A lens barrel including a telescopic cylinder configured to be accommodated within a fixed frame; a plurality of lens groups configured to be retained in the telescopic cylinder; a lens driving device configured to drive the plurality of lens groups along a longitudinal axis of the telescopic cylinder between a collapsed position in which at least one portion of the plurality of lens groups is stored in the fixed frame and an extended position in which the at least one portion of the plurality of lens groups is extended out of the fixed frame; and a retractable lens group configured to be retracted into the fixed frame through an opening in a wall of the fixed frame when the telescopic cylinder is in the extended position.