A laser range finder is dead easy, but moderately expensive to build.

It takes a laser pointer, two PSDs (position sensitive detectors), two
lenses, some ADCs, and a micro with decent math handling. (you really
want something capable of divide for this).

It's a simple concept, really, you don't actually need to make the beam
parallel.  You need to know the baseline between the centres of the two
lenses, and that needs to be the same as the baseline between the
centres of the two PSDs.

For best results, I would mount the laser pointer between the two PSDs.

The lenses focus the far-off laser spot into a point on the PSD, and
since they should (ideally) be the brightest thing around, they should
override any other light sources around.  You can improve the quality by
putting a red filter behind the lenses.

The PSDs will give you a voltage offset that can be converted to a
distance fairly easily.  From there, you can calculate an angle for each
PSD.
Now you have a trig problem.  You have two angle and a side of a
triangle.  The last angle solves itself, which gives you something you
can use the sine rule on (this is where the math handling comes in).

Using the sine rule, you get the two long sides, and I think to simplify
the math, I would take the average of the two long sides, as that works
out to the centre of the baseline, which is where your laser pointer is
mounted.

2D PSDs are expensive.  You should be able to get away without actually
using the 2D sensors.  I think you can probably use 1D sensors so long
as the the laser pointer is lined up well enough to keep it on the PSD.

There was a circuit cellar issue in the past year that detailed using a
2D PSD fot position sensing off of a laser level, which chould have some
nice info in interfacing to them.

Hamamatsu has some really good info on this.
(usa.hamamatsu.com)
This PDF is really good:
http://usa.hamamatsu.com/assets/pdf/catsandguides/Psd.pdf?GLBSESSID=e0ec2522731b5412ea91cdc543d25d1d

I know that these PSDs are available somewhere, but I'm not really sure
where to look.  You could have a look around at soem larger suppliers,
and hamamatsu may even have a few links to their distributors.

I think that 1D PSDs should greatly reduce the costs you're looking at.

Anyway, I think this should answer your question.  Hope it helps =D,

--Brendan

>I've recently got a couple of cheap laser pointers.
>
>And I was wondering if there is a way to measure distance with them?
>
>I have a crazy idea, but I'd like to ask the question first and see if there
>is a standard answer to this question.
>
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>http://www.piclist.com hint: The PICList is archived three different
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>
>
>
>

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