Patent ID: 7019914

Claim:
A lens barrel which holds a zoom lens consisting of a plurality of lens groups, the lens barrel comprising: a fixed tube, a straight-ahead key member which is engaged with the fixed tube to be able to advance or retract, a middle tube which is rotatably engaged with the straight-ahead key member and is caused by cam engagement with the fixed tube to advance or retract along with the rotation; and a front tube which is engaged with the straight-ahead key member to be able to advance or retract and is caused by cam engagement with the middle tube to advance or retract along with the rotation of the middle tube, wherein the zoom lens is configured of a plurality of lens groups consisting of a first lens group which is fixed to the front tube, a second lens group, a third lens group and a fourth lens group which are fixed to the straight-ahead key member or supported by the straight-ahead key member to be able to advance or retract.