|
|
- beamsplitter
- A device used to divide
the light from a laser into two separate beams--the reference beam and
the object beam. It consists of a partially transparent mirror that
reflects part of the laser beam and transmits the rest.
- coherent
light
- Light which is of the same
frequency and is vibrating in phase. A laser produces coherent light.
- film
- Whether photographic or
holographic, film consists of light sensitive chemicals (the emulsion)
spread on a surface. A film's resolution measures the ability to distinguish
between details. Because holographic films must be able to record very
detailed information, they have a resolving power of 50 or more times
that of photographic film. They require either exposure to a high-intensity
pulsed laser or a long exposure to a continuous wave laser. Holographic
film is developed in a manner similar to photographic film, by bathing
it in a series of chemical agents.
- hologram
- Unlike photography which
records an image as seen from a single viewpoint, a hologram is a record
of an image as seen from many viewpoints.
- holography
- A medium for bending and
focusing light that uses the interference of monochromatic object and
reference waves to record and reproduce multiple two-dimensional images
for three-dimensional viewing.
- interference
pattern
- When two waves overlap,
their amplitudes add at every point. This results in an interference
pattern which records the relative phase relationship between the two
waves, storing each individual wave's characteristics. This is how a
hologram works.
- laser
- A laser is a device that
produces a concentrated beam of coherent light. Some, called continuous
wave lasers, produce a continuous beam of light. Others, called pulsed
lasers, emit more light in brief pulses that are able to freeze motion.
- lenses
- Lenses are devices that
redirect light. In photography, lenses are used to focus an image for
the film. Holographers use lenses to widen a laser's beam to illuminate
all of the object being holographed.
- object
beam
- The light from a laser beam
that illuminated the object and is reflected to the holographic film.
- phase
- The position of a wave in
space, measured at a particular point in time.
- reference
beam
- The portion of a laser beam
that goes directly to the holographic film. The interference pattern
that results from the object beam meeting the reference beam at the
holographic film is recorded on the film.
- reflection
hologram
- One that forms an image
by reflected light. Reflection holograms are lit from the front, reflecting
the light to the viewer.
- transmission
hologram
- One that forms an image
from the light passing through the holographic emulsion. Transmission
holograms are lit from behind, bending the light as it passes through
the hologram to your eyes.
- white
light
- Light that contains most
of the wavelengths in the visible spectrum, such as light from the sun
or from a spotlight. White light is incoherent, while laser light is
coherent. A white light transmission hologram, or rainbow hologram,
is one which can be displayed using ordinary white light. Early holograms
required viewing with coherent laser light.
|
