In surveillance applications there is a need for infrared zoom systems which give two fields of view. For such
systems long operation range is the most critical parameter which is bound up with focal length and transmittance of
systems. In this paper the design of an infrared zoom system with rotating lens group is described. Different from the
conventional axially moving zoom systems, this system is based on a rotating mechanism consisting of two
separated lenses. The system achieves dual FOVs due to different magnifications. In narrow field of view mode, the
system has long focal length and higher transmittance because the rotating lens group is outside the optical path.
The final design is an infrared zoom system operating in 3μm~5μm, with a F number of 4.0, EFL of 250mm/62.5mm.
This paper contains the calculation of first-order parameter, the optimum design of rotating motion, the analysis of
aberrations, MTF, and Narcissus, This designed system has diffraction limited image quality of in both FOVs.