Chicken Little: The Inside Story (A Jungian ... - Inner City Books

106 Chicken Little: The Inside Story
window. For the purposes of holography, one can think of the laser
as simply a special kind of bulb emitting a single color of coherent
light, which means light waves of the same wavelength moving in
parallel at the same speed.”
“To make a hologram, an unexposed photographic film, or glass
plate, is set up facing the object in total darkness. Part of a laser
beam illuminates the object, and the rest of the beam is deflected
by mirrors to the film. The film receives the wave pattern of both
the direct laser beam and the laser light reflected from the object.
The result is an interference pattern which is recorded on the film.
That’s a hologram.”
D. nodded. “This sounds familiar.”
“When the film is developed,” I continued, “it looks no more
like a picture than a gramophone record or a cassette tape looks
like music. But when it’s illuminated by a monochromatic light
source, the interference pattern enables the original holographed
object to become visible in three dimensions. When you move your
head, you can see ‘around’ the object, just as if it were there, right
in front of your eyes.
“Early holograms were of the transmission type. To be viewed,
they had to be illuminated with either laser light or a white light
source which had been filtered to one particular wavelength. Most
modern holograms—like those on credit cards—are of the reflection
type; they can be viewed in ordinary light.
“Now, a major difficulty from the beginning was to create a vibration-free
environment for everything involved in the making of
a hologram—the object, the laser, all the lenses and mirrors and so
on—because the film has to be exposed for several seconds. As it
happens, this problem was solved by an artist.”
I pulled a slim booklet from my pocket and held it up.
“You may recognize this,” I said to D., and read the title: “On
Holography and a Way To Make Holograms.”
“Holy smoke!” exclaimed D. “Pethick wrote that over twenty
years ago! I used to have a copy.”
“You may recall, then,” I said, “that it describes a simple set-up
for making holograms in a sandbox. The box itself rests on an inflated
inner tube, so nothing shakes.”