Speckle pattern modulation for high-resolution displacement measurements

Abstract

For digital image speckle correlation (DISC), a novel approach is introduced where an ensemble average over multiple different speckle patterns is calculated. As a result, the measurement uncertainty of the displacement is reduced by an order of magnitude without deteriorating the spatial resolution. This enables precise surface displacement field measurements in the micrometer range with a measurement uncertainty lower than 100nm at a spatial resolution below 20 μm. By using a digital micromirror device (DMD) for illumination modulation, measuring rates in the range of 25 Hz are possible while each measurement is based on 80 images.