Development of a 16X zoom lens for an aeronautical application and evaluation of its performance

‘Ab initio’ design and its prototype development of a compact 16X zoom lens are reported in this paper. The principle of mechanical compensation is used in this design. From the prespecified size of the target located at a specific range and given specifications of the sensor, the required optical specifications of the zoom lens are worked out based on Johnson’s criterion. Axial positions of the variator and the compensator were worked out for the thin lens layout for nine different zoom lens configurations. The configurations were suitably chosen to cover the zoom range. Each thin lens component of the zoom lens was thickened keeping the overall paraxial characteristics of the system unaltered. A prophylactic strategy was adopted to prevent the occurrence of unwanted aberrations by splitting the elements as and when necessary. Tolerancing of all optical and optomechanical elements was performed to ensure the required zoom lens performance at a reasonable cost. The procedure adopted for environmental stress screening as per military standard of the developed zoom lens is described. The design data is used to evaluate image quality at three field positions for each of the nine zoom lens configurations. Results for seven different image evaluation parameters are presented.