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Difference between revisions of "Lenses"
add reference and update KD and flashlight lens links for AR lenses
(add reference and update KD and flashlight lens links for AR lenses) |
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'''Sapphire''' Another choice is a sapphire lens made of synthetic sapphire (not actually glass) which is stronger than tempered glass and very resistant to scratches. Due to it scratch resistance, sapphire is often used for watch crystals, but is also available as a flashlight lens. | '''Sapphire''' Another choice is a sapphire lens made of synthetic sapphire (not actually glass) which is stronger than tempered glass and very resistant to scratches. Due to it scratch resistance, sapphire is often used for watch crystals, but is also available as a flashlight lens. | ||
'''Anti-reflective coating''' For the same reason telescopes, binoculars, and camera lenses have coated lenses, better flashlights include a coating on the lens surface that allows more light through by preventing light from the emitter from reflecting off of the lens instead of going through it. A typical loss for uncoated glass is 4% as light enters the lens and another 4% as it passes through back into the air. However high-end coated lenses might only have a total loss of 1%. For LED's this is like getting an extra bin of brightness from a light. Because an AR coating improves transmission of only a narrow wavelength of light, multiple layers of different thicknesses are used to get improved transmission of more wavelengths of light. Coated lenses are available from [http://www.flashlightlens.com | '''Anti-reflective coating''' For the same reason telescopes, binoculars, and camera lenses have coated lenses, better flashlights include a coating on the lens surface that allows more light through by preventing light from the emitter from reflecting off of the lens instead of going through it. A typical loss for uncoated glass is 4% as light enters the lens and another 4% as it passes through back into the air. However high-end coated lenses might only have a total loss of 1%. For LED's this is like getting an extra bin of brightness from a light. Because an AR coating improves transmission of only a narrow wavelength of light, multiple layers of different thicknesses are used to get improved transmission of more wavelengths of light. Coated lenses are available from [http://www.flashlightlens.com/index.php?app=ecom&ns=prodshow&ref=ucl_lens FlashlightLens.com] and [http://www.kaidomain.com/Search/SearchResult.coated%20lens KaiDomain] also has some of the most common sizes, including [http://www.kaidomain.com/product/details.S008213 28mm] for many [[P60]] hosts.<ref>[http://budgetlightforum.com/node/1026 Where do you get good replacement lenses for P60 hosts?] BLF Thread</ref> | ||
==Aspheric lens== | ==Aspheric lens== | ||
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[[File:Tir-optic.jpg|thumb|300px|Plastic TIR optic gives a very tight hotspot]]Also called a "collimating lens", a TIR optic takes advantage of "total internal reflection" where light that strikes a surface at a shallow angle will bounce off the surface and continue through the material instead of scattering. The optic collimates the light and sends a concentrated beam of light out in the same direction, giving a tight hotspot with greater throw. With a TIR optic in place, a reflector is not needed. A typical TIR lens looks like a cone with a hole where the point should be extending about halfway through the lens. This hole fits over the LED and any rays that strike the flat bottom of the hole will go straight out the front, giving a small hotspot. | [[File:Tir-optic.jpg|thumb|300px|Plastic TIR optic gives a very tight hotspot]]Also called a "collimating lens", a TIR optic takes advantage of "total internal reflection" where light that strikes a surface at a shallow angle will bounce off the surface and continue through the material instead of scattering. The optic collimates the light and sends a concentrated beam of light out in the same direction, giving a tight hotspot with greater throw. With a TIR optic in place, a reflector is not needed. A typical TIR lens looks like a cone with a hole where the point should be extending about halfway through the lens. This hole fits over the LED and any rays that strike the flat bottom of the hole will go straight out the front, giving a small hotspot. | ||
==References== | |||
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