Abstract: A vari-focal lens system having short total length comprising, in the order from the object side, a vari-focal subsystem consisting of a first lens unit having a positive refractive power and a second lens unit having a negative refractive power; and an imaging subsystem consisting of a third lens unit having a positive refractive power and always kept stationary, and a fourth lens unit having a positive refractive power and movable for correcting deviation of image point; said third lens unit being composed of four or a smaller number of lens elements including a positive lens element which is arranged on the object side in the third lens unit and has a convex surface on the object side, and a negative lens element, and said imaging subsystem comprising at least one aspherical surface.

Abstract: A variable focal length lens system comprising a plurality of lens units, arranged with an imaging lens unit with a positive refractive power being located at the image side, and at least one lens unit being movable to change an airspace for varying focal length. The positive lens unit for image formation is made of at least one radial GRIN lens, arranged to distribute a stop at the object side of said lens unit. By utilizing a lesser numbers of lenses, it is possible for this vari-focal lens to have simpler processing, assembly, and adjustment of lenses and lens burrels with an efficient performance.

Abstract: A zoom lens system comprising a first lens unit having negative refractive power and a second lens unit having positive refractive power, so adapted as to change focal length thereof by varying the airspace reserved between said first lens unit and said second lens unit, and using at least one radial GRIN lens in said first lens unit. Said zoom lens system comprises a very small number of lens elements, and has distortion and chromatic aberration corrected especially favorably.

Abstract: A zoom lens system having a wide field angle, a long back focal length, a high zooming ratio, and comprising a small number of lens elements. Said zoom lens system comprises, in the order from the object side, a front lens unit having negative refractive power and a rear lens unit having positive refractive power, and is so adapted as to perform variation of focal length, said front lens unit consisting of a negative meniscus lens element having a convex surface on the object side, a negative lens element and a positive lens element, whereas said rear lens unit comprising, on the extremely image side therein, a positive lens component consisting of a positive lens element having a short radius of curvature on the image side surface thereof and a positive lens element having a short radius of curvature on the object side surface thereof.