Method and scanning transmission charged-particle microscope

A method of obtaining a through-focus series (TFS) of a sample using a scanning transmission charged-particle microscopy (STCPM), the method comprising:

• performing a plurality of STCPM scans on the sample at a plurality of different respective focus depths to obtain a first TFS comprising a plurality of first TFS image data sets;
• performing the method of any preceding claim on each of the first TFS image data sets to obtain, for each first TFS image data set, at least one representation of an unknown structure of the STCPM;
• and
• generating a second TFS comprising, for each first TFS image data set, reconstructed image data generated from the at least one representation of the unknown structure.

A scanning transmission charged-particle microscope (STCPM) comprising:

• a charged-particle source;
• particle optics configured to direct charged particles from the charged-particle source towards a sample to cause the charged particles to pass through the sample;
• a detector configured to detect charged particles passing through the sample to provide image data;
• and
• a processor configured to cause the STCPM to:
• receive 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;
• process a system of equations expressing the image data as a sum of contributions from a plurality of virtual 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 from the first focus depth;
• and at least one set of representations of unknown structures of the STCPM, each unknown structure in a set being at a different respective focus depth from the first focus depth;
• wherein at least one of the plurality of representations of the unknown structures of the STCPM is obtained through solving the system of equations;
• and
• generate, from the obtained representations, reconstructed image data respectively corresponding to the plurality of virtual slices of the sample at the plurality of focus depths.