where H'(u,v) is the bleached hologram response. The phase-only

information and the phase modulation obtained through bleaching are

entirely independent of one another. That is, a phase-modulated

hologram can be created from an image whose amplitude and phase are

intact or from an image whose amplitude or phase are modified or

removed. Considerable confusion continues to exist in the literature

in which a phase modulation process seems to imply, by default, phase-

only information. Cathey attempted to clarify this confusion in 1970

by defining specific terms for each case.39 The holographic process,

which is independent of the recorded information, was described as (1)

phase holography when only phase modulation was present, (2) amplitude

holography when only amplitude modulation was present, and (3) complex

holography when both amplitude and phase modulation were present. In

an equivalent fashion, the information to be recorded on the hologram

can be described as (1) phase-only information or (2) amplitude-only

information when either the amplitude or phase portion of the complex

waveform are deleted. Thus, for example, an amplitude hologram can be

created from phase-only information.

 When an amplitude hologram is bleached, the density at each point

on the film is mapped to a phase delay. This mapping is linear when

the bleaching chemistry is correct. This new phase function on the

film is related to the original pattern on the film.


 H(u,v) = exp j{F(u,v)} (4.8)


where H(u,v) is the complex function on the film after bleaching and

F(u,v) was the original transmission pattern recorded on the film.