On 1/14/2013 7:37 AM, RussellMc wrote:
>
>
> A few years ago I had a 150 mW white LED formally evaluated by its
> manufacturer. This is a very low power level by most standards for power
> white LEDs. To my surprise it  constituted a eye hazard at the blue end o=
f
> the spectrum when assessed to the relevant standard. While in this case t=
he
> chances of anyone staring into the beam from the minimum distance for lon=
g
> enough was vanishingly small, in other situations and with LEDs in the 1
> Watt + class, real hazards may exist.
>

I think you are right. I have noticed some of the  white LED  have high=20
output below what most people are capable of seeing. I was using a laser=20
power meter to measure the output of different LED and found some LED=20
that appeared to have a higher output on a meter but didn't appear=20
brighter to my eyes, some seemed dimmer.
The only thing that made sense to me was that they were outputting more=20
light in the non-visible spectrum . I have also seen white LED that are=20
capable of being used for exposing UV film on PC boards so those LED=20
have to be outputting some UV as well.

Mark

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.