Abstract: The invention relates to a method and an apparatus for measuring masks for photolithography. In this case, structures to be measured on the mask on a movable mask carrier are illuminated and imaged as an aerial image onto a detector, the illumination being set in a manner corresponding to the illumination in a photolithography scanner during a wafer exposure. A selection of positions at which the structures to be measured are situated on the mask is predetermined, and the positions on the mask in the selection are successively brought to the focus of an imaging optical system, where they are illuminated and in each case imaged as a magnified aerial image onto a detector, and the aerial images are subsequently stored. The structure properties of the structures are then analyzed by means of predetermined evaluation algorithms. The accuracy of the setting of the positions and of the determination of structure properties is increased in this case.

Abstract: The invention relates to a method for analyzing the imaging behavior of a first optical imaging element, whereby an object is imaged into an image plane by a second optical imaging element and light in the image plane is detected in a spatially resolved manner, the two optical imaging elements differing in terms of at least one imaging characteristic. Values are determined for the intensity and for at least one second characteristic of the light, said values being then stored in image points, and processed in an emulation step. An emulation image is produced, emulating the imaging of the object by the first optical imaging element, taking into account the influence of the second characteristic.