confirmed, developer
1,668
edits
Difference between revisions of "Lenses"
→Flat lens: cleanup
(some links for AR lenses) |
(→Flat lens: cleanup) |
||
| Line 9: | Line 9: | ||
'''Glass''' Glass lenses are more common in better lights. Borosilicate glass like Pyrex has lower thermal expansion than regular glass and therefore is less likely to crack when the lens is exposed to higher temperatures, like from an incandescent light. Tempered glass is heated and cooled to introduce stresses in the glass that make it stronger than regular glass, but it can not be ground after tempering. | '''Glass''' Glass lenses are more common in better lights. Borosilicate glass like Pyrex has lower thermal expansion than regular glass and therefore is less likely to crack when the lens is exposed to higher temperatures, like from an incandescent light. Tempered glass is heated and cooled to introduce stresses in the glass that make it stronger than regular glass, but it can not be ground after tempering. | ||
'''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 | '''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 | '''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/str/index.php?app=ccp0&ns=prodshow&ref=ucl_lens FlashlightLens.com] and [http://www.kaidomain.com/ProductDetails.aspx?ProductId=9064 KaiDomain] also has some of the most common sizes, including 28mm for many [[P60]] hosts. | ||
==Aspheric lens== | ==Aspheric lens== | ||