1. Knowledge points of optical coating
Optical coating involves coating an optical element with one or more thin layers of material to alter its light reflection and transmission properties.
2. Types of optical coatings
Anti-reflective coating: Products of this coating technology are often used in optical components that require high transmittance. In complex systems such as cameras, telescopes and microscopes, reducing reflections not only increases transmittance but also improves image contrast by minimizing stray light.
Reflective coatings: This type includes highly reflective films used in the manufacture of polarizing reflectors, dichroic filters, luminescence and interference filters. Interference filters can be further divided into cut-off filters and band-pass filters. Cut-off filters are mainly used as edge filters of long-wave pass, short-wave pass and dichroic mirror types.
3. Traditional optical coating methods
Resistive evaporation source
Good for low melting point materials, but heater life may be shorter.
Electron beam evaporation source
High-energy electrons from an electron gun evaporate high-melting point, high-purity coating materials onto the substrate. Ion-assisted deposition (IAD) accelerates particle mobility and increases film density.
4. Technical comparison of optical coating
Sputter deposition method
In this method, the solid coating material is bombarded by high-energy particles such as plasma, producing surface particles that are sprayed onto the substrate to condense.
Evaporative deposition method
Involves heating a solid coating material to induce evaporation, with the evaporated particles then condensing onto the substrate.
Ion deposition method
evaporate solid coating materials, use glow discharge to charge the evaporated gas, and condense on the substrate. This method combines evaporation and sputtering.