Peg reflective tape attached to reflecting plexiglass?

I was talking to a fellow coach and he mentioned that during their week 1 event, they were planning on using vision to place the gear on the peg.

But when they show up at their event, the tape around the peg was placed on plexiglass, and with the reflection, making their vision system ineffective.

Anyone else ran into this issue ? if so , what did you do to prevent this problem from happening?

in our case it’s a matter of exposure on the camera. yes, the plexi reflects some light, but the tape reflects much more. We also evaluate the returned blobs to make sure they have a width/height ratio close to the target tape sizes. a reflection of the vision light would be roughly equal for width/height in our case.

This presentation talks a bit about image filtering to eliminate glare and other lighting and a million other awesome points. Totally worth a watch… or 12.


When you get to competition you should have time to mess with the thresholds, contrast etc on the vision system. That should help a bit.

One trick that helps here is trying to make the angle between the camera and the vision target as oblique as possible (which is a bit tricky due to the robot height restriction). The retro reflective tape will appear just as intense from this vantage point (yay retro reflectors), but the plastic will not reflect as much light due to the angle.

I second the recommendation to watch/read Team 254’s materials on the subject, and repeat my thanks to them for the excellent introduction!

In addition, I strongly recommend using sunglasses on your camera instead of (or in addition to) adjusting the camera’s exposure. Our camera is mounted 2 1/2 inches from the floor and has 3 layers of cheap plastic sunglasses for exposure control. With the oblique angle and the filtering, we’ve gotten very crisp images at every one of our events:

The very few stray artifacts present are easily filtered out by our opencv filter pipeline.



Or, maybe you don’t need a camera…

This is exactly what we’ve done. Our Pixy and light source are about 20 inches above the floor, angled downward toward the peg. Reflection from the backing plastic is no longer an issue.

retro-reflective tape reflects directly back to the light source.
Poly-carbonate reflects angle of incidence = angle of reflection.

Aim your camera at an angle so that it is not 90 degrees from the poly-carbonate