ABSTRACT
The earliest man-made mirrors were of polished stone, some of which have been found in Turkey and date back at least 6000 years. Most front-surface modern mirrors are made by the deposition of a thin layer of aluminum on glass under vacuum. Dielectric mirror coatings can be used for laser applications that require ultra-high reflectance at a specific design wavelength. The back-surfaced mirrors are commonly used for inspection, as well as for everyday use, because the metallic reflecting layer is protected behind the glass. A plane mirror is commonly used to change the propagation direction of a light beam. Cold mirrors have a dielectric coating, which has high reflectance for visible light and low reflectance for infrared (IR). Hot mirrors use a multi-layer dielectric coating, which has low reflectance for visible light and high reflectance for IR. On-axis parabolic mirrors are used as collimators for light sources located at the focal point.
