High-speed holographic microscopy of a reflection type is described which has been developed to photograph the instant of bifurcation of fast propagating cracks. Spatial resolution is more than 180 lines/mm, frame interval is 1#mu#sec or more and the number of frames is three. When a fast propagating crack of opening mode bifurcates into two cracks, three pulsed ruby lasers oscillate successively. The laser pulses illuminate the specimen and the crack is recorded as three holograms on a photographic plate by means of angle-multiplexing holography. Lens assisted method reconstructs the three crackimages separately from the holograms, which images are photographed through a microscope. The high-speed holographic microscopy is applied to a fast propagating crack in PMMA, and crack tips are photographed just before bifurcation.
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