A linear guide mechanism for guiding rings supporting components of a lens barrel along an optical axis includes an outer ring supporting a first imaging component; an inner ring positioned radially inwardly of the outer ring for supporting a second imaging component; a first guide ring configured to linearly guide the outer ring without rotation of the outer ring; a second guide ring configured to linearly guide the inner ring without rotation of the inner ring; and a linear guide ring having at least one guide portion located on an inner peripheral surface of the linear guide ring, the at least one guide portion engageable with the first and second guide rings, the outer ring and the inner ring being independently guidable via the respective first and second guide rings and are movable linearly along the optical axis without rotating.