Abstract: Lenses, which include at least one plastic lens, are supported in a lens barrel by a lens holding structure which includes shoulder surfaces and inner circumferential surfaces of a lens barrel, at least one annular elastic member, and a retainer ring. The lenses are radially positioned in coaxial alignment with the lens barrel by the inner circumferential surfaces of the lens barrel, and axially positioned in engagement with the shoulder surfaces by the elastic member and the retainer ring. The elastic member elastically presses one of the lenses against one of the shoulder surfaces, and the retainer ring is threadedly mounted on the outer end of the lens barrel end holds the other lens against the other shoulder surface. Annular spacers may be disposed between the outer circumferential edges of the lenses and the inner circumferential surfaces of the lens barrel, for holding the lenses in coaxial alignment with the lens barrel.