Abstract: The present invention provides a lens barrel in which all lens groups are attached to a leading cylindrical body. A movable lens group of the lens groups is moved by a driving source incorporated in the leading cylindrical body. The lens barrel is less likely to be influenced by external forces and can be made smaller. The lens barrel includes first, second, and third cylinders, and first, second, and third lens groups attached to the third cylinder, which is extended first among the first, second, and third cylinders. The first and third lens groups are fixed to the third cylinder, and the second lens group is disposed between the first and third lens groups and movable along the optical axis.

Abstract: A moving mechanism for a cylinder is provided, in which a projection and groove are engaged by relative movement different from that of a helicoid mechanism and movement of inner and outer cylinders relative to each other can be freely set. In the moving mechanism, a first helicoid thread is helically formed on the inner surface of an intermediate cylinder, a second helicoid thread that threadably engages with the first helicoid thread is helically formed on the outer surface of a movable cylinder, and the intermediate cylinder is rotated so the movable cylinder is moved relative to the intermediate cylinder. A projection is formed on the outer surface of the movable cylinder and a groove engageable with the projection is formed in the inner surface of the intermediate cylinder. In a range where the first and second helicoid threads threadably engage with each other upon relative movement of the movable cylinder, the groove is formed parallel to the first helicoid thread.

Abstract: The present invention provides a lens barrel which can carry out barrier opening/closing operations and lens moving operations of a lens optical system by use of a single driving source, and can adjust the focus without any obstruction even in a state allowing the barrier to open/close. A state capable of transmitting a driving force to a barrier opening/closing mechanism is attained when collapsing a lens barrel 1 to a predetermined extent or more, and a state incapable of transmitting the driving force to the barrier opening/closing mechanism is attained when the lens barrel 1 is expanded to a predetermined extent or more, whereby a single motor can carry out barrier opening/closing operations and lens moving operations of a lens optical system.

Abstract: A barrier opening and closing apparatus for opening and closing a barrier according to a rotation of a lens barrel containing an optical lens system comprises a ring member disposed rotatable about an optical axis of the optical lens system and adapted to open and close the barrier according to a rotation thereof, whereas the ring member forms a plurality of rotational force transmitting parts extending rearward therefrom in parallel to the optical axis so as to be engaged with the lens barrel. The ring member is directly rotated by way of the plurality of rotational force transmitting parts engaged with the lens barrel, so as to open and close the barrier, whereby the cost of apparatus can be cut down.