US Patent 7477456 Zoom lens

A zoom lens includes in the order from an object a first lens group having a negative refractive power, including at least one negative lens and one positive lens, wherein a negative plastic lens having one or more aspherical surfaces is arranged on a side closest to the object; a second lens group having positive refractive power, including a first positive lens, a second positive lens and a negative lens in the order from the object; and a third lens group, wherein each lens group is moved in a direction of an optical axis for zooming, and the following expressions are satisfied:2.0<|f1/fw|<3.01.2<|f1a/fw|<1.8where f1, f1a and fw represent focal lengths of the first lens group, of the negative plastic lens arranged closest to the object, and at a wide-angle end of an entire zoom lens, respectively.