to produce a high-performance imaging optical system at comparatively low cost.
  • [0006]
    To achieve this objective, for example, Japanese Laid-open Patent Applications Nos. H1-183615 and H9-311273 propose optical systems having a first lens unit of a negative-negative-positive configuration and a second lens unit of a positive-negative-positive configuration. Moreover, the optical systems proposed in Japanese Laid-open Patent Applications Nos. H7-113956, H6-300969, and H7-63991 have a second lens unit including a doublet lens element formed by cementing together negative lens elements; and the optical system proposed in Japanese Laid-open Patent Application No. H5-93858 has a second lens unit including a doublet lens element formed by cementing together, from the object side, a positive lens element and a negative lens element. If a doublet lens element is considered to be a single lens element, it is assumed that those optical systems are each composed of a first lens unit of a negative-negative-positive configuration and a second lens unit of a positive-negative-positive configuration.
  • [0007]
    Furthermore, Japanese Laid-open Patent Applications Nos. H6-201993 and H1-191820 propose optical systems that are composed of a first lens unit having a negative optical power, a second lens unit having a positive optical power, and a third lens unit having a positive optical power and employ a plastic lens element.
  • [0008]
    In the optical systems proposed in the above-mentioned patent applications, however, there is still plenty of room for improvement from the viewpoint of miniaturization, high performance, and cost reduction.
  • SUMMARY OF THE INVENTION
  • [0009]
    An object of the present invention is to provide a compact, high-resolution, and low-cost zoom lens system suitable, in particular, for use in a digital still camera by arranging plastic lens elements effectively in a two-unit zoom lens system of a negative-positive configuration.
  • [0010]
    To achieve the above object, according to one aspect of the present invention, a zoom lens system includes, from the object side, a first lens unit and a second lens unit. The first lens unit is composed of a negative, a negative, and a positive lens element and has a negative optical power as a whole. The second lens unit is composed of a positive, a negative, and a positive lens element and has a positive optical power as a whole. In the zoom lens system, zooming is achieved by varying the distance between the first and second lens units, and at least one of those lens elements is a plastic lens element.
  • [0011]
    According to another aspect of the present invention, a zoom lens system includes, from the object side, a first lens unit having a negative optical power and a second lens unit having a positive optical power. In the zoom lens system, zooming is achieved by varying the distance between the first and second lens units, and at least a negative lens element and a positive lens element of the lens elements included in the lens units are plastic lens elements that fulfill the following condition:
  • −1.2<φPi/φWhi<1.2
  • [0012]
    where
  • [0013]
    φW represents the optical power of the entire zoom lens system at the wide-angle end;
  • [0014]
    φPi represents the optical power of the ith plastic lens element; and
  • [0015]
    hi represents the height of incidence at which a paraxial ray enters the object-side surface of the ith plastic lens element at the telephoto end, assuming that the initial values of the converted inclination a 1 and the height h1, for paraxial tracing, are 0 and 1, respectively.
  • [0016]
    According to another aspect of the present invention, an image taking apparatus is composed of a zoom lens system, a photoelectric conversion device, and an optical low-pass filter. The photoelectric conversion device has a light sensing surface on which an image is formed by the zoom lens system. The optical low-pass filter is disposed on the object side of the photoelectric conversion device. The zoom lens system is composed of, from the object side, a first lens unit and a second lens unit. The first lens unit is composed of a negative, a negative, and a positive lens element, and has a negative optical power as a whole. The second lens unit is composed of a positive, a negative, and a positive lens element, and has a positive optical power as a whole. In the zoom lens system, zooming is achieved by varying the distance between the first and second lens units, and at least one of those lens elements is a plastic lens element.
  • [0017]
    According to another aspect of the present invention, a zoom lens system is composed of, from the object side, a first lens unit, a second lens unit, and a third lens unit. The first lens unit has a negative optical power. The second lens unit is composed of at least a positive and a negative lens element, and has a positive optical power. The third lens unit has a positive optical power. In the zoom lens system, zooming is achieved by moving at least two lens units so as to vary the distance between the first and second lens units and the distance between the second and third lens units, and at least one of the lens elements included in the lens units is a plastic lens element that fulfills the following conditions:
  • −0.8<Cp(N′−N)/φW<0.8
  • −0.45<M3/M2<0.90(where φT/φW>1.6)
  • [0018]
    where
  • [0019]
    Cp represents the curvature of the plastic lens element;
  • [0020]
    HW represents the optical power of the entire zoom lens system at the wide-angle end;
  • [0021]
    N′ represents the refractive index of the object-side medium of the aspherical surface for the d line;
  • [0022]
    N represents the refractive index of the image-side medium of the aspherical surface for the d line;
  • [0023]
    M3 represents the amount of movement of the third lens unit (the direction pointing to the object side is negative with respect to the wide-angle end);
  • [0024]
    M2 represents the amount of movement of the second lens unit (the direction pointing to the object side is negative with respect to the wide-angle end); and
  • [0025]
    φT represents the optical power of the entire zoom lens system at the telephoto end.
  • [0026]
    According to another aspect of the present invention, a zoom lens system is composed of, from the object side, a first lens unit, a second lens unit, and a third lens unit. The first lens unit is composed of at least a positive and a negative lens element, and has a negative optical power. The second and third lens units have a positive optical power. In the zoom lens system, zooming is achieved by moving at least two lens units so as to vary the distance between the first and second lens units and the distance between the second and third lens units, and at least one of the lens elements included in the first lens unit is a plastic lens element that fulfills the following conditions:
  • P/φ1|<1.20
  • 0.20<|φ1/φW|<0.70
  • −0.45<M3/M2<0.90(where φT/φW>1.6)
  • [0027]
    where
  • [0028]
    φP represents the optical power of the plastic lens element;
  • [0029]
    φ1 represents the optical power of the first lens unit;
  • [0030]
    φW represents the optical power of the entire zoom lens system at the wide-angle end;
  • [0031]
    M3 represents the amount of movement of the third lens unit (the direction pointing to the object side is negative with respect to the wide-angle end);
  • [0032]
    M2 represents the amount of movement of the second lens unit (the direction pointing to the object side is negative with respect to the wide-angle end); and
  • [0033]
    φT represents the optical power of the entire zoom lens system at the telephoto end.
  • [0034]
    According to another aspect of the present invention, a zoom lens system is composed of, from the object side, a first lens unit, a second lens unit, and a third lens unit. The first lens unit has a negative optical power. The second lens unit is composed of at least a positive and a negative lens element, and has a positive optical power. The third lens unit has a positive optical power. In the zoom lens system, zooming is achieved by varying the distance between the first and second lens units and the distance between the second and third lens units, and at least one of the lens elements included in the second lens unit is a plastic lens element that fulfills the following conditions:
  • P/φ2|<2.5
  • 0.25<φ2/φW<0.75
  • [0035]
    where
  • [0036]
    φP represents the optical power of the plastic lens element;
  • [0037]
    φ2 represents the optical power of the second lens unit; and
  • [0038]
    φW represents the optical power of the entire zoom lens system at the wide-angle end.
  • [0039]
    According to another aspect of the present invention, a zoom lens system is composed of, from the object side, a first lens unit, a second lens unit, and a third lens unit. The first lens unit has a negative optical power. The second and third lens units have a positive optical power. In the zoom lens system, zooming is achieved by moving at least two lens units so as to vary the distance between the first and second lens units and the distance between the second and third lens units, and at least one of the lens elements included in the third lens unit is a plastic lens element that fulfills the following conditions:
  • −0.30<M3/M2<0.90
  • P/φ3|<1.70
  • 0.1<φ3/φW<0.60
  • [0040]
    where
  • [0041]
    M3 represents the amount of movement of the third lens unit (the direction pointing to the object side is negative with respect to the wide-angle end);
  • [0042]
    M2 represents the amount of movement of the second lens unit (the direction pointing to the object side is negative with respect to the wide-angle end);
  • [0043]
    φP represents the optical power of the plastic lens element;
  • [0044]
    φ3 represents the optical power of the third lens unit; and
  • [0045]
    φW represents the optical power of the entire zoom lens system at the wide-angle end.
  • [0046]
    According to another aspect of the present invention, a zoom lens system is composed of, from the object side, a first lens unit, a second lens unit, and a third lens unit. The first lens unit has a negative optical power. The second and third lens units have a positive optical power. In the zoom lens system, zooming is achieved by moving at least two lens units so as to vary the distance between the first and second lens units and the distance between the second and third lens units, and at least one of the lens elements included in the first lens unit and at least one of the lens elements included in the second lens unit are plastic lens elements that fulfill the following conditions:
  • −1.4<φPi/Whi<1.4
  • 0.5<log(β2T/β2W)/log Z<2.2
  • [0047]
    where
  • [0048]
    φPi represents the optical power of the ith plastic lens element;
  • [0049]
    φW represents the optical power of the entire zoom lens system at the wide-angle end;
  • [0050]
    hi represents the height of incidence at which a paraxial ray enters the object-side surface of the ith plastic lens element at the telephoto end, assuming that the initial values of the converted inclination α1 and the height h1, for paraxial tracing, are 0 and 1, respectively;
  • [0051]
    β2W represents the lateral magnification of the second lens unit at the wide-angle end;
  • [0052]
    β2T represents the lateral magnification of the second lens unit at the telephoto end;
  • [0053]
    Z represents the zoom ratio; and
  • [0054]
    log represents a natural logarithm (since the condition defines a proportion, the base does not matter).
  • [0055]
    According to another aspect of the present invention, a zoom lens system is composed of, from the object side, a first lens unit, a second lens unit, and a third lens unit. The first lens unit has a negative optical power. The second lens unit is composed of at least a positive and a negative lens element, and has a positive optical power. The third lens unit has a positive optical power. In the zoom lens system, zooming is achieved by moving at least two lens units so as to vary the distance between the first and second lens units and the distance between the second and third lens units, and at least one of the lens elements included in the first lens unit and at least one of the lens elements included in the third lens unit are plastic lens elements that fulfill the following conditions:
  • −1.4<φPi/φWhi<1.4
  • 1.2<log(β3T/β3W)/log Z<0.5
  • [0056]
    where
  • [0057]
    φPi represents the optical power of the ith plastic lens element;
  • [0058]
    φW represents the optical power of the entire zoom lens system at the wide-angle end;
  • [0059]
    hi represents the height of incidence at which a paraxial ray enters the object-side surface of the ith plastic lens element at the telephoto end, assuming that the initial values of the converted inclination a 1 and the height h1, for paraxial tracing, are 0 and 1, respectively;
  • [0060]
    β3W represents the lateral magnification of the third lens unit at the wide-angle end;
  • [0061]
    β3T represents the lateral magnification of the third lens unit at the telephoto end;
  • [0062]
    Z represents the zoom ratio; and
  • [0063]
    log represents a natural logarithm (since the condition defines a proportion, the base does not matter).
  • [0064]
    According to still another aspect of the present invention, a zoom lens system is composed of, from the object side, a first lens unit, a second lens unit, and a third lens unit. The first lens unit has a negative optical power. The second lens unit is composed of at least a positive and a negative lens element, and has a positive optical power. The third lens unit has a positive optical power. In the zoom lens system, zooming is achieved by moving at least two lens units so as to vary the distance between the first and second lens units and the distance between the second and third lens units, and at least one of the lens elements included in the second lens unit and at least one of the lens elements included in the third lens unit are plastic lens elements that fulfill the following conditions:
  • −1.4<φPi/φWhi<1.4
  • −0.75<log(β3T/β3W)/log(β2T/β2W)<0.65
  • [0065]
    where
  • [0066]
    φPi represents the optical power of the ith plastic lens element;
  • [0067]
    φW represents the optical power of the entire zoom lens system at the wide-angle end;
  • [0068]
    hi represents the height of incidence at which a paraxial ray enters the object-side surface of the ith plastic lens element at the telephoto end, assuming that the initial values of the converted inclination α1 and the height h1, for paraxial tracing, are 0 and 1, respectively;
  • [0069]
    β2W represents the lateral magnification of the second lens unit at the wide-angle end;
  • [0070]
    β2T represents the lateral magnification of the second lens unit at the telephoto end;
  • [0071]
    β3W represents the lateral magnification of the third lens unit at the wide-angle end;
  • [0072]
    β3T represents the lateral magnification of the third lens unit at the telephoto end; and
  • [0073]
    log represents a natural logarithm (since the condition defines a proportion, the base does not matter).
