18 August 2010 LED camera light with a compact wide-range zoom
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A design concept for an extremely compact zoom optics which is suitable for illumination applications is presented. Such optics is especially useful for camera or flash lights as the illuminated area can be adjusted according to the picture content of the photo or film camera. The principle of the design is as follows: Collimated light passes through two lenses, each with a freeform surface. The freeform surfaces face each other and fit into one another perfectly. When the two lenses are merged together, they basically represent a coplanar plate: The cone angle entering the merged lenses does not change while passing them. When the plates are separated, the light is scattered at the freeform surfaces. Due to the smooth characteristics of the freeform surfaces shape, the cone angle can be adjusted continuously with the distance of the zoom lenses. The distance of the zoom lenses, which is necessary for maximum angle widening, is dependent on the size of the structures of the freeform surfaces and can be reduced to the sub-millimeter range. The compactness of the resulting device is a major advantage of the design concept. The principle of operation of the design could be shown by the construction of a prototype. It features a LED light source and a zoom range of 5° to 30° (cone angle). The luminous flux of the device is approx. 650 lm.
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Ulrich Hartwig, Ulrich Hartwig, Henning Rehn, Henning Rehn, "LED camera light with a compact wide-range zoom", Proc. SPIE 7785, Nonimaging Optics: Efficient Design for Illumination and Solar Concentration VII, 77850G (18 August 2010); doi: 10.1117/12.859442; https://doi.org/10.1117/12.859442


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