Zoom lens and camera
View Patent ↗To obtain a high imaging performance even for a relatively long focal length in a zoom lens provided with an optical-path bending member for bending an optical path. The following are included: a first group of lenses G 1 having a positive refracting power, a second group of lenses G 2 having a negative refracting power, a third group of lenses G 3 having a positive refracting power, and a fourth group of lenses G 4 having a positive refracting power arranged in that order from the object side to the image surface side. Zooming is performed by moving the second group of lenses G 2 and fourth group of lenses G 4 along an optical axis. The first group of lenses G 1 is constituted of a group of positive lenses L 1 having a positive refracting power and an optical-path bending member L 2 for bending an optical path arranged in that order from the object side to the image face side.
1. A zoom lens comprising:
a first group of lenses having a positive refracting power;
a second group of lenses having a negative refracting power;
a third group of lenses having a positive refracting power; and
a fourth group of lenses having a positive refracting power, the first through fourth groups of lenses being formed in that order from an object side toward an image surface side, wherein
the zoom lens is configured such that zooming is performed by moving the second group of lenses and the fourth group of lenses along an optical axis, and
the first group of lenses comprises:
a group of positive lenses having a positive refracting power; and
an optical path bending member that bends an optical path, the group of positive lenses and the optical path bending member being formed in that order from the object side toward the image surface side;
wherein a relation of d/fw<0.194 is satisfied where d is the maximum image height on an image face and fw is the focal length of all lens systems constituting the zoom lens at a wide angle end.
2. The zoom lens according to claim 1 , wherein
the group of positive lenses comprises a single lens having a positive refracting power.
3. The zoom lens according to claim 1 , wherein
the group of positive lenses comprises a cemented lens obtained by cementing a single lens having a negative refracting power with a single lens having a positive refracting power from the object side in that order to the image face side.
4. The zoom lens according to claim 1 , wherein
the group of positive lenses comprises a cemented lens obtained by cementing a single lens having a negative refracting power with a single lens having a positive refracting power, and
a single lens having a positive refracting power, arranged in that order from the object side to the image face side.
5. The zoom lens according to any one of claims 1 to 4 , wherein
the optical-path bending member is disposed to the most image surface side among the first group of lenses.
6. The zoom lens according to claim 1 , wherein
a relationship of 1.0<f 1 /fw<3.5 is satisfied where fl is the focal length of all lens systems constituting the first group of lenses disposed to the object side of the optical-path bending member and fw is the focal length of all lens systems constituting the zoom lens at the wide angle end.
7. The zoom lens according to claim 1 , wherein
the fourth group of lenses is moved to the third group of lenses along the optical axis when focusing from an infinite object to a near range object, and
the following relationships are satisfied:
0.55<β4 T <0.92,
0.8<|β4 T /β4 w |<2.0, and
0.04< |D 34 w /f 4|<0.4
where;
β 4W is the lateral magnification of the fourth group of lenses when focusing on an infinite object at a wide angle end,
β4 T is the lateral magnification of the fourth group of lenses when focusing on an infinite object at a telephoto end,
D34 W is the air gap between the third group of lenses and the fourth group of lenses at a wide angle end, and
f 4 is the synthetic focal length of the fourth group of lenses.
8. The zoom lens according to claim 1 , wherein
the optical-path bending member is a prism using a glass material for satisfying a relationship of 1.6<nd<1.85 and vd<40, where nd is the refractive index of the optical-path bending member at a d-line and vd is the Abbe number of the optical-path bending member on the d-line.
9. A camera provided with the zoom lens described in claim 1 and a solid-state image pickup device disposed to the image face side of the zoom lens.