Astigmatism, Curvature and Distortion of Diffractive Lenses on Finite Substrates

Reports on aberrational characteristics of diffractive lens usually assume the lens to be thin, with zero substrate thickness placed in air. Under these assumptions, the curvature and distortion becomes zero for both plane and curved diffractive lenses, with astigmatism given by H2K, where H is the paraxial invariant and K the lens power. However in real diffractive lenses on finite substrates, large variations in these aberrations take place from the ideal model. This paper presents analytical expressions for these aberrations with numerical results highlighting these variations for diffractive lenses.