DESIGN OF A TRIPLE FIELD-OF-VIEW OPTICAL SYSTEM FOR MID-WAVELENGTH INFRARED STEP-ZOOM CAMERA

Abstract

The design of a triple field-of-view optical system operating in a mid-wavelength infrared band for thermal imagers is presented in this work. The FOV-changing is done by using different FOV-changing lens-group. The designed optical system has a simple structure, consisting of 6 lenses and made by just one material (Si). They are divided into 3 groups: the front objective, the FOV-changing lens-group and the relay lens, including only three conic surfaces. The designed optical system has relatively high imaging performance: modulation transfer function (MTF) at a frequency of 20 cycles/mm is higher than 0.24, image distortion less than 2.5% and is suitable for mid-wavelength infrared step-zoom camera.