of recording and reconstructing
the wave front
emanating from an illuminated object. Coherent light from a laser
is split in two; one is a reference
beam and the other illuminates
the object. The waves scattered by the object and the reference
beam are recombined to form an interference pattern
on a photographic plate, the hologram
; this records both the amplitude
and the phase
of the scattered light.
When the hologram is then illuminated by light from a laser or other point source, two images are produced - one is virtual but the other is real and can be viewed directly. Thus a 3-dimensional image of the object can be produced.