Overview
Advantages
Shape Mirror
Mass production silvering process is usually applied on plane glass. Silvering on shape mirrors such as curve, concave, convex, spherical or irregular shape is possible but relatively costly. If silver reflective metal is not compulsory, shape mirrors are alternatively made of vacuum evaporation process.
UV & IR Reflection
Aluminium mirror reflects UV and IR regions better than any other silver mirror.
Less Expansive
Aluminium coating on spherical mirrors are usually less costly than silvering plating.
Plastic Mirror
Plastic mirror are usually made by vacuum evaporation process.
Front Surface Mirror
When we look at a piece of ordinary mirror, metal deposition is on the other side of the mirror covered by paint. Mirror front surface has no coating. Light passes through glass layer before reflecting off on mirror back. Images are dim because glass is slightly reflective and not 100% transparent. Images are also blurred by "ghost images" that reflect off the glass front surface. In some applications, vague images are not allowed, for example, cameras, projectors, laser printers, telescopes, optical instruments and kaleidoscopes. Front surface mirrors, also known as first surface mirrors, eliminate ghost images inherent in second surface mirrors. Front surface mirrors provide brighter images and reduce light losses. First surface mirrors are usually made by aluminum coating instead of silver plating.
Although aluminium is active and is oxidized rapidly when exposed to air and humid, it does not affect mirror performance when everything is properly done. The reasons are,
- aluminum oxide layer is extremely thin and highly transparent which does not affect mirror optical characteristic
- aluminium oxide is very hard and this resists scratches
- aluminium oxide bonds to aluminum metal surface firmly and is extremely difficult to separate
- new protective layer of oxide will reform for further protection when mirror is scratched
There are quite a number of mirrors made of aluminium evaporation vacuum process coating on front surface.
Silver tarnishes quicker and is not recovered when applied on front surface. Front silvered mirrors have to be resurfaced occasionally to maintain quality.
- Astronomical Mirrors
- Telescopes
- Microscopes
- Cameras
- Projectors
- Lasers
- Sextant
- Optics Instruments
Parts & Components
Many parts and components around us everyday are made of vacuum deposition process. Electrical and electronics appliances, automotive exterior and interiors parts, tools, components for machineries are usually plated with chromium, nickel and other metals when shiny but at low cost are required.
