Zoom Lens Four-Group Configuration for Compact Size

The zoom lens is divided into four distinct lens groups (first, second, intermediate, and final lens groups) with specific refractive power distributions. The intermediate lens group is further segmented into one or two sub-groups, allowing independent movement control. This segmentation enables the patent to achieve structural stability through defined group boundaries while reducing overall length by allowing all distances between adjacent groups to change dynamically during zooming, rather than maintaining fixed distances between some groups as in conventional designs.

The patent optimizes optical performance by precisely controlling refractive power parameters and material properties (Abbe numbers and refractive indices) of each lens group. Specific conditional expressions define the relationships between these parameters: the first lens group has positive refractive power with specific Abbe number ranges, the second lens group has negative refractive power with controlled temperature coefficients, and the intermediate and final groups have configured refractive powers that satisfy mathematical relationships. This parameter optimization allows achieving excellent optical performance with a relatively compact four-group configuration rather than requiring more complex multi-group designs.

The patent implements full dynamic zooming capability where the second lens group moves along the optical axis and all distances between adjacent lens groups change simultaneously during zooming operations. This dynamic configuration provides superior zooming flexibility compared to conventional designs with fixed distances between certain groups. The mechanical complexity is managed by defining clear movement relationships: the first lens group may remain stationary or move, the second lens group moves to enable zooming, and the intermediate and final groups move in coordinated fashion, creating a systematic dynamic structure rather than an ad-hoc complex mechanism.