Gordon McComb
Guest
|
 Posted:
Thu Mar 31, 2005 4:10 am Post subject:
Re: 10m-10cm distance measurement with 1cm accuracy at a rat |
|
|
Thread Ender wrote:
| Quote: | What is the theory behind laser ranging?
Time of flight. Just like sonar, but MUCH faster.
|
Not always. A cheaper approach is to modulate the light beam, and then
compare the phase of the return beam with an internal reference beam (or
clock). Sometimes referred to as tone ranging. Yet another type, more
suitable for shorter distances (say, up to 50-60 feet), uses
interferometric methods, and are accurate to a quarter wavelength.
Leica's DISTO transits use phase measurement. They'd be much more
expensive if they used time-of-flight.
File this under the "FWIW" and "who the heck cares?" departments! <g>
-- Gordon
|
|
Thread Ender
Guest
|
| Posted:
Thu Mar 31, 2005 1:10 pm Post subject:
Re: 10m-10cm distance measurement with 1cm accuracy at a rat |
|
|
"Gordon McComb" <NOSPAMgmccomb@gmccomb.com> wrote in message
news:424B4D6F.3D39@gmccomb.com...
| Quote: | Thread Ender wrote:
What is the theory behind laser ranging?
Time of flight. Just like sonar, but MUCH faster.
Not always. A cheaper approach is to modulate the light beam, and then
compare the phase of the return beam with an internal reference beam (or
clock). Sometimes referred to as tone ranging. Yet another type, more
suitable for shorter distances (say, up to 50-60 feet), uses
interferometric methods, and are accurate to a quarter wavelength.
Leica's DISTO transits use phase measurement. They'd be much more
expensive if they used time-of-flight.
File this under the "FWIW" and "who the heck cares?" departments! <g
-- Gordon
|
Gordon,
I thought the DISTO was time of flight. When using the phase technique or
the interferometric method, is it still possible to use a servo mounted
45degree mirror to "pan" the beam around or does it mess up the measurement?
I have been planning to use a DISTO on a future robot project.
--TE |
|
FAQ
Memberlist
Register
Profile
Log in to check your private messages
Log in