echelon lens

English

Noun

echelon lens (plural echelon lenses)

1. (optics) A large lens constructed in several parts or layers, extending in a series of annular rings beyond the central lens, and used in lighthouses.

Part or all of this entry has been imported from the 1913 edition of Webster’s Dictionary, which is now free of copyright and hence in the public domain. The imported definitions may be significantly out of date, and any more recent senses may be completely missing.
(See the entry for “echelon lens”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.)