Razako
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Regular glasses for nearsightedness.
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Eye glasses ruin the beam of 405nm lasers?
- Thread starter Razako
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I have pairs for nearsightedness, one clear and one transition. I never really thought about it before, but I do believe they cut UV considerably.
Benm
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This is just to material the lenses are made off. They are probably polycarbonate, which as a pretty steep cut-off in transmission around 400 nm.
The exact cut-off wavelength depends on the composition of the polymer since it's often more than pure polycarbonate, but could easily explain why they (partially) block 405 nm light, a further UV light like blacklights completely.
Under normal circumstances this is not a problem: this light is not very visible to begin with, and it carries little information either. The glasses will not look coloured or anything. A possible upside of using this material is that it actually blocks UV light getting in your eyes which could reduce the risk of cataracts developing from sunlight exposure and such - essentially it has sunglass protection built in by default
The exact cut-off wavelength depends on the composition of the polymer since it's often more than pure polycarbonate, but could easily explain why they (partially) block 405 nm light, a further UV light like blacklights completely.
Under normal circumstances this is not a problem: this light is not very visible to begin with, and it carries little information either. The glasses will not look coloured or anything. A possible upside of using this material is that it actually blocks UV light getting in your eyes which could reduce the risk of cataracts developing from sunlight exposure and such - essentially it has sunglass protection built in by default
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As Benm said this is specific to poly glasses. I have some old ones made of glass and they don't filter out 405nm at all.
Also some new poly ones have a filter meant to remove most of the low-WL blue in order to decrease "blue light hazard". IMO that is bullshit and I stay away from them.
Also some new poly ones have a filter meant to remove most of the low-WL blue in order to decrease "blue light hazard". IMO that is bullshit and I stay away from them.
Benm
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It's a basic property of polycarbonate though, it has a very sharp cut-off in transmission around 400 nm. For ordinary applications this is rarely noticeable, certainly not to how things look (it doesnt have a yellow tint or anything like that).
One practical difference is that you cannot get a sun tan (or burn) through polycarbonate windows, while you can through ordinary float glass ones. This could happen for example in a car with strong sunlight from the side (the windshield usually is a laminate construction that blocks most uv, side windows are usually tempered glass that does not block it that well).
As for doing it on purpose: I suppose some companies will offer blue-limiting filters, probably at a premium price, just as they do anti-glare and scratch resistant coatings.
Plain polycarbonate glasses block UV, so do high-index (extra thin) glasses. Nothing can be done about this since it's just a material property, apart from getting glasses that are made out of actual glass (quite rare these days).
One practical difference is that you cannot get a sun tan (or burn) through polycarbonate windows, while you can through ordinary float glass ones. This could happen for example in a car with strong sunlight from the side (the windshield usually is a laminate construction that blocks most uv, side windows are usually tempered glass that does not block it that well).
As for doing it on purpose: I suppose some companies will offer blue-limiting filters, probably at a premium price, just as they do anti-glare and scratch resistant coatings.
Plain polycarbonate glasses block UV, so do high-index (extra thin) glasses. Nothing can be done about this since it's just a material property, apart from getting glasses that are made out of actual glass (quite rare these days).
