Validation of MAPS: a novel 6-degree-of-freedom position sensor for nanopositioning

Anemos’ multi-dimensional absolute position sensors (MAPS) consists of a photolithographically defined reference scale, a camera, and computer image processing that decodes the relative position of a camera to the scale. A series of experiments tested the novel opto-electronic sensor against traceable National Physical Laboratory optical interferometers (OI) with motion provided by nanopositioning stages. Initially, MAPS to OI agreement was verified to be within 5 nm in the lateral ( XY ) axes across 100 μm travel. However, when MAPS, OI, and stage position were correlated across much finer steps, MAPS demonstrated repeatability and noise below 100 pm, indicating that the larger discrepancies seen previously were due to Abbe effects, servo-mechanical, and other OI/MAPS-extrinsic factors. In a third experiment, the outputs of four orthogonally placed MAPS 6-degree-of-freedom (6DoF) sensors were correlated against each other, OI, and feedback from a single-axis stage. Here, MAPS displayed sub-nanometre agreement with other sensors, and consistency across independent MAPS sensors. A fourth experiment collected millions of MAPS sample points during repetitive 1 nm circular motion. Spectral analysis of these large datasets, correlations between noise in multiple axes and repeatability indicate MAPS may resolve single digit picometre movements. These results corroborate simulations and supports the feasibly of million-to-one position interpolation from the MAPS 5 μm-grid reference scale. This equates to an unprecedented 40-bit dynamic range since MAPS can sustain measurement resolution over metres of travel. Overall, the experimental series highlight the challenges of nanoscale calibration and benefit of full 6DoF sensing in real-world nano-positioning systems.