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • [0074]
    The objects and features of this invention will become clear from the following description, taken in conjunction with the preferred embodiments with reference to the accompanied drawings in which:
  • [0075]
    [0075]FIG. 1 is a lens arrangement diagram of the zoom lens system of a first embodiment (Example 1) of the present invention;
  • [0076]
    [0076]FIG. 2 is a lens arrangement diagram of the zoom lens system of a second embodiment (Example 2) of the present invention;
  • [0077]
    [0077]FIG. 3 is a lens arrangement diagram of the zoom lens system of a third embodiment (Example 3) of the present invention;
  • [0078]
    [0078]FIG. 4 is a lens arrangement diagram of the zoom lens system of a fourth embodiment (Example 4) of the present invention;
  • [0079]
    [0079]FIG. 5 is a lens arrangement diagram of the zoom lens system of a fifth embodiment (Example 5) of the present invention;
  • [0080]
    [0080]FIGS. 6A to 6I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 1;
  • [0081]
    [0081]FIGS. 7A to 7I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 2;
  • [0082]
    [0082]FIGS. 8A to 8I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 3;
  • [0083]
    [0083]FIGS. 9A to 9I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 4;
  • [0084]
    [0084]FIGS. 10A to 10I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 5;
  • [0085]
    [0085]FIG. 11 is a lens arrangement diagram of the zoom lens system of a sixth embodiment (Example 6) of the present invention;
  • [0086]
    [0086]FIG. 12 is a lens arrangement diagram of the zoom lens system of a seventh embodiment (Example 7) of the present invention;
  • [0087]
    [0087]FIG. 13 is a lens arrangement diagram of the zoom lens system of an eighth embodiment (Example 8) of the present invention;
  • [0088]
    [0088]FIG. 14 is a lens arrangement diagram of the zoom lens system of a ninth embodiment (Example 9) of the present invention;
  • [0089]
    [0089]FIG. 15 is a lens arrangement diagram of the zoom lens system of a tenth embodiment (Example 10) of the present invention;
  • [0090]
    [0090]FIG. 16 is a lens arrangement diagram of the zoom lens system of an eleventh embodiment (Example 11) of the present invention;
  • [0091]
    [0091]FIG. 17 is a lens arrangement diagram of the zoom lens system of a twelfth embodiment (Example 12) of the present invention;
  • [0092]
    [0092]FIG. 18 is a lens arrangement diagram of the zoom lens system of a thirteenth embodiment (Example 13) of the present invention;
  • [0093]
    [0093]FIG. 19 is a lens arrangement diagram of the zoom lens system of a fourteenth embodiment (Example 14) of the present invention;
  • [0094]
    [0094]FIGS. 20A to 20I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 6;
  • [0095]
    [0095]FIGS. 21A to 21I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 7;
  • [0096]
    [0096]FIGS. 22A to 22I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 8;
  • [0097]
    [0097]FIGS. 23A to 23I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 9;
  • [0098]
    [0098]FIGS. 24A to 24I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 10;
  • [0099]
    [0099]FIGS. 25A to 25I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 11;
  • [0100]
    [0100]FIGS. 26A to 26I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 12;
  • [0101]
    [0101]FIGS. 27A to 27I are graphic representations of the aberrations observed -in an infinite-distance shooting condition in the zoom lens system of the Example 13;
  • [0102]
    [0102]FIGS. 28A to 28I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of the Example 14;
  • [0103]
    [0103]FIG. 29 is a lens arrangement diagram of the zoom lens system of a fifteenth embodiment (Example 15) of the present invention;
  • [0104]
    [0104]FIGS. 30A to 30I are graphic representations of the aberrations observed in an infinite-distance shooting condition in the zoom lens system of Example 15; and
  • [0105]
    [0105]FIG. 31 is a schematic illustration of the optical components of a digital camera.
  • DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • [0106]
    Embodiments 1 to 5
  • [0107]
    Hereinafter, zoom lens systems embodying the present invention will be described with reference to the drawings. FIGS. 1 to 5 are lens arrangement diagrams of the zoom lens systems of a first, a second, a third, a fourth, and a fifth embodiment, respectively. In each diagram, the left-hand side corresponds to the object side, and the right-hand side corresponds to the image side. Note that, in each diagram, arrows schematically indicate the movement of the lens units during zooming from the wide-angle end to the telephoto end. Moreover, each diagram shows the lens arrangement of the zoom lens system during zooming, as observed at the wide-angle end. As shown in these diagrams, the zoom lens systems of the embodiments are each built as a two-unit zoom lens system of a negative-positive configuration that is composed of, from the object side, a first lens unit Gr1 and a second lens unit Gr2. Both the first and second lens units (Gr1 and Gr2) are movably disposed in the zoom lens system.
  • [0108]
    The first lens unit Gr1 is composed of, from the object side, a negative lens element, a negative lens element, and a positive lens element and has a negative optical power as a whole. The second lens unit Gr2 is composed of an aperture stop S, a positive lens element, a negative lens element, and a positive lens element and has a positive optical power as a whole. In the zoom lens system, the first to sixth lens elements counted from the object side are represented as G1 to G6, respectively. Note that a flat plate disposed at the image-side end of the zoom lens system is a low-pass filter LPF. As illustrated in FIG. 31, within a digital camera the low-pass filter LPP is disposed between the zoom lens system ZLS and a photoelectric image sensor is having a light-sensing surface on which an image is formed by the zoom lens system.
  • [0109]
    As shown in FIG. 1, in the first embodiment, the second and sixth lens elements (G2 and G6) counted from the object side (hatched in the figure) are plastic lens elements. As shown in FIG. 2, in the second embodiment, the second, third, fifth, and sixth lens elements (G2, G3, G5, and G6) counted from the object side (hatched in the figure) are plastic lens elements.
  • [0110]
    Moreover, as shown in FIG. 3, in the third embodiment, the second, fifth, and sixth lens elements (G2, G5, and G6) counted from the object side (hatched in the figure) are plastic lens elements. As shown in FIG. 4, in the fourth embodiment, the third and fifth lens elements (G3 and G5) counted from the object side (hatched in the figure) are plastic lens elements. Lastly, as shown in FIG. 5, in the fifth embodiment, the second and sixth lens elements (G2 and G6) counted from the object side (hatched in the figure) are plastic lens elements.
  • [0111]
    The conditions to be preferably fulfilled by an optical system will be described below. It is preferable that the zoom lens systems of the embodiments fulfill Condition (1) below.
  • 0.25<|φ1/φW51 <0.80  (1)
  • [0112]
    where
  • [0113]
    φ1 represents the optical power of the first lens unit; and
  • [0114]
    φW represents the optical power of the entire zoom lens system at the wide-angle end.
  • [0115]
    Condition (1) defines, in the form of the optical power of the first lens unit, the condition to be fulfilled to achieve proper correction of aberrations and keep the size of the zoom lens system appropriate. If the value of Condition (1) is equal to or less than its lower limit, the optical power of the first lens unit is so weak that aberrations can be corrected properly, but simultaneously the total length, as well as the diameter of the front-end lens unit, of the zoom lens system becomes unduly large. In contrast, if the value of Condition (1) is equal to or greater than its upper limit, the optical power of the first lens unit is so strong that the total length of the zoom lens system is successfully minimized, but simultaneously the inclination of the image plane toward the over side becomes unduly large. In addition, barrel-shaped distortion becomes unduly large at the wide-angle end.
  • [0116]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (2) below.
  • 0.35<φ2/φW<0.75  (2)
  • [0117]
    where
  • [0118]
    φ2 represents the optical power of the second lens unit.
  • [0119]
    Condition (2) defines, in the form of the optical power of the second lens unit, the condition to be fulfilled to achieve, as in Condition (1), proper correction of aberrations and keep the size of the zoom lens system appropriate. If the value of Condition (2) is equal to or less than its lower limit, the optical power of the second lens unit is so weak that aberrations can be corrected properly, but simultaneously the total length, as well as the diameter of the front-end lens unit, of the zoom lens system becomes unduly large. In contrast, if the value of Condition (2) is equal to or greater than its upper limit, the optical power of the second lens unit is so strong that the total length of the zoom lens system is successfully minimized, but simultaneously spherical aberration appears notably on the under side.
  • [0120]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (3) below.
  • −1.2<φPi/φWhi<1.2  (3)
  • [0121]
    where
  • [0122]
    φPi represents the optical power of the ith plastic lens element; and
  • [0123]
    hi represents the height of incidence at which a paraxial ray enters the object-side surface of the ith plastic lens element at the telephoto end, assuming that the initial values of the converted inclination α1 and the height h1, for paraxial tracing, are 0 and 1, respectively.
  • [0124]
    Condition (3) defines, in the form of the sum of the degrees in which the individual plastic lens elements, by their temperature variation, affect the back focal distance, the condition to be fulfilled to suppress variation in the back focal distance resulting from temperature variation. When a plurality of plastic lens elements are used, it is preferable that positively-powered and negatively-powered lens elements be combined in such a way that the degree in which they affect the back focal distance are canceled out by one another. If the value of Condition (3) is equal to or less than its lower limit, the variation in the back focal distance caused by temperature variation in the negatively-powered plastic lens element becomes unduly great. In contrast, if the value of Condition (3) is equal to or greater than its upper limit, the variation in the back focal distance caused by temperature variation in the positively-powered plastic lens element becomes unduly great. Thus, in either case, the zoom lens system needs to be provided with a mechanism that corrects the back focal distance in accordance with temperature variation.
  • [0125]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (4) below.
  • P/φ1|<1.35  (4)
  • [0126]
    where
  • [0127]
    φP represents the optical power of the plastic lens element.
  • [0128]
    Condition (4) defines, in the form of the optical power of the plastic lens element included in the first lens unit, the condition to be fulfilled to keep the variation of aberrations resulting from temperature variation within an appropriate range. If the value of Condition (4) is equal to or greater than its upper limit curvature of field, in particular, the curvature of field on the wide-angle side varies too greatly with temperature.
  • [0129]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (5) below.
  • P/φ2|<2.15  (5)
  • [0130]
    Condition (5) defines, in the form of the optical power of the plastic lens element included in the second lens unit, the condition to be fulfilled to keep, as in Condition (4), the variation of aberrations resulting from temperature variation within an appropriate range. If the value of Condition (5) is equal to or greater than its upper limit, spherical aberration, in particular, the spherical aberration on the telephoto side, varies too greatly with temperature.
  • [0131]
    No lower limit is given for Conditions (4) and (5). This is because, as the value of either of the conditions decreases, the optical power of the plastic lens element becomes weaker, and this is desirable in terms of suppression of the variation of aberrations resulting from temperature variation. This, however, has no effect on correction of aberrations under normal temperature, and accordingly makes the use of plastic lenses meaningless. To avoid this, where the plastic lens element fulfills Condition (6) below, it is essential to use an aspherical surface.
  • 0≦|φP/φA|<0.45  (6)
  • [0132]
    where
  • [0133]
    φA represents the optical power of the lens unit including the plastic lens element.
  • [0134]
    Note however that this is not to discourage providing an aspherical surface on the lens surface of a plastic lens element having an optical power that makes the value of Condition (6) equal to or greater than its upper limit.
  • [0135]
    As described above, if an aspherical surface is used, it is preferable that the following conditions be fulfilled. First, where an aspherical surface is used in the first lens unit, it is preferable that Condition (7) below be fulfilled.
  • −0.85<(|X|−|X 0|)/{C 0(N′−N)f1}<−0.05  (7)
  • [0136]
    where
  • [0137]
    C0 represents the curvature of the reference spherical surface of the aspherical surface;
  • [0138]
    N represents the refractive index of the image-side medium of the aspherical surface for the d line;
  • [0139]
    N′ represents the refractive index of the object-side medium of the aspherical surface for the d line;
  • [0140]
    X represents the deviation of the aspherical surface along the optical axis at the height in a direction perpendicular to the optical axis (the direction pointing to the object side is negative);
  • [0141]
    X0 represents the deviation of the reference spherical surface of the aspherical surface along the optical axis at the height in a direction perpendicular to the optical axis (the direction pointing to the object side is negative); and
  • [0142]
    f1 represents the focal length of the first lens unit.
