LENS BARREL AND HELICOID SCREW APPLIED TO LENS BARREL

PROBLEM TO BE SOLVED: To provide a lens barrel having a helicoid screw which is much higher in impact resistance.SOLUTION: A lens barrel 1 having a helicoid screw includes: a first cylindrical member 14 having a male helicoid screw 14b formed in the outer periphery of a cylindrical member, the male helicoid screw which being configured such that the tooth width of the male helicoid screw is gradually made wider along a flank surface 14d according as it descends from the summit of the male helicoid screw to the direction of a valley bottom on a cross section which is vertical to the tooth line direction, and that a ridge line 14e extending in the tooth line direction in parallel with the summit of the male helicoid screw in the middle of the flank surface 14d of the male helicoid screw, and that tooth width W2 on the valley bottom is made smaller than tooth width W1 on the ridge line with the ridge line as a boundary; and a second cylindrical member 12 having a female helicoid screw 12b formed so as to be screwed into the male helicoid screw in the inner periphery of the cylindrical member, the female helicoid screw which being configured such that the ridge line slides on a flank surface 12d of the female helicoid screw.