Zoom lens system having enlarged range of variation in magnification

Claim 1

A zoom lens system having an enlarged range of variation in magnification, comprising: an afocal zoom lens section, having a focusing lens group, a variator lens group, a compensator lens group and a fixed convergent lens group composed of a plurality of lens elements; a diaphragm arranged between the compensator lens group and the fixed convergent lens groups; a convergent image forming lens arranged apart and a certain length from the convergent lens group of the zoom lens section; and an afocal extending assembly for changing image magnification composed of a front convergent group and a rear divergent group being axially apart from the front convergent group, said front convergent group and said rear divergent group being composed of a plurality of spherical lenses, said assembly being removably inserted between the convergent lens group of the zoom lens portion and the convergent image forming lens, said zoom lens system haing an increased focal length when said assembly is inserted in comparison to the focal length of the zoom lens when said assembly is removed while maintaining the same image position, wherein said converging group in said afocal extending assembly is composed of a negative meniscus lens and an axially spaced positive lens, and wherein said divergent group is composed of a positive lens arranged at the object side and an axially spaced biconcave lens, whereby an image of equal quality is formed on the focal plane when the afocal extending assembly is mounted and dismounted.