2D Visual Micro-Position Measurement based on Intertwined Twin-Scale Patterns

International audiencePosition measurement at nanoscale currently raises issues such as making significant compromise between range andresolution or as the difficulty to measure several directions with a single sensor. This paper presents a novel visualmethod to measure displacements at nanometric scale along two axes. This method allows subpixelic measurement ofposition by using a pseudo-periodic pattern observed by a regular visual setup. This micrometric pattern correspondsto the intertwining of two perpendicular copies of a single-axis pattern made of two frequency carriers with slightlydifferent periods. It was realized in clean room by photolythography of aluminium on glass. The algorithm is based ona twin-scale principle, itself based on direct phase measurement of periodic grids. Experiments are performed at videorate (30 fps) and show a linearity below 0.16 % and a repeatability below 14 nm over an unambiguous range of 221 µm.A resolution below 0.5 nm is demonstrated by the use of 2000 images. The method can be adjusted to different ranges,according to the needs.&nbsp