Low cost vision system, thoughts

JGCASEY wrote:


More for image rendition, likely. Skin looks REALLY bad under IR light. Veins show through, and skin looks mottled. With a color imager, the color tone of skin can look pasty.
For reasons I won't go into here, more and more cameras now have an integrated filter as part of the imager. It cannot be removed. The very cheapest IR security cameras are, by design, IR-sensitive and don't have the filter. But their image quality tends to be really, really bad. I've tried about a half dozen of them, and they're all useless for vision.
For anyone considering a stationary IR laser on a robot: it's a dumb idea, not legal (in the US) if you demonstrate it in public, and (usually) not allowed if you enter the robot in competitions. By federal law, the output of a IR laser, especially one that is not scanning, must not be exposed where it could enter a person's eyes. The danger here is obvious. There are plenty of sites and FAQs that talk about laser safety.
Visible light laser is safer, and just as good, if not better because under IR all the pixels in an imager will pick up at least some light, regardless of the color filter in front of them. For a color camera IR light is not "colorless."
-- Gordon
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If not stated here already...
On a color imager, you have a bayer pattern of colored filters. It looks something like :
RGRGRGRGRG GBGBGBGBGB
Thit means there are 2x as many green pixels as red or blue. I.E. a green laser is a good choice for structured light.
The reason for having an IR cut on the imager is that the Bayer' pattern's dyes all pass IR. You lose color sensitivity unless you remove the IR
Mike

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btw, chook = chicken (in Australian).

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chook = "sweater cap" in USA, AlsoKnownAs a "beanie",
http://www.eastbay.com/catalog/productdetail.cfm?model_nbrW577&skuU052&SID 32&inceptor=1
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mlw wrote:

If you're looking for a low-cost, fast embedded vision system to experiment with, I would suggest the AVRcam...check out http://www.jrobot.net/Projects/AVRcam.html . It is $99 for a basic kit which includes everything you need (camera, embedded board, software that runs on your Windoze/Linux PC or Mac, and cabling). The resolution is reduced from what you need (its only 88 x 144), but may be sufficient for what you need. It process and tracks color blobs at 30 frames/second, so your real-time processing should be no problem.
Oh yeah...and its all open-source, so you can dive into the code and fiddle to your hearts content:
http://www.jrobot.net/Download.html
Standard disclaimer: I developed the AVRcam but have had quite a bit of positive feedback regarding its performance. At the very least you may get some ideas of spinning your own system from scratch. I'm also interested in hearing about other people's projects in the low-cost embedded vision arena, so keep us posted!
Regards, John Orlando www.jrobot.net
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Double-posted from the "$75 vision system" thread:
Here's my current setup for vision on a PC.
- Use a webcam - Logitech 4000Pro's are a good model near the specified price point.
- Use the Intel's OpenCV to import the pictures on a PC. (http://www.intel.com/technology/computing/opencv/index.htm )
- Use CMVision to quickly find colored objects (http://www.cs.cmu.edu/~jbruce/cmvision/)
- Use Qt for a nice GUI interface. (http://www.trolltech.com/download/opensource.html )
- Use MinGW for a MSWindows compiler (http://mingw.org /)
For a robot, the steps are similar. We have some custom camera to DSP interface boards at my school. Reading in the images doesn't require any fancy library. I will probably port CMVision or something similar to C for the DSP this semester.
Later, Daniel
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