Optical Windows

An Optical Window is a mechanically flat, sometimes optically flat, depending on resolution requirements, ) piece of transparent (for a wavelength range of interest, not necessarily for visible light) optical material that allows light into an optical instrument. A window is usually parallel and is likely to be anti-reflection coated, at least if it is designed for visible light. An optical window may be built into a piece of equipment (such as a vacuum chamber) to allow optical instruments to view inside that equipment.