Patent ID: 11906716
Assignee: NIKON CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 19:
20. A method for manufacturing a zoom optical system comprising a plurality of lens groups, the method comprising:
arranging the lens groups in a lens barrel such that:
upon zooming, distances between adjacent lens groups change, and
the method further comprising at least one of the following features A or B,
the feature A including:
configuring the zoom optical system to comprise a focusing lens group that moves upon focusing and an image-side lens group disposed adjacent to an image side of the focusing lens group,
the focusing lens group comprises a first focusing lens group that moves upon focusing and a second focusing lens group that is disposed closer to an image than the first focusing lens group and moves upon focusing,
the first focusing lends group and the second focusing lens group have positive refractive powers,
the second focusing lens group consists of a single lens, and
satisfying the following conditional expressions:

0.000<dL0t/dL1t<1.000

0.20<fF1/fF2<3.00

where dL0t: a distance on an optical axis between the focusing lens group and the image-side lens group upon focusing on an infinity object in a telephoto end state,
dL1t: a distance on the optical axis between the focusing lens group and the image-side lens group upon focusing on a short-distance object in the telephoto end state,
fF 1: a focal length of the first focusing lens group, and
fF2: a focal length of the second focusing lens group, the feature B including:
configuring the zoom optical system to comprise a focusing lens group that moves upon focusing and a cylindrical member to which a driving apparatus for moving the focusing lens group is fixed,
the cylindrical member moving upon zooming,
the focusing lens group being relatively movable with respect to the cylindrical member by the driving apparatus,
an amount of movement of a lens disposed to an object side or an image side of the focusing lens group upon zooming being different from the amount of movement of the cylindrical member upon zooming,
the focusing lens group comprises a first focusing lens group that moves upon focusing and a second focusing lens group that is disposed closer to an image than the first focusing lens group and moves upon focusing,
the first focusing lends group and the second focusing lens group have positive refractive powers,
the second focusing lens group consists of a single lens, and
satisfying the following conditional expression:

−1.000<dA/dB<2.000

where dA: an amount of movement of the second focusing lens group with respect to an image surface upon zooming from a wide-angle end state to a telephoto end state, a sign of movement toward an object being assumed to be +, and a sign of movement toward an image being assumed to be −, and
dB: an amount of movement of the cylindrical member with respect to the image surface upon zooming from the wide-angle end state to the telephoto end state, a sign of movement toward the object being assumed to be +, and a sign of movement toward the image being assumed to be −.