Influence of side diffraction orders on image quality formated by a refractive-diffractive mid-IR optical system

The image formed by a refractive-diffractive optical system for the mid-IR range (3–5 $\mu$m) is investigated. The effect of the side diffraction orders of the diffractive corrector on the quality of this image near the optical axis is estimated both by computer simulation and experimentally. It is shown that the side diffraction orders of a single-layer sawtooth relief-phase microstructure will not noticeably affect the image quality under the following condition: the diffraction efficiency of the microstructure at the central wavelength of the operating spectral range is close to unity, and within the entire indicated spectral range it does not drop below 0.67.