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Flipping surfaces

Flipping surfaces means to reverse the order and radius of curvature of a set of consecutive surfaces, as if the set of surfaces was removed from the lens, mirrored along the optical axis, and reinserted in the lens. For an axisymmetric lens this is the same as rotating the the set of surfaces a half turn about any axis perpendicular to the optical axis. Note that only the glass between the surfaces is included in the flip. The glass after the last surface is left where it was.

In the case of aspheric surfaces, the aspheric coefficients are also negated so that the new surface profile is the reverse of the old one.

See also