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Vision Systems Questions

Question Asked:

I currently have an outdoor vision system that detects logs on a stepfeeder. I am using a Cognex insight 7050 with 3.5mm focal length lens to provide me with a FOV of around 3 meters. This works well except I am having problems with sunlight causing glare and shadows that either causes the camera to false detect, or not detect at all. Could anyone recommend lighting/lens/filters that may help?

2 Answers

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Brian Durand - AIA Certified Vision Professional, Advanced Level
I4 Solutions, LLC
bdurand [at] i4solutions [dot] us
(612) 888-6000

You can try a polarizing filter to reduce glare. A hood around the lens might also help, though that may be hard to accomplish given your lens's very wide field of view. I assume you're using the sun as your source of illumination, so you have little choice but to accept what it gives you. The alternative would be blocking the sun (a roof?) and installing your own LED lighting that you can control. The geometry (direction) and wavelength of the light will be important to optimizing contrast. If I understand your brief description, light coming from behind the log may be a good solution. Also, a camera having a better dynamic range would be more forgiving of the bright and dark areas.

Andy Long - CEO
Cyth Systems, Inc.
andy [dot] long [at] cyth.com
(858) 342-6795 cell

Simon, I would agree with Brian, right now you are using natural light and its variation to illuminate the object, and as this changes, this affects all the algorithms that have written to deal with "specific light setup". Having driven the coast road from Melbourne to Adelaide I know that you are lucky enough to not see too much change in weather, but your challenge remains the same as everyone else doing outside work with machine vision, having light changes makes everything else much more complicated. Brian suggested covering the environment and using lights that you control your environment - is that a practical option? If not another option is measure the light available using some other technique, get a lot of samples of images of logs for different lighting conditions, and change the algorithm based on the "type" of light available. Also you could look at different parts of the spectrum depending on your unique needs. Are you trying to measure diameter of logs as a silouett

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