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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. It was given an R&D 100 Award in 2010.[2] In the TSOM method a target is scanned through the focus of an optical microscope, acquiring conventional optical images at different focal positions. The TSOM images are constructed using the through-focus optical images. 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] applications ranging form nanoparticles to through-silicon-vias (TSV).


  • Ravikiran Attota ; Ronald G. Dixson and Andras E. Vladár "Through-focus scanning optical microscopy", Proc. SPIE 8036, Scanning Microscopies 2011: Advanced Microscopy Technologies for Defense, Homeland Security, Forensic, Life, Environmental, and Industrial Sciences, 803610 (June 01, 2011); doi:10.1117/12.884706