MOTION MOUNTAIN

170 4 images and the eye – optics
F I G U R E 119 A hologram of a train and the reflection hologram on a Euro bill (© Anonymous,
Hans-Ulrich Pötsch).
Holograms can be transmission holograms, like those in seen in museums, or reflection
holograms, like those found on credit cards or currency bills. Holograms can be laser
holograms and white light holograms. Most coloured holograms are rainbow holograms,
showing false colours that are unrelated to the original objects. Real colour holograms,
made and rendered with three different lasers, are possible but expensive.
Holograms are based on interference. Interference images can also be used in other
ways. By a double illumination at two different times, one obtains a so-called interferogram,
which allows visualizing and measuring the deformation of an object. Interferogramsareusedtoobserve
and measure deformation, oscillation or temperature effects.
Is it possible to make moving holograms? Yes; however, the technical set-upsare still
subject of research. So far, such systems exist only in a few laboratories (for example,
www.optics.arizona.edu/pstg/index.html) and are expensive. By the way, can you describe
how you would distinguish a high quality moving hologram from a real body
Motion Mountain – The Adventure of Physics copyright © Christoph Schiller June 1990–November 2015 free pdf file available at www.motionmountain.net