Concentric Circle Detection in image using Hough Transform in AForge.NET

Question

I'm trying to detect concentric circles in an image of a paper target using AForge.NET. I can clean up the image using Threshold(88) or Edges, but can't work out how to detect the circles.

Original image size = 450 x 479 px

Steps so far:

1. convert image to greyscale
2. use Edge to find circles (Threshold(88) also works)
3. Run HoughTransform with radius of = 100, output using 'ToBitmap'
4. Count the circles found (I get 69750 circles detected)
5. Draw the 20 most intensive circles

I don't have a background in image processing; any guidance very much appreciated.

Answer 1

The Solution, in this case, was not to use a Hough Transform at all.

1. I used a threshold and blob detection to find the outer circle which gave me the centre.
2. Then an horizontal-intensity histogram to find the peaks that correlate with each ring
3. Then compare this against the peaks from a vertical-intensity histogram, to get the radius of each ring
4. Then some sanity checking.

I haven't got the peak detection working yet, but it's in progress and it all looks like working.