Optical design of uncooled high zoom ratio continuous-zoom lens

Aiming at the long-wave uncooled vanadium oxide focal plane arrays ( FPA) detector with 320240 pixels and 25 m25 m pixel pitch, an long-wave infrared continuous zoom optical system is designed, based on the optical zoom theory, as well as the aspheric and diffractive aberration balancing method. Its spectral range is 8 m～12 m, field of view(FOV) is 2.86～50,F number is 1.2 and zoom ratio is 18∶1. In the all optical zoom range, the modulation transfer function (MTF) is above 0.5 approaching the diffraction limit, and 70 % of the encircled energy is concentrated in one pixel of detector. Moreover, only one common infrared material of germanium is used to balance the aberration.