Re: Camera software

In order for the stereo cameras to do depth measurements, they'd need
to see the same speckle pattern. The way I understand interference,
they should see different patterns in each camera. I'll do an
experiment, shine one on the wall and draw in a few of the bright
spots. If someone else sees the same thing, then this might work.

If you use a laser pointer, the beam cross-section is pretty small
(about 1mm on my green one), but the speckle pattern you see on a wall
is much bigger. Why? I understood that the reflection was still pretty
coherent leading to a visually larger spot of speckle than was being
exposed to by the laser because of the way it reinforces at your
retina. Is this not correct? If so, then the whole reflected speckle
pattern that I can see is generated by the texture under the 1mm beam.

What I thought would work would be a hologram beam spreader like the
ones you screw on the end of a laser pointer. They're cheap and if you
alternate two laser diodes with crosshatch patterned outputs, it'd be
almost as good as white noise for averaging. And you wouldn't need a
lens or projector or any of that other nonsense. Heck, you may well be
able to use it with a decent LED.

And it's only a helper for the stereo algorithms, so it wouldn't need
to overwhelm ambient. Should work in the shop (but unfortunately not
in my other project which looks at much bigger things in bright
sunlight).

On 8/3/06, Graham Stabler <eexgs@...> wrote:
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Dennis Schmitz"
>
> Speckle is caused by interference, if you take two plane waves and
> interfere them you get fringes, if you take a large set of plane waves
> that are going in all different directions you get the superposition
> of lots of fringe patterns, that is the speckle.