Varifocal optical system for zoom lens having ultra-high zoom ratio

Claim 1

A varifocal optical system for zoom lens systems located in front of a rear convergent optical system and having an ultra high zoom ratio comprising; A first convergent stational lens group consisting of a first positive meniscus doublet of which the front and rear surfaces and the cemented surfaces are convex toward the object, a second biconvex doublet provided behind said first doublet, the cemented surfaces of said second doublet being concave toward the object, and a third positive meniscus simple component placed behind said second doublet, the surfaces of said third component being convex toward the object; A second divergent moveable lens group consisting of first and second negative meniscus simple components of which the surfaces are convex toward the object, and a third biconcave doublet placed behind said second meniscus component, the cemented surfaces of said third doublet being convex toward the object; an A third convergent moveable lens group consisting of a first positive meniscus component of which the front surface is concave toward the object, second and third biconvex simple components placed behind said first positive meniscus component, and a fourth biconvex doublet placed behind said third biconvex component, the cemented surfaces of said fourth doublet being concave toward the object, whereby said second lens group is moved over a wide range for affecting zooming operation, while the third lens group is moved in the direction opposite to that of said second lens group for maintaining the position of the image surface constant.