JP2008197534A5 - - Google Patents

Claims (6)

In order from the object side to the image side, the lens unit includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power. The first lens group has at least one diffractive optical element, the focal length of the diffractive portion of the diffractive optical element is f _DOE , the focal length at the telephoto end of the entire system is f _T , and the first lens When the average value of the Abbe number of the material of the positive lens included in the group is ν _{G1 + av} ,
0.02 <f _T / f _DOE <0.2
30 <ν _{G1 + av} <80
A zoom lens satisfying the following conditional expression:   The first lens group is a lens group that is fixed during zooming, and the second lens group is a lens group that monotonously moves to the image side during zooming from the wide-angle end to the telephoto end, and the third lens group 2. The zoom lens according to claim 1, wherein the zoom lens unit is a lens group that moves toward the object side and corrects image plane variation caused by zooming. The zoom lens according to claim 1, wherein an aperture stop is provided between the third lens group and the fourth lens group.   The first lens group includes a 1a lens group that is fixed during focusing and a 1b lens group that moves toward the object side during focusing from an object at infinity to a close object. The zoom lens according to item. When the focal length of the first lens group and f _1,
0.1 <f ₁ / f _T <0.5
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.   6. An image pickup apparatus comprising: the zoom lens according to claim 1; and a solid-state image pickup device that receives an image formed by the zoom lens.