IR in sufficient power will damage eyes - as a welder I have been taught th=
at the IR emitted=20
from Oxy-acetylene gas welding can damage the eyes if a shield is not used.

I suspect that the typical 20mA that an IR LED is in the safe zone, but as =
a previous poster
mentioned our blink reflex does not protect us from the non-visible spectru=
m.

It is interesting to note that the FDA considers a Class II laser safe by s=
pecifically citing
protection afforded by the blink reflex.

On Feb 15, 2012, at 5:05 AM, V G wrote:

> On Wed, Feb 15, 2012 at 4:18 AM, Mike Harrison <mike@whitewing.co.uk> wro=
te:
>=20
>> On Wed, 15 Feb 2012 02:34:27 -0500, you wrote:
>>=20
>>> 1. It seems that some infrared LEDs also produce a very small amount of
>> red
>>> light. I powered some on, and looked at them directly for a few seconds
>> and
>>> saw a small amount of red light being emitted. Why does this happen?
>>>=20
>>> 2. What are the effects of staring into a bright infrared LED for some
>> time
>>> (about the brightness of a bright flashlight that you normally couldn't
>>> look at for  more than a few seconds)? Since you can't detect the light=
,
>>> you don't have that reflex to look away from the bright source. Does th=
is
>>> damage the eye if you continue to stare at it for some time (longer tha=
n
>>> you normally could into a bright flashlight)?
>>=20
>> It's not that the LED emits red, but some eyes have some sensitivity  to
>> near IR.
>> The problem is that as the eye sensitivity is low, the amount of IR
>> entering the eye could be very
>> high, and can't be judged by the perceived intensity.
>>=20
>> I doubt a normal 20mA LED carries any hazard, but high power emitters an=
d
>> laser diodes could well
>> cause damage.
>>=20
>=20
> Well the photopigments in the eye absorb light in the "visible spectrum"
> and molecules like retinal isomerize from 11-cis retinal to all-trans
> retinal and dissociate from the G-protein when a photon hits them. IR
> shouldn't cause the isomerization and dissociation from the G-protein and
> therefore energy isn't absorbed that way, so I don't think damage would
> occur that way.
>=20
> But how else can damage be done? Other than the heat transfer from the
> light, like burning from a LASER.
>=20
> Also, I do know that I have EXCELLENT vision, so I could be sensitive to
> some IR, good point.
> --=20
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist


--=20
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