Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: LASER diodes
Message-ID: <1988Mar30.181100.922@utzoo.uucp>
Organization: U of Toronto Zoology
References: <5451@spool.cs.wisc.edu| <2547@ihuxv.ATT.COM>, <5479@spool.cs.wisc.edu>
Date: Wed, 30 Mar 88 18:11:00 GMT

> Well it was visible, although I suspect that most of the energy
> was in the infrared spectrum...
> it was never bright (never close to an LED), but if we
> turned out all the lights and waited for our eyes to
> adjust, we could just make out a little spot of red
> on a sheet of paper.

Remember that there is no sharp dividing line between visible light and
infrared.  There is no frequency above which the stuff is visible and
below which it is not; the sensitivity of the eye simply gets poorer and
poorer as the frequency gets lower.  Eventually sensitivity falls to
essentially zero, but it's a gradual decline rather than a sharp transition.
Near-visible infrared is not completely invisible, especially in favorable
conditions (bright source, darkened room).
-- 
"Noalias must go.  This is           |  Henry Spencer @ U of Toronto Zoology
non-negotiable."  --DMR              | {allegra,ihnp4,decvax,utai}!utzoo!henry