High-performance zoom lenses with a forward-located stop

Abstract

With the advent of digital camera systems which provide high performance imaging combined with reduced size, weight and cost, this has created a demand for zoom lenses to meet new specific requirements. In addition, there is also a need to meet preferred optical characteristics; therefore, contemporary zoom lens optical designs may become less attractive for use with modern digital camera systems. Zoom lens optical designs which more closely match digital camera requirements such as high resolution, high contrast, high relative illumination (for low picture shading), low residual chromatic aberration and near telecentric radiation output at the image sensor, are described in this paper. To achieve the desired requirements, the optical design power configuration of these zoom lenses comprise four lens groups, with a first negatively powered lens group followed by three positively powered lens groups. To provide zooming, a movable optical stop is located after the negatively powered lens group and is followed by two positively powered movable lens groups. Additional features including low ‘breathing’ throughout the focus and zoom ranges are also described via the optical design examples given.