Posted by
Filip Rooms on
May 08, 2007; 8:59am
URL: http://imagej.273.s1.nabble.com/FT-math-motion-blur-removal-tp3699574p3699580.html
On 5/8/07, roger bourne <
[hidden email]> wrote:
> How do I divide an FT by another FT (or the image of its power spectrum)?
>
> I am trying to demonstrate removal of motion blur by division of the
> blurred image FT by the FT of the blur vector.
That's what is called the inverse filter. This only works in complete
absence of any noise (sensor, discretization, ...), but is a highly
unstable computation, since you will divide the highest frequencies by
very small numbers (dividing by e.g. 0.001 is in fact multiplying with
1000, thus amplifying noise). If I am not mistaken, a motion blur
point spread function even has zero's in its spectrum, so for those
frequencies you divide by 0 (and every one knows that dividing by 0 is
not a good thing).
The simplest way to stabilize this is to add a small number to the
denominator, but better yet is to apply a Wiener filter instead,
taking into account the estimated spectra of the image and the noise.
Of course there are still better techniques involving other sharpening
procedures and stabilization methods... See my thesis, e.g., for more
explanation:
http://www.filiprooms.be/frooms-phd.pdfKind regards,
Filip Rooms