Zoom lens and imaging apparatus having the same
A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, and a rear group having a positive refractive power as a whole including at least one lens unit. During zooming from a wide-angle end to a telephoto end, a distance between adjacent lens units changes. The first lens unit includes at least three negative single lenses, and a predetermined condition is satisfied.
1. A zoom lens comprising, in order from an object side to an image side, a first lens unit having a negative refractive power, and a rear group having a positive refractive power as a whole including at least one lens unit,
wherein during zooming from a wide-angle end to a telephoto end, a distance between adjacent lens units changes,
wherein the first lens unit includes at least three negative single lenses, and
wherein the following conditional expressions are satisfied:
1.93<| f 1|/ fw< 6.50,
0.10< fG 1 N/f 1<2.00, and
1.80 <ndLN <2.20,
Where f1 is a focal length of the first lens unit, fw is a focal length of the zoom lens at the wide-angle end, fG1N is a focal length of a negative lens G1N closest to the object side in the first lens unit, and ndLN is a refractive index of a negative lens LN disposed closest to the image side among the negative lenses included in the rear group.
2. The zoom lens according to claim 1 , wherein a distance on an optical axis from a lens surface closest to the object side to an image plane of the zoom lens at the telephoto end is shorter than that on the optical axis from the lens surface closest to the object side to the image plane of the zoom lens at the wide-angle end.
3. The zoom lens according to claim 1 , wherein the rear group includes, in order from the object side to the image side, a second lens unit having a positive refractive power and a third lens unit having a positive refractive power.
4. The zoom lens according to claim 1 , wherein the negative lens LN is disposed closest to the image side in the rear group.
5. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.5< TDt/TDw< 0.9,
where TDw and TDt are lengths on an optical axis from a lens surface closest to the object side to a lens surface closest to the image side of the zoom lens at the wide-angle end and the telephoto end, respectively.
6. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.5< SKw/fw< 2.0,
where SKw is a distance from a lens surface closest to the image side to an image surface of the zoom lens at the wide-angle end when an object at infinity is focused.
7. The zoom lens according to claim 1 , wherein the first lens unit includes a negative lens G2N disposed adjacent to the image side of the negative lens G1N, and
wherein the following conditional expression is satisfied:
0.5< fG 1 N/fG 2 N< 1.0,
where fG2N is a focal length of the negative lens G2N.
8. The zoom lens according to claim 1 , wherein the first lens unit includes the at least three negative lenses continuously disposed from the object side to the image side.
9. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
−2.5< f 1/ fRw<− 0.3,
where fRw is a focal length in the rear group at the wide-angle end when an object at infinity is focused.
10. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
−0.7<β Rw<− 0.1,
where βRw is a lateral magnification of the rear group at the wide-angle end when an object at infinity is focused.
11. The zoom lens according to claim 1 , wherein at least one of the negative lenses included in the first lens unit has a biconcave shape.
12. The zoom lens according to claim 11 , wherein at least one of second and subsequent negative lenses counted from the object side among the negative lenses included in the first lens unit has a biconcave shape.
13. The zoom lens according to claim 1 , wherein the first lens unit includes a negative lens G2N disposed adjacent to the image side of the negative lens G1N, and
wherein among distances between adjacent lenses in the first lens unit, a distance between the negative lens G1N and the negative lens G2N is the widest.
14. The zoom lens according to claim 1 , wherein the negative lens G1N has a meniscus shape convex to the object side, in which both an object-side lens surface and an image-side lens surface are spherical.
15. The zoom lens according to claim 1 , wherein all lenses included in the first lens unit are spherical lenses.
16. The zoom lens according to claim 1 , wherein the first lens unit includes a negative lens G2N disposed adjacent to the image side of the negative lens G1N, and
wherein a refractive index of the negative lens G1N is larger than that of the negative lens G2N.
17. An imaging apparatus comprising:
a zoom lens; and
an image sensor configured to receive 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 negative refractive power, and a rear group having a positive refractive power as a whole including at least one lens unit,
wherein during zooming from a wide-angle end to a telephoto end, a distance between adjacent lens units changes,
wherein the first lens unit includes at least three negative single lenses, and
wherein the following conditional expressions are satisfied:
1.93<| f 1|/ fw< 6.50,
0.10< fG 1 N/f 1<2.00, and
1.80 <ndLN <2.20,
where f1 is a focal length of the first lens unit, fw is a focal length of the zoom lens at the wide-angle end, fG1N is a focal length of a negative lens G1N closest to the object side in the first lens unit, and ndLN is a refractive index of a negative lens LN disposed closest to the image side among the negative lenses included in the rear group.
18. A zoom lens comprising, in order from an object side to an image side, a first lens unit having a negative refractive power, and a rear group having a positive refractive power as a whole including at least one lens unit,
wherein during zooming from a wide-angle end to a telephoto end, a distance between adjacent lens units changes,
wherein the first lens unit includes at least three negative single lenses,
wherein the rear group includes, in order from the object side to the image side, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power, and
wherein the following conditional expressions are satisfied:
1.93<| f 1|/ fw< 6.50, and
0.10< fG 1 N/f 1<2.00,
where f1 is a focal length of the first lens unit, fw is a focal length of the zoom lens at the wide-angle end, and fG1N is a focal length of a negative lens G1N closest to the object side in the first lens unit.
19. A zoom lens comprising, in order from an object side to an image side, a first lens unit having a negative refractive power, and a rear group having a positive refractive power as a whole including at least one lens unit,
wherein during zooming from a wide-angle end to a telephoto end, a distance between adjacent lens units changes,
wherein the first lens unit includes at least three negative single lenses, and
wherein the following conditional expressions are satisfied:
1.93 |f 1|/ fw< 6.50,
0.10 <fG 1 N/f 1<2.00, and
80<ω w< 100,
where f1 is a focal length of the first lens unit, fw is a focal length of the zoom lens at the wide-angle end, fG1N is a focal length of a negative lens G1N closest to the object side in the first lens unit, and ωw (degree) is a half angle of view when an object at infinity is focused at the wide-angle end.