Subject:
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RE: laser diodes II
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 12 Dec 1996 20:06:00 GMT
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Original-From:
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Chuck McManis <cmcmanis@freegate!AvoidSpam!.net>
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Viewed:
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1551 times
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Any laser diode will work for sensing objects. The trick is that they are _so_
bright that you can't just look for the reflection (unless your are sensing objects
at a few hundred feet) There was a Circuit Cellar contest entry which used a
laser diode to to range finding. It relied on the fact that if you put the laser
and the detector a fixed distance apart, and turned the laser at an angle,
then by using a linear detector (they used a one line CCD) you can use
some basic trig to figure out where the reflection is coming from.
If you want to do time of flight measurements there is the issue a speed.
One way to do this is to put a beam splitter in front of the laser and have
the split beam travel a known distance to a detector, then use another
detector to monitor the beam that has travelled an unknown difference.
Finally, modulate the beam and the phase difference (it will be small)
between the detectors is proportional to the distance travelled.
At Hacker's Conference Cliff Stoll used this technique to compute the
speed of light (same equation except the distance was held constant)
--Chuck
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From: Scott Sherman[SMTP:sherman@plains.nodak.edu]
Sent: Thursday, December 12, 1996 4:31 AM
To: handyboard@media.mit.edu
Subject: laser diodes II
Hi,
I am still looking for information on what type of laser diode would work
for sensing objects. Any info or opinion would be helpfull.
Has anyone tried using laser diodes for detecting objects? I would be
interested in finding out how they were connected and how they are read
by the controller board. I am also interested in finding out what would
be best. I have been looking at the Panasonic Infrared Laser Diodes
on pg 434 of the Digi-Key catalog. Any suggestions would be appreciated.
thanks,
Scott
sherman@plains.nodak.edu
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