Method for ascertaining an image of an object

Abstract

To ascertain an image of an object which emerges when the object is illuminated with illumination light from a partly coherent light source with a target illumination setting having an illumination-side numerical aperture NA_illu and an imaging-side numerical aperture NA_detection, the following procedure is performed: initially, a section of the object is illuminated with illumination light from a coherent measurement light source with an illumination setting having an illumination-side numerical aperture NA_i, which is at least as large as NA_detection. Then, a diffraction image of the illuminated section is recorded. This is implemented by way of a spatially resolved detection in a far field detection plane of a diffraction intensity of illumination light diffracted by the illuminated section with a recording-side numerical aperture NA by way of a plurality of sensor pixels. This recording-side aperture must be greater than or equal to the maximum of NA_illu and NA_detection. From the recorded diffraction image data, the image of the section of the object for the target illumination setting is then ascertained from the recorded diffraction image data. An apparatus for carrying out the method comprises a measurement light source for providing the illumination light and a spatially resolving detector, arranged in the detection plane, for recording the diffraction image. This yields a method and an apparatus by means of which a flexible image ascertainment of sections of the object is facilitated, in particular for different target illumination settings.