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How could i use a laser to .? Answered

How would i make a laser when pointed at a building it shows on a computer screen (or anything) how far away the thing that the laser is pointed at Is . it doesnt need to be  a laser just something like a camera or anything reeally.

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lemonie (author)2010-02-15

Webcam with a laser strapped to it? I'm not quite sure what you're after.

L

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Re-design (author)2010-02-15

A laser measuring device works by sending out a laser pulse and measuring very accurately the amount of time it takes to return.

If you can write software that will measure that time and calculate the distance then you can do it.

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stephenniall (author)Re-design2010-02-15

So technically i could Make a piece of software to find the time it took for 1 cm then divide the time for one cm by the time it took and get it accurate with 1 cm .


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Re-design (author)stephenniall2010-02-15

Naw, I've since found out it's more difficult than that.  The time slices are too small to be accurate.  Check out this link for an explanation of the process.

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Jack A Lopez (author)Re-design2010-02-15
Some powerful magic indeed.  Thanks for posting that link.

I'd always wondered how that stuff worked, and honestly I'm still not sure.  There must be a trick to it.  I mean if:
φ = 2π*Tof*fm=2π*Tof/Tm
Then there are going to be a whole bunch of different frequencies that give the same phase shift (since φ+2π*n looks like φ) I think you have to start out with (Tof*fm) < 1, then try measurements at higher fm to try to get answer with better resolution. 

Just a guess. Like I said, I'm still not sure exactly how they do it.

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steveastrouk (author)Re-design2010-02-15

Actually time-of-flight (TOF) laser ranging is pretty rare, because of the astonishing timing required to get good resolution.

Bear in mind that the cheapie Bosch laser ranger that cost <<500 USD are ACCURATE to 0.125" - a TIME resolution of 10 PICO seconds,

....which is why they don't work by TOF.

To get a 1 foot resolution STILL needs a time resolution of 1 nanosecond.

There isn't the space here to explain how they actually do it.

Steve

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Re-design (author)steveastrouk2010-02-15

I wouldn't doubt that I don't have it quite right.  The one that I used didn't cost that much but is more accurate than I need.  I assumed that they used time measurement to cal. distance as I had read but don't doubt that there is some other "magic" used and don't doubt you at all.

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