A zoom lens is disclosed that is formed of only two lens groups. The first lens
group includes, from the object side, a plastic lens element having negative refractive
power and an aspheric surface, and a lens element having positive refractive power.
The second lens group includes, from the object side: a biconvex lens element having
an aspheric surface; a lens element having negative refractive power, a smaller
curvature on its object side, and with its image-side surface joined to a biconvex
lens element. The zoom lens satisfies specified conditions to: (a) allow for ease
of manufacture and assembly while maintaining favorable correction of various aberrations,
(b) assure that the zoom lens is compact in both the operational and retracted
positions, (c) assure that the zoom lens is not easily damaged, and (d) assure
that the optical performance is well-maintained despite changes in ambient conditions,
such as temperature.