modulation due to index changes dominates any residual amplitude

modulation. Phase modulators prove to be more efficient in terms of

the portion of incident illumination that is diffracted to form the

desired correlation. A sinusoidal hologram using absorption or

amplitude modulation can theoretically diffract only 6.25% of the

incident energy into an image. Experimentally, the number is about

4%.38 A phase-modulated hologram transmits all of the light (ignoring

the emulsion, substrate, and reflection losses). A sinusoidal phase

hologram can diffract as much as 33.9% of the incident light into the

first order.

 The bleaching process converts the real function F(u,v), recorded

in silver on the film, to a phase delay.


 H(u,v) = exp j[ F(u,v) ] (4.5)


To produce a kinoform, the film is exposed to the phase function

e(u,v) of the image transform. Upon subsequent bleaching, the film

contains the response


 H(u,v) = exp j[ 6(u,v) ]. (4.6)


The kinoform, produced in this fashion, records the phase-only

information of the image transform. The bleaching process is not

restricted to phase-only information. Rather, the absorption hologram

created from equation 2.35 can also be bleached.


H'(u,v) = exp j[ H(u,v) ] (4.7)


 = exp j[1 + IF(u,v)12 + F(u,v)exp j2irav + F*(u,v)exp -j2rav]