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How Holography Works
The
theory behind holograms is that the two lasers are
shown through a holographic plate where one of the lasers is the reference beam
and the other laser is the object beam. Both these laser beams are reflected off
the object you want to make the hologram of such that the beams meet at the
holographic plate and make a recording of the amplitude and phase of the
resulting wave.
To reconstruct the hologram, a beam is shown through the
holographic plate at the same angle that the reference beam was shown through and
the beam is guided by the record on the holographic plate so the image appears
where the object was during the recording. That was reflection holograms. The
other type of hologram is a transmission hologram. Transmission holograms record
the image in the same way but reconstruct the image differently. They are
reconstructed by shining a laser though the holographic plate at the same angle
as the reference beam was shown though during the recording three beams of light
will pass though the hologram the first beam of light will be un-diffracted and
not produce an image the second beam of light will produce a virtual image and
the third beam of light will produce the real image if we look at the hologram
at the same angle as the primary image beam we will see a virtual image of the
object located behind the hologram.
Image-Holography Demonstration
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