Variable magnification optical system, optical apparatus, imaging apparatus and method for manufacturing variable magnification optical system

A variable magnification optical system, comprising:

• a first lens group disposed at a most object side and having positive refractive power;
• an intermediate group disposed at an image side of the first lens group and having negative refractive power;
• a focusing group disposed at an image side of the intermediate group and having positive refractive power, the focusing group being moved upon focusing;
• and
• an image side group disposed at an image side of the focusing group and having positive refractive power;
• upon varying magnification, a distance between the first lens group and the intermediate group, a distance between the intermediate group and the focusing group and a distance between the focusing group and the image side group being varied;
• the image side group comprising, in order from an object side, an A group having positive refractive power, a B group satisfying the following conditional expression with respect to the A group and having negative refractive power, and a C group:
• 1.67<fA/(−fB)<2.80
• where fA denotes a focal length of the A group, and fB denotes a focal length of the B group;
• and
• the following conditional expression being satisfied:
• 0.492≤ff/fi<1.10
• where ff denotes a focal length of the focusing group, and fi denotes a focal length of the image side group.

A variable magnification optical system, comprising:

• a first lens group disposed at a most object side and having positive refractive power;
• an intermediate group disposed at an image side of the first lens group and having negative refractive power;
• a focusing group disposed at an image side of the intermediate group and having positive refractive power, the focusing group being moved upon focusing;
• and
• an image side group disposed at an image side of the focusing group and having positive refractive power;
• upon varying magnification, a distance between the first lens group and the intermediate group, a distance between the intermediate group and the focusing group and a distance between the focusing group and the image side group being varied;
• and
• the image side group comprising, in order from an object side, an A group having positive refractive power, a B group satisfying the following conditional expression with respect to the A group and having negative refractive power, and a C group:
• 1.67<fA/(−fB)≤1.836
• where fA denotes a focal length of the A group, and fB denotes a focal length of the B group.

A method for manufacturing a variable magnification optical system, comprising steps of:

• arranging a first lens group disposed at a most object side and having positive refractive power, an intermediate group disposed at an image side of the first lens group and having negative refractive power, a focusing group disposed at an image side of the intermediate group and having positive refractive power, the focusing group being moved upon focusing, and an image side group disposed at an image side of the focusing group and having positive refractive power;
• the arrangement being such that, upon varying magnification, a distance between the first lens group and the intermediate group, a distance between the intermediate group and the focusing group and a distance between the focusing group and the image side group are varied;
• and
• the method further comprising at least one or more of the following features (A), (B) and (C):
• (A) configuring the image side group to comprise, in order from an object side, an A group having positive refractive power, a B group satisfying the following conditional expression with respect to the A group and having negative refractive power, and a C group:
• 1.67<fA/(−fB)<2.80
• where fA denotes a focal length of the A group, and fB denotes a focal length of the B group, and
• satisfying the following conditional expression:
• 2.50<f1/(−fc)≤4.365
• where f1 denotes a focal length of the first lens group, and fc denotes a focal length of the intermediate group;
• (B) configuring the image side group to comprise, in order from an object side, an A group having positive refractive power, a B group satisfying the following conditional expression with respect to the A group and having negative refractive power, and a C group:
• 1.67<fA/(−fB)<2.80
• where fA denotes a focal length of the A group, and fB denotes a focal length of the B group, and satisfying the following conditional expression:
• 0.492≤ff/fi<1.10
• where ff denotes a focal length of the focusing group, and fi denotes a focal length of the image side group;
• (C) configuring the image side group to comprise, in order from an object side, an A group having positive refractive power, a B group satisfying the following conditional expression with respect to the A group and having negative refractive power, and a C group:
• 1.67<fA/(−fB)≤1.836
• where fA denotes a focal length of the A group, and fB denotes a focal length of the B group.