Provided is a pattern inspection system, including a scanning electron microscope (SEM) including an electron gun configured to generate a first electron beam and emit the generated first electron beam toward a first wafer, a detector configured to detect electrons emitted from the first wafer based on the first electron beam emitted toward the first wafer, and at least one processor configured to generate a first SEM image including a plurality of pixels based on the detected electrons, and determine, based on a period of a pattern extracted from the first SEM image, a pixel size of a second SEM image to be generated by the SEM with respect to a second wafer.

A method of determining an energy spectrum or energy width of a charged particle beam (11) focused by a focusing lens (120) toward a sample plane (p.sub.S) in a charged particle beam imaging device is described. The method includes (a) introducing an energy-dependent deflection of the charged particle beam (11) that leads to a spot broadening along a dispersion axis in the sample plane (p.sub.S), and taking an image of a sample (10) arranged in the sample plane using the charged particle beam; (b) retrieving a beam profile of the charged particle beam from the image; and (c) determining the energy spectrum or energy width from the beam profile. Further embodiments described herein relate to a charged particle beam imaging device configured to determine the energy spectrum or energy width of a charged particle beam, particularly according to any of the methods described herein.

A computer-implemented method of processing image data according to the present disclosure comprises: receiving the image data, wherein the image data is scanning transmission charged-particle microscope (STCPM) image data representing a STCPM scan obtained at a first focus depth; and processing a system of equations expressing the image data as a sum of contributions from a plurality of slices of the sample at a plurality of focus depths, wherein each equation of the system of equations relates at least a portion of the image data to: at least one of a plurality of contrast transfer functions of the STCPM, each contrast transfer function of the STCPM being determined at a different respective focus depth; and at least one set of unknown objects of the STCPM, each unknown object in a set being at a different respective focus depth. The step of processing comprises solving the system of equations to obtain at least one of the plurality of unknown objects of the STCPM.