Optical windows are made of optical grade glass with plane parallel surfaces. They are used to admit light into an optical system and to protect it from dirt and moisture. Windows made of BK7 material have high transmission in the visible spectral region, do not scratch easily, do not degrade under normal operating environment and hence do not need any special precaution or treatment. Anti-Reflective Coating will provide higher transmission.
Ross Optical Industries
BK7 Precision Window
10 mm (0.3937 inch)
40-20 Scratch / Dig
Window Diameter, Side Length, or Rectangular Length