Would subtracting the phases of two images be a superior difference metric than subtracting the images directly?

asked 2015-10-20 11:10:46 -0600

Brandon212 gravatar image

updated 2015-10-20 11:12:40 -0600

I'm hoping someone can sanity check this idea as I am admittedly a bit of a noob when it comes to working with FFT's.

Say I have two (registered) images of two of the same object and want to use one as a baseline to check for differences in quality control (looking for scratches and whatnot). My initial naive approach is to just subtract the two images directly and then whatever remains can be treated as defects. However, this method is subject to error in the presence of illumination differences.

I'm thinking that I would be better served if I take the FFT of the images, and subtract only the phase information, and then use the IFFT of that result as the defect map, and that this should hopefully eliminate false positives due to lighting.

Does this seem like a reasonable assumption or is there some kind of detail that I'm overlooking? Thanks for any advice you can offer!

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