🌐EnglishEnglishDeutschEspañolFrançaisItalianoNederlandsPolskiРусскийالعربية日本語EntityQ2920313· pop 15optical systemassembly of optical components, or equivalently a system consisting of regions of material with varying refractive indicesAvailable in 15 languagesEspañolFrançaisDeutschРусскийالعربيةArmenianBelarusianBulgarianCatalanCroatian