Compact zoom lens

A zoom lens comprising:na substrate defining a plurality of openings thereon;an imaging unit attached on the substrate;a stationary lens barrel mounted on the substrate and surrounding the imaging unit, the stationary lens barrel defining a plurality of first sliding grooves angled from the optical axis of the zoom lens and a plurality of second sliding grooves parallel to the optical axis of the zoom lens in the inner circumference thereof;a cam lens barrel rotatably received in the stationary lens barrel and moveable along the optical axis of the zoom lens following the rotation thereof along the inner circumference of the stationary lens barrel; anda guide lens barrel received in the cam lens barrel and moveable along the optical axis of the zoom lens following the motion of the cam lens barrel, the guide lens barrel comprising a plurality of key members protruding outwards from the outer circumference corresponding to and received in the openings of the substrate when the zoom lens is in the minimum focal length position, wherein the key members extend beyond the rear end of the cam lens barrel adjacent to the substrate and align with the second sliding grooves.