Nonimaging speckle interferometry for high-speed nanometer-scale position detection

Author(s): E. G. van Putten, A. Lagendijk, and A. P. Mosk Abstract: “We experimentally demonstrate a nonimaging approach to displacement measurement for complex scattering materials. By spatially controlling the wavefront of the light that incidents on the material, we concentrate the scattered light in a focus on a designated position. This wavefront acts as a unique optical fingerprint that enables precise position detection of the illuminated material by simply measuring the intensity in the focus. By combining two fingerprints we demonstrate position detection along one in-plane dimension with a displacement resolution of 2.1 nm. As our approach does not require…

Advanced Scanning Laser-Doppler Vibrometer with Computer Generated Holograms

Author(s): S. Zwick, M. Warber, T. Haist, F. Schaal, W. Osten, S. Boedecker, and C. Rembe Abstract: “In this paper we present a novel technique for steering the beam of a scanning laser-Doppler vibrometer (LDV) using a Spatial Light Modulator (SLM). Computer Generated Holograms (CGH) are employed to obtain the phase maps displayed by the SLM. Due to this approach, spurious diffraction orders are generated. We present concepts to suppress these diffraction orders so as to realize a scanning vibrometer. We discuss the properties and limitations of this solution. Different SLMs have been evalutated and a compact scanning vibrometer based…

Comparison and unification of speckle-based phase retrieval and holography with applications in phasefront alignment and recognition

Author(s): P. F. Almoro, G. Pedrini, F. Zhang, A. M. S. Maallo, A. Anand, P. N. Gundu, W. Wang, A. Asundi, W. Osten and S. G. Hanson Abstract: “Comparisons between various wavefront reconstruction methods such as wavefront curvature sensing and phase diversity have been reported in the literature. These comparative studies highlight the differences, similarities, relative advantages, operating regimes and main applications of the various reconstruction methods. For coherent light metrological applications, especially on rough objects, Digital Holography (DH) is considered one of the established interferometric methods because of its sub-wavelength accuracy. For investigations of smooth surfaces, Phase Retrieval (PR)…

Generation of fractal speckles by means of a spatial light modulator

Author(s): Hideki Funamizu and Jun Uozumi Abstract: “It was shown in previous studies that, when a diffuser is illuminated by coherent light with an average spatial intensity distribution obeying a negative power function, the scattered field in the Fraunhofer diffraction region exhibits random fractal properties. The method employed so far for producing such fields has a disadvantage in that generated speckle intensities are low due to small transmittance of fractal apertures used in the illumination optics. To overcome this disadvantage, a generation of fractal speckles by means of a spatial light modulator is proposed. The principle is explained and experimental…