1. A method for adjusting a projection exposure machine used for microlithography in the fabrication of semiconductor components and having an illumination device for providing an illumination beam and a projection objective comprising a plurality of optical elements in the path of the illumination beam for projecting an image of structures on a reticle onto a substrate at an image plane, said method comprising the steps of: (a) measuring initial values for two or more parameters at each of a plurality of points in a field at the image plane, each parameter corresponding to a respective imaging property of the projection objective, wherein for each parameter there are one or more corresponding points in the field having an initial value that has a largest absolute value compared to the initial values of the other points in the field; and; (b) adjusting the reticle and/or at least one of the optical elements of the projection objective such that, for each of the parameters, the largest absolute value for the points in the field is reduced compared to the initial values.