Zoom optical system, optical apparatus, imaging apparatus and method for manufacturing the zoom optical system
A zoom optical system comprises, in order from an object: a front lens group (GFS) having a positive refractive power; an M 1 lens group (GM 1 ) having a negative refractive power; an M 2 lens group (GM 2 ) having a positive refractive power; and an RN lens group (GRN) having a negative refractive power, wherein upon zooming, distances between the front lens group and the M 1 lens group, between the M 1 lens group and the M 2 lens group, and between the M 2 lens group and the RN lens group change, upon focusing from an infinite distant object to a short distant object, the RN lens group moves, and the M 2 lens group comprises an A lens group that satisfies a following conditional expression, 1.10<fvr/fTM2<2.00, where, fvr: a focal length of the A lens group, and fTM2: a focal length of the M 2 lens group in a telephoto end state.
1. A zoom optical system comprising, in order from an object:
a front lens group having a positive refractive power;
an M 1 lens group having a negative refractive power;
an M 2 lens group having a positive refractive power; and
an RN lens group having a negative refractive power, wherein
upon zooming, a distance between the front lens group and the M 1 lens group changes, a distance between the M 1 lens group and the M 2 lens group changes, and a distance between the M 2 lens group and the RN lens group changes,
upon zooming, a lens group nearest to an image moves along an optical axis,
upon focusing from an infinite distant object to a short distant object, the RN lens group moves,
the zoom optical system further comprises, in order from the object, a lens having a negative refractive power and a lens having a positive refractive power provided adjacent to the RN lens group on an image side,
the M 2 lens group comprises an A lens group, and following conditional expressions are satisfied,
1.10< fvr/fTM 2<2.00
3.20< f 1/( fTM 2)<5.00
where
fvr: a focal length of the A lens group,
fTM 2 : a focal length of the M 2 lens group in a telephoto end state, and
f 1 : a focal length of the front lens group.
2. The zoom optical system according to claim 1 , wherein
upon zooming from a wide-angle end state to a telephoto end state, the front lens group moves toward the object.
3. The zoom optical system according to claim 1 , wherein
upon zooming, a lens group nearest to the object in the M 1 lens group is fixed with respect to an image surface.
4. The zoom optical system according to claim 1 , wherein
the A lens group consists of, in order from the object:
a lens having a negative refractive power; and
a lens having a positive refractive power.
5. The zoom optical system according to claim 4 , wherein
a following conditional expression is satisfied,
1.00 <nvrN/nvrP <1.25
where
nvrN: a refractive index of the lens having the negative refractive power in the A lens group, and
nvrP: a refractive index of the lens having the positive refractive power in the A lens group.
6. The zoom optical system according to claim 4 , wherein
a following conditional expression is satisfied,
0.30<ν vrN/νvrP< 0.90
where
νvrN: an Abbe number of the lens having the negative refractive power in the A lens group, and
νvrP: an Abbe number of the lens having the positive refractive power in the A lens group.
7. The zoom optical system according to claim 1 , wherein
a following conditional expression is satisfied,
0.15<(− fTM 1)/ f 1<0.35
where
fTM1: a focal length of the M 1 lens group in a telephoto end state, and
f1: a focal length of the front lens group.
8. The zoom optical system according to claim 1 , wherein
a following conditional expression is satisfied,
0.20 <fTM 2 /f 1<0.40
f1: a focal length of the front lens group.
9. The zoom optical system according to claim 1 , wherein
the A lens group is a vibration-proof lens group movable in a direction orthogonal to an optical axis to correct an imaging position displacement due to a camera shake or the like.
10. The zoom optical system according to claim 1 , further comprising a negative meniscus lens that has a concave surface facing the object, which is provided adjacent to the RN lens group on the image side.
11. The zoom optical system according to claim 1 , wherein
a following conditional expression is satisfied,
0.70<(− fN )/ fP <2.00
where
fN: a focal length of a lens that has a strongest negative refractive power among lenses disposed to the image side of the RN lens group, and
fP: a focal length of a lens that has a strongest positive refractive power among lenses disposed to the image side of the RN lens group.
12. The zoom optical system according to claim 1 , wherein
a following conditional expression is satisfied,
1.80 <f 1 /fw <3.50
where
fw: a focal length of the zoom optical system in a wide-angle end state, and
f1: a focal length of the front lens group.
13. The zoom optical system according to claim 1 , wherein
a following conditional expression is satisfied,
3.70 <f 1/(− fTM 1)<5.00
where
fTM 1 : a focal length of the M 1 lens group in a telephoto end state, and
f 1 : a focal length of the front lens group.
14. An optical apparatus comprising the zoom optical system according to claim 1 .
15. An imaging apparatus comprising:
the zoom optical system according to claim 1 ; and
an imaging unit that takes an image formed by the zoom optical system.
16. A method for manufacturing a zoom optical system comprising, in order from an object, a front lens group having a positive refractive power, an M 1 lens group having a negative refractive power, an M 2 lens group having a positive refractive power, and an RN lens group having a negative refractive power,
the method comprising one of features (A) and (B), wherein
feature (A) comprises:
achieving an arrangement where upon zooming, a distance between the front lens group and the M 1 lens group changes, a distance between the M 1 lens group and the M 2 lens group changes, a distance between the M 2 lens group and the RN lens group changes, and a lens group nearest to an image moves along an optical axis,
wherein
upon focusing from an infinite distant object to a short distant object, the RN lens group moves,
the zoom optical system further comprises, in order from the object, a lens having a negative refractive power and a lens having a positive refractive power provided adjacent to the RN lens group on an image side,
the M 2 lens group comprises an A lens group, and following conditional expressions are satisfied,
1.10 <fvr/fTM 2<2.00
3.20 <f 1 /fTM 2<5.00
where fvr: a focal length of the A lens group,
fTM 2 : a focal length of the M 2 lens group in a telephoto end state, and
f 1 : a focal length of the front lens group, and
feature (B) comprises:
achieving an arrangement where upon zooming, a distance between the front lens group and the M 1 lens group changes, a distance between the M 1 lens group and the M 1 lens group changes, and a distance between the M 2 lens group and the RN lens group changes,
wherein
upon focusing from an infinite distant object to a short distant object, the RN lens group moves,
a negative meniscus lens that has a concave surface facing the object is provided adjacent to the RN lens group on an image side,
the M 2 lens group comprises an A lens group, and
following conditional expressions are satisfied,
1.10 <fvr/fTM 2<2.00
0.15<(− fTM 1 ;/f 1<0.30
where
fvr: a focal length of the A lens group,
fTM 2 : a focal length of the M 2 lens group in a telephoto end state,
fTM 1 : a focal length of the M 1 lens group in a telephoto end state, and
f 1 : a focal length of the front lens group.
17. A zoom optical system comprising, in order from an object:
a front lens group having a positive refractive power;
an M 1 lens group having a negative refractive power;
an M 2 lens group having a positive refractive power; and
an RN lens group having a negative refractive power, wherein
upon zooming, a distance between the front lens group and the M 1 lens group changes, a distance between the M 1 lens group and the M 2 lens group changes, and a distance between the M 2 lens group and the RN lens group changes,
upon focusing from an infinite distant object to a short distant object, the RN lens group moves,
a negative meniscus lens that has a concave surface facing the object is provided adjacent to the RN lens group on an image side,
the M 2 lens group comprises an A lens group, and
following conditional expressions are satisfied,
1.10 <fvr/fTM 2<2.00
0.15<(− fTM 1)/ f 1<0.35
where
fvr: a focal length of the A lens group,
fTM 2 : a focal length of the M 2 lens group in a telephoto end state,
fTM 1 : a focal length of the M 1 lens group in a telephoto end state, and
f 1 : a focal length of the front lens group.