Zoom lens and image pickup apparatus
A zoom lens includes first to fourth lens groups arranged in that order from the object side and having positive, negative, positive, and positive refractive powers. The first lens group includes a single first lens having a negative refractive power, a right-angle prism bending an optical path, and a second lens including at least a lens having a positive refractive power in that order from the object side. The second lens group includes a third lens including an aspherical surface and having a negative refractive power, a fourth lens having a negative refractive power, a fifth lens having a positive refractive power, and a sixth lens having a negative refractive power in that order from the object side. The second and fourth lens groups are moved in an optical-axis direction during zooming.
1. A zoom lens comprising:
a first lens group including a first lens, a right-angle prism, and a second lens in that order from the object side, the first lens being a single lens having a negative refractive power, the right-angle prism bending an optical path, the second lens including at least a lens having a positive refractive power, the first lens group having a positive refractive power;
a second lens group arranged at the image plane side of the first lens group and including a third lens, a fourth lens, a fifth lens, and a sixth lens in that order from the object side, the third lens including an aspherical surface and having a negative refractive power, the fourth lens having a negative refractive power, the fifth lens having a positive refractive power, the sixth lens having a negative refractive power, the second lens group having a negative refractive power, the second lens group being moved in an optical-axis direction during zooming;
a third lens group arranged at the image plane side of the second lens group, the third lens group having a positive refractive power; and
a fourth lens group arranged at the image plane side of the third lens group, the fourth lens group having a positive refractive power, the fourth lens group being moved in the optical-axis direction during zooming.
2. The zoom lens according to claim 1 , wherein Conditional Expression (1) is satisfied as follows
0.62 <fGP 2 /fw< 0.7 (1)
where fGP 2 is a focal length of the second lens group, and fw is a focal length of a whole system of the zoom lens at the wide-angle end, in Conditional Expression (1).
3. The zoom lens according to claim 1 , wherein Conditional Expression (2) is satisfied as follows
1.5 <|fG 1 /fG 2|<1.7 (2)
where fG 1 is a focal length of the first lens, and fG 2 is a focal length of the second lens, in Conditional Expression (2).
4. The zoom lens according to claim 1 , wherein Conditional Expression (3) is satisfied as follows
NdL 1>1.75 (3)
where NdL 1 is a refractive index of the first lens at the d-line, in Conditional Expression (3).
5. The zoom lens according to claim 1 , wherein Conditional Expression (4) is satisfied as follows
VdL 1<35 (4)
where VdL 1 is an Abbe number of the first lens at the d-line, in Conditional Expression (4).
6. The zoom lens according to claim 1 , wherein Conditional Expression (5) is satisfied as follows
NdP> 1.80 (5)
where NdP is a refractive index of the right-angle prism at the d-line, in Conditional Expression (5).
7. The zoom lens according to claim 1 , wherein at least a surface of the second lens is an aspherical surface.
8. An image pickup apparatus comprising:
a zoom lens including
a first lens group including a first lens, a right-angle prism, and a second lens in that order from the object side, the first lens being a single lens having a negative refractive power, the right-angle prism bending an optical path, the second lens including at least a lens having a positive refractive power, the first lens group having a positive refractive power,
a second lens group arranged at the image plane side of the first lens group and including a third lens, a fourth lens, a fifth lens, and a sixth lens in that order from the object side, the third lens including an aspherical surface and having a negative refractive power, the fourth lens having a negative refractive power, the fifth lens having a positive refractive power, the sixth lens having a negative refractive power, the second lens group having a negative refractive power, the second lens group being moved in an optical-axis direction during zooming,
a third lens group arranged at the image plane side of the second lens group, the third lens group having a positive refractive power, and
a fourth lens group arranged at the image plane side of the third lens group, the fourth lens group having a positive refractive power, the fourth lens group being moved in the optical-axis direction during zooming; and
an image pickup device having an image plane on which an object image is formed by the zoom lens.
9. A zoom lens comprising:
a first lens group including, in order from the object plane side, a first lens, a right-angle prism, and a second lens, the first lens being a single lens having a negative refractive power, the right-angle prism bending an optical path, the second lens having a positive refractive power, the first lens group having a positive refractive power;
a second lens group arranged at the image plane side of the first lens group and including, in order from the object plane side, a third lens, a fourth lens, a fifth lens, and a sixth lens, the third lens including an aspherical surface and having a negative refractive power, the fourth lens having a negative refractive power, the fifth lens having a positive refractive power, the sixth lens having a negative refractive power, the second lens group configured to be moved in an optical-axis direction during zooming;
a third lens group arranged at the image plane side of the second lens group, the third lens group having a positive refractive power; and
a fourth lens group arranged at the image plane side of the third lens group, the fourth lens group having a positive refractive power, the fourth lens group configured to be moved in the optical-axis direction during zooming.
10. The zoom lens according to claim 9 , wherein the second lens is arranged without an intervening lens between the second lens and the right-angle prism.
11. The zoom lens according to claim 9 , wherein Conditional Expression (1) is satisfied as follows:
0.62 <|fGP 2 /fw|< 0.7 (1),
where fGP 2 is a focal length of the second lens group, and fw is a focal length of a whole system of the zoom lens at the wide-angle end, in Conditional Expression (1).
12. The zoom lens according to claim 9 , wherein the second lens is arranged with an axial surface distance of about 0.2 mm between a surface of the right-angle prism.
13. The zoom lens according to claim 9 , wherein Conditional Expression (2) is satisfied as follows:
1.5 <|fG 1 /fG 2|<1.7 (2),
where fG 1 is a focal length of the first lens, and fG 2 is a focal length of the second lens, in Conditional Expression (2).
14. The zoom lens according to claim 11 , wherein Conditional Expression (2) is satisfied as follows:
1.5 <|fG 1 /fG 2|<1.7 (2),
where fG 1 is a focal length of the first lens, and fG 2 is a focal length of the second lens, in Conditional Expression (2).
15. The zoom lens according to claim 9 , wherein Conditional Expression (3) is satisfied as follows:
NdL 1>1.75 (3),
where NdL 1 is a refractive index of the first lens at the d-line, in Conditional Expression (3).
16. The zoom lens according to claim 9 , wherein Conditional Expression (4) is satisfied as follows:
VdL 1<35 (4),
where VdL 1 is an Abbe number of the first lens at the d-line, in Conditional Expression (4).
17. The zoom lens according to claim 9 , wherein Conditional Expression (5) is satisfied as follows:
NdP> 1.80 (5),
where NdP is a refractive index of the right-angle prism at the d-line, in Conditional Expression (5).
18. An image pickup apparatus comprising:
the zoom lens according to claim 9 ; and
an image pickup device having an image plane on which an object image is formed by the zoom lens.
19. The zoom lens according to claim 9 , further comprising
a fifth lens group arranged at the image plane side of the fourth lens group, the fifth lens group having a negative refractive power and including, in order from the object plane side, a tenth lens and an eleventh lens, the tenth lens having a negative refractive power and the eleventh lens having a positive refractive power.
20. The zoom lens according to claim 9 , wherein the right-angle prism has a refractive power.