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

An optical system consisting of a plurality of lens groups, which comprises a leading lens group, a first focusing lens group, and a second focusing lens group, the lens groups being arranged in line on an optical axis,

• wherein:
• the leading lens group is arranged closer to an object side than the first focusing lens group;
• the second focusing lens group is arranged closer to an image surface than the first focusing lens group;
• the leading lens group is fixed with respect to the image surface upon focusing,
• the first focusing lens group has positive refractive power and moves toward the image surface along the optical axis upon focusing from an infinity object to a short distance object;
• the second focusing lens group has negative refractive power and moves toward the object side along the optical axis upon focusing from an infinity object to a short distance object;
• and
• the following conditional expression is satisfied:
• 0.20<dFF/TL<0.65 and
• at least one of the following two conditional expressions is satisfied:
• 0.20<f1/fL1<1.50
• 0.10<f1/fR<0.80
• where
• dFF:
• a distance on the optical axis, upon focusing on an infinity object, from an image-facing surface of a lens arranged closest to the image surface in the first focusing lens group to an object-facing surface of a lens arranged closest to the object side in the second focusing lens group,
• TL:
• an entire length of the optical system upon focusing on an infinity object,
• fL1:
• a focal length of the first lens from the object side, among the lenses configuring the leading lens group,
• f1:
• a focal length of the leading lens group, and
• fR:
• a focal length of a lens group including the second focusing lens group and a succeeding lens group, upon focusing on an infinity object.

A method for manufacturing an optical system consisting of a plurality of lens groups, which comprises a leading lens group, a first focusing lens group, and a second focusing lens group, the lens groups being arranged in line on an optical axis,

• the method comprising a step of disposing the lens groups in a lens barrel so that:
• the leading lens group is arranged closer to an object side than the first focusing lens group;
• the second focusing lens group is arranged closer to an image surface than the first focusing lens group;
• the first focusing lens group has positive refractive power and moves toward the image surface along the optical axis upon focusing from an infinity object to a short distance object;
• the second focusing lens group has negative refractive power and moves toward the object side along the optical axis upon focusing from an infinity object to a short distance object;
• and
• the method further comprising at least one of the following features A or B:
• the feature A including:
• disposing an intermediate lens group between the first focusing lens group and the second focusing lens group, the intermediate lens group comprising at least one lens, and
• satisfying at least one of the following two conditional expressions:
• 0.20<f1/fL1<1.50
• 0.10<f1/fR<0.80
• where
• fL1:
• a focal length of the first lens from the object side, among the lenses configuring the leading lens group,
• f1:
• a focal length of the leading lens group, and
• fR:
• a focal length of a lens group including the second focusing lens group and a succeeding lens group, upon focusing on an infinity object, and
• the feature B including:
• arranging the leading lens group to be fixed with respect to the image surface upon focusing, and
• satisfying the following conditional expression:
• 0.20<dFF/TL<0.65 and
• satisfying at least one of the following two conditional expressions:
• 0.20<f1/fL1<1.50
• 0.10<f1/fR<0.80
• where
• dFF:
• a distance on the optical axis, upon focusing on an infinity object, from an image-facing surface, of a lens arranged closest to the image surface in the first focusing lens group to an object-facing surface of a lens arranged closest to the object side in the second focusing lens group,
• TL:
• an entire length of the optical system upon focusing on an infinity object,
• fL1:
• a focal length of the first lens from the object side, among the lenses configuring the leading lens group,
• f1:
• a focal length of the leading lens group, and
• fR:
• a focal length of a lens group including the second focusing lens group and a succeeding lens group, upon focusing on an infinity object.