BLIND.....Re: [Laser] medium power IR diode

[John Schnurer]

	Dear Andrew,

	I mention this because of an incident, I will not mention the
facility.  
	In any event this was an IR system and one of the Optical Design
Professionals.... we will just use ODP .... was lining up the optical
train. The system was not SUPPOSED to be on. 
	It was a couple of hours later when the ODP noticed a ding in
their vision.  As this did not go away he finally went to the doc.... and
after a couple of hours sweating ... he got the news.... Permanent ding.

	Some time later EVERYONE who might have EVER been able to do ANY 
hands on work with lasers or any part of the systems, emitters, detectors,
optical...  We all took Federal Laser Safety training course.  This was a
very good thing, but too late for the ODP.
	After... months after ... i thought it would be OK to talk to him
about it.
	 He said he felt "kind of stupid" ....but that he would like to do
anything to have it not happen, and since that was not an option.... he
said he would like to make sure that it never happened to ANYONE else....
if he could help it.

	SO:	Some of the device protection method I came up with:

	1]	Simple cut-off, fails in the OFF mode.
	2]	Detector system... if the detector sees ANY of the
radiation, then OFF..... and locks out until re set intentionally ....
again... lock out-fail in OFF.

	3]	Emitter tied to laser that points in same general or exact
direction .... and this is a "safe emitter" ...maybe visible and visible
with IR at low level.....
	When you decide to "turn it on" ...  the Safe Emitter comes on....
then MAYBE you can see if you are going to kazchang someone's eye....
	and then AFTER you have checked... you over-ride the over-ride.

	Let me know if you want some help with people design.

	4]	One general addition is a sensitive passive IR detector...
that is overlapping and aimed at any place  person would be ....

	(A)
	The system goes off if ANY of the elements to be listed below
triggers:

	IR from source, from sensitive passive IR detector, from safe
emitter.....

	(B)
	And these feed to FAST cut-off ......positive feedback IGBT
hold-off/turn off.

	(C)
	laser power on activates 3 (THREE!!!) stages of audio and visual
pilot lights and AND and sound.... you have to do some checks before you
can "light up the laser"

				let me know if I can help.

								JH
	



On Wed, 23 Jul 2003, Andrew T. Flowers, K0SM wrote:

> John,
> 
> Not to worry, I'm fully aware of the danger of such a beast.  Quite 
> honestly, I don't want to be using this fully collimated into a tiny 
> beam at 100mw.  It should be possible to operate this a little above Ith 
> to get something in the 40-50mw range (still, not a toy).  Also, I think 
> I would want some sort of beam expander to reduce the power density in 
> the near field, just in case.
> 
> Andy
> 
> John Schnurer wrote:
> 
> >
> >	Dear AT.,
> >
> >	I will try to write some more on the topic, but at 50 mw IR lasers
> >are not toys.... at 100 mw plus, you can do permanent damage to your eyes
> >VERY easily by accidental specular incidence on a wide range of
> >surfaces...
> >	This can REALLY ding your eyes and the eyes of OTHERS in 100
> >milliseconds and less.
> >
> >	We all might do well to help design a "safe-switch" that
> >interrupts power under a number of overlapping conditions.
> >
> 
> 
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