Lens barrel and image pickup apparatus

An image pickup apparatus including a lens barrel,

• comprising an image-capturing optical system disposed inside the lens barrel;
• wherein
• the image-capturing optical system includes a movable lens disposed movably in an optical axis direction thereof, and a drive mechanism for moving the movable lens in the optical axis direction;
• the movable lens includes a lens and a lens frame holding the lens;
• the drive mechanism includes
• a male screw member extending along the optical axis direction,
• a motor revolving the male screw member,
• a female screw member being engaged with the male screw member and moving along the male screw member in response to the revolution of the male screw member,
• an engagement section provided on the lens frame so as to face an end along the optical axis direction of the female screw member, and
• a forcing member to force the lens frame in a direction abutting the engagement section to the end of the female screw member;
• the male screw member includes
• a male screw engaged with the female screw member, and
• a shaft having an outside diameter equal or less than an inside diameter of a female threaded element included in the female screw member, the shaft extending on a same shaft of the male screw from an end of the male screw, the end being positioned at an opposite direction to a direction in which the engagement section is in abutment with the end of the female screw member;
• and
• the female screw member is disposed such that the female screw member can move along the male screw of the male screw member and that the female screw member can move from the male screw to a spot on the shaft in abutment with the male screw whereat the female screw is no longer engaged with the male screw and the female screw member is prevented from moving past said spot on the shaft in the direction opposite the direction abutting the engagement section even if the male screw member continues to revolve.