How to distribute lot of rings evenly over an image?

I want to put lot of rings distributed over an image. The ring sizes should be the same and should be distributed evenly. Can someone give me some tips. The reason for this is i want to do the difference of gaussian on an image but like in this picture below with two concentric circles which is a ring.

Answer 1

[Image Analyst]

Something like

numCircles = 20;
xCenter = xMax * rand(numCircles, 1);
yCenter = yMax * rand(numCircles, 1);
radius = 30 * ones(numCircles, 1);
viscircles([xCenter, yCenter], radius);

[ThaBask]

thx i can work with that!