A guide mechanism for a lens barrel includes a support frame supporting an imaging component, and a linear guide configured to guide the support frame along an axis. The linear guide can include a ring portion defining an opening through which the support frame can pass, and further includes at least one linear guide key extending along the axis from the ring portion and positioned substantially radially inwardly of the opening. The support frame has at least one linear guide groove located at the outer peripheral surface thereof and configured to slidably engage with a respective the at least one linear guide key, and each of the opposite ends of the at least one linear guide groove are open such that the support frame is movable to extend from either of the sides of the ring portion.