Variable magnification optical system, optical apparatus, and method for manufacturing variable magnification optical system
A variable magnification optical system includes, in order from an object: a first lens group (G 1 ) having a negative refractive power; a second lens group (G 2 ); a third lens group (G 3 ); a fourth lens group (G 4 ) having a negative refractive power; and a fifth lens group (G 5 ) having a positive refractive power, the system performing varying magnification by changing the distance between the first and second lens groups, the distance between the second and third lens groups, the distance between the third and fourth lens groups, and the distance between the fourth and fifth lens groups, and the fourth lens group including a 42nd lens group (G 42 ) configured to be movable so as to have a component in a direction orthogonal to an optical axis and a 41st lens group (G 41 ) disposed at an object-side of the 42nd lens group.
1. A variable magnification optical system constituted by, in order from an object:
a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a positive refractive power; a fourth lens group having a negative refractive power; and a fifth lens group having a positive refractive power, wherein
the system performs varying magnification by changing the distance between the first lens group and the second lens group, the distance between the second lens group and the third lens group, the distance between the third lens group and the fourth lens group, and the distance between the fourth lens group and the fifth lens group,
the first lens group has, in order from an object side, a first negative lens, a second negative lens and a third negative lens,
a lens, which is closest to an image side, of the first lens group is a positive lens,
one lens group among the first to fifth lens groups is immovable in an optical axis direction upon varying magnification, and
the system satisfies the following conditional expression:
0.350<f1/f4<0.750
where
f1: a focal length of the first lens group
f4: a focal length of the fourth lens group.
2. The variable magnification optical system according to claim 1 , wherein
the fourth lens group includes four lenses.
3. The variable magnification optical system according to claim 1 , wherein
the fourth lens group has a vibration-reduction group arranged to be movable so as to have a movement component in a direction orthogonal to an optical axis, and
the system satisfies the following conditional expression:
0.700<f42/f4<1.700
where
f42: a focal length of the vibration-reduction group
f4: a focal length of the fourth lens group.
4. The variable magnification optical system according to claim 3 , wherein
the fourth lens group has an object side group disposed to an object side of the vibration-reduction group, and
the system satisfies the following conditional expression:
−0.400<f4/f41<0.500
where
f4: a focal length of the fourth lens group
f41: a focal length of the object side group.
5. The variable magnification optical system according to claim 4 , wherein
the object side group has a negative lens and a positive lens.
6. The variable magnification optical system according to claim 3 , wherein
the vibration-reduction group is constituted by a cemented lens including a positive lens and a negative lens.
7. The variable magnification optical system according to claim 1 , wherein
a lens surface closest to an image, of the fourth lens group is an aspherical surface, and
the system satisfies the following conditional expression:
1.100<A(T3.5)/A(T4.0)<5.000
where
A(T3.5): an asphericity at a point on the aspherical surface where light corresponding to F-value of 3.5 passes through the aspherical surface in a telephoto end state
A(T4.0): an asphericity at a point on the aspherical surface where light corresponding to F-value of 4.0 passes through the aspherical surface in a telephoto end state.
8. An optical apparatus having the variable magnification optical system of claim 1 mounted thereon.
9. A method for manufacturing a variable magnification optical system, wherein
the variable magnification optical system is constituted by, in order from an object: a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a positive refractive power; a fourth lens group having a negative refractive power; and a fifth lens group having a positive refractive power, the system performing varying magnification by changing the distance between the first lens group and the second lens group, the distance between the second lens group and the third lens group, the distance between the third lens group and the fourth lens group, and the distance between the fourth lens group and the fifth lens group, and wherein
the method comprises:
arranging the respective lens groups in a lens barrel such that
the first lens group has, in order from an object side, a first negative lens, a second negative lens and a third negative lens,
a lens, which is closest to an image side, of the first lens group is a positive lens,
one lens group among the first to fifth lens groups is immovable in an optical axis direction upon varying magnification, and
the system satisfies the following conditional expression:
0.350<f1/f4<0 75
where
f1: a focal length of the first lens group
f4: a focal length of the fourth lens group.
10. A variable magnification optical system comprising, in order from an object:
a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group; a fourth lens group; and a fifth lens group having a positive refractive power, wherein
the system performs varying magnification by changing the distance between the first lens group and the second lens group, the distance between the second lens group and the third lens group, the distance between the third lens group and the fourth lens group, and the distance between the fourth lens group and the fifth lens group,
at least a portion of the fourth lens group is configured to be movable so as to have a component in a direction orthogonal to an optical axis, and
the system satisfies the following conditional expressions:
−0.400<(D34T−D34W)/(D23T−D23W)<1.000
−0.400<f4/f3<0.450
where
D34T: an air distance between the third and fourth lens groups in a telephoto end state
D34W: an air distance between the third and fourth lens groups in a wide-angle end state
D23T: an air distance between the second and third lens groups in a telephoto end state
D23W: an air distance between the second and third lens groups in a wide-angle end state
f4: a focal length of the fourth lens group
f3: a focal length of the third lens group.
11. The variable magnification optical system according to claim 10 , wherein
the fourth lens group has a negative refractive power.
12. The variable magnification optical system according to claim 10 , wherein
the system satisfies the following conditional expression:
0.200<f1/f4<0.900
where
f1: a focal length of the first lens group.
