Zoom optical system, optical apparatus and method for manufacturing the zoom optical system
A zoom optical system includes a plurality of lens groups, and upon zooming distances between adjacent lens groups change. The zoom optical system has 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 zoom optical system satisfies the conditional expression 0.000<dL0t/dL1t<1.000, where dL0t denotes 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, and dL1t denotes 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.
1. A zoom optical system comprising a plurality of lens groups, wherein
upon zooming, distances between adjacent lens groups change,
the zoom optical system comprises: 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
the zoom optical system satisfies the following conditional expressions:
0.000< dL 0 t/dL 1 t< 1.000
0.20< fF 1/ fF 2<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.
2. The zoom optical system according to claim 1 , wherein
the plurality of lens groups include, in order from an object: a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; a fourth lens group having a positive refractive power; and a succeeding lens group, and
the succeeding lens group includes the focusing lens group and the image-side lens group.
3. The zoom optical system according to claim 1 , wherein
the zoom optical system satisfies the following conditional expression:
0.20< MTF 1/ MTF 2<3.00
where MTF1: an absolute value of an amount of movement of the first focusing lens group upon focusing from an infinity object to the short-distance object in the telephoto end state, and
MTF2: an absolute value of an amount of movement of the second focusing lens group upon focusing from the infinity object to the short-distance object in the telephoto end state.
4. The zoom optical system according to claim 1 , wherein
the zoom optical system satisfies the following conditional expression:
0.20<|β TF 1|/|β TF 2|<5.00
where βTF1: a lateral magnification of the first focusing lens group upon focusing on the infinity object in the telephoto end state, and
βTF2: a lateral magnification of the second focusing lens group upon focusing on the infinity object in the telephoto end state.
5. The zoom optical system according to claim 1 , wherein
the first focusing lens group and the second focusing lens group are adjacent to each other.
6. The zoom optical system according to claim 1 , wherein the focusing lens groups consist of three or less single lenses.
7. The zoom optical system according to claim 1 , wherein the first focusing lens group includes a single lens having a negative refractive power.
8. The zoom optical system according to claim 1 , wherein the focusing lens groups are disposed closer to an image than an aperture stop.
9. The zoom optical system according to claim 1 , wherein
the zoom optical system satisfies the following conditional expression:
0.20<| fF|/ft< 4.00
where fF: a focal length of the focusing lens group having a strongest refractive power among the focusing lens groups, and
ft: a focal length of the zoom optical system in the telephoto end state.
10. An optical apparatus, comprising the zoom optical system according to claim 1 mounted thereon.
11. A zoom optical system comprising a plurality of lens groups, wherein
upon zooming, distances between adjacent lens groups change,
the zoom optical system comprises: 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,
upon zooming, the cylindrical member moves,
the focusing lens group is 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 is 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
the zoom optical system satisfies 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 is assumed to be +, and a sign of movement toward the image is assumed to be −.
12. The zoom optical system according to claim 11 , further comprising an image-side lens group disposed adjacent to an image side of the focusing lens group, wherein
upon zooming, a distance between the focusing lens group and the image-side lens group changes, and
the zoom optical system satisfies the following conditional expression:
−1.000 <dB/dE< 1.500
where dE: an amount of movement of the image-side lens group with respect to an image surface upon zooming from the wide-angle end state to the 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 −.
13. The zoom optical system according to claim 11 , further comprising an object-side lens group disposed adjacent to an object side of the focusing lens group, wherein
upon zooming, a distance between the object-side lens group and the focusing lens group changes, and
the zoom optical system satisfies the following conditional expression:
−1.000 <dB/dD< 1.000
where dD: an amount of movement of the object-side lens group with respect to an image surface upon zooming from the wide-angle end state to the 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 −.
14. The zoom optical system according to claim 11 , wherein the driving apparatus comprises a stepping motor.
15. The zoom optical system according to claim 11 , wherein
a movement trajectory of the first focusing lens group upon zooming is different from a movement trajectory of the second focusing lens group upon zooming.
16. The zoom optical system according to claim 15 , wherein a first driving apparatus for moving the first focusing lens group, and a second driving apparatus for moving the second focusing lens group are fixed to the cylindrical member.
17. The zoom optical system according to claim 15 , wherein a guide shaft that linearly guides the first focusing lens group and the second focusing lens group in an optical axis direction is fixed to the cylindrical member.
18. The zoom optical system according to claim 11 , wherein
the plurality of lens groups include, in order from an object: a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; a fourth lens group having a positive refractive power; and a succeeding lens group, and
the succeeding lens group includes the focusing lens group.
19. An optical apparatus, comprising the zoom optical system according to claim 11 mounted thereon.
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< dL 0 t/dL 1 t< 1.000
0.20< fF 1/ fF 2<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 −.