Circle equation = (x-a) ²+ (y-b)²= r² (a,b is the center and r is the radius)
Circle Hough Space is represented using a as the horizontal axis and b as the vertical axis.
Each point from x,y is represented in hough space using its a,b as center of the circle, and a circumference is calculated and stored.
Then the intersection points where the circle circumferences meet are voted for using the voting system used just as detecting lines , and the result which has the most votes is the center of the circle , which is a point in a, b, that is then represented back in x,y Image Space.
