First surface mirrors
Encyclopedia
A first surface mirror or front surface mirror (also commonly abbreviated FS mirror) is a mirror
with the reflective surface being above a backing, as opposed to the conventional, second surface mirror with the reflective surface behind a transparent substrate such as glass
or acrylic.
They are made for applications requiring a strict reflection without a ghosting effect as seen with a second surface mirror - where a faint secondary reflection could be observed, coming from the front surface of the glass. This includes most optics applications where light is being manipulated in a specific manner. Telescope
s, rear-projection television
s, periscope
s, Non-reversing mirror
s, and high quality kaleidoscopes use this type of mirror.
" on a front surface mirror is usually aluminium.
The "silvering" on a front surface mirror in an infrared instrument is usually gold.
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...
with the reflective surface being above a backing, as opposed to the conventional, second surface mirror with the reflective surface behind a transparent substrate such as glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
or acrylic.
They are made for applications requiring a strict reflection without a ghosting effect as seen with a second surface mirror - where a faint secondary reflection could be observed, coming from the front surface of the glass. This includes most optics applications where light is being manipulated in a specific manner. Telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
s, rear-projection television
Rear-projection television
Rear-projection television or RPTV is a type of large-screen television display technology. Up until the mid-2000s, most of the relatively affordable consumer large screen TVs up to used rear-projection technology...
s, periscope
Periscope
A periscope is an instrument for observation from a concealed position. In its simplest form it consists of a tube with mirrors at each end set parallel to each other at a 45-degree angle....
s, Non-reversing mirror
Non-reversing mirror
A Non-reversing mirror is a mirror that presents its subject as it would be seen from the mirror. It is possible to make a non-reversing mirror by connecting two regular mirrors at their edges at a 90 degree angle. If you position the join so that it is vertical and look into the angle, you will...
s, and high quality kaleidoscopes use this type of mirror.
Silvering
The "silveringSilvering
Silvering is the chemical process of coating glass with a reflective substance. When glass mirrors first gained widespread usage in Europe during the 16th century, most were made of an amalgam of tin and mercury, but by the 19th century mirrors were commonly made through a process by which silver...
" on a front surface mirror is usually aluminium.
The "silvering" on a front surface mirror in an infrared instrument is usually gold.
External links
- Message board thread describing a DIY way to make a first surface mirror - widely referenced by hobbyists in areas of projection and display projects