Hologram Schlieren and Phase-Contrast Methods

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Abstract
Holography was applied to the schlieren and phase-contrast methods and enabled the visualization of a minute phase change occurring in an object which scattered light. One makes a hologram first with the phase object in position and afterwards illuminates it by the object illuminating beam with the object out of the path. Then the phase change due to the object is made to add to the reconstructed reference wavefront and is rendered visible by spatial-filtering the point image formed by the wavefront. First experiment was carried out of a striation of liquid in a cell which was illuminated diffusely from behind. This principle is also applicable to the removal of aberrations of a conventional arrangement for transparent objects. The second experiment was performed of a hot soldering iron placed in a pipe of glass and a sensitivity competitive to that realized by using an aberration-free arrangement was obtained. An accuracy necessary to locate the hologram plate to its original position and the effect of the emulsion shrinkage were also discussed.