13. The variable magnification optical system according to claim 10 , wherein
the third lens group has a negative lens and a positive lens.
14. The variable magnification optical system according to claim 10 , wherein
the fourth lens group is constituted by a cemented lens including a positive lens and a negative lens.
15. The variable magnification optical system according to claim 10 , wherein
a lens surface closest to an image, of the fourth lens group is an aspherical surface, and
the system satisfies the following conditional expression:
1.100<A(T3.5)/A(T4.0)<5.000
where
A(T3.5): an asphericity at a point on the aspherical surface where light corresponding to F-value of 3.5 passes through the aspherical surface in a telephoto end state
A(T4.0): an asphericity at a point on the aspherical surface where light corresponding to F-value of 4.0 passes through the aspherical surface in a telephoto end state.
16. An optical apparatus having the variable magnification optical system of claim 10 mounted thereon.
17. A method for manufacturing a variable magnification optical system, wherein
the variable magnification optical system comprises, in order from an object: a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group; a fourth lens group; and a fifth lens group having a positive refractive power, the system performing varying magnification by changing the distance between the first lens group and the second lens group, the distance between the second lens group and the third lens group, the distance between the third lens group and the fourth lens group, and the distance between the fourth lens group and the fifth lens group, wherein
at least a portion of the fourth lens group is configured to be movable so as to have a component in a direction orthogonal to an optical axis, and wherein
the method comprises:
arranging the respective groups in a lens barrel so as to satisfy the following conditional expressions:
−0.400<(D34T−D34W)/(D23T−D23W)<1.000
−0.400<f4/f3<0.450
where
D34T: an air distance between the third and fourth lens groups in a telephoto end state
D34W: an air distance between the third and fourth lens groups in a wide-angle end state
D23T: an air distance between the second and third lens groups in a telephoto end state
D23W: an air distance between the second and third lens groups in a wide-angle end state
f4: a focal length of the fourth lens group
f3: a focal length of the third lens group.
18. A variable magnification optical system comprising, in order from an object:
a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a positive refractive power; a fourth lens group; a fifth lens group having a negative refractive power; and a sixth lens group having a positive refractive power, wherein
the system performs varying magnification by changing the distance between the first lens group and the second lens group, the distance between the second lens group and the third lens group, the distance between the third lens group and the fourth lens group, the distance between the fourth lens group and the fifth lens group, and the distance between the fifth lens group and the sixth lens group,
at least a portion of any one lens group among the first to sixth lens groups is configured to be movable so as to have a component in a direction orthogonal to an optical axis, and
the system satisfies the following conditional expression:
−0.500<f5/f4<0.500
where
f5: a focal length of the fifth lens group
f4: a focal length of the fourth lens group.
19. The variable magnification optical system according to claim 18 , wherein
at least a portion of the fifth lens group is configured to be movable so as to have a component in the direction orthogonal to the optical axis in order to correct image blur.
20. The variable magnification optical system according to claim 18 , wherein
the system satisfies the following conditional expression:
0.300<(−f1)/f6<0.900
where
f1: a focal length of the first lens group
f6: a focal length of the sixth lens group.
21. The variable magnification optical system according to claim 18 , wherein
the system satisfies the following conditional expression:
−0.400<f1/f4<0.400
where
f1: a focal length of the first lens group
f4: a focal length of the fourth lens group.
22. The variable magnification optical system according to claim 18 , wherein
the fourth lens group has a negative lens and a positive lens.
23. The variable magnification optical system according to claim 18 , wherein
the fifth lens group is constituted by a cemented lens including a positive lens and a negative lens.
24. The variable magnification optical system according to claim 18 , wherein
a lens surface closest to an image, of the fourth lens group is an aspherical surface, and
the system satisfies the following conditional expression:
1.100<A(T3.5)/A(T4.0)<5.000
where
A(T3.5): an asphericity at a point on the aspherical surface where light corresponding to F-value of 3.5 passes through the aspherical surface in a telephoto end state
A(T4.0): an asphericity at a point on the aspherical surface where light corresponding to F-value of 4.0 passes through the aspherical surface in a telephoto end state.
25. The variable magnification optical system according to claim 18 , wherein
the system satisfies the following conditional expression:
0.500<f2/f3<2.000
where
f2: a focal length of the second lens group
f3: a focal length of the third lens group.
26. An optical apparatus having the variable magnification optical system of claim 18 mounted thereon.
27. A method for manufacturing a variable magnification optical system, wherein
the variable magnification optical system comprises, in order from an object: a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a positive refractive power; a fourth lens group; a fifth lens group having a negative refractive power; and a sixth lens group having a positive refractive power, the system performing varying magnification by changing the distance between the first lens group and the second lens group, the distance between the second lens group and the third lens group, the distance between the third lens group and the fourth lens group, the distance between the fourth lens group and the fifth lens group, and the distance between the fifth lens group and the sixth lens group, and wherein
the method comprises:
arranging the respective groups in a lens barrel such that
at least a portion of any one lens group among the first to sixth lens groups is configured to be movable so as to have a component in a direction orthogonal to an optical axis, and
the system satisfies the following conditional expression:
−0.500<f5/f4<0.500
where
f5: a focal length of the fifth lens group
f4: a focal length of the fourth lens group.