Preliminary design of a three-element zoom system based on a variable-focal-power lens

In this paper, we present the evaluation of a predesign of a zoom system based on a variable-focal-power lens by paraxial and aberration analyses only. This zoom system involves less mechanics and has a more compact design than those using a fixed-power lens. We derive corresponding formulas between the focal power of each lens and the magnification of the zoom system, and the bendings of the variable-focal-power lens elements are determined by introducing primary spherical aberrations. The calculation of the paraxial properties of zoom systems involves finding the solution of sets of simultaneous equations. Examples of the procedure are shown by applying it to previously designed three-element zoom systems. The results of this study are valuable in the design of future zoom systems.