Newsgroups: comp.robotics
Path: brunix!uunet!portal!acuity!rrc
From: rrc@acuity.portal.com (Bob Clark)
Subject: Laser Rangefinder
Message-ID: <1992Sep22.192709.6767@unix.portal.com>
Sender: news@unix.portal.com
Nntp-Posting-Host: acuity
Reply-To: rrc@acuity.portal.com
Organization: Acuity Research
Date: Tue, 22 Sep 1992 19:27:09 GMT
Lines: 50

Yes, there are many laser rangefinging and laser radar systems out
there, generally complex, specialized, and expensive. There are two
common methods of range measurement, depending on the range and
resolution required.
 
The first method uses pulsed lasers, and the time of flight of the pulse
is measured using the fastest timer obtainable. Systems are available with
resolutions down to a few cm, and ranges can be up to several km with high
power, low duty cycle pulsing. Applications include military rangefinding
and police laser radar, now being tested in some states.
 
The other method uses a continuous-wave laser and modulates it
sinusoidally, measuring the phase difference between the transmitted and
reflected signals. These devices have been demonstrated to have
resolution as good as 0.1 mm in laboratory tests with 300 MHz modulation. 
Typically, multiple modulation frequencies are used to resolve the 
ambiguity caused by possiblity of having multiple cycles in the
transmission path. Range can be up to a few tens of meters with laser
power up to 100 milliwatts, and several Km with retroreflectors at
the target location. Applications include surveying equipment, advertised
with accuracies of about 5 mm, and 3D object scanning.
 
At Acuity Research, we are working on a distance measurement sensor that
is intended to be a general purpose device at reasonable cost. It is 
laser diode based, and the range will be from a minimum of zero to a 
maximum of up to 20 meters, depending on the power of the laser used.
 
Resolution will be programmable to better than 0.1 millimeter. Absolute
accuracy figures have yet to be obtained and will depend on the  
environment in which the sensor is used, but we hope to attain better
than 1 millimeter. The first interface will be SCSI-bus based. Sample
rate will be programmable at up to 300 KHz (with reduced resolution).
  
Working prototypes have been developed and mounted on a mobile robot 
and used in navigation demonstrations. It will be several months before
the rangefinder is commercially available. However, we will need test
sites during the next few months, preferably in the San Francisco  
bay area. Anyone interested should email me or write to  
 
Bob Clark 
Acuity Research, Inc. 
20863 Stevens Creek Blvd #200 
Cupertino, CA  95014 
 
-Bob Clark 
rrc@acuity.com




