Through-Focus Scanning Optical Microscopy (TSOM) is an imaging method that produces nanometer-scale three-dimensional measurement sensitivity using a conventional bright-field optical microscope.
TSOM has been introduced and maintained by Ravikiran Attota[1] at NIST.
A TSOM image is unique under given experimental conditions and is sensitive to changes in the dimensions of a target in a distinct way, which is very well applicable in nanoscale dimensional metrology.
The TSOM method is alleged to have several nanometrology[3][4][5][6][7][8] applications ranging from nanoparticles to through-silicon-vias (TSV).
The National Institute of Standards and Technology, USA, produced a short Video on YouTube on the TSOM method.