# How could i use a laser to .?

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.

sort by: active | newest | oldest
lemonie7 years ago
Webcam with a laser strapped to it? I'm not quite sure what you're after.

L
7 years ago
Mutant sea bass?
7 years ago
Or sharks?

L
Re-design7 years ago
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.
stephenniall (author)  Re-design7 years ago
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 .

7 years ago
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.
7 years ago
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.
7 years ago
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
7 years ago
AH!  Phase shift.
7 years ago
Cunning innit ?
7 years ago
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.