Convention for sign of radius of curvature

Normally, a negative radius of curvature indicates a divergent lens, while a positive radius is used for a focusing lens 8e.g. Thorlabs).

Here, the property of the lens depends not only on the sign but also whether the radius is defined on the read or front surface.

For example a lens with ROC1: 515, ROC2 infinity is not the same as an inverted ROC1 infinity, ROC2 515.

This may lead to confusion