Surface-profile optimization of diffractive 1 : 1 imaging lenses

Local optimization of surface-relief profiles of diffractive high-numerical -aperture imaging lenses is considered in the 1:1 imaging geometry for both linearly polarized illumination and unpolarized illumination by using the transition points of a four-level grating as design parameters. In the imag ing geometry the optimized surface profiles differ considerably from those optimized previously for focusing or collimation geometries. Binary surface -relief grating structures are shown to provide high local diffraction effi ciencies (up to 95%) in the outer regions of a high-numerical-aperture diff ractive imaging lens because of the near-Littrow configuration. (C) 2001 Op tical Society of America.