Zoom lens and image pickup apparatus
Provided is a zoom lens consisting of: a positive first lens unit; a negative second lens unit; a positive third lens unit; and a rear lens group including at least one lens unit, wherein an interval between each pair of adjacent lens units is changed during zooming. The rear lens group includes a negative lens unit LR including at least one positive lens and at least one negative lens. The at least one negative lens includes a negative lens made of a material having a largest Abbe number of the at least one negative lens. Each of an extraordinary partial dispersion ratio of the material, distances of a lens surface on an image side of the lens unit LR to an image plane at a telephoto end and at a wide angle end, and a focal length of the lens unit LR is appropriately set.
1. A zoom lens comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power;
a third lens unit having a positive refractive power; and
a rear lens group including at least one lens unit,
wherein an interval between each pair of adjacent lens units is changed during zooming,
wherein the rear lens group includes a lens unit LR having a negative refractive power,
wherein the lens unit LR includes at least one positive lens and at least one negative lens,
wherein the at least one negative lens includes a negative lens LRN made of a material having a largest Abbe number of the at least one negative lens and satisfying the following conditional expression:
0.0<Δθ gF< 0.3,
where ΔθgF represents an extraordinary partial dispersion ratio of the material, and
wherein the following conditional expressions are satisfied:
3.5< bft/bfw< 50.0; and
−100.0< fr/bfw<− 5.0,
where “bft” represents a distance from a lens surface on the image side of the lens unit LR to an image plane at a telephoto end, “bfw” represents a distance from the lens surface on the image side of the lens unit LR to the image plane at a wide angle end, and “fr” represents a focal length of the lens unit LR.
2. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
−10.0< TLt/Mr<− 2.0,
where TLt represents a total length of the zoom lens at the telephoto end, Mr represents a movement amount of the lens unit LR during zooming from the wide angle end to the telephoto end, the movement amount having a positive sign when the lens unit LR is located closer to the image side at the telephoto end than at the wide angle end, and having a negative sign when the lens unit LR is located closer to the object side at the telephoto end than at the wide angle end.
3. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
2.0< ear/bfw< 10.0,
where “ear” represents an effective diameter of a lens surface closest to the image side in the lens unit LR.
4. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
−30.0< frn/bfw<− 2.0,
where “frn” represents a focal length of the negative lens LRN.
5. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
2.0< D 23 w/D 23 t< 20.0,
where D 23 w represents an interval on an optical axis between the second lens unit and the third lens unit at the wide angle end, and D 23 t represents a lens interval between the second lens unit and the third lens unit at the telephoto end.
6. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
4.0< fw/bfw< 25.0,
where “fw” represents a focal length of the zoom lens at the wide angle end.
7. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
3.0< ft/bft< 6.0,
where “ft” represents a focal length of the zoom lens at the telephoto end.
8. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.2< f 1/ ft< 1.1,
where f1 represents a focal length of the first lens unit, and “ft” represents a focal length of the zoom lens at the telephoto end.
9. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
1.0<β rt/βrw< 2.5,
where “βrw” represents a lateral magnification of the lens unit LR at the wide angle end, and “βrt” represents a lateral magnification of the lens unit LR at the telephoto end when focused at infinity.
10. A zoom lens according to claim 1 , wherein the lens unit LR is arranged closest to the image side in the rear lens group.
11. A zoom lens according to claim 1 ,
wherein the rear lens group consists of, in order from the object side to the image side:
a fourth lens unit having a positive refractive power;
a fifth lens unit having a negative refractive power;
a sixth lens unit having a positive refractive power; and
a seventh lens unit having a negative refractive power, and
wherein the lens unit LR is the seventh lens unit.
12. A zoom lens according to claim 1 ,
wherein the rear lens group consists of, in order from the object side to the image side:
a fourth lens unit having a positive refractive power;
a fifth lens unit having a negative refractive power; and
a sixth lens unit having a negative refractive power, and
wherein the lens unit LR is the sixth lens unit.
13. A zoom lens according to claim 1 ,
wherein the rear lens group consists of a fourth lens unit having a negative refractive power, and
wherein the lens unit LR is the fourth lens unit.
14. A zoom lens according to claim 1 ,
wherein the rear lens group consists of, in order from the object side to the image side:
a fourth lens unit having a negative refractive power; and
a fifth lens unit having a positive refractive power; and
wherein the lens unit LR is the fourth lens unit.
15. An image pickup apparatus comprising:
a zoom lens; and
a photoelectric conversion element configured to receive light of an image formed by the zoom lens,
wherein the zoom lens includes, in order from an object side to an image side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power;
a third lens unit having a positive refractive power; and
a rear lens group including at least one lens unit,
wherein an interval between each pair of adjacent lens units is changed during zooming,
wherein the rear lens group includes a lens unit LR having a negative refractive power,
wherein the lens unit LR includes at least one positive lens and at least one negative lens,
wherein the at least one negative lens includes a negative lens LRN made of a material having a largest Abbe number of the at least one negative lens and satisfying the following conditional expression:
0.0<Δθ gF< 0.3,
where ΔθgF represents an extraordinary partial dispersion ratio of the material, and
wherein the following conditional expressions are satisfied:
3.5< bft/bfw< 50.0; and
−100.0< fr/bfw<− 5.0,
where “bft” represents a distance from a lens surface on the image side of the lens unit LR to an image plane at a telephoto end, “bfw” represents a distance from the lens surface on the image side of the lens unit LR to the image plane at a wide angle end, and “fr” represents a focal length of the lens unit LR.