Patent ID: 7310796

Claim:
A method for generating a simulated aerial image, comprising: forming a reference aerial image of a first mask for an optical system; capturing and processing the reference aerial image so as to generate a set of expansion functions representative of aberrations in the optical system; and computing the simulated aerial image of a second mask for use in the optical system by applying the expansion functions to a design of the second mask, wherein the first mask comprises a pseudo-noise pattern characterized by a transmission function g that approximates a condition: ∫∫ g ( {right arrow over (x)}−{right arrow over (z)} 1 )● g ( {right arrow over (x)}−{right arrow over (z)} 2 ) ● g ( {right arrow over (x)}−{right arrow over (z)} 3 )● g ({right arrow over (x)}−{right arrow over (z)} 4 ) d{right arrow over (x)}=G δ( {right arrow over (z)} 1 −{right arrow over (z)} 3 ,{right arrow over (z)} 2 −{right arrow over (z)} 4 ) wherein: G is a constant, {right arrow over (z)} j {j=1, 2, 3, 4} are arbitrary vectors. {right arrow over (x)} is a vector in a mask plane in the optical system, and δ is a function of {right arrow over (z)} j {j=1, 2, 3, 4}.