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, and a fifth lens group;
upon varying a magnification, distances between the neighboring respective lens groups being varied; and
the following conditional expressions being satisfied:
1.00 <f 3/(− f 2)≤2.10
1.00 <f 1/(− f 5)<2.50
where f3 denotes a focal length of the third lens group, f2 denotes a focal length of the second lens group, f1 denotes a focal length of the first lens group, and f5 denotes a focal length of the fifth lens group.
2. A variable magnification optical system according to claim 1 , wherein, upon focusing, at least a portion of the fourth lens group is moved.
3. A variable magnification optical system according to claim 1 , wherein the third lens group comprises a lens having positive refractive power at the most object side.
4. A variable magnification optical system according to claim 1 , wherein the first lens group comprises a lens having positive refractive power at the most image side.
5. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.20 <f 5 /f 2<3.60.
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.
7. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.00 <f 1/(− f 2)<4.50.
8. An optical system comprising a variable magnification optical system according to claim 1 .
9. 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, and a fifth lens group;
upon varying a magnification, distances between the neighboring respective lens groups being varied; and
the following conditional expressions being satisfied:
2.60 <f 1/(− f 2)<4.50
1.00 <f 3/(− f 2)≤2.10
where f1 denotes a focal length of the first lens group, f2 denotes a focal length of the second lens group, and f3 denotes a focal length of the third lens group.
10. A variable magnification optical system according to claim 9 , wherein, upon focusing, at least a portion of the fourth lens group is moved.
11. A variable magnification optical system according to claim 9 , wherein the first lens group comprises a cemented lens constructed by, in order from the object side, a lens having negative refractive power and a lens having positive refractive power.
12. A variable magnification optical system according to claim 9 , wherein the third lens group comprises a lens having positive refractive power at the most object side.
13. A variable magnification optical system according to claim 9 , 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.
14. A variable magnification optical system according to claim 9 , 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.
15. An optical system comprising a variable magnification optical system according to claim 9 .
16. 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; and
the following conditional expressions being satisfied:
0.64 <f 4/(− f 2)<2.20
1.00 <f 3/(− f 2)<3.00
where f4 denotes a focal length of the fourth lens group, f2 denotes a focal length of the second lens group, and f3 denotes a focal length of the third lens group.
17. A variable magnification optical system according to claim 16 , 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.
18. A variable magnification optical system according to claim 16 , wherein the following conditional expression is satisfied:
0.80 <f 3 /f 4<2.20.
19. A variable magnification optical system according to claim 16 , 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.
20. A variable magnification optical system according to claim 16 , 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.
21. A variable magnification optical system according to claim 16 , 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.
22. An optical system comprising a variable magnification optical system according to claim 16 .
23. A method for manufacturing one of the variable magnification optical systems A and B:
the optical system A 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, and a fifth lens group;
the optical system B 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 for manufacturing the optical system A comprising steps of:
constructing such that, upon varying a magnification, distances between the neighboring respective lens groups are varied; and
constructing such that one of the following features X and Y is satisfied:
the feature X comprising:
constructing such that the following conditional expressions are satisfied:
1.00 <f 3/(− f 2)≤2.10
1.00 <f 1/(− f 5)<2.50
where f3 denotes a focal length of the third lens group, f2 denotes a focal length of the second lens group, f1 denotes a focal length of the first lens group, and f5 denotes a focal length of the fifth lens group; and
the feature Y comprising:
constructing such that the following conditional expressions are satisfied:
2.60 <f 1/(− f 2)<4.50
1.00 <f 3/(− f 2)≤2.10
where f1 denotes a focal length of the first lens group, f2 denotes a focal length of the second lens group, and f3 denotes a focal length of the third lens group; and
the method for manufacturing the optical system B comprising steps of:
constructing such that, upon varying a magnification, distances between the neighboring respective lens groups are varied; and
constructing such that the following conditional expressions are satisfied:
0.64 <f 4/(− f 2)<2.20
1.00 <f 3/(− f 2)<3.00
where f4 denotes a focal length of the fourth lens group, f2 denotes a focal length of the second lens group, and f3 denotes a focal length of the third lens group.