Caustics in a meridional plane produced by plano-convex aspheric lenses

We study the formation of caustic surfaces formed in both convex-plano and plano-convex aspheric lenses by considering a plane wave incident on the lens along the optical axis. Using the caustic formulas and a paraxial approximation we derive expressions to evaluate the spherical aberration at third-order and also provide a formula to reduce it, where the first-order aspheric term is given in a simply analytic equation. Furthermore, we redefine the method to evaluate the circle of least confusion for a positive lens as a function of all parameters involved in the process of refraction through the aspheric lenses.