Abstract: A zoom lens system comprises, from the object side, a first lens unit having a positive refractive power, a second lens unit having a positive refractive power and a third lens unit having a negative refractive power. During zooming, the sizes of the first area of empty space between the first lens unit and the second lens unit and the second area of empty space between the second lens unit and the third lens unit change.

Abstract: A zoom lens system includes from the object side a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power. The third lens unit includes from the object side a positive lens and a negative lens. The zoom lens system meets the following conditions.1<.vertline.f.sub.3P /f.sub.3 .vertline.<3.050.1<.vertline.f.sub.3 /f.sub.T .vertline.<0.22wheref.sub.3P : focal length of the positive lens,f.sub.3 : focal length of the third lens unit, andf.sub.T : longest focal length of the entire system.

Abstract: A zoom lens system includes a positive lens unit and a negative lens unit. Focusing in a focal length range from a shortest focal length condition to a middle focal length condition is performed by moving the positive lens unit, and focusing in a focal length range from the middle focal length condition to a longest focal length condition is performed by moving the negative lens unit. The zoom lens system fulfills the following condition: ##EQU1## where B.sub.f is a distance from a rear end surface of the zoom lens system to a film at the shortest focal length condition and .DELTA.t is a diagonal length of the film.

Abstract: A zoom lens system consists of sequentially from the object side a first lens unit having a negative refractive power, a second lens unit having a positive refractive power and a third lens unit having a negative refractive power. Zooming is performed by shifting the second lens unit and the third lens unit. The first lens unit keeps stationary during the zooming. Focusing is accomplished by shifting the second lens unit. The lengths of the first and the second lens unit along the optical axis are optimized so as to fulfill the conditions. The zoom lens system is suitable for particularly underwater cameras.

Abstract: An apparatus for driving a collapsible lens mount having several telescoping segments includes, for each movable segment, a transducer that expands and contracts responsive to a wave pulse and a drive shaft coupled to the transducer. By varying the wave pulse conditions, the expansion and contraction are made to occur at different rates. A coupling member on each segment frictionally engages the drive shaft and transmits movement of the drive shaft during relatively slow drive shaft movements to the lens segment. The apparatus may also include a lens hood driven by the transducer and drive shaft apparatus of the invention.

Abstract: A zoom lens system has, from the object side to the image side, a first lens unit of positive power, a second lens unit of positive power and a third lens unit of negative power. Each lens unit has two lens elements. The air space between the first and second lens units and the air space between the second and third lens units are varied during a zooming operation. The zoom lens system fulfills the following condition: ##EQU1## Here, f1 is a focal length of the first lens unit and fW is a focal length of the entire lens system at the shortest focal length condition.

Abstract: A zoom lens system for a limited conjugate distance comprises at least three lens units which can be divided into, from an object side to an image side, a front lens group having a positive refracting power and a rear lens group having a positive refracting power. An axial distance between the front lens group and the rear lens group varies by a focusing operation. A zooming operation is performed by one of the front lens group and the rear lens group including at least two lens units. The zoom lens system fulfills the condition of l=m wherein l represents an object focal length of the zoom lens system, and m represents an axial distance between an object point and an object principal point of the front lens group.