> --- In oopic@yahoogroups.com, Brian Lloyd <brian-wb6rqn@...> wrote:
>>
>
>
> As it turns out, a couple of months ago I bought an inexpensive $10
> laser level, and then completely forgot about it. Found it in a box
> yesterday. It transmits both a bright spot and also a less bright
> straight line, emanating from the spot. It is very interesting to
> scan it around onto different surfaces. You can easily distinquish
> different shapes by how the "line" beam bends around the surfaces.
This is the system I was describing a week ago.
> For boxlike shapes, you see 2 straight beams at an angle, with a bend
> at the edge of the box.
If you think about it, for vertical serfaces, the "altitude"
corresponds to distance to that point on the scan line.
> For complex-shaped objects, you see multiple discontinuities in the
> reflected beam.
>
> For close on objects, you see a discontinuous line, as the beam falls
> off the edge of the object. It's easy to distinquish an object
> isolated from the background.
Yes.
> You can also do rough ranging measurements directly. Eg, at 6" from a
> flat surface, the line beam is 4" long. Of course, if the surface is
> not perpendicular to the sensor, then the line is elongated.
>
> I am thinking one could use 2 such devices [or else laser pointers
> with line outputs], one with a vertical beam and one with a
> horizontal beam to pan around on a 2-D servo mount. I imagine the
> beams are bright enough, compared to normal ambient lighting, that
> one could easily filter the red output from a vid-cam, and isolate
> the beams from the background. This technique is like simple computer
> vision with about 10,000X less processing power required.
Yes.
> One probably needs to adopt some safety measures, so the beams aren't
> projected directly in people's eyes. Also, depending upon the
> sensitivty of the vid-cam used, it may be possible to reduce the beam
> intensity.
Yes. Also consider using an IR laser so the beam in not visible. Most
silicon-based imagers are more sensitive in the near-IR anyway, thus
allowing you to reduce output. Also, most lasers work at specific
emission lines for which narrow-band low-loss filters are available.
You place that in front of your imager to reduce noise from ambient
light.
--
Brian Lloyd Granite Bay Montessori
brian AT gbmontessori DOT com 9330 Sierra College Blvd.
+1.916.367.2131 (voice) Roseville, CA 95661, USA
I fly because it releases my mind from the tyranny of petty things . . .
— Antoine de Saint-Exupéry
PGP key ID: 12095C52A32A1B6C
PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C
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