Design of dual-band infrared lens with multilayer diffractive optical element

Diffractive optical elements (DOEs) are widely used in different kinds of optical systems with its special dispersion characteristics, which include the dual-band lens. However, the single-layer DOEs (SLDOEs) suffer from the problem that the diffraction efficiency decreases significantly as the wavelength deviates from the design wavelength. So the selection of DOE is not necessary. A high diffraction efficiency of the multilayer diffractive optical element in the dual frequency band was investigated, Based on the scalar diffraction theory. The relationship between substrate material selection and diffraction efficiency of obliquely incident dual-band multi-layer diffractive optical elements under universal working conditions is derived. The influence factors of diffraction efficiency are analyzed. A material selection for quickly obtaining high-bandwidth integral diffraction efficiency is proposed. By this method, the optimal base material combination of the multilayer diffractive optical element can be quickly selected in a large-angle dual-band system. A medium wave-long wave infrared double frequency lens is designed by the ZEMAX commercial software.The transfer function of the system is greater than 0.4 in the medium wave and greater than 0.3 in the long wave. So the chromatic aberration of hybrid lens is corrected in infrared dual-band, and high image quality can be achieved.