1. A method for preparing a pattern to be printed on a plate or mask by electron beam lithography, comprising: modelling of the pattern by breaking down this pattern into a set of elementary geometric shapes intended to be printed individually in order to reproduce said pattern, and recording of the model obtained in memory, and for each elementary geometric shape of the model, determination, by a processor having access to the memory, of a dose of electrical charges to be applied to the electron beam during the individual printing of this elementary geometric shape, this dose being chosen from a discrete set of doses including several non-zero predetermined doses recorded in memory, wherein the set of elementary geometric shapes is a bidimensional paving of identical elementary geometric shapes covering the pattern to be printed, and wherein, when the doses to be applied to the geometric shapes are determined, a discretisation error correction is performed by dithering.