[Laser] Big IR LEDs

[Andrew T. Flowers, K0SM]

Actually, I wasn't planning on using it on a LOS path, but rather using 
vegetation as a scattering medium. It turns out that many plants 
(particularly lawn grass!) are quite reflective above 700 nm.  Something 
centered around 780nm would be great for the reasons you say, and I was 
kinda hoping someone might be manufacturing one for the night-vision 
industry.

Andy
K0SM/2

Chris L wrote:

>
>   Dear Andrew,
>
>   No,  they  don't seem to make them. Even the red 1 watt is NOT made in
>   the  3 watt or 5 watt rating, and it's on 630 nM, not 660 nM like most
>   other  super  brite  red  LEDs  - probably to make better usage of the
>   eye's wavelength response curve.
>
>   If  it was a 930 nM IR LED it wouldn't be much use - that hits a major
>   H2O absorbtion band. If it were 830 nM that might help. But only a red
>   light can be focussed by eye and seen in a rifle sight - and if you've
>   ever stood on a mountaintop and TRIED to line up an IR beam you'd soon
>   give it away.
>
>   As  I  mentioned  in a previous posting, in 1991 I tried a high output
>   830  nM  LED against a 3000 mCd 5mm LED (660 nM) and the difference in
>   transmitted  flux  was  not that great - only a few dB in the IR LED's
>   favour   -  and  that  was  hard  to  even  notice  as  the  beam  was
>   scintillating  up  and  down  about  a  5 Hz rate some 7 dB or so! Red
>   Luxeons  leave  both for dead, particularly as the source size matches
>   the focal spot of many of the better fresnels.
>
>   If  only someone DID make an IR Luxeon, or even one out around 700 nM,
>   the  beam might not attract quite so much attention, but believe me, a
>   VISIBLE beam is so much easier to align.
>
>   All the best to all,
>
>   Chris Long.
>   >From: "Andrew T. Flowers, K0SM" <aflowers at frontiernet.net>
>   >Reply-To: Free Space LASER Communications <laser at mailman.qth.net>
>   >To: laser at mailman.qth.net
>   >Subject: [Laser] Big IR LEDs
>   >Date: Fri, 01 Apr 2005 23:54:14 -0500
>   >
>   >Does anyone know of a large IR LED on the order of the Luxeon
>   >devices?  I imagine the market isn't quite as large for such an
>   >item, but I wonder if such a thing is obtainable.
>   >
>   >Andy
>   >K0SM/2
>   >
>   >
>   >
>   >
>   >--
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