
276 7 Restoration
approximately constant, then the denominator in (15) is essentially constant,
so that (15) determines
H(u,v)
up to a multiplicative constant. More realisti-
cally, if we write
In Fi(u,v) = \n\Fi(u,v)\ + φ&,ν)
where φ^ϋ,ν) is the phase of F
t
(w,
*;),
then it may be reasonable to assume
that the average of the φ/s is approximately constant, but we still need to
know something about the average of ln|F;(w, v)\ in order to obtain H(u
y
v)
from (15). The reader is referred to [14, 59, 68, 95] for ways to approximate
the average of In F^u, v\ and also for techniques that specifically estimate
either the phase of the original image