The largest telescopes (ELT) involve a highly segmented primary mirror. The monitoring of the mirror shape use
thousands of sensors, located on segment edges, which measure the relative piston, tip and tilt of all segments.
Today, telescopes with segmented primary mirrors use
capacitance-based edge sensors. Although this technology offers
excellent metrological performances, its practical use is limited by the intrinsic sensitivity to humidity, dust and
condensation, whose effect exceeds the requirements for future ELTs.
Being specialized in both capacitive and inductive metrology, Fogale nanotech has developed a novel concept of edge
sensors using the inductive technology, which does not suffer from humidity, condensation, and dust effects. Cost
effective sensor with specific layout, associated electronics, demonstrated metrological performance (sub-nanometer
resolution and nanometer stability) that outperforms the capacitive concept.