Patent ID: 6392817
Filing Date: 2002-05-21
Classification: G02B

Abstract:
A rear focus type zoom lens having, in succession from the object side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, wherein said third lens unit has a stop most adjacent to the image plane side, the surface thereof adjacent to said stop being convex toward the image plane side and aspherical, and when the focal lengths of the entire system at the wide angle end and the telephoto end are defined as fw and ft, respectively, and the F number of the wide angle end is defined as FNW, and the focal length of the second lens unit is defined as f2, the following conditional expression is satisfied:0.8f2/fA|}Ã—FNW<1.6 (fA={square root over (fwÂ·ft)}).