A holographic interferometer system for measuring density profiles in high-velocity flows

This paper describes a holographic interferometric technique for obtaining density measurements across a test gas that is traveling at a velocity of over 5500 m/sec in an expansion tube facility. Interferometric data describing the flow in the test section are obtained using a long coherence length CW argon laser in a holographic system and a rotating drum camera recorder. The object beam, which passes through the test section, intersects the reference beam at a small angle to form an interference pattern of about 170 lines/mm, and is recorded as a hologram. Before a test, this hologram is placed in its original position and rotated slightly so that an interference pattern is generated by the intersection of the reconstructed and real-time object beams.