Coatings on glass
Magnesium fluoride (n = 1.38 instead of the optimal 1.234) is the major material used to AR coat glass lenses.
- The glass is cleaned.
- The glass is heated to 300o C.
- Coating is vaporized at 2,500o C.
- Vaporized coating is deposited on lens surface.
- Photoelectric cells ‘watch’ the surface reflection, and when it is ‘just right’ the coating is the correct thickness and the process is stopped.