Proceedings PaperToward the global optimum in zoom lens design
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After more than a century from the introduction of zoom lenses, the selection of the right zoom lens type for a given specification is still a challenge for the optical designer. In the process of lens design, the optical designer is permanently searching for the best zoom lens structure in order to fulfill the complex balance between weight, cost and optical performance. This is a continuous optimization process and the result is a global optimum. The most important factors influencing zoom lens cost are: the number of spherical and aspherical lenses, the number of moving groups and lenses and finally the group sensitivity to displacement and tilt. Every lens group whether moving or not inside the zoom lens, has a specific complexity and sensitivity behavior dependent on the zoom lens type. It is not obvious which type of zoom lens will optimally satisfy the required specification. This paper describes the selection process exemplary for a zoom lens with a medium focal length range from 28mm to 80mm and a quasi constant f-number (FNO) during zooming. The lens is used mainly for cinematographic applications and must be able to maintain best image position for the entire range of object positions during zooming. Alternative solutions with their advantages and disadvantages are shown, analyzed and evaluated.