Image-processing ASIC

Question

A video-camera is mounted opposite a blackboard on which several concentric circles are roughly drawn in chalk. The circles are non-ideal, and the camera is not quite steady. The camera has a CVBS (composite) output.

I need to make a mission-specific hardware that would take snapshots from the camera, calculate circle diameters, and output them to a simple LED display.

So I have to: 1) capture an image; 2) apply a few alogorithms to improve the image (like thinning etc.); 3) recognize & measure the circles.

Since I'm totally new to this area, I would appreciate any inputs: schematic description of how such a circuit can be designed, keywords to google-around, examples, existing solutions that can be re-used -- I'd appreciate any pointer.

P.S. No, it's not a homework :). Just thinking of an idea and trying to estimate its complexity.