Infrared lens selection using weighted dispersion derivative

With the increased prevalence of dual-band infrared systems arising for a variety of imaging applications, lens material selection becomes a key point of interest in optical design activities. Correcting chromatic aberration across infrared bands is challenging due to unique material dispersion and limited viable substrates. Procurement issues affecting infrared substrates also make sufficient achromatic solutions less trivial. For achromatization, optical designers often use software optimization or effective glass maps, which may be computationally expensive or inadequate for dual-band projects. In addition, many selection frameworks do not consider wavelength weights or importance in dispersion calculations. We develop a computational method to nominate the best achromatic material sets for a given wavelength weighting scheme. Conditions for a minimally varying paraxial spot size over a band are derived, and a dispersion metric for several materials is computed over a test waveband with atmospheric transmission weighting. Material selection choices are cross-verified with literature to demonstrate credibility. Finally, air-spaced achromatic doublet and triplet solutions are proposed for the dual-band mid- and long-wave infrared. This technique can drastically increase the efficiency of the design process for optical engineers tasked with dual-band or multi-band requirements and provide accurate/reliable achromatic solutions for a variety of customizable applications.