Research engineer Ravi Attota of the National Institute of Standards and Technology (NIST) has shown that a technique developed several years ago at NIST can enable optical microscopes to measure the 3D shape of objects at nanometer-scale resolution — far below the normal resolution limit for optical microscopy. The technique could be a useful quality control tool in the manufacture of nanoscale devices such as next-generation computer chips. Attota’s experiments show that Through-focus Scanning Optical Microscopy (TSOM) is able to detect tiny differences in 3D shapes, revealing variations of less than one nanometer in size among objects less than 50 nm across. Last year, simulation studies at NIST indicated that TSOM should, in theory, be able to make such distinctions, and now the new measurements confirm it in practice. TSOM can be used for 3D shape analysis without needing complex optical simulations, making the process simple and usable even for low-cost nanomanufacturing applications.