Design of a compact wide-band optical system based on double-layer diffractive elements

Diffraction optical elements(DOEs) have significant advantages in wideband achromatization and athermalization and are widely used in wideband optical systems. Based on the bandwidth-integrated average diffraction efficiency (BIADE) model, a double-layer diffractive optical element (D-DOE) suitable for wideband applications is designed using BaF₂ and Sapphire materials.By combining it with refractive elements, a wideband optical system with an F-number of 4.9 and a focal length of 24 mm for the ultraviolet-shortwave infrared (0.35~2 µm) range is designed, which can achieve athermalization within the temperature range of−40~80 ℃. At the Nyquist cutoff frequency of 41 lp/mm, the modulation transfer function (MTF) of all fields of view in the ultraviolet-visible (0.35~0.78 µm) and near-infrared-shortwave infrared (0.78~2 µm) bands is greater than 0.65 and 0.5, while maintaining an ultra-compact form factor measuring just 30 mm×11 mm with a total weight of only 2.35 g. This system has significant advantages in improving image quality and miniaturizing the system.