Correction of chromatism of dual-infrared zoom lenses

Using the example of a simple-by-design mid-wave and long-wave dual-band infrared zoom lens consisting of three two-lens components made of silicone and germanium, the possibility of reducing chromatic and monochromatic aberrations to a level that ensures sufficiently high quality of the formed image is demonstrated at spatial frequencies of up to 25 inverse millimeters. As one of the possible ways to modify the zoom lens, it is proposed to place a two-layer two-relief diffractive microstructure on the flat surface of the refractive lens closest to the aperture stop. The efficiency of the transition to the refractive-diffraction scheme is confirmed by the results of calculation and optimization of a zoom lens, the two-lens components of which are made of silicone and amorphous glass of the IRG26 brand.