Coating takes place in a large vacuum unit called a vaporizing hood. An electron gun is heated from below to vaporize the coating material (about 300°C) so that the film adheres uniformly to the lens. The excess reflection of the lens is about 10% before coating and can be suppressed to less than 1% after coating.

The coating material is heated while the inside of the device is kept in a vacuum, so that the material evaporates and dissolves, and adheres to the surface of the lens.