Patent ID: 7336427

Claim:
An inner zoom lens system, comprising: a first, fixed lens group having a minus refractive power; a second, moving lens group for performing a zooming operation such that an interval between the first lens group and the second lens group is reduced when zooming from a wide angle end to a telephoto end, said second, moving lens group having a plus refractive power; a third, moving lens group having a minus refractive power and being moveable such that a position of an image plane is corrected depending on the zooming operation of the second lens group; and a fourth, fixed lens group having a plus refractive power; wherein the refractive powers of said lens groups satisfy Equations 1 to 4 below: 0.5 <|f I |/f W <2.0 Equation 1 0.3 <f II /f W <1.0 Equation 2 0.2 <|f III |/f W <1.5 Equation 3 0.5 <f IV /f W <3.0 Equation4 where, f I : effective focal length of the first lens group wherein f I <0; f II : effective focal length of the second lens group; f III : effective focal length of the third lens group wherein f III <0; f IV : effective focal length of the fourth lens group; and f W : effective focal length of the entire lens system at the wide angle end.