Camera lenses are made of multiple individual glass lenses assembled together inside a cylindrical barrel. Sometimes these individual lens elements are assembled closely together to form a group.
Elements in a group are frequently cemented together with optically transparent glue to form a single physical unit. The advantage of cemented elements is that the elements have no glass-air surfaces within the group, which reduces reflections.
cf. barrel, Canada balsam, cemented element, compound lens, doublet, element, lens separation, transparent.
Entry last updated 2002-05-07. Term 577 of 1487.
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