Dual-band antireflection coatings on 3rd Gen lenses

Use of a dual band FPA necessitates an optical system that is capable of imaging both mid wave infrared (MWIR) and long wave infrared (LWIR) spectral bands simultaneously. Such optical system can have up to 10 lenses, (20 surfaces that require antireflection (AR) coatings) which, if 95% transmitting in each band, will result in overall throughput of just under 60%(1). With 99% transmitting in each band, overall throughput would be just over 90%, a relative improvement of 50%. An earlier paper presented dual band antireflection designs, as well as early fabrication attempts on plano Ge, ZnSe, ZnS, AMTIR-1, and CaF2 windows(2). This paper presents results of prototype coating fabrication on ZnSe, Ge, and BaF2 lenses that comprise a 7 lens set. The measured performance of the individual elements is used to model overall system performance. The elements were incorporated into an optical assembly and measured overall imager performance is analyzed and presented.