How is a transmission hologram made?
• A hologram captures the object in three dimensions. • Before the object beam arrives at the object, all the light is of the same wavelength and in phase. • As this coherent light strikes different parts of the object, some parts being further away from the film from others, the beam arrives at the film out of phase. • The reference and object beams interfere with one another as they are recorded on the film. • It is for this reason that two beams, including one such standard reference beam, are necessary to record the phase difference of the light waves and thus capture the information which supplies the vital dimensions and depth to the hologram.
