cracked candle have to be rejected out. a vision system is being designed to handle this job which currently done by operator. the candle is white color and the crack very hard to be capture in the image. even using Ultraviolet light, the crack still not visible. but, with our naked eye, the crack is there. please help!

Thank you.

 

It would help to see your candles, but I would depend on
the translucency of wax and the difference in transmission
that a crack causes. I would illuminate with a strong enough backlight to make the candle "glow" masked so the camera sees no light except as transmitted through the candle. I would mask the camera image so nothing but the candle is visible, then I would enhance the gamma (contrast) so that the lighting irregularities are detectable. You might well have to ignore the wick shadow. This helps the camera to be as sensitive to the differences as our eyes are. This is fairly simple when you are writing your own code, but it might be difficult to find a canned program with the flexibility to do this. Proof of concept can be done with a box with a slot for the candle and a light inside in a darkened room. The cracks should be quite visible to the eye. To perform in normal light a monochromatic light source and matching filter for the camera can reject ambient light.

Regards

cww

 

I'm not sure how familiar you are with vision systems. But you may want to contact the folks at http://dvtsensors.com/home/

I'm just putting finishing touches on a vision system that was also very unconventional.

If you can see the cracks with the naked eye, a camera will also be able to "see" them. It's identifying and defining them as defects that is the difficult part.

Good luck!