blurs into a spot with a Gaussian distribution of brightness whose variance is
proportional to kx\ we can thus estimate kx by fitting a Gaussian to the point
spread function.
Several modifications to this Laplacian method have been proposed, with
the aim of reducing noise sensitivity. One suggestion is to use, instead of the
Laplacian, the second partial derivative in the gradient direction 9
n
. A further
refinement is to use a linear combination of the second partial derivatives in
the two perpendicular directions θ
η
and 9
t
. This last scheme can be designed
to smooth the picture in the direction along an edge at the same tim ...
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