Zoom lens, optical apparatus equipped therewith and method for manufacturing the zoom lens

A zoom lens comprising, in order from an object:

• a first lens group having positive refractive power;
• a second lens group having negative refractive power;
• and
• a rear lens group having positive refractive power;
• the second lens group including at least one positive lens and a negative lens disposed adjacent to the object side of the positive lens having largest refractive power among the positive lenses,
• upon zooming from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group varying, and a distance between the second lens group and the rear lens group varying, and
• the following conditional expressions being satisfied:
• 0.80<(r2+r1)/(r2−r1)<3.50
• 0.30<(−f2)/BFw<0.60
• 0.45<fw/BFw<0.80
• where r1 denotes a radius of curvature of the object side surface of the negative lens in the second lens group, r2 denotes a radius of curvature of the image side surface of the negative lens in the second lens group, fw denotes a focal length of the zoom lens in the wide-angle end state, f2 denotes a focal length of the second lens group, and BFw denotes a back focal length in the wide-angle end state.

A method for manufacturing a zoom lens that includes, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear lens group having positive refractive power, the method comprising steps of:

• providing in the second lens group at least one positive lens and a negative lens disposed adjacent to the object side of the positive lens having largest refractive power among the positive lenses;
• providing the first lens group, the second lens group and the rear lens group such that a distance between the first lens group and the second lens group varies, and a distance between the second lens group and the rear lens group varies upon zooming from a wide-angle end state to a telephoto end state;
• providing the second lens group with satisfying the following conditional expressions:
• 0.80<(r2+r1)/(r2−r1)<3.50
• 0.50<(−f2)/fw<0.90
• where r1 denotes a radius of curvature of the object side lens surface of the negative lens in the second lens group, r2 denotes a radius of curvature of the image side lens surface of the negative lens in the second lens group, fw denotes a focal length of the zoom lens in the wide-angle end state, and f2 denotes a focal length of the second lens group.

A method for manufacturing a zoom lens that includes, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear lens group having positive refractive power, the method comprising steps of:

• providing in the second lens group at least one positive lens and a negative lens disposed adjacent to the object side of the positive lens having largest refractive power among the positive lenses;
• providing the first lens group, the second lens group and the rear lens group such that a distance between the first lens group and the second lens group varies and a distance between the second lens group and the rear lens group varies, upon zooming from a wide-angle end state to a telephoto end state;
• providing the second lens group with satisfying the following conditional expressions:
• 0.80<(r2+r1)/(r2−r1)<3.50
• 0.30<(−f2)/BFw <0.60
• 0.45<fw/BFw <0.80
• where r1 denotes a radius of curvature of the object side surface of the negative lens in the second lens group, r2 denotes a radius of curvature of the image side surface of the negative lens in the second lens group, fw denotes a focal length of the zoom lens in the wide-angle end state, f2 denotes a focal length of the second lens group, and BFw denotes a back focal length in the wide-angle end state.