Gray level imaging masks, optical imaging apparatus for gray level imaging masks and methods for encoding mask and use of the masks

Abstract

A grayscale mask for imaging operations, including a substrate layer and a mask layer having a plurality of apertures forming a mask pattern to form a grayscale image. Each edge of each aperture includes a plurality segments forming a serrated edge, resulting in mixed edge diffraction. The apertures may be in an irregular and non-symmetric pattern and may be of variable size. A random diffusing layer may be in proximity to or integral with the substrate layer. The grayscale mask may be used for generating an optical element by printing the initial grayscale mask onto a photoresist layer and transferring the photoresist pattern onto a transparent layer and the mask may include areas or layers of variable transmission. Also described are methods for diffractive intensity averaging, diffractive error diffusion, diffractive spatial dithering, and diffractive intensity averaging.