  • [0143]
    Condition (7) defines the surface shape of the aspherical surface and assumes that the aspherical surface is so shaped as to weaken the optical power of the first lens unit. Fulfillment of Condition (7) makes it possible to achieve proper correction of the distortion and the image plane on the wide-angle side, in particular. If the value of Condition (7) is equal to or less than its lower limit, positive distortion becomes unduly large on the wide-angle side, in particular, in a close-shooting condition, and simultaneously the inclination of the image plane toward the over side becomes unduly large. In contrast, if the value of Condition (7) is equal to or greater than its upper limit, negative distortion becomes unduly large on the wide-angle side, in particular, in a close-shooting condition, and simultaneously the inclination of the image plane toward the under side becomes unduly large. Note that, in a case where the first lens unit includes a plurality of aspherical surfaces, at least one of those aspherical surfaces needs to fulfill Condition (7) above; that is, the other aspherical surfaces do not necessarily have to fulfill Condition (7) above, if that is advantageous for the correction of other aberrations.
  • [0144]
    In a case where an aspherical surface is used in the second lens unit, it is preferable that Condition (8) below be fulfilled.
  • −0.95<(|X|−|X 0|)/{C 0(N′−N)f2}<−0.05  (8)
  • [0145]
    where
  • [0146]
    f2 represents the focal length of the second lens unit.
  • [0147]
    Condition (8) defines the surface shape of the aspherical surface and assumes that the aspherical surface is so shaped as to weaken the optical power of the second lens unit. Fulfillment of Condition (8) makes it possible to achieve proper correction of spherical aberration, in particular. If the value of Condition (8) is equal to or less than its lower limit, in particular, spherical aberration appears notably on the over side at the telephoto end. In contrast, if the value of Condition (8) is equal to or greater than its upper limit, spherical aberration appears notably on the under side at the telephoto end. Note that, in a case where the second lens unit includes a plurality of aspherical surfaces, at least one of those aspherical surfaces needs to fulfill Condition (8) above; that is, the other aspherical surfaces do not necessarily have to fulfill Condition (8) above, if that is advantageous for the correction of other aberrations.
  • [0148]
    Embodiments 6 to 15
  • [0149]
    FIGS. 11 to 19 and 29 are lens arrangement diagrams of the zoom lens systems of a sixth, a seventh, an eighth, a ninth, a tenth, an eleventh, a twelfth, a thirteenth, a fourteenth and a fifteenth embodiment, respectively. In each diagram, the left-hand side corresponds to the object side, and the right-hand side corresponds to the image side. In addition, in each diagram, arrows schematically indicate the movement of the lens units during zooming from the wide-angle end to the telephoto end. Note that arrows with a broken line indicate that the lens unit is kept in a fixed position during zooming. Moreover, each diagram shows the lens arrangement of the zoom lens system during zooming, as observed at the wide-angle end. As shown in these diagrams, the zoom lens systems of the embodiments are each built as a three-unit zoom lens system of a negative-positive-positive configuration that is composed of, from the object side, a first lens unit Gr1, a second lens unit Gr2, and a third lens unit Gr3. In this zoom lens system, at least two lens units are moved during zooming.
  • [0150]
    The first lens unit Gr1 has a negative optical power as a whole. The second and third lens units (Gr2 and Gr3) have a positive optical power as a whole. In the zoom lens system, the first to eighth lens elements counted from the object side are represented as G1 to G8, respectively. The lens units provided in the zoom lens system of each embodiment are each realized by the use of a plurality of lens elements out of those lens elements G1 to G8. The second lens unit Gr2 includes an aperture stop S. Note that a flat plate disposed at the image-side end of the zoom lens system is a low-pass filter LPF.
  • [0151]
    As shown in FIG. 11, in the sixth embodiment, the second and sixth lens elements (G2 and G6) counted from the object side (hatched in the figure) are plastic lens elements. Moreover, as shown in FIG. 12, in the seventh embodiment, the second and seventh lens elements (G2 and G7) counted from the object side (hatched in the figure) are plastic lens elements.
  • [0152]
    As shown in FIG. 13, in the eighth embodiment, the first and seventh lens elements (G1 and G7) counted from the object side (hatched in the figure) are plastic lens elements. Moreover, as shown in FIG. 14, in the ninth embodiment, the second and fifth lens elements (G2 and G5) counted from the object side (hatched in the figure) are plastic lens elements. Furthermore, as shown in FIG. 15, in the tenth embodiment, the first and seventh lens elements (G1 and G7) counted from the object side (hatched in the figure) are plastic lens elements.
  • [0153]
    As shown in FIG. 16, in the eleventh embodiment, the second and fifth lens elements (G2 and G5) counted from the object side (hatched in the figure) are plastic lens elements. Moreover, as shown in FIG. 17, in the twelfth embodiment, the second, fifth, sixth, and seventh lens elements (G2, G5, G6, and G7) counted from the object side (hatched in the figure) are plastic lens elements.
  • [0154]
    As shown in FIG. 18, in the thirteenth embodiment, the second, fifth, sixth, seventh, and eighth lens elements (G2, G5, G6, G7, and G8) counted from the object side (hatched in the figure) are plastic lens elements. As shown in FIG. 19, in the fourteenth embodiment, the second, sixth, and seventh lens elements (G2, G6, and G7) counted from the object side (hatched in the figure) are plastic lens elements. Referring to FIG. 29, in the fifteenth embodiment, the first and fifth lens elements (G1 and G5) are plastic lens elements.
  • [0155]
    The conditions to be preferably fulfilled by an optical system will be described below. It is preferable that the zoom lens systems of the sixth to fifteenth embodiments fulfill Condition (9) below.
  • −0.8<Cp(N′−N)/φW<0.8  (9)
  • [0156]
    where
  • [0157]
    Cp represents the curvature of the plastic lens element;
  • [0158]
    φW represents the optical power of the entire zoom lens system at the wide-angle end;
  • [0159]
    N′ represents the refractive index of the object-side medium of the aspherical surface for the d line; and
  • [0160]
    N represents the refractive index of the image-side medium of the aspherical surface for the d line.
  • [0161]
    Condition (9) defines the optical power of the lens surface of the plastic lens element. If the optical power of the lens surface is too strong, the surface shape varies with temperature, with the result that various aberrations become unduly large. If the value of Condition (9) is equal to or less than its lower limit, the negative optical power is too strong. In contrast, if the value of Condition (9) is equal to or greater than its upper limit, the positive optical power is too strong. As a result, in the plastic lens element provided in the first lens unit, curvature of field varies too greatly with temperature, in particular; in the plastic lens element provided in the second lens unit, spherical aberration varies too greatly with temperature, in particular; and, in the plastic lens element provided in the third lens unit, spherical aberration and the coma aberration in marginal rays vary greatly with temperature, in particular.
  • [0162]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (10) below.
  • −0.45<M3/M2<0.90  (10)
  • [0163]
    where
  • [0164]
    M3 represents the amount of movement of the third lens unit (the direction pointing to the object side is negative with respect to the wide-angle end); and
  • [0165]
    M2 represents the amount of movement of the second lens unit (the direction pointing to the object side is negative with respect to the wide-angle end).
  • [0166]
    Condition (10) defines, in the form of the ratio of the amount of movement of the second lens unit to that of the third lens unit, the condition to be fulfilled to keep the amount of movement of the second and third lens units in appropriate ranges in order to achieve zooming efficiently. Thus, in an optical system in which a sufficient zoom ratio needs to be secured, fulfillment of Condition (10) is effective. Moreover, it is more preferable that the following condition be additionally fulfilled.
  • φT/φW>1.6
  • [0167]
    where
  • [0168]
    φT represents the optical power of the entire zoom lens system at the telephoto end.
  • [0169]
    If the value of Condition (10) is equal to or less than its lower limit, the responsibility of the third lens unit for zooming is so heavy that spherical aberration and the coma aberration in marginal rays vary too greatly with zooming. In contrast, if the value of Condition (10) is equal to or greater than its upper limit, the amount of the movement of the second lens unit is so large that the diameter of the front-end lens unit needs to be unduly large in order to secure sufficient amount of peripheral light on the wide-angle side, and simultaneously, the responsibility of the second lens unit for zooming is so heavy that spherical aberration varies too greatly with zooming.
  • [0170]
    Moreover, where a plastic lens element is used in the third lens unit, the ability of the third lens unit to correct aberrations tends to be insufficient. To avoid this, it is preferable to make the range of Condition (10) narrower so as to obtain the following condition:
  • −0.30<M3/M2<0.90  (10)
  • [0171]
    In a case where a plastic lens element is used in the first lens unit, it is preferable that Condition (11) below be fulfilled.
  • P/φ1)φ1|<1.20  (11)
  • [0172]
    where
  • [0173]
    φP represents the optical power of the plastic lens element; and
  • [0174]
    φ1 represents the optical power of the first lens unit.
  • [0175]
    Condition (11) defines, in the form of the ratio of the optical power of the first lens unit to that of the plastic lens element included in the first lens unit, the condition to be fulfilled to keep the variation of aberrations resulting from temperature variation within an appropriate range. If the value of Condition (11) is equal to or greater than its upper limit, curvature of field, in particular, the curvature of field on the wide-angle side, varies too greatly with temperature. Moreover, to correct the aberrations that occur in the first lens unit, it is preferable to use at least a positive and a negative lens element.
  • [0176]
    In a case where a plastic lens element is used in the second lens unit, it is preferable that Condition (12) below be fulfilled.
  • P/φ2|<2.5  (12)
  • [0177]
    where
  • [0178]
    φ2 represents the optical power of the second lens unit.
  • [0179]
    Condition (12) defines, in the form of the ratio of the optical power of the second lens unit to that of the plastic lens element included in the second lens unit, the condition to be fulfilled to keep the variation of aberrations resulting from temperature variation within an appropriate range. If the value of Condition (12) is equal to or greater than its upper limit, spherical aberration, in particular, the spherical aberration on the telephoto side, varies too greatly with temperature. Moreover, to correct the aberrations that occur in the second lens unit, it is preferable to use at least a positive and a negative lens element.
  • [0180]
    In a case where a plastic lens element is used in the third lens unit, it is preferable that Condition (13) below be fulfilled.
  • P/φ3|<1.70  (13)
  • [0181]
    where
  • [0182]
    φ3 represents the optical power of the third lens unit.
  • [0183]
    Condition (13) defines, in the form of the ratio of the optical power of the third lens unit to that of the plastic lens element included in the third lens unit, the condition to be fulfilled to keep the variation of aberrations resulting from temperature variation within an appropriate range. If the value of Condition (13) is equal to or greater than its upper limit, spherical aberration and the coma aberration in marginal rays vary too greatly with temperature. Moreover, to correct the aberrations that occur in the third lens unit, it is preferable to use at least a positive and a negative lens element.
  • [0184]
    No lower limit is given for Conditions (11) to (13). This is because, as the value of either of the conditions decreases, the optical power of the plastic lens element becomes weaker, and this is desirable in terms of suppression of the variation of aberrations resulting from temperature variation. This, however, has no effect on correction of aberrations under normal temperature, and accordingly makes the use of plastic lenses meaningless. To avoid this, where the plastic lens element fulfills Condition (14) below, it is essential to use an aspherical surface.
  • 0≦|φP/φA|<0.45  (14)
  • [0185]
    where
  • [0186]
    φA represents the optical power of the lens unit including the plastic lens element.
  • [0187]
    Note however that this is not to discourage providing an aspherical surface on the lens surface of a plastic lens element having an optical power that makes the value of Condition (14) equal to or greater than its upper limit.
  • [0188]
    As described above, if an aspherical surface is used, it is preferable that the following conditions be fulfilled. First, where an aspherical surface is provided on the lens surface of the plastic lens element of the first lens unit, it is preferable that Condition (15) below be fulfilled.
