Research on development of aspheric diffractive optical element for mid-infrared imaging

The aspheric diffractive singlet achromat design in precision infrared optical systems is used to reduce chromatic aberration. With the advancement in micro-optics, conventional lenses are replaced by diffractive and aspheric diffractive lenses with sub-structures to fulfill the requirements of miniaturized and compact designs of the optical devices. In this paper, the design and development of a high precision aspheric diffractive germanium lens is described. Specifically, the aspheric diffractive lens was designed for Mid Wave Infrared (MWIR) range to achieve an aberration free and diffracted limited surface fabricated by the diamond turning process. The profile of the machined aspherical diffractive lens was measured by optical profilometer and the results demonstrated a step height error of 0.001 µm and radial error of 0.001 mm. A smooth quality aspheric diffractive lens was fabricated with 99.57% diffraction efficiency.