Re: Low cost vision system, thoughts

JGCASEY wrote:


...

jgc wrote:
I presume here you are thinking about vision for
navigation, (positional recognition?) and obstacle
avoidance?

mlw wrote:
As a start, yes.

...

You should get a web cam and point your IR remote
control at it. It comes through clear as day as
"white" light.

Well blow me down you are right I had never actually
tried that before :)

What's really fun is using a bunch of high output IR LEDS as illumination
for a "night vision" webcam.


Actually, the advantage of an IR LED is that
color is not returned.

Well, actually, very little color info is returned.

Why? Color is invariant to position and rotation
and many things can be identified by color alone.

Using color to identify things is tricky, if the lighting varies, i.e.
illumination with an incandescent light, fluorescent light, or even candle
light, or even if the position of the sun and the weather all affect color.
(I used to do a lot photography and contracted at Polaroid for their
electronic camera) The issue of color mapping is huge in imaging, you can't
rely on color at all unless you have control over illumination and color
response of the imaging device.

To use color reliably, you would have to do an amount of imagine processing
on the image just to normalize the RGB data into some known color space.



Or do you mean the advantage is they don't absorb
color the way a red laser does?

Is IR evenly reflected despite the color?

I haven't done any spectral analysis, but it looks almost monochrome in that
the light colors are reflected lightly (more), and dark colors are
reflected darkly (less).

...

I have done a bit of thinking (and investigating with
my quick cam) about it, and the first problems to be
solved is navigation and object avoidance. The IR laser
should help this, it would be sweet if we could get an
IR laser grid projector, but I digress.

If you can get a cheap IR laser maybe the lens used
in the red laser pens for making a line would work?

I don't see why they wouldn't. "IR" is just light that our eyes can't see.

That would be a start. Have you thought about what
you would do with the line data and how you would use
it to recognize a position?

Say, we have a 320x240 camera, we would have 320 Y references, one for every
X or horizontal pixels. Take this data and normalize it to zero, or treat
it like a series of differentials, something along those lines.

The rest is all vague and conjecture:

It should be possible to hash this data into a really reduced quick search
format that can be close with a probability of error.

Ideally, if the hash algorithm is good, the same view from acceptably
different distances and/or perspectives should be the same. (That's the
hard part)
.

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