Fresnel Profile (of a lens or fixed lens)
A stepped profile of both dioptric and catadioptric elements, the dioptric part of which presents one straight side towards the focus.
(Figs. 10, 14 and 16)
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM