🚀 go-pugleaf

In article <1992Sep14.161207.22138@mail.cornell.edu>, YAQX@cornella (Richard Zimmerman) writes:
|> 
|> 	Does anyone have any information on the theory behind a laser range
|> finder?  I assume it works by sensing the phase change on the returning
|> reflected beam, but I'm not sure of all the smaller details.
|> 	Also, does anyone have any information on constructing such a device at
|> a minimal cost.  (what would a minimal cost really be?)  I'm looking for
|> a device to mount on a mobile robot as a obstacle detection device.
|> 
|> ----Richard Zimmerman  (rsz1@cornell.edu)

I know of one system that sends a pulsed beam to the object, which reflects 
the beam back to a sensor, which is a known disance from the emitter.  The
receiver can sense the position and shape of the reflected beam (which is pulsed
to avoid interference from other light sources), and calculates the disatnce
through triangulation.  It's commonly used in seam detection and tracking
for welding robots, and my guess is that it is expensive.  If you want more info,
email me and I'll give you the journal title and date (which I've temporarily misplaced)
in which it is published.

I came across this while looking for a highly accurate range sensor, and I
would appreciate any suggestions anyone can offer.  The application would be for 
collision avoidance and vertical axis guidance for a gantry mounted borescope that's
used for filming scale models of cities.  The the gantry robot drives the borescope
down the street, simulating the point of view of a motorist or pedestrian.  The range
sensor would control vertical motion over uneven terrain.  An ideal device would reflect
off of any opaque surface, operate from about 2-3 feet from the surface, be accurate 
to +/- 1/8" (ideally better), and update the position at least 30 Hz.  Again, any suggestions, leads
would be greatly appreciated.  Does have any info on the Polaroid range sensors?

Thanks
Chris Hamilton  hamilton@ced.berkeley.edu