Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!cs.utexas.edu!sun-barr!newstop!texsun!letni!doug
From: doug@letni.UUCP (Doug Davis)
Newsgroups: sci.electronics
Subject: Re: Are checkout-counter lasers hazardous?
Message-ID: <7971@letni.UUCP>
Date: 10 Jan 90 15:50:05 GMT
References: <189@bucsb.UUCP> <446@sierra.stanford.edu> <2826@dciem.dciem.dnd.ca>
Reply-To: doug@letni.lonestar.org (Doug Davis)
Organization: Death Rays Inc.
Lines: 37
Keywords:

In article <2826@dciem.dciem.dnd.ca> king@dretor.dciem.dnd.ca (Stephen King) writes:
>In article <446@sierra.stanford.edu> siegman@sierra.UUCP (Anthony E. Siegman) writes:
>>I'd be very surprised if a supermarket laser scanner were hazardous.
>
>They aren't. The output of the laser tube is VERY carefully controlled. 
>The scanning is done via a rotating mirror, so the beam never lingers on
>one spot, but is always in motion. There are numerous safety features which
>shut the laser off should emmission exceed a certain amount, or should the
>scanning motor fail. Nevertheless, it's still not a good idea to look
>directly into one when it is operating.

Actually they aren't even as sophisticated as a spinning mirror,
I have several surplus NCR laser scanners, the way these are set up
the laser light goes into a beam splitter which splits the light into two
directions the both light beams strike separate mirrors that vibrate
at 60hz making up the x-y axis of the scanning beam. The separate
beams are recombined and sent upwards at several angles based on yet another
vibrating mirror.  The reflected light from the scanned barcode is then
directed back into a photo-multiplier producing the electrical pulses
used the figure out what just passed over the scanner.

The vibrating mirrors are great, hook one thru a transformer to each
channel of your stereo and you have an instant laser light show.  Of
course you could always tape mirrors to the cones of the speakers ;-)

Oh yeah, the lasers are .9mw output power (Class II - Non harmful.) BTW,
Class III lasers are >= 1mw and are classified as slightly harmful.  Read
the food and drug adminstration book 21CFR section 93.(somthing)
for all the regulations concerning lasers.

And if you want to BUY a laser I have several .9mw He-Ne lasers and
24vdc power supplies left from a project I was working on, email me for details.

doug
__
Doug Davis/1030 Pleasant Valley Lane/Arlington/Texas/76015/817-467-3740
{texsun, motown!sys1, uiucuxc!sys1 lawnet, attctc, texbell} letni!doug