Pulsed Laser Holography

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Abstract
In most cases, holography of high-speed phenomena necessitates the use of a ruby laser to record the hologram. Work at this Laboratory has led to the development of `holocameras' - optical systems which compensate for the limited spatial and temporal coherence of common Q-switched ruby laser illuminators. Holocameras for both transmission and reflection action holography have been built. One of the former types has been employed to holograph combustion phenomena in liquid rocket engines, including one of 18 inch diameter and 25,000 pounds thrust. It can also be used to record projectiles in flight, aerodynamic wakes (via holographic interferometry ), electric discharge plasmas, etc. A reflected light holocamera has been used to record holographic inteferograms of impulsively loaded plates. Ruby laser holograms made with these `holocameras' reconstruct as brightly as comparable holograms made with a helium-neon gas laser. They exhibit high contrast ratios and are free of extraneous fringes and mottling throughout the reconstruction volume. Pulsed laser holography is important because it bypasses the depth of field problem of conventional photography. Thus, it is applicable to the recording of either events of unpredictable position or distributed phenomena. The added feature of double exposure holography mades interferometric measurement applicable to hitherto impossible situations.

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