Dealing with bright lighting at competitions and vision

[mabster314]

We use a green ring light and a single HSV filter, then use GRIP to find contours, filter out ones that are too small, and publish a report to a NetworkTable. The system has worked really well everywhere but Iowa, where the light was just too bright for our camera.

At Iowa, we were having similar problems. There were very large windows on either side of the field, and pointing a camera at the goals from our low bot was impossible without getting them into frame. Even with minimum exposure settings on the Axis camera, the windows were always the light it set the exposure based off of. We share a shop with 3130, who use the LifeCam, and they were having similar problems.

At North Star, we had no problems, and neither did 3130. We both used green ring lights, and they were bright enough to get a very good picture back from the camera. If you want, I can get you in touch with a member from 3130, as I'm not sure what they did with the LifeCam to set it up.

[Greg McKaskle]

Thanks for posting the images.

The images you posted have virtually no green in them because the colors are being washed out due to the bright lights. The tape is essentially the same as the tower's gray colors. Despite what CSI shows like to claim, you can't fix everything by tapping computer keys or waving your hand in front of your face. Image processing is best done on images that are in focus, have good contrast, and don't contain lots of extraneous details. For color images, contrast also means good saturation (not washed out).

If you compare to the pictures that are part of the example code, you'll see that they are darker. This is affected by the exposure and brightness settings on the camera, and as others have mentioned, you can also use a Neutral Density filter (a gray plastic sheet) to block some of the light similar to sun glasses. This will increase saturation of color and allow the HSV filter to mask properly and not include bricks and mortar of the tower to be considered part of the target.

Also, the retroreflective material returns light emitted near the camera lens to the camera lens. So if you have mounted something else like a flashlight near the camera, you are diluting the green and washing it out.

Once you have a high contrast, saturated image, the task is far easier, and the rest of your code should work much better. If you need more help setting up your camera, post the camera setup code or a description of it.

Greg McKaskle

[Greg Young]

We ended up using two pieces of polarizing filter material. Adjust the angle between the filters until you reduce the intensity enough to see the led color in the target.

This worked great on the practice field but on the field we shot high or low. The horizontal tracking was perfect but our ranging was off.

Greg

[MichaelBick]

We found these instructions for tuning our axis camera settings very useful

[ajhammond123]

Definitely change your camera settings. After playing around with our axis camera settings using a model of the goal our images went from something like what you have to an image where everything except the brightest sunlight was too dark to be anything but black, and the reflection off of the tape is a distinct shade and color unique to the LEDs you use. You would have to re-adjust HSV values in your program after doing this, but it provides an easy method of reducing the number of potential targets in your image.