Universität Stuttgart
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Item Open Access Double pulse-electronic speckle interferometry (DP-ESPI)(1993) Pedrini, Giancarlo; Tiziani, Hans J.The double-pulsed speckle interferometry method is very much simpler than the double pulse holographic interferometry and allows a quick analysis of the interferograms without the development of films and hologram reconstructions. It is thus well suited to be used in an industrial environment. Using 3 cameras and three illumination directions (in order to have three sensitivi ty vectors) it is possible to measure 3-D deformations.Item Open Access Double-pulse electronic speckle interferometry for vibration analysis(1994) Pedrini, Giancarlo; Tiziani, Hans J.We describe a double-pulse electronic-speckle-interferometry system. Two separate speckle patterns of an object being tested are recorded within a few microseconds with a CCD camera. Their two images are stored in a frame grabber. The fringes obtained from subtraction are quantitatively analyzed by the spatial-carrier phase-shift method. Using three directions of illumination and one direction of observation, one can record at the same time all the information necessary for the reconstruction of the three-dimensional deformation vector. Applications of this system for measuring the rotating objects are discussed for the case for which a derotator needs to be used. Experimental results are presented.Item Open Access Editorial - optical microscopic and spectroscopic techniques targeting biological applications(2021) Micó, Vicente; Pedrini, Giancarlo; Lei, Ming; Zuo, Chao; Gao, PengItem Open Access A simplified multi-wavelength ESPI contouring technique based on a diode laser system. 2, Automatic fringe analysis(1993) Peng, Xiang; Zou, Yunlu; Pedrini, Giancarlo; Tiziani, Hans J.A quantitative fringe analyses of interference patterns generated by a multi-wavelength laser diode ESPI contouring system is discussed. The goal is the accurate determination of the topography of an object with steep surface. The phase change related to the surface geometry is calculated with phase-shifting techniques and the results with different contour sensitivities are presented. Some limitations of this ESPI contouring system are also considered from the point of view of practical applications.Item Open Access Double pulse-electronic speckle interferometry(1993) Pedrini, Giancarlo; Pfister, Berthold P.; Tiziani, Hans J.In this paper we describe a double-pulsed electronic speckle interferometry system. Two separated speckle patterns are recorded within few microseconds using a charge-coupled device camera, the two images are then stored in a frame grabber and the subtraction method is applied. A quantitative analysis of the fringes using the spatial-carrier phase-shift method is presented. The results show that this method is well suited to study transient vibrations.Item Open Access Double pulse-electronic speckle interferometry(1994) Pedrini, Giancarlo; Tiziani, Hans J.The double-pulsed speckle interferometry method is very much simpler than the double pulse holographic interferometry and allows a quick analysis of the interferograms without the development of films and hologram reconstructions. It is thus well suited for industrial applications. The system can be extended to determine the three components of the deformation by illuminating the object from three directions and by observing with three cameras. Double-pulsed ESPI can be used to measure rotating objects with an optical derotator which compensates the rotation of the object optically.Item Open Access Derivatives obtained directly from displacement data(1994) Zou, Yunlu; Pedrini, Giancarlo; Tiziani, Hans J.Two flexible shearing methods taking the derivative information directly from the data for displacement measurement are reported. The displacement information is obtained using a holographic recording directly on a CCD (charge-coupled-device) chip. Besides the advantage of taking the displacement information and the derivative information from a same set of data, other characteristics of these methods are that the derivative sensitivity can be controlled after recordings and displacement derivatives along arbitrary directions can be chosen easily. One method is based on the electronic recording which keeps the complex amplitudes of the wave fronts in a computer. The other needs only the phase modulo 2π of the displacement.Item Open Access Opposed-view dark-field digital holographic microscopy(2014) Faridian, Ahmad; Pedrini, Giancarlo; Osten, WolfgangScattering and absorption belong to the major problems in imaging the internal layers of a biological specimen. Due to the structural inhomogeneity of the specimen, the distribution of the structures in the upper layers of a given internal structure of interest is different from the lower layers that may result in different interception of scattered light, falling into the angular aperture of the microscope objective, from the object in each imaging view. Therefore, different spatial frequencies of the scattered light can be acquired from different (top and bottom) views. We have arranged an opposed-view dark-field digital holographic microscope (DHM) to collect the scattered light concurrently from both views with the aim to increase the contrast of internal structures and improve the signal-to-noise ratio. Implementing a DHM system gives the possibility to implement digital refocusing process and obtain multilayer images from each side without a depth scan of the object. The method is explained and the results are presented exemplary for a Drosophila embryo.Item Open Access Advantages of holographic imaging through fog(2023) Gröger, Alexander; Pedrini, Giancarlo; Claus, Daniel; Alekseenko, Igor; Gloeckler, Felix; Reichelt, StephanItem Open Access Scatter-plate microscopy with spatially coherent illumination and temporal scatter modulation(2021) Ludwig, Stephan; Ruchka, Pavel; Pedrini, Giancarlo; Peng, Xiang; Osten, WolfgangScatter-plate microscopy (SPM) is a lensless imaging technique for high-resolution imaging through scattering media. So far, the method was demonstrated for spatially incoherent illumination and static scattering media. In this publication, we demonstrate that these restrictions are not necessary. We realized imaging with spatially coherent and spatially incoherent illumination. We further demonstrate that SPM is still a valid imaging method for scatter-plates, which change their scattering behaviour (i.e. the phase-shift) at each position on the plate continuously but independently from other positions. Especially we realized imaging through rotating ground glass diffusers.