Abstract: A vari-focal lens system comprising, in the order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power and an aperture stop arranged on the image side of said third lens unit, using at least one radial GRIN lens, axial GRIN lens or aspherical surface, and having a high vari-focal ratio and a wide field angle at the wide position.

Abstract: A lens system comprising, at locations in the vicinity of each other, radial type graded refractive index lens elements made of a medium having a positive refractive power and other radial type graded refractive index lens elements made of a medium having a negative refractive power. This lens system has aberrations corrected favorably with the radial type graded refractive index lens elements which are made of materials easily preparable.

Abstract: A compact vari-focal lens system having a high vari-focal ratio, comprising a plurality of lens units including at least one lens unit having a positive refractive power and at least one lens unit having a negative refractive power, and adapted so as to change focal length thereof by moving one of said lens units along the optical axis, the lens unit arranged on the extremely object in said lens system having a positive refractive power and at least one radial GRIN lens being used in a negative lens unit.

Abstract: A rear converter lens system comprising, in the order from the object side, a first lens component having positive refractive power and a second lens component having negative refractive power, and having aberrations, especially Petzval's sum and chromatic aberration, corrected favorably by using at least one GRIN lens element in the lens system.

Abstract: A large-aperture quasi-telephone lens system having favorably corrected aberrations, especially chromatic aberration, and providing images of high quality comprising, in the order from the object side, a front lens group, a stop and a rear lens group, said rear lens group consisting of a lens component having negative refractive power and a lens group having positive refractive power, and comprising at least one graded refractive index lens element.

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 vari-focal lens system comprising, in the order from the object side a movable front lens unit having negative refractive power and a movable rear lens unit having positive refractive power, said front lens unit consists of a negative lens component and a positive lens component or a single negative lens component, and said rear lens unit comprising at least one negative lens component. Said vari-focal lens system consists of a very small number of lens components, concretely specifically three or four lens components.

Abstract: A light-weight zoom lens system manufacturable at a low cost 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 positive refractive power, and adapted in such a manner that said first lens unit and said fourth lens unit are fixed at the zooming time, whereas said second lens unit and said third lens unit are shifted along the optical axis while varying the airspace reserved therebetween. Said second lens unit comprises one or two lens elements and said third lens unit comprises a single lens element, whereby said zoom lens system comprises a small number of lens elements.

Abstract: A zoom lens system comprising a first lens group having positive refractive power and a second lens group having negative refractive power, and so adapted as to perform zooming from the wide position to the teleposition by narrowing the airspace reserved between the two lens groups. In said zoom lens system, at least one graded refractive index lens component is arranged in the second lens group, or at least one graded refractive index lens component is arranged in the first lens group and at least one aspherical surface is adopted in the second lens group.

Abstract: A compact zoom lens system with a zooming ratio of about 2 and a large aperture ratio comprises, in order from the object side, a front lens group having a positive refracting power and a rear lens group having a negative refracting power, which is arranged to be zoomed by varying the space between the both lens groups, and in which the front lens group comprises a negative lens component and a positive lens component and the rear lens group comprises a positive lens component and a negative lens component so that this lens system comprises four components as a whole.