Examples range from a polished bulk metal block with electrophoretic surface coating to a metalized foil (think of a silver or golden first-aid blanket). As an optical component, reflectors have a reflective layer or coating (or multiple coatings) and a substrate to be handled and mounted to provide a base for the reflective surface layer. The surface finish either causes specular reflection or involves scattering. Reflectors can have various surface finish qualities. This has led to a noteworthy renaissance of lens designs for LED lighting.Ī reflector is an optical device that redirects incident light back to the side of incidence. Most commercial LED packages are half-space emitters that have an emitting front and a non-emitting back side. flames or bulbs) emit radiation into almost the full sphere of angular space. For many of these applications, diffuse as well as directed or even sharp light patterns are required. When electrical lighting became the standard in homes, industry, transportation, as well as for portable lighting, reflectors remained the dominant optical component. In lighting applications, the use of metal reflectors to collimate light dates back to combustion sources, such as candles and carbide lamps. Other fields of imaging optics are dominated by lens design, based on today’s sophisticated quality of glass works and technical plastics. Their principles and designs are successfully used to this day. A variety of telescopes based on one or two reflectors resulted from this era. While the reflectors shared imaging properties of mirrors, they were not flat rather, they were spherical or parabolic to create image magnification. In the middle of the 17th century, Gregory, Newton, and their contemporaries were thinking of and working on reflector-based telescopes for astronomical applications. While Ptolemy’s Optics from about 400 AD discussed the principles of geometric optics including reflectors, it was not until the Renaissance that reflectors were used in optical systems. At the ancient Olympic games, the Olympic fire was ignited with a parabolic mirror focusing sunlight onto a torch – a tradition preserved today. The use of flat and smooth reflecting surfaces as mirrors – beginning maybe with a calm water surface and evolving into polished metal pieces and modern metal-coated glasses – has a long tradition in human craftsmanship. While mirrors have been used to view images for over 2000 years, optical reflectors are a more recent development.
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