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1. (US20180275381) ZOOM LENS AND IMAGE PICKUP APPARATUS USING THE SAME
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Claims

1. A zoom lens, comprising in order from an object side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power; and
a rear-side lens unit, wherein:
the second lens unit includes a first sub-unit having a negative refractive power and a second sub-unit having a negative refractive power, and
the rear-side lens unit is disposed on an image side of the second lens unit, and has a positive refractive power as a whole, and
the rear-side lens unit includes a plurality of lens units, and includes a third lens unit having a positive refractive power which is disposed nearest to object, and
an aperture stop is disposed on the image side of the second lens unit, and
a distance between the first lens unit and the second lens unit changes to become wider at a telephoto end than at a wide angle end, and
a distance between the second lens unit and the third lens unit changes to become narrower at the telephoto end than at the wide angle end, and
the first lens unit includes at least a negative lens and a positive lens, and
the first sub-unit includes at least a negative lens and a positive lens, and
the third lens unit includes at least two lens components having a positive refractive power, and
the following conditional expressions (1) and (2) are satisfied:

          61≤ vd 1G _ max _ p  (1), and

          −0.03≤ Tp 2Ga _ min _ p≤0.0165  (2)
where,
vd 1G _ max _ p denotes a maximum Abbe number from among Abbe numbers for a positive lens in the first lens unit,

           Tp 2Ga _ min _ p =θgF 2Ga _ p−(−0.0016× vd 2Ga _ p+0.6415), here

          θ gF 2Ga _ p=( ng 2Ga _ p −nF 2Ga _ p)/( nF 2Ga _ p −nC 2Ga _ p),
vd 2Ga _ p denotes Abbe number for a predetermined positive lens in the first sub-unit,
ng 2Ga _ p, nF 2Ga _ p, and nC 2Ga _ p are refractive indices of the predetermined positive lens in the first sub-unit for a g-line, an F-line, and a C-line respectively,
the predetermined positive lens in the first sub-unit is a positive lens for which Abbe number is the minimum, from among the positive lenses in the first sub-unit, and
the lens component is one of a single lens and a cemented lens.
2. A zoom lens, comprising in order from an object side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power; and
a rear-side lens unit, wherein:
the second lens unit includes a first sub-unit having a negative refractive power and a second sub-unit having a negative refractive power, and
the rear-side lens unit is disposed on an image side of the second lens unit, and has a positive refractive power as a whole, and
the rear-side lens unit includes a plurality of lens units, and includes a third lens unit having a positive refractive power which is disposed nearest to object, and
an aperture stop is disposed on the image side of the second lens unit, and
a distance between the first lens unit and the second lens unit changes to become wider at a telephoto end than at a wide angle end, and
a distance between the second lens unit and the third lens unit changes to become narrower at the telephoto end than at the wide angle end, and
the first lens unit includes at least a negative lens and a positive lens, and
the second lens unit includes at least a negative lens and a positive lens, and
the following conditional expressions (1′) and (3) are satisfied:

          69≤ vd 1G _ max _ p  (1′), and

          50≤ vd 2G _ max _ n  (3)
where,
vd 1G _ max _ p denotes a maximum Abbe number from among Abbe numbers for a positive lens in the first lens unit, and
vd 2G _ max _ n denotes a maximum Abbe number from among Abbe numbers for a negative lens in the second lens unit.
3. A zoom lens, comprising in order from an object side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power; and
a rear-side lens unit, wherein:
the second lens unit includes a first sub-unit having a negative refractive power and a second sub-unit having a negative refractive power, and
the rear-side lens unit is disposed on an image side of the second lens unit, and has a positive refractive power as a whole, and
the rear-side lens unit includes a plurality of lens units, and includes a third lens unit having a positive refractive power which is disposed nearest to object, and
an aperture stop is disposed on the image side of the second lens unit, and
a distance between the first lens unit and the second lens unit changes to become wider at a telephoto end than at a wide angle end, and
a distance between the second lens unit and the third lens unit changes to become narrower at the telephoto end than at the wide angle end, and
the first sub-unit includes at least a negative lens and a positive lens, and
the following conditional expressions (2) and (4) are satisfied:

