Influence of Secondary Diffraction Orders on the Quality of Image Formed by a Mid-IR Refractive–Diffractive Optical System

The influence of secondary diffraction orders of a diffraction corrector of chromatic aberration on the quality of an image near the optical axis formed by a refractive–diffractive optical system operating in the mid-IR range (3–5 µm) has been investigated experimentally and using computer simulation. It is shown that secondary diffraction orders of a single-layer sawtooth relief-phase microstructure, the diffraction efficiency of which at the central wavelength of the operating spectral range is close to unity, barely affect the image quality provided that the diffraction efficiency is not below 0.67 within the entire spectral range.