  • −1.10<(|X|−|X 0|)/{C 0(N′−N)φ1}<−0.10  (15)
  • [0189]
    where
  • [0190]
    C0 represents the curvature of the reference spherical surface of the aspherical surface;
  • [0191]
    N represents the refractive index of the image-side medium of the aspherical surface for the d line;
  • [0192]
    N′ represents the refractive index of the object-side medium of the aspherical surface for the d line;
  • [0193]
    X represents the deviation of the aspherical surface along the optical axis at the height in a direction perpendicular to the optical axis (the direction pointing to the object side is negative);
  • [0194]
    X0 represents the deviation of the reference spherical surface of the aspherical surface along the optical axis at the height in a direction perpendicular to the optical axis (the direction pointing to the object side is negative); and
  • [0195]
    f1 represents the focal length of the first lens unit.
  • [0196]
    If the value of Condition (15) is equal to or less than its lower limit, positive distortion becomes unduly large on the wide-angle side, in particular, in a close-shooting condition, and simultaneously the inclination of the image plane toward the over side becomes unduly large. In contrast, if the value of Condition (15) is equal to or greater than its upper limit, it is impossible to make efficient use of the aspherical surface, which makes the use of an aspherical surface meaningless. As a result, the negative distortion on the wide-angle side, in particular, in a close-shooting condition, and the inclination of the image plane toward the under side are undercorrected. Note that, in a case where the first lens unit includes a plurality of aspherical surfaces, at least one of those aspherical surfaces needs to fulfill Condition (15) above; that is, the other aspherical surfaces do not necessarily have to fulfill Condition (15) above, if that is advantageous for the correction of other aberrations.
  • [0197]
    In a case where an aspherical surface is provided on the lens surface of the plastic lens element of the second lens unit, it is preferable that Condition (16) below be fulfilled.
  • −0.35<(|X|−|X 0|)/{C 0(N′−N)f2}<−0.03  (16)
  • [0198]
    where
  • [0199]
    f2 represents the focal length of the second lens unit.
  • [0200]
    Condition (16) assumes that the aspherical surface is so shaped as to weaken the positive optical power of the second lens unit. Fulfillment of Condition (16) makes it possible to achieve proper correction of spherical aberration, in particular. If the value of Condition (16) is equal to or less than its lower limit, in particular, spherical aberration appears notably on the over side at the telephoto end. In contrast, if the value of Condition (16) is equal to or greater than its upper limit, it is impossible to make efficient use of the aspherical surface, which makes the use of an aspherical surface meaningless. As a result, spherical aberration is undercorrected on the telephoto side, in particular. Note that, in a case where the second lens unit includes a plurality of aspherical surfaces, at least one of those aspherical surfaces needs to fulfill Condition (16) above; that is, the other aspherical surfaces do not necessarily have to fulfill Condition (16) above, if that is advantageous for the correction of other aberrations.
  • [0201]
    In a case where an aspherical surface is provided on the lens surface of the plastic lens element of the third lens unit, it is preferable that Condition (17) below be fulfilled.
  • −0.70<(|X|−|X 0|)/{C 0(N′−N)f3}<−0.01  (17)
  • [0202]
    where
  • [0203]
    f3 represents the focal length of the third lens unit.
  • [0204]
    Condition (17) assumes that the aspherical surface is so shaped as to weaken the positive optical power of the third lens unit. Fulfillment of Condition (17) makes it possible to achieve proper correction of spherical aberration and the coma aberration in marginal rays. If the value of Condition (17) is equal to or less than its lower limit, spherical aberration appears notably on the over side, and simultaneously the coma aberration in marginal rays becomes unduly large. In contrast, if the value of Condition (17) is equal to or greater than its upper limit, it is impossible to make efficient use of the aspherical surface, which makes the use of an aspherical surface meaningless. As a result, spherical aberration and the coma aberration in marginal rays are undercorrected. Note that, in a case where the third lens unit includes a plurality of aspherical surfaces, at least one of those aspherical surfaces needs to fulfill Condition (17) above; that is, the other aspherical surfaces do not necessarily have to fulfill Condition (17) above, if that is advantageous for the correction of other aberrations.
  • [0205]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (18) below.
  • 0.20<|φ1/φW|<0.70  (18)
  • [0206]
    Condition (18) defines, in the form of the optical power of the first lens unit, the condition to be fulfilled to achieve proper correction of aberrations and keep the size of the zoom lens system appropriate. If the value of Condition (18) is equal to or less than its lower limit, the optical power of the first lens unit is so weak that aberrations can be corrected properly, but simultaneously the total length, as well as the diameter of the front-end lens unit, of the zoom lens system becomes unduly large. In contrast, if the value of Condition (18) is equal to or greater than its upper limit, the optical power of the first lens unit is so strong that aberrations become unduly large, in particular, the inclination of the image plane toward the over side becomes unduly large, and simultaneously barrel-shaped distortion becomes unduly large on the wide-angle side. In this case, the use of a plastic lens element, which offers a relatively low refractive index and a strictly restricted range of dispersion, makes it difficult to correct aberrations properly and thus requires more lens elements in the zoom lens system.
  • [0207]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (19) below.
  • 0.25<φ2/φW<0.75  (19)
  • [0208]
    Condition (19) defines, in the form of the optical power of the second lens unit, the condition to be fulfilled to achieve proper correction of aberrations and keep the size of the zoom lens system appropriate. If the value of Condition (19) is equal to or less than its lower limit, the optical power of the second lens unit is so weak that aberrations can be corrected properly, but simultaneously the total length, as well as the diameter of the front-end lens unit, of the zoom lens system becomes unduly large. In contrast, if the value of Condition (19) is equal to or greater than its upper limit, the optical power of the second lens unit is so strong that aberrations become unduly large, in particular, spherical aberration appears notably on the under side. In this case, the use of a plastic lens element, which offers a relatively low refractive index and a strictly restricted range of dispersion, makes it difficult to correct aberrations properly and thus requires more lens elements in the zoom lens system.
  • [0209]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (20) below.
  • 0.1<φ3/φW<0.60  (20)
  • [0210]
    Condition (20) defines, in the form of the optical power of the third lens unit, the condition to be fulfilled to achieve proper correction of aberrations and keep the size of the zoom lens system appropriate. If the value of Condition (20) is equal to or less than its lower limit, the optical power of the third lens unit is so weak that aberrations can be corrected properly, but simultaneously the total length, as well as the diameter of the front-end lens unit, of the zoom lens system becomes unduly large. In contrast, if the value of Condition (20) is equal to or greater than its upper limit, the optical power of the third lens unit is so strong that aberrations become unduly large, in particular, spherical aberration appears notably on the under side. In this case, the use of a plastic lens element, which offers a relatively low refractive index and a strictly restricted range of dispersion, makes it difficult to correct aberrations properly and thus requires more lens elements in the zoom lens system.
  • [0211]
    Moreover, if the values of Conditions (18) to (20) are equal to or greater than their upper limits, the optical power of the plastic lens element tends to be unduly strong. Thus, it is preferable that Conditions (11) and (18); (12) and (19); and (13) and (20) be fulfilled at the same time, respectively.
  • [0212]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (21) below.
  • −1.4<φPi/φWhi<1.4  (21)
  • [0213]
    where
  • [0214]
    φPi represents the optical power of the ith plastic lens element; and
  • [0215]
    hi represents the height of incidence at which a paraxial ray enters the object-side surface of the ith plastic lens element at the telephoto end, assuming that the initial values of the converted inclination al and the height h1, for paraxial tracing, are 0 and 1, respectively.
  • [0216]
    Condition (21) defines, in the form of the sum of the degrees in which the individual plastic lens elements, by their temperature variation, affect the back focal distance, the condition to be fulfilled to suppress variation in the back focal distance resulting from temperature variation. When a plurality of plastic lens elements are used, it is preferable that positively-powered and negatively-powered lens elements be combined in such a way that the degree in which they affect the back focal distance are canceled out by one another. If the value of Condition (21) is equal to or less than its lower limit, the variation in the back focal distance caused by temperature variation in the negatively-powered plastic lens element becomes unduly great. In contrast, if the value of Condition (21) is equal to or greater than its upper limit, the variation in the back focal distance caused by temperature variation in the positively-powered plastic lens element becomes unduly great. Thus, in either case, the zoom lens system needs to be provided with a mechanism that corrects the back focal distance in accordance with temperature variation.
  • [0217]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (22) below.
  • 0.5<log(β2T/β2W)/log Z<2.2  (22)
  • [0218]
    where
  • [0219]
    β2W represents the lateral magnification of the second lens unit at the wide-angle end;
  • [0220]
    β2T represents the lateral magnification of the second lens unit at the telephoto end;
  • [0221]
    Z represents the zoom ratio; and
  • [0222]
    log represents a natural logarithm (since the condition defines a proportion, the base does not matter).
  • [0223]
    In a zoom lens system of the types like those of the present invention, the responsibility of the second lens unit for zooming is heavier than that of any other lens unit. The heavier the responsibility for zooming, the larger the aberrations that accompany zooming. Thus, in order to achieve proper correction of aberrations, it is preferable to distribute the responsibility for zooming among a plurality of lens units. Condition (22) defines the responsibility for zooming of the second lens unit, to which the heaviest responsibility for zooming is distributed in a zoom lens system of the types like those of the present invention.
  • [0224]
    If the value of Condition (22) is equal to or less than its lower limit, the responsibility of the second lens unit for zooming is so light that the aberrations occurring in the second lens unit can be corrected properly. This, however, affects the responsibility of the other lens units for correcting aberrations, and thus requires more lens elements in those other lens units, with the result that the entire optical system needs to have an unduly large size. In contrast, if the value of Condition (22) is equal to or greater than its upper limit, the responsibility of the second lens unit for zooming is so heavy that spherical aberration varies too greatly with zooming, in particular.
  • [0225]
    It is preferable that the zoom lens systems of the embodiments fulfill Condition (23) below.
  • −1.2<log(β3T/β3W)/log Z<0.5  (23)
  • [0226]
    where
  • [0227]
    β3W represents the lateral magnification of the third lens unit at the wide-angle end; and
  • [0228]
    β3T represents the lateral magnification of the third lens unit at the telephoto end.
  • [0229]
    Condition (23) defines the responsibility of the third lens unit for zooming. If the value of Condition (23) is negative, the third lens unit reduces its magnification during zooming. This is disadvantageous from the viewpoint of zooming. In this case, however, by moving the third lens unit during zooming, it is possible to correct the aberrations occurring in the other lens units during zooming. If the value of Condition (23) is equal to or less than its lower limit, the third lens unit reduces its magnification at an unduly high rate during zooming, and thus the resulting loss in magnification needs to be compensated by the other lens units. This requires an unduly large number of lens elements in those other lens units and thus makes the entire optical system unduly long. In contrast, if the value of Condition (23) is equal to or greater than its upper limit, the responsibility of the third lens unit for zooming is so heavy that spherical aberration and coma aberration vary too greatly with zooming.
  • [0230]
    Moreover, it is preferable that the zoom lens systems of the embodiments fulfill Condition (24) below.
  • −0.75<log(β3T/B3W)/log(β2T/β2W)<0.65  (24)
  • [0231]
    Condition (24) defines the preferable ratio of the responsibility of the second lens unit for zooming to the responsibility of the third lens unit for zooming. If the value of Condition (24) is equal to or less than its lower limit, the third lens unit reduces its magnification, and thus the responsibility of the second lens unit for zooming is excessively heavy. As a result, spherical aberration varies too greatly with zooming. In contrast, if the value of Condition (24) is equal to or greater than its upper limit, the responsibility of the third lens unit for zooming is so heavy that spherical aberration and coma aberration vary too greatly with zooming.
  • [0232]
    Hereinafter, examples of zoom lens systems embodying the present invention will be presented with reference to their construction data, graphic representations of aberrations, and other data. Tables 1 to 5 list the construction data of Examples 1 to 5, which respectively correspond to the first to fifth embodiments described above and have lens arrangements as shown in FIGS. 1 to 5. Tables 6 to 15 list the construction data of Examples 6 to 15, which respectively correspond to the sixth to fifteenth embodiments described above and have lens arrangements as shown in FIGS. 11 to 19 and 29.
