A new technique that combines
optical plates to manipulate laser light improves the quality of holograms. Holography
makes use of the peculiar properties of laser light to record and later
recreate three-dimensional images, adding depth to conventionally flat
pictures. Researchers at the A*STAR Data Storage Institute, Singapore, have now
developed a method for increasing the number of pixels that constitute a
hologram, thus enabling larger and more realistic three-dimensional (3D) images. Holographic
imaging works by passing a laser beam through a plate on which an encoded
pattern, known as a hologram, is stored or recorded. The laser light scatters
from features on the plate in a way that gives the impression of a real
three-dimensional object. With the help of a scanning mirror, the system built researchers
combines 24 of these plates to generate a hologram consisting of 377.5 million
pixels. A previous approach by a different team only managed to achieve
approximately 100 million pixels.
The researchers patterned the
plates, made of a liquid-crystal material on a silicon substrate, with a
computer-generated hologram. Each plate, also called a spatial light modulator
(SLM), consisted of an array of 1,280 by 1,024 pixels. Simply stacking the
plates to increase the total number of pixels, however, created ‘optical gaps’
between them. As a workaround, the researchers tiled 24 SLMs into an 8 by 3
array on two perpendicular mounting plates separated by an optical beam
splitter. They then utilized a scanning mirror to direct the laser light from
the combined SLM array to several predetermined positions. The team
demonstrated that by shining green laser light onto this composite holographic
plate, they could create 3D objects that replayed at a rate of 60 FPS in a 10
by 3-inch display window. This simple approach for increasing the pixel count of
holograms should help researchers develop 3D holographic displays that are much
more realistic than those commercially available.
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