Limelight blink advantages?

So I’ve noticed some teams having their limelight’s Leds blinking when they target, for example team 1986, aka Team Titanium at the Greater KC Regional. Is there an advantage to having your limelight blink? Alternatively, what’s the use of having limelight leds blink?

I think I’ve seen some teams blink their limelights where they are trying to locate the target for odemetry. So if the limelight can’t find the target, instead of it staying on, it blinks until it can lock on to the target again. I’m not really sure of the benefits of this methods, other than not blinding everyone.

I’m guessing that if you compare a picture with the lights on to one without, then you can exclude things that are illuminated by something other than the lights (e.g. a TV screen behind the hub, or a huge skylight above the field), and focus only on things that are retroreflective.


I know we blink our limelight for a couple reasons. It narrows the target window as in we position the robot about close to the vision target and then the LL takes over. It reduces the chances of false positives. Also, we snapshot the distance data and then compute trajectory. If you continuously do this (leave the LL on) you get more up to date info but you also take longer to shoot. Since our robot can shoot in under half a second there’s no real reason to keep updating it (unless you are shooting and moving). There’s more to it but that’s just a basic explanation.

Then the next reason is unrelated to strategy. You don’t need the LL on the whole time and since they are bright some inspectors/refs have asked teams to turn down or off the LEDs. So basically we don’t want to blind people either.

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While we don’t do this, it would be a way for you to reject outliers like lights on the ceiling. If the LEDs aren’t on, and you’re still finding something in the hue you’re expecting you can likely reject it.

For example, in this year’s hub they have a couple of green LED control lights that are really close to the limelight LED green.

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At the Greater KC Regional, 1986 didn’t use their limelight. I talked to one of their members and, if I remember correctly, he said they couldn’t get it programmed. I also remember the FTA telling them that somewhere in the settings page they could find a setting for blinking, so I think they didn’t know why it blinked and were trying to make it stop.

The only reason I know of that teams would intentionally make their limelight blink would be safety and/or power draw.

Could you expand on the methods one would use to reject targets that are visible while the lights are off?

If target is visible when leds are both on and off, ignore it because its a light, not the tape

However, this is more complicated than just tuning the color balance so the lights on the ceiling are orange and won’t get picked up

How exactly? How does one keep track of the targets that are present with lights off, then compare them to the ones present when the lights are on. Are there limelight settings for that? Or is that done in your code?

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I think this would have to be a custom implementation and I don’t think it is really necessary with good tuning unless you playing under really bright lights.

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