  • [0233]
    In the construction data of each example, ri (i =1, 2, 3, . . . ) represents the ith surface counted from the object side and its radius of curvature, di (i=1, 2, 3, . . . ) represents the ith axial distance counted from the object side, and Ni (i=1, 2, 3, . . . ) and ni (i=1, 2, 3, . . . ) respectively represent the refractive index for the d line and the Abbe number of the ith lens element counted from the object side. The values listed for the focal length f and the F number FNO of the, entire zoom lens system in Examples 1 to 5; the distance between the first and second lens units; and the distance between the second lens unit and the low-pass filter LPF are the values at, from left, the wide-angle end (W), the middle-focal-length position (M), and the telephoto end (T).
  • [0234]
    Moreover, the values listed for the focal length f and the F number FNO of the entire zoom lens system in Examples 6 to 15; the distance between the first and second lens units; the distance between the second and third lens units; and the distance between the third lens unit and the low-pass filter LPF are the values at, from left, the wide-angle end (W), the middle-focal-length position (M), and the telephoto end (T). Note that, in all of Examples, a surface whose radius of curvature ri is marked with an asterisk (*) is an aspherical surface, whose surface shape is defined by the following formulae.
  • X=X 0 +ΣSA i Y i  (a)
  • X 0 =CY 2/{1+(1−εC 2 Y 2)}  (b)
  • [0235]
    where
  • [0236]
    X represents the displacement from the reference surface in the optical axis direction;
  • [0237]
    Y represents the height in a direction perpendicular to the optical axis;
  • [0238]
    C represents the paraxial curvature;
  • [0239]
    ε represents the quadric surface parameter; and
  • [0240]
    Ai represents the aspherical coefficient of the ith order.
  • [0241]
    [0241]FIGS. 6A to 6I, 7A to 7I, 8A to 8I, 9A to 9I, and 10A to 10I show the aberrations observed in the infinite-distance shooting condition in Examples 1 to 5, respectively. Of these diagrams, FIGS. 6A to 6C, 7A to 7C, 8A to 8C, 9A to 9C, and 10A to 10C show the aberrations observed at the wide-angle end [W]; FIGS. 6D to 6F, 7D to 7F, 8D to 8F, 9D to 9F, and 10D to 10F show the aberrations observed at the middle focal length [M]; and FIGS. 6G to 6I, 7G to 7I, 8G to 8I, 9G to 9I, and 10G to 10I show the aberrations observed at the telephoto end [T]. In the spherical aberration diagrams, the solid line (d) represents the d line and the broken line (SC) represents the sine condition. In the astigmatism diagrams, the solid line (DS) and the broken line (DM) represent the astigmatism on the sagittal plane and on the meridional plane, respectively. In Examples 1 to 5, Conditions (1) to (5) mentioned above are fulfilled.
  • [0242]
    [0242]FIGS. 20A to 20I, 21A to 21I, 22A to 22I, 23A to 23I, 24A to 24I, 25A to 25I, 26A to 26I, 27A to 27I, 28A to 28I, and 30A to 30I show the aberrations observed in the infinite-distance shooting condition in Examples 6 to 15, respectively. Of these diagrams, FIGS. 20A to 20C, 21A to 21C, 22A to 22C, 23A to 23C, 24A to 24C, 25A to 25C, 26A to 26C, 27A to 27C, 28A to 28C, and 30A to 30C show the aberrations observed at the wide-angle end [W]; FIGS. 20D to 20F, 21D to 21F, 22D to 22F, 23D to 23F, 24D to 24F, 25D to 25F, 26D to 26F, 27D to 27F, 28D to 28F, and 30D and 30F show the aberrations observed at the middle focal length [M]; and FIGS. 20G to 20I, 21G to 21I, 22G to 22I, 23G to 23I, 24G to 24I, 25G to 25I, 26G to 26I, 27G to 27I, 28G to 28I, and 30G to 30I show the aberrations observed at the telephoto end [T]. In the spherical aberration diagrams, the solid line (d) represents the d line and the broken line (SC) represents the sine condition. In the astigmatism diagrams, the solid line (DS) and the broken line (DM) represent the astigmatism on the sagittal plane and on the meridional plane, respectively. In Examples 6 to 15, the conditions mentioned above are fulfilled.
  • [0243]
    The variables used in Conditions (1) to (5) in Examples 1 to 5 are listed in Table 16.
  • [0244]
    The values corresponding to Conditions (1) to (5) in Examples 1 to 5 are listed in Table 17.
  • [0245]
    The values corresponding to Conditions (9) to (13) and (18) to (24) in Examples 6 to 15 are listed in Table 18.
  • [0246]
    The values corresponding to Conditions (7) and (8) to be fulfilled by the aspherical surface in Examples 1 to 5 are listed in Table 19. Note that Y represents the maximum height of the optical path on the aspherical surface.
  • [0247]
    The values corresponding to Conditions (15) to (17) to be fulfilled by the aspherical surface in Examples 6 to 15 are listed in Table 20. Note that Y represents the maximum height of the optical path on the aspherical surface.
    TABLE 1
    Construction Data of Example 1
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of the Entire Optical System)
    FNO = 2.96 mm 3.24 mm 3.6 mm (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 11.333 d1 = 0.779 N1 = 1.85000 ν1 = 40.04
    r2 = 6.007 d2 = 1.940
    r3* = 17.418 d3 = 1.400 N2 = 1.52510 ν2 = 56.38
    r4 = 6.396 d4 = 1.895
    r5 = 7.432 d5 = 1.763 N3 = 1.84666 ν3 = 23.82
    r6 = 10.246 d6 = 13.009 6.374 1.500
    r7 = ∞ (Aperture Stop) d7 = 1.500
    r8 = 5.989 d8 = 1.829 N4 = 1.75450 ν4 = 51.57
    r9 = −125.715 d9 = 1.268
    r10 = −12.153 d10 = 0.635 N5 = 1.75000 ν5 = 25.14
    r11 = 9.023 d11 = 0.447
    r12* = 13.010 d12 = 2.293 N6 = 1.52510 ν6 = 56.38
    r13 = −6.778 d13 = 1.000 2.559 4.786
    r14 = ∞ d14 = 3.400 N7 = 1.54426 ν7 = 69.60
    r15 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.21447 10−3
    A6 = 0.50169 10−5
    A8 = 0.14584 10−6
    [Aspherical Coefficients of 12th Surface (r12)]
    ε = 0.10000 10
    A4 = −0.20572 10−2
    A6 = −0.42994 10−5
    A8 = −0.32617 10−5
  • [0248]
    [0248]
    TABLE 2
    Construction Data of Example 2
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of the Entire Optical System)
    FNO = 2.96 mm 3.24 mm 3.6 mm (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 14.260 d1 = 0.650 N1 = 1.53359 ν1 = 64.66
    r2 = 6.334 d2 = 2.341
    r3* = 24.115 d3 = 1.400 N2 = 1.52510 ν2 = 56.38
    r4 = 5.871 d4 = 1.561
    r5 = 6.894 d5 = 2.091 N3 = 1.58340 ν3 = 30.23
    r6 = 13.124 d6 = 14.102 6.837 1.500
    r7 = ∞ (Aperture Stop) d7 = 1.500
    r8 = 5.164 d8 = 2.262 N4 = 1.61555 ν4 = 57.97
    r9 = −9.593 d9 = 0.479
    r10* = −5.666 d10 = 1.472 N5 = 1.58340 ν5 = 30.23
    r11 = 9.833 d11 = 0.604
    r12* = 22.822 d12 = 1.943 N6 = 1.52510 ν6 = 56.38
    r13 = −8.802 d13 = 1.000 2.422 4.454
    r14 = ∞ d14 = 3.400 N7 = 1.54426 ν7 = 69.60
    r15 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.16907 10−3
    A6 = 0.35415 10−5
    A8 = 0.80238 10−7
    [Aspherical Coefficients of 10th Surface (r10)]
    ε = 0.10000 10
    A4 = 0.79103 10−3
    A6 = 0.24186 10−4
    A8 = 0.30525 10−5
    [Aspherical Coefficients of 12th Surface (r12)]
    ε = 0.10000 10
    A4 = −0.25573 10−2
    A6 = −0.15034 10−5
    A8 = −0.18614 10−4
  • [0249]
    [0249]
    TABLE 3
    Construction Data of Example 3
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of the Entire Optical System)
    FNO = 2.96 mm 3.24 mm 3.6 mm (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 11.551 d1 = 1.213 N1 = 1.75450 ν1 = 51.57
    r2 = 6.152 d2 = 2.230
    r3* = 21.819 d3 = 1.400 N2 = 1.52510 ν2 = 56.38
    r4 = 6.113 d4 = 1.835
    r5 = 7.256 d5 = 2.216 N3 = 1.69961 ν3 = 26.60
    r6 = 11.287 d6 = 13.126 6.424 1.500
    r7 = ∞ (Aperture Stop) d7 = 1.500
    r8 = 5.207 d8 = 2.259 N4 = 1.61213 ν4 = 58.19
    r9 = −9.240 d9 = 0.467
    r10* = −5.774 d10 = 1.430 N5 = 1.58340 ν5 = 30.23
    r11 = 9.548 d11 = 0.601
    r12* = 22.409 d12 = 1.984 N6 = 1.52510 ν6 = 56.38
    r13 = −8.485 d13 = 1.000 2.495 4.630
    r14 = ∞ d14 = 3.400 N7 = 1.54426 ν7 = 69.60
    r15 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.19262 10−3
    A6 = 0.34894 10−5
    A8 = 0.12515 10−6
    [Aspherical Coefficients of 10th Surface (r10)]
    ε = 0.10000 10
    A4 = 0.43913 10−3
    A6 = 0.33312 10−4
    A8 = 0.24577 10−5
    [Aspherical Coefficients of 12th Surface (r12)]
    ε = 0.10000 10
    A4 = −0.22305 10−2
    A6 = −0.11486 10−4
    A8 = −0.15332 10−4
  • [0250]
    [0250]
    TABLE 4
    Construction Data of Example 4
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of the Entire Optical System)
    FNO = 2.9 mm 3.25 mm 3.6 mm (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 13.912 d1 = 1.500 N1 = 1.75450 ν1 = 51.57
    r2 = 6.626 d2 = 2.111
    r3 = 25.350 d3 = 1.000 N2 = 1.75450 ν2 = 51.57
    r4 = 7.001 d4 = 0.893
    r5* = 14.283 d5 = 4.843 N3 = 1.58340 ν3 = 30.23
    r6* = −45.283 d6 = 15.765 7.542 1.500
    r7 = ∞ (Aperture Stop) d7 = 1.500
    r8 = 5.964 d8 = 4.216 N4 = 1.65656 ν4 = 55.63
    r9 = −7.373 d9 = 0.208
