Patent ID: 7544939

Claim:
A method for determining the aberration coefficients of the aberration function of a particle-optical lens, comprising: providing an amorphous sample with sample details, providing a beam of particles, providing a lens for focusing said beam in the vicinity of the sample, recording a 1 st transmission Ronchigram showing an image of a plurality of sample details, changing a beam parameter by a known quantity, recording a 2 nd transmission Ronchigram showing an image of approximately the same sample details, characterized in that the 1 st derivative of the aberration function as a function of the position in the image plane of the lens is defined as a polynomial function with coefficients to be determined, for a plurality of sample details the position of the image of the sample details is determined in each of the Ronchigrams, giving a plurality of position pairs, with the use of these position pairs and with the use of an algorithm, said algorithm dependent on the type of beam parameter changed, the coefficients of the polynomial function are determined by solving a set of equations.