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Practical experiences of interpreting time-average hologram fringe patterns from three-dimensional objects

Andrews, Ian and Long, R.J. (1976) Practical experiences of interpreting time-average hologram fringe patterns from three-dimensional objects. In: Electro-optics/laser international '76 UK, Brighton, 9-11 March 1976: conference proceedings. IPC Science and Technology Press, Brighton, UK, pp. 77-83. ISBN 0902852639

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    In industrial situations, vibration tends to be measured using
    accelerometers. Interest in the measurement of the modal
    behaviour of test objects, as a means for determining ways
    of controlling their vibratory response, led to the use of
    holographic interferometry and thence to the comparative
    exercise which was the basis for this paper. To establish the
    bona fides of the interpretation procedures for the analysis
    of the optical fringe patterns, the behaviour of a complex
    three-dimensional test object was determined using both
    holography and multiple accelerometers. The purpose of this
    paper is to review some of the problems encountered when
    endeavouring to interpret the fringe patterns and to discuss
    methods which may be used to surmount them. The problem
    lies in the determination of the local vector of object motion.
    Since this motion can have six degrees of freedom, it is of the
    utmost importance to understand exactly what displacement
    is indicated by the fringe pattern. The second stage is to
    ascertain exactly the order of each fringe. In simple cases
    this is quite easy but when the object shape contains discontinuities,
    such direct identification methods are no longer
    valid. The most expedient method then is to employ an
    auxiliary reference to which the test position can be coupled
    by flexible tape; fringe counting along the tape providing the
    requisite order clarification. In the paper we shall present
    an explanation of the means for determining object displacements
    from interferograms and indicate the agreement that
    can be achieved with measurement data obtained using
    accelerometers. We shall discuss the problems to be expected
    when attempting to interpret fringe patterns on real
    engineering test pieces of complex shape and will summarise
    the methods we have now adopted to achieve successful
    application of holographic interferometry to this type of task.

    Item Type: Book Chapter
    Subjects: Q Science > Q Science (General)
    Q Science > QC Physics
    Schools: School of Art, Design and Architecture
    Related URLs:
    Depositing User: Sara Taylor
    Date Deposited: 14 Dec 2010 14:27
    Last Modified: 14 Dec 2010 14:27


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