Tech

How cutting-edge technology captures 3D objects and re-creates them with light in ever-more realistic ways

The principle of making a hologram is
similar to recording an orchestra in
surround sound – once the sound has
been recorded, the orchestra can stop playing
and the sound can be re-created again and
again without any instruments.
Instead of recording audio, a hologram stores
the interference pattern generated by light
scattered by an object. This allows that light
scatter to be reproduced later, giving the
illusion the object is still there.
Capturing a hologram requires a laser light
source – most often a red helium-neon laser.
The light is divided by a beam splitter and each
new beam travels a separate path to the
holographic recording plate. The first beam –
the object beam – travels to the object itself,
while the second goes to a recording plate as a
reference to obtain the interference pattern.
Before they reach their targets, each beam
travels through a lens. Unlike the lens of a
camera, the lenses of a holographic recorder are
not designed to focus light, but instead spread it
out. As the object beam strikes the object, light
is reflected and refracted, some of it in the
direction of the holographic recording plate. As
the object beam reaches the plate, it collides
with the reference beam, generating an
interference pattern. Interference is recorded
using fine grains of photosensitive chemicals,
similar to those used in photography.
In essence, the exposed holographic plate is
more like a CD than a photographic negative.
The stored information cannot be deciphered
with the naked eye, instead appearing as a
series of bumps and wavy lines. In order to
actually view a hologram, a light source must
be applied to the film.
There are two main types of hologram, with
each viewed in a different way. To look at a
transmission hologram, a monochromatic light
is passed through the film, producing a floating
three-dimensional image of a single colour
(most often green). Alternatively, reflection
holograms, like those found on bank notes,
bounce back light and can be multicoloured.
The process of creating a hologram is
incredibly light-sensitive, much like traditional
photography, so holographic recording is done
in a darkroom. Due to the red colour of most
holography lasers, traditional red darkroom
lights damage the holographic plates, so green
or blue-green lights are used instead.
Holography is also much more sensitive to
environmental conditions than photography;
so much information is packed into such a
small space that even minute deviations in the
lasers can ruin the hologram. Vibrations in the
floor, in the air from body movement or even as
people breathe can disrupt the delicate
recording process.
Despite the difficulties in creating holograms,
the storage capacity they provide is quite