Different lens shapes, same focal length

AndyW

Have a look at the graph on this page...

http://www.mellesgriot.com/products/optics/fo_3_3.htm

The lenses at the top all have different shape factors (q), but have the the same focal length.

I'm using optics software in which I can specify the radius of curvature for each side of the lens. How can I generate a series of lenses within these constraints?