  We experimentally demonstrate a non-imaging approach to displacement
measurement for complex scattering materials. By spatially controlling the wave
front of the light that incidents on the material we concentrate the scattered
light in a focus on a designated position. This wave front acts as an unique
optical fingerprint that enables precise position detection of the illuminated
material by simply measuring the intensity in the focus. By combining two
optical fingerprints we demonstrate position detection along one dimension with
a displacement resolution of 2.1 nm. As our approach does not require an image
of the scattered field, it is possible to employ fast non-imaging detectors to
enable high-speed position detection of scattering materials.
