Newsgroups: comp.robotics
Path: brunix!news.Brown.EDU!noc.near.net!howland.reston.ans.net!spool.mu.edu!torn!newshub.ccs.yorku.ca!newshub.ariel.yorku.ca!cs911225
From: cs911225@ariel.yorku.ca (KEN E WILLMOTT)
Subject: laser diode safety
Message-ID: <1993Aug26.151805.28818@newshub.ariel.yorku.ca>
Sender: news@newshub.ariel.yorku.ca (USENET News System)
Organization: York University, Toronto, Canada
References: <1993Aug26.084151.2444@hemlock.cray.com>
Date: Thu, 26 Aug 1993 15:18:05 GMT
Lines: 32

>From: browen@lyapunov.aoc.nrao.edu (Bruce Rowen)
>Subject: Re: Q: IR - beacon

>I found a Laser diode once and pondered using it as a transmitter that
>would be so powerful, you could flash it in a room and the reflections
>could be received *anywhere*. (did you ever look at a IR led with a
>CCD camera with no IR filter? Damn bright!). Well (as R. Reagen would
>say), I dug the diode out from my junk collection a while back (these
>can be bought for about $5) and set up a power FET driver that would
>send 10 amp pulses through the thing at a 1% duty cycle. The receiver
>was a fat photo diode and low noise op amp circuit to test for the
>signal.

>I set the "transmitter" up in one room of my house and turned it on.
>Then I walked around the house with the receiver to find places where I
>could get a signal. The problem was finding a place where I could
>*not* get a signal! The transmitter must look like a camera flash in
>the IR band. I could get a reliable signal in every room, even though
>it was not line-of-sight. I even got a signal behind a closed door via
>leakage around and under the door. Heating vents also distribute the
>signal quite well.

>I am convinced this would make a neat way to command a mobile robot in
>a house via IR with a single laser diode transmitter mounted near the
>"control computer".


Geez, I'd be a little concerned about *eye safety* in the vicinity
of the transmitter, wouldn't you?

	-Ken Willmott