    r10 = −6.131 d10 = 1.300 N5 = 1.58340 ν5 = 30.23
    r11* = 9.768 d11 = 2.852
    r12 = −77.516 d12 = 1.708 N6 = 1.52200 ν6 = 65.93
    r13 = −8.818 d13 = 1.000 2.668 5.052
    r14 = ∞ d14 = 3.400 N7 = 1.54426 ν7 = 69.60
    r15 = ∞
    [Aspherical Coefficients of 5th Surface (r5)]
    ε = 0.10000 10
    A4 = 0.90348 10−4
    A6 = 0.13458 10−5
    A8 = 0.14476 10−6
    [Aspherical Coefficients of 6th Surface (r6)]
    ε = 0.10000 10
    A4 = −0.32219 10−3
    A6 = −0.25483 10−5
    A8 = −0.86784 10−7
    [Aspherical Coefficients of 11th Surface (r11)]
    ε = 0.10000 10
    A4 = 0.20489 10−2
    A6 = 0.27321 10−4
    A8 = 0.40971 10−5
    A10 = −0.20451 10−6
  • [0251]
    [0251]
    TABLE 5
    Construction Data of Example 5
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of the Entire Optical System)
    FNO = 3.18 mm 3.55 mm 4.08 mm (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 10.456 d1= 2.128 N1 = 1.85000 ν1 = 40.04
    r2 = 3.870 d2 = 2.166
    r3* = 16.226 d3 = 1.400 N2 = 1.52510 ν2 = 56.38
    r4 = 6.827 d4 = 1.322
    r5 = 8.144 d5 = 1.514 N3 = 1.83350 ν3 = 21.00
    r6 = 13.791 d6 = 8.994 4.674 1.500
    r7 = ∞ (Aperture Stop) d7 = 1.500
    r8 = 5.950 d8 = 1.897 N4 = 1.74989 ν4 = 51.73
    r9 = −43.969 d9 = 1.242
    r10 = −11.144 d10 = 0.753 N5 = 1.84714 ν5 = 25.28
    r11 = 10.245 d11 = 0.400
    r12* = 12.590 d12 = 2.297 N6 = 1.52510 ν6 = 56.38
    r13 = −6.634 d13 = 1.000 3.314 6.620
    r14 = ∞ d14 = 3.400 N7 = 1.54426 ν7 = 69.60
    r15 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.13045 10−2
    A6 = 0.11643 10−4
    A8 = 0.51406 10−5
    [Aspherical Coefficients of 12th Surface (r12)]
    ε = 0.10000 10
    A4 = −0.22747 10−2
    A6 = −0.36716 10−5
    A8 = −0.32887 10−6
  • [0252]
    [0252]
    TABLE 6
    Construction Data of Example 6
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of the Entire Optical System)
    FNO = 2.74 3.11 3.60 (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 13.380 d1 = 0.650 N1 = 1.75450 ν1 = 51.57
    r2 = 5.890 d2 = 1.499
    r3* = 12.328 d3 = 1.400 N2 = 1.52510 ν2 = 56.38
    r4 = 5.632 d4 = 1.632
    r5 = 7.068 d5 = 1.753 N3 = 1.84777 ν3 = 27.54
    r6 = 10.246 d6 = 10.406 5.264 1.500
    r7 = ∞ (Aperture Stop) d7 = 1.500
    r8 = 5.643 d8 = 1.901 N4 = 1.79073 ν4 = 46.15
    r9 = −74.805 d9 = 0.921
    r10 = −12.842 d10 = 0.600 N5 = 1.72145 ν5 = 25.50
    r11 = 5.928 d11 = 0.400
    r12* = 11.144 d12 = 2.170 N6 = 1.52510 ν6 = 56.38
    r13 = −9.099 d13 = 1.000 3.519 7.154
    r14 = 11.107 d14 = 3.164 N7 = 1.51680 ν7 = 64.20
    r15 = 56.703 d15 = 0.796
    r16 = ∞ d16 = 3.400 N8 = 1.54426 ν8 = 69.60
    r17 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.38905 10−3
    A6 = 0.24379 10−5
    A8 = 0.38282 10−6
    [Aspherical Coefficients of 12th Surface (r12)]
    ε = 0.10000 10
    A4 = −0.13386 10−2
    A6 = −0.11975 10−4
    A8 = −0.53773 10−5
  • [0253]
    [0253]
    TABLE 7
    Construction Data of Example 7
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of the Entire Optical System)
    FNO = 2.73 3.10 3.60 (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 14.718 d1 = 0.650 N1 = 1.75450 ν1 = 51.57
    r2 = 6.639 d2 = 1.307
    r3* = 11.594 d3 = 1.400 N2 = 1.52510 ν2 = 56.38
    r4 = 5.294 d4 = 1.465
    r5 = 6.937 d5 = 1.858 N3 = 1.84759 ν3 = 26.85
    r6 = 10.034 d6 = 10.621 5.340 1.500
    r7 = ∞ (Aperture Stop) d7 = 1.500
    r8 = 6.969 d8 = 2.905 N4 = 1.85000 ν4 = 40.04
    r9 = −11.743 d9 = 0.210
    r10 = −8.399 d10 = 1.855 N5 = 1.72131 ν5 = 25.51
    r11 = 5.522 d11 = 0.400
    r12 = 11.032 d12 = 2.012 N6 = 1.75450 ν6 = 51.57
    r13 = −21.657 d13 = 1.000 3.398 6.919
    r14* = 8.536 d14 = 3.241 N7 = 1.52510 ν7 = 56.38
    r15 = 29.006 d15 = 0.676
    r16 = ∞ d16 = 3.400 N8 = 1.54426 ν8 = 69.60
    r17 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.35342 10−3
    A6 = 0.71258 10−6
    A8 = 0.33647 10−6
    [Aspherical Coefficients of 14th Surface (r14)]
    ε = 0.10000 10
    A4 = −0.23473 10−3
    A6 = 0.43912 10−5
    A8 = 0.10409 10−6
  • [0254]
    [0254]
    TABLE 8
    Construction Data of Example 8
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of the Entire Optical System)
    FNO = 2.75 3.10 3.60 (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1* = 14.652 d1 = 1.200 N1 = 1.58340 ν1 = 30.23
    r2 = 8.289 d2 = 1.623
    r3 = 26.068 d3 = 0.900 N2 = 1.79271 ν2 = 45.90
    r4 = 5.496 d4 = 1.179
    r5 = 7.356 d5 = 1.921 N3 = 1.84666 ν3 = 23.82
    r6 = 15.373 d6 = 10.224 5.176 1.500
    r7 = ∞ (Aperture Stop) d7 = 1.500
    r8 = 7.124 d8 = 3.411 N4 = 1.85000 ν4 = 40.04
    r9 = −11.538 d9 = 0.154
    r10 = −8.339 d10 = 1.713 N5 = 1.72418 ν5 = 25.37
    r11 = 5.686 d11 = 0.401
    r12 = 10.731 d12 = 2.078 N6 = 1.75450 ν6 = 51.57
    r13 = −18.326 d13 = 1.000 3.307 6.708
    r14* = 8.148 d14 = 3.002 N7 = 1.52510 ν7 = 56.38
    r15 = 16.995 d15 = 0.795
    r16 = ∞ d16 = 3.400 N8 = 1.54426 ν8 = 69.60
    r17 = ∞
    [Aspherical Coefficients of 1st Surface (r1)]
    ε = 0.10000 10
    A4 = 0.15951 10−3
    A6 = 0.14779 10−6
    A8 = 0.56026 10−7
    [Aspherical Coefficients of 14th Surface (r14)]
    ε = 0.10000 10
    A4 = −0.27776 10−3
    A6 = 0.23365 10−5
    A8 = 0.19731 10−6
  • [0255]
    [0255]
    TABLE 9
    Construction Data of Example 9
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of tile Entire Optical System)
    FNO = 2.73 3.10 3.60 (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 52.355 d1 = 1.100 N1 = 1.72677 ν1 = 52.55
    r2 = 6.927 d2 = 3.324
    r3* = 23.902 d3 = 1.940 N2 = 1.58340 ν2 = 30.23
    r4 = −100.448 d4 = 14.827 7.138 1.500
    r5 = ∞ (Aperture Stop) d5 = 1.500
    r6 = 5.036 d6 = 3.339 N3 = 1.77742 ν3 = 47.95
    r7 = −12.586 d7 = 0.234
    r8 = −10.396 d8 = 0.800 N4 = 1.79850 ν4 = 22.60
    r9 = 16.524 d9 = 0.740
    r10 = −7.142 d10 = 1.200 N5 = 1.58340 ν5 = 30.23
    r11* = −26.834 d11 = 1.000 2.921 5.663
    r12 = 15.086 d12 = 2.096 N6 = 1.48749 ν6 = 70.44
    r13 = −14.941 d13 = 0.500
    r14 = ∞ d14 = 3.400 N7 = 1.54426 ν7 = 69.60
    r15 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.24908 10−3
    A6 = −0.62198 10−7
    A8 = 0.10295 10−6
    [Aspherical Coefficients of 11th Surface (r11)]
    ε = 0.10000 10
    A4 = 0.39625 10−2
    A6 = 0.16585 10−3
    A8 = 0.13563 10−4
  • [0256]
    [0256]
    TABLE 10
    Construction Data of Example 10
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of the Entire Optical System)
    FNO = 2.75 3.11 3.60 (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1* = 17.928 d1 = 1.200 N1 = 1.58340 ν1 = 30.23
    r2 = 9.608 d2 = 1.325
    r3 = 19.410 d3 = 0.900 N2 = 1.80280 ν2 = 44.68
    r4 = 5.204 d4 = 1.288
    r5 = 7.294 d5 = 1.940 N3 = 1.84666 ν3 = 23.82
    r6 = 14.586 d6 = 10.102 5.348 1.500
    r7 = ∞ (Aperture Stop) d7 = 1.500
    r8 = 6.594 d8 = 4.206 N4 = 1.81063 ν4 = 43.80
    r9 = −10.411 d9 = 0.208
    r10 = −7.270 d10 = 0.600 N5= 1.70098 ν5 = 26.53
    r11 = 5.447 d11 = 0.504
    r12 = 10.684 d12 = 2.062 N6 = 1.75450 ν6 = 51.57
    r13 = −20.769 d13 = 1.000 3.880 6.996
    r14* = 6.351 d14 = 2.209 N7 = 1.52510 ν7 = 56.38
    r15 = 12.184 d15 = 1.055 0.800 1.067
    r16 = ∞ d16 = 3.400 N8 = 1.54426 ν8 = 69.60
    r17 = ∞
    [Aspherical Coefficients of 1st Surface (r1)]
    ε = 0.10000 10
    A4 = 0.19398 10−3
    A6 = 0.47895 10−6
    A8 = 0.46069 10−7
    [Aspherical Coefficients of 14th Surface (r14)]
    ε = 0.10000 10
    A4 = −0.37579 10−3
    A6 = −0.11089 10−5
    A8 = 0.87379 10−7
  • [0257]
    [0257]
    TABLE 11
    Construction Data of Example 11
    f = 5.4 mm 7.5 mm 10.5 mm (Focal Length of the Entire Optical System)
    FNO = 2.97 3.27 3.60  (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = −112.214
    d1 = 1.200 N1 = 1.63347 ν1 = 56.87
    r2 = 7.682
    d2 = 1.473
    r3* = 17.799
    d3 = 2.175 N2 = 1.58340 ν2 = 30.23
    r4 = 274.206
    d4 = 16.482 8.078 1.500
    r5 = ∞(Aperture Stop)
    d5 = 1.500
    r6 = 5.066
    d6 = 2.164 N3 = 1.84746 ν4 = 40.25
    r7 = −15.255
    d7 = 0.208
    r8 = −13.752
    d8 = 0.800 N4 = 1.79850 ν5 = 22.60
    r9 = 7.640
    d9 = 0.352
    r10* = 8.419
    d10 = 1.200 N5 = 1.58340 ν6 = 30.23
    r11 = 4.700
    d11 = 1.000 1.802 2.808
    r12 = 40.534
    d12 = 2.262 N6 = 1.51838 ν7 = 66.35
    r13 * = −6.756
    d13 = 1.131 2.007 3.472
    r14 = ∞
    d14 = 3.400 N7 = 1.54426 ν8 = 69.60
    r15 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.24372 10−3
    A6 = −0.10309 10−6
    A8 = 0.84837 10−7
    [Aspherical Coefficients of 10th Surface (r10)]
    ε = 0.10000 10
    A4 = −0.35107 10−2
    A6 = −0.17279 10−3
    A8 = −0.80824 10−5
    [Aspherical Coefficients of 13th Surface (r13)]
    ε = 0.10000 10
    A4 = 0.11613 10−3
    A6 = −0.34635 10−4
    A8 = 0.66386 10−6
  • [0258]
    [0258]
    TABLE 12
    Construction Data of Example 12
    f = 5.4 mm 8.0 mm 12.0 mm (Focal Length of the Entire Optical System)
    FNO = 2.55 2.95 3.60 (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 64.355
