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[DPRG] Phase Shift

Subject: [DPRG] Phase Shift
From: Triffid Hunter triffid_hunter at funkmunch.net
Date: Tue Jul 22 21:15:33 CDT 2008

On Tue, 22 Jul 2008, Tom Brusehaver wrote:

> There was a very clever trick that one guy used. The article was in
> circuit cellar
> about 10 years ago.
>
> Using a linear CCD (like out of a scanner), it measures the angle offset
> from the laser and the CCD.
>
> don't point the laser straight ahead, but at a slight angle. The reflection
> will traverse the CCD. Some quick trig, and you can get an angle.

this is how the sharp gp2d12 and friends work, although instead of a CCD 
they use a special pickup that resembles an array of phototransistors 
connected to a strip of resistors so the combination of the lens and the 
resistance gives distance.

There's an article in seattlerobotics' encoder about parallax too.

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