Variable magnification optical system, optical apparatus, and method for producing variable magnification optical system
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, and a rear lens group having positive refractive power; upon varying a magnification, a distance between the first lens group and the second lens group being varied, a distance between the second lens group and the third lens group being varied, and a distance between the third lens group and the rear lens group being varied; the rear lens group comprising a focusing lens group which is moved upon carrying out focusing from an infinitely distant object to a closely distant object; and predetermined conditional expression(s) being satisfied, thereby various aberrations being corrected superbly.
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, and a rear lens group having positive refractive power;
the rear lens group comprising, in order from the object side, a fourth lens group having positive refractive power and a fifth lens group having negative refractive power;
upon varying a magnification, a distance between the first lens group and the second lens group being varied, a distance between the second lens group and the third lens group being varied, a distance between the third lens group and the fourth lens group being varied, and a distance between the fourth lens group and the fifth lens group being varied;
the rear lens group comprising a focusing lens group which is moved upon carrying out focusing;
the fifth lens group consisting of one lens component constituted by a single lens or a cemented lens composed of a plurality of lenses cemented together; and
the following conditional expressions being satisfied:
4.00 <f 1 /fw< 6.500
0.100 <BFw/fw< 1.00
−3.000< f 5/ f 3<−0.500
where f1 denotes a focal length of the first lens group, fw denotes a focal length of the variable magnification optical system in a wide angle end state, BFw denotes a back focus of the variable magnification optical system in the wide angle end state, f3 denotes a focal length of the third lens group, and f5 denotes a focal length of the fifth lens group.
2. A variable magnification optical system according to claim 1 , wherein
the following conditional expression is satisfied:
4.000< f 1/ f 1 Rw< 9.000
where f1 denotes a focal length of the first lens group, and f1Rw denotes a composite focal length of all of the lens groups in the wide angle end state disposed on the side which is closer to the image plane than the first lens group.
3. A variable magnification optical system according to claim 2 , wherein
the following conditional expression is satisfied:
nd 3 fp< 1.800
where nd3fp denotes refractive index of a lens having the largest refractive index in the third lens group.
4. A variable magnification optical system according to claim 3 , wherein
the following conditional expression is satisfied:
40.00°<ω w< 85.00°
where ωw denotes a half angle of view of the variable magnification optical system in the telephoto end state.
5. An optical apparatus comprising a variable magnification optical system according to claim 1 .
6. A variable magnification optical system according to claim 1 , wherein the rear lens group comprises a sixth lens group having negative refractive power adjacent to the image side of the fifth lens group.
7. A variable magnification optical system comprises, 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, and a rear lens group having positive refractive power;
the rear lens group comprising, in order from the object side, a fourth lens group having positive refractive power and a fifth lens group having negative refractive power;
upon varying a magnification, a distance between the first lens group and the second lens group being varied, a distance between the second lens group and the third lens group being varied, and a distance between the third lens group and the fourth lens group being varied, and a distance between the fourth lens group and the fifth lens group being varied;
the rear lens group comprising a focusing lens group which is moved upon carrying out focusing;
the fifth lens group consisting of one lens component constituted by a single lens or a cemented lens composed of a plurality of lenses cemented together; and
the following conditional expressions being satisfied:
2.00< f 1/ fw< 6.500
0.100< BFw/fw< 0.91
−3.000< f 5/ f 3<−0.500
where f1 denotes a focal length of the first lens group, fw denotes a focal length of the variable magnification optical system in a wide angle end state, BFw denotes a back focus of the variable magnification optical system in the wide angle end state, f3 denotes a focal length of the third lens group, and f5 denotes a focal length of the fifth lens group.
8. A variable magnification optical system according to claim 7 , wherein
the following conditional expression is satisfied:
0.500<1/β Rw< 1.000
where βRw denotes a transverse magnification of lens group disposed at the most image plane side in the wide angle end state.
9. A variable magnification optical system according to claim 7 , wherein
the following conditional expression is satisfied:
4.000< f 1/ f 1 Rw< 9.000
where f1 denotes a focal length of the first lens group, and f1Rw denotes a composite focal length of all of the lens groups in the wide angle end state disposed on the side which is closer to the image plane than the first lens group.
10. A variable magnification optical system according to claim 7 , wherein the rear lens group comprises a sixth lens group having negative refractive power adjacent to the image side of the fifth lens group.
11. An optical apparatus comprising a variable magnification optical system according to claim 7 .
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, and a rear lens group having positive refractive power;
the rear lens group comprising, in order from the object side, a fourth lens group having positive refractive power and a fifth lens group having negative refractive power;
the rear lens group further comprising a sixth lens group having negative refractive power adjacent to the image side of the fifth lens group;
upon varying a magnification, a distance between the first lens group and the second lens group being varied, a distance between the second lens group and the third lens group being varied, a distance between the third lens group and the fourth lens group being varied, and a distance between the fourth lens group and the fifth lens group being varied;
the rear lens group comprising a focusing lens group which is moved upon carrying out focusing;
the fifth lens group consisting of one lens component constituted by a single lens or a cemented lens composed of a plurality of lenses cemented together; and
the following conditional expressions being satisfied:
4.00< f 1/ fw< 6.500
0.100< BFw/fw< 1.00
where f1 denotes a focal length of the first lens group, fw denotes a focal length of the variable magnification optical system in a wide angle end state, and BFw denotes a back focus of the variable magnification optical system in the wide angle end state.
13. An optical apparatus comprising a variable magnification optical system according to claim 12 .
14. A method for manufacturing a variable magnification optical system which comprises, 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 and a rear lens group having positive refractive power;
the method comprising the following steps:
constructing such that the rear lens group comprises, in order from the object side, a fourth lens group having positive refractive power and a fifth lens group having negative refractive power;
constructing such that, upon varying a magnification, a distance between the first lens group and the second lens group is varied, a distance between the second lens group and the third lens group is varied, a distance between the third lens group and the fourth lens group is varied, and a distance between the fourth lens group and the fifth lens group is varied;
constructing such that the rear lens group comprises a focusing lens group which is moved upon carrying out focusing; and
constructing such that the fifth lens group consists of one lens component constituted by a single lens or a cemented lens composed of a plurality of lenses cemented together,
the method further comprising one of the following steps (A), (B), and (C):
(A) satisfying the following conditional expressions:
4.00< f 1/ fw< 6.500
0.100< BFw/fw< 1.00
−3.000< f 5/ f 3<−0.500
(B) satisfying the following conditional expressions:
2.00< f 1/ fw< 6.500
0.100< BFw/fw< 0.91
−3.000< f 5/ f 3<−0.500
(C) constructing such that the rear lens group further comprises a sixth lens group having negative refractive power adjacent to the image side of the fifth lens group, and
satisfying the following conditional expressions:
4.00< f 1/ fw< 6.500
0.100< BFw/fw< 1.00
where f1 denotes a focal length of the first lens group, fw denotes a focal length of the variable magnification optical system in a wide angle end state, BFw denotes a back focus of the variable magnification optical system in the wide angle end state, f3 denotes a focal length of the third lens group, and f5 denotes a focal length of the fifth lens group.