          −0.03≤ Tp 2Ga _ min _ p≤0.0165  (2), and

          2.7≤ f 1 /f 3≤10.0  (4)
where,

           Tp 2Ga _ min _ p =θgF 2Ga _ p−(−0.0016× vd 2Ga _ p+0.6415), here

          θ gF 2Ga _ p=( ng 2Ga _ p −nF 2Ga _ p)/( nF 2Ga _ p −nC 2Ga _ p),
vd 2Ga _ p denotes Abbe number for a predetermined positive lens in the first sub-unit,
ng 2Ga _ p, nF 2Ga _ p, and nC 2Ga _ p are refractive indices of the predetermined positive lens in the first sub-unit for a g-line, an F-line, and a C-line respectively,
the predetermined positive lens in the first sub-unit is a positive lens for which Abbe number is the minimum, from among the positive lenses in the first sub-unit,
f 1 denotes a focal length of the first lens unit, and
f 3 denotes a focal length of the third lens unit.
4. The zoom lens according to claim 1, wherein:
the rear-side lens unit includes a fourth lens unit having a negative refractive power, and
the third lens unit and the fourth lens unit move such that the fourth lens unit is positioned on the object side at the telephoto end than at the wide angle end.
5. The zoom lens according to claim 1, wherein:
the rear-side lens unit includes the fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power, and
the third lens unit and the fourth lens unit move such that the fourth lens unit is positioned on the object side at the telephoto end than at the wide angle end.
6. The zoom lens according to claim 3, wherein:
the first lens unit includes at least a negative lens and a positive lens, and the following conditional expression (1) is satisfied:

          61≤ vd 1G _ max _ p  (1), and
where,
vd 1G _ max _ p denotes a maximum Abbe number from among Abbe numbers for a positive lens in the first lens unit.
7. The zoom lens according to claim 1, wherein:
the second lens unit includes at least a negative lens and a positive lens, and
the following conditional expression (3) is satisfied:

          50≤ vd 2G _ max _ n  (3)
where,
vd 2G _ max _ n denotes a maximum Abbe number from among Abbe numbers for a negative lens in the second lens unit.
8. The zoom lens according to claim 1, wherein:
the first sub-unit includes at least a negative lens and a positive lens, and
the following conditional expression (5) is satisfied:

          15≤ vd G2a _ min _ p≤32  (5)
where,
vd G2a _ min _ p denotes a minimum Abbe number from among Abbe numbers for the positive lenses in the second lens unit.
9. The zoom lens according to claim 1, wherein:
the third lens unit includes at least a positive lens and a negative lens, and
the following conditional expression (6) is satisfied:

          70.5≤ vd 3G _ max _ p  (6)
where,
vd 3G _ max _ p denotes a maximum Abbe number from among Abbe numbers for the positive lenses in the third lens unit.
10. The zoom lens according to claim 1, wherein:
the first sub-unit includes at least a negative lens and a positive lens, and
the following conditional expressions (7) is satisfied:

          1.76≤ nd 2G _ max _ p≤2.3  (7)
where,
nd 2G _ max _ p denotes a maximum refractive index from among refractive indices of the positive lenses in the first sub-unit.
11. The zoom lens according to claim 1, wherein the following conditional expression (8) is satisfied

          1.05≤|φ maxt /f 2|≤3.0  (8)
where,
φ maxt denotes a maximum diameter of an entrance pupil at a telephoto end, and is expressed by φ maxt=f t/Fno t, here
f t denotes a focal length of the overall zoom lens system at the telephoto end, and
Fno t denotes a smallest F-number at the telephoto end, and
f 2 denotes a focal length of the second lens unit.
12. The zoom lens according to claim 1, wherein the following conditional expression (4) is satisfied:

