BK7与K9的基本特性对比  Comparison of basic characteristics between BK7 and K9
特性 Characteristic	BK7	K9
材料类型 Material Type	硼硅酸盐玻璃（德国肖特牌号） Borosilicate glass (German Schott Brand)	中国标准的光学玻璃 Chinese standard optical glass
国际对应牌号 International Corresponding Brand	Schott BK7, Ohara S-BSL7	中国GB标准，成分与BK7相近
主要成分 Main Ingredient	SiO₂ + B₂O₃ + K₂O	SiO₂ + B₂O₃ + K₂O（类似配方）

What is the role of the BK7 (K9) window in the visible wavelength?
Use: protect sensitive optical components (sensors, detectors, lenses) from dust, moisture or mechanical damage.
For example: laboratory instruments (microscopes, spectrometers), industrial cameras, surveillance cameras, laser printers, scanners.