Optical design for refractive/diffractive long wavelength infrared continuous zoom system

A refractive/diffractive long wavelength infrared continuous zoom system was designed based on the new staring focal plane array (384 pixel × 288 pixels) in order to improve the resolution of image, detecting distance and accuracy of the infrared system and to satisfy multifarious situations. The operating wavelength of this system ranged from 8 μm to 12 μm, F number was 1.5 and the zoom ratio was 25:1. The binary surface was introduced to correct the lateral color and other high order aberrations and to modify the system. Moreover, detailed design and image quality were given by CODE V optical design software. When spatial frequency was 20 lp/mm, modulation transfer function (MTF) in the whole field of view exceeded 0.4', approaching diffraction limit. The final results show that this optical system has large zoom ratio, high resolution, small volume and excellent image quality. Thus, it can be applied in many kinds of optoelectronic detection fields.