          2.7≤ f 1 /f 3≤10.0  (4)
where,
f 1 denotes a focal length of the first lens unit, and
f 3 denotes a focal length of the third lens unit.
13. The zoom lens according to claim 1, wherein the following conditional expression (9) is satisfied:

          0.3≤| f 2 /f 3|≤0.89  (9)
where,
f 2 denotes a focal length of the second lens unit, and
f 3 denotes a focal length of the third lens unit.
14. The zoom lens according to claim 1, wherein:
the second lens unit includes a negative lens having a concave surface directed toward the image side, which is positioned nearest to object, and
in the negative lens which is positioned nearest to object, an absolute value of a radius of curvature of an image-side surface is smaller as compared to an absolute value of a radius of curvature of an object-side surface, and
the following conditional expression (10) is satisfied:

          1.78≤ nd 2G _ n1≤2.3  (10)
where,
nd 2G _ n1 denotes a refractive index of the negative lens nearest to object in the second lens unit.
15. The zoom lens according to claim 1, wherein:
the second lens unit includes a negative lens having a concave surface directed toward the image side, which is disposed nearest to object, and
in the negative lens which is disposed nearest to object, an absolute value of a radius of curvature of an image-side surface is smaller as compared to an absolute value of a radius of curvature of an object-side surface, and
the following conditional expression (11) is satisfied:

          1.78≤ nd 2G _ max _ n≤2.3  (11)
where,
nd 2G _ max _ n denotes a maximum refractive index from among refractive indices of the negative lens in the second lens unit.
16. The zoom lens according to claim 1, wherein the following conditional expression (12) is satisfied:

          −0.005≤ Tp 2G _ max _ n≤0.06  (12)
where,

           Tp 2G _ max _ n =θgF 2G _ n−(−0.0016× vd 2G _ n+0.6415),

          θ gF 2G _ n=( ng 2G _ n −nF 2G _ n)/( nF 2G _ n −nC 2G _ n),
vd 2G _ n denotes Abbe number for a predetermined negative lens in the second lens unit, and
ng 2G _ n, nF 2G _ n, and nC 2G _ n denote refractive indices of the predetermined negative lens in the second lens unit, for a g-line, for an F-line, and for a C-line respectively, here
the predetermined negative lens in the second lens unit is a lens for which Abbe number is the largest, from among the negative lenses in the second lens unit.
17. The zoom lens according to claim 1, wherein at a time of zooming, a distance between the first sub-unit and the second sub-unit changes.
18. The zoom lens according to claim 1, wherein:
the third lens unit includes a lens for image stabilization, and
the lens for image stabilization is positioned on the image side of the aperture stop, and
image stabilization is carried out by shifting the lens for image stabilization in a direction perpendicular to an optical axis.
19. The zoom lens according to claim 1, wherein;
the rear-side lens unit includes a fourth lens unit having a negative refractive power,
the fourth lens unit includes a lens for image stabilization, and
the lens for image stabilization is positioned on the image side of the aperture stop, and
image stabilization is carried out by shifting the lens for image stabilization in a direction perpendicular to an optical axis.
20. The zoom lens according to claim 1, wherein:
the rear-side lens unit includes the fourth lens unit having a negative refractive power, on the image side of the aperture stop, and
focusing is carried out by the fourth lens unit.
21. The zoom lens according to claim 1, wherein the first lens unit includes at least one negative lens and two positive lenses.
22. The zoom lens according to claim 1, wherein:
the first sub-unit includes in order from the object side to the image side, a negative lens having a concave surface directed toward the image side, a negative lens, and a positive lens having a convex surface directed toward the image side, and
in the negative lens having the concave surface directed toward the image side, an absolute value of a radius of curvature of an image-side surface is smaller as compared to an absolute value of a radius of curvature of an object-side surface.
23. The zoom lens according to claim 1, wherein:
the rear-side lens unit includes a fourth lens unit having a negative refractive power,
the fourth lens unit includes a negative lens and a positive lens, and
the following conditional expression (13) is satisfied:

          6.0≤ vd 4G _ max _ n −vd 4G _ min _ p≤45  (13)
where,
vd 4G _ max _ n denotes a maximum Abbe number from among Abbe numbers for the negative lenses in the fourth lens unit, and
vd 4G _ min _ p denotes a minimum Abbe number from among Abbe numbers for the positive lenses in the fourth lens unit.
24. The zoom according to claim 1, wherein:
the third lens unit includes a positive lens for image stabilization, and
an image shift due to camera shake is corrected by shifting the positive lens for image stabilization in a direction perpendicular to an optical axis.
25. The zoom lens according to claim 24, wherein:
the third lens unit includes a negative lens for image stabilization, and
the following conditional expression (14) is satisfied:

          17≤ vd G3 _ IS _ p −vd G3 _ IS _ n≤65  (14)
where,
vd G3 _ IS _ p is denotes a maximum Abbe number from among Abbe numbers for the positive lens for image stabilization, and
vd G3 _ IS _ n denotes a minimum Abbe number from among Abbe numbers for the negative lens for image stabilization.
26. The zoom lens according to claim 1, wherein the first lens unit moves to be positioned on the object side at the telephoto end than at the wide angle end.
27. The zoom lens according to claim 1, wherein an aperture stop is disposed between the second lens unit and the third lens unit.
28. The zoom lens according to claim 2, wherein:
the first sub-unit includes at least a negative lens and a positive lens, and
the following conditional expression (2) is satisfied:

          −0.03≤ Tp 2Ga _ min _ p≤0.0165  (2)
where,

           Tp 2Ga _ min _ p =θgF 2Ga _ p−(−0.0016× vd 2Ga _ p+0.6415), here

          θ gF 2Ga _ p=( ng 2Ga _ p −nF 2Ga _ p)/( nF 2Ga _ p −nC 2Ga _ p),
vd 2Ga _ p denotes Abbe number for a predetermined positive lens in the first sub-unit,
ng 2Ga _ p, nF 2Ga _ p, and nC 2Ga _ p are refractive indices of the predetermined positive lens in the first sub-unit for a g-line, an F-line, and a C-line respectively, and
the predetermined positive lens in the first sub-unit is a positive lens for which Abbe number is the minimum, from among the positive lenses in the first sub-unit.
29. The zoom lens according to claim 1, wherein the third lens unit includes at least two lens units having a positive refractive power.
30. The zoom lens according to claim 1, wherein the following conditional expression (15) is satisfied:

          −2.5≤ f t/exp t≤0.3  (15)
where,
f t denotes a focal length of the overall zoom lens system at the telephoto end, and
exp t denotes a distance from a paraxial image forming surface up to an exit pupil of the zoom lens at the telephoto end.
31. The zoom lens according to claim 1, wherein focusing is carried out by the second sub-unit.
32. An image pickup apparatus, comprising:
a zoom lens according to claim 1; and
an image pickup element which has an image pickup surface.
33. The zoom lens according to claim 1, wherein the following conditional expression (16) is satisfied:

          1.4≤ LTL t /f t≤2  (16)
where,
LTL t denotes a total length of the overall zoom lens system at the telephoto end, and
f t denotes a focal length of the overall zoom lens system at the telephoto end.
34. The zoom lens according to claim 1, wherein the following conditional expression (17) is satisfied:

          1≤ LTL w /f t≤1.5  (17)
where,
LTL w denotes a total length of the overall zoom lens system at the wide angle end, and
f t denotes a focal length of the overall zoom lens system at the telephoto end.
35. The zoom lens according to claim 1, wherein the following conditional expression (23) is satisfied:

          4.9< f t /f w<10  (23)
where,
f t denotes a focal length of the overall zoom lens system at the telephoto end, and
f w denotes a focal length of the overall zoom lens system at the wide angle end.
36. The zoom lens according to claim 1, wherein the following conditional expression (24) is satisfied:

          3< Fno t<5.7  (24)
where,
Fno t denotes a smallest F-number at the telephoto end.