Papers by Author: Anand Krishna Asundi

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Authors: S. Iqbal, Anand Krishna Asundi
Abstract: A Multipoint Diffraction Strain Sensor (MISS) with the novel feature of simultaneous strain measurement at multiple points is characterized. Unlike conventional interferometry based systems, this patented sensor uses principles of diffraction to directly measure strain at large number of points. In this sensor, a high-frequency diffraction grating is illuminated by two symmetric laser beams and the diffracted beams are sampled on a CCD camera via a micro-lens array into an array of dots. The shift of the individual dots is sensed and strains or rigid body tilt are calculated directly. This novel technique is expected to be very valuable in numerous industrial applications.
Authors: Taslima Khanam, Ahmad Rashedi, Sujan Chowdhury, Anand Krishna Asundi
Abstract: Two image processing methods for the detection of particle based on digital holography are presented and compared. The image processing methods are developed based on edge detection and threshold based segmentation. The proposed methods have been applied on reconstructed images of holograms of ceramic beads and certified microspheres. Particle size distribution obtained for both methods are found to be in good agreement with the actual size, but the processing speed for threshold based detection has found to be faster in compared to the edge detection method.
Authors: Lei Huang, Anand Krishna Asundi
Abstract: Phase retrieval from fringe patterns is a primary procedure in fringe projection profilometry. Only accurate phase values result in three dimensions with certain accuracy. Phase shifting method plus temporal phase unwrapping approach provides not only the unwrapped absolute phase, but also the modulation map, background map, root mean square errors of least squares fitting, and phase relationship between two neighboring pixels, which can be used for the identification of phase invalidity. A practical phase retrieval frame work is presented to accurately calculate the absolute phase within reliable regions only, with which those unavailable phase points can be automatically identified with thresholds selection and criterion testing and then removed or interpolated according to applications. Experimental results show practical feasibility of the proposed framework.
Authors: Vijay Raj Singh, Anand Krishna Asundi
Abstract: In this paper, in-line digital holography is combined with time average method and applied for vibration analysis of an aluminum membrane. The numerically reconstructed wave from time average holograms contains information of mode shape and mean deformation of the vibrating objects. At lower amplitudes of vibration only the deformation fringes are observed and as the amplitude is increases, the Bessel fringes representing the time average vibration amplitude also become visible. Experimental results for a 10mm size membrane are presented.
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