Zoom lens and electronic imaging apparatus incorporating the same
The zoom lens of the invention comprises, in order from an object side thereof, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power, a fourth lens group having positive refracting power, a fifth lens group having negative refracting power, and a sixth lens group having positive refracting power. The first lens group includes a reflective optical element, and the lens component in, and on the most image side of, the fourth lens group has negative refracting power.
1. A zoom lens, comprising, in order from an object side thereof, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power, a fourth lens group having positive refracting power, a fifth lens group having negative refracting power, and a sixth lens group having positive refracting power, wherein:
the first lens group includes a reflective optical element, and
the fourth lens group has a plurality of lens components in which a most image side lens component of the plurality of lens components has negative refracting power.
2. The zoom lens according to claim 1 , wherein the fifth lens group is movable during zooming from a wide-angle end to a telephoto end, and focusing.
3. The zoom lens according to claim 1 , which satisfies the following Condition (1):
−3≦ F G5 /F G6 ≦−0.91 (1)
where F G5 is a focal length of the fifth lens group, and F G6 is a focal length of the sixth lens group.
4. The zoom lens according to claim 1 , which satisfies the following Condition (2):
−6≦ F G5 /F W ≦−2.2 (2)
where F G5 is a focal length of the fifth lens group, and F W is a focal length of the zoom lens at a wide-angle end.
5. The zoom lens according to claim 1 , which satisfies the following Condition (3):
−1.50≦ F G5 /F T ≦−0.32 (3)
where F G5 is a focal length of the fifth lens group, and F T is a focal length of the zoom lens at a telephoto end.
6. The zoom lens according to claim 1 , which satisfies the following Condition (4):
−15≦( R G4L +R G4M )/( R G4L −R G4M )≦−1.5 (4)
where R G4M is s radius of curvature of an object-side surface of the lens component in and on the most image side of the fourth lens group, and R G4L is a radius of curvature of an image-side surface of the lens component in and on the most image side of the fourth lens group.
7. The zoom lens according to claim 1 , which satisfies the following Condition (5):
0.9 ≦F W5G6G /F T5G6G ≦2.3 (5)
where F W5G6G is a combined focal length of the fifth lens group and the sixth lens group at a wide-angle end, and F T5G6G is a combined focal length of the fifth lens group and the sixth lens group at a telephoto end.
8. The zoom lens according to claim 1 , which satisfies the following Condition (6):
0.95 ≦MG G5T /MG G5W ≦1.25 (6)
where MG G5W is a transverse magnification of the fifth lens group at a time when the zoom lens is at a wide-angle end, and M G5T is a transverse magnification of the fifth lens group at a time when the zoom lens is at a telephoto end.
9. The zoom lens according to claim 1 , which satisfies the following Condition (7):
−0.5 ≦ΔL G5 /F W ≦1 (7)
where ΔL G5 is a difference between a distance from the surface in and on the most image side of the fifth lens group to an image plane at a time when the zoom lens is at a wide-angle end and a distance from the surface in and on the most image side of the fifth lens group to the image plane at a time when the zoom lens is at a telephoto end, and F W is a focal length of the whole zoom lens optical system at the wide-angle end.
10. The zoom lens according to claim 1 , which satisfies the following Condition (8):
−0.005≦(Δ L G5 /F W )/ M 2 ≦0.023 (8)
where ΔL G5 is a difference between a distance from the surface in and on the most image side of the fifth lens group to an image plane at a time when the zoom lens is at a wide-angle end and a distance from the surface in and on the most image side of the fifth lens group to the image plane at a time when the zoom lens is at a telephoto end, F W is a focal length of the whole zoom lens optical system at the wide-angle end, and M is an optical magnification of the zoom lens.
11. The zoom lens according to claim 1 , which satisfies the following Condition (9):
0.15 ≦L Wg4G5 /L TG4G5 1.7 (9)
where L WG4G5 is an air separation distance between the fourth lens group and the fifth lens group at a wide-angle end of the zoom lens, and L TG4G5 is an air separation distance between the fourth lens group and the fifth lens group at a telephoto end of the zoom lens.
12. The zoom lens according to claim 1 , which satisfies the following Condition (10):
0.3 ≦L WG5G6 /L TG5G6 ≦1.8 (10)
where L WG5G6 is an air separation distance between the fifth lens group and the sixth lens group at a wide-angle end of the zoom lens, and L TG5G6 is an air separation distance between the fifth lens group and the sixth lens group at a telephoto end of the zoom lens.
13. The zoom lens according to claim 1 , wherein the surface in and on the most image side of the fourth lens group is a surface concave on its image side.
14. The zoom lens according to any one of claim 1 , wherein:
upon zooming a wide-angle end to a telephoto end, a separation between the first lens group and the second lens group grows wide, a separation between the second lens group and the third lens group becomes narrow, a separation between the third lens group and the fourth lens group becomes narrow, a separation between the fourth lens group and the fifth lens group changes, and a separation between the fifth lens group and the sixth lens group changes.
15. The zoom lens according to claim 1 , wherein the fifth lens group moves in a convex orbit toward an image side upon zooming from a wide-angle end to a telephoto end.
16. The zoom lens according to claim 1 , wherein the surface in and on the most object side of the fifth lens group is a surface concave on its object side.
17. The zoom lens according to claim 1 , which satisfies the following Condition (11):
1.1 ≦F G5 /F G4Ln ≦5 (11)
where F G5 is a focal length of the fifth lens group in the zoom lens, and F G4Ln is a focal length of the negative lens in and on the most image side of the fourth lens group in the zoom lens.
18. The zoom lens according to claim 1 , which satisfies the following Condition (12):
0.1≦( R G5S +R G4L )/( R G5S −R G4L )≦0.9 (12)
where R G5S is a radius of curvature of the surface in and on the most object side of the fifth lens group, and R G4L is a radius of curvature of the surface in and on the most image side of the fourth lens group.
19. The zoom lens according to claim 1 , wherein the sixth lens group remains fixed during zooming.
20. The zoom lens according to claim 1 , which satisfies the following Condition (13):
1.9≦|( R G4L +R G4S )/( R G4L −R G4S )| (13)
where R G4S is a radius of curvature of the surface in and on the most object side of the fourth lens group, and R G4L is a radius of curvature of the surface in and on the most image side of the fourth lens group.
21. The zoom lens according to claim 1 , wherein the second lens group includes at least two negative lenses located back-to-back and side-by-side.
22. An electronic imaging apparatus, comprising:
a zoom lens as recited in claim 1 , and
an imaging device located on an image side of the zoom lens and having an imaging plane for converting an optical image into electrical signals.