noun Optics, Photography.
a mirror or prism that divides a beam of light into two parts by reflecting a part of the beam, used in camera range finders.
Origin of beam splitter
First recorded in 1930–35
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a system that divides a beam of light, electrons, etc, into two or more paths
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