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This article discusses the use of a narrow band, non-laser light source such as a filtered mercury vapor lamp, in copying holograms.
English (United States)
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Low Noise Hologram Copying Process
This article discusses the use of a narrow band, non-laser light source such
as a filtered mercury vapor lamp, in copying holograms.
A known process for copying a volume hologram requires that an unexposed
film of holographic recording material be placed in close proximity to the
hologram to be copied. This process is described in U.S. Patent 3,752,557.
According to that patent, a laser is used to illuminate the hologram to be copied.
When the laser beam is transmitted through the hologram being copied, it is split
into a zero order (undiffracted) beam and a first order (diffracted) beam. The two
beams interfere at the previously unexposed copy material to form new
interference patterns having the same image-forming capabilities as the
interference pattern in the original hologram.
Due to its relatively long coherence length, a laser produces reflections from
support surfaces and within the holographic recording material. The holographic
recording of these reflections causes spurious light noise when the finished copy
A narrow band, non-laser light source, such as a filtered mercury vapor lamp,
has a very short coherence length. The short coherence length should inhibit or
eliminate the holographic copying of reflections, thereby reducing the amount of
light noise produced when the finished copy is illuminated.