Zoom lens system and image pickup apparatus including the same
A zoom lens system includes a first lens unit, a lens unit having a positive optical power placed on an image side of the first lens unit, and a lens unit having a negative optical power placed on the image side of the lens unit having a positive optical power. In the zoom lens system, the lens unit having a negative optical power is closest to the image side. A compact zoom lens system is obtained by adequately setting the movement of each lens unit during zooming and the optical power of each lens unit.
1. A zoom lens system comprising:
a first lens unit including a reflective member that deflects an optical path;
a lens unit having a positive optical power placed on an image side of the first lens unit; and
a lens unit having a negative optical power placed on the image side of the lens unit having a positive optical power, the lens unit having a negative optical power is positioned closest to the image side in the zoom lens system, wherein a distance between the first lens unit and the lens unit having a positive optical power and a distance between the lens unit having a positive optical power and the lens unit having a negative optical power vary during zooming from the wide-angle end to the telephoto end, and wherein when Fe is the focal length of the lens unit having a negative optical power and Fw is the focal length of the overall system at the wide-angle end, the following expression is satisfied:
0.8<| Fe/Fw|< 2.5.
2. The zoom lens system according to claim 1 , wherein when βew is the lateral magnification of the lens unit having a negative optical power at the wide-angle end and βeT is the lateral magnification of the lens unit having a negative optical power at the telephoto end, the following expression is satisfied:
1.4<β eT/βeW< 3.0.
3. The zoom lens system according to claim 1 , wherein the lens unit having a positive optical power and the lens unit having a negative optical power both move toward an object side during zooming from the wide-angle end to the telephoto end.
4. The zoom lens system according to claim 1 , wherein the first lens unit includes a negative lens and a positive lens.
5. The zoom lens system according to claim 1 , wherein the first lens unit includes a positive meniscus lens having a convex surface on the image side, the positive meniscus lens being closest to the image side in the first lens unit.
6. The zoom lens system according to claim 1 , wherein the lens unit having a negative optical power includes only a negative meniscus lens having a convex surface on the image side.
7. The zoom lens system according to claim 1 , wherein the zoom lens system forms an image on a solid-state image pickup device.
8. An image pickup apparatus, comprising:
the zoom lens system according to claim 1 ; and
a solid-state image pickup device that receives an image formed by the zoom lens system.