    d1 = 0.650 N1 = 1.48749 ν1 = 70.44
    r2 = 9.616
    d2 = 1.136
    r3* = 15.072
    d3 = 1.400 N2 = 1.52510 ν2 = 56.38
    r4 = 6.352
    d4 = 1.939
    r5 = 8.584
    d5 = 2.060 N3 = 1.84877 ν3 = 32.01
    r6 = 12.547
    d6 = 15.531 7.207 1.500
    r7 = ∞Aperture Stop)
    d7 = 1.500
    r8 = 5.666
    d8 = 3.346 N4 = 1.75450 ν4 = 51.57
    r9 = −8.847
    d9 = 0.100
    r10 = −7.390
    d10 = 0.600 N5 = 1.58340 ν5 = 30.23
    r11 = 4.818
    d11 = 0.400
    r12* = 6.048
    d12 = 2.459 N6 = 1.52510 ν6 = 56.38
    r13 = 9.906
    d13 = 1.000 3.334 6.995
    r14 = 11.941
    d14 = 1.979 N7 = 1.52510 ν7 = 56.38
    r15* = −29.235
    d15 = 0.500
    r16 = ∞
    d16 = 3.400 N8 = 1.54426 ν8 = 69.60
    r17 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.17978 10−3
    A6 = −0.30828 10−6
    A8 = 0.71904 10−7
    [Aspherical Coefficients of 12th Surface (r12)]
    ε 0.10000 10
    A4 = −0.18066 10−2
    A6 = −0.54257 10−4
    A8 = −0.76508 10−5
    [Aspherical Coefficients of 15th Surface (r15)]
    ε = 0.10000 10
    A4 = 0.29756 10−3
    A6 = −0.62953 10−5
    A8 = −0.77785 10−7
  • [0259]
    [0259]
    TABLE 13
    Construction Data of Example 13
    f = 5.4 mm 8.8 mm 14.0mm (Focal Length of the Entire Optical System)
    FNO = 2.34 2.84 3.60 (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 25.623
    d1 = 0.650 N1 = 1.48749 ν1 = 70.44
    r2 = 9.290
    d2 = 1.626
    r3* = 19.577
    d3 = 1.400 N2 = 1.52510 ν2 = 56.38
    r4 = 5.973
    d4 = 2.273
    r5 = 7.949
    d5 = 2.008 N3 = 1.84807 ν3 = 28.75
    r6 = 10.541
    d6 = 16.801 7.154 1.500
    r7 = ∞(Aperture Stop)
    d7 = 1.500
    r8 = 5.107
    d8 = 2.743 N4 = 1.64626 ν4 = 56.17
    r9 = −9.178
    d9 = 0.100
    r10 = −8.533
    d10 = 0.600 N5 = 1.58340 ν5 = 30.23
    r11 = 7.962
    d11 = 0.849
    r12* = 7.572
    d12 = 1.401 N6 = 1.52510 ν6 = 56.38
    r13 = 8.290
    d13 = 1.000 4.278 9.371
    r14* = 9.062
    d14 = 1.423 N7 = 1.58340 ν7 = 30.23
    r15 = 6.924
    d15 = 0.747
    r16 = 11.941
    d16 = 1.979 N8 = 1.52510 ν8 = 56.38
    r17* = −29.488
    d17 = 0.500
    r18 = ∞
    d18 = 3.400 N9 = 1.54426 ν9 = 69.60
    r19 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.16055 10−3
    A6 = 0.48397 10−7
    A8 = 0.67121 10−7
    [Aspherical Coefficients of 12th Surface (r12)]
    ε = 0.10000 10
    A4 = −0.25048 10−2
    A6 = −0.87701 10−4
    A8 = −0.12082 10−4
    [Aspherical Coefficients of 14th Surface (r14)]
    ε = 0.10000 10
    A4 = −0.52484 1031 3
    A6 = 0.58442 10−5
    A8 = 0.87159 10−8
    [Aspherical Coefficients of 17th Surface (r17)]
    ε = 0.10000 10
    A4 = −0.91828 10−3
    A6 = −0.59033 10−5
    A8 = 0.27335 10−6
  • [0260]
    [0260]
    TABLE 14
    Construction Data of Example 14
    f = 5.4 mm 7.5 mm 13.5 mm (Focal Length of the Entire Optical System)
    FNO = 2.08 2.48 3.60 (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 14.018
    d1 = 0.650 N1 = 1.74388 ν1 = 51.93
    r2 = 6.286
    d2 = 1.790
    r3* = 17.191
    d3 = 1.400 N2 = 1.52510 ν2 = 56.38
    r4 = 5.770
    d4 = 0.907
    r5 = 6.726
    d5 = 1.953 N3 = 1.84666 ν3 = 23.82
    r6 = 10.531
    d6 = 9.731 5.843 1.500
    r7 = ∞(Aperture Stop)
    d7 = 1.500
    r8 = 6.489
    d8 = 1.774 N4 = 1.85000 ν4 = 40.04
    r9 = 52.968
    d9 = 0.665
    r10 = −31.304
    d10 = 0.600 N5 = 1.77185 ν5 = 23.46
    r11 = 6.642
    d11 = 0.400
    r12* = 11.190
    d12 = 2.101 N6 = 1.52510 ν6 = 56.38
    r13 = −9.334
    d13 = 1.000 5.310 15.247
    r14 = −10.861
    d14 = 1.200 N7 = 1.58340 ν7 = 30.23
    r15* = 16.708
    d15 = 0.100
    r16 = 12.354
    d16 = 2.934 N8 = 1.84353 ν8 = 40.59
    r17 = −10.876
    d17 = 2.914 2.385 0.717
    r18 = ∞
    d18 = 3.400 N9 = 1.54426 ν9 = 69.60
    r19 = ∞
    [Aspherical Coefficients of 3rd Surface (r3)]
    ε = 0.10000 10
    A4 = 0.28799 10−3
    A6 = 0.40089 10−5
    A8 = 0.14823 10−6
    [Aspherical Coefficients of 12th Surface (r12)]
    ε = 0.10000 10
    A4 = −0.62816 10−3
    A6 = −0.22891 10−4
    A8 = 0.42945 10−6
    [Aspherical Coefficients of 15th Surface (r15)]
    ε = 0.10000 10
    A4 = 0.60130 10−3
    A6 = −0.42374 10−5
    A8 = 0.11268 10−7
  • [0261]
    [0261]
    TABLE 15
    Construction Data of Example 15
    f = 5.4 mm 8.4 mm 15.6 mm (Focal Length of the Entire Optical System)
    FNO = 2.57 3.04 4.20 (F numbers)
    Radius of Axial Refractive Abbe
    Curvature Distance Index (Nd) Number (d)
    r1 = 34.564
    d1 = 1.600 N1 = 1.52510 ν1 = 56.38
    r2 = 7.185
    d2 = 3.500
    r3* = 10.666
    d3 = 2.344 N2 = 1.75000 ν2 = 25.14
    r4 = 17.516
    d4 = 22.572 11.179 1.713
    r5 = ∞
    d5 = 1.500
    r6 = 8.000
    d6 = 2.941 N3 = 1.80420 ν3 = 46.50
    r7 = −8.598
    d7 = 0.010 N4 = 1.51400 ν4 = 42.83
    r8 = −8.598
    d8 = 0.600 N5 = 1.70055 ν5 = 30.11
    r9 = 8.182
    d9 = 0.200
    r10* = 5.244
    d10 = 3.249 N6 = 1.52510 ν6 = 56.38
    r11* = 6.000
    d11 = 2.740 5.844 13.277
    r12 = 21.195
    d12 = 2.000 N7 = 1.48749 ν7 = 70.44
    r13 = −16.672
    d13 = 1.086
    r14 = ∞
    d14 = 3.400 N8 = 1.51680 ν8 = 64.20
    r15 = ∞
    [Aspherical Coefficients of 3rd Surface (r1)]
    ε = 0.10000 10
    A4 = 0.43400 10−3
    A6 = −0.55461 10−5
    A8 = 0.27915 10−7
    [Aspherical Coefficients of 12th Surface (r2)]
    ε = 0.10000 10
    A4 = 0.26861 10−3
    A6 = 0.25040 10−5
    A8 = 0.23353 10−6
    [Aspherical Coefficients of 15th Surface (r10)]
    ε = 0.10000 10
    A4 = −0.30306 10−3
    A6 = −0.13415 10−4
    A8 = −0.19911 10−5
    [Aspherical Coefficients of 15th Surface (r11]
    ε = 0.10000 10
    A4 = 0.19342 10−2
    A6 = 0.59893 10−4
    A8 = −0.42081 10−5
  • [0262]
    [0262]
    TABLE 16
    The variables used in Conditions (1) to (5) in Examples 1 to 5
    φ1 φ2 φW
    Example 1 0.076171 0.102604 0.185185
    φPi hi φPi/φW hi Sum
    Example 1 G2: −0.04968 1.088763 −0.292107
    G6: 0.11313 1.264821 0.7726821 0.480575
    φ1 φ2 φW
    Example 2 0.069512 0.102665 0.185162
    φPi hi φPi/φW hi Sum
    Example 2 G2: −0.06587 1.090648 −0.387944
    G3: 0.045137 1.299594 0.3167591
    G5: −0.16797 1.270288 −1.152222
    G6: 0.080916 1.2079 0.5277862 −0.69562
    φ1 φ2 φW
    Example 3 0.07421 0.104252 0.185186
    φPi hi φPi/φW hi Sum
    Example 3 G2: −0.05994 1.070319 −0.346422
    G3: −0.16771 1.288669 −1.167062
    G5: 0.083429 1.23342 0.555676 −0.95781
    φ1 φ2
    Example 4 0.070779 0.089085 0.185184
    φPi hi φPi/φW hi Sum
    Example 4 G3: 0.05212 1.068396 0.3006979
    G5: −0.15954 1.348671 −1.161906 −0.86121
    φ1 φ2 φW
    Example 5 0.115 0.104369 0.185185
    φPi hi φPi/φW hi Sum
    Example 5 G2: −0.04227 1.161585 −0.265113
    G6: 0.11589 1.553375 0.9721086 0.706996
  • [0263]
    [0263]
    TABLE 17
    The values corresponding to Conditions (1) to (5) in Examples 1 to 5
    |φ1/φ2| φ2/φW |φP/φ1| |φP/φ2| ΕφPi/φW hi
    Example 1 0.41 0.55 G2: 0.65 G6: 1.10  0.48
    Example 2 0.38 0.55 G2: 0.95 G5: 1.64 −0.70
    G3: 0.65 G6: 0.79
    Example 3 0.40 0.56 G2: 0.81 G5: 1.61 −0.96
    G6: 0.80
    Example 4 0.38 0.48 G3: 0.74 G5: 1.79 −0.86
    Example 5 0.62 0.56 G2: 0.37 G6: 1.11  0.71
  • [0264]
    [0264]
    TABLE 18
    The values corresponding to Conditions (9) to
    (13) and (18) to (2φin Examples 6 to 15
    |φP/φW| |φP/φ1| |φP/φ2| |φP/φ3| M3/M2
    Example 6 G2: 0.25 0.63 0.00
    G6: 0.55 1.10
    Example 7 G2: 0.27 0.72 0.00
    G7: 0.25 1.00
    Example 8 G1: 0.15 0.39 0.00
    G7: 0.20 1.00
    Example 9 G2: 0.16 0.59 0.00
    G5: 0.32 0.68
    Example 10 G1: 0.14 0.38 0.00
    G7: 0.24 0.47 1.00
    Example 11 G2: 0.17 0.57 0.56
    G5: 0.26 0.65
    Example 12 G2: 0.24 0.86 0.00
    G5: 1.10 2.27
    G6: 0.22 0.46
    G7: 0.33 1.00
    Example 13 G2: 0.32 0.97 0.00
    G5: 0.78 1.64
    G6: 0.05 0.11
    G7: 0.08 0.35
    G8: 0.33 1.40
    Example 14 G2: 0.31271 0.79 −0.18
    G6: 0.5375 1.19
    G7: 0.48626 1.38
    log(β2T/β2W)/logZ log(β3T/β3W)/logZ
    Example 6 G2: 1.00 0.00
    Example 7 G2: 1.00 0.00
    Example 8 G1: 1.00 0.00
    Example 9 G2: 0.99 0.01
    Example 10 G1: 1.00 0.00
    Example 11 G2: 1.87 −0.87
    Example 12 G2: 0.99 0.01
    Example 13 G2: 1.00 0.00
    Example 14 G2: 0.75 0.25
    log(β3T/β3W)/log(β2T/β2W)
    Example 6 G2: 0.00
    Example 7 G2: 0.00
    Example 8 G1: 0.00
    Example 9 G2: 0.01
    Example 10 G1: 0.00
    Example 11 G2: −0.46
    Example 12 G2: 0.01
    Example 13 G2: 0.00
    Example 14 G2: 0.34
    ∩P/ 0W h ΕφPi/φW hi
    Example 6 G2: −0.27
    G6: 0.66 0.39
    Example 7 G2: −0.28
    G7: 0.17 −0.12
    Example 8 G1: −0.15
    G7: 0.14 −0.01
    Example 9 G2: 0.21
    G5: −0.30 −0.09
    Example 10 G1: −0.14
    G7: 0.16 0.02
    Example 11 G2: 0.19
    G5: −0.26 −0.08
    Example 12 G2: −0.26
    G5: −1.20
    G6: 0.23
    G7: 0.16 −1.06
    Example 13 G2: −0.33
    G5: −0.93
    G6: 0.06
    G7: −0.04
    G8: 0.14 −1.10
    Example 14 G2: −0.34
    G6: 0.68
    G7: −0.25 0.09
    |φ1/φW| φ2/φW φ3/φW
