Digital image processing of velocity-interferometer data obtained from laser-driven shock experiments

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Abstract
This paper discusses digital image processing techniques suitable for use with the velocity interferometric records obtained from shock-wave experiments using ORVIS (optically recorded velocity interferometer system). An ORVIS system is capable of measuring shock events with subnanosecond time resolution, the data consisting of fringe motion (proportional to the impacted material velocity) recorded with a streak camera. Two image processing methods are described which permit the determination of accurate velocity-time data from the records. The first, based on global analysis of the records, requires no operator intervention during reduction of the data, but breaks down when records show very rapid acceleration of the target under observation. The second, based on a thinning algorithm, can be used to treat rapid acceleration data and data in which the fringes are less than ideal. It requires operator intervention in some cases. The two techniques are shown to agree well when applied to the same data.