Abstract: A lens system including a first lens group having positive refractive power, a second lens group positioned forward the first lens group and having negative refractive power and including a zoom lens, and a third lens group having positive refractive power and positioned forward the first and second lens groups is disclosed. The zoom lens is movable relative to the other lenses of the lens system. The configuration and relative positioning of the lenses, along with the relative movement of the zoom lens, allows a laser transmitted through the lens system to be focused with a minimal spot size over a significant scanning field size and over a range of depths.