The Dichroic Coating Process
The term ‘Dichroic‘ is derived from the Greek language ( di – twice, and Khros-colour ) and literally means ‘two colours’. In practical terms, this means if you hold a piece of coated glass and look through it you will see different colours than you will see if you look at light reflected from the glass. This is achieved by multiple layers of compounds on the glass. These dichroic coatings can be used for a variety of purposes, anti reflection coatings ( on binoculars for example ) astronaut visors to protect the astronaut from harmful radiations, ultra violet and infra red filters and more. They can also be used to make fabulous jewelry and art glass work.
Here is a picture of one of our vacuum machines, this one an E Beam coater.
What that means is that the machine uses a very high energy electron beam to vapourise oxides of various materials. The vapourised material then condenses onto the glass. The oxides are vapourised one after the other and deposited in extremely thin layers. The layers are monitored as they are deposited, and when the required layer thickness is achieved, the next material is brought under the electron beam, evaporated, then the next layer and so on. Depending on the desired final outcome, many layers may be needed. All this is done under a very good level of vacuum, to ensure the purity of the deposits.