Circle detection

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Hello,

I'm trying to find circles around the white disks (see example pictures below). The background is always darker than the foreground. The dots can sometimes be a bit damaged and therefore not of a full disk shape. Nevertheless I would like to fit circles as accurate as possible to the white disks. The found circles should all have a very similar radius (max. 5-10% difference). The circle detection should be focusing on determining the disks radius as accurate as possible.

What I tried so far: - Hough circle detection with various settings and preprocessing of the images - findContours

I was not able to produce satisfying results with these two algorithms. I guess it must have something to do how I preprocess the image but I have no idea where to start. Can anyone give me any advice for a setup that will solve this kind of problem?

Thank you very much in advance!

C:\fakepath\CC-T.jpg C:\fakepath\Laminat_X200_klein.tiff