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From: ee8kh@gdt.bath.ac.uk (K House)
Newsgroups: sci.electronics,sci.optics
Subject: Laser diodes/ optics (esp. IR)
Keywords: Lasers,Infra-red,optics
Message-ID: <1991Mar5.164506.18567@gdt.bath.ac.uk>
Date: 5 Mar 91 16:45:06 GMT
Sender: ee8kh@gdt.bath.ac.uk (K House)
Followup-To: sci.electronics
Organization: University of Bath, UK
Lines: 35

I'm currently undertaking a small project using Infra-red LEDs to transmit 
information over distances of about 50 metres (through air).
However, the range I am currently achieving is not really high enough for the
application I have in mind and so I am toying with the idea of using laser 
diodes as emitters instead of the diodes I am using at present.

My current two emitters are a CQX19 and a (TW?)5202 both being driven by pulse
currents of about 8amps for a couple of microseconds at a repetition rate of
about 60kHz. With either of these two diodes I can achieve distances of 50metres
or so, but I am aiming to achieve at least 200metres. (I cannot easily make any
changes to the sensor, so I need to improve the emitter).

To get to the point, can anybody out there tell me where I can find out about
infra-red laser diodes and their transmission distances esp. w.r.t. power output
The only laser-diodes I have found so far are 10mW, which I think is far too
high an output to be eye-safe (another very important requirement). Please bear in mind that I intend to collimate(sp?) the beam to a spread angle of less than
1 degree. What level of power output is acceptable, for how long, what duty
factor etc.... ?

I am currently using a converging lens to try to narrow the beam-spread, can 
anybody tell me how much more effective a proper collimater would be, or where
I might get one ? (my budget is very limited).

In addition, any information regarding low power visible lasers (also eye-safe)
would be greatly appreciated.

I will gladly offer further details of the problem if required, just drop me an
email note. Thanks in advance for any help you may be able to offer.

Kevin House
-- 

" If I was someone, I would like to be the fool.             ___           
  No-one would know me and I think that would be cool. "    / / )__ __ ^__ __
__-_This_Mortal_Coil ______________________________________/ / ((_(( (((_((_.__