Sci. Adv. 2, e1600077 (2016)
A microscopy scheme that can detect nanometre-scale thickness irregularities in transparent materials such as glass and polymers has been developed by scientists in Spain. Valerio Pruneri and co-workers from ICFO, ICREA and the Universitat Politècnica de Catalunya say that their interferometric on-chip microscopy scheme operates by the principle of phase-shifting interferometry. It offers a field of view of up to 20 mm2 combined with an axial sensitivity of 1 nm and a lateral resolution of 35 μm. The sample to be analysed is placed between a pair of Savart plates and a pair of polarizers, two overlapping sheared beams from a LED are sent through the assembly and the resulting interference pattern imaged by a CMOS image sensor array. Experiments with thin layers of indium tin oxide, silica dot patterns or proteins, all on a silica glass substrate indicate good agreement with comparison measurements made by atomic force microscopy. Potential applications for the system include defect inspection in glass and polymer materials or label-free reading of microarrays of biomarkers.
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