The invention relates to a method of determining the distortions in the projection system of a TEM, and a method of correcting for these aberrations. The aberrations are determined by collecting a large number of images of a sample, the sample slightly displaced between each acquisition of an image. On the images sub-fields (303, 304-i) showing identical parts of the sample are compared. These sub-fields (303, 304-i) will show small differences, corresponding to differential aberrations. In this way the differential aberrations in a large number of points can determined, after which the aberrations for each point can be determined by integration. By now correcting the position of each detected pixel in an image to be displayed, the displayed image has much reduced aberrations. An advantage of the method according to the invention is that no highly accurate steps of the sample are needed, nor is a sample with known geometry needed.