    Example 6 G2: 0.40 0.50 0.21
    Example 7 G2: 0.37 0.50 0.25
    Example 8 G1: 0.40 0.52 0.20
    Example 9 G2: 0.27 0.47 0.34
    Example 10 G1: 0.38 0.51 0.24
    Example 11 G2: 0.29 0.40 0.48
    Example 12 G2: 0.29 0.48 0.33
    Example 13 G2: 0.33 0.47 0.23
    Example 14 G2: 0.39 0.45 0.35
    Cp (N′-N)/φW
    Object side Image side
    Example 6 G2: 0.23 −0.50
    G6: 0.25 0.31
    Example 7 G2: 0.25 −0.54
    G7: 0.33 −0.10
    Example 8 G1: 0.22 −0.38
    G7: 0.35 −0.17
    Example 9 G2: 0.13 0.031
    G5: −0.44 0.12
    Example 10 G1: 0.18 −0.33
    G7: 0.45 −0.23
    Example 11 G2: 0.18 −0.01
    G5: 0.37 −0.67
    Example 12 G2: 0.19 −0.45
    G5: −0.43 −0.65
    G6: 0.47 −0.29
    G7: 0.24 0.10
    Example 13 G2: 0.15 −0.48
    G5: −0.37 −0.40
    G6: 0.37 −0.34
    G7: 0.35 −0.46
    G8: 0.24 0.10
    Example 14 G2: 0.17 −0.49
    G6: 0.25 0.30
    G7: −0.29 −0.19
  • [0265]
    [0265]
    TABLE 19
    The values corresponding to Conditions (7) and (8) in Examples 1 to 5
    Example 1
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00037
    0.40Y −0.00634
    0.60Y −0.03585
    0.80Y −0.13341
    1.00Y −0.40394
    [12th Surface (r12)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y −0.00000
    0.20Y −0.00037
    0.40Y −0.00598
    0.60Y −0.03057
    0.80Y −0.09885
    1.00Y −0.25219
    Example 2
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00051
    0.40Y −0.00870
    0.60Y −0.04931
    0.80Y −0.18376
    1.00Y −0.55608
    [10th Surface (r10)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y  0.00000
    0.20Y  0.00005
    0.40Y  0.00077
    0.60Y  0.00408
    0.80Y  0.01399
    1.00Y  0.03852
    [12th Surface (r12)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y  0.00000
    0.20Y −0.00072
    0.40Y −0.01169
    0.60Y −0.06096
    0.80Y −0.20787
    1.00Y −0.58532
    Example 3
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00050
    0.40Y −0.00851
    0.60Y −0.04778
    0.80Y −0.17765
    1.00Y −0.54143
    [10th Surface (r10)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y −0.00000
    0.20Y  0.00003
    0.40Y  0.00046
    0.60Y  0.00259
    0.80Y  0.00945
    1.00Y  0.02790
    [12th Surface (r12)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y  0.00000
    0.20Y −0.00065
    0.40Y −0.01058
    0.60Y −0.05546
    0.80Y −0.19007
    1.00Y −0.53702
    Example 4
    [5th Surface (r5)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00008
    0.40Y −0.00129
    0.60Y −0.00719
    0.80Y −0.02684
    1.00Y −0.08390
    [6th Surface (r6)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00066
    0.40Y −0.01070
    0.60Y −0.05580
    0.80Y −0.18492
    1.00Y −0.48426
    [11th Surface (r11)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y −0.00000
    0.20Y −0.00017
    0.40Y −0.00282
    0.60Y −0.01457
    0.80Y −0.04772
    1.00Y −0.12247
    Example 5
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00058
    0.40Y −0.00938
    0.60Y −0.04968
    0.80Y −0.17281
    1.00Y −0.49672
    [12th Surface (n12)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y  0.00000
    0.20Y −0.00039
    0.40Y −0.00630
    0.60Y −0.03215
    0.80Y −0.10366
    1.00Y −0.26303
    The values corresponding to Conditions (15) and (17) in Examples 6 to 15
    Example 6
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00036
    0.40Y −0.00585
    0.60Y −0.03124
    0.80Y −0.10983
    1.00Y −0.31946
    [12th Surface (r12)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y  0.00000
    0.20Y −0.00016
    0.40Y −0.00266
    0.60Y −0.01382
    0.80Y −0.04620
    1.00Y −0.12441
    Example 7
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00040
    0.40Y −0.00645
    0.60Y −0.03442
    0.80Y −0.12249
    1.00Y −0.36724
    [14th Surface (r14)]
    Height (|X| − |X0|)/{C0(N′-N) f3}
    0.00Y  0.00000
    0.20Y −0.00005
    0.40Y −0.00072
    0.60Y −0.00343
    0.80Y −0.00979
    1.00Y −0.02004
    Example 8
    [1st Surface (r1)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00047
    0.40Y −0.00762
    0.60Y −0.04017
    0.80Y −0.13975
    1.00Y −0.40512
    [14th Surface (r14)]
    Height (|X| − |X0|)/{C0(N′-N) f3}
    0.00Y  0.00000
    0.20Y −0.00007
    0.40Y −0.00103
    0.60Y −0.00497
    0.80Y −0.01421
    1.00Y −0.02846
    Example 9
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00034
    0.40Y −0.00549
    0.60Y −0.02824
    0.80Y −0.09332
    1.00Y −0.24896
    [11th Surface (r11)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y  0.00000
    0.20Y −0.00086
    0.40Y −0.01414
    0.60Y −0.07574
    0.80Y −0.26114
    1.00Y −0.14147
    Example 10
    [1st Surface (r1)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00077
    0.40Y −0.01256
    0.60Y −0.06639
    0.80Y −0.22928
    1.00Y −0.65070
    [14th Surface (r14)]
    Height (|X| − |X0|)/{C0(N′-N) f3}
    0.00Y  0.00000
    0.20Y −0.00008
    0.40Y −0.00129
    0.60Y −0.00655
    0.80Y −0.02065
    1.00Y −0.04955
    Example 11
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00041
    0.40Y −0.00663
    0.60Y −0.03428
    0.80Y −0.11465
    1.00Y −0.31309
    [10th Surface (r10)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y  0.00000
    0.20Y −0.00016
    0.40Y −0.00260
    0.60Y −0.01388
    0.80Y −0.04736
    1.00Y −0.12790
    Example 12
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00058
    0.40Y −0.00940
    0.60Y −0.04961
    0.80Y −0.17667
    1.00Y −0.53893
    [12th Surface (r12)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y  0.00000
    0.20Y −0.00011
    0.40Y −0.00182
    0.60Y −0.00969
    0.80Y −0.03330
    1.00Y −0.09218
    [15th Surface (r15)]
    Height (|X| − |X0|)/{C0(N′-N) f3}
    0.00Y  0.00000
    0.20Y −0.00033
    0.40Y −0.00502
    0.60Y −0.02364
    0.80Y −0.06629
    1.00Y −0.13286
    Example 13
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00082
    0.40Y −0.01333
    0.60Y −0.07171
    0.80Y −0.26196
    1.00Y −0.82010
    [12th Surface (r12)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y  0.00000
    0.20Y −0.00020
    0.40Y −0.00328
    0.60Y −0.01759
    0.80Y −0.06132
    1.00Y −0.17301
    [14th Surface (r14)]
    Height (|X| − |X0|)/{C0(N′-N) f3}
    0.00Y  0.00000
    0.20Y −0.00020
    0.40Y −0.00311
    0.60Y −0.01525
    0.80Y −0.04605
    1.00Y −0.10564
    [17th Surface (r17)]
    Height (|X| − |X0|)/{C0(N′-N) f3}
    0.00Y  0.00000
    0.20Y  0.00068
    0.40Y  0.01090
    0.60Y  0.05583
    0.80Y  0.17801
    1.00Y  0.43402
    Example 14
    [3rd Surface (r3)]
    Height (|X| − |X0|)/{C0(N′-N) f1}
    0.00Y −0.00000
    0.20Y −0.00048
    0.40Y −0.00802
    0.60Y −0.04370
    0.80Y −0.15559
    1.00Y −0.44995
    [12th Surface (r12)]
    Height (|X| − |X0|)/{C0(N′-N) f2}
    0.00Y  0.00000
    0.20Y −0.00007
    0.40Y −0.00110
    0.60Y −0.00579
    0.80Y −0.01922
    1.00Y −0.04962
    [15th Surface (r15)]
    Height (|X| − |X0|)/{C0(N′-N) f3}
    0.00Y  0.00000
    0.20Y −0.00067
    0.40Y −0.01051
    0.60Y −0.05178
    0.80Y −0.15744
    1.00Y −0.36553
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6862143 *Jan 31, 2003Mar 1, 2005Canon Kabushiki KaishaZoom lens and optical apparatus having the same
US6999242Sep 8, 2004Feb 14, 2006Canon Kabushiki KaishaZoom lens and optical apparatus having the same
US7023625Sep 8, 2004Apr 4, 2006Canon Kabushiki KaishaZoom lens and optical apparatus having the same
US7113347Sep 7, 2004Sep 26, 2006Canon Kabushiki KaishaZoom lens and optical apparatus having the same
US7113348Sep 29, 2005Sep 26, 2006Canon Kabushiki KaishaZoom lens and optical apparatus having the same
US7227701Jun 29, 2006Jun 5, 2007Canon Kabushiki KaishaZoom lens and optical apparatus having the same
US7450318Jun 29, 2006Nov 11, 2008Canon Kabushiki KaishaZoom lens and optical apparatus having the same
US8094382Nov 19, 2009Jan 10, 2012Hoya CorporationZoom lens system and electronic imaging device using the same
US20030197951 *Jan 31, 2003Oct 23, 2003Canon Kabushiki KaishaZoom lens and optical apparatus having the same
US20050041303 *Sep 8, 2004Feb 24, 2005Canon Kabushiki KaishaZoom lens and optical apparatus having the same
US20060072212 *Sep 29, 2005Apr 6, 2006Canon Kabushiki KaishaZoom lens and optical apparatus having the same
US20060238889 *Jun 29, 2006Oct 26, 2006Canon Kabushiki KaishaZoom Lens and Optical Apparatus Having the Same
US20060238890 *Jun 29, 2006Oct 26, 2006Canon Kabushiki KaishaZoom Lens and Optical Apparatus Having the Same
US20100128364 *Nov 19, 2009May 27, 2010Hoya CorporationZoom lens system and electronic imaging device using the same
Classifications
U.S. Classification359/689, 359/694, 359/683, 359/676, 359/684
International ClassificationG02B15/177
Cooperative ClassificationG02B15/177
European ClassificationG02B15/177
Legal Events
DateCodeEventDescription
Feb 24, 2006FPAYFee payment
Year of fee payment: 4
Mar 18, 2010FPAYFee payment
Year of fee payment: 8
Mar 20, 2014FPAYFee payment
Year of fee payment: 12