a lens made of crown glass, usually used as the converging lens component of an achromatic lens.
Origin of crown lens
First recorded in 1825–35
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a lens made of optical crown, esp the optical-crown part of a compound achromatic lens
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012