title: Measurement of transient deformations with dual-pulse addition electronic speckle-pattern interferometry.
abstract: We describe an electronic speckle-pattern interferometry system for analyzing addition fringes generated by the transient deformation of a test object. The system is based on a frequency-doubled twin Nd:YAG laser emitting dual pulses at a TV camera field rate (50 Hz). The main advance has been the automatic, quantitative analysis of dual-pulse addition electronic speckle-pattern interferometry data by the introduction of carrier fringes and the application of Fourier methods. The carrier fringes are introduced between dual pulses by a rotating mirror that tilts the reference beam. The resulting deformation-modulated addition fringes are enhanced with a deviation filter, giving fringe visibility close to that of subtraction fringes. The phase distribution is evaluated with a Fourier-transform method with bandpass filtering. From the wrapped phase distribution, a continuous phase map is reconstructed with an iterative weighted least-squares unwrapper. Preliminary results for a thin plate excited by an acoustic shock show the suitability of the system for the quantitative evaluation of transient deformation fields.
authors.forename: D I
authors.initials: DI
authors.lastname: Farrant
authors.forename: G H
authors.initials: GH
authors.lastname: Kaufmann
authors.forename: J N
authors.initials: JN
authors.lastname: Petzing
authors.forename: J R
authors.initials: JR
authors.lastname: Tyrer
authors.forename: B F
authors.initials: BF
authors.lastname: Oreb
authors.forename: D
authors.initials: D
authors.lastname: Kerr