Abstract: A zoom lens system comprising, in the order from the object side, a first lens unit having a positive refractive power, a second lens unit having a positive or negative refractive power, a third lens unit having a positive refractive power and a fourth lens unit having a negative refractive power, adapted so as to perform variation of focal length by moving said lens units along the optical axis, and adapted so as to perform focusing by moving at least one of the lens units other than said first lens unit. This zoom lens system can be focused on an object located at a very short distance.

Abstract: A zoom lens system comprising, in the order from the object side, a first lens unit having a positive refractive power, a second lens unit having a weak refractive power (i.e., less than 0.01), a third lens unit having a positive refractive power and a fourth lens unit having a negative refractive power, and adapted so as to perform variation of focal length thereof by varying airspaces reserved between the lens units. This zoom lens system has a broad vari-focal range covering a super wide field angle.

Abstract: The present invention provides a zoom lens system comprising, in the order from the object side, a first lens unit having positive refractive power, a second lens unit having positive refractive power and a third lens unit having negative refractive power, and adapted so as to perform zooming by varying the airspaces reserved between the lens units and permit photographing at an expanded tele position providing a focal length longer than that of the zoom lens system as a whole at the tele position by setting the airspace reserved between the second lens unit and the third lens unit at a width smaller than that at the tele position.

Abstract: A zoom lens system of inner focus type including a first lens group having positive refractive power, a second lens group having positive refractive power and a third lens group having negative refractive power. The zoom lens system is so designed as to perform focusing by shifting the second or third lens group for a short distance along the optical axis and to minimize variation of aberrations caused due to focusing.

Abstract: A compact high vari-focal lens system permitting simplifying the lens barrel structure and having favorable performance; comprising a first lens group having positive refractive power, a second lens group having positive refractive power and a third lens group having negative refractive power, and so adapted as to perform zooming by shifting the first lens group integrally with the third lens group and shifting the second lens group.

Abstract: A compact zoom lens system with a high zooming ratio comprises, in order from the object side, a first lens group having a positive refracting power, a second lens group having a positive refracting power and a third lens group having a negative refracting power, in which the first lens group, the second lens group and the third lens group are respectively moved on the optical axis toward the object side during the zooming operation taking place from the wide-angle position as the reference point to the telephoto position, and at least one graded refractive index lens of an axial type which has the distribution of its refractive index in the direction of the optical axis is arranged in at least one lens group, so that the zooming ratio exceeds 2, the fluctuation of aberrations during the zooming operation is small and the flatness of the image surface is favorable.

Abstract: A telephoto zoom lens system comprising a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a stop fixedly arranged in respect to the third lens group, wherein the first lens group comprises a positive lens and a negative lens, the telephoto zoom lens sytem being arranged to be zoomed by moving the first lens group, the third lens group and the stop in the same direction and further arranged that the variation in the position of the entrance pupil to be caused at the time of zooming is small, it is possible to ensure satisfactory intensity of light in the marginal portion, and aberrations are corrected favorably.

Abstract: A compact high vari-focal ratio zoom lens system comprising a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having negative refractive power, in the order from the object side, and arranged to move respective lens groups toward the object side at the time of zooming from the wide position to the teleposition, the compact high vari-focal ratio zoom lens system being arranged to adequately distribute the refractive power to respective lens groups and thereby arranged to have a high vari-focal ratio, to be small in sized and to have favorable performance.

Abstract: A telephoto zoom lens system comprising a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group comprising a front subgroup, which has positive refractive power, and a rear subgroup, the telephoto zoom lens system being arranged that the focal length thereof is varied by moving the first, second and third lens groups along the optical axis in the state that the varifocal functions is alloted to the second and third lens groups so that the magnifications of both of them increase at that time, the telephoto zoom lens system being thereby arranged to be small in size, high-performanced and low cost.

Abstract: A zoom lens system comprising a first lens group G.sub.1 having positive refractive power, a second lens group G.sub.2 having negative refractive power, a third lens group G.sub.3 having positive refractive power, a fourth lens group G.sub.4 having positive refractive power, and a fifth lens group G.sub.5 having negative refractive power, in the order from the object side, and arranged to vary the focal length or the lens system as a whole by moving, out of the above-mentioned lens groups, at least the first lens group G.sub.1, third lens group G.sub.3 and fourth lens group G.sub.4 along the optical axis, the zoom lens system being arranged that the vari-focal range thereof includes a position in the range of wide field angle, the vair-focal ratio thereof is high, i.e., 6, favorable performance is maintained over the whole vari-focal range, and the lens system as a whole is made small in size.

Abstract: A compact zoom lens system with a high zooming ratio comprises a first lens group having a positive refracting power, a second lens group having a positive refracting power and a third lens group having a negative refracting power, and is a three groups-type lens system arranged to be zoomed by respectively varying the spaces on the optical axis among the respective lens groups in which optical performance is favorable through out the zooming range.

Abstract: A telephoto lens system comprising, in the order from the object side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, and a fourth lens unit having negative or positive refractive power, the telephoto lens system being arranged to be focused by integrally moving the first through the third lens unit and arranged that the secondary spectrum is corrected extremely favorably, and the variation of aberrations to be caused is small when the lens units are moved for the purpose of focusing, the telephoto lens system being small in size and having high performance.