Zoom lens system, optical apparatus and method for manufacturing zoom lens system

A method for manufacturing a zoom lens system consisting of, in order from an object side, a first lens group having negative refractive power and a second lens group having positive refractive power, or a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group, the method comprising:

• disposing the second lens group such that the second lens group consists of, in order from the object side, a front sub-lens group and a rear sub-lens group, the front sub-lens group consists of a plurality of lens components each having the same sign of refractive power, and the rear sub-lens group includes a lens component that is disposed to the most object side and has a different sign of refractive power from the sign of refractive power of the plurality of lens components in the front sub-lens group;
• disposing the front sub-lens group and the rear sub-lens group with satisfying the following conditional expression:
• 1.82<Σ2a/Σ2b<18.00 (6A)
• where Σ2a denotes a distance along an optical axis between the object side lens surface of a lens component disposed to the most object side in the front sub-lens group and the image side lens surface of a lens component disposed to the most image side in the front sub-lens group, and Σ2b denotes a distance along the optical axis between the object side lens surface of a lens component disposed to the most object side in the rear sub-lens group and the image side lens surface of a lens component disposed to the most image side in the rear sub-lens group;
• disposing the first lens group and the second lens group movably so that a distance between the first lens group and the second lens group may be varied upon zooming from a wide-angle end state to a telephoto end state;
• constructing at least a portion in the plurality of lens components in the front sub-lens group to move as a focusing lens group along the optical axis, thereby carrying out focusing from an infinitely distant object to a close object;
• disposing the front sub-lens group and the rear sub-lens group with satisfying the following conditional expression:
• 0.282≤|fa/fb|<2.00 (7A)
• where fa denotes a focal length of the front sub-lens group, and fb denotes a focal length of the rear sub-lens group;
• and
• disposing such that a distance between the front sub-lens group and the rear sub-lens group is fixed at all times for zooming.

A zoom lens system consisting of, in order from an object side;

• a first lens group having negative refractive power;
• and a second lens group having positive refractive power, or a first lens group having negative refractive power;
• a second lens group having positive refractive power;
• and a third lens group,
• a distance between the first lens group and the second lens group varying upon zooming from a wide-angle end state to a telephoto end state,
• the second lens group consisting of, in order from the object side, a front sub-lens group and a rear sub-lens group,
• the front sub-lens group consisting of a plurality of lens components having the same sign of refractive power,
• the rear sub-lens group including a lens component that is disposed to the most object side and has a different sign of refractive power from the sign of refractive power of the plurality of lens components in the front sub-lens group, and
• the following conditional expression being satisfied:
• 3.087≤Σ2a/Σ2b<5.10 (6B)
• where Σ2a denotes a distance along an optical axis between the object side lens surface of a lens component disposed to the most object side in the front sub-lens group and the image side lens surface of a lens component disposed to the most image side in the front sub-lens group, and Σ2b denotes a distance along the optical axis between the object side lens surface of a lens component disposed to the most object side in the rear sub-lens group and a image side lens surface of a lens component disposed to the most image side in the rear sub-lens group,
• wherein at least a portion in the plurality of lens components in the front sub-lens group is moved as a focusing lens group along the optical axis, thereby carrying out focusing from an infinitely distant object to a close object, and
• wherein a distance between the front sub-lens group and the rear sub-lens group is fixed at all times for zooming.

A method for manufacturing a zoom lens system consisting of, in order from an object side, a first lens group having negative refractive power and a second lens group having positive refractive power, or a first lens group having negative refractive power, a second lens group having positive refractive power and a third lens group, the method comprising:

• disposing the second lens group such that the second lens group consists of, in order from the object side, a front sub-lens group and a rear sub-lens group, the front sub-lens group consists of a plurality of lens components each having the same sign of refractive power, and the rear sub-lens group includes a lens component that is disposed to the most object side and has a different sign of refractive power from the sign of refractive power of the plurality of lens components in the front sub-lens group;
• disposing the front sub-lens group and the rear sub-lens group with satisfying the following conditional expression:
• 3.087≤Σ2a/Σ2b<5.10 (6B)
• where Σ2a denotes a distance along an optical axis between the object side lens surface of a lens component disposed to the most object side in the front sub-lens group and the image side lens surface of a lens component disposed to the most image side in the front sub-lens group, and Σ2b denotes a distance along the optical axis between the object side lens surface of a lens component disposed to the most object side in the rear sub-lens group and the image side lens surface of a lens component disposed to the most image side in the rear sub-lens group;
• disposing at least a portion in the plurality of lens components in the front sub-lens group is moved as a focusing lens group along the optical axis, thereby carrying out focusing from an infinitely distant object to a close object,
• disposing the first lens group and the second lens group movably so that a distance between the first lens group and the second lens group may be varied upon zooming from a wide-angle end state to a telephoto end state;
• and
• disposing such that a distance between the front sub-lens group and the rear sub-lens group is fixed at all times for zooming.