https://www.laserfocusworld.com/optics/optics-design/article/16555294/aspheres-the-impact-of-shape-factor-on-asphere-design?
Aspheres: The impact of shape factor on asphere design | Laser Focus World
An aspheric lens of a certain power can have many shapes; matching the shape factor of the lens to its application is important.
laser focus worldshape factoraspheresimpactdesign