Author Topic: Toxic materials in IR lens?  (Read 4040 times)

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Offline frenkyTopic starter

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Toxic materials in IR lens?
« on: November 02, 2016, 10:16:17 am »
GaAs (Gallium arsenide):
https://www3.nd.edu/~exafs/msds/GaAs.htm

ZnSe (Zinc selenide)
https://www3.nd.edu/~exafs/msds/ZnSe.htm

At both there is:

After skin contact

Immediately wash with water and soap and rinse thoroughly.
Seek immediate medical advice.

Are lens from this materials safe to handle? Or should you always wear rubber gloves?
 

Offline TassiloH

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Re: Toxic materials in IR lens?
« Reply #1 on: November 02, 2016, 11:13:04 am »
Handling of the solid material is low risk. But I'd wear gloves anyway because fingerprints can be difficult to remove (especially if there is a little sweat present). Be careful with dust (don't grind GaAs/ZnSe) and don't bring acids or acidic cleaners in contact with ZnSe.
 

Offline Fraser

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Re: Toxic materials in IR lens?
« Reply #2 on: November 02, 2016, 09:31:17 pm »
Totally agree with TassiloU.

Thermal cameras and lenses do not come with a health warning as the lens material is not considered a hazard in its finished form. There is normally an AR coating between your fingers and the lens material unless handled by their sides. Wearing of soft cotton lint free gloves is a good idea to avoid contamination of the lens AR coating which can be very fragile.

I would not recommend licking any thermal lens, no matter what it is made of  ;D

Fraser
« Last Edit: November 02, 2016, 10:35:05 pm by Fraser »
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Offline frenkyTopic starter

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Re: Toxic materials in IR lens?
« Reply #3 on: November 02, 2016, 10:09:57 pm »
Tnx to both.  :-+
 

Offline Bill W

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Re: Toxic materials in IR lens?
« Reply #4 on: November 02, 2016, 11:43:06 pm »
The coatings are not nice either.  Definitely a wash hands after handling job if there are any flakes or chips.

Very old lenses may have AR coatings containing Thorium which is a mild alpha emitter, but unlikely to be anything since 1990 for that.

One story goes that the alpha emissions helped keep up the helium trace in 'soft vacuum' Pevicon tubes !

Bill

Offline helius

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Re: Toxic materials in IR lens?
« Reply #5 on: November 03, 2016, 12:13:16 am »
Thoriated cathodes were also used for a long time due to their low work function. I don't know if today's vacuum tubes still use it, it must be a pain from an environmental compliance standpoint.
Going back further, there were many lenses made from thoriated glass because it has a very high refractive index. The radiation from the thorium caused yellowing, either of the glass or the optic cement, which could in some cases be reversed using UV stimulation.
« Last Edit: November 03, 2016, 12:17:12 am by helius »
 

Offline -jeffB

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Re: Toxic materials in IR lens?
« Reply #6 on: November 04, 2016, 06:14:14 pm »
Bulk, solid GaAs is nearly insoluble, and I can't imagine that it poses a contact risk if intact. I'm pretty sure the MSDS is referring to powder or fragments where there's a danger of getting them under your skin.

As others have said, touching the optics is a lot more hazardous to the optics than it is to you.
 

Offline LukeW

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Re: Toxic materials in IR lens?
« Reply #7 on: November 16, 2016, 12:22:10 am »
It's pretty safe, unless you're grinding lenses or something.

Don't expose the lens material to acids - for either ZnSe or GaAs.
Acid dissolution may give you gaseous arsine or hydrogen selenide.
(This is far more likely to ruin an expensive lens than it is to poison you, though.)

KRS-5 (thallium bromoiodide) is also used in some specialist IR optics and is very poisonous.
http://www.globalopticsuk.com/KRS-5.htm
 


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