Optical system, optical apparatus and method for manufacturing the optical system

An optical system comprising:

• a first lens group with positive refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power, and a fourth lens group with negative refractive power, which are disposed in order from an object on an optical axis, wherein
• during focusing, the second lens group and the third lens group move on the optical axis, and
• the following conditional expression is satisfied:
• 0.03<D1/TL<0.25
• where
• D1:
• distance on optical axis from lens surface closest to object to lens surface closest to image in the first lens group
• TL:
• entire length of the optical system.

A method for manufacturing an optical system, comprising one of the following three steps A, B and C, wherein

• the step A comprises:
• disposing a first lens group with positive refractive power and a succeeding group in a lens barrel in order from an object on an optical axis,
• configuring the succeeding group to comprise a first focusing lens group that moves on the optical axis during focusing and a second focusing lens group which is disposed closer to the image than the first focusing lens group and which moves on the optical axis during focusing, and
• satisfying the following conditional expression:
• 0.03<D1/TL<0.25
• where
• D1:
• distance on optical axis from lens surface closest to object to lens surface closest to image in the first lens group
• TL:
• entire length of the optical system,
• the step B comprises:
• disposing a first lens group with positive refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power, and a fourth lens group with negative refractive power in a lens barrel in order from an object on an optical axis so that, during focusing, distances between adjacent lens groups vary, and
• the step C comprises:
• disposing a first lens group with positive refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power, and a fourth lens group with negative refractive power in a lens barrel in order from an object on an optical axis so that, during focusing, the second lens group and the third lens group move on the optical axis, and
• satisfying the following conditional expression:
• 0.03<D1/TL<0.25
• where
• D1:
• distance on optical axis from lens surface closest to object to lens surface closest to image in the first lens group
• TL:
• entire length of the optical system.