This picture shows the basic set-up for making a hologram.
Actual set-ups are much more complex
than this, but the principle is always the same.
To make holograms you need laserlight.
This is produced by a suitable laser.
The laser-beam is split by a semi-transparent
mirror. Each beam
is spread out by a lens.
One beam is used to light the object, which reflects
toward a plate. This holographic plate is
used to record the information contained in the
light that is reflected by the object.
To be able to record this information, it is
necessary to shine
the other beam of laser-light
directly onto the plate. When the two beams cross,
colliding lightwaves create an interference-pattern of microscopic bands of light and
is recorded on the plate.
During the exposure the whole set-up must be absolutely
motionless. Even the tiniest vibration or
movement in any of the components will cause the
resulting hologram to be heavily banded or even
completely invisible. A heavy,
vibration-isolated table is therefore used to create a stable environment.
After the exposure, the hologram has to be developed using
It is also possible to make more than one recording on the same
holographic plate. To do this, the angle
of the plate is changed after the first exposure.
The object is altered, or replaced by another object, and
a second exposure is made. This
results in a hologram which contains different images that can be seen
from different angles.
Film or video can also be incorporated into a hologram. A
special recording technique is used: a camera
moves around the object, producing a film in
which each image is shot under a slightly dfferent angle.
These images (about 150) are
then transferred one-by-one onto a hologram, each under a slightly
different angle. This
results in a hologram of a "live"-scene that moves when you walk past it.
And, of course, computers are also being used to produce
holograms. Using a computer-aided design
(CAD) system, a 3-D scene is "built",
which can include movement. The computer calculates the
necessary sequence of images.
These images are then transferred onto a hologram, each under
its own angle.
With this technique it is possible to make holograms of non-existing
..... and with the advent of
it is now possible to create
one-off custom holograms from video or CAD at very
reasonable prices !