Zoom lens and imaging apparatus
A zoom lens includes a positive first lens group, which is fixed during changing magnification and during focusing, a negative second lens group, which is moved during changing magnification, a positive third lens group, which is fixed during changing magnification and during focusing, a positive fourth lens group, which is moved during changing magnification and during focusing, and a negative fifth lens group, which is moved during changing magnification, which are in this order from an object side. A lens group constituting the first lens group consists of a negative front group and a positive rear group in this order from the object side. The second lens group consists of four lenses of a negative lens, a positive lens, a negative lens, and a positive lens or a negative lens arranged in this order from the object side.
1. A zoom lens consisting of:
a first lens group having positive refractive power, and which is fixed during changing magnification and during focusing;
a second lens group having negative refractive power, and which is moved during changing magnification;
a third lens group having positive refractive power, and which is fixed during changing magnification and during focusing;
a fourth lens group having positive refractive power, and which is moved during changing magnification and during focusing; and
a fifth lens group having negative refractive power, and which is moved during changing magnification, which are in this order from an object side, and
wherein a lens group constituting the first lens group consists of a front group having negative refractive power and a rear group having positive refractive power in this order from the object side, and
wherein the second lens group consists of four lenses of a negative lens, a positive lens, a negative lens, and a positive lens arranged in this order from the object side, or consists of four lenses of a negative lens, a positive lens, a negative lens, and a negative lens arranged in this order from the object side.
2. A zoom lens, as defined in claim 1 , further comprising:
a reflection member that bends an optical path between the front group and the rear group in the first lens group.
3. A zoom lens, as defined in claim 1 , wherein the following formula (1) is satisfied:
0.70 <IH/fw< 0.90 (1), where
IH: maximum image height, and
fw: the focal length of an entire system at a wide angle end.
4. A zoom lens, as defined in claim 1 , wherein the following formula (2) is satisfied:
0.70 <|fG 2/ fw|< 0.95 (2), where
fG 2 : the focal length of the second lens group, and
fw: the focal length of an entire system at a wide angle end.
5. A zoom lens, as defined in claim 1 ,
wherein a most-image-side lens in the second lens group has at least one aspherical surface, and
wherein the following formula (3) is satisfied:
−0.3 <fw/f 24<0.3 (3), where
fw: the focal length of an entire system at a wide angle end, and
f 24 : the focal length of a most-image-side lens in the second lens group.
6. A zoom lens, as defined in claim 1 , wherein the second lens group includes at least one aspherical lens made of plastic material.
7. A zoom lens, as defined in claim 1 , wherein the following formula (4) is satisfied:
10.0 <TL /( fw ×tan(ω w ))<13.0 (4), where
TL: a length on an optical axis from an object-side surface of a most-object-side lens in an entire system to an image plane;
fw: the focal length of an entire system at a wide angle end; and
ωw: a half angle of view at a wide angle end.
8. A zoom lens, as defined in claim 1 , wherein the front group in the first lens group consists of a spherical lens having negative refractive power.
9. A zoom lens, as defined in claim 8 , wherein the rear group in the first lens group consists of two lenses, each having positive refractive power, and
wherein at least an object-side lens of the two lenses has a shape in which a part of an outer diameter shape is cut off.
10. A zoom lens, as defined in claim 1 , wherein the following formula (1A) is satisfied:
0.70 <IH/fw< 0.85 (1A), where
IH: maximum image height; and
fw: the focal length of an entire system at a wide angle end.
11. A zoom lens, as defined in claim 1 , wherein the following formula (2B) is satisfied:
0.80 <|fG 2/ fw|< 0.89 (2B), where
fG 2 : the focal length of the second lens group;
fw: the focal length of an entire system at a wide angle end.
12. A zoom lens, as defined in claim 1 , wherein the following formula (3B) is satisfied:
−0.1 <fw/f 24<0.25 (3B), where
fw: the focal length of an entire system at a wide angle end; and
f 24 : the focal length of a most-image-side lens in the second lens group.
13. A zoom lens, as defined in claim 1 , wherein the following formula (4A) is satisfied:
11.0 <TL /( fw ×tan(ω w ))<12.5 (4A), where
TL: a length on an optical path from an object-side surface of a most-object-side lens in an entire system to an image plane;
fw: the focal length of the entire system at a wide angle end; and
ωw: a half angle of view at a wide angle end.
14. An imaging apparatus comprising:
a zoom lens, as defined in claim 1 ; and
an imaging device that images an optical image formed by the zoom lens, and that outputs an electrical signal.