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
     the light 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,
     the colliding lightwaves create an interference-pattern of microscopic bands of light and darkness, which
     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 special chemicals.

     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 objects....

     ..... and with the advent of   DIGITAL HOLOGRAPHY   it is now possible to create
     one-off custom holograms from video or CAD at very reasonable prices !