If you look at this image:
It's easy to find by human eyes that there are 3 circles which share the same center.
How could I detect/fit these 3 circles ? I try cvFindContours() but the middle and inner circles are detected as a single contours. I also try cvHoughCircles(), it give me a lot of circles ... but not the 3 circles I expected.
What should I do for this kind of situation ? I'm new in computer vision, is this an easy question ? Or this is a known difficult problem ?