Abstract

Digital speckle pattern photography is applied to the measurement of light deflection profiles of inhomogeneous transparent objects by transmission of a He–Ne laser speckle field through the object. The speckles are recorded with a CCD camera, and the local displacements are evaluated by comparison of the deflected speckle field with the undeflected field by a digital cross-correlation technique. In this way a complete two-dimensional deflection field can be obtained from a single pair of CCD records. The basic technique and two experimental setups suitable for objects with a size larger than that of the CCD chip are described. These novel techniques are applied to determine profiles of the refractive index of a free-burning arc in air. In addition, a cinematographic setup is described, which allows the investigation of transient objects by means of a video tape recorder.

© 1997 Optical Society of America

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