JPS6431109A - Lens barrel - Google Patents

Abstract

PURPOSE:To reduce the outside diameter of a lens barrel and to stabilize the core of a lens group by transmitting the quantity of backward and forward movement in an optical-axis direction at the time of zooming to a cam member, transmitting the quantity of backward and forward movement of the cam member to a focusing lens frame through a driving shaft, and rotating the driving axis around its axis with the driving force of a driving source. CONSTITUTION:When a lens group II moves linearly from its wide-angle (wide: W) position to its telephoto (tele: T) position, a lens group I also shifts in extension position according to variation in focal length. Then the lens group I enters focusing operation from an infinite distance to a short distance according to a object distance. Namely, when a cam cylinder 10 also moves by the movement of a II group lens frame 2 in the optical-axis direction and reaches a position T, a I group lens frame 1 reaches an extension position corresponding to the position T. Thus, the cam member 10 which is fitted onto a fixed shaft is used to reduce the outside diameter of the lens barrel and the focusing frame need not be separated from zooming, so the core of the focusing lens group can be stabilized.