Variable magnification optical system, optical device, and method for manufacturing variable magnification optical system
Comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power; upon varying a magnification, the first lens group being fixed with respect to the image plane, and each distance between the neighboring lens groups being varied; upon focusing, at least a portion of the fourth lens group being moved; and predetermined conditional expression(s) being satisfied, thereby variations in various aberrations upon varying magnification being superbly suppressed.
1. A variable magnification optical system comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power;
upon varying a magnification, the first lens group being fixed with respect to the image plane, and distances between the neighboring respective lens groups being varied;
upon focusing, at least a portion of the fourth lens group being moved; and
the following conditional expressions being satisfied:
1.20< f 5/ f 2<2.80
0.80< f 3/ f 4<2.20
where f5 denotes a focal length of the fifth lens group, f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group.
2. A variable magnification optical system according to claim 1 , wherein, upon varying magnification, the third lens group is fixed with respect to the image plane.
3. A variable magnification optical system according to claim 1 , wherein, upon varying magnification, the fifth lens group is fixed with respect to the image plane.
4. A variable magnification optical system according to claim 1 , wherein an aperture stop is disposed between the second lens group and the fourth lens group.
5. A variable magnification optical system according to claim 1 , wherein at least a portion of the fifth lens group is movable to have a component in a direction perpendicular to the optical axis.
6. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.64< f 4/(− f 2)<2.20
where f4 denotes a focal length of the fourth lens group, and f2 denotes a focal length of the second lens group.
7. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.94<(− f 5)/ f 4<3.00
where f5 denotes a focal length of the fifth lens group, and f4 denotes a focal length of the fourth lens group.
8. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.00< f 1/(− f 2)<4.50
where f1 denotes a focal length of the first lens group, and f2 denotes a focal length of the second lens group.
9. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.00< f 3/(− f 2)<4.20
where f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group.
10. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.60< f 1/(− f 5)<2.70
where f1 denotes a focal length of the first lens group, and f5 denotes a focal length of the fifth lens group.
11. An optical system comprising a variable magnification optical system according to claim 1 .
12. A variable magnification optical system comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power;
upon varying a magnification, distances between the neighboring respective lens groups being varied;
an aperture stop being disposed between the second lens group and the fourth lens group; and
the following conditional expressions being satisfied:
1.55≤(− f 5)/ f 4<3.00
1.00 <f 3/(− f 2)<4.20
where f5 denotes a focal length of the fifth lens group, f4 denotes a focal length of the fourth lens group, f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group.
13. A variable magnification optical system according to claim 12 , wherein the following conditional expression is satisfied:
1.20< f 5/ f 2<3.60
where f5 denotes a focal length of the fifth lens group, and f2 denotes a focal length of the second lens group.
14. A variable magnification optical system according to claim 12 , wherein the following conditional expression is satisfied:
0.80< f 3/ f 4<2.20
where f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group.
15. A variable magnification optical system according to claim 12 , wherein the following conditional expression is satisfied:
0.64< f 4/(− f 2)<2.20
where f4 denotes a focal length of the fourth lens group, and f2 denotes a focal length of the second lens group.
16. A variable magnification optical system according to claim 12 , wherein the following conditional expression is satisfied:
1.00< f 1/(− f 2)<4.50
where f1 denotes a focal length of the first lens group, and f2 denotes a focal length of the second lens group.
17. A variable magnification optical system according to claim 12 , wherein the following conditional expression is satisfied:
0.60< f 1/(− f 5)<2.70
where f1 denotes a focal length of the first lens group, and f5 denotes a focal length of the fifth lens group.
18. An optical system comprising a variable magnification optical system according to claim 12 .
19. A method for manufacturing a variable magnification optical system comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power and a fifth lens group having negative refractive power; the method comprising one of steps (A) and (B):
step (A) including:
constituting to satisfy the following conditional expressions:
1.20< f 5/ f 2<2.80
0.80< f 3/ f 4<2.20
where f5 denotes a focal length of the fifth lens group, f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group;
constituting such that, upon varying magnification, the first lens group is fixed with respect to the image plane, and each distance between the neighboring lens groups is varied; and
constituting such that, upon focusing, at least a portion of the fourth lens group is moved along the optical axis; and
step (B) including:
constituting to satisfy the following conditional expressions:
1.55≤(− f 5)/ f 4<3.00
1.00< f 3/(− f 2)<4.20
where f5 denotes a focal length of the fifth lens group, f4 denotes a focal length of the fourth lens group, f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group;
constituting such that, upon varying a magnification, each distance between the neighboring lens groups is varied; and
constituting such that an aperture stop is disposed between the second lens group and the fourth lens group.