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From: gerry@cmu.edu (Gerry Roston)
Subject: Re: Laser Range Finder
In-Reply-To: nagle@netcom.com's message of Wed, 16 Sep 92 07:34:55 GMT
Message-ID: <GERRY.92Sep16182525@onion.cmu.edu>
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Reply-To: gerry@cmu.edu (Gerry Roston)
Organization: Field Robotics Center, CMU
References: <1992Sep14.161207.22138@mail.cornell.edu> <hb1nfph.nagle@netcom.com>
Date: Wed, 16 Sep 1992 23:25:25 GMT
Lines: 54

Okay, I'll open my big mouth...

A laser range finder, by it self, can sense the distance to a point.
By using mirrors, this can be made into a line scan or an area scan.
Devices of all three types ae available on the market, and here at
FRC/CMU we have extensive experience with all three.  [Needless to
say, I am not the one who has done the work, so I can not provide
manufacturers names in most cases.]

For the UAV project (an autonmous landing aircraft), we used a trio of
lasers to detect the ditance to the landing platform and the attitude
of the platform with respect to the aircraft model.  These were point
devices and have a range, I believe, up to 30 meters.

For the autonomous coal mining/navigation and the Erebus Explorer, we
use line scanning devices.  I say line, but these devices sweep out
360 degrees in the world and the interpretation of their data is a
slice through the world.  I know that the Erebus device was made
in-house and the other may have been also.  The Erebus device has some
special requirements (in particular due to the operating environment)
and may have cost as much as $25,000 (but DON'T quote me!)  This
device sweeps out 360 in under a second and has an accuracy of 
< 10 cm (I seem to recall).  Because of the way it is mounted, its
range is limited to less than 10 meters.

For the NavLab, HMWWV and the Ambler, we have used scanning laser
range finders that produce images.  The older one (Damn, I can't
remember who made it!) has a resolution of about 10 cm and a 256
square images, both range and reflectance. It can produce an image
every other second.  The newer one is made be Perceptron.  This unit
has a reported accuracy of less than 1 cm and an image size of 512
square pixels.  The reported image rate is six images per second.  So
as not to get into trouble, if you are interested in the actual,
measured capabilities of the device, call the CMU library and ask fo
rht etech report authored by In So Kweon, published in 90 or 91 I
think.   Anyway, this device costs about $100K and weighs about 50 kg.

So, in summary, though I appluade your efforts to build your own
device, there is nothing mysterious about these scanners as they are
well understood.  Many papers a year are published at conferences
about laser range finders.  In addition, the manufacturers of these
device will rpovide you with literature.

--
Gerry Roston (gerry@cmu.edu)    | What is it the Bible teaches us? - rapine,
Field Robotics Center,          | cruelty, and murder.  What is it the
Carnegie Mellon University      | Testament teaches us? - to believe that the
Pittsburgh, PA, 15213           | Almighty committed debauchery with a woman
(412) 268-3856                  | engaged to be married, and the belief of
                                | this debauchery is called faith.
The opinions expressed are mine | Thomas Paine
and do not reflect the official | 
position of CMU, FRC, RedZone,  | 
or any other organization.      | 
