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This means the lens's F-number value is fixed to the overall designed focal ratio of the optical system (the diameter of the primary mirror divided into the focal length). The inability to stop down the lens results in the catadioptric lens having a short depth of field.
The company was founded in 1840 when its founder, 22-year-old Robert Edwin Dietz, purchased a lamp and oil business in Brooklyn, New York. Though famous for well-built indoor and outdoor kerosene lanterns, it was a major player in the automotive lighting industry from the 1920s into the 1960s.
The collimator lens has the lower focal length and is placed closer to the light source, and the collector lens, which focuses the light into the triplet lens, is placed after the projection image (an active matrix LCD panel in LCD projectors). Fresnel lenses are also used as collimators in overhead projectors.
The Bardic Rail Signalling Lamp was the original name of a particular type of battery powered railway signalling handlamp made from 1962 by Bardic, Ltd. [1] for use by rail and trackside workers. It became the standard battery operated handlamp in use on British Rail , replacing oil-lit lamps.
For example, a PAR16 lamp is approximately 2 inches or 50.8 mm in diameter. [1] The size of rectangular PAR lamps is expressed as the letters REC followed by the reflector's mouth height, the letter "X", and the reflector's mouth width—with both dimensions in millimeters. For example, REC142X200 lamps are 142 high and 200 mm wide. [2] [3]
Signal lamp training during World War II. A signal lamp (sometimes called an Aldis lamp or a Morse lamp [1]) is a visual signaling device for optical communication by flashes of a lamp, typically using Morse code. The idea of flashing dots and dashes from a lantern was first put into practice by Captain Philip Howard Colomb, of the Royal Navy ...
A Tensor lamp is a trademarked brand of small high-intensity low-voltage desk lamp invented by Jay Monroe. [ 1 ] [ 2 ] The lamp was mainly popular during the 1960s and 1970s. [ 3 ] [ 4 ] The lamp was originally used by doctors and dentists, and later became more widely used. [ 5 ]
The first lens was the 60 mm f/2.8 2 x Ultra Macro, a full frame lens with a magnification factor of 2:1 that could also be focused to infinity which is unique. [8] In the same year, Venus Optics released the widest angle macro lens to offer a 1:1 magnification ratio, the 15 mm f/4 Wide Angle Macro.