- double-exposure holography
The formation of an interferogram by means of two holograms on the same recording medium, often used for determining small changes in an object. One hologram produces a primary image that constitutes a comparison wave. The second exposure images the object, which has been changed, and yields the test wave. Interference is the result of the changes in the object that occurred between exposures and is formed when the double hologram